A UNITED STATES
DEPARTMENT OF
COMMERCE
PUBLICATION
C5S. 6>/? • ? 'tjrl-
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
COLLECTED REPRINTS-1971
Volume II
ATLANTIC OCEANOGRAPHIC
ND METEOROLOGICAL LABORATORIES
^2J2SS2*»
'WENT O^
U.S. DEPARTMENT OF COMMERCE
Peter G. Peterson, Secretary
NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION
Robert M. White, Administrator
ENVIRONMENTAL RESEARCH LABORATORIES
Wilmot N. Hess, Director
Collected Reprints— 1971
Volume II
ATLANTIC OCEANOGRAPHIC
AND METEOROLOGICAL LABORATORIES
ISSUED JULY 1972
T,
o
Atlantic Oceanographic and Meteorological Laboratories
Miami, Florida 33149
For sale by the Superintendent of Documents, U. S. Government Printing Office, Washington, D. C. 20402
■•
FOREWORD
An increased understanding of the ocean and its processes,
of the underlying geological and geophysical structures, and of
the overlying atmosphere and its interactions with the sea will
result in man's increased ability to deal intelligently with the
problems of this environment.
The scientific and technical accomplishments of the National
Oceanic and Atmospheric Administration's Environmental Re-
search Laboratories are contributing to this understanding. Be-
cause the published results of the Atlantic Oceanographic and
Meteorological Laboratories are broadly scattered through the
literature, they are being brought together in a series of annual
publications. These provide a convenient summary of the results
of the work of these laboratories for researchers and interested
laymen alike.
This volume, the sixth in the series, contains the published
results of NOAA's Atlantic Oceanographic and Meteorological
Laboratories for the year 1971.
Director, Atlantic Oceanographic
and Meteorological Laboratories
Digitized by the Internet Archive
in 2012 with funding from
LYRASIS Members and Sloan Foundation
http://archive.org/details/collectedreprintv2atla
CONTENTS
VOLUME
General
Ape 1 , John R .
Wave Interactions in Solid State Plasmas: Book Review.
Physics Today 2_4, No. 2, p. 47.
Stewart, Harris B. Jr.
CICAR - An International Ocea nog rap h i c Program in the
Caribbean: Oceanic Citation Journal 8_, No. 5, 2-5-
S tewa rt, Harris B. Jr.
Ecological Aspects of Industrial Development: Muse
News _M_> No. 12, 411-413-
Stewart, Harris B. Jr.
Exploring America's Mediterranean: NOAA 1, No. 2, 9-11.
Stewart, Harris B. Jr.
Man and the Sea: Book Review. Bulletin of the American
Meteorological Society 5_2_, No. 8, 739-740.
Stewart, Harris B. Jr.
Non-Food Resources as Viewed by: Federal Oceanog raph i c
Research: Third Proceedings of the Third Sea Grant
Conference, sponsored by Oregon State University,
March 1970, 47-48.
S tewa rt, Harris B. Jr.
Ocean Symposium: AAAS Symposia Annual Meeting: Phila-
delphia. Science 1 74 , No. 4012, 964-965.
Staff
Satellite Data Requirements of Atlantic Oceanog raph i c
and Meteorological Laboratories for Studies of Ocean
Physics and Solid Earth. NOAA TR ERL 225-AOML 5-
Physical Oceanography
9. Chew, Frank, and G. A. Berber ion
A Determination of Horizontal Divergence in the Gulf
Stream Off Cape Lookout: Journal of Physical Oceanog-
raphy J_, No. 1 , 13-kk .
1 0 . Hansen , Dona Id V .
Oceanography for the 1970's. The Science Teacher 38 ,
No . 1 .
11. Hansen, Donald V.
Oceans from Space: Book Review. Bulletin of the
American Meteorological Society 5_2_, No. 8, 738-739-
12. Low, James K., and George A. Maul
Precise Two-Point STD Calibrations: Marine Technology
Society Journal 5_, No. 5, 22-33.
13. Zet 1 e r , Bernard D .
Earth Tides. McGraw-Hill Yearbook of Science Tech
no 1 ogy , 174-177-
\h. Zetler, Bernard D., and George A. Maul
Precision Requirements for a Spacecraft Tide Program:
Journal of Geophysical Research 7_6_, No. 27, 6601-6605-
1 5 - Zet 1 er , Berna rd D .
Radiational Ocean Tides Along the Coasts of the United
States: Journal of Physical Oceanography ]_, No. 1,
34-38.
16. Zetler, Bernard D., D. Cartwright, and W. Munk
Tidal Constants Derived from Response Admittances:
Sixth International Symposium on Earth Tides, Stras-
bourg 1 969 , 1 -4 .
17- Zetler, Bernard D .
Tide: Encyclopedia Americana, 7 3 1 ~ 7 3 5 •
18. Zet ler , Bernard D .
Tsunamis and the Seismic Sea Wave Warning System:
Man and the Sea, American Museum of Natural History,
301 -306.
Meteorology
19- Anthes , R i chard A .
A Numerical Model of the Slowly Varying Tropical Cyclone
in Isotropic Coordinates: Monthly Weather Review 99 ,
No. 8, 617-635.
20 . Anthes , Richard A .
Iterative Solutions to the Steady-State Ax i symme t r i c
Bounda ry- Laye r Equations under an Intense Pressure
Gradient: Monthly Weather Review 99_, No. 4, 261-268.
2 1. Anthes , R i cha rd A .
Numerical Experiments with a Slowly Varying Model of
the Tropical Cyclone: Monthly Weather Review 99 ,
No. 8, 636-643.
22 . Anthes , R i cha rd A .
The Development of Asymmetries in a Th r ee-D i men s i ona 1
Numerical Model of the Tropical Cyclone: NOAA Tech
Memo ERL NHRL-94 .
23 • Anthes , R i chard A .
The Response of a Three-Level Axisymmetric Hurricane
Model to Artificial Redistribution of the Convective
Heat Release: NOAA Tech Memo ERL NHRL-92.
24. Anthes, Richard A., Stanley L. Rosenthal, and James W. Trout
Preliminary Results from an Asymmetric Model of the
Tropical Cyclone: Monthly Weather Review 9_9.» No. 10,
744-758.
25. Anthes, Richard A., James W. Trout, and Stellan S. Ostlund
Three-Dimensional Particle Trajectories in a Model
Hurricane: Weatherwjse 2_4, No. 4, 174-178.
26. Anthes, Richard A., James W. Trout, and Stanley L. Rosenthal
Comparisons of Tropical Cyclone Simulations With and
Without the Assumption of Circular Symmetry: Monthly
Weather Review 99, No. 10, 7 59 - 766 .
27 • Bl ack , Peter G .
Cumulonimbus Modification of Tropical Nature: Bulletin
of the American Meteorological Society 52, No. 7, 562-
565.
28. Black, Peter G., and Richard A. Anthes
On the Asymmetric Structure of the Tropical Cyclone
Outflow Layer: Journal of Atmospheric Sciences 28,
No. 8, 13^8-1366.
29 . Carl son , Toby N .
A Detailed Analysis of Some African Disturbances: NOAA
Tech Memo ERL NHRL-90.
30. Carl son , Toby N.
Weather Note: An Apparent Relationship Between the
Sea-Surface Temperature of the Tropical Atlantic and
the Development of African Disturbances into Tropical
Storms: Monthly Weather Review 99., No. k, 309 - 3 1 0 .
31. Carlson, Toby N., and Robert C. Sheets
Comparison of Draft Scale Vertical Velocities Computed
from Gust Probe and Conventional Data Collected by a
DC-6 Aircraft: NOAA Tech Memo ERL NHRL-91.
32 . Gentry , R . Cec i 1
To Tame a Hurricane: Science Journal, 49 ~ 5 5 .
33- Koss, Walter James
Numerical Integration Experiments with Variable-Reso-
lution Two- D i men s i ona 1 Cartesian Grids Using the Box
Method: Monthly Weather Review 99., No. 10, 725~ 738 .
3^. Rosenthal, Stanley L.
The Response of a Tropical Cyclone Model to Variations
in Boundary Layer Parameters, Initial Conditions,
Lateral Boundary Conditions and Domain Size: Monthly
Weather Review 99, No. 10, 767~ 777 .
35- Rosenthal, Stanley L., and Michael S. Moss
Numerical Experiments of Relevance to Project Stormfury
NOAA Tech Memo ERL NHRL-95.
36. Rosenthal, Stanley L., and Michael S. Moss
The Responses of a Tropical Cyclone Model to Radical
Changes in Data Fields During the Mature Stage: NOAA
Tech Memo ERL NHRL-96.
37 . Scott , Wi 1 1 iam D .
Aerosol Sampling and Data Analysis with the NCAR Coun-
ter: The Second International Workshop on Condensation
and Ice Nuclei sponsored by National Science Foundation,
August 1970, 49-52.
38. Scott, William D., Robert K . Cunningham, Robert G.
Knollenberg, and William R. Cotton
Symposium on the Measurements of Cloud Elements:
Bulletin of the American Meteorological Society 52 ,
No. 9, 889-890.
39- Sugg, Arnold L., Leonard G. Pardue, and Robert L. Carrodus
Memorable Hurricanes of the United States Since 1873:
NOAA Tech Memo NWS SR-56.
Vo 1 ume I I
Meteorology (continued)
40. Staff
Project Stormfury 1970 Annual Report.
41. Trout, James W., and Richard A. Anthes
Horizontal Asymmetries in a Numerical Model of a Hur
ricane: NOAA Tech Memo ERL NHRL-93-
42 . Barday , Robert J .
Free-Air Gravity Anomalies South of Panama and Costa
Rica (NOAA Ship Oceanog raphye r - August 1969) : NOAA
Tech Memo ERL A0ML-14.
43
44
Bassinger, B. G
R
N. Harbison, and L. Austin Weeks
Marine Geophysical Study Northeast of Trinidad-Tobago
The American Association of Petroleum Geologists
Bulletin 55_, No. 10, 1730-1740.
Bennett, Richard H., and Douglas N. Lambert
Rapid and Reliable Technique for Determining Unit
Weight and Porosity of Deep-Sea Sediments: Marine
Geology 11, 201 -207-
45. Bennett, Richard H., Douglas N. Lambert, and Paul J. Grim
Tables for Determining Unit Weight of Deep-Sea Sedi-
ments from Water Content and Average Grain Density
Measurements: NOAA Tech Memo ERL AOML-13.
46 . D ietz , Robert S .
North Atlantic-Geology and Continental Drift (A Sympo-
sium): Marine Technology Society Journal 5, No. 5, 33
47 . D i etz , Robert S .
Shatter Cones (Shock Fractures) in Astroblemes: Mete-
or i tics 6, No. 4, 258-259.
48 . D ie tz , Robert S .
Sudbury Astrobleme: A Review. Meteorftics 6_, No. 4,
259-260.
49 . D i etz , Robert S .
The Sea: Ideas and Observations on Progress in the
Study of the Seas. Book Review American Scientist 59 ,
No. 5, 627.
50 . D i etz , Robert S .
Those Shifty Continents
204-21 2.
Sea Frontiers 17, No. 4,
Dietz, Robert S., and K. D.
Portrait of a Scientist:
Rev iews 7 , No. 1 , A9~A1 5
Erne ry
Francis Shepa rd
Earth-Science
52. Dietz, Robert S,, and John C. Holden
Pre-Mesozoic Oceanic Crust in the Eastern Indian Ocean
(Wharton Basin): Nature 229, No. 5283, 309-312.
53. Dietz, Robert S., John C. Holden, and Walter P. Sproll
Geotectonic Evolution and Subsidence of Bahama Platform
Reply. Geological Society of America Bulletin 82 ,
811-814.
54. Dietz, Robert S., and Harley J. Knebel
Trou Sans Fond Submarine Canyon: Ivory Coast, Africa:
Deep Sea Research 18, 441-447.
55- Freeland, George L., and Robert S. Dietz
Plate Tectonic Evolution of Caribbean - Gulf of
Mexico Region: Nature 232 , 20-23.
56. Keller, George H.
Engineering Properties of North Atlantic Deep-Sea
Sediments: Interocean '70 2_, 6 5 ~ 7 1 -
57 • Ke 1 1 er , George H .
Mass Properties of the Sea Floor in a Selected Deposi-
tional Environment: Proceedings Civil Engineering in
the Oceans II, Miami Beach, December 1969, 857-877-
58 . La 1 1 imore , R
62
63
6k
K
L. Austin Weeks, and L. W. Mordock
Marine Geophysical Reconnaissance of Continental
Margin North of Paria Peninsula, Venezuela: The
American Association of Petroleum Geologists Bulletin
55., No. 10, 1719-1729.
59- Peter, George and Omar E. DeWald
Deformation of the Sea Floor off the North-west Coast
of the United States: Nature Physical Science 232 ,
No. 31 , 97-98.
60. Peter, George, Barrett H. Erickson, and Paul J. Grim
Magnetic Structure of the Aleutian Trench and Northeast
Pacific Basin (I968): The Sea, Ed. A. E. Maxwell, Pub-
lished by Wi 1 ey- I n terse i ence , k, pt. 2, 191-222, 1971.
John Wiley & Sons, Inc., 1971.
6 1 . Rona , Peter A .
Bathymetry Off Central Northwest Africa
Research 18, 321-327.
Deep Sea
Rona , Peter A .
Deep Sea Salt Diapirs: Letter to editor Geotimes, p. 8
Rona , Peter A .
Depth Distribution in Ocean Basins and Plate Tectonics:
Nature 2_3J_, 179-180.
Starr, Robert B., and Robert G. Bassinger
Marine Geophysical Observations of the Eastern Puerto
Rico-Virgin Islands Region: Trans-Fifth Caribbean Geo-
logical Conference, Geology Bulletin No. 5, Queens
Col 1 ege Press , 25-29-
65
66
Weeks, L. Austin, and Robert K. Lattimore
Continental Terrace and Deep Plain Offshore Central
California: Marine Geophysical Research 1, 145-161.
Weeks, L. Austin, R. K. Lattimore, R
B. G. Bassinger, and G. F. Merrill
N . Harbison,
Structureal Relations Among Lesser Antilles, Venezuela,
and Tr i n i dad -Tobago : The American Association of
Petroleum Geologists Bulletin 55, No. 10, 1741-1752.
67
68
69
70
71
72
Sea-Air Interaction
Hanson, K i r by J .
Studies of Cloud and Satellite Parameterization of
Solar Irradiance at the Earth's Surface: Proceedings
of the Miami Workshop on Remote Sensing March 29-31,
1971 , M iami , Florida , 133-148.
McAl i s ter , E
William McLeish, and Ernst A. Corduan
Airborne Measurements of the Total Heat Flux from the
Sea during BOMEX: Journal of Geophysical Research 76 ,
No. 18, 4172-4180.
Nordbert, W., J. Conway, Duncan B. Ross, and T. Wilheit
Measurements of Microwave Emission from a Foam-
Covered Wind-Driven Sea: Journal of Atmospheric
Sciences 2_8_, No. 3, 429-435-
Ostapof f , F .
Introductory Remarks - Sea-Air Interaction Instrumen-
tation: IEEE Transactions on Geoscience Electronics
GE-9, No. 4, 197-198.
Ostapoff, F.
Ocean-Atmosphere Interaction in the Caribbean Sea:
Viewed from the Ocea nog ra phe r Side: Proceedings Sym-
posium on Investigations and Resources of the Caribbean
Sea and Adjacent Regions, 1 3 7 - 1 4 5 .
Shinners, W i 1 lard W., Gerald E. Putland, and Peter B.
Connors
Tests of Modified Radiosonde Hygristor Duct: NOAA
Tech Memo ERL A0ML-15.
U.S. DEPARTMENT OF THE NAVY
J. H. CHAFEE, Secretary
Naval Weather Service Command
W. J. KOTSCH, Rear Admiral, USN, Commander
40
U. S. DEPARTMENT OF COMMERCE
M. H. STANS, Secretary
National Oceanic and Atmospheric Administration
R. M. WHITE, Administrator
PROJECT STORMFURY
ANNUAL REPORT
1970
MIAMI, FLORIDA
MAY 1971
Project STORMFURY was established by an Interdepartmental
agreement between the Department of Commerce and the Department
of Defense, signed July 30, 1962. Additional support has been
provided by the National Science Foundation under Grant NSF-G-17993
This report is the ninth of a series of annual reports to
be prepared by the Office of the Director in accordance with the
Project STORMFURY interdepartmental agreement.
Additional copies of this report may be obtained from:
U. S. Naval Weather Service Command
Department of the Navy
Washington Navy Yard
Washington, D. C. 20390
or
National Hurricane Research Laboratory
P. 0. Box 8265, University of Miami Branch
Coral Gables, Florida 3312A.
NOTICE
The National Hurricane Research Laboratory and the Naval
Weather Service Command, do not approve, recommend, or endorse
any proprietary product or proprietary material mentioned in
this publication. No reference shall be made to either or-
ganization or to this publication in any advertising or sales
promotion which would indicate or imply that the National Hur-
ricane Research Laboratory or the Naval Weather Service Com-
mand approves, recommends, or endorses any proprietary product
or material mentioned herein, or which has as its purpose an
intent to cause directly or indirectly the advertised product
to be used or purchased because of this publication.
TABLE OF CONTENTS
INTRODUCTION
HISTORY AND ORGANIZATION
PROJECT STORMFURY ADVISORY PANEL
PUBLIC AFFAIRS
PYROTECHNIC DEVICES - SILVER IODIDE
AREAS OF OPERATIONS
PLANS FOR FIELD OPERATIONS - 1970
FIELD OPERATIONS
RESEARCH ACTIVITIES
OPERATIONAL AND RESEARCH DATA COLLECTION
OUTLOOK FOR 1971
REFERENCES AND SPECIAL REPORTS
APPENDIX A. Report On Meeting Of Project Advisory
Panel
APPENDIX B. A Hypothesis For Modification Of
Hurricanes
APPENDIX C.
APPENDIX D.
APPENDIX E.
APPENDIX F.
APPENDIX G.
APPENDIX H.
APPENDIX I.
APPENDIX J.
H u r r i
H u r r i
Summa
Asymm
Respo
To Ag
Sol ut
Measu
Eyewa
An Es
Tropi
Ice-P
Cumul
Use 0
Activ
Use 0
H u r r i
cane Model ing At T
cane Research Labo
ry Of Prel i mi nary
etric Model Of The
nse of STORMFURY C
I And Agl-Nal Ice
ion-Combustion Gen
he National
ratory (1970)
Results From An
Tropical Cyclone
loudline Cumuli
Nuclei From A
era tor
1 Motion In The
Hurricane Debbie
rements Of Vertica
11 Cloud Region Of
timate Of The Fraction Ice In
cal Storms
hase Modification
us Clouds In Hurri
Potential Of
canes
f Light Aircraft In STORMFURY
i t i e s
f Echo Velocities
cane Modification
To Evaluate
Experiments
Page
1
2
3
4
4
5
5
8
10
12
13
14
A-l
B-l
C-l
D-l
E-l
F-l
G-l
H-l
1-1
J-l
1 1 1
APPENDIX K.
APPENDIX L.
A Summary Of Radar Precipitation
Echo Heights In Hurricanes
Project STORMFURY Experimental
Eligibility In The Western North
Pacific
Page
K-l
L-l
1 v
PROJECT STORMFURY ANNUAL REPORT
1970
INTRODUCTION
The apparently successful seeding operations on Hurri-
cane Debbie in 1969 made it most urgent that similar experi-
ments be carried out on a 1970 storm to provide further eval-
uation of the effectiveness of the technique. The 1970
hurricane season, however, produced no tropical cyclones
which were eligible for seeding experiments. In spite of
this, or perhaps because of it, the 1970 season was undoubt-
edly the most productive research period for Project STORMFURY
to date.
forces
line ex
Storm D
the Nav
24 July
e x e r c i s
forces
on 1 9 A
a h u r r i
not i n t
ment, s
FURY mo
c i e n 1 1 y
to Puer
weaken
e r a t i o n
needed
Even th
did ope
peri men
orothy .
al Stat
, and t
e s d u r i
were ag
ugus t t
cane an
en si fy
he coul
ni tori n
stabl e
to Rico
after c
revert
i n forma
ough
rate
ts , a
The
ion R
hese
ng th
ai n d
hat T
d mov
and b
d sti
g mis
. On
on 2
rossi
ed to
ti on
no e 1 i g i
together
nd on a
dry-run
oosevel t
were fol
e last 6
epl oyed
ropi cal
e into t
ecome el
1 1 have
s i o n if
this b a
0 August
n g the i
a data-
on a tro
bl e s
dun*
data-
exer
Road
1 owed
days
to Pu
Storm
he Ca
igibl
provi
her i
sis,
. Do
si and
gathe
p i c a 1
torm d
ng dry
gather
c i s e s
s , Pue
immed
of th
erto R
Dorot
r i b b e a
e for
ded a
n t e n s i
the ST
rothy ,
of Ma
ring m
wave .
evel
-run
ing
were
rto
i ate
e mo
i co
hy m
n .
a mo
good
ty r
ORMF
how
rti n
i s s i
oped, t
e x e r c i
mission
conduc
Rico, o
ly by t
nth. T
when it
i g h t d e
Even if
d i f i c a t
storm
emai ned
URY for
ever , s
i q u e , a
on to p
he STO
ses , c
in Tr
ted f r
n 21 t
he cl o
he STO
appea
vel op
shed
ion ex
for a
suff i
ces mo
tarted
nd the
r o v i d e
RMFURY
1 oud-
o p i c a 1
om
hrough
udl i ne
RMFURY
red
i nto
id
p e r i -
ST0RM-
ved
to
op-
badly
With the lack of eligible storms in 1970, the hurri-
cane research efforts were intensified and carried out with-
out operational interruptions. The results of these various
research activities are extremely interesting particularly
as they relate to future STORMFURY operations, and the more
significant results are given in the Appendices to this re-
port. Of special interest in this connection is Appendix B
which details a new and better explanation for the apparent
success of the 1969 "Debbie" experiments than was possible
with the pre-existing hypothesis.
The optimism generated by the "Debbie" work also re-
sulted in increased emphasis being placed on the Project by
the Government. In 1970 Project STORMFURY was designated a
National Pilot Project by the Interdepartmental Committee for
Atmospheric Science (ICAS), and some additional STORMFURY
funding was made available in the FY-1971 budget of the
Department of Commerce.
HISTORY AND ORGANIZATION
Project STORMFURY is a joint Department of Commerce
(NOAA) -Department of Defense (Navy) program of scientific ex-
periments designed to explore the structure and dynamics of
tropical cyclones and their potential for modification. The
Project which was formally established in 1962 has as its
principal objective experimentation directed towards changing
the hurricane's energy exchange by strategic seeding from
aircraft with silver iodide crystals. The crystals are dis-
pensed from pyrotechnic devices developed by the U.S. Navy.
The hypothesis calls for a measurable decrease in the maximum
wind velocities near the center of the storm. Navy and NOAA
scientists and aircraft, supplemented by those of the U.S.
Air Force, have cooperated in STORMFURY experimental opera-
tions since 1961 when the first informal agreement was pro-
posed. To date, the experiments conducted by the Project
consist of:
Hurricane Esther
Hurricane Beulah
Tropical Cumulus
Tropical Cumulus
- seeded in 1961 - Single seeding
- seeded in 1963 - Single seeding
Cloud Seedings - 1963
Cloud Seedings - 1965
Tropical Cloudline Seedings - 1968
Tropical Cloudline Seedings - 1969
Hurricane Debbie Seedings - 1969 - Multiple seeding
Tropical Cloudline Seedings - 1970.
Since 1962, only two hurricanes have been seeded1. The
results of the Hurricane Debbie multiple seeding experiments
conducted on 18 and 20 August 1969, were extremely encour-
aging in that a decrease in the maximum wind velocity of the
hurricane was observed on both days. Although by no means
conclusive, these observations coupled with radar and other
meteorological data strongly suggest that a modification to
Hurricane Debbie was achieved. The exact amount of effect
caused by seeding is still s/ery difficult to determine due
to the natural fluctuations which occur in each tropical cy-
cl one.
The initial 1962 Project STORMFURY agreement between
the Department of Commerce and the Department of the Navy
covered 3 years and was renewed annually from 1965 to 1968.
The 1969 renewal was extended to cover a 3 year period.
1 See Project STORMFURY Annual Reports 1963 through 1969.
Dr. Robert M. White, NOAA Administrator, and Rear
Admiral W. J. Kotsch, U.S. Navy, Commander Naval Weather
Service Command, had overall responsibility for the coopera-
tively administered project.
D i r e c
Miami
H a w k i
Navy
Navy,
Jacks
A s s i s
Navy ,
Weath
was T
Naval
ject
mand
d u t i e
(NHRL
and N
The
tor o
, Flo
ns , a
Pro je
Comm
o n v i 1
tant
also
er Re
e c h n i
Weap
Offic
Headq
s rep
) was
OAA a
Proje
f the
r i d a .
1 so of
ct Coo
a n d i n g
le, Fl
Projec
of FL
search
cal Ad
ons Ce
er; Mr
uarter
resent
a s s i g
nd act
ct Di
N a t i o
The
NHRL
r d i n a
Offi
o r i d a
t Dir
EWEAF
Faci
visor
nter ,
. Max
s , Wa
ing t
ned 1
ed as
recto
nal H
Alter
. Th
tor w
cer o
(FLE
ector
AC JA
1 i ty ,
to t
Chin
Edel
shi ng
he Na
i a i s o
Data
r i n
u r r i c
nate
e Ass
as Ca
f the
WEAFA
was
X. M
Norf
he Na
a Lak
stein
ton ,
vy ; a
n dut
Qual
1970 wa
ane Res
Di recto
i stant
ptain L
Fleet
C JAX) .
Command
r. Jero
oik, Vi
vy ; Dr.
e , Cali
, Naval
D.C. , w
nd Mr.
ies for
i ty Con
s Dr.
earch
r was
Proje
. J.
Weath
The
er J .
me W .
r g i n i
S. D
form'
Weat
as as
Willi
the
trol
R. Ceci
Laborat
Dr. Har
ct Direc
Underwoo
e r F a c i 1
Al terna
0. Heft
Ni ckers
a (WEARS
. El 1 iot
a , was N
her Serv
signed 1
am D. Ma
Project
Coordi na
I Gentry,
ory (NHRL) ,
ry F.
tor and
d, U.S.
i ty ,
te to the
, U.S.
on, Navy
CHFAX) ,
t , Jr. ,
WC Pro-
ice Com-
i ai son
I I i n g e r
Director
tor.
PROJECT STORMFURY ADVISORY PANEL
The Advisory Panel of five members is representative
of the scientific community and provides guidance through its
consideration of various scientific and technical problems
involved with the project. Their recommendations have proved
to be of great value to the project since its inception.
The Panel reviews results from previous experiments,
proposals for new experiments and their priorities, and makes
recommendations concerning the effectiveness of data collec-
tion and evaluation, eligibility criteria for storms to be
seeded, and other items as applicable.
During 1970, the Advisory Panel consisted of the fol-
lowing prominent scientists: Professor Noel E. LaSuer,
Chairman (Florida State University), Professor Jerome Spar
(Department of Meteorology and Oceanography, New York Uni-
versity), Professor Edward Lorenz (Department of Meteorology,
Massachusetts Institute of Technology), Professor Charles L.
Hosier (Dean, College of Earth and Mineral Sciences, Pennsyl-
vania State University), and Professor James E. McDonald
(Institute of Atmospheric Sciences, University of Arizona).
The Panel met in Miami on 29 and 30 September 1970 to
discuss numerical hurricane modeling research and the simula-
ted seeding experiments with the hurricane models conducted
by Dr. S. L. Rosenthal and his group at NHRL.
The Panel again met in Washington, D.C., on 28-30
January 1971. The first day, the Panel members participated
in a briefing to NOAA about research on "Decision Analysis of
Hurricane Modification" done at the Stanford Research Insti-
tute. The Panel meeting on 29 and 30 January was attended
by representatives from cooperating agencies and included
full discussions of research on past experiments and future
plans for the Project. Professor Lorenz resigned from the
Panel in October due to the pressure of other work in which
he is engaged. He was replaced by Professor Norman A. Phillips
(Department of Meteorology, Massachusetts Institute of Tech-
nology). Recommendations from the Panel meetings in Miami,
Florida, and Washington, D.C., are included in this report
as Appendix A.
PUBLIC AFFAIRS
A coordinated press release and fact sheet for STORM-
FURY were distributed to the media prior to the experimental
season. Although no hurricane seeding opportunities occur-
red, the public affairs team was prepared to operate with a
plan similar to that used during the "Debbie" experiments of
1969. Two seats on the Project aircraft were to be made
available on a pool basis to media representatives. One seat
was to go to a reporter and the other to a cameraman repre-
senting TV networks. Additional seats for the media may be
possible for future operations if sufficient interest for
additional coverage becomes apparent.
PYROTECHNIC DEVICES - SILVER IODIDE
The pyrotechnics prepared for the 1970 season were
similar to the STORMFURY I unit used in the 1969 seeding
experiments, but incorporated several improvements that made
them safer to handle. This new unit, developed under the
leadership of Dr. Pierre St. Amand of the Naval Weapons Cen-
ter, China Lake, California, was provisionally designated
WMU-2(XCL-1 )/B.
The new unit is fired from the same type of rack and
cartridge case as is the STORMFURY I round. Its pyrotechnic
grain is also similar in composition and performance to that
of the earlier unit, but it incorporates pressure relief,
bore-safety, and time delay functions that will permit it to
be certified for general use in all appropriate racks and
aircraft without special supervision.
More details of the pyrotechnics used can be found in
Appendix D of the 1969 Project STORMFURY Annual Report.
AREAS OF OPERATIONS
Eligible areas for experimentation in 1970 were the
Gulf of Mexico, the Caribbean Sea, and the southwestern
North Atlantic region.
Operations in these areas were limited by the following
guideline: A tropical cyclone was considered eligible for
seeding as long as there was only a small probability (10
percent or less) of the hurricane center coming within 50
miles of a populated land area within 18 hours after seeding.
There are two primary reasons for not seeding a storm
near land. First, a storm seeded further at sea will have
reverted to its natural state prior to affecting a land area.
Second, large changes in the hurricane structure occur when
it passes over land. These land- induced modifications would
obscure the short period effects expected to be produced by
the seeding experiments and greatly complicate the scientific
evaluation of the results.
PLANS FOR FIELD OPERATIONS - 1970
The period 20 July to 31 October was established for
STORMFURY operations in 1970. The following aircraft were
planned as STORMFURY forces during the season:
1. Navy Weather Reconnaissance Squadron Four
Four WC-121N's
2. Marine All-Weather Attack Squadron Two Two Four
Four A-6 Intruders
3. NOAA Research Flight Facility
Two DC-6's
One B-57
One C-54 (replaced by a C-130 during the season)
4. Air Force 53rd Weather Reconnaissance Squadron
Two WC-130's
5. Air Force 55th Weather Reconnaissance Squadron
One WC-135
6. Air Force 58th Weather Reconnaissance Squadron
One RB-57F
7. Naval Air Test Center
One P3
8. Naval Weapons Center
One Cessna 401 .
The plan also provided for a series of fall-back re-
search missions to be used when no eligible hurricane was
available for seeding after deployment of project forces.
These research missions are primarily data gathering or
storm monitoring missions in unseeded cloud systems or storms
As recommended by the STORMFURY Advisory Panel, first
priority was given to the eyewal 1 experiment in order to gain
additional data which could be correlated with those collected
during the 1969 "Debbie" seeding experiments.
This multiple seeding of the clouds in the annulus
radially outward from the maximum hurricane winds calls for
five seedings at 2-hour intervals. Each seeding consists of
dropping 208 pyrotechnic units along a radially outward flight
path, starting just outside the radius of maximum winds. The
hypothesis in 1969 and early 1970 stated that the introduction
of freezing nuclei (silver iodide crystals produced by the
pyrotechnics) into the clouds in and around the eyewal 1 should
cause a chain of events that includes the release of latent
heat, warming of the air outside the central core, changes in
temperature and pressure gradients, and a reduction in maxi-
mum winds. Data from several experiments and individual
cases are needed before definite conclusions regarding the
validity of this hypotehsis can be assumed.
Because the magnitude of natural variations in hurri-
canes is sometimes as large as the hypothesized artificially
induced changes, it is frequently difficult to distinguish
between the two.
Second priority was given to the rai
to the rainband experiments. The rainsecto
designed to test whether some of the latent
air flowing toward the center of the hurric
cepted and released while it is still betwe
miles from the center. If successful, this
result in the dispersal of the energy over
rather than concentration near the center,
degree sector between 50 and 75 miles radiu
stimulate growth. This sector is selected
area where an abundance of warm moist tropi
carried by the low-level winds toward the c
center of the storm. If cloud growth in th
moist air to ascend to the outflow layer at
large radius, some of the energy normally r
center of the storm would be released at gr
could result in a reduction in the storms'
nsector and third
r experiment is
energy in the
ane can be inter-
en 50 and 100
experiment should
a 1 arger area
Clouds in a 4 5-
s are seeded to
because it is an
cal air is being
louds nearer the
is sector causes
a relatively
el eased near the
eater radi us and
wind maxi ma .
All suitable clouds in the designated sector are
seeded while monitoring aircraft continue to collect data to
document changes in storm structure or intensity. The seed-
ings are made in four periods of 50 minutes each, separated
by non-seeding periods of 50 minutes.
The Rainband Experiment has the same objectives as
does the Rainsector Experiment and, in addition, should per-
mit the opportunity to study the interaction of seeded clouds
with other clouds in the same and nearby rainbands. Clouds
are seeded along a rainband (a line of clouds spiraling a-
round and toward the center of the storm) at 50 to 150 miles
from the storm center. Seeding of such a rainband may pro-
duce a dispersion of the energy of the hurricane over a larger
area and should provide information and data needed to improve
the design of other modification experiments. The rainband
experiment provides data needed for studies of cloud inter-
actions. A rainband can be selected that is well removed
from the central vortex area and not obscured by the main
cloud system of the hurricane. This selection facilitates
visual observations.
The Advisory Panel has recommended that cloudline ex-
periments continue to be conducted in order to collect data
vital to the understanding of the dynamics of clouds organized
into systems such as rainbands. These experiments can be con-
ducted when there are no hurricanes and should provide addi-
tional opportunities for evaluation of seeding effects. Dur-
ing these experiments, tests of various seeding agents and
dispersing techniques can also be conducted. Cloudline ex-
periments were scheduled for 24-31 July 1970, in the military
operational areas near Puerto Rico.
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qui p-
FIELD OPERATIONS
Dry-runs were conducted from the Naval Station Roose-
velt Roads, Puerto Rico, on 21 and 23 July, following a gen-
eral briefing on 20 July. Participating in the dry-runs
were aircraft from the Navy Weather Reconnaissance Squadron
FOUR (VW-4), NAS Jacksonville, Florida; NOAA's Research
Flight Facility, Miami, Florida; Marine All-Weather Attack
Squadron Two Two Four ( VMA-AW-224 ) , MCAS Cherry Point, North
Carolina; Air Force 53rd Weather Reconnaissance Squadron,
Ramey AFB, Puerto Rico; and the 55th Weather Reconnaissance
Squadron, McClellan AFB, Sacramento, California.
Also taking part were scientists from the Naval Weather
Service Command Headquarters, Washington, D.C.; Naval Weapons
Center, China Lake, California; Fleet Weather Facility,
Jacksonville, Florida; Navy Weather Research Facility, Norfolk
Virginia; University of Miami, Coral Gables, Florida; and
NOAA's National Hurricane Research Laboratory, Coral Gables,
Florida.
Dry-run exercises for the STORMFURY eyewal 1 experiment
were conducted on 21 July and for the rai nsector/ rai nband ex-
periment on 23 July. Extensive individual debriefs of each
flight were made followed by a general critique covering the
total operations after each experiment.
A series of cloudline type experiments were carried
out at the conclusion of the dry-runs with a portion of the
forces. (The Marine A-6 aircraft, the Air Force WC-135,
and two of the Navy WC-121N's were released.) Flight opera-
tions were carried out on 24, 27, 28, 29, 30, and 31 July,
utilizing three types of seeding aircraft (Cessna 401, DC-6,
B-57). See appendix I for report on the Cessna 401 opera-
tions.
The DC-6 was used on the last three operating days to
seed with various silver iodide compositions generated from
a burner attached to the wing. A report on these operations
is included as appendix E.
On 19 August, Tropical Storm Dorothy developed east
of the Caribbean Sea and was predicted to move into the Car-
ibbean on the 20th. In anticipation that the storm would
either intensify into a hurricane or remain stable enough
in intensity as a tropical storm to serve as a fit subject
for a STORMFURY monitoring mission, the forces (with the
exception of seeder aircraft) were requested to deploy to
Puerto Rico on 20 August. The monitoring mission was to
include the flight patterns used to monitor a seeded hurri-
cane. These data collected in an unseeded storm were to be
used for comparison purposes and for research on the natural
variability of storms.
The Research Flight Facility flew a three-plane mis-
sion of the monitoring type on 21 August, and the other pro-
ject aircraft (less seeders) arrived for the major effort on
Saturday, 22 August.
After crossing Marti
slowly. On Friday, the 21s
culation, but the Research
difficulty orienting their
weak center. By Saturday,
to a tropical wave with max
STORMFURY monitoring missio
research flight mission whi
on a tropical wave. These
able for studying the struc
of this type have been extr
nique, Dorothy started weakening
t, there was still a closed cir-
Flight Facility aircraft had
flight patterns about the broad
the 22nd, the storm had reverted
imum winds of about 45 knots. The
n was then changed to a fall-back
ch collects data at several levels
data should prove to be \/ery val u-
ture of easterly waves, for data
emely rare in the past.
Forces performed in an outstanding manner throughout
the dry-run exercises, the cloudline experiments, and the
Tropical Storm Dorothy operations. The fall-back exercise
gave the first opportunity to work with all three of the
Air Force participants (WC-130, WC-135, RB57F) . Several
problems were found in data collection and were resolved as
a result of experience gained during these operations.
RESEARCH ACTIVITIES
Progress in the hurricane modification work was quite
considerable in 1970 even though nature did not provide a
suitable hurricane for a field experiment. This progress was
due to the efforts of the research workers, and their find-
ings provide a much broader and firmer base for the future
work of the Project. This research took place primarily at
the National Hurricane Research Laboratory, Coral Gables,
Florida; the Navy Weather Research Facility, Norfolk, Vir-
ginia; and at cooperating Universities. Appendices B through
L are reports on some of these STORMFURY research efforts.
Appendix B "A hypothesis for modification of hurri-
canes," by Drs. R. C. Gentry and H. F. Hawkins, explains the
new hypothesis on hurricane modification experiments that
was developed this year. The article summarizes the evolu-
tion of ideas concerning the use of freezing nuclei for mod-
ifying hurricanes, explains how the new hypothesis accounts
for the apparently favorable results from the experiments on
Hurricanes Esther (1961), Beulah (1963), and Debbie (1969),
and discusses some of the questions concerning hurricane
modification which still need to be answered either by the
theoretical investigations or by the field experiments.
Appendix C "Hurricane modeling at the National Hurri-
cane Research Laboratory, 1970," by Dr. S. L. Rosenthal, re-
views the NHRL's more significant achievements in the general
area of time-dependent hurricane modeling. Dr. Rosenthal dis-
cusses the specific problem of modeling a Debbie-like field
experiment and summarizes efforts less directly related to the
development of time-dependent models. He also outlines inves-
tigations planned by this group for the next few years.
Appendix D "Summary of the preliminary results from an
asymmetric model of the tropical cyclone," by Dr. R. A. Anthes,
Dr. S. L. Rosenthal, and J. W. Trout, shows that the asymmetri-
cal hurricane model reproduces many observed features of the
three-dimensional tropical cyclone. Realistic portrayals of
10
spiral rainbands and the strongly asymmetric structure of the
outflow layer are obtained. The kinetic energy budget of the
model compares favorably with empirical estimates and also
shows the loss of kinetic energy by truncation errors to be
s/ery small. Large-scale horizontal asymmetries in the out-
flow are found to play a significant role in the radial trans-
port of vorticity during the mature stage and are of the same
magnitude as the transport by the mean circulation. In agree-
ment with empirical studies, the outflow layer of the model
storm shows substantial areas of negative absolute vorticity
and anomalous winds.
Appendix E "Response of STORMFURY cloudline cumuli to
Agl and Ag I • N a I ice nuclei from a solution-combustion genera-
tor," by E. E. Hindman, II., Dr. S. D. Elliott, Jr., Dr. W. G.
Finnegan, and B. T. Patton, studies the responses of cumulus
clouds to silver iodide seedings during the 1970 STORMFURY
cloudline operations and compares the effectiveness of two
different silver iodide solutions burned in a solution-
combustion generator.
Appendix F "Measurements of vertical motion in the
eyewall cloud region of Hurricane Debbie," by Dr. T. N. Carlson
discusses the estimates of cumulus cloud vertical motions re-
corded by an RFF DC-6 aircraft while flying in Hurricane
Debbie. The accuracy of the vertical motions obtained is dis-
cussed, and various factors which may affect the accuracy are
explained.
Appendix H "Ice phase modification potential of cumulus
clouds in hurricanes," by D. A. Matthews, presents an examina-
tion of ice-phase modification potential of cumulus clouds.
Predicted results of modification potential by a one-dimensional
steady-state cumulus model are used to test the suggestion
(Gentry, 1971) that an important effect on hurricanes may be
realized by seeding the less fully developed cumulus cells
that are located slightly outward from the mammoth clouds in
the inner eyewall. Mr. Matthews's paper also describes the
decreases in surface pressure, the increases in rainfall, and
the increases in cloud top height as derived from model simu-
lation of the ice-phase modification. In the calculations,
he uses 87 temperature soundings observed within 100 n miles
of hurricane eyes and five average hurricane soundings pre-
pared by Sheets (1969) .
11
Appendix I "Use of light aircraft in STORMFURY activi-
ties," by Dr. S. D. Elliott, Jr., and Dr. W. G. Finnegan,
describes the use of contractor-operated light aircraft in
Project STORMFURY dry-run and cloudline experiments and offers
conclusions and recommendations involving the use of light
aircraft in future STORMFURY activities.
Appendix J "Use of echo velocities to evaluate hurri-
cane modification experiments," by P. G. Black, examines
radar echo velocities computed over the entire storm for six
time intervals before and during the seeding of Hurricane
Debbie on 20 August 1969. He finds that mean echo speeds
equaled or exceeded cycl os trophi c winds computed from 12,000-
ft D-value data as well as measured 12,000-ft winds after a
correction for water motion was applied to the original
"Doppler winds." Mr. Black further examines mean echo cross-
ing angles to determine their variations and angular rotation
in relation to the storm's major and minor axes.
Appendix K "A summary of radar precipitation echo
heights in hurricanes," by H. V. Senn, surveys radar height
data and hurricane case histories to determine likely occur-
rence of clouds that can be significantly modified in various
sectors of a hurricane. This information suggests that clouds
exist in hurricanes of the type that the new hypothesis (app.
B) suggests are needed in the hurricane modification work.
Appendix L "Project STORMFURY experimental eligibility
in the Western North Pacific," by W. D. Mallinger, updates
and reviews numbers of typhoons eligible for Pacific STORMFURY
experiments. This study strongly indicates that both Guam and
Okinawa must be available as bases for Project forces in order
to expect a profitable number of experimental storms during a
3-month operation.
OPERATIONAL AND RESEARCH DATA COLLECTION
Data collection procedures appeared adequate for the
Project. While problems with radar still existed on some of
the Project aircraft, continuous efforts were made during the
season to improve these observational tools.
Two special Polaroid cameras (CU-5) were purchased and
modified for use on the Air Force WC-130 aircraft radar. Al-
though automatic time-lapse radar cameras are preferred, the
Polaroid cameras produced good research data where none had
been previously available from these aircraft.
12
The Research Flight Facility conducted several research
missions in tropical circulations, but the 1970 hurricane sea-
son was generally one in which few good data collection op-
portunities occurred.
A one-plane mission was flown into Hurricane Ella in
the far southwest Gulf of Mexico on 11 September.
A three-plane, five-level mission was flown into Trop-
ical Storm Felice on 15 September. Felice was almost up to
minimal hurricane force, and wind gusts as high as 64 knots
were noted as it passed to the south of the Mississippi Delta
regi on .
A three-plane, five-level mission on 2 October and a
two-plane mission on 3 October were flown in Tropical Depres-
sion No. 14 as it passed through the eastern Caribbean.
Processing of STORMFURY films was again accomplished
at a commercial firm in Miami. Some experiments in reducing
costs by obtaining work prints to satisfy requirements for
duplicates were attempted, but technical difficulties in
processing were encountered. These difficulties are now be-
lieved to be surmounted, and a modified version of this pro-
cedure will be tried during the 1971 STORMFURY season.
OUTLOOK FOR 1971
Project STORMFURY operations are expected to be \/ery
similar to those planned for 1970. It is likely that the
dry-run exercises will be conducted from the Naval Station
Roosevelt Roads, Puerto Rico, followed by a series of cloud-
line experiments with forces based at Barbados.
Continued emphasis will be placed on repeating the
"Debbie" type experiment and conducting monitoring missions
in unseeded storms for comparisons purposes.
Project aircraft will be essentially the same as in
1970, except that a WP-3 weather reconnaissance aircraft be-
longing to Navy Weather Reconnaissance Squadron FOUR (VW-4)
is expected to participate in STORMFURY missions for data
collection and for additional use and evaluation as a seeder
aircraft.
13
REFERENCES AND SPECIAL REPORTS
Anthes, R. A., S. L. Rosenthal, and J. W. Trout (1970): Num-
erical simulation of a hurricane. Proceedings of the
Meteorological Technical Exchange Conference t 21-24
September, Annapolis, Md., U.S. Naval Weather Service
Command.
Anthes, R. A. (1971): The response of a 3-level axisymmetric
hurricane model to aritificial redistribution of con-
vective heat release. Technical Memorandum ERLTM-NHRL
No. 92, NOAA, Dept. of Commerce, NHRL , Miami.
Black, P. G. , and T
T. Fuji ta
Debbie as
of Hurricane Debbie as reve
ocities from airborne radar
Proceedings of the 14th Ann
(1970): In- and outflow field
evealed by echo and cloud vel-
dar and ATS - 1 1 1 pictures.
Annunl. P. nrt ■?£>. Y>an r> a nn 'Rnrlny
al Conference on Radar
Black,
Meteorology , Tucson, Ariz. November, pp. 353-358.
P. G., H. V. Senn, and C. L. Courtright (1971): Some
airborne radar observations of precipitation tilt,
bright band distribution, and eye configuration changes
during the 1969 multiple seeding experiments in Hurri-
cane Debbie. Submitted for publication in the Monthly
Weather Review.
Carlson, T. N., and R. C. Sheets (1971): Comparison of draft
scale vertical velocities computed from gust probe and
conventional data collected by a DC-6 aircraft. Tech-
nical Memorandum ERLTM-NHRL No . 91, NOAA, U.S. Dept.
of Commerce, NHRL, Miami, Fla.
Gentry, R. C. (1970): Progress on hurricane modification re-
search - October 1969 to October 1970. Presented at
the Twelfth Interagency Conference on Weather Modifi-
cation;, October 28-30, Virginia Beach, Va.
Gentry, R. C. (1970): Hurricane modification - Experiments
and prospects. Presented at Hurricane Foresight Con-
ference,, New Orleans, La., April 30, and distributed
by the New Orleans States-Item.
Gentry, R. C. (1970): Modification experiments on Hurricane
Debbie, August 1969. Proceedings of the Second National
Conference on Weather Modification^ American Meteorolo-
gical Society, pp. 205-208.
Gentry, R. C. (19 70): The hurricane modification project:
Past results and future prospects. Proceedings of the
Seventh Space Congress^ April 22-24, Cocoa Beach, Fla.
14
Gentry, R. C. (1970): Modifying the great storm on earth --
the hurricane. Underwater Science and Technology Jour-
nal, December, pp. 204-214.
Gentry, R. C. (1971): To tame a hurricane. Science Journal,
7, (1), January, pp. 49-55.
Gentry, R. C. (1971): Hurricane. McGraw-Hill Yearbook of
Science and Technology , pp. 232-234.
Hawkins, H. F. (1971): Modifying the hurricane. Submitted
for publication in UMSCHAU (German publication), April.
Hawkins, H. F. (1971): Comparison of results of the Hurricane
Debbie (1969) modification experiments with those from
Rosenthal's numerical model simulation experiments.
Monthly Weather Review, 99, (5), May, pp. 427-434.
Mallinger, W. D. (1970): Project STORMFURY operations and
plans. Mariners Weather Log, 14, (5), September,
pp. 262-266.
Underwood, L. J. (1970): Project STORMFURY operations 1970.
Presented at the Twelfth Interagency Conference on
Weather Modification, October 28-30, Virginia Beach,
Va.
15
APPENDIX A
REPORT ON MEETING OF PROJECT STORMFURY
ADVISORY PANEL
Miami, Florida
29-30 September 1970
INTRODUCTION
In response to the recognition of the increasing im-
portance of computer simulation of both "natural" and "seeded"
hurricanes to the interpretation and design of Project STORM-
FURY field experiments, the Advisory Panel met at NHRL on
29-30 September to undertake a more intensive evaluation of
models developed by Rosenthal and colleagues at NHRL. From
this assessment, several conclusions and recommendations
emerged .
EVALUATION OF HURRICANE MODELING
Results of computer simulations of natural hurricanes
were available from two models: the improved symmetric (two-
dimensional) model with explicit water cycle and air-sea en-
ergy exchanges and better horizontal resolution of 10 km, as
well as preliminary results from a simplified asymmetrical
(three-dimensional) model which neglects interaction with the
environment, has constant Coriolis parameter, and rather
coarse vertical and horizontal resolution. Simulation of
seeded hurricanes was carried out solely with the use of the
symmetrical model. Varying augmented heating rates were
applied at different radial increments both continuously and
intermittently for 10 hours in an attempt to simulate the
multiple eyewall experiment of Project STORMFURY.
From a study of these results the Panel reached the
following conclusions:
(1) Within the limitations imposed by symmetry and
convective parameterization, the simulation of
the natural hurricane is impressively realistic.
The distributions of temperature, pressure, and
horizontal and vertical motion of the model storm
compare favorable with those observed in typical
mature hurricanes in nature.
(2) Within the limitations of the simple asymme
model given above, plus the recognition tha
asymmetry is introduced artificially by rou
errors and boundary geometry, an asymmetric
structure develops in a manner and with a s
that is not unrealistic. When averaged in
azimuthal direction, the structure is suffi
similar to the symmetrical analog to give i
confidence in the validity of the symmetric
The favorable comparison of model storm str
with observation lends credence to the simu
of seeded hurricane structure. In spite of
realistic simulation of hurricane structure
Panel noted that neither the symmetrical no
asymmetrical model is able to give any info
on the effects of internal or external infl
on the motion of natural or seeded hurrican
(3) The essential result which emerges from the
ing simulation is the formation ot a new wi
imum and zone of strongest upward motion at
greater radius than those existing in the n
model storm if the augmented heating rate i
outside these pre-existing maxima. Only mi
differences in this essential result appear
experiments with different augmented heatin
at di f f eren t radi i .
(4) This new wind maximum which forms in the se
storm is weaker than the model control by a
10 percent. Larger reductions of wind spee
at the radius of maximum wind of the contro
and smaller increases occur at radii beyond
new maximum. The decreases in wind speed a
sociated with decreased horizontal temperat
gradients in the upper and middle troposphe
weakened surface pressure gradients togethe
the fact that inflowing air rises at a grea
radius, thus acquiring smaller tangential r
momentum. The augmented heating also incre
the static stability which is associated wi
smaller rates of release of latent heat and
version of available potential to kinetic e
(5) Evidence from available simulations has, so
always indicated that seeding at radii outs
the original wind maximum results in reduct
the maximum winds. However, the augmented
associated with the simulated seeding resul
an increase in the total kinetic energy of
hurricane winds by about 20 percent. Since
could result in a significant increase in t
t r i c a 1
t some
nd-of f
al
tructure
the
c i e n 1 1 y
ncreased
al model
uctures
1 a ti on
the
, the
r the
rma tion
uences
es .
seed-
nd max-
a
a tural
s added
nor
i n
g rates
eded
bout
d occur
1 storm
the
re as -
ure
re and
r with
ter
e 1 a t i v e
ases
th
con-
nergy .
far ,
i de
ion of
heating
ts in
the
this
he
A-2
(6)
s tor
seed
more
of m
s tro
The
ing
from
reas
that
the
ing
pi ac
grea
cond
prob
i n t
m surge ,
ing does
, "simul
a x i m u m w
n g e s t w i
augmente
probably
rel ease
onabl e a
convect
existing
to more
ing the
t e r r a d i
e n s a t i o n
ably exc
he seedi
we c
not
ated
i nds
nds .
d hea
cann
of 1
nal og
i ve c
eyew
a c t i v
previ
us .
, plu
eeds
ng si
aution against con
make the storm "wo
seeding" inside th
resul ts in a si i gh
ting rate
ot be rea
atent hea
in n a t u r
1 o u d s in
al 1 coul d
e growth
ous eyewa
Augmented
s freezin
the augme
mul ati ons
s used to
I i z e d in
t of fusi
e is the
the regio
be stimu
and in ten
II with a
heating
g i n such
nted heat
elusions that
rse . " Further-
e original radius
t increase of
simulate seed-
nature solely
on. The most
possi bi 1 i ty
n just outside
lated by seed-
sity thus re-
new one at a
from enhanced
ci rcumstances ,
ing rates used
RECOMMENDATIONS
Based upon the above conclusions, the Advisory Panel
makes the following recommendations with regard to Project
STORMFURY:
Recommendation ONE: More detailed diagnostic studies
of existing simulations of seeding should be carried out to
verify the tentative conclusions reached above as to the mech-
inisms of the seeding influences. In particular, other quan-
tities than those now available should be studied with greater
time resolution.
Reasons: It is essential to understand the seeding
simulations in as great detail as possible to gain confidence
in the results and for comparison with field experimental re-
sults.
Recommendation TWO: Development of the asymmetrical
(three-dimensional) model should be continued with the ulti-
mate objective of modeling the nons tationary hurricane as it
moves through and interacts with the larger scale environment.
When this has been achieved for natural storms, simulation of
seeding should be carried out.
Reasons: Only with such a model it is possible to in-
vestigate interactions between the hurricane and its environ-
ment and remove the constraint of axial symmetry. Furthermore,
simulation of seeding in only one sector of the storm will be
possible, as well as investigating the possible effects of
seeding on the motion of hurricanes.
A-3
Recommendation THREE: Further simulations of seeding
should be made with the symmetrical (two-dimensional) model
to supplement the diagnostic studies of existing seeding
simulations recommended above.
Reasons: Additional information on varying augmented
heating rates and radii of seeding is needed. It is also
anticipated that the diagnostic studies will reveal points
in need of further clarification.
Recommendation FOUR: The resources of the computer
simulation group under Dr. Rosenthal at NHRL should be aug-
mented by: (a) two Ph.D. level scientists with appropriate
qualifications, and (b) computer facilities of greater speed
and capacity.
Reasons: Although excellent progress has been made
by this group in the past 2 years, the experiments recommended
above will require additional personnel and computer facili-
ties to accelerate this rate of progress in the next 2 years.
Recommendation FIVE: Available radar data should be
studied in an attempt to verify the existence of convective
clouds just outside existing eyewalls with a structure sus-
ceptible to enhanced growth through seeding. Results from
Hurricane Debbie should be reviewed once more from this point
of view.
Reasons: If verified, the existence of such clouds
and their enhan cement by seeding would provide a sounder
hypothesis for STORMFURY field experiments.
Recommendation SIX: Radar and cloud physics instru-
mentation on the research aircraft should be further improved
to give more quantitative information on the distribution of
convective and other clouds and all phases of water in the
hurricane.
Reasons: The essence of possible modification of hur-
ricanes rests in the questions of influencing the intensity
and organization of convection and the associated phase
changes of water. Unless more and better data can be acquired
on these questions, residual doubt will always remain in the
interpretation of experimental results.
Professor Noel E. LaSeur, Chairman
Dean Charl es L . Hosl er
Professor James E. McDonald
Professor Edward N. Lorenz
Professor Jerome Spar
10 November 1970
A-4
RECOMMENDATIONS OF THE ADVISORY PANEL
FOR PROJECT STORMFURY
Washington. D.C.
February, 1971
INTRODUCTION
In the course of the meeting of the Advisory Panel for
Project STORMFURY held in Washington, D.C, 28-30 January
1971, two aspects of Project activities emerged which need
immediate action if necessary planning is to be accomplished.
These are: the proposed operations of Project STORMFURY in
the Pacific during the summer of 1972; and the acquisition,
outfitting, and testing of alternate seeding aircraft. Be-
cause of the immediacy of these problems, the Advisory Panel
is issuing these recommendations; further recommendations on
other aspects of Project activities discussed will be forth-
coming.
pri a
the
ci a t
typh
s umm
expe
quen
ocea
to m
reas
Paci
cane
R
te a
f i na
ed w
oon
er o
R
ri me
cy o
ni c
ove
on t
fie
s .
eaomme
g e n c i e
n c i a 1 ,
i th pr
region
f 1972
easons
n ts to
f Paci
regi on
Pro jec
o be 1 i
typhoo
ndation ONE: The Panel re
s of the government intens
logistic, diplomatic, and
oposed operations of Proje
of the Western North Paci
The increased opportuni
be expected from the typi
fie typhoons in a large, s
fully justify the expense
t operations to that area.
eve that experimental resu
ns will be completely vali
commends that appro-
i fy efforts to sol ve
other problems asso
ct STORMFURY in the
fie Ocean during the
ties for STORMFURY
cal ly greater fre-
parsely populated
and effort requi red
There is every
Its obtained in
d for Atlantic hurri
Recommendation TWO: The Panel recommends that Project
STORMFURY continue efforts to acquire, outfit, and test alter-
nate seeding aircraft with the following capabilities: in-
creased capacity to carry Project personnel and seeding
pyrotechnics; increased range and time "on-station" in the
storm; and capability to seed at levels in the range from
25,000 ft to 30,000 ft or at lower levels if suitable temp-
eratures for seedings exist.
Reasons: The Panel considers it undesirable for the
Project to have to rely on seeder aircraft from external
units. In the past, available aircraft have lacked capacity
for Project personnel to fly on-board, and thus provide better
A-5
control of the time and place of seeding. They have also
lacked range, capability for mulitple seeding without refueling,
and were limited to high altitudes. Acquisition by the Pro-
ject of aircraft with the recommended capabilities could
eliminate significant uncertainties inherent in the presently
available planes.-
Professor Noel E. LaSeur, Chairman
Dean Charles L. Hosier
Professor James E. McDonald
Professor Jerome Spar
A-6
APPENDIX B
A HYPOTHESIS FOR MODIFICATION OF HURRICANES
R. Cecil Gentry and Harry F. Hawkins
National Hurricane Research Laboratory
INTRODUCTION
The encouraging results from the Hurricane Debbie mod-
ification experiments of August, 1969 (Gentry, 1970a) have
stimulated research on many problems related to hurricane
modification experiments. One of the more interesting devel-
opments during 1970 was a new hypothesis which accounted for
results from the "Debbie" experiments and offered a more ac-
ceptable rationale that details how seeding a hurricane can
cause a reduction in its maximum intensity.
mo d i f
wal 1
was s
1965;
cool e
sudde
to pe
ass urn
and u
mum p
perce
area .
by a
R. H.
i ed by
surroun
et fort
1964b)
d water
nly fro
rmi t i n
i n g t h a
sing a
ress ure
nt if t
He fu
similar
Simpson
i n troduc
ding the
h i n a n
It su
( p a r t i c
zen, wou
creasi ng
t there
hydros ta
g r a d i e n
he h e a t i
rther hy
percent
propo
i n g f r
cen te
umber
ggeste
ul arly
Id rel
the c
was an
tic mo
tint
ng eff
pothes
age re
s e d in
eezi ng
r of a
of pap
d that
in th
ease e
1 oud t
ef fee
del , h
he sto
ects c
ized t
ducti o
1961
nucl
hurr
ers (
ther
e "ch
nough
emper
ti ve
e cal
rm mi
oul d
hat t
n i n
that
e i i n t
i c a n e .
e.g. ,
e was
i mney "
1 aten
atures
lid on
cul ate
ght be
be con
his wo
the ma
h u r r i
o the
His
Simps
s u f f i
area
t hea
1 to
top
d tha
redu
fined
uld b
xi mum
canes m
mas si v
hypoth
on and
c i e n t s
) whi ch
t of fu
2°C.
of the
t the m
ced by
to a s
e accom
wi nds .
i g h t be
e cloud
esi s
Mai kus ,
uper-
, if
si on
By
s torm
axi -
10-15
el ected
p a n i e d
was
i f i c
seed
i ng
suff
hour
crea
stor
the
woul
of w
In
used
a t i o n
i ng o
woul d
i c i e n
for
sing
m. I
level
d mos
a ter.
1968
for s
hypo
f the
resu
t to
h hou
the h
n the
s whe
t lik
Cal
, a hu
ome pr
thesis
cl oud
It in
change
r. Th
eating
model
re int
ely re
cul ati
rri ca
el i m i
( Gen
s was
enhan
the
at is
f unc
, hea
roduc
suit
ons w
ne mode
nary ex
try, 19
Simula
ced hea
tempera
, the s
ti on in
t was a
t i o n of
in free
ere the
1 developed by S. L, Rosenthal
periments relative to the mod-
69). In these experiments,
ted by assuming that the seed-
ting of the seeded clouds
ture at the rate of 2°C per h
eeding was simulated by in-
a specified volume of the
dded at 500 mb and 300 mb ,
artificial freezing nuclei
zing of significant amounts
n made with the model to
determine in which portion of the storm addition of heat would
most likely result in reduction of the maximum winds; in an:
(1) annular band radially inward from the maximum winds, (2)
annular band spanning the radius of maximum winds, or (3) an-
nular band radially outward from the radius of maximum winds.
The answer from the model was that reductions were most likely
when the heat was added radially outward from the maximum
wi nds .
Based on these experiments with the model, crude as
they were, the seeding pattern for the experiment was rede-
signed. Formerly, the seeding aircraft crossed the eye of
the hurricane and started dropping the pyrotechnic silver
iodide generators at the inner edge of the eyewall. The run
continued radially outward for 15 to 25 miles (Simpson and
Malkus, 1964a). Prior to the 1969 hurricane season, this
pattern was altered to have the run start about 3 miles radi-
ally outward from the inner edge of the eyewall (past the
ring of maximum winds) and continue on for 15-25 miles. This
meant a relatively small change in the annular band seeded be-
cause there was about an 85 percent overlap in this pattern
and the one used in the earlier seeding runs on hurricanes.
Debbie was seeded five times at 2-hour intervals on
18 August 1969, and again on 20 August (Gentry, 1970b). The
operational plan called for the seeding runs to be from the
radius of maximum wind outward for 15-25 miles (the spread
was somewhat a function of the reaction time of the man in
the seeder aircraft and the turbulence encountered). When
operations are conducted, it is frequently difficult for the
Project Director in the command-control aircraft to know the
exact location of the radius of maximum winds, but he does
have a good radar picture of the hurricane. R. Sheets, Na-
tional Hurricane Research Laboratory, has studied the flight
data collected by the Research Flight Facility and the Na-
tional Hurricane Research Laboratory during the last 14 years,
and has concluded that in mature hurricanes the most likely
radius for the maximum winds was 2 or 3 miles radially out-
ward from the inner edge of the eyewall (as seen by radar)1.
By the time of the Debbie experiments, S. L. Rosen-
thal had made several improvements in the hurricane model.
The encouraging results from the field experiments put much
greater emphasis on all phases of the research effort, and a
new series of experiments simulating the modification effects
were made with the more sophisticated model (Rosenthal, 1970).
Personal communication
B-2
The new experiments also simulated the modification
experiment by assuming that seeding would add heat to the
clouds. It was again found that a reduction in maximum winds
was most likely if the heat was added radially outward from
the radius of maximum winds. Several variations were run in
which changes were made in the intensity of the enhanced heat-
ing function, in the radial bands at which it was applied,
and in the length of time of application. There were also
experiments to consider whether the heating should be applied
continuously or in pulses to simulate the multiple seeding ex-
periments conducted on Debbie.
In general, the results showed that a reduction in
maximum winds was most likely if the heat were added radially
outward from the radius of maximum winds. They also showed
that there was little difference in the reactions between
heat added continuously and heat added in pulses. Larger
amounts of enhanced heating caused quicker responses in the
wind field, but eventually the reduction in maximum winds
became about the same. There did seem to be a lower limit
to the rate at which heat should be added below which no sig-
nificant change in the maximum winds occurred within 10 to
20 hours (Rosenthal , 1971 ) .
During the 1968, 1969, and 1970 seasons, the National
Hurricane Research Laboratory with the assistance of the Re-
search Flight Facility of NOAA made some measurements of the
liquid- and solid-water content of hurricane clouds (Sheets,
1969).
the i
bases
less,
might
nucl e
bly e
f u r n i
all t
s i d e r
con te
for t
throu
treme
model
or wh
shoul
The
nf req
and
some
be f
i . 0
nough
sh la
his 1
abl e
nt ov
he he
gh he
ly da
runs
ateve
d be
se meas
uency o
due to
i nform
urni she
ne tent
superc
tent he
i q u i d w
doubt a
er the
a t i n g r
at of f
ngerous
, wheth
r, into
used as
urem
f hu
fail
ati o
d hu
ati v
ool e
at t
as f
bout
enti
ates
us io
to
er i
di r
qua
ents
rri c
ure
n be
rri c
e co
d wa
0 ch
roze
whe
re s
sug
n al
tran
n te
ect
1 i ta
were
anes
of me
came
ane c
ncl us
ter i
ange
n "si
ther
eeded
ges te
one .
sfer
rms o
exper
ti ve
1 i mi ted
within r a
a s u r i n g e
available
louds by
i on was t
n the maj
the tempe
mul taneou
the avera
band was
d by Rose
On the o
the quant
f heating
i mental v
guides on
in nu
nge o
q u i p m
on h
i ntro
hat t
or ey
ratur
sly."
ge su
suff
nthal
ther
i t a t i
rate
al ues
ly.
mber be
f the a
ent. N
ow much
d u c i n g
here wa
ewal 1 c
e 1 or
There
percool
i c i e n t
1 s mode
hand, i
ve aspe
s , reac
. The
cause of
i r c r a f t
everthe-
heat
f reezi ng
s p o s s i -
louds to
2°C if
was con-
ed water
to account
1 runs
t is e x -
cts of
ti on ti mes ,
runs
B-3
When the multiple seedings were considered, however,
there appeared to be too little supercooled water for the
latent heat of fusion to be an adequate sole heat source.
Once the liquid in the clouds has been frozen, one cannot
keep refreezing it to get more heat. Only by introducing
fresh supercooled water into the clouds can one get the addi-
tional heat by this mechanism. Simple calculations suggest
that heating rates through the release of latent heat of
fusion would be 1 to 2 orders of magnitude less than the a-
mount calculations with Rosenthal's hurricane model suggest
is needed if one is to get significant reductions in the max-
imum winds within 4 to 10 hours. In further view of the fact
that there appears to be a lower limit below which the heat-
ing has no apparent effect, this limited small heat source
gave serious concern to the scientists involved.
A new hypothesis for the source of the enhanced heat-
ing has been developed. We have reviewed the seeding proce-
dures used in the Hurricane Esther, 1969 (Simpson et al . ,
1963), Hurricane Beulah, 1963 (Simpson and Malkus, 1964a),
and Hurricane Debbie, 1969 (Gentry, 1970a, b) experiments
and believe that the changes observed in each of these storms
may be accounted for much more reasonably by the new hypothesis
than by the original hypothesis. It provides for an improved
interpretation of the Debbie results without requiring any
drastic revision of the seeding patterns used in the hurri-
cane experiments. If this hypothesis is confirmed, however,
it will permit changes in the seeding patterns and seeding
altitudes to allow more efficient use of the Project aircraft
that are likely to be available in future years.
A NEW SEEDING HYPOTHESIS
The new explanation reemphasi zes that the seeding
should be done radially outward beyond the tallest clouds in
the eyewall and at radii greater than that of either the
greatest ascending motion or the maximum winds. The first
goal of the seeding with silver iodide crystals is to cause
freezing of supercooled water droplets in towering cumulus
with tops at temperatures of -5 to -20°C and to release the
latent heat of fusion. In the old explanation, the latter
was the main reaction expected. In the new explanation, it
is the initiation of a bigger reaction, i.e., the trigger
that sets off a chain reaction. The latent heat of fusion
is expected to increase the buoyancy of the towers to cause
greater growth of the ascending plumes in the clouds, and
ultimately to result in condensation or sublimation of extra
water vapor at the radii of the seeding. Either of the latter
B-4
two processes can release many times as much heat as would be
released by merely freezing the supercooled water droplets in
the clouds. The stimulation of cloud growth at these radii
accomplishes two ends: it allows the clouds to grow verti-
cally up into the outflow layer so that air "circulating
through this duct" never penetrates to smaller radii, and at
the same time it increases the heat release at the radii of
seeding. Obviously, air which is thus diverted upward never
spirals on into the eyewall and is therefore unable to contri-
bute its heat and angular momentum to maintaining the old ring
of maximum wi nds .
Thus, one purpose of seeding the clouds outside the
old eyewall is to develop a "new eyewall" at a greater radius.
If this is accomplished, and most of the air flowing inward
ascends at a larger radius, lower maximum wind speeds should
result simply from conservation of angular momentum. H.
Sundqvist (1970), who has also developed a hurricane model,
recently expressed this same idea when he wrote, "Regarding
the radial distribution of heating by condensation, we can
conclude that the farther from the centre the maximum is, the
farther from the centre will the maximum radial wind occur.
And from absolute angular momentum considerations it is clear
that the earlier (coming from the outside) the inflow ceases
the less will the tangential wind be."
A first reaction to this proposal may be, "Hurricane
clouds already extend to great heights. How can one make
them grow taller?" In the eyewall this may indeed be diffi-
cult, but in all other regions it may be quite practical.
H. V. Senn (app. K) studied RHI (vertical profiles of radar
targets) radar pictures of hurricanes. He found many echoes
whose tops were between 20,000 and 30,000 ft. Such clouds
occupied much of the outer portions of the hurricane, and
there were many even within 5 n miles outward from the inner
edge of the eyewall. His data show that more than 50 percent
of the echoes within 30 n miles of the center have tops in
this range. These data are not adequate support for any
strong conclusions, but Senn found nothing to indicate that
most echoes in the vital annular ring naturally grew to the
top of the troposphere. Thus, current radar data suggest it
is possible to make the cumuliform clouds grow sufficiently
to cause extra condensation (sublimation) of water vapor in
the region where the simulation experiment with the Rosenthal
model indicates that application of the enhanced heating
function results in the greatest reduction in maximum winds.
Scientists in the Naval Weapons Center at China Lake,
California (St. Amand, 1970; Schleusener et al . , 1970), the
Experimental Meteorology Laboratory of N0AA (Simpson and
Woodley, 1971), Pennsylvania State University (Davis, 1966;
B-5
Davis et al . , 1968) and other groups have all
sively that under certain conditions, cumulus
ing those in the tropics, can be made to grow
and horizontally by seeding and in some cases
grow expl os i vely .
shown concl u-
clouds, includ-
both vertically
can be made to
The cloud environment in a hurricane is different from
the mean tropical atmosphere, but there are reasons for be-
lieving that clouds outside the eyewall in a hurricane also
can be made to grow by seeding. R. Sheets (1969a) using the
cloud model developed at the Experimental Meteorology Labora-
tory (Simpson and Wiggert, 1969) has made computations as to
the seedability of hurricane clouds using the mean soundings
he developed for different radii (surface pressure) in hurri-
canes. Using assumptions considered reasonable, he calculated
that cumuliform clouds similar to those found beyond the eye-
wall of hurricanes might be expected to grow considerably
more than 5000 additional feet after being seeded. D. A.
Matthews obtained similar results using a different cloud
model ( app . H ) .
left
shown
Navy '
fine
from
f i g u r
craft
is at
diffe
radar
craft
bove
betwe
the p
the p
the s
conte
A ra
rear q
in f i
s APS-
scal e
this p
e B-2.
(A/C)
40,00
rence
saw t
in th
40,000
en the
i cture
i cture
tronge
nt.
dar p
uadra
gure
45 (3
s true
i c t u r
Not
, ext
0 ft.
canno
hroug
e are
ft,
rada
exce
s pre
r asc
i cture
nt of H
B-l . T
cm) ra
ture of
e have
e that
ends to
The o
t be ex
h these
a repor
so ther
r echoe
p t in t
sumabl y
ending
s h o w i n
u r r i c a
his pi
dars .
some
been r
the ey
at le
ther e
p 1 a i n e
echoe
ted cl
e must
s thro
he eye
are a
curren
g a v
ne De
cture
It s
of th
eprod
ewal 1
as t t
choes
d by
s to
ouds
have
ughou
of t
s s o c i
ts an
e r t i c a
b b i e ,
was t
hows t
e rain
uced i
, 40 n
he top
end b
attenu
the ey
from n
been
t the
he sto
ated w
d the
1 slice
20 Augus
aken by
he eyewa
bands .
n the r i
miles f
of the
el ow 30 ,
a t i o n be
ewal 1 .
ear sea
s trat i fo
area rep
rm. The
i th clou
greater
throu
t 196
one o
11 an
The e
ght s
rom t
scope
000 f
cause
Other
1 evel
rm cl
resen
echo
ds th
1 i q u i
g h the
9, is
f the
d the
choes
i de of
he a i r -
which
t. The
the
ai in-
to a-
ouds
ted by
es in
at have
d -water
The left side of figure B-2 illustrates the basic fac-
tors considered in simulating the modification experiment with
Rosenthal's model (1970b). The enhanced heating function was
such as to change the temperature at the rate of 4°C hour-1
and was applied at 300 mb and 500 mb . The temperatures do
not actually change this much because the extra heat is rap-
idly dispersed to other portions of the storm. Considering
the levels used in the model and interpolations between
levels, this means that the enhanced heating affects the
layer between 600 mb and 250 mb or a layer 350 mb thick.
B-6
■x*v,
M rM
,«Jr •«»-'♦♦ »-«»-«- ».#•*><#> »
*** «MI * %** ~|
v^iar#l 'I * "** s*
Figure B-l. Photo of the rainbands and southern eyewall of
Hurricane Debbie, 20 August 1969, taken by the APS-45 (X-
Band) radar operating in RHI mode on U.S. Navy Reconnais-
sance aircraft . The white line shows 20,000 ft elevation.
The tallest echo (about 40 n miles from aircraft) is the
eyewa 11 .
Consi
t e n d i
f unct
In th
the c
The s
5.5 g
rel ea
cl oud
2000
then
woul d
der any
ng thro
ion c a 1
e repro
ol umn (
p e c i f i c
kg"1 o
se of 1
buoyan
a d d i t i o
be 4.5
be sub
vertical column 1 cm2 in cross section and ex-
ugh a depth of 350 mb. Then the enhanced heating
Is for adding 0.0934 cal sec-1 to this column,
duct ion of the radar band just to the right of
fig. B-2), some potential for growth is suggested
humidity at the top of the radar echo was about
f air. If by seeding, one could initiate the
atent heat of fusion and sufficient increase in
cy to cause the ascending column to rise about
nal feet, the specific humidity at the top would
g kg-1. That is, 1 extra gram of water vapor
limated or condensed and would release up to
B-7
r(lOOmb)
SIMULATING A HURRICANE
MODIFICATION EXPERIMENT
-<200mb)
-(SOOmb)
HURRICANE "DEBBIE"
AUGUST 20,1969
AH-.0934
cal./ttc.
AH- H(4*C/hr)
-(SOOfflb)
-C7G©e?feS
AH»L,qj
-4
q "i.37 xlO qmtJfc
Wj-180 cm./»tc.
-(1000 mb
f — _ r 50 40 SO 20 iO 0
NAUTICAL MILES from AIRCRAFT
Figure B-2. Radar echoes from the original picture reproduced
in Fig. 1 are in the right side of the diagram . The center
of Hurricane Debbie was about 50 n miles north-northwest of
the aircraft . The eyewall (40 n miles from aircraft) ex-
tended higher than 403000 ft (limit of the radars cope) .
The left portion refers to calculations of amount of heat
that can be released by seeding and to the amount of heat
required for modification of a hurricane in the simulation
experiment with a theoretical model (see text).
B-8
made of the divergence fields in hurricanes. Obviously up-
drafts will be stronger in the clouds in order for the aver-
age vertical velocity to be 180 cm sec"1. Since we do not
have accurate estimates of the percentage of the area that is
covered by the active convective towers, we cannot state pre-
cisely what the average updraft speeds will be, but order of
magnitude type calculations again suggest values that are in
line with observations. Thus, it seems reasonable that the
amount of heat required under the assumption of an enhanced
heating function sufficient to cause temperature change at
rates of 4°C hour-1 can be provided by the latent heat of
sublimation (or condensation) if the seeding will cause the
clouds to grow an additional few thousand feet.
The U.S. Air Force Air Weather Service will make spe-
cial efforts in 1971 to release dropsondes at radii outside
the eyewall of tropical cyclones to provide data needed to
make more reliable computations of the seedability (differ-
ence in height of seeded cloud and expected natural growth
of the same cloud) of hurricane clouds outside the eyewall.
Qualitative support is provided by Rosenthal's model-
ing results to the idea that adding heat above the freezing
level and outside the eyewall can cause a new eyewall to
develop at a greater radius. In part of the volume in the
model where the enhanced heating was applied, "natural fac-
tors" started operating and 13 times as much heat was re-
leased in the model computations as was added due to the
artificial enhancement of the heating function. For the
volume as a whole, the natural enhancement as represented
by the increases in enthalphy was approximately 10 times as
great as that added by the enhanced heating function (Rosen-
thal, 1971). This is further evidence that there is a latent
instability present which can be triggered by properly ap-
plied heating.
The increased "natural" heating in the model is ex-
d by what happened to the vertical motion in the "mod-
model hurricane. Initially, the maximum updraft vel-
s were located between the 15 and 25 km radii. After
hanced heating was applied between radii of 25-45 km,
maxima of vertical motion developed there, and within
han 10 hours, the original maxima had disappeared. The
to the radii of enhanced heating resulted in much
r condensation at those radii. Since the total volume
annulus increases when its radii increases, the same
al velocity results in a larger total rainfall for the
ed storm. A detailed analysis of the vertical motion
revealed two maxima for a short period, one at the
of the original maximum, and the other at the radii
p 1 a i n e
if ied"
o c i t i e
the en
a new
less t
shift
greate
of the
verti c
modi f i
fields
radi us
B-9
of the enhanced heating function. Eventually the latter be-
came the larger, and a new eyewall (or at least the maximum
vertical velocity) developed at the greater radii. Once the
inflowing air at the low levels started ascending at the lar-
ger radii, the calculations with the model indicated a reduc-
tion in maximum winds. Winds at the new maximum wind radius
were stronger than the old winds at that radius but less than
the old maximum winds.
h u r r i c a n
Beulah (
i n rough
cases , t
wall and
outwa rd
extended
about 20
i n g run
ward fro
15 to 30
the radi
changes
p e r i m e n t
xami na
es tha
1963) ,
ly the
he see
i n De
from t
r a d i a
n mil
shoul d
m the
n mil
i from
from t
s to t
t i o n of t
t have be
and Debb
same rad
ding run
b b i e star
he inner
1 1 y outwa
es . The
start at
inner e d g
e s . This
those us
he s e e d i n
hose of t
he see
en see
ie (19
i a 1 b a
s tarte
ted at
edge o
rd 14
new hy
a poi
e of t
const
ed i n
g radi
he Deb
di ng
ded,
69),
nd or
d at
a po
f the
to 30
pothe
nt ab
he ey
i t u t e
the D
i use
bi e e
runs
that
re ve
ann
the
i nt
eye
n m
s i s
out
ewal
s an
ebbi
d fo
xper
made
is, E
als th
ul us .
inner
about
wal 1 .
i 1 e s a
sugges
5 n mi
1 and
even
e expe
r the
i men t .
in the v
s ther ( 1
ey were
In the
edge of
3 n mile
All see
nd most
ts that
1 e s radi
go outwa
smal 1 er
ri ment t
1961 and
an ous
961),
al 1 seeded
earl i e r
the eye-
s radially
ding runs
extended
the seed-
ally out-
rd for
change in
nan the
1963 ex-
The present plans for the seeding and those used in
the Debbie experiment call for the pyrotechnics to produce a
curtain of silver iodide crystals from about 33,000 ft down
to the freezing level. If the new hypothesis is correct, the
seeding might be equally effective if the silver iodide gene-
rators produced the crystals from some lower level, for ex-
ample, 27,000 ft, down to the freezing level.
QUESTIONS NEEDING BETTER ANSWERS
While the new hypothesis does suggest better answers
to some of the questions that have been asked by critics of
the hurricane modification experiments, there are still sev-
eral questions which have not been adequately answered. A
few of these are discussed in the following paragraphs:
(1) The basic question, of course, is, will the modi-
fication experiment work and, if so, under what
conditions? Thus far we have been seeking answers
to this question from the modeling experiments
with back-up from information derived from the
Hurricane Debbie experiments. While the latest
version of the hurricane model does simulate many
B-10
features of hurricanes very well ( Ro
developer says it is still in some r
crude model. It should not be depen
authoritative, and quantitative answ
suits to expect from a modification
actual hurricane. More experience w
sophisticated models is needed.
(2) How do we get the freezing nuclei in
they are most likely to produce resu
problems here. The first involves g
airplane to the right position to pu
into the clouds. While pilots are v
flying aircraft through hurricanes,
them to identify and fly to the port
having the strongest updraft and to
dide without encountering hazardous
The second question is what happens
freezing nuclei that are released in
ascending current. Presumably, they
the storm by the winds. Are they en
updraft that they pass or do they sk
et al . (1971) and Hawkins and Rubsam
data about the radar bright band whi
are already many naturally created i
hurricane clouds outside of the acti
the artificial freezing nuclei that
updrafts initially may be mixed with
crystals and have little influence o
(3) The most difficult question we have
Debbie and earlier experiments is ho
results. It is comparatively simple
the storm weakens or intensifies. I
learn whether the seeding caused the
the change was a result of natural f
planation for why the seeding should
tunities, however, for answering thi
a sequence of events which should oc
convective clouds present which cont
and relatively few natural freezing
clouds do not extend to the top of t
Seeding these clouds with silver iod
grow. (d) When the clouds grow, the
creases slightly in the area of the
eyewall starts to develop in that ar
craft currently assigned to the Proj
monitor the clouds and record change
the seeded band for several hours to
proper times and at rates expected t
seeding. If changes occur in con for
thesis, this would be very convincin
seeding contributed to these changes
changes in the wind speed.
senthal , 1970) , i ts
espects a rather
ded upon for f i nal ,
ers about what re-
experiment on an
i th this and more
to the clouds where
1 ts ? There are two
etting the seeder
t freezi ng nucl ei
ery experienced in
it is difficult for
ion of the cloud
drop the silver i o-
f 1 i gh t condi ti ons .
to the si 1 ver i odi de
a cloud without an
are swept around
trained into the next
irt around it? Senn
(1968) have presented
ch suggest that there
ce crys tal s in the
ve updrafts . I f so ,
do not get into the
the natural ice
n later developments,
had to answer in the
w to eval uate the
to determine whether
t is difficult to
change or whether
orces. The new ex-
work offers oppor-
s ques ti on . We have
cur : ( a ) There are
ain supercooled water
nuclei. (b) These
he hurricane. (c)
ide causes them to
temperature in-
seeding, (e) A new
ea . The radar on ai r-
ect can be used to
s in the clouds in
see if they grow at
o resul t from the
mance with the hypo-
g evidence that the
and to simultaneous
B-ll
(4) Where does water vapor come from that is
(or sublimated) to provide the heat requi
the new hypothesis? In the simulation ex
made with the Rosenthal model, it was ass
the enhanced heat came from releasing the
heat of fusion from water already in the
In the new version of the hypothesis, we
count for new supplies of water vapor bei
densed in greater quantities at greater r
and this vapor must come either from the
the low atmospheric levels, or from some
portion of the storm. Anthes (1971) has
gated this problem and concluded that the
in the maximum winds that the model sugge
take place varies greatly depending on th
of the water vapor that goes into the gro
seeded clouds. S. L. Rosenthal discusses
dix C, another method of simulating the s
the modeling experiments. Perhaps these
peri men ts he is planning will answer this
In any case, this is a problem that will
much more research on both the hurricane
scales of motion and their interactions.
(5) As has already been mentioned, there is a
know more about the seedability of hurric
That is, can they be made to grow taller
by seeding? How numerous are they, how h
they grow, what volumes of low-level air
divert?
conden
red in
perime
umed t
1 aten
vol ume
must a
ng con
ad i i ,
ocean ,
m i d - 1 e
i nvest
reduc
s t s w i
e o r i g
wing
in ap
e e d i n g
new ex
quest
r e q u i r
and cl
sed
nt
hat
t
c-
vel
i -
tion
11
i n
pen-
in
ion .
e
oud
need to
ane clouds
and larger
i g h should
might they
FUTURE PLANS
The Air Weather Service (USAF) has already issued in-
structions to the hurricane hunter squadrons in the Atlantic
and Pacific to make special efforts to get dropsonde data
from the 300-mb level in tropical cyclones in the annulus,
5 to 40 miles radially outward from the inner edge of the
eyewall. These data will make possible more definitive com-
putations of the seedability of the hurricane clouds.
The Navy, NOAA, and Air Force aircraft will make extra
efforts to get consistent radar coverage not only of experi-
mental hurricanes, but also of nonexperimental hurricanes.
The latter data will be used for establishing a range of nat-
ural variability that can be compared with the changes occur-
ring in experimental hurricanes following seedings. The Navy
aircraft have radar especially wel 1 -designed for this task.
The radar data should also provide more information about the
number and location of clouds that have seedability.
B-12
The Research Flight Facility and the National Hurri-
cane Research Laboratory will continue their efforts to get
more information about the amount and distribution of the
liquid- and solid-water contents of the hurricane clouds.
As outlined in appendix C, greatly increased efforts
will be devoted to improving the theoretical models of hurri-
canes .
Finally, ewery effort will be made to conduct addi-
tional modification experiments on hurricanes. These are
necessary. No matter how the theoretical models are improved,
and no matter how much cloud physics, radar, and other data
are accumulated, they in themselves will be insufficient (for
the foreseeable future) to determine whether we can modify
hurricanes. The final answer will have to come from experi-
ments on real storms.
ACKNOWLEDGEMENTS
Many people have contributed to the development of the
new hypothesis. Some of these have been referenced in this
paper. The first presentation of a preliminary version of
the new hypothesis was made by the senior author at a meeting
of the STORMFURY Advisory Panel on 29 September 1970. Many
improvements in the hypothesis were suggested at that time.
Among those participating were Professor Noel E. LaSeur, Pro-
fessor Charles Hosier, Professor Edward Lorenz, Professor
James E. McDonald, Professor Jerome Spar, Dr. Stanley Rosenthal,
Dr. Harry F. Hawkins, Dr. Richard Anthes, Mr. William Mallinger,
Mr. Peter Black, and Dr. William Cotton.
This presentation of the hypothesis is the work of the
writers and any deficiencies should be attributed to them. If,
however, the hypothesis proves to have great merit, credits
should be shared with the ones listed above and the many
people whose research has been referenced herein.
In addition, credit should be given to the scientists
and technicians of the National Hurricane Research Labora-
tory (NOAA), Research Flight Facility (NOAA), Navy Weather
Research Facility, and the Navy and Air Force Hurricane
Hunter Squadrons who collected, processed, and analyzed the
data needed to support the new ideas.
B-13
REFERENCES
Anthes, R. A. (1971): The response of a 3-level axi symmetri c
hurricane model to artificial redistribution of con-
vective heat release. Technical Memorandum ERLTM-NHRL
No. 92, NOAA, Dept. of Commerce, NHRL, Miami, Fl a .
Davis, L. G. (1966): Alternation of buoyancy in cumuli. Ph.D
Thesis, The Pennsylvania State University, University
Park , Penn .
Davis, L. G., J. I. Kelley, A. Weinstein, and H. Nicholson
(1968): Weather modification experiments in Arizona.
NSF Report 1 2A and Final Report NSF GA-777, Department
of Meteorology, The Pennsylvania State University,
University Park, Penn. 129 pp.
Gentry, R. C. (1969): Project STORMFURY. AMS Bulletin, 50,
(6) , June, pp. 404-409.
Gentry, R. C. (1970a): Hurricane Debbie modification experi-
ments, August, 1969. Science, 1683 pp. 473-475.
Gentry, R. C. (1970b): The hurricane modification project:
Past results and future prospects. Project STORMFURY
Annual Report 1969, U.S. Department of Navy and U.S.
Department of Commerce, Appendix B.
Rosenthal, S. L. (1970a): A circularly symmetric primitive
equation model of tropical cyclone development con-
taining an explicit water vapor cycle. Monthly
Weather Review, 98, (9) September, pp. 643-663.
Rosenthal, S. L. (1970b): A circularly symmetric, primitive
equation model of tropical cyclones and its response
to artificial enhancement of the convective heating
functions. Monthly Weather Review, 99, (5), May,
pp. 414-426.
Schleusener, R. A., P. St. Amand, W. Sand, and J. A. Donnan
(1970): Pyrotechnic production of nucleants for cloud
modification. Journal of Weather Modification, 2,
(4), May, pp. 98-117.
Sheets, R. C. (1969): Computations of the seedability of
clouds in a hurricane environment. Project STORMFURY
Annual Report 1968, U.S. Department of Navy and U.S.
Department of Commerce, Appendix E.
B-14
Sheets, R. C. (1969): Preliminary analysis of cloud physics
data collected in hurricane Gladys, 1968. Project
STOEMFURY Annual Report 1968, U.S. Department of Navy
and U.S. Department of Commerce, Appendix D.
Simpson, J., and V. Wiggert (1969): Models of precipitation
cumulus towers. Monthly Weather Review, 97 , (7),
July, pp. 471-489.
Simpson, J., and W. L. Woodley (1971): Seeding cumulus in
Florida--New 1970 results. Science, 17 2, (3979),
April 9, pp. 117-126.
Simpson, R. H., M. R. Ahrens , and R. D. Decker (1963): A
cloud seeding experiment in Hurricane Esther, 1961.
National Hurricane Research Project Report No. 60,
Weather Bureau, U.S. Department of Commerce, Washing-
ton , D. C. , 30 pp .
Simpson, R. H., and J. S. Mai kus (1964a): A cloud seeding
experiment in Hurricane Beulah, 1963. Project STORM-
FURY Annual Report 1963, U.S. Department of Navy and
U.S. Department of Commerce, Appendix E.
Simpson, R. H., and J. S. Malkus (1964b): Experiments in
hurricane modification. Scientific American, 211,
pp. 27-37.
Simpson, R. H., and J. S. Malkus (1965): Hurricane modifica-
tion: Progress and prospects, 1964. Project STORMFURY
Annual Report 1964. U.S. Department of Navy and U.S.
Department of Commerce, Appendix A.
St. Am and, P. (1970): Techniques for seeding tropical cumu-
lus clouds. AMS Second National Conference on Weather
Modification, April, Santa Barbara, Cal .
Sundqvist, H. (1970): Numerical simulation of the develop-
ment of tropical cyclones with a ten-level model.
Part I. Tellus, XXII, Nov. 4, pp. 359-390.
B-15
APPENDIX C
HURRICANE MODELING AT THE NATIONAL
HURRICANE RESEARCH LABORATORY (1970)
Stanley L. Rosenthal
National Hurricane Research Laboratory
INTRODUCTION
The major achievement of this period has been the de-
velopment of a working, asymmetric model of the hurricane
(app. D). Substantial progress has, however, also been made
in other areas. Brief summaries of these efforts will be
given in later sections of this appendix.
Section 2 reviews our more significant achievements in
the general area of time-dependent hurricane modeling. Sec-
tion 3 reviews the specific problem of modeling a Debbie- like
field experiment. Section 4 summarizes efforts less directly
related to the development of time-dependent models. Section
5 outlines investigations planned by the group for the next
few years .
TIME-DEPENDENT MODELS
(a) The Asymmetric Model: As already noted, progress
with this model has been sufficient to warrant a separate
discussion (app. D) in this year's annual report. An expanded
version of appendix D (Anthes, Rosenthal, Trout, 1970) will
appear in the Monthly Weather* Review. A second paper which
compares results of the asymmetric model with a symmetric
analog of equivalent vertical resolution has also been ac-
cepted for publication (Anthes, Trout, and Rosenthal, 1970).
Computing economics dictate rather coarse vertical and
horizontal resolution for the asymmetric model. The atmo-
sphere's vertical structure is represented by only three
layers and horizontal spacing of grid points is 30 km. The
radial extent of the computational domain is approximately
435 km. The version used to obtain the results shown in
appendix D did not contain an explicit water vapor cycle.
Although the model allows azimuthal variations, the hurricane
remains an isolated, stationary vortex on an f-plane similar
in fashion to the circularly symmetric models. Like the cir-
cularly symmetric models, this model is a theoretical tool
with no potential for dealing skillfully with real data.
Despite obvious deficiencies due to the lack of ade-
quate resolution, the model reproduces many of the observed
asymmetrical features of the hurricane. Realistic portrayals
of spiral rainbands are obtained. The anticyclonic eddies of
the upper troposphere are reproduced as are the observed areas
of negative absolute vorticity and anomalous winds.
Since the preparation of appendix D, the asymmetric
model has been generalized to include an explicit water vapor
cycle and has been recoded for a staggered horizontal grid.
The latter reduces local truncation error without either in-
creasing the number of grid points or reducing the spacing
between them. A number of experiments have been conducted
with the revised model and results even more promising than
those described in appendix D have been obtained. These data
are now undergoing careful study.
Despite the realism of the
creased accuracy obtained through
variables, the model continues to
quate resolution. Improvement of
appears to be economically beyond
poss ibi 1 i ty , on
at least in the
results and despite the in
horizontal staggering of
suffer from a lack of ade-
the vertical resolution
our reach. There is a
the other hand, that horizontal resolution,
inner core of the hurricane, may be improved
through the use of horizontally variable grids
NHRL
f o rm
spac
This
size
at t
(b)
tran
(c)
fami
asso
i s m
(e)
othe
1 i ne
sour
Tw
. On
ati on
e to
syst
of a
he ce
Since
sf orm
In th
liar
c i a t e
i n i m u
The m
r han
arte
ce of
o such g
e of the
from a
an ortho
em posse
gri d el
nter of
the var
a t i o n , t
e 1 i m i t i
two-di me
d with t
m at the
a c h i n e p
d , the t
rms than
d i f f i c u
ri d
se (
non-
gona
sses
emen
the
iabl
he d
ng c
ns io
he n
cen
rogr
rans
the
lty
syste
Anthe
ortho
1 con
the
t var
array
e gri
egree
ase ,
nal ,
on-or
ter a
ammi n
forme
ori g
i n ve
ms h
s , 1
gona
stan
foil
i es
to
d i s
of
the
squa
thog
nd m
g is
d eq
i nal
ry 1
a ve b
970a)
1 , va
t mes
owi ng
smoot
a max
deri
v a r i a
v a r i a
re gr
o n a 1 i
a x i m u
rel a
uati o
equa
ong i
een des
is an
r i a b 1 e
h i n a
charac
hly fro
i m u m a 1
ved fro
bill ty
b 1 e gri
id. (d
ty of t
m al ong
t i v e 1 y
ns do c
t i o n s w
ntegrat
i g n e d
analyt
mesh i
comput
t e r i s t
m a mi
ong th
m an a
is e a s
d coll
) The
he var
the b
s i mpl e
o n t a i n
h i c h m
ions.
and te
i c a 1 t
n phys
a tiona
i cs :
n i m u m
e boun
n a 1 y t i
i 1 y c h
apses
d i s t o r
i a b 1 e
oundar
. On
more
ay be
sted at
rans -
i cal
1 space
(a) The
val ue
dary .
cal
anged .
to the
tion
grid
i es .
the
non-
a
C-2
pose
surr
larg
grid
"tel
wi th
Howe
grid
tral
The
na te
addi
tion
gral
the
form
appe
extr
The s
d of a c
ounded b
er size,
s . A de
escope"
ref eren
v e r , o t h
squares
core , s
advantag
s are us
t i o n a 1 n
s . A fu
s are pr
equation
a t i o n co
ar. The
emely 1 a
econd typ
entral co
y ' square
The con
generate
grid w h i c
ce to loc
er member
increase
eem to be
es of Kos
ed and , h
o n 1 i n e a r
rther adv
eserved t
s are exp
eff i ci ent
major d i
borious .
e of v
re of
annul
struct
member
h has
al for
soft
rathe
more
s ' s ap
ence ,
terms
antage
o with
ressed
s ( s i m
sadvan
a r i a b
equal
i ' of
ion d
of t
been
ecas t
he fa
r gra
s u i t a
proac
n e i t h
appea
i s t
in t i
in f
i 1 ar
tage
1 e g r i
area
squar
e f i n e s
he fam
discus
ing by
mily ,
dual ly
ble fo
h are
er tra
r i n t
hat ma
me dif
1 ux fo
to map
is t h a
d (Ko
squar
e gri
a fa
i 1 y i
sed i
nume
in wh
outw
r the
that
nsf or
he hy
ss an
f eren
rm an
-seal
t mac
ss, 197
e grid
d eleme
mily of
s the f
n the 1
ri cal m
i c h the
ard fro
hurr i c
C a r t e s i
mati on
drodyna
d momen
c i n g e r
d v a r i a
e facto
h i n e c o
0) is
el erne
nts o
vari
ami 1 i
i tera
ethod
size
m the
ane p
an co
terms
mi c e
turn i
rors
ble c
rs ) d
ding
com-
nts
f even
abl e
a r
ture
s .
s of
cen-
robl em
o r d i -
nor
qua-
nte-
since
rans -
o not
i s
Numerical tests (Anthes, 1970a; Koss, 1970) indicate
that both types of variable grids show promise for the hur-
ricane problem. Further tests are planned for both systems.
Two other studies related to the asymmetric model are
in progress. It has been suggested that the vertical stag-
gering of variables (see app. D) may severely distort the
basic C I S K mechanism which drives the model hurricane. While
the realism of the results counteracts this suggestion, we
are investigating the matter through a linear analysis. The
analysis requires solution of a ninth order characteristic
equation with complex coefficients. Results are not yet
available.
ami ne
i nsi g
With
the c
ti me .
proce
ci rcu
4 and
the a
all o
and 2
bound
cul ar
wave
Out
d i n
h t in
c i r c u
al cul
Asy
dure
1 ar .
, to
symme
f the
. An
ary w
vari
numbe
put da
detai 1
to the
1 arly
a t i o n
mmetri
and by
Both
a less
tri c s
c i r c u
excep
here w
ance n
r 4 , o
ta from
in an
asymme
symmetr
shoul d
es are
the fa
of thes
er exte
tage of
1 ar var
tion to
ave num
ear the
ver-al 1
the a
attemp
tri c s
i c in i
remai n
i ntrod
ct tha
e ef f e
nt , wa
the n
i a n c e
this
ber 4
bound
, is r
symme
t to
truct
ti al
ci re
uced
t the
cts t
ve nu
umeri
is co
occur
i s mo
ary i
a ther
trie mo
gain gr
ure of
and bou
ul arly
through
bounda
end to
mber 8.
cal i n t
ntai ned
s qui te
st sign
s quite
i n s i g n
del are b
eater phy
the model
ndary con
symme tri c
the i n i t
ries are
excite w a
However
egrati on ,
in wave
cl ose to
i f i cant .
smal 1 an
i f i c a n t .
ei ng
si ca
sto
d i t i
for
i a 1 i
not
ve n
, du
vi r
numb
the
The
d, h
ex-
1
rm.
ons ,
all
zation
qui te
umber
ring
tual ly
ers 1
outer
ci r-
ence ,
C-3
While the growth of the symmetric part of the systems
is understandable from earlier work with symmetric models,
and while the dominance of wave numbers 1 and 2 over higher
wave numbers is empirically reasonable, we would like to know
more about the physical mechanisms involved. The investiga-
tion involves a program of harmonic analysis in an attempt
to understand the behavior of the governing equations in the
spectral domain.
(b) The Seven-Level Symmetric Model: The basic de-
sign of this model, as well as typical results to be expected,
were documented in three reports which appeared during the
year (Rosenthal, 1970a, 1970b, 1970c).
The only significant revisions during the past year
(and since the experiments discussed in the papers cited a-
bove) are concerned with the boundary layer formulation.
Whereas air-sea exchanges of sensible and latent heat had
been simulated by some rather pragmatic constraints on the
Ekman layer temperatures and humidities, these energy ex-
changes are now computed explicitly through the bulk aerody-
namic method. The constant drag coefficient used in previous
experiments has been replaced with Deacon's empirical rela-
tionship.
The revised model was used for a number of experiments
(Rosenthal, 1970d) in which boundary layer parameters, initial
conditions, lateral boundary conditions, and computational
domain size were varied.
When the drag coefficient is varied during the imma-
ture stage, the response of the model follows linear theory,
and growth is more rapid with larger drag coefficients. How-
ever, the ultimate intensity reached by model storms varies
inversely with drag coefficient. In the mature stage, small
decreases of drag coefficient lead to stronger peak winds;
but when the drag coefficient is reduced by large amounts,
peak winds diminish. In the latter situation, there is in-
sufficient low-level convergence to sustain convection in
the storm core.
Oceanic evaporation was found to be an essential in-
gredient without which immature storms would not develop and
mature storms could not sustain themselves. The air-sea ex-
change of sensible heat was of lesser importance and only
small changes occurred when this energy source was completely
suppressed. The relative importance of the air-sea exchanges
of sensible and latent heat can be explained rather easily
(Rosenthal , 1970d) .
C-4
Comparisons between experiments with open and mechani-
cally closed lateral boundaries show these boundary conditions
to be extremely important. For computational domains of 2000
km or less, model storms with closed lateral boundaries are
less intense than their counterparts with open lateral bound-
aries. The intensity of closed systems increases markedly
with domain size, while that of open systems varies only
slowly with domain size. The experiments indicate that dif-
ferences due to lateral boundary conditions might be mini-
mized if the computational domain exceeded 2000 km.
Experiments conducted with open lateral boundaries
revealed that the structure and intensity of the mature stage
of the model cyclone is relatively insensitive to variations
in the scale and intensity of the initial perturbation. The
time required to reach the mature stage is, however, quite
sensitive to these factors.
MODELING AND GUIDANCE FOR PROJECT ST0RMFURY (1970)
Appendix C of the 1969 Project ST0RMFURY Annual Report
summarized a number of calculations performed with the seven-
level symmetric model in which extremely crude attempts were
made to simulate a Debbie-like field experiment. (A revised
version of that summary appears in the Monthly Weather Review
(Rosenthal, 1970e).) Additional calculations of this type
have been carried out during the last few months and provide
results which differ in varying degrees from those reported
on last year.
Before proceeding with a discussion of these differ-
ences, some words of caution are in order. These comments
arise from having an additional year of thought and discus-
sion devoted to the simulation problem. Rosenthal (1970e)
pointed out that the assumption of circular symmetry pre-
cluded direct comparisons between model calculations and
specific real tropical cyclones. It was our feeling at that
time, and it continues to be our feeling, that the model
should only be considered representative of some sort of
"average" hurricane. We pointed out that real hurricanes
are strongly influenced by interactions with neighboring
synoptic systems and that these interactions may vary mark-
edly in character from storm to storm and cannot realisti-
cally be modeled with a symmetric, isolated vortex.
C-5
The calculations discussed in Rosenthal (
additional questions concerning certain aspects
In previous reports (Rosenthal, 1970e, for examp
shown the model to yield a highly realistic stor
during the mature stage. However, since the mod
and cannot be tested using real observations as
ditions, we cannot examine the model's realism w
the time required for it to pass through a serie
sients as it proceeds from one slowly varying st
Furthermore, Rosenthal (1970d) showed that the t
for a model storm to reach its mature stage vari
days according to the values of several rather a
rameters (see discussion in Time Dependent Model
1970d), raise
of the model .
le) we have
m structure
el has not
initial c o n -
ith regard to
s of tran-
ate to another
ime required
ed by several
rbi trary pa-
s p. C-l).
Both the field experiments and the model simulations
involve adding a small perturbation to a mature hurricane
with the hope that it will be unstable. Since no clear-cut
theoretical path for establishing the model's credibility
with regard to small perturbations is at hand, and since we
cannot be entirely certain that Debbie's changes were pro-
duced by the seeding, the realism of the model's response to
artificial enhancement of the heating functions must also
remain an open question. This will be discussed later in
this section.
A major difficulty with regard to interpretation of
model simulations is related to the so-called "new hypothesis"
(discussed elsewhere in this report, see app. B). The arti-
ficial enhancement of the model heating functions, which was
designed on the basis of the old hypothesis, appears, from a
conceptual point of view, to be inconsistent with the new
hypo the si s .
Under the old hypothesis, the source of this additional
heat was attributed to the freezing of supercooled water in
the upper tropospheric portions of tall Cb. In the model
calculations, this was represented by adding a fixed amount
of heat to the upper troposphere over periods of several
hours. While valid arguments could be raised concerning the
reality of the magnitude of this heat source and the length
of time over which it was added, we could at least visualize
a clear relationship between the model procedure and the pos-
tulated real atmospheric process.
The hurricane could be pictured as a system which con-
tinually generates new Cb whose upper tropospheric positions
consist of supercooled water. The seeding operation could
then be visualized as a process in which this newly generated
supercooled water is continually frozen through artificial
nucleation. With this view of the field experiment, it is
C-6
not unreasonable to attempt a simulation by adding fixed
amounts of heat (intended to be the released heat of fusion)
to the upper troposphere at each time step for some period of
time .
Under the new hypothesis, however, heat of fusion re-
leased through silver iodide nucleation is considered only
as a stimulus for increasing the buoyancy of Cb (outward from
the main eyewall) which by natural processes would reach only
to middle tropospheric levels. Under this hypothesis, the
major source of energy for modification purposes is sought in
the additional condensation and/or sublimation heating re-
leased as the seeded clouds grow to upper tropospheric levels.
The difficulty with a simulation relevant to the new
hypothesis is that all model Cb which originate in the bound-
ary layer reach upper tropospheric levels by natural proces-
ses. This stems from the fact that the model Cb are comprised
of undilute ascent. Entrainment is not taken into account.
Wit.h the current version of the model, therefore, the eyewall
region differs from other regions of the storm in cloud con-
centration but not in cloud depth.
vi sua!
One ca
new hy
1 arger
of the
moi stu
field
t i v e 1 y
paragr
c e i v a b
concen
this p
convec
Si mu
ized
n , ho
po the
than
boun
re an
exper
shor
aph.
1 e an
tvati
oi nt
ti on
1 ati on
unl ess
wever ,
sis is
that
dary 1
d angu
iment ,
t cl ou
In th
al ogue
on of
of vie
is s t i
of th
one a
argue
the s
of the
ayer i
1 ar mo
this
ds to
e mode
to th
tall c
w has
mul ate
e new hypo
d o p t s a hi
as fol 1 ow
t i m u 1 a t i o n
eyewal 1 i
nflow thus
mentum to
is to be a
become tal
1 , where a
e field ex
1 ouds at t
been accep
d becomes
thesis is then not easily
ghly philosophical attitude,
s. The basic feature of the
of tall convection at radii
n the hope of diverting some
reducing the supply of
the eyewall region. In the
ccomplished by causing rela-
I as described in a previous
II clouds are tall, a con-
periment is to increase the
he corresponding radii. Once
ted, the means by which model
rather arbitrary.
The addition of a fixed amount of heat as in Rosenthal
(1970e) is only one of many possibilities. Others include
arbitrary changes of boundary layer convergence, changes of
the humidity patterns, and changes in static stability. Of
course, these alterations can also be made in various combi-
nations.
While calculations of the Rosenthal (1970e) type can
still provide helpful information for Project STORMFURY if
properly interpreted, clearly literal comparisons between
the calculations and the Debbie experiment are unwarranted.
Aside from the arbitrary procedures used to simulate seeding,
C-7
the questions concerning the response time of the model
raised earlier in this section must be considered as must the
lack of interaction with other synoptic features.
It is abundantly clear that we must strive to provide
more direct numerical tests of the new hypothesis. To achieve
this end, it will be essential to include entrainment and some
simple representation of the more significant mi crophys i cal
processes. It may also be necessary to make improvements in
the modeling of the interactions between the Cb and hurricane
scales. This will be a high priority item for the next year.
I
t i n u e .
mat ion w
di f f eren
1 a t i o n s
months .
to a rev
This rev
c o e f f i c i
(see d i s
dependen
reached
the diff
i n g e n h a
series o
aspect o
n the
These
hen c
ces o
repor
Some
i s i o n
i s i o n
ent (
c u s s i
ce on
until
erenc
nceme
f con
f the
meant
have
ompare
f vary
ted on
of th
of th
consi
3 x 10
on in
wind
wi nds
es may
nt is
trol 1 e
probl
l me , c
and w i
d a g a i
i ng de
1 ast
e s e d i
e mode
sted o
"3) by
Sectio
speed ,
appro
wel 1
depend
d expe
em.
al cu
11 c
ns t
gree
year
f fer
1 du
f re
Dea
n 2)
and
ach
be t
ent
rime
1 ati ons
onti nue
each ot
have a
and th
ences a
ring t h
pi aceme
con ' s e
. The
val ues
50 m se
hat mod
on the
n t s is
of t
to p
her .
ri sen
ose p
re pr
e i nt
nt of
mpi ri
1 a tte
of 3
c-1.1
el re
i n i t i
pi ann
he ol d
rovi de
As not
betwee
erforme
obably
erveni n
the co
cal rel
r gives
x 10-3
A sec
sponse
al cond
ed to s
type
usef u
ed ea
n the
din
a 1 1 r i
g per
ns tan
ation
a li
are
ond s
to th
i t i o n
tudy
wi 1 1 con'
1 infor-
rl i er ,
cal cu-
recent
butabl e
iod.
t drag
ship
near
not
ource of
e heat-
s. A
this
presen
the fo
i ncrea
ing) ,
( extre
radi al
e x p e r i
The se
20 km.
the he
i mum.
was at
add he
radii
peri me
the ey
To ma
ted in
rmer a
sed at
3 kj-t
me hea
i nter
ments )
a-1 eve
Henc
at was
The c
25 km
at fro
experi
nts we
ewal 1
ke m
the
re b
500
on- l
ting
val s
and
1 wi
e, i
app
ente
rad
m th
ment
re a
cent
e a n i n g f u
1969 re
riefly s
and 300
sec"1 (
) for 10
sel ecte
35, 45,
nd maxim
n both t
lied at
r of the
i u s . T h
e eyewal
s do not
lso cond
er inwar
1 compa
port an
ummari z
mb by
large h
-hour i
d were
and 55
urn for
he smal
radii b
eyewal
e small
1 cente
add he
ucted i
d.
r i s o n s be
d those o
ed below.
1 kj-ton"
eating) ,
hterval s
25, 35, a
km ( larg
the contr
I and lav
eyond the
1 for the
radii ca
r outward
at at the
n which h
tween t
b t a i n e d
H e a t i
1 sec" 1
and 9 k
at v a r i
nd 45 k
e radii
ol expe
ge radi
sea-1 e
contro
1 c u 1 a t i
wherea
eyewal
eat was
he res
more
ng rat
( norm
j-ton"
ous ra
m ( sma
exper
riment
i expe
vel wi
1 expe
ons , t
s the
1 cent
added
ul ts
recently ,
es were
al heat-
I sec- 1
d i i . The
II radii
i ments ) .
was at
ri ments ,
nd max-
ri ment
herefore ,
large
er. Ex-
f rom
For a discussion of the effect of this change on the typical
results to be expected from the model, the reader is referred
to Rosentha 1 ( 1 970d) .
C-8
Small and large radii experiments were consistent in
showing the development of a new eyewall at 35 km and destruc
tion of the original eyewall. A new surface-wind maximum was
consistently formed at a radius of 40 km, and the original
maximum (at 20 km) was eventually destroyed. In general, the
newly formed maximum was about 5 m sec-1 less intense than
the original.
for
hour
wi th
howe
wind
trem
lati
gave
al so
radi
2 ho
es ta
face
sec
trem
i n s
arti
stat
tras
stab
arti
- i
With normal heating at small radii3 the time required
the new wind maximum to become established was about 8
s. Differences between small and large radii experiments
normal heating were minor. In both of these experiments,
ver, prior to the development of the new wind maximum,
s stronger than the control were found at all radii. Ex-
e heating experiments differed from normal heating calcu-
ons only in response time. Extreme heating at large radii
results which differed from extreme heating at small radii
only in response time. With extreme heating at large
ij the new surface-wind maximum was established within
urs. Extreme heating at small radii required 4 hours to
blish the new velocity maximum. Prior to this time, sur-
winds in the modified calculation were as large as 5 m
greater than in the control. Application of the ex-
e heating rate inside the radius of maximum wind resulted
urface wind increases of 3 m sec-1. However, when the
ficial heating was terminated, the system recovered to a
e close to that of the control within 4 hours. In con-
t, the large and small radii experiments reached rather
le configurations which were maintained even after the
ficial heating was terminated.
While the general evolution of the sea-level winds in
the experiments described above was in the sense predicted by
either the "old" or the "new" hypothesis, the model's behavior
at 700 mb raised some questions. The sense of the 700 mb
changes was more or less similar to those changes at sea
level. However, the 700 mb responses were more rapid and
extreme. The early intensification found at the surface was
even more pronounced at 700 mb. The new wind maximum, when
formed at 700 mb, was generally more intense than the origi-
nal maximum until after termination of the enhanced heating
C-9
original maximum. In the old calculations the displacement
was 20 km. In the old calculations, with the normal heating
rate, the magnitude and timing of the response were similar
for both large and small radii experiments. In the new cal-
culations, normal heating at large radii generates the new
sea-level wind maximum about 6 hours earlier than does normal
heating at small radii. Calculations with the k the normal
heating rate at small radii shows an ultimate effect similar
to that obtained for the experiments with normal heating.
However, approximately 2h days of enhanced heating are re-
quired to obtain the effect.
Despite the differences which have been emphasized in
the last few paragraphs, the experiments do show a consistent
pattern which is useful for the design of field experiments.
Enhancement of the upper tropospheric heating functions for
a sufficiently long period at radii greater than the eyewall
center and surface wind maximum will ultimately produce a new
eyewall and a new, less intense, sea-level wind maximum at
radii greater than those of the "naturally" occurring features
The time required to produce these changes is reduced as the
rate of heating enhancement is increased. Application of
enhanced, heating from the eyewall center inward or only at
the eyewall center will result in stronger winds at sea level.
In this case, the eyewall and the wind maximum will remain
at the natural locations.
OTHER INVESTIGATIONS
Anthes (1970b) examined the role of azimuthal asymme-
tries in satisfying the mean angular momentum budget for the
steady-state hurricane.
Anthes (1970c) developed a circularly symmetric model
in isentropic coordinates to study the effects of differen-
tial heating on the dynamics and energetics of the steady-
state tropical cyclone. From specified heating functions,
he obtained nearly steady-state solutions for the mass and
momentum fields. These solutions were then used to evaluate
the available potential energy cycle for the theoretical hur-
ricane. The major results of this investigation will appear
in the Monthly Weather Review (Anthes, 1970d, 1970e).
Anthes (1970f) examined the problem of truncation error
in the calculation of vertical motions at the top of the Ekman
layer under an imposed hurricane-like, circularly symmetric
press ure field.
C-10
Black and Anthes (1971) constructed detailed wind anal-
yses of the outflow layer for four hurricanes and one tropical
storm. Harmonic analysis of these data, together with that of
the composite storms of Miller and Izawa, shows wave numbers
1 and 2 to account for most of the circular variance in the
momentum and kinetic energy fields.
FUTURE PLANS
High priority will be given the development of a more
sophisticated cloud representation to be used with the seven-
level, circularly symmetric hurricane model so that closer
simulations of the "new" STORMFURY hypothesis may be per-
formed .
Simulations of hurricane seeding will be carried out
with the asymmetric hurricane model during the next year.
Horizontal resolution in the central portions of the
asymmetric hurricane model may be improved through recoding
for one of the variable mesh systems discussed in Section 2.
Beyond this, the next logical step would seem to be removal
of the stationary, isolated vortex assumptions. This will
be a major step and will increase our computing requirements
by an order of magnitude.
We envision a model in which a fine mesh moves with
the hurricane center through a coarse mesh on which the large-
scale synoptic patterns are forecast. This type of model will
not only serve as a theoretical tool but also will have the
potential for real hurricane forecasting. Whether or not
this potential will ever be realized will, to a major extent,
be dependent upon the development of real time observational
techniques for providing adequate high resolution initial
data (-10 km horizontal resolution) in the hurricane vortex.
To develop such a model, important background investi-
gations will be required. The mathematical and physical con-
siderations for linking a moving fine mesh with a stationary
coarse mesh in the framework of a primitive equation model
will require extensive research. The problem of hurricane
displacement forecasting by dynamic methods must be reexam-
ined. It is not clear whether the characteristic errors of
the existing filtered (primarily barotropic) models are pri-
marily a result of erroneous initial data or physical simpli-
fications.
C-ll
While these problems must ultimately be faced in the
real data context, it is our feeling that the most promising
start lies with the use of hypothetical initial data and a
philosophical attitude similar to that adopted for our earlier
work .
REFERENCES
Anthes, R. A. (1970a): Numerical experiments with a two-
dimensional horizontal variable grid. Monthly Weather
Review* 983 (11), November, pp. 810-822.
Anthes, R. A. (1970b): The role of large-scale asymmetries
and internal mixing in computing meridional circula-
tions associated with steady-state hurricanes. Monthly
Weather Review, 98* (7), July, pp. 521-529.
Anthes, R. Z. (1970c): A diagnostic model of the tropical
cyclone in isentropic coordinates. ERLTM-NHRL Techni-
cal Memorandum No. 89, ESSA, U.S. Dept. of Commerce,
NHRL, Miami , Fla. , 147 pp.
Anthes, R. A. ( 1 9 7 0 d ) : A numerical model of the steady-state
tropical cyclone in isentropic coordinates. Paper
accepted for publication in the Monthly Weather Review.
Anthes, R. A. (1970e): Numerical experiments with a steady-
state model of the tropical cyclone. Paper accepted
for publication in the Monthly Weather Review.
Anthes, R. A. (1970f): Iterative solutions to the steady-
state axisymmetric boundary layer equations under an
intense pressure gradient. Paper accepted for publi-
cation in the Monthly Weather Review.
Anthes, R. A., S. L. Rosenthal, and J. W. Trout (1970): Pre-
liminary results from an asymmetric model of the
tropical cyclone. Accepted for publication in the
Monthly Weather Review.
Anthes, R. A., J. W. Trout, and S. L. Rosenthal (1970): Com-
parisons of tropical cyclone simulations with and
without the assumption of circular symmetry. Accepted
for publication in the Monthly Weather Review.
C-12
Black, P. G., and R. A. Anthes (1971): On the asymmetric
structure of the tropical cyclone outflow layer.
Paper submitted to the Monthly Weather Review.
Koss, W. J. (1970): Numerical integration experiments with
variable resolution two-dimensional Cartesian grids
using the box method. Accepted for publication in
the Monthly Weather Review.
Rosenthal, S. L. (1970a): A survey of experimental results
obtained from a numerical model designed to simulate
tropical cyclone development. ERLTM-NHRL Technical
Memorandum No. 88, ESSA, U.S. Dept. of Commerce, NHRL,
Miami, Fl a . , 78 pp .
Rosenthal, S. L. (1970b): Experiments with a numerical model
of tropical cyclone development. Some effects of
radial resolution. Monthly Weather Review, 98, (2),
February, pp. 106-120.
Rosenthal, S. L. (1970c): A circularly symmetric primitive
equation model of tropical cyclone development con-
taining an explicit water vapor cycle. Monthly Weather
Review, 98, (9), September, pp. 643-663.
Rosenthal, S. L. ( 1 9 7 0 d ) : The response of a tropical cyclone
model to variations in boundary layer parameters, ini-
tial conditions, lateral boundary conditions, and
domain size. Accepted for publication in the Monthly
Weather Review.
Rosenthal, S. L. (1970e): A circularly symmetric, primitive
equation model of tropical cyclones and its response
to aritificial enhancement of the convective heating
functions. Monthly Weather Review, 99, (5), May,
pp. 414-426.
C-13
APPENDIX D
SUMMARY OF PRELIMINARY RESULTS FROM AN ASYMMETRIC
MODEL OF THE TROPICAL CYCLONE1
Richard A. Anthes, Stanley L. Rosenthal, and James W. Trout
National Hurricane Research Laboratory
The results show that the model reproduces many ob-
served features of the three-dimensional tropical cyclone.
Realistic portrayals of spiral rainbands and the strongly
asymmetric structure of the outflow layer are obtained. The
kinetic energy budget of the model compares favorably with
empirical estimates and also shows the loss of kinetic energy
to truncation errors to be very small.
Large scale horizontal asymmetries in the outflow are
found to play a significant role in the radial transport of
vorticity during the mature stage and are of the same magni-
tude as the transport by the circulation.
In agreement with empirical studies, the outflow layer
of the model storm shows substantial areas of negative abso-
lute vorticity and anomalous winds.
This report summarizes a more complete version to be pub
lished in the Monthly Weather Review in 1971.
INTRODUCTION
cycle o
(Ooyama
They ha
i c s , en
the 1 at
With th
b i 1 i ty ,
metri c
these a
h u r r i c a
and nea
Axi symme tr
f tropical
, 1969; Ya
v e also y i
e r g e t i c s ,
ent heat r
is backgro
it is not
features o
re the upp
ne motion,
rby synopt
ic numerical models have simulated the life
cyclones with a large degree of realism
masaki, 1968a, 1968b; Rosenthal, 1970b).
elded valuable insight into hurricane dynam-
and the important problem of parameterizing
eleased in organized cumulus convection,
und, and with ever increasing computer capa-
premature to begin the study of the asym-
f the hurricane. Among the more notable of
er tropospheric outflow layer, the rainbands
and the interactions between the hurricane
ic systems.
To incorporate all of these features in a single nu-
merical model is an extremely ambitious goal that will require
further investigation. The model developed here represents
an isolated stationary vortex and appears to be the logical
first step beyond the axisymmetric models. For computational
economy, we have limited the model to three vertical levels,
a coarse horizontal resolution of 30 km, and a relatively
small domain of radius 435 km.
DESIGN OF MODEL
The equations of motion are written in a coordinates
(Phillips, 1957) on an f-plane, where f, the Coriolis param-
eter, is appropriate to approximately 20°N (5 x 10"5 sec-1)-
The equations of motion, continuity equation, thermodynamic
equation, and hydrostatic equation are identical to those
employed by Smagorinsky et al . (1965) for general circulation
studies. The basic equations are given in Anthes et al.
(1971a), hereafter referred to as I, and are not repeated
here .
STRUCTURE OF THE MODEL
The vertical structure of the model is shown by figure
D-la. The atmosphere is divided into upper and lower layers
of equal pressure depth and a thinner Ekman boundary layer.
The information levels for the dynamic and thermodynamic var-
iables (fig. D-la) are staggered according to the scheme
used by Kurihara and Holloway (1967).
D-2
The horizontal mesh (fig. vertical structure
D-lb) is rectangular with a
uniform spacing of 30 km. The
lateral boundary points approx- °-=o ' ' ' ' ' < ' ' < < ' < < '
imate a circle, and all bound-
ary points are contained be-
tween radii of 450 and 435 km. CT-* — - - *™
All variables are defined at
all grid points on the a-sur-
faces .
VARIABLE K P(mb)
V.T iv2 225
V,T 2V, 675
THE FINITE DIFFERENCE
EQUATIONS
O".* ■ 3 900
V,T 3V2 9575
<t>--v-Q 4 1015
(a)
HORIZONTAL STRUCTURE - Northwest Section
«-E»tenor Boundary Point
o-lntenor Boundary Point
-Interior Point
>
The finite difference « > ° ° ° 0 o legend
analogs to the horizontal der- ,11°.°.'.'.
ivatives are similar to those ... °. '.'.'. '.
in Grammel tvedt ' s (1969) scheme * • 4 center of end
"B". The vertical portion of \ I '.'.'.'.'.'.'. '.
the differencing scheme is i- • •
dentical to that of Kurihara « . ! ! .' ! .' '. '.'.'.'.
and Holloway (1967) with the < .
exception that potential temp- ". ° ."!!'.!'.!!! !
erature rather than tempera- . . ......... '.
ture is interpolated where (b)
needed. The details are given _. _ . > . „ ,. 7.
• t 3 F%guve D-l. (a) Vertical in-
formation levels; (b) North-
For adiabatic, inviscid west quadrant of the hori-
flow in a laterally closed do- zontal grid.
main with a = 0 at a = 0 and 1,
Kurihara and Holloway showed this system to conserve the fi-
nite difference analog to
/ / /V fd + "2 \ VH dadydx. (D.l)
x y o L v J
VERTICAL DIFFUSION OF MOMENTUM
Although vertical transport of horizontal momentum by
the cumulus-scale motions has been shown to 'be an important
element in maintaining the observed structure of hurricanes
(Gray, 1967; Rosenthal, 1970b), this effect is not included
in the preliminary calculations reported on here. Therefore,
D-3
vertical diffusive and "frictional" effects in this experiment
are due to the vertical transports of horizontal momentum by
subgrid scale eddies smaller than the cumulus scale. The
most important aspect of these terms is the surface drag which
produces frictional convergence in the cyclone boundary layer
and, therefore, a water vapor supply which controls the param-
eterized cumulus convection (Charney and Eliassen, 1964;
Ooyama, 1969; Rosenthal, 1970b).
The surface drag is modeled using the well-known quad-
ratic stress law, and a constant value of 3 x 10~3 was adop-
ted for C[). For the remaining o-levels we use the Austausch
formulation with the Rossby-Montgomery formulation adopted
for the vertical kinematic coefficient of eddy viscosity, Kz
(Smogorinsky et al . , 1965). The details are given in I.
LATERAL MIXING TERMS
After Smagorinsky et al . (1965), the lateral exchange
of horizontal momentum by subgrid scale eddies is written
FH<V> =j;
(D.2)
where V
sure
is the horizontal vector velocity,
and K|-| is the horizontal coefficient
of
is surface pres
eddy vi scosi ty
The formulation ultimately adopted was
Ku = Ci V + C
(D.3)
where Ci = 103 and C2 = 5 x
103m2
sec
_ i
D-4
While this selection was based primarily on the results
of numerical tests, the form was suggested by the encouraging
results obtained from symmetrical models (Rosenthal, 1970b;
Yamasaki , 1968b) which employed upstream differencing of ad-
vection terms with forward time steps. This scheme introduces
a computational viscosity (Molenkamp, 1968) which is similar
to the variable portion of (D.3).
Although (D.3) is not terribly satisfying from a phys-
ical point of view, it does afford a useful interim represen-
tation of the statistical effect of horizontal interactions
between the momentum fields of the cumuli and macroscale.
More satisfying formulations are dependent on the success of
future theoretical and observational studies of these inter-
actions.
The preliminary tests also indicated that adequate
results can be obtained if the lateral diffusion of heat is
computed with a constant thermal diffusivity (Kj) of 5 x 101*
m2 sec-1. The lateral mixing term in the thermodynamic
equation was, therefore, expressed in the form
FH(T)
p*K-
/ill + ill\
\3x2 8y2/
(D.4)
where T is temperature.
TIME INTEGRATION
of s
made
Wend
(196
di ab
supe
base
suit
due
this
f req
grav
heat
effe
A
elect
betw
rof f
6) si
ati c
rior
d on
s. P
to i t
mode
uency
i ty w
ing.
ct.
numbe
ing a
een t
schem
mul at
ef fee
to th
i n t u i
resum
s sev
1 has
i ner
ave)
The
r of
meth
he us
e (Ri
ed fo
ts in
e oth
ti ve
ably,
ere d
very
t i a - g
are p
Matsu
experi me
o d of t i
ual leap
ch tmyer
rward-ba
cl uded ,
er schem
meteorol
the sup
a m p i n g o
limited
ravi ty w
robably
no dampi
nts we
me i n t
-frog
and Mo
ckward
the Ma
es tes
o g i c a 1
e r i o r i
f high
v e r t i
aves (
overly
ng may
re cond
eg rati o
method ,
rton, 1
scheme
tsuno t
ted. T
i n s p e c
ty of t
tempor
cal res
p a r t i c u
exci te
, then,
ucted
n . Co
the t
967),
. Wit
e c h n i q
his co
t i o n o
he Mat
al f re
o 1 u t i o
larly ,
d by t
compe
for th
mpari s
wo-ste
and th
h vi sc
ue was
ncl us i
f the
suno s
q u e n c i
n , the
the e
he d i a
nsa te
e purpose
ons were
p Lax-
e Matsuno
ous and
cl early
on was
test re-
cheme is
e s . Since
high-
xternal
b a t i c
for this
D-5
LATERAL BOUNDARY CONDITIONS
The small domain size and the irregular boundary make
the choice of lateral boundary conditions extremely important.
Preliminary experimentation showed that realistic results could
be obtained for steady-state pressure and temperature on the
boundary and a variable momentum based on extrapolation out-
ward from the interior of the domain.
LATENT HEAT RELEASED IN ORGANIZED CUMULUS CONVECTION
ment
The basic characteristics of this convective adjust-
are summarized as follows:
1. Convection occurs only in the presence of low-level
convergence and conditional instability for air
parcels rising from the surface.
2. All the water vapor that converges in the boundary
layer rises in convective clouds, condenses, and
falls out as precipitation.
3. All the latent heat thus released
able to the macroscale flow.
4. The vertical distribution of this
that the macroscale lapse rate is
the pseudo-adi abat appropriate to
surface .
Empirical justfication for these characteristics
is made avail-
heating is such
adjusted towards
ascent from the
by Rosenthal (1969)
is presented
The convective adjustment, described above, applies
only when the atmosphere is conditionally unstable; i.e., the
cloud temperature, Tc, exceeds the environmental temperature,
T. In mature hurricanes, however, prolonged and intense
cumulus convection substantially reduces parcel buoyancy and
lapse rates approach the moist adiabatic. Under these circum-
stances, significant amounts of nonconvecti ve precipitation
(and, hence, latent heat release) may occur (Hawkins and
Rubsam, 1968). Since, in this experiment, water vapor is not
explicitly forecast, it is necessary to parameterize this effect
D-6
The parameterization of nonconvecti ve latent heat re-
lease under nearly moist adiabatic conditions proceeds as
follows. Whenever (Tc - T) < 0.5°C in the middle or upper
tropospheric layers, this quantity is arbitrarily set to 0.5°C.
Under a nearly moist adiabatic lapse rate, therefore, Tc - T =
0.5°C at both levels, and the latent heat is partitioned equally
between the upper and lower troposphere. Therefore, latent
heat is released in the column as long as a water vapor supply
from the boundary layer is present.
The value of specific humidity, q, in the boundary
layer, needed for the evaluation of the moisture convergence,
is assumed to be given by
q = mi
nimum <
(0.
90
020
(D.5)
where qs is the saturation specific humidity. The upper
boundary of 0.020 avoids excessive moisture values at points
close to the storm center in the late stages of development
when warm temperatures associated with an "eye" appear.
Finally, the surface humidity and temperature are re-
quired to establish the pseudoadi abat appropriate to parcel
ascent from the surface.
The surface temperature, T*, is computed by a downward
extrapolation from the temperature at level k = 7/2 assuming
a constant lapse rate between the dry and moist adiabatic
rates. The surface specific humidity, q*, is obtained from
q through the assumption that the relative humidity is con-
stant in the boundary layer.
AIR-SEA EXCHANGE OF SENSIBLE HEAT
The sensible heat flux at the air-sea interface is as
sumed to obey the bulk aerodynamic relationship. It is fur-
ther assumed that the heat flux decreases linearly with a
until it reaches a value of zero at the k = 3 level. This
gives
1 gcpcEi \/[ P
■*(T -T*)
v sea '
e*Qk=7/2 =
, T, >T*
sea
T <T*
sea-
CD. 6)
D-7
h7^7;
where
time a
to Cd (0.003)
cussed below.
s the sensible heat added per unit mass and
/ 2 . The exchange coefficient Cf: is taken equal
sea
= 302°K is used for the experiment dis-
INITIAL CONDITIONS
The initial conditions consist of an a xi symmetric vor-
tex in gradient balance. The minimum pressure is 1011 mb and
the environmental pressure on the lateral boundaries is 1015
mb, yielding a maximum gradient wind of 18
of 240 km.
msec
_ i
at a radius
EXPERIMENTAL RESULTS
The history of the cyclone is summarized by figure D-2
which shows the evolution of the minimum surface pressure and
the maximum wind speed in the boundary layer (k = 7/2). Due
P(mb)
1020
MINIMUM SURFACE PRESSURE
1000 -
980 -
960
i i 1
■SYMMETRIC STAGE-
20 40 60 80 100 120 140 160 180 200 220
MAXIMUM SURFACE WIND SPEED
240 260
(a)
r
100 120 140 160
TIME(HOURS)
240 260
(b)
Figure D-2. Time variation of the minimum surface pressure
and the maximum surface wind speed.
D-8
to the
q a n i z a
i ntens
bout 4
mai ns
poi nt ,
mum wi
of the
devel o
f 1 ow r
nents
versio
subs
t i o n a
i f i c a
0 hou
i n a
a se
nd ev
stor
pment
egi on
Fi gu
of th
n of
tanti
1 pha
tion
rs an
quasi
cond
entua
m dur
of p
). T
re D-
e kin
poten
al st
se" o
begi n
d, th
-stea
perio
lly e
ing t
ronou
hese
3 sho
eti c
tial
rength
f only
s. Hu
ereaft
dy sta
d of i
xceeds
his pe
need a
asymme
ws the
energy
to kin
of the initial vortex, a short "or-
12 hours is needed before steady
rricane force winds appear at a-
er, the relatively weak storm re-
te until about 120 hours. At this
ntensi fi cation begins and the maxi-
60 m sec"1. The unsteady nature
riod seems to be related to the
symmetries (especially in the out-
tries are discussed in detail later.
temporal variations of the compo-
budget. The sum of, (1) the con-
etic energy (C(K)), (b) the flux
10
5 -
' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I I I ' I ' I ' I I I ' I ' I i I '
KINETIC ENERGY CHANGE
~ TRUNCATION ERROR
,swg*igacsgBggggw
S5>"
at
ANALYTIC TENDENCY
AK
At
OBSERVED TENDENCY
I , i , i , I i
I I I l
i ■ i ■ i ■ i i i ■ i i i i i i i i
0 12 24 36 48 60 72 84 96 108 120 132 144 156 162 174 186 198 210 222 234 246 258 270
TIME(HOURS)
40 -
20-
<
9
^ -20
-40-
-60
I I i I ' I ' I i I i I i I ' I i I ' I i I ' I i I ' I ' I ' I ' I i I i I XJ ' I i I i
COMPONENTS OF ENERGY BUDGET
■ ■ ■ i.i.
12 24
' ' ' '
I ' I
I ' ' ' , l i I i I i l
-V(mix)
'.'.'.'.'
36 48 60 72 84 96 108 120 132 144 156 162 174 186 192 210 222 234 246 258 270
TIME(HOURS)
Figure D-3. (a) Time variation of the observed kinetic energy
(Lk/Lt) and the change computed from the kinetic energy equa-
tion (dk/dt): (b) Time variation of individual components of
the kinetic energy tendency: C(k) is the conversion of poten-
tial to kinetic energy 3 B(k) is the flow of kinetic energy
through the lateral boundary, H(mix) is the loss of kinetic
energy through lateral eddy viscosity , V(mix) is the^ loss of
kinetic energy through vertical eddy viscosity and includes
the effect of surface drag friction.
D-9
of kinetic energy across the lateral boundary (B(K)), (3) the
dissipation due to lateral mixing (H(mix)), and (4) the dis-
sipation due to vertical mixing (V(mix)) equals the ''analytic"
kinetic energy tendency (3k/9t). Also shown by figure D-3 are
the observed rates of change of kinetic energy (Ak/At). The
difference between 3 k/ 9 1 and Ak/At is a measure of the trun-
cation error and, as figure D-4 shows, this difference is
quite small. Furthermore, the individual components of the
budget are reasonable when compared to empirical estimates
(Hawkins and Rubsam, 1968; Miller, 1962; Pal men and Riehl,
1957; and Riehl and Malkus, 1961).
For purposes of discussion, it is convenient to divide
the history of the storm into two stages. From the initial
instant until about 120 hours, all features are quite sym-
metric with respect to the storm center. During this period,
there is neither evidence of a banded structure in the rain-
fall (analogous to rainbands in real hurricanes) nor does the
20
o
■**
--40
MINIMUM
— r r
RELATIVE VORTICITY
SYMMETRIC STAGE-
T
ASYMMETRIC STAGE
-CORIOLIS PARAMETER ( 5X1Q-3 SEC"*)
ll>
20 40 60 80 100 120 140 160 180 200 220
MAXIMUM TEMPERATURE ANOMALY
240 260
o 5 -
UJ
120 140
TIME (HOURS)
160
260
Figure D-4. (a) Time variation of the minimum relative vorti-
oity in upper troposphere (level lh) ; (b) Time variation of
the maximum temperature anomaly (departure of temperature
from the steady-state value at the lateral boundary ) in the
upper troposphere (level lh) .
D-10
upper tropospheric outflow show any preference for particular
quadrants. We refer to this interval as the "early symmetric
stage." After 120 hours, the upper outflow is quite asymmet-
ric while the rainfall and vertical motions show distinct pat-
terns analogous to the spiral rainbands found in real storms.
We refer to this period as the "asymmetric stage." The "sym-
metric" and "asymmetric" stages refer to the model calculation
only, and, because of the arbitrary nature of the initial con-
ditions, are not meant to have direct counterparts in natural
storms .
EARLY, SYMMETRIC STAGE OF THE MODEL STORM
A representative view of the structure during this per
iod is provided by the data at 84 hours. The region of hur-
ricane force winds is \/ery small, extending only about 75 km
from the center. Gale force winds extend outward to 150 km.
The maximum tangential and radial winds are 34.0 m sec"1 and
-19.4 m sec"1, respectively, yielding an inflow angle of a-
bout 29 degrees .
^h)
The circulation in the upper troposphere (level
shows a fairly symmetric outflow pattern. Cyclonic outflow
occurs inside a radius of about 200 km. Beyond 200 km, the
circulation is anti cycl oni c , reaching a maximum velocity of
about 6 m sec"1 around the outer boundary. The figures are
shown in I.
Dynamic (or inert ial) instability of the upper tropo-
spheric outflow has been suggested by Alaka (1961, 1962, 1963)
and others as a contributory factor in the intensification of
tropical cyclones. An approximate necessary condition for
this instability is given by
(^H
< o
(D.7)
where | V | is the wind speed, R is the radius of curvature of
the streamlines, and ca is the absolute vorticity.
Strictly speaking, this criterion for instability re-
fers to horizontal parcel displacements normal, to a stream-
line and is derived under the assumption that the velocity
and pressure fields are invariant along the streamline. A
D-ll
necessary criterion for a closely related instability is
/8V.
\3r
")GH
< 0
(D.8)
The criterion (D.8) relates to the instability of horizontal
symmetric fluid ring displacement in a symmetric vortex.
A third type of dynamic instability is governed by the
necessary condition that the radial gradient of the absolute
vorticity of the tangential flow have at least one zero. That
is, the condition
_9_
8r
dv
8r
+ f
}••
(D.9)
is satisfied somewhere i.n the fluid system. This is a neces-
sary condition for asymmetric (azimuthally varying) horizontal
perturbations to be unstable.
metri
Since
s t a b i
t i o n .
i n i t i
cl ose
(maxi
appro
like
waves
round
tial
cl ear
is be
eddy
At t
c and
the i
1 i t i e s
On t
al dat
to th
mum of
xima te
pertur
of th
-off d
symmet
that
i n g co
vi scos
he in
tange
n i t i a
do n
he ot
a sin
e cen
an ti
ly 34
b a t i o
is ty
i f fer
ry i s
the i
unter
ity.
i ti al
nti al
1 dat
o t co
her h
ce th
ter o
cycl o
5 km.
ns in
pe ar
ences
reta
nstab
acted
i nst
, (D.
a sat
ntri b
and ,
ere i
f the
ni c r
Th i
the
e pre
, and
i ned
i 1 i ty
by o
ant, wh
7) and
isfy ne
ute to
(D.9) 1
s a max
storm
e 1 a t i v e
s shoul
azimuth
sent in
since,
for the
is e i t
ther ef
en th
(D.8)
i t h e r
the v
s sat
imum
and a
vort
d fav
al di
the
as a
f i rs
her q
fects
e flow i
become
c o n d i t i
ery earl
i s f i e d e
of cyclo
vorti ci
icity) a
or the g
recti on .
initial
1 ready n
t 120 ho
uite we a
such as
s ne
equi
on ,
y in
ven
ni c
ty m
t a
rowt
Si
data
oted
urs ,
k or
tho
arly
val en
these
tensi
in th
vorti
i n i m u
r a d i u
h of
nee w
due
, sub
it i
that
se du
sym-
t.
i n-
f i c a •
e
ci ty
m
s of
wave-
eak
to
s tan-
s
it
e to
Figure D-4 shows the time evolution of the minimum
value of relative vorticity in the upper level within 350 km
of the storm center. During the initial deepening stage the
minimum value of absolute vorticity becomes slightly nega-
tive. However, this occurs after the intensification and
only over a small region.
D-12
The term (2|V|/R + f) was also evaluated for several
times during the first 120 hours. These calculations revealed
only small patches of anomalous winds. We, therefore, also
feel that the instabilities represented by (D.7) and (D.8)
played no significant role in the early symmetric stage of
the model storm.
Azimuthally averaged vertical cross sections provide
an adequate description of the storm structure during the
early symmetric stage. Mean cross sections2 for the tangen-
tial wind, radial wind, and the temperature departure at 84
hours are shown by figure D-5. These cross sections reveal a
structure \/ery typical of that of a weak hurricane (Hawkins
and Rubsam, 1968).
MEAN VERTICAL CROSS SECTION
84 HOURS
TANGENTIAL WIND (M./SEC.)
435
405 435
J I I L
i05 135 165 195 225 255 285 315
RADIUS (KM.)
375 405 435
Figure D-5. Azimuthal mean vertical cross sections for the
tangential wind, the radial wind, and the temperature anom-
aly at 84 hours. Isotherms are labeled in °C; isotachs are
labeled in m sec'1.
The circular averages were computed through linear interpc
lation of gridpoint values to a polar grid with a radial in-
crement of 30 km and an angular increment of 22.5 degrees.
D-13
The vertical
84 hours shows a nea
extends from the cen
about -140 mb hour-1
the center. Weak su
180 km. The stronge
troposphere (level 5
sec" * ) . These val ue
30 km interval of a
conv
the
wi th
cane
ti me
i cal
fall
time
surf
vi de
The
a ma
(Col
shap
wel 1
(Fie
iod
1 ows
deve
a qu
i n w
ly r
The
symm
i n t
a na
ward
outf
beyo
abso
f 1 ow
i n s
pres
lies
comp
ergy
for
The a
e r s i o n o
e q u i v a 1 e
the est
Daisy (
is 5.0
es ti mat
pattern
F i g u r
s along
ace i s o b
an adeq
minimum
x i m u m w i
on, 1963
es of th
with ob
tcher, 1
The e
may be s
. After
1 opment
asi -stea
hi ch the
esembl es
c i r c u 1 a t
e t r i c .
he low 1
rrow ri n
in the
low beco
nd 200 k
1 ute vor
layer i
mall are
sure, te
, rainfa
onents o
budget
a weak h
verage r
f the to
nt water
i mates m
1958).
x ^0lk W
es (Anth
at 84 h
e D-6 sh
one r a d i
ars are
uate des
val ue at
nd of 32
) . The
e profil
s e r v a t i o
955; Mil
arly sym
ummari ze
a short
(about 2
dy state
model s
a weak
ion is n
Air s p i r
evel s , a
g , and f
upper le
mes anti
m. Howe
t i c i ty i
s p o s i t i
as. The
mperatur
1 1 rates
f the ki
are all
u r r i c a n e
motion a
rly circ
ter to a
(about
bsi dence
st upwar
II) and
s appear
weak hur
ai nfal 1
tal rele
depth ,
ade by R
The tota
. This
es and J
ours sho
ows surf
us from
very nea
c r i p t i o n
84 hour
m sec" l
general
es agree
ns
ler, 196
metric p
d as fol
period
4 hours)
is reac
torm clo
h u r r i c a n
early ax
al s i nwa
scends i
lows out
vel s . T
cycl onic
ver, the
n the ou
ve excep
central
e anoma-
, and th
n e t i c en
reasonab
t th
ul ar
bout
0.4
occ
d ve
reac
rea
ri ca
over
ase
i s 6
iehl
1 re
al so
ohns
ws n
e top
regio
180 k
m sec"
u r s in
1 o c i t i
h -230
sonabl
ne (Ca
the i
of lat
5 cm d
and M
1 ease
compa
on, 19
o e v i d
of the
n of u
m. Ma
1 ) occ
the e
es occ
mb ho
e for
rl son
nner 1
ent he
ay"1 w
al kus
of lat
res fa
68) .
ence o
ace pressure pro
the center of th
rly circular, th
of the surface
s (995 mb) is qu
boun
pward
xi mum
ur i n
nvi ro
ur in
ur" 1
avera
and S
00 km
at i n
hi ch
(1961
ent h
vorab
Fi nal
f spi
f i les
e gri
ese p
press
i te r
dary
mot
vel
a r
nmen
the
(abo
ges
heet
, CO
a c
i s c
) fo
eat
ly w
ly,
ral
laye
ion t
0 c i t i
ing n
t bey
mi dd
ut 0.
over
s, 19
mpute
01 umn
ompar
r Hur
at th
i th e
the r
bands
r at
hat
es of
ear
ond
le
7 m
a
71).
d by
to
able
ri -
i s
mpi r-
ain-
for various
d. Since the
rofiles pro-
ure field,
ealistic for
1030
1020
1010
3).
er-
of
>
ned~iooo
se- ™
e . -
Q.
1 "
rd
n
he
t-
t
990
980
970 -
960
"I 1 1 1 1 1 1 1 P
RADIAL PROFILES
OF SURFACE PRESSURE
84 HOURS
156 HOURS
192 HOURS
J 1 1 1 I I ■ I I
100
200 300
R (KM.)
400
500
le
Figure D-6. Radial profiles
of surface pressure along an
east-west axis at 843 1563
and 192 hours.
D-14
ASYMMETRIC STAGE OF THE MODEL
and ma
begi ns
The lo
but sh
maxi mu
extend
averag
i n a h
occurs
about
i s typ
1963) .
As sh
xi mum
a sec
w-1 eve
ows an
m wind
outwa
e angl
In co
i g h 1 y
i n tw
the ma
i c a 1 o
own by th
temperatu
ond perio
1 inflow
i ncrease
speed is
rd to 80
e of i n f 1
ntrast to
asymmetri
o quadran
in center
f many hu
e central press
re anomaly (fig
d of in ten si fie
at 156 hours is
d intensity ove
now 46 m sec"1
km, and gale fo
ow has increase
the symmetric
c fashion (figs
ts, and several
This asymmet
r r i canes (e.g.,
ure, ma
s. D-3
a t i o n a
still
r that
, h u r r i
rce win
d to 38
inflow,
. D-7 a
smal 1
ric nat
Alaka,
ximum w
and D-4
t about
fai rly
at 84 h
cane fo
ds to 2
degree
the ou
nd D-8)
eddies
ure of
1961 ,
i n d speed,
) , the storm
120 hours,
symmetri c ,
ours. The
rce winds
10 km. The
s .
tflow occurs
Outflow
are located
the outflow
1962; Miller,
The vorticity
ative absolute vortic
sec-1. This is in co
hours. These regions
in various sectors of
havior of the outflow
oscillations in the c
during the latter por
is noted that negativ
ture of hurricane out
feature of composite
The presence o
ticity suggests the p
dynamic instability d
Since the condition (
since (D.9) is satisf
able effect, atte^ntio
The quantity, 2|V|/R,
In contrast to the ea
to coy^er substantial
of 2 | V | / R exceed 40 x
winds in hurricane ou
at 1 e
i ty ,
ntras
are
the
i s p
entra
t i o n s
e abs
f 1 ow
mean
f lar
resen
i s c u s
D.8)
i ed i
n was
was
rly s
areas
io-5
tflow
vel 3/2 shows large regions of neg-
with minimum values about -30 x 10~5
t with the vorticity pattern at 84
transient. They form and reform
outflow level. This unsteady be-
robably related closely to the
1 pressure and maximum surface wind
of the computation (fig. D-2). It
olute vorticity is an observed fea-
(Alaka, 1962) and even appears as a
storms ( Izawa , 1 964 ) .
ge va
ce of
sed i
refer
n the
focu
compu
tages
of t
sec
has
_ i
lues of negative absolute vor-
one or more of the types of
n the previous subsection.
s to symmetric instability and
initial data without notice-
sed on the condition (D.7).
ted for level 3/2 at 156 hours.
, anomalous winds are found
he domain and negative values
The presence of anomalous
been documented by Alaka (1961)
The role of dynamic instability in the development of
tropical cyclones has been subjected to prolonged debate and
will not be discussed in detail here. We merely note that
the second period of intensification in this model calcula-
tion appears to be related to the development of areas of
dynamic instability. If we refer to figure D-9, we note that
the minimum vorticity in the outflow layer shows a sudden de-
crease at about 100 hours. The second period of deepening
(as measured by central pressure and maximum winds) follows
this decrease in absolute vorticity by about 20 hours.
D-15
STREAMLINES
LEVEL
156 HOURS
Figure D-7.
Streamline analysis for the upper troposphere
(level lh) at 156 hours.
Coincident with the formation of asymmetries in the
outflow is the appearance of spiral bands of rising motion
which closely resemble hurricane rainbands. The vertical
motion pattern at level 2h (fig- D-9) shows two bands of
upward motion which begin at the edge of the domain and
spiral inward toward the primary ring of upward motion near
the center. The maximum vertical velocity near the center
is -440 mb hour-1 (about 1.5 m sec-1).
The precipitation pattern, shown in figure D-10, re-
sembles a radar picture of a mature hurricane (e.g., Colon,
1962; Colo et al . , 1961). Strong convection occurs near the
center in an irregular circle corresponding to an "eyewall."
D-16
ISOTACHS (M./SEC.) LEVEL lV2
156 HOURS
Figure D-8. Isotaoh analysis for the upper troposphere (level
lh) at 156 hours. Isopheths are labeled in m see-1.
Maximum rainfall rates in this region are over 100 cm day-1.
Two bands of weaker convection spiral in toward the center.
The rainfall rates in the spiral bands are much less than
those near the center of the storm, averaging only about 3
cm day" 1 .
The fact that the spiral bands do not appear in the
model calculation until the symmetry of the outflow pattern
has been destroyed suggests that the generation of the bands
and the breakdown of the outflow pattern may be related. As
we have noted above, the loss of symmetry in the outflow ap-
pears to be associated with dynamic instability. It should
D-17
OMEGA M(CBVHOUR)
LEVEL 3%
156 HOURS
F%gure D-9 .
for level 3-2
of ob hour~ 1
Individual rate of change of pressure ( L^-dp/dt)
at 156 hours. Isophleths are labeled in units
be emphasized, however, that this linkage is merely specula-
tion at this time and will be pursued further when we have
had the opportunity to perform experiments with greater hor-
izontal resolution.
In a recent paper, Anthes (1970) hypothesized that
large scale asymmetries between radii of 400 and 1000 km from
the hurricane center may play an important role in satisfying
the angular momentum budget of the mature hurricane. The mean
radial flux of vorticity may be written
A _
A e v' c' + v,
A A
(D.10)
D-18
RAINFALL RATES
(CM./DAY)
156 HOURS
LEGEND
© 1 < R < 10
© 10 < R < 100
• 100 < R
Figure D-10. Rainfall rates (em day~l) computed from the total
release of latent heat at 156 hours. Isopheths are labeled
in units of cm day-1.
X
where the ( ) operator refers to the azimuthal mean at a
given radius and ( )' refers to departures from this mean.
,. , \ A A
Figure D-ll shows the radial profiles of v 5' and v^ z,
r a r a
computed for the model storm at 192 hours. Both mean and
eddy transports of vorticity are positive inside 200 km. Be-
yond 200 km, however, where the vertical motion is small,
there is a negative correlation between outflow and absolute
vorticity, and the eddy flux \/ery nearly balances the mean
flux from there to the limit of the domain.
D-19
Although the maximum value of v' c' in figure D-ll is
j r a
-70 x 10_lt cm sec-2, which is about half the maximum value
found by Anthes (1970), the qualitative agreement is good.
Figure D-12 shows the azimuthally averaged vertical
cross sections at 156 hours.
circulations are more intense
The temperature section shows
anomaly from 2.5 to 4.1°C and
cold core maximum from -1.5°C
level cold region located between 105 and
has disappeared by 156 hours.
The mean tangential and radial
than at 84 hours (see fig. D-5)
an increase in mean temperature
in the low-level
The weak middle-
225 km at 84 hours
a reduction
to -1 .0°C.
In summary, beginning at
about 100 hours, substantial
areas of negative absolute vor-
ticity appear in the upper
level and the outflow pattern
becomes asymmetric. Rainbands
appear during this asymmetric
stage. The storm is consider-
ably less steady than during
the earlier, symmetric stage,
and the central pressure and
maximum winds oscillate with
a period of about 6 hours.
This unsteady behavior appears
to be related to the transient
behavior of the regions of
negative vorticity in the out-
flow layer.
1000
From
ance of the
hours , more
the time of appear-
asymmetries at 120
or less continuous
deepening occurs until the
storm reaches a maximum inten-
sity at about 2 30 hours (see
fig. D-3) . At this time the
storm corresponds to a strong
hurricane, with a central pres
sure of 963 mb and a maximum
wind speed of 65 m sec-1. The
lapse rate in the inner region
is wery nearly pseudoadi aba ti c
at this time. After 230 hours
the storm begins to slowly
fill and the calculation is
terminated at 260 hours.
-200
J i L
j_
JL.
100
200 300
R(KM.)
Figure
D-ll
X
Azimuthal
and eddy
(v '
r
400
mean
A
500
(vr Ca j r 'a
horizontal vortioity flux in
the upper troposphere (level
lh) at 192 hours.
D-20
MEAN VERTICAL CROSS SECTION — 156 HOURS
TANGENTIAL WIND (M./SEC.)
500 -20
CD
S- 1000
a:
15 45
0
75 105 135 165 195 225 255 285 315 345 375 405 435
RADIAL WIND (M./SEC.)
<
1000
15 45 75 105 135 165 195 225 255 285 315 345 375 405 435
TEMPERATURE DEPARTURE (°C)
1000
15 45 75 105 135 165 195 225 255 285 315 345 375 405 435
RADIUS (KM.)
Figure D-12. Asimuthal mean-vertical cross sections for the
tangential wind, the radial wind, and the temperature anom-
ally at 156 hours. Isotherms are labeled in °C. Isotachs
are labeled in m sec'1.
SUMMARY AND CONCLUSIONS
Preliminary results show that the model is capable of
reproducing many observed features of the three-dimensional
tropical cyclone. Rather realistic simulations of spiral
rainbands and the strongly asymmetric structure of the outflow
are obtained.
Despite a relatively coarse horizontal resolution of
30 km, the model produces a storm with maximum winds exceeding
65 m sec"1 and a kinetic energy budget which compares favor-
ably with empirical estimates.
D-21
In the mature, asymmetric stage of the storm, substan-
tial regions of negative absolute vorticity, anomalous winds,
and dynamic instability are present in the upper troposphere.
There is a suggestion that the breakdown of the early symmetry
of the flow as well as the deepening which takes place during
the asymmetric stage are related to the dynamic instability.
Large scale, horizontal asymmetries in the outflow are found
to play a significant role in the transport of vorticity dur-
ing the mature stage. Beyond 200 km, the eddy transport of
vorticity is opposite in sign and nearly equal in magnitude
to the mean transport.
REFERENCES
Alaka, M. A. (1961): The occurrence of anomalous winds and
their significance. National Hurricane Research Pro-
ject Report No. 45, U.S. Weather Bureau, Washington,
D. C. , June , 25 pp .
Al aka,
M. A. (1962): On the occurrence of dynamic
ity in incipient and developing hurricanes.
Hurricane Research Project Report No. 50, U
Bureau, Washington, D.C., March, pp. 51-56.
i n s t a b i 1 -
National
S. Weather
Alaka
M. A. (1963): Instability aspects of hurricane gene-
sis. National Hurricane Research Project Report No.
64, U.S. Weather Bureau, Washington, D.C., June, 23 pp
Anthes, R. A., and D. R. Johnson (1968): Generation of avail
able potential energy in Hurricane Hilda (1964).
Monthly Weather Review, 96, (5) May, pp. 291-302.
Anthes, R. A. (1970): The role of large-scale asymmetries
and internal mixing in computing meridional circula-
tions associated with steady-state hurricanes.
Monthly Weather Review, 98, (7) July, pp. 521-529.
Anthes, R. A., S. L. Rosenthal, and J. W. Trout (1971): Pre-
liminary results from an asymmetric model of the trop-
ical cyclone. Accepted for publication in the Monthly
Weather Review.
Anthes, R. A., J. W. Trout, and S. L. Rosenthal (1971): Com-
parisons of tropical cyclone simulations with and
without the assumption of circular symmetry. Accepted
for publication in the Monthly Weather Review.
D-22
Carlson, T. C, and R. C. Sheets (1971): Comparison of draft
scale vertical velocities computed from gust probe and
conventional data collected by a DC-6 aircraft. Tech-
nical Memorandum ERLTM-NHRL No. 91, NOAA, U.S. Dept.
of Commerce, Miami, Fla.
Charney, J. G., and A. Eliassen (1964): On the growth of the
hurricane depression. Journal of the Atmospheric
Sciences 3 21 3 (1), January, pp. 68-75.
Colon, J. A., and Staff NHRL (1961): On the structure of
Hurricane Daisy, 1958. National Hurricane Research
Project Report No. 463 U.S. Weather Bureau, Washington,
D.C. , October, 102 pp.
Colon, J. A. (1962): Changes in the eye properties during the
life cycle of tropical hurricanes. National Hurricane
Research Project Report No. 503 U.S. Weather Bureau,
Washington, D.C, March, pp. 341-354.
Col on
J. A. (1963): On the evolution of the wmiu
ing the life cycle of tropical cyclones. N
Hurricane Research Project Report No. 653 U
Bureau, Washington, D.C, November, 36 pp.
wind field dur-
National
S . Weather
Fletcher, R. D. (1955): Computation of maximum surface winds
in hurricanes. Bulletin of the American Meteorologi-
cal Society* 363 (6), June, pp. 247-250.
Grammel tvedt , A. (1969): A survey of finite-difference schemes
for the primative equations. Monthly Weather Review,
97 3 (5) , May, pp. 384-404.
Gray, W. M. (1967): The mutual variation of wind, shear, and
barocl i ni ci ty in the cumulus convective atmosphere of
the hurricane. Monthly Weather Review* 953 (5),
February, pp. 55-73.
Hawkins, H. F., and D. T. Rubsam (1968): Hurricane Hilda,
1963 II: Structure and budgets of the hurricane on
October 1, 1964. Monthly Weather Review* 963 (9),
September, pp. 617-636.
Izawa, T. (1964) : On
Technical Note
Meteorologi cal
March, 19 pp.
the mean wind structure of typhoon
No. 23 Typhoon Research Laboratory
Research Institute, Tokyo, Japan,
D-23
Kuo, H. L. (1965): On formation and intensification of trop-
ical cyclones through latent heat release of cumulus
convection. Journal of the Atmospheric Sciences 3 22,
(1), January, pp. 40-63.
Kurihara, Y., and J. L. Holloway (1967): Numerican integra-
tion of a nine-level global primitive equation model
formulated by the box method. Monthly Weather Review,
95, (8), August, pp. 509-530.
Matsuno, T. (1966): Numerical integrations of the primitive
equations by a simulated backward difference method.
Journal of the Meteorological Society of Japan, 44,
(1), February, pp. 76-83.
Miller, B. I. (1962): On the momentum and energy balance of
Hurricane Helene (1958). National Hurricane Research
Project Report No. 53, U.S. Weather Bureau, Washington,
D.C. , April , 19 pp.
Miller, B. I. (1963): On the filling of tropical cyclones
over land. National Hurricane Research Project Report
No. 66, U.S. Weather Bureau, Washington, D.C, Decem-
ber, 82 pp.
Molenkamp, C. R. (1968): Accuracy of finite difference methods
applied to the advection equation. Journal of Applied
Meteorology, 7, (2), April, pp. 160-167.
Ogura, Y. (1964): Frictionally controlled, thermally driven
circulations in a circular vortex with application to
tropical cyclones. Journal of the Atmospheric Sciences ,
21, (6), November, pp. 610-621.
Ooyama, K. (1969): Numerical simulation of the life cycle of
tropical cyclones. Journal of the Atmospheric Sciences ,
26, (1), January, pp. 3-40.
Palmen, E., and H. Riehl (1957): Budget of angular momentum
and kinetic energy in tropical cyclones. Journal of
Meteorology , 14, (2), March, pp. 150-159.
Phillips, N. A. (1957): A coordinate system having some
special advantages for numerical forecasting. Journal
of Meteorology, 14, (2), April, pp. 184-185.
Richtmyer, R. D. , and K. W. Morton (1967): Difference methods
for i ni ti al -val ue problems. Second edition, Inter-
science, New York, 405 pp.
D-24
Riehl, H., and J. S. Malkus (1961): Some aspects of Hurricane
Daisy, 1958. Tellus, 139 (2), May, pp. 181-213.
Rosenthal, S. L. (1969): Numerical experiments with a multi-
level primitive equation model designed to simulate the
development of tropical cyclones: Experiment I. Tech-
nical Memorandum ERLTM-NHRL No. 82, ESSA, U.S. Dept.
of Commerce, Miami, Fla., January, 33 pp.
Rosenthal, S. L. (1970): A circularly symmetric, primitive
equation model of tropical cyclone development con-
taining an explicit water vapor cycle. Monthly Weather
Review, 98, (9), September, pp. 643-663.
Smagorinsky, J., S. Manabe, and J. L. Holloway, Jr. (1965):
Numerical results from a nine-level general circula-
tion model of the atmosphere. Monthly Weather Review,
93, (12), December, pp. 727-768.
Syono, S., and M. Yamasaki (1966): Stability of symmetrical
motions driven by latent heat release by cumulus con-
vection under the existence of surface friction.
Journal of the Meteorological Society of Japan, Ser. 2,
44, (6), December, pp. 353-375.
Yamasaki, M. (1968a): A tropical cyclone model with param-
eterized vertical partition of released latent heat.
Journal of the Meteorological Society of Japan, 46,
(3), June, pp. 202-214.
Yamasaki, M. (1968b): Detailed analysis of a tropical cyclone
simulated with a 13-layer model. Papers in Meteorology
and Geophysics , 19, (4), December, pp. 559-585.
D-25
APPENDIX E
RESPONSE OF STORMFURY CLOUDLINE CUMULI TO Agl AND
Agl-Nal ICE NUCLEI FROM A SOLUTION-COMBUSTION GENERATOR
Edward E. Hindman, II
Navy Weather Research Facility
Shelden D. Elliott, Jr., and William G. Finnegan
Naval Weapons Center
and
Bradley T. Patton
Research Flight Facility
INTRODUCTION
The existing basis for reducing destructive hurricane
winds has been the seeding of eyewall cumulus clouds with
silver iodide ice nuclei (Simpson and Malkus, 1964; Gentry,
1970). Recent investigations (Woodley, 1970; Gentry, 1971)
suggest that less fully developed cumuli at slightly greater
distances outward from the present eyewall seeding location
may be more responsive to seeding than eyewall cumulus clouds,
The responses of such cumuli to silver iodide seedings were
studied during the 1970 STORMFURY cloudline operation.
In addition, at the suggestion of Naval Weapons Center,
China Lake, California, a special experiment to compare the
effectiveness of two different silver iodide solutions was
conducted during the 1970 STORMFURY cloudline operation. Sil-
ver iodide-sodium iodide-acetone and silver iodide-ammonium
iodide-acetone solutions were burned in the solution-combustion
generator designed by Patton (1970). Vonnegut (1949, 1950)
discovered that combustion products from both solutions were
effective ice nuclei. Recent evidence (Finnegan et al., 1971)
suggests that the sodium solution produces complexed nuclei
(AgI*NaI), and the ammonium solution produces uncomplexed
nuclei (Agl). Laboratory and field evidence (Donnan et al . ,
1970; Auer and Veal, 1970) have shown that this difference
in nucleus structure affects the nucleus activation; the Agl
nuclei become active at -5°C and the Agl'Nal nuclei become
active at -10°C when both nuclei are released in the warmer-
than-f reezi ng regions of cumulus clouds. Furthermore, when
both nuclei are released in clouds at -5°C the Agl nuclei are
the more active.
PROCEDURE
A NOAA-Research Flight Facility (RFF) DC-6 aircraft was
utilized for both seeding the cloudline cumuli and monitoring
the effects of seeding. The NOAA-RFF solution-combustion gen-
erator (Patton, 1970) was used to produce the ice nuclei (see
fig. E-l). The nuclei delivery rate was nearly equivalent to
the rate (~1 g sec"1) of the WMU-2 pyrotechnic flares presently
used in hurricane seedings.
The cloud response to the nuclei was indicated by simul-
taneous in-cloud measurements of vertical motions and liquid-
water contents (LWC) and ice-water contents (IWC). N0AA-
National Hurricane Research Laboratory (NHRL) derived the ver-
tical-motion values from the DC-6 aircraft pitch-angle and
Figure E-l. The NOAA-Besearch Flight Facility solution-
Qombustion ice nuclei generator is pictured mounted on the
NOAA-RFF DC-6 (N85S9C). The seeding solution is contained
in the tank and the solution is burned in the two cylindri-
cal chambers . The resulting ice nuclei exhaust from the
rear of the chambers .
E-2
radio-altimeter data (Carlson and Sheets, 1971). The LWC and
IWC of the precipitation size particles (dia > 200 ym) were
determined by Navy Weather Research Facility (WEARSCHFAC) from
NOAA-NHRL foil inpactor data (Hindman, 1970)(see fig. E-2).
The water contents of the cloud size particles (dia < 200 ym)
can be reduced from simultaneously gathered formvar replicator
data in a manner similar to the analysis of foil impactor data
and will be accomplished at a later data. Results will be de-
scribed in a subsequent report. These results should provide
an important follow-on to previous studies of IWC increases
in cumulus clouds that were attributed to seeding (Todd, 1965;
Sax, 1969; and Weinstein and Takeuchi, 1970).
Figure E-2. The Mete-
orology Research > Inc.;
foil impactor is ■pic-
tured mounted on the
NOAA-RFF DC-6(N8539C) .
The particle impres-
sions from this im-
pactor are analyzed
by Navy Weather Re-
search Facility to
produce liquid-water
and ice-water contents
and liquid and ice
particle size-distri-
bution.
E-3
The water-content values were computed from particle
size-distributions which were reduced from foil impactor data
using a CALMA 302 digitizer, a UNIVAC 1107 computer, and a
Calcomp plotter. The digitizer was used to code particle
sizes and type onto magnetic tapes which were processed on the
computer. The resulting water-contents and size-distributions
were displayed by means of the plotter. The verti cal -motion
values were retrived from data cards provided by NOAA-NHRL.
The procedure of seeding and monitoring 1970 STORMFURY
cloudline cumuli is illustrated in figure E-3. Seeding was
conducted at +5°C in the Cloud I experiment and monitoring
penetrations were made at 0 and -5°C, 14 and 27 minutes after
seeding, respectively. Immediately following the -5°C moni-
toring penetration in Cloud I, seeding was conducted on the
first -5°C penetration of the Cloud II experiment. Subse-
quently, two monitoring penetrations were made through Cloud
II, both at -5°C at intervals of 15 and 30 minutes after seed-
ing, respe.cti vely .
The Agl nuclei were tested on 29 and 30 July, and the
Agl-Nal nuclei were tested on 31 July. The procedure outlined
in figure E-3 was followed on all 3 days. The flight path in
the Cloud I experiment tested the effectiveness of both nuc-
lei when released in the warmer-than-f reezi ng cloud region.
The flight path in the Cloud II experiment tested both nuc-
lei when released in the subcooled region of the clouds.
CLOUD I
cloud n
mlJpt
j&fi/tt/si/f/
Figure E-3. Procedure for seeding and monitoring STORMFURY
oloudline cumuli 3 29 3 30 3 31 July 1970. Seeding was done
at + 5°C in Cloud I and monitoring passes were made at 0°C
and -5°C. Seeding was done on the first pass at -5°C in
Cloud II. Two counter-clockwise monitoring passes then
were made at -5°C in Cloud II. Cloud I tested warm-cloud
release of ice nuclei and Cloud II tested cold-cloud re-
lease of ice nuclei.
E-4
RESULTS
An example of the average liquid and ice particle size-
distributions computed from the foil impactor data gathered in
Cloud I is given in figure E-4. The largest particles were
ice suggesting that ice particle growth by accretion was more
effective than liquid particle growth by coalescence.
Simultaneous foil impactor
were gathered on each penetration
An example of the water-content
and verti cal -motion results
from these data is presented
in figure E-5. The average LWC
and IWC for the precipitation
size particles (dia > 200 ym)
are plotted along with the ver-
ticle-motion values. Positive
water-content deviations indi- ;
cate the precipitation core
within the cloud. The verti-
cal-motion values are studied
to diagnose the extent of the
interaction of cloud dynamical
and micro physical processes.
Similar results from Cloud II
are not presented because the
analysis of these data has not
been completed.
The average LWC and IWC
of the precipitation-size par-
ticles were computed from the
water-content data gathered
during the 0°C and -5°C moni-
toring passes of the Cloud I
experiment on 29 and 31 July.
The values are presented in
table E-l. The IWC was greater
than the LWC on all passes.
All precipitation mea-
surements (total, LWC and IWC)
were considerably larger on
the 29 July Cloud I experiment
than in the 31 July experiment.
and verti cal- mot ion data
of Cloud I on 29 and 31 July.
FLIGHT 700729-A , CLOUD I , PASS 2
INITIAL TIME 160731Z
TEMPERATURE + 1°C ALT 15.000FT
_i>
is
CC
LU
Q.
ce
100r
2 3
iAMETER (mm)
Figure E-4. Liquid and iae par-
ticle size-distribution aver-
aged along the 0°C monitoring
pass of Cloud I, 29 July 1970
are shown. The unknown parti-
ales (u) and small particles
(s) contain both ice and liq-
uid particles but are too small
to differentiate between either
ice or water.
E-5
FLIGHT 7700729-A , CLOUD I , PASS 2
INITIAL TIME 160731Z
TEMPERATURE + 1°C ALT 15.000FT.
Figure E-5. Navy Weather Re-
search Facility water- content
deviations about the average
water-content value are plot-
ted with the simultaneously
observed NOAA-NHEL vertical-
motion values. The data are
from the 0°C monitoring-pass
of Cloud I on 29 July 1970.
The initial time is the time
the aircraft entered the
cloud. The aircraft flew at
100 m sec'1; as a result } 10
sec on the time equals 1 km.
The average LWC and IWC val-
ues are 0.715 and 0.958 g
m~ 3 j respectively .
0 10 20 30 40
TIME FROM INITIAL TIME (sec)
On both days, however, the absolute precipitation amounts
(total, LWC and IWC) at the lower level (0°C) were from five
fold to an order of magnitude greater than at the upper
level (-5°C), and the percentage of liquid content with res-
pect to ice content was greater at the lower level. These
figures indicate that the layer between 0°C and -5°C was an
active precipitation formation region and that the increases
in both the LWC and the IWC between -5°C and 0°C may indicate
significant contributions from both coalescence and accretion
The ratio of the LWC to the IWC at the 0°C level was
approximately the same on both days but was somewhat lower at
the -5°C level for the Agl experiment, suggesting effects of
seeding which will be discussed in more detail.
While these results are quite useful, their re analysis
in conjunction with cloud particle distributions from the
formvar replicator data should contribute to improved under-
standing and improved parameterization of microphysi cal pro-
cesses in numerical simulation models.
E-6
Table E-l. Average Liquid-Water and lee-Water Content
of Precipitation (g m~z).
CLOUD I Experiment*
Test Day Nuclei
0°C
Monitoring Level
-5°C
LWC
IWC LWC/IWC LWC IWC LWC/IWC
2?97(jly AgI °-715 0.958 0.75 0.074 0.188
3197Qly A9I#NaI 0-078 0.106 0.74 0.010 0.022
0.39
0.45
* Cloud II Experiment data not reduced yet
The average vertical motions were computed and the
maximum updrafts were isolated from the verti cal -motion data
gathered on all passes in the Cloud I and Cloud II experi-
ments on 29 and 31 July. The values are presented in table
E-2. The maximum positive verti cal -motion and updrafts for
all passes occurred during the seeding pass and then tapered
off during the monitoring passes.
Table E-2. Observed Average Vertical Motion/Observed
Maximum Updrafts (m sec~l).
Test Day
u c 1 e i
CLOUD I
Experiment
Seed Monitor
+5°C 0°C -5°C
CLOUD II
Seed
-5°C -5°C
Mom* tor
-5°C
29 July
1970
31 July
1970
AgI
Agl-Nal
3.0/
9.3
1.5/
7.5
0.5/
3.5
0.7/
5.2
1 .0/
4.0
0.2/
2.5
1 .0/
6.2
2.7/
8.2
0.3/
2.6
2.7/
5.7
0.8/
4.0
■0.3/
2.1
DISCUSSION
E-7
aircraft reached the 0° and -5° levels 14 and 27 minutes after
seeding, respectively. Hence, it is likely that most of the
seeding material had been carried up and through these levels
prior to the aircraft penetration.
Th
have been
The media
observed
cles were
minutes i
LWC) (Hin
ci ty af te
than the
from the
Agl nucl e
passed -5
ice parti
the time
e preci
observ
n mass
at -5°C
e s t i m a
n the o
dman an
r 17 mi
updraf t
rising
i are a
°C, the
cles is
it took
p i t a t i
ed at
di a met
was a
ted to
bserve
d John
nutes
, thus
s e e d i n
c t i v a t
n the
7 mi n
the a
on resu
the -5°
er of t
pproxi m
grow f
d i n - c 1
son , 1 9
of grow
permi t
g regio
e d in 3
total t
+ 3 mi
i r c r a f t
1 ti ng
C 1 eve
he i ce
ately
r o m i c
oud co
70).
th was
ting t
n. As
m i n u t
ime fr
n + 17
to re
from seed
1 in Clou
preci pi t
1.5 mm .
e nuclei
n d i t i o n s
The parti
estimate
he p a r t i c
suming th
es after
o m s e e d i n
min = 27
ach the -
i ng , however , may
d I on 29 July,
ati on parti cl es
These ice parti-
to 1.5 mm in 17
(-5°C, 1 g m"3
cles' fa 1 1 vel o-
d to be faster
les to settle
at a majority of
the seeded region
g to grow 1 . 5 mm
minutes which is
5°C level .
The LWC/IWC ratio illustrated in table E-l shows that
the 0°C passes in Cloud I on 29 and 31 July had similar LWC/
IWC ratios. The -5°C passes, however (which presumably mea-
sure the seeding effects on the precipitation), had a lower
ratio on the 29th (0.39) than on the 31st (0.45). The higher
relative ice content of the Agl-seeded cloud (29th) at -5°C
compared to that of the Agl »NaI-seeded cloud (31st) suggests
that the aircraft may have intercepted the ice precipitation
particles settling from the region of the cloud affected by
the Agl .
Random interpretation error of approximately ±19 per-
cent has been estimated when differentiating between ice and
water particle impressions from the foil sampler. The dif-
ference in the LWC/IWC ratio is slightly greater than the
possible random error, therefore the difference is considered
real .
settl
woul d
-10°C
the -
and t
that
serve
regi o
becau
falli
the o
It w
i n g f r
be in
and p
5°C le
he mon
preci p
d on r
n. Th
se a 4
ng fro
bserva
oul d
om th
terce
robab
vel i
i tori
i t a t i
adar
i s re
m se
m the
ti on
not be expected that the ice precipitation
e region of Cloud I affected by the Agl-Nal
pted. These particles formed at and below
ly did not overcome the updraft to reach
n the 27-minute interval between seeding
ng passes. Simpson (1970) recently showed
on assumed to result from seeding was ob-
within 10 minutes at 6 km below the seeded
markably short period of time was possible
c-1 downdraft assisted the precipitation in
formation level (6-7 km above cloud base) to
level (1 km above cloud base).
E-8
Significant decreases in the average vertical motion
after seeding were measured in both the Agl and Agl-Nal ex-
periments in Cloud II (see table E-2). An unexpected reduc-
tion was registered in the Agl-seeded cloud on the first
monitoring pass followed by a restoration trend on the second
monitoring pass. In contrast, the Agl «NaI-seeded cloud showed
a slight decrease during the first monitoring pass but a more
significant reduction during the second monitoring pass.
Admittedly the vertical motion values constitute a
limited sample and the magnitudes are near the data's noise
level. If these observations are considered somewhat credi-
ble, they still present a paradox and suggest certain weaknes-
ses in current parcel and bubble theories of convection. The
theories may not adequately explain the paradoxical decrease
in updrafts following seeding. A more rigorous application
of the hydrodynamic and thermodynamic equations integrated
with a more realistic mi crophys i cal parameterization may be
required for adequate simulation of cumulus convective pro-
cesses. Such a formulation is currently being considered at
WEARSCHFAC which would explain the sequence of events in the
Cloud II experiments according to the suggested processes
bel ow.
vel oci
f i c i a 1
in u p d
effect
updraf
i ncrea
this r
of the
the se
active
drafts
the fi
gan to
updraf
rel eas
higher
are 1 e
drafts
of val
For
ties
nucl
rafts
s of
ts in
sing
e g i o n
late
e d i n g
at -
woul
rs t m
dimi
ts in
e of
1 eve
ss ac
woul
ues s
both
were
e i in
foil
s e e d i
and
the s
. In
nt he
and
5°C.
d be
oni to
ni sh
creas
the 1
Is th
ti ve
d be
hown
s e e d i
measu
creas
owi ng
ng de
above
tabil
the
at of
s e n s i
Henc
n o t i c
ring
by th
ed.
atent
an in
than
del ay
in th
ngs l n
red bel
ed natu
these
crease
the in
i ty and
Agl exp
fusion
ng leve
e the s
ed rath
penetra
e time
In the
heat o
the Ag
the Agl
e d , w h i
e CI oud
Cloud
ow th
ral g
seedi
the s
creas
supp
eri me
woul
1 s be
uppre
er qu
t i o n ,
of th
Agl -N
f fus
I exp
nucl
ch is
II e
II,
e reg
1 a c i a
ngs s
tabil
ed gl
res si
nt th
d tak
cause
s s i n g
i c k 1 y
and
e sec
al ex
ion w
eri me
ei .
cons
x p e r i
the av
ion in
tion .
uggest
i ty an
a c i a t i
ng the
e i n c r
e pi ac
these
ef fee
Sue
perhap
ond pa
peri me
oul d t
nt bee
The i m
i stent
ment i
erage
whi c
The
that
d i nc
on re
updr
eased
e di r
nucl
ts on
h was
s the
ss be
nt , t
ake p
ause
pact
with
n tab
v e r t i
h the
decrea
the i
rease
gi on w
afts b
rel ea
ectly
ei bee
the u
the c
ef fee
cause
he i n c
1 ace a
the Ag
on the
the t
le E-2
cal
a r t i -
ses
n i t i a 1
the
hile
el ow
se
above
ome
P-
ase on
t be-
the
reased
t
I-Nal
up-
rend
These processes suggest the following cycle of events
which may occur after a cumulus cloud is seeded:
a. The seeding material will be carried upward with
increased glaciation taking place at the level
according to the activation of the seeding material
E-9
and will be followed by increased condensation
and increased precipitation.
b. Initially, the increased release of latent heat
will augment the updrafts in and above the in-
creased glaciation level and suppress updrafts
bel ow this 1 eve! .
c. Subsequently, the net effect of the whole process
will warm the cloud core as well as create a
divergent outflow in the upper levels. The
warming and outflow will decrease the surface
pressure which will cause an increased inflow at
the lower levels and produce a general increase
in upward motion throughout the cloud.
This cycle suggests prospects of developing a ration-
ale for increasing cloud growth by successive pulsed seedings
Empirical evidence compiled by St. Amand (1969) indicates
that pulsed seedings may increase cloud growth and merge in-
dividual clouds into cloud systems. While the cycle is not
properly reflected in current simple cloud models, its phys-
ical reasoning is qualitatively consistent.
1 ce
figu
were
Matt
crea
gl ac
clou
than
grow
woul
The
beca
1 eve
1 eve
An
nuclei
re E-6
s i m u 1
hews i
se to
iate a
d seed
6.3 k
to ro
d i ncr
cl oud
use th
1 . Th
1 i t w
advan
rath
. II
ated
n thi
zero
t -25
ed wi
m. T
ughly
ease
seede
ese n
is gl
oul d
tage
er th
1 ustr
wi th
s rep
at 6.
°C, i
th Ag
he cl
the
na tur
d wit
ucl ei
a c i a t
have
of gl
an Ag
ated
a num
ort (
3 km
n d i c a
I-Nal
oud r
-10°C
al gl
h Agl
i ncr
ion b
grown
aci ati
I-Nal
are cl
e r i c a 1
app . H
for th
ting a
ice n
eached
1 evel
a c i a t i
ice n
eased
oosted
to na
ng tr
ice n
oud v
cumu
)• T
e nat
cl ou
u c 1 e i
the
befo
on an
u c 1 e i
natur
the
tural
0 p i c a 1
u c 1 e i i
erti cal
1 us mod
he vert
ural cl
d top a
also d
-6°C le
re the
d incre
, howev
al gl ac
cloud p
cumul
s ill
moti
el de
i cal
oud a
t 6.3
i d no
vel b
Agl-N
ase c
er, g
i a t i o
as t t
i wit
ustra
ons t
scrib
moti o
ssume
km .
t gro
ut ne
al i c
1 oud
rew t
n at
he 6.
h Agl
ted in
hat
ed by
ns de-
d to
The
w more
eded to
e nuclei
growth .
o 1 1 km
the -5°C
3 km
CONCLUSIONS
Ice-water content data and verti cal -motion data from
two cloudline cumuli seeded with Agl ice nuclei tentatively
indicate that the cumuli began to glaciate at approximately
-5°C. Similar data from two other cloudline cumuli seeded
with Agl'Nal indicate that the cumuli began to glaciate at
a colder temperature, possibly -10°C. These tentative con-
clusions are in agreement with previous laboratory results
E-10
Donnan et al . (1970) and field
results of Auer and Veal (1970).
This agreement suggests that
given a choice of acetone solu-
tions to burn in a solution-
combustion generator, the Ag I -
NH4-acetone solution would be
the choice if glaciation at
temperatures near -5°C is de-
sired.
Vertical- motion data from
two cloudline cumuli seeded and
monitored at the -5°C level sug-
gest that the initial effects of
seeding may have suppressed the
updrafts below the regions of
increased glaciation and heating
Further testing, however,
is needed to confirm these pre-
liminary conclusions. The ex-
tremely limited number of seeded
clouds prevented a statistically
significant sample. Furthermore
the lack of control clouds pre-
vented objective comparisons
of the seeded clouds with those
developing naturally.
The operational data
gathered from the NOAA-RFF
solution-combustion generator
indicated that the device can
be used routinely to seed
STORMFURY cloudline cumuli.
Figure E-
on updr
aloud i
onment 3
Matthew
dimensi
Cloud b
sumed t
pheric
aloud g
was fro
sure re
6. Effect
afts in a
n a hurrio
as simula
s (1971) u
onal oumul
ase diamet
o be 3 km.
sounding >
rowth was
m the 996-
gion of a
of seeding
cumulus
ane envir-
ted by
sing a one-
us model,
er was as-
The atmos-
from which
simulated^
999 mb pres-
hurricane .
E
UJ
>
LU
-I
<
LU
(/)
LU
>
O
CD
<
I
CD
LU
I
I
Ag I SEEDING
(Active at
-5C )
- -35
- -30
-25
-20
-15
NATURAL SEEDING
(Active at - 25 C )
Agl Nal SEEDING
(Active of -IOC )
J I I L
io L
LU
CE
h-
<
5 *
J LU
a.
LU
I-
LU
15
20
5 10
W ( m sec"1)
o
LU
E-ll
RECOMMENDATIONS
1 . C o n c 1 u s i
STORMFURY cloudline
by the prel i mi nary n
experiments should b
tial effect of seedi
pression of updrafts
2. The need
i ng and moni tori ng p
above the seeding le
3. The diff
rapid succession and
indicates the desira
within the core and
the seeded updraft.
2-32 sai 1 pi ane ( Schr
requi rements . This
of the rising air an
Resul ts from such f 1
seeding is glaciatin
vide a measure of th
tions. These result
provement in the par
numerical cloud mode
ons derived from
data presented i n
ature of the expe
e more extensive
ng tropical cloud
the evaluation of 1970
the report are limited
ri merits. Subsequent
to determine if the ini
line cumuli is the sup-
for s
asses
vel su
i cul ty
moni t
bil i ty
rise a
The c
i bner ,
a i rcra
d cont
i g h t s
g the
e ef fe
s shou
ame ter
Is.
horte
and t
ggest
i n e
0 r i n g
of h
t app
loud
1966
ft wo
i n u o u
woul d
avail
cts o
1 d co
i z a t i
r time
he nee
a dua
xecut i
passe
avi ng
roxi ma
physi c
) i s s
ul d be
sly mo
i 1 1 u s
able s
f seed
n t r i b u
on of
-sepa
d for
1 -air
ng mo
s abo
an ai
tely
s ins
ui ted
abl e
ni tor
trate
uperc
i ng o
te to
seedi
rati o
moni
craft
n i t o r
ve th
rcraf
the s
trume
for
to s
the
how
ool ed
n ver
a mu
ng ef
n bet
t o r i n
expe
i ng p
e see
t tha
ame s
nted
these
eed t
seedi
thoro
wate
t i c a 1
ch ne
fects
ween
g pas
r i m e n
asses
ding
t can
peed
NCAR
flig
he co
ng ef
ughly
r and
acce
eded
i n
seed-
ses
t.
i n
1 evel
stay
as
SGS
ht
re
fects
the
pro-
1 era-
i m-
REFERENCES
Auer, A. H., Jr. and D. Veal (1970): Evaluation of cloud
seeding devices in an outdoor laboratory. Project
Report, Naval Weapons Center Contract N6 600 1- 70-C-O 639
November, (on file, Naval Weapons Center (code 602),
China Lake, California).
Carlson, T. N., and R. C. Sheets (1971): Comparison of draft
scale vertical velocities computed from gust probe
and conventional data collected by a DC-6 aircraft.
Technical Memorandum ERLTM-NHRL No. 91, NOAA, Dept.
of Commerce, NHRL, Miami, Fla.
Donnan, J. A., D. N. Blair, W. G. Finnegan and P. St. Amand
(1970): Nucleation efficiencies of A g I - N H4 1 and A g I •
Nai-Acetone solutions and pyrotechnic generators as
a function of LWC and generator flame temperature.
A Preliminary Report. The Journal of Weather Modifi-
cation, 2, pp. 155-164.
E-12
Finnegan, W. G., P. St. Amand and L. A. Burkardt (1971): An
evaluation of ice nuclei generator systems. Submitted
to Science .
Gentry, R. C. (1970): Hurricane Debbie modification experi-
ments, August 1969. Science, 164, pp. 473-475.
Gentry, R. C. (1971): Progress on hurricane modification
research-October 1969 to October 1970. Presented at
Twelfth Interagency Conference on Weather Modification ,
October 28-30, Virginia Beach, Va.
Hindman, E. E., II (1970): Cloud particle samples and water
contents from a 1969 STORMFURY cloudline cumulus.
Project STORMFURY Annual Report 1969, U.S. Dept. of
Navy and U.S. Dept. of Commerce, Appendix F.
Hindman, E. E., II and D. B. Johnson (1970): Numerical simu-
lation of ice hydrometeor development. Preprints -
Conference on Cloud Physics. American Meteorological
Society, Boston, Mass., pp. 63-64.
Patton, B. T. (1970): Preliminary report on the Patton mark
series generators. On file at N0AA-RFF, Miami, Fla.,
5 pp.
Sax, R. I. (1969): The importance of natural glaciation of
the modification of tropical maritime cumuli by silver
iodide seeding. Journal of Applied Meteorology , 8,
pp. 92-104.
Schribner, K. (1966): The explorer. Journal Soaring Society
of America, pp. 12-13.
Simpson, J. (1970): On the radar-measured increase in precip-
itation within ten minutes following seeding. Journal
of Applied Meteorology , 9, pp. '318-320.
Simpson, R. H., and J. S. Malkus (1964): Experiments in hur-
ricane modification. Scientific American, 211, p. 27.
St. Amand, P. (1969): Weather modification techniques devel-
opment. Appears in "A Summary of the U.S. Navy Pro-
gram and FY - 1 969 Progress in Weather Modification and
Control." WEARSCHFAC Technical Paper No. 26-69, pp.
38-39.
Todd, C. J. (1965): Ice crystal development in a seeded cum-
ulus cloud. Journal of Atmospheric Science, 4, pp. 70-78
E-13
Vonnegut, B. (1949): Nucleation of supercooled water clouds
by silver iodide smokes. Chemical Review, 44, pp. 277'
289.
Vonnegut, B. (1950): Techniques for generating silver iodide
smoke. Journal of Colloid. Sciences 3 S3 p. 377.
Weinstein, A. I., and D. M. Takeuchi (1970): Observation of
ice crystals in a cumulus cloud seeded by vertical-
fall pyrotechnics. Journal of Applied Meteorology , 93
pp. 265-268.
Woodley, W. L. (1970): Precipitation results from a pyrotech
nic cumulus seeding experiment. Journal of Applied
Meteorology 3 93 pp. 242-257.
E-14
APPENDIX F
MEASUREMENTS OF VERTICAL MOTION IN THE EYEWALL
CLOUD REGION OF HURRICANE DEBBIE
Toby N . Carl son
National Hurricane Research Laboratory
INTRODUCTION
Vertical motions on a cumulus cloud scale (1 to 100 km)
can be estimated using various parameters recorded by the RFF
DC-6 aircraft (Carlson and Sheets, 1971). The formula used
to obtain the drift scale vertical velocity, W, is
W = V+ (a.
) + W,
(F.l)
where V. is the true air speed, a, and 0. are the angle of
attack and pitch angle of the aircraft with respect to the
equilibrium values of these angles, and Wp is the aircraft
vertical velocity. In the DC-6 aircraft, the latter is de-
termined by differentiating the radio-altimeter values to
give change in aircraft height with time. The true airspeed
and pitch angle are directly measured; the equilibrium value
of the pitch angle must be continuously determined since it
is found to drift slowly with time.
The equilibrium pitch angle
suming that the mean vertical moti
straight line pass is zero for sho
clouds; in longer passes, such as
through hurricanes, it is assumed
over a longer interval, L, (-50 to
is thereby determined at the mid-p
length L which will be shorter tha
Inspection of the vertical motion
vertical velocity averaged over L
case the zero vertical velocity ax
eye; for example, if the values fa
undisturbed environment of a cumul
of the hurricane eye. The angle o
but is computed indirectly from th
aircraft lift. In practice during
» oe ,
on thr
rt pas
strai g
that W
75 mi
oi nt o
n the
trace
need n
is sho
il to
us cl o
f atta
e equa
fligh
is deter
oughout
ses thro
h t line
is zero
1 es ) ; a
f a slid
length o
may indi
ot be ze
uld be a
approach
u d or in
c k is no
t i o n of
ts in hu
mi ned
a give
ugh cu
radi al
when
v a r i a b
i n g s c
f the
cate t
ro , in
d juste
zero
the c
t meas
moti on
r r i c a n
by as-
n
mul us
legs
averaged
le 9e
ale of
pass .
hat the
which
d by
i n the
enter
ured
for
es ,
the basic 1 sec digital values are converted to a 6 sec block
average in order to minimize noise in the data. For cumulus
clouds, a weighted 4 sec (binomially smoothed) running mean
is used.
PROFILE OF VERTICAL MOTION IN HURRICANE DEBBIE (1969)
The draft scale vertical motion computations were de-
termined for all radial legs in Hurricane Debbie on 18 and 20
August 1969, by the 39 - C DC-6 aircraft which was the only
aircraft capable of making such measurements on those occa-
sions. Of the 10 radial penetrations made on the 20th, and
of seven made on the 18th by this aircraft a total of eight
and five passes, respectively, were made along a southwest-
northeast azimuth. Most of the penetrations began and ended
about 70 km from the center and all of them penetrated both
of the eyewalls and the inner clear region of the eye.
showe
pass
a r r i v
m o t i o
meti c
and t
eye w
ai rcr
clear
regi o
compo
eight
(The
and i
Exa
d tha
due t
e at
n pro
ally
he fi
as av
aft i
eye.
n i n
si te
or f
inner
s not
m i n a t i
t ther
o the
a comp
f i 1 es
averag
ve pas
eraged
nto (o
Exce
f i gure
prof i 1
ive po
p o r t i
shown
on of th
e was co
rapidly
osite pi
for the
ed toget
ses on t
with re
r from)
pt for t
F-l whe
es of ve
i nts , re
on of th
here . )
e i rid i
nsi der
s h i f t i
cture
southw
her fo
he 18t
s p e c t
the ey
he out
re the
r t i c a 1
s p e c t i
e clea
v i d u a 1 v
able var
ng echo
for the
es t-nort
r the e i
h . Each
to the p
ewall cl
er porti
re were
moti on
vely, fo
r eye wa
ertical mo
i a b i 1 i ty f
patterns .
storm, the
heast legs
ght passes
radial 1 e
oi nt of en
oud from (
ons of the
fewer obse
represent
r the 20th
s compos it
tion
rom p
In o
vert
were
on t
g fro
try o
or i n
eyew
r v a t i
an av
and
ed se
prof i 1 es
ass to
rder to
i cal
ari th-
he 20th
m the
f the
to) the
all cl oud
ons , the
erage of
18th.
parately
doma
whi c
near
i nsi
regi
the
deep
maxi
sect
ing
vert
pass
Bot
in of
hiss
ly neu
de the
on . T
same o
ened a
mum as
or) , w
annul u
i cal m
e s w h i
h pro
r i s i n
urrou
tral )
eye)
he st
n the
pprec
cent
hi 1 e
s was
o t i o n
ch sp
files
g mo t
nded
vert
and
rengt
18th
i ably
was 2
the m
abou
meas
anned
show s
ion is
by a mo
ical mo
al so on
h of th
as on
in the
-3 m se
e a n r i s
t 1 m s
urement
only a
ome si
found
re nar
tion n
the o
e updr
the 20
i nter
c"1 (s
ing mo
ec" 1 o
s were
few h
milarity in that a broad
in the eyewall cloud region
row ring of descending (or
ear the eyewall (and just
uter edges of the wall cloud
afts appeared to be about
th, although the storm had
val. In figure F-l, the
trongest in the southwest
tion averaged over the ris-
n both days. Because the
made from a series of
ours, it is difficult to
F-2
VERTICAL VELOCITY (DEBBIE, 1969)
b 2.0
LU
in
o
tr»-
>o
_j
>
0.0
2.0
Aug 18
WIDTH OF EYE
Aug 18
sAug 20
WIDTH OF EYE
Aug 20
_L
1
-L
_L
I
_L
J_
_L
2.0
0.0
•2.0
60 40 20 0 20 40 60
NE DISTANCE FROM EYE CENTER (KM.) SW
Figure F-l. Composited vertical velocity profile for Hurri-
cane Debbie as determined from the RFF 39-C DC-6 aircraft .
The profile represents an average of 8 radial legs on 20
August 19693 and 5 radial legs on 18 August^ which were on a
northeast-southwest azimuth . Compositing was done with
respect to the inner face of the eyewall cloudy the mean
positions of which are indicated by the width of the eye.
assess the effects of seeding on the updraft profile in Hur-
ricane Debbie. The composite profiles, however, demonstrate
the possible use of vertical motions in evaluating seeding
experiments (see app. E in this report).
ACCURACY OF THE VERTICAL MOTIONS
Carlson and Sheets (1971) have discussed deficiencies
in the measurement of draft scale vertical motion and the ac-
curacy of the calculations, based on a comparison with simul-
taneous measurements made with the RFF gust probe system in
a series of test passes through individual cumulus clouds.
Their results indicate that the measurement accuracy depends
on the scale in question and on the intensity of the turbulent
motions (the variance of W). Reliability of the measurements
is considered to be greatest for updrafts on the scale of the
cumulus cloud (1 to 10 km) and for strong vertical motions.
F-3
But f
decre
A pos
exist
0.5 m
ing i
i n a
the d
the a
per s
1 ar u
weake
litud
air w
less,
even
this
(fig.
fore ,
downd
in an
or scales
ases rapi
s i b 1 e n o i
with a f
sec- * .
ntens i ty
p a r t i c u 1 a
raft , and
mpl i tude
econd. C
pdraft or
r v e r t i c a
e of the
here the
A minim
in clear
order. I
F-l ) , th
the magn
rafts may
i n d i v i d u
of mo
d 1 y w i
se f re
requen
Absol u
of the
r draf
the u
val ue
onvers
downd
1 moti
moti on
maxi mu
urn unc
air w h
n comp
e n o i s
i tude
have
al pas
tion
th de
quenc
cy of
te er
vert
t pro
ncert
when
ely ,
raft
ons a
s the
m dra
ertai
ere t
o s i t e
e may
of th
more
s .
a kilome
creasing
y (that
5-10 se
rors app
ical mot
file dec
ainty is
the peak
the perc
prof i 1 e
nd may b
msel ves
ft speed
nty of 0
he verti
s such a
be cane
e broad
s i g n i f i c
ter o
wave
of ai
c and
ear t
ions,
rease
prob
val u
entag
decre
ecome
i n we
s are
.4-0.
cal v
s the
el ed
prof i
ance
r 1 es
1 engt
rcraf
an a
o i nc
but
s wit
ably
e exc
e err
ases
comp
ak cu
a me
8ms
e 1 o c i
one
to so
le of
than
s , th
h of
t osc
mpl i t
rease
the p
h the
a sma
eeds
or fo
with
arabl
mul us
ter p
ec" l
ty va
s hown
me ex
updr
i t wo
e uncert
the updr
illation
ude of a
with in
ercent e
a m p 1 i t u
11 fract
a few me
r a part
i ncreasi
e to the
or in c
er secon
may be p
r i a n c e i
for Deb
tent ; th
afts and
ul d have
ai nty
aft.
) may
bout
creas-
rro r
de of
ion of
ters
i cu-
ngly
amp-
1 ear
dor
resent
s of
bi e
ere-
had
V
turns an
brought
For that
i ty only
s tan t 1 e
kept to
are nece
cumul us
detri men
critical
ting c h a
silver i
In the f
ai rcraf t
vertical
known .
e r t i c
d dur
about
reas
i n s
vel w
a mi n
s s a r i
updra
tal t
i n d
nges
o d i d e
uture
wh i c
vel o
al motio
ing sign
by the
on the c
trai ght
here the
i m u m . 0
ly made
fts of t
o the me
e t e r m i n i
are also
burner
, an ang
h will h
city sin
ns are a
i f i c a n t
pilot at
a 1 c u 1 a t i
line (or
power s
c c a s i o n a
by the p
he eyewa
asuremen
ng the b
made du
is opera
1 e of at
opef ul ly
ce , at p
1 so adve
changes
tempti ng
ons are
radial )
e 1 1 i n g c
I power
i 1 o t in
I I cl oud
ts but a
asic dra
ring c 1 o
ted on b
tack van
i mprove
resent ,
rsely
in ai
to c
felt
pass
hange
s e 1 1 i
penet
of a
re no
ft pr
ud se
oard
e wi 1
the
aj i s
affected
rcraft al
limb or d
to have s
es flown
s by the
ng change
rati ng i n
h u r r i c a n
t c o n s i d e
ofile. P
e d i n g run
the DC-6
1 be moun
measureme
not accu
by sharp
t i t u d e
escend .
ome val i d-
at a con-
pilot are
s , which
tense
e , are
red to be
ower set-
s when the
aircraft,
ted on the
nts of
rately
REFERENCE
Carlson, T. N., and R. C. Sheets (1971): Comparison of draft
scale vertical velocities computed from gust probe and
conventional data collected by a DC-6 aircraft. Tech-
nical Memorandum ERLTM-NHRL No. 91, NOAA, Dept. of
Commerce, NHRL, Miami, Fla.
F-4
APPENDIX G
AN ESTIMATE OF THE FRACTION ICE IN TROPICAL STORMS
W. D. Scott and C. K. Dossett
National Hurricane Research Laboratory
INTRODUCTION
With the present concept of the modification of tropi-
cal storms, a considerable amount of supercooled water must
exist above the freezing level in the storm cloud system.
This thinking precludes modification of the storm if the
supercooled water has already frozen and turned to ice. Hence,
an estimate of the ice content of the clouds at levels between
0° and -20°C would help us assess the probability of being
able to modify the storm, and, perhaps, give an a posteriori
judgment on the success of a seeding mission.
We currently have acquired three instruments that
should give an estimate of ice concentration during a flight
into a storm. These are the foil impactor, the continuous
particle replicator, and the ice particle counter. The foil
impactor has been described in previous STORMFURY Reports
(see Sheets, 1969; Hindman, 1970) and some data from the cloud-
line experiments are presented in this report by Hindman (app.
E). The particles are impacted on a strip of aluminum foil
and the size and character of the particles are derived from
the impressions they make.
The ice particle counter was recently acq
a contract with Mee Industries, Altadena, Califo
an optical technique which measures the scintill
"twinkles" ice crystals make when they reflect 1
secular faces. It is now undergoing calibration
preliminary test results indicate that it can co
tides in real time with a 75 percent or better
even in the worst case when large water drops ar
the sampl e .
The continuous particle (formvar) replica
vice which captures cloud particles (i.e., dropl
and ice crystals) and forms plastic replicas of
mm motion picture film. The device currently in
was also manufactured by Mee Industries. Its es
tures are nearly identical to the instrument man
uired through
rnia. It uses
a t i o n s or
ight off their
tests , but
unt ice par-
rel i abi 1 i ty
e present in
tor is a d e -
ets , rai ndrops
them on a 16-
operation
sential fea-
ufactured by
Meteorology Research, Inc., and described by Sheets (1969);
the instrument and its basic principles have been used for
years, and several different versions of it are presently
being used (see for example: MacCready and Todd, 1964;
Spyers-Duran and Braham, 1967; Ruskin, 1967; Patrick and
Gagin, 1971). It has several deficiencies, but it does seem
reasonable that the instrument can be used to obtain a sub-
jective estimate of the fraction ice in clouds, i.e., that
fraction of the total hydrometeor population considered to be
ice. With the continued operation of the instrument in hur-
ricanes and tropical storms, a large quantity of in-cloud
data has been amassed. In this report some of the more recent
data are considered, and the fraction ice at different levels
in these storms estimated.
THE FLIGHT TRACKS
The aircraft flight tracks on which the data were
taken are presented in figures G-la, G-lb, and G-lc and are
represented by arrows. On figures G-la and G-lb the orienta
tion and the relative locations of the clouds are preserved;
STORM INGA
FLIGHT 690930B
//
CLOUD CENTER
~ 60 N M
NE of Storm
Center
% IC E
l.lln
HYDROMETEOR /^f/
COVERAGE
jL ill llllllllllll llllllllLll,„,Lll llLyl !Hnl uljlLJ LlillllL
/mdtAgt/mdt/ /mdt/mdt/mdt/ /mdwvv /lgt
(See text for on explanation of
Symbols)
CLOUD CENTER S
~ 20 N.M
N of Storm Center
25
SCALE ( N M )
50
STORM FELICE
ALT 18,000
TEMP -0 3°to-1.2°C
FLIGHT TRACK
~70 N M
NE of Storm Center
Figure G-la. Sampling locations in Tropical Storms "Inga"
and "Fe lice . "
G-2
STORM : TD# 14
FLIGHT^ 701002A
X
CLOUD CENTER
150 N.M. E
from Storm Center
(See text for meaning
of Symbols)
CLOUD CENTER
~150 N.M. from
Storm Center
oh
25
SCALE (N.M.)
50
Figure G-lb. Sampling locations in Tropical Depression
Number 14.
G-3
STORM: TD*14
FLIGHT: 701003A
(See text for explanation
of symbols)
CLOUD CENTER
~10N.M
E. of Storm
Center
CLOUD CENTER
~90N.M.
NE of Storm
Center
22222
% ICE
ooooooou-
COVERAGE
LGT MDT
25
SCALE (N M.)
50
Figure G-lo. Sampling locations for Tropical Depression
Number 14.
on figure G-lc the two clouds were slightly farther apart
than is shown. The cloudy shapes represent the approximate
extent of visible cloudiness, and the crosshatched area on
figure G-la is the area where a significant radar echo was ob-
served. The scale is constant on all the figures; altitudes,
temperatures, and the relationship of each cloud to the storm
center are indicated.
G-4
A summary of all the results is shown in figure G-2.
At the time the data were taken Tropical Storm Inga was in-
creasing in intensity and had just produced hurricane-force
winds. "Felice" appeared to be developing into a hurricane
but it never became one. Tropical Depression No. 14 never did
reach the status of a tropical storm, but the same storm sys-
tem had flooded the island of Barbados and subsequently
caused massive flooding in Puerto Rico.
STORM
TIME
ALTITUDE
TEMP
% ICE
% COVERED
TROPICAL
DEPRESS.
#14
2003-
2003-
2011 Z
2019 Z
18K
18K
■3.5° to -4.5°C
-3.0° to -4.0° C
TROPICAL
DEPRESS.
#14
1804-
1711 •
1702-
1632-
1543
1427
1405
i819 Z
1727 Z
1704 Z
1633 Z
1544 Z
1429 Z
1406 Z
18K
18 K
18K
17.6 K
11. 6K
11.6 K
11.6 K
-3.0° to -4.0°C
-2.5° to -4.0° C
- 3.0° to- 3.5° C
-2.0° to- 3.0° C
6.0° C
7.0° C
8.0° to 7 5°C
700915 A
"FELICE"
1743-1745 Z
18 K
-0.3° to -1.2° C
690930 B
"INGA"
1414
1354
1247
1418 Z
1408 Z
1249 Z
19 K
19 K
9K
12° to- 2.0° C
2.0° to 1.0° C
11.5° C
0%
0%
Figure G-2. Storm data.
6-5
THE ESTIMATED FRACTION ICE
The data were interpreted by viewing the projected
image of the replaced crystals with a 16-mm motion picture
projector. The magnification was such that 1 mm of distance
on the film was projected to make 8 inches on the screen.
All particles that appeared to have a crystalline character
were assumed to be ice. That is, any particle with a non-
spherical shape was assumed to be ice. As overall judgment
was made on a single frame; one frame in approximately eyery
200 frames was chosen. The estimates of fraction ice are
shown in detail in figures G-la, G-lb, and G-lc. The bars
represent the fraction ice which is the fraction of the total
hydrometeor population that was considered ice. Below the
abscissas are shown the relative quantity of hydrometeors
that were sampled in terms of coverage of the 16-mm film.
The blank areas indicate yery light coverage. The circles
represent hydrometeor samples that contained no detectable
ice; the vacant spaces between the bars indicate either that
no sample was taken, that there was an insufficient number
of hydrometeors to estimate the fraction ice, or that the
sample was too poor to make a judgment.
Several small clouds in the same general position rela-
tive to Tropical Depression No. 14 are not shown on figure
G-lb. A sample taken from 1406Z to 1407Z in clear air showed
the presence of cloud droplets with what appears as a small
amount of ice. In this instance there were three small clouds
showing radar returns within 10 n miles. An in-cloud sample
taken between 1427Z and 1428Z indicated a moderate amount of
liquid water and little ice. A third sample between 1632Z
and 1633Z was taken outside the visible cloud and contained
only ice in small quantities; again, a cloud with a radar
echo was within 10 n miles. Of these samples, all were taken
between the 6° and 8°C levels except the last which was taken
between -2° and -3°C and, accordingly, contains mostly ice.
DISCUSSION
The observations of appreciable quantities of both
liquid and solid hydrometeors outside the cloud boundaries
is interesting and may shed light on the possibility of natu-
ral seeding by nearly glaciated clouds. It also points to
the intangible character of a cloud boundary. At this time,
however, in many of the samples, the possibility still exists
G-6
that there is an improper time correlation. An electronic
counter with a digital readout is currently being added to
the instrument which should help to alleviate this problem
in future flights.
at diff
much as
data in
warmer
course ,
all the
Depress
d i s s i p a
that th
by simu
ogy Res
of rema
tal s ( s
f ormvar
were re
Figure
erent t
1 ° C in
d i c a t e
tempera
the da
data a
ion No.
t i o n st
e data
1 taneou
earch ,
rkably
ee fig.
sampl e
pi i c a t e
G-3 sh
empera
error
that a
tures
ta may
t the
14, a
age at
for Tr
s samp
Inc. ) .
detail
G-4) .
s ; but
d.
ows a
tures
and
1 arg
(belo
mere
col de
nd it
the
o p i c a
les t
The
ed im
The
nume
plot of
The vo
most like
e portion
w the -5°
ly ref 1 ec
r tempera
was pass
time. It
1 Depress
aken by t
foil sam
pressions
se crysta
rous , sma
the e
rtex
ly ar
of i
C el e
t the
tures
ing t
i s i
ion N
he fo
pi es
of s
Is di
1 1 er ,
s tima
tempe
e a 1
ce i s
v a t i o
age
are
hroug
ntere
o. 14
i 1 i m
showe
tel la
d not
amor
ted f
ratur
it tie
pres
n 1 ev
of th
from
hat
sting
are
pacto
d a 1
r and
appe
phous
r a c t i
es ma
1 ow.
en t a
el),
e s to
Tropi
empor
, how
corro
r ( Me
arge
need
ar in
i ce
on l ce
y be as
The
t the
Of
rm since
cal
ary
ever ,
borated
teorol -
number
le crys-
the
pi eces
The data of figure G-3
amount of ice at the warm temp
suit of drop breakup and disto
before drying that created som
rEMP
°c
6-i
4-
2-
0
2-
4-
6
8-
10-
12
0
50
FRACTION ICE
Figure G-3. Fraction ice at
different temperatures in
tropical storms.
100
al so
erat
rtio
ewha
i ce
part
like
pure
meas
of o
tic!
m i s i
The
sure
+ 11 .
i ce-
four
of p
the
the
be p
most
deri
f ram
sed
flig
Stor
show a
ures .
ns of t
t cryst
may hav
i a 1 1 y m
ly, how
ly stat
ure of
ccurren
e r e p 1 i
n terpre
worst d
ment of
5°C, co
like c h
frames
oor qua
error b
1 evel o
laced i
s i g n i f
ved fro
es . )
All
without
ht 1 eve
m I nga ,
n ano
This
he dr
a 1 1 i n
e bee
el ted
ever ,
i s t i c
the r
ce of
c a t i o
tati o
i s c r e
50 p
rresp
aract
i n e
1 i ty .
ars i
f con
n the
i c a n t
m j ud
mal ou
may b
ops d
e sha
n pre
stat
this
al an
e 1 a t i
i nad
n and
n of
pancy
ercen
onds
e r i s t
ight
The
n d i c a
f i d e n
val u
data
gment
sly hi
e the
uri ng
pes .
sent i
e . Mo
res ul
d give
ve f re
equate
subse
the da
, a me
t ice
to obs
i c s in
i n a s
size
tes ro
ce tha
e. (T
poi nt
s on 2
gh
re-
or
Al so ,
n a
st
t i s
s a
quency
par-
quent
ta.
a-
at
e r v i n g
only
ampl e
of
ughly
t can
he
i s
78
the data were proces-
knowledge of the
Is, and in Tropi cal
the analysis was
G-7
., ,<s.i
Figure G-4
Impressions of stellar and needle ice crystals on
the foil impaotor .
repeated by both authors independently on alternate, but
staggered, frames. The results are shown in figure G-5, and
the data points with the error bars represent this comparison.
Another comparison was made between samples in Tropical Depres-
sion No. 14, in flights at the same temperature but at slightly
different times. These data are represented by the triangles.
The airborne continuous particle replicator has been
criticized on several points, including: (a) the nonstatis-
tical size of the sample; (b) the possibility of particle
breakup producing misleading numbers of ice particles; and
(c) the unknown collection efficiency of the sampling boom
due to pressure fluctuations and flow in and out of the boom.
Niemann and Mee (1970) have completed the analysis of the
1968 cloud hydrometeor data for the Experimental Meteorology
Laboratory. Occasionally they found gross discrepancies in
the data, even as regards the presence or absence of ice.
Figure G-5 presents an appraisal of the possible data hand-
ling problems as the usefulness of the instrument is limited
by one's ability to interpret the data it presents. It ap-
pears that the criticisms above (a, b, and c) are not limiting
G-8
the v
i n s t e
m i s j u
thems
ure G
that
pect
( perh
the t
error
to es
al ue o
ad, t h
dgment
el ves
-5, al
o c c a s i
to mis
aps 10
i m e ) b
, the
tima te
f the data
e p o s s i b i 1
s of the d
are i nvol v
1 i n a 1 1 ,
onal ly one
i nterpret
to 20 per
ut , accept
device can
the tract
, but
i ty of
a ta
e d . F i g -
says
can ex-
the data
cent of
i n g this
be used
ion ice.
CONCLUSIONS
that
i ce
s tor
-5°C
ment
(196
us i n
here
s tor
i ns t
es ti
come
Thes
c o n s i d
can occ
ms a t t
, an ob
with t
7) but
g data
are of
ms . Bu
ruments
mates o
more r
e data
erabl e
ur i n
empera
servat
he wor
in con
from H
a 1 im
t , as
and d
f the
el i a b 1
i nd
amo
trop
ture
i on
k of
trad
urri
i ted
data
ata
f rac
e .
i ca te
unts of
i cal
s above
in agree
R u s k i n
i c t i o n t
cane Gl a
nature
from mo
r e d u c t i o
t i o n ice
100
80
t-
LJ
LJ
en
CO
<
60
40
20 x
I l I I
SIZE 8 SHAPE INDICATES ACCURACY
Staggered measurements by
different observers
Measurements at different times
TD « 14, Temp~ -3 to "4°C
+
0
20 40 60 80
MEASUREMENT NO. 1
100
Figure G-5. The accuracy of
the measurement of the frac-
tion ice with the continuous
particle replicator .
o the findings of Sheets (1969)
dys . However, the data presented
and may not apply to mature
re storms are analyzed and our
n techniques are improved, our
in tropical storms should be-
MacCready, P. I
sampl er
REFERENCES
, and C. J. Todd (1964): Continuous particle
Journal of Applied Meteorology 3 3} pp. 450-460
Niemann, B. L., and T. R. Mee (1970): Analysis of cloud par-
ticle samples for ESSA-NRL cumulus experiments. Final
Report to Experimental Meteorology Branch, ESSA, Miami ,
Fla., Contract E22-96-69 (N ) , p. 8.
Patrick, J., and A. Gag in (1971): Ice crystals in cumulus
cl ouds--prel imi nary results, Studies of the microphys-
ical aspects of cloud processes leading to the forma-
tion of precipitation. Report No. 4, The Hebrew Uni-
versity of Jerusalem, Dept. of Meteorology, Cloud and
Rain Physics Laboratory.
G-9
Ruskin, R. E. (1967): Measurements of water-ice budget charges
at -5°C in Agl-seeded tropical cumulus. Journal of
Applied Meteorology 3 63 pp. 72-81.
Sheets, R. C. (1969): Preliminary analysis of cloud physics
data collected in Hurricane Gladys (1968). Project
STORMFURY Annual Report 1969, U.S. Dept. of Navy and
U.S. Dept. of Commerce, Appendix D.
Spyers-Duran , P. A., and R. R. Braham, Jr. (1967): An air-
borne continuous cloud particle replicator. Journal
of Applied Meteorology 3 63 pp. 1108-1113.
G-10
APPENDIX H
ICE-PHASE MODIFICATION POTENTIAL OF CUMULUS
CLOUDS IN HURRICANES
David A. Matthews
Navy Weather Research Facility
INTRODUCTION
cumul u
modi f i
natura
cl oud
verti c
modi f i
steady
et al .
test t
may be
that a
s e e d i n
An e
s cl o
c a t i o
1 and
virtu
al ve
c a t i o
-stat
, 197
he su
real
re di
g are
x a m i n a t i
u d s in a
n potent
modi f i e
al tempe
locity m
n potent
e cumul u
1). Mod
ggestion
ized by
spl aced
a .
on of
hurr
i al i
d (1)
ratur
a x i m u
i a 1 i
s mod
i f i c a
s (Ge
s e e d i
s 1 i g h
i ce-
i c a n e
s def
rai n
e dep
m , an
s pre
el (W
tion
ntry ,
ng 1 e
tly o
phase
envi
i ned
fall ,
artur
d (5)
di cte
e i n s t
poten
1971
ss f u
utwar
modi
ronme
as th
(2)
e fro
hei g
d by
ei n a
ti al
) tha
lly d
d fro
f i c a t i o
n t is p
e diffe
surface
m the e
ht of c
a one-d
n d D a v i
resul ts
t i n c r e
evel ope
m the p
n pote
resent
rence
press
nvi ron
1 oud t
imensi
s, 196
are u
ased e
d cumu
resent
n t i a 1 of
ed. The
between
ure , (3)
ment , (4)
ops. The
onal
8; Lowe
sed to
f fects
1 us eel 1 s
eyewal 1
This paper will describe the decreases in surface pres
sure, the increases in rainfall, and the increases in cloud
top height as derived from model simulation of ice-phase modi
fi cation using 87 soundings observed within 100 n miles of
hurricane eyes as well as five average hurricane soundings
from Sheets (1969) .
CLOUD MODEL
The Pennsylvania State University-Navy Weather Research
Facility one-dimensional cumulus model (Lowe et al . , 1971) was
used to determine the modification potential. This model per-
forms an integration of the vertical equation of kinetic energy
for a rising cloud tower (a rising parcel in the cloud core).
The basic physical assumptions of the model are as follows:
(1) None of the physical parameters investigated varies
with time.
(2)
(3)
(4)
(5)
(6)
(7)
The
trai
Entr
towe
Vert
of b
Clou
dens
1 eve
1 i qu
grow
of d
CI ou
tion
dew
Seed
at a
cloud t
n i n g j e
ai nment
r radiu
i cal ac
uoyancy
d buoya
a t i o n u
1 , late
id wate
t h is s
eposi ti
d base
1 evel
point v
i n g is
specif
ower exa
t.
is inve
s .
c e 1 e r a t i
forces
ncy is g
p to the
nt heat
r stimul
ol ely a
on .
is 1 o c a t
(CCL) ba
al ues .
simul ate
ied temp
mined has the form of an en-
rsely proportional to the cloud
on is expressed as a function
and drag forces,
enerated by latent heat of con-
level of nucleation. At this
of fusion from freezing all
ates buoyancy. Subsequent
result of the released heat
ed at the convective condensa-
sed on surface temperature and
d by freezing all liquid water
erature .
Seeding was simulated by using two nucleation tempera-
tures, permitting an examination of the effects of different
seeding materials. Temperatures of -5°C and -10°C simulated
seeding by an Agl -NH.+ I-acetone system and an Agl «NaI-acetone
system, respectively (see app. E).
Cloud core radii were selected to correspond with those
selected by Sheets (1969). Cloud bases located at the CCL
were found to be in agreement with those assumed by Sheets;
however, they were generally about 200 m higher (see table
H-l).
Table H-l. A Comparison of Cloud Bases Selected by Sheets
(1969) and Those Corresponding to the Convective Condensa-
tion Level (CCL) for the Same Five Average Soundings . Sam-
ple Size from Which the Average Soundings Were Compiled Is
Also Shown.
Surface Pressure
(mb)
Cloud Base
Sheets
CCL
(m)
Sampl e Size
P
<
995
200
443
995
<
P
<
999
200,
300
415
1000
<
P
<
1004
300,
500
492
1005
<
P
<
1009
500,
750
720
1010
<
P
<
1014
500,
750
997
8
12
19
26
22
H-2
DISCUSSION OF MODIFICATION POTENTIAL RESULTS
Table H-2 presents average values of model results and
the modification potential for five average hurricane soundings
presented by Sheets (1969). The results of three cloud radii
(1.5, 3.2, 5.0 km) and three nucleation temperatures (-5°,
-10°, -25°C) are presented. The -5° and -10°C temperatures
simulated artificial modification by Agl and Agl'Nal ice
nuclei, respectively; the -25°C temperature simulated natural
f reezi ng .
Average values of cloud model results for the modified
clouds in table H-2(a) show increases over values for the
natural cloud. In table H-2(b) a comparison of seeding with
Agl ice nuclei (-5°C) and Agl-Nal ice nuclei (-10°C) shows
significant increases in the average values over those of
natural nucleation. The rainfall and surface pressure values
in table H-2(c) for the -5°C nucleation temperature are 8 and
63 percent higher, respectively, than those values at -10°C.
This difference indicates that the Agl ice nuclei may be ex-
pected to be somewhat more effective than AgI*NaI ice nuclei
in glaciating clouds. The use of a seeding material active
Table H-2. Modification 'Potential Results
1 2
a) Average Values From the Natural Cloud and the Modified Clouds
Nucleation
Temp. (°C)
-5
10
•25
-5
10 -25
-10
■25
-5 -10
25
10 -25
Radi u:
(km)
Rainfall
(in)
Base Press .
Change ( mb )
Cloud Top
(m)
Vi rt . Temp .
Depart . (°C]
Max. Ve
(tn sec"
')
1.5 3.32.92.2 0.5 0.4
3.2 5.2 5.1 4.8 1.3 1.3
5.0 5.9 5.7 5.6 2.3 2.1
0.2 11094 10174 8254
1 .0 13050 1 3174 12454
1 .7 14094 13814 1 3854
1.9 1.9 1.7
3.6 3.5 3.4
4.2 4.4 4.2
4.4 9
13.8 13
17.4 18
.4 9.3
.0 11.9
.2 14.9
Nucl e
Temp .
(b) Differences in Average Values Between the Modified Clouds and
Cloud
a ti on r
(°C) "J
the Natural
10
-5
10
-10
-5
10
Nucleation temperature -25°C.
Nucleation temperature -5°, - 1 0° C .
•10
1 .5
1 .1
0.7
0.2
0.2
2840
2400
0.5
0.3
0.6
0.7
3.2
0.4
0.3
0.2
0.3
750
720
0.2
0.2
3.1
2.1
5.0
0.3
0.1
0.6
0.4
400
-50
0.3
0.2
3.7
3.2
(c
) Avera
ge Percent Chan
ges of
Modi fi cat i
on Potei
1 1 i a 1
Nucleation
Temp. (°C)
-5
-10
-5
-10
-5
-10
-5
-10
-5
-10
1.5
50%
42%
187%
124%
40%
32%
46%
19%
7%
7%
3.2
9%
8%
58%
60%
10%
9%
7%
6%
25%
16%
5.0
9%
4%
34%
21%
3%
-.2%
10%
8%
25%
22%
H-3
at warmer temperatures al
clouds (whose tops have r
levels) earlier in their
colder activation tempera
The greatest chang
1.5 km radius. This re la
perty of one-dimensional
qualitatively valid. The
as fol 1 ows :
( 1 ) In the model t
latent heat of
the hydrometeo
total increase
upon the verti
meteor content
must produce s
upper level hy
set the effect
t i o n level.
(2) The maximum gr
i s often 1 i mi t
which prevent
i f i cations in
lesser entrain
clouds permit
ble layers and
the increased
smal 1 er radi i
1 ayers , thus r
increase of to
(3) Large radii cl
state al ready
grow only slig
many larger ra
experiments sh
meteor content
this is a qual
quantitative i
model resul ts ,
These models d
flow at the to
permit a net i
saturated air.
val i di ty of th
sul ts .
so enables modification of smaller
eached -5°C levels but not -10°C
development than does material having
tures .
e in potential occurs in clouds of
tionship is to some extent the pro-
steady-state models and, at best, is
explanation for the relationship is
he initial effect of the additional
fusion from seeding will decrease
r concentration by evaporation. The
in rainfall is directly dependent
cally integrated increase of hydro-
; hence, the net effect of seeding
ufficient cloud growth to increase
drometeor content to more than off-
of increased warming at the glacia-
owth o
ed by
growth
the am
ment r
them t
grow
buoyan
cl ouds
e s u 1 1 i
tal hy
ouds ,
have t
htly t
d i i c 1
ow a n
(see
i tati v
nterpr
i n th
o not
p of t
ncreas
Howe
e qual
f uns
the h
thro
b i e n t
ates
o pen
up to
cy fr
to p
ng in
drome
howev
ops a
hroug
ouds
et de
Lowe
ely v
etati
i s re
accom
hese
e i n
ver ,
i tati
eeded smal
igher entr
ugh smal 1 ,
atmospher
of unseede
etrate the
the tropo
om seeding
ush throug
a large n
teor conte
er, which
t the trop
h seeding,
in o n e - d i m
crease in
et al . , 19
alid relat
on of one-
spec t , is
modate the
1 arge cl ou
the total
experi ence
ve aspects
1 radii c
ainment r
stable s
e. Where
d 1 arger
se smal 1 ,
pause . H
permi ts
h any sta
et growth
nt .
in the u n
opause , w
As a re
ensi onal
total hyd
71). Whi
i o n s h i p ,
dimensi on
not valid
i ncreas e
ds and do
upward fl
supports
of model
1 ouds
ates
trat-
as
radi i
s ta-
ence ,
the
ble
and
seeded
ill
suit,
model
ro-
le
strict
al
•
d out-
not
ux of
the
re-
Within the limitations of the one-dimensional model and
the sounding data used, the modification potential of average
cloud top heights shows increases in cloud top heights of 2800
m for 1.5 km and 750 m for 5.0 km cloud-core radii.
H-4
Ex
sounding
1 i s h e d by
those of
average h
Cloud mod
surface p
and H-2(a
into five
g o r i e s .
model , an
averaged .
the avera
soundings
a m i n a t i o
1 oca ti on
five s u
Sheets (
u r r i c a n e
el resul
ressures
) , and H
groups
Each sou
d the mo
Fi gure
ge modif
n of mo
rel ati
rface p
1969) (
s o u n d i
ts of m
are pr
-2(b).
a c c o r d i
n d i n g w
di f i cat
s H-l (c
i c a t i o n
d i f i c
ve to
ressu
see t
ngs c
o d i f i
esent
The
ng to
i t h i n
ion p
), H-
pote
a t i o n
the h
re cat
able H
orresp
cati on
ed in
87 sou
the s
a gro
o t e n t i
Kd),
n t i a 1
potent
u r r i c a
e g o r i e
-1).
o n d i n g
poten
f i gure
n d i n g s
ame su
up was
a 1 wit
H-2(c)
of the
i al a
ne ce
s cor
Sheet
to t
tial
s H-l
were
rface
exam
hi n e
, and
f i ve
s a fun
nter wa
respond
s d e r i v
hese ca
for the
(a), H-
al so d
pressu
i n e d w i
ach gro
H-2(d)
groups
c t i o n of
s accomp'
ing to
ed five
t e g o r i e s
s e five
Kb),
i v i d e d
re cate-
th the
up was
present
of
radii
modi f i
H-l(b)
of 100
from 1
than t
s i s t e n
ures b
cation
is a 1 s
two mo
of pat
t i m u m
h u r r i c
Figu
there
catio
, thi
0 mb.
015 m
he in
t for
oth f
pote
o con
d i f i c
tern
modi f
ane c
res H
may
n pot
s pre
The
b to
d i v i d
all
or f i
n t i a 1
s i s t e
a t i o n
adds
i c a t i
enter
-1 an
be a
e n t i a
f erre
patt
1005
ual m
plots
ve av
for
nt fo
nucl
f urth
on po
d H-2
prefer
1 in h
d 1 oca
ern of
mb is,
a x i m u m
of mo
erage
f i ve g
r the
eati on
er sup
t e n t i a
i ndi ca
red pr
u r r i c a
t i o n a
i ncre
howev
at 10
d i f i c a
soundi
roups
three
tempe
port t
1 ard
te th
essur
nes .
ppear
a s i n g
er, p
00 mb
ti on
ngs a
of so
cloud
ratur
oar
1 ocat
at fo
e 1 oc
In f
s at
modi
robab
. Th
poten
nd fo
u n d i n
radi
es .
el ati
ion w
r cloud
a t i o n f
i g u r e s
a surfa
f i c a t i o
ly more
is patt
tial in
r avera
gs . Th
i exami
This co
onshi p
ith res
s of 1
or opt
H-l(a)
ce pre
n pote
i mpor
ern is
these
ge mod
i s pat
ned an
nsi s te
betwee
pect t
. 5 km
i mum
and
ssure
n t i a 1
tant
con-
fig-
ifi-
tern
d the
ncy
n op-
o the
The pattern of high modification potential at 995-1005
mb suggests the existence of cumuli which have vertical growth
arrested by small stable stratifications induced in the ambient
air, but which are high enough to permit the unseeded cloud
tops to reach nucleation temperature. Sounding data were not
available with lower pressures to check the potential at smal-
ler radii. The pattern of decrease of potential with further
increasing pressure (to 1010 mb), however, suggests that
stable stratifications and upper level dryness restrict the
cloud tops to levels below the required nucleation tempera-
ture in which case the clouds would not respond to silver
iodide seeding. This restriction in cloud tops is consistent
with the pattern of tropical hurricane structures discussed
by Palmen and Newton (1970).
H-5
CLOUD RADIUS = 1.5 km
NUCLEATION TEMPERATURE = -5C
MODIFICATION POTENTIAL OF 5 AVERAGE SOUNDINGS
995 IOOO 1009 1010 1015 (mb)
SURFACE PRES.'.URE
995 IOOO 1005 1010 1015 (mb)
SURFACE PRESSURE
MODIFICA TION POTENTIAL OF 5 GROUPS OF INDIVIDUAL SOUNDINGS
4H
z 3
<
I
UJ
3
S OH
m
d
J L
(c)
995 IOOO 1005 1010 1015 (mb)
SURFACE PRESSURE
4O0H
UJ
£2 300-
200-
u
or
LU
a
100-
0-
-loo-
(d)
J L
995 IOOO 1005 1010 101^ ( mb I
SURFACE PRESSURE
AZ , CLOUD TOP CHANGE (km)
AR, RAINFALL CHANGE (in) x
AP, CLOUD BASE PRESSURE CHANGE (mb) o
Figure H-l. Modification potential vs. surface pressure (-5°C
nucleation temperature) . Modification potential is divided
into three categories : Cloud top change from natural cloud
top 3 rainfall change, and surface pressure changes for
clouds modified at -5°C. Both values of modification poten-
tial (a} c) and percentage changes (b 3 d) in modification
potential are shown for five average soundings (a3 b) and
five groups of individual soundings (c3 d) .
CLOUD RADIUS = 1.5 km
NUCLEATION TEMPERATURE = -IOC
MODIFICATION POTENTIAL OF 5 AVERAGE SOUNDINGS
995 IOOO 1003 1010 1015 (mb)
SURFACE PRESSURE
100
995 IOOO 1003 1010 1015 (mb)
SURFACE PRESSURE
MODIFICATION POTENTIAL OF 5 GROUPS OF INDIVIDUAL SOUNDINGS
3-
LU
z
<
I
u 2
UJ
t: h
8 o.
CD
<
(c.)
993 IOOO 1005 1010 1013
SURFACE PRESSURE
( mb)
400'
UJ
| 300-
<
5 200-1
z
LU
O
or
UJ
a.
100-
0-
-100'
J L
(d.)
995 IOOO 1005 1010 IOIS (mb)
SURFACE PRESSURE
AZ , CLOUD TOP CHANGE (km)
AR, RAINFALL CHANGE (in) x
AP, CLOUD BASE PRESSURE CHANGE (mb)
Figure H-2. Modification potential vs. surface pressure (-10°C
nucleation temperature) . Modification potential is divided
into three categories : Cloud top change from natural cloud
top j rainfall change^ and surface pressure changes for
clouds modified at -5°C. Both values of modification poten-
tial (a3 c) and percentage changes (b3 d) in modification
potential are shown for five average soundings (a} b) and
five groups of individual sounding s (c3 d) .
H-7
CONCLUSIONS
Significant increases in cloud growth, precipitation,
and surface pressure change indicated by a one-dimensional
model appear to support the latest STORMFURY hypothesis which
postulates these increases from seeding. However, the effect
of these increases on the storm's maximum winds still needs
to be demonstrated.
Preferred seeding distances from the eye appear to
exist in the hurricane environment. These may be a function
of seeding material, cloud top temperature, and cloud radii.
RECOMMENDATIONS
(1) A detailed study of modification pote
ious regions of the hurricane should be made usi
data and cloud models. Such a study would provi
information on regions of optimum modification p
Dropsonde data should be collected from the 100-
level down to the surface. These soundings coul
using a WC-135 flying at 40,000 ft in a large "f
pattern centered on the hurricane eye. Dropsond
10 minutes during a 1-hour pattern would provide
data at systematic intervals from the eye in dif
of the hurricane.
(2) Improved convective models would help
mum seeding regions and levels for hurricane aba
rect transmission of dropsonde data from reconna
craft to ground computer facilities would enable
cloud model analysis of modification potential t
seeding operations.
(3) A study of cloud top temperatures thr
ricane would also provide information on which r
optimum cloud populations for modification.
(4) The feasibility of warm cloud modific
to cold cloud modification should be examined be
cloud modification may permit growth of small wa
temperatures at which cold cloud modification wi
tive. The combined use of warm cloud and cold c
cation techniques would permit selective seeding
without cloud top temperature restrictions.
ntial of var-
ng dropsonde
de val uabl e
o tenti al .
to 200-mb
d be made
i gure-ei gh t "
es made every
soundi ng
ferent regions
define opti-
tement. Di-
issance air-
real -time
hroughout
oughout a hur-
egions have
a t i o n prior
cause warm
rm clouds to
1 1 be ef fec-
loud modifi-
i n all regions
H-8
REFERENCES
Gentry, R. C. (1971): Progress on hurricane modification
research-October 1969 to October 1970. Presented at
Twelfth Inter agency Conference on Weather Modification,
October 28-30, Virginia Beach, Va .
Lowe, P. R., D. C. Schertz and D. A. Matthews (1971): A
climatology of cumulus seeding potential for the Wes-
tern United States. WEARSCHFAC Technical Paper No. 4-
71, 78 pp.
Palmen, E., and C. Newton (1969): Atmospheric Circulation
Systems. Academic Press, N.Y., pp. 471-522.
Sheets, R. C. (1969): Computations of the seedability of
clouds in the environment of a hurricane. Project
STORMFURY Annual Report 1968, U.S. Dept. of Navy and
U.S. Dept. of Commerce, Appendix E.
Weinstein, A. I., and L. G. Davis (1968): A parameterized
model of cumulus convection. Report No. 11 to NSF,
NSFGA-777, 41 pp.
H-9
APPENDIX I
USE OF LIGHT AIRCRAFT IN STORMFURY ACTIVITIES
Dr. S. D. Elliott, Jr., and Dr. William G. Finnegan
Naval Weapons Center
INTRODUCTION
During the past three STORMFURY operating seasons, the
Naval Weapons Center (NWC) has made one or two Navy-leased or
contractor operated light aircraft available to the program
for use during dry -run and cloudline experiment periods. This
type of aircraft has provided a mainstay to other NWC programs
in weather investigation and modification, and the opportun-
ity was welcomed, both to pass on NWC experience in the effec-
tive employment of such aircraft to other STORMFURY partici-
pants, and to assess their utility in the STORMFURY operational
context. As a result of three seasons' experience, some con-
clusions may be drawn on this topic and some recommendations
offered for future STORMFURY activities.
BACKGROUND
In 1965 and 1966, NWC participation in STORMFURY in-
cluded making available an A3B jet aircraft and crew to aug-
ment the RA3B's of VAP 62 in their employment as seeders.
This aircraft and its military crew participated in both dry-
runs, in the 1965 cumulus cloud experiments (Simpson et al . ,
1965) and in the aborted deployments for Betsy in 1965
(STORMFURY Annual Report 1965) and Faith in 1966 (STORMFURY
Annual Report 1966). Unfortunately, the NWC A3B was lost in
1967 on a cross-country flight.
In 1967 the Naval Air Facility (NAF), China Lake, made
arrangements for long-term leasing of a Cessna 210 single-
engine, high-wing, four-place aircraft (fig. 1-1). Equipped
with retractable landing gear, full IFR instrumentation, a
built-in oxygen system, and a turbo-charged engine, this 210,
registry number N6877R, was capable of airspeeds in excess
of 200 mph, altitudes exceeding 30,000 feet, and flight dur-
ations of 5 hours or more. Special meteorological instrumen-
tation was installed, and external racks designed to accom-
modate a variety of attached and air-dropped pyrotechnic
Figure 1-1. Navy-leased Cessna 210 ( 7 7R) . Streamlined rack
for STOBMFURY type air-dropped flares on pent wing ^ boom
for burn-in-place flares on starboard wing.
nucleant generators. This aircraft and similar contractor-
operated aircraft provided economical and flexible tools for
the development and assessment of weather modification tech-
niques in numerous experimental projects.
The 1968 STORMFURY schedule (Project STORMFURY, Opera-
tion Plan No. 1-68) called for a dry-run exercise based at
Naval Station Roosevelt Roads, Puerto Rico, with a briefing
session on Monday, 5 August, and eyewall and rainband dry-
runs on the 6th and 7th, the latter also to incorporate a
test of the proposed cloudline experiment procedures. Cessna
210(77R) was flown to Puerto Rico for the week of 5-9 August
and provided orientation and indoctrination for STORMFURY
participants in current Navy-developed seeding techniques.
For 1969, the cloudline exercises were expanded to a
full-scale experimental program scheduled to take place dur-
ing the period 9 through 19 September (Project STORMFURY, Op-
eration Plan No. 1-69). For this program, NWC made available
two contractor-operated Cessna 401 low-wing, twin-engine, six
to-eight place aircraft (fig. 1-2), having performance com-
parable to that of the 210 but with considerably greater
1-2
paylo
Opera
a pro
devel
only
N3221
had f
the 4
a i r c r
voi da
80 n
carry
terna
Debbi
ro tec
e n v i r
a i r c r
two N
ad c a p a c i
t i o n s , In
totype me
oped by t
three sea
0Q, opera
ive seats
01 permit
aft were
nee radar
miles d i s
and d i s p
1 1 y s i m i 1
e , but 1 o
h n i c m i x t
onment (P
aft sched
OAA DC-6'
ty. One 40
c. , of Holl
teorol ogi ca
he NWC Avia
t s a v a i 1 a b 1
ted by Weat
available,
s the use o
equipped w i
systems co
tance. Bot
ense 52 STO
ar to the S
aded with a
ure better
roject STOR
uled to par
s , two Navy
1 , N32
i ster ,
1 data
t i o n 0
e for
her Se
The
f a no
th Ben
veri ng
h aire
RMFURY
TORMFU
short
sui ted
MFURY
t i c i p a
WC-12
20Q, operat
Cal i form" a
sensing an
rdnance Dep
passengers .
rvi ce , Inc .
twi n-engi ne
se-mounted
dix RDR-100
a 90 degre
raft were a
III a i r - d r
RY I units
er burning
to the clo
Annual Repo
te in these
1 N ' s , and a
ed by Met
, was equ
d recordi
artmen t ,
The sec
, Norman,
conf i gur
radar, an
K-band w
e forward
1 so equip
opped fla
used on H
grain of
udl i ne op
rt, 1969)
exerci se
USAF WC-
eorologi cal
i p p e d with
ng system
1 eavi ng
ond 401 ,
Okl ahoma ,
a t i o n of
d both
eather a-
sector to
ped to
res, ex-
urri cane
EW-20 py-
erational
. Other
s were the
130.
All forces gathered at Naval Station Roosevelt Roads on
8 September. Cloudline experiments were conducted on 7 days
during the period 9 through 18 September. The normal proce-
dure was for the USAF WC-130 to depart Ramey AFB about 0900
local to scout the assigned operating areas for suitable cloud
Figure 1-2. Cessna 401 (20Q) in flight over NAVSTA Roosevelt
Roads3 Puerto Rico ( STORMFURY Cloudline Experiments } Sep^
tember 1969).
1-3
groups. When these were located, within a range of 100 t
n miles to the northeast or southeast of Roosevelt Roads,
WC-121N's and DC-6's departed to take up their stations a
establish radar surveillance and traffic control patterns
1 21 N ' s at 4,000 and 7,000 ft, on racetrack paths parallel
and to either side of the cloudline) and instrumented pen
tration and photographic tracks (DC-6's at cloud base and
18,000 ft, in a squared "figure-eight" around and through
target group). The first 401 departed the base shortly a
ward, rendezvoused with the other aircraft once the latte
pre-seeding flight patterns had been established, and spe
60 to 90 minutes alternately seeding updrafts and growing
cells at 18-19,000 ft (-5°C to -7°C) and withdrawing to c
the area for penetration by the upper-level DC-6. If con
tions warranted, the second 401 was called out from Roose
Roads about 90 minutes after the first, and either contin
seeding the selected group or joined the other aircraft a
newly selected target. The two 401 's participated in six
(20Q) and five (21Q) missions, flying a total of 30.5 hou
normally carrying three Project officials and observers e
Approximately 125 STORMFURY III flares were fired into cl
line targets. In addition to seeding and indoctrination
seeding procedures, the 401's provided photographic and v
ual coverage of the experiment and aided in target select
Only limited use of the instrument package installed aboa
20Q was made, but the potentialities of the system and pr
cedures for its maintenance and use under field condition
were established. Otherwise, aircraft performance was ex
lent, only one mission being aborted due to a pyrotechnic
rack wiring problem aboard 20Q; 21Q was, however, able to
take over and complete the mission. In addition, both 40
were used on a stand-down day for a 1.5-hour air-to-air p
tography mission, yielding valuable motion picture footag
which has since been incorporated in NWC documentary film
The aircraft were also used for several logistic flights
transport personnel and equipment between Roosevelt Roads
San Juan .
0 250
the
nd
(WC-
to
e-
the
f ter-
rs
nt
1 ear
di-
vel t
ued
t a
rs ,
ach .
oud-
i n
i s-
ion.
rd
o-
s
eel -
1 's
ho-
e
s .
to
and
as en
es tab
trol
Addi t
beha v
array
key p
to Na
vidua
h i g h -
cl oud
avai 1
Annua
Opera
ti rely
1 i s h i n g
procedu
i o n a 1 1 y
i o r of
s s i m i 1
ersonne
vy deve
1 cloud
perform
line ex
abi 1 i ty
1 Repor
t i o n a
succe
the
res t
, val
natur
ar to
1 in
1 oped
s , wh
ance
p e r i m
and
t, 19
iiy.
ssf ul
fligh
o be
uabl e
al an
hurr
the S
proc
i ch w
A6 je
ents
capab
69) .
the c
i n a
t pat
used
mete
d art
i c a n e
T0RMF
edure
oul d
t see
was t
il i ti
1 oudl i
c h i e v i
terns ,
in fut
orol og
i f i c i a
rai nb
URY pr
s for
not ha
der ai
hus du
es of
ne expe
ng thei
and co
ure ST0
i c a 1 da
1 ly mod
ands .
ogram w
sel ecti
ve been
rcraf t .
e in no
20Q and
ri men
r pri
mmuni
RMFUR
ta we
i f i e d
Final
ere d
ng an
poss
The
smal
21Q
ts were
mary pu
cations
Y opera
re secu
1 i near
ly, mos
i recti y
d seedi
i b 1 e w i
succes
1 measu
(Projec
regarded
rpose of
and con-
tions .
red on the
cl oud
t of the
exposed
n g i ndi -
th the
s of the
re to the
t STORMFURY
1-4
1970 DRY-RUN/ CLOUDLINE OPERATIONS
ul ed
run
(Pro
vi ou
had
the
deve
fore
by t
a da
spac
Wedn
ing
sonn
ti on
i ndo
stan
miss
flar
On t
expe
1 21 N
Cess
I n s
tal
appr
were
flig
prov
expe
Fo
for
exerc
ject
s yea
been
WMU-2
1 oped
deci
he NW
ta-co
e. T
esday
m i s s i
el i n
al ac
c t r i n
d-dow
ion t
es un
he 27
ri men
1 s , a
na de
ummar
fligh
o x i m a
f i re
hts w
i ded
ri men
r 1970, t
the perio
ises 20-2
STORMFURY
r , one of
equipped
type, wh
acetone-
ded that
C staff,
"Meeting
he Cessna
, 23 July
o n s , d u r i
v o 1 v e d in
t i v i t i e s
a t i o n in
n day, me
o test tw
der consi
th, 28th,
ts togeth
nd the WC
parted fo
y, 21Q ma
ts , for a
tely 80 r
d . I n ad
ere condu
a s i g n i f i
tal a c t i v
he STORMFURY
d 24-31 July
3 July at Na
Operation 0
the NOAA DC
to dispense
ile the DC-6
burning nucl
only one Ces
equipped for
system in or
arrived in
. On the 24
ng which var
ordnance de
connected wi
seeding proc
mbers of the
o newly deve
deration for
and 29th, 2
er with the
-130. On th
r China Lake
de a total o
total durat
ounds of var
dition, seve
cted. These
cant contrib
i t i e s .
CI oudl i
, immedi
val Stat
rder No.
-6's (39
ST0RMFUR
a d d i t i o
eant gen
sna 401
ai r-dro
der to r
Puerto R
th and 2
i o u s mil
vel opmen
th STORM
edures .
NWC sta
loped ty
future
1 Q parti
two DC-6
e e v e n i n
, to mee
f eight
ion of 1
ious typ
ral phot
1 i ght a
ution to
ne exerc
ately fo
ion Roos
1-70).
C) as we
Y pyrote
nal ly ca
era tor .
(21 Q) wo
pped fla
etain ma
i c o on t
5th it f
itary an
t, seedi
FURY rec
On the
ff flew
pes of a
ST0RMFUR
ci pated
's, the
g of the
t other
trai ni ng
7 . 7 hour
es of py
ographi c
i rcraf t
ST0RMFU
i ses w
1 1 owi n
evel t
Duri n
11 as
c h n i c
r r i e d
It wa
u 1 d be
res bu
x i m u m
he eve
1 ew f o
d civi
ng , an
e i v e d
26th,
an exp
i r - d r o
Y appl
in c 1 o
B-57,
29th,
commi t
and e
s , dur
rotech
and 1
thus o
RY tra
ere s
g the
Roads
g the
the B
fl are
an RF
s the
brou
t wit
seati
ning
ur tr
1 i an
d ope
i nten
a pro
erime
pped
i c a t i
udl i n
two W
the
ments
x p e r i
i ng w
ni c f
o g i s t
nee a
i ni ng
ched-
dry-
pre-
-57
s of
F-
re-
ght
hout
ng
of
ai n-
per-
ra-
s i ve
ject
ntal
ons .
e
C-
men-
hi ch
1 ares
i c
gain
and
CONCLUSIONS
Experience with the use of light aircraft in connection
with STORMFURY activities, as cited above, leads to certain
conclusions regarding their utility in the following fields:
(a) Training. NWC-sponsored light aircraft provided
training in seeding techniques pertinent to the hurricane
environment for key STORMFURY personnel during one flight in
1968 and four in 1970, in connection with the dry-run exer-
cises. The cloudline experiments in 1969 and 1970 provided
further opportunities for such indoctrination. This was ac-
complished at much lower cost ($50 per flight hour for the
single-engined 210, and $100 per hour for the 401 twin), and
1-5
with much greater flexibility than woul
had the larger aircraft employed in STO
ations been used for this task. This u
be continued during future STORMFURY se
(b) Independent Experiments . As
pyrotechnic tests conducted on 26 July
the tests carried out during the 1969 a
ercises, these light aircraft are ideal
ing of novel seeding materials and tech
either alone, or in conjunction with at
craft. It is essential that such tests
maximum flexibility in operations, sine
have only limited predictability. Such
be carried out in future seasons, as ne
systems are developed.
(c) Organized Experiments . The
aircraft in complex, preplanned operati
other airplanes is more limited, althou
Although the Cessna 210 and 401 aircraf
capabilities not significantly inferior
W C - 1 2 1 N ' s and superior in the case of a
flight duration (4^ to 5 hours for over
a full passenger load, and 2 to 3 hours
altitude flight) requires their use in
and with the B-57 in 1970) for protract
larly, their maximum effective operatin
approximately 250 miles, when coupled w
that experimental activities be conduct
at sea (to avoid complications inherent
trolled airspace) limits their usefulne
are scarce. It should be noted, howeve
aircraft such as the A6 and B-57 are si
flight duration, although not in range,
and radio equipment (VHF only) are also
range use at sea. Within these limitat
ued use of light aircraft in cloudline
des i rabl e .
(d) Hurriaane Operations . It is
aircraft of this class would be of any
hurricane seeding operation, except pos
in which outlying rainbands pass relati
able operating base.
(e) Miscellaneous . On many occa
3 years, the NWC-provided aircraft prov
rapid, and flexible means for transport
ment. They also proved highly effectiv
graphy for both documentation and data
d have been the case
RMFURY hurricane oper-
se shoul d def i ni tely
asons .
exemplified by the
1970 and by some of
nd 1970 cloudline e x -
for preliminary test-
niques, operati ng
most , two other ai r-
be pi anned to permi t
e the results obtained
tests will undoubtedly
w nucleant-generating
util
ons
gh s
t ha
to
1 ti t
-wat
of
rela
ed e
g ra
i th
ed a
i n
ss w
r, t
mi 1 a
Av
uns
ions
expe
i ty of th
i nvol vi ng
till subs
ve perfor
the DC-6'
u d e , t h e i
er operat
oxygen fo
y s (as in
xperimen t
d i u s at s
the requi
t 1 east 1
the use o
hen s u i t a
hat high-
r 1 y limit
a i 1 a b 1 e n
u i t e d for
, however
riments a
e 1 ight
several
tanti al .
mance
s and
r 1 i mi ted
i ons wi th
r high
1969,
s . S i m i -
ea of
rement
00 n miles
f con-
bl e cl ouds
performance
ed in
a v i g a t i o n
long
, conti n-
ppears
doubtful whether light
utility in an actual
sibly in a situation
vely close to a suit-
si ons during the last
ided an inexpensive,
ing personnel and equip
e in obtaining photo-
assessment purposes.
1-6
It thus appears that continued use of at least one
light aircraft (preferably twin-engined for safety and per-
formance reasons) is desirable for future STORMFURY seasons,
at least in connection with dry-run, cloudline and equivalent
activities. The Naval Weapons Center, plans to continue pro-
viding this c a p a b i 1 i ty .
REFERENCES
Simpson, J., et al . (1965): STORMFURY Cumulus Seeding Experi-
ment, 1965, Preliminary Summary, Project STORMFURY Re-
port No. 1-65. U.S. Navy/Weather Bureau, 1 November.
STORMFURY Staff (1966): Project STORMFURY Annual Report,
1965. U.S. Dept. of Navy and U.S. Dept. of Commerce.
STORMFURY Staff (1967): Project STORMFURY Annual Report,
1966. U.S. Dept. of Navy and U.S. Dept. of Commerce.
STORMFURY Staff (1968): Project STORMFURY Operation Plan
No. 1-6 8. U.S. Fleet Weather Facility, Jacksonville,
Florida. p . D-l .
STORMFURY Staff (1969): Project STORMFURY Operation Plan
No. 1-69. U.S. Fleet Weather Facility, Jacksonville,
Florida. p. G-l.
STORMFURY Staff (1970): Project STORMFURY Annual Report,
1969. U.S. Dept. of Navy and U.S. Dept. of Commerce.
STORMFURY Staff (1970): Project STORMFURY Operation Order
No. 1-70. U.S. Fleet Weather Facility, Jacksonville,
Florida. pp. D-I-l , D-V-l .
1-7
APPENDIX J
USE OF ECHO VELOCITIES TO EVALUATE HURRICANE
MODIFICATION EXPERIMENTS
Peter G. Black
National Hurricane Research Laboratory
ABSTRACT
Echo velocities computed from airborne
radar at six time intervals over the entire
storm before and during the seeding of Hurri-
cane Debbie on 20 August 1969, reveal that mean
echo speeds equaled or exceeded cycl ostrophi c
winds computed from 12,000-ft. D-value data
as well as measured 12,000-ft winds after a
correction for water motion was applied. In
the time period from just before seeding began
to just after seeding ended, azimuthal mean
echo speed increases ranging from 30 knots at
the 100 n mile radius to 10 knots in the outer
eyewall were found. In this same period, the
mean echo crossing angle changed from 5 degrees
inward to 5 degrees outward at the 100 n mile
radius. Deviations about the azimuthal mean
echo speed and crossing angle indicated that
wave number 2 accounted for nearly all of the
variance around the storm's circumference at
all radii. The deviations remained fixed in
time between radii of 25 and 150 n mile, but
rotated with the major axis in the inner and
outer eyewalls. It is suggested that these
echo motions approximate the air flow in the
lower levels of the hurricane.
INTRODUCTION
For some time attention has been focused on the symmet-
rical features of the hurricane circulation, with the only
asymmetry on the scale larger than that of the rainbands being
introduced by the motion of the storm. Aircraft and ship data
collected in storms have been too sparse in space and time to
adequately describe other asymmetries of these larger scales.
Considerable time variation in wind speed profiles on the
rainband scale and smaller through several hurricanes has
been measured. This has been attributed to the "natural var-
iation" in storm intensity. However, it is a distinct possi-
bility that the time change in these wind speed profiles can
be partly due to the advection of horizontal asymmetries.
Furthermore, in hurricane modification experiments, the pos-
sibility exists that the seeding location relative to hori-
zontal asymmetries may have an important bearing on the out-
come of the experiment.
Therefore, in this report, an attempt has been made
to define the low-level asymmetries in a hurricane and their
change with time using the motion of small precipitation
echoes. Ten-minute time periods were used to define a motion
field over a portion of the hurricane circulation within 150
n miles of the storm center. Several of these time periods
were composited to give an average 1-hour motion field over
the entire hurricane circulation. Radial and azimuthal pro-
files of the echo speed and crossing angle were constructed
for 6 one-hour time periods. These profiles were compared
with aircraft wind measurements where they were available.
canes
p a r t i c
Florid
August
motion
rel ate
and Se
1 a t i o n
Conn i e
Hel ene
He f ou
around
s torm
echo v
the ec
(1963)
a grou
ment b
the me
Many
and a
ul ar
a to
1949
of i
d wel
nn (1
of e
, Dia
of 1
nd sy
the
speed
e 1 o c i
hoes
comp
nd ba
etwee
an wi
auth
ttemp
1 evel
compu
. He
sol at
1 wit
963,
cho v
ne , a
958;
sterna
storm
, and
ties
moved
uted
sed r
n the
nd be
ors ha
ted to
Li g
te ech
c o i n e
ed con
h the
1965)
e 1 o c i t
nd Ion
Debra
tic v a
, with
with
with a
s 1 owe
echo v
adar o
echo
tween
ve co
rel a
da (1
o vel
d the
v e c t i
700 m
have
i es w
e of
of 19
r i a t i
day
echo
i rcra
r tha
e 1 o c i
n Ok i
vel oc
cl oud
mpute
te th
955)
o c i t i
term
ve ce
b win
done
i t h i n
1955;
59 ; a
ons i
vs . n
cross
ft wi
n the
ties
nawa .
i t i e s
base
d ech
ese v
used
es in
"spa
lis s
ds.
ex ten
Hurr
Audr
nd pr
n ech
i g h t ,
ing a
nds a
wind
in Ty
He
near
and
o vel o
e 1 o c i t
land b
the h
winds"
ince h
Senn e
s i v e w
i c a n e s
ey of
i n c i p a
o vel o
with
ngle.
nd fou
s at a
phoon
found
r a w i n
cloud
cities
ies to
ased r
u r r i c a
to re
e said
t al .
ork on
Edna
1957;
lly, d
c i ty w
I and v
Senn
nd tha
II lev
Nancy
wery g
sonde
top .
i n h
wind
adar
ne of
f er t
they
(1960
the
of 19
Dai sy
onna
i th a
s . se
compa
t i n
els.
of 19
ood a
s t a t i
urn -
s at a
i n
23-28
o the
cor-
a, 1960b)
cal cu-
54;
and
of 1960.
zimu th
a , with
red
general
Watanabe
61 from
gree-
ons and
Fujita (1959) used airborne radar to compute echo vel-
ocities in Hurricane Carrie of 1957. His technique involved
placing each radar photograph at the aircraft position given
by the Doppler navigation system and then tracing the succes-
sive position of various radar echoes. However, any error in
J-2
the Doppler fix will result in an error in the echo velocity.
Jordan (1960) also used airborne radar to compute echo velo-
cities in Hurricane Daisy of 1958. He used the hurricane cen
ter as a reference point for his calculations. He noted rela
tively good agreement between his echo velocities within the
eyewall region and aircraft measured winds at 13,000 ft
The ab
ship appears
particular level
DATA ANALYSIS
the s
were
puted
board
compu
fly in
c a t i o
used
photo
wi th
techn
t i n u i
posit
point
north
the e
In t
e e d i n g
used .
from
a WB-
ted f r
g at 1
ns of
to con
graphs
respec
i q u e y
ty on
i o n i n g
and o
, resp
cho po
his st
exper
Echo
pr imar
47 fly
om the
,000 f
these
struct
taken
t to t
i el ds
the ec
the p
r i e n t a
e c t i v e
s i t i o n
udy , a
i ment
v e 1 o c i
11 y th
i rig at
Navy
t. Se
radars
p i c t u
at 30
he hur
extrem
ho mot
hotogr
t i o n (
ly) wi
when
i r b o r n
in Hur
ties o
e Ai r
39,00
APS-20
e Bl ac
Fuj
re seq
-sec i
r i c a n e
ely ac
ion c a
aphs w
namely
11 be
pro jec
e rad
r i c a n
vera
Force
0 ft.
, 10-
k et
i ta ' s
uence
nterv
cent
curat
n be
i th r
the
immed
ted i
ar data
e Debbi
1 0 - m i n
APS-64
Echo
cm rada
al . (19
movi e-
s using
al s whi
er and
e resul
o b t a i n e
espect
h u r r i c a
i ately
n movie
col 1 ect
e, 20 Au
ute peri
, 3-cm r
v e 1 o c i t i
r on boa
71) for
loop tec
ai rborn
ch had b
true nor
ts since
d , and a
to the s
ne cente
obvi ous
form on
ed du
gust
od we
adar
es we
rd a
the s
hni qu
e rad
een r
th.
30 s
ny er
ame f
r and
by a
a sc
ri ng
1969,
re corn-
on
re also
WC-121N
p e c i f i -
e was
ar
egistered
This
ec con-
rors in
i xed
true
jump in
reen .
Short period oscillations in the storm speed during
the 10-minute interval used for computing echo velocities are
not thought to be large enough to bias the echo velocities by
more than 1 or 2 knots. Senn (1965) has indicated average
fluctuations in the speed of Hurricane Donna on the order of
about 5 knots in 1 hour with maximum fluctuations on the or-
der of 10 knots in 1 hour. Such fluctuations were not detected
in the motion of Hurricane Debbie. However, errors in air-
craft navigation and eye location were such that they could
have existed.
J-3
Usually, four or five 10-minute average echo velocity
fields were composited to obtain the echo velocity field
characteristic of a 1-hour time interval. The short period
storm motion fluctuations should be sufficiently random to
cancel out when the 1-hour composites are compared with each
other .
ECHO VELOCITY PROFILES
One-hour echo velocity composites were prepared for
the time periods 1100-1200Z, 1600-1700Z, 1700-1800Z, 1800-
1900Z, 1900-2000Z, and 2000-2100Z. Usable data were not
available for any other time periods. The above times cover
a period from 1 hour before seeding began (about 1200A) to 1
hour after seeding ended (about 2000Z).
The storm was divided into four quadrants defined by
perpendicular lines oriented 45 degrees to the left and right
of the storm motion vector (310 degrees in this case). All
the echo velocity vectors within each quadrant were then com-
posited into radial profiles of speed and crossing angle
(defined as positive inward). The resulting scatter diagrams
for selected time periods are shown in figures J-l to J-3.
The mean scatter was about 10 knots for the speed and about
10 degrees for the crossing angle, which is well within the
scatter that would be introduced by short period fluctuations
in the storm speed. A portion of this scatter (perhaps half)
can be accounted for by azimuthal variations in echo velocity
as will be seen in a later section.
Relative wind profiles measured by RFF aircraft at
12,000 ft as well as computed cycl ostrophi c wind profiles
were superimposed, where available, in the left and right
quadrants. The cycl ostrophi c winds were computed from
C =
V
AD
f9 A?
(J.l)
where r is the radius from the storm center, Ar was chosen
as 2 n miles, and AD was the D-value gradient which was sub
jectively smoothed. Relative winds based on reports from
Navy aircraft at 1,000 ft, 6,000 ft, and 10,000 ft are also
plotted where available.
J-4
HURRICANE DEBBIE
AUGUST 20, 1969 1100-1200 Z
+ 2<f- -
-20°-
120
100
80
60
40
20 -
J.
I
- +20°
-20°
RIGHT (3)
J I I L
120
100
80
60
40
20
140 120 100 80 60 40 20
20 40 60 80 100 120 140
t20"
0'
-20'
120
100
80
60
40
20
_L
J_
FRONT (3)
J J I Li
INNER
EYE
*e*
OUTER EYE
_L
.—A'.'--'
M>
• Qr
BACK (23)
J I I I
JL
+20°
0°
-20°
H120
100
80
60
40
20
140 120 100 80 60 40 20 0 20 40 60 80 100 120 140
RADIUS (N.MI.)
RELATIVE ECHO MOTION
PROFILE
RELATIVE WIND PROFILE
(12,000 FT.)
GRADIENT WIND PROFILE
A ESTIMATED SURFACE
A 1,000 FT. WIND
O 6,000 FT. WIND
□ 10,000 FT. WIND
WIND
Figure J-l. Relative echo speed (bottom panel) and crossing
angle (top panel) profiles compared with relative 1 2 , 000- ft
wind and cyclostrophic wind profiles , as well as scattered
surface, 1,000 ft, 6,000 ft, and 10,000 ft relative wind
reports for 1100 to 1200Z, 20 August 1969. The vertical
lines indicate the inner edges of the inner and outer eye-
walls.
J-5
HURRICANE DEBBIE
AUGUST 20, 1969 1600- 1700 Z
+ 20° -
CO
140 120 100 80 60 40 20
20 40 60 80 100 120 140
CO
+ 20°
0°
-20°
120
100
80
60
40
20
x" . / \-
FRONT (56)
1
i
INNER
EYE
«y-
OUTER EYE
f\ i
/V
l'\
I
"13
i
A
l&
BACK (33)
i i I
+20'
-?n°
20<
-1120
100
80
60
40
20
140 120 100 80 60 40 20 0 20 40 60 80 100 120 140
RADIUS (N. Ml.)
RELATIVE ECHO MOTION
PROFILE
RELATIVE WIND PROFILE
(12,000 FT.)
GRADIENT WIND PROFILE
A ESTIMATED SURFACE WIND
▲ 1,000 FT. WIND
O 6,000 FT. WIND
□ 10,000 FT. WIND
Figure J-2. Same as figure 1 except for the time period from
1600 to 1700Z3 20 August 1969.
J-6
HURRICANE DEBBIE
AUGUST 20, 1969 1700-1800 Z
+ 20°-
to
140 120 100 80 60 40 20 0 20 40 60 80 100 120 140
CO
+ 20°
1 1 1 1 1 1
i
1 1 1 1 1 1
• -* '• •• -"A
0°
-20°
s'r\> •".".* ..' * '*- '-':-
r>
>
*1
INNER
EYE
i
— <
^"^'A!^-
120
- — •
01
ITER EYE
—
100
• *
/
1
v0
''t
b
X
80
60
\
/
I
. /
/
/
40
* y
— <* • .- x
* ** • ^- -* ~*
20
n
FRONT (75)
i i i i i i
1
BACK (59)'
i i i i i i
+20°
H-20°
120
100
80
60
40
20
140 120 100 80 60 40 20 0 20 40 60 80 100 120 140
RADIUS (N.MI.)
RELATIVE ECHO MOTION
PROFILE
RELATIVE WIND PROFILE
(12,000 FT.)
GRADIENT WIND PROFILE
A ESTIMATED SURFACE WIND
A 1,000 FT. WIND
O 6,000 FT. WIND
□ 10,000 FT. WIND
Figure J-3. Same as figure 1 except for the time period from
1700 to 1800Z3 20 August 1969.
J-7
The mean location of the inner edge of the inner and
outer eyewalls during the hour is indicated by the vertical
lines. Seeding times, radii, and azimuths are given in table
J-l .
are
12,0
exce
quad
30-5
at 1
rel a
radi
radi
prof
cl OS
of t
to m
cal c
(196
move
1963
wind
75 k
40 n
10 k
show
the
The
wind
cent
wind
the
The results indicate that the mea
generally in balance with the cyclos
00 ft. However, in some cases, the
ed the cycl os trophi c winds by about
rant, 30-40 n miles radius, fig. J-l
0 n miles radius, fig. J -3). The me
2,000 ft appeared to be about 10 kno
tive echo speeds and the cyclostroph
us of 40 n miles. Where data are av
us, there appears to be much closer
i 1 es .
n relative echo speeds
trophi c wi nds at
rel ati ve echo speeds
5 knots (e.g., 1 eft
; and right quadrant,
asured relative winds
ts less than the mean
ic winds out to a
ailable beyond that
agreement between the
Th
troph
he mo
eas ur
ul ate
3 ) wo
ment
, the
s. F
nots
mile
nots
n to
radi u
Doppl
by 5
er .
s bee
cycl o
e disc
i c win
v i n g s
e the
d. Fi
rk by
to wi n
data
i gure
to 100
s of H
or mor
be nea
s of m
e r win
to 10
When t
ome eq
s troph
repancy b
d s might
ea surfac
ai re raft
gure J-4
Black et
d speed .
of Grocot
J-4 indie
knots (c
u r r i c a n e
e woul d b
rly paral
a x i m u m w i
ds would
knots or
his cor re
ual to an
i c winds.
etwee
p o s s i
e on
groun
repre
al. (
Us i n
t wer
ates
orres
Debbi
e pos
lei t
nd (2
thus
more
c t i o n
d i n
n the
bly b
the a
d spe
sents
1967)
g dat
e ext
that
pondi
e) a
s i b 1 e
o the
2 n m
be an
wi th
i s a
come
rel at
e expl
i r b o r n
ed fro
an ex
i n re
a from
ended
for wi
ng to
water
. The
wind
i 1 e s i
under
in 40
p p 1 i e d
cases
l ve
ai ne
e Do
m wh
tens
1 ati
Hur
to h
nd s
thos
moti
wat
out
n th
esti
n mi
, th
si ig
wi nds
d by t
ppl er
i ch th
ion of
ng sea
ri cane
u r r i c a
peeds
e meas
on of
er mot
to at
e case
mate o
1 es of
e rel a
htly g
and
he e
rada
e wi
Gro
sur
Flo
ne f
rang
ured
from
i on
1 eas
of
f th
the
ti ve
reat
the cy-
f f ects
r used
nds are
cott ' s
face
ra of
orce
i ng from
wi th i n
5 to
has been
t twice
Debbie) .
e true
s to rm
measured
er than
Table J-l. Seeding Times and Locations for Hurricane
Debbie, 20 August 1969.
Seeding Time
(Z)
Range Interval
( n miles)
Azi muth
(from true North)
115630-11 5830
140140-140330
161345-161545
175750-1 75950
195350-195620
15-22
12-25
11-25
12-27
18-34
022-001
044-034
357-351
018-010
356-359
J-8
WM
1
^
(kts)
O - FROM GROCOTT
•/
20
• J*
/
•
*/
10
^i—
•
•
•
o __«— ■
. ■ •
• •
1
**^m
•
• •
1
-20
10
0
50
WS (kts)
100
Figure J-4. Sea surface water motion (WM) as a function of
wind speed (WS) (after Black, 1967; Grocott, 1963).
There are several possible theoretical explanations for
the suggested inbalance between cycl os trophi c and measured
relative winds. Among these are (1) storm not in steady
state (especially true if storm is responding to seeding),
(2) frictional accelerations, and (3) vertical and horizontal
advection of momentum by the asymmetries.
Relative winds measured at 1,000 ft and surface winds
estimated from the appearance of the state of the sea were
made generally between radii of 50 and 125 n miles and tended
to agree remarkably well. They were in general about 10 knots
greater than the mean relative echo speed profiles in the left
and back quadrants, but about 15 knots less than the echo
speed profiles in the right and front quadrants. Ross (1971),
in a recent study, has been able to relate areal coverage of
white caps on the sea surface to wind speed at the 20-m level,
up to a wind speed of 50 knots. He has found that the 20-m
wind is about 20 percent less than the wind at a flight alti-
tude of about 1,000 ft. Therefore, it is felt that the esti-
mated surface winds are too high and should be reduced by at
least 10 to 15 knots. The 6,000 ft and 10,000 ft winds were
in relatively good agreement with the echo speed profiles.
J-9
A time history of the mean relative echo speed and
crossing angle profiles is given in figure J-5. The figure
indicates that the echo speeds tend to increase with time at
radii of from 40 to 150 n miles in all quadrants of the storm
The increase was on the order of 10 to 20 knots. This result
is consistent with the results of Hawkins (1971) which indi-
cated an increase in the winds in the left quadrant at radii
from 75 to 200 n miles of 10 to 15 knots from well before to
well after the seeding experiment. This result is further
substantiated by the time change of the azimuthal mean echo
speed given in a later section.
It should be noted that the echo speeds fall off most
rapidly in the left quadrant, reaching a mean value of about
10 knots at 150 n miles radius. A sharp shear line has been
shown to exist in this quadrant at radii larger than 150 n
miles by the low-level streamline analysis of Fujita and
Black (1970), based on low cloud motions. The echo speeds
fall off to about 30 knots at 150 n miles radius in the right
and back quadrants. This result is also illustrated clearly
in the azimuthal profiles.
Figure J-5 also shows that the crossing angle becomes
more negative with time in all quadrants, indicating the
echoes are tending to move outward more as time progresses.
Of special note is the change evident in the back quadrant
where crossing angle changes from 20 degrees inward at 75 n
miles radius before seeding to 15 degrees outward after seed-
ing are evident.
These results tend to be in the sense anticipated by
the numerical modification experiments of Rosenthal (1971)
which predicted an increase in the winds outside the seeded
eyewall region, even as the maximum wind was reduced and
moved outward. Therefore, these results appear to support
the contention that a modification of Hurricane Debbie was
indeed achieved.
A POSSIBLE MECHANISM GOVERNING ECHO MOTIONS IN A HURRICANE
Some clarification is needed concerning the mechanism
responsible for the observed echo velocities. It was men-
tioned earlier that in some cases, agreement was found be-
tween echo speeds and the 700 mb winds. This is probably
fortuitous. Watanabe (1963) has suggested, using rawinsonde
data, that echo velocities agree best with the mean wind be-
tween the echo base and the echo top, which Senn (see app. !<)
has shown is generally not much higher than 30,000 ft. This
J-10
HURRICANE DEBBIE
TIME HISTORY OF ECHO
AUGUST 20, 1969
MOTION PROFILES
+ 20°
0°
-20°
120
100
80
60
40
20
0
+ 20°
0°
-20°
120
100
80
1 1 1 1 1 1 1
- INFLOW CROSSING
1 1 I I I I
ANGLE
1 i
— ' L'- m — — f <ii , , _, _ 1 — !■
.___"_.- .^•"
■"~*i'.,
-^
OUTFLOW
SPEED
PROFILE
-
•M
h
_
••#
.'.'V.
-
•-'''yy 1
:V V ^ — ..
—
- — ^^ •
I *-»-.
_
— ^~- ~^^^s'
s
,''■■- LEFT
II
RIGHT
1 1 I I I I
1
140 120 100 80 60 40 20
20 40 60 80 100 120 140
</)
60
40
20 -
- /A/FLOW
1 I I
CROSSING
OUTFLOW
SPEED
;/ ,/ I' V
■' »
FRONT
j
J_
JL
I
PROFILE
+20°
0°
-20°
120
100
80
60
40
20
0
+20°
0°
-20°
120
\ 100
80
60
40
20
BACK
I L
I
140 120 100 80 60 40 20 0
RADIUS
1100 - 1200 Z
1600- 17002
1700- 1800 Z
Figure J-5. Time change of echo
files for four quadrants
20 40 60 80 100 120 140
(N. Ml.)
1800 - 1900 Z
1900 -2000Z
2000-2100Z
speed and crossing angle pro-
of Hurricane Debbie.
J-ll
mean wind, in many cases, appears to be nearly that at 10,000
ft (about 700 mb). However, Senn (1965) has observed that in
general, echoes move fast early in their lifetime and slower
later in their lifetime. Watanabe, in order to account for
the scatter in his data about the 700 mb wind, suggests he
was observing echo velocities at different stages in their
lifetime, and hence moving at different velocities.
I
ported b
a substa
sec" * ) ,
air near
echo may
boundary
move wit
vel oci ty
(1971 ) h
the shea
their t e
the rada
the echo
the low-
most of
resul tan
The echo
t i v e of
agree be
t is n
e h a v i o
nti al
moves
cloud
be ti
, as o
h the
is su
ave us
r , ass
rmi nal
r i s o
bound
level
it was
t echo
moti o
the le
tter w
0 w s u g
r coul
verti c
with t
base .
1 ted,
u 1 1 i n e
1 ow-1 e
s tai ne
ed the
u m i n g
vel oc
bservi
ary of
speed .
taken
vel oc
n data
vel f r
ith th
gested
d be t
al vel
he hor
Even
due to
d by G
vel wi
d. In
verti
preci p
i t i e s .
ng act
an ac
The
from
i t i e s
of Jo
om 20,
e 1 owe
that t
hat the
ocity (
i z o n t a 1
though
verti c
entry e
nd spee
fact S
c a 1 til
i t a t i o n
There
i vely g
ti vely
present
an aire
agreed
rdan (1
000 to
r-1 evel
he re
grow
proba
mome
the v
al wi
t al .
d as
enn (
t of
part
fore ,
rowi n
growi
data
raft
best
960),
30,00
wind
ason fo
i n g e c h
bly gre
ntum of
erti cal
nd shea
(1970)
long as
1966) a
radar e
i c 1 e s w
at al 1
g conve
ng echo
i nd i ca
at 39,0
with th
which
0 ft, a
s .
r the
o , su
ater
the
prof
r, th
, wi 1
the
nd Bl
choes
ere f
1 eve
cti ve
will
te th
00 ft
e 1 ow
were
1 so t
above
s t a i n e
than 1
i nf 1 ow
i 1 e of
e echo
1 stil
v e r t i c
ack et
to i n
ailing
Is in
echoe
move
is sin
, and
-1 evel
repres
ended
re-
d by
0 m
i ng
the
1
al
al .
fer
at
whi ch
s ,
with
ce
the
winds
enta-
to
In the case of precipitation falling through weak di-
luted updrafts (on the order of 1 or 2 m sec1) , the tilt of
the echo would still be in the same sense as outlined in the
above paragraph, but more tilted. In this case, the echo
boundary could be expected to move with nearly the speed of
the wind at the precipitation generating level. However, this
type of echo tends to be more diffuse than the actively grow-
ing one and hence harder to follow. Therefore, most of the
echoes used in this study were most probably near their ma-
ture stage.
If the above argument is valid, most of the echoes
probably represent the flow in the inflow layer, modified
slightly by entrainment. Trends in the mean echo velocities
in particular quadrants or range intervals should therefore
indicate trends in the low-level flow field. Deviations
from the mean echo velocities around the circumference of
the storm at different radii are then a measure of the asym-
metries in the low-level flow.
J-12
THE LOW-LEVEL ASYMMETRIC STRUCTURE OF HURRICANE DEBBIE
AS REVEALED BY ECHO VELOCITIES
Study of the variation in echo velocity with azimuth
in Hurricane Debbie is presently underway. Preliminary re-
sults indicate the following:
( 1 ) The mean echo s
the storm at ra
(outer eyewal 1 )
75-150 n miles
f i gure J-6 . In
began until % h
30 knots at the
knots in the ou
creased in this
from 10-15 n mi
knots .
(2) Superimposed on
eyewal 1 was a s
cated by the th
each range inte
to f ol 1 ow each
smal 1 er decreas
another increas
pear to be thre
the 1 ong peri od
shorter period
hour or two, an
with a period o
( 3) The echo speed
about 1 1 knots .
the deviations
inner range int
with time .
(4) The mean cross i
of the storm de
d i c a t i n g less i
Th i s is s hown i
occurred in the
of from about 5
outward was mea
val s the decrea
about zero. Th
the mean genera
time period stu
tion during the
the 1 arges t dev
range interval.
peeds around the circumference of
nge intervals of 18-28 n miles
, 28-50 n miles, 50-75 n miles, and
increased with time as shown in
creases from h. hour before seeding
our after seeding ended ranged from
outermost range interval to 10
ter eyewall. The echo speeds de-
time period in the range interval
les (inner eyewall) by about 20
the
horte
in so
rval ,
s e e d i
e unt
e occ
e ti m
tren
fluct
d (c)
f les
devi a
At
i n c r e
erval
ng an
creas
nf 1 ow
n fig
oute
degr
sured
se wa
e ave
lly t
died.
time
i a t i o
upward trend beyond the inner
r period fluctuation, indi-
lid lines on figure J-6. At
a 5-10 knot increase appeared
ng followed by a slightly
il the next seeding, when
urred. Therefore, there ap-
e scales of echo motion: (a)
d over several hours, (b) the
uations with a period of an
the deviations about the mean
s than 1 hour.
tions from the mean averaged
the two outer range intervals,
ased with time. At the three
s, the deviations decreased
gle a
ed at
i n t
ure J
r ran
ees i
. At
s abo
rage
ended
The
peri
ns oc
round the
al 1 rang
he time p
-7. The
g e i n t e r v
nward to
the othe
ut 5 degr
maximum d
to decre
average
od was ab
c u r r i n g a
ci rcumf erence
e intervals, i n -
eriod studied,
largest decrease
al where a change
about 5 degrees
r range inter-
ees i nward to
eviations from
ase during the
maximum devi a -
out 8 degrees,
t the outermost
J-13
HURRICANE "DEBBIE"
AUGUST 20, 1969
*i #2 #3 #4 #5
11 12 13 14 15 16 17 18 19 20 21
11 12 13 14 15 16 17 18 19 20 21
#1 #2 #3 #4 #5
TIME (GMT)
MEAN ECHO SPEED AND DEVIATION (KTS.)
Figure J-G. Azimuth ally averaged echo speeds at selected
range intervals together with the mean maximum deviations
about the azimuthal mean. Scale for the mean values (solid
circles ) is on the left and the scale for the deviations
(open circles) is on the right. The thin vertical lines
indicate the seeding times.
J-14
HURRICANE "DEBBIE
AUGUST 20. 1969
#1 #2 #3 #4 #5
11 12 13 14 15 16 17 18 19 20 21_
11 12 13 14 15 16 17 18 19 20 21
#1 #2 #3 #4 #5
TIME (GMT.)
MEAN ECHO CROSSING ANGLE AND DEVIATION
(DEGREES)
Figure J-7. Azimuthally averaged echo crossing angles at se-
lected range intervals together with the mean maximum devia-
tions about the azimuthal mean. Scale for the mean values
(solid circles) is on the left and the scale for the devia-
tions (open circles ) is on the right. The thin vertical
lines indicate the seeding times.
J-15
(5) When the echo speed devi
as a function of azimuth
dominant wave number at
iods studied. This was
deviations were plotted
(6) The general tendency was
viations in the outer th
in the front and right r
viations in the right fr
in figure J-8.
(7) The phase of the cross in
exactly one-half wavelen
deviations in each of th
This meant that negative
ward moving echoes) were
and rear quadrants, with
tions (inward moving ech
right front quadrants,
and minima are located a
angle. Likewise, the ma
angles occur at the mean
echo speed is decelerati
is outward, and as the e
stream, the crossing ang
(8) Figure J-9 illustrates h
deviations around the in
rotate cyclonically with
tion rate of the major a
(1971). Fol 1 owi ng each
relative location of the
crossing angle maximum c
different amounts during
after seeding to 1 hour
ting, maintaining their
eration. The significan
sent. However, it seems
for the period of about
rate of rotation of the
tions nearly matches tha
(9) The relation between the
angle deviations was not
intervals, but generally
with crossing angle mini
(10) The faster moving, outwa
outer eyewall regions te
solid looking echoes whe
posite at the same time
inward moving echoes ten
portion of the eyewall b
which tended to protrude
ations from the mean were plo
, wave number 2 appeared to b
all radius intervals and time
true also when the crossing a
as a function of azimuth.
for the positive echo speed
ree range intervals to be loc
ear quadrants with negative d
ont and left quadrants, as sh
g angle deviations was almost
gth out of phase with the spe
e outer three range intervals
crossing angle deviations (o
most common in the left fron
positive crossing angle devi
oes) located in the rear and
This means that the speed max
t the position of zero cross i
ximum inward and outward cros
echo speed. Furthermore, as
ng downstream the crossing an
cho speed is accelerating dow
le is inward.
ow the speed and crossing ang
ner and outer eyewalls tended
time nearly matching the rot
xis as described by Black et
of the last three seedings th
major axis, speed maximum, a
Ranged as each decelerated by
the time period from 15 minu
after seeding and then accele
new phases until the next dec
ce of this is not known at pr
quite significant that, exce
an hour after each seeding, t
speed and crossing angle devi
t of the major axis.
phases of the speed and cros
as clear-cut as the outer ra
the speed maxima corresponde
ma (outward motion ) .
rd moving echoes in the inner
nded to be correlated with mo
n compared with a PPI radar c
interval, while the slower mo
ded to be correlated with the
roken into individual cells,
into the eye occasionally.
tted
e the
per-
ngl e
de-
ated
e-
own
ed
ut-
t
a-
i ma
ng
sing
the
gle
n -
le
to
a-
al .
e
nd
tes
ra-
el-
e-
pt
he
a-
sing
di us
d
and
re
om-
v i n g ,
This
J-16
HURRICANE "DEBBIE"
AUGUST 20, 1969
CO
10
w 0
>•
-10
1130- 2030 Z
-LEFT-REAR-
-LEFT-FRONT*
A"
150 >R >25
-BRIGHT — FR0NT-^|<^RI6HT- REAR-
BACK H«« LEFT M* FRONT H* RIGHT H*— BACK
10°
0"
1
H-io«
ECHO SPEED AND CROSSING ANGLE DEVIATIONS
Figure J-8. Azimuthal variation of eoho speed [solid curve)
and crossing angle (dashed curve) beyond the eyewall dur-
ing the time period studied.
result is in agreement with echo velocity analyses
of the eyewall region of Hurricane Carrie by
Fujita (1959), of Hurricane Daisy by Jordon (1960),
and of Hurricane Celia by Fujita (1971).
CONCLUSIONS
J-17
HURRICANE "DEBBIE"
1600 1700
1800
AUGUST 20, 1969
1900 2000 2100
' A V ' /' /'
150°
STORM MOTION
3 30'
300°
STORM MOTION
2000
2100
FAST
( , — ) ANGULAR R
( . ) ANGULAR R
1900
SLOW
TIME (GMT)
) ANGULAR ROTATION OF EYEWALL MAJOR AXIS
OTATION OF ECHO CROSSING ANGLE MAXIMUM
OTATION OF ECHO SPEED MAXIMUM
Figure J-9. Angular rotation of the eyewall major axis ini-
tially in the front quadrant together with the eoho speed
and crossing angle maxima initially just upstream from this
major axis position are all indicated by thick lines. The
position of the major axis initially in the rear quadrant
together with the echo speed and crossing angle maxima just
upstream are indicated by thin lines.
The top panel is the rotation rates for the inner eyewall
and the bottom panel is the rotation rates for the outer
eyewall . Black retangles indicate the seeding time and
location for the third, fourth, and fifth seedings . Thin
vertical lines delineate the slow moving time periods fol-
lowing each seeding from the fast moving time periods .
J-18
experiments since the appearance of the eyewall region on
radar could then be used to direct seeding aircraft to the
locations where the seeding agent will be most effective.
REFERENCES
Black, P. G., J. J. O'Brien and B. M. Lewis (1967): Ocean
motion beneath a hurricane and its influence on the
operation of airborne Doppler radar. Fifth Technical
Conference on Hurricanes and Tropical Meteorology,
Caracas, Venezuela, November.
Black, P. G., H. V. Senn and C. L. Courtright (1971): Some
airborne radar observations of precipitation tilt,
bright band distribution and eye configuration changes
during the 1969 multiple seeding experiments in Hurri-
cane Debbie. Submitted to Monthly Weather Review.
Fujita, T. T. (1959): A computation method of velocity of
individual echoes inside hurricanes. Final Report CWB
9530, May, 7 pp.
Fujita, T. T., and H. Grandoso (1968): Split of a thunder-
storm into anticyclonic and cyclonic storms and their
motion as determined from numerical model experiments.
Journal of Atmospheric Sciences , 25, (3), May, pp.
416-438.
Fujita, T. T. (1971): private communication.
Gentry, R. C, T. T. Fujita and R. C. Sheets (1970): Air-
craft, spacecraft, satellite and radar observations
of Hurricane Gladys, 1968. Journal of Applied Meteor-
ology s 9, (6), December, pp. 837-850.
Grocott, D. F. H. (1963): Doppler correction for surface
movement. Journal of the Institute for Navigation,
16, pp. 57-63.
Hawkins, H. F. (1971): Comparison results of the Hurricane
Debbie, 1969, modification experiments with those from
Rosenthal's numerical model simulation experiments.
Monthly Weather Review, 99, (5), May, pp. 427-434.
Jordon, C. L. (1960): Spawinds for the eyewall of Hurricane
Daisy of 1958. Proceedings of the Eighth Weather
Radar Conference, April 11-14, pp. 219-226.
J-19
Ligda, M. G. H. (1955): Analysis of motion of small precipi-
tation areas and bands in the hurricane of August 23-
28, 1949. Technical Note No. 3, Massachussets Insti-
tude of Technology, 41 pp.
Rosenthal, S. L. (1971): A circularly symmetric, primitive
equation model of tropical cyclones and its response
to artificial enhancement of the convective heating
function. Monthly Weather Review, 99, (5), May, pp.
414-426.
Ross, D. (1971): private communication.
Senn, H. V. (1960): The mean motion of radar echoes in the
complete hurricane. Proceedings of the Eight Weather
Radar Conference, April 11-14, pp. 427-434.
Senn, H. V., H. W. Hiser and R. D. Nelson (1960): Studies of
the evolution and motion of radar echoes from hurri-
canes. Final report, U.S. Weather Bureau, Report No.
8944-1, August.
Senn, H. V. (1963): Radar precipitation echo motion in Hurri-
cane Donna. Proceedings of the Third Technical Confer-
ence on Hurricanes and Tropical Meteorology , June 6-12.
Senn, H. V., and J. A. Stevens (1965): A summary of empirical
studies of the horizontal motion of small radar precip-
itation echoes in Hurricane Donna and other tropical
storms. Technical Note 17-NHRL-74, November, 55 pp.
Senn, H. V. (1966): Precipitation shear and bright band ob-
servations in Hurricane Betsy, 1965. Proceedings of
the Twelfth Weather Radar Conference, American Meteor-
ological Society, October, pp. 447-453.
Watanabe, K. (1963): Vertical wind distribution and weather
echo (in the case of the typhoon). Proceedings of the
Tenth Weather Radar Conference . April 22-25, pp. 222-
225.
J-20
APPENDIX K
A SUMMARY OF RADAR PRECIPITATION ECHO
HEIGHTS IN HURRICANES
Harry V. Senn
Rosenstiel School of Marine and Atmospheric Science
Uni versi ty of Miami
INTRODUCTION
In recent years the need for three-dimensional radar
precipitation data in hurricanes has increased greatly. This
is due partly to requirements of the National Weather Service
for such information on existing storms, partly to satisfy
the interests of those who must reconnoiter the storms with
aircraft, but most importantly to fill gaps in the knowledge
necessary for intelligent planning and execution of attempts
to significantly modify hurricanes.
A large amount of height data and many case histories
are available for various types of storms which occur over
the United States because of the presence of radars capable
of making observations. Some land-based RHI data on hurri-
canes exist for storms approaching or over land, but these
cases are not typical of over-water situations in the tropics
Furthermore, such data are rarely obtained with radars having
optimum vertical beamwidths (1 degree or less), transmitting
frequencies, peak power, or data recording equipment. For
instance, in several hurricanes which affected the southeast
coast of Florida, each of the WSR-57 radars at Miami and Key
West obtained only two or three Polaroid RHI photographs for
later analysis. The sparsity of RHI data was due to lack of
automatic data gathering equipment. During the same period,
many days of routine, excellent PPI data were collected.
Unfortunately, RHI data for hurricanes farther from
land are even more limited. Although nearly optimum airborne
equipment has existed for almost two decades, Project STORM-
FURY impetus was necessary before the APS-45 radars aboard
the WC-121N reconnaissance aircraft were capable of obtaining
documented RHI data useful to researchers.
The following is an attempt to summarize the RHI data
from all sources on hurricanes in an attempt to arrive at a
model which might be used to help determine where one might
profitably direct modification efforts.
HURRICANES PRIOR TO 1958
Early observations by Wexler (1947), Ligda (1951),
Jordan and Stowell (1955) either do not even mention radar
echo top observations or they report on heights in a single
narrow area of interest without indicating the general height
population in hurricanes. Probably the most complete early
report on echo heights was by Kessler and Atlas (1956) on
Hurricane Edna, 1954, using the TPQ-6, FPS-4, and FPS-6 radars
However, the observations were made at latitudes and times in
the life history of the storm that they were most probably not
representative of hurricanes in more tropical latitudes.
HURRICANE DAISY, 1958
Jordan et al . (1960) presented many features of Hurri-
cane Daisy, 1958, including some RHI radar data taken in and
near the eyewall region. They found the maximum echo tops
to be about 65,000 ft with echoes "away from the eye..." less
than 45,000 ft. "Daisy" was a \/ery well formed storm just
northeast of the Bahama Islands at the time. The eye was
open with classically clear blue skies above it, and the pre-
cipitation pattern fairly typical (Senn and Hiser, 1959) ex-
cept for the fact that the eyewall was open to the west and
the heaviest precipitation, as well as spiral bands, had
rotated to the southern regions.
HURRICANE JUDITH, 1959
In 1960, Senn et al . presented RHI data taken on the
University of Miami MPS-4 radar on minimal Hurricane Judith,
1959, a small, late season
typical of most hurricanes
fi gurations .
storm. However, "Judith" was not
in either PPI or RHI pattern con-
HURRICANE DONNA, 1960
Jordan and Schatzle (1961) published the first RHI
picture of the eye taken on the U.S. Navy's APS-45 airborne
radar when reporting on the "Double Eye of Hurricane Donna."
Although the picture did not show it, they described the inner
eyewall echo tops as 45,000 ft with the outer eyewall topped
K-2
near 30,000 ft. Using the land-based Univers
MPS-4 radar, Senn and Hiser (1961) presented
hensive data on echo tops in a major storm at
latitudes. Table K-l summarizes the heights
in the four quadrants of Hurricane Donna base
tion of motion of the storm. (Since this was
ing most of the period of observation, little
be apparent if the reference line were north,
ting to note that over 95 percent of the echo
tops of less than 30,000 ft and over 78 perce
low 20,000 ft. However, it is just as obviou
one-third of all echoes had tops above the me
suming this storm was typical with respect to
echoes, probably only a small fraction of tho
bright band were active towers; the rest had
the mature stages. In the absence of suffici
Senn et al . (1963) attempted to use far more
PPI data using range variations to indicate a
heights for comparisons with observed winds,
was somewhat rewarding in the absence of othe
but obviously did not produce echo heights to
limits of an RHI radar, so no detailed compar
storm data are presented.
i ty of Mia
the f i rs t
sub- tropi
of 3709 ec
d on the d
northerly
di fferenc
) It is i
es observe
nt had top
s that mor
Iting leve
bright b a
se above t
reached or
ent RHI da
vol umi nous
pproximate
The techn
r better d
the accur
i sons wi th
mi s
compre-
cal
hoes
i rec-
dur-
e would
nteres-
d had
s be-
e than
1. As-
nd
he
passed
ta ,
"Donna1
echo
iq ue
ata
acy
other
HURRICANE DEBRA, 1961
Bigler and Hexter (1960) used CAPPI techniques to show
the echo coverage at "standard," 10,000, 20,000, and 30,000 ft
levels in Hurricane Debra (1961) as viewed by the 3-cm CPS-9
Table K-l. Number of Echoes by Height, Range, and Quadrant
From MPS-4 Radar, Eurrioane Donna, 1960.
Quad.
0-89°
90-
179°
180-
269°
270-
■359°
TOTAL
% OF
Range*
<45
55
65
75
<45
55
65
75
<45
55
65
75
<45
55
65
75
TOTAL
02-10
19
7
4
2
2
5
5
6
5
7
2
1
25
1 1
9
4
114
03.1
12-20
293
154
97
41
250
214
151
97
325
1 72
119
53
34 8
330
1 70
97
2 801
75.5
22-30 ** 76
33
27
12
85
55
27
9
100
32
36
1 1
79
52
44
23
701
18.9
32-40
8
8
9
4
6
2
4
9
4
0
1
2
4
6
0
1
68
01 .8
42-50
2
5
4
2
2
6
0
0
1
0
1
0
0
2
0
0
25
00.7
TOTAL
398
207
141
61
345
282
187
121
435
211
159
67
456
291
223
125
3709
100.0
- Range
f ron
storm center nautic;
1 m i
les.
**HT.K'
FROM: Senn and Hiser (1961
K-3
radar. Although this radar is subject to very appreciable at-
tenuation in such situations, the data are interesting from
several points of view.
Some of those that did
eye; others were 25 to
is about 50 miles long
This is the area which
normal storms (Senn and
Very few echoes exceeded 30,000 ft.
were in the northeast portion of the
50 miles north; but the largest area
and 50 miles west of the storm center
has fewer and less intense echoes in
Hiser, 1959). However, "Debra" was
under increasing influence from land areas and no longer typ
ical of an over-water, undisturbed low latitude formation.
HURRICANE CLE0, 1963
of Hu
Miami
30-40
cores
great
eye t
In th
above
"Cleo
ti ve
to 25
i n th
excep
ft, o
Echo
r r i c a n
1 s MPS
miles
in th
er ran
he f re
e eyew
32,00
" PP I
p o r t i o
,000 f
e rain
t for
nee to
heights
e Cleo a
-4 radar
from th
at regio
g e s , h e i
quency o
all, tow
0 ft. F
and RHI
ns of sp
t near t
shield,
their co
33,000
were
gain
. He
e s to
n ext
ghts
f hig
ers g
i gure
data
i ral
he ey
and g
res w
ft.
stud
using
foun
rm ce
e n d i n
were
her p
enera
s K-l
super
bands
e. H
enera
hi ch
ied by
the 1
d the
nter t
g sign
mostly
reci pi
1 1 y ex
and K
impose
had t
eights
lly th
o c c a s i
Senn
and-ba
medi an
o be 2
i f i c a n
1 ower
tati on
ceeded
-2 are
d. In
ops on
were
e same
onal ly
(1965
sed U
hei g
0,000
tly h
; and
towe
28,0
typi
that
the
15,00
i n s
were
) in all
ni versi ty
hts of ec
ft with
i g h e r . A
nearer t
rs was gr
00 ft wit
cal views
study mo
order of
0 ft fart
pi ral ban
found at
regi ons
of
hoes
some
t
he
eater .
h some
of
st ac-
20,000
her out
d tails
25,000
HURRICANE BETSY, 1965
Hurricane Betsy (1965) echoes were studied both from
the land-based University of Miami's radars and the APS-45
airborne set by Senn (1966). In fact, this was the first
comprehensive study of most quadrants and ranges of a storm
in a completely over-water environment. Unfortunately, when
the APS-45 RHI data were gathered on 1 September 1965, "Betsy"
was a minimal hurricane gradually increasing in intensity.
However, the Betsy precipitation pattern was much more normal
than Cleo's in 1963. The Betsy echo heights occasionally
exceeded 40,000 ft in the eyewall, and the echoes tended to
be higher in the front of the storm; whereas, in Cleo they
were higher i n the right rear. Figures K-3 and K-4 show typ-
ical Betsy composites of echo heights superimposed on PPI pre-
sentations, and figures K-5 and K-6 show breakdowns of echo
heights within 20 miles of the eyewall.
K-4
Figure K-l. Composite of typical PPI and RHI Cleo data 26-27
August 1964 from University of Miami MPS-4 radar.
K-5
N
Figure K-2. Hurricane Cleo3 26 August 1964, 2130 EST 3 UM/10-
cm PPI with IEC; heights in k ft from MPS-^4; Circle includes
eyewall precipitation; eye diameter 14 miles.
HURRICANE INEZ, 1966
Hurricane Inez (1966) echoes were also studied by Senn
(1967) using an IEC device on the University of Miami's RHI
radar. "Inez" was moving southwest toward the Florida Keys
and was a most unusual, asymmetrical hurricane. Figures K-7
and K-8 show that some echoes exceeded 60,000 ft while almost
all of the heaviest cores exceeded 20,000 ft. Almost the
entire precipitation pattern consisted of a rather intense
band of weather to the east and southeast of the storm cen-
ter over the warm Straits of Florida waters with the entire
western quadrants precipitation free. A further breakdown of
K-6
Figure K-3
Hurricane Betsy PPI with echo heights in k ftt
APS-45, 1 September 1965.
K-7
Figure K-4
Hurricane Betsy PPI with echo heights in k ft3
MPS-43 7 and 8 September 1965.
K-8
STORM DIR W
0849-
-1433Z
2
40-
5
6
3
40-
3
4
40-
30-
7
5
1
2 30-
3
6 3
3 30-
5
4
3
3
2
4 5
1
20-
5
2
l 20-
5
5 4
3 2
3 20-
1
10-
10-
10-
r
r
~
X
M
x
—
•g
^
mi 5
10
1
15
20
mi 5
10 15
2
20
40
3 30
2
I 20-
ioH
20
10
4
QUAD
15
20
40-
2
30-
6
4
4
1
20-
3
2
2
3
10-
-
ac
■£
10
15
40-
4
1
30-
e
3
5
i
6
20-
1
2
10
-
X-
3
20
10
15
20
40-
6
2
30-
6
4
5
5
4
3
2
20-
5
6
1
10-
c
x
s
10
15
40-
3
4
5
4
5
30-
6
2
4
2
8
3
3
i 20-
2
6
5
io-
r
i«
, E
20
10
8
15
20
Figure K- 5 . Number and height of echoes within 20 miles of
eyewall by quadrant in Hurricane Betsy j 1 September 19653
APS-4 5.
heights by quadrant and range within 20 miles of the eyewall
was made using data from an earlier period northeast of Miami
and these are shown in figure K-9.
HURRICANE FAITH, 1966, AND HURRICANES
BEULAH AND HEIDI , 1967
Also underway is a study of echo tops in Hurricanes
Faith (1966), Beulah and Heidi (1967) using the APS-45 data
However, these data are seriously lacking in important de-
tails and are expected to yield only general results. Some
of these are discussed and shown in the summary.
K-9
STORM
Uo
3
h
2
3
30
7
6
3
S
k
2
20
2
3
5
e
2
1
4
5
10
"^
4-
c
r mi
10
15 20
Uo
30
i*
it
3
6
20
it
5
5 3
3
3
5 2
10
u
X
r mi 5 1Q
2
Uo
30
20
10
15 20
r mi 5 10
15 20
Uo
30
1
2
1
i*
3
2
20
9
It
2
10
5
10
4
Dm v
15 20
UO
30
20
10
UO
1 30
3
k 20
10
10 15 20
10
6
15 20
Uo
1
30
5
3
1
20
2
2 1
10
«
10
7
15
20
UO
2
30
5
3
2
1
20
1
2
1 2
10
10
8
15
20
Figure K-6. Number and height of echoes within 20 miles of
eyewall by quadrant in Hurricane Betsy 3 8 September 19653
MPS-4, 0012-1140Z.
HURRICANE DEBBIE, 1969
Hurricane Debbie (1969) was studied by Senn and Court
right (1970), but results are only available for the eyewall
region at present. These are shown on figures K-10 and K-ll
A more complete study of the echo tops using the APS-45 air-
borne data is underway.
SUMMARY
Figure K-12 summarizes the number of echoes by height
categories for five storms, all over water and below 26°N
latitude. Note that the data are not comparable in the sense
K-10
Figure K-7. Hurricane Inez, 4 October 19663 0750 EST, UM/10-
cm PPI with IEC; heights in k ft from MPS-4; circle includes
eyewall precipitation; eye diameter 20 miles.
that although all echoes were found within 20 n miles of the
eyewall (not the storm center), the number of echoes is a
function of the flight path, quality of data collected, etc.,
as well as the actual height population produced in the storm.
Consequently, the data for each category are also given in
percentages of the total for that storm.
Although echoes penetrate significantly above 30,000 to
35,000 ft at greater ranges, a summary of the composite fig-
ures presented above shows that most of the taller echoes are
within 20 n miles of the eyewall. Frequency distributions
show the vast majority of all echoes to have
15,000 to 30,000 ft categories at all ranges
should have no trouble finding echoes in the
ft category in and near the eyewall.
tops in the
Generally, one
20,000 to 25,000
K-ll
60,000 ft +
50-59,999 ft
45-49,999 ft
40-44,999 ft
35-39,999 ft
30-34,999 ft
25-29,999 ft
Height
of Echoes
20-24,999 ft
15-19,999 ft
10-14,999 ft
5-9,999 ft
0-4,999 ft
Figure K-8. Numb
eaoh of
er and height of Hur
three iso-echo oonto
rioane Inez eohoes
ur intensities .
tn
K-12
60
50
Uo
30
20
10
ifcl
10
2
6
9
15
.c r in
60
5o
Uo
30
20
10
10
7
10
8
lh
12
5
u r mi
2 1
6 3
10 6
it 7
60
50
Uo
30
* 20
8
2 10
50
Uo
30
20
10
10 15 20
3
3
e
e
7
12
5
10 15 20 " r mi 5
1
60
5
5
6
7
19
12
5
1
3 2
5 3
9 i»
6 7
10
2
10
6
15
5 1
5 ■»
8 7
7 6
15
60
50
Uo
30
l
2 2©
7
1 10
20
20 u
60
50
Uo
3 30
7
4 20
10
5
7
8
1 1
7
7
7
2
3
5
i*
10
17
10
7
10
3
10
7
15
15
60
50
Uo
30
l
i 20
3
10
STORM
DIR HSW
20 u
J5
60
50
Uo
3 30
5
5 20
10
20
9
10
7
10
3
10
9
Ik
10
4
10
8
15
15
20
3 3
5 3
7 5
1
20
Figure K-9 . Number and height of echoes within 20 miles of
eyewall by quadrant in Hurricane Inez> 4 October 19663
MPS-4, 0030-2S40Z.
Not shown in these figures, but deduced from earlier
work, is the fact that, except when a storm is approaching
land, the echo height populations remain relatively station-
ary with respect to the direction of storm motion rather than
exhibiting a rotation around the storm center. It is not yet
clear whether that also holds with respect to north, since
most of the storms that could be considered representative
were headed westerly or northerly when the observations were
made. The tallest echoes, likewise, appear to be to the
east and north of the storm center, and the south (or general
rear) quadrants have the weakest, lowest echoes (sometimes
not at all).
K-13
N "
/
/
/
NE-
(
(
I
(
E "
\
\
|
\
SE-
\
\
\
s -
|
\
J
)
SW
(
/
•
1
1
w •
NW
/
'
)
)
/
(
•
/
I
i i i I
1 1 1 1
l 1 1 1
1 1 1 1
I 1 1 l
l f I i
fill
i I i i
i i 1 i
o o
<J- CN
o o
o o
o o
<r cn
o o
<r cn
o o
<r cn
o o
<r cn
o o
<r cn
o o
<r cn
Time: Z
Figure K-10.
1230 1245 1300 1315 1330 1430 1445 1500 1515
MAX. HT. K' OF ECHOES EACH QUADRANT APS-45 FURY G
Height of eyewall echoes 3 Hurricane Debbie
18 August 1969.
N
NE
E
SE
S
SW
w
NW
i_l_l_l
JUL!
JJ
*%J
^
*Mr
m*
k**#
^
1415 1430 1445 1500 1515 1530 1545 1600 1615 1630 1645 1700 1715 1730 1745 1800
MAX. HT. K* OF ECHOES EACH QUADRANT APS-45 FURY H
Figure K-ll
Height of eyewall echoes^ Hurricane Debbie
20 August 1969.
K-14
Debbie F/H
8-20-69
Debbie F/G
8-20-69
<15 K'
>15 K' < 30 K'
>30 K'
8 8 (12%)
2 6 7 (38%)
3 5 1 (50%)
7 2 (13%)
2 ' 3 (39%)
2 5 9 (48%)
Debbie F/G
8-18-69
5 1 (10%)
1 8 2 (38%)
2 4 9 (52%)
Heidi '67
5 1 (24%)
8 3 (39%)
7 7 (37%)
Beulah '67
3 2 (19%)
6 0 (36%)
7 4 (45%)
Faith '66
1 9 (16%)
5 8 (50%)
3 9 (34%)
Cleo '64
3 8 (22%)
7 1 (41%)
6 4 (37%)
Figure K-12.
Number and percent of echoes by height within
20 miles of eyewall.
CONCLUSIONS
If one is looking for precipitation towers on the order
of 20,000 to 25,000 ft outside the eyewall of a normal mature
hurricane, he should find them in the north and east quadrants.
A good RHI radar is a necessity, however, in a brief analysis
of such clouds prior to any modification attempts since these
quadrants are generally badly messed up by multi-layers of
clouds, ample regions of "bright bands" (indicating melting
hydrometers), etc., which make action purely on the basis of
visual observations subject to uncertainty.
K-15
In fact, some of the above data lead to some rather
perplexing questions regarding the seeding hypothesis used
in Project STORMFURY. We have found the bright band in most
quadrants and ranges of several hurricanes, as indicated in
another paper in process. The results above show widespread
echoes at heights where one expects glaciation, and certainly
high level reconnaissance photos and satellite observations
show an abundance of cirrus. However, one is also impressed
with the general convective nature most echoes have on the
RHI scope, many times in close proximity to the bright band.
These observations suggest that echoes exist in all stages
of generation and dissipation; but they do little to help an-
swer the question of whether there is enough mixing of ice nu-
clei in the wall cloud regions of interest to significantly
alter the possible effects of seeding active towers there.
The results above show widespread echoes at heights where one
expects glaciation, and certainly high level reconnaissance
photos and satellite observations show an abundance of cirrus.
However, one is also impressed with the general convective
nature most echoes have on the RHI scope, many times in close
proximity to the bright band. These observations suggest that
echoes exist in all stages of generation and dissipation; but
they do little to help answer the question of whether there
is enough mixing of ice nuclei in the wall cloud regions of
interest to significantly alter the possible effects of seed-
ing active towers there.
Unfortunately, it is not possible to draw a series of
PPI-RHI composites for any storm found in a relatively undis-
turbed tropical over-water environment simply because the data
are too limited to date. Consequently, it seems essential
that eyery effort be made to obtain such records with the
only airborne radar presently capable of gathering high qual-
ity RHI data, the Navy APS-45. Secondarily, more effort
should be made to gather RHI data on WSR-57's, the new WMO
supplied RC-32B weather radars in the Lesser Antillies, and
others, in an attempt to better describe this most important
hurricane precipitation pattern dimension, including the
bright band and shear in e\/ery sector of the storm.
Bi gl er , S
REFERENCES
Jr
S. G., and P. L. Hexter, Jr. (1960): Radar analysis
f Hurricane Debra. Proceedings 8th Weather Radar
onferenae3 American Meteorological Society, Cal . ,
pril , pp. 25-32.
K-16
Jordan, C. L., D. A. Hurt, and C. A. Lowrey (1960): On the
structure of Hurricane Daisy on 27 August 1958. Journal
of Meteorology 3 American Meteorological Society, 17,
pp. 337-348.
Jordan, C. L., and F. J. Schatzle (1961): The 'Double Eye'
Hurricane Donna. Monthly Weather Review, 89, (9),
September, pp. 354-356.
of
Jordan, H. M., and D. J. Stowell (1955): Some small-scale
features of the track of Hurricane lone. Monthly
Weather Review, 83, (9), September, pp. 210-215.
Kessler, E., and D. Atlas (1956): Radar-synoptic analysis of
Hurricane Edna, 1954. Geophysical Research Papers
No. 50, A.F.C.R.L., Bedford, Mass., July, p. 113.
Ligda, M. G. H. (1951): Radar storm detection. Compendium of
Meteorology , American Meteorological Society, Boston,
Mass. , pp. 1265-1289.
Senn, H. V. (1963): Radar precipitation echo motion in Hurri-
cane Donna. Proceedings 3rd Technical Conference on
Hurricanes and Tropical Meteorology. A. M.S., A.G.I. ,
and H.G.I, and M.G.U., Mexico City, Mexico, June 6-12,
R.S.M.A.S. Contr. No. 463.
Senn, H. V. (1965): The three-dimensional distribution of
precipitation in Hurricane Cleo. 4th Technical Con-
ference on Hurricanes and Tropical Meteorology. A. M.S.,
Miami Beach, Fla., November.
Senn, H. V. (1966): Precipitation shear and bright band ob-
servations in Hurricane Betsy, 1965. Proceedings 12th
Weather Radar Conference, October 17-20, Oklahoma City,
Okla., R.S.M.A.S. Contr. No. 710.
Senn, H. V. (1967): Radar Hurricane Research, Final Report,
ESSA, NHRL Contract No. E22-84-67(N ) , Report No. 8208-1,
September, DDC AD 821-860.
Senn, H. V., and H. W. Hiser (1959): On the origin of hurri-
cane spiral bands. A. M.S., Journal of Meteorology, 16,
(4), August, pp. 419-426, R.S.M.A.S. Contr. No. 215.
Senn, H. V., H. W. Hiser, and R. D. Nelson (1960): Studies
of the evolution and motion of radar echoes from hurri-
canes 1 July 1959 to 30 June 1960, Final Report. U.S.
Weather Bureau, Contract CWB-9727, Report No. 8944-1,
August.
K-17
Serin, H. V., and H. W. Hiser (1961): Effectiveness of various
radars in tracking hurricanes. Proceedings 2nd Techni-
aan Conference on Hurricanes^ A. M.S., Miami Beach, Fla.
June, pp. 101-114, R.S.M.A.S. Contr. No. 318.
Senn, H. V., and C. L. Courtright (1970):
Research, Final Report, ESSA, NHRL
41 -70 (N ) , October.
Radar Hurricane
Contract No. E21-
Wexler, H. (1947): Structure of Hurricanes as determined by
radar. Annals of N.Y. Academy Sciences 3 48t September
15, pp. 821-944.
K-18
APPENDIX L
PROJECT STORMFURY EXPERIMENTAL ELIGIBILITY IN
THE WESTERN NORTH PACIFIC
William D. Mai 1 i nger
National Hurricane Research Laboratory
INTRODUCTION
cane
Si nc
b i 1 i
towa
rul e
in 1
sout
Mexi
that
hurr
wi th
Ocea
whi c
1963
Pro
modi f
e that
ty rul
rd fur
s for
970 an
hwest
co is
there
i c a n e
in 18
n area
h expe
; and
ject
i c a t i
ti me
es ha
ther
this
d are
North
e 1 i g i
i s a
co mi n
hours
has
ri men
Debbi
STORM
on ex
the
ve be
rel ax
area
now
Atla
ble f
smal
g wit
af te
been
ts ha
e, 19
FURY
peri
oper
en c
a tio
el ig
as f
nti c
or s
1 pr
hi n
r se
util
ve b
69) .
, the i
ments ,
a t i n g a
hanged
ns of t
i b i 1 i ty
ol lows :
, the C
e e d i n g
o b a b i 1 i
50 n mi
e d i n g . "
ized to
een con
ntera
was f
reas
sever
he se
for
"A
a r i b b
as 1 o
ty (1
1 es o
To
seed
ducte
gency p
ormal ly
a u t h o r i
al time
e d i n g r
seeding
storm o
ean Sea
ng as t
0 perce
f a pop
date on
the th
d (Esth
ro ject
organ
zed an
s prog
e s t r i c
were
r hurr
, or t
he for
nt or
ul ated
ly the
ree hu
er, 19
for
ized
d the
ressi
t i o n s
1 ast
i c a n e
he Gu
ecast
1 ess)
1 and
Atla
r r i c a
61 ; B
hurri -
in 1962.
el igi-
vely
. The
changed
i n the
If of
states
of the
area
nti c
nes upon
eul ah ,
St
canes and
and publ i
1969. Th
Gulf of M
and the w
in the e a
Mexico) a
for STORM
this repo
18-hour r
poses of
Western P
because p
if there
p o r t u n i t i
u d i e s of
typhoons
shed in t
ese repor
exico are
estern No
stern Nor
re not co
FURY seed
rt. An u
ule for t
compari so
a c i f i c .
roper bas
is to be
es to jus
s t a t i s
under
he STO
ts cov
as ; th
rth Pa
th Pac
n s i d e r
i n g an
pdate
he Atl
n with
Thi s c
es for
a suf f
tify t
t i c a 1
the o
RMFURY
ered t
e east
c i f i c
i f i c a
ed to
d will
to inc
antic
the s
ompari
opera
i c i e n t
he Pro
proba
1 der
Annu
he At
ern P
area .
rea (
be su
not
1 ude
areas
e e d i n
son i
t i o n s
i ncr
ject'
b i 1 i ti e
el i g i b i
al Repo
1 anti c ,
a c i f i c
The h
off the
i tabl e
be furt
1970 ca
will b
g oppor
s parti
in the
ease in
s move
s of
1 i ty
rts
Car
hurr
urri
wes
expe
her
ses
e i n
turn"
cul a
Pac
exp
to t
el ig
rul e
for 1
i b b e a
i cane
canes
t coa
rimen
d i s c u
under
cl ude
ties
rly i
i f i c
erime
he Pa
ible
s we
968
n , a
reg
occ
st o
tal
ssed
the
d fo
i n t
mpor
are
ntal
ci f i
hurri -
re made
and
nd
ions ;
u r r i n g
f
targets
i n
new
r pur-
he
tant
needed
op-
c .
ATLANTIC OCEAN, CARIBBEAN SEA, AND
GULF OF MEXICO STORMFURY AREAS
Figure L-l shows the eligible ar
from 1968 through 1970. Table L-l show
rences of hurricanes eligible for STORM
ing the months of August, September, an
through 1970 using the "18-hour after s
rule. The addition of the storms which
the change from the "24-hour" to "18-ho
storms to the Atlantic, two to the Gulf
the Caribbean. These additions increas
tunities per year from an average of ap
hurricanes per year eligible for seed in
seeding eligibility rules regarding pos
eas for
s the nu
FURY exp
d Octobe
e e d i n g "
became
ur" rule
of Mexi
ed the e
proxi ma t
g under
i t i o n of
s e e d i
mber
eri me
r fro
e 1 i g i
e 1 i g i
adds
co , a
xpect
ely 2
the c
the
ng used
of occur-
nts dur-
m 1954
b i 1 i ty
bl e under
three
nd one to
ed oppor-
to 2.35
urren t
storm.
35°
30'
25°
20'
15'
10'
PROJECT STORMFURY
OPERATIONAL AREAS
(1968 — 1970)
ELIGIBLE EXPERIMENTAL STORM
MUST BE PREDICTED TO REMAIN
WITHIN OPERATIONAL AREA FOR/
Figure L-l. Project STORMFURY operational areas ( 1968-1970) .
Eligible experimental storm must be predicted to remain
within operational area for 18 hours after seeding.
L-2
1954
2
1955
4
1956
1
1957
1
1958
5
1959
2
1960
2
1961
2
1962
2
1963
3
1964
4
1965
2
1966
1
1967
0
1968
0
1969
2
1970
0
Table L-l. Annual Frequency of Hurricanes Eligible for Seed-
ing Between 1 August and 31 October Under Forecasting Tech-
niques Criteria Approved for STORMFURY Operations Subsequent
to 1970.
Year Atlantic Gulf of Mexico Caribbean Sea Total
0 1 3
0 1 5
0 0 1
0 0 1
0 0 5
0 0 2
0 1 3
1 0 3
0 0 2
0 1 4
1 0 5
0 0 2
0 0 1
0 0 0
0 0 0
1 0 3
0 0 0
TOTAL 33 3 4 40
This number is misleading on the high side because some of
these storms either had structure considered unsuitable for
experimentation or were changing rapidly in intensity at the
time and might not have been used for experiments even though
they fell within the criteria established for area seeding
eligibility. In addition, some of the storms considered eli-
gible in the Gulf of Mexico and Caribbean Sea might not have
been seeded for political reasons.
WESTERN NORTH PACIFIC
Figure L-2 shows the proposed operational areas if ex-
periments are to be conducted from Guam and Okinawa. The el-
igibility rules considered in this study for the Western
Pacific are: (1) The typhoon must be within 600 miles of the
operations base for a minimum of 12 daylight hours, (2) maxi-
mum winds must be at least 65 knots, and (3) the predicted
movement of the typhoon must indicate that it will not be with'
in 50 n miles of a populated land area within 24 hours after
seeding.
L-3
120°E
130°E
140°E
150°E
160°E
170°E
180°E
40°N
TMOJECT STOHMFUMY
A.XEJL
30°N
THREE MONTH AVERAGE OF
4.8 ELIGIBLE TYPHOON'S
AUGUST , SEPTEMBER .OCTOBER
(1961-1970)
20°N
10°N
Wake]
40°N
30° N
20°N
10°N
120°E 130°E 140°E 150°E 160°E 170°E 180°E
Figure L-2. Project STORMFURY area in the Western Pacific.
The list of Western Pacific typhoons eligible for seed
ing was updated to include 1970 tropical cyclones and was
divided into two categories: (1) those that could be used
for STORMFURY experiments with forces limited to operations
from Guam only, and (2) those which permitted free use of
either Guam or Okinawa from which to launch experiments (see
table L-2) .
Two of the 24 "Guam only" opportunities would have re-
quired such rapid reaction in order to mount a seeding experi
ment that they would probably have been missed. These storms
formed within the 600 n mile radius of Guam and rapidly deep-
ened while they continued to move out of the area. If a 48-
hour notice to alert, deploy, and brief the participants in
the experiment were required, both storms would definitely
have been missed. A WP-3 or C-130 type aircraft might be
used as a seeder in such cases when time does not permit the
deployment of jet seeders to the operating base. If this is
jt feasible, STORMFURY monitoring missions without seeding
might be conducted on shorter notice in these storms.
L-4
Table L-2. Western Pacific Typhoons Eligible for STORMFURY
Experiments - August^ September > and October (1961-1970).
~7, ~~r n , Combined use of
Year Guam 0n]y Guam and Okinawa
1961 2 6
1962 3 7
1963 2 6
1964 1 2
1965 3 7
1966 1 3
1967 3 4
1968 5 8
1969 2 2
1970 2 3
TOTAL 24 (2.4Q 48 (4.8i)
1 Number of storms per year
Seven of the 24 "Guam only" typhoons were also eligible
later in their lives if forces operated from Okinawa. Several
of these storms would have been eligible for seeding both from
Guam and later from Okinawa, permitting two experiments on the
same storm. It is also possible that a storm could be subjec-
ted to two experiments from either Guam or Okinawa although
this opportunity occurs infrequently.
The free use of both Guam and Okinawa as STORMFURY
bases of operation is essential to obtaining a suitable num-
ber of experiments during the 3-month period. Safety of per-
sonnel and aircraft is paramount and will require a multitude
of decisions concerning the best and safest use of the STORM-
FURY forces. Examples of this are as follows: (1) A storm
or typhoon approaching Guam from the east which, while eligi-
ble for experimentation, would not be seeded because forces
would have to execute a typhoon evacuation (aircraft flyaway)
for safety reasons. If these aircraft could be deployed to
Okinawa for their evacuation, when the storm had passed Guam
a mission could be mounted from Okinawa and terminated in
Guam. Some changes in operational plans and techniques will
be required to execute this type of experiment. (2) A typhoon
that develops while approaching the 600 n mile radius to the
west of Guam would be eligible in many cases if Project air-
craft could terminate their missions in Okinawa. This also
will require modified STORMFURY flight plans and schedules in
order to accomplish the experiment.
L-5
If the flexibility of using both Guam and Okinawa as
STORMFURY operational bases is not possible, opportunities to
seed some of the storms would be lost because Project aircraft
might have to fly away from Guam until an approaching typhoon
had safely passed. Upon return of the forces to Guam and
after mission preparations, the typhoon would have approached
or exceeded the maximum operating range of STORMFURY forces.
The study was further expanded to examine the number
of calendar days during which a large number of tropical cy-
clones exists in the Western Pacific to determine the effect
that this factor would have on the availability and partici-
pation of reconnaissance aircraft for STORMFURY operations.
Cyclone activity (tropical depressions, tropical storms, and
typhoons) during the 3- mo nth period of August, September, and
October is listed by the number and percentage of days occur-
rence in table L-3.
During the months of August, September, and October
tropical cyclones occur somewhere in the western North Pacific
Ocean 84 percent of the time or an average of 77 days out of
the 92. Three or more tropical cyclones occur simultaneously
during an average of about 9 of these 77 days. Fortunately,
during some of these periods, because of their location and
strength, the tropical cyclones did not all require full re-
connaissance coverage. Reconnaissance forces may be hard
Table L-3,
Year
Tropical Cyclone Days in Western North Pacific
August 3 September 3 October .
0
Number of Days with 0 to 5 Cyclones"
12 3 4
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
8
7
15
23
10
24
11
9
15
32
8
41
22
14
4
38
39
8
0
23
39
15
0
40
25
4
0
42
29
1 1
0
35
24
9
0
40
25
16
0
39
30
8
6
31
37
9
0
48
11
1
0
60
23
1
0
437
304
96
10
39.7
27.6
8.7
0.9
43.1
30.0
9.5
1 .0
TOTAL DAYS 162
AVERAGE DAYS 14.8
% OF DAYS 16.1
3
0.3
0.3
% of tropical cyclone days with one or two cyclones - 87.2
% of tropical cyclone days with three or more cyclones-1 2 .8
L-6
pressed at times to participate in full scale Project STORM-
FURY experiments during periods when there are three or more
active cyclones, but should be able to provide reconnaissance
on one cyclone while participating in Project STQRMFURY oper-
ations on another. There are exceptions to these assumptions;
but, in general, sufficient forces to conduct experiments
should be available during 68 of the 77 cyclone days. When,
because of other commitments, DOD reconnaissance and seeder
aircraft are not available to mount a full seeding experiment,
the remaining available Project aircraft can be utilized to
gather data on the natural variability within typhoons.
CONCLUSIONS AND RECOMMENDATIONS
(1) Conducting operations in the Western Pacific is
worthwhile and should increase the number of experimental op-
portunities per average season by a factor of 2-3 over those
experienced in the Atlantic regions provided that both Guam
and Okinawa are available for use by STORMFURY forces. Addi-
tion of a base in the Philippines and in other locations in
the Pacific adds a few opportunities per 10 years, but most
of the eligible storms can be worked from either Guam or
Okinawa. If Guam is available, but Okinawa is not, the
desirability of moving the project to the Pacific should be
reconsidered because of the limited increase in the number
of expected opportunities over those in the Atlantic operating
areas .
(2) During periods when there are three or more tropi-
cal cyclones occurring simultaneously (13 percent of the
cyclone active periods during August, September, and October),
monitoring missions could be conducted on suitable storms
using fewer forces and without actual seeding.
(3) Some additional experiments could be conducted on
tropical storms and tropical depressions during periods when
no eligible typhoon activity was occurring.
L-7
GPO 836 -595
41
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
Environmental Research Laboratories
NOAA Technical Memorandum ERL NHRL-93
HORIZONTAL ASYMMETRIES
IN A NUMERICAL MODEL OF A HURRICANE
James W. Trout
Richard A. Anthes
National Hurricane Research Laboratory
Coral Gables, Florida
November 1971
TABLE OF CONTENTS
Page
ABSTRACT 1
1. INTRODUCTION 1
2. SUMMARY OF THE MODEL 2
3. COMPUTATIONAL PROCEDURE 1»
3.1 The Polar Grid 5
3-2 Interpolation Schemes to the Polar Grid 5
k. THE ASYMMETRIC STAGE 7
*t.1 Time Variations of Azimuthal Standard Deviations. . 9
k.2 Harmonic Analysis of the Momentum and Temperature
Fields 13
5. EDDY FLOW RELATED TO THE MATURE VORTEX 17
5.1 Asymmetries in the Outflow Layer 20
5.2 Asymmetries in the Inflow Layer 2 5
6. HORIZONTAL TRANSPORT MECHANISM 27
6.1 Flux of Absolute Vorticity 28
6.2 Flux of Angular Momentum 30
6.3 Vertical Flux of Relative Angular Momentum 32
7- SUMMARY AND CONCLUSIONS 33
8. REFERENCES 36
i i i
HORIZONTAL ASYMMETRIES IN A NUMERICAL MODEL OF A HURRICANE
James W. Trout and Richard A. Anthes
Statistical techniques are employed to investigate the
development and structure of horizontal asymmetries in the
numerical model of a hurricane developed by Anthes et al.
(1971a). Strong asymmetries in the momentum and temperature
fields develop in the outflow layer at approximately 120
hours. Weaker asymmetries also develop in the inflow layer
at this time. Harmonic analyses are used to determine the
predominant scale of asymmetries. Detailed spatial analyses
are carried out for the momentum and temperature fields in
the mature asymmetric stage of the model. The analyses are
compared to observational data compiled by Black and Anthes
(1971). The results show that the model reproduces many
observed features of a three-dimensional tropical cyclone.
1. INTRODUCTION
Recent experiments conducted with an asymmetric hurricane model
(Anthes et al . , 1971a) dramatically illustrate certain asymmetric proper-
ties of the horizontal and vertical motion fields. Examples of these are
horizontal eddies in the upper tropospheric outflow layer, rainbands, and
meandering of the hurricane eye. Two distinct stages are observed in a
typical experiment. During the early stages, the storm circulation is
quite symmetric about the vertical axis of rotation. In the second stage,
the storm acquires marked asymmetric characteristics in the outflow layer,
and the vertical motion patterns form spiral bands which resemble hurri-
cane rainbands.
The purpose of this paper is to report the quantitative investigation
of the nature and importance of the asymmetric character of the model
storm. Various statistical measures are employed to show the
time-dependent development and locations of the asymmetries. Harmonic
analysis of the radial and tangential wind components determines the pre-
dominant scale of the asymmetries. Computations of fluxes of angular
momentum and absolute vorticity show the importance of asymmetries as
horizontal transport mechanisms. The asymmetries in the model outflow
layer are compared with the asymmetric features of real storms (Black and
Anthes, 197D .
2. SUMMARY OF THE MODEL
The equations are written in a-coordi nates (Phillips, 1957) on an
f-plane. The equations of motion and the continuity, thermodynamic, and
hydrostatic equations are identical to those utilized by Smagorinsky et
al. (1965) for general circulation studies. The basic equations are
given in Anthes et al . (1971a). The vertical structure of the model con-
sists of an upper layer and a lower layer of equal pressure depth and a
thinner Ekman boundary layer. The information levels for the dynamic and
thermodynamic variables are staggered according to the method used by
Kurihara and Holloway (19&7) •
For computational economy, the horizontal mesh has been limited to a
square grid with a uniform spacing of 30 km. The lateral boundary points
approximate a circle, and all points are contained between radii of ^35
and 450 km. The thermodynamic grid points are staggered from the veloc-
ity component grid points on the a-surfaces. A comprehensive summary of
the mathematical details is given elsewhere (Anthes, 1972) and need not
be repeated here.
The Matsuno ( 1 966 ) simulated forward-backward scheme is utilized in
the model for the time integration scheme. The Matsuno scheme has the
property of dampening the very high temporal frequencies associated with
internal and external gravity waves. The lateral boundary conditions
consist of a steady-state pressure and temperature on the boundary and a
variable momentum based on extrapolation outward from the interior of the
domain. The cumulus scale convective processes are parameterized simi-
larly to the version of Rosenthal's (1970b) symmetric model. The current
model also contains an explicit water vapor cycle. For further details
refer to Anthes (1972). The initial conditions consist of an axisym-
metric vortex in gradient balance. The minimum pressure is 1011 mb ,
and the environmental pressure on the lateral boundary is 1015 mb , yield-
ing a maximum gradient wind of 18 m sec-1 at a radius of 2^0 km. With
these initial conditions and utilizing a time step of k5 seconds, the
experiment has been executed for 192 hours.
With symmetric initial and boundary conditions, the solutions to the
differential equations must remain symmetric for all time. However,
truncation and roundoff errors in the finite difference equations, as
well as the lack of complete circular symmetry in boundary conditions,
produce extremely weak asymmetries after the first time step. Although
objections might be raised concerning the desirability of allowing the
initial asymmetries to be generated by truncation, later experiments in
which asymmetries were deliberately introduced in a random fashion yield
essentially the same results during the asymmetric stage (Anthes, 1972).
Thus, it appears that the actual source of the initial asymmetries is un-
important in the mature asymmetric stage.
3. COMPUTATIONAL PROCEDURE
During the asymmetric stage an interesting anticyclonic looping of
the eye is observed. This looping appears to be related to the asym-
metric outflow and is discussed by Anthes (1972). The center of the grid
is depicted as zero (fig. 1), with north-south, east-west deviations from
the center plotted in kilometers.
NORTH 30
A
15-
0
(Km) -15
-30
-45
SOUTH
-60-
«*»""'
192
•
162 /
***\ 168
i
/
X
i
/
/
N
\
wm
\
i
\
mm
\
i
\
\
\
\
m m,~ \
138 \
—
\
> 156 \
•• • • • •
••.. 174*
-
\
132
\
-
\ \
\ \
* 144 i
/ !
-
\
. 150
i
±86^
^•^^_
' i
i
i
i
mm
X
/
«■
X.
/
•
^,
**
-'
- • — -
180
i
1 1 1
-_l
i i | £
-0
-60 -45 -30 -15 0 15 30 45 60
WEST - ( Km ) -EAST
Figure 1: Model vortex motion. Positions are labeled in hours.
3. 1 The Polar Grid
The computation of circular averages and mean and eddy fluxes of
vorticity and momentum requires interpolation from the cartesian grid
system to a polar grid system whose origin is coincident with the looping
vortex center. The rectangular (u) and (v) wind components are converted
into tangential (V-v) and radial (V ) wind components by use of:
VA = (vX - uY)/R (1)
and
Vr = (uX - vY)/R (2)
where X and Y are the distances along the x and y axis between the vor-
tex center and a given grid point;
and R = (X2 + Y2)*. (3)
The cartesian arrays are interpolated to a polar coordinate grid
consisting of 15 radial increments of 30 km (r = 15, ^5, 75-...) and 16
azimuthal increments of 22.5 degrees. The calculation extends to a
radius of 435 km when the storm center is located on the center of the
cartesian grid. When the storm center is located away from the grid
center, the maximum radius of the polar grid is reduced.
3.2 Interpolation Schemes to the Polar Grid
The accuracy of two interpolation formulae is tested. The first of
these is a bilinear interpolation formula:
s" =s,,j + hts,,J+rsi,j] + wVi.j-Si.j) (1-h)
+ <S|+1,J+r5|iJ+i>J3
eo
I-i
I+i
T(p)
J-i
J+l
Figure 2: Interpolation to polar grid point (P) .
Here the interpolated value of S , at the location of the polar point
(fig. 2), is denoted by P. In (4), (l, J) is the grid point (row, column)
index in the usual matrix sense; h and K are the coordinate distances
from point P to grid point (I, J). Satisfactory results are obtainable
with (*t) at large radii. However, at smaller radii the curvature in the
variables associated with the hurricane vortex is too extreme for linear
interpolation. The second method is a nine point interpolation function.
The formula is a finite difference form of the truncated Taylor's expan-
sion of a function of two independent variables.
s = s|J + .5h<s|>Jt1-s|>iM) + •5K(s|_,iJ-s|+1J)
+ •»,<si.j*i4Si.j-r2Si.j> + •5k2(si-i,j+si+i,j-2Si,j)
+ •25hK(S|_1)J+l-S|_1jJ_,-S|+,jJ+l+S|+1 (J_,). (5)
For all interpolations the base Doint (I, J) is selected so that h and K
are not greater than one-half a grid increment.
6
Both interpolation formulae are applied to the function,
f(r) = (r+15)/30 (r in km). (6)
With the vortex center coincident with the grid center, (6) yields
integer values increasing from 1 at r = 15 km to 15 at r = 435 km at al
azimuth angles. Table 1 shows circular averages, for the first five
radii, computed from data obtained by use of (4) and (5).
Table 1: Circular Averages Computed from Interpolation
Scheme (4) and (5)
Radius Bilinear Interpolation 9-Point Interpolation
(km) Eqn. (4) Eqn. (5)
15 1.2071 1.0969
45 2.0529 2.0137
75 3-0447 2.9920
90 4.0211 4.0022
105 5.0230 5.0008
Table 1 clearly shows the superiority of the 9~Point Interpolation for-
mula at small radii. Hence, interpolation formula (5) is utilized
throughout this paper.
4. THE ASYMMETRIC STAGE
Notable asymmetries of the cyclone circulation include large hori-
zontal eddies in the upper tropospheric outflow region. Figure 3 shows
the trajectories of 10 particles which are released in the lower levels
of the cyclone and provides a qualitative view of the asymmetric circu-
lation over the life cycle of a typical experiment. The trajectories are
T=90-282 HOURS
9 HOUR INTERVALS
Figure 3: Ten trajectories of parcels released in the
boundary layer over an 8-day period.
computed over an 8-day period from the forecast velocity components. For
additional illustrations and computational procedure refer to Anthes et
al . (1971c). The figure greatly exaggerates the vertical dimension of
the storm but clearly illustrates the asymmetric outflow characteristics.
Particles, upon reaching the upper levels of the model, are carried out-
ward from the vortex center, mainly in the northeast and southwest quad-
rants. This should be contrasted to the nearly symmetric inflow depicted
in the lower layers. The preferred quadrants of outflow reflect the
asymmetric circulation around upper level horizontal eddies that are
present during the 8-day period.
4.1 Time Variations of Azimuthal Standard Deviations
The principal measure of asymmetry employed here is the standard
deviations (SD) from the azimuthal averages of momentum and temperature.
Figure k and figure 5 are plots of SD versus time for the radial winds,
tangential winds and temperature at selected radii in the inflow and out-
flow layers.
Large SD are computed at very small radii (not plotted), where the
interpolation error due to the relatively few cartesian grid point values
is the greatest. However, the asymmetries are relatively small compared
to the azimuthal means. The inflow asymmetries diminish rapidly with in-
creasing radius. The outflow asymmetries, on the other hand, appear to
be greatest near the 165 km radius (fig. k) . The ratio of the standard
deviation to the mean at all radii is larger in the outflow layer.
Three distinct development phases of the model can be defined from
the time variation of the SD. First, there is an "organizational phase,"
LEGEND
LEVEL 1
LEVEL 3
TEMPERATURE
0*1— i—i— r
285 Km.
345 Km.
0 24 46 72 96 120 144 166 192
TIME (HOURS)
285 Km.
0 24 46 72 96 120 144 168 192
TIME (HOURS)
285 Km.
0 24 48 72 96 120 144 168 192
TIME (HOURS)
RADIAL
WIND
345 Km.
0 24 48 72 96 120 144 168 192
TIME (HOURS)
TANGENTIAL
WIND
345 Km.
i I i I i I i I i
0 24 48 72 96 120 144 168 192
TIME (HOURS)
--f---r' I
24 46 72 96 120 144 168 192
TIME (HOURS)
Figure k\ Time variations of the standard deviations for temp
eratures, radial winds, and tangential winds at inner radii.
10
TEMPERATURE
105 Km
0 24 46 72 96 120 144 168 192
TIME (HOURS)
105 Km
0 24 48 72 96 120 144 168 192
TIME (HOURS)
TANGENTIAL
WIND
105 Km.
0 24 48 72 96 120 144 168 192
TIME (HOURS)
TEMPERATURE
Mr— r
165 Km
TEMPERATURE
225 Km
0 24 48 72 96 120 144 168 192
TIME (HOURS)
RADIAL
WIND
165 Km.
0 24 48 72 96 120 144 168 132
TIME (HOURS)
TANGENTIAL
WIND 165 Km.
' I ' I ' I ' I ' I ' I ' I i
o 6 -
24 48 72 96 120 144 168 192
TIME (HOURS)
L£C€ND
0 24 48 72 96 120 144 168 192
TIME (HOURS)
RADIAL
WIND
225 Km.
fc 5 -
' I ' I ' I ' I ' I ' I ' I i
pfcHT agga
0 24 48 72 96 120 144 168 192
TIME (HOURS)
TANGENTIAL
WIND 225 Km
i I i I ' I ' I ' I i I i I
> 5
E«
24 48 72 96 120 144 168 192
TIME (HOURS)
LEVEL 1
LEVEL 3
Figure 5' Time variations of the standard deviations for temp'
eratures, radial winds, and tangential winds at outer radii.
1 1
exhibited initially by the lack of asymmetries. Standard deviations of
0.5 m sec-1 or less are computed for both the radial and tangential winds
during this phase. Increasing deviations first appear in the inflow
layer and this is closely followed by the development of small asym-
metries in the outflow layer. A period (symmetric phase) in which the
SD's are small and relatively steady follows. Finally, an asymmetric
phase begins at approximately 120 hours. This is characterized by the
development of large scale asymmetries in the outflow layer and spiral
bands of convection in the lower layer. At small radii, the SD of the
tangential winds increases to 8 m sec x in the outflow layer. The asym-
metries in the outflow layer radial wind field also experience rapid
growth, but the magnitude of the SD is somewhat smaller than that of the
tangential winds. The magnitude of the asymmetries of the two components
is comparable in the inflow layer as are the circular means.
At the larger radii, both the inflow and outflow asymmetries de-
crease with increasing radius (figs, k and 5). However, at a radius of
350 km from the vortex center, the asymmetries are still well defined and
contain SD approximately equal to the magnitude of the mean radial and
tangential flow. The lateral boundary conditions require the boundary
velocity components to vanish at inflow points, and thus contribute to
decreased SD's at large radii in the inflow layer.
The plots of temperature SD versus time also distinctly illustrate
the three phases of the development of the model. However, the tempera-
ture field is much more symmetric than the momentum field, as indicated
by the small standard deviations of temperature. The decrease of SD with
12
increasing radius is due to the boundary conditions of a steady symmetric
temperature .
h.2 Harmonic Analysis of the Momentum and Temperature Fields
The previous section established the rapid development of asym-
metries at model time equal to 120 hours. In this section harmonic anal-
ysis establishes the predominant scale of the asymmetries for both the
inflow and outflow levels. Figures 6, 7, and 8 show the time variation
of the scale of the percent variance accounted for by harmonic 1, 2, 3,
k, and 8 at a typical inner {kS km) and outer (285 km) radius of the
vortex.
An important feature revealed by the harmonic analysis is the pre-
dominance of wave numbers k and 8 during the organizational and sym-
metric stages of the vortex development. The grid boundary is an 8-sided
figure comprised of k regular sides and k irregular sides. Wave number 8
is, therefore, probably a manifestation of the octagon shaped boundary of
the grid. Wave number k is apparently a manifestation of the k irregular
corners of the grid. Both wave patterns are also affected by errors
associated with the numerical differencing scheme, especially in corner
regions of the grid where the lateral boundary conditions may cause dif-
ferent truncation errors. Recent investigations by Koss (1971) show that
the numerical differencing utilized in an asymmetric vortex model can
also induce error patterns that persist with time in the form of wave
number k. Caution must be exercised in interpreting figures 6, 7, and 8.
During the early stages of the experiment, the percent of variance con-
tained by wave number k is very high (70% to 95%); however, the total
13
100%
RAOIAL WIND
LEVEL i 45 Km.
100%
90%
24 48 72 96 120 144 168 192
TIME (HOURS)
RADIAL WIND
LEVEL 3 45 Km.
100%l ■ I ' I ' I ' I ' I ' I ' I ' I '
90%
80%
70%
UJ 60%
u
z
<
(E 50%
^40%
90%
20%
10%
0%
24 48
0%
100%
RADIAL WIND
LEVEL i 285 Km.
■ I ' I ' I ' I ' I ' I ' I ' I '
24 48
72 96 120 144 168 192
TIME (HOURS)
"T
RADIAL WIND
LEVEL 3 285 Km
I ' I ' I ' I
T
I'M
72 96 120 144 168 192
TIME (HOURS)
72 96 120 144 166 192
TIME (HOURS)
L EGEND
Ht -■
H4
Figure 6: Harmonic analysis of the model outflow layer and
inflow layer radial wind component. Wave numbers 1, 2,
3, A, and 8 are illustrated at an inner and outer radius.
\k
100%
10% -
0%
TANGENTIAL WIND
LEVEL i 45 Km.
i I i I i I i l i I ■ i i ■ ii ■
' ■"■' ' ■ ■
1D0%
0 24 48 72 96 120 144 168 192
TIME (HOURS)
TANGENTIAL WIND
LEVEL 3 45 Km
i I i I i I i I i I i I i I i I i
90% -
80% -
0%
TANGENTIAL WIND
LEVEL 1 285 Km.
100%
90%
80%
70%
60%
Id
O
Z
| 50%
^40%
30%:
20%-
10%
0%«r
I I I I I I I I I I I I ' I I I I
100°/,
0 24 48 72 96 120 144 168 192
TIME (HOURS)
TANGENTIAL WIND
LEVEL 3 285 Km.
i I i I i I i I i I i I i I i I i
80% -
0 24 48 72 96 120 144 168 192
TIME (HOURS)
0%
0 24 48 72 96 120 144 168 192
TIME (HOURS)
LEGEND
Figure 7: Harmonic analysis of the model outflow layer and
inflow layer tangential wind component. Wave numbers 1,
2, 3, k, and 8 are illustrated at an inner and outer radius
15
TEMPERATURE
LEVEL i 45 Km.
IOOXi I I I I I I I I I | I I I 1 I I I
0%,
-^ -, **■ I V I 1 I
0 24 48 72 96 120 144 168 192
TIME (HOURS)
TEMPERATURE
LEVEL 3 45 Km.
100%
0%
100%
90%
TEMPERATURE
LEVEL 1 285 Km.
1 I ' I
I ' I
-i — i — i i i
72 96 120 144
TIME (HOURS)
TEMPERATURE
LEVEL 3 285 Km.
100%| 1 | I |
192
0 24 48 72 96 120 144 168 192
TIME (HOURS)
72 96 120 144 168 192
TIME (HOURS)
LEGEND
Hi
H,
H4
Figure 8: Harmonic analysis of the model outlfow layer and
inflow layer temperatures. Wave numbers 1, 2, 3, b , and
8 are illustrated at an inner and outer radius.
16
variance is very small. The SD of the tangential wind, for example, is
only about 0.5 rn sec-1 contrasted with the mean flow of about 10 m sec
in the outflow and 30 m sec-1 in the inflow layers.
The boundary induced wave numbers k and 8 are rapidly obscured by
the presumably meteorological waves, 1, 2 and 3 with the onset of the
asymmetric stages of the model. Figures 6, 7, and 8 all show the wave h
trace and wave 1 trace intersecting at a time slightly less than 120
hours. Thereafter, the predominant wave is clearly wave 1 for both in-
flow and outflow layers. Recent results (Anthes, 1972) show the growth
of asymmetries in the outflow layer to be a result of barotropic insta-
bility in which the energy source of the eddies is the kinetic energy of
the mean flow. The temperature harmonic analysis shows essentially the
same behavior as the momentum analysis, with wave number 1 becoming pre-
dominant during the asymmetric stage. In summary it should be reempha-
sized that the total variance in the inflow layer is small and that the
temperature variance is small at both levels.
5. EDDY FLOW RELATED TO THE MATURE VORTEX
This section presents a detailed analysis of the eddy flow in both
the inflow and outflow levels during the mature stage of the vortex (17^
hours). Figures 9 and 10 are the streamline and isotjch analysis for the
outflow and inflow levels, respectively. The asymmetric circulation in
the outflow layer, the displacement of the vortex center from the grid
center, and the relative symmetry of the inflow level, discussed earlier,
are again illustrated by these figures. The isotach analysis shows that
17
STREAMLINES
LEVEL i
174 HOURS
Figure 9A: Streamlines - Level 1
ISOTACHS (M./SEC.) LEVEL 1
17** hours.
174 HOURS
Figure 9B: Isotachs (m./sec.) - Level 1 - 17^ hours
18
STREAMLINES
LEVEL 3
174 HOURS
Figure 10A: Streamlines - Level 3 - 1 74 hours.
ISOTACHS (M./SEC.) LEVEL 3 174 HOURS
Figure 10B: Isotachs (m./sec.) - Level 3 - 1 74 hours
19
at least one or two maxima and minima can be located about the storm's
center in the outflow layer.
5-1 Asymmetries in the Outflow Layer
Figure 11 shows the azimuthal means and SD for the upper level wind
components at 1 7*t hours. The radial component is characterized by out-
flow at all radii, with a maximum value of 7 m sec-1 at 75 km. The out-
flow velocities decrease with increasing radii to a value of 2 m sec-1 at
^35 km, the edge of the domain. The tangential component is character-
ized by a strong band of cyclonic winds near the center, with a maximum
of Ik m sec"1 at hS km. The mean tangential winds become anticyclonic at
a radius of 135 km and remain anticyclonic with increasing radii.
Black and Anthes (1971) used cirrus band motions, radiosonde winds,
and limited aircraft data to construct similar figures for six individual
Atlantic storms. They also presented data from Miller's (1958) mean
Atlantic storm and Izawa's ( 1 964) mean Pacific storm. However, their
calculations begin at approximately 105 km from the center and extend
well beyond ^35 km. Two limitations exist in comparing the real storm
data to the model storm data. First, the isolated nature of the vortex
implies that the asymmetries and the mean flow diminish as the boundary
is approached. In contrast, in the real atmosphere, the flow patterns at
large radii interact with other atmospheric systems which produce addi-
tional asymmetries. Second, near the center of the storms, Black and
Anthes' data are compiled utilizing a coarse grid of 111 km as compared
to the 30 km model grid. With these limitations in mind, a comparison be-
tween the model figures and the actual storm data shows:
20
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1. There is favorable agreement between the magnitude of the model
mean radial wind component (V ) compared with the six Atlantic storms.
However, the magnitude of V is larger than either the Pacific or
Atlantic mean profiles. Defining symmetry as a high ratio of the mean to
the SD, the following comparisons of real and model outflow can be made:
(a) The SD approaches the magnitude of the mean radial wind in
both the model and actual storm data.
(b) The magnitude of \l falls within the range of the magnitude
of the real storm's radial winds.
(c) At large radii, the real storm tends to be more asymmetric
than the model storm because the latter diminishes in in-
tensity with increasing radius and the former merges with
other large scale circulations.
(d) The magnitude of the asymmetries compares favorably with
that of the mean Atlantic and Pacific storm's radial winds.
The harmonic analyses reveal the dominance of wave number 1 for
both the model and the actual storm outflow. The percent of variance
accounted for by the higher order wave numbers at increasing radii indi-
cates the presence of more than one eddy in the outflow layer far from
the model vortex center.
2. There is also favorable agreement between the magnitude of the
model mean tangential wind component (V ) compared with the actual storm
A
data, although again the model storm circulation is somewhat smaller in
radial extent than the real storm circulation. Specifically, the model
storm and the real storm show:
22
(a) a low ratio of the SD to the mean at inner radii, indica-
ting symmetry;
(b) a higher ratio of the SD to the mean at the outer radii,
indicating asymmetry;
(c) standard deviations for both tangential and radial wind
components of about the same order of magnitude.
The harmonic analysis again shows a predominance of wave number 1
associated with the V,. Higher wave numbers appear at radii greater than
200 km and account for a larger percent of the variance than the higher
wave numbers associated with V .
r
Figure 12 shows the temperature departures from the mean tropical
sounding (Herbert and Jordan, 1959) for both the inflow and outflow
levels. The maximum departure of 7 degrees occurs to the east of the
vortex center with smaller departures occurring to the west of the center
The SD are small (less than 1°C) at all radii and approach zero with in-
creasing radius, reflecting the steady state, uniform boundary conditions
imposed on the temperature fields. The symmetry ratio of the mean to the
SD is large, indicating that the temperature is nearly symmetric. The
harmonic analysis shows a large percentage of the variance to be con-
tained in harmonic one, with higher harmonics becoming more important at
large radi i .
In summary, the model outflow momentum components are quite asym-
metric, in agreement with the outflow asymmetries of the wind fields
found in real storms. The temperature field is considerably more sym-
metric than the corresponding wind fields.
23
TEMPERATURE DEPARTURES
174 HOURS
LEVEL 3
LEVEL 1
Figure 12: Temperature departures - 17*4 hours
2k
5.2 Asymmetries in the Inflow Layer
Figure 13 exhibits the inflow level mean radial profiles and har-
monic analysis for the model momentum and temperature fields at time
equal to 17^ hours. Real storm data for a direct comparison are diffi-
cult to obtain since most low-level studies have been performed at
elevations considerably above the boundary layer.
The radial wind component is characterized by an inflow maximum of
28 m sec occurring at a radius of 75 km (same radius as the maxi
mum
outflow component). The inflow maximum rapidly diminishes to a value of
approximately 1 m sec" at R (k35 km). The small ratio of the SD to
max
the mean indicates some minor asymmetry at the outer radii. These fea-
tures are within observable limits, but they are difficult to substanti-
ate. This ratio is much smaller in the inflow layer than in the outflow
layer, indicating a closer approximation to axial symmetry in the low
levels .
The radial wind harmonic analysis shows that wave number 1 explains
approximately 80-90 percent of the variance from 135 km outward. A
possible verification of the dominance of wave 1 in the boundary level
could be the track of low-level actual storm radar echoes as reported by
Black (1971). By tracking and plotting the variations of echo velocities
about an actual hurricane, Black found patterns which reproduced a nearly
sinusoidal wave--hence, wave number 1.
Inward from 135 km, wave number h is large in the model storm.
Additional data (not presented) show wave number h to be a persistent
feature of the model during its life history before and after ]Jh hours.
25
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This condition is probably artificial and is a manifestation of the ini-
tialization error due to the finite differencing scheme and boundary
conditions. The standing wave number k does not occur in the upper out-
flow layer which is upstream from the lateral boundary.
The mean tangential wind component is characterized by a maximum
cyclonic circulation of k~J m sec-1 at a radius of 15 km (fig. 13) which
gradually diminishes to a value of k m sec-1 at R . For all radii, the
max
SD remains small with a maximum of 7 m sec-1 at hS km. The harmonic
analysis shows that the greatest percent of the variance is contained in
wave number 1. In summary, the small ratio of the SD to the mean indi-
cates that the asymmetries in the boundary layer are much smaller than
the asymmetries in the outflow layer.
The low-level temperature analysis (fig. 12) shows a maximum tem-
perature deficit of 1.5°C. The deficit occurs at the vortex center with
the remaining field characterized by flat gradients. Figure 13 displays
the small SD found in the azimuthal mean temperatures and the strong
boundary effects. Wave number 1 and 2 explain over 90% of the variance.
Wave number k accounts for a smaller percent of the variance of tempera-
ture than of momentum.
6. HORIZONTAL TRANSPORT MECHANISMS
The time variations and the scale of the boundary and outflow layer
asymmetries have been discussed in previous sections. This section in-
vestigates the importance of asymmetries as horizontal transport mecha-
nisms. Computations of radially averaged horizontal and vertical fluxes
of absolute vorticity and angular momentum are presented, with the great-
est emphasis placed on the horizontal transports.
27
6.1 Flux of Absolute Vorticity
The mean and eddy transports of absolute vorticity, v L and
r a
-A
v1 £' , for both the inflow and outflow levels of the model are presented
in figure \k. The circularly averaged absolute vorticity, £ , is given
CI
by
C = JL^~ + f (7)
r9r '
where f is the coriolis parameter. The operator ( ) refers to the
azimuthal mean at a given radius and ( )' refers to the departure from
the mean. The outflow level flux of absolute vorticity shows that the
eddy transports oppose the mean flux beyond 75 km. From 75 km to 165 km
the eddy transport of vorticity is positive (outward) and dominant over
the negative mean flux. Beyond 1 65 km, the mean flux becomes positive
and is opposed by a negative eddy transport of vorticity of comparable
magnitude. At the inner radii the mean and eddy transports are both
positive with the mean flux much larger than the eddy flux.
The mean and eddy profiles of vorticity flux computed from the
model experiment may be compared to similar profiles computed by Black
and Anthes (1971) for real storms. Both model and real storms exhibit
a radial annulus of substantial area in which the eddy transport of vor-
ticity is negative and nearly balances the mean. This annular ring
appears to be somewhat smaller in the model storm, a consequence perhaps
of the overall small size of the model circulation. Comparisons near the
center of the storm are difficult, because Black and Anthes1 data begin
at 111 km from the storm center, and the errors associated with their
28
-1200
ABSOLUTE VORTICITY FLUX
LEVEL i 174 HOURS
i — r
T
i — I — r
j I i l_J I i I i I i l L
75 135 195 255 315
RADIUS (Km)
375 435
2000
1000
o
Id
?
ABSOLUTE VORTICITY FLUX
LEVEL 3 174 HOURS
-1000-
-2000
1 1 •
• 1
• 1
1 | 1 | V
jUfoX
v/C'aX
' r^m
-X^-X
VrCa
Axrx
V / vr£a
\/ 1 .
1 1
■ "
. I.I.
0-
200
-0
- -100
15
75
135 195 255 315 375
RADIUS (Km)
-200
Figure \h: Profiles of mean and eddy transports of
absolute vorticity for the model outflow and inflow
levels.
29
measurements are maximum in this region. At the outer radii (r — 195 km)
the model transports agree in sign and magnitude with observations.
In summary, the eddies in the outflow layer (at moderate distances
from the storm center) convey absolute vorticity inward toward the storm
center and oppose the outward vorticity flux by the mean flow in both
the real and model storm.
The boundary layer flux of absolute vorticity (fig. ]k) shows small
positive eddy transports of vorticity at all radii in agreement with
previous theoretical estimates (Anthes, 1970). The mean flux is strongly
negative (inward) at all radii. Values range over two orders of magni-
tude. Therefore, vorticity is conveyed inward by the mean flow and com-
pletely dominates the eddy flow. This again emphasizes the basic sym-
metry in the inflow layer.
6.2 Flux of Angular Momentum
The mean, the eddy and the total transports of relative angular mo-
mentum, (weighted by radial distance), for both the outflow and inflow
levels of the model are presented in figure 15- In the outflow layer,
the mean flow transports negative momentum outward, while the eddies op-
pose the mean flow by transporting pos i t i ve angular momentum outward.
The mean and eddy terms are the same order of magnitude and tend to com-
pensate for each other. In contrast, actual storm data of Black and
Anthes (1971) show both components to have a net outward transport of
negative relative angular momentum. However, the radial extent of the
model is only half of that of the actual storm data and does not extend
to the outer radii where the larger negative angular momentum fluxes are
30
o
id
V)
15
ANGULAR MOMENTUM FLUX
LEVEL i 174 HOURS
10
i i i i i r
— l — r — r-
r2(v^vx+vTv()
1 1 1 1
0
i i ■ i i i
s
-10
1 1 1
75
135 195 255 315 375 435
RADIUS (Km)
2o r- 1 — r
-60
ANGULAR MOMENTUM FLUX
LEVEL 3 174 HOURS
1 1 — I — I — I — l — T
i — r
J I I l I I L
J I I L
15 75 135 195 255
RADIUS (Km)
315
375 435
Figure 15: Profj_le_s of mea n (rvrvx^» eddy (r v'vp ,
and total (r2(v vx+v'vi) transports of angular
momentum for the model outflow and inflow levels.
31
found (Palmen and Riehl, 1957)- In general, the magni tudes of the eddy
momentum flux associated with the model and real storms are small inside
^tOO km. The model flux tends to be positive, and the flux associated •
with real storms tends to be negative.
The boundary layer flux of relative angular momentum (fig. 15) shows
a very small outward eddy flux of positive angular momentum. The mean
transport shows a strong inward flux of positive angular momentum. The
mean completely dominates the eddy transport at all radii. This result
is in agreement with Riehl and Malkus (1958), who found the eddy trans-
ports of momentum to be either negligible or outward in the inflow layer
of hurricane Daisy. These results also agree with Pfeffer (1958) who
found that within a few hundred kilometers from the vortex center the
horizontal -eddy processes are of the wrong sign to account for the inward
transport of angular momentum in the inflow layer of hurricane Connie,
1955.
In summary, the eddy transport of angular momentum in the model out-
flow layer is slightly positive; while in contrast, the eddy flux in real
storms appears to be slightly negative. There is good agreement between
the model and observations in the mean flux, however. In the inflow
layer, the mean flux is dominant and is directed inward. The eddy flux
is small, but directed outward, in good agreement with observations.
6.3 Vertical Flux of Relative Angular Momentum
It is of considerable importance to the overall dynamics of the
model to determine the origin of the asymmetries in the outflow layer.
As previously established, the outflow level is characterized by two
32
preferred quadrants of outflow (fig. 3). It is conceivable that azimuth-
al variation in the vertical flux of relative angular momentum could be
responsible for the two streams of outflow.
Figure 16 shows azimuthal mean radial profiles of the mean vertical
transport and eddy vertical transport of relative angular momentum,
— \-\ X
( r v-v o ) , (r v|a ' ), where a is the "vertical velocity in the a-system.
The a information levels are staggered in the vertical from the dynamic
variables, necessitating the interpolation of the wind components to the
•
a levels. The radial profiles clearly show that the vertical flux of mo-
mentum is predominantly from the mean current. Although the outflow
occurs in two quadrants the vertical motion is bringing momentum to the
outflow level in a symmetric fashion. Thus the asymmetries are develop-
ing after the air reaches the outflow layer. This result is consistent
with Anthes ' (1972) findings that the asymmetries are a result of dynamic
instability in the horizontal flow, with the eddies growing at the ex-
pense of the mean horizontal flow.
7. SUMMARY AND CONCLUSIONS
Conventional statistical techniques have been utilized to show the
formation and structure of horizontal asymmetries in the outflow and in-
flow levels of a numerical hurricane model. The outflow layer is highly
asymmetric, especially at the outer radii. The inflow layer contains
relatively small asymmetries, and the approximation to axial symmetry is
very good in the low levels. These results agree well with observations.
33
VERTICAL FLUX OF RELATIVE MOMENTUM
LEVEL 2' 174 HOURS
50
0-w
o
CO
CM
-50
-100-
1
.... r — p.- T T ,- — ! r r T
"T"
<<*'"
rvxx*x
-
-
1
i . i . i . i .
_l_
15 75 135 195 255 315
RADIUS (Km)
375 435
VERTICAL FLUX OF RELATIVE MOMENTUM
LEVEL 3' 174 HOURS
T r
-200
13.5 195 255 315
RADIUS (Km)
435
Figure 16: Profiles of mean and eddy vertical transports
of relative momentum for the model outflow and inflow levels
3*»
A comparison with real storms reveals that the model is capable of
reproducing many observed features of the mature three-dimensional
tropical cyclone. Slight differences between the observed and model
vortices are attributed to the limited lateral extent of the model as
the errors associated with the irregular boundary.
The mean transport of absolute vorticity beyond 200 km in the out-
flow layer is outward from the storm center and is opposed by the eddy
flux of absolute vorticity in both the real and model vortices. The
mean flux of absolute vorticity in the model inflow layer is strongly in-
ward and completely dominates the small eddy flow, in agreement with real
storms. Beyond 135 km, the mean transport of relative angular momentum
in the outflow layer is negative; the eddy flux of angular momentum is
positive. Radial profiles of the vertical flux of momentum show that the
vertical transport of momentum is dominated by the mean current, indica-
ting that vertical eddies play no important role in the formation of the
eddies in the outflow layer.
35
8. REFERENCES
Anthes, R. A. (1972), The development of asymmetries in a three-dimen-
sional numerical model of a tropical cyclone, Monthly Weather Review,
( i n press) .
Anthes, R. A. (1970), The role of large-scale asymmetries and internal
mixing in computing meridional circulations associated with the
steady-state hurricane, Monthly Weather Review, 98, No. 7, July,
521-528.
Anthes, R. A., S. L. Rosenthal, and J. W. Trout (1971a), Preliminary re-
sults from an asymmetric model of the tropical cyclone, Monthly
Weather Review, (in press).
Anthes, R. A., J. W. Trout, and S. S. Ostlund (1971b), Three dimensional
particle trajectories in a model hurricane, Weatherwise, (in press).
Anthes, R. A., J. W. Trout, and S. L. Rosenthal (1971c), Comparisons of
tropical cyclone simulations with and without the assumption of
circular symmetry, Monthly Weather Review, (in press).
Black, P. G. and R. A. Anthes (1971), On the asymmetric structure of the
tropical cyclone outflow layer, Journal of the Atmospheric Sciences,
(in press) .
Black, P. G. (1971), Use of echo velocities to evaluate hurricane modi-
fication experiments, Project STORMFURY Annual Report 1970, U. S.
Department of the Navy and U. S. Department of Commerce, Appendix J,
J-1 - J-20.
Gray, W. M. ( 1 967) , The mutual variation of wind, shear and barocl i nici ty
in the cumulus convective atmosphere of the hurricane, Monthly
Weather Review, 95, No. 2, February, 55~73-
I zawa , T. (1964), On the mean wind structure of typhoons, Typhoon Research
Laboratory, Technical Note N . 2, Meteorological Research Institute,
Tokyo, Japan.
Koss , W. J. (1971), Numerical integration experiments with variable reso-
lution two-dimensional cartesian grids using the box method, Monthly
Weather Review, (in press).
Kurihara, Y. and J. L. Holloway (1967), Numerical integrations of a nine-
level global primitive equation model formulated by the box method,
Monthly Weather Review, 95, No. 8, August, 509-530.
36
Matsuno, T. (1966), Numerical integrations of the primitive equations by
a simulated backward difference method, Journal of the Meteorologi-
cal Society of Japan, kk , February, 76-83.
Miller, B. I. (1958), The three-dimensional wind structure around a
tropical cyclone, National Hurricane Research Project Report 15,
U. S. Department of Commerce, National Hurricane Research Labora-
tory, Miami, Florida, January, 41 pp.
Palmen, E. and H. Riehl (1957) , Budget of angular momentum and energy in
tropical cyclones, Journal of Meteorology, 14, 1 50- 1 59 -
Pfeffer, R. L. (1958), Concerning the mechanics of hurricanes, Journal
of Meteorology, 15, 113-119-
Phillips, N. A. (1957), A coordinate system having some special advan-
tages for numerical forecasting, Journal of Meteorology, 1A, April,
184-185.
Riehl, H. and J. S. Malkus (1958), Some aspects of hurricane Daisy,
Tellus, 13, 181-213.
Rosenthal, S. L. (1971), A circularly symmetric primitive equation model
of tropical cyclones and its response to artificial enhancement of
the convective heating functions, Monthly Weather Review, 99, No. 5,
May, k]k-k26.
Rosenthal, S. L. (1970a), Experiments with a numerical model of tropical
cyclone development — some effects of radial resolution, Monthly
Weather Review, 98, No. 2, February, 106-120.
Rosenthal, S. L. (19 70b) , A circularly symmetric primitive equation
model of tropical cyclone development containing an explicit water
vapor cycle, Monthly Weather Review, 98, Vol. 9, September, 6^3~663.
Rosenthal, S. L. (1969), Numerical experiments with a multilevel primi-
tive equation model designed to simulate the development of tropical
cyclones: experiment I, ESSA Technical Memorandum ERLTM-NHRL 82,
U. S. Department of Commerce, National Hurricane Research Labora-
tory, Miami, Florida, 36 pp.
Smagorinsky, J., S. Manage, and J. L. Hoi loway (1965), Numerical results
from a nine-level general circulation model of the atmosphere,
Monthly Weather Review, 93, No. 12, December, 727-768.
37
USCOMM ■ ERL
42
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
Environmental Research Laboratories
NOAA Technical Memorandum ERL AOML-14
FREE-AIR GRAVITY ANOMALIES
SOUTH OF PANAMA AND COSTA RICA
(NOAA SHIP OCEANOGRAPHER - AUGUST 1969)
Robert J. Barday
Marine Geology and Geophysics Laboratory
Atlantic Oceanographic and Meteorological Laboratories
Miami, Florida
September 1971
TABLE OF CONTENTS
PAGE
1. INTRODUCTION 1
2. DATA ACQUISITION AND REDUCTION 2
2.1 Zeroed Meter Gravity 2
2.2 Gravity Meter Reading 3
2 . 3 Eotvos Correction 3
2.4 Drift Correction 8
3. DATA QUALITY 12
4. DATA PRESENTATION 12
5. DISCUSSION 14
6. ACKNOWLEDGEMENTS 18
7. REFERENCES 19
APPENDIX: Profiles 21
in
ILLUSTRATIONS
PAGE
Figure 1 6
Figure 2 9
Figure 3 11
Figure 4 13
Plate 1 (in pocket)
IV
FREE-AIR GRAVITY ANOMALIES SOUTH OF PANAMA AND COSTA RICA
(NOAA SHIP OCEANOGRAPHER - August 1969)
Robert J. Barday
Free-air anomaly profiles from a geophysical
investigation centered on the Panama Fracture Zone
are presented with their corresponding bathymetric
profiles. The quality of these profiles is indi-
cated by a mean free-air anomaly discrepancy of
3.48 milligals with a standard deviation of 3.28
milligals for 99 crossings of the ship's track.
These data support the existence of a deep, sedi-
ment-filled depression at the northern end of the
Panama Fracture Zone, the presence of a sediment-
filled marginal trough east of the Coiba Ridge,
and the accumulation of thick sedimentary deposits
on the eastern flanks of both the Cocos and Coiba
Ridges. The gravity data also suggest that there
is no large-scale change in crustal structure
across the Panama Fracture Zone, and the entire
survey area may be slightly out of isostatic
adjustment .
1. INTRODUCTION
In August 1969 a geophysical investigation of the
Panama Fracture Zone was conducted by the National Oceanic
and Atmospheric Administration Ship OCEANOGRAPHER. Depth,
total magnetic intensity, and gravity meter readings were
recorded continuously over approximately 11,200 km of track-
line controlled by satellite navigation. This report
presents free-air anomaly profiles and discusses certain
geological conclusions that are consistent with the observed
gravity data.
2. DATA ACQUISITION AND REDUCTION
By definition, the free-air anomaly can be expressed as
FA=g0-Y0 CD
where Yo=978 • 0i+9 (1 + 0 • 0052884sin2c}>-0 . 0000059sin22<f>) is the
theoretical sea level gravity given by the 19 30 internation-
al gravity formula, and gQ is the observed gravity reduced
to sea level. For sea level gravity observations
go=ZMG+R+Ec+Dc (2)
where ZMG (zeroed meter gravity) is a value equivalent to a
gravity meter reading of zero, R is the meter reading (in
milligals), Ec is the Eotvos correction, and Dc is the drift
correction.
Both data acquisition and reduction can most easily be
discussed from a term-by-term consideration of (2).
2.1 Zeroed Meter Gravity
The ZMG was obtained from a land tie at Rodman Naval
Station, Canal Zone, immediately before the survey. [The
details of the ZMG computation have been discussed by Orlin
and Sibila (1966).] The base station is described by
Woollard and Rose (1963) as follows:
WH 1015. Rodman Naval Base, at shore end of
center of three piers next to large valve
block painted black and yellow, Lamont No.
BE 1-1.
2 . 2 Gravity Meter Reading
The gravity meter used for this survey was Askania "Sea
Gravimeter Gss2 after Graf, Model C, No. 22 (Graf and
Schulze, 1961; Schulze, 1962) mounted on an electrically
erected Anschiitz Gyrotable. The gravity meter dial reading,
Rj (R(j=R/Kcj where K, is a constant necessary to convert dial
divisions into milligals), was recorded both digitally and
on analog strip chart.
All digitized dial readings were plotted against time,
and the values appearing to be inconsistent were checked
against the analog strip chart. If discrepancies were found,
the digitized values were adjusted. If the inconsistencies-
persisted, the values in question were deleted unless they
could be related to any changes in speed or changes in
course less than 90°.
2 . 3 Eotvos Correction
Accurate navigation is critical to marine gravity ob-
servations. At 5°N, the mean latitude of this survey, and
at 2 7 km/hr, the average speed of this survey, the rates at
which the Eotvos correction changes with respect to course
and speed are 2.1 milligals/0 (for a N-S trackline) and 3.7
milligals/km/hr (for an E-W trackline). If the free-air
anomaly is to be determined to an accuracy of 1 milligal
(the accuracy to which R was measured), the course and speed
must be known within 0.5° and 0.2 km/hr, respectively.
Because the course and speed are computed from the
smooth plotted track, their accuracy depends upon the accu-
racy of the fixes, the elapsed time between fixes, and the
interpolation method used to determine the ship's track
between fixes .
This survey was controlled by the Navy's satellite
navigation system with the AN/SRN-9 equipment (Guier, 1966).
The accuracy of this system is largely influenced by uncer-
tainty in the .ship's velocity. As a first approximation, a
1.8-km/hr error in the ship's velocity results in a 0.45-km
error in the computed satellite fix (Stansell, 1970). If
the velocity is estimated from sea trial data or the speed
made good between previous fixes, as in the case of this
survey, then the computed fixes may be in error by as much
as 2 km.
The average time interval between fixes was 2 hr . At
this interval an error of 45 km in the satellite fixes
would result in a one-milligal error in the computed Eotvos
correction. However, the elapsed time between fixes ranged
downward to 2 2 minutes implying a possible error in the
Eotvos correction of 10 milligals or more.
The interpolation method used to determine the smooth
plotted track was based on the assumption that the course
and speed made good are constant between navigation points.
(Navigation point is used here to mean a point where there
is a satellite fix or a change in course and/or speed.)
The computed Eotvos correction was, therefore, a discontin-
uous step function rather than a continuous function between
course and speed changes.
To remove these artificial discontinuities and minimize
error in the Eotvos correction, the following technique was
used (refer to fig. 1):
(1) For all but E-W lines both the speed made good, SMG
(B, fig. 1), and the difference between the course made
good and the course steered, CMG-CST (A, fig. 1), were
plotted against time. Both plots were then approxi-
mated by piecewise continuous curves in which
discontinuities occurred at any changes in speed and at
changes in course greater than 10°.
(2) For E-W lines the Eotvos correction (C, fig. 1), rather
than SMG and CMG-CST, was similarly treated.
(3) These piecewise continuous curves were, in turn,
approximated by straight line segments.
10 11 12 1J 14 15 16 17 1800
Sgl
Figure 1. Based on the assumption that the course and speed
made good are constant between navigation points , the
difference between the course made good and the course
steered (CMG-CST), the speed made good (SMG), and the
Eotvos correction become piecewise continuous step
functions of time [dashed curves ( )]. The solid
curves ( ) illustrate a technique whereby these param-
eters can be made to more closely approximate continuous
functions of time (not shown for clarity). Curves A
and B are from a N-S profile (No. 14) and curve C is
from an E-W profile (No. 3). The numbers enclosed in
boxes ( I3b91 ) signify the course steered for each seg-
ment of the CMG-CST curve bounded by circles (o). The
Eotvos correction used to compute the free-air anomaly
is determined from a linear time interpolation of the
circled values.
(4) The time, course, and speed or the time and Eotvos
correction at each break in slope were entered into a
computer program that obtained the free-air anomaly at
each data point using the Eotvos correction computed
from a linear time interpolation of these parameters.
For all but E-W lines the program also requires course
and speed values immediately before and after each
change in course steered.
This technique is based on the assumption that the differ-
ence between the course and speed made good and the ordered
course and speed is the result of the current acting on the
ship. Although current in this sense of the word includes
many factors in addition to horizontal movement of the water,
its effect on the ship should vary smoothly between large
changes in course and speed. Therefore, the speed made good
and the difference between the course made good and the
course steered should be continuous functions of time be-
tween speed changes and large changes in course steered.
Because the Eotvos correction computed for E-W lines is
insensitive to small changes in course, it must likewise be
continuous .
2.4 Drift Correction
Because of instrumentation failure it was impossible to
complete a land tie at the conclusion of this survey. The
drift, D [D=-D /(t-t ) where t is the time of observation
and tQ is the time of ZMG determination] , was determined as
follows :
(1) The free-air anomaly was computed without a drift cor-
rection.
(2) The differences AFA. . and At., where i<j were deter-
mined for each trackline intersection: AFA- • =FA. . -FA. .
ID 31 13
and At . . =t . . -t • + where FA., is the free-air anomaly and
ID 31 ^ D1
t.. is the time of profile j at its intersection with
profile i.
(3) The drift was computed by a least squares fit of the
function AFA=DxAt to the pairs AFA-., At...
Illustrated in figure 2 , this procedure follows from the
identities FAN-; • EFA- • -Dx( t . . -t ) and FAN . . EFA. . -Dx(t . . -t )
1D ID !D o di D1 D1 °
where FAN., is the drift-corrected free-air anomaly of pro-
Di
file j at its intersection with profile i. Therefore,
AFAN. .=FAN. .-FAN. .
3-D 31 ID
=FAji-Dx(tji-t0)-FAij+Dx(tij-t0)
=FA. .-FA- .-Dx(t. .-t. .)
Di ID Di ID
=AFAi.-DxAti- .
+APA
'PAij
*VM±i-**Aifl>.^
-/\FA
Figure 2. A statistical method for determining drift. The
free-air anomaly difference for each crossing of the
ship's track is plotted against the corresponding time
difference. The drift, D, is the slope of the straight
line through the origin which (in a least squares
sense) most closely fits all the points ( AFA— ,At.j_ • ) .
Assuming that the correct drift would minimize the crossing
errors ,
3D
N
^ '
l_j 13 13
i,3=l
N
= 0
-2x \ 'a. .x(AFA. .-DxAt. . )xAt.
Z , ^ x3 ^ i:
= 0
N
N
/ (a- -xFAn- -xAt. • )-Dx Y~ a..x(At..) =0
Z , !3 !3 13 L , 13 13
i»j=l i>3=l
2ZL a^xFA^xAt^
D=
EL^.-xCAt..)2
N
r
i,3=l
where N=the number of tracklines and ^--=1 if i< j , or a...=0
if i>j .
The method outlined above is valid if a statistically
significant number of crossings are available. For this
survey (fig. 3), 99 crossings were used, and the computed
drift of 0.17 milligals per day is consistent with the
gravimeter's drift history.
In the final stages of data processing, time profiles
of the free-air anomaly were plotted on an automatic X-Y
plotter. Residual discontinuities at course and speed
10
FREE-AIR ANOMALY DIFFERENCE (JIILLIGALS)
<n * fooa)g>-frroOro-frg>coOM-frc*
rv>
w
yi
o>
oo
O (0
5
IB
c*i
Ui
-i 1 1 r
o o
o
o
o o
o I
o
o
■ ' i , i I i 1,1
Figure 3. The free-air anomaly differences plotted against
the corresponding time differences for 99 crossings of
the ship's track. The slope of the solid line through
the origin (0.17 milligals per day) is the drift of the
gravimeter during this survey.
11
changes were smoothed out by eye or deleted, and appropriate
corrections were applied to the raw data tape.
3. DATA QUALITY
Figure 4 is a histogram of free-air anomaly discrepan-
cies [free-air anomaly discrepancy is defined here as the
absolute value of the free-air anomaly difference, AFA. .
(sect. 2.4)] at crossings of the ship's track. For 99
usable crossings the mean free-air anomaly discrepancy is
3.48 milligals with a standard deviation of 3.28 milligals.
Free-air anomaly discrepancies larger than 10 milligals are
without exception from regions of very steep gravitational
gradient .
In regions of gentle gravitational gradient the free-
air anomalies compare within 10 milligals to those furnished
by Oregon State University and Lamont-Doherty Geological
Observatory .
Satellite navigation contributed immeasurably to the
data quality, and the calm seas (sea state 3 or less) en-
countered throughout the survey kept the cross-coupling and
off-leveling errors to a minimum.
4. DATA PRESENTATION
The data are presented in profile form with the free-
air anomaly plotted above the corresponding bathymetry. All
12
24
23
22
21
20
19
18
17
16
15
14
g 13
12
11
10
9
8
7
6
5
4
3
2
1
0
-Mean
99 Crossings
Mean = 3.48 milligals
Standard Deviation = 3.28 milligals
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
FREE-AIR ANOMALY DISCREPANCY (MILLIGALS )
Figure 4. Histogram of free-air anomaly discrepancies at
crossings of the ship's track.
13
profiles are numbered and keyed to an index map (see Appen-
dix and Plate 1). The free-air anomaly profiles are plotted
with a vertical scale labeled in milligals and selected to
give them a "relief" comparable with the accompanying ba-
thymetric profiles. Depths (after Grim, 1970a) are plotted
in meters with a vertical exaggeration of 50:1. Those pro-
files from trackline segments that are essentially N-S or
E-W are plotted against latitude or longitude, respectively.
All other profiles are plotted against distance.
The profiles are in three groups. The first includes
all E-W profiles south of 7°N. Generally these profiles are
arranged according to decreasing latitude. Included in the
second group and arranged according to decreasing longitude
are all the N-S profiles south of 7°N. The third group in-
cludes the relatively short profiles north of 7°N and those
profiles that are oblique to meridians and parallels of
latitude .
The profiles presented were produced by an off line
CalComp plotter with a computer program written by Grim
(1970b) .
5. DISCUSSION
If the vertical exaggeration of the free-air anomaly
profiles is selected to give them about the same "relief" as
the bathymetric profiles , then they should look like
14
filtered versions of the bottom topography. Departures
from this relationship are attributable to lateral varia-
tions in the subsurface density.
The most striking departure of the free-air anomaly
profiles from their corresponding bathymetric profiles is a
negative anomaly, shown in profiles 33, 36, 38, 53, 54, and
55, associated with the northern extension of the Panama
Fracture Zone. North of 7°N the western trough of the
Panama Fracture Zone bends slightly to the west and develops
an asymmetric V-shaped profile (profiles 38 and 55). Where-
as the western flank of this trough is very steep, the
nearshore, eastern flank has a gentle slope with a charac-
teristically rugged appearance. The free-air anomaly
associated with the western flank follows the bathymetry
quite closely, decreasing sharply from +25 milligals or
more to less than -25 milligals. The eastern flank free-air
anomaly, however, departs radically from the bottom profile;
whereas the bottom profile slopes toward the trough, the
free-air anomaly in most cases slopes away from the trough.
Furthermore, the free-air anomaly shoreward of the trough
is considerably more negative than would be expected from
the bathymetry.
In profile 5 5 the trough is marked only by an inflexion
in the free-air anomaly. A -68-milligal low in the free-air
anomaly profile lies about 40 km shoreward of the trough.
15
Similarly, the -6 2-milligal low of profile 36 is displaced
about 20 km east of the trough. The f^ree-air anomaly of
profile 38, on the other hand, apparently does not continue
to decrease east of the trough. Profiles 33, 53, and the
extreme eastern end of profile 54 show an inverse relation-
ship between the slopes of the free-air anomaly and the
characteristically rugged bathymetry.
These observations are consistent with the occurrence
of a deep, sediment-filled depression that van Andel et al .
(19 71) have proposed to exist between the Cocos and Coiba
Ridges .
Another similar departure of the free-air anomaly from
the bathymetry is the negative anomaly associated with a
gentle bathymetric depression extending from the eastern
edge of the survey area (80°W) to about 81°40'W on the east-
ern flank of the Coiba Ridge. Although the axis of this
depression is not crossed by any of the survey lines, it
appears to be nearly coincident with profile 31 . The free-
air anomaly, on the other hand, continues to decrease at
least as far north as profile 1.
It is evident that this free-air anomaly pattern is a
continuation of the negative anomaly belt (Hayes, 1966) that
extends around the Gulf of Panama from the Peru-Chile Trench.
Hayes suggested that the most significant contribution to
this negative anomaly belt may be the "edge effect" (Worzel,
16
1965) of a steep continental slope. However, the observa-
tion that west of 80°W the axis of this negative anomaly
belt lies well shoreward of the bathymetric depression axis
is better explained by the sequence of deep, sediment-filled
marginal troughs proposed by van Andel et al . (19 71).
Especially evident in profile 3 is the departure of the
free-air anomaly from the bathymetry on the eastern flanks
of the Cocos and Coiba Ridges. West of the Panama Fracture
Zone the eastern flank of the Cocos Ridge rises rather
uniformly while the free-air anomaly levels off west of
8 3°40'W. The free-air anomaly centered over the crest of
the Coiba Ridge falls off more rapidly to the east than
might be expected from the bathymetry. These deviations of
the free-air anomaly from the bottom topography are the re-
flection of thick accumulations of sediment on the eastern
flanks of both ridges (van Andel et al., 19 71, figs. 5B and
11G) . This profile also suggests that there is no large-
scale change in crustal structure across the Panama
Fracture Zone.
The entire survey area may be slightly out of isostatic
adjustment, as indicated by an average free-air anomaly of
between +10 and +20 milligals.
17
6 . ACKNOWLEDGEMENTS
I thank the officers and crew of the National Oceanic
and Atmospheric Administration Ship OCEANOGRAPHER who made
this study possible. Paul Grim furnished the data pre-
sented in this report. He also supplied most of the
computer programs used and assisted in many ways throughout
this study. Additional gravity data were provided by
Dr. Richard Couch, Oregon State University, and Manik
Talwani, Lamont-Doherty Geological Observatory. R. K.
Lattimore, Paul Grim, and Dr. George Peter assisted by
reviewing the manuscript.
18
7. REFERENCES
Graf, A. and R. Schulze (1961), Improvements in the sea
gravimeter Gss2, J. Geophys . Res. 6_6, 1811-1821.
Grim, P. J. (1970a), Bathymetric and magnetic anomaly pro-
files from a survey south of Panama and Costa Rica,
(unpublished report) ESSA Tech. Memo, ERLTM-AOML 9.
(Environmental Research Laboratories, Boulder, Colorado
80302) .
Grim, P. J. (1970b), Computer program for automatic plotting
of bathymetric and magnetic anomaly profiles , (unpub-
lished report) ESSA Tech. Memo, ERLTM-AOML 8.
(Environmental Research Laboratories, Boulder, Colorado
80302) .
Guier, W. H. (1966), Satellite navigation using integral
Doppler data -- the AN/SRN-9 equipment, J. Geophys. Res.
71, 5903-5910.
Hayes, D. E. (1966), A geophysical investigation of the
Peru-Chile trench, Marine Geology ^ 309-351.
Orlin, H. and D. V. Sibila (1966), General instructions,
gravity observations at sea, part II: askania stable
platform mounted seagravimeter , U. S. Department of
Commerce, ESSA, Coast and Geodetic Survey.
Schulze, R (1962), Automation of the sea gravimeter Gss2,
J. Geophys. Res. 67, 3397-34-01.
19
Stansell, P. A., Jr. (1970), The Navy navigation satellite
system: description and status, The International Hydro-
graphic Review, XLVII , 51-70.
van Andel, T. H., G. R. Heath, B. T. Malfait, D. F.
Heinrichs , and J. I. Ewing (1971), Tectonics of the
Panama Basin, eastern equatorial Pacific, Geol . Soc.
Amer. Bull. 8_2, 1489-1508.
Woollard, G. P. and J. C. Rose (196 3), International Gravity
Measurements, Society of Exploration Geophysicists ,
Tulsa, Oklahoma, 518 p.
Worzel, J. L. (19 65), Deep structure of continental margins
and mid-ocean ridges, In: W. F. Whittard and R. Brad-
shaw (Editors), Submarine Geology and Geophysics --
Colston Papers, Butterworth, Washington, D.C., 335-359.
20
APPENDIX
Profiles
The following pages display the computer-produced pro-
files from the survey area
Profile
Page
Profile
Page
Profile
Page
Profile
Page
1
22
14
35
27
23
42
27
3
24
15
49
28
44
43
37
4
40
16
36
29
51
44
29
5
26
17
25
30
44
45
43
6
37
18
39
31
23
46
31
7
28
19
49
32
48
47
38
8
42
20
40
33
48
48
29
9
30
21
27
34
46
49
38
10
34
22
41
36
46
50
31
11
32
23
49
38
47
51
34
12
51
24
42
39
37
52
50
13A
33
25
51
40
25
53
48
13B
33
26
43
41
43 |
54
55
62
47
45
45
Table 1. Index of Profiles
21
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PLATE 1
Reprinted from The American Association of Petroleum
Geologists Bulletin 55, No. 10, 17 30-1740 .
43
Marine Geophysical Study Northeast of Trinidad-Tobago1
B. G. BASSINGER,2 R. N. HARBISON,2 and L. AUSTIN WEEKS3
Miami, Florida 33130, 33158
Abstract Marine geophysical measurements off Trinidad-
Tobago delineate prominent structural trends revealed in
the shallow sedimentary strata. Pilar block is one of the
prominent structures along the boundary between the
South American continent and Caribbean plate. The block
is a narrow horst bounded on the north and south by
major fault zones, which apparently continue from the
Araya Peninsula of Venezuela eastward to about
58°50'W. Structural features north and south of the Pilar
block either die out at the block or veer subparallel with
it. North of the block, the Barbados Ridge is an anti-
clinorium which shows evidence of folding and fracturing
apparently as a single tectonic unit. Long-period, high-
amplitude magnetic anomalies, forming a zone somewhat
parallel with the Lesser Antilles arcuate trend, suggest
that the prominent trends of the anticlinorium extend
across the continental shelf to the Pilar block. Within the
study area, the geophysical data show no evidence for
extensive translation between the South American con-
tinent and the Caribbean plate in comparatively recent
time.
Introduction
During the summers of 1968 and 1969, the
USC&GS ship Discoverer conducted recon-
naissance marine geophysical investigations in
the area off northern Venezuela and Trinidad
and around the southern end of the Lesser An-
tilles arc. Ship's traverses for this study covered
the area south of 12°30'N between the To-
bago Trough and Trinidad to 58°30'W (Fig.
1 ). The investigation was designed to study the
eastward extension of the predominantly east-
west-trending structures of northern Venezuela
and Trinidad, and their structural relation to
the island of Tobago and the Barbados Ridge
on the north. Data collected west of the study
1 Manuscript received, August 24, 1970; accepted,
December 3, 1970.
2 National Oceanic and Atmospheric Administration
(NOAA), Atlantic Oceanographic and Meteorological
Laboratories.
3 Consultant; formerly, Environmental Science Ser-
vices Administration.
The writers are grateful to the officers and men of
the USC&GS (NOAA) ship Discoverer and the
AOML personnel who participated in the project. We
are particularly indebted to G. A. Lapiene, Jr., and
L. W. Mordock (USESSA) for their assistance in con-
ducting the field work and to Sue O'Brien and George
Merrill for drafting the figures. L. W. Butler and G. H.
Keller critically reviewed the paper.
© 1971. The American Association of Petroleum Geologists.
All rights reserved.
area are presented by Lattimore et al. (1971).
Regional implications of both studies are dis-
cussed by Weeks et al. (1971).
Seismic reflection profiles (SRP) were made
only on traverses across postulated major struc-
tural trends. Continuous gravity, magnetic, and
bathymetric observations were recorded on all
traverses. Within the study area of this paper,
geophysical data were obtained along approxi-
mately 3,430 km (1,850 n. mi) of ship's track
with SRP records made over about 2,410 km
(1,300 n. mi) of the area traversed. The sound
source for the SRP system was a 164-cc (10 cu
in.) pneumatic gun. Gravity and magnetic ob-
servations were made with an Askania seagra-
vimeter and a Varian nuclear resonance mag-
netometer respectively. Position control was de-
termined by the best source available — dead
reckoning, land ties by visual fixes and radar,
Loran A and C, and Omega. These data were
collected by methods described in Lattimore et
al. (1971).
The track-line pattern and bathymetry in the
study area are shown in Figure 1 of Weeks et
al. (1971). Line drawings of representative
SRP records correlated with gravity and mag-
netic observations are presented in Figure 2.
Parts of original SRP traverses are reproduced
in Figures 3-7. In the interpretation of the
SRP records, the reflector generally referred to
as basement is the deepest observed reverberant
reflector beyond which no penetration is ob-
tained within the resolution of the equipment.
This reflector, varying in acoustic character
over the study area, corresponds in depth to the
3.97 km/sec (13,000 ft/sec) or higher veloc-
ity material reported by Ewing et al. (1957).
Previous Investigations
Geologic structures of the islands of Trini-
dad-Tobago and surrounding area have been
described by numerous investigators. Some of
the results have been presented by Schuchert
(1935), Maxwell (1948), and Suter (1960).
In the study area, near-surface, shallow-water
sedimentation and geologic structure were stud-
ied by Koldewijn (1958), van Andel and Sachs
(1964), and van Andel (1967). Deep crustal
studies based on seismic refraction results in
1730
Marine Geophysical Study Northeast of Trinidad-Tobago
1731
Fig. 1. — Major structural trends and location of representative traverses. Barbados anticlinorium is complex of
structures lying east of Tobago Trough through East ridge.
the Caribbean, across the Lesser Antilles island
arc, and in the Atlantic were summarized by
Officer et al. (1959). Some of these velocity
data were analyzed by Ewing et al. (1957) and
later utilized in presenting a summary of the
crustal section of the Caribbean area (Edgar,
1968). Higgins (1959) compared the offshore
velocity data with similar velocities from geo-
logic structures on Trinidad. Recently, Sykes
and Ewing (1965) discussed the seismicity of
the Caribbean for the period 1950-1964 and
related its occurrence to boundaries between
prominent structures.
The Caribbean plate and adjacent South
American continent have been described as
contrasting crustal blocks with great horizontal
movements along major boundary faults. Di-
verse interpretations were made concerning the
interaction between these crustal blocks and the
boundary fault systems. Hess (1938) suggested
that the Caribbean block was translated east-
ward 80-160 km (50-100 mi). However,
Eardley (1954) summarized the earlier hy-
potheses and presented an argument for subsi-
dence of the Caribbean basin. On the contrary,
Rod (1956) implied that the overall displace-
ment within the Caribbean area of more than
100 km (62 mi) was not unreasonable, based
on an analysis of the supposed strike-slip fault
system along northern Venezuela. In further
support of strike-slip movement, Alberding
(1957), applying the principle of wrench-fault
tectonics of Moody and Hill ( 1956) to northern
South America, concluded that during the Cre-
1732
B. G. Bassinger, R. N. Harbison and L. Austin Weeks
MILUGAIS
J -1-50
-1-100
I PB
- -50
- -50
-1-100
"BASEMENT"
HORIZONTAL SCALE VARIABLE
Fig. 2. — Residual magnetic field intensity (regional field removed by inspection), free-air gravity anomaly,
and seismic reflection profiles. Vertical scale of seismic records is two-way time. Position numbers are hours.
CS, Central syncline; ER, East ridge; ETS, East Tobago syncline; NTA, North Tobago anticline; PB, Pilar
block; TT, Tobago Trough; and WR, West ridge.
taceous the Araya and Paria Peninsulas of
Venezuela and the Northern Range of Trinidad
formerly were 475 km (295 n. mi) west. A
study of the pre-Tertiary rocks along one of the
several prominent east-west-trending faults
across northern Venezuela suggested no more
than 10-15 km (6-9 n. mi) of strike-slip
movement along the El Pilar fault (Metz,
1964). However, recent field mapping in the
Northern Range of Trinidad (Potter, 1968) re-
vealed only vertical displacement of up to 1.8
km (6,000 ft). In addition, seismic-reflection
profiling and sediment coring indicated that the
tectonics of the margins of the Caribbean ba-
sins show vertical rather than horizontal dis-
placements (Ewing et ah, 1967).
Results and Discussion
The geophysical data suggest a division of
the study area into three prominent structural
features: (1) Pilar block, (2) Barbados anticli-
norium, and (3) Tobago Trough. Pilar block is
defined as the tectonically positive element
bounded on the north and south by faults of
major displacement. The block consists of the
Araya and Paria Peninsulas of Venezuela and
their continuation through the Northern Range
of Trinidad. Barbados anticlinorium is the
Marine Geophysica! Study Northeast of Trinidad-Tobago
1733
r GAMMAS
-200 L
-i i_
■ '
MILLIGALS
-|0
- -50
-J -100
GAMMAS
NTA?
°[
-200 L
20
22
E'
- 0
MILLIGALS
i _j_,
-1 L_
-50
SEC
1 -
2 -
3 -
<! -
L
^T
ER
■
1
PB
A
■^^^=r - ==-
~-
□ "BASEMENT"
HORIZONTAL SCALE
VARIABLE
CS
Fig. 2 (Continued)
complex of structures lying between the To-
bago Trough and the Atlantic basin, and is di-
vided into two separate tectonically positive
structures separated by a medial syncline
(Weeks et ah, 1969). These structures are:
West ridge, Central syncline, and East ridge.
North Tobago anticline and East Tobago syn-
cline are two subsidiary structures west of the
West ridge. Tobago Trough is the tectonically
negative element separating the Lesser Antilles
from the Barbados anticlinorium (Fig. 1).
Pilar Block
A correlation of earthquake epicenter loca-
tions with structural units in the Paria Penin-
sula region of Venezuela seems to indicate two
sequences of tectonic events (Sykes and Ewing,
1965). According to that study, one series of
events north and another south of 10°36'N
may suggest movements along two major fault
zones. Although the epicenter locations are
confined to a small area of the Paria Peninsula,
our data farther east support their conclusion.
Within the study area, the Pilar block is a dis-
tinct structural unit, bounded on the north and
south by prominent fault zones which appar-
ently continue eastward to about 58°50'W
(Fig. 1).
The traverse through the Dragon's Mouth
(profile A- A', Figs. 2, 3) shows the Pilar block
as a partly buried horst flanked by sedimentary
strata. Presumably, this basement block is the
lateral continuation of pre-Late Jurassic to Late
Cretaceous metamorphic rocks of the Northern
Range and Paria Peninsula mapped by Kugler
(1961). Small down-to-the-north growth faults
are present near the north end of the profile.
The southern half of the profile shows a shal-
low zone of relatively transparent sediments ap-
parently transgressing the block from the south.
B. G. Bassinger, R. N. Harbison and L. Austin Weeks
SEC |8 19
PILAR BLOCK
Fig. 3.-
-North-south seismic reflection profile through Dragon's Mouth (profile A-A', Fig. 1) showing Pilar block
adjacent to thick sedimentary sequences. Vertical scale is two-way time.
In the same area the free-air gravity gradient of
90 mgals is consistent with a thick accumula-
tion of sediments in the Gulf of Paria on the
south, but is also in part a reflection of the re-
gional gradient. This regional gravity trend is
the northern flank of an arcuate gravity low
paralleling the Lesser Antilles (Bush and Bush,
1969), which is coincident with a negative
Bouguer anomaly along the Barbados Ridge.
This negative anomaly is apparently the result
of intermediate velocity material that lies in
downwarped high-velocity layers (Officer et al.,
1959). In addition to the regional field, local
anomalies of a few milligals are related to the
block and to the near-surface arched structure
observed in the SRP records near location 19.5.
The suggestion of major tectonic activity is
confirmed further by a change from a high-am-
plitude, long-period to a low-amplitude, short
period magnetic trace near the northern margin
of the block. These short-period variations of up
to 10 y may be caused by lithologic changes in
the observed part of the Pilar block similar to
those found in exposed rocks of the Paria Pen-
insula and Northern Range.
The SRP record off the north coast of Trini-
dad suggests a basement complex that is most
probably an eastward continuation of the Pilar
block (profile B-B', Fig. 2). North of the base-
ment block, a zone of normal down-to-the-north
growth faulting correlates well with similar fea-
tures on the west in profile A-A'. These occur-
rences, which coincide with an increase in grav-
ity also suggest a rise in the basement complex.
A seismic refraction traverse (line 24 of Ew-
ing et al., 1957) crosses the northern ends of
profile A-A' and B-B'. It shows relatively flat-
lying sedimentary sequences with velocities of
1.66-1.93 km/sec (5,500-6,300 ft/sec) un-
derlain by north-dipping velocity sequences of
2.75-4.80 km/sec (9,000-15,800 ft/sec). A
comparison of these velocities with those re-
corded in south and central Trinidad suggests
that the uppermost sedimentary layers above
the 2.75 km/ sec (9,000 ft/ sec) layer are post-
Pliocene material (Higgins, 1959). The upper
half of the 1.93 km/sec (6,300 ft/sec) sedi-
ment sequence, showing evidence of down-to-
the-north normal growth faults, can be traced
close to the surface near the southern end of
the profile adjacent to a basement complex
(Profile B-B', Fig. 2).
Near the north end of profile A-A' (Fig. 2),
Ewing et al. (1957) obtained a depth of 3.1
km (10,200 ft) to the top of the 4.8 km/ sec
(15,800 ft/ sec) layer and related it to the
north flank of the Northern Range. In support
of that conclusion, Higgins (1959), correlating
these velocities with those recorded in Trinidad,
suggested that material with the same velocity
Marine Geophysical Study Northeast of Trinidad-Tobago
1735
may be related to the Northern Range meta-
morphic rocks. If the top of the 4.8 km/ sec
(15,800 ft/sec) interface is projected to the
northern margin of the exposed Pilar block and
if one assumes that the exposed block in the
Dragon's Mouth is comparable material, a min-
imum vertical displacement of 2.3 km (7,800
ft) is indicated along the north boundary fault
system of Trinidad. This displacement is com-
parable with, but somewhat greater than, the
1.8 km (6,000 ft) uplift reported by Potter
(1968) for the Northern Range along the El
Pilar fault system.
The impression conveyed by the structural
cross sections through Trinidad (Kugler, 1961)
is that the Pilar block becomes less pronounced
toward the east. Our geophysical information is
in agreement with that conclusion. From loca-
t;on 20 (profile C-C, Fig. 2) off the northern
coast of Trinidad to midway between the off-
shore projection of the Pilar block, the SRP rec-
ords show well-stratified, shallow sedimentary
strata of up to 1.0-sec penetration in an area
where, according to Koldewijn (1958), only a
few centimeters of recent sediments have been
found above older deposits. These relatively
undeformed sediments are a strong indication
of a lack of postdepositional tectonic activity in
the vicinity of the northern boundary fault sys-
tem of Trinidad.
The stratigraphic section south of the pro-
jected El Pilar fault system contrasts markedly
with that on the north (profile C-C, Fig. 2).
Off the east coast of Trinidad, the shallow sedi-
mentary strata are faulted, folded, and broadly
arched, and thus resemble the structures of
southern Trinidad shown by Kugler (1961).
The basement complex centered around loca-
tion 3.7 can be traced across the shelf through
shoals and banks to Radix Point. These occur-
rences seem to indicate that the northeast-south-
west-striking tectonic belts of Trinidad continue
across the continental shelf — a conclusion in
general agreement with Koldewijn's (1958)
structural trend map.
Gravity observations in the area of the off-
shore projection of the Pilar block (profile C-
C, Fig. 2) show no large density contrast at
any depth within the crust as found in the
Dragon's Mouth profile (profile A-A', Fig. 2).
However, the only positive suggestion of the
continuation of an uplifted feature across the
shelf is revealed by a minor gravity anomaly of
less than 8 mgal between locations 0.2 and 1.5.
This anomaly coincides with low-amplitude
magnetic signatures of approximately 10 y,
which may be the result of faulting with subse-
quent intrusion or local susceptibility contrasts.
Off the east coast of Trinidad, the Pilar
block is easily identified in the vicinity of loca-
tion 23.8 (profile D-D', Figs. 2, 4) as an ex-
posed basement complex showing evidence of
planation. On six successive crossings to 58°50'
W, the El Pilar fault is characterized by a base-
ment-sediment contact, but the northern
boundary fault is less obvious (profile E-E',
Figs. 2, 5, 6). These observations confirm the
interpretation of Collette et al. (1969), that the
block apparently acts as a barrier preventing
the northward flow of sediments.
Barbados Anticlinorium
The East ridge could not be traced west of
60 °W, just off the Trinidad shelf. In that area,
4. ^tfSju-v
jrr^^^p, ^multiple:! -
1 °- "."
PILAR BLOCK
Fig. 4. — Part of north-south seismic reflection profile D-D' (Fig. 1) showing Pilar block near shelf edge.
Vertical scale is two-way time.
1736
B. G. Bassinger, R. N. Harbison and L. Austin Weeks
SEC
2 3
%a4
(4,/.- 1- .•
:'Jt?':P: irv^s*
^IW
PILAR BLOCK
Fig. 5.-
-Part of north-south seismic reflection profile E-E' (Fig. 1) showing Pilar block adjacent to level
sedimentary sequences of different depths. Vertical scale is two-way time.
the ridge apparently either dies out or plunges
below the flat-lying sediments of the Central
syncline (Fig. 1). Its northward projection east
of 59° 10' is based primarily on bathymetry
(Fig. 1 of Weeks et al, 1971). Near the Pilar
block, much of the trend is characterized by
three basement highs, with intervening strata
whose sedimentary layers seem to exhibit a pro-
gressive increase in dip with increasing depth
(profile E-E', Figs. 2, 5). This deformation and
the apparent termination of the East ridge be-
low the Central syncline imply that the process
which formed the ridge has been primarily ver-
tical and persistently active during the period of
sedimentation.
The Central syncline separates the West and
East ridges and extends from near the Pilar
block between Trinidad and Tobago to the
northeast limit of the study area. Within the
shelf area north of Trinidad, the syncline occu-
pies a topographic depression with somewhat
conformable sedimentary reflectors (profile C-
C, Fig. 2), probably reflecting a continuation
of a linear bathymetric low southeast of To-
bago (Fig. 1 of Weeks et al., 1971). Along the
line of track, the feature is bounded on the
southeast by a fault that extends to the surface.
There, the gravity anomaly is produced in part
by an accumulation of lower density sediments
and in part by a density differential resulting
from faulting at depth. Off the shelf edge the
syncline is defined more clearly by relatively
undeformed, gently downfolded reflectors
which continue under a layered sequence (pro-
file D-D', Figs. 2, 7).
Off the continental shelf the prominent flank-
ing unconformities of the Central syncline gen-
erally die out toward the northeast (Fig. 1).
The older folded sediments of the West and East
ridges plunge under the syncline beneath a
younger unconformable wedge of well-strati-
fied, almost horizontal sediments (profile E-E',
Fig. 2).
The West ridge is a continuous element of
the Barbados anticlinorium that extends from
north of Barbados, across the study area
through Tobago, and well into the shelf area off
Trinidad. First indications of this feature are
thinning sedimentary sequences below the ap-
parently flat shelf at the beginning of profile C-
C (Fig. 2). However, the rise is more apparent
on seismic reflection profiles about 10°55'N
(Lowrie and Escowitz, 1969) . In this area of the
shelf, an arched sedimentary zone is marked by
a change of sedimentary environment with dis-
tinctive patterns of reflectors. The characteristic
pattern of reflectors, presumably post-Pliocene
material, occupies the near-surface area be-
Marine Geophysical Study Northeast of Trinidad-Tobago
1737
tween the Dragon's Mouth and the West ridge
axis. The suggestion of an arched zone is con-
firmed further by an increase in gravity and a
small isolated magnetic anomaly that may re-
flect a shallowing of the basement surface.
Near the shelf edge the West ridge is ex-
pressed as an exposed basement complex (pro-
file D-D', Figs. 2, 7). Northeastward the ridge
is marked by an irregular surface that widens
rapidly and plunges well below thick sedimen-
tary sequences (profile E-E', Fig. 2). Although
the reflected basement surface has different
acoustic characteristics across the traverse, near
location 13 it corresponds in depth to the 3.97
km/sec (13,000 ft/ sec) material reported by
Ewing et al. (1957). On the margins of the
ridge, the basement surface and its sediment
overburden plunge well below the seismic pene-
tration limit in both the Central syncline and
Tobago Trough.
North Tobago anticline and East Tobago
syncline are separate tectonic elements within
the Barbados anticlinorium. In the Tobago area
the North Tobago anticline shows well-defined
reflectors cut by small, normal down-to-the-
south faults, principally south of the crest of
the anticline (profile D-D', Fig. 2). These
strata belong to the pre-unconformity suite of
rocks, for they plunge under the younger beds
of the Tobago Trough (profile E-E', Fig. 2).
Over this general area, the magnitude of the
gravity anomaly (in part reflecting sea-floor
topography) compared to the surrounding area
and the disruption of the regional magnetic
field suggest deeper structural implications as a
result of the development of the structures near
Tobago. A definite correlation exists between
the magnetic anomalies in this area and the
magnetic anomaly zone traced across the shelf
by Lattimore et al. (1971). Even though the
amplitudes of the anomalies are considerably
less than those identified farther southwest, the
overall disruption of the magnetic field is com-
parable in extent.
The close double-anomaly (two source) pat-
tern observed on profile B-B' (Fig. 2) is help-
ful in making a reasonable correlation within
the study area (Fig. 1). These anomalies ap-
pear to be part of a large arcuate magnetic
anomaly zone, occupying an area approxi-
PILAR BLOCK
Fig. 6. — North-south seismic reflection profile F-F (Fig. 1) showing Pilar block (on south) adjacent to thick
sedimentary sequence near 59°W. Vertical scale is two-way time.
1738
B. G. Bassinger, R. N. Harbison and L. Austin Weeks
lO
•.-**
\ij •!
X
_J
I
.S..1
o
O <u
^>
c •
S o
> I/)
o
J3 C
^ o
■S 3
mately 60 km (35 n. mi) wide that extends
across the shelf somewhat parallel with the is-
land arc system. They continue across the shelf
in a northeast direction, disrupting the mag-
netic field as multiple source anomalies off To-
bago (profile D-D', Fig. 2) and terminating be-
fore profile E-E' (Fig. 2). On the south the
anomalies appear to terminate abruptly at the
Pilar block (profile A-A', Fig. 2). These prom-
inent features can be attributed only to deep-
seated structures related to the island arc sys-
tem.
Peters' method (Peters, 1949) of depth de-
termination applied to the magnetic anomaly
observed near 11°17'N and 61°19'W reveals a
depth to source of approximately 3.7 km
(12,000 ft). The depth reliability of such deter-
minations, however, depends on the absence of
disturbing effects from other magnetic bodies,
and assumes that polarization of the body is
uniform and essentially vertical. In this general
area, seismic refraction data indicate a depth of
3.2 km (10,500 ft) to the top of the 4.85 km/
sec (15,900 ft/sec) layer, which Ewing et al.
( 1957) considered to be the north flank of the
Northern Range metamorphic rocks. Conse-
quently, the material causing the magnetic
anomaly apparently would be emplaced near
the top of the material having comparable ve-
locity to that of the metamorphic rocks of the
Northern Range.
Off the northeast coast of Tobago between
11°12'N and 11°23'N to 60°25'W, a distinc-
tive magnetic pattern of short-period, high-am-
plitude anomalies is in sharp contrast to the
high-amplitude, long-period anomalies of the
surrounding area (Fig. 1). These high-fre-
quency observations are attributed to shallow
variations in the magnetic susceptibility, proba-
bly caused by near-surface intrusive activity.
This zone is considered to be related to a tec-
tonic unit of high magnetic susceptibility that is
useful in delineating the near-surface eastern
limit of the volcanic rocks similar to those
mapped on Tobago by Maxwell (1948).
Summary and Conclusions
The Pilar block is a distinct structural unit
expressed as a relatively narrow horst, bounded
both north and south by prominent fault zones.
From the Dragon's Mouth to about 61°12'W,
the block appears to be flanked on the north by
moderately deformed sediments of presumably
post-Pliocene age. In this general area, refrac-
tion data indicate an overall displacement of at
least 2.3 km (7,800 ft), which is comparable to
Marine Geophysical Study Northeast of Trinidad-Tobago
1739
an earlier estimate of 1.8 km (6,000 ft) of
uplift along the El Pilar fault. The block is a
rigid unit traceable from the Araya Peninsula
of Venezuela to 59°50'W however, it is not
immune to extensional collapse features, such
as the Dragon's Mouth. Outside the shelf edge
the El Pilar fault system is characterized by its
sediment-basement contact. In this area the
block apparently acts as a barrier preventing
the northward flow of sediments. As a result,
sedimentary accumulations equivalent to more
than 2.0 sec of penetration are found south of
the fault near 59°W. Prominent structures on
the north and south either die out or change
trend to subparallel with the Pilar block. South
of the block, structures apparently continue
across the various shoals and banks of the shelf
and terminate at the block. In this area, struc-
tures revealed by the SRP records near the
shelf edge are similar to those in structural
cross sections of eastern Trinidad.
Barbados anticlinorium is folded and faulted
apparently as a tectonic unit. The observed
basement complex plunges to depths beneath
the sediments of the shelf beyond the limit of
penetration of the SRP equipment. Much of
the trend of the anticlinorium within the study
area is occupied by magnetic anomalies of var-
ied characteristics. A zone approximately 60
km (35 n, mi) wide, approximately parallel
with the principal arcuate trend of the island
arc system, contains high-amplitude, long-pe-
riod magnetic anomalies. This zone continues
across the shelf and through Tobago but does
not extend east of about 60°W. Depth compu-
tations on one of these anomalies reveals a
depth to source of about 3.7 km (12,000 ft),
implying that the source is emplaced near the
surface of the 4.85 km/sec (15,900 ft/ sec)
velocity material, which is believed to be com-
parable with the Northern Range metamorphic
rocks. If these are in fact related, a sedimentary
accumulation of 3.2 km (10,500 ft) as re-
vealed by refraction data is expected in the area
off northern Trinidad. In sharp contrast to
these prominent magnetic anomalies, but per-
haps originating from the same source, high-
amplitude, short-period anomalies indicative of
a near-surface source occupy an area 1 1 km (6
n, mi) northeast of Tobago. These anomalies
are apparently related to the igneous rocks ex-
posed in Tobago,
Off the shelf the Barbados anticlinorium is
characterized by a basement complex of 3.97
km/ sec (13,000 ft/sec) velocity rraterial
with a sedimentary overburden. These older
sediments plunge under the flat-lying deposits
of the Tobago Trough and Central syncline.
The younger, relatively undeformed, sediments
to 1.0-sec penetration have not been affected by
any significant tectonic activity since their de-
position.
If the Caribbean plate and the adjacent
South American continent are contrasting crus-
tal blocks with great horizontal movements
along major boundary faults, a condition re-
quired by "new global tectonics," some evi-
dence of transform faulting should be observed
near the shelf edge, along the north boundary
fault zone of Trinidad, or along the El Pilar
fault zone. The following points lend little sup-
port to extensive translation of such plates.
1. The observation that the deeper trends of
the Barbados anticlinorium continue well into
the shelf area implies that there is no major
translation near the shelf edge. This conclusion
is supported also by the continuation of the
deeper structural trends of the volcanic island
arc across the shelf and through Los Testigos
Islands.
2. The north boundary fault zone of Trini-
dad apparently terminates or plunges under at
least 1.0 sec penetration of relatively unde-
formed sedimentary strata in an area where the
recent depositional rate is low. Consequently,
the north-bounding fault system shows no evi-
dence of relatively recent movement.
3. The lack of an obvious gouge zone along
the El Pilar fault system, as might be expected
in wrench faulting, and the absence of a mea-
surable offset in the continental slope near the
continuation of the fault system do not support
extensive translation in comparatively recent
time.
References Cited
Alberding, H., 1957, Application of principles of
wrench-fault tectonics of Moody and Hill to north-
ern South America: Geol. Soc. America Bull., v. 68,
p. 785-790.
Bush, S. A., and P. A. Bush, 1969, Isostatic gravity
map of the eastern Caribbean region: Gulf Coast
Assoc. Geol. Socs. Trans., v. 19, p. 281-285.
Collette B. J., J. I. Ewing, R. A. Lagaay, and M. Tru-
chan, 1969, Sediment distribution in the oceans — the
Atlantic between 10° and 19°N: Marine Geology, v.
7, p. 279-347.
Eardley, A. J., 1954, Tectonic relations of North and
South America: Am. Assoc. Petroleum Geologists
Bull., v. 38, no. 5, p. 707-773.
Edgar, N. T., 1968, Seismic refraction and reflection in
the Caribbean Sea: Ph.D. dissert., Columbia Univ.,
163 p.
Ewing, J. I , C. B. Officer, H. R. Johnson, and R. S.
Edwards, 1957, Geophysical investigations in the
eastern Caribbean — Trinidad shelf, Tobago Trough,
1740
B. G. Bassinger, R. N. Harbison and L. Austin Weeks
Barbados ridge, Atlantic Ocean: Geol. Soc. America
Bull., v. 68, p. 897-912.
M. Talwani, M. Ewing, and T. Edgar, 1967,
Sediments of the Caribbean: Internat. Conf. Tropi-
cal Oceanography Proc, Miami Univ., 1965, p. 88-
102.
Hess, H. H., 1938, Gravity anomalies and island arc
structure with particular reference to the West In-
dies: Am. Philos. Soc. Proc, v. 79, p. 71-96.
Higgins, G. E., 1959, Seismic velocity data from Trini-
dad, B. W. I., and comparison with the Caribbean
area: Geophysics, v. 24, p. 580-597.
Koldewijn, B. W., 1958, Sediments of the Paria-Trini-
dad shelf, v. 3 of Reports of the Orinoco Shelf expe-
dition: The Hague, Mouton and Co., 109 p.
Kugler, H. K., 1961, Geological map of Trinidad and
geological sections through Trinidad: pub. for Petro-
leum Assoc. Trinidad; Zurich, Orell Fussli, and Lon-
don, E. Strand.
Lattimore, R. K., L. A. Weeks, and L. W. Mordock,
1971, Marine geophysical reconnaissance of con-
tinental margin north of Paria Peninsula, Venezuela:
Am. Assoc. Petroleum Geologists Bull., v. 55, no. 10,
p. 1719-1729.
Lowrie, A., and E. Escowitz, 1969, Global ocean floor
analysis and research data series, v. 1: U. S. Naval
Oceanog. Office, p. 971.
Maxwell, J. C, 1948, Geology of Tobago, B. W. I.:
Geol. Soc. America Bull., v. 59, p. 801-854.
Metz, H. L., 1964, Geology of the El Pilar fault zone,
state of Sucre, Venezuela: Ph.D. thesis, Princeton
Univ., 102 p. .
Moody, J. D., and M. J. Hill, 1956, Wrench-fault tec-
tonics: Geol. Soc. America Bull., v. 67, p. 1207-
1246.
Officer, C. B., J. I. Ewing, J. F. Hennion, D. G. Hark-
rider, and D. E. Miller, 1959, Geophysical investi-
gations in the eastern Caribbean: summary of 1955
and 1956 cruises, in L. H. Ahrens et al., eds., Physics
and chemistry of the earth, v. 3 : New York, Perga-
mon Press, p. 17-109.
Peters, L. J., 1949, The direct approach to magnetic
interpretation and its practical applications: Geo-
physics, v. 14, p. 290-320.
Potter, H. C, 1968, Faulting in the Northern Range of
Trinidad (abs) : 23d Internat. Geol. Cong. Rept,
Prague, p. 95.
Rod, E, 1956, Strike-slip faults of northern Venezuela:
Am. Assoc. Petroleum Geologists Bull., v. 40, no. 3,
p. 457-476.
Schuchert, C, 1935 (1968 Reprint), Historical geology
of the Antillean-Caribbean region: New York and
London, Hafner Pub. Co., 811 p.
Suter, H. H., 1960, The general and economic geology
of Trinidad, B.W.I. : London, Her Majesty's Statio-
nery Office, 145 p.
Sykes, L. R., and M. Ewing, 1965, The seismicity of
the Caribbean region: Jour. Geophys. Research, v.
70, p. 5065-5074.
van Andel, Tj. H., 1967, The Orinoco delta: Jour. Sed.
Petrology, v. 37, no. 2, p. 297-310.
■ and P. L. Sachs, 1964, Sedimentation in the
Gulf of Paria during the Holocene transgressions — a
subsurface acoustic reflection study: Jour. Marine
Research, v. 22, p. 30-50.
Weeks, L. A., R. K. Lattimore, R. N. Harbison, B. G.
Bassinger, and G. F. Merrill, 1969, Structural rela-
tionships between Lesser Antilles, Venezuela, and
Trinidad-Tobago (abs.): Gulf Coast Assoc. Geol.
Socs. Trans., v. 19, p. 321.
and 1971, Struc-
tural relations among Lesser Antilles, Venezuela, and
Trinidad-Tobago: Am. Assoc. Petroleum Geologists
Bull., v. 55, no. 10, p. 1741-1752.
44
Reprinted from Marine Geology 11, 201-207
RAPID AND RELIABLE TECHNIQUE FOR DETERMINING UNIT
WEIGHT AND POROSITY OF DEEP-SEA SEDIMENTS
RICHARD H. BENNETT and DOUGLAS N. LAMBERT
National Oceanic and Atmospheric Administration, Atlantic Oceanographic and Meteorological
Laboratories, Marine Geology and Geophysics Laboratory, Miami, Fla. (U.S.A.)
(Received March 10, 1971)
ABSTRACT
Bennett, R. H. and Lambert, D. N., 1971. Rapid and reliable technique for determining unit
weight and porosity of deep-sea sediments. Marine Geo/., 11: 201-207.
A rapid and reliable technique is explained for determining unit weight and porosity
of deep-sea sediment from water content and average grain density measurements. Comparisons
are made between this method and the standard tube method (volumetric), with 77 samples. The
correlation coefficient is found to be 0.994 with a standard deviation between the methods of
± 0.01 g/cm3. The two techniques used to determine porosity are found to have a correlation
coefficient of 0.998 with a standard deviation of 0.42%.
A nomographic chart is shown which permits rapid determination of unit weight using
water content and average grain density.
INTRODUCTION
Unit weight of submarine sediments, also referred to as wet bulk density or
saturated unit weight, is a function of the grain specific gravity and water content.
By definition, unit weight is the weight per unit of volume regardless of the degree
of saturation (A.S.T.M., 1967). However, submarine sediments, especially deep-sea
sediments, are usually totally saturated.
A common technique for measuring unit weight is by inserting a tube of
known volume into a sediment mass, such as a core, extracting the tube and
sediment and determining the sediment weight. This gives a measure of the mass
in grams per unit of volume. Difficulty in eliminating small voids between the
cylinder wall and the sample as well as the influence of gases which may be present
in the interstitial water due to the change from high hydrostatic pressure to at-
mospheric pressure could affect the unit weight as measured in the laboratory.
In an undisturbed sediment sample the relative proportions of water to solids are
not destroyed and at 100% saturation, unit weight is at a maximum. Bennett et al.
(1970) consider + 1 % of the observed value to be a reasonable estimate of the
reproducibility of the tube method.
Porosity (/?), defined as the ratio of the volume of the voids to the total
volume of the sediment mass, is usually computed from unit weight, average grain
Marine Geo/., 11(1971) 201-207
202 R. H. BENNETT AND D. N. LAMBERT
density, water content and an assumed interstitial water density. It is sometimes
determined from the void ratio by the relationship n = e/(l + e ). Void ratio (e) is
defined as the ratio of the volume of the voids to the volume of the solids.
The purpose of this study is to describe a rapid and reliable technique for
determining unit weight and porosity of deep-sea sediment with an evaluation
of the method using various sediment types. Carbonate content of the sediments
ranged from less than 10% to greater than 98%, and textures ranged from less
than 1 % to greater than 66 % sand-size particles.
TECHNIQUES AND BASIC PRINCIPLES
An advantage of the technique employed here for determining unit weight
and porosity is that raw data from water content and grain density measurements
are used. These data are frequently studied by the marine geologist and ocean
engineer concerned with mass physical properties of submarine sediments and are
usually numerous and readily available from laboratory reports.
Water content measurements are determined from approximately 10-20 g
samples of sediment taken from the center of a core. The sample is immediately
weighed and dried for about 24 h at 1 10°C and then reweighed to determine water
loss. Average grain density is usually found by volumetric displacement of distilled
water by the solids in a calibrated flask (Lambe, 1951). From these three measure-
ments, weight of dry solids, weight of water driven off during drying, and the
average grain density, the unit weight (y) can be easily determined by the following
relationships:
W WD
y = ^ = ^ — (1)
7 W± , w W, + WWD% K '
Dg + W"
where Wx = Wv + fVd; IVW = weight of the water = approximately the volume
of water; WA = weight of dry solids including salts; Dg — average grain
density.
The total weight (Wt) of the sample taken for water content determination
is equal to the weight of the water lost during oven drying (Ww) plus the weight
of the dry solids (Wd). For practical purposes Wv is equivalent to the volume of
water in the cgs system. The weight of the solids divided by the average grain
density (WJDg) is the volume of the dry solids. The weight of the dry solids con-
tains the weight of the salt. However, this increase in the volume of the solids, due
to the presence of salts, closely approximates the slight deficit in the volume of
the water (W^) owing to the dissolved salts in the interstitial water. Therefore, by
definition, the unit weight of the sample is equal to the total weight divided by the
total volume. Similar expressions may be equated with eq.l in text books on soil
mechanics such as Terzaghi and Peck (1967), Scott (1963) and Wu (1966) and
Marine Geol., 11(1971) 201-207
UNIT WEIGHT AND POROSITY OF DEEP-SEA SEDIMENTS 203
are usually intended to show the relationships among density, porosity, and void
ratio for a given sediment mass.
Porosity (n), expressed in percent, is the ratio of the volume of the voids
to the total volume of the sediment mass and can be determined by the relationship:
V + V
n = w + "ss x 100 (2)
-^ + W
D, w
Vs% is the volume of the salts in solution. Again, Vv is equal to the volume of
the water and approximately equal to the weight of the water in grams. If V%& is
neglected or considered negligible the equation then becomes:
W
Y- x 100 (3)
£ + *
Vss is very close to 1.2% of Vw for concentrations of dissolved salts of 35%0.
RELIABILITY
As a measure of the reliability of the above technique expressed by eq.l, 77
unit weight measurements were determined using this method and compared
with unit weight determinations using the tube method. In addition, porosity was
determined using eq.3 from the same raw data used to obtain unit weight. These
values were compared with porosities calculated from unit weight measurements
determined by the tube method, average grain density and water content values
with no corrections for salt content. Correlation coefficients were determined
for unit weight and porosity. A linear correlation coefficient of +0.994 was found
between the two unit weight techniques with 67% of all measured values falling
within +0.01 g/cm3 of each other. A linear correlation coefficient of +0.998 was
found between the two porosity methods with 67% of all measured values falling
within +0.42% of each other. The significance of these data shows that for all
practical purposes, the correlation between the techniques is nearly perfect and
that either method for determining unit weight and porosity is as good as the other.
RELATIONSHIPS
The effect of large differences in drying temperatures has been found to be
not as critical as might be expected. Using eq.l and data from Lambe (1951),
differences in drying temperatures from 90 °C to 190°C increase the unit weight
measurement by only 0.002-0.004 g/cm3. Porosity values determined by eq.3
however, show differences ranging between 1 % and 3% when drying temperature
varies from 90 °C to 190°C. Usually consistent techniques and control of tem-
Marine Geo!., 11(1971) 201-207
204 K. H. BENNETT AND D. N. LAMBERT
perature within reasonable limits are well within the means of most soils labo-
ratories.
Examination of eq.l reveals that large changes in average grain density
are necessary to appreciably affect the unit weight measurement. Clearly, the higher
the water content the less average grain density variation influences those deter-
minations. For example, with a water content of 50% an increase in average grain
density from 2.75 to 2.80 increases the unit weight from 1.736 to 1.750. However,
at a water content of 100 % a change in the grain density of 0.05 changes the unit
weight by only 0.007 g/cm3. The other parameters Wt, Ww and Wd depend upon
the accuracy of the balance which is usually well within the reproducibility of the
technique described here.
Due to the above relationships, difficulty in determining unit weight and
porosity of relatively clean sands by the proposed method might be encountered
because such sediments are usually characterized by low water contents. Obtaining
a true water content for this sediment type may be difficult. However, accurate
unit weight and porosity values of a relatively clean sand are also difficult to
obtain with the tube method because of possible loss of pore water in inserting
the tube into the sediment and its subsequent handling.
DISCUSSION
Several advantages of the technique expressed in eq.l for determining unit
weight are apparent. If gas is present it does not affect the measurement, and
values of unit weight for 100% saturation at a given water content are obtained.
This is considered by the authors to be a closer approximation of the actual unit
weight, in situ, than values obtained by the tube method (volumetric), especially
for sediment that includes gas. In addition, unit weight and porosity can be deter-
mined for relatively thin stratified sediment with a minimum amount of material
and for small irregularly shaped pieces of cohesive sediment not amenable to the
tube method. Volumetric errors introduced in the tube method include error
resulting in the incomplete filling of the tube with sediment and inaccurate meas-
urement of the radius of the tube (any error in the radius is squared).
Unit weight and porosity, using the relationships of eq.l and 3, are deter-
mined from measured parameters which consequently avoids the use of any as-
sumed values such as the density of interstitial water and average grain density.
However, relatively large variations in the average grain density are required to
appreciably influence the unit weight determination by eq.l. Large changes in
the drying temperatures such as 90°-190 C usually have small affects on the
unit weight determination; however, porosity by eq.3 is more responsive to these
temperature differences. Control of temperature is important when porosity values
are critical and comparable to within 1 % of the observed values.
Fig. 1 was constructed using eq.l with a range of average grain density
Marine Geo/., 1 1 ( 1 97 1 ) 20 1 -207
UNIT WEIGHT AND POROSITY OF DEEP-SEA SEDIMENTS
205
f8
o
-a
c
60
o
E
c
2
A1ISN3Q NlVilO 30V»3AV
Mviw Ceo/., 11(1971) 201-207
206 R- H. BENNETT AND D. N. LAMBERT
values from 1.70 to 3.19 and a number of selected weights of dry solids (Wd) and
water (H/w). This nomographic chart shows average grain density plotted against
unit weight with isolines for water content (used here as WJWA x 100) ranging
between 25% and 600"^,. Clearly, the relationship is non-linear and the isolines
(delineating water content) would ultimately converge at a value of 1.00. The
relationships among porosity, unit weight, and grain density have been clearly
depicted by Richards (1962). The advantage of this chart is that, given values
of average grain density and water content, values for unit weight can be readily
determined. The chart covers values for average grain density and water content
most commonly found in submarine sediments (Keller and Bennett, 1970).
Detailed tables for determining unit weight from water content and average grain
density have been compiled and will form the bulk of a N.O.A.A. Technical
Memorandum (Bennett and Lambert, in preparation).
In deep-sea sediments, unit weight as measured in the laboratory, may be
lower than in situ unit weight owing to the increase in the density of interstitial water
at high hydrostatic pressures. This effect has been shown by Hamilton (1969) to
be significant, especially for deep-sea sediments with high porosities (75 %— 85 % ).
At these porosities, such as in the deep Central Pacific (5,000 m), the increase in
unit weight can be 0.02 g/cm3.
Sediments high in organic carbon content may significantly influence meas-
urement of average grain density, therefore caution should be exercised when
dealing with such materials.
acknowledgements
The authors express their sincere appreciation to Drs. George H. Keller,
Edwin L. Hamilton, Peter A. Rona, Louis W. Butler and Adrian F. Richards for
their critical review of the manuscript. Many thanks are due to Paul J. Grim and
Alan Herman for their competent computer programming of the nomographic
chart and statistical parameters. The helpful discussions with John W. van Lan-
dingham are appreciated.
references
American Society for Testing Materials, 1967. 1967 Book of A.S.T.M. Standards, Part II.
A.S.T.M., Philadelphia, Pa., pp. 285-302.
Bennett, R. H., Lambert, D. N. and Grim, P. J., in preparation. Tables for determining unit
weight of deep-sea sediments using water content and average grain density. Natl. Oceanic
Atmospheric Admin., Tech. Mem., ERL TM-AOML.
Bennett, R. H., Keller, G. H. and Busby, R. F., 1970. Mass property variability in three closely
spaced deep-sea sediment cores. J. Sediment. Petrol., 40: 1038-1043.
Hamilton, E. L., 1969. Sound velocity, elasticity, and related properties of marine sediments,
North Pacific III. Prediction of in situ properties. Naval Undersea Res., Develop. Center,
NUC TP: 145 pp.
Marine Geo/., 1 1(1971) 201-207
UNIT WEIGHT AND POROSITY OF DEEP-SEA SEDIMENTS 207
Keller, G. H. and Bennett, R. H., 1970. Variations in the mass physical properties of selected
submarine sediments. Marine Geol., 9: 215-223.
Lambe, T. W., 1951. So/7 Testing for Engineers. Wiley, New York, N.Y., 165 pp.
Richards, A. F., 1962. Investigations of deep-sea sediment cores, II. Mass physical properties.
U.S. Navy Hydrograph. Office, Tech. Rept., TR-106: 146 pp.
Scott, R. F., 1963. Principles of Soil Mechanics. Addison-Wesley, Reading, Mass., 550 pp.
Terzaghi, K. and Peck, R., 1967. Soil Mechanics in Engineering Practice. Wiley, New York,
N.Y., 2nd ed., 729 pp.
Wu, T. H., 1966. Soil Mechanics. Allyn and Bacon, Boston, Mass., 431 pp.
Marine Geol., 11(1971) 201-207
45
U.S. DEPARTMENT OF COMMERCE ™
National Oceanic and Atmospheric Administration
Environmental Research Laboratories
NOAA Technical Memorandum ERL AOML-13
TABLES FOR DETERMINING UNIT WEIGHT
OF DEEP-SEA SEDIMENTS FROM WATER CONTENT
AND AVERAGE GRAIN DENSITY MEASUREMENTS
Richard H. Bennett
Douglas N. Lambert
Paul J. Grim
Marine Geology and Geophysics Laboratory
Atlantic Oceanographic and Meteorological Laboratories
Miami, Florida
August 1971
TABLE OF CONTENTS
PAGE
1. INTRODUCTION 1
2. MEASUREMENTS AND PROCEDURES 2
3. TABULAR RESULTS 3
4. SUMMARY AND CONCLUSIONS 5
5. REFERENCES 5
FIGURE 7
TABLES 8-56
in
TABLES FOR DETERMINING UNIT WEIGHT OF DEEP-SEA SEDIMENTS
FROM WATER CONTENT AND AVERAGE GRAIN DENSITY MEASUREMENTS
Richard H. Bennett, Douglas N. Lambert and Paul J. Grim
An expedient and reliable method is shown for
determining unit weight of deep-sea sediment using
water content and average grain density measure-
ments. Tables form the bulk of this report with
water contents ranging from 25 percent to 700 per-
cent and average grain densities ranging from 1.70
to 3.10. A nomographic chart is included to
supplement the tables .
1. INTRODUCTION
Unit weight of submarine sediments, also referred to as
mass unit weight, is a function of the grain specific grav-
ity and water content. By definition, unit weight is the
weight (solids plus water) per unit of total volume of a
sediment mass, regardless of the degree of saturation (ASTM,
1967). Bennett and Lambert (in press) have presented a
rapid and reliable technique, using the above relationships,
to determine unit weight (y) for laboratory measured values
of water content (Ww/W^ x 100, the weight of the water to
the weight of the dried solids) and average grain density
(DG) . This relationship is expressed as
W. W W DG
Y = t = t _ t
V W
d + v,
w d w
t d+W W + W DG
DG
where total weight (W. ) of a sediment sample equals the
weight of water (W ) , approximately equal to the volume of
w
water, plus the weight of the dry solids (W^) including
salts. The total volume is the dry solids (Wj/DG) plus the
volume of the water.
2. MEASUREMENTS AND PROCEDURES
As a measure of the reliability of the above technique,
77 unit weights were determined using this method and com-
pared with analyses by the standard tube method (volumetric)
(Richards, 1962). A linear correlation coefficient of
+ 0.99M- was found between the two unit weight techniques with
67 percent of all measured values falling within ± 0.01 g/cc
of each other. These data show that for all practical pur-
poses , correlation between the techniques is nearly perfect
and that either method for determining unit weight is
equally useable.
Several advantages of the technique expressed in the
above equation are apparent. If gas is present it does not
affect the measurement, and values of unit weight for 100
percent saturation at a given water content are obtained.
This is considered by the authors to be a closer approxima-
tion of the actual in_ situ unit weight, of deep-sea
sediment, than values obtained by the tube method (volumet-
ric), especially for sediment that includes gas. In
addition, unit weight can be determined for relatively thin
stratified sediment with a minimum amount of material and
for small irregularly shaped pieces of cohesive sediment
not amenable to the tube method. Volumetric errors intro-
duced in the tube method include error resulting in the
incomplete filling of the tube with sediment and inaccurate
measurement of the radius of the tube (any error in the
radius is squared) .
3. TABULAR RESULTS
The bulk of this report consists of tables for deter-
mining unit weight using the given equation. These tables
include the range of values for water content and average
grain density commonly found in submarine sediments (Keller
and Bennett, 19 70). The respective tables are established
for water contents at one-percent intervals from 2 5 to 100
percent, five-percent intervals from 100 to 200 percent and
at ten-percent intervals from 200 to 700 percent. Water
content is given at the heading of each table, and the left-
hand column (DG) shows the range of average grain densities
(1.70 to 3.10). To find the unit weight of a particular
sediment sample, select the table which nearly approximates
or equals the water content for that sample and then locate
the grain density of the sample to the first decimal place
in the lefthand column. Move across the row to the appro-
priate column (numbered zero through nine at the top of each
column) for the second decimal place of the average grain
density. The number given in this column is the unit weight
for that particular sample given to the third decimal place.
Also included in this report is a nomographic chart
(fig. 1) constructed using the above equation with a range
of average grain density values from 1.70 to 3.19 and a num-
ber of selected weights of dry solids (W-,) and water (W ) .
The chart shows average grain density plotted against unit
weight with isolines for water content (used here as
W /W, x 100) ranging between 25 and 600 percent. Clearly
the relationship is non-linear and the isolines (delineating
water content) would ultimately converge at a value of 1.00.
The advantage of this chart is that, given values of average
grain density and water content, reliable values for wet
unit weight are readily determined. For more detailed
values of unit weight the authors recommend the use of the
included tables .
4. SUMMARY AND CONCLUSIONS
Laboratory measurement of water content and average
grain density is particularly useful for determining unit
weight of deep-sea sediment especially for samples not amen-
able to the tube (volumetric) method. Data show that for
all practical purposes, correlation between techniques is
nearly perfect. Use of the tables or nomographic chart is
expedient and reliable.
5. REFERENCES
American Society for Testing Materials, 1967, 1967 Book of
ASTM Standards, Part II. Philadelphia, Pa., p. 285-302
Bennett, Richard H. and Douglas N. Lambert, 19 71, Rapid and
Reliable Technique for Determining Unit Weight and
Porosity of Deep-Sea sediments, Vol. 11 (in press
Marine Geology) .
Keller, G. H. and R. H. Bennett, 1970, Variations in the
mass physical properties of selected submarine sedi-
ments, Marine Geology, 9: p. 215-223.
Richards, A. F., 1962, Investigations of deep-sea sediment
cores, II. Mass Physical Properties: Tech. Rept . ,
TR-10 6 U.S. Navy Hydrographic Office, Washington, D.C.
146 p.
3
O)
UISN3Q NIVaO 30V83AV
TABLE 1 — Unit weight as a function of average grain density and water content
Unit Weights
WATER CONTENT 25 PERCENT
0G01 23456789
1.70
1.491
1.497
1.503
1.510
1.516
1.522
1.528
1.534
1.540
1.546
1.80
1.552
1.558
1.564
1.569
1.575
1.581
1.587
1.593
1.599
1.604
1.90
1.61C
1.616
1.62?
1.627
1.633
1.639
1.644
1.650
1.656
1.661
2.00
1.667
1.672
1.673
1.683
1.689
1.694
1.700
1.705
1.711
1.716
2.10
1.721
1.727
1.732
1.737
1.743
1.748
1.753
1.759
1.764
1.769
2.20
1.774
1.779
1.785
1.790
1.795
1.800
1.305
1.810
1.815
1.820
2.30
1.825
1.830
1.835
1.840
1. 845
1.850
1.855
1.860
1.865
1.870
2.40
1.875
1.880
1.885
1.390
1.894
1.899
1.904
1.909
1.914
1.918
2.50
1.923
1.928
1.933
1.937
1 .942
1.947
1.951
1.956
1.960
1.965
2.60
1.970
1.974
1.979
1.983
1.988
1.992
1.997
2.001
2.006
2.010
2.70
2.015
2.019
2.024
2.028
2.033
2.037
2.041
2.046
2.050
2.054
2.80
2.059
2.063
2.067
2.072
2.076
2.080
2.035
2.089
2.093
2.097
2.°0
2.101
2. 106
2.110
2.114
2.118
2.122
2.126
2.131
2.135
2.139
3.00
2. 143
2.147
2.151
2.155
2.159
2.163
2.167
2.171
2.175
2.179
3.10
2.183
2.187
2.191
2.195
2. 199
2.203
2.207
2.211
2.214
2.218
WATER CONTENT 26 PERCENT
DG 0 1 2 :
>-
(SI
1.70
1.485
1.491
1.498
1.504
1.510
1.515
1.521
1.527
1.533
1.539
1.80
1.545
1.551
1.557
1.562
1.563
1.574
1.580
1.585
1.591
1.597
Z
1.90
1.602
1.608
1.614
1.619
1.625
1.630
1.636
1.641
1.647
1.652
LU
Q
2.00
1.658
1.663
1.669
1.674
1.630
1.635
1.6 90
1.696
1.701
1.706
2.10
1.712
1.717
1.722
1.727
1.732
1.738
1.743
1.748
1.753
1.758
Z
2.20
1.763
1.768
1. 774
1.779
1.784
1.789
1.794
1.799
1.804
1.809
<
o
2.30
1.814
1.318
1.32 3
1.828
1.833
1.838
1.843
1.848
1.852
1.857
2.40
1.862
1.867
1.372
1.8 76
1.881
1.886
1.3 90
1.395
1.900
1.904
Ui
o
2.50
1.909
1.914
1.918
1.923
1.927
1.932
1.937
1.941
1 .946
1.950
2.60
1.955
1.959
1.964
1.963
1.972
1.977
1.981
1.986
1.990
1.994
<
2.70
1.999
2.003
2.007
2.012
2.016
2.020
2.025
2.029
2.033
2.037
ex
m
2.80
2.042
2.046
2.050
2.054
2.058
2.063
2.067
2.071
2.075
2.079
>
2.90
2.08.3
2.087
2.0Q1
2.095
2. 100
2.104
2.108
2.112
2.116
2.120
<
3.00
2.124
2. 128
2. 132
2. 135
2. 139
2. 143
2.147
2.151
2.155
2.159
3.10
2.163
2.167
2.170
2.174
2. 178
2.182
2.186
2. 190
2.193
2.197
WATER CONTENT 27 PERCENT
DO 0 1 2
1.70
1.480
1.486
1.492
1.498
1.503
1.509
1.515
1.521
1.527
1.533
1.80
1.538
1.544
1.550
1.556
1.561
1.567
1.572
1.578
1.534
1.589
1.90
1.595
1.600
1.606
1.611
1.617
1.622
1.628
1.633
1.639
1.644
2.00
1.649
1.655
1.660
1.665
1.671
1.676
1.681
1.636
1.692
1.697
2.10
1.702
1.707
1.712
1.717
1.723
1.728
1.733
1.738
1.743
1.748
2.20
1.753
1.758
1.763
1.768
1.77*3
1.778
1.783
1.787
1.792
1.797
2.30
1.802
1.807
1.312
1.816
1.321
1.826
1.831
1.335
1.840
1.845
2.40
1.850
1.854
1.859
1.863
1.868
1.873
1.877
1.8«2
1.886
1.891
2.50
1.896
1.900
1.905
1.909
1.914
1.918
1.922
1.927
1.931
1.936
2.60
1.940
1.944
1.949
1.953
1.957
1.962
1.966
1.970
1.975
1.979
2.70
1.983
1.987
1.992
1.996
2.000
2.004
2.008
2.013
2.017
2.021
2.80
2.025
2.029
2.033
2.037
2.041
2.045
2.050
2.054
2.058
2.062
2.90
2.066
2.070
2.074
2.078
2.081
2.085
2.089
2.093
2.007
2.101
3.00
2.105
2.109
2.113
2.117
2.120
2.124
2.128
2.132
2.136
2.139
3. 10
2.143
2.147
2.151
2.154
2.158
2.162
2.166
2.169
2.173
2.177
WATER CONTENT
2* PERCENT
DG
1.70
1.474
1.480
1.486
1.492
1.498
1.503
1.509
1.515
1.521
1.526
1.80
1.532
1.538
1.543
1.549
1.554
1.560
1.565
1.571
1.577
1.582
1.90
1.587
1.593
1.598
1.604
1.609
1.614
1.620
1.625
1.630
1.636
2.00
1.641
1.646
1.652
1.657
1.662
1.667
1.672
1.677
1.683
1.688
2.10
1.693
1.698
1.703
1.708
1.713
1.718
1.723
1.728
1.733
1.738
2.20
1.743
1.747
1.752
1.757
1 .762
1.767
1.772
1.776
1.781
1.786
2.30
1.791
1.795
1.800
1.805
1.810
1.814
1.819
1.824
1.828
1.833
2.40
1.837
1.842
1.846
1.351
1.856
1.860
1.865
1.869
1.873
1.878
2.50
1.882
1.887
l.d91
1.396
1.900
1.904
1.909
1.913
1.917
1.922
2.60
1.926
1.930
1.934
1.939
1.943
1.947
1.951
1.956
1.960
1.964
2.70
1.963
1.972
1.976
1.981
1.985
1.989
1.993
1.997
2.001
2.005
2.80
2.009
2.013
2.017
2.021
2.025
2.029
2.033
2.037
2.041
2.045
2.Q0
2.049
2.052
2.056
2.060
2.064
2.068
2.072
2.076
2.079
2.083
3.00
2.087
2.091
2.094
2.098
2.102
2.106
2.109
2.113
2.117
2.121
3.10
2.124
2. 123
2.132
2.135
2.139
2.142
2.146
2. 150
2.153
2.157
WATER CONTENT
29 PERCENT
OG
1.70
1.469
1.475
1.480
1.486
1.492
1.498
1.503
1.509
1.514
1.520
1.80
1.526
1.531
1.537
1.542
1.548
1.553
1.559
1.564
1.570
1.575
1.90
1.580
1.586
1.591
1.596
1.602
1 .607
1.612
1.617
1.623
1.623
2.00
1.633
1.638
1.643
1.648
1.653
1.659
1.664
1.669
1.674
1.679
2.10
1.684
1.689
1.694
1.699
1.703
1.708
1.713
1.718
1.723
1.728
2.20
1.733
1.737
1.742
1.747
1.752
1.756
1.761
1.766
1.771
1 .775
2.30
1.780
1.734
1.789
1.794
1. 798
1.803
1.807
1.812
1.816
1.821
2.40
1.325
1.830
1.834
1.839
1.843
1.848
1.852
1.856
1.861
1.865
2.50
1.8 70
1.874
1.378
1.383
1.887
1.391
1.895
1.900
1.904
1 .908
2.60
l.°12
1.916
1.921
1.925
1.929
1.933
1.937
1.941
1.945
1.949
2.70
1.953
1.957
1.962
l.Q66
1.970
1.974
1.978
1.932
1.985
1.989
2.80
1.993
1.997
2.001
2.005
2.009
2.013
2.017
2.021
2.024
2.028
2.90
2.032
2.036
2.040
2.043
2.047
2.051
2.055
2.058
2.062
2.066
3.00
2.070
2.073
2.077
2.0R1
2.034
2.088
2.091
2.095
2.099
2.102
3.10
2.106
2.109
2.U3
2.1 17
2. 120
2.124
2.127
2. 131
2.134
2.138
WATER CONTENT
30 PERCENT
DG
1.70
1.464
1.469
1.475
1.481
1.436
1.492
1.497
1.503
1.508
1.514
1.30
1.519
1.525
1.530
1.536
1.541
1.547
1.552
1.557
1.563
1.568
1.90
1.573
1.579
1.584
1.5 39
1.594
1.599
1.605
1.610
1.615
1.620
2.00
1.625
1.630
1.635
1.640
1.645
1.650
1.655
1.660
1.665
1.670
2.10
1.675
1.680
1.685
1.689
1.694
1.699
1.704
1.709
1.713
1.718
2.20
1.723
1.72S
1.732
1.737
1.742
1.746
1.751
1.756
1.760
1.765
2.30
1.769
1.774
1.773
1.783
1.787
1.792
1.796
1.801
1.805
1.810
2.40
1.814
1.818
1.823
1.827
1.831
1.836
1.840
1.844
1.849
1.853
2.50
1.857
1.861
1.366
1.8 70
1.874
1.878
1.882
1.337
1.891
1.895
2.60
1.899
1.903
1.907
1.911
1.915
1.919
1.923
1.927
1.931
1.935
2.70
1.939
1.943
I.947
1.951
1.955
1.959
1.963
1.967
1.971
1.974
2.30
1.978
1.982
1.986
1.990
1.994
1.997
2.001
2.005
2.009
2.012
2.90
2.016
2.020
2.023
2.027
2.031
2.034
2.038
2.042
2.045
2.049
3.00
2.053
2.056
2.060
2.063
2.067
2.070
2.074
2.078
2.081
2.085
3.10
2.088
2.092
2.095
2.098
2.102
2.105
2.109
2.112
2.116
2.119
WATFR CONTENT 31 PERCENT
DG 0 1 2 3
1.70
1.458
1.464
1.470
1.475
1.481
1.486
1.492
1.497
1.503
1 .508
1.80
1.513
1.519
1.524
1.530
1 .535
1.540
1.545
1.551
1.556
1.561
1.90
1.566
1.572
1.577
1.592
1.537
1.592
1.597
1.602
1.607
1.612
2.00
1.617
1.622
1.627
1.632
1.637
1.642
1.647
1.652
1.657
1.661
2.10
1.666
1.671
1.676
1.681
1.635
1.690
1.695
1.699
1.704
1 .709
2.20
1.713
1.719
1.723
1.727
1.732
1.736
1.741
1.745
1.750
1.754
2.30
1.759
1.763
1.760
1.772
1.777
1.781
1.785
1.790
1.794
1.798
2.40
1.803
1.807
1.811
1.816
1.820
1.824
1.828
1.833
1.837
1.841
2.50
1.845
1.849
1.853
1.857
1.862
1 .866
1.870
1.374
1.978
1.882
2.60
1.886
1.890
1.894
1.898
1.902
1.906
1.910
1.914
1.918
1.92k;
2.70
1.925
1.929
1.933
1.937
1.941
1.945
1.948
1.952
1.956
1 .960
2.80
1.964
1.967
1.971
1.975
1.979
1 .982
1.986
1.990
1.993
1.9Q7
2.90
2.001
2.004
2.0C8
2.011
2.015
2.019
2.022
2.026
2.029
2.033
3.00
2.036
2.040
2.043
2.047
2.050
2.054
2.057
2.061
2.064
2.067
3.10
2.071
2.074
2.078
2.081
2.084
2.03e
2.091
2.094
2.0°8
2.101
WATER CONTENT
OG
32 PERCENT
1.70
1.453
1.459
1.464
1.470
1.475
1.431
1.486
1.49 2
1.497
1.502
1.80
1.509
1.513
1.518
1.523
1.529
1.534
1.539
1.544
1.549
1.555
1.90
1.560
1.565
1.570
1.575
1.530
1 .535
1.5 90
1.595
1.600
1.605
2.00
1.610
1.615
1.620
1.624
1.629
1.634
1.639
1.644
1.648
1.653
2.10
1.658
1.663
1.667
1.672
1.677
1.681
1.686
1.691
1.695
1 .700
2.20
1.704
1.709
1.713
1.718
1.722
1.727
1.731
1.736
1.740
1.744
2.30
1.749
1.753
1.753
1.762
1. 766
1.771
1.775
1.7 79
1.783
1.783
2.40
1.792
1.796
1.800
1.8 04
1.809
1.313
1.817
1.821
1.825
1 .329
2.50
1.833
1.837
1.841
1.845
1.850
1.854
1.858
1.862
1.865
1 .869
2.60
1.873
1.877
1.381
1.885
1.889
1 .893
1.897
1.901
1.904
1.908
2.70
1.912
1.916
1.920
1.923
1.927
1.931
1.935
1.938
1.942
1.946
2.80
I.049
1.953
1.957
1.960
1.964
1.96 3
1.971
1.975
1.978
1.982
2.90
1.985
1.989
1.993
1.996
2.000
2.003
2.007
2.010
2.014
2.017
3.00
2.020
2.024
2.027
2.031
2. C34
2.03 7
2.041
2.044
2.048
2.051
3.10
2.054
2.058
2.061
2.064
2.067
2.071
2.074
2.077
2.080
2.084
WATER CONTENT
DG
33 PERCENT
1.70
1.448
1.454
1.459
1.465
1.470
1.475
1.481
1.486
1.491
1.497
1.80
1.502
1.507
1.51?
1.517
1.523
1.528
1.533
1.538
1.543
1.548
1.90
1.553
1.558
1.563
1.563
1.573
1.578
1.583
1.588
1.593
1.593
2.00
1.602
1.607
1.612
1.617
1.622
1.626
1.631
1.636
1.640
1.645
2.10
1.650
1.654
1.659
1.664
1.669
1.673
1.677
1.682
1.636
1.691
2.20
1.6^5
1.700
1.704
1.709
1.713
1.717
1.722
1.726
1.730
1.735
2.30
1.739
1.743
1.749
1.752
1.756
1.760
1.765
1.769
1 .773
1.777
2.40
1.781
1.785
1.790
1.794
1.798
1.802
1.8 06
1.810
1.814
1 .818
2.50
1.822
1.826
1.830
1.834
1.838
1 .842
1.846
1.850
1.853
1.857
2.60
1.361
1.865
1.36°
1.873
1.876
1.880
1.884
1.888
1.892
1.895
2.70
1.899
1.903
1.906
1.910
1.914
1.917
1.921
1.^25
1.928
1.932
2.80
1.936
1.939
1.943
1.946
1.950
1.953
1. 957
1.960
1.964
1.967
2.90
1.971
1.974
1.978
1.981
1.985
1.938
1.991
1.995
1.998
2.002
3.00
2.005
2.008
2.012
2.015
2.018
2.022
2.025
2.028
2.032
2.035
3.10
2.038
2.041
2.045
2.048
2.051
2.054
2.057
2.061
2.064
2.067
10
WATER CONTENT
34 PERCENT
DG
1.70
1.444
1.449
1.454
1.460
1.465
1.470
1.475
1.481
1.486
1.491
1.80
1.496
1.501
1.507
1.512
1 .517
1.522
1.527
1.532
1.537
1.542
1.90
1.547
1.552
1.557
1.562
1.566
1.571
1.576
1.581
1.586
1.590
2.00
1.595
1.600
1.605
1.609
1.614
1.619
1.623
1.628
1.633
1.637
2. 10
1.642
1.646
1.651
1.655
1.660
1.664
1.669
1.673
1.678
1.682
2.20
1.686
1.601
1.695
1.700
1.704
1.708
1.713
1.717
1.721
1.725
2.30
V730
1.734
1 .738
1.742
1.746
1.750
1.755
1.759
1.763
1.767
2.40
1.771
1.775
1.779
1.783
1.787
1.791
1.795
1.799
1.803
1.807
2.50
1.811
1.815
1.819
1.822
1. 826
1.830
1.834
1.838
1.842
1 .845
2.60
1.849
1.853
1.857
1.861
1. 864
1.868
1.872
1.875
1.879
1.883
2.70
1.886
L890
1.894
1.897
1.901
1.904
1.903
1.012
1.915
1.919
2.80
1.922
1.926
1.920
1.933
1.936
1.940
1.943
1.946
1.950
1.953
2.90
1.957
1.960
1.963
1.967
1.970
1.974
1.977
1.980
1.984
1.987
3.00
1.990
1.993
1.997
2.000
2.003
2.006
2.010
2.013
2.016
2.019
3.10
2.022
2.026
2.029
2.032
2.035
2.038
2.041
2.044
2.047
2.051
WATER CONTENT
35 PERCENT
DG
1.70
1.439
1.444
1.440
1.455
1.460
1.465
1.470
1.475
1.481
1 .486
1.80
1.491
1.496
1.501
1.506
1.511
1.3-1 6
1.521
1.526
1.531
1.536
1.90
1.541
1.545
1.550
1.555
1.560
1.565
1.560
1.574
1.579
1.584
2.00
1.588
1.593
1.598
1.602
1.607
1.611
1.616
1.620
1.625
1.630
2.10
1.6 34
1.638
1.64 3
1.647
1.652
1.656
1.661
1.665
1.669
1.674
2.20
1.678
1.682
1.687
1.6°1
1.695
1.609
1.7 04
1.708
1.712
1.716
2.30
1.720
1.724
1.728
1.733
1.737
1.741
1.745
1.749
1.753
1.757
2.40
1.761
1.765
1.769
1.773
1.777
1.781
1.785
1.788
1.792
1.796
2.50
1.0CC
1. «04
l.ROR
1.811
1.815
1.819
1.823
1.827
1.830
1.834
2.60
1.838
1.841
1.845
1.849
1.852
1.856
1.860
1.P63
1.867
1.870
2.70
1.874
1.878
1.381
1.885
1.888
1.892
1.895
1.899
1.902
1.906
2.80
1.909
1.913
1.916
1.91Q
1.923
1.926
1.930
1.933
1.936
1.940
2.90
1.943
1.946
1.95C
1.953
1.956
1.959
1.963
1.966
1.969
1.972
3.00
1.976
1.979
1.98 2
1.985
1.988
1.992
1.995
1.998
2.001
2.004
3.10
2.0C7
2.010
2.013
2.016
2.020
2.02 3
2.026
2.029
2.032
2.035
WATER CONTENT
36 PERCENT
DG
1.70
1.434
1.439
1.445
1.450
1.455
1.460
1.465
1.470
1.475
1.480
1.80
1.485
1.490
1.495
1.500
1.505
1.510
1.515
1.520
1.525
1.530
1.90
1.534
1.5 39
1.54 4
1.549
1.553
1.558
1.563
1.568
1.572
1.577
2.00
1.531
1.586
1.591
I.505
1.600
1.604
1.6 09
1.613
1.618
1.622
2.10
1.626
1.631
1.635
1.640
1.644
1.648
1.653
1.657
1.661
1 .665
2.20
1.670
1.6 74
1.678
1.6 82
1.686
1.691
1.695
1.699
1.703
1.707
2.30
1.711
1.715
1.719
1.723
1.727
1.731
1.735
1.739
1.743
1.747
2.40
1.751
1.755
1.759
1.763
1.767
1.770
1.774
1.778
1.782
1.786
2.50
1.789
1.793
1.797
1.801
1.804
1.808
1.812
1.815
1.819
1.823
2.60
1.826
1.830
1.334
1.837
1.841
1.844
1.848
1.852
1.355
1.359
2.70
1.862
1.866
1.369
1.873
1.876
1.879
1.883
1.886
1.890
1.893
2.80
1.896
1.900
1 .903
1.906
l.oio
1 .913
1.916
1.920
1.923
1.926
2.90
1.930
1.933
1.936
1.939
1.942
1.946
1.949
1.952
1.955
1.953
3.00
1.962
1.965
1.968
1.971
1.974
1.977
1.980
1.983
1.986
1.989
3.10
1.992
1.905
1.998
2.001
2.004
2.007
2.010
2.013
2.016
2.019
11
WATER CONTENT
37 PERCENT
DG
1.70
1.430
1.435
1.440
1.445
1.450
1.455
1.460
1.465
1.470
1.475
1.80
1.480
1.485
1.490
1.495
1.500
1.505
1.509
1.514
1.519
1.524
1.90
1.528
1.533
1.538
1.543
1.547
1.552
1.556
1.561
1.566
1.570
2.00
1.575
1.5 7Q
1.584
1.588
1.593
1.597
1.602
1.606
1.610
1.615
2.10
1.619
1.623
1.628
1.632
1.636
1.640
1.645
1.649
1.653
1.657
2.20
1.662
1.666
1.670
1.674
1.678
1.682
1.686
1.690
1.694
1.698
2.30
1.702
1.706
1.710
1.714
1.718
1.722
1.726
1.730
1.734
1.738
2.40
1.742
1.745
1.74Q
1.753
1.757
1.761
1.764
1. 768
1.772
1.776
2.50
1.779
1.783
1.787
1.790
1.794
1.798
1.801
1.805
1.808
1.812
2.60
1.815
1.819
1.823
1.826
1.830
1.813
1.837
1.840
1.844
1.847
2.70
1.850
1.854
1.857
1.861
1.864
1.867
1.871
1.874
1.877
1.881
2.80
1.884
1.887
1.891
1.894
1.897
1.900
1.904
1.907
1.910
1.913
2.90
1.917
1.920
1.923
1.926
1.929
l.°32
1.935
1.939
1.942
1.945
3.00
1.948
1.951
1.954
1.957
1.960
1.963
1.966
1.969
1.972
1.975
3.10
1.978
1.981
1.984
1.987
1.990
I.Q93
1.996
1.999
2.002
2.004
WATER CONTENT
38 PERCENT
DG
1.70
1.425
1.430
1.435
1.440
1.445
1.450
1.455
1.460
1.465
1.470
1.80
1.475
1.480
1.485
1.490
1.494
1.499
1.504
1.509
1.513
1.518
1.90
1.523
1.527
1.532
1.537
1.541
1.546
1.550
1.555
1.559
1.564
2.00
1.568
1.573
1.577
1.581
1.586
1.590
1.595
1.599
1.603
1.608
2.10
1.612
1.616
1.620
1.625
1.629
1.633
1.637
1.641
1.645
1.649
2.20
1.654
1.658
1.662
1.666
1.670
1.674
1.678
1.682
1.686
1.690
2.30
1.694
1.698
1.702
1.705
1.709
1.713
1.717
1.721
1.725
1.728
2.40
1.732
1.736
1.740
1.743
1.747
1.751
1.755
1.758
1.762
1.766
2.50
1.769
1.773
1.776
1.780
1.784
1.787
1.791
1.794
1.798
1.801
2.60
1.805
1.808
1.812
1.815
1.819
1.822
1.826
1.829
1.832
1.836
2.70
1.839
1.842
1.846
1.849
1.852
1.856
1.859
1.862
1.866
1.869
2.80
1.872
1.875
1.879
1.882
1. 885
1.888
1.891
1.894
1.898
1.901
2.90
l.°04
1.907
1.910
1.913
1.916
1.919
1.922
1.925
1.929
1.932
3.00
1.935
1.93 8
1.941
1.944
1.947
1.950
1.952
1.955
1.958
1.961
3.10
1.964
1.967
1.970
1.973
1.976
1.979
1.981
1.984
1.987
1.990
WATER CONTENT
39 PERCENT
DG
1.70
1.421
1.426
1.431
1.436
1.441
1.446
1.451
1.456
1.460
1.465
1.80
1.470
1.475
1.480
1.484
1.489
1.494
1.498
1.503
1 .508
1.512
1.90
1.517
1.522
1.526
1.531
1.535
1.540
1.544
1.549
1.553
1.557
2.00
1.562
1.566
1.571
1.575
1.579
1.583
1.588
1.592
1.596
1.601
2.10
1.605
1.609
1.613
1.617
1.621
1.626
1.6 30
1.634
1.638
1.642
2.20
1.646
1.650
1.654
1.658
1.662
1.666
1.670
1.674
1.678
1.681
2.30
1.685
1.689
1.693
1.697
1.701
1.704
1.708
1.712
1.716
1.719
2.40
1.723
1.727
1.731
1.734
1.738
1.741
1.745
1.749
1.752
1.756
2.50
1.759
1.763
1.767
1.770
1.774
1.777
1.781
1.784
1.788
1.791
2.60
1.794
1.798
1.801
1.805
1.808
1.811
1.815
1.818
1.821
1.825
2.70
1.828
1.831
1.835
1.838
1.841
1.844
1.848
1.851
1.854
1.857
2.80
1.860
1.864
1.867
1.870
1.873
1.876
1.8 79
1.882
1.885
1.889
2.90
1.892
1.895
1.898
1.901
1.904
1.907
1.910
1.913
1.916
1.919
3.00
1.922
1.925
1.928
1.930
1.933
1.936
1.939
1.942
1.945
1.948
3.10
1.951
1.953
1.956
1.959
1.962
1.965
1.968
1.970
1.973
1.976
12
WATER CONTENT 40 PERCENT
OG 0123456789
1.70 1.417 1.422 1.427 1.431 1.436 1.441 1.446 1.451 1.456 1.460
1.80 1.465 1.470 1.475 1.479 1.484 1.489 1.493 1.498 1.502 1.507
1.^0 1.511 1.516 1.520 1.525 1.529 1.534 1.538 1.543 1.547 1.551
2.00 1.556 1.560 1.564 1.568 1.573 1.577 1.581 1.585 1.590 1.594
2.10 1.598 1.602 1.606 1.610 1.614 1.618 1.622 1.626 1.630 1.634
2.20 1.638 1.642 1.646 1.650 1.654 1.658 1.662 1.666 1.669 1.673
2.30 1.677 1.681 1.685 1.688 1.692 1.696 1.700 1.703 1.707 1.711
2.40 1.714 1.718 1.722 1.725 1.729 1.732 1.736 1.739 1.743 1.746
2.50 1.750 1.753 1.757 1.760 1.764 1.767 1.771 1.774 1.778 1.781
2.60 1.784 1.788 1.791 1.794 1.798 1.801 1.804 1.808 1.811 1.814
2.70 1.817 1.821 1.824 1.827 1.830 1.833 1.837 1.840 1.843 1.846
2.80 1.849 1.852 1.855 1.858 1.861 1.864 1.868 1.871 1.874 1.877
2.90 1.880 1.883 1.886 1.889 1.892 1.894 1.897 1.900 1.903 1.906
3.00 1.909 1.912 1.915 1.918 1.Q21 1.923 1.926 1.929 1.932 1.935
3.10 1.937 1.940 1.943 1.946 1.949 1.951 1.954 1.957 1.959 1.962
WATER CONTENT 41 PERCENT
OG 0123456789
1.70 1.412 1.417 1.422 1,427 1.432 1.437 1.441 1.446 1.451 1.456
1.80 1.460 1.465 1.470 1.474 1.479 1.483 1.488 1.492 1.497 1.501
1.90 1.506 1.510 1.515 1.519 1.524 1.528 1.532 1.537 1.541 1.545
2.00 1.549 1.554 1.558 1.562 1.566 1.570 1.575 1.579 1.583 1.587
2.10 1.591 1.595 1.599 1.603 1.607 1.611 1.615 1.619 1.623 1.627
2.20 1.631 1.635 1.639 1.643 1.646 1.650 1.654 1.658 1.662 1.665
2.30 1.669 1.673 1.677 1.680 1.684 1.688 1.691 1.695 1.69-8 1.702
2.40 1.706 1.709 1.713 1.716 1.720 1.723 1.727 1.730 1.734 1.737
2.50 1.741 1.744 1.748 1.751 1.754 1.758 1.761 1.764 1.768 1.771
2.60 1.774 1.778 1.781 1.784 1.788 1.791 1.794 1.797 1.800 1.804
2.70 1.807 1.810 1.813 1.816 1.819 1.823 1.826 1.829 1.832 1.835
2.80 1.838 1.841 1.844 1.847 1.850 1.853 1.856 1.859 1.862 1.865
2.90 1.868 1.971 1.874 1.877 1.880 1.883 1.885 1.888 1.891 1.894
3.00 1.897 1.900 1.903 1.905 1.908 1.911 1.914 1.916 1.919 1.922
3.10 1.925 1.927 1.930 1.933 1.936 1.938 1.941 1.944 1.946 1.949
WATER CONTENT 42 PERCENT
DG 0123456789
1.70 1.408 1.413 1.418 1.423 1.428 1.432 1.437 1.442 1.446 1.451
1.80 1.456 1.460 1.465 1.469 1.474 1.478 1.483 1.487 1.492 1.496
1.90 1.501 1.505 1.509 1.514 1.518 1.522 1.527 1.531 1.535 1.539
2.00 1.543 1.548 1.552 1.556 1.560 1.564 1.568 1.572 1.576 1.580
2.10 1.584 1.588 1.592 1.596 1.600 1.604 1.608 1.612 1.616 1.620
2.20 1.624 1.623 1.631 1.635 1.639 1.643 1.646 1.650 1.654 1.658
2.30 1.661 1.665 1.669 1.672 1.676 1.679 1.683 1.687 1.690 1.694
2.40 1.697 1.701 1.704 1.708 1.711 1.715 1.718 1.722 1.725 1.728
2.50 1.732 1.735 1.738 1.742 1.745 1.748 1.752 1.755 1.758 1.762
2.60 1.765 1.768 1.771 1.774 1.778 1.781 1.784 1.787 1.790 1.794
2.70 1.797 l.ROO 1.803 1.806 1.809 1.812 1.815 1.813 1.821 1.824
2.80 1.827 1.830 1.833 1.836 1.839 1.342 1.845 1.848 1.851 1.854
2.90 1.857 1.860 1.862 1.865 1.868 1.871 1.874 1.877 1.879 1.882
3.00 1.885 1.888 1.890 1.893 1.896 1.899 1.901 1.904 1.907 1.910
3.10 1.912 1.915 1.918 1.920 1.923 1.926 1.928 1.931 1.933 1.934
13
WATER CONTENT
43 PERCENT
DG
1.70
1.404
1.409
1.414
1.419
1.423
1.42 8
1.433
1.437
1.442
1.446
1.80
1.451
1.455
1.460
1.464
1.469
1.473
1.478
1.482
1.487
1.491
1.90
1.495
1.500
1.504
1.508
1.512
1.517
1.521
1.525
1.529
1.533
2.00
1.538
1.542
1.546
1.550
1.554
1.558
1.562
1.566
1.570
1.574
2.10
1.578
1.582
1.5 86
1.5Q0
1.594
1.598
1.601
1.605
1.609
1.613
2.20
1.617
1.620
1.624
1.628
1.632
1.635
1.639
1.643
1.646
1.650
2.30
1.654
1.657
1.661
1.664
1.668
1.671
1.675
1.679
1.682
1.686
2.40
1.689
1.692
1.696
1.699
1.703
1.706
1.709
1.713
1.716
1.720
2.50
1.723
1.726
1.730
1.733
1.736
1.739
1.743
1.746
1.749
1.752
2.60
1.755
1.759
1.762
1.765
1.768
1.771
1.774
1.777
1.781
1.784
2.70
1.787
1.790
1.793
1.796
1.799
1.802
1.805
1.808
1.811
1.814
2.80
1.817
1.820
1.823
1.825
1.828
1.831
1.834
1.837
1.840
1.843
2.90
1.846
1.848
1.851
1.854
1.857
1.860
1.862
1.865
1.868
1.871
3.00
1.873
1.876
1.879
1.881
1.884
1.887
1.890
1.892
1.895
1.897
3.10
1.900
1.903
1.905
1.908
1.911
1.913
1.916
1.918
1.921
1.923
WATER CONTENT
44 PERCENT
DC
1.70
1.400
1.405
1.410
1.414
1.419
1.424
1.428
1.433
1.437
1.442
1.80
1.446
1.451
1.455
1.460
1.464
1.469
1.473
1.477
1.482
1.486
1.90
1.490
1.494
1.499
1.503
1.507
1.511
1.515
1.520
1.524
1.528
2.00
1.532
1.536
1.540
1.544
1.548
1.552
1.556
1.560
1.564
1.568
2.10
1.572
1.576
1.579
1.583
1.587
1.591
1.595
1.599
1.602
1.606
2.20
1.610
1.613
1.617
1.621
1.624
1.628
1.632
1.635
1.639
1.643
2.30
1.646
1.650
1.653
1.657
1.660
1.664
1.667
1.671
1.674
1.678
2.40
1.681
1.684
1.688
1.691
1.694
1.698
1.701
1.704
1.708
1.711
2.50
1.714
1.718
1.721
1.724
1.727
1.730
1.734
1.737
1.740
1.743
2.60
1.746
1.749
1.753
1.756
1.759
1.762
1.765
1.768
1.771
1.774
2.70
1.777
1.780
1.783
1.786
1.78Q
1.792
1.795
1.798
1.801
1.804
2.80
1.806
1.809
1.812
1.815
1.818
1.821
1.824
1.826
1.829
1.832
2.90
1.835
1.83-8
1.840
1.843
1.846
1.849
1.851
1.854
1.857
1.859
3.00
1.862
1.865
1.867
1.870
1.873
1.875
1.878
1.881
1.883
1.886
3.10
1.888
1.891
1.893
1.896
1.899
1.901
1.904
1.906
1.909
1.911
WATER CONTENT
45 PERCENT
DG
1.70
1.397
1.401
1.406
1.410
1.415
1.420
1.424
1.429
1.433
1.438
1.80
1.442
1.446
1.451
1.455
1.460
1.464
1.468
1.472
1.477
1.481
1.90
1.485
1.489
1.494
1.498
1.502
1.506
1.510
1.514
1.518
1.522
2.00
1.526
1.530
1.534
1.538
1.542
1.546
1.550
1.554
1.558
1.562
2.10
1.566
1.569
1.573
1.577
1.581
1.584
1.588
1.592
1.596
1.599
2.20
1.603
1.607
1.610
1.614
1.618
1.621
1.625
1.628
1.632
1.635
2.30
1.639
1.642
1.646
1.649
1.653
1.656
1.660
1.66 3
1.666
1.670
2.40
1.673
1.676
1.680
1.683
1.686
1.690
1.693
1.696
1.699
1.703
2.50
1.706
1.709
1.712
1.715
1.719
1.722
1.725
1.728
1.731
1.734
2.60
1.737
1.740
1.743
1.747
1.750
1.753
1.756
1.759
1.762
1.765
2.70
1.767
1.770
1.773
1.776
1.779
1.782
1.785
1.788
1.791
1.794
2.80
1.796
1.799
1.802
1.805
1.808
1.811
1.813
1.816
1.819
1.822
2*90
1.824
1.827
1.830
1.832
1.835
1.838
1.840
1.843
1.846
1.848
3.00
1.851
1.854
1.856
1.859
1.861
1.864
1.867
1.869
1.872
1.874
3.10
1.877
1.879
1.882
1.884
1.887
1.889
1.892
1.894
1.897
1.899
14
WATFR CONTENT
46 PERCENT
DG
1.70
1.393
1.397
1.402
1.407
1.411
1.416
1.420
1.424
1.429
1.433
1.80
1.438
1.442
1.446
1.451
1.455
1.459
1.463
1.468
1.472
1.476
1.90
1.480
1.484
1.489
1.493
1.497
1.501
1.505
1.509
1.513
1.517
2.00
1.521
1.525
1.529
1.533
1.537
1.540
1.544
1.548
1.552
1.556
2.10
1.560
1.563
1.567
1.571
1.574
1.578
1.582
1.586
1.589
1.593
2.20
1.596
1.600
1.604
1.607
1.611
1.614
1.618
1.621
1.625
1.628
2.30
1.632
1.635
1.639
1.642
1.645
1.649
1.652
1.655
1.659
1.662
2.40
1.665
1.669
1.672
1.675
1.678
1.682
1.685
1.688
1.691
1.695
2.50
1.698
1.701
1.704
1.707
1.710
1.713
1.716
1.719
1.723
1.726
2.60
1.729
1.732
1.735
1.738
1.741
1.744
1.747
1.749
1.752
1.755
2.70
1.758
1.761
1.764
1.767
1.770
1.773
1.775
1.778
1.781
1.784
2.80
1.787
1.789
1.792
1.795
1.798
1.801
1.803
1.806
1.809
1.811
2.90
1.814
1.817
1.819
1.822
1.82 5
1.827
1.830
1.833
1.835
1.838
3.00
1.840
1.843
1.845
1.848
1.851
1.853
1.856
1.858
1.861
1.863
3.10
1.866
1.868
1.871
1.873
1.875
1.878
1.880
1.883
1.885
1.888
WATER CONTENT 47 PERCENT
DG 0 1 2 3
1.70
1.389
1.394
1.398
1.403
1.407
1,412
1.416
1.420
1.425
1.429
1.80
1.433
1.439
1.442
1.446
1.450
1.455
1.459
1.463
1.467
1.471
1.90
1.475
1.480
1.484
1.488
1.492
1.496
1.500
1.504
1.508
1.512
2.00
1.515
1.519
1.523
1.527
1.531
1.535
1.539
1.542
1.546
1.550
2.10
1.554
1.557
1.561
1.565
1.568
1.572
1.576
1.579
1.583
1.586
2.20
1.590
1.594
1.597
1.601
1.604
1.608
1.611
1.614
1.618
1.621
2.30
1.625
1.628
1.631
1.635
1.638
1.641
1.645
1.648
1.651
1.655
2.40
1.658
1.661
1.664
1.668
1.671
1.674
1.677
1.680
1.683
1.687
2.50
1.690
1.693
1.696
1.699
1.702
1.705
1.708
1.711
1.714
1.717
2.60
1.720
1.723
1.726
1.729
1.732
1.735
1.738
1.741
1.743
1.746
2.70
1.749
1.752
1.755
1.758
1.761
1.763
1.766
1.769
1.772
1.774
2.80
1.777
1.780
1.783
1.785
1.788
1.791
1.793
1.796
1.799
1.801
2.^0
1.804
1.807
1.809
1.812
1.815
1.817
1.820
1.822
1.825
1.827
3.00
1.830
1.832
1.835
1.837
1.840
1.842
1.845
1.847
1.850
1.852
3.10
1.855
1.857
1.860
1.862
1.864
1.867
1.869
1.872
1.874
1.876
WATER CONTENT
48 PERCENT
DG
1.70
1.80
1.90
2.00
2.10
2.20
2.30
2.40
2.50
2.60
2.70
2.80
2.90
3.00
3.10
0
1.385
1.429
1.471
1.510
1.548
1.584
1.618
1.651
1.682
1.712
1.740
1.768
1.794
1.820
1.844
1
1.390
1.433
1.475
1.514
1.551
1.587
1.621
1.654
1.685
1.715
1.743
1.771
1.797
1.822
1.846
1.394
1.438
1.479
1.518
1.555
1.591
1.625
1.657
1.688
1.718
1.746
1.773
1.799
1.825
1.849
1.399
1.442
1.483
1.522
1.559
1.594
1.628
1.660
1.691
1.720
1.749
1.776
1.802
1.827
1.851
1.403
1.446
1.487
1.525
1.562
1.598
1.631
1.663
1.694
1.723
1.752
1.779
1.805
1.830
1.854
1.408
1.450
1.491
1.529
1.566
1.601
1.634
1.666
1.697
1.726
1.754
1.781
1.807
1.832
1.856
1.412
1.454
1.495
1.533
1.570
1.604
1.638
1.669
1.700
1.729
1.757
1.784
1.810
1.834
1.858
1.416
1.458
1.499
1.537
1.573
1.608
1.641
1.673
1.703
1.732
1.760
1.787
1.812
1.837
1.861
8
1.421
1.463
1.502
1.540
1.577
1.611
1.644
1.676
1.706
1.735
1.763
1.789
1.815
1.839
1.863
1.425
1.467
1.506
1.544
1.580
1.615
1.647
1.679
1.709
1.738
1.765
1.792
1.817
1.842
1.865
15
WATER CONTENT
49 PERCENT
DG
1.70
1.382
1.386
1.391
1.395
1.399
1.404
1.408
1.412
1.417
1.421
1.80
1.425
1.429
1.433
1.438
1.442
1.446
1.450
1.454
1.458
1.462
1.90
1.466
1.470
1.474
1.478
1.482
1.486
1.490
1.494
1.497
1.501
2.00
1.505
1 .509
1.513
1.516
1.520
1.524
1.528
1.531
1.535
1.539
2.10
1.542
1.546
1.549
1.553
1.556
1.560
1.564
1.567
1.571
1.574
2.20
1.577
1.581
1.584
1.588
1.591
1.595
1.598
1.601
1.605
1.608
2.30
1.611
1.614
1.618
1.621
1.624
1.627
1.631
1.634
1.637
1 .640
2.40
1.643
1.647
1.650
1.653
1.656
1.659
1.662
1.665
1.668
1.671
2.50
1.674
1.677
1.680
1.683
1.686
1.689
1.692
1.695
1.699
1.701
2.60
1.704
1.706
1.709
1.712
1.715
1.718
1.721
1.723
1.726
1.729
2.70
1.732
1.735
1.737
1.740
1.743
1.745
1.748
1.751
1.754
1.756
2.80
1.759
1.761
1.764
1.767
1.769
1.772
1.775
1.777
1.780
1.782
2.90
1.785
1.787
1.790
1.792
1.795
1.797
1.800
1.802
1.805
1.807
3.00
1.810
1.812
1.815
1.817
1.810
1.822
1.824
1.827
1.829
1.831
3.10
1.834
1.836
1.838
1.841
1.843
1.845
1.848
1.850
1.852
1.854
WATER CONTENT
50 PERCENT
OG
1.70
1.378
1.383
1.387
1.391
1.396
1.400
1.4 04
1.408
1.413
1.417
1.80
1.421
1.425
1.429
1.433
1.437
1.442
1.446
1.450
1.454
1.458
1.90
1.462
1.465
1.469
1.473
1.477
1.481
1.485
1.489
1.492
1.496
2.00
1.500
1.504
1.507
1.511
1.515
1.519
1.522
1.526
1.529
1.533
2.10
1.537
1.540
1.544
1.547
1.551
1.554
1.558
1.561
1.565
1.568
2.20
1.571
1.575
1.578
1.582
1.585
1.598
1.592
1.595
1.598
1.601
2.30
1.605
1.608
1.611
1.614
1.619
1.621
1.624
1.627
1.630
1.633
2.40
1.636
1.639
1.643
1.646
1.649
1.652
1.655
1.658
1.661
1.664
2.50
1.667
1.670
1.673
1.6 75
1.678
1.681
1.684
1.687
1.690
1.69 3
2.60
1.696
1.698
1.701
1.704
1.707
1.710
1.712
1.715
1.718
1.721
2.70
1.723
1.726
1.729
1.732
1.734
1.737
1.739
1.742
1.745
1.747
2.80
1.750
1.753
1.755
1.758
1.760
1.763
1.765
1.768
1.770
1.773
2.90
1.776
1.778
1.780
1.783
1.785
1.788
1.7 90
1. 793
1.795
1.798
3.00
1.800
1.802
1.805
1.807
1.810
1.812
1.814
1.817
1.819
1.821
3.10
1.824
1.826
1.828
1.830
1.833
1.835
1.837
1.839
1.842
1.944
WATER CONTENT
51 PERCENT
DG
1.70
1.375
1.379
1.384
1.388
1.392
1.396
1.401
1.405
1.409
1.413
1.80
1.417
1.421
1.425
1.429
1.433
1.437
1.441
1.445
1.449
1.453
1.90
1.457
1.461
1.465
1.469
1.473
1.476
1.480
1.484
1.488
1.491
2.00
1.495
1.499
1.502
1.506
1.510
1.513
1.517
1.521
1.524
1.528
2.10
1.531
1.535
1.538
1.542
1.545
1.549
1.552
1.555
1.559
1.562
2.20
1.566
1.569
1.572
1.575
1.579
1.582
1.585
1.589
1.592
1.595
2.30
1.598
1.601
1.605
1.608
1.611
1.614
1.617
1.620
1.623
1.626
2.40
1.629
1.633
1.636
1.639
1.642
1.645
1.648
1.651
1.653
1.656
2.50
1.65^
1.662
1.665
1.668
1.671
1.674
1.677
1.679
1.682
1.685
2.60
1.688
1.691
1.693
1.696
1.699
1.702
1.704
1.707
1.710
1.713
2.70
1.715
1.718
1.721
1.723
1.726
1.728
1.731
1.734
1.736
1.739
2.80
1.741
1.744
1.746
1.749
1.752
1.754
1.757
1.759
1.762
1.764
2.90
1.766
1.769
1.771
1.774
1.776
1.779
1.781
1.78 3
1.786
1.788
3.00
1.791
1.793
1.795
1.798
1.800
1.802
1.804
1.807
1.809
1.811
3.iu
1.814
1.816
1.818
1.820
1.823
1.825
1.827
1.829
1.831
1.834
16
WATER CONTENT
52 PERCENT
DG
1.70
1.372
1.376
1.380
1.384
1.388
1.393
1.397
1.401
1.405
1.409
1.80
1.413
1.417
1.421
1.425
1.429
1.433
1.437
1.441
1.445
1.449
1.90
1.453
1.457
1.460
1.464
1.468
1.472
1.475
1.479
1.483
1.48 7
2.00
1.4P0
1.494
1.497
1.501
1.505
1.508
1.512
1.515
1.519
1.522
2. 10
1.526
1.529
1.533
1.536
1.540
1.543
1.546
1.550
1.553
1.556
2.20
1.560
1.563
1.566
1.570
1.573
1.576
1.5 79
1.582
1.586
1.589
2.30
1.592
1.595
1.598
1.601
1.604
1.608
1.611
1.614
1.617
1.620
2.40
1.623
1.626
1.629
1.632
1.635
1.638
1.641
1.643
1.646
1.649
2.50
1.652
1.655
1.658
1.661
1.664
1.666
1.669
1.672
1.675
1.678
2.60
1.680
1.683
1.686
1.638
1.691
1.694
1.697
1.699
1.702
1.705
2.70
1.707
1.710
1.712
1.715
1.718
1.720
1.723
1.725
1.728
1.730
2.80
1.733
1.735
1.738
1.740
1.743
1.745
1.748
1.750
1.753
1.755
2.90
1.758
1.760
1.762
1.765
1.767
1.770
1.7 72
1.774
1.777
1.779
3.00
1.781
1.784
1.786
1.788
1.790
1.793
1.795
1.797
1.800
1.802
3.10
1.804
1.806
1.808
1.811
1.813
1.815
1.817
1.819
1.822
1.824
WATER CONTENT
53 PERCENT
DG
1.70
1.368
1.372
1.377
1.381
1.385
1.389
1.393
1.397
1.401
1.405
1.80
1.409
1.413
1.417
1.421
1.425
1.429
1.433
1.437
1.441
1.445
1.90
1.448
1.45?
1.456
1.460
1.463
1.467
1.471
1.475
1.478
1.482
2.00
1.485
1.489
1.493
1.496
1.500
1.503
1.507
1.510
1.514
1.517
2.10
1.521
1.524
1.527
1.531
1. 534
1.538
1.541
1.544
1.547
1.551
2.20
1.554
1.557
1.561
1.564
1.567
1.570
1.573
1.576
1.580
1.583
2.30
1.586
1.589
1.592
1.595
1.598
1.601
1.604
1.607
1.610
1.613
2.40
1.616
1.619
1.622
1.625
1.623
1.631
1.634
1.637
1.639
1.642
2.50
1.645
1.648
1.651
1.654
1.656
1.659
1.662
1.665
1.667
1.670
2.60
1.673
1.676
1.678
1.681
1.684
1.686
1.689
1.691
1.694
1.697
2.70
1.699
1.702
1.704
1.707
1.710
1.712
1.715
1.717
1.720
1.722
2.80
1.725
1.727
L730
1.732
1.734
1.737
1.739
1.742
1.744
1.747
2.90
1.749
1.751
1.754
1.756
1.758
1.761
1.763
1.765
1.768
1.770
3.00
1.772
1.774
1.777
1.779
1.781
1.793
1.786
1.788
1.790
1.792
3.10
1.795
1.797
1.799
1.801
1.803
1. 805
1.808
1.810
1.812
1.814
WATER CONTENT
54 PERCENT
OG
1.70
1.365
1.369
1.373
1.377
1.382
1.396
1.390
1.394
1.398
1.402
1.80
1.406
1.410
1.414
1.417
1.421
1.425
1.429
1.433
1.437
1.440
1.90
1.444
1.449
1.452
1.455
1.459
1.463
1.466
1.470
1.474
1.477
2.00
1.481
1.484
1.488
1.491
1 .495
1.498
1.502
1.505
1.509
1.512
2.10
1.515
1.519
1.522
1.526
1.529
1.532
1.535
1.539
1.542
1.545
2.20
1.548
1.552
1.555
1.558
1.561
1.564
1.567
1.571
1.574
1.577
2.30
1.580
1.583
1.586
1.589
1.592
1.595
1.598
1.601
1.604
1.607
2.40
1.610
1.613
1.616
1.618
1.621
1.624
1.627
1.630
1.633
1.636
2.50
1.638
1.641
1.644
1.647
1.649
1.652
1.655
1.658
1.660
1.663
2.60
1.666
1.668
1.671
1.673
1.676
1.679
1.681
1.684
1.686
1.689
2.70
1.692
1.694
1.6^7
1.699
1.702
1.704
1.707
1.709
1.712
1.714
2.80
1.717
1.719
1.721
1.724
1.726
1.729
1.731
1.733
1.736
1.738
2.90
1.740
1.743
1.745
1.747
1.750
1.752
1.754
1.757
1.759
1.761
3.00
1.763
1.766
1.768
1.770
1.772
1.774
1.777
1.779
1.781
1.783
3.10
1.785
1.787
1.790
1.792
1.794
1.796
1.798
1.800
1.802
1.804
17
MATER CONTENT 55 PERCENT
DG 0 1 2 3
1.70
1.362
1.366
1.370
1.3 74
1.378
1.382
1.386
1.390
1.394
1.398
1.80
1.402
1.406
1.410
1.414
1.417
1.421
1.425
1.429
1.433
1.436
1.90
1.440
1.444
1.447
1.451
1.455
1.458
1.462
1.466
1.469
1.473
2.00
1.476
1.480
1.483
1.487
1.490
1.494
1.497
1.500
1.504
1.507
2.10
1.510
1.514
1.517
1.520
1.524
1.527
1.530
1.533
1.537
1.540
2.20
1.543
1.546
1.549
1.552
1.556
1.559
1.562
1.565
1.568
1.571
2.30
1.574
1.577
1.580
1.583
1.586
1.589
1.592
1.595
1.598
1.601
2.40
1.603
1.606
1.609
1.612
1.615
1.618
1.620
1.623
1.626
1.629
2.50
1.632
1.634
1.637
1.640
1.642
1.645
1.648
1.651
1.653
1.656
2.60
1.658
1.661
1.664
1.666
1.669
1.671
1.674
1.677
1.679
1.682
2.70
1.684
1.687
1.689
1.692
1.694
1.697
1.699
1.701
1.704
1.706
2.80
1.709
1.711
1.713
1.716
1.718
1.721
1.723
1.725
1.728
1.730
2.90
1.732
1.734
1.737
1.739
1.741
1.744
1.746
1.748
1.750
1.753
3.00
1.755
1.75 7
1.759
1.761
1.763
1.766
1.768
1.770
1.772
1.774
3.10
1.776
1.778
1.781
1.783
1.785
1.787
1.789
1.791
1.793
1.795
WATER CONTENT
DG
56 PERCENT
1.70
1.359
1.3 63
1.367
1.371
1.375
1.379
1.383
1.387
1.391
1.395
1.80
1.398
1.402
1.406
1.410
1.414
1.417
1.421
1.42 5
1.429
1.432
1.90
1.436
1.440
1.443
1.447
1.451
1.454
1.458
1.461
1.465
1.468
2.00
1.472
1.475
1.479
1.482
1.485
1.489
1.492
1.496
1.499
1.502
2.10
1.506
1.509
1.512
1.515
1.519
1.522
1.525
1.528
1.531
1.534
2.20
1.538
1.541
1.544
1.547
1.550
1.553
1.556
1.559
1.562
1.565
2.30
1.568
1.571
1.574
1.577
1.580
1.583
1.5 86
1.589
1.592
1.594
2.40
1.597
1.600
1.603
1.606
1.609
1.611
1.614
1.617
1.620
1.622
2.50
1.625
1.628
1.630
1.633
1.636
1.638
1.641
1.644
1.646
1.649
2.60
1.651
1.654
1.657
1.659
1.662
1.664
1.667
1.669
1.672
1.674
2.70
1.677
1.679
1.682
1.684
1.687
1.689
1.691
1.694
1.696
1.699
2.80
1.701
1.703
1.706
1.708
1.710
1.713
1.715
1.717
1.720
1.722
2.90
1.724
1.726
1.729
1.731
1.733
1.735
1.738
1.740
1.742
1.744
3.00
1.746
1.748
1.751
1.753
1.755
1.757
1.759
1.761
1.763
1.765
3.10
1.768
1.770
1.772
1.774
1.776
1.778
1.780
1.782
1.784
1.786
WATER CONTENT
OG
57 PERCENT
1.70
1.356
1.360
1.364
1.368
1.372
1.3 75
1.379
1.383
1.387
1.391
1.80
1.395
1.399
1.402
1.406
1.410
1.414
1.417
1 . 42 1
1.425
1.428
1.90
1.432
1.436
1.439
1.443
1.446
1.450
1.453
1.457
1.460
1.464
2.00
1.467
1.471
1.474
1.477
1.481
1.484
1.488
1.491
1.494
1.497
2.10
1.501
1.504
1.507
1.510
1.514
1.517
1.520
1.523
1.526
1.529
2.20
1.532
1.535
1.539
1.542
1. 545
1.548
1.551
1.554
1.557
1.560
2.30
1.563
1.565
1.568
1.571
1.574
1.577
1.580
1.583
1.586
1.588
2.40
1.591
1.594
1.597
1.600
1.602
1.605
1.608
1.610
1.613
1.616
2.50
1.619
1.621
1.624
1.627
1.629
1.632
1.634
1.637
1.640
1.642
2.60
1.645
1.647
1.650
1.652
1.655
1.657
1.660
1.662
1.665
1.667
2.70
1.670
1.672
1.674
1.677
1.679
1.682
1.684
1.686
1.689
1.691
2.80
1.693
1.696
1.698
1.700
1.703
1.705
1.707
1.709
1.712
1.714
2.90
1.716
1.718
1.721
1.723
1.725
1.727
1.729
1.732
1.734
1.736
3.00
i.738
1.740
1.742
1.744
1.746
1.749
1.751
1.753
1.755
1.757
3.10
1.759
1.761
1.763
1.765
1.767
1.769
1.771
1.773
1.775
1.777
18
WATER CONTENT
58 PERCENT
OG
1.70
1.352
1.356
1.360
1.364
1.368
1.372
1.376
1.380
1.384
1.388
1.80
1.391
I. 395
1.399
1.403
1.406
1.410
1.414
1.417
1.421
1.425
1.90
1.428
1.432
1.435
1.439
1.442
1.446
1.449
1.453
1.456
1.460
2.00
1.463
1.466
1.470
1.473
1.476
1.480
1.483
1.486
1.489
1.493
2.10
1.496
1.49Q
1.502
1.506
1.509
1.512
1.515
1.518
1.521
1.524
2.20
1.527
1.530
1.533
1.536
1.539
1.542
1.545
1.548
1.551
1.554
2.30
1.557
1.560
1.563
1.566
1.568
1.571
1.574
1.577
1.580
1.583
2.40
1.585
1.588
1.591
1.594
1.596
1.599
1.602
1.604
1.607
1.610
2.50
1.612
1.615
1.617
1.620
1.623
1.625
1.628
1.630
1.633
1.635
2.60
1.638
1.640
1.643
1.645
1.648
1.650
1.653
1.655
1.658
1.660
2.70
1.663
1.665
1.667
1.670
1.672
1.674
1.677
1.679
1.681
1.684
2.80
1.686
1.688
1.691
1.693
1.695
1.697
1.700
1.702
1.704
1.706
2.90
1.708
1.711
1.713
1.715
1.717
1.719
1.721
1.724
1.726
1.728
3.00
1.730
1.732
1.734
1.736
1.738
1.740
1.742
1.744
1.746
1.749
3.10
1.751
1.753
1.755
1.757
1.759
1.761
1.762
1.764
1.766
1.768
WATER CONTENT
59 PERCENT
OG
1.70
1.349
1.353
1.357
1.361
1.365
T.369
1.373
1.377
1.380
1.384
1.80
1.388
1.392
1.395
1.399
1.403
1.406
1.410
1.414
1.417
1.421
1.90
1.424
1.428
1.431
1.435
1.438
1.442
1.445
1.449
1.452
1.455
2.00
1.459
1.462
1.465
1.469
1.472
1.475
1.478
1.482
1.485
1.488
2.10
1.491
1.494
1.498
1.501
1.504
1.507
1.510
1.513
1.516
1.519
2.20
1.522
1.525
1.528
1.531
1.534
1.537
1.540
1.543
1.546
1.549
2.30
1.552
1.554
1.557
1.560
1.563
1.566
1.568
1.571
1.574
1.577
2.40
1.579
1.5*2
1.585
1.588
1.590
1.503
1.596
1.598
1.601
1.603
2.50
1.606
1.609
1.611
1.614
1.616
1.619
1.621
1.624
1.626
1.629
2.60
1.631
1.634
1.636
1.639
1.641
1.644
1.646
1.648
1.651
1.653
2.70
1.656
1.658
1.660
1.663
1.665
1.667
1.670
1.672
1.674
1.676
2.80
1.679
1.681
1.683
1.685
1.688
1.690
1.692
1.694
1.697
1.699
2.90
1.701
1.703
1.705
1.707
1.709
1.712
1.714
1.716
1.718
1.720
3.00
1.722
1.724
1.726
1.728
1.730
1.732
1.734
1.736
1.738
1.740
3.10
1.742
1.744
1.746
1.748
1.750
1.752
1.754
1.756
1.758
1.760
WATER CONTENT
60 PERCENT
DG
1.70
1.347
1.350
1.354
1.358
1.362
1.366
1.370
1.373
1.377
1.381
1.80
1.385
1.388
1.392
1.396
1.399
1.403
1.406
1.410
1.414
1.417
l.°0
1.421
1.424
1.428
1.431
1.434
1.438
1.441
1.445
1.448
1.451
2.00
1.455
1.458
1.461
1.464
1.468
1.471
1.474
1.477
1.480
1.484
2.10
1.487
1.490
1.493
1.496
1.499
1.502
1.505
1.508
1.511
1.514
2.20
1.517
1.520
1.523
1.526
1.529
1.532
1.535
1.538
1.541
1.543
2.30
1.546
1.549
1.552
1.555
1.557
1.560
1.563
1.566
1.568
1.571
2.40
1.574
1.576
1.579
1.582
1. 584
1.587
1.590
1.592
1.595
1.597
2.50
1.600
1.603
1.605
1.608
1.610
1.613
1.615
1.618
1.620
1.623
2.60
1.625
1.627
1.630
1.632
1.635
1.637
1.639
1.642
1.644
1.647
2.70
1.649
1.651
1.653
1.656
1.658
1.660
1.663
1.665
1.667
1.669
2.80
1.672
1.674
1.676
1.678
1.680
1.683
1.685
1.687
1.689
1.691
2.90
1.693
1.696
1.698
1.700
1.702
1.704
1.706
1.708
1.710
1.712
3.00
1.714
1.716
1.718
1.720
1.722
1.724
1.726
1.728
1.7J0
1.732
3.10
1.734
1.736
1.738
1.740
1.742
1.744
1.746
1.748
1.750
1.752
19
WATER CONTENT
61 PERCENT
DG
1.70
1.344
1.348
1.351
1.355
1.359
1.363
1.367
1.370
1.374
1.378
1.80
1.381
1.385
1.389
1.392
1.396
1.399
1.403
1.406
1.410
1.413
1.90
1.417
1.420
1.424
1.427
1.431
1.434
1.437
1.441
1.444
1.447
2.00
1.450
1.454
1.457
1.460
1.463
1.467
1.4 70
1.473
1.476
1.479
2.10
1.482
1.485
1.488
1.491
1.494
1.498
1.501
1.504
1.506
1.509
2.20
1.512
1.515
1.518
1.521
1.524
1.527
1.530
1.533
1.535
1.538
2.30
1.541
1.544
1.547
1.549
1.552
1.555
1.557
1.560
1.563
1.566
2.40
1.568
1.571
1.573
1.576
1.579
1.581
1.534
1.586
1.589
1.592
2.50
1.594
1.597
1.599
1.602
1.604
1.607
1.609
1.611
1.614
1 .616
2.60
1.619
1.621
1.624
1.626
1.628
1.631
1.633
1.635
1.638
1.640
2.70
1.642
1.645
1.647
1.649
1.651
1.654
1.656
1.658
1.660
1.662
2.80
1.665
1.667
1.669
1.671
1.673
1.676
1.678
1.680
1.682
1.684
2.90
1.686
1.638
1.690
1.692
1.694
1.697
1.699
1.701
1.703
1.705
3.00
1.707
1.709
1.711
1.713
1.715
1.717
1.719
1.721
1.723
1.724
3.10
1.726
1.728
1.730
1.732
1.734
1.736
1.738
1.740
1.742
1.743
WATER CONTENT
62 PERCENT
DG
1.70
1.341
1.345
1.348
1.352
1.356
1.360
1.363
1.367
1.371
1.374
1.80
1.378
1.382
1.385
1.389
1.392
1.396
1.399
1.403
1.406
1.410
1.90
1.413
1.417
1.420
1.423
1.427
1.430
1.433
1.437
1.440
1.443
2.00
1.446
1.450
1.453
1.456
1.459
1.462
1.465
1.469
1.472
1.475
2.10
1.478
1.481
1.484
1.487
1.490
1.493
1.496
1.499
1.502
1.505
2.20
1.508
1.511
1.513
1.516
1.519
1.522
1.525
1.528
1.530
1.533
2.30
1.536
1. 539
1.541
1.544
1.547
1.549
1.552
1.555
1.557
1.560
2.40
1.563
1.565
1.568
1.570
1.573
1.576
1.578
1.581
1.533
1.536
2.50
1.588
1.591
1.593
1.596
1.598
1.601
1.603
1.605
1.608
1.610
2.60
1.613
1.615
1.617
1.620
1.622
1.624
1.627
1.629
1.631
1.633
2.70
1.636
1.638
1.640
1.643
1. 645
1.647
1.649
1.651
1.654
1.656
2.80
1.658
1.660
1.662
1.664
1.666
1.669
1.671
1.673
1.675
1.677
2.90
1.679
1.681
1.683
1.635
1.687
1.639
1.691
1.693
1.695
1.697
3.00
1.699
1.701
1.703
1.705
1.707
1.709
1.711
1.713
1.715
1.717
3.10
1,719
1.721
1.722
1.724
1.726
1.728
1.730
1.732
1.734
1.735
WATER CONTENT
63 PERCENT
DG
1.70
1.338
1.342
1.346
1.349
1.353
1.357
1.360
1.364
1.368
1.371
1.80
1.375
1.3 78
1.382
1.386
1.38^
1.393
1.396
1.399
1.403
1.406
1.90
1.410
1.413
1.416
1.420
1.423
1.426
1.430
1.433
1.436
1.439
2.00
1.442
1.446
1.449
1.452
1.455
1.458
1.461
1.464
1.467
1.470
2.10
1.474
1.477
1.430
1.483
1.485
1.488
1.491
1.494
1.497
1.500
2.20
1.503
1.506
1.509
1.511
1.514
1.517
1.520
1.523
1.525
1.528
2.30
1.531
1.534
1.536
1.539
1.542
1.544
1.547
1.550
1.552
1.555
2.40
1.557
1.560
1.562
1.565
1.568
1.570
1.573
1.575
1.578
1.580
2.50
1.583
1.585
1.587
1.590
1.592
1.595
1.597
1.599
1.602
1.604
2.60
1.607
1.609
1.611
1.613
1.616
1.618
1.620
1.623
1.625
1.627
2.70
1.629
1.632
1.634
1.636
1.638
1.640
1.643
1.645
1.647
1.649
2.80
1.651
1.653
1.655
1.658
1.660
1.662
1.664
1.666
1.668
1.670
2.90
1.672
1.674
1.676
1.678
1.680
1.682
1.684
1.636
1.688
1.690
3.00
1.692
1.694
1.696
1.698
1.700
1.702
1.704
1.705
1.707
1.709
3.10
1.711
1.713
t.715
1.717
1.719
1.720
1.722
1.724
1.726
1.728
20
WATER CONTENT
64 PERCENT
DG
1.70
1.335
1.339
1.343
1.346
1.350
1.354
1.357
1.361
1.365
1.368
1.80
1.372
1.375
1.379
1.382
1.386
1.389
1.393
1.396
1.399
1.403
1.90
1.406
1.409
1.413
1.416
1.419
1.423
1.426
1.429
1.432
1.435
2.00
1.439
1.442
1.445
1.448
1.451
1.454
1.457
1.460
1.463
1.466
2.10
1.469
1.472
1.475
1.478
1.481
1.484
1.487
1.490
1.493
1.496
2.20
1.498
1.501
1.504
1.507
1.510
1.512
1.515
1.518
1.520
1.523
2.30
1.526
1.529
1.531
1.534
1.537
1.539
1.542
1.544
1.547
1.549
2.40
1.552
1.555
1.557
1.560
1.562
1.565
1.567
1.570
1.572
1.574
2.50
1.577
1.579
1.582
1.584
1.587
1.589
1.591
1.594
1.596
1.598
2.60
1.601
1.603
1.605
1.607
1.610
1.612
1.614
1.617
1.619
1.621
2.70
1.623
1.625
1.628
1.630
1.632
1.634
1.636
1.638
1.640
1.643
2.80
1.645
1.647
1.649
1.651
1.653
1.655
1.657
1.659
1.661
1.663
2.90
1.665
1.667
1.669
1.671
1.673
1.675
1.677
1.679
1.681
1.683
3.00
1.685
1.687
1.689
1.691
1.693
1.694
1.696
1.698
1.700
1.702
3.10
1.704
1.706
1.707
1.709
1.711
1.713
1.715
1.716
1.718
1.720
WATER CONTENT
65 PERCENT
DG
1.70
1.333
1.336
1.340
1.344
1.347
1.351
1.354
1.358
1.362
1.365
1.80
1.369
1.37?
1.376
1.379
1.383
1.3 86
1.389
1.393
1.396
1.399
1.90
1.403
1.406
1.409
1.413
1.416
1.419
1.422
1.425
1.429
1.432
2.00
1.435
1.438
1.441
1.444
1.447
1.450
1.453
1.456
1.459
1.462
2.10
1.465
1.468
1.471
1.474
1.477
1.480
1.483
1.485
1.488
1.491
2.20
1.494
1.497
1.499
1.502
1.505
1.508
1.510
1.513
1.516
1.518
2.30
1.521
1.524
1.526
1.529
1.532
1.534
1.537
1.539
1.542
1.544
2.40
1.547
1.549
1.552
1.554
1.557
1.559
1.562
1.564
1.567
1.569
2.50
1.571
1.574
1.576
1.579
1.581
1.583
1.586
1.588
1.590
1.593
2.60
1.595
1.597
1.599
1.602
1.604
1.606
1.608
1.610
1.613
1.615
2.70
1.617
1.619
1.621
1.624
1.626
1.628
1.630
1.632
1.634
1.636
2.80
1.638
1.640
1.642
1.644
1.647
1.649
1.651
1.653
1.655
1.657
2.90
1.659
1.661
1.663
1.664
1.666
1.668
1.670
1.672
1.674
1.676
3.00
1.678
1.680
1.682
1.684
1.685
1.687
1.689
1.691
1.693
1.695
3.10
1.697
1.698
1.700
1.702
1.704
1.705
1.707
1.709
1.711
1.713
WATER CONTENT
66 PERCENT
DG
1
8
1.70
1.80
l.°0
2.00
2.10
2.20
2.30
2.40
2.50
2.60
2.70
2.80
2.90
3.00
3.10
1.330
1.366
1.399
1.431
1.461
1.489
1.516
1.542
1.566
1.589
1.611
1.632
1.652
1.671
1.689
1.3 34
1.369
1.403
1.434
1.464
1.492
1.519
1.544
1.568
1.591
1.613
1.634
1.654
1.673
1.691
1.337
1.373
1.406
1.437
1.467
1.495
1.521
1.547
1.571
1.594
1.615
1.636
1.656
1.675
1.693
1.341
1.3 76
1.409
1.440
1.470
1.498
1.524
1.549
1.573
1.596
1.617
1.638
1.658
1.677
1.695
1.344
1.379
1.412
1.443
1.473
1.500
1.527
1.552
1.575
1.598
1.620
1.640
1.660
1.679
1.697
1.348
1.383
1.415
1.446
1.475
1.503
1.529
1.554
1.578
1.600
1.622
1.642
1.662
1.680
1.698
1.352
1.386
1.419
1.449
1.478
1.506
1.532
1.556
1.580
1.602
1.624
1.644
1.664
1.682
1.700
1.355
1.389
1.422
1.452
1.481
1.508
1.534
1.559
1.582
1.605
1.626
1.646
1.665
1.684
1.702
1.359
1.393
1.425
1.455
1.484
1.511
1.537
1.561
1.585
1.607
1.628
1.648
1.667
1.686
1.703
1.362
1.396
1.428
1.458
1.487
1.514
1.539
1.564
1.587
1.609
1.630
1.650
1.669
1.688
1.705
21
WATER CONTENT
67 PERCENT
DG
1.70
1.327
1.331
1.335
1.338
1.342
1.345
1.349
1.352
1.356
1.359
1.80
1.363
1.366
1.369
1.373
1.376
1.380
1.383
1.386
1.389
1.393
1.90
1.396
1.399
1.402
1.406
1.409
1.412
1.415
1.418
1.421
1.424
2.00
1.427
1.430
1.433
1.436
1.439
1.442
1.445
1.448
1.451
1.454
2.10
1.457
1.460
1.463
1.466
1.468
1.471
1.474
1.477
1.480
1.482
2.20
1.485
1.488
1.490
1.493
1.496
1.499
1.501
1.504
1.506
1.509
2.30
1.512
1.514
1.517
1.519
1.522
1.524
1.527
1.529
1.532
1.534
2.40
1.537
1.539
1.542
1.544
1.547
1.549
1.551
1.554
1.556
1.558
2.50
1.561
1.563
1.565
1.568
1.570
1.572
1.575
1.577
1.579
1.581
2.60
1.584
1.586
1.588
1.590
1.592
1.594
1.5 97
1.599
1.601
1.603
2.70
1.605
1.607
1.609
1.612
1.614
1.616
1.618
1.620
1.622
1.624
2.80
1.626
1.628
1.630
1.632
1.634
1.636
1.638
1.640
1.642
1.644
2.90
1.646
1.648
1.649
1.651
1.653
1.655
1.657
1.659
1.661
1.663
3.00
1.664
1.666
1.668
1.670
1.672
1.674
1.675
1.677
1.679
1.681
3.10
1.682
1.684
1.686
1.688
1.689
1.691
1.693
1.695
1.696
1.698
WATER CONTENT
68 PERCENT
OG
1.70
1.325
1.328
1.332
1.335
1.339
1.342
1.346
1.349
1.353
1.356
1.80
1.360
1.363
1.366
1.370
1.373
1.376
1.380
1.383
1.386
1.389
1.90
1.393
1.396
1.399
1.402
1.405
1.408
1.412
1.415
1.418
1.421
2.00
1.424
1.427
1.430
1.433
1.436
1.439
1.442
1.444
1.447
1.450
2.10
1.453
1.456
1.459
1.462
1.464
1.467
1.470
1.473
1.475
1.478
2.20
1.481
1.483
1.486
1.489
1.491
1.494
1.497
1.499
1.502
1.504
2.30
1.507
1.510
1.512
1.515
1.517
1.520
1.522
1.525
1.527
1.529
2.40
1.532
1.534
1.537
1.539
1.542
1.544
1.546
1.549
1.551
1.553
2.50
1.556
1.558
1.560
1.562
1.565
1.567
1.569
1.571
1.574
1.576
2.60
1.578
1.580
1.582
1.585
1.587
1.589
1.591
1.593
1.595
1.597
2.70
1.599
1.602
1.604
1.606
1.608
1.610
1.612
1.614
1.616
1.618
2.80
1.620
1.622
1.624
1.626
1 .628
1.630
1.632
1.634
1.635
1.637
2.90
1.639
1.641
1.643
1.645
1.647
1.649
1.651
1.652
1.654
1.656
3.00
1.658
1.660
1.662
1.663
1.665
1.667
1.669
1.670
1.672
1.674
3.10
1.676
1.677
1.679
1.681
1.683
1.684
1.686
1.688
1.689
1.691
WATER CONTENT
69 PERCENT
DG
1.70
1.322
1.326
1.329
1.333
1.336
1.340
1.343
1.347
1.350
1.353
1.80
1.357
1.360
1.364
1.367
1.370
1.373
1.377
1.380
1.383
1.386
1.90
1.389
1.393
1.396
1.399
1.402
1.405
1.408
1.411
1.414
1.417
2.00
1.420
1.423
1.426
1.429
1.432
1.435
1.438
1.441
1.443
1.446
2.10
1.449
1.452
1.455
1.458
1 . 460
1.463
1.466
1.469
1.471
1.474
2.20
1.477
1.479
1.482
1.484
1.487
1.490
1.492
1.495
1.497
1.500
2.30
1.503
1.505
1.508
1.510
1.513
1.515
1.517
1.520
1.522
1.525
2.40
1.527
1.529
1.532
1.534
1.537
1.539
1.541
1.544
1.546
1.548
2.50
1.550
1.553
1.555
1.557
1.559
1.562
1.564
1.566
1.568
1.570
2.60
1.573
1.575
1.577
1.579
1.581
1.583
1.585
1.588
1.590
1.592
2.70
1.594
1.596
1.598
1.600
1.602
1.604
1.606
1.608
1.610
1.612
2.80
1.614
1.616
1.618
1.620
1.622
1.624
1.626
1.627
1.629
1.631
2.90
1.633
1.635
1.637
1.639
1.641
1.642
1.644
1.646
1.648
1.650
3.00
1.651
1.653
1.655
1.657
1.659
1.660
1.662
1.664
1.666
1.667
3.10
1.669
1.671
1.672
1.674
1.676
1.677
1.679
1.681
1.682
1.684
22
WATER CONTENT 70 PERCENT
DG 0123456789
1.70 1.320 1.323 1.327 1.330 1.334 1.337 1.341 1.344 1.347 1.351
1.80 1.354 1.357 1.361 1.364 1.367 1.370 1.374 1.377 1.380 1.383
1.90 1.386 1.389 1.392 1.396 1.3°Q 1.402 1.405 1.408 1.411 1.414
2.00 1.417 1.420 1.423 1.425 1.428 1.431 1.434 1.437 1.440 1.443
2.10 1.445 1.448 1.451 1.454 1.456 1.459 1.462 1.464 1.467 1.470
2.20 1.472 1.475 1.478 1.480 1.483 1.485 1.488 1.491 1.493 1.496
2.30 1.498 1.501 1.503 1.506 1.508 1.510 1.513 1.515 1.518 1.520
2.40 1.522 1.525 1.527 1.529 1.532 1.534 1.536 1.539 1.541 1.543
2.50 1.545 1.548 1.550 1.552 1.554 1.557 1.559 1.561 1.563 1.565
2.60 1.567 1.570 1.572 1.574 1.576 1.578 1.580 1.582 1.584 1.586
2.70 1.588 1.590 1.592 1.594 1.596 1.598 1.600 1.602 1.604 1.606
2.80 1.608 1.610 1.612 1.614 1.616 1.618 1.620 1.621 1.623 1.625
2.90 1.627 1.629 1.631 1.633 1.634 1.636 1.638 1.640 1.642 1.643
3.00 1.645 1.647 1.649 1.650 1.652 1.654 1.656 1.657 1.659 1.661
3.10 1.662 1.664 1.666 1.667 1.669 1.671 1.672 1.674 1.676 1.677
WATER CONTENT 71 PERCENT
DG 0123456789
1.70 1.317 1.321 1.324 1.328 1.331 1.334 1.338 1.341 1.345 1.348
1.80 1.351 1.354 1.358 1.361 1.364 1.367 1,371 1.374 1.377 1.380
1.90 1.383 1.386 1.389 1.392 1.395 1.398 1.401 1.404 1.407 1.410
2.00 1.413 1.416 1.419 1.422 1.425 1.428 1.430 1.433 1.436 1.439
2.10 1.442 1.444 1.447 1.450 1.452 1.455 1.458 1.461 1.463 1.466
2.20 1.468 1.471 1.474 1.476 1.479 1.481 1.484 1.486 1.489 1.491
2.30 1.494 1.496 1.499 1.501 1.503 1.506 1.508 1.511 1.513 1.515
2.40 1.518 1.520 1.522 1.525 1.527 1.529 1.532 1.534 1.536 1.538
2.50 1.541 1.543 1.545 1.547 1.549 1.552 1.554 1.556 1.558 1.560
2.60 1.562 1.564 1.566 1.568 1.571 1.573 1.575 1.577 1.579 1.581
2.70 1.583 1.585 1.587 1.589 1.591 1.593 1.595 1.597 1.599 1.600
2.80 1.602 1.604 1.606 1.608 1.610 1.612 1.614 1.616 1.617 1.619
2.°0 1.621 1.623 1.625 1.627 1.628 1.630 1.632 1.634 1.635 1.637
3.00 1.639 1.641 1.642 1.644 1.646 1.648 1.649 1.651 1.653 1.654
3.10 1.656 1.658 1.659 1.661 1.663 1.664 1.666 1.668 1.669 1.671
WATER CONTENT 72 PERCENT
DG 0123456789
1.70 1.315 1.318 1.322 1.325 1.328 1.332 1.335 1.339 1.342 1.345
1.80 1.348 1.352 1.355 1.358 1.361 1.364 1.368 1.371 1.374 1.377
1.90 1.380 1.383 1.386 1.389 1.392 1.395 1.398 1.401 1.404 1.407
2.00 1.410 1.413 1.416 1.418 1.421 1.424 1.427 1.430 1.432 1.435
2.10 1.438 1.441 1.443 1.446 1.449 1.451 1.454 1.457 1.459 1.462
2.20 1.464 1.467 1.470 1.472 1.475 1.477 1.480 1.482 1.485 1.487
2.30 1.489 1.492 1.494 1.497 1.499 1.501 1.504 1.506 1.509 1.511
2.40 1.513 1.516 1.518 1.520 1.522 1.525 1.527 1.529 1.531 1.534
2.50 1.536 1.538 1.540 1.542 1.544 1.547 1.549 1.551 1.553 1.555
2.60 1.557 1.559 1.561 1.563 1.565 1.567 1.569 1.571 1.573 1.575
2.70 1.577 1.579 1.581 1.583 1.585 1.587 1.589 1.591 1.593 1.595
2.80 1.597 1.599 1.601 1.602 1.604 1.606 1.608 1.610 1.612 1.613
2.90 1.615 1.617 1.619 1.621 1.622 1.624 1.626 1.628 1.629 1.631
3.00 1.633 1.635 1.636 1.638 1.640 1.641 1.643 1.645 1.646 1.648
3.10 1.650 1.651 1.653 1.655 1.656 1.658 1.659 1.661 1.663 1.664
23
WATER CONTENT
73 PERCENT
DG
1.70
1.312
1.316
1.319
1.323
1.326
1.329
1.333
1.336
1.339
1.342
1.80
1.346
1.349
1.352
1.355
1.358
1.362
1.365
1.368
1.371
1.374
1.90
1.377
1.380
1.383
1.386
1.389
1.392
1.395
1.398
1.401
1.404
2.00
1.407
1.409
1.412
1.415
1.418
1.421
1.423
1.426
1.429
1.432
2.10
1.434
1.437
1.440
1.442
1.445
1.448
1.450
1.453
1.455
1.458
2.20
1.460
1.463
1.466
1.468
1.471
1.473
1.4 76
1.478
1.480
1.483
2.30
1.485
1.488
1.490
1.492
1.495
1.497
1.499
1.502
1.504
1.506
2.40
1.509
1.511
1.513
1.516
1.518
1.520
1.522
1.524
1.527
1.529
2.50
1.531
1.533
1.535
1.537
1.540
1.542
1.544
1.546
1.548
1.550
2.60
1.552
1.554
1.556
1.558
1.560
1.562
1.564
1.566
1.568
1.570
2.70
1.572
1.5 74
1.576
1.578
1.580
1.582
1.584
1.586
1.588
1.589
2.80
1.591
1.593
1.595
1.597
1.599
1.601
1.602
1.604
1.606
1.608
2.90
1.610
1.611
1.613
1.615
1.617
1.618
1.620
1.622
1.624
1.625
3.00
1.627
1.629
1.630
1.632
1.634
1.635
1.637
1.639
1.640
1.642
3.10
1.644
1.645
1.647
1.648
1.650
1.652
1.653
1.655
1.656
1.658
WATER CONTENT
7* PERCENT
DG
1.70
1.310
1.313
1.317
1.320
1.323
1.327
1.330
1.333
1.337
1.340
1.80
1.343
1.346
1.349
1.353
1.356
1.359
1.362
1.365
1.368
1.371
1.90
1.374
1.377
1.380
1.383
1.386
1.389
1.392
1.395
1.398
1.400
2.00
1.40 3
1.406
1.409
1.412
1.414
1.417
1.420
1.423
1.425
1.428
2.10
1.431
1.433
1.436
1.439
1.441
1.444
1.446
1.449
1.452
1.454
2.20
1.457
1.45Q
1.462
1.464
1.467
1.469
1.471
1.474
1.476
1.479
2.30
1.481
1.484
1.486
1.488
1.491
1.493
1.495
1.497
1.500
1.502
2.40
1.504
1.507
1.509
1.511
1.513
1.515
1.518
1.520
1.522
1.524
2.50
1.526
1.528
1.531
1.533
1.535
1.537
1.539
1.541
1.543
1.545
2.60
1.547
1.549
1.551
1.553
1.555
1.557
1.559
1.561
1.563
1.565
2.70
1.567
1.569
1.571
1.573
1.575
1.577
1.578
1.580
1.582
1.584
2.80
1.5 86
1.588
1.590
1.591
1.593
1.595
1.597
1.599
1.600
1.602
2.90
1.604
1.606
1.607
1.609
1.611
1.613
1.614
1.616
1.618
1.619
3.00
1.621
1.623
1.624
1.626
1 .628
1.629
1.631
1.633
1.634
1.636
3.10
1.638
1.639
1.641
1.642
1.644
1.645
1.647
1.649
1.650
1.652
WATER CONTENT
75 PERCENT
DG
1.70
1.308
1.311
1.314
1.318
1.321
1.324
1.328
1.331
1.334
1.337
1.80
1.340
1.344
1.347
1.350
1.353
1.356
1.3 59
1.362
1.365
1.368
1.90
1.371
1.374
1.377
1.380
1.383
1.386
1.389
1.392
1.3 94
1.397
2.00
1.400
1.403
1.406
1.408
1.411
1.414
1.417
1.419
1.422
1.425
2.10
1.427
1.430
1.432
1.435
1.438
1.440
1.443
1.445
1.448
1.450
2.20
1.453
1.455
1.458
1.460
1.463
1.465
1.468
1.470
1.472
1.475
2.30
1.477
1.479
1.482
1.484
1.486
1.489
1.491
1.493
1.496
1.498
2.40
1.500
1.502
1.504
1.507
1.509
1.511
1.513
1.515
1.517
1.520
2.50
1.522
1.524
1.526
1.528
1.530
1.532
1.534
1.536
1.538
1.540
2.60
1.542
1.544
1.546
1.548
1.550
1.552
1.554
1.556
1.558
1.560
2.70
1.562
1.564
1. 566
1.568
1.570
1.571
1.573
1.575
1.577
1.579
2.80
1.581
1.582
1.584
1.586
1.588
1.590
1.591
1.593
1.595
1.597
2.00
1.598
1.600
1.602
1.604
1.605
1.607
1.609
1.610
1.612
1.614
3.00
1.615
1.617
1.619
1.620
1.622
1.624
1.625
1.627
1.628
1.630
3.10
1.632
1.633
1.635
1.636
1.638
1.639
1.641
1.642
1.644
1.646
24
WATER CONTENT 76 PERCENT
DG 0123456789
1.70 1.305 1.309 1.312 1.315 1.319 1.322 1.325 1.328 1.332 1.335
1.80 1.338 1.341 1.344 1.347 1.350 1.353 1.356 1.359 1.362 1.365
1.90 1.368 1.371 1.374 1.377 1.380 1.383 1.386 1.388 1.391 1.394
2.00 1.397 1.400 1.402 1.405 1.408 1.410 1.413 1.416 1.418 1.421
2.10 1.424 1.426 1.429 1.431 1.434 1.437 1.439 1.442 1.444 1.447
2.20 1.449 1.452 1.454 1.456 1.459 1.461 1.464 1.466 1.468 1.471
2.30 1.473 1.475 1.478 1.480 1.482 1.485 1.487 1.489 1.491 1.494
2.40 1.496 1.498 1.500 1.502 1.504 1.507 1.509 1.511 1.513 1.515
2.50 1.517 1.519 1.521 1.523 1.526 1.528 1.530 1.532 1.534 1.536
2.60 1.538 1.540 1.542 1.544 1.546 1.547 1.549 1.551 1.553 1.555
2.70 1.557 1.559 1.561 1.563 1.564 1.566 1.568 1.570 1.572 1.574
2.80 1.575 1.577 1.579 1.581 1.583 1.584 1.586 1.588 1.590 1.591
2.90 1.593 1.595 1.596 1.598 1.600 1.601 1.603 1.605 1.606 1.608
3.00 1.610 1.611 1.613 1.615 1.616 1.618 1.619 1.621 1.623 1.624
3.10 1.626 1.627 1.629 1.630 1.632 1.633 1.635 1.637 1.638 1.640
WATER CONTENT 77 PERCENT
DG 0123456789
1.70 1.303 1.306 1.310 1.313 1.316 1.319 1.323 1.326 1.329 1.332
1.80 1.335 1.338 1.341 1.345 1.348 1.351 1.354 1.357 1.360 1.362
1.90 1.365 1.368 1.371 1.374 1.377 1.380 1.383 1.385 1.388 1.391
2.00 1.394 1.396 1.399 1.402 1.405 1.407 1.410 1.413 1.415 1.418
2.10 1.420 1.423 1.425 1.428 1.431 1.433 1.436 1.438 1.441 1.443
2.20 1.445 1.448 1.450 1.453 1.455 1.457 1.460 1.462 1.465 1.467
2.30 1.469 1.471 1.474 1.476 1.478 1.481 1.4*3 1.435 1.487 1.489
2.40 1.492 1.494 1.496 1.4^8 1.500 1.502 1.504 1.507 1.509 1.511
2.50 1.513 1.515 1.517 1.519 1.521 1.523 1.525 1.527 1.529 1.531
2.60 1.533 1.535 1.537 1.539 1.541 1.543 1.545 1.546 1.548 1.550
2.70 1.552 1.554 1.556 1.558 1.560 1.561 1.563 1.565 1.567 1.569
2.80 1.570 1.572 1.574 1.576 1.577 1.579 1.581 1.583 1.584 1.586
2.90 1.588 1.589 1.591 1.593 1.594 1.596 1.598 1.599 1.601 1.603
3.00 1.604 1.606 1.607 1.609 1.611 1.612 1.614 1.615 1.617 1.618
3.10 1.620 1.622 1.623 1.625 1.626 1.628 1.629 1.631 1.632 1.634
WATER CONTENT 78 PERCENT
DG 0123456789
1.70 1.301 1.304 1.307 1.311 1.314 1.317 1.320 1.323 1.327 1.330
1.80 1.333 1.336 1.33° 1.342 1.345 1.348 1.351 1.354 1.357 1.360
1.90 1.363 1.365 1.368 1.371 1.374 1.377 1.380 1.382 1.385 1.388
2.00 1.391 1.3Q3 1.3<?6 1.399 1.401 1.404 1.407 1.409 1.412 1.414
2.10 1.417 1.420 1.422 1.425 1.427 1.430 1.432 1.435 1.437 1.439
2.20 1.442 1.444 1.447 1.449 1.451 1.454 1.456 1.458 1.461 1.463
2.30 1.465 1.468 1.470 1.472 1.474 1.477 1.479 1.481 1.483 1.485
2.40 1.487 1.490 1.492 1.494 1.496 1.498 1.500 1.502 1.504 1.506
2.50 1.508 1.511 1.513 1.515 1.517 1.519 1.521 1.523 1.524 1.526
2.60 1.528 1.530 1.532 1.534 1.536 1.538 1.540 1.542 1.544 1.545
2.70 1.547 1.549 1.551 1.553 1.555 1.556 1.558 1.560 1.562 1.564
2.80 1.565 1.567 1.569 1.571 1.572 1.574 1.576 1.577 1.579 1.581
2.90 1.582 1.584 1.586 1.587 1.589 1.591 1.592 1.59% 1.596 1.597
3.00 1.599 1.600 1.602 1.604 1.605 1.607 1.608 1.610 1.611 1.619
3.10 1.614 1.616 1.617 1.619 1.620 1.622 1.623 1.625 1.626 1.628
25
WATER CONTENT 79 PERCENT
DG 0 1 2
1.70
1.299
1.302
1.305
1.308
1. 312
1.315
1.318
1.321
1.324
1.327
1.80
1.330
1.333
1.336
1.339
1.342
1.345
1.348
1.351
1.354
1.357
1.90
1.360
1.363
1.366
1.368
1.371
1.374
1.377
1.379
1.382
1.385
2.00
1.388
1.390
1.393
1.396
1.398
1.401
1.403
1.406
1.409
1.411
2.10
1.414
1.416
1.419
1.421
1.424
1.426
1.429
1.431
1.433
1.436
2.20
1.438
1.441
1.443
1.445
1.448
1.450
1.452
1.455
1.457
1.459
2.30
1.461
1.464
1.466
1.468
1.470
1.473
1.475
1.477
1.479
1.481
2.40
1.483
1.486
1.488
1.490
1.492
1.494
1.496
1.498
1.500
1.502
2.50
1.504
1.506
1.508
1.510
1.512
1.514
1.516
1.518
1.520
1.522
2.60
1.524
1.526
1.528
1.530
1.532
1.533
1.535
1.537
1.539
1.541
2.70
1.543
1.544
1.546
1.548
1.550
1.552
1.553
1.555
1.557
1.559
2.80
1.560
1.562
1.564
1.5 66
1.567
1.569
1.571
1.572
1.574
1.576
2.90
1.577
1.579
1.581
1.582
1.584
1.585
1.587
1.589
1.590
1.592
3.00
1.593
1.595
1.597
1.598
1.600
1.601
1.603
1.604
1.606
1.607
3.10
1.609
1.610
1.612
1.613
1.615
1.616
1.618
1.619
1.621
1.622
WATER CONTENT 80 PERCENT
OG 0123456789
1.70 1.297 1.300 1.303 1.306 1.309 1.312 1.316 1.319 1.322 1.325
1.80 1.328 1.331 1.334 1.337 1.340 1.343 1.346 1.349 1.351 1.354
1.90 1.357 1.360 1.363 1.366 1.368 1.371 1.374 1.377 1.379 1.382
2.00 1.385 1.387 1.390 1.393 1.395 1.398 1.400 1.403 1.405 1.408
2.10 1.410 1.413 1.415 1.418 1.420 1.423 1.425 1.428 1.430 1.432
2.20 1.435 1.437 1.439 1.442 1.444 1.446 1.449 1.451 1.453 1.456
2.30 1.458 1.460 1.462 1.464 1.467 1.469 1.471 1.473 1.475 1.477
2.40 1.479 1.482 1.484 1.486 1.488 1.490 1.492 1.494 1.496 1.498
2.50 1.500 1.502 1.504 1.506 1.508 1.510 1.512 1.514 1.516 1.518
2.60 1.519 1.521 1.523 1.525 1.527 1.529 1.531 1.533 1.534 1.536
2.70 1.538 1.540 1.542 1.543 1.545 1.547 1.549 1.550 1.552 1.554
2.80 1.556 1.557 1.559 1.561 1.562 1.564 1.566 1.567 1.569 1.571
2.90 1.572 1.574 1.576 1.577 1.579 1.580 1.582 1.584 1.585 1.587
3.00 1.588 1.590 1.591 l.5°3 1.594 1.596 1.597 1.599 1.600 1.602
3.10 1.603 1.605 1.606 1.608 1.609 1.611 1.612 1.614 1.615 1.617
WATER CONTENT 81 PERCENT
OG 0123456789
1.70 1.294 1.298 1.301 1.304 1.307 1.310 1.313 1.316 1.319 1.322
1.80 1.325 1.328 1.331 1.334 1.337 1.340 1.343 1.346 1.349 1.352
1.90 1.354 1.357 1.360 1.363 1.366 1.368 1.371 1.374 1.376 1.379
2.00 1.382 1.384 1.387 1.390 1.392 1.395 1.397 1.400 1.402 1.405
2.10 1.407 1.410 1.412 1.415 1.417 1.419 1.422 1.424 1.427 1.429
2.20 1.431 1.434 1.436 1.438 1.441 1.443 1.445 1.447 1.450 1.452
2.30 1.454 1.456 1.458 1.461 1.463 1.465 1.467 1.469 1.471 1.473
2.40 1.476 1.478 1.480 1.482 1.484 1.486 1.488 1.490 1.492 1.494
2.50 1.496 1.498 1.500 1.502 1.504 1.506 1.508 1.509 1.511 1.513
2.60 1.515 1.517 1.519 1.521 1.523 1.524 1.526 1.528 1.530 1.532
2.70 1.533 1.535 1.537 1.539 1.540 1.542 1.544 1.546 1.547 1.549
2.80 1.551 1.552 1.554 1.556 1.558 1.559 1.561 1.562 1.564 1.566
2.90 1.567 1.569 1.571 1.572 1.574 1.575 1.577 i.578 1.580 1.582
3.00 1.583 1.585 1.586 1.588 1.589 1.591 1.592 1.594 1.595 1.597
3.10 1.598 1.600 1.601 i.602 1.604 1.605 1.607 1.608 1.610 1.611
26
WATER CONTENT
82 PERCENT
DG
1.70
1.292
1.296
1.299
1.302
1.305
1.308
1.311
1.314
1.317
1.320
1.80
1.323
1.326
1.329
1.332
1.335
1.338
1.341
1.343
1.346
1.349
l.°0
1.352
1.355
1.357
1.360
1.363
1.366
1.368
1.371
1.374
1.376
2.00
1.379
1.381
1.384
1.387
1.389
1.392
1.394
1.397
1.399
1.402
2.10
1.404
1.407
1.409
1.411
1.414
1.416
1.419
1.421
1.423
1.426
2.20
1.428
1.430
1.433
1.435
1.437
1.439
1.442
1.444
1.446
1.448
2.30
1.450
1.453
1.455
1.457
1.459
1.461
1.463
1.465
1.468
1.470
2.40
1.472
1.474
1.476
1.478
1.480
1.482
1.484
1.486
1.488
1.490
2.50
1.492
1.4<?4
1.496
1.498
1.500
1.501
1.503
1.505
1.507
1.509
2.60
1.511
1.513
1.515
1.516
1.518
1.520
1.522
1.524
1.525
1.527
2.70
1.529
1.531
1.532
1.534
1. 536
1.538
1.539
1.541
1.543
1.544
2.80
1.546
1.548
1.549
1.551
1.553
1.554
1.556
1.558
1.559
1.561
2.90
1.562
1.564
1.566
1.567
1.569
1.570
1.572
1.573
1.575
1.577
3.00
1.578
1.580
1.581
1.583
1.584
1.5 86
1.587
1.589
1.590
1.591
3.10
1.503
1.504
1.596
1.597
1.599
1.600
1.601
1.603
1.604
1.606
WATER CONTENT
83 PERCENT
DG
1.70
1.290
1.293
1.297
1.300
1.303
1.306
1.309
1.312
1.315
1.318
1.80
1.321
1.324
1.327
1.330
1.332
1.335
1.338
1.341
1.344
1.346
I. <»0
1.349
1.352
1.355
1.357
1.360
1.363
1.365
1.368
1.371
1.373
2.00
1.376
1.379
1.381
1.384
1.386
1.389
1.391
1.394
1.396
1.399
2.10
1.401
1.403
1.406
1.408
1.411
1.413
1.415
1.418
1.420
1.422
2.20
1.425
1.427
1.429
1.431
1.434
1.436
1.438
1.440
1.443
1.445
2.30
1.447
1.449
1.451
1.453
1.455
1.458
1.460
1.462
1.464
1.466
2.40
1.468
1.470
1.472
1.474
1.476
1.478
1.4 30
1.482
1.484
1.486
2.50
1.488
1.490
1.492
1.494
1.495
1.497
1.499
1.501
1.503
1.505
2.60
1.507
1.508
1.510
1.512
1.514
1.516
1.517
1.519
1.521
1.523
2.70
1.525
1.526
1.528
1.530
1.531
1.533
1.535
1.537
1.538
1.540
2.80
1.542
1.543
1.545
1.546
1.548
1.550
1.551
1.553
1.555
1.556
2.90
1.558
1.559
1.561
1.562
1.564
1.565
1.567
1.569
1.570
1.572
3.00
1.573
1.575
1.576
1.578
1.579
1.580
1.582
1.583
1.585
1.586
3.10
1.588
1.589
1.591
1.592
1.593
1.595
1.596
1.598
1.599
1.600
WATER CONTENT
84 PERCENT
DG
1.70
1.288
1.291
1.295
1.298
1.301
1.304
1.307
1.310
1.313
1.316
1.80
1.318
1.321
1.324
1.327
1.330
1.333
1.3 36
1.338
1.341
1.344
1.90
1.347
1.349
1.352
1.355
1.357
1.360
1.363
1.365
1.368
1.371
2.00
1.373
1.376
1.378
1.381
1. 383
1.386
1.388
1.391
1.393
1.396
2.10
1.398
1.400
1.403
1.405
1.407
1.410
1.412
1.414
1.417
1.419
2.20
1.421
1.424
1.426
1.428
1.430
1.433
1.435
1.437
1.439
1.441
2.30
1.443
1.446
1.448
1.450
1.452
1.454
1.456
1.458
1.460
1.462
2.40
1.464
1.466
1.468
1.470
1.472
1.474
1.476
1.478
1.480
1.482
2.50
1.484
1.486
1.488
1.490
1.491
1.493
1.495
1.497
1.499
1.501
2.60
1.503
1.504
1.506
1.508
1.510
1.511
1.513
1.515
1.517
1.518
2.70
1.520
1.522
1.524
1.525
1.527
1.529
1.530
1.532
1.534
1.535
2.80
1.537
1.539
1.540
1.542
1.543
1.545
1.547
1.548
1.550
1.551
2.90
1.553
1.555
1.556
1.558
1.559
1.561
1.562
1.564
1.565
1.567
3.00
1.568
1.570
i.571
1.573
1.574
1.576
1.577
1.578
1.580
1.581
3.10
1.583
1.584
1.586
1.587
1.588
1.590
1.591
1.592
1.594
1.595
27
WATER CONTENT
85 PERCENT
DG
1.70
1.286
1.289
1.292
1.295
1.299
1.302
1.304
1.307
1.310
1.313
1.80
1.316
1.31-9
1.322
1.325
1.328
1.330
1.333
1.336
1.339
1.341
1.90
1.344
1.347
1.350
1.352
1.355
1.357
1.360
1.36 3
1.365
1.368
2.00
1.370
1.373
1.375
1.378
1.380
1.333
1.385
1.388
1.390
1.393
2.10
1.395
1.397
1.400
1.402
1.404
1.407
1.409
1.411
1.414
1.416
2.20
1.418
1.420
1.423
1.425
1.427
1.429
1.431
1.434
1.436
1.438
2.30
1.440
1.442
1.444
1.446
1.448
1.450
1.452
1.454
1.457
1.459
2.40
1.461
1.463
1.465
1.466
1.468
1.470
1.472
1.474
1.476
1.478
2.50
1.480
1.482
1.484
1.486
1.487
1.489
1.491
1.49 3
1.495
1.497
2.60
1.498
1.500
1.502
1.504
1.506
1.507
1.5 09
1.511
1.513
1.514
2.70
1.516
1.518
1.519
1.521
1.523
1.524
1.526
1.528
1.529
1.531
2.80
1.533
1.534
1.536
1.537
1.539
1.541
1.542
1.544
1.545
1.547
2.90
1.548
1.550
1.551
1.553
1.554
1.556
1.557
1.559
1.560
1.562
3.00
1.563
1.565
1.566
1.568
1.569
1.571
1.572
1.573
1.575
1.576
3.10
1.578
1.579
1.581
1.582
1.583
1.585
1.586
1.587
1.589
1.590
WATER CONTENT
86 PERCENT
PG
1.70
1.284
1.287
1.290
1.293
1.206
1.299
1.302
1.305
1.308
1.311
1.80
1.314
1.317
1.320
1.322
1.325
1.328
1.331
1.334
1.336
1.339
1.90
1.342
1.344
1.347
1.350
1.352
1.355
1.357
1.360
1.363
1.365
2.00
1.368
1.370
1.373
1.375
1.378
1.380
1.382
1.385
1.387
1.390
2.10
1.392
1.394
1.397
1.399
1.401
1.404
1.406
1.408
1.410
1.413
2.20
1.415
1.417
1.419
1.422
1.424
1.426
1.428
1.430
1.432
1.434
2.30
1.437
1.439
1.441
1.443
1.445
1.447
1.449
1.451
1.453
1.455
2.40
1.457
1.459
1.461
1.463
1.465
1.467
1.469
1.471
1.472
1.474
2.50
1.476
1.478
1.480
1.482
1.484
1.485
1.487
1.489
1.491
1.493
2.60
1.494
1.496
1.498
1.500
1.501
1.503
1.505
1.507
1.508
1.510
2.70
1.512
1.513
1.515
1.517
1.518
1.520
1.522
1.523
1.525
1.527
2.80
1.528
1.530
1.531
1.533
1.535
1.536
1.538
1.539
1.541
1.542
2.90
1.544
1.545
1.547
1.548
1.550
1.551
1.553
1.554
1.556
1.557
3.00
1.559
1.560
1.562
1.563
1.564
1.566
1.567
1.569
1.570
1.571
3.10
1.573
1.574
1.576
1.577
1.578
1.580
1.581
1.582
1.584
1.585
WATER CONTENT
87 PERCENT
DG
1.70
1.282
1.285
1.288
1.291
1.294
1.297
1.300
1.303
1.306
1.309
1.80
1.312
1.315
1.317
1.320
1.323
1.326
1.328
1.331
1.334
1.337
1.90
1.339
1.342
1.345
1.347
1.350
1.352
1.355
1.357
1.360
1.362
2.00
1.365
1.367
1.370
1.372
1.375
1.377
1.380
1.382
1.384
1.387
2.10
1.389
1.391
1.394
1.396
1.398
1.401
1.403
1.405
1.407
1.410
2.20
1.412
1.414
1.416
1.418
1.421
1.423
1.425
1.427
1.429
1.431
2.30
1.433
1.435
1.437
1.439
1.441
1.443
1.445
1.447
1.449
1.451
2.40
1.453
1.455
1.457
1.459
1.461
1.463
1.465
1.467
1.469
1.471
2.50
1.472
1.474
1.476
1.478
1.480
1.482
1.483
1.485
1.487
1.489
2.60
1.490
1.492
1.494
1.496
1.497
1.499
1.501
1.503
1.504
1.506
2.70
1.508
1.509
1.511
1.513
1.514
1.516
1.517
1.519
1.521
1.522
2.80
1.524
1.525
1.527
1.529
1.530
1.532
1.533
1.535
1.536
1.538
2.90
1.539
1.541
1.542
1.544
1.545
1.547
1.548
1.550
1.551
1.553
3.00
1.554
1.555
1.557
1.558
1.560
1.561
1.563
1.564
1.565
1.567
3.10
1.568
1.569
1.571
1.572
1.573
1.575
1.576
1.577
1.579
1.580
28
WATER CONTFNT
88 PERCENT
DG
1.70
1.280
1.283
1.286
1.289
1.292
1.295
1.298
1.301
1.304
1.307
1.80
1.310
1.312
1.315
1.318
1.321
1.323
1.326
1.329
1.332
1.334
1.90
1.337
1.339
1.342
1.345
1.347
1.350
1.352
1.355
1.357
1.360
2.00
1.362
1.365
1.367
1.370
1.372
1.374
1.377
1.379
1.382
1.384
2.10
1.3P6
1.389
1.391
1.393
1.395
1.308
1.400
1.402
1.404
1.407
2.20
1.409
1.411
1.413
1.415
1.417
1.419
1.422
1.424
1.426
1.428
2.30
1.430
1.432
1.434
1.436
1.438
1.440
1.442
1.444
1.446
1.448
2.40
1.450
1.452
1.454
1.456
1.458
1.459
1.461
1.463
1.465
1.467
2.50
1.469
1.471
1.472
1.474
1.476
1.478
1.480
1.481
1.483
1.485
2.60
1.487
1.488
1.490
1.492
1.494
1.495
1.497
1.499
1.500
1.502
2.70
1.504
1.505
1.507
1.508
1.510
1.512
1.513
1.515
1.516
1.518
2.80
1.520
1.521
1.523
1.524
1.526
1.527
1.529
1.530
1.532
1.533
2.90
1.535
1.536
1.538
1.539
1.541
1.542
1.544
1.545
1.547
1.548
3.00
1.549
1.551
1.552
1.554
1.555
1.556
1.558
1.559
1.561
1.562
3.10
1.563
1.565
1.566
1.567
1.569
1.570
1.571
1.573
1.574
1.575
HATER CONTENT
89 PERCENT
DG
1.70
1.279
1.282
1.284
1.287
1.290
1.2Q3
1.296
1.299
1.302
1.305
1.80
1.307
1.310
1.313
1.316
1.318
1.321
1*324
1.327
1.329
1.332
1.90
1.334
1.3 37
1.340
1.342
1.345
1.347
1.350
1.352
1.355
1.357
2.00
1.360
1.362
1.365
1.367
1.369
1.372
1.374
1.376
1.379
1.381
2.10
1.38 3
1.386
1.388
1.390
1.392
1.395
1.397
1.399
1.401
1.404
2.20
1.406
1.408
1.410
1.412
1.414
1.416
1.418
1.420
1.423
1.425
2.30
1.427
1.429
1.431
1.433
1.435
1.437
1.439
1.441
1.443
1.445
2.40
1.446
1.448
1.450
1.452
1.454
1.456
1.458
1.460
1.461
1.463
2.50
1.465
1.467
1.469
1.471
1.472
1.474
1.476
1.478
1.479
1.481
2.60
1.483
1.485
1.486
1.488
1.490
1.491
1.493
1.495
1.496
1.498
2.70
1.500
1.501
1.503
1.504
1. 506
1.508
1.509
1.511
1.512
1.514
2.80
1.515
1.517
1.519
1.520
1.522
1.523
1.525
1.526
1.528
1.529
2.90
1.531
1.532
1.534
1.535
1. 536
1.538
1.539
1.541
1.542
1.544
3.00
1.545
1.546
1.548
1.549
1.551
1.552
1.553
1.555
1.556
1.557
3.10
1.559
1.560
1.561
1.563
1.564
1.565
1.567
1.568
1.569
1.570
WATER CONTENT
90 PERCENT
DG
8
1.70
1.30
1.90
2.00
2.10
2.20
2.30
2.40
2.50
2.60
2.70
2.80
2.90
3.00
3.10
1.277
1.305
1.332
1.357
1.381
1.403
1.423
1.443
1.462
1.479
1.496
1.511
1.526
1.541
1.554
1.280
1.308
1.335
1.360
1.383
1.405
1.425
1.445
1.463
1.481
1.497
1.513
1.528
1.542
1.555
1.283
1.311
1.337
1.362
1.385
1.407
1.427
1.447
1.465
1.482
1.499
1.514
1.529
1.543
1.557
1.285
1.314
1.340
1.364
1.387
1.409
1.429
1.449
1.467
1.484
1.500
1.516
1.531
1.545
1.558
1.288
1.316
1.342
1.367
1.390
1.411
1.431
1.451
1.469
1.486
1.502
1.517
1.532
1.546
1.559
1.291
1.319
1.345
1.369
1.392
1.413
1.433
1.452
1.470
1.487
1.504
1.519
1.534
1.547
1.561
1.2 94
1.322
1.347
1.371
1.394
1.415
1.435
1.454
1.472
1.489
1.505
1.520
1.535
1.549
1.562
1.297
1.324
1.350
1.374
1.396
1.417
1.437
1.456
1.474
1.491
1.507
1.522
1.536
1.550
1.563
1.300
1.327
1.352
1.376
1.398
1.419
1.439
1.458
1.476
1.492
1.508
1.523
1.538
1.551
1.564
1.303
1.330
1.355
1.378
1.401
1.421
1.441
1.460
1.477
1.494
1.510
1.525
1.539
1.553
1.564
29
WATER CONTENT 91 PERCENT
DG 0123456789
1.70 1.275 1.278 1.281 1.284 1.286 1.289 1.292 1.295 1.298 1.301
1.80 1.303 1.306 1.309 1.311 1.314 1.317 1.319 1.322 1.325 1.327
1.90 1.330 1.332 1.335 1.337 1.340 1.342 1.345 1.347 1.350 1.352
2.00 1.355 1.357 1.359 1.362 1.364 1.366 1.369 1.371 1.373 1.376
2.10 1.378 1.380 1.382 1.385 1.387 1.389 1.391 1.393 1.395 1.398
2.20 1.400 1.402 1.404 1.406 1.408 1.410 1.412 1.414 1.416 1.418
2.30 1.420 1.422 1.424 1.426 1.428 1.430 1.432 1.434 1.436 1.438
2.40 1.440 1.442 1.443 1.445 1.447 1.449 1.451 1.453 1.454 1.456
2.50 1.458 1.460 1.462 1.463 1.465 1.467 1.469 1.470 1.472 1.474
2.60 1.475 1.477 1.479 1.480 1.482 1.484 1.485 1.487 1.489 1.490
2.70 1.492 1.493 1.495 1.497 1.498 1.500 1.501 1.503 1.504 1.506
2.80 1.507 1.509 1.510 1.512 1.513 1.515 1.516 1.518 1.519 1.521
2.90 1.522 1.524 1.525 1.526 1.528 1.529 1.531 1.532 1.533 1.535
3.00 1.536 1.538 1.539 1.540 1.542 1.543 1.544 1.546 1.547 1.548
3.10 1.550 1.551 1.552 1.553 1.555 1.556 1.557 1.559 1.560 1.561
WATER CONTENT 92 PERCENT
DG 0123456789
1.70 1.273 1.276 1.279 1.282 1.285 1.287 1.290 1.293 1.296 1.298
1.80 1.301 1.304 1.307 1.309 1.312 1.315 1.317 1.320 1.322 1.325
1.90 1.328 1.330 1.333 1.335 1.338 1.340 1.342 1.345 1.347 1.350
2.00 1.352 1.354 1.357 1.359 1.362 1.364 1.366 1.368 1.371 1.373
2.10 1.375 1.377 1.380 1.382 1.384 1.386 1.388 1.390 1.393 1.395
2.20 1.397 1.399 1.401 1.403 1.405 1.407 1.409 1.411 1.413 1.415
2.30 1.417 1.419 1.421 1.423 1.425 1.427 1.429 1.431 1.433 1.435
2.40 1.436 1.438 1.440 1.442 1.444 1.446 1.447 1.449 1.451 1.453
2.50 1.455 1.456 1.458 1.460 1.462 1.463 1.465 1.467 1.468 1.470
2.60 1.472 1.473 1.475 1.477 1.478 1.480 1.482 1.483 1.485 1.486
2.70 1.488 1.490 1.491 1.493 1.494 1.496 1.497 1.499 1.500 1.502
2.80 1.503 1.505 1.506 1.508 1.509 1.511 1.512 1.514 1.515 1.517
2.90 1.518 1.519 1.521 1.522 1.524 1.525 1.526 1.528 1.529 1.531
3.00 1.532 1.533 1.535 1.536 1.537 1.539 1.540 1.541 1.543 1.544
3.10 1.545 1.546 1.548 1.549 1.550 1.552 1.553 1.554 1.555 1.557
WATER CONTENT 93 PERCENT
DG 0123456789
1.70 1.271 1.274 1.277 1.280 1.283 1.285 1.288 1.291 1.294 1.296
1.80 1.299 1.302 1.305 1.307 1.310 1.312 1.315 1.318 1.320 1.323
1.90 1.325 1.328 1.330 1.333 1.335 1.333 1.340 1.343 1.345 1.347
2.00 1.350 1.352 1.354 1.357 1.359 1.361 1.364 1.366 1.368 1.370
2.10 1.373 1.375 1.377 1.379 1.381 1.383 1.386 1.388 1.390 1.392
2.20 1.394 1.396 1.398 1.400 1.402 1.404 1.406 1.408 1.410 1.412
2.30 1.414 1.416 1.418 1.420 1.422 1.424 1.426 1.428 1.429 1.431
2.40 1.433 1.435 1.437 1.439 1.440 1.442 1.444 1.446 1.448 1.449
2.50 1.451 1.453 1.455 1.456 1.458 1.460 1.461 1.463 1.465 1.466
2.60 1.468 1.470 1.471 1.473 1.475 1.476 1.478 1.479 1.481 1.483
2.70 1.484 1.486 1.487 1.489 1.490 1.492 1.493 1.495 1.496 1.498
2.30 1.499 1.501 1.502 1.504 1.505 1.507 1.508 1.510 1.511 1.513
2.90 1.514 1.515 1.517 1.518 1.520 1.521 1.522 1.524 1.525 1.526
J. 00 1.528 1.529 1.530 1.532 1.533 1.534 1.536 1.537 1.538 1.540
3.10 1,541 1.542 1.543 1.545 1.546 1.547 1.548 1.550 1.551 1.552
30
WATER CONTENT
94 PERCENT
DG
1.70
1.269
1.272
1.275
1.278
1.281
1.284
1.286
1.289
1.292
1.294
1.80
1.297
1.300
1.302
1.305
1.308
1.310
1.313
1.315
1.318
1.321
l.Q0
1.323
1.326
1.328
1.330
1.333
1.335
1.338
1.340
1.343
1.345
2.00
1.347
1.350
1.352
1.354
1.356
1.359
1.361
1.363
1.365
1.368
2.10
1.370
1.372
1.374
1.376
1. 3 79
1.381
1.383
1.385
1.387
1.389
2.20
1.391
1.393
1.395
1.397
1.399
1.401
1.403
1.405
1.407
1.409
2.30
1.411
1.413
1.415
1.417
1.419
1.421
1.423
1.424
1.426
1.428
2.40
1.430
1.432
1.434
1.435
1.437
1.439
1.441
1.443
1.444
1.446
2.50
1.448
1.449
1.451
1.453
1.455
1.456
1.458
1.460
1.461
1.463
2.60
1.465
1.466
1.468
1.469
1.471
1.473
1.474
1.476
1.477
1.479
2.70
1.480
1.482
1.484
1.4«5
1.487
1.483
1.490
1.491
1.493
1.494
2.80
1.496
1.497
1.499
1.500
1.501
1.503
1.5 04
1.506
1.507
1.509
2.90
1.510
1.511
1.513
1.514
1.515
1.517
1.518
1.520
1.521
1.522
3.00
1.5 24
1.525
1.526
1.528
1.529
1.530
1.531
1.533
1.534
1.535
3.10
1.537
1.538
1.539
1.540
1.542
1.543
1.544
1.545
1.546
1.543
WATER CONTENT
95 PERCENT
DG
1.70
1.268
1.271
1.273
1.276
1.2 79
1.282
1.284
1.287
1.290
1.293
1.90
1.295
1.298
1.300
1.303
1.306
1.308
1.311
1.313
1.316
1.318
1.90
1.321
1.323
1.326
1.328
1.331
1.333
1.335
1.338
1.340
1.343
2.00
1.345
1.347
1.349
1.352
1.354
1.356
1.358
1.361
1.363
1.365
2.10
1.367
1.369
1.372
1.374
1.376
1.378
1.380
1.382
1.384
1.386
2.20
1.388
1.390
1.392
1.394
1.396
1.398
1.400
1.402
1.404
1.406
2.30
1.409
1.410
1.412
1.414
1.416
1.418
1.419
1.421
1.423
1.425
2.40
1.427
1.429
1.430
1.432
1.434
1.436
1.438
1.439
1.441
1.443
2.50
1.444
1.446
1.448
1.450
1.451
1.453
1.455
1.456
1.459
1.459
2.60
1.461
1.463
1.464
1.466
1.468
1.469
1.471
1.472
1.474
1.475
2.70
1.477
1.478
1.480
1.431
1.483
1.484
1.486
1.487
1.489
1.490
2.80
1.492
1.493
1.4^5
1.496
1.498
1.499
1.500
1.502
1.503
1.505
2.90
1.506
1.507
1.509
1.510
1.511
1.513
1.514
1.516
1.517
1.519
3.00
1.519
1.521
1.522
1.523
1.525
1.526
1.527
1.529
1.530
1.531
3.10
1.532
1.534
1.535
1.536
1.537
1.539
1.540
1.541
1.542
1.543
WATER CONTENT
96 PERCENT
DG
1.70
1.266
1.269
1.272
1.2 74
1.277
1.280
1.283
1.285
1.288
1.291
1.80
1.293
1.296
1.298
1.301
1.304
1.306
1.309
1.311
1.314
1.316
1.90
1.319
1.321
1.324
1.326
1.328
1.331
1.333
1.335
1.338
1.340
2.00
1.342
1.345
1.347
1.349
1.352
1.354
1.356
1.358
1.360
1.363
2.10
1.365
1.367
1.369
1.371
1.373
1.375
1.377
1.379
1.382
1.384
2.20
1.386
1.388
1.390
1.392
1.394
1.396
1.398
1.399
1.401
1.403
2.30
1.405
1.407
1.409
1.411
1.413
1.415
1.416
1.418
1.420
1.422
2.40
1.424
1.426
1.427
1.429
1.431
1.433
1.434
1.436
1.439
1.439
2.50
1.441
1.443
1.445
1.446
1.448
1.450
1.451
1.453
1.454
1.456
2.60
1.458
1.459
1.461
1.462
1.464
1.466
1.467
1.469
1.470
1.472
2.70
1.473
1.475
1.476
1.478
1.47°
1.481
1.482
1.484
1.485
1.487
2.30
1.488
1.490
1.40 1
1.4P2
1.494
1.495
1.497
1.498
1.499
1.501
2.90
1.502
1.503
1.505
1.506
1.508
1.509
1.510
1.512
1.513
1.514
3.00
1.515
1.517
1.518
1.519
1.521
1.522
1.523
1.524
1.526
1.527
3.10
1.528
1.529
1.531
1.532
1.533
1.534
1.535
1.537
1.538
1.539
31
WATER CONTENT
97 PERCENT
DG
1.70
1.264
1.267
1.270
1.273
1.275
1.278
1.281
1.283
1.286
1.289
1.80
1.2<U
1.294
1.297
1.299
1. 302
1.304
1.307
1.309
1.312
1.314
1.90
1.317
1.319
1.321
1.324
1.326
1.329
1.331
1.333
1.336
1.338
2.00
1.340
1.342
1.345
1.347
1.349
1.351
1.354
1.356
1.358
1.360
2.10
1.362
1.364
1.366
1.369
1.371
1.373
1.375
1.377
1.379
1.381
2.20
1.383
1.3 85
1.387
1.389
1.391
1.393
1.395
1.397
1.399
1.400
2.30
1.402
1.404
1.406
1.408
1.410
1.412
1.413
1.415
1.417
1.419
2.40
1.421
1.422
1.424
1.426
1.428
1.429
1.431
1.433
1.435
1.436
2.50
1.438
1.440
1.441
1.443
1.445
1.446
1.448
1.449
1.451
1.453
2.60
1.454
1.456
1.457
1.459
1.461
1.462
1.464
1.465
1.467
1.468
2.70
1.470
1.471
1.473
1.474
1.476
1.477
1.4 79
1.480
1.482
1.48 3
2.80
1.484
1.486
1.487
1.489
1.490
1.491
1.493
1.494
1.496
1.497
2.90
1.498
1.500
1.501
1.502
1.504
1.505
1.506
1.508
1.509
1.510
3.00
1.512
1.513
1.514
1.515
1.517
1.518
1.519
1.520
1.522
1.523
3.10
1.524
1.525
1.527
1.528
1.529
1.530
1.531
1.533
1.534
1.535
WATER CONTENT
98 PERCENT
DG
1.70
1.263
1.265
1.268
1.271
1.274
1.276
1.2 79
1.282
1.234
1.287
1.80
1.289
1.292
1.295
1.297
1.300
1.302
1.305
1.307
1.310
1.312
1.90
1.314
1.317
1.319
1.322
1.324
1.326
1.329
1.331
1.333
1.336
2.00
1.338
1.340
1.342
1.345
1.347
1.349
1.351
1.353
1.355
1.358
2.10
1.360
1.362
1.364
1.3 66
1.368
1.370
1.372
1.374
1.376
1.378
2.20
1.380
1.382
1.384
1.386
1.388
1.390
1.392
1.394
1.396
1.398
2.30
1.400
1.401
1.403
1.405
1.407
1.409
1.411
1.412
1.414
1.416
2.40
1.418
1.419
1.421
1.423
1.425
1.426
1.428
1.430
1.431
1.433
2.50
1.435
1.436
1.438
1.440
1.441
1.443
1.445
1.446
1.448
1.449
2.60
1.451
1.453
1.454
1.456
1.457
1.459
1.460
1.462
1.463
1.465
2.70
1.466
1.468
1.469
1.471
1.472
1.474
1.475
1.476
1.478
1.479
2.30
1.481
1.482
1.484
1.485
1.486
1.488
1.489
1.490
1.492
1.493
2.90
1.495
1.496
1.497
1.499
1.500
1.501
1.502
1.504
1.505
1.506
3.00
1.508
1.509
1.510
1.511
1.513
1.514
1.515
1.516
1.518
1.519
3.10
1.520
1.521
1.522
1.524
1.525
1.526
1.527
1.528
1.530
1.531
WATER CONTENT
99 PERCENT
DG
1.70
1.261
1.264
1.266
1.269
1.272
1.274
1.277
1.280
1.282
1.285
1.80
1.288
1.290
1.293
1.295
1.298
1.300
1.303
1.305
1.308
1.310
1.90
1.312
1.315
1.317
1.320
1.322
1.324
1.326
1.329
1.331
1.333
2.00
1.336
1.338
1.340
1. 342
1.344
1.347
1.349
1.351
1.353
1.355
2.10
1.357
1.359
1.361
1.363
1.366
1.368
1.370
1.372
1.374
1.376
2.20
1.378
1.380
1.382
1.383
1.385
1.387
1.389
1.391
1.393
1.395
2.30
1.397
1.399
1.400
1.402
1.404
1.406
1.408
1.409
1.411
1.413
2.40
1.415
1.416
1.418
1.420
1.422
1.423
1.425
1.427
1.423
1.430
2.50
1.432
1.433
1.435
1.437
1.438
1.440
1.441
1.443
1.445
1.446
2.60
1.448
1.449
1.451
1.452
1.454
1.455
1.457
1.458
1.460
1.461
2.70
1.463
1.464
1.466
1.467
1.469
1.470
1.472
1.473
1.474
1.476
2.80
1.477
1.479
1.480
1.481
1.483
1.484
1.485
1.487
1.488
1.489
2.90
1.491
1.492
1.493
1.495
1.496
1.497
1.499
1.500
1.501
1.503
3.00
1.504
1.505
1.506
1.508
1.509
1.510
1.511
1.512
1.514
1.515
3.10
1.516
1.517
1.518
1.520
1.521
1.522
1.523
1.524
1.526
1.527
32
WATER CONTENT 100 PERCENT
OG
1.70
1.259
1.262
1.265
1.267
1.270
1.273
1.275
1.278
1.281
1.283
1.80
1.286
1.288
1.291
1.293
1.296
1.298
1.301
1.303
1.306
1.308
1.90
1.310
1.313
1.315
1.317
1.320
1.322
1.324
1.327
1.329
1.331
2.00
1.333
1.336
1.338
1.340
1.342
1.344
1.346
1.349
1.351
1.353
2.10
1.355
1.357
1.359
1.361
1.363
1.365
1.367
1.369
1.371
1.373
2.20
1.375
1.377
1.379
1.381
1.383
1.385
1.387
1.388
1.390
1.392
2.30
1.394
1.396
1.398
1.399
1.401
1.403
1.405
1.407
1.408
1.410
2.40
1.412
1.413
1.415
1.417
1.419
1.420
1.422
1.424
1.425
1.427
2.50
1.429
1.430
1.432
1.433
1.435
1.437
1.438
1.440
1.441
1.443
2.60
1.444
1.446
1.448
1.449
1.451
1.452
1.454
1.455
1.457
1.458
2.70
1.459
1.461
1.462
1.464
1.465
1.467
1.468
1.469
1.471
1.472
2.80
1.474
1.475
1.476
1.478
1.479
1.481
1.482
1.483
1.485
1.486
2.90
1.487
1.488
1.490
1.491
1.492
1.494
1.495
1.496
1.497
1.499
3.00
1.500
1.501
1.502
1.504
1.505
1.506
1.507
1.509
1.510
1.511
3.10
1.512
1.513
1.515
1.516
1.517
1.518
1.519
1.520
1.522
1.523
WATER CONTENT 105 PERCENT
DG
1.70
1.251
1.254
1.257
1.259
1.262
1.264
1 .267
1.269
1.272
1.274
1.80
1.277
1.279
1.282
1.284
1.286
1.289
1.291
1.294
1.296
1.298
1.90
1.301
1.303
1.305
1.307
1.310
1.312
1. 314
1.316
1.318
1.320
2.00
1.323
1.325
1.327
1.329
1.331
1.333
1.335
1.337
1.339
1.341
2.10
1.343
1.345
1.347
1.349
1.351
1.353
1.355
1.357
1.359
1.361
2.20
1.363
1.364
1.366
1.368
1.370
1.372
1.3 74
1.3 75
1.377
1.379
2.30
1.381
1.382
1.384
1.386
1.388
1.389
1.391
1.393
1.394
1.396
2.40
1.398
1.399
1.401
1.403
1.404
1.406
1.407
1.409
1.411
1.412
2.50
1.414
1.415
1.417
1.418
1.420
1.421
1.423
1.424
1.426
1.427
2.60
1.429
1.430
1.432
1.433
1.435
1.436
1.438
1.439
1.440
1.442
2.70
1.443
1.445
1.446
1.447
1.449
1.450
1.452
1.453
1.454
1.456
2.80
1.457
1.458
1.459
1.461
1.462
1.463
1.465
1.466
1.467
1.468
2.90
1.470
1.471
1.472
1.473
1.475
1.476
1.477
1.478
1.480
1.481
3.00
1.482
1.483
1.484
1.485
1.4*7
1.488
1.489
1.490
1.491
1.492
3.10
1.494
1.495
1.4°6
1.497
1.498
1.499
1.500
1.501
1.502
1.504
WATER CONTENT 110 PERCENT
DG
1.70
1.244
1.246
1.249
1.251
1.254
1.256
1.259
1.261
1.264
1.266
1.80
1.268
1.271
1.273
1.275
1.278
1.280
1.282
1.285
1.287
1.289
1.90
1.291
1.293
1.296
1.298
1.300
1.302
1.304
1.306
1.308
1.310
2.00
1.312
1.315
1.317
1.319
1.321
1.323
1.325
1.327
1.328
1.330
2.10
1.332
1.334
1.336
1.338
1.340
1.342
1.344
1.345
1.347
1.349
2.20
1.351
1.353
1.354
1.356
1.358
1.360
1.361
1.363
1.365
1.367
2.30
1.368
1.370
1.372
1.373
1.375
1.377
1.378
1.380
1.381
1.383
2.40
1.385
1.386
1.388
1.389
1.391
1.392
1.394
1.395
1.397
1.399
2.50
1.400
1.40L
1.403
1.404
1.406
1.407
1.409
1.410
1.412
1.413
2.60
1.415
1.416
1.417
1.419
1.420
1.421
1.423
1.424
1.426
1.427
2.70
1.428
1.430
1.431
1.432
1.433
1.435
1.436
1.437
1.439
1.440
2.80
1.441
1.442
1.444
1.445
1.446
1.447
1.449
1.450
1.451
1.452
2.90
1.453
1.455
1.456
1.457
1.458
1.459
1.461
1.462
1.463
1.464
3.00
1.465
1.466
1.467
1.468
1.470
1.471
1.472
1.473
1.474
1.475
3.10
1.476
1.477
1.478
1.4 79
1.480
1.482
1.483
1.484
1.485
1.486
33
WATER CONTENT 115 PERCENT
DG 0123456789
1.70 1.237 1.239 1.242 1.244 1.247 1.249 1.251 1.254 1.256 1.258
1.80 1.261 1.263 1.265 1.267 1.270 1.272 1.274 1.276 1.278 1.280
1.90 1.283 1.285 1.287 1.289 1.291 1.293 1.295 1.297 1.299 1.301
2.00 1.303 1.305 1.307 1.309 1.311 1.313 1.315 1.317 1.318 1.320
2.10 1.322 1.324 1.326 1.328 1.329 1.331 1.333 1.335 1.336 1.338
2.20 1.340 1.342 1.343 1.345 1.347 1.348 1.350 1.352 1.353 1.355
2.30 1.357 1.358 1.360 1.361 1.363 1.365 1.366 1.368 1.369 1.371
2.40 1.372 1.374 1.375 1.377 1.378 1.380 1.381 1.383 1.384 1.386
2.50 1.387 1.389 1.390 1.391 1.393 1.394 1.396 1.397 1.398 1.400
2.60 1.401 1.402 1.404 1.405 1.406 1.408 1.409 1.410 1.412 1.413
2.70 1.414 1.415 1.417 1.418 1.419 1.420 1.422 1.423 1.424 1.425
2.80 1.427 1.428 1.429 1.430 1.431 1.432 1.434 1.435 1.436 1.437
2.90 1.438 1.439 1.441 1.442 1.443 1.444 1.445 1.446 1.447 1.448
3.00 1.449 1.451 1.452 1.453 1.454 1.455 1.456 1.457 1.458 1.459
3.10 1.460 1.461 1.462 1.463 1.464 1.465 1.466 1.467 1.468 1.469
HATER CONTENT 120 PERCENT
DG 0123456789
1.70 1.230 1.233 1.235 1.237 1.240 1.242 1.244 1.246 1.249 1.251
1.80 1.253 1.255 1.258 1.260 1.262 1.264 1.266 1.268 1.270 1.272
1.90 1.274 1.276 1.278 1.280 1.282 1.284 1.286 1.288 1.290 1.292
2.00 1.294 1.296 1.298 1.300 1.302 1.303 1.305 1.307 1.309 1.311
2.10 1.313 1.314 1.316 1.318 1.320 1.321 1.323 1.325 1.326 1.328
2.20 1.330 1.331 1.333 1.335 1.336 1.338 1.339 1.341 1.343 1.344
2.30 1.346 1.347 1.349 1.350 1.352 1.353 1.355 1.356 1.358 1.359
2.40 1.361 1.362 1.364 1.365 1.367 1.368 1.369 1.371 1.372 1.374
2.50 1.375 1.376 1.378 1.379 1.380 1.382 1.383 1.384 1.386 1.387
2.60 1.388 1.390 1.391 1.392 1.393 1.395 1.396 1.397 1.398 1.400
2.70 1.401 1.402 1.403 1.405 1.406 1.407 1.408 1.409 1.411 1.412
2.80 1.413 1.414 1.415 1.416 1.417 1.419 1.420 1.421 1.422 1.423
2.Q0 1.424 1.425 1.426 1.427 1.428 1.430 1.431 1.432 1.433 1.434
3.00 1.435 1.436 1.437 1.438 1.439 1.440 1.441 1.442 1.443 1.444
3.10 1.445 1.446 1.447 1.448 1.449 1.450 1.451 1.452 1.453 1.454
WATER CONTENT 125 PERCENT
DG 0123456789
1.70 1.224 1.226 1.229 1.231 1.233 1.235 1.237 1.240 1.242 1.244
1.80 1.246 1.248 1.250 1.252 1.255 1.257 1.259 1.261 1.263 1.265
1.90 1.267 1.269 1.271 1.273 1.274 1.276 1.278 1.280 1.282 1.284
2.00 1.286 1.288 1.289 1.291 1.293 1.295 1.297 1.298 1.300 1.302
2.10 1.303 1.305 1.307 1.309 1.310 1.312 1.314 1.315 1.317 1.318
2.20 1.320 1.322 1.323 1.325 1.326 1.328 1.329 1.331 1.332 1.334
2.30 1.335 1.337 1.338 1.340 1.341 1.343 1.344 1.346 1.347 1.349
2.40 1.350 1.351 1.353 1.354 1.356 1.357 1.358 1.360 1.361 1.362
2.50 1.364 1.365 1.366 1.368 1.369 1.370 1.371 1.373 1.374 1.375
2.60 1.376 1.378 1.379 1.380 1.381 1.383 1.384 1.385 1.386 1.387
2.70 1.389 1.390 1.391 1.392 1.393 1.394 1.396 1.397 1.398 1.399
2.80 1.400 1.401 1.402 1.403 1.404 1.405 1.407 1.408 1.409 1.410
2.90 1.411 1.412 1.413 1.414 1.415 1.416 1.417 1.418 1.419 1.420
9.00 1.421 1.422 1.423 1.424 1.425 1.426 1.427 1.428 1.429 1.430
3.10 1.431 1.432 1.433 1.434 1.435 1.435 1.436 1.437 1.438 1.439
31+
WATER CONTENT 130 PERCENT
OG
1.70
1.218
1.220
1.222
1.225
1.227
1.229
1.231
1.233
1.235
1.237
1.80
1.240
1.242
1.244
1.246
1.248
1.250
1.252
1.254
1.256
1.257
1.90
1.259
1.261
1.263
1.265
1.267
1.269
1.271
1.272
1.274
1.276
2.00
1.278
1.280
1.281
1.283
1.285
1.286
1.288
1.290
1.292
1.293
2.10
1.295
1.297
1.298
1.300
1.301
1.303
1.305
1.306
1.308
1.309
2.20
1.311
1.312
1.314
1.315
1.317
1.313
1.320
1.321
1.323
1.324
2.30
1.326
1.327
1.329
1.330
1.332
1.333
1.334
1.336
1.337
1.338
2.40
1.340
1.341
1.342
1.344
1.345
1.346
1.348
1.349
1.350
1.352
2.50
1.353
1.3 54
1.355
1.357
1.358
1.359
1.360
1.362
1.363
1.364
2.60
1.365
1.366
1.368
1.369
1.370
1.371
1.372
1.374
1.375
1.376
2.70
1.377
1.378
1.379
1.380
1.381
1.383
1.384
1.385
1.386
1.387
2.80
1.388
1.389
1.390
1.391
1.392
1.3Q3
1.394
1.395
1.396
1.397
2.90
1.398
1.399
1.400
1.401
1.402
1.40 3
1.404
1.405
1.406
1.407
3.00
1.408
1.409
1.41C
1.411
1.412
1.413
1.414
1.415
1.416
1.417
3.10
1.417
1.418
1.419
1.420
1.421
1.422
1.423
1.424
1.425
1.425
WATER CONTENT 135 PERCFNT
DG
1.70
1.212
1.215
1.217
1.210
1.221
1.223
1.225
1.227
1.229
1.231
1.80
1.233
1.235
1.237
1.239
1.241
1.243
1.245
1.247
1.249
1.251
1.90
1.252
1.254
1.256
1.253
1.260
1.262
1.263
1.265
1.267
1.269
2.00
1.270
1.272
1.274
1.275
1.277
1.279
1.230
1.282
1.284
1.285
2.10
1.287
1.233
1.290
1.292
1.2^3
1.295
1.296
1.298
1.299
1.301
2.20
1.302
1.304
1.305
1.307
1.308
1.310
1.311
1.312
1.314
1.315
2.30
1.317
1.318
1.319
1.321
1.322
1.324
1.325
1.326
1.328
1.329
2.40
1.330
1. 331
1.333
1.334
1.335
1.337
1.338
1.339
1.340
1.342
2.50
1.343
1.344
1.345
1.347
1.348
1.349
1.350
1.351
1.352
1.354
2.60
1.355
1.356
1.357
1.358
1.359
1.360
1.362
1.363
1.364
1.365
2.70
1.366
1.367
1.368
1.369
1.370
1.371
1.372
1.373
1.374
1.376
2.80
1.377
1.378
1.379
1.380
1.381
1.382
1.383
1.384
1.385
1.386
2.90
1.387
1.388
1.389
1.389
1.3°0
1.391
1.392
1.393
1.394
1.395
3.00
1.396
1.397
1.398
1.399
1.400
1.401
1.401
1.402
1.40 3
1.404
3.10
1.405
1.406
1.407
1.408
1.408
1.409
1.410
1.411
1.412
1.413
WATER CONTENT 140 PERCENT
OG
1 .70
1.207
1.209
1.211
1.213
1.215
1.217
1.219
1.221
1.223
1.225
1.80
1.227
1.229
1.231
1.233
1.235
1.237
1.239
1.240
1.242
1.244
1.90
1.246
1.248
1.240
1.251
1.253
1.255
1.256
1.258
1.260
1.261
2.00
1.263
1.265
1.266
1.268
1.270
1.271
1.273
1.274
1.276
1.278
2.10
1.279
1.281
1.282
1.2«4
1.285
1.287
1.288
1.290
1.291
1.293
2.20
1.294
1.296
1.297
1.298
1.300
1.301
1.303
1.304
1.305
1.307
2.30
1.308
1.30O
1.311
1.312
1.313
1.315
1.316
1.317
1.319
1.320
2.40
1.321
1.322
1.324
1.325
1.326
1.327
1.329
1.330
1.331
1.332
2.50
1.333
1.335
1.336
1.337
1.338
1.339
1.340
1.341
1.343
1.344
2.60
1.345
1.346
1.347
1.348
1.349
1.350
1.351
1.352
1.354
1.355
2.70
1.356
1.357
1.358
1.350
1. 360
1.361
1.362
1.363
1.364
1.365
2.80
1.366
1.367
1.368
1.369
1.370
1.371
1.372
1.373
1.374
1.375
2.90
1.375
1.376
1.377
1.378
1.379
1.380
1.331
1.332
1.383
1.384
3.00
1.385
1.385
1.386
1.387
1.388
1.389
1.390
1.391
1.392
1.392
3.10
1.393
1.394
1.395
1.396
1.397
1.397
1.398
1.399
1.400
1.401
3 5
WATER CONTENT 145 PERCENT
OG
1.70
1.202
1.204
1.206
1.208
1.210
1.212
1.214
1.216
1.218
1.220
1.80
1.222
1.223
1.225
1.227
1.229
1.231
1.233
1.234
1.236
1.238
1.90
1.240
1.241
1.243
1.245
1.247
1.248
1.250
1.252
1.253
1.255
2.00
1.256
1.258
1.260
1.261
1.263
1.264
1.266
1.267
1.269
1.270
2.10
1.272
1.273
1.275
1.276
1.278
1.279
1.281
1.282
1.284
1.235
2.20
1.296
1.288
1.289
1.291
1.292
1.293
1.295
1.296
1.297
1.299
2.30
1.300
1.301
1.302
1.304
1.305
1.306
1.308
1.309
1.310
1.311
2.40
1.312
1.314
1. 315
1.316
1.317
1.319
1.320
1.321
1.322
1.323
2.50
1.324
1.325
1.327
1.328
1.329
1.330
1.331
1.332
1.333
1.334
2.60
1.335
1.337
1.338
1.339
1.340
1.341
1.342
1.343
1.344
1.345
2.70
1.346
1.347
1.348
1.349
1.350
1.351
1.352
1.353
1.354
1.355
2.80
1.356
1.357
1.358
1.359
1.360
1.360
1.361
1.362
1.363
1.364
2.°0
1.365
1.366
1.367
1.368
1.369
1.369
1.370
1.371
1.372
1.373
3.00
1.374
1.375
1.376
1.376
1.377
1.378
1.3 79
1.380
1.381
1.381
3.10
1.382
1.383
1.384
1.3 85
1.385
1.386
1.387
1.398
1.389
1.389
WATER CONTENT 150 PERCENT
DG
1.70
1. 197
1.199
1.201
1.203
1.205
1.207
1.209
1.211
1.213
1.214
1.80
1.216
1.218
1.220
1.222
1.223
1.225
1.227
1.229
1.230
1.232
1.90
1.234
1.235
1.237
1.239
1.240
1.242
1.244
1.245
1.247
1.248
2.00
1.250
1.252
1.253
1.255
1.256
1.258
1.2 59
1.261
1.262
1.264
2.10
1.265
1.267
1.268
1.269
1.271
1.272
1.274
1.2 75
1.276
1.278
2.20
1.279
1.280
1.282
1.283
1.284
1.286
1.287
1.288
1.290
1.291
2.30
1.292
1.293
1.295
1.296
1.297
1.298
1.300
1.301
1.30 2
1.303
2.40
1.304
1.306
1.307
1.308
1.309
1.310
1.311
1.312
1.314
1.315
2.50
1.316
1.317
1.318
1.319
1.320
1.321
1.322
1.323
1.324
1.325
2.60
1.327
1.328
1.329
1.330
1.331
1.332
1.333
1.334
1.335
1.336
2.70
1.337
1.338
1.339
1.340
1.341
1.341
1.342
1.343
1.344
1.345
2.80
1.346
1.347
1.348
1.349
1.350
1.351
1.352
1.352
1.353
1.354
2.Q0
1.355
1.356
1.357
1.358
1.359
1.359
1.3 60
1.361
1.362
1.363
3.00
1.364
1.364
1.365
1.366
1.367
1.368
1.3 69
1.369
1.370
1.371
3.10
1.372
1.372
1.373
1.374
1.375
1.376
1.3 76
1.377
1.373
1.379
WATER CONTENT 155 PERCENT
DG
1.70
1.193
1.194
1.196
1. 198
1.200
1.202
1.204
1.206
1.208
1.209
1.80
1.211
1.213
1.215
1.216
1.218
1.220
1.221
1.223
1.225
1.226
1.90
1.228
1.230
1.231
1.233
1.235
1.236
1.238
1.239
1.241
1.242
2.00
1.244
1.245
1.247
1.248
1.250
1.251
1.253
1.254
1.256
1.257
2.10
1.259
1.260
1.261
1.263
1.264
1.265
1.267
1.268
1.269
1.271
2.20
1.272
1.273
1.275
1.276
1.277
1.279
1.280
1.281
1.232
1.284
2.30
1.285
1.236
1.287
1.288
1.290
1.291
1.292
1.293
1.294
1.295
2.40
1.297
1.298
1.299
1.300
1.301
1.302
1.303
1.304
1.306
1.307
2.50
1.308
1.3 09
1.310
1.311
1.312
1.313
1.314
1.315
1.316
1.317
2.60
1.318
1.319
1.320
1.321
1.322
1.323
1.324
1.325
1.326
1.327
2.70
1.328
1.329
1.330
1.331
1.332
1.333
1.333
1.334
1.335
1.336
2.80
1.337
1.338
1.339
1.340
1.341
1.341
1.342
1.343
1.344
1.345
2.90
1.346
1.347
1.347
1.348
1.349
1.350
1.351
1.352
1.352
1.353
3.00
1.354
1.355
1.356
1.356
1.357
1.358
1.359
1.359
1.360
1.361
3.10
1.362
1.363
1.363
i.364
1.365
1.365
1.366
1.367
1.368
1.368
36
WATER CONTENT 160 PERCENT
DG
1.70
1. 188
1.190
1.192
1. 194
1.196
1.197
1.199
1.201
1.203
1.204
1.80
1.206
1.208
1.210
1.211
1.213
1.215
1.216
1.218
1.220
1.221
1.90
1.223
1.224
1.226
1.227
1.229
1.231
1.232
1.234
1.235
1.237
2.00
1.238
1.240
1.241
1.242
1.244
1.245
1.247
1.248
1.250
1.251
2.10
1.252
1.254
1.255
1.256
1.258
1.259
1.260
1.262
1.263
1.264
2.20
1.265
1.267
1.268
1.269
1.271
1.272
1.273
1.274
1.275
1.277
2.30
1.278
1.2 79
1.280
1.281
1.282
1.234
1.285
1.286
1.287
1.288
2.40
1.289
1.290
1.291
1.293
1.294
1.295
1.2 96
1.297
1.298
1.299
2.50
1.300
1.301
1.302
1.303
1.304
1.305
1.306
1.307
1.308
1.309
2.60
1.310
1.311
1.312
1.313
1.314
1.315
1.316
1.317
1.318
1.319
2.70
1.320
1.320
1.321
1.322
1.323
1.324
1.325
1.326
1.327
1.328
2.80
1.328
1.329
1.330
1.331
1.332
1.333
1. 334
1.334
1.335
1.336
2.90
1.337
1.338
1.339
1.339
1.340
1.341
1.342
1.342
1.343
1.344
3.00
1.345
1.346
1.346
1.347
1.348
1.349
1.349
1.350
1.351
1.352
3.10
1.352
1.353
1.354
1.355
1.355
1.356
1.357
1.357
1.358
1.359
WATER CONTENT 165 PERCENT
DG
1.70
1. 184
1. 186
1.188
1.189
1.191
1.193
1. 195
1. 196
1.198
1.200
1.80
1.202
1.203
1.205
1.206
1.208
1.210
1.211
1.213
1.215
1.216
1.90
1.218
1.219
1.221
1.222
1.224
1.225
1.227
1.228
1.230
1.231
2.00
1.233
1.234
1.235
1.237
1.238
1.240
1.241
1.242
1.244
1.245
2.10
1.246
1.248
1.249
1.250
1.252
1.253
1.254
1.255
1.257
1.258
2.20
1.259
1.260
1.262
1.263
1.264
1.265
1.266
1.268
1.269
1.270
2.30
1.271
1.272
1.273
1.275
1.276
1.277
1.278
1.279
1.280
1.281
2.40
1.282
1.283
1.284
1.285
1.287
1.288
1.289
1.290
1.291
1.292
2.50
1.293
1.294
1.295
1.296
1.297
1.299
1.299
1.300
1.301
1.302
2.60
1.302
1.303
1.304
1.305
1.306
1.307
1.308
1.309
1.310
1.311
2.70
1.312
1.313
1.313
1.314
1.315
1.316
1.317
1.318
1.319
1.319
2.80
1.320
1.321
1.322
1.323
1.324
1.324
1.325
1.326
1.327
1.328
2.90
1.328
1.329
1.330
1.331
1.332
1.332
1.333
1.334
1.335
1.335
3.00
1.336
1.337
1.338
1.338
1.33^
1.340
1.341
1.341
1.342
1.343
3. 10
1.343
1.344
1.345
1.346
1.346
1.34 7
1.348
1.348
1.349
1.350
WATER CONTENT 170 PERCENT
DG
1.70
1.180
1.182
1.183
1.185
1.137
1.199
1.190
1.192
1.194
1.195
1.80
1.197
1.199
1.200
1.202
1.203
1.205
1.207
1.208
1.210
1.211
1.90
1.213
1.214
1.216
1.217
1.219
1.220
1.222
1.223
1.224
1.226
2.00
1.227
1.229
1.230
1.231
1.233
1.234
1.235
1.237
1.238
1.2 39
2.10
1.241
1.242
1.243
1.245
1.246
1.247
1.248
1.250
1.251
1.252
2.20
1.253
1.254
1.256
1.257
1.258
1.259
1.260
1.261
1.263
1.264
2.30
1.265
1.266
1.267
1.268
1.269
1.270
1.271
1.272
1.273
1.275
2.40
1.276
1.277
1.278
1.279
1.280
1.281
1.282
1.283
1.284
1.285
2.50
1.286
1.287
1.288
1.289
1.290
1.291
1.291
1.292
1.293
1.294
2.60
1.295
1.296
1.297
1.298
1.299
1.300
1.301
1.301
1.302
1.303
2.70
1.304
1.305
1.306
1.307
1.308
1.308
1.3 09
1.310
1.311
1.312
2.80
1.312
1.313
1.314
1.315
1.316
1.317
1.317
1.318
1.319
1.320
2.90
1.320
1.321
1.322
1.323
1.323
1.324
1.325
1.326
1.326
1.327
3.00
1.328
1.329
1.329
1.330
1.331
1.331
1.332
1.333
1.334
1.334
3.10
1.335
1.336
1.336
1.337
1.338
1.338
1.339
1.340
1.340
1.341
37
WATER CONTENT 175 PERCENT
DG 0 1 2
1.70
1.176
1.178
I. 180
1.181
1.183
1.185
1.186
1.188
1.190
1.191
1.80
1.193
1.194
1. 196
1.198
1. 199
1.201
1.202
1.204
1.205
1.207
1.90
1.208
1.210
1.211
1.212
1.214
1.215
1.217
1.218
1.219
1.221
2.00
1.222
1.224
1.225
1.226
1.228
1.229
1.230
1.231
1.233
1.234
2.10
1.235
1.237
1.238
1.239
1.240
1.241
1.243
1.244
1.245
1.246
2.20
1.247
1.249
1.250
1.251
1.252
1.253
1.254
1.255
1.257
1.258
2.30
1.2 59
1.260
1.261
1.262
1.263
1.264
1.265
1.266
1.267
1.268
2.40
1.269
1.270
1.271
1.272
1.273
1.274
1.275
1.276
1.277
1.278
2.50
1.279
1.280
1.281
1.282
1.283
1.284
1.285
1.286
1.286
1.287
2.60
1.288
1.289
1.290
1.291
1.292
1.293
1.294
1.294
1.295
1.296
2.70
1.297
1.298
1.299
1.299
1.300
1.301
1.302
1.303
1.303
1.304
2.80
1.305
1.306
1.307
1.307
1.308
1.30Q
1.310
1.311
1.311
1.312
2.90
1.313
1.313
1.314
1.315
1.316
1.316
1.317
1.318
1.319
1.319
3.00
1.320
1.321
1.321
1.322
1.323
1.323
1.324
1.325
1.326
1.326
3.10
1.327
1.328
1.328
1.329
1.329
1.330
1.331
1.331
1.332
1.333
WATER CONTENT 180 PERCENT
DG 0 1 2 :
1.70
1.172
1.174
1.176
1.1^7
1.179
1.181
1. 182
1.184
1.186
1.187
1.80
1.189
1.190
I. 192
1.193
1.195
1.196
1.198
1.199
1.201
1.202
1.90
1.204
1.205
1.206
1.208
1.209
1.211
1.212
1.213
1.215
1.216
2.00
1.217
1.219
1.220
1.221
1.223
1.224
1.225
1.226
1.228
1.229
2.10
1.230
1.231
1.233
1.234
1.235
1.236
1.237
1.238
1.240
1.241
2.20
1.242
1.243
1.244
1.245
1.246
1.248
1.249
1.250
1.251
1.252
2.30
1.253
1.254
1.255
1.256
1.257
1.258
1.2 59
1.260
1.261
1.262
2.40
1.263
1.2 64
1.265
1.266
1.267
1.268
1.269
1.270
1.271
1.272
2.50
1.273
1.274
1.275
1.275
1.276
1.277
1.278
1.279
1.280
1.281
2.60
1.282
1.283
1.283
1.284
1.285
1.286
1.287
1.288
1.288
1.289
2.70
1.290
1.291
1.292
1.293
1.293
1.294
1.295
1.296
1.296
1.297
2.80
1.298
1.299
1.300
1.300
1.301
1.302
1.303
1.303
1.304
1.305
2.90
1.305
1.306
1.307
1.308
1.308
1.309
1.310
1.310
1.311
1.312
3.00
1.312
1.313
1.314
1.315
1.315
1,316
1.317
1.317
1.318
1.318
3.10
1.319
1.320
1.320
1.321
1.322
1.322
1.323
1.324
1.324
1.325
WATER CONTENT 185 PERCENT
DG 0 1 2
1.70
1.16Q
1.171
I. 172
1.174
1. 175
1.177
1.179
1.180
1.182
1.183
1.80
1.185
1.186
1.188
1.189
1.191
1.192
1.194
1. 195
1.197
1.198
1.90
1.199
1.201
1.202
1.203
1.205
1.206
1.208
1.209
1.210
1.211
2.00
1.213
1.214
1.215
1.217
1.218
1.219
1.220
1.222
1.223
1.224
2.10
1.225
1.226
1.228
1.229
1.230
1.231
1.232
1.233
1.234
1.236
2.20
1.237
1.238
1.239
1.240
1.241
1.242
1.243
1.244
1.245
1.246
2.30
1.247
1.248
1.249
1.250
1.251
1.252
1.253
1.254
1.255
1.256
2.40
1.257
1.258
1.259
1.260
1.261
1.262
1.263
1.264
1.265
1.266
2.50
1.267
1.268
1.268
1.269
1.270
1.271
1.272
1.273
1.274
1.275
2.60
1.275
1.276
1.277
1.278
1.2 79
1.280
1.280
1.281
1.282
1.283
2.70
1.284
1.284
1.285
1.286
1.287
1.287
1.288
1.289
1.290
1.291
2.80
1.291
1.292
1.293
1.293
1.294
1.295
1.296
1.296
1.297
1.298
2.90
1.299
1.299
1.300
1.301
1.301
1.302
1.303
1.303
1.304
1.305
3.00
1.305
1.306
1.307
1.307
1.308
1.309
1.309
1.310
1.311
1.311
3.10
1.312
1.312
1.313
1.314
1.314
1.315
1.316
1.316
1.317
1.317
38
WATER CONTENT 190 PERCENT
DG
1.70
1. 165
1.167
1.169
1.170
1.172
1.173
1.175
1.176
1.178
1.180
1.80
1.181
1.182
1.184
1.185
1.187
1.188
1.190
1.191
1.192
1.194
1.90
1. 195
1.197
1.198
1. 199
1.201
1.202
1.203
1.205
1.206
1.207
2.00
1.208
1.210
1.211
1.212
1.213
1.215
1.216
1.217
1.218
1.219
2.10
1.220
1.222
1.223
1.224
1.225
1.226
1.227
1.228
1.229
1.231
2.20
1.232
1.233
1.234
1.235
1.236
1.237
1.238
1.239
1.240
1.241
2.30
1.242
1.243
1.244
1.245
1.246
1.247
1.248
1.249
1.250
1.251
2.40
1.252
1.253
1.254
1.255
1.255
1.256
1.257
1.258
1.259
1.260
2.50
1.261
1.262
1.263
1.263
1.264
1.265
1.266
1.267
1.268
1.269
2.60
1.269
1.270
1.271
1.272
1.273
1.273
1.274
1.275
1.276
1.277
2.70
1.277
1.278
1.279
1.280
1.280
1.281
1.282
1.283
1.283
1.284
2.80
1.285
1.286
1.286
1.287
1.288
1.288
1.289
1.290
1.290
1.291
2.90
1.292
1.2Q3
1.293
1.294
1.295
1.295
1.296
1.297
1.297
1.298
3.00
1.299
1.299
1.300
1.300
1.301
1.302
1.302
1.303
1.304
1.304
3.10
1.305
1.305
1.306
1.307
1.307
1.308
1.308
1.309
1.310
1.310
WATER CONTENT 195 PERCENT
DG
1.70
1.162
1.164
1.165
1.167
1. 168
1.170
1.171
1. 173
1.174
1.176
1.80
1.177
1.179
1.180
1.182
1.183
1.184
1. 186
1.187
1.189
1.190
1.90
1.191
1.193
1.194
1.195
1. 197
1.198
1.199
1.200
1.202
1.203
2.00
1.204
1.205
1.207
1.208
1.209
1.210
1.211
1.212
1.214
1.215
2.10
1.216
1.217
1.218
1.219
1.220
1.221
1.223
1.224
1.225
1.226
2.20
1.227
1.228
1.229
1.230
1.231
1.232
1.233
1.234
1.235
1.236
2.30
1.237
1.238
1.239
1.240
1.241
1.242
1.243
1.244
1.245
1.246
2.40
1.246
1.247
1.248
1.249
1.250
1.251
1.252
1.253
1.254
1.254
2.50
1.255
1.256
1.257
1.258
1.259
1.260
1.260
1.261
1.262
1.263
2.60
1.264
1.264
1.265
1.266
1.267
1.268
1.268
1.269
1.270
1.271
2.70
1.271
1.272
1.273
1.274
1.274
1.275
1.2 76
1.276
1.277
1.278
2.80
1.279
1.279
1.280
1.281
1.281
1.282
1.283
1.283
1.284
1.285
2.°0
1.285
1.286
1.287
1.287
1.288
1.289
1.289
1.290
1.291
1.291
3.00
1.292
1.2Q3
1.293
1.294
1.294
1.295
1.296
1.296
1.297
1.297
3.10
1.298
1.299
1.299
1.300
1.300
1.301
1.302
1.302
1.303
1.303
WATER CONTENT 200 PERCENT
DG
1.70
1.159
1.161
1.162
1.164
1.165
1.167
1.168
1. 170
1.171
1.172
1.80
1.174
1.175
1.177
1.178
1.179
1.181
1.182
1.184
1.185
1.186
1.90
1. 188
1.189
1.190
1.191
1.193
1.1 Q4
1.195
1.196
1.198
1.199
2.00
1.200
1.201
1.202
1.204
1.205
1.206
1.2 07
1.208
1.209
1.210
2.10
1.212
1.213
1.214
1.215
1.216
1.217
1.218
1.219
1.220
1.221
2.20
1.222
1.223
1.224
1.225
1.226
1.227
1.228
1.229
1.230
1.231
2.30
1.232
1.233
1.234
1.235
1.236
1.237
1.238
1.239
1.240
1.240
2.40
1.241
1.242
1.243
1.244
1.245
1.246
1.247
1.247
1.248
1.249
2.50
1.2 50
1.251
1.252
1.252
1.253
1.254
1.255
1.256
1.256
1.257
2.60
1.258
1.2 59
1.260
1.260
1.261
1.262
1.263
1.263
1.264
1.265
2.70
1.266
1.266
1.267
1.268
1.269
1.269
1.2 70
1.271
1.271
1.272
2.80
1.273
1.273
1.274
1.275
1.275
1.276
1.277
1.277
1.278
1.279
2.90
1.279
1.280
1.281
1.281
1.282
1.283
1.283
1.284
1.284
1.285
3.00
1.286
1.286
1.287
1.288
1.288
1.289
1.289
1.290
1.291
1.291
3.10
1.292
1.292
1.293
1.293
1.294
1.295
1.295
1.296
1.296
1.297
39
WATER CONTENT 210 PERCENT
OG
1.70
1.153
1.155
1.156
1.158
1.159
1.160
1.162
1.163
1.165
1.166
1.80
1.167
1.169
1.170
1.171
1.173
1.174
1.175
1.177
1.178
1.179
1.90
1. 180
1.182
1. 183
1.184
1. 185
1.186
1. 188
1.189
1.190
1.191
2.00
1.192
1.193
1.195
1.196
1.197
1.198
1.199
1.200
1.201
1.202
2.10
1.203
1.204
1.205
1.206
1.207
1.209
1.210
1.211
1.212
1.213
2.20
1.214
1.215
1.215
1.216
1.217
1.218
1.219
1.220
1.221
1.222
2.30
1.223
1.224
1.225
1.226
1.227
1.227
1.228
1.229
1.230
1.231
2.40
1.232
1.233
1.233
1.234
1.235
1.236
1.237
1.238
1.238
1.239
2.50
1.240
1.241
1.242
1.242
1.243
1.244
1.245
1.245
1.246
1.247
2.60
1.248
1.248
1.249
1.250
1.251
1.251
1.252
1.253
1.253
1.254
2.70
1.255
1.256
1.256
1.257
1.258
1.258
1.259
1.260
1.260
1.261
2.80
1.262
1.262
1.263
1.2 64
1.264
1.265
1.265
1.266
1.267
1.267
2.90
1.268
1.269
1.269
1.270
1.270
1.271
1.272
1.272
1.273
1.273
3.00
1.274
1.275
1.275
1.276
1.276
1.277
1.2 77
1.278
1.279
1.279
3.10
1.280
1.280
1.281
1.281
1.282
1.282
1.283
1.283
1.284
1.284
WATER CONTENT 220 PERCENT
OG
1.70
1. 148
1.149
1.151
1.152
1.153
1.155
1.156
1.157
1.159
1.160
1.80
1.161
1.163
1.164
1.165
1.166
1.168
1.169
1. 170
1.171
1.173
1.90
1.174
1.175
1.176
1.177
1.178
1. 180
1.181
1. 182
1.183
1.184
2.00
1.185
1.186
1.187
1.188
1.190
1.191
1.192
1.193
1.194
1.195
2.10
1.196
1.197
1.198
1.199
1.200
1.201
1.202
1.203
1.204
1.205
2.20
1.205
1.206
1.207
1.208
1.209
1.210
1.211
1.212
1.213
1.214
2.30
1.215
1.215
1.216
1.217
1.218
1.219
1.220
1.220
1.221
1.222
2.40
1.223
1.224
1.225
1.225
1.226
1.227
1.228
1.228
1.229
1.230
2.50
1.231
1.232
1.232
1.233
1.234
1.234
1.235
1.236
1.237
1.237
2.60
1.238
1.239
1.240
1.240
1.241
1.242
1.242
1.243
1.244
1.244
2.70
1.245
1.246
1.246
1.247
1.248
1.248
1.249
1.250
1.250
1.251
2.80
1.251
1.252
1.253
1.253
1.254
1.254
1.255
1.256
1.256
1.257
2.90
1.257
1.258
1.259
1.259
1.260
1.260
1.261
1.261
1.262
1.263
3.00
1.263
1.264
1.264
1.265
1.265
1.266
1.266
1.267
1.267
1.2 68
3.10
1.26Q
1.269
1.270
1.270
1.271
1.271
1.272
1.272
1.273
1.273
WATER CONTENT 230 PERCENT
OG
1.70
1.143
1.144
1. 145
1.147
1. 148
1.149
1.151
1.152
1.153
1.154
1.80
1.156
1.157
1.158
1.159
1.161
1.162
1.163
1.164
1.165
1.166
1.90
1.168
1. 169
1.170
1.171
1.172
1.173
1.174
1.175
1.176
1.178
2.00
1.179
1. 180
1. 181
1. 182
1.183
1.184
1. 185
1. 186
1.187
1.188
2.10
1.189
1.190
1.191
1.192
1.193
1.193
1.194
1. 195
1.196
1.197
2.20
1.198
1.199
1.200
1.201
1.202
1.202
1.203
1.204
1.205
1.206
2.30
1.207
1.208
1.208
1.209
1.210
1.211
1.212
1.212
1.213
1.214
2.40
1.215
1.215
1.216
1.217
1.218
1.219
1.219
1.220
1.221
1.221
2.50
1.222
1.223
1.224
1.224
1.225
1.226
1.226
1.227
1.228
1.229
2.60
1.229
1.230
1.231
1.231
1.232
1.233
1.233
1.234
1.235
1.235
2.70
1.236
1.236
1.237
1.238
1.238
1.2 39
1.240
1.240
1.241
1.241
2.80
1.242
1.243
1.243
1.244
1.244
1.245
1.245
1.246
1.247
1.247
2.90
1.248
1.248
1.249
1.249
1.250
1.250
1.251
1.252
1.252
1.253
3.00
1.2 53
1.254
1.254
1.255
1.255
1.256
1.256
1.257
1.257
1.258
*• 10
1.^58
LEDI
1.259
1.260
1.260
1.261
1.261
1.262
1.262
1.263
40
WATER CONTENT 240 PERCENT
DG
1.70
1. 138
1.139
1.140
1.142
1. 143
1.144
1.145
1.147
1.143
1.149
1.80
1.150
1.152
1.153
1.154
1.155
1.156
1.157
1.159
1.160
1.161
1.90
1.162
1. 163
1.164
1.165
1. 166
1.167
1. 168
1. 169
1.170
1.171
2.00
1.172
1.173
1.174
1.175
1. 176
1.177
1.178
1. 179
1.180
1.181
2.10
1.182
1.183
1.184
1.185
1.186
1.187
1.188
1.138
1.189
1.190
2.20
1. 191
1.192
1.193
1.194
1.194
1.195
1.196
1.197
1.198
1.199
2.30
1.199
1.200
1.201
1.202
1.203
1.203
1.204
1.205
1.206
1.206
2.40
1.207
1.203
1.209
1.209
1.210
1.211
1.211
1.212
1.213
1.214
2.50
1.214
1.215
1.216
1.216
1.217
1.218
1.218
1.219
1.220
1.220
2.60
1.221
1.222
1.222
1.223
1.224
1.224
1.225
1.225
1.226
1.227
2.70
1.227
1.228
1.228
1.229
1.230
1.230
1.231
1.231
1.232
1.233
2.80
1.233
1.234
1.234
1.235
1.235
1.236
1.237
1.237
1.238
1.238
2.90
1.239
1.239
1.240
1.240
1.241
1.241
1.242
1.242
1.243
1.243
3.00
1.244
1.244
1.245
1.245
1.246
1.246
1.247
1.247
1.248
1.248
3.10
1.249
1.249
1.250
1.250
1.251
1.251
1.252
1.252
1.253
1.253
WATER CONTENT 250 PERCENT
DG
1.70
1.133
1. 135
1.136
1.137
1.138
1.140
1.141
1.142
1.143
1.144
1.80
1. 145
1.147
1.148
1. 149
1. 150
1.151
1.152
1.153
1.154
1.155
1.90
1.157
1.158
1.159
1. 160
1.161
1.162
1.163
1.164
1.165
1.166
2.00
1.167
1. 168
I. 169
1.170
1.170
1.171
1. 172
1. 173
1.174
1.175
2.10
1.176
1.177
1.178
1.179
1.180
1.180
1.181
1. 182
1.183
1.184
2.20
1.185
1.185
1.186
1.187
1. 188
1.189
1.189
1.190
1.191
1.192
2.30
1.193
1.193
1. 194
1.195
1. 196
1.196
1.197
1. 198
1.199
1.199
2.40
1.200
1.201
1.201
1.202
1.203
1.204
1.204
1.205
1.206
1.206
2.50
1.207
1.208
1.208
1.200
1.210
1.210
1.211
1.211
1.212
1.213
2.60
1.213
1.214
1.215
1.215
1.216
1.216
1.217
1.218
1.218
1.219
2.70
1.219
1.220
1.221
1.221
1.222
1.222
1.223
1.223
1.224
1.224
2.80
1.225
1.226
1.226
1.227
1.227
1.228
1.228
1.229
1.229
1.230
2.Q0
1.230
1.231
1.231
1.232
1. 232
1.233
1.233
1.234
1.234
1.235
3.00
1.235
1.236
1.236
1.237
1.237
1.238
1.238
1.239
1.239
1.240
3. 10
1.240
1.240
1.241
1.241
1.242
1.242
1.243
1.243
1.244
1.244
WATER CONTENT 260 PERCENT
DG
1.7Q
1. 129
1.130
1.132
1. 133
1.134
1.135
1.136
1. 137
1.139
1.140
1.80
1. 141
1.142
1.143
1. 144
1. 145
1.146
1.147
1.148
1.149
1.150
1.90
1.152
1. 153
1.154
1.155
1.156
1.157
1.157
1. 158
1.159
1.160
2.00
1.161
1.162
1.163
1.164
1. 165
1.166
1.167
1. 168
1.169
1.169
2.10
1.170
1.171
1.172
I. 173
1.174
1.175
1.175
1. 176
1.177
1.178
2.20
1.179
1. 179
1.180
1.181
1.182
1.132
1.183
1. 184
1.185
1.186
2.30
1. 186
1. 187
1. 188
1.18 8
1.189
1.190
1.191
1.191
1.192
1.193
2.40
1.193
1. 194
1.195
1.195
1. 196
1.197
1.197
1.198
1.199
1.199
2.50
1.200
1.201
1.201
1.202
1.203
1.203
1.204
1.204
1.205
1.206
2.60
1.206
1.207
1.207
1.208
1.209
1.209
1.210
1.210
1.211
1.211
2.70
1.212
1.21 3
1.213
1.214
1.214
1.215
1.215
1.216
1.216
1.217
2.80
1.217
1.218
1.218
1.219
1.219
1.220
1.220
1.221
1.221
1.222
2.90
1.222
1.223
1.223
1.224
1.224
1.225
1.225
1.226
1.226
1.227
3.00
1.227
1.228
1.228
1.229
1.229
1.230
1.230
1.230
1.231
1.231
3.10
1.232
1.232
1.233
1.233
1.234
1.234
1.2 34
1.235
1.235
1.236
41
WATER CONTENT 270 PERCENT
DG
1.70
1.125
1.126
1.128
1.129
1.130
1.131
1.132
1. 133
1.134
1.135
1.80
1.137
1.138
1.139
1.140
1.141
1.142
1.143
1.144
1.145
1.146
1.90
1.147
1.148
1. 149
1.150
I. 151
1.152
1.153
1.154
1.154
1.155
2.00
1.156
1.157
1.158
1.159
1.160
1.161
1.162
1.162
1.163
1.164
2.10
1.165
1.166
1.167
1.167
1.168
1.169
1.170
1. 171
1.171
1.172
2.20
1.173
1.174
1.174
1.175
I. 176
1.177
1.177
1. 178
1.179
1.180
2.30
1.180
1.181
1.182
1.182
1. 183
1.184
1.184
1.185
1.186
1.187
2.40
1.187
1.188
1.188
1.189
1.190
1.190
1.191
1.192
1.192
1.193
2.50
1.194
1.194
1. 195
1.195
1.196
1.197
1.197
1.198
1.198
1.199
2.60
1.200
1.200
1.201
1.201
1.202
1.202
1.203
1.203
1.204
1.205
2.70
1.205
1.206
1.206
1.207
1.207
1.208
1.208
1.209
1.209
1.210
2.80
1.210
1.211
1.211
1.212
1.212
1.213
1.213
1.214
1.214
1.215
2.°0
1.215
1.216
1.216
1.217
1.217
1.218
1.218
1.218
1.219
1.219
3.00
1.220
1.220
1.221
1.221
1.222
1.222
1.222
1.223
1.223
1.224
3.10
1.224
1.225
1.225
1.225
1.226
1.226
1.227
1.227
1.227
1.228
WATER CONTENT 280 PERCENT
DG
1.70 1
L.122
1.123
1.124
1.125
1.126
1.127
1.128
1. 129
1.130
1.131
1.80 1
L. 132
1.133
1.135
1.136
1. 137
1.138
1.139
1.140
1.140
1.141
1.90 1
1.142
1.143
1. 144
1.145
1. 146
1.147
1.148
1.149
1.150
1.151
2.00 1
1.152
1.152
1.153
1.154
1.155
1.156
1.157
1.157
1.158
1.159
2.10 ]
L.160
1.161
1.161
1.162
1.163
1.164
1.165
1.165
1.166
1.167
2.20 1
L. 168
I. 168
1.169
1. 170
1. 171
1.171
1.172
1. 173
1.173
1.174
2.30 1
1.175
1.175
1.176
I. 177
1. 177
1.178
1.179
1.179
1.180
1.181
2.40 ]
L.181
1.132
1.183
1.183
1. 184
1.184
1.185
1. 186
1.186
1.187
2.50 1
[.187
1.188
1.189
1.189
I. 190
1.190
1.191
1. 192
1.192
1.193
2.60 1
1.193
1.194
1.194
1.195
1.195
1.196
1.196
1.197
1.198
1.198
2.70 1
1.199
1.199
1.200
1.200
1.201
1.201
1.202
1.202
1.203
1.203
2.80 ]
L.204
1.204
1.205
1.205
1.206
1.206
1.206
1.207
1.207
1.208
2.90 1
..208
1.209
1..209
1.210
1.210
1.211
1.211
1.211
1.212
1.212
3.00 1
1.213
1.213
1.214
1.214
1.214
1.215
1.215
1.216
1.216
1.217
3.10 ]
L.217
1.217
1.218
1.218
1.219
1.219
1.219
1.220
1.220
1.220
WATER CONTENT 290 PERCENT
DG
1.70 ]
I. 118
1.119
1.120
1.121
1. 122
1.123
1.125
1. 126
1.127
1.128
1.80 1
.. 129
1.130
1.131
1. 132
1.133
1.134
1. 135
1.135
1.136
1.137
1.90 1
L. 138
1. 139
1.140
1.141
1.142
1.143
1.144
1.144
1.145
1.146
2.00 1
L.147
1.148
1.149
1.150
1. 150
1.151
1.152
1.153
1.154
1.154
2.10 ]
L.155
1.156
1.157
1.157
1. 158
1.159
1.160
1. 160
1.161
1.162
2.20 ]
L.163
1.163
1.164
1. 165
1.165
1.166
1.167
1.167
1.168
1.169
2.30 1
L. 169
1.170
1.171
1. 171
1.172
1.173
1.173
1. 174
1.175
1.175
2.40 1
L.176
1.176
1.177
1. 178
1. 178
1.179
1.179
1.180
1.181
1.181
2.50 1
L.182
1.182
1.183
1.184
1.184
1.185
1.185
1. 186
1.186
1.187
2.60 ]
L.187
1.188
1.188
1.189
1. 189
1.190
1.190
1.191
1.192
1.192
2.70 ]
1.193
1.193
1.194
1.194
1.194
1.195
1.195
I. 196
1.106
1.197
2.80 ]
L.197
1.198
1.198
1.199
1.199
1.200
1.200
1.201
1.201
1.201
2.90 1
1.202
1.202
1.203
1.203
1.204
1.204
1.205
1.205
1.205
1.206
3.00 1
1.206
1.207
1.207
1.207
1.208
1.208
1.209
1.209
1.209
1.210
3.10 ]
1.210
1.211
1.211
1.211
1.212
1.212
1.213
1.213
1.213
1.214
42
WATER CONTENT 300 PERCENT
DG
1.70 1
L.115
1.116
1.117
1.118
1. 119
1.120
1.121
1.122
1.123
1.124
1.80 I
L, 125
1.126
1.127
1.128
1. 129
1.130
1.131
1. 132
1.133
1.133
1.90 1
L.134
1. 135
1. 136
1.137
1. 138
1.139
1. 140
1.140
1.141
1.142
2.00 ]
L.143
1.144
1.144
1.145
1. 146
1.147
1.148
1. 148
1.149
1.150
2.io ;
L.151
1.151
1.152
1.153
1. 154
1.154
1. 155
1. 156
1.156
1.157
2.20 ]
L.158
1.159
1.159
1.160
1.161
1.161
1.162
1.163
1.163
1.164
2.30 ]
L. 165
1.165
1.166
1.166
1. 167
1.168
1.168
1.169
1.170
1.170
2.40 ]
L.171
1.171
1.172
1.172
1.173
1.174
1.174
1. 175
1.175
1.176
2.50 ]
L. 176
1. 177
1. 178
1. 178
1.179
1.179
1.180
1.180
1.181
1.181
2.60 ]
1.182
1.182
1. 183
1. 183
1. 184
1.184
1.185
1. 185
1.186
1.186
2.70 ]
L.187
1.187
1.188
1.188
1. 189
1.189
1.190
1.190
1.191
1.191
2.80 3
L.191
1.19?
1.192
1.193
1.193
1.194
1.194
1.195
1.195
1.195
2.90 ]
L.196
1.196
1. 197
1. 197
1. 198
1.198
1.198
1.199
1.199
1.200
3.00 ]
1.200
1.200
1.201
1.201
1.202
1.202
1.202
1.203
1.203
1.204
3.10 ]
1.2C4
1.204
1.205
1.205
1.205
1.206
1.2 06
1.206
1.207
1.207
WATER CONTENT 310 PERCENT
DG
1.70 ]
t.112
1.113
1.114
1.115
1. 116
1.117
1.118
1.119
1.120
1.121
1.80 1
..122
1.123
1.123
1.124
1.125
1.126
1.127
1.128
1.129
1.130
1.90 ]
L. 131
1. 131
1.132
1. 133
1.134
1. 135
1. 136
1.136
1.137
1.138
2-. 00 1
L.139
1.140
1.140
1.141
1. 142
1.143
1.144
1.144
1.145
1.146
2.10 1
L. 146
1.147
1.148
1. 149
1. 149
1.150
1.151
1. 151
1.152
1.153
2.20 1
L.153
1. 154
1.155
1. 155
1.156
1.157
1.157
1. 158
1.159
1.159
2.30 ]
.. 160
1. 161
1.161
1.162
1. 162
1.163
1.164
1.164
1.165
1.165
2.40 ]
L. 166
1.166
1.167
1. 168
1.168
1.169
1.169
1. 170
1.170
1.171
2.50
I. 171
1.17?
1.172
1.173
1. 174
1.174
1.175
1. 175
1.176
1.176
2.60 1
.. 177
1. 177
I. 178
r. 178
1.179
1.179
1.180
1.180
1.180
1.181
2.70 1
L.181
1.182
1.182
1.183
1.183
1.184
1.184
1. 185
1.185
1.186
2.80 1
L. 186
1. 186
1.187
1.187
1.188
1.188
1.189
1.189
1.189
1.190
2.90 1
..190
1.191
1.191
1.191
1.192
1.192
1.193
1. 193
1.193
1.194
3.00 1
L.194
1.195
1.195
1. 1°5
1.1*56
1.196
1. 196
1.197
1.197
1.198
3.10 1
L.198
1.198
1.199
1.199
1.199
1.200
1.200
1.200
1.201
1.201
WATER CONTENT 320 PERCENT
DG
1.70 ]
.. 109
1.110
1.111
1.112
1. 113
1.114
1.115
1. 116
1.116
1.117
1.80 1
. 118
1.119
1.120
1.121
1.122
1.123
1.124
1.125
1.125
1.126
l.°0 ]
L. 127
1.128
1.129
1. 130
1. 130
1. 131
1.132
1. 133
1.134
1.134
2.00 1
..135
1.136
1. 137
1.137
1.138
1.139
1.140
1,140
1.141
1.142
2.10 J
.. 142
1.143
1.144
1.145
1.145
1.146
1.147
1.147
1.148
1.149
2.20 1
..149
1.150
1.151
1. 151
1.152
1.152
1. 153
1.154
1.154
1.155
2.30 ]
1.156
1.156
1.157
1. 157
1.158
1.158
1.159
1.160
1.160
1.161
2.40 1
..161
1.162
1.162
1. 163
1.163
1.164
1.165
1.165
1.166
1.166
2.50 1
. 167
1. 167
1.168
1.168
1. 169
1.169
1.170
1. 170
1.171
1.171
2.60 ]
.. 172
1.172
1.173
1.173
1. 174
1.174
1. 175
1.175
1.175
1.176
2.70 ]
.176
1.177
1.177
1.178
1. 178
1.179
1. 179
1.179
1.180
1.180
2. 80 1
..1«1
1.181
1.182
1.182
I. 182
1.183
1.183
1. 184
1.184
1.184
2.90 1
.185
1.185
I. 186
1.186
1.186
1.187
1.187
1.188
1.188
1.188
3.00 ]
,.189
1.189
1.189
1.190
1.190
1.191
1.191
1.191
1.192
1.192
3.10
t.192
1.193
1.193
1.193
1.194
1.194
1.194
1.195
1.195
1.195
43
WATER CONTENT 330 PERCENT
DG
1.70 I
I. 106
1.107
1.108
1. 109
1.110
1.111
1.112
1.113
1.113
1.114
1.80 ]
L.115
1.1L6
1.117
1.118
1.119
1.120
1.120
1.121
1.122
1.123
1.90
L.124
1.125
1.125
1.126
1. 127
1.128
1.129
1.129
1.130
1.131
2.00 ]
L. 132
1.132
1. 133
1. 134
1. 135
1.135
1. 136
1. 137
1.137
1 .138
2.10 1
L.139
1.139
1.140
1.141
1.141
1.142
1. 143
1. 143
1.144
1.145
2.20 ]
..145
1.146
1. 147
1.147
1. 148
1.148
1.149
1.150
1.150
1.151
2.30 ]
L.151
1.152
1.152
1.153
1. 154
1.154
1.155
1.155
1.156
1.156
2.40 ]
L.157
1.157
1.158
1.159
1.159
1.160
1.160
1. 161
1.161
1.162
2.50 1
..162
1.163
1. 163
1.164
1.164
1.165
1.165
1.166
1.166
1.167
2.60 1
..167
1.167
1.168
1.168
1.169
1.169
1. 170
1. 170
1.171
1.171
2.70 ]
L. 172
1. 172
1.172
1. 173
1. 173
1.174
1.174
1.175
1.175
1.175
2.80 1
I. 176
1.176
1.177
1.177
1.177
1.178
1.178
1.179
1.179
1.179
2.90 1
L.180
1.180
1.181
1.181
1.181
1.182
1.182
1.182
1.183
1.183
3.00 ]
I. 183
1. 184
1.184
1.185
1.185
1.185
1. 186
1. 186
1.186
1.187
3.10 1
..187
1.187
1.188
1.188
1. 188
1.189
1.189
1. 189
1.190
1.190
WATER CONTENT 340 PERCENT
DG
1.70 ]
L. 103
1.104
1.105
1.106
1. 107
1.108
1. 109
I,
no
1.111
1.111
1.80 ]
L.112
1.113
1.114
1.115
1.116
1.117
1. 117
1,
118
1.119
1.120
1.90
L.121
1.121
1.122
1.123
1.124
1.125
1.125
1.
.126
1.127
1.127
2.00 ]
L.128
1.129
1. 130
1.130
1.131
1.132
1.132
1.
133
1.134
1.134
2.10 1
L.135
1*136
1.136
1.137
1. 138
1.138
1.139
1.
, 140
1.140
1.141
2.20 ]
L.142
1.142
1.143
1.143
I. 144
1.145
1.145
1.
146
1.146
1.147
2.30 ]
L.147
1.148
1.149
1.149
1. 150
1.150
1.151
1,
151
1.152
1.152
2.40 ]
L. 153
1.153
I. 154
1.154
1. 155
1.155
1.156
1.
156
1.157
1.157
2.50 i
1.158
1. 158
1.159
1.159
1.160
1.160
1. 161
1-
161
1.162
1.162
2.60 1
L. 163
1. 163
1.164
1.164
1.164
1.165
1.165
1.
,166
1.166
1.167
2.70 1
L. 167
1.167
1.168
1.168
1.169
1.169
1.169
1,
170
1.170
1.171
2.80 1
L. 171
1.171
1.172
1. 172
1. 173
1.173
I. 173
1,
174
1.174
1.175
2.90 ]
L.175
1.175
1.176
1. 176
1.176
1.177
1.177
1.
178
1.178
1.178
3.00
L.179
1.179
1.179
1. 180
I. 180
1.180
1.181
1,
181
1.181
1.182
3.10 1
L. 182
1. 182
1.183
1. 183
1. 183
1.184
1.184
1,
184
1.185
1.185
WATER CONTENT 350 PERCENT
OG
1.70 1
.. 101
1.102
1.103
1.103
1.104
1.105
1. 106
I.
107
1.108
1.109
1.80 !
.110
1.110
1.111
1.112
1. 113
1.114
1.115
L.
115
1.116
1.117
1.90 1
L.118
1.118
1.119
1.120
1.121
1.121
1.122
1.
123
1.124
1.124
2.00 1
.125
1. 126
1.126
1.127
1.128
1.128
1.129
1.
130
1.130
1.131
2.10 1
.. 132
1.132
1.133
1.134
1. 134
1.135
1. 136
1.
136
1.137
1.137
2.20 1
L. 138
1.139
1. 13Q
I. 140
1 . 140*
1.141
1.141
1.
142
1.143
1.143
2.30 ]
L. 144
1.144
1.145
1.145
1. 146
1.146
1. 147
1 .
147
1.148
1.148
2.40 1
..149
1.149
1.150
1.150
1.151
1.151
1.152
1.
152
1.153
1.153
2.50 ]
L.154
1.154
1.155
1.155
1. 156
1.156
1.157
1.
157
1.158
1.158
2.60 1
L. 158
1.159
1.159
1.160
1. 160
1.161
1.161
1.
161
1.162
1.162
2.70 I
L. 163
1.163
1.163
1.164
1.164
1.165
1.165
1.
165
1.166
1.166
2.80 1
..167
1.167
1.167
1. 168
1. 168
1.169
1.169
1.
169
1.170
1.170
2.90 ]
1.170
1.171
1.171
1.171
1.172
1.172
1.173
1.
173
1.173
1.174
3.00 ]
1.174
1.174
1.175
1.175
1.175
1.176
1.176
1.
176
1.177
1.177
3.10 1
L. 177
1.178
1.178
1.178
1.178
1.179
1.179
1.
179
1.180
1.180
44
WATER CONTENT 360 PERCENT
DG
1.70 ]
1.098
1.099
I. 100
1.101
1.102
1.103
1.104
1.104
1.105
1.106
1.80 J
1.107
1.108
1.109
1.109
I. 110
1.111
1.112
1.113
1.113
1.114
l.QO ]
L.115
1.116
1.116
1. 117
1.118
1.118
1.119
1.120
1.121
1.121
2.00 1
L.122
1.123
1.123
1.124
1.125
1.125
1.126
1.127
1.127
1.128
2.10 1
L, 129
1. 129
1.130
1.130
1. 131
1.132
1.132
1. 133
1.133
1.134
2.20 ]
1.135
1.135
1.136
1.136
1.137
1.137
1.138
1. 138
1.139
1.140
2.30 ]
1.140
1.141
1.141
1.142
1. 142
1.143
1.143
1.144
1.144
1.145
2.40 1
L.145
1.146
1.146
1.147
1.147
1.148
1.148
1. 149
1.149
1.150
2.50 ]
L. 150
1.150
1.151
1.151
1. 152
1.152
1.153
1.153
1.154
1.154
2.60 1
L.154
1.155
1.155
1.156
1.156
1.157
1.157
1. 157
1.158
1.158
2.70 ]
L.159
1.159
1. 159
1.160
1. 160
1.161
1.161
1.161
1.162
1.162
2.80 ]
L.162
1.163
1.163
1. 164
1.164
1.164
1.165
1.165
1.165
1.166
2.90 ]
L. 166
1.166
1.167
1.167
1.167
1.168
1.168
1.168
1.169
1.169
3.00 ]
L. 169
1.170
1.170
1.170
1.171
1.171
1.171
1.172
1.172
1.172
3.10 ]
L.173
1.173
1.173
I. 174
1. 174
1.174
1.175
1.175
1.175
1.175
WATER CONTENT 370 PERCENT
DG
1.70 1
.096
1.097
1.098
1.099
1.099
1.100
1.101
1.102
1.103
1.104
1.80 ]
L.104
1.105
1.106
1.107
1. 108
1.109
1.109
1. 110
1.111
1.111
1.90 1
..112
1.113
1. 114
1.114
1.115
1.116
1.116
1. 117
1.118
1.118
2.00 1
..119
1.120
1.120
1.121
1.122
1.122
1.123
1.124
1.124
1.125
2.10 ]
L- 125
1.126
1.127
1.127
1.128
1.128
1.129
1. 130
1.130
1.131
2.20 1
L.131
1.132
1.132
1.133
1. 134
1.134
1.135
1.135
1.136
1.136
2.30 1
..137
1.137
1.138
1.138
1. 139
1.139
1.140
1. 140
1.141
1.141
2.40 ]
L.142
1. 142
1.143
1. 143
1. 144
1.144
1.145
1.145
1.145
1.146
2.50 1
L. 146
1. 147
1.147
1. 148
1. 148
1.149
1.149
1.149
1.150
1.150
2.60 1
L- 151
1.151
1.151
1.152
1.152
1.153
1.153
1.154
1.154
1.154
2.70 ]
L. 155
1.155
1. 155
1.156
I. 156
1.157
1.157
1. 157
1.158
1.158
2.80 ]
L- 158
1.159
1.159
1.160
1.160
1.160
1.161
1. 161
1.161
1.162
2.90 ]
L.162
1.162
1.163
1.163
1. 163
1.164
1.164
1.164
1.165
1.165
3.00 1
..165
1.166
1.166
1.166
1.167
1.167
1.167
1.167
1.168
1.168
3.10 1
1.168
1.169
1.169
1.16°
1. 170
1.170
1.170
1. 170
1.171
1.171
WATER CONTENT 380 PERCENT
DG
1.70 ]
.094
1.095
1.096
1.096
1.097
1.098
1.099
1.100
1.100
1.101
1.80 1
.102
1.103
1.104
1.104
1.105
1.106
1.107
1.107
1.108
1.109
1.90 1
.109
1.110
1.111
1.112
1.112
1.113
1.114
1.114
1.115
1.116
2.00 1
. 116
1.117
1.118
1.118
1. 119
1.119
1.120
1.121
1.121
1.122
2.10 1
.122
1.123
1.124
1.124
1.125
1.125
1.126
1.127
1.127
1.128
2.20 1
..128
1.129
1.129
1. 130
1.130
1.131
1.131
1.132
1.132
1.133
2.30 1
.133
1. 134
1.134
1.135
1.135
1.136
1.136
1.137
1.137
1.138
2.40 1
..138
1.139
1.139
1. 140
1.140
1.141
1.141
1.142
1.142
1.142
2.50 1
.143
1.143
1.144
1.144
1.145
1.145
1.145
1.146
1.146
1.147
2.60 1
.147
1.147
1.148
1. 148
1.149
1.149
1.149
1.150
1.150
1.151
2.70 1
1.151
1.151
1.152
1.152
1.152
1.153
1.153
1.154
1.154
1.154
2.80 1
..155
1.155
1.155
1.156
1.156
1.156
1.157
1.157
1.157
1.158
2.90 1
1.158
1.158
1.159
1.159
1.159
1.160
1.160
1.160
1.161
1.161
3.00 1
1.161
1.162
1.162
1.162
1.163
1.163
1.163
1. 163
1.164
1.164
3.10
L. 164
1.165
1.165
1.165
1.165
1.166
1.166
1.166
1.167
1.167
45
WATER CONTENT 390 PERCENT
DG
1.70 1
L.092
1.093
1.093
1.094
1.095
1.096
1.097
1.097
1.098
1.099
1.80 1
L.100
1.101
1.101
1.102
1. 103
1.103
1.104
1.105
1.106
1.106
1.90 ]
1.107
1.108
1.108
1.109
1. 110
1.110
1.111
1.112
1.112
1.113
2.00 1
L.114
1.114
1.115
1.116
1. 116
1.117
1. 117
1. 118
1.119
1.119
2.10 1
L.120
1.120
1.121
1.121
1. 122
1. 123
1.123
1.124
1.124
1.125
2.20 1
.125
1.126
1.126
1.127
1.127
1.128
1.128
1.129
1.129
1.130
2.30 ]
L.130
1.131
1.131
1. 132
1.132
1.133
1.133
1.134
1.134
1.135
2.40 1
L.135
1.136
1.136
1.136
1. 137
1.137
1.138
1. 138
1.139
1.139
2.50 1
I. 140
1.140
1. 140
1.141
1. 141
1.142
1. 142
1. 142
1. 143
1.143
2.60 ]
L. 144
1. 144
1.144
1. 145
1. 145
1.146
1. 146
1. 146
1.147
1.147
2.70 1
i.147
1.148
1.148
1. 149
1.149
1.149
1.150
1. 150
1.150
1.151
2.80 ]
1.151
1.151
1.152
1.152
1.152
1.153
1.153
1. 153
1.154
1.154
2.90 ]
L.154
1.155
1.155
1.155
1.156
1.156
1.156
1.157
1.157
1.157
3.00 1
..157
1.153
1.158
1.158
1.159
1.159
1. 159
1. 160
1.160
1.160
3.10 ]
.160
1.161
1.161
1.161
1. 162
1.162
1.162
1.162
1.163
1.163
WATER CONTENT 400 PERCENT
DG
1.70 1
..090
1.091
1.091
1.092
1.093
1.094
1.095
1.095
1.096
1.097
1.80 ]
L.098
1.098
1.09°
1.100
1.100
1.101
1.102
1. 103
1.103
1.104
1.90 1
L.105
1.105
1.106
1.107
1. 107
1.108
1. 109
1. 109
1.110
1.110
2.00 1
L.lll
1.112
1.112
1. 11 3
1. 114
1.114
1.115
1. 115
1.116
1.116
2.10 !
L.117
1.118
1.118
1.119
1. 119
1.120
1. 120
1. 121
1.121
1.122
2.20 ]
L.122
1.123
1.123
1.124
1. 124
1.125
1.125
1. 126
1.126
1.127
2.30 1
.127
1.128
1.128
1 .129
1.129
1.130
1.130
1. 131
1.131
1.132
2.40 1
L.132
1. 133
1.133
1. 133
1. 134
1.134
1.135
1. 135
I. 136
1.136
2.50 1
L.136
1. 137
1. 137
1. 138
1. 138
1.138
1. 139
1. 139
1.140
1.140
2.60 1
. . 140
1.141
1.141
1.141
1.142
1.142
1. 143
1.143
1.143
1.144
2.70 ]
L. 144
1. 144
1.145
1.145
1. 145
1.146
1. 146
1.147
1.147
1.147
2.80 ]
.. 148
1.148
1.148
1.149
I. 149
1.149
1.150
1.150
1.150
1.150
2.90 ]
L.151
1. 151
1.151
1.152
1. 152
1.152
1.153
1.153
1.153
1.154
3.00 I
L. 154
1. 154
1.154
1. 155
1.155
1.155
1.156
1.156
1.156
1 .156
3.10 1
..157
1.157
1. 157
1. 158
1.158
1.158
1. 158
1.159
1.159
1.159
WATER CONTENT 410 PERCENT
DG
1.70 1
..0«3
1.089
1.089
1.090
1.091
1.092
1.093
1.093
1.094
1.095
1.80 1
..095
1.096
1.097
1.098
1.098
1.099
1. 100
1.100
1.101
1.102
1.90 1
..102
1.103
1.104
1.104
1. 105
1.106
1. 106
1.107
1.107
1.108
2.00 1
. 109
1.109
1.110
1. 110
1. Ill
1.112
1. 112
1. 113
1.113
1.114
2.10 ]
..114
1.115
1.116
1.116
1. 117
1.117
1.118
1. 118
l.l 19
1.119
2.20 ]
.. 120
1.120
1.121
1.121
1. 122
1.122
1.123
1. 123
1.124
1.124
2.30 1
.125
1.125
1.126
1.126
1. 126
1.127
1. 127
1.128
1.128
1.129
2.40 3
L.129
1. 130
1. 130
1 .130
1. 131
1.131
1. 132
1.132
1.133
1.133
2.50 1
.. 133
1. 134
1. 134
1.135
1. 135
1. 135
1.136
1.136
1.136
1.137
2.60 1
.137
1. 138
1.138
1.138
1. 139
1.139
1. 139
1. 140
1.140
1.140
2.70 1
L.141
1.141
1.142
1. 142
1. 142
1.143
1. 143
1. 143
1.144
1. 144
2.80 1
I. 144
1.145
1. 145
1. 145
1. 146
1.146
1.146
1. 146
1.147
1.147
2.90 1
,.147
1.148
1.148
1.148
1.149
1.149
1.149
1.150
1.150
1.150
3.00 1
L. 150
1.151
1.151
1.151
1.152
1.152
1.152
1.152
1.153
1.153
3.10
L.153
1.153
1.154
1.154
1.154
1.155
1.155
1.155
1.155
1.156
i+6
WATER CONTENT 420 PERCENT
DG
1.70 ]
L.086
1.087
1.088
1.088
1.089
1.090
1.091
1.091
1.092
1.093
1.80 1
L.093
1.094
1.095
1.096
1.096
1.097
1.098
1.098
1.099
1.100
1.90 1
I. 100
1.101
1.101
1.102
1.103
1.103
1.104
1.105
1.105
1.106
2.00 1
L. 106
I. 107
1.108
1.108
1.109
1.109
1.110
1.110
1.111
1.111
2.10 ]
L. 112
1. 113
1.113
1. 114
1. 114
1.115
1.115
1. 116
1.116
1.117
2.20 1
L. 117
1.118
1.118
1.119
1.119
1.120
1.120
1.121
1.121
1.121
2.30 ]
L. 122
1.122
1.123
1.123
1.124
1.124
1.125
1.125
1.125
1.126
2.40 1
L.126
1.127
1.127
1.128
1.128
1.128
1.129
1.129
1.130
1.130
2.50 ]
L.130
1.131
1.131
1.132
1.132
1.132
1.133
1.133
1.133
1.134
2.60 ]
L.134
1.135
1.135
1. 135
1. 136
1.136
1.136
1. 137
1.137
1.137
2.70 J
I. 138
1. 138
1.138
1. 139
1.139
1.139
1. 140
1.140
1.140
1.141
2.80 ]
L.141
1.141
1.142
1.142
1. 142
1.143
1.143
1.143
1.144
1.144
2.90 1
L.144
1.144
1.145
1.145
1.145
1.146
1.146
1.146
1.146
1.147
3.00 1
-.147
1.147
1.148
1.148
1.148
1.148
1.149
1.149
1.149
1.150
3.10 1
.. 150
1.150
1. 150
1.151
1.151
1.151
1.151
1. 152
1.152
1.152
WATEP CONTENT 430 PERCENT
DG
1.70 1
L.084
1.085
1.086
1.087
1.087
1.088
1.089
1.089
1.090
1.091
1.80 ]
L.092
1.092
1.093
1.094
1.094
1.095
1.096
1.096
1.097
1.098
1.90 1
L.098
1.099
1.099
1.100
1.101
1.101
1.102
1. 102
1.103
1.104
2.00 ]
L. 104
1.105
1.105
1.106
1.106
1.107
1.108
1.108
1.109
1.109
2.10 1
L. 110
1. 110
1.111
1.111
1.112
1.112
1.113
1.113
1.114
1.114
2.20 1
L.U5
1.115
1.116
1.116
1.117
1.117
1. 118
1.118
1.118
1.119
2.30 ]
L.119
1.120
1.120
1.121
1.121
1.122
1.122
1.122
1.123
1.123
2.40 1
L.124
1. 124
1.124
1.125
1.125
1.126
1.126
1. 126
1.127
1.127
2.50 1
L.128
1.128
1.128
1.129
1.129
1.130
1.130
1. 130
1.131
1.131
2.60 ]
L. 131
1.132
1. 132
1.132
1.133
1.133
1. 133
1.134
1.134
1.134
2.70 1
L.135
1.135
1.135
1.136
1.136
1.136
1. 137
1. 137
1.137
1.138
2.80 ]
L. 138
1.138
1.139
1.139
1. 139
1.140
1.140
1. 140
1.140
1.141
2.90 1
L.141
1.141
1.142
1.142
1. 142
1.142
1.143
1.143
1.143
1.144
3.00 1
L. 144
1. 144
1.144
1.145
1.145
1.145
1.145
1.146
1.146
1.146
3. 10 1
1.147
1. 147
1.147
1.147
1. 148
1.148
1.148
1. 148
1.149
1.149
WATER CONTENT 440 PERCENT
DG
1.70 1
..083
1.083
1.084
1.085
1.085
1.086
1.087
1.088
1.088
1.089
1 .80 1
..090
1.090
1.091
1.092
1.092
1.093
1.094
1.094
1.095
1.096
1.90 1
.096
1.097
1.097
1.098
1.099
1.099
1.100
1.100
1.101
1.101
2.00 1
.102
1.103
1.103
1.104
1.104
1.105
1.105
1.106
1.106
1.107
2.10 1
.107
1.108
1.108
1.109
1.109
1.110
1.110
1-111
1.11 1
1.112
2.20 1
I. 112
1.113
1.113
1.114
1.114
1.115
1.115
1.116
1.116
1.116
2.30 1
.117
1.117
1.118
1.118
1.119
1.119
1.119
1.120
1.120
1.121
2.40 1
.121
1.122
1.122
1.122
1.123
1.123
1.123
1.124
1.124
1.125
2.50 1
.125
1.125
1.126
1.126
1.126
1.127
1.127
1.128
1.128
1.128
2.60 1
..129
1.129
1.129
1.130
1.130
1.130
1.131
1.131
1.131
1.132
2.70 1
.132
1. 132
I. 133
1. 133
1. 133
1.134
1.134
1.134
1.135
1.135
2.80 1
..135
1. 135
1. 136
1. 136
1. 136
1.137
1. 137
1.137
1.138
1.138
2.90 1
>.138
1.138
1.139
1.139
1.139
1.139
1.140
1.140
1.140
1.141
3.00 1
.141
1.141
1.141
1.142
1.142
1.142
1.142
1.143
1.143
1.143
3.10 ]
L.143
1.144
1.144
1.144
1.144
1.145
1.145
1.145
1.145
1.146
47
WATER CONTENT 450 PERCENT
OG
1.70
L .08 1
1.082
1.082
1.083
1.084
1.085
1.085
1.086
1.087
1.087
1.80 1
L.088
1.089
1.089
1.090
1.091
1.091
1.092
1.092
1.093
1.094
1.90 ]
L.094
1.095
1.095
1.096
1.097
1.007
1.098
1.098
1.099
1.099
2.00 1
..100
1.101
1.101
1.102
1.102
1.103
1.103
1.104
1.104
1.105
2.10 1
L.105
1.106
1.106
1.107
1.107
1.108
1.108
1.109
1.109
I. 110
2.20 1
L.110
1.111
1.111
1.111
1.112
1.112
1.113
1.113
1.114
1.114
2.30 1
L.115
1.115
1.115
1.116
1.116
1.117
1.117
1.117
1.118
1.118
2.40 1
L.119
1.119
1.119
1.120
1.120
1.121
1.121
1.121
1.122
1.122
2.50 1
L. 122
1. 123
1.123
1.124
1.124
1.124
1.125
1.125
1.125
1.126
2.60 1
.126
1.126
1.127
1.127
I. 127
1.128
1.128
1.128
1.129
1.129
2.70 ]
..129
1.130
1.130
1.130
1. 131
1.131
1.131
1.131
1.132
1.132
2.80 1
L. 132
1.133
1.133
1.133
1. 134
1.134
1.134
1.134
1.135
1.135
2.90 1
1.135
1.136
1.136
1.136
1.136
1.137
1.137
1. 137
1.137
1.138
3.00 1
..138
1. 138
1.138
1.139
1.139
1.139
1.139
1.140
1.140
1.140
3. 10 1
..140
1.141
1.141
1.141
1.141
1.142
1.142
) . 142
1.142
1.143
WATER CONTENT 460 PERCENT
OG
1.70 1
L.079
1.080
1.081
1.081
1.082
1.083
1.084
1.084
1.085
1.086
1.80 1
L.086
1.087
1.08 7
1.088
1.089
1.089
1.090
1.091
1.091
1.092
1.90 ]
L.092
1.093
1.094
1.094
1.095
1.095
1.096
1.096
1.097
1.097
2.00 i
L.098
1.099
1.099
1.100
1.100
1.101
1.101
1. 102
1.102
1.103
2.10 1
L.103
1.104
1.104
1.105
1.105
1.106
1.106
1.107
1.107
1.107
2.20 1
L.108
1.108
1.109
1.109
1. 110
1.110
I. Ill
1. ill
1.111
1.112
2.30 1
[.112
1.113
1.113
1.113
1. 114
1.114
1.115
1.115
1.116
1.116
2.40 ]
L.116
1.117
1. 117
1. 117
1.118
1. 118
1.119
1.119
1.119
1.120
2.50 ]
L.120
1.120
1.121
1.121
1.121
1.122
1.122
1.122
1.123
1.123
2.60 1
L. 123
1.124
1.124
1.124
1.125
1.125
1.125
1.126
1.126
1.126
2.70 ]
L. 127
1.127
1.127
1.128
1. 128
1.128
1.129
1.129
1.129
1.129
2.80 1
L. 130
1.130
1.130
1.131
1.131
1.131
1.131
1. 132
1.132
1.132
2.90 ]
L. 132
1. 133
1.133
1.133
1.134
1.134
1.134
1.134
1.135
1.135
3.00 I
L.135
1. 135
1.136
1.136
1. 136
1.136
1. 137
1. 137
1.137
1.137
3.10 ]
L.138
1.138
1.138
1.138
1. 139
1.139
1. 139
1. 139
1.139
1.140
WATER CONTENT 470 PERCENT
OG
1.70
1.073
1.079
1.079
1.080
1.081
1.081
1.082
1.083
1.083
1.084
1.80
1.085
1.085
1.086
1.086
1.087
1.088
1.088
1.089
1.089
1.090
1.90
1.091
1.091
1.092
1.092
1.093
1.093
1.094
1.095
1.095
1.096
2.00
1.096
1.097
1.097
1.098
1.098
1.099
1.099
1.100
1.100
1. 101
2.10
I. 101
1.102
1.102
1.103
1. 103
1.104
1.104
1.104
1.105
1.105
2.20
1.106
1.106
1.107
1.107
1.108
1.108
1.108
1. 109
1.109
1.110
2.30
1.110
1.110
1- 111
1.111
1.112
1.112
1.112
1.113
1.113
1.114
2.40
1.114
1.114
1.115
1.115
1.115
1.116
1.116
1. 117
1.117
1.117
2.50
1.118
1.118
1.118
1.119
1.119
1.119
1.120
1.120
1.120
1.121
2.60
1.121
1.121
1.122
1.122
1.122
1.123
1.123
1.123
1.124
1.124
2.70
1.124
1.124
1.125
1.125
1.125
1.126
1.126
1.126
1.127
1.127
2.80
1.127
1.127
1.128
1.128
1.128
1.129
1.129
1.129
1.129
1.130
2.90
1.130
1.130
1.130
1.131
1.131
1.131
1.131
1.132
1.132
1.132
9.00
1.132
1.133
1.133
1.133
1.133
1.134
1.136
1.136
1.134
1.135
3.10
1.135
1.135
1.135
1.136
1.136
1.136
1.136
1.136
1.137
1.137
48
WATER CONTENT 480 PERCENT
DG
1.70 1
L.076
1.077
1.078
1.078
1.079
1.080
1.080
1.081
1.082
1.082
1.80 1
1.083
1.084
1.084
1.085
1.085
1.086
1.087
1.087
1.088
1.088
1.90 1
1.089
1.089
1.090
1.091
1.091
1.092
1.092
1.0^3
1.093
1.094
2.00 ]
L.094
1.095
1.095
1.096
1.096
1.097
1.097
1.098
1.098
1.099
2.10 1
L.099
1.100
1.100
1.101
1. 101
1.102
1.102
1. 102
1.103
1.103
2.20 ]
1.104
1.104
1.105
1.105
1.106
1.106
1. 106
1.107
1.107
1.108
2.30 ]
L.108
1.108
1. 109
1.109
1. 110
1.110
I. 110
1.111
I. Ill
1.111
2.40 ]
L. 112
1.112
1.113
1.113
1.113
1.114
1.114
1.114
1.115
1.115
2.50 1
L. 115
1.116
1.116
1.116
1. 117
1.117
1. 117
1. 118
1.118
1.118
2.60 ]
L.11Q
1.119
1.119
1.120
1. 120
1.120
1.121
1.121
1.121
1.121
2.70 1
L.122
1.122
1.122
1.123
1. 123
1.123
1.124
1. 124
1.124
1.124
2.80 1
L.125
1.125
1.125
1.125
1.126
1.126
1.126
1.127
1.127
1.127
2.90 ]
1.127
1.128
1.128
1.128
1.128
1.129
1.129
1.129
1.129
1.130
3.00 1
L. 130
1.130
1.130
1.131
1. 131
1.131
1.131
1.132
1.132
1.132
3.10 ]
..132
1.132
1. 133
1. 133
I. 133
1. 133
1.134
1.134
1.134
1.134
WATER CONTENT 490 PERCENT
DG
1.70 ]
L.075
1.076
1.076
1.077
1.078
1.078
1.079
1.080
1.080
1.081
1.80 1
L.081
1.082
1.083
1.083
1.084
1.084
1.085
1.086
1.086
1.087
1.90 ]
1.087
1.038
1.088
1.089
1.089
1.090
1.091
1.091
1.092
1.092
2.00 1
L.093
1.093
1.094
1.094
1.095
1.095
1.096
1.096
1.096
1.097
2.10 ]
L.097
1.098
1.098
1.099
1.099
1.100
1.100
1. 101
1.101
1.101
2.20 1
L.102
1.102
1.103
1. 103
1. 104
1.104
1.104
I. 105
1.105
1.106
2.30 ]
L.106
1.106
1.107
1.107
1.107
1.108
1.108
1.109
1.109
1.109
2.40 ]
L. 110
1.110
1.110
1.111
1. Ill
1.111
1.1 12
1. 112
1.113
1.113
2.50 1
L.113
1.114
1. 114
1.114
1.115
1.115
1.115
1.116
1.116
1.116
2.60 ]
1.116
1.117
1.117
1.117
1. 118
1.118
1.118
1. 119
1.119
1.119
2.70 ]
1.119
1.120
1. 120
1.120
1.121
1.121
1.121
1.121
1.122
1.122
2.80 1
1.122
1.123
1.123
1.123
1.123
1.124
1.124
1.124
1.124
1.125
2.90 1
L.125
1.125
1.125
1.126
1.126
1.126
1.126
1.127
1.127
1.127
3.00 ]
L.127
1.128
1.128
1.128
1.128
1.129
1.129
1.129
1.129
1.129
3.10 ]
L. 130
1.130
1.130
1.130
1.131
1.131
1.131
1. 131
1.131
1.132
WATER CONTENT 500 PERCENT
no
1.70
1.074
1.074
1.075
1.076
1.076
1.077
1.078
1.078
1.079
1.0 79
1.80
1.080
1.081
1.081
1.082
1.082
1.083
1.083
1.084
1.085
1.085
1.90
1.086
1.086
1.037
1.087
1.088
1.088
1.089
1.089
1.090
1.090
2.00
1.091
1*091
1.092
1.092
1.093
1.093
1.094
1.094
1.095
1.095
2.10
1.096
1.096
1.097
1.097
1.097
1.098
1.098
1.099
1.099
1.100
2.20
1.100
1.100
1.101
I. 101
1. 102
1.102
1.102
1. 103
1.103
1.104
2.30
1.104
1.104
1.105
1.105
1. 106
1.106
1.106
1.107
1.107
1.107
2.40
1.108
1.108
1.108
1.109
1.109
1.109
1.110
1.110
1.110
1.111
2.50
1.111
1.111
1.112
1.112
1.112
1.113
1.113
1.113
1.114
1.114
2.60
1.114
1.115
1.115
1.115
1.115
1.116
1.116
1.116
1.117
1.117
2.70
1. 117
1.118
1.118
1.118
1.113
1.119
1.119
1. 119
1.119
1.120
2.80
1.120
1.120
1.121
1.121
1.121
1.121
1.122
1.122
1.122
1.122
2.90
1.123
1.123
1.123
1.123
1.124
1.124
1.124
1.124
1.125
1.125
3.00
1.125
1.125
1.125
1.126
1.126
1.126
1.126
1.127
1.127
1.127
3.10
1.127
1.127
1.128
1.128
1.128
1.128
1.129
1.129
1.129
1.129
49
WATER CONTENT 510 PERCENT
OG
1.70
1.072
1.073
1.074
1.074
1.075
1.076
1.076
1.077
1.077
1.078
1.80
1.079
1.079
1.080
1.0 80
1.081
1.081
1.082
1.083
1.083
1.084
1.90
1.084
1.085
1.085
1.086
1.086
1.087
1.087
1.088
1.088
1.089
2.00
1.089
1.090
1.090
1.091
1.091
1.092
1.092
1.093
1.093
1.093
2.10
1.094
1.094
1.095
1.095
1.096
1.096
1.097
1.097
1.097
1.098
2.20
1.098
1.099
1.099
1.099
1.100
1.100
1.101
1.101
1.101
1.102
2.30
1.102
1.102
1.103
1.103
1.104
1.104
1.104
1.105
1.105
1.105
2.40
1.106
1.106
1.106
1.107
1.107
1.107
1.108
1.108
1.108
1.109
2.50
1. 109
1.109
1.110
1.110
1.110
1.111
1.111
1.111
1.112
1.112
2.60
1.112
1.113
1.113
1.113
1.113
1.114
1.114
1.114
1.115
1.115
2.70
1.115
1.115
1.116
1.116
1.116
1.116
1.117
1.117
1.117
1.118
2.80
1.118
1.118
1.118
1.119
1.119
1.119
1.119
1. 120
1.120
1.120
2.90
1.120
1.121
1.121
1.121
1.121
1.122
1.122
1.122
1.122
1.122
3.00
1.123
1.123
1.123
1.123
1.124
1.124
1.124
1.124
1.124
1.125
3.10
1.125
1.125
1.125
1.126
1.126
1.126
1.126
1.126
1.127
1.127
WATER CONTENT 520 PERCENT
OG
1.70
1.071
1.072
1.072
1.073
1.074
1.074
1.075
1.075
1.076
1.077
1.80
1.077
1.078
1.078
1.079
1.079
1.080
1.081
1.081
1.082
1.082
1.90
1.083
1.083
1.084
1.084
1.085
1.085
1.086
1.086
1.087
1.087
2.00
1.088
1.088
1.089
1.089
1.090
1.090
1.091
1.091
1.091
1.092
2.10
1.092
1.093
1.093
1.094
1.094
1.094
1.095
1.095
1.096
1.096
2.20
1.096
1.097
1.097
1.098
1.098
1.0Q8
1.099
1.099
1.100
1.100
2.30
1.100
1.101
1.101
1.101
1.102
1.102
1.102
1.103
1.103
1.104
2.40
1.104
1.104
1.105
1.105
1.105
1.106
1.106
1.106
1.107
1.107
2.50
1.107
1.107
1.10R
1.108
1.108
1.109
1.109
1. 109
1.110
1.110
2.60
1.110
1.110
1.111
1.111
1. Ill
1.112
1.112
1.112
1.112
1.113
2.70
1.113
1.113
1.114
1. 114
1.114
1.114
1.115
1.115
1.115
1.115
2.80
1.116
1.116
1.116
1.116
1.117
1.117
1.117
1.117
1.118
1.118
2.90
1.118
1.118
1.119
1.119
1.119
1.119
1.120
1.120
1.120
1.120
3.00
1.120
1.121
1.121
1.121
1.121
1.122
1.122
1.122
1.122
1.122
3.10
1.123
1.123
1.123
1.123
1.123
1.124
1.124
1.124
1.124
1.125
WATER CONTENT 530 PERCENT
OG
1.70
1.070
1.071
1.071
1.072
1.072
1.
,073
1.074
1.074
1.075
1 .075
1.80
1.076
1.076
1.077
1.078
1.078
1.
,079
1.0 79
1.080
1.080
1.081
1.90
1.081
1.082
1.082
1.083
1.083
1.
,084
1.084
1.085
1.085
1.086
2.00
1.086
1.087
1.08 7
1.088
1.088
1.
,088
1.089
1.089
1.090
1.090
2.10
1.091
1.091
1.092
1.092
1.092
1,
,093
1.093
1.094
1.094
1.094
2.20
1.095
1.095
1.096
1.096
1.096
1.
,097
1.097
1.097
1.098
1.098
2.30
1.099
1.099
1.09°
1.100
1. 100
1
.100
1.101
1. 101
1.101
1.102
2.40
1.102
1.102
1.103
1.103
1.103
1
,104
1.104
1.104
1.105
1.105
2.50
1.105
1.106
1.106
1.106
1.106
1.
,107
1.107
1.107
1.108
1.108
2.60
1.108
1.109
1.109
1.109
1.109
1.
,110
1.110
1.110
1.110
1.111
2.70
1.111
1.111
1.112
1.112
1.112
1.
,112
1.113
1.113
1.113
1.113
2.80
1.114
1.114
1.114
1.114
1.115
1
.115
1. 115
1. 115
1.116
1.116
2.90
1.116
1.116
1.117
1.117
1.117
1.
,117
1.117
1.118
1.118
1.118
3.00
1.118
1.119
1.119
1.119
1.119
1.
.119
1.120
1.120
1.120
1.120
3.10
1.120
1.121
1.121
1.121
1.121
1,
.122
1.122
1.122
1.122
1.122
50
WATER CONTENT 540 PERCENT
DG 0 1 2 3
1.70
1.069
1.069
1
,070
1
.071
1.071
1.
072
1.072
1.073
1.074
1.074
1.80
1.075
1.075
1
.076
1
.076
1.077
1,
077
1.078
1.078
1.079
1.079
1.90
1.080
1.08C
1,
,081
I
.081
1.082
1,
082
1.083
1.093
1.084
1.084
2.00
1.085
1.085
1
,086
1
,086
1.087
1.
.087
1.087
1.088
1.088
1.089
2.10
1.089
1.090
1
.090
1
.090
1.091
1 ,
.091
1.092
1.092
1.092
1.093
2.20
1.093
1.094
1,
,094
1,
.094
1.095
I.
095
1.095
1.096
1.096
1.097
2.30
1.097
1.097
1
.098
1
.098
1.098
I
.099
1.099
1.099
1.100
1.100
2.40
1.100
1.101
i
.101
1
.101
1.102
1
.102
1.102
1. 103
1.103
1.103
2.50
1. 103
1.104
I,
, 104
1,
.104
1.105
1<
,105
1.105
1. 106
1.106
1.106
2.60
1. 106
1.107
1
.107
1
.107
1.107
1
.108
1.108
1.108
1.109
1.109
2.70
1.109
1.109
1
.110
1
.110
1.110
1.
.110
1.111
1.111
1.111
1.111
2.80
I. 112
1.112
I,
.112
1<
. 112
1. 113
1,
,113
1.113
1.113
1.114
1.114
2.90
1. 114
1.114
1
.115
1
.115
L.115
1
.115
1.115
1.116
1.116
1.116
3.00
1.116
1.116
1
,117
1«
,117
1. 117
I,
,117
1.118
1.118
1.118
1.118
3.10
1.1 18
1.119
1
.119
1
.119
1.119
I
.119
1.120
1.120
1.120
1.120
WATER CONTENT 550 PERCENT
DG
1.70
1.068
1.068
1.069
1.069
1.070
1.-071
1.071
1.072
1.072
1.073
1.80
1.073
1.074
1.074
1.075
1.076
1.076
1.077
1.077
1.078
1.078
1.90
1.079
1.079
1.080
1.080
1.081
1.081
1.081
1.082
1.082
1.083
2.00
1.083
1.084
1.084
1.085
1.085
1.086
1.086
1.086
1.087
1.087
2.10
1.088
1.088
1.088
1.089
1.099
1.090
1.090
1.090
1.091
1.091
2.20
1.092
1.092
1.092
1.093
1.093
1.093
1.094
1.094
1.095
1.095
2.30
1.095
1.096
1.096
1.096
1.097
1.097
1.097
1.098
1.098
1.098
2.40
1.099
1.099
1.099
1.100
1.100
1.100
1.100
1.101
1.101
1.101
2.50
1.102
1.102
1.102
1.103
1.103
1.103
1.103
1. 104
1.104
1.104
2.60
1.105
1.105
1.105
1.105
1.106
1.106
1.106
1. 106
1.107
1.107
2.70
1.107
1.108
1.108
1.108
1.108
1.109
1.109
I. 109
1.109
1.110
2.80
1. 110
1. no
1. 110
I. 110
1. Ill
1.111
1.111
1.111
1.112
1.112
2.Q0
1. 112
1. 112
1. 113
1.113
1. 113
1.113
1. 113
1. 114
1.114
1.114
3.00
1.114
1.114
1. 115
1.115
1. 115
1.115
1.116
1.116
1.116
1.116
3.10
1.116
1.117
1.117
1. 117
1. 117
1.117
1.118
1. 118
1.118
1.118
WATER CONTENT 560 PERCENT
or,
1.70
1.067
1.067
1.068
1.068
1.069
1.069
1.070
1.071
1.071
1.072
1.80
1.072
1.073
1.07 3
1.074
1.074
1.075
1.075
1.076
1.076
1.077
1.90
1.077
1.078
1.C78
1.079
1.079
1.080
1.080
1.081
1.081
1.082
2.00
1.082
1.082
1.083
1.083
1.084
1.084
1.085
1.095
1.085
1.086
2.10
1.086
1.087
1.087
1.087
1.088
1.08 8
1.089
1.089
1.089
1.090
2.20
1.090
1.090
1.091
1.091
1.0Q2
1.092
1.092
1.093
1.093
1.093
2.30
1.094
1.094
1.094
1.095
1.095
1.095
1.096
1.096
1.096
1.097
2.40
1.097
1.097
1.098
1.098
1.098
1.099
1.099
1.099
1.099
1.100
2.50
1. 100
1. 100
1.101
1.101
1.101
I. 101
1.102
1. 102
1.102
1.103
2.60
1. 103
1.103
I. 103
1. 104
1. 104
1.104
1.104
1.105
1.105
1.105
2.70
1. 105
1.106
I. 106
1.106
1. 106
1.107
1. 107
1. 107
1.107
1.108
2.80
1. 108
1.108
1.108
1.109
1.109
1.109
1.109
1.110
1.110
1.110
2.90
1. 110
1.110
I. Ill
I. Ill
1. Ill
1.111
1.112
1.112
1.112
1.112
3.00
1.112
1.113
1.113
1.113
1.113
1.113
1.114
1.114
1.114
1.114
3.10
1.114
1.115
1.115
1.115
1.115
1.115
1.116
1.116
1.116
1.116
51
WATER CONTENT 570 PERCENT
DG 0 I 2 3
1.70
1.065
1.066
1.067
1.067
1.068
1.068
1.069
1.069
1.070
1.071
1.80
1.071
1.072
1.072
1.073
1.073
1.074
1.074
1.075
1.075
1.076
1.90
1.076
1.077
1.077
1.077
1.078
1.078
1.0 79
1.079
1.080
1.080
2.00
1.081
1.081
1.082
1.082
1.082
1.083
1.083
1.084
1.084
1.084
2.10
1.085
1.085
1.086
1.086
1.086
1.087
1.087
1.08 8
1.088
1 .088
2.20
1.089
1.089
1.089
1.090
1.090
1.090
1.091
1.091
1.091
1.092
2.30
1.092
1.092
1.093
1.093
1.093
1.094
1.094
1.094
1.095
1.095
2.40
1.095
1.096
1.096
1.096
1.097
1.097
1.097
1.097
1.098
1.098
2.50
1.098
1.099
1.099
1.099
1.099
1.100
1. 100
1.100
1.101
1.101
2.60
1.101
1.101
1.102
1.102
I. 102
1.102
1.103
1.103
1.103
1.103
2.70
1.104
1.104
1.104
1.104
1.105
1.105
1.105
1.105
1.106
1.106
2.80
1.106
1.106
1.107
1.107
1.107
1.107
1.108
I. 108
1.108
1.108
2.90
1.108
1.109
1. 109
1. 109
1.109
1.109
1.110
1.110
1.110
1.110
3.00
1.110
1. Ill
1.111
1. Ill
1.111
1.112
1. 112
1.112
1.112
1.112
3.10
1. 112
1.113
1.113
1.113
1.113
1.113
1.114
1. 114
1.114
1.114
WATER CONTENT 580 PERCENT
DG C 1 2 3
1.70
1.064
1.065
1.066
1.066
1.067
1.067
1.068
1.068
1.069
1.069
1.80
1.070
1.070
1.071
1.071
1.072
1.072
1.073
1.073
1.074
1.074
1.90
1.075
1.075
1.076
1.076
1.077
1.077
1.078
1.078
1.078
1.079
2.00
1.079
1.080
1.080
1.081
1.081
1.081
1.082
1.082
1.083
1.083
2.10
1.083
1.084
1.084
1.085
1.085
1.085
1.086
1.086
1.086
1.087
2.20
1.087
1.088
1.088
1.088
1.089
1.089
1.089
1.090
1.090
1.090
2.30
1.091
1.091
1.091
1.092
1.092
1.0^2
1.093
1.093
1.0°3
1.094
2.40
1.094
1.094
1.094
1.095
1.095
1.0°5
1.096
1.096
1.096
1.096
2.50
1.097
1.097
1.097
1.098
1.098
1.098
1.098
1.099
1.099
1.099
2.60
1.100
1.100
1.100
1.100
I. 101
1.101
1.101
1. 101
1.102
1.102
2.70
1.102
1.102
1.103
1.103
1.103
1.103
1.103
1.104
1.104
1.104
2.80
1.104
1.105
1.105
1.105
1.105
1.106
1.106
1.106
1.106
1.106
2.90
1.107
1.107
1.107
1. 107
1.107
1.108
1. 108
1. 108
1.108
1.108
3.00
1.109
1.109
1.10Q
1.109
1. 109
1.110
1. 110
1. no
1.110
1.110
3.10
1.111
1.111
1.111
1.111
1.111
1.112
1.112
1.112
1.112
1.112
WATER CONTENT 590 PERCENT
DG
1.70
1.063
1.064
1.065
1.065
1.066
1.066
1.067
1.067
1.068
1.068
1.80
1.069
1.069
1.070
1.070
1.071
1.071
1.072
1.072
1.073
1.073
1.90
1.074
1.074
1.075
1.075
1.076
1.076
1.076
1.077
1.077
1.078
2.00
1.078
1.079
1.079
1.079
1.080
1.080
1.081
1.081
1.081
1.082
2.10
1.082
1.083
1.083
1.083
1.084
1.084
1.084
1.085
1.085
1.085
2.20
1.086
1.086
1.087
1.087
1.087*
1.088
1.088
1.088
1.089
1.089
2.30
1.089
1.090
1.090
1.090
1.091
1.091
1.091
1.091
1.0Q2
1.092
2.40
1.092
1.093
1.093
1.093
1.094
1.094
1.094
1.094
1.095
1.095
2.50
1.095
1.096
1.096
1.096
1.096
1.097
1.097
1.097
1.097
1.098
2.60
1.098
1.098
1.098
1.099
1.099
1.099
1.099
1.100
1.100
1.100
2.70
1.100
1. 101
1. 101
1.101
1. 101
1.102
1. 102
1. 102
1. 102
1.103
2.80
1.103
1. 103
1.103
1. 103
1. 104
1.104
1.104
1.104
1.104
1.105
2.90
1.105
1.105
1.105
1.106
1.106
1.106
1.106
1.106
1.107
1.107
3.00
1.107
1.107
1.107
1.108
1.108
1.108
1.108
1.108
1.108
1.109
3.10
1.109
1.109
1.109
1.109
I. 110
1.110
1.110
1.110
1.110
1.110
52
WATER CONTENT 600 PERCENT
DG
1.70
1.063
1.063
1.064
1.064
1.065
1.065
1.066
1.066
1.067
1.067
1.80
1.068
1.068
1.069
1.069
1.070
1.070
1.071
1.071
1.072
1.072
1.90
1.073
1.073
1.073
1.074
1.074
1.075
1.075
1.076
1.076
1.077
2.00
1.077
1.077
1.C78
1.078
1.079
1.079
1.079
1.080
1.080
1.081
2.10
1.081
1.081
1.082
1.082
1.082
1.083
1.083
1.083
1.084
1.084
2.20
1.085
1.085
1.085
1.086
1.086
1.086
1.087
1.087
1.087
1.088
2.30
1.088
1.088
1.088
1.089
1.089
1.089
1.090
1.090
1.090
1.091
2.40
1.091
1.091
1.091
1.092
1.092
1.092
1.093
1.093
1.093
1.093
2.50
1.094
1.094
1.094
1.095
1.095
1.095
1.095
1.096
1.096
1.096
2.60
1.096
1.097
1.097
1.097
1.097
1.098
1.098
1.098
1.098
1.099
2.70
1 .099
1.099
1.099
1.100
1.100
1.100
1.100
I. 100
1.101
1.101
2.80
1.101
1.101
1.102
1.102
1.102
1.102
1.102
1.103
1.103
1.103
2.90
1.103
1.103
1. 104
1.104
1. 104
1.104
1.104
1.105
1.105
1.105
3.00
1.105
1.105
1.106
1.106
1. 106
1.106
1. 106
1. 107
1.107
1.107
3.10
1.107
1.107
1.108
1.108
1.108
1.108
1.108
1.108
1.109
1.109
WATER CONTENT 610 PERCENT
OG
1.70
1.062
1.062
1.063
1.063
1.064
1.064
1.065
1.065
1.066
1.066
1.80
1.067
1.067
1.068
1.068
1.069
1.069
1.070
1.070
1.071
1.071
1.90
1.071
1.072
1.072
1.073
1.073
1.074
1.074
1.075
1.075
1.075
2.00
1.076
1.076
1.07 7
1.077
1.077
1.078
1.078
1.079
1.079
1.079
2.10
1.080
1.080
1.08C
1.081
1.081
1.081
1.082
1.082
1.083
1.083
2.20
1.083
1.084
1.084
1.084
1.085
1.085
1.085
1.086
1.086
1.086
2.30
1.086
1.087
1.08 7
1.087
1.088
1.088
1.088
1.089
1.089
1.089
2.40
1.090
1.090
1.090
1.090
1.091
1.091
1.091
1.091
1.092
1.092
2.50
1.092
1.093
1.093
1.093
1.093
1.094
1.094
1.094
1.094
1.095
2.60
1.095
1.0Q5
1.095
1.096
1.096
1.096
1.096
1.097
1.097
1.097
2.70
1.097
1.098
1.098
1.098
1.098
1.098
1.099
1.099
1.099
1.099
2.80
1.100
1.100
1.100
1.100
1. 100
1.101
1.101
1.101
1.101
1.101
2.90
1.102
1.102
1.102
1.102
1.102
1.103
1. 103
1.103
1.103
1.103
3.00
1.104
1.104
1.104
1.104
1.104
1.105
1.105
1.105
1.105
1.105
3.10
1.105
1.106
1. 106
1.106
1.106
1.106
1.107
1. 107
1.107
1.107
WATER CONTENT 620 PERCENT
DG
1.70
1.061
1.061
1.062
1.062
1.063
1.063
1.064
1.064
1.065
1.065
1.80
1.066
1.066
1.067
1.067
1.068
1.068
1.069
1.069
1.070
1.070
1.90
1.070
1.071
1.071
1.072
1.072
1.073
1.073
1.073
1.074
1.074
2.00
1.075
1.075
1.075
1.076
1.076
1.077
1.077
1.077
1.078
1.078
2.10
1.078
1.079
1.079
1.080
1.080
1.080
1.081
1.081
1.081
1.082
2.20
1.082
1.082
1.083
1.083
1.083
1.084
1.084
1.034
1.085
1.085
2.30
1.085
1.085
1.086
1.0 86
1.086
1.087
1.087
1.087
1.088
1.088
2.40
1.088
1.088
1.089
1.089
1.089
1.090
1.090
1.090
1.090
1.091
2.50
1.091
1.091
1.091
1.092
1.092
1.092
1.092
1.093
1.093
1.093
2.60
1.093
1.094
1.094
1.094
1.094
1.095
1.095
1.095
1.095
1.096
2.70
1.0°6
1.0Q6
1.096
1.097
1.097
1.097
1.097
1.097
1.098
1.098
2.80
1.098
1.098
1.098
1.099
1.099
1.099
1.099
1.099
1.100
1.100
2.90
1.100
1.100
1.101
I. 101
1.101
1.101
1.101
1.101
1.102
1.102
3.00
1.102
1.102
1.102
1.103
1.103
1.103
1.103
1.103
1.104
1.104
3.10
1.104
1.104
1.104
1.104
1.105
1.105
1.105
1.105
1.105
1.105
53
WATER CONTENT 630 PERCENT
DG 0 1 2 :
1.70
1.060
1.060
1.061
1.061
1.062
1.062
1.063
1.063
1.064
1.064
1.80
1.065
1.065
1.066
1.066
1.067
1.067
1.068
1.068
1.069
1.069
1.90
1.069
1.070
1.070
1.071
1.071
1.072
1.072
1.072
1.073
1.073
2.00
1.074
1.074
1.074
1.075
1.075
1.075
1.076
1.076
1.077
1.077
2.10
1.077
1.078
1.078
1.078
1.079
1.079
1.079
1.080
1.080
1.080
2.20
1.081
1.081
1.081
1.082
1.082
1.082
1.083
1.083
1.083
1.084
2.30
1.0F4
1.084
1.085
1.085
1.085
1.085
1.086
1.086
1.086
1.087
2.40
1.087
1.087
1.087
1.088
1.088
1.088
1.088
1.089
1.089
1.089
2.50
1.090
1.090
1.090
1.090
1.091
1.0^1
1.091
1.091
1.092
1.092
2.60
1.092
1.092
1.093
1.093
1.093
1.093
1.093
1.094
1.094
1.094
2.70
1.094
1.095
1.095
1.095
1.095
1.095
1.096
1.096
1.096
1.096
2.80
1.097
1.097
1.097
1.097
1.097
1.098
1.098
1.098
1.098
1.098
2.90
1.0<*9
1.099
1.099
1.099
1.099
1.100
1.100
1. 100
1.100
1.100
3.00
1.101
1.101
1.101
I. 101
1.101
1.101
1.102
1.102
1.102
1.102
3.10
1.102
1.102
1.103
1. 103
1.103
1.103
1.103
1. 103
1.104
1.104
WATER CONTENT 640 PERCENT
DG 0123456789
1.70 1.059 1.059 1.060 1.060 1.061 1.061 1.062 1.062 1.063 1.063
1.80 1.064 1.064 1.065 1.065 1.066 1.066 1.067 1.067 1.068 1.068
1.90 1.068 1.069 1.069 1.070 1.070 1.070 1.071 1.071 1.072 1.072
2.00 1.072 1.073 1.073 1.074 1.074 1.074 1.075 1.075 1.075 1.076
2.10 1.076 1.077 1.077 1.077 1.078 1.078 1.078 1.079 1.079 1.079
2.20 1.080 1.080 1.080 1.081 1.081 1.081 1.081 1.082 1.092 1.082
2.30 1.083 1.083 1.083 1.084 1.084 1.084 1.084 1.085 1.085 1.085
2.40 1.086 1.086 1.086 1.086 1.087 1.087 1.087 1.087 1.088 1.088
2.50 1.088 1.088 1.089 1.089 1 . 08« 1.089 1.090 1.090 1.090 1.090
2.60 1.091 1.091 1.091 1.091 1.092 1.092 1.092 1.092 1.093 1.093
2.70 1.093 1.093 1.093 1.094 1.094 1.094 1.094 1.095 1.095 1.095
2.80 1.095 1.095 1.096 1.096 1.096 1.096 1.096 1.097 1.097 1.097
2.90 1.097 1.097 K098 1.098 1.098 1.098 1.098 1.098 1.099 1.099
3.00 1.099 1.099 1.099 1.100 1.100 1.100 1.100 1.100 1.100 1.101
3.10 1.101 1.101 1.101 1.101 1.101 1.102 1.102 1.102 1.102 1.102
WATER CONTENT 650 PERCENT
DG 0123456789
1.70 1.058 1.059 1.059 1.060 1.060 1.061 1.061 1.062 1.062 1.063
1.80 1.063 1.063 1.064 1.064 1.065 1.065 1.066 1.066 1.067 1.067
1.90 1.067 1.068 1.068 1.069 1.069 1.069 1.070 1.070 1.071 1.071
2.00 1.071 1.072 1.072 1.073 1.073 1.073 1.074 1.074 1.074 1.075
2.10 1.075 1.075 1.076 1.076 1.076 1.077 1.077 1.077 1.078 1.078
2.20 1.078 1.079 1.079 1.079 1.080 1.080 1.080 1.081 1.081 1.081
2.30 1.082 1.082 1.082 1.082 1.083 1.083 1.083 1.084 1.084 1.084
2.40 1.084 1.085 1.085 1.065 i.085 1.086 1.086 1.086 1.086 1.087
2.50 1.087 1.087 1.087 I.Q08 1.088 1.088 1.088 1.089 1.089 1.089
2.60 1.089 1.090 1.09C I. "90 1.090 1.091 1.091 1.091 1.091 1.091
2.70 1.092 1.092 1.09T ».~S92 \.0°^ 1.0^3 1.093 ?.0Q3 !..0°3 1.094
2.80 1.094 1.094 1.09' -.194 1 . 0°5 1 . ooc \.095 1.095 1.095 1.096
2.90 1.096 1.096 1.0*6 '.0°6 1.^96 1.097 1.097 1.097 1.097 1.097
3.00 1.098 1.098 1.098 !.*•*•• 1.098 1.098 1.099 1.099 1.099 1.099
3.10 1.099 1.099 1.100 1.100 l.lOO 1.100 1.100 1.100 1.101 1 .101
54
WATER CONTENT 660 PERCENT
OG
1.70
1.057
1.058
1.058
1.059
1.059
1.060
1.060
1.061
1.061
1.062
1.80
1.062
1.063
1.063
1.063
1.064
1.064
1.065
1.065
1.066
1.066
1 .90
1.066
1.067
1.067
1.068
1.068
1.068
1.069
1.069
1.070
1.070
2.00
1.070
1.071
1.071
1.072
1.072
1.072
1.073
1.073
1.073
1.074
2.10
1.074
1.074
1.075
1.075
1.075
1.076
1.076
1.076
1.077
1.077
2.20
1.077
1.078
1.078
1.078
1.079
1.079
1.079
1.079
1.080
1.080
2.30
1.080
1.081
1.081
1.081
1.081
1.082
1.082
1.082
1.083
1.083
2.40
1.083
1.083
1.0*4
1.0 84
1.084
1.084
1.085
1.085
1.085
1.085
2.50
1.086
1.086
1.086
1.086
1.087
1.087
1.087
1.087
1.088
1.088
2.60
1.088
1.088
1.089
1.089
1.089
1.089
1.089
1.090
1.090
1.090
2.70
1.09C
1.091
1.091
1.091
1.091
1.091
1.092
1.092
1.0^2
1.092
2.80
1.092
1.093
1.093
1.093
1.093
1.093
1.094
1.094
1.094
1.094
2.90
1.0Q4
1.095
1.095
1.095
1.095
1.095
1.095
1.096
1.096
1.096
3.00
1.096
1.096
1.097
1.097
1.097
1.097
1.097
1.097
1.098
1.098
3.10
1.098
1.098
1.09 8
1.098
1.099
1.099
1.099
1.099
1.099
1.099
WATER CONTENT 670 PERCENT
n>G
1.70
1.056
1.057
1.057
1.058
1.058
1.059
1.059
1.060
1.060
1.061
1.80
1.061
1.062
1.062
1.063
1.063
1.063
1.064
1.064
1.065
1.065
1.90
1.066
1.066
1.066
1.067
1.067
1.068
1.068
1.068
1.069
1.069
2.00
1.069
1.070
1.070
1.071
1.071
1.071
1.072
1.072
1.072
1.073
2.10
1.073
1.073
1.074
1.074
1.074
1.075
1.075
1.075
1.076
1.076
2.20
1.076
1.077
1.077
1.077
1.077
1.078
1.078
1.078
1.079
1.079
2.30
1.079
1.080
1.080
1.080
1.080
1.081
1.081
1.081
1.081
1.082
2.40
1.082
1.082
1.082
1.083
1.083
1.083
1.084
1.084
1.084
1.084
2.50
1.085
1.035
1.085
1.085
1.085
1.086
1.086
1.036
1.036
1.087
2.60
1.087
1.087
1.087
1.088
1.088
1.088
1.088
1.088
1.089
1.089
2.70
1.089
1.089
1.089
1.090
1.090
1.090
1.090
1.090
1.091
1.091
2.80
1.091
1.091
1.091
1.092
1.092
1.092
1.092
1.092
I.O03
1.093
2.90
1.093
1.093
1.093
1.094
1.094
1.094
1.094
1.094
1.094
1.095
3.00
1.095
1.095
1.095
1.095
1.095
1.096
1.096
1.096
1.096
1.096
3.10
1.096
1.097
1.097
1.097
1.097
1.097
1.0O7
1.098
1.098
1.098
WATER CONTENT 680 PERCENT
OG
1.70
1.056
1.056
1.057
1.057
1.053
1.058
1.059
1.059
1.060
1.060
1.80
1.060
1.061
1.061
1.062
1.062
1.063
1.063
1.063
1.064
1.064
1.90
1.065
1.065
1.065
1.066
1.066
1.067
1.067
1.067
1.068
1.068
2.00
1.068
1.069
1.069
1.070
1.070
1.070
1.071
1.071
1.071
1.072
2.10
1.072
1.072
1.073
1.073
1.073
1.074
1.074
1.074
1.075
1.075
2.20
1.075
1.075
1.076
1.076
1.076
1.077
1.077
1.077
1.078
1.078
2.30
1.078
1.073
1.079
1 .079
1.079
1.080
1.080
1.080
1.080
1.081
2.40
1.081
1.081
1.081
1.082
1.082
1.082
1.082
1.083
1.083
1.083
2.50
1.083
1.034
1.084
1.084
1.084
1.085
1.085
1.085
1.085
1.085
2.60
1.086
1.036
1.086
1.086
1.087
1.087
1.087
1.087
1.08 7
1.088
2.70
1.088
1.038
1.088
1.088
1.089
1.089
1.089
1.089
1.089
1.090
2.R0
1.090
1.090
l.OOO
1.090
1.091
1.091
1.091
1.001
1.091
1.092
2.90
1.092
1.092
1.092
1.092
1.092
1.093
1.093
1.093
1.093
1.093
3.00
1.093
1.094
1.094
1.094
1.094
1.094
1.094
1.095
1.095
1.095
3.10
1.0O5
1.095
1.095
1.096
1.096
1.0O6
1.0O6
1.096
1.096
1.097
55
WATER CONTENT 690 PERCENT
DG 0123456789
1.70 1.055 1.055 1.056 1.056 1.057 1.057 1.058 1.058 1.059 1.059
t.80 1.060 1.0*0 1.060 1.061 1.061 1.062 1.062 1.063 1.063 1.063
1.90 1.064 1.064 1.065 1.065 1.065 1.066 1.066 1.066 1.067 1.067
2.00 1.068 1.068 1.068 1.069 1.069 1.069 1.070 1.070 1.070 1.071
2.10 1.071 1.071 1.072 1.072 1.072 1.073 1.073 1.073 1.074 1.074
2.20 1.074 1.074 1.075 1.075 1.075 1.076 1.076 1.076 1.076 1.077
2.30 1.077 1.077 1.078 1.078 1.078 1.078 1.079 1.079 1.079 1.079
2.40 1.080 1.030 1.080 1.080 1.081 1.081 1.081 1.081 1.082 1.082
2.50 1-082 1.032 1.083 1.083 1.083 1.083 1.084 1.084 1.084 1.084
2.60 1.084 1.085 1.085 1.085 1.035 1.086 1.086 1.086 1.086 1.086
2.70 1.087 1.037 1.087 1.087 1.087 1.088 1.088 1.088 1.088 1.088
2.80 1.089 1.039 1.089 1.089 1.089 1.090 1.090 1.090 1.090 1.090
2.90 1.090 1.0°1 1.091 1.091 1.091 1.091 1.091 1.092 1.092 1.092
3.00 1.092 1.092 1.092 1.0°3 1.093 1.093 1.093 1.093 1.093 1.094
3.10 1.094 1.094 1.004 1.094 1.094 1.095 1.095 1.095 1.095 1.095
WATER CONTENT 700 PERCENT
OG 0123456789
1.70
1.80
1.90
2.00
2.10
2.20
2.30
2.40
2.50
2.60
2.70
2.30
2.°0
3.00
3.10 1.093 1.093 1.093 1.093 1.093 1.093 1.093 1.094 1.094 1.094
1.054
1.055
1.055
1.056
1.056
1.057
1.057
1.058
1.058
1.058
1.059
1.059
1.060
1.060
1.061
1.061
1.061
1.062
1.062
1.063
1.063
1.063
1.064
1.064
1.064
1.065
1.065
1.066
1.066
1.066
1.067
1.067
1.067
1.068
1.068
1.068
1.069
1.069
1.069
1.070
1.07C
1.070
1.071
1.071
1.071
1.072
1.0 72
1.072
1.073
1.073
1.073
1.073
1.074
1.074
1.074
1.075
1.075
1.075
1.075
1.076
1.076
1.076
1.077
1.077
1 .077
1.077
1.078
1.078
1.078
1.078
1.079
1.079
1.079
1.079
1.080
1.080
1.080
1.080
1.081
1.081
1.081
1.081
1.082
1.082
1.082
1.082
1.082
1.083
1.083
1.083
1.083
1.084
1.084
1.084
1.084
1.034
1.085
1.085
1.085
1.085
1.085
1.086
1.086
1.086
1.086
1.086
1.087
1.087
1.087
1.037
1.087
1.088
1.08 8
1.088
1.038
1.088
1.088
1.089
1.089
1.039
1.089
1.089
1.090
1.090
1.090
1.090
1.090
1.090
1.091
1.091
1.091
1.091
l.OOl
1.091
1.092
1.092
1.092
1.092
1.092
1.092
56
46
Reprinted from Marine Technology Society Journal 5_,
No. 5, 33.
NORTH ATLANTIC - GEOLOGY AND CONTINENTAL
DRIFT (A Symposium)
Edited by Marshall Kay
Published by AAPG Press, Tulsa, Okla. 1081 pp; $32.00.
Reviewed by: Robert S. Dietz, National Oceanic &
Atmospheric Adm., Atlantic Oceanographic and Meteo-
rological Lab. 901 S. Miami Ave., Miami, Fla. 33130
This weighty tome is a collection of 66 papers which
examines in depth the stratigraphic and structural evidence
that the far north Atlantic Ocean has been opened by
continental drift. The papers were originally presented in
August 1967 at the Gander Conference on "Stratigraphy
and Structure Bearing on the Origin of the North Atlantic
Ocean." Emphasis is placed upon paleontologic and
orogenic-style comparisons between Appalachian foldbelt
and presumably formerly contiguous foldbelts in Ireland
and Great Britain but which now strike into the Atlantic
discordantly. The book contains little information bearing
upon marine geology except for a review paper by J.E. Nafe
and C.L. Drake on the "Floor of the North Atlantic — A
Summary of Geophysical Data."
The volume contains the most comprehensive strati-
graphic and structural comparison between Newfoundland
and the British Isles ever published. It is divided into the
following principle topics: — (1) introductory papers, (2)
the southeastern border of the orogenic belt, (3) the central
orogenic belt, (4) the northwestern border of the orogenic
belt, (5) late orogenic stratigraphy and structure, (6) arctic
regions, and (7) interpretations of drift.
W.H. Harland's proposal for the opening of the far
north Atlantic based mainly on studies in Spitzbergen is
especially interesting. He advocates an ancestral Atlantic
Ocean which closed in the Precambrian or early Paleozoic.
The present blocking out of Greenland and the separation
of Europe from North America then began in late
Cretaceous. His arguments are supported by a series of
palinspastic maps.
The scholarly treatise replete with its massive array of
references is not easy reading, but it will interest the serious
students of land geology and is an excellent source book
which any good technical library should hold. With but few
exceptions the authors appear to accept the probable
validity of continental drift controlled by the process of sea
floor spreading.
47
Reprinted from Meteoritics 6, No. 4, 258-259 .
SHATTER CONES (SHOCK FRACTURES) IN ASTROBLEMES
Robert S. Dietz
NOAA, Atlantic Oceanographic and Meteorological Laboratories,
Miami, Florida 33130
Shatter cones, conical shock fractures, are known from more than a
score of crypotoexplosion structures, presumed to be astroblemes (ancient
meteorite or comet-head impact scars) around the world. These structures
include: Steinheim Basin and Ries Basin in Germany; Vredefort Ring in
South Africa; Gosses Bluff in Australia; Rochechouart in France; Kentland,
Wells Creek Basin, Crooked Creek, Serpent Mound, Flynn Creek, Sierra
Madera, Decaturville, and Middlesboro in the U.S.A., and at Sudbury,
Manicouagan, Nicholson Lake, Carswell Lake, Clearwater Lake West, Lake
Mistastin, and Charlevoix in Canada. In addition, they occur at Kaalijarv and
Lake Bosumtwi, modern meteorite craters. In addition to indicating shock
overloading in excess of that which can be created by any endogenic
explosion (e.g., cryptovolcanism), they permit vectoring of the force field
since their formation precedes disruption and the cones point toward the
oncoming shock wave. At several locations (Vredefort, Sudbury, Decaturville,
Wells Creek, Sierra Madera, Kentland, Gosses Bluff and Charlevoix) they
indicate that the explosion focus (ground zero) was either from above and/or
inward toward the center of the structure. At Charlevoix, the finding of
shatter cones by Rondot led to the discovery of the cryptoexplosion
structure. Shatter cones are an especially useful criterion of shock in
carbonate terranes, where shock metamorphic effects commonly are absent.
Recently, Alexander and Hawk have used shatter cone distribution at Wells
Creek Basin and Vredefort to compute the total energy of impact. Other
aspects of the shatter cone criterion for astroblemes are reviewed. There
remains little doubt but that, when shatter cones can be identified with
certainty, they are a valid and definitive criterion for an astrobleme.
258
Reprinted from Meteoritics 6, No. 4, 259-260.
SUDBURY ASTROBLEME: A REVIEW
Robert S. Dietz
NOAA, Atlantic Oceanographic and Meteorological Laboratories
Miami, Florida 33130
The Sudbury Basin in Ontario, Canada, is a now widely accepted
astrobleme, or meteorite impact scar, created about 1700 m.y. ago. Evidence
is provided by shatter coning, shock metamorphic effects, the Sudbury
breccia, "geologic overkill," etc. A thick deposit of impact microbreecia
(Onaping suevite) also was laid down in the crater. This astrobleme is of
unusual interest not only because of its economic importance (dominating
the world's nickel production), but also because extensive magmatism was
associated with the impact, creating an extrusive lopolith. The origin of the
so-called sublayer is now of critical importance in understanding the Sudbury
event. The sublayer, composed of "quartz diorite," breccia and sulfides,
forms a liner to the crater and invades the surrounding country rock as a
spokelike injection extending 10 km or more. The sublayer appears to be the
product of splash emplacement, a mixture of bolide and target rock injected
just prior to the extrusion of the lopolith. It seems possible that the sulfide
ores may be, at least in part, cosmogenic, derived from the substance of the
bolide. The history of the Sudbury Basin as an astrobleme is also reviewed.
The significance of shatter coning as evidence of shock, for reconstructing the
force vector field, and for unraveling the timing of the event is also
emphasized.
259
Reprinted from American Scientist 59_, No. 5, 627
49
MAXWELL, Arthur E., ed. The Sea:
Ideas and Observations on Progress in the
Study of the Seas. Vol. 4: New Concepts of
Sea Floor Evolution. Part 1 : 791 pp. Part
2: 664 pp. Wiley-Interscience, 1970.
$32.50 each.
This weighty and comprehensive volume
of invited papers by 77 authors covering
recent advances in our understanding of
the ocean floor marks a major milestone.
Its contents emphasize that a modern
scientific revolution has been wrought by
the new model of the earth based on plate
tectonics and sea floor spreading. The
ocean basins are young; they are born,
expand, contract, and die while the con-
tinents live on. The authors have been
carefully chosen for their eminence, and
the contents reveal that marine geology
and geophysics is dominated by American
scientists. Some papers jointly offered by
American and Russian authors indicate
a new level of workable collaboration be-
tween the East and the West.
Volume 4 is subdivided into two tomes:
the first, which concerns general observa-
tions, contains 20 articles that treat the
ocean floor worldwide on a discipline
basis. Included are papers on marine
geodesy; acidic, basic, and ultramafic
rocks of the ocean floor; gravity; magnetic
reversal anomalies; seismic reflection and
refraction; paleomagnetism; seamount
magnetism; gravity; heat flow; earth-
quakes and tectonics; pre-Quaternary
microfossil distribution ; etc.
The second tome describes the ocean
floor regionally. Among its 14 articles are
5 on the Pacific floor, while the others
cover most of the other oceans of the world.
Two thorough papers on the structure of
the little-known Indian Ocean and the
Mediterranean basin are especially wel-
come. A final part, which offers new con-
cepts, contains a paper on sea floor spread-
ing, by Fred Vine and the late Harry Hess,
and one by J. Tuzo Wilson on transform
faults.
Shortcomings are few in this excellent
volume, but some may be noted. (1) In
these times of voluminous literature, ab-
stracts seem essential, but there are none.
(2) The lack of any treatment of the Atlan-
tic basin leaves a gap in an otherwise
balanced regional coverage of the ocean
floors of the world. (3) The high price
places the volume beyond the grasp of
most individual researchers, let alone the
impecunious student. Thus, this series will
serve only as a library source book and
not as a replacement for the classic textbook
The Oceans, arr avowed original intention.
(4) The long delay between receipt of
manuscripts (2-3 years) and the availabil-
ity of the book means that the papers are
somewhat out of date. (The volume is
dated 1970, but actually was not available
until spring 1971.) Fortunately, the papers
were prepared after the 1967 sweeping
conversion of marine geologists to sea
floor spreading and plate tectonics. There
is, however, no impact of the JOIDES
(deep-sea drilling program) results. (5)
Typographical errors are rather numer-
ous.— Robert S. Dietz, Environmental Science
Services, U. S. Department of Commerce
1971 September-October 627
50
Reprinted from Sea Frontiers 17, No. 4, 204-212
Those Shifty Continents
By Robert S. Dietz
NOAA, Atlantic Oceanographic and Meteorological Laboratories
Miami, Florida
During the past decade, the con-
cept of continental drift has
undergone a remarkable transforma-
tion from an outrageous hypothesis,
through a period of nagging reapprais-
al and finally to verification. The reality
of drift is no longer questioned by the
large majority of earth scientists but
many problems remain unresolved.
Most importantly, when did this drift
begin and where were the continents
in the beginning? In short, we need to
understand the pattern of the conti-
nental breakup and dispersion in space
and time.
In modern context, continental
drift is simply a necessary consequence
of the even grander theory of plate
tectonics. The term tectonics refers to
the slow geological motions of the
earth crust (up, down or sideways) and
also to compressional folding and ex-
tensional rifting. This concept holds
that the earth's outer crust is divided
into about nine major rigid plates, or
spherical caps, separated by seams
something like the segments on a tur-
tle's carapace. These 60-mile-thick
plates are in slow but inexorable motion
and they interact along their bound-
aries, causing earthquakes among
other things, in the process. The 22-
mile-thick continents are granitic
"plateaus" embedded within the plate.
With the exception of the Pacific plate,
each plate contains a continent, if India
is included as a subcontinent. As the
plates move so must the continents
that ride piggyback upon them.
A Humpty-Dumpty Problem
We now believe that about 200 mil-
lion years ago the continents were all
joined together, forming the super-
continent of Pangaea, meaning "all
earth." Although the solution is not
straightforward, we can in principle
solve this jigsaw reconstruction or
"Humpty-Dumpty" problem, and fit
all of the continents back together
again. We cannot do this for the plates
since they change their size and shape.
204
The continental drift concept is not new. Reproduced here in lithograph is the first
depiction of the drift opening of the Atlantic Ocean in The Creation and its Mysteries
Explained: A Treatise. ..which Explains the Origin of America and its Primitive In-
habitants, by A. Snider, published in Paris in 1859. Snider supposed that the Atlantic
Ocean did not exist prior to the biblical flood. During the Deluge great volcanoes
erupted which split off the Americas along with the island of Atlantis both of which
drifted westward. Snider argued, by a series of farfetched assumptions, that the
Americas somehow escaped the Deluge and were not covered with water. The ante-
diluvian population therefore escaped the catastrophe and eventually evolved into the
indigenes found by the European explorers. Snider concluded that "L'Amerique est
reellement I'ancienne Atlantide de I'epoque antediluvienne," or "America is really
the ancient Atlantis of antediluvian times."
They can grow either larger or smaller
by adding new crust or resorbing old
crust. The growth occurs at the so-
called mid-ocean ridges, where the
plates are pulled apart and new lava
from the earth's mantle rises into the
crack. The process may be likened to
the freezing of newly exposed water as
ice floes drift apart.
Where the Crust is Sucked In
Resorption of crust occurs in
trenches or subduction (lead down)
zones, those areas where the crustal
plate dives steeply into the earth's
mantle. Those rock components that
are fusible in the earth's hot mantle
rise again, causing volcanic activity,
granitic intrusions and mountain build-
ing. These subduction zones are found
in the Pacific trenches and a line of
filled trenches extending from Gibral-
tar through the Himalayas to New
Guinea — known as the great Tethys
subduction zone.
We may visualize the ideal crustal
plate as being rectangular with a rift
(a mid-ocean ridge) and a trench
forming one pair of opposing margins.
The other two opposing sides would be
great shear zones, called transform
faults, which are regions of slippage,
along which crust is neither made nor
destroyed, but rather conserved. An
example well known to Americans is
the San Andreas fault, which strikes
through California and is a portion of
the margin of the Pacific plate. Slip-
page along this plate boundary was re-
sponsible for the disastrous San Fran-
cisco earthquake of 1906.
This remarkable new understanding
of the earth, as important to geology
(Continued on page 210)
Continental drift as envisioned by Al-
fred Wegener, in his book Origin of Con-
tinents and Ocean Basins. This volume
was published in 1929, just prior to his
death on the Greenland ice cap, where
he had gone to prove by precise geodetic
measurements that this subcontinent was
drifting westward. Wegener first formal-
ized the concept of drifting continents
and is regarded the founder of the drift
hypothesis. Considering its vintage, Wege-
ner's idea that the world's land masses
emerged from the single continent of
Pangaea (a name he coined) was remark-
ably precocious.
Wegener's interest in drift was trig-
gered by "the direct impression produced
by the congruency of the coastlines on
either side of the Atlantic." Accordingly
he fitted the continents together as in a
jigsaw puzzle, but he distorted their out-
lines. The enlargement of India is a good
example. He also considered India as
always being an integral part of Asia.
The stippled areas in the lowest diagram
are modern continental shelves.
Wegener's timing of the initial break-
up of Pangaea (Upper Carboniferous, or
300 million years ago) is somewhat earli-
er than the late Triassic breakup (200
million years ago) proposed by modern
theorists. Wegener also erroneously sup-
posed that much of the drifting occurred
late in geologic time with Europe remain-
ing attached to Greenland until about
1 million years ago. He also considered
Africa and Eurasia to be fixed in position
and used an arbitrary map grid. He ac-
commodated the northward motion of
India simply by the distortion of Eurasia.
206
UPPER CARBONIFEROUS
EOCENE
LOWER QUATERNARY
I: End of Permian, 225 million years ago
Map$ adapted from Journal of
Geophysical Research
2: End of Triassic, 190 million years ago 3: End of Jurassic, 135 million years ago
4: End of Cretaceous, 65 million years ago
5: Today
A much simplified series of drawings which depict the breakup of Pangaea accord-
ing to R. S. Dietz and John C. Holden, adapted from the original presentation in
J. Geophysical Research (1970:75: p. 4939). The universal landmass is believed to
have undergone initial separation into the supercontinents of Laurasia (northern group)
and Gondwana (southern group) in the late Triassic, 200 million years ago. An east-
west rift near the equator opened the proto-North Atlantic Ocean. Simultaneously
the Indian Ocean commenced forming as well. In general, the new world has drifted
westward while the continents surrounding the Indian Ocean (Africa, India and
Australia) moved northward. Although his mechanisms for drift are no longer ac-
cepted, Wegener interestingly proposed a "westward wandering" and a "flight from
the poles." These maps confirm this westward drift but Wegener's flight from the poles
is replaced as a drift from the south pole only.
This time-sequence map series is the first attempt ever to show the past positions
of continents in absolute geographic coordinates. To achieve this absolute tracking of
the continents, Dietz and Holden used as fix markers lavas thought to be derived in
ascending plumes from the earth's deep mantle. Unlike earlier reconstructions none
of the continents remain anchored in position, although Antarctica has moved rela-
tively little. India and Australia have undergone exceedingly fast drift rates of more
than 4 inches per year. Although moving at a slower rate of about 1 inch per year,
North America has nevertheless drifted northwestward for 5,000 miles. (This drift rate
is about equivalent to the length of a human body in a lifetime.) New York, now at
40°N latitude, originally was near the equator. The last major event was the detach-
ment of Australia from Antarctica only 45 million years ago. The Himalaya Mountains
were pushed up when India struck the underbelly of Asia about 25 million years ago.
The Atlantic Ocean is wholly new with the central North Atlantic opening first,
the South Atlantic opening second, and finally, with the detachment of Greenland from
Europe, the far North Atlantic opened and created a passage into the Arctic Ocean.
The Indian Ocean is a complex basin created by the repositioning of landmasses asso-
ciated with the closing of the Tethys Sea — a huge embayment which once extended
westward from the ancestral Pacific Ocean. Although still covering nearly a full hemi-
sphere, the Pacific is growing ever smaller. Drift theorists call the ancestral Pacific
Panthalassa, meaning universal sea.
To help clarify the breakup of Pangaea, two well-known oceanic landmarks, the
Antilles and the Scotia arcs, are placed in their modern position on all of the charts.
Also, for best centering of the landmasses, the vertical center line of the projection is
the 20° E longitude meridian rather than Greenwich.
as the theory of evolution was to biol-
ogy, was preceded by two develop-
ments in the study of terrestrial magne-
tism. The first involves detecting the
changes in the position of the earth's
magnetic pole (the polar method),
and the other, reversals of the earth's
magnetic field (the reversal method).
These were critical to the ultimate
proof of continental drift.
Where Did the North Pole Go?
In the late 1940's, scientists recog-
nized that certain rocks, especially
ancient lavas, are in effect "fossil com-
passes." As freshly extruded lava cools
through the Curie point at about 575°
C, an imprint of the earth's magnetic
field, as it existed at that point in time,
is "frozen in.*' By collecting oriented
samples of ancient lavas, specialists
in paleomagnetism have clearly shown
that these "fossil compasses" generally
give a different solution for both the
direction and the dip of the North
Magnetic Pole than does a modern
compass needle placed on the point
from which the lava sample was taken.
Some of these differences (but not-all) ,
established through thousands of mea-
surements, could only be explained if
continents had drifted.
As with many scientific techniques,
there are significant limitations. The
earth's surface is curved, so that three
coordinates are needed to establish a
fix on the globe. The "fossil compasses"
of paleomagnetism can only provide
orientation and magnetic latitude;
longitude remains forever indetermi-
nate. In the same way the navigator at
sea with only a dip compass can, in
principle, roughly determine his orien-
tation with respect to the geographic
grid as well as his magnetic latitude —
but not his longitude. Unfortunately,
using paleomagnetism no one has dis-
covered as yet the equivalent of the
chronometer, which makes the deter-
mination of a ship's longitude possible.
Because of this restriction, many scien-
tists remained skeptical of the paleo-
pole position evidence for continental
drift.
Fortunately, an even more powerful
method — magnetic reversal — was dis-
covered within the past decade. In the
late fifties, extensive regions of the
ocean floor were first found to be char-
acterized by strongmagnetic anomalies,
or departures from the earth's normal
ambient magnetic field. These were dis-
posed in horizontal patterns like zebra
stripes. British workers soon realized
that these could be explained as
growth increments of new ocean crust
being added as the crustal plates spread
apart at the mid-ocean ridges. There
also was good evidence to show that the
earth's magnetic poles flipped, with the
North Magnetic Pole becoming the
South Magnetic Pole and vice versa,
every million years or so. This flipping
is related to circulation patterns within
the earth's nickel-iron core and not to
any geographic tipping of the earth.
With each flip a new anomaly is added
to the pattern of a spreading ocean
floor so that large regions of the ocean
floor acted like a magnetic tape re-
corder. It soon became possible to
measure quite precisely the horizontal
shifts of the plates — a new dimension
to which terrestrial geology was blind.
We now have a magnetic chronology,
rather analogous to the method of
aging trees by ring counting, which
extends 80 million years back in time.
210
The African crustal plate, upon which the continent of Africa is superimposed,
is depicted in this diagram. Throughout its history the African plate has drifted north-
ward and rotated counterclockwise. The plate is bordered on three sides by the Pan-
African rift system, which has acted at various times as both a shear zone (especially
on the Indian Ocean side) for accommodating the shifting of the plate, and a zone
of sea floor spreading (especially on the Atlantic side) where new ocean floor has been
extruded. The northward drift of the African plate is accommodated by a descent and
resorption of the outer crust of the earth into the Tethyan trench system, a remnant of
which now lies beneath the Mediterranean Sea. (Drawing by John C. Holden)
Thus it is now known that the earth's
crust not only goes up and down but
also moves sideways. The horizontal
velocities of a few centimeters per year
are slow by human standards, but they
are ten, one hundred or a thousand
times faster than other grand geologic
processes like the rising of mountains,
subsidence of land masses or the ero-
sion of continents. It has long been
known that Florida and the adjacent
Bahama platform reveal a long history
of continued subsidence of a few miles
over the past 150 million years. But
geologists have only recently realized
that during this same interval these
crustal blocks have drifted northwest-
ward for more than 3,000 miles. When
added to the vertical displacements and
time — the substance of classical geol-
ogy— this new horizontal drift gives
earth history a fourth dimension and
increases its complexity.
Rewrite the Texts
The textbooks are now being re-
written to incorporate this new mobil-
istic philosophy, and an exciting era
has come to the earth sciences. Practi-
cal benefits may ensue, once we under-
stand the plate motions in detail. For
example, it should then be possible to
predict earthquakes with some preci-
sion. A step in this direction was made
recently by Robert Wallace of the
United States Geological Survey. By
analyzing the motions along Califor-
nia's San Andreas fault, he predicts
that there will be an important earth-
quake every five years and a large
earthquake every 15 years. A really
disastrous quake, like that which shook
San Francisco in 1906, will occur once
each century.
ADDITIONAL READING
Other articles on continental drift that
have appeared in Sea Frontiers:
Pothier, R. J. "Deep Sea Drilling Rec-
ord," Vol. 14, No. 6, page 322.
Dietz, R. S. "More About Continental
Drift," Vol. 13, No. 2, page 66.
Runcorn, S. K. "Corals and the History
of the Earth's Rotation," Vol. 13, No. 1,
page 4.
Creer, K. M. "Continents on the Move,"
Vol. 12, No. 3, page 148.
212
Reprinted from Earth-Science Reviews 7_
No
A9-A15
51
PORTRAIT
OF A SCIENTIST
FRANCIS
SHEPARD
ROBERT S. DIETZ1
and K.O. EMERY2
Where Alph, the sacred river ran/ Through caverns measureless to man/ Down to the sunless sea. . . .
Coleridge
Geology has undergone a revolution during the past decade paced by discoveries about
the ocean floor — and this is where the geologic action is. To a significant degree, this
revolution can be traced to one man, Francis Parker Shepard. His researches and those
of his many students, numbering more than threescore, have left an indelible imprint on
marine geology.
Francis P. Shepard (now Professor Emeritus of Submarine Geology at Scripps Institu-
tion of Oceanography of the University of California at San Diego), a native of Brookline,
Massachusetts, received his AB from Harvard University in 1920 and his PhD in 1922 from
the University of Chicago. From 1923 to 1937 he was a faculty member of the University
of Illinois, but his growing commitment to submarine geology drew him to the Scripps
Institution of Oceanography at La Jolla, California — firstly part time, and then full time
after World War II. During the war years he served with the University of California Divi-
sion of War Research, making sediment studies to help understand the behavior of under-
National Oceanic and Atmospheric Administration, Atlantic Oceanographic and Meteorological La-
boratories, Miami, Florida.
2Woods Hole Oceanographic Institution, Woods Hole, Massachusetts
A9
water sound in relation to submarine detection, and compiling shelf sediment charts of
foreign areas to support military operations. With the termination of hostilities, he re-
turned to Scripps Institution where he has remained even after his retirement in 1966,
and where he now continues to actively pursue his interests in marine geology.
A PROFILIC WRITER
Shepard's eminence derives from his cascade of scientific papers numbering nearly
200, plus several books. This output reflects his boundless energy and enthusiasm. Sub-
marine Geology (Harper and Row) now is the standard text in the field. It was first pub-
lished in 1948, went into a completely rewritten second edition in 1963, and a third
edition is now under preparation. He also authored the popular book, The Earth Beneath
the Sea (Johns Hopkins Press) in 1959, which has recently been reissued. In 1966 he pub-
lished Submarine Canyons and Other Sea Valleys with Robert F. Dill as co-author. Ear-
lier he also edited the monograph, Sediments of the Northwest Gulf of Mexico, published
by the American Association of Petroleum Geologists. This was a byproduct of the Ameri-
can Petroleum Institute's Project 51, which he directed from 1951 to 1957, on the paralic
and deltaic sedimentation along the Gulf coast1 . Currently in press is Our Changing
Coastlines, written with the late Harold R. Wanless. This book examines the coastline
changes around the United States, including Alaska and the Hawaiian Islands, by com-
paring early charts and aerial photographs with their modern counterparts. It is a final
chapter in a theme which Shepard has pursued throughout his life — the geomorphology
and classification of shorelines. Early in his career he led the breakaway from the then
widely accepted genetic shoreline classification of Douglas Johnson after William Morris
Davis' philosophy of historical sequences.
ORIGINAL IDEAS
Among the many original ideas which can be ascribed to Shepard are the following:
(1) troughs and fjords of shelves in high latitudes resulted primarily from glacial erosion
and not from faulting; (2) the pattern of shelf sedimentation is complex, and beyond the
surf zone there is no general gradation of sediments from coarse to fine across continental
shelves; (3) submarine canyons are maintained by periodic and sudden removal of clog-
ging sediments; (4) the shelf-edge topographic highs and much of the slope relief of the
continental margin off Texas are related to salt intrusions; (5) undertow is largely a myth,
and rip currents are responsible, instead, for numerous drownings; (6) tsunamis are mostly
the direct result of fault displacements rather than of landslides; and (7) there has been no
high stand of sea level associated with a climatic optimum during the Holocene.
To Shepard, geology is an observational and descriptive science. He is skeptical of
highly sophisticated theoretical analysis and is impatient with oblique contemplation of
of the sea from ivory towers. He prefers to overwhelm a problem by an extensive collec-
tion of data. Utilizing T.C. Chamberlain's principle of multiple working hypotheses,
Shepard, in turn, likes to set up "truth tables," listing the points for or against any idea.
His predilection is to jump on his horse (or, rather, ship) and go and see. He develops his
views in the field rather than accepting answers recorded in authoritative books, thus
"counting the lion's teeth instead of consulting Aristotle."
Of iconoclastic bent, many of Shepard's early writings were directed towards proving
that some accepted principle of geology (such as periodic diastrophism) is wrong. His
doctoral dissertation on the structural geology of the Rocky Mountain trench proposed
that this feature was not a graben, as previously supposed, but even in one place a horst.
R.A. Daly and R.T. Chamberlain, his early mentors at Harvard and Chicago respectively,
were among those with whom Shepard quickly found reason to disagree. An interesting
A10 footnote to this background is that Shepard in 1966 followed Daly as the next American
recipient of the coveted Wollaston Medal of the Geological Society of London. It had been
bestowed on Daly in 1942.
SHIPBOARD OBSERVATIONS
Shepard's focus on shipboard observations beginning in the early thirties marked a
change of method in marine geology. He had developed an early love for the sea aboard
his father's yacht out of Marblehead, Massachusetts. The spark that propelled him into
marine geology was his observation that the sediment samples he collected with the yacht
off the New England coast strikingly disagreed with the classical dogma that they would
become finer grained offshore and toward a "wave base" marked by the shelf break. Once
bitten by the taste of the sea, Shepard never returned to classical geology. He kept ties to
the land, however, for he became a "green-water" marine geologist, confining his inter-
ests largely to the shoreline, the shelf and slope, and especially the precipitous canyons
which incised the continental slope. He became a marine geologist and not a geological
oceanographer and has treated marine geology as an extension of land geology.
Shepard's canyon studies had modest beginnings — a rowboat, a sounding line, and a
sextant. With these simple tools, he made repetitive surveys in the nineteen-thirties of
several canyon heads along the California coast. His report that some canyon heads had
deepened or shoaled within a six-month interval was at first dismissed with a smile. Were
they not due to surveying inaccuracies?2 Shepard's findings subsequently have been fully
verified. Some of the canyon heads gradually fill with sand and then are periodically
cleaned out by some process which still is not fully understood.
Shepard has never been a man with a "greasy thumb" and has little patience with com-
plex mechanical gadgets, let alone electronic black boxes. He likes to rely solely upon
simple devices which are foolproof and have stood the test of shipboard use. One master-
stroke of simple instrumentation was dispatching 2m-high Roger Revelle (later Director
Fig. 2. Francis Shepard inspecting the Westinghouse Deepstar 4000, a deep-research vehicle, just
prior to a dive into Mississippi Submarine Trough. Commencing with dives in Cousteau's Diving
Saucer in 1964, Shepard has carried out a program of visual studies of submarine canyons. (Photo by
Ron Church.)
All
of Scripps Institution of Oceanography) into the surf zone to act as a calibrated wave staff.
This interest in simplicity probably in part stems from his involvement in attempting to
develop, in the mid-nineteen-thirties a highly touted hydrostatic corer which would utilize
the ambient pressure of the deep ocean to drive a core barrel into the bottom. On its first
deep trial off California, this device imploded, and all that was recovered was the cable's
frayed bitter end. This loss virtually wiped out the instrumentation funds in Shepard's
grant for studying canyons off the California coast.
Over the years, the techniques of marine geology have, of course, become ever more
sophisticated. By 1966 it was even possible for Shepard to break away from remote
sensing and directly inspect the La Jolla Submarine Canyon off California through the
portholes of the Cousteau diving saucer. He describes this as "a thrilling experience and
the greatest day in my life."
A TURNING POINT IN MARINE GEOLOGY
A turning point in Shepard's career was a $10,000 grant in 1936 from the Penrose
Fund of the Geological Society of America for investigating the submarine canyons off
California. This was a large grant for those years and the largest ever granted to that date
by the G.S.A. With these funds, Shepard was able to use the oceanographic research ship,
"E.W. Scripps", for six months, support two student assistants (the authors of this article),
and supply the equipment needed. Along with H.C. Stetson's studies during the same
period at Woods Hole Oceanographic Institution, this effort founded sea-going marine
geology in the United States. A spate of papers resulted from this research, including the
monograph, Submarine Topography off the California Coast: Canyons and Tectonic Inter-
pretation (GSA Special Paper No. 31, with K.O. Emery). With a follow-on G.S.A. grant,
Shepard in 1940 did extensive work in the Gulf of California.
Shepard is perhaps best known for his vigorous espousal of the belief that submarine
canyons resulted from river cutting when the continental slopes were exposed due to
lowering of sea level as much as 2000m during the Pleistocene. Many sharp exchanges of
opinion were published by Shepard and his antagonists, who included Daly and
D.W. Johnson, but eventually the turbidity-current origin won the dominating role in the
origin of these canyons. To err is human, and Shepard retracted his hypothesis once suffi-
cient data accumulated to show that it was not tenable. He now believes that a highly
complex set of processes have been at work in submarine canyons, including not only
modest sea level lowering and turbidity currents, but also many other types of water cur-
rents and mass movements. His recent work has been directed toward learning more
about the transportation of sands from shallow to deep water, on cable breaks associated
with turbidity currents, and on the scouring of canyon walls by creeping sand masses.
In his treatise on submarine canyons, he has modestly written, "The book. . . should be
considered only an installment in a continued story."
In association with Hans Suess, Shepard in 1956 made a classic study of the post-
glacial rise of sea level using radiocarbon dating. Recently he led a large team investigation
to the coral reefs of the west Pacific Ocean, Daly's type locality for his plus-two-meter
Holocene high sea level during the so-called Climatic Optimum*. This team found no sup-
porting evidence of any such high stand as advocated in recent years by Rhodes Fair-
bridge and others.
PROFOUND LOVE OF THE SEA
When not actually at sea, Shepard prefers to work within the sight and sound of the
surf. This attachment for the sea cost Shepard the first draft of his textbook on sub-
marine geology and nearly his life, as well. In 1946 while writing the manuscript, he was
A12 living in a small cottage on the north coast of Hawaii. When the April 1 tsunami, triggered
o
o
E
o
A13
by an earthquake in the Aleutian trench, struck, his wife, Elizabeth, quickly retreated
to high ground. Shepard himself incautiously remained behind to observe and photograph
this rare natural phenomenon. The cottage was completely demolished, the manuscript
was washed away, and only by climbing a tree was he able to avoid being washed away by
the inundating eighth wave. With characteristic energy and enthusiasm, Shepard (with
D.C. Cox and G.A. MacDonald) immediately initiated a now-classic investigation of the
coastal effects of that tsunami on the Hawaiian Islands.
Fig. 4. F.P. Shepard as a Navy cadet at Harvard with his future bride, Elizabeth Buchner. World
War I ended before Shepard was called to duty overseas.
A14
Surely we can identify Shepard as the first American marine geologist3 . During the
late nineteen-thirties, when the submarine-canyon controversy was raging, Shepard was
the only participant who had actually ever sounded and sampled a submarine canyon.
Shepard's approach has always been direct as he quickly moved to the ocean's edge and
grappled intimately with his chosen subject. His overall time at sea must run about five
years and there probably are few oceanographers who have spent any more than this on
a rolling deck. His wife, Elizabeth, has accompanied him on many of these cruises, espe-
cially in recent years, in a supporting role such as monitoring the echo sounder.
HONORS AND RECOGNITION
In 1964 Shepard's students presented him with a book of their papers in his honor
entitled Papers in Marine Geology: Shepard Commemorative Volume (Macmillan).4 To
keep this effort a secret until published it was given the code name "Project Sextant" in
recognition of Shepard's numerous hydrographic surveys in which he utilized this instru-
ment. Shepard has received many other honors including an honorary DSc from Beloit
College in 1968. In 1968 he was also selected as the San Diego Man of Distinction in rec-
ognition of his scientific achievements. From 1958 to 1963 he was President of the Inter-
national Association of Sedimentologists and presided over the Association's general
meetings at Copenhagen in 1960 and at Amsterdam in 1963. He is a member or fellow of
many scientific societies which are too numerous to list here.
A signal honor and token of high regard by his colleagues was the recent establishment
of an award in his name by the Society of Economic Geologists. The SEPM has designated
it as the Francis P. Shepard Award for Excellence in Marine Geology. It is presented usually
annually to an outstanding marine geologist, based on "excellence in marine geology, with
primary consideration for excellence in those fields for which Professor Shepard has be-
come well known. These fields are the distribution and characteristics of sediments,
marine geomorphology, and structure of the continental margins of the world".
Shepard's accomplishments of the past are part of a continuing series. Retirement
means little other than providing more unfettered time for marine studies. Judging from
the longevity of his parents, Shepard has yet several decades of productivity. We look
forward to reading the results of this work.
REFERENCES AND NOTES
1. (see page A10) During this period, one of his students, Harris B. Stewart, composed a
poem entitled "An Ode to F.P. Shepard's 100th Reprint* - or, One Sansicle, Please, and
No Mud.V
We had drinks and hors d'oeuvres from the platter / The Department was there to a man
It was during a lull in the chatter / That Shepard put forth his new plan.
"If clay and silt are contiguous, / And next to the silt is the sand,
Then 'mud' as a term is ambiguous, / And in consequence should be banned.
If a triangle's used in the riddle, / And sand, silt, and clay juxtaposed,
For the triangle left in the middle, /The term 'sansicle' is proposed."
*(We can excuse this inaccuracy as poetic licence, but in the interest of precise reporting
we must point out that the paper in question (Nomenclature based on sand-silt-clay
ratios. /. Sediment. Petrol, 24(3): 151-158, 1954) was actually his 1 12th.)
2. (see page All) As Shepard's student assistants in these early surveys, the authors of
this article must now admit nagging doubts about the validity of these surveys. But, after
all, are not apprentice scientists supposed to be skeptics?
3. (see page A14) We have hesitated in referring to Shepard as the "father of marine geol-
ogy." However, the venerable Madame Klenova of the U.S.S.R. Institute of Oceanology
did so upon the occasion of the International Geological Congress in Mexico City in 1956,
when the cold war first had thawed sufficiently for Russian scientists to attend such
functions. As they met for the first time, Mme. Klenova warmly remarked, "You are the
father of marine geology and I am the mother of marine geology." To this, Elizabeth
Shepard replied, "And that, in turn, must make me the concubine."
4. (see page A15) In addition to its 24 papers by his students, this volume contains a
biographical foreward about Francis P. Shepard, a "Vita," and a listing of his 141 publi-
cations to 1961. A15
52
Reprinted from Nature 229 , No. 5283, 309-312.
Pre-Mesozoic Oceanic Crust in the Eastern
Indian Ocean (Wharton Basin)?
by
ROBERT S. DIETZ & JOHN C. HOLDEN
ESSA, Atlantic Oceanographic and Meteorological Laboratories, 901 South Miami Avenue, Miami, Florida 33130
A search for ocean basins underlain by
old crust has suggested that the Wharton
Basin would be a likely place to investi-
gate.
There is now great interest in the search for old Earth's crust,
not only for the sake of a better understanding of ocean floor
evolution but also because such material would be more highly
mineralized and the thick cover of sediments would offer
enticing prospects for petroleum. In what follows, by "old
crust" we mean merely pre-Mesozoic crust, older than 225
m.y. Even this modest antiquity would, however, antedate
the great sequence of events beginning with the breakup and
dispersion of Pangaea, which probably commenced in mid-
Triassic, 200 m.y. ago1.
The half spreading rates associated with seafloor spreading
(that is, the spreading on each limb of a spreading mid-ocean
rift) of 1-6 cm per year are suggested by the magnetic anomaly
growth lines reaching back over the past 4 m.y. If these rates
can be extrapolated linearly back in time to anomaly 32 of
Heirtzler et cil.2, about half of the ocean floor is of Cainozoic
age (less than 65 m.y.)3 except in special situations; nearly all
the remainder must be Mesozoic.
The scientific staff on JOIDES (Deep Sea Drilling Project)
leg 6 concluded that the North-west Pacific basin was the oldest
part of the oldest ocean4. Upper Jurassic sediments (Tithon-
ian, 140 m.y.) were encountered in two cores but, by inference,
Lower Jurassic or even Triassic ocean floor might be present
closer to the Marianas subduction zone. The Philippine Sea,
which lies behind the Japan-Marianas-Palau trench system,
was found to be young, probably not older than early Caino-
zoic. (In deep sea drilling, the assumption is made that the
age of the sediments immediately overlying basement basalts,
as indicated by seismic reflexion profiling, is the age of the
oceanic crust. This interpretation is reasonable if the crust
was emplaced according to the seafloor spreading concept.)
The search for Palaeozoic crust was also a primary aim of
the recent JOIDES leg 11 off the eastern United States5.
Only mid-Jurassic (about 160 m.y.) strata were found, but this
is the oldest rock so far recovered from any ocean basin. This
makes it unlikely that the Atlantic commenced opening at the
beginning of the Permian and that the peripheral quiet magnetic
zone of the Central North Atlantic represents crust emplaced
in the 50 m.y. long Kiaman interval of constantly reversed
magnetic polarity essentially during the Permian6-7. We
agree with Vogt et al." that the magnetic quiet zone represents
crustal emplacement during the Triassic. The South Atlantic-
is clearly younger than the North Atlantic, and so this entire
rift ocean (excluding subplates) is unlikely to contain Palaeo-
zoic ocean crust.
It is possible, but perhaps unlikely, that the Arctic Ocea i
contains old crust. Apparently there was an ancestral Arctic
basin within the framework of Pangaea, which we have named
Sinus Borealis (Latin for northern embayment)9. The Eurasian
Basin, between the Lomonosov Ridge and Eurasia, must be
neo-oceanic, for it contains a central spreading rift, an exten-
sion of the mid-Atlantic ridge10. Perhaps the Canadian Basin
contains old crust. But a likely history for the Arctic Ocean
is that the Alpha Ridge in the Canadian Basin is a "fossil" but
now abandoned spreading rift. This old rift then "jumped"
to its present location, splitting off a sector of the Eurasian
craton (the Lomonosov Ridge) in the process". This would
infer that the oceanic crust of the Canadian Basin is not very
old, at least in its northern portion. On the other hand,
Churkin's12 interpretation, based on the marginal lower
Palaeozoic geosynclines of Alaska and Canada, may be
correct. He believes that the oceanic crust of the Canadian
Basin must be early Palaeozoic or even Pre-Cambrian.
Seafloor marginal to Antarctica also seems at first to contain
sectors of Palaeozoic crust for the following reasons. This
continent is surrounded by a rift-megashear system (the pan-
Antarctic rift) bounding the Antarctic crustal plate. No
trenches are associated with this plate, into which ocean crust
is being subducted. It is unique in this respect, for the other
major crustal plates — North American, South American,
Eurasian, African, Indian, Australian, main Pacific and East
Pacific plates — include a subduction zone. Clearly the Antarc-
tic crustal plate has evolved by the outward migration of the
pan-Antarctic rift with time. Inside those sectors, where the
rift did not initially block out Antarctica's continental slope,
areas of old seafloor might be stranded and preserved. The
broad sector of West Antarctica which faces the Pacific Ocean
seems to offer such a possibility, for this is obviously not a
rift margin. A Mesozoic foldbelt, however, a portion of the
circum-Pacific orogenic girdle, makes up the periphery of
West Antarctica, suggesting that seafloor was once subducted
along this margin even if not now. Although volcanic zone
extends along the Pacific margin of East Antarctica, the
volcanoes are alkaline, not calc-alkaline, and provide no evid-
ence for crustal subduction today. Future seismic profiling,
however, will probably indicate the former presence of a
trench zone there.
Pursuing the question of old crust, attention is drawn to the
so-called subplates. The small ocean basins, such as the Sea
of Japan, seem to be of prime interest, for they lie isolated
and "protected" behind the subduction zones (trenches) where
a descending lithospheric plate is being consumed. Geological
and heat flow studies, however, suggest that the Japan Sea is
also neo-oceanic13. There are Asiatic strata along the inner
margin of the Honshu arc, suggesting that Japan was once
attached to Asia, but that the Japanese arc subsequently moved
outward. Apparently a mid-ocean rift is not a necessity for the
emplacement of new oceanic crust, for there are no linear
magnetic anomalies in the Japan Sea. The Fuji Basin, behind
the Tonga-Kermadec trench, also has been inferred to have
young crust14. It seems likely that the small ocean basins
of the Pacific which form subplates are generally neo-oceanic.
The Caribbean is another type of isolated subplate which is
protected by a subduction zone — the east by the Antilles
trench and the west by the Central American trench. The
crust, however, is probably Mesozoic, not Palaeozoic. It was
probably created with extension associated with the initial
breakup of Pangaea into North America/Eurasia and South
America/Africa in the mid-Triassic1. There is only a small
chance that old Pacific floor is trapped within the Caribbean
region.
The history of the Gulf of Mexico is an open question
310
NATURE VOL. 229 JANUARY 29 1971
Fig. 1 Reconstruction of the continents into Pangaea before
200 m.y. ago (adapted from Dietz and Holden1).
depending largely on whether it was an arm of the world ocean
(Panthalassa), a sinus occidentalism or was created, like the
Caribbean, with the initial breakup of Pangaea. Results from
JOIDES leg 10 indicate that the central Gulf of Mexico was
already deep water in the late Cretaceous (Santonian, — 80 m.y.)
and the south-east part since Cainomanian time ( — 100 m.y.)15.
If the Luann salt is a deep water salt laid down with the initial
formation of the Gulf of Mexico, its age would be late Triassic
or early Jurassic. It seems most likely that the Gulf of Mexico
is neo-oceanic, forming in mid-Triassic with the clockwise
rotation of the Honduras and Yucatan blocks which rotated
outward to form Central America.
Generally regarded as a rift ocean like the Atlantic, the
Indian Ocean would seem at first thought to offer little prospect
of containing old ocean floor, but its history is much more
complex than the Atlantic. It differs markedly from the
Atlantic Ocean in that there was an ancestral Indian Ocean —
namely, the eastern reaches of Tethys. As well as being a rift
ocean, it is of the Pacific type, its northern boundary being
margined by a subduction zone — the Himalayan-Java trench
system. We suggest that the eastern Indian Ocean floor, or
the Wharton Basin in the broad sense (as defined by the
Ninetyeast ridge, the Java trench, the western Australian
margin, and the Diamantina fracture zone), is underlain by
pre-Mesozoic crust, for the following reasons.
A generalized reconstruction of Pangaea, adapted from
an earlier publication of ours (Fig. 1), shows that the Tethys
Sea occupied the region of the Indian Ocean. The region
between India and Australia is occupied by a bay of Tethys
which we have termed Sinus Australis. A more detailed and
precise reconstruction of the continents around Antarctica is
shown in Fig. 2, which is quite similar to the assembly offered
by Smith and Hallam16. We believe that this reconstruction in
essentially correct and provides a basis on which the subses
quent history of breakup and continental drift dispersion i-
terms of plate tectonics can be reasonably determined and
schematized (Fig. 3).
Fig. 3/1 (a Hammer transverse elliptical projection centred
on 90 E longitude and 70° S latitude) shows the probable
assembly of the continents around the Indian Ocean before
continental drift breakup. Regions to the east of Australia
and to the west of India are not considered. India and Aus-
tralia are joined to Antarctica within the framework of the
universal continent of Pangaea before the mid-Triassic, or
- 200 m.y. In Fig. 3/) Antarctica is fixed in position and the
geographical coordinates are drawn relative to modern co-
ordinates. This is not entirely gratuitous, for Antarctica
probably has remained almost fixed with the other continents
doing most of the drifting".
Fig. 3B shows the situation in the early Cainozoic or about
— 45 m.y., just before the detachment of Australia from
Fig. 2
Detailed depiction showing the reconstruction of continents around Antarctica before 200 m.y. ago.
Zealand has been broken into two parts along the Alpine fault.
New
NATURE VOL. 229 JANUARY 29 1971
311
Fig. 3 Time sequence diagram showing the
breakup and drift dispersion of India and
Australia from Antarctica and consequent
preservation of old crust in the Wharton
Basin.
Antarctica. India had previously been detached from Antarc-
tica, drifted far northward and almost reached the Tethyan
subduction zone (Himalaya "trench"). The Indian plate was
bounded on the west by the Chagos-Laccodive megashear
and on the east by the Ninetyeast megashear (rift-trench
strike-slip transform faults) and on the south by a rift. Old
ocean floor was subducted into the Tethyan trench while new
ocean crust was emplaced by seafloor spreading in the "wake"
of India on both limbs of a northward migrating rift ("mid-
ocean ridge"). Thus a broad swath of Tethys was "repaved".
An undersea plateau (possibly a partially differentiated out-
pouring of lava of semi-simatic composition) is shown as
having come into existence — the ancestral Kerguelen Plateau-
Broken Ridge highground. It had been incipiently split into
two parts by the penetration of the India rift.
Fig. 3C shows the position of the continents and the dis-
position of the crustal plates today. According to the magnetic
reversal chronology impressed on the oceanic crust between
Australia and Antarctica, these two continents were not
detached until the early Cainozoic, for no anomalies older than
anomaly 18 (Eocene, -45 m.y.) are present17. Consequently
the old Tethyan seafloor, especially Sinus Australis, forming
the western part of the Australian plate remains undisturbed.
This plate later underwent subduction into the Java trench,
but the Wharton Basin remains as unconsumed old crust
while new ocean floor is being emplaced between Antarctica
and Australia. Also, as we have depicted the drift dispersion
of continents in this region, a small sector of old crust has been
trapped along the margin of Antarctica near 90° E longitude.
The reality of such details of this interpretation depends, of
course, on the exact timing and geometry of the breakup.
This treatment considers that both Broken Ridge and the
Kerguelen Plateau are of simatic composition. If either or
both of these features should be identified as microcontinents
312
NATURE VOL.229 JANUARY 29 1971
there is some evidence that Broken Ridge may be so18 — our
proposed history would have to be modified. For example, if
Kerguelen proves to be young sima while Broken Ridge is old
sial, it would most likely have been detached from Antarctica
by the rift shown in Fig. 3fl and little, if any, pre-Mesozoic
crust would remain stranded adjacent to Antarctica.
We have not treated that portion of the Australian plate in
the Pacific Ocean to the east of Australia. However, if the
New Zealand subcontinent (a reasonable term as the area of
the New Zealand platform is almost as large as India) was once
attached to Australia, as seems probable, spreading has
occurred between these two sialic platforms such that most of
the ocean floor in between must be new.
(An alternative solution to closing the Indian Ocean by our
continental drift reconstruction is to place India's east coast
against Australia. Such a reconstruction leaves a large
triangular mediterranean sea within Gondwana, margined by
western India, Africa/Madagascar and Central East Antarctica.
We suggest that this inland small ocean basin, if it existed
(and we are inclined to doubt it) be termed Mare Gondwanis
(Latin for sea of Gondwana). The breakup of this assembly
would then involve the insertion of a spreading rift into the
centre of this mediterranean and, in turn, would imply that
old ocean .floor would now be stranded marginal to parts of
India, Africa and Antarctica (from 40°-80° E longitude), the
exact sectors involved depending on how the spreading rift
was initially inserted. We believe, however, that such a breakup
and dispersion history for the Indian Ocean continents is
unlikely.)
There is some suggestive evidence that the Wharton Basin
is at least of modest antiquity, and its unusual topography sup-
ports this interpretation. There are numerous large ridges,
marginal plateaus, and blocky highs quite unlike ocean floors
elsewhere. This is strikingly revealed by the National Geo-
graphic Society's 1967 map of the Indian Ocean floor based
on the bathymetric studies of B. C. Heezen and M. Tharp.
Sixty million year old basalt has been dredged from Ninety-
east ridge, so that this feature is not young19. Upper Cretace-
ous (Turanian) ooze has been cored on the Naturaliste plateau20
and Cretaceous ooze has been recovered from the centre of
this basin21. Our interpretation awaits testing by seismic
reflexion profiling, dredging, coring and, we hope, drilling by
the Deep Sea Sampling Project. If our view is correct,
the Wharton Basin is the only broad expanse of pre-Mesozoic
seafloor in the world.
Received October 20, 1970.
1 Dietz, R. S., and Holden, J. C, J. Geophys. Res., 75, 26, 4939
(1970).
2 Heirtzler, J., Dickson, G., Herron, E., Pitman, W., and Le Pichon,
X., /. Geophys. Res., 73, 6, 21 19 (1968).
3 Vine, F. J., J. Geol. Education, 18, 2 87 (1970).
1 Geotimes, 14, 8, 13 (1969).
5 Geotimes, 15, 7, 14(1970).
6 Heirtzler, J. R„ and Hayes, D. E., Science, 157, 185 (1967).
7 Emery, K. O., Uchupi, E., Phillips, J., Bowin, C, Bunce, E.,
and Knott, S., Amer. Assoc. Petrol. Geol. Bull., 54, 1, 44
(1970).
8 Vogt, P., Anderson, C, Bracey, D., and Schneider, E., J. Geo-
phys. Res. 75, 20, 3955 (1970).
9 Dietz, R. S., and Holden, J. C, Sci. Amer., 223, 4, 30 (1970).
10 Demenitskaya, R., and Karasik, A., Tectonophysics, 8, 345 (1969).
11 Ostenso, N. A., and Wold, K. I., Intern. Assoc. Geomag. Aeron.
Bull., 24, 67 (1967).
12 Churkin, H., Science, 165, 549 (1969).
13 Fujii, N., Intern. Symp. Mechanical Properties and Processes
in the Mantle, Flagstaff, abstract (1970).
14 Karig, D., J. Geophys. Res., 75, 2, 239 (1970).
15 Geotimes, 15, 6, 11 (1970).
16 Smith, A. C, and Hallam, A., Nature, 225, 139 (1970).
17 Le Pichon, X., and Heirtz, J. R., /. Geophys. Res., 72, 6,
2101 (1968).
18 Francis, T„ and Raitt, R., J. Geophys. Res., 72, 12, 3015 (1967).
19 Bezrukov, P., Krylov, A., and Cernishev, V., Oceanologia, 6,
261 (1966).
20 Burkle, L., Saito, T., and Ewing, M., Deep-Sea Res., 14, 4,
421 (1967).
21 Saito, T., Symp. Micropaleontology of Marine Bottom Sediments
(Special Committee on Oceanic Research, 19, 1967).
53
Reprinted from Geological Society of America Bulletin
82 , 811-814.
ROBERTS. DIETZ ) NO AA, Atlantic Oceanographic and Meteorological Laboratories, 901 South
JOHN C. HOLDEN \ Miami Ave., Miami, Florida 33130
WALTER P. SPROLL
Geotectonic Evolution and Subsidence of
Bahama Platform: Reply
The preceding discussion by Sheridan of
our paper provides a welcome chance to
clarify and amplify certain aspects of our
views on the evolution of the Bahama plat-
form (Dietz and others, 1970).
We agree with Sheridan that our crustal
model for the Bahamas is a liberation from
the standard concept that all continental
regions (defined here as those at or near sea
level) need not be necessarily underlain by
"mountain roots" — a sialic basement com-
plex. In particular, we suppose that other
marginal plateaus formed at former Y-junc-
tions of crustal plates may be thick sedimen-
tary accumulations emplaced directly on
oceanic crust (such as Demerara marginal
plateau) or volcanic accumulations (such as
Afar triangle). We are inclined to doubt,
however, Sheridan's speculation that the
Jurassic Luann salt of the Gulf of Mexico is
a shallow-water deposit. More likely it was
deposited as a deep-water salt. The recent
finding by oil companies that there is 3000 to
4000 m of Miocene salt beneath the Red
Sea, without associated marginal facies char-
acteristic of evaporites (gypsum and lime-
stone), provides a strong case for deep-sea
deposition of halite.
We agree that our presumed crustal section
beneath the Bahama platform may be un-
realistic in that the density chosen for the
oceanic crust is too low. Sheridan's proposal
for a more probable crustal section, in which
he infers the existence of a thick intermediate
layer between the normal oceanic crust and
the Moho, is certainly an improvement. The
problem to be faced, of course, is to some-
how fill up with sediments a small ocean
basin, or quasi-ocean basin, to sea level with-
out grossly violating isostasy so that algal-
coral carbonate deposition can gain a foot-
hold. We are open to any suggestions for
accomplishing this solution.
Sheridan (1969) believes that the deep
Atlantic (Blake-Bahama basin) to the east of
the Bahama platform was once much shal-
lower than now. Results from JOIDES Leg 11
seem to support this point of view to some
degree. For example, the Tithonian lime-
stones penetrated in Hole 99 just east of
San Salvador Island "probably indicate de-
position in a relatively shallow pelagic en-
vironment," and from Hole 100 nearby, "The
nature of these sediments and character of
the microfauna suggest a neritic-upper bathyal
environment during their deposition"
(Scientific staff, 1970). By the sea-floor-
spreading concept, all of the floor in a rift
ocean was originally generated at the rifted
crest of a mid-ocean ridge. Subsequently,
these mid-ocean ridges subside, and the
original floor is further isostatically depressed
by sedimentary loading. The subsidence of
the basal sedimentary layers would be the
expected history with depression of basal
carbonate layers below the modern lysocline
(carbonate compensation depth).
We regard as unlikely, however, Sheridan's
supposition that the adjacent deep Atlantic
has taken part in the full subsidence of the
Bahama platform of about 5 km, which would
mean that the Blake-Bahama basin was once
almost at sea level. We know of no evidence
that the Bahama carbonate section mono-
clinally dips toward the shelf edge, as do
those sections of the Atlantic continental
shelf. This dip suggests a coupling between
the craton and the ocean floor and suggests
regional isostatic compensation. If the
Bahama carbonates are really flat lying, the
presence of a fault along the platform boun-
dary remains probable. Because ocean-floor
sedimentary layers are incompetent, we would
not expect seismic profiler records to indicate
any marked disturbance or drag effect such
as would make the fault evident.
Geological Society of America Bulletin, v. 82, p. 811-814, 1 fig., March 1971
811
812 DIETZ AND OTHERS-GEOTECTONIC EVOLUTION, BAHAMA PLATFORM
We caution also that deep-ocean sediments
do not recotd latge vertical displacement with
clarity, and displaced shallow-water sediments
create much confusion. Rather remarkably,
with the new chtonology of magnetic reversal
anomalies, we can for the first time identify
large horizontal shifts of the ocean floor.
This stands in sharp contrast to continental
geology which is largely blind to horizontal
shifts while clearly recording vertical shifts,
especially those which penetrate the plane
of sea level.
Although the Bahama platform is an
aseismic region, this cannot be taken to prove
that a normal fault does not exist along the
platform margin. Faulting of this type may
occur in small increments with little buildup
of stress and, as such, would not produce
measurable seisms. Also, most of the sub-
sidence of the Bahamas occurred in the
Mesozoic when the platform was young,
with only a small amount of sinking subse-
quent to the Eocene.
The dredging of a limestone block with
slickensides parallel to bedding from Abaco
Canyon by Sheridan, Elliott, and Oostdam
(in press) and Sheridan, Berman, and Corman
(1971) is most interesting and suggestive,
but it does not really constitute a weighty
argument favoring an important role for
strike-slip tectonics in the Bahama region.
The development of this carbonate platform
is doubtless complex and defies any simple
or single interpretation. Our thoughts on the
environmental development of the curious
indentations (such as Tongue of the Ocean)
was incidental to the main theme. Neverthe-
less, it seemed worthwhile to emphasize an
aspect of carbonate bank evolution that pre-
viously had been overlooked in favor of
these re-entrants that were either tectonic or
inherited features. We note that "textbook"
atolls, whose perfect circularity reflects the
circularity of subsided seamount tops, ate
rare. Atolls become more irregular with in-
creasing size — and more and more reflect
environmental factors. The Bahama platform
is positioned in a strongly asymmetrical part
of the Atlantic with respect to planetary
currents and tradewinds. The Bahamian
islands themselves have marked environ-
mental disposition; nearly all are located on
the windward side of deep-water passes. We
suspect that environmental factors are im-
portant and even may dominate in account-
A
a
— LEGENO —
PflEJENT DAV LAND ^
/ Sum-ic rlAB&IN 1000^ . \ NORTH
-/*«,«.Tiooofw ' AMERICA
'flj*' TriaaSk ro Rtcewr
/Hi
Figure 1. Formation of the Bahama plat-
form following the mid-Triassic opening of
the central North Atlantic. Events in the Gulf
of Mexico and the Caribbean are left unspeci-
fied. Most likely, the region was closed with
cratonic blocks which later became Honduras,
Yucatan, and the Antilles islands. A. Shortly
after rifting, late Triassic. B. After further open-
ing, as of mid-Jurassic.
ing for the irregularities of the Bahama
platform.
We were aware of the view of Sheridan and
othets (1969), that the "Guinea Nose" (a
marginal plateau) is underlain by an exten-
sion in basement sttuctural arch and, thus, is
an integral part of the Aftican craton, but
thete is conflicting evidence. On one hand,
this intetpretation accords with that of Sougy
(1962), who extrapolates his Paleozoic
Mautitanides foldbelt across the Guinea Nose.
On the other hand, from recent oil company
surveys Templeton (in press) believes that
this foldbelt bifurcates well inshore of the
Guinea Nose and that a syncline lies athwart
Sougy's trend and yet is inshore of the Guinea
Nose. Templeton shows the pre-Mesozoic
REPLY
813
^winimnir .
surface to be 3000 to 5000 m deep over the
Guinea Nose. From their magnetic survey,
McMaster and others (1970, p. 161) also
specifically question the existence of a west-
southwest-trending "Guinea Arch" under-
lying the Guinea Nose as proposed by
Sheridan. It should be borne in mind, how-
ever, that Sheridan, using the seismic refrac-
tion method, may have measured Paleozoic
structure in sedimentary strata, while
McMaster and others measured Precambrian
basement effects. We suppose that the pos-
sibility remains that the Guinea marginal
plateau is a postrift deposition excrescence
to the African craton and so, in a small way,
a mirror counterpart of the Bahama platform.
We would like to offer a novel way in which
one might determine whether or not the
Guinea Nose is old craton or postdrift ex-
crescence ("new ground"). The ghost out-
line of the African margin is rather faithfully
reproduced in the mid-ocean rift. Probably
the Guinea Nose is sufficiently large to be
reflected thus, if it, in fact, was present at
the time of breakup (;^ 200 m.y. ago). We
have examined the shape of the rift zone
where it is intersected by what appears to be
the Guinea fracture zone. It appears to re-
semble more closely the African margin with
the Guinea Nose subtracted rather than added,
which supports the idea that it is "new
ground." However, detailed survey of the
mid-ocean rift is necessary before much cre-
dence can be placed in this evaluation.
814 DIETZ AND OTHERS-GEOTECTONIC EVOLUTION, BAHAMA PLATFORM
Some new evidence, that the Bahamas ate
a postrift exctescence to North America,
follows from the finding of Vogt (written
commun., 1970). Magnetic reversal anom-
alies created by sea-floor spreading should,
and in fact do, generally parallel the margins
of North America and Africa. However, the
J-series anomalies identified by the Gofar
Project of the Naval Oceanographic Office
parallel the Atlantic coast, but strike abruptly
into the north margin of the Bahama plat-
form. Therefore, these spreading anomalies
originally may have underrun the Bahama
platform and subsequently have been covered
by the growth of that platform.
It is also worth noting that the results of
JOIDES Leg 11, which drilled in the deep
Atlantic off the Bahamas, is consistent with
our interpretation (Scientific staff, 1970). The
oldest rocks yet found in the Atlantic were
recovered just east of San Salvador Island and
are estimated to be 160 m.y. old. This obser-
vation supports our suggestion that the clastic
sediments of the inferred Bahama crypto-
basin, undetlying the carbonate cap, must
be Late Triassic or Early Jurassic.
REFERENCES CITED
Dietz, R. S.; HoldenJ. C; and Sproll,W. P.
Geotectonic evolution and subsidence of
Bahama platform: Geol. Soc. Amer., Bull.,
Vol. 81, p. 1915-1928, 1970.
McMaster, R. L.; De Boer, J.; and Ashraf,
A. Magnetic and seismic reflection studies
on continental shelf off Portuguese Guinea,
Guinea, and Sierra Leone, West Africa:
Amer. Ass. Petrol. Geol., Bull., Vol. 54,
No. 1, p. 158-167, 1970.
Scientific staff. Deep sea drilling project: Leg
11: Geotimes, Vol. 15, No. 7, p. 14-16,
1970.
Sheridan, R. E. Subsidence of continental
margins: Tectonophys., Vol. 7, p. 219-229,
1969.
Sheridan, R. E.; Berman, R.; and Corman,
D. Faulted limestone block dredged from
Blake escarpment: Geol. Soc. Amer., Bull.,
Vol. 82, No. 1, p. 199-206, 1971.
Sheridan, R. E; Elliott, G. K.; and Oostdam,
B. L. Seismic-reflection profile across Blake
escarpment near Great Abaco Canyon:
Amer. Ass. Petrol. Geol., Bull., in press.
Sheridan, R. E.; Houtz, R. E.; Drake, C. L.;
and Ewing, M. Structure ot continental
margin off Sierra Leone, West Africa: ).
Geophys. Res., Vol. 74, p. 2512-2530,
1969.
Sougy, J. West Africa fold belt: Geol. Soc.
Amer., Bull., Vol. 73, p. 871-876, 1962.
Templeton, R. Geology of the continental
margin between Dakar and Cape Palmas:
SCOR symposium on Geology of the East
Atlantic continental margin, Cambridge,
England, March 1970, H.M.S. Stationery
Office, London, in press.
Manuscript Received by The Society
November 9, 1970
54
Reprinted from Deep Seas Research 18, 441-447
SHORTER CONTRIBUTION
Trou sans Fond submarine canyon: Ivory Coast, Africa
Robert S. Dietz* and Harley J. KNEBELf
(Received 10 June 1970; /'/; revised form 16 November 1970; accepted 18 November 1970)
Abstract — A bathymetric chart of the Trou sans Fond (Bottomless Hole) submarine canyon off the
Ivory Coast, Africa, is presented, based upon a 1400-km survey in 1968 by the O.S.S. Discoverer.
The canyon originates with a double head just off the beach and cuts a deep V-shaped furrow across
the 30-km-wide shelf, attaining a maximum relief of 450 fm (823 m) near the shelf break. The canyon
has a slightly sinuous and rugged relief down the continental slope, indicating an active erosional
regime. At 1500 fm (2745 m) where the continental rise commences, the canyon is abruptly offset
20 km to the west, suggesting that the present outer fan valley is a newly developed channel. On the
continental rise a depositional regime is indicated by well developed natural levees which have a cross-
sectional area 60 times that of the Mississippi in the delta region. The Trou sans Fond appears to be
the only canyon which taps the paralic zone between the Cayar Canyon to the north and the Congo
Canyon to the south.
INTRODUCTION
In February 1968 the O.S.S. Discoverer, a research ship operated by the National Ocean Survey of
the National Oceanic and Atmospheric Administration, surveyed the Trou sans Fond (Bottomless
Hole) submarine canyon which lies off the Ivory Coast. Its existence has been known since at least
1846 when it first appeared on a chart published by the French engineer, Bellin. More recently the
canyon head has been studied by French engineers for harbor entrance purposes, but its over-all
bathymetry remained little known. No mention of it was made, for example, in the excellent mono-
graph on the world's submarine canyons by Shepard and Dill (1964). This survey provides for the
first time a detailed chart showing its bathymetry to 100 nautical miles offshore. Canyons such as the
Trou sans Fond which tap the paralic zone are of unusual geologic interest, as they funnel neritic
sediments to the deep ocean floor. By incising the continental shelf almost to the shore, they partially
intercept the longshore ' river of sand ' and thus may be called ' sand-eating ' canyons.
The Trou sans Fond is of unusual economic significance in that it provides an access route for
deep draft ships to nearshore. Taking advantage of the naturally deep water, the artificial Vridi ship
channel was cut in 1952 through the longshore bar to an interior lagoon, making a major regional port
and, in turn, creating the practically new city of Abidjan. Presumably owing to flushing of sand into
the canyon head, silting-up of the canal entrance has not been a problem; on the contrary, a deepen-
ing has occurred over the past 15 years. The canyon head was also the site of an abortive attempt by
Georges Claude in the 1930's to create a novel type of power plant which would have utilized the
thermal contrast between the cold, deep canyon head waters and the hot lagoonal waters to create a
thermal engine. An excellent recent account of the general marine geology of the Ivory Coast continen-
tal shelf and the inner portion of the Trou sans Fond was published by Martin (1969). Aspects of
physical oceanography and shoreline dynamics have been treated by Varlet (1958).
♦National Oceanic and Atmospheric Administration, Atlantic Oceanographic and Meteorological
Laboratories, 901 South Miami Ave., Miami, Florida 33130.
fNow at Department of Oceanography, University of Washington, Seattle, Wash.
441
442
Shorter Contribution
LIBERIAf ,-- ' ..V:*'*' /'//•.'•".- /$'BH-V-. £
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JUATERNABY
TERTIARY (PLIOCENE)
CONTINENTAL
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MIOCENE - CRETACEOUS I MJj
CRETACEOUS
CRETACEOUS -
JURASSIC
PRECAMBRIAN
METAMORPHIC
PRECAMBRIAN
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INFRA. CRETACEOUS
BEDDING SURFACE
SHELF BREAK
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Fig. 1. Regional geologic setting of the Trou sans Fond canyon. Adapted from Spengler and
Deteil (1966).
Shorter Contribution 443
REGIONAL SETTING
The regional setting of the Trou sans Fond is sketched in Fig. 1. The canyon is cut into a narrow
continental shelf about 30-km-wide near the midpoint of a 600-km-wide shallow bight in the African
margin extending from Cape Palmas in Liberia to Cape Three Points in Ghana. Although most of the
Ivory Coast is a peneplained, early mid-Precambrian shield, a late Mesozoic-Cenozoic basin is present
along the shoreline and on the central shelf of the Ivory Coast. Its inner margin is marked by large,
down-to-the-basin normal faults. The filling is mostly Cretaceous sediments probably in excess of
5 km thick (Spengler and Deteil, 1966). The creation of this basin is probably related to the shearing
and taphrogenisis associated with the continental drift rifting of South America from Africa probably
near the end of the Jurassic (Dietz and Holden, 1970).
Some submarine canyons are found off large rivers, but this is not true for the Trou sans Fond, at
least today. There are four rivers of moderate size along the Ivory Coast, but they enter estuaries or
lagoons, as this is a ria coastline owing to the post-glacial sea level rise. None now reach the strand
line, but apparently the Comoe River did so until recently (Martin, 1969). This river is the nearest
one to the canyon head, lying 30 km east.
BATHYMETRIC SURVEY
Echograms from 760 nautical miles (1400 km) of trackline were obtained from aboard the O.S.S.
Discoverer during February 1968. A Precision Depth Recorder coupled with an Edo transducer was
used throughout the survey. This echo sounder is calibrated for an assumed velocity of 800 fm/sec
(1463 m/sec), but the soundings were later corrected for velocity variations in the water column due
to temperature and salinity. Navigation control was obtained nearshore by visual and radar bearings.
Further offshore, positions were maintained by dead reckoning with respect to land ties and celestial
fixes, and a constant drift set was assumed. The positional accuracy for the nearshore areas is probably
within one nautical mile, while that offshore may be as much as two or three miles, because strong
and confusing east-setting currents of the Guinea Current were encountered.
A bathymetric chart contoured at 100-fm intervals is presented as Fig. 2. The canyon commences
at the shoreline in an amphitheater-shaped double head, but quickly assumes a deep V-shaped cross
section as it incises the continental shelf. It cuts deeply into both the shelf and upper continental
slope, attaining a maximum relief near the shelf break of 450 fm (823 m). The sidewall slopes in the
steeper portions of the canyon generally average about 15°.
The canyon cuts through four physiographic provinces: the continental shelf, the steep upper
continental slope to 1000 fm (1830 m), the more gentle lower continental slope to 1500 fm (2740 m),
and the continental rise from 1500 fm to the limit of the survey at 2200 fm. The survey extended for
100 nautical miles offshore, but it is likely that the canyon extends for another 120 nautical miles until
it reaches the Guinea abyssal plain at a depth of 2760 fm (5038 m). The long profile of the canyon is
concave and is cut normal to the regional slope. At the canyon head, the thalweg declivity attains 1 2 %
but quickly decreases to 3%. A steepening occurs near the shelf break to 8%, then decreases to 3-5%
across the upper continental slope. The thalweg slope then slowly decreases seaward, being about
1 % in the lower reaches of the continental rise. This canyon has no well developed abyssal cone,
but rather cuts across an abyssal fan which forms the upper continental rise. Although clearly erosional
across the shelf and upper continental slope, the canyon appears to be dominantly depositional on
the continental rise and has developed large natural levees.
Between 1500 and 1900 fm (2745-3477 m), the canyon axis is sharply offset 20 km to the west.
This may represent a relatively new course selected by the canyon in seeking a steeper gradient. The
former course of the canyon across the continental rise may be marked by a broad channel which
lies more exactly along the extended strike of the upper portion of the Trou sans Fond Canyon. Its
subdued outline may be due to blanketing pelagic sedimentation since it became inactive.
The stratigraphy of the canyon head probably can be inferred from a deep well drilled in 1959,
on shore at Port Bouet but near the canyon, by the Societe Africaine des Petroles (Martin, 1969).
This well revealed the following section: 0-71 m, Quaternary, coarse sand; 71-123 m, Miocene,
fine sand; 123-706 m, marine Miocene, plastic clay; 706-757 m, Senonian, slightly sandy clay with
shell debris; 757-1037 m, Turonian, calcareous sands with sand and clay; 1037-1408 m, Cenomanian,
conglomerates, sandstones, calcareous sands, clays with gypsum; 1408-3938 m, Albo-Aptian, fossili-
ferous clays, sandstones and gravels, also limestones and arkoses, some lignite. It appears likely that
444
Shorter Contribution
Fig. 2. Bathymetric chart of the Trou sans Fond submarine canyon, Ivory Coast, Africa.
Based on 1968 survey by O.S.S. Discoverer, of the National Oceanic and Atmospheric
Administration.
Shorter Contribution 445
the upper portion of the Trou sans Fond Canyon is cut entirely in soft sedimentary rocks of Cretaceous
and Cenozoic age.
Our attempt to sample the thalweg of the canyon failed, but suggested firm bottom presumably
well swept by turbidity currents. A dredge haul up the west face of the canyon head produced only
large blocks of slightly indurated, non-fossiliferous green clay which, from the above stratigraphy,
was inferred to be marine Miocene. Martin (1969) also reports only soft sedimentary rocks comprising
the canyon wall and an axis of hard sand and gravel. The continental shelf fringing the Trou sans Fond
was found to be covered with green mud and silt rich in glauconitized ovoid coprolitic pellets. The
shelf is generally smooth and featureless, but interrupted to the west by patches of irregular and
hummocky bottom. The high acoustic reflectivity of these patches suggests they contain rocky reefs.
DISCUSSION
Inspection of existing bathymetric charts reveals that Trou sans Fond probably is the only canyon
tapping the paralic zone between the Cayar Canyon north of Dakar in Senegal and the Congo
Canyon off the Congo River in the Congo. For the sector between the Trou sans Fond and Dakar,
this was further established by our own reconnaissance survey of that continental margin. This
emphasizes the importance of this canyon as a conduit for funneling neritic sediments onto the
abyssal floor. On the other hand, our survey identified numerous large canyons which were either
entirely confined to the continental slope or incised the shelf break at the edge of the continental shelf
for only a few miles.
A comparison of the Trou sans Fond with the Congo Canyon (Heezen et al., 1964) and the Cayar
Canyon (Dietz et al., 1968) is interesting. Both of them are located at the classical positions for
submarine canyons which tap the shoreline, the former off a river mouth and the latter upcurrent of a
headland. The Congo Canyon enters the estuary of the Congo River, which is second in the world
only to the Amazon River in terms of total water flow. A direct relationship between a river mouth
and a submarine canyon is nowhere more evident. The principal role of the river presumably has been
to supply sediments for turbidity currents rather than for cutting this canyon during lower sea level
stands. The Cayar Canyon is positioned north of the prominent headland of Cap Verte, the western-
most salient of Africa, toward which sand is transported by strong south-setting longshore currents.
The ultimate source of much of this sediment is the Sahara Desert, from which sand has been blown
onto the beaches of Mauritania and Senegal by the prevailing northeasterly winds.
We surmise that the Trou sans Fond canyon head has also been cut in response to an abundant
supply of sand, although a strong case cannot be made. The Trou sans Fond is located near the
center of a broad concavity in the continental margin of Africa, an indentation which pertains to the
continental slope as well as the shoreline. It undergoes an abrupt 18° flexure at the canyon head. This
shoreline is a region of large waves and plunging breakers creating a high energy regime. Sand
transport is largely toward the east, owing to the prevailing swell direction and the east-setting Guinea
Current, but this direction at times may reverse nearshore, especially in the subsurface. Under these
conditions, sand may tend to accumulate in the center of the bight. The eastward offset of the canyon
head from the exact center of this bight may represent a skewness impressed by the prevailing swell
direction plus the usual set of the Guinea current (Fig. 1). One may suppose that, were it not for canyon
head funneling sand into the deep ocean, the usual shoreline straightening processes would tend to
fill in this bight or even create a cuspate foreland at the site of the canyon head. Possibly other factors
have played a role as well in localizing the canyon head, such as an easily eroded fault zone, but any
such fault remains to be identified.
The Trou sans Fond may be said, in a sense, to extend above sea level because the beach inside
the canyon head has an abrupt foreshore, considerably steeper than is normal for the region. A narrow
shallow bench, however, separates the brink of the canyon head proper from the beach. Presumably,
this is a sand embankment formed in response to the vigorous surf regime.
In the early twentieth century two slumps which carried large volumes of sediment into the canyon
head occurred along this shoreline. In 1905 a slump lasting 35 min slowly swallowed a wharf 70 m
long upon which were a hundred barrels of cement and a warehouse. The shoreline receded 70 m and
formed a small bight 280 m wide and an area formerly 5 m deep deepened to 25 m. Subsequently the
strand line was rapidly reshaped by longshore processes. Sand budget surveys prior to modification
of the beach environment by the Vridi Canal jetties showed 800,000 m3 of sand moving from the west
446 Shorter Contribution
into the canyon head region of the shoreline but only 400,000 m3 continuing on to the east, indicating
a loss of 400,000 m3 of sand to the canyon head (Varlet, 1958).
There is another argument which favors active erosion within the Trou sans Fond canyon head.
The abruptness of the shelf break around the world is now generally regarded as having been sharpened
by erosional bevelling during the last glacial eustatic lowering of sea level to a depth of about 65 fm
(120 m) (Dietz and Menard, 1951). Hence, if a canyon head has not experienced considerable side-
wall erosion, a terrace should be etched into the canyon mouth at the shelf break depth, which lies at
about 60 fm (110 m) for the Trou sans Fond. No such bench is now present, indicating that it must
have been removed by erosion subsequent to the post-glacial rise of sea level.
Canyons which tap the paralic zone, as distinct from those incising the continental slope only, are
distinguished by large natural levees on the continental rise. Upon approaching the survey region
aboard the Discoverer while still in deep water, the Trou sans Fond was readily detected amongst a
wealth of other bottom irregularities by its prominent levees. These levees and the underlying delta
fans have a sedimentary volume clearly much larger than can be accounted for by the volume of
material eroded from the upper erosional portion of the canyon. This emphasizes the important role
of such canyons in conveying shelf and shoreline sediments to the deep ocean floor.
The large size of the undersea leveed fan valleys associated with the lower reaches of submarine
canyons is not generally appreciated. For example, profile VII (Fig. 2) across the leveed outer channel
of the Trou sans Fond shows a width of 6 km and a depth of 100 m, for a cross-sectional area of
600,000 m2. This is 60 times as large as the cross-sectional area of the Mississippi River below its
natural levees in the delta region. Huge volumes of water are needed to overflow such giant channels
and create the natural levee system. It would appear that such flows must only be triggered at in-
frequent intervals. Perhaps low-volume, high-density turbidity currents are first generated in the can-
yon heads and then through turbulent mixing are transformed into flows only slightly more dense than
the ambient sea water, but of sufficient volume to overflow, and promote the growth of, the levees.
The mode of triggering turbidity flows in a canyon head is largely unknown, but instrumented
observations over several years by Inman (1970) in the Scripps submarine canyon off California
indicate the existence of current sufficient to initiate strong sand transport.
Little can be said with assurance about the age of the Trou sans Fond Canyon. Its present head,
however, must be younger than the Miocene marine claystone through which it is apparently cut and
which is not of an open shelf facies. On the other hand, the great scale of the canyon indicates at least
moderate geologic antiquity. Some students regard submarine canyon cutting as a Pleistocene
process, but it seems more reasonable that ice age low stands of sea level only enhanced the vigor of
turbidity currents. The basic processes involved in canyon cutting must have been active since the
continental slope was created which, in this particular case, would have commenced with the breakup
of the South America-Africa supercontinent in the mid-Mesozoic. Doubtless, the history of this can-
yon is complex and involves the switching of channels, the filling of old canyon heads, and the cutting
of new ones.
Acknowledgements — We thank Captain Lorne Taylor, the officers and crew of the O.S.S. Discoverer
for performing this survey. J. P. Pinot and J. R. Vanney of the Institut de Geographic University
of Paris, assisted in preparing the bathymetric map of the canyon. Also contributing to the survey
were geologists Philippe Bouysse, Carlos Urien, Don Hawkes and Lee Somers.
REFERENCES
Dietz R. and H Menard (1951) Origin of the abrupt change of slope at the continental shelf margin.
Bull. Am. Ass. Petrol. GeoL, 35, 1994-2016.
Dietz R., H. Knebel and L. Somers (1968) Cayar submarine canyon. Geol. Soc. Am. Bull, 79,
1821-1828.
Dietz R. and J. Holden (1970) Reconstruction of Pangaea: breakup and dispersion of continents,
Permian to Present. /. Geophys. Res., 75, (26) 4939^956.
Heezen B., R. Menzies, E. Schneider, W. Ewtng and N. Granelli (1964) Congo submarine
canyon. Am. Ass. Petrol. Geol. Bull., 48, 1126-1149.
Inman D. (1970) Strong currents in submarine canyons. Eos, 51 (4) 319 (abs).
Shorter Contribution 447
Martin L. (1969) Introduction a I'etude geologique du plateau continental ivoirien: premiers resultats.
Ivory Coast Center for Oceanographic Research (ORSTOM), No. 034, 163 pp.
Shepard F. and R. Dill (1966) Submarine Canyons and other Sea Valleys. Rand McNally Co., 381 pp.
Spengler A. and J. Deteil (1966) Le bassin secondaire-tertiare de Cote d'lvoire. In D. Reyre,
editor, Sedimentary basins of the African coasts. Ass. African Geol. Surv., Paris, 108-112.
Varlet F. (1958) Le regime de V Atlantique pres Abijan. Inst. Francaise Afrique Noire, Etudes Ebur-
neennes, No. 7, 97-222.
Reprinted from Nature 232 , 20-23
55
Plate Tectonic Evolution of Caribbean-Gulf
of Mexico Region
GEORGE L. FREELAND & ROBERT S. DIETZ
National Oceanic and Atmospheric Administration, Atlantic Oceanographic and Meteorological Laboratories,
901 South Miami Avenue, Miami, Florida 33130
A geotectonic history of the American
Mediterranean is presented in terms of
plate tectonics. The development of
this region is presented as seven time
sequence reconstructions from past
Palaeozoic to present times.
Previous attempts to write a geotectonic history of the Ameri-
can Mediterranean (Caribbean-Gulf of Mexico area) based on
continental drift models' 3 or, more classically, the foundering
of a Palaeozoic landmass4 need revision because of the success
of plate tectonics. New data are available from recent land field
work5-" and marine surveys12-21. Apparently, the evolution
of this region is related to former plate junctions between North
America, South America, and Africa and to strike-slip, exten-
sional, and compressional motions as the new world drifted
westward22. This is the theme of the synthesis presented in this
article.
The geotectonic evolution of the American Mediterranean is
presented as seven time sequence reconstructions which are
azimuthal equidistant projections.
Reconstruction of Drift
Pre-dnft reconstruction: The closure of the Atlantic Ocean
at the end of the Palaeozoic according to Bullard et al2i is
modified by us (Fig. 1 ) to show the overlaps (in dashed lines) of
the Bahama platform, southern Mexico, and Central America
on to Africa and South America. In our reconstruction, we
have eliminated the overlaps and the oceanic areas by rotations
of these cratons (Fig. 2). Three of these, Yucatan24, Honduras-
Nicaragua25, and Oaxaca (southern Mexico)9, are underlain by
pre-Mesozoic basement. The isthmus of Panama and the
Antilles are thought to be neo-cratons ("new ground"), created
in Mesozoic-Caenozoic time, and are omitted.
The Bahama platform (more exactly, the Blake-Flonda-
Bahama platform) is a crescent-shaped craton with a 3-5 km
post-Triassic carbonate capping26. Although the nature of the
basement remains unknown, we assume here that it is pre-
Mesozoic, thus differing from the neo-cratonic origin of Dietz
era/.27. We propose that the south-eastern Bahama spur moved
eastward to its modern position along a shear now marked by
the Straits of Florida and the North-east Providence (Bahamas)
Channel. This spur would then have originally filled the
V-shaped gap between Africa and South America.
Our fit of the Oaxaca craton along western Mexico is
speculative, but not unreasonable. In the Bullard tit, southern
Mexico south of the Trans-Mexican Volcanic Belt (clearly "old
ground")9 overlaps onto South America. The overlapped
portion (mostly the Andean foldbelt of north-western Colum-
bia) may be partly a marginal Meso/oic accretionary belt2",
but the gap created would still be too small to accommodate the
Oaxaca craton.
We identify the initial suture of the Gulf of Mexico hy the
margin of the mid-Jurassic (Collovian-Oxfordian) basin.
Starting from DeSoto submarine canyon, it trends north-
westward through southern Alabama and central Mississippi,
westward along the Arkansas-Louisiana state line, south-
westward around the East Texas Basin, and southward into
Mexico29 u. This model is supported by subsurface Tnassic
redbeds, located by drilling, which lie just inland from the basin
margin12. These presumably represent taphrogenic basins
associated with detachment of the Yucatan-Nicaraguan craton.
Although Fig. 2 shows some gaps, the area probably was
fully closed originally. Part of the central gap may be inter-
Fig. 1 The Bullard continental drift closure of the Atlantic-
Ocean, modified by adding areas of craronic overlap shown in
dashed lines. The fit is made at the 500-fm isobath
NATURE VOL 232 JULY 2 1971
21
Fit>. 2 Closure of the \tlantic Ocean and American Mediter-
ranean in late Triassic (about 200 my. bp) according to this
article. Microcontinents which are later translated are O,
Oaxaca; Y, Yucatan: N, Nicaragua-Honduras: and B, south-
eastern Bahama platform The northern Bahamas-Blake
Plateau area is accommodated by subtracting the neo-cratonic,
western Senegal Basin Continental margins are drawn to the
1.000-lm isobath, except where dashed.
Fig. 3 Initial rifting and breakup al the end of the Triable,
I SO m.y. HP. Initial movement was rapid Arrows are vectors
showing drill relative to Africa South America, which is
arbitrarily held lived Hotted bands arc where new oceanic
crusl is implaced. the dashed lines are transform laulis and or
shear zones. Dotted lines on the continents outline Triassic
taphrogeniL basins PR is the pole ol rotation for the North
•\merican plate.
mediate crust which has been incorporated, after lectonization,
into the nco-cratons of the Greater \nlilles, The western part
was squeezed into the Guatemala foldbelt. \\ c would not
expect a solution in the form of a simple jigsaw -lit due to the
complexity of the problem
Initial breakup Fig, 3 shows the initial opening of the proto-
North Atlantic Ocean and the pull-apart of North and South
America. This is dated at or alter 2(K1 m.y HP I laic I riassic14)
by basalts presumably associated with this rifling1'
The rotation pole of Dietz and Holderr* near south-eastern
Spain for the opening of the North Atlantic is used with an
initial clockwise rotation of North America of 10°. South
America and Africa remained joined. The split between North
and South America was accomplished mostly by the opening
of the Gulf of Mexico, with the Yucatan and Honduras-
Nicaragua blocks rotating as a single unit about a point near
the Isthmus of Tehuantepec. Sinistral shear occurred along
northern South America (the El Pilar or South Caribbean
shear zone). The Bahama block also started moving north-
eastward.
Early Jurassic: Fig. 4 shows the plate positions at early
Jurassic time (170 m.y. bp). Laurasia drifted south-westward,
accommodated by sinistral shear along the Tethys seaway and
the El Pilar fault zone of northern South America. Opening
continued in the Gulf of Mexico. The Yucatan-Nicaraguan
craton was split, creating the Gulf of Honduras sphenochasm.
The Bahama craton lagged behind North America with respect
to Africa and thus continued moving north-eastward. As the
Gulf of Mexico, Caribbean Sea, and North Atlantic Ocean
were small ocean basins at this time, lacking open circulation
with the world ocean, deep-water evaporitcs such as the Louann
were laid down.
Mid-Jurassic: Fig. 5 shows the plate positions at the end of
mid-Jurassic (150 m.y. bp). As North America rotated north-
westward, Newfoundland separated from Spain. Continued
left-lateral shear occurred along the Tethys and El Pilar zones.
The Gulf of Mexico, Caribbean, and North Atlantic remained
as intracratonic ocean basins with continued salt deposition.
During the initial Atlantic opening the lack of reversals in
the Earth's magnetic field is reflected in the magnetic quiet zone
(MQZ). Starting at about 155 m.y. bp, however, reversals
created the magnetic anomalies seen in the North Atlantic
floor35 The absence of anomalies in the Gulf of Mexico is
mostly due to opening during the magnetic quiet time. During
the last stages of opening, rapid sedimentation into the rift zone
probably prevented rapid chilling of the pillow lavas which
record the polarity of the magnetic field.
As the Gulf of Honduras sphenochasm completed its opening,
the Yucatan and Nicaraguan cratons assumed their modern
positions relative to North America. West of the sphenochasm
hinge, the east-west Guatemalan foldbelt was formed, accom-
panied by the emplacement of serpentine bodies. Highlands
produced by this orogenesis shed a thick sequence of continental
and marine Jurassic sediments in Central America25. We
propose that this deposition extended the eastern continental
margin of the Nicaragua craton and filled the western end of
the Gulf of Honduras. This sedimentary wedge would later
form the nucleus of the Greater Antilles.
^..
Fip. 4 Blocking out of the American Mediterranean 30 m.y.
after commencement of drift X indicates salt deposits; other
symbols as in Fig. 3.
22
NATURE VOL 232 JULY 2 1971
The formation of the Gulf of Mexico was complete at this
stage; the Nicaraguan block had rotated about 2,500 km over
50 m.y., an opening rate of 5.0 cm/yr.
Lower Cretaceous: Fig. 6 shows the plate positions at the
end of the Lower Cretaceous (100 m.y. bp). South America
separated from Africa at about 135 m.y. bp and became a new
plate. Both the North and South American plates encountered
subduction zones (trenches) along their western margins which
probably had west-dipping Benioff zones. On impingement
with the continents, the zones flipped to east-dipping. Marginal
orogeny with attendant volcanism ensued.
Soon after South America separated from Africa, Nicaragua
separated from South America as a result of the more northerly
motion of the North American plate. An open connexion to
the Pacific Ocean was established. The Caribbean Sea, thus
created, opened wider than it is today. Towards the end of the
Lower Cretaceous, the South American plate shifted to a more
northerly motion. This resulted in cessation of strike-slip
motion along the El Pilar zone and the initiation of subduction,
compression, and orogeny along northern Venezuela36.
We propose that the Jurassic sedimentary accretionary
wedge within the Gulf of Honduras (the proto-Cayman trench)
and under the eastern edge of the Nicaraguan block split away
from the Nicaraguan craton on both sides of the proto-Cayman
trough to form the nucleus of proto-Cuba and proto-Hispaniola.
As North America drifted westward, these blocks lagged
behind, drifting north-eastward with respect to North America.
Subduction zones formed along their northern margins causing
orogeny, metamorphism of the Jurassic sediments, and volcan-
ism. Rocks from the central gap in the original fit (Fig. 2) were
also incorporated. Later, platform sediments were deposited
along the northern edge of Cuba, completing the geosynclinal
sequence there.
The Lesser Antilles arc was also initiated as a subduction
zone, reflecting the faster rate of westward drift of the North
American plate. We suggest that the Aves Ridge, located
250 km west of the modern Lesser Antilles, was the initial arc
which was later abandoned by eastward migration of the
Benioff zone. The plate boundary between the North and
South American plates in the Atlantic Ocean is thought to be
marked by several shear zones extending eastward from the
Lesser Antilles1.
Mid-Eocene: The Caribbean region attained essentially its
modern aspect by the end of the Middle Eocene (45 m.y. bp)
Fig. 6 Positions at the end of the Lower Cretaceous after 100
m.y. of drift. Hatched arrow on North American plate shows
the relative motion between the North and South American
plates; open arrows show motion relative to Africa as in
previous diagrams. Heavy dashed lines are subduction (trench
or compression) zones. The Jurassic sediment wedge from
Fig. 5 has split off into two parts to form the nucleus of the
Greater Antilles. The Lesser Antilles subduction zone is at
the Aves Ridge. The Caribbean Sea is seen to be wider than it
is today. Venezuelan orogenesis starts.
END OF
MIDDLE EOCENE
Fig. 5 The Gulf of Mexico Caribbean near the end of the
mid-Jurassic (150 m.y. bp). Note area of Jurassic sediments
along the Nicaraguan craton. MQZ is the Magnetic Quiet
Zone. Yucatan, Nicaragua, and the south-eastern Bahamas
have reached their present position relative to North America
Heavy dashed line west of South America is a trench zone
Fig. 7 The end of the mid-Eocene. The plates arc essentially
in their present position The Panama twist is formed due to
differential motion between the North and South American
plates.
(Fig. 7). Cuba and Mispaniola completed their north-eastward
relative motion. Additional spreading centres south of the
Cayman trough are postulated to have split proto-Hispaniola
into further numerous sub-blocks — that is, Jamaica, Hispaniola,
Puerto Rico, the Virgin Islands and so on — whose edges are
reflected by intermediate depths. The Beata Ridge may also
be one of these. Interaction along the leading plate boundaries
and within the Caribbean blocks continued orogeny throughout
the Tertiary"117 19. Active subduction beneath the Lesser
Antilles arc moved eastward to its modern position during the
lioccne. As North America drifted faster than South America,
the Caribbean region closed slightly. Continued compression
along northern Venezuela and distortion of the Panamanian
reuion resulted Vulcanism slowly closed the Isthmus land gap.
NATURE VOL. 232 JULY 2 1971
23
Fig. 8 Present situation. Continued motion between the
North and South American plates is accommodated mainly by
the Cayman-Puerto Rico shear zones, the Lesser Antilles
subduction zone (which has migrated eastward), and a poorly
defined shear zone extending eastward from the Lesser Antilles.
Orogeny also continued along the Pacific plate margins,
responding to this subduction zone which was pushed westward
along the leading continental edge.
Present: Throughout the remainder of the Caenozoic to
the Present there was and is continued differential motion,
interaction and closure between the two American plates
(Fig. 8). We regard these two plates as distinct entities separated
mainly by the Cayman-Puerto Rico megashear. Thus, the
east-west plate boundary has shifted from the northern margin
of South America to the Cayman-Puerto Rican shear zone.
The Gulf of Mexico is part of the North American plate, while
the Caribbean region is part of the South American plate. The
El Pilar zone is mostly inactive today40.
In the Neogene interaction of the North American plate with
part of the East Pacific Rise caused separation and northward
slippage of Baja California. The Galapagos-Panama ridge-
fracture system was created within the East Pacific plate during
the last 10 m.y.41.
Consequences of the Model
The foregoing is an attempt to formulate a reasonable plate
tectonic history of the Gulf of Mexico/Caribbean region within
the context of known geology. Some consequences of our model
are as follows.
(1) The age of the sea floor crust of the region would be
largely early drift — that is, early Jurassic for the Gulf of
Mexico and mostly Lower Cretaceous for the Caribbean. There
was a large amount of early extension and emplacement of new
crust, followed by slight closure during the Tertiary. No
Palaeozoic oceanic crust would be present.
(2) The Yucatan and Nicaraguan blocks are clearly old
cratons which, by their movement, formed the Gulf of Mexico
before the mid-Jurassic period. Movement of these blocks was
completed before South America separated from Africa at
about 135 m.y. bp. The Caribbean Sea attained a modern
aspect by Upper Cretaceous time at 100 m.y. bp.
(3) Both the Greater and Lesser Antilles are regarded as
primarily neocratonic (that is, post-breakup in origin). Meta-
morphism has obscured the central pre-drift "gap" mateiial
which, if present, was incorporated into the eugeosynclinal
belts of the Greater Antilles.
(4) The Caribbean area is a subplate presently attached to
the South American plate, with little or no movement between
them at this time. It is protected from destruction by inward-
dipping subduction zones on both cast and west. The Gulf of
Mexico, Yucatan, Cuba, and Bahama areas are parts of the
North American plate.
(5) The early differential motion between the North and
South American plates was accommodated by a shear zone
along the northern margin of South America. The present
differential motion is accommodated by shear along the
northern Caribbean margin (the Cayman-Puerto Rico trench
system), and is much less than during the initial stages of
movement.
(6) Unlike the solution from Bullard's fit, the region was
fully closed before 200 m.y. bp so that there was no "Mare
Occidentalis" — western bay indenting Pangaea.
Received March 23 ; revised May 24, 1971.
1 Ball, M. M., and Harrison, C. G. A., Trans. Gulf Coast Assoc.
Geol. Soc, 287 (1969).
2 Carey, S. W., in A Symposium on Continental Drift, 177 (Univ.
Tasmania, Hobart, 1958).
3 MacGillavry, H. J., Proc. Kon. Neder. Akad. van Weten., B, 73,
64(1970).
4 Meyerhoff, A. A., Trans. Gulf Coast Assoc. Geol. Soc, 217 (1967).
5 Almy, jun., C. C, Trans. Gulf Coast Assoc. Geol. Soc, 269 (1969).
6 Bass, M. N., in Tectonic Relations of North Central America and
the Western Caribbean, 283 (AAPG Mem. 11, 1969).
7 Dengo, G., and Bohnenberger, O., in Backbone of the Americas,
203 (AAPG Mem. 11, 1969).
8 Hess, H. H., in Caribbean Geological Investigations, 1 (Geol. Soc.
Amer. Mem. 98, 1966).
9 Kesler. S. E., and Heath, S. A., Bull. Geol. Soc. Amer., 81, 2471
(1970).
10 Khudoley, K. M., Amer. Assoc. Petrol. Geol. Bull., 51, 668 (1967).
' ' McBirney, A. R., and Bass, M. N., in Tectonic Relations of North
Central America and the Western Caribbean, 203 and 269
(AAPG Mem. II, 1969).
12 Bowin, C. O.J. Geophvs. Res., 73, 5159(1968).
13 Bracey, D. R., Geophysics, 33, 950 (1968).
14 Bush, S. A., and Bush, P., Trans. Gulf Coast Assoc Geol. Soc,
281(1969).
5 Chase, R. L , and Bunce, E. T.,J. Geophvs. Res., 74, 1413 (1969).
6 Malloy, R. J., and Hurley, R. J., Geol. Soc Amer. Bull., 81,
1947(1970).
7 Molnar, P., and Sykes, L. R., Geol. Soc. Amer. Bull., 80, 1639
(1969).
8 Rona, P. A., Nature, 224, 141 (1969).
9 Uchupi, E., and Emery, K. O., Amer. Assoc. Petrol. Geol. Bull.,
51,223(1967).
0 Uchupi, E., and Emery, K. O., Amer. Assoc Petrol. Geol. Bull.,
52, 1162(1968).
' Uchupi, E., and Emery, K. O., Woods Hole Oceanog. Inst.
Contrib., 2525 (1970).
2 Dietz, R. S., and Holden, J. C, J. Geophys. Res., 75, 4939 (1970).
3 Bullard, E., Everett, J. E., and Smith, G. E., in A Symposium on
Continental Drift, 41 (Royal Soc, London, Philos. Trans.,
1965).
4 Dengo, G., Trans. Gulf Coast Assoc. Geol. Soc, 311 (1969).
5 Mills, R. A., Hugh, K. E., Feray, D. E., and Swolfs, H. C, Amer.
Assoc. Petrol. Geol. Bull., 51, 171 1 (1967).
6 Sheridan, R. E., Draie, C. L., Nafe, J. E., and Hennion, J.,
Amer. Assoc. Petrol. Geol. Bull., 50. 1972 (1966).
7 Dietz, R. S., Holden, J. C, and Sproll, W. P., Geol. Soc. Amer.
Bull., 81, 1915(1970).
8 Jacobs, C, Burgl, H., and Daniel, L. C, in Backbone of the
Americas, 62 (AAPG Mem. 2, 1963).
9 Bayley, R. W.and Muehlberger, W. R., Basement Map of the US
(US Geol. Surv., 1968).
0 deCserna, Z., Bol. Soc. Geol. Mexico, 30, 159 (1969).
' Flawn, P., The Ouachita System (Univ. Texas Pub. 6120, 1961).
2 Scott, K. R . Hayes, W. E., and Fietz, R. P., Trans. Gulf Coast
Assoc. Geol. Soc, 11, 1 (1961).
3 deBoer. J.. Geol. Soc. Amer. Bull., 79, 609 (1968).
4 Geol. Soc. Phanerozoic Time Scale: Quart. J. Geol. Soc. London,
1 20S, 260(1964).
5 Talwani, M., Windisch, C. G , and Langsett, jun., M. G., J.
Geophvs. Res., 76,473(1971).
6 Mencher, E . Fichter, H. J., Renz, H. H., Wallis, W. E., Patterson,
J. M., and Robic. R. H., Amer. Assoc. Petrol. Geol. Bull., 37,
690(1953).
7 Bowin. C. O, in Caribbean Geological Investigations, II (Geol.
Soc. Amer. Mem. 9X, 1966).
8 Mattson, P. H.. in Continental Margins and Island Arcs (edit, by
Poole. W. H), 124 (Geol. Surv Canada, 1966).
" Whctten, J. T., in Caribbean Geological Investigations, 177 (Geol.
Soc. Amer Mem. 98. 1966).
0 Metz. H. L , Proc. IV Caribbean Geol. Conf., 293 (1965).
' Grim, P. J., Marine Geophvs. Res., 1, 85 (1970).
Reprinted from Interocean '70 2, 65-71
56
Engineering Properties of North Atlantic Deep-Sea Sediments
George H. Keller, National Oceanic and Atmospheric Administration, Atlantic Oceanographic and Meteorological Laboratories,
Miami, Florida, USA
Abstract
The engineering characteristics of river, harbor and certain coastal
sediments have been investigated since man found it necessary
to construct structures such as wharves, jetties and various pile
supported platforms. Only during the past decade has some atten-
tion been devoted to the engineering properties of deeper coastal
water deposits and even more recently to the similar aspects of
deep-sea sediments. Initial studies of North Atlantic deposits
(upper 10 to 20 m [33 to 66 ft.]) for such properties as shear
strength, unit weight, water content, and porosity reveal consider-
able variation, yet in some areas there exists a definite correlation
between these properties and sediment type, current flow and sea
floor topography. With the advent of the U. S. Deep Sea Drilling
Project, our knowledge of the sediment blanket covering the
ocean basins has been advanced appreciably. Among the many
analyses made on the Deep Sea Drilling Project cores are those for
water content, unit weight (bulk density) and porosity to depths
of 1070 m (3 5 10 ft.) below the sea floor. This program has
provided a significant insight into range and variation of these
properties to depths greater than has been possible to reach by
conventional deep-sea coring techniques. Although some general-
izations can be made about the area! distribution and range of
certain engineering properties within the surface layers of deep-
sea deposits, local lateral variation may be considerable, in some
cases exhibiting coefficients of variation as high as 147 percent
and more frequently on the order of 30 to 50 percent. To date,
we have but little insight into the engineering properties of deep-
sea sediments. Before significant data is available to deal with the
stability of sea floor deposits both in regard to their foundation
characteristics as well as their mass movement, much more
regional and detailed sampling is required.
Introduction
Relatively little is known about the engineering properties of
deep-sea sediments and as yet only broad generalizations can be
made concerning these properties within the upper few meters of
the sea floor. An untold number of engineering investigations have
been made in river and coastal waters for various projects such as
the construction of wharves and jetties or the installation of sub-
marine pipelines. Since about 1950 an increasing number of
foundation studies have been carried out on the continental
shelves in conjunction with the erection of offshore drilling plat-
forms. To date, the majority of the engineering studies conducted
on deep-sea deposits have been made by marine geologists investi-
gating different aspects of the deep ocean environment (Richards,
1961, 1962). A number of these studies have dealt with specific
relationships such as sound velocity and mass properties
(Hamilton, 1956; Buchan et al., 1967), density variation with
depth (Igelman and Hamilton, 1963), consolidation charac-
teristics and depositional history (Bryant et al., 1967; Richards
and Hamilton, 1967) or have discussed the engineering properties
of a local area (Moore and Shumway, 1959; Harrison et al., 1964).
Utilizing data from approximately 500 sediment cores
(Atlantik - 300, Pacific - 200), Keller (1968) provided the first
regional generalization of the distribution of selected engineering
properties in the North Atlantic and North Pacific basins.
Commencing with the U. S. Deep Sea Drilling Project in 1968 an
entirely new aspect of these studies has been made possible. This
program has provided deep-sea cores from depths as great as
1070 m (3 510 ft.) below the sea floor on which engineering tests
have been made for unit weight (bulk density), water content,
porosity and relative strength. A discussion of some of these data
follow in a later section.
This paper is a discussion of the available engineering properties
data for the North Atlantic basin deposits. In addition to presenting
the areal distribution of selected properties, it also includes a sec-
tion dealing with ultimate bearing capacity of surface materials
and the consolidation characteristics of deep-sea sediments. Local
variation of engineering properties both laterally and vertically
proves to be significant in contrast to some early speculations that
deep-sea deposits are homogeneous. These findings, in conjunction
with presentation of data from one of the deepest holes yet
drilled in the North Atlantic are discussed herein.
Areal Distribution of Engineering Properties
Sediment Types
To set the stage for later discussions it is important to visualize
the overall types of sediment that occur in the North Atlantic
basin. The distribution pattern of bottom sediments as it is known
today has been presented in various publications (U. S. Naval
Oceanographic Office, 1965; Keller and Bennett, 1968; and Inter-
departmental Geophysical Committee of the Academy of Sciences,
USSR, 1969). Using the classification of Keller and Bennett
(1968) it is seen that much of the North Atlantic is blanketed by
calcareous ooze, Fig. 1, which, as used here, is a sediment con-
sisting of at least 30 percent calcium carbonate in the form of
skeletal material from various planktonic animals and plants.
Deposits of terrestrial origin, later reworked by the sea, consti-
tute the major sediment type (fluvial marine) along the margin of
the basin.These deposits are relatively widespread and extend
considerable distances into the basin revealing the strong influence
terrestrial drainage has on the sediments of the North Atlantic.
Unlike the Pacific basin, the occurrence of "red clay" is not very
extensive. Unique deposits of calcareous sand and silt (commonly
shell fragments and coralline debris) occur in the area of the
Bahama Islands and the Straits of Florida. Although the distribu-
tion pattern shown in Fig. 1 is relatively simple, it is highly prob-
able that it will increase in complexity as more samples become
available. The reader is referred to the study by Keller and Bennett
(1968) for a more detailed discussion of the classification used
here.
Shear Strength
Shear strength measurements were made on samples consisting
primarily of fine grained cohesive material (silty clay and clayey
silt) with an occasional stringer of fine sand occurring in some of
the cores. Shear strength of this sediment type is a function ot
© VDI-Verlag GmbH, Diisseldorf, West-Germany
cohesion, the angle of internal friction of the material und the
effective stress normal to the shear plane, commonly expressed as:
Z{ = c + a tan </>
where c is cohesion, a the effective stress and <p the angle of
internal friction. Cohesive, saturated sediments stressed without
loss of pore water behave with respect to the applied load as if
they were materials without any angle of internal friction (0=0).
In which case, shear strength is equal to the cohesion (Tf = c). A
more detailed discussion of shear strength can be found in soil
mechanics texts such as Taylor (1948) and Scott (1963).
Shear strength measurements were made by either of two
methods: unconfined compression test or laboratory vane shear.
Testing procedures used to accommodate the relatively weak sub-
marine sediments have been discussed by Richards (1961). In the
case of the unconfined test, the sediments were considered to be
clays or materials behaving like clays and the shear strength was
taken as one-half the unconfined compressive strength.
along the Mid-Atlantic Ridge. Available data indicates that a band
of low shear strength material may extend in an east-west direc-
tion across the Atlantic at approximately 15CN. A definite ex-
planation for this occurrence is not readily available without
additional data. However, the westward flow of the Equatorial
Currents across this portion of the basin may in some way account
for the distribution of these relatively low strength sediments.
Sediments along this band tend also to possess low unit weights
and high water contents.
Sediments east of Greenland display unique properties relative to
most of the North Atlantic deposits. Here, shear strengths are
some of the lowest yet reported for the North Atlantic and pos-
sibly may be attributed to the influx of sediment from Greenland
and the Arctic as well as reflecting the general current circulation
pattern for this area (Keller and Bennett, 1968). The highest
average shear strengths ( 1 ,5 to 2,0 psi [105 to 141 g/cm2]) yet
found in the Atlantic are those associated with the calcareous
Figure 1. Sediment distribution in the North Atlantic
Figure 2. Distribution of average shear strength in the North Atlantic
Sediment cores used in this study vary from 30 cm (12 in.) to
approximately 7 m (23 ft.) in length. Values of shear strength and
water content shown in Fig. 2 and 3 respectively, represent
averages of the measured parameter over the entire length of each
core. As a rule of thumb, these data can be considered als repre-
senting average values for the upper 2,5 m (8 ft.) of the sea floor.
Shear strengths in the upper few meters of the sea floor are found
to vary from 0,5 to 2,0 psi (35 to 141 g/cm2). As shown in Fig. 2,
much of the basin consists of deposits possessing average shear
strengths of 0,5 to 1 ,0 psi (35 to 70 g/cm2). Strengths of less than
0,5 psi (35 g/cm2) are often observed in coastal areas where local
drainage or current conditions result in the deposition of relatively
weak deposits. Other areas of low shear strength are found
associated with the "red clay" deposits and in isolated patches
deposits surrounding the Bahama Islands and on the Blake Plateau
off the southeast coast of the United States.
Water Content
Water content is expressed as a percent of the ratio: weight of
water to the weight of oven dried solids in a given sediment mass.
Laboratory techniques for this determination can be found in
most texts dealing with soil mechanics and are not discussed here.
Average sediment water contents for the North Atlantic range
from 30 to 175 percent, but more commonly are between 50
and 1 00 percent (Keller and Bennett, 1 968) (Fig. 3). Higher water
contents are found in areas influenced by major drainage systems
such as off the Mississippi and St. Lawrence rivers. A sizable area
of relatively high water content extends from Africa westward to
the Caribbean and may, as noted earlier, possibly be attributed to
the general current pattern in this part of the basin. The isolated
patches of high and low water content sediments found in the
basin may be related to topographic irregularities, which by
influencing current conditions have altered the depositional
environment on a local basis (Keller and Bennett, 1968). As ob-
served in the case of shear strength, the sediments east of Green-
land display anomalous water contents relative to those of other
portions of the basin. Water contents of less than 50 percent
predominate throughout much of the Greenland Sea area.
Unit Weight and Porosity
The distribution of average sediment unit weight (bulk density)
and porosity for the North Atlantic has been discussed by Keller
and Bennett ( 1968) and will only be summarized here. Unit
weights range from 80 to 125 pcf (1,3 to 2,0 g/cc), with the
majority of the basin deposits exhibiting values between 95 and
■ n u
30- 0-
Figure 3. Distribution of average water content in North Atlantic sediments
110 pcf (1,5 to 1,8 g/cc)-. Offshore from large drainage systems
(Mississippi and St. Lawrence rivers) densities are commonly below
95 pcf (1,5 g/cc). A prominent feature in the regional distribution
of bulk density is a band of relatively low density (78 to 94 pcf
[1,2 to 1,5 g/cc]) material characterizing a 350 mile (563 km)
wide portion of the sea floor between Africa and the Caribbean
in the vicinity of latitude 1 5°N.
Average sediment porosities for most of the North Atlantic
seldom exceed 70 percent and more commonly range between 60
and 65 percent. Only in small isolated portions of the basin and in
the area influenced by the St. Lawrence River are porosities
greater than 80 percent found (Keller and Bennett. 1968). Average
porosities of less than 50 percent are relatively rare in the Noth
Atlantic.
Ultimate Bearing Capacity
For the engineer concerned with the placement of an installation
on the sea floor, the bearing capacity and consolidation charac-
teristics of the foundation material must be ascertained. If the
load is relatively small, it may only be necessary to determine the
bearing capacity in order to know the depth to which a structure
or piece of hardware will penetrate the sea floor during the initial
installation.
Ultimate bearing capacity is the average load per unit area required
to provide failure by rupture of a supporting sediment mass. It is
a function of the product of the shear strength and one or more
factors, which are dependent on the size and shape of the load as
well as the depth of loading. For the purpose of this discussion, a
formula for the ultimate bearing capacity of sediment under a
strip load (load infinitely long relative to width) at the surface is
used for the determination of the values shown in Fig. 4. The
general bearing capacity formula for a shallow strip foundation
developed by Prandtl (1920) and later modified by Terzaghi
(1943) is:
Qc
cNc + 7DNq +
7BN7
(1)
when Qc is the ultimate bearing capacity, 7 the sediment unit
weight, B the width of the load, D the depth of the load below
the surface, and Nc, N , and N7 are dimensionless factors depend-
ent on the angle of internal friction, depth and shape of the
foundation and roughness of the base. For the case of a surface
load and zero angle of internal friction, the factors N and N7 are
equal to unity and zero respectively and equation ( 1 ) is simplified
to:
Qc = cNc
90°
(2)
60°
45 ■
5- 15'
ULTIMATE BEARING CAPACITY
Jgf- .3 3 •!' »6 9
^ I 3 .0 I .25
Figure 4. Ultimate bearing capacity values at the sea-floor surface for
a strip load
where Nc equals 5,14 according to Prandtl. Other values for Nc
are found to be in use by various investigators. Using equation (2)
and a selected number of essentially surface (0-5 cm [0-2 in.])
shear strength values, ultimate bearing capacities have been deter-
mined for portions of the North Atlantic (Fig. 4).
An example comparing values shown in Fig. 4 with a calculated
load will serve to illustrate the significance of these bearing capy-
city values. If a strip load whose buoyed weight is 1 ,000 pounds
(454 kg) and has a surface area of 400 in2 (2 581 cm2), is placed
on the sea floor without impact, the resulting stress on the sedi-
ment will be 2,5 psi (176 g/cm2). An ultimate bearing capacity of
at least this amount is necessary to prevent a shear failure. As can
be seen from Fig. 4, such a load would not cause a shear failure at
most of the core sites. This assumes no safety factor is used, which
generally is never the case in actual practice. Depending on the
safety factor used, much of the North Atlantic deposits would not
be considered capable of supporting the strip load used in this
example.
Consolidation Characteristics
Consolidation in the engineering sense refers to the gradual de-
crease in volume of a sediment under an imposed load. Consolida-
tion characteristics are rather important since they indicate the
depth to which a structure or some load will settle into a sedi-
ment, and, in conjunction with studies of overburden pressures,
they may result in geological conclusions as to the volume of
original sediment and the vertical variations of density and poros-
ity in the sedimentary deposit. Based on the consolidation test,
sediments are usually classified as normally consolidated, under-
consolidated or overconsolidated. They are classed as normally
consolidated if the present effective overburden pressure is the
greatest yet imposed on the deposit; they are said to be over-
consolidated if the test indicates that the deposit has been sub-
jected to pressures greater than those presently effective. If a
deposit has not yet been consolidated under the present pressure,
it is considered to be underconsolidated.
A majority of the deep-sea sediments that have been tested for
their consolidation characteristics reveal they are slightly over-
consolidated (Hamilton, 1964; Bryant et al., 1967; and R ichards
and Hamilton, 1967). Although there is little doubt about the
validity of the consolidation tests, it is obvious that the deposits
have not been subjected to loads greater than their present over-
burden pressure nor have they been dessicated. Factual data are
not yet available, but a number of investigators have proposed
that this unique overconsolidation condition may result from very
slow rates of deposition, and "chemical cementation" by inter-
particle or ionic bonding {Rittenberg et al., 1963; Hamilton,
1964). This unique property of deep-sea sediments would indicate
that they can support greater loads than might have been anti-
cipated.
Lateral Variations of Engineering Properties
The earlier figures displaying regional distribution of shear strength
and water content may be deceiving in that they suggest that
sediments possessing relatively uniform properties extend over
large areas of the North Atlantic. In reviewing the available
engineering data for deep-sea sediments within the upper 7 m
(23 ft.) of the sea floor, Keller and Bennett (1970) reported on
the variations of selected properties both for the North Atlantic
as a whole as well as for specific sediment types found in the basin,
Table 1. These data clearly point out some of the large variations
that can be anticipated in this environment.
Variation of engineering properties within a local area have re-
cently been examined by Bennett etal. ( 1970). Their study con-
sisted of determining certain engineering properties in three sedi-
ment cores collected from an area of 400 cm2 (6,2 in.2) in a basin %
approximately 2000 m (6560 ft.) deep off the island of Puerto z
Rico. Tests were carried out on three corresponding horizons in i
each core and a comparison made of the variation among the 2j
measured parameters in these horizons using the statistical ex-
pression, "coefficient of variation". As shown in Table 2, a con-
siderable degree of variation exists in even such a small area. The
greatest variations occurred among such properties as sensitivity
(ratio of natural to remolded strength), shear strength and texture,
whereas unit weight and grain specific gravity displayed relatively
little change. This same discussion included a comparison of data
taken from a study by Richards (1964) on four cores collected
from an area approximately 0,2 km2 (0,08 mile2) in the northwest
Table 1 . Variation of Engineering Properties for the North
Atlantic as a whole (modified from Keller and Bennett, 1970)
y
w
T)
h
St
G
WL
wp
(pcf)
(%)
(%)
(psi)
Max.
Min.
Ave.
165
78
95
207
15
86
85
32
66
12.9
.01
0.7
88
1
4
2.86
2.45
2.73
109
47
65
38
20
27
Variation of Engineering Properties for Selected Sediment Types in
North Atlantic Basin
the
Carbonates
y
w
1
h
St
G
WL
Wp
(pcf)
(%)
(%)
(psi)
Max.
Min.
Ave.
114
84
94
132
15
96
78
45
72
Fluv
12.9
0.1
1.1
al Marine
88
1
10
2.86
2.63
2.71
109
77
101
30
26
29
Max.
Min.
Ave.
165
80
91
188
28
112
80
44
73
10.1
.01
0.9
57
1
4
2.81
2.45
2.67
101
47
85
38
20
29
"Red Clay"
Max.
Min.
Ave.
127
78
90
207
23
159
85
32
74
3.3
.01
0.6
25
1
9
2.84
2.46
2.54
107
102
105
-
>
w
'J
s
unit weight of soil
water content (% dry wt.)
porosity
shear strength
St
G
WL
Wp
sensitivity
grain specific gravity
liquid limit
plastic limit
Atlantic. Although covering a much larger area and a different
sediment type than that represented by the three cores, the rela-
tive degrees of variation were much the same among all seven
cores.
Vertical Variation of Engineering Properties
Until recently, sediment cores collected from the deep-sea floor
seldom reached lengths greater than 20 m (66 ft.). As a result, very
Little is yet known about the variation of engineering properties
to any great depth below the sea floor. Certain changes with depth
such as increasing shear strength and unit weight and decreasing
water content might be anticipated, based on terrestrial studies.
Care must be used, however, in applying such generalizations to
deep-sea deposits. Detailed studies on the upper few meters of
Figure 5. Variation of selected mass properties with depth in
two turbidite sequences
Table 2. Mass Physical Properties and Coefficients of Variation (V*) of three
Whiting Basin Cores (modified from Bennet, Keller and Busby, 1970)
Horizon Sampling Interval Water Content
(cm) (% dry weight)
Unit Weight
(pcO
Core 1 Core 2 Core 3 12 3V 1
2 3V
A 0-8 0-7 0-9 75 66 78 17 97.3
B 8-15 10-17 10-17 67 60 65 11 100.5
C 17-25 17-25 17-26 59 57 63 10 103.0
98.0 96.7 1.3
102.3 101.1 1.8
104.2 101.1 3.0
Grain Specific Gravity Shear Strength Sensitivity
(psi)
Liquid Limit
(%)
123V 123V 123V
12 3V
2.78 2.77 2.78 0.4 0.3 0.3 0.2 37 3.2 2.7 2.5 25
2.79 2.78 2.78 0.4 0.7 0.6 0.5 33 3.3 5.4 2.8 63
2.78 2.80 2.79 0.7 1.1 2.1 0.8 100 6.2 40.7 7.4 147
34 35 35 3
41 39 37 10
35 34 38 11
Plastic Limit Porosity Sand Silt
(%) (%) (%) (%)
Clay
(%)
123V 1 2 3V123V 123
V
12 3V
29 29 28 3 67.8 65.9 68.6 4 42 36 41 15 35 40 37
29 31 31 7 65.6 63.1 64.7 5 29 22 36 48 42 46 40
28 25 31 21 62.6 62.1 64.4 3 29 40 25 46 43 39 45
13
14
14
23 24 22 9
29 32 24 29
28 21 30 35
100 -
o
O
^» UJ
> I- 400
2s
UJ -—
to
I
2; 500
600
UNIT WEIGHT •
80 100 120 (pcf)
BREAKS IN
CORED INTERVAL
*) coefficient of variation represents a measure of the range of values expressed as ;
percent of the median value (Balsley, 1964)
the sea floor indicated that some portions of the ocean basins
contain sediments exhibiting considerable degrees of variation
with depth (Richards, 1961 ).
Turbidite sequences (layers of relatively coarse material interlaid
with fine sediments) are common to many portions of the deep-
sea and possess extreme variations among their mass properties
within relatively short intervals. Analyses of cored samples from
two such deposits clearly attest to this distinctive characteristic.
Fig. 5. Richards and Keller (1962) found in their detailed study
of a sediment core from off Nova Scotia, that within the uppei
180 cm (71 in.) of the sea floor, water contents varied from 27 to
100 percent.
It was not until 1961, during the United States MOHOLE project,
that sediment cores longer than 25 m (82 ft.) were obtained from
the sea floor. More recently the U. S. Deep Sea Drilling Project
has provided sediment cores from as deep as 1070 m (3 510 ft.)
below the ocean floor. Although these samples are disturbed to
some degree, it has been possible to make tests for certain en-
gineeruig properties of these cores.
The 1961 MOHOLE drilling off Guadalupe Island in the Pacific
(28° 59'N, 1 1 7° 30'W) obtained cores through the 1 70 m (558 ft.)
of sediment overlying the basaltic basement. At this site water
contents ranged from 1 10 percent at the surface to 40 percent at
a depth of 170 m (558 ft.) (Rittenberg et al., 1963). There was
not, however, a continual decrease in water content with depth.
Within the interval 100 to 140 m (328 to 459 ft.) values as high
as 120 percent were reported. Hamilton (1964) reported the
somewhat surprising finding, that porosity varied little (5 percent)
within the 170 m (558 ft.) interval.
20 40 60 80 100
WATER CONTENT (7.DRY WT )
20 40 60 80
POROSITY (%) ▲
Figure 6. Variation of unit weight, water content and porosity with depth
at Site 9 (32° 37' N, 59° 10' W) of the Deep Sea Drilling Project
Recent deep-sea drilling in the North Atlantic has contributed
significant data on deposits as much as 834,5 m (2737 ft.) below
the sea floor (Peterson et al., 1970). Site 9 (32° 37'N, 59° 10' W)
of the Deep Sea Drilling Project provides the deepest cored inter-
val in the North Atlantic basin yet obtained. Although the hole
was not cored continuously, these samples are of the utmost value
in any study pertaining to deep-sea sedimentation. Variations with
depth of porosity, unit weight and water content have been
plotted, Fig. 6, based on the report of Peterson et al. ( 1970). Sur-
face values were obtained from unpublished data obtained from
short cores collected in the vicinity of Site 9. Porosity and water
content tend to decrease with depth. Contrary to the findings of
Hamilton (1964) at the Guadalupe site, porosity decreases signifi-
cantly from approximately 82 percent at the surface to 43 per-
cent at a depth of 764 m (2506 ft.) It should be noted, however,
that there is very little change in porosity below 450 m (1 476 ft.).
Unit weight (bulk density) increases gradually with depth, ranging
from 1 ,5 g/cc (94 pcf) at the surface to 2,0 g/cc (1 25 pcf) at a
depth of 682 m (2237 ft.). An anomalous interval between 204
and 213 m (669 to 699 ft.) is attributed to the interbedding of
clay and foraminiferal ooze.
Summary
Investigation of the engineering properties of deep-sea sediments
has only received serious consideration in the past ten to fifteen
years, and as yet, relatively little has been learned in this area of
study. To date, most of the studies have been carried out by
marine geologists, who, by applying certain aspects of soil me-
chanics, have and are attempting to investigate the various sedi-
mentological and environmental characteristics of the unconsoli-
dated deposits blanketing much of the sea floor. Thousands of
sediment cores have been collected from the North Atlantic,
however, relatively few (400 to 500) were obtained for the spe-
cific purpose of investigating the engineering properties of sub-
marine sediments. Although 400 to 500 cores from an area of
approximately 41 X 106 km2 (15,8 X 106 miles2) do not provide
representative samples of all the North Atlantic deposits, some
generalizations are possible based on these few data:
(a) Calcareous oozes constitute the greatest single sediment type
blanketing the North Atlantic basin. Fluvial-marine deposits are
the second most abundant sediment type, occurring primarily
along the basin margins and in the area between Greenland and
Europe.
Although "red clays" are present, they make up only a small
percentage of the sediment types found in the North Atlantic.
(b) Average shear strength values for the upper few meters of the
sea floor vary from less than 0,5 psi (35g/cm2) to 2 psi (1 40 g/cm2),
but more commonly are found to range from 0,5 to 1 psi (35 to
70 g/cm2) over most of the North Atlantic. The highest values yet
observed are found in association with the almost pure carbonate
deposits of the Bahamas.
(c) Average water contents within the upper 9 to 10 m (30 to
33 ft.) of deep-sea sediments range from slightly less than 50 per-
cent to about 175 percent by dry weigth. The majority of the
North Atlantic deposits exhibit water contents on the order of
50 to 100 percent.
(d) Unit weight (bulk density) varies from 80 to 125 pcf (1,3 to
2,0 g/cc), but more frequently from 95 to 109 pcf (1,5 to 1,8 g/cc)
for the majority of the sediments yet investigated in this basin.
Lower densities are commonly found in areas influenced by the
debouching of large drainage systems such as the Mississippi and
St. Lawrence rivers. Sediment porosities seldom exceed 70 per-
cent, but do reach as high as 85 percent in a limited number of
areas. More commonly, average porosities are on the order of
60 to 65 percent over most of the basin.
(e) Using the bearing capacity equation for surface loading of a
strip load, ultimate bearing capacities were calculated for 22 sites
in the North Atlantic. These values ranged from 0,1 to 6,9 psi
(7 to 485 g/cm2), with the majority being 1,5 psi (105 g/cm2) or
higher.
Deep-sea sediments are commonly found to exhibit consolidation
characteristics similar to those terrestrial deposits classed as
slightly overconsolidated. This property is undoubtedly not due
to previous loading or desiccation, but may be a result of the very
slow rate of deposition taking place in the deep-sea along with
possible "cementation" from interparticle or ionic bonding forces.
A few studies of the degree of lateral variation of engineering
properties within a local area indicate that rapid changes of these
properties often occur over short distances. In one such study of
a 400 cm2 (6,2 in.2) area, coefficients of variation (degree of
dispersion) were found to be as great as 147 percent and 100 per-
cent for sensitivity and shear strength respectively.
Not only are laterial variations important in some areas, but as
might be expected, vertical changes in engineering properties can
be quite significant even within the upper few meters of the sea
floor. Turbidity current deposits, which are found to varying
degrees over most of the North Atlantic, exhibit some of the
severest variations in mass properties over intervals as small as a
few centimeters. Not until the advent of the U. S. Deep Sea
Drilling Project have sediment cores longer than 25 m (82 ft.) been
collected from the deep sea. Analysis of cored sediments collected
during this project to a depth of 834,5 m (2737 ft.) in the North
Atlantic ^as provided an insight into the changes of such proper-
ties as unit weight, water content, and porosity to this relatively
great depth. At drilling Site 9, the most drastic changes in these
properties occurred within the upper 40 m (131 ft.) of the sea
floor. Water content and porosity decreased considerably as unit
weight increased significantly. Below this depth water content
decreased continually throughout the cored interval, whereas
below a depth of 400 m (1 312 ft.) no significant change in poro-
sity was observed. Unit weight increased gradually with depth
except in a few intervals where relatively thin layers of contrasting
sediments such as foraminiferal ooze caused notable decrease in
the unit weight.
The distribution and range of values presented here for selected
engineering properties is indeed an over simplification as to the
characteristics of deep-sea sediments. We have only begun to study
these properties and as with any new investigation there will be
continued revisions as more information becomes available.
Acknowledgements
I express my sincere appreciation to Joseph Kravitz of the U. S.
Naval Oceanographic Office and Suzanne Bershad of the National
Oceanographic Data Center for providing much of the basic data
used in this study. Critical review of the manuscript by Louis
Butler is gratefully acknowledged.
References
Balsley, H.L.: Introduction to statistical method. Littlefield, Adams & Co.,
Paterson, New Jersey 1964, 347 p.
Bennett. R.H., G.H. Keller and R.F. Busby: Mass property variability in
three closely spaced deep-sea sediment cores. J. Sedimentary Petrology (in
press), (1970).
Bryant, W.R., P. Cernock and J. Morelock Jr.: Shear strength and consolida-
tion characteristics of marine sediments from the western Gulf of Mexico,
pp. 41-62, in: Richards, A.F. (ed.) Marine Geotechnique, Univ. 111. Press,
Urbana, 111., 1967, 327 p.
Buchan, S., F.C.D. Dewes, DM. McCann and D. Taylor Smith: Measure-
ments of the acoustic and geotechnical properties of marine sediment cores,
pp. 65-92, in: Richards, A.F. (ed.) Marine Geotechnique, Univ. 111. Press,
Urbana, 111., 1967, 327 p.
Hamilton. E.L.: Low sound velocities in high porosity sediments. J. Acousti-
cal Soc. America, v. 28 (1956) pp. 16/19.
Hamilton, E.L.: Consolidation characteristics and related properties of sedi-
ments from experimental Mohole (Guadalupe site). J. Geophysical Research
v. 69 (1964) pp. 4257/269.
Harrison, W., M.P. Lynch and A.G. Altschaeffl: Sediments of lotver
Chesapeake Bay, with emphasis on mass properties. J. Sedimentary Petro-
logy, v. 34 (1964) pp. 727/55.
lgelman, K.R. and E.L. Hamilton: Bulk densities of mineral grains from
Mohole samples (Guadalupe site). J. Sedimentary Petrology, v. 33 (1963),
pp. 474/78.
Interdepartmental Geophysical Committee of the Academy of Sciences,
USSR: Bottom sediment chart. Main Administration for Geodesy and
Cartography, Moscow, USSR, 1969.
Keller, G.H.: Shear strength and other physical properties of sediments
from some ocean basins, pp. 391-417 in: Proceedings, Civil Engineering in
the Oceans. American Society of Civil Engineering, 1968, 926 p.
Keller, G.H. and K.W.Bennett: Mass physical properties of submarine sedi-
ments in the Atlantic and Pacific basins, pp. 33-50, in: Proceedings, XXIII
International Geological Congress, Sec. 8, 1968, 321 p.
Keller, G.H. and R.H. Bennett: Variations in the mass physical properties of
selected submarine sediments. Marine Geology (in press), 1970.
Moore, D.G. and G. Shumway: Sediment thickness and physical properties:
Pigeon Point Shelf, California. J. Geophysical Research, v. 64 (1959),
pp. 367/74.
Peterson, M.N. A., N.T.Edgar, M. Gta, S. Gartner Jr., R. Goll, C.Nigrini,
C. von der Boreh: Initial reports of the Deep Sea Drilling Project, v. II.
Washington, D. C, 1970, 501 p.
Prandtl, L.: (Jber die Harte plastischer Korper. Kbnigliche Gesellschaft der
Wissenschaften zu Gottingen, Mathematisch-physikalische Klasse, 1920,
p. 74/85.
Richards, A.F.: Investigations of deep-sea sediment cores, I. Shear strength,
bearing capacity, and consolidation. U. S. Navy Hydrographic Office, Tech*
Rept. 63, 1961, 70 p.
Richards, A.F.: Investigations of deep-sea sediment cores, II. Mass physical
properties. U. S. Navy Hydrographic Office, Tech. Rept. 106, 1962, 146 p.
Richards, A.F.: Local sediment shear strength and water content.
pp. 474-487, in: Miller, R.L. (ed.) Papers in Marine Geology, Shepard
Commemorative Volume. MacMillan Co., New York, 1964, 531 p.
Richards, A.F. and G.H. Keller Water content variability in a silty clay
core from off Nova Scotia. J. Limnology & Oceanography, v. 7, (1962),
pp. 426/27.
Richards, A.F. and E. L. Hamilton: Investigations of deep-sea sediment
cores, III Consolidation, pp. 93-117, in: Richards, A.F. (ed.) Marine Geo-
technique, Univ. 111. Press, Urbana, 111., 1967, 327 p.
Rittenberg, S.C., K.O.Emery, J. Hiilseman, E.T. Degens, R.C. Fay.
J.H. Reuter, J.R. Grady, S.H. Richardson and E.E. Bray: Biochemistry of
sediments in experimental Mohole. J. Sedimentary Petrology, v. 33 (1963),
pp. 140/72.
Scott, R.F.: Principles of soil mechanics. Addison-Wesley Pub. Co., Inc.,
Reading, Massachusetts, 1963, 550 p.
Taylor, D. W.: Fundamentals of soil mechanics. New York: John Wiley &
Sons, Inc., 1948, 700 p.
Terzaghi, K.: Theoretical soil mechanics. New York: John Wiley & Sons,
Inc., 1943, 510 p.
U. S. Naval Oceanographic Office: Oceanographic atlas of the North
Atlantic Ocean. Section V. Marine Geology, Pub. 700, 1965, 71 p.
57
Reprinted from Proceedings Civil Engineering in the
Oceans II, 857.
MASS PROPERTIES OF THE SEA FLOOR IN A SELECTED
DEPOSITIONAL ENVIRONMENT
fey
GEORGE H. KELLER1
INTRODUCTION
Man has only begun in the last twenty years to give
serious thought to exploiting the sea floor and subsea
floor. These interests have progressed gradually from
the shoreline to the continental shelf and now, in a few
specific areas such as sea-floor mining, into the deep
sea. As a result of rapid advances in science and tech-
nology, along with man's increasing desire to understand
and utilize the marine environment, the new field of
ocean engineering has evolved and is fast taking its
place beside the other areas of engineering. At this
early stage, much of the effort in this field consists of
adapting already established engineering principles to
the marine environment. This approach has worked reason-
ably well for the civil engineer concerned with the soil
mechanics or foundation aspects of the sea floor in the
relatively shallow waters of the continental shelf.
Investigation of the engineering properties of deep-sea
deposits has been limited to a small number of studies,
generally by marine geologists interested in the depo-
sitional processes taking place in the ocean basins.
In contrast to the wealth of soil mechanics data
available for terrestrial soils, very little is known
about the engineering properties of deep-sea sediments
and even less is understood about the influence this
unique environment may have on these properties. As might
be expected, a number of these properties, particularly
in the upper few meters of the ocean floor, differ con-
siderably from those reported for terrestrial deposits.
This study was undertaken to investigate the engineer-
ing properties of deposits occurring in a somewhat unique
deep-sea environment, specifically one consisting of a
volcanic cone (seamount) surrounded by the abyssal plain.
By examining a number of sediment cores from a small area
it was anticipated that not only could the engineering
properties be determined, but also ascertain the variation
and possible relationship of these properties to the con-
trasting topography found at the site. A detailed analysis
was made of selected mass properties (cohesion, water con-
tent, wet bulk density, texture, porosity, and calcium
carbonate content) in order to determine their lateral and
vertical variability within the confines of the study area
ESSA, Atlantic Oceanographic and Meteorological Laborato-
ries, Miami, Florida 33130
857
858 CIVIL ENGINEERING IN THE OCEANS - II
PREVIOUS INVESTIGATIONS
It is estimated that on the order of 1500 to 2000
sediment cores have been collected from the deep sea for
the purpose of studying the engineering properties of sea-
floor deposits. Considering the extent to which the sea
covers the earth (70 percent), this sampling density
clearly points out our lack of information in this environ-
ment .
Very few data are available that can be related to the
deeper foundation characteristics of the sea floor. This
primarily stems from limitations of the sampling techniques
presently used by marine geologists to collect deep-sea
sediments. Core samples suitable for engineering studies
seldom exceed 7m (21 ft.) in length. Studies conducted to
date, can only be related to the upper few meters of the
sea floor.
The first report on wet unit weight, water content,
and shear strength of deep-sea sediments was made by
Arrhenius (1952) from his study of a number of Pacific
cores collected during the 19l+7-I+8 Swedish Deep-Sea Expe-
dition. Shear strength was determined with a fall cone
and only relative strengths reported. These values have
since been converted to conventional units (Moore and
Richards, 1962). Later interest in the engineering prop-
erties of submarine sediments stem from the requirements
of various military programs for an increased knowledge of
the sea-floor environment (Hamilton, 1956; Hamilton, et al.,
1956; and Keller, 196*+).
In their efforts to investigate depositional processes
or specific characteristics of deep-sea sediments, scien-
tists have conducted a number of studies either on specific
relationships such as sound velocity and mass properties
(Buchan, et al,, 1967), density and depth of burial (Igelman
and Hamilton, 1963), consolidation and depositional history
(Hamilton, I96W; Richards and Hamilton, 1967) or they have
studied the mass properties of a local area (Moore and
Shumway, 1959; Richards, 196*+; and Almagor, 1967).
One of the early comprehensive studies on the mass
physical properties of deep-sea sediments was that by
Richards (1961, 1962) which reported in detail on the test-
ing and analysis of 35 sediment cores collected from the
north Atlantic, western Mediterranean and north Pacific.
This work has provided the basis and impetus for many
recent investigations in this field, now referred to as
"Marine Geotechnique" (Richards, 1967). As more data have
SEA FLOOR 859
become available, larger scale studies have provided basic
engineering properties data on a regional basis, for
example, the work of Moore (1962) in the north Pacific.
Einsele (1967) in the Red Sea, Bryant and Wallin (1968) in
the Gulf of Mexico, and that of Keller and Bennett (1968)
who compiled data from approximately 800 cores from the
north Pacific and north Atlantic.
Although there is little doubt that considerable
instability of the sea floor exists as shown by the occur-
rence of numerous slump features and turbidites (graded
beds indicative of turbidity flows), only limited informa-
tion is available as to the stability of submarine slopes.
Terzaghi (1956) presented a lengthy discussion on the
various types of failures in submarine slopes, but dealt
primarily with the nearshore zone. Moore (1961) investi-
gated the shear strength of a number of cores collected
from the continental shelf off California. From this study
he concluded that submarine sediments were essentially in
a stable state on most slopes, except in specialized envi-
ronments where the rate of sedimentation was rapid, e.g.,
deltas and submarine canyons.
An after the fact study of the gullied portion of the
San Diego trough by Inderbitzen (1965) presented the
characteristic properties of what were reported to be slump
deposits. Most recently, Morgenstein (1967) has brought
together much of the available information on submarine
slumping and has presented a detailed discussion of the
mechanics of slumping and the transformation of some such
slumps into high density turbidity flows.
STUDY SITE
The setting for this study is 370 km (230 mi.) south-
west of San Diego, California in a tectonically active area
referred to as the Baja California Seamount province. An
abundance of volcanic cones (seamounts) and a micro-relief
(*+0 to 100 m [132 to 330 ft.]) of the abyssal sea floor,
too rough to permit a generalization regarding depth,
characterized this province (Fig. 1). The irregular micro-
topography results from tectonic activity, but the specific
mechanism such as volcanism or faulting, is not clearly
defined. A clear indication of the wide spread volcanism
in this area was revealed from a 1,1+00,000 km^ (538,000 mi/)
survey of the province by Menard (1959) in which the pres-
ence of 1000 seamounts was reported. The eastern margin
860
CIVIL ENGINEERING IN THE OCEANS - II
10
o
o
_
UJ
z
o
CM
*
P
; •
o
I— I
SEA FLOOR 861
of this province is bordered by a number of basins and
troughs (southern continuation of the continental border-
land) which appear to trap sediment being eroded from Baja
California (Menard, 1955). Lack of an extensive smooth
sediment blanket covering the sea floor, as is found north
and south of the province, indicates that little sediment
actually bypasses these traps.
Near-bottom currents in the vicinity of the study
area trend in a southeast direction at velocities of 2.1+
to if. 10 cm/sec (.08 to 0.1*+ ft. /sec) (Isaacs, et al. , 1966).
These investigators also reported similar velocities from
the flank of a seamount approximately U8 km (30 mi.) west
of the study site. Although their data did not show
stronger currents in the vicinity of the seamount they did
find, using bottom photographs, that the sea floor was a
pavement of pillow lava swept clean of sediment. The
occurrence of stronger currents is highly possible since
the reported measurements were only for periods of 23.5 to
80.5 hours and during one time of the year.
The actual study area extends over 23,6I+0 km2 (7,200
mi. ) and consists of a prominent seamount rising 2960 m
(9768 ft.) above an abyssal plain characterized by a rough
micro-relief (Fig. 2). Lack of sufficient bathymetric data
precludes the display of this micro-topography. The gentle
westerly slope of the sea floor is common to much of the
province.
SAMPLING
Twenty sediment cores varying in length from 128 to
320 cm (50 to 128 in.) were collected by the U. S. Naval
Oceanographic Office from a small area incorporating a
portion of the Pacific abyssal plain and a prominent sea-
mount (Fig. 2). Modified Ewing and Kullenberg corers were
used, providing samples 6.05 and if. 76 cm (2.38 and 1.88 in.)
in diameter respectively (U. S. Navy Hydrographic Office,
1955). The characteristics of these samplers are not ideal
for obtaining "undisturbed" material (Richards and Keller,
1961), however, no visible disturbance of the tested por-
tions of the cores was noted and the samples were considered
on a par with others reported in the literature.
Inert plastic (cellulose acetate butyrate) liners were
used in the corers in an effort to reduce chemical reactions
between the sediment and the steel barrel and to provide a
container in which to transport the sample to the laboratory,
862
CIVIL ENGINEERING IN THE OCEANS - II
3J°5CT
3l°00'h
30° 30'
I22°00'
I2I°00'
120° 30'
FIGURE 2. BATHYMETRIC MAP AND SAMPLE LOCATIONS
SEA FLOOR 863
Since water loss through such a liner can be appreciable
(Keller, et al. , 1961), each liner was coated with a micro-
crystalline wax after the sample was retrieved.
LABORATORY TESTS
A total of 365 subsamples was tested for selected
engineering properties (cohesion, water content, wet bulk
density, and grain specific gravity), of these, 207 sam-
ples were also analysed for their textural characteristics
and calcium carbonate content. Testing procedures for the
engineering properties are essentially the same as those
established by the American Society for Testing Materials
(1958) and have been discussed specifically in regard to
submarine sediments by Richards (I96I). Because of the
characteristics of this sediment (low cohesion and rela-
tively high water content) the standard tests for shear
strength were scaled down, but otherwise not altered. The
majority of the tests were made with a laboratory-vane
shear apparatus (Evans and Sherratt, 19^8 ) and only in a
few instances could a modified unconfined compression
apparatus be used (Richards, 1961). Undrained shear
strength tests were conducted on totally saturated, uncon-
solidated sediments. Under these special conditions,
shear strength is equal to cohesion, and the strength
measured by these tests is a measure of cohesion and is so
used here. No corrections have been made for the salt
content of the sediment.
Textural determinations were made by the sieving and
pipette technique and the analyses for calcium carbonate
by the insoluble residue method (Krumbein and Pettijohn,
1938).
Some degree of desiccation or slight disturbance was
observed at the ends of almost all the cores. For this
reason only those data obtained from the middle portion of
the cored interval have been used in this study. The
values reported herein are the averages of the respective
parameters over the tested portion of the core.
DISCUSSION
The study area consists primarily of an abyssal plain
environment with water depths varying from 3712 to ^133 m
(12,175 to 13,556 ft.). For the purpose of this study,
the abyssal plain is considered to be a relatively flat
864 CIVIL ENGINEERING IN THE OCEANS - II
surface sloping gently to the west, although a micro-
topography exists in this area as noted earlier. The sea
floor is interrupted in the southwest sector of the study
area by a seamount displaying 2960 m (9768 ft.) of relief.
The depositional environment of the site is that of
the deep-sea "red clay" deposits, indicating a slow and
somewhat uniform rate of sedimentation (few mm per 1000
years). These deposits are terrestrial in origin and are
primarily carried in suspension out from the land.
Abyssal plain deposits in the study area are texturally
quite uniform and exhibit only very minor variation both
laterally and with depth (Fig. 3). In 191+ out of the 207
subsamples examined, the median diameter ranged from 1 to
5^ with an average of 2\i. As is commonly found in asso-
ciation with "red clays", a silty clay texture predominates
in the study area.
Only in those samples taken from the flank of the sea-
mount was any noticeable difference observed in the
textural characteristics. These sediments were notably
coarser than the abyssal plain deposits and were character-
ized by a median diameter of Y]\x and a clayey silt texture.
The coarser texture is attributed to the winnowing out of
a portion of the finer material by currents, along with an
increased concentration of calcareous foraminif eral tests
which comprise most of the fine sand- and silt-size parti-
cles. Although the tests were present in the abyssal plain
sediments the relative concentration is considerably higher
at the shallow depths of the seamount owing to the lower
rate of calcium carbonate solution.
Calcium carbonate content of the surface sediments
was low in the abyssal "red clays", averaging about 7 per-
cent, but considerably higher (17 percent) on the flank of
the seamount (Fig. h) . Microfaunal tests constitute the
bulk of the carbonate material, thus the coarser deposits
on the seamount correspond to the areas of higher calcium
carbonate. A slight decrease in carbonate content is ob-
served from east to west on the abyssal plain which may
reflect the corresponding gradual increase in water depth
in the same direction. The effects of solution at the
deeper depths was observed on a number of tests.
Organic carbon analyses of the upper few centimeters
of each core revealed an overall average of 0.7*+ percent
for the "red clay" and 0.17 percent for the coarser sea-
mount sediments. As a general rule, all other things being
equal, organic carbon content is directly proportional to
SEA FLOOR
865
I22°00'
3I°50'
3I°00' -
30°30'
I22°00'
121*00'
— i —
T 1 1
— i —
1 '
1 —
-
4
4
2
MEDIAN
(v
DIA.
)
-
2
2
3
2
2
2
2
-
—
3
3
—
"*
3
2
2
—
-
rr
-
_i
• » i
•
1 .
»
□ SILTY
CLAY
I2J°00'
CLAYEY
» SILT
I20°30'
3I°50'
- 3I°00'
30° 30'
120° 30'
FIGURE 3. MEDIAN DIAMETER AND TEXTURAL DISTRIBUTION.
TEXTURE BASED ON SHEPARD'S (195^) NOMENCLATURE.
866
CIVIL ENGINEERING IN THE OCEANS - II
!. 50
^°00
3I°00
30°30'
122° 00
I2I°00'
120° 30' ,
2I°00
12030
FIGURE k, CALCIUM CARBONATE CONTENT OF SURFACE SEDIMENTS.
SEA FLOOR 867
the concentration of finer particles. It is also found
in some instances to have a definite correlation with
such properties as cohesion and sensitivity of sediments
(Jerbo, 1966).
Specific gravity of the solids varies only slightly
in this area, as might be expected for deposits which are
not influenced by a number of different source areas.
Average values determined for each core range from 2.68
to 2.73. An occasional value as high as 2.93 was found
in conjunction with a few thin layers of coarse material
(volcanic debris).
Variations in wet bulk density in the area of the
abyssal plain are relatively minor and reflect the uniform
sediment type comprising most of this portion of the
Pacific sea floor. Values range from I.36 to 1.1+2 g/cm^
(8^.9 to 88.6 pcf), which are reasonably close to an
average value of l.1!-^ g/cnP (89.9 pcf) reported by Keller
and Bennett (1970) for "red clay" deposits. Bulk density
values were noticeably higher on the flank of the seamount,
varying from 1.57 to 1.70 g/cnP (98 to 106 pcf) with an
average of 1.65 g/cm3 (103 pcf). These higher values are
attributed to the effects of currents acting on the sea-
mount. Winnowing by currents apparently results in the
removal of softer (less dense) material and leaving both
coarser and denser sediments behind. The distribution
pattern shown in Figure 5 clearly reflects the influence
pronounced changes in relief have on bulk density.
Water content (percent dry weight) of the deep-sea
sediments reveals a gradual increased away from the sea-
mount (Fig. 6). Water contents of the abyssal-plain
deposits vary from 119 to l'+l percent and do not appear to
be influenced by the minor regional changes in topography.
The lowest water content values observed (68 percent) occur
on the flanks of the seamount, correlating with the coarser
and denser sediments also found there.
Although porosity is a calculated value (Terzaghi and
Peck, 19^+8) based on other parameters (water content, bulk
density and grain specific gravity) it has been included
here because of its importance to those investigating the
acoustic properties of the sea floor. Porosity was essen-
tially uniform throughout the abyssal plain deposits,
varying only h percentage points within the study area
(Fig. 7). In contrast, the porosity of the seamount sedi-
ments was considerably lower (12 to 13 percentage points)
than that of the surrounding sea floor.
868
CIVIL ENGINEERING IN THE OCEANS - II
I22°00'
I2I°00'
3I°50
3I°00' -
30°30'
I22°00
I20°30'
3I°50'
3l°00
30°30'
2I°00'
I20°30
FIGURE 5. AVERAGE WET BULK DENSITY OF THE MIDDLE SEGMENT
OF THE CORED INTERVAL.
SEA FLOOR
869
I22°00'
3I°50'
\AO
I2|°00'
r- 1 1 -r
WATER CONTENT
I20°30'
3I°50'
3I°00'
30°30' I l
I22°CX)'
I2I°00'
3I°00'
30° 30'
1 20° 30'
FIGURE 6. AVERAGE WATER CONTENT OF THE MIDDLE SEGMENT OF
THE CORED INTERVAL.
870 CIVIL ENGINEERING IN THE OCEANS - H
I22°00'
3I°50'
3I°00' -
30#30' ' I
T r
? 8
.80 I
-77
.78
78
77
.77
77
76
64
^ 75 '
I2I°00'
t r
79
I20°30'
si^o1
POROSITY
(%)
78
78
J
78
3I°00'
77
7*
1
I22°00'
I2I°00'
30*30'
120° 30'
FIGURE 7. AVERAGE POROSITY OF THE MIDDLE SEGMENT OF THE
CORED INTERVAL.
SEA FLOOR 871
The distribution pattern for cohesion is not as
simple as that shown by the other parameters (Fig. 8),
however, a clear distinction exists between the cohesion
of abyssal plain sediments and that of the seamount just
as has been found for the other properties. Although the
other measured parameters appear to show very little
variation in the abyssal plain sediments, a noticeable
contrast in cohesion is found within these deposits. Much
of the area exhibits a cohesion of 60 to 70 g/cm^ (.85 to
1.0 psi) which approximates an average value of ^5 g/cm^
(.6^ psi) reported for "red clay" (Keller and Bennett,
1970). A prominent portion of the sea floor north of the
seamount, however, possesses a relatively high cohesion
which does not appear to correlate with variations in any
of the other measured properties. Sediments on the sea-
mount clearly possess higher cohesion as would be
anticipated in conjunction with the lower water content
and higher bulk densities found there.
CONCLUSIONS
Abyssal plain deposits commonly display rather uniform
mass physical properties as nas been shown for a large
portion of the north Pacific (Keller and Bennett, 1968).
During this study a similar uniformity was observed for the
overall sea floor indicating a normal abyssal plain environ-
ment. Only in the case of cohesion were anomalous areas of
high values observed. Since the other properties measured
in this area exhibit no distinct contrast to other portions
of the abyssal plain, it is assumed that some other factor
has contributed to the zone of higher cohesion. The pres-
ence of micro-relief may in some way have affected cohesion
yet not have been significant enough to influence the other
measured properties. Another possible source for increased
cohesion could be local cementation or bonding as a result
of pore-water migration. Without considerably more data, a
clear explanation for this occurrence is not readily
available.
The distribution of the various mass properties is
clearly affected by the presence of a volcanic peak rising
2960 m (9768 ft.) above the relatively flat sea floor. As
in any dynamic environment a projection above a plain
serves to concentrate whatever forces are active in the
environment, ocean currents in this case. Samples taken
from the flanks of the seamount possess distinctly different
characteristics than those of the abyssal plain.
872
CIVIL ENGINEERING IN THE OCEANS - H
I22°00'
3l#50,r~
t r
3I*00'
so^so*
I2I°00' I20°30'
— r—
T
COHESION
( g/cm2)
/ J
i
_1*
1
l22#00'
I2I°00*
rv
i \
J L
3I»50'
— 3l#00'
1 3Q;30'
120° 30'
FIGURE 8. AVERAGE COHESION OF THE MIDDLE SEGMENT OF THE
CORED INTERVAL.
SEA FLOOR 873
In viewing the distribution patterns of the various
parameters, there is basically little difference found
among them. Values tend to increase (grain size, bulk
density and cohesion) or decrease (water content and poros-
ity) in a radial pattern away from the seamount. Such a
pattern would be expected in an area where current veloc-
ities are lower away from a topographic high. Relatively
higher current velocities acting on the seamount would
tend to winnow out much of the finer particles and leave
behind both a coarser and denser deposit.
Although micro-relief of ifO-100 m (132 - 330 ft.)
exists on the abyssal plain, this scale of relief did not
appear to effect the properties of these deposits. This
study clearly reveals that a pronounced relationship does
exist between the sediment mass physical properties and
abrupt changes in relief such as the presence of a seamount
on a relatively flat portion of the sea floor.
874 CIVIL ENGINEERING IN THE OCEANS - II
REFERENCES
Almagor, G. , (1967): Interpretation of strength and
consolidation data from some bottom cores off
Tel-Aviv — Palmakhim Coast, Israel: in Marine Geo-
technique, Richards, A. F. , Ed., Univ. 111. press,
pp. 131-153.
American Society for Testing Materials, (1958): 1958 book
of ASTM standards including tentatives, part >+.
Philadelphia, Pa., lM-26 pages.
Arrhenius, G. , (1952): Sediment cores from the East
Pacific: Reports of the Swedish Deep-Sea Expedition
19'-+7-191+8, V. 5, No. 1, 227 pages.
Bryant, W. R. , and C. S. Wallin, (1968): Stability and
geotechnical characteristics of marine sediments,
Gulf of Mexico: Trans. 18th Ann. meeting, Gulf Coast
Assoc. Geol. Societies, pp. 33^-356.
Buchan, S. , F. C. D. Dewes, D. M. McCann, and D. Taylor
Smith, (1967): Measurements of the acoustic and geo-
technical properties of marine sediment cores: in
Marine Geotechnique, Richards, A. F. , Ed., Univ. 111.
press, pp. 65-92.
Einsele, G. , (1967): Sedimentary processes and physical
properties of cores from the Red Sea, Gulf of Aden,
and off the Nile delta: in Marine Geotechnique,
Richards, A. F. , Ed., Univ. 111. press, pp. 151+-169.
Evans, I., and G. G. Sherratt, (19^8): A simple and con-
venient instrument for measuring the shearing
resistance of clay soils: Jour. Sci. Instruments -
Physics in Industry, V. 25, pp. Li-ll-1+l1+.
Hamilton, E. L. , (1956): Low sound velocities in high
porosity sediments: Jour. Acoustical Soc. America,
V. 28, pp. 16-19.
Hamilton, E. L. , ( 196^-) : Consolidation characteristics and
related properties of sediments for experimental
Mohole (Guadalupe site): Jour. Geoph. Research, V. 69,
pp. L+257-I+269.
Hamilton, E. L. , G. Shumway, H. W. Menard, and C. J. Shipek,
(1956): Acoustic and other physical properties of
shallow water sediments off San Diego: Jour. Acousti-
cal Soc. America, V. 28, pp. 1-15.
SEA FLOOR 875
Igelman, K. R. , and E. L. Hamilton, (1963): Bulk densities
of mineral grains from Mohole samples (Guadalupe
site): Jour. Sed. Petrology, V. 33, pp. ^7^+- J+yB.
Inderbitzen, A. L. , (1965): An investigation of submarine
slope stability: Trans. Conf. on Ocean Science and
Ocean Eng. 1965, Marine Tech. Soc. , and Amer. Soc.
Limn, and Oceanography, V. 2, pp. 1309-13I^l+.
Isaac, J. D. , J. L. Reid. Jr., G. B. Schick, and R. A.
Schwartzlose, (1966): Near-bottom currents measured
in h kilometers depth off the Baja California coast:
Jour. Geoph. Research, V. 71, pp. ^297-^303.
Jerbo, A., (1966): Bothnian Clay Sediments - a geological -
geotechnical survey: Stockholm, Geotechnical Dept.,
Swedish State Railways, Bull. 11, 159 pages.
Keller, G. H. , (196^): Investigation of the application of
standard soil mechanics techniques and principles to
bay sediments: Proc. 1st U. S. Navy Symposium on
Military Oceanography, pp. 329-360.
Keller, G. H. , A. F. Richards, and J. H. Recknagel, (I96I):
Prevention of water loss through CAB plastic sediment
core liners: Deep-Sea Res., V. 8, pp. lt+8-l5l.
Keller, G. H. , and R. H. Bennett, (1968): Mass physical
properties of submarine sediments in the Atlantic and
Pacific basins: Proc. XXIII Internat'l Geol. Congress,
Sect. 8, pp. 33-50.
Keller, G. H. , and R. H. Bennett, (1970): Variations in the
mass physical properties of submarine sediments:
Marine Geology, (in press).
Krumbein, W. C. , and F. J. Petti John, (1938): Manual of
Sedimentary Petrography: New York, Appleton-Century-
Crofts, Inc., 5^9 pages.
Menard, H. W. , (1955): Deformation of the northeastern
Pacific basin and the west coast of North America:
Geol. Soc. America Bull. , V. 66, pp. 11^9-1198.
Menard, H. W. , (1959): Geology of the Pacific sea floor:
Experientia, V. 15, pp. 205-213.
Moore, D. G. , (1961): Submarine slumps: Jour. Sed. Petrol-
ogy, V. 31, pp. 3^3-357.
876 CIVIL ENGINEERING IN THE OCEANS - II
Moore, D. G. , (1962): Bearing strength and other physical
properties of some shallow and deep-sea sediments
from the North Pacific: Geol. Soc. America Bull.,
V. 73, PP. 1163-1166.
Moore, D. G. , and G. Shumway, (1959): Sediment thickness
and physical properties: Pigeon Point Shelf, Cali-
fornia: Jour. Geoph. Research, V. 6h, pp. 367-37I+.
Moore, D. G. , and A. F. Richards, (1962): Conversion of
"relative shear strength" measurements by Arrhenius
on East Pacific cores to conventional units of shear
stress: Geotechnique, V. 11, pp. 55_59.
Morgenstein, N. R. , (1967): Submarine slumping and the
initiation of turbidity currents: in Marine Geotech-
nique. Richards, A. F. , Ed., Univ. 111. press,
pp. 189-220.
Richards, A. F. , (1961): Investigations of deep-sea sedi-
ment cores, I. Shear strength, bearing capacity, and
consolidation: U. S. Navy Hydrographic Office Tech.
Rept. 63, 70 pages.
Richards, A. F. , (1962): Investigations of deep-sea sedi-
ment cores, II. Mass physical properties: IT. S. Navy
Hydrographic Office, Tech. Rept. 106 , 1^6 pages.
Richards, A. F. , (196Li): Local sediment shear strength and
water content: in Papers in Marine Geology, Shepard
Commemorative Volume, Miller, R. L. , Ed., The
Macmillan Co., New York, pp. K7h-K8J .
Richards, A. F. , (1967): Marine Geotechnique: Univ. 111.
press, 327 pages.
Richards, A. F. , and G. H. Keller, (1961): A plastic-
barrell sediment corer: Deep-Sea Res., V. 8,
pp. 306-312.
Richards, A. F. , and E. L. Hamilton, (1967): Investigation
of deep-sea sediment cores, III. Consolidation: in
Marine Geotechnique, Richards, A. F. , Ed., Univ. 111.
press, pp. 93-117.
Shepard, F. P., (195*+): Nomenclature based on sand-silt-
clay ratios: Jour. Sed. Petrology, V. 21*, pp. 151-158.
Terzaghi, K. , (1956): Varieties of submarine slope fail-
ures: Proc. 8th Texas Conf. on Soil Mech. and Found.
Eng. Spec. Pub. No. 29, Univ. Texas, Austin, Texas,
h2 pages.
SEA FLOOR 877
Terzaghi, K. , and R. B. Peck, (19^8): Soil mechanics in
engineering practice: John A. Wiley & Sons, New York,
566 pages.
U. S. Navy Hydrographic Office, (1955): Instruction manual
for oceanographic observations: U. S. Navy Hydro-
graphic Office Pub. No. 607, Washington, 210 pages.
Reprinted from The American Association of Petroleum
Geologists Bulletin 55_, No. 10, 1719-1729 .
Marine Geophysical Reconnaissance of Continental Margin North of
Paria Peninsula, Venezuela1
R. K. LATTIMORE,' L. AUSTIN WEEKS,' and L. W. MORDOCK4
Miami, Florida 33130, 33158, and Seattle, Washington 98102
58
Abstract Marine geophysical observations north of the
Paria (Venezuela) Peninsula and westernmost Trinidad
have delineated three features that dominate the shallow
structural pattern of the shelf: (1) Carupano Sea Valley,
which extends eastward along the Paria-Araya shoreline
and occupies a structural depression bounded on the
south by a major fault system; (2) Cumberland Rise, a
locally complex structural and topographic high north of
the sea valley; and (3) Tobago Trough, which appears to
extend southwest across the shelf almost to the Paria-
Trinidad coast. The orientation of the positive elements
of Cumberland Rise and the trend of magnetic anomalies
that seem to be associated with the Carupano depression
suggest that both features may be related to the Lesser
Antilles arc. Detritus eroded from the Paria-Araya Penin-
sulas is inferred to have been transported eastward
through Carupano Sea Valley info Tobago Trough; the
Paria shelf has been built upward and northward by
sediments which bypassed the valley and were carried
directly offshore, over the Cumberland Rise, to be de-
posited as foreset beds on an old erosion surface.
The extension of the Lesser Antilles arc southwest into
the Paria-Araya shelf is marked by a +60 to +100 mgal
free-air gravity anomaly. A shallow igneous intrusive
extends from Los Testigos Islands northeast along the
trend of this anomaly to the upper continental slope,
where the intrusive is truncated by a northwest-southeast
fault. The fact that the trends of the arc can be traced
well into the Paria shelf militates against the presence of
an east-west transcurrent fault between Carupano Sea
Valley and the Grenada platform.
Introduction
As part of an Environmental Science Ser-
vices Administration program for the investiga-
tion of the structure of ocean basins and their
margins, marine geophysical observations have
been made in an extensive area of the Carib-
bean Sea and Atlantic Ocean adjacent to the
Paria-Araya Peninsulas of Venezuela, and sur-
rounding the islands of Trinidad, Tobago, and
Grenada. The results of reconnaissance seis-
mic-reflection, bathymetric, gravimetric, and
magnetic observations made by USC&GSS Dis-
coverer in the summers of 1968 and 1969 will
be presented in a series of reports, the first of
which are three papers in this issue of the Bul-
letin. Our study, which covers measurements
made over the Paria-Trinidad shelf and Gre-
nada platform between 61°30'W and 63°00/W
(Fig. 1), is addressed to two specific objec-
tives: (1) determination of the structure
of the Paria-Trinidad shelf and its relation to
the Lesser Antilles island arc and the South
American continent; and (2) location of the
transcurrent or transform fault which, accord-
ing to the hypotheses of the "new global tecton-
ics" (Isacks et al., 1968), must separat; the
Caribbean "plate" from the South American
continent.
Previous Study
The earliest marine geophysical observations
in the southeast Caribbean were isolated sub-
marine gravity measurements made in 1936—
1937 (M. Ewing et al, 1957). In 1947, addi-
tional gravity measurements were made along
a northwest-southeast traverse of the Paria shelf
(M. Ewing et al, 1957). The first detailed
bathymetric map of the Paria and Trinidad
shelves was published by Koldewijn (1958) as
part of a study of the near-surface sediments.
Seismic-refraction investigations of the shelf,
Tobago Trough, and adjacent parts of the
Lesser Antilles arc, conducted by Lamont Geo-
logical Observatory in 1955, were reported by
J. Ewing et al (1957) and Officer et al
(1959). This and subsequent work have been
summarized and reviewed by Edgar (1968)
and J. Ewing et al (in press).
1 Manuscript received, August 24, 1970; accepted,
December 3, 1970.
2 National Oceanic and Atmospheric Administration
(NOAA), Atlantic Oceanographic and Meteorological
Laboratories.
3 Consultant; formerly. Environmental Science Ser-
vices Administration.
4 NOAA, National Ocean Survey, Pacific Marine
Center; formerly, seismic-profile officer, USC&GS ship
Discoverer.
The writers thank the officers and crew of USC&GS
(now NOAA) ship Discoverer, W. W. Doeringsfeld,
Jr., William Everard, G. A. Lapiene, Jr., N. J. Malo-
ney, Wendell Mickey, and Paul Miller, for their sup-
port and cooperation in conducting the field work. G.
H. Keller served as chief scientist during part of the
survey. Geophysical data were reduced and plotted us-
ing programs developed by Paul Grim and Bobby Bas-
singer. Sue O'Brien drafted the figures. The paper was
reviewed critically by L. W. Butler and B. J. Szenk.
© 1971. The American Association of Petroleum Geologists.
All rights reserved.
1719
1720
R. K. Lattimore, L. Austin Weeks and L. W. Mordock
ARAYA-PARIA-TRINIDAD SHELF
SOUNDINGS IN FATHOMS
MERCATOR PROJECTION
Fig. 1. — Track-line index and bathymetric map, Araya-Paria-Trinidad shelf and Grenada platform.
(Sound-velocity corrections were not applied to soundings.)
Methods
Continuous underway seismic-reflection,
bathymetric, gravimetric, and magnetic obser-
vations were made along the ship's tracks
shown on the bathymetric map (Fig. 1). The
profiles were run at a nominal speed of 5 knots
(9 km/hr); as a result of sea conditions and
equipment testing, actual speeds varied from 2
to 9 knots (3.7 to 17 km/hr). Navigational
control was by radar range and bearing, visual
bearings, and astronomical fixes. The estimated
probable error in any ship's position is ± 2
n.mi (±3.7 km).
The seismic reflection profiles were made
with a Bolt Associates, Inc., 10-cu in. (164 cc)
air gun system with a 25-ft (7.6 m) array of 10
variable reluctance hydrophones. The sound
source was fired at 2- or 4-second intervals; the
return signal was subjected to a 39-320 Hz
bandpass filter and recorded on an Alpine-
Muirhead recorder. Interpretative line drawings
of representative seismic profiles are presented
in Figure 2.
In water depths greater than 100 fm (183
m), soundings were taken with a General In-
strument Corporation "narrow-beam echo-
sounding system" which utilizes an electroni-
cally-stabilized beam having an effective cone-
width of 2%°. Shallow-water soundings were
obtained with Raytheon DE-723 fathometer.
Soundings are considered accurate to ±1 per-
cent (L. G. Taylor, personal commun.). The
bathymetric map (Fig. 1) was prepared from
published and unpublished data collected by
the U.S. Navy and other sources, in addition to
our own profiles.
Underway gravity measurements were made
with an Askania-Graf seagravimeter mounted
on an Anschutz gyro-stabilized platform. The
data, corrected for instrumental drift and
Eotvos effect5, are presented in the form of
free-air anomaly profiles in Figure 3. Although
gravity values at track intersections consis-
tently were within 10 mgal of each other, dis-
crepancies with older data (e.g., M. Ewing
et al., 1957) range up to ±20 mgal.
Continuous profiles of earth's total magnetic
field were obtained with a Varian Associates,
5 Observed gravity values are relative to Barbados:
Seawell Airport f = 978.2997.
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1722
R. K. Lattimore, L. Austin Weeks and L. W. Mordock
\ 1 J'
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50 n.mi
Fia. 3. — Free- air gravity anomaly profiles, Paria
shelf (AA'-DD') and Grenada platform (JJ'-MM').
From top to bottom, the profiles are arranged from
west to east.
Inc., direct-reading proton precession magne-
tometer. Critical values were scaled from the
graphic record and reduced to residual anoma-
lies by using the parameters of the Interna-
tional Geomagnetic Reference Field. The mag-
netic-anomaly profiles (Fig. 4) are considered
to be internally consistent to ±20 y.
Regional Setting
A nearly flat continental shelf, 40-60 n.mi
(75-110 km) across, lies where the trends of
the Lesser Antilles arc intersect the margin of
the South American continent (Fig. 1). This
shelf extends from the island of Tobago west-
ward beyond 64 °W; it is bounded on the south
by the rugged coast ranges of Trinidad and the
Paria-Araya Peninsulas of Venezuela. The
coast ranges are breached at Dragon's Mouth,
where depths greater than 120 fm (220 m)
were measured.
West of Dragon's Mouth, the southernmost
part of the shelf is occupied by a shallow valley
which Maloney (1967) named the Carupano
Sea Valley (Fig. 1). This valley extends from
southeast of Isla Margarita due east to about
62 °W, where it opens into a north- to north-
east-trending embayment that is considered to
be an extension of Tobago Trough (Edgar,
1968). North of the sea valley a broad, very
gentle swell can be traced for about 70 n.mi
(130 km) east from Isla Margarita; shoals of
10fm(18m)or less occur on this swell south
of Los Testigos Islands. We propose the name
"Cumberland Rise," for this feature.
The nearly flat part of the Paria shelf termi-
nates in a scarp of 50-80 fm (90-150 m) re-
lief, which extends east along 11°30'N from
63 °W to approximately 61°40'W. North of
this scarp, a gradient of 1:100 or less persists
to depths of approximately 400 fm (730 m),
where the slope increases by a factor of two or
more. Below 700-800 fm (1,280-1,460 m)
the smooth slope gives way to a zone of rough,
rolling topography.
A platform extends southwest of the island
of Grenada to approximately 62 °W, where the
sea floor dips abruptly to depths of 300-500
fm (550-910 m; Fig. 1). This platform is sep-
arated from the Paria shelf by a broad, asym-
metric trough or basin in which depths do not
exceed 500 fm (910 m). The floor of this basin
generally is smooth and undissected, although
shallow channels near the western end of the
Grenada platform suggest that local drainage is
toward the northwest. On its eastern end, at
about 61°40'W, this valley opens into Tobago
Trough.
Paria Shelf
Within the depths penetrated by the seismic
profile equipment — 0.3-0.5 sec two-way travel
time — the flat continental shelf consists of
nearly horizontal stratified rocks. Reflectors
near the outer edge of the shelf suggest foreset
bedding, and it is clear that the shelf has been
built upward and northward by progradation
(AA\ BB', DD', JJ', Fig. 2). The shallow sedi-
ments of the central and inner shelf are charac-
terized by well-defined, subparallel, continuous
reflectors; individual beds dip gently and
thicken very gradually toward the south (AA\
BB', DD', Fig. 2). Although the sediments
Marine Geophysical Reconnaissance of Venezuela
1723
which make up the shelf are relatively unde-
formed, faults of small displacement, open
folds, and gentle flexures affect near-surface as
well as deeper strata. Few individual structural
features are of sufficient magnitude so that they
can be traced from one profile to the next.
Coastline Fault System
The abrupt transition from the folded and
intruded Mesozoic rocks which form the moun-
tainous Paria-Araya Peninsulas (Maxwell and
Dengo, 1951; Bucher, 1952; Gonzalez de Juana
et ah, 1968) to the nearly horizontal younger
strata that comprise the shelf is best explained
in terms of major faulting along the shoreline.
Fault contact between rocks of the coast ranges
and the shelf sediments can be demonstrated in
a profile taken through Dragon's Mouth (Bas-
singer et al., 1971, this issue of Bulletin). Both
profiles east of 62°30'W (CC and DD') show
that near-horizontal to north-dipping, com-
monly gently folded strata near the coast have
been uplifted in relation to apparently equiva-
lent, south-dipping sediments farther seaward, a
feature that suggests that uplift of the coast
ranges has taken place along several faults
which form a system oriented generally east-
west, parallel with the shoreline.
Carupano Sea Valley
Carupano Sea Valley occupies a structural
depression bounded on the south by one or
more faults of the coastline system. At 62° 50'
W (AA', Fig. 2), this depression is a well-de-
fined graben, perhaps 10 n. mi (18 km) across.
The graben, or at least the northern bounding
fault, can be recognized on the two profiles far-
ther east (BB', Fig. 2, and CC), so it may be
inferred that the structure extends at least to
62°15'W. At 61°50'W (DD', Fig. 2) the
northern fault could not be recognized, but
nearly the entire central part of the shelf is
tilted southward along a pair of faults that are
in line with the presumed southern boundary of
the graben. Although Koldewijn (1958) has
concluded that sediments derived from the
coast ranges since the last glacial period have
not yet been moved out of the littoral, the
mountainous coastal provinces should supply
sufficient detritus to fill the Carupano Sea Val-
ley during any extended period of quiescence.
Persistence of the sea valley and thickening of
individual sedimentary units across faults are
strong indications of continuing subsidence.
12°N
Fig. 4. — Residual magnetic anomaly profiles, Paria
shelf (AA'-DD') and Grenada platform (JJ'-MM').
Dashed lines indicate correlated anomalies whose
trends are shown in Figure 6. The shaded area de-
notes zone of short-wavelength anomalies which are
attributed to shallow igneous intrusive.
Cumberland Rise
Cumberland Rise (Fig. 1) reflects a locally
complex, structurally positive feature whose
general trend is slightly north of east. At
62°50'W (AA', Fig. 2), the predominant
southward apparent dip of the shelf sediments
is broken at, and in places reversed along, sev-
eral faults of varying sense and amount of dis-
placement. At 62°30'W (BB', Fig. 2), an esti-
mated 0.35 sec or more of net displacement is
distributed along a series of faults south of the
axis of the rise; with but one exception, motion
along these faults is down-to-the-south, and dis-
placement generally increases with depth. Far-
1724
R. K. Lattimore, L Austin Weeks and L W. Mordock
ther east, at 62°20'W down-to-the-south dis-
placement is manifested in abrupt, slight in-
creases in the south dip component of the sub-
surface reflectors; the only significant faults are
those which form the graben associated with
Carupano Sea Valley. Along 61°50'W (DD',
Fig. 2), the sediments dip south from a struc-
tural high on the outer shelf at 11°20'N; the
only discernible faults v/ould be part of the
coastline system. Although topographic relief
of Cumberland Rise dies out east of 62°30'W
(Fig. 1), the writers suggest that the anticlinal
structure at 61°50'W, north of Dragon's
Mouth (DD', Fig. 2), is on the main axis of
the underlying structure. Alignment of this
trend suggests kinship with an older positive
structural element that includes Isla Margarita.
Tobago Trough
From seismic-refraction data collected by
Lamont Geological Observatory, Edgar (1968)
concluded that Tobago Trough extends south-
west into the Paria-Trinidad shelf. This conclu-
sion is supported by the nearshore bathymetry
(Fig. 1) as well as by our geophysical observa-
tions. The pronounced negative gravity anom-
aly which occurs over the shelf north of Drag-
on's Mouth (DD', Fig. 3) is consistent with the
accumulation of a thick column of sediments in
the trough, as postulated by Edgar (1968). In
the central part of the shelf north of Dragon's
Mouth, the seismic profile (DD', Fig. 2) shows
0.2 sec of sediments containing angular to sub-
parallel, poorly defined, discontinuous, com-
monly curved or arcuate reflectors, sandwiched
between sequences of the continuous, well-de-
fined reflectors characteristic of the shelf sedi-
ments (Fig. 5). The discontinuous, curved re-
flectors are believed to represent foreset beds
traversed at a small angle to the strike of the
slope face. Structures more readily identified as
foreset beds were observed at similar depths
along profiles at 61°30'W and 61°10'W, 15-
30 n.mi (30-55 km) from the shoreline. The
approximate limit of these beds is shown on the
"structural" diagram (Fig. 6). The presence of
foreset beds interbedded with the normal shelf
sediments is considered to be indicative of
rapid local subsidence of the central part of the
shelf, and also is consistent with incursion of
Tobago Trough.
The narrow, —20 to —40 mgal free-air
anomaly which is developed over the southern-
most part of the shelf east of 62°30'W (CC,
DD', Fig. 3) supports the conclusion of Edgar
(1968) that a wedge of sediments, 5-7 km
I N.Mi
^ II°I8'N
Fig. 5. — Part of seismic-reflection profile DD', showing foreset beds traversed at acute angle to strike
of slope face.
Marine Geophysical Reconnaissance of Venezuela
63°W 62°
1725
61°W
12°N
11°N-
Fic. 6. — Trends and structural patterns of Paria shelf and parts of Tobago Trough and
Grenada platform. (Contours are in fathoms.)
(16,400-23,000 ft) thick, extends from To-
bago Trough along the Paria coast to 63 °W.
The Dragon's Mouth profile (DD', Fig. 3) sug-
gests that this minimum is isolated from the
broad low associated with incursion of the shelf
by Tobago Trough. Bassinger et al. (1971)
show that this low is present at 61°30'W.
Sedimentary Framework of Paria Shelf
West of 62 °W the edge of the Paria shelf is
built up by at least two distinct sequences of
foreset bedding superimposed on each other
(AA', BB', JJ', Fig. 2); the younger of these
sequences forms the scarp at 11°30'N, de-
scribed heretofore. An easily recognized reflect-
ing horizon separates the two series of foreset
beds; reflectors above this horizon are subparal-
lel to angular with respect to those below it. In
several localities a slope face developed on the
lower sequence can be discerned beneath 0.1-
0.15 sec of younger detritus (e.g., BB', Fig. 2);
such fossil scarps lie a few nautical miles land-
ward of the present slope. The lower series of
sediments is unconformable on broadly folded
and intruded older rocks (JJ', Fig. 2). The
gently graded terrace in the 200-300-fm
(350-550 m) depth range is considered to be a
manifestation of this unconformity, as is the
near-level surface of the "basement" ridge at
62°30'W (BB', Fig. 2; Fig. 7). The erosion
surface at 200-300 fm (350-550 m) lies far
below the generally accepted Pleistocene sea-
level minimum, so at least an element of subsi-
dence must be invoked to explain its position.
Subsidence alone, however, does not account
satisfactorily for the near-coincidence of the
fossil and present foreset slope faces — a re-
peated event or, more likely, a cyclic series of
events is required.
The structures interpreted as foreset bedding,
which suggest subsidence of the central part of
the shelf north of Dragon's Mouth (DD', Fig.
2), also suggest that the foreset slope face was
oriented at an acute angle to the ship's track
(i.e., north or northwest) and that the path of
sediment transport across this part of the shelf
had a significant east-west component. From
these inferences and the evidence of repeated
or continuous subsidence of Carupano Sea Val-
ley, it may be postulated that sediments derived
from the Paria-Araya Peninsulas, and possibly
from as far west as Margarita, have been trans-
ported east through Carupano Sea Valley to
about 62 °W, and then northeast across the
1726
R. K. Lattimore, L. Austin Weeks and L. W. Mordock
3H
P o
v. o
03 £
U
r.I
CQ g
« 8
o «
I5-
62°W 61°W
i \\^^0~'XX
^
11°N
PARir^X^7 "^-n. TRINIDAD r
-
62W
61"W
</>
Fig. 8. — Distribution of epidote-hornblende-augite
(EHA) heavy-mineral assemblage, after Koldewijn
(1958).
shelf into Tobago Trough. This pattern corre-
sponds closely with the distribution of a distinc-
tive Holocene heavy-mineral assemblage
mapped by Koldewijn (1958: Fig. 8). If this hy-
pothesis is valid, intervals of quiescence must
be postulated, during which Carupano Sea Val-
ley was filled completely and the sediments
were transported directly offshore. Detritus car-
ried seaward and dumped over Cumberland
Rise would have built the edge of the shelf up-
ward and seaward, producing sedimentary
structures like those seen in the seismic profiles
from the western part of the shelf.
Trends of Lesser Antilles Arc
A broad, asymmetric magnetic-anomaly
maximum can be traced for about 30 n.mi (55
km) eastward along the edge of the Paria shelf
to 62°10'W, where it is abruptly truncated
(AA', BB', JJ', Fig. 4). This anomaly is correl-
ated with a broad, asymmetric maximum that
has been mapped, east of the Grenadine plat-
form, by J. Ewing et at. (1960); it probably is
related to the island arc and not to the shelf.
Data from outside the study area suggest that
the irregular maximum which is present over
the continental slope at 62°W (MM', Fig. 4),
and the increasing values at the northern end of
the easternmost track line (DD', Fig. 4) also
may be identified with this feature.
The presence of a thick wedge of sediments
along the Paria coast strongly suggests that the
Carupano Sea Valley depression is structurally
continuous with Tobago Trough. However, a
pattern of magnetic-anomaly maxima, which in
the western part of the shelf seems to coincide
with Carupano Sea Valley (BB', CC, DD',
Fig. 4), can be traced across the axis of the
trough to at least 61°15'W; east of 62°30'W
the trend swings slightly north (Fig. 6). If the
anomalies are genetically related to the Cam-
Marine Geophysical Reconnaissance of Venezuela
1727
pano Sea Valley depression then this structure,
at depth, must extend nearly as far east as To-
bago; it is not likely to be part of the present
Tobago Trough.
Extension of Trends of Lesser Antilles
Arc into Paria Shelf
The presence of "basement" landward of the
foreset edge of the shelf at 62°50'W (A A', Fig.
2) was deduced from the presence of undulat-
ing, discontinuous, strong reflectors having pro-
nounced multiples. These reflectors coincide
with a zone of short-wavelength magnetic
anomalies, superimposed on a broad maximum
which is believed to be related to the island arc
(AA', Fig. 4); the short-wavelength anomalies
are indicative of a shallow crystalline source,
most probably an igneous body. A well-defined
basement structure, its top presumably planed
off by wave action, is present along 62°30'W
(BB', Fig. 2; Fig. 7), north of the foreset slope
face at depths of 200-300 fm (350-550 m).
In a third locality, the westernmost of four pro-
files that were run at right angles to the trend
of the Grenada platform, possible basement
crops out on the sea floor below 400 fm (730
m; JJ', Fig. 2). The fact that basement in these
two profiles also is crystalline is shown by dis-
tinctive magnetic signatures which coincide with
the structural features (BB', JJ', Fig. 4).
The three occurrences of crystalline base-
ment fall on a line which, if extended toward
the southwest, includes Los Testigos Islands.
Maloney (1967) reported that the largest of
these islands consists of a granitic intrusive sur-
rounded by younger volcanics. We suggest that
the islands and the three profile crossings define
a single, essentially continuous, northeast-
southwest-trending intrusive igneous body.
The investigation of the Grenada platform
included four profiles run on northwest or
southeast headings, normal to the long axis of
the platform. The westernmost of these profiles
(JJ') contains convincing evidence of "base-
ment" structure, but the next profile (KB'),
taken parallel with and about 5 n.mi (9 km)
east of the first, contains no evidence of base-
ment, even though the records show penetration
of a half-second or more with good resolution.
The short-wavelength magnetic anomalies at-
tributed to the intrusive do not extend east of
62°20'W (profile JJ') ; instead, the broad low is
broken by a distinctive, local maximum which
can be traced east-southeastward for about 15
n.mi (28 km; KB', LL', KK", Fig. 4).
The igneous ridge probably disappears at
62°20'W because of a fault. This possibility in-
vites speculation that the fault extends south-
eastward and also truncates the broad, asym-
metric magnetic-anomaly maximum mapped
near the edge of the shelf in the western part of
the area (e.g., BB', Fig. 4). Such a fault might
be confined to the intruded older sedimentary
rocks and would not necessarily have any ex-
pression in the shallow strata.
The offshore basement ridge and Los Testi-
gos Islands are so clearly on strike with the Gre-
nada platform and the trend of the Lesser An-
tilles arc that truncation of the ridge at
62°20'W and development of a different mag-
netic-anomaly pattern are presumed to represent
only relatively shallow effects. The gravity
anomalies show that the deeper trend of the is-
land arc does extend into the Paria shelf. A dis-
tinctive + 60 to +100 mgal free-air anomaly,
which patently is related to the Grenada plat-
form (MM', Fig. 3), can be traced southwest-
ward through all three remaining oblique lines
(LL', KB', and JJ', Fig. 3) and across the two
western north-south lines (BB', AA', Fig. 3),
where it coincides with the crystalline basement
ridge. The regional study of Bush and Bush
(1969) suggests that this anomaly continues
across Los Testigos Islands to Isla Margarita
where, much reduced in amplitude, it turns al-
most due west.
Grenada Platform
The Grenada platform — physiographically if
not structurally the southern end of the Lesser
Antilles arc — is a massive core complex overlain
by layered sedimentary rocks that range in
thickness from 0 to 0.5 sec penetration. The
deeper strata usually exhibit variable, commonly
comparatively steep apparent dips. The core
complex is exposed on the sea floor near the
western end of the platform.
A +60 to +100 mgal free-air gravity anom-
aly and a broad, fairly smooth magnetic-anom-
aly minimum were observed over the western
end of Grenada platform (MM', Figs. 3, 4).
The free-air anomaly indicates the presence of
excess mass and tends to corroborate the exis-
tence of a dense, high seismic-velocity "root"
beneath the island arc (Edgar, 1968). Observa-
tions by other investigators (e.g., J. Ewing et
ah, 1960; Bunce et al., 1970) suggest that the
magnetic-anomaly profile is not atypical, and
that the southern Lesser Antilles platform gen-
erally is marked by a fairly smooth, broad min-
imum. This minimum can be explained only by
the presence of a reversely magnetized body
1728
R. K. Lattimore, L. Austin Weeks and L. W. Mordock
(G. Peter, personal commun.). Local, short-
wavelength anomalies mark presumably young-
er intrusives.
Inter-Platform Basin
At about 62°05'W northward-dipping sedi-
ments of the Paria shelf and slope nearly lap
onto the intensely folded layered rocks and
core complex of the Grenada platform. The
two provinces are separated only by a V-shaped
sea-floor valley, no more than 2 n. mi (3.7 km)
wide and having perhaps 50 fm (90 m) relief.
East of 62°05'W this valley widens into an
asymmetric, shallow basin (Fig. 1) which
opens into Tobago Trough.
Most of the shallow sediments in the inter-
platform basin appear to have been carried
across the Paria shelf and dumped over the
foreset slope face. Exhibiting a variety of struc-
tures indicative of penecontemporaneous de-
formation and submarine erosion, they form a
wedge 0.2-0.5 sec thick which occupies the
floor of the basin (KK", Fig. 2). Detritus from
the Grenada platform seems to be restricted to
a narrow band near its base.
Summary and Conclusions
The Paria shelf is underlain by more than
1,000 ft (0.3-0.5 sec penetration) of sediments
and sedimentary rocks exhibiting subparallel,
generally well-defined, continuous reflectors. In
general, these beds dip gently and thicken
southward; they are cut by numerous faults,
commonly of small displacement. Thickening
of individual beds across these faults and other
evidence attest to continued or repeated epeiro-
genic activity.
Three major structural-physiographic ele-
ments can be delineated within the Paria shelf.
Carupano Sea Valley, which extends eastward
along the inner shelf parallel with the Paria-Ar-
aya shoreline, occupies a structural depression
— in places a graben — bounded on the south by
a zone of faults along which the coast ranges
were uplifted. Cumberland Rise, a topographic
and locally complex structural high north of
the sea valley, is believed to reflect a positive
element extending from Isla Margarita east-
northeast beyond 62 CW. The southwest exten-
sion of Tobago Trough (as shown by Edgar,
1968) is manifested (1) as a shallow embay-
ment that extends across the shelf almost to
Dragon's Mouth; (2) in a negative free-air
gravity anomaly associated with the outer shelf
north of Dragon's Mouth; and (3) in the oc-
currence of foreset beds intercalated with "nor-
mal" strata, interpreted as representing sudden,
local subsidence of the central part of the shelf.
East of 62°30'W the distinctive topography of
Cumberland Rise disappears, and the associ-
ated shallow structures become less complex,
probably because of the accumulation of an in-
creasingly thick blanket of trough sediments.
The overall structural pattern of the shelf sug-
gests a block that has been tilted down toward
the south along the Araya-Paria-Trinidad coast,
and further depressed by Tobago Trough,
north of Dragon's Mouth. Our investigations
do not exclude the possibility that the Caru-
pano Sea Valley depression is a structural ex-
tension of Tobago Trough, but magnetic anom-
alies, which seem to be associated with the de-
pression in the western part of the study area,
extend beyond the axis of the trough nearly as
far east as Tobago. East of 62°30'W the trend
of these anomalies develops a pronounced
northward curvature, parallel with the trend of
the Lesser Antilles arc.
Of the three major features which comprise
the Paria shelf, only Tobago Trough is gener-
ally accepted as being part of the island arc sys-
tem, but the east-northeast orientation of Cum-
berland Rise and the magnetic anomalies asso-
ciated with Carupano Sea Valley raise the pos-
sibility that the other two elements are more
closely related to the arc than to the South
American continent. A broad, asymmetric mag-
netic-anomaly maximum over the outer shelf
west of 62°10'W is correlated with a similar
pattern mapped by J. Ewing et al. (1960)
north of Grenada; this pattern almost certainly
is associated with the arc.
The physiography and shallow structure of
the shelf, together with distribution of a Holo-
cene heavy-mineral assemblage (Koldewijn,
1958), support a hypothesis that the principal
path for sediment eroded from the Paria-Araya
Peninsulas has been alongshore through Caru-
pano Sea Valley and northeastward across the
shelf into Tobago Trough. At such times as the
trough or the sea valley was filled to a local
base level, detritus was transported directly off-
shore; prograding or foreset sediments, depos-
ited unconformably on older folded and in-
truded sedimentary rocks, have built the edge
of the shelf upward and seaward. East of
62 °W, sediments carried over the foreset slope
face have been deposited in a comparatively
shallow, asymmetric basin that opens on the
east into Tobago Trough; this basin constitutes
a second route by which detritus eroded from
larine Geophysical Reconnaissance of Venezuela
1729
the Paria-Araya Peninsulas can be conveyed
into Tobago Trough.
Geophysical evidence indicates that Grenada
platform — and by extension the southern
Lesser Antilles arc — is composed of a relatively
uniform, reversely magnetized, crystalline body
of rock and a dense, high seismic-velocity
"root." Seismic-reflection and magnetic-anom-
aly data support the existence of a shallow ig-
neous body extending from Los Testigos Is-
lands northeast toward Grenada. Although this
structure is truncated at 62°20'W (probably by
faulting), gravity data substantiate extension of
the Lesser Antilles trend into the Paria-Araya
shelf; the intrusive body coincides with the
trend.
The fact that the trends of the Lesser Antilles
and Tobago Trough can be traced well into the
Paria shelf implies that any recent transcurrent
faulting within the area of investigation could
occur only near the Paria-Araya shoreline. If,
as is required by the "new global tectonics"
(Isacks et al., 1968), the Caribbean plate is sep-
arated from the South American continent by a
fault along which._great lateral displacement has
taken place, this fault — if it does not predate
the island arc — must occur south of 1 1 °N. Evi-
dence against this possibility is presented in
Bassinger et al. ( 1971, this issue) and discussed
by Weeks et al. (1971, this issue).
References Cited
Bassinger, B. G., R. N. Harbison, and L. A. Weeks,
1971, Marine geophysical study northeast of Trini-
dad-Tobago: Am. Assoc. Petroleum Geologists Bull.,
v. 55, no. 10, p. 1730-1740.
Bucher, W. H., 1952, Geologic structure and orogenic
history of Venezuela: Geol. Soc. America Mem. 49,
113 p.
Bunce, E. T, J. D. Phillips, R. L. Chase, and C. O.
Bovvin, 1970, Lesser Antilles Arc and the eastern
margin of the Caribbean Sea: Woods Hole Oceanog.
Inst. Contrib. 2288, 36 p.; in press, in A. E. Max-
well, ed., The sea, v. 4: New York, Wiley-Intersci-
ence.
Bush, S. A., and P. A. Bush, 1969, Isostatic gravity map
of the eastern Caribbean region: Gulf Coast Assoc.
Geol. Soc. Trans., v. 19, p. 281-285.
Edgar, N. T, 1968, Seismic refraction and reflection in
the Caribbean Sea: Ph.D. dissert., Columbia Univ.,
163 p.
Ewing, J. I., C. B. Officer, H. R. Johnson, and R. S.
Edwards, 1957, Geophysical investigations in the
eastern Caribbean — Trinidad shelf, Tobago trough,
Barbados ridge, Atlantic Ocean: Geol. Soc. America
Bull., v. 68, p. 897-912.
J. W. Antoine, and W. M. Ewing, 1960, Geo-
physical measurements in the western Caribbean Sea
and in the Gulf of Mexico: Jour. Geophys. Re-
search, v. 65, p. 4087-4126.
N. T. Edgar, and J. VV. Antoine, in press, Gulf
of Mexico and Caribbean Sea, in A. E. Maxwell,
ed., The sea, v. 4: New York, Wiley-Interscience.
Ewing, W. M., J. L. Worzel, and G. L. Shurbet, 1957,
Gravity observations at sea in U.S. submarines Bar-
racuda, Tusk, Conger, Argonaut and Medregal:
Koninkl. Nederlandsch Geol.-Mijn. Genoot. Verh.,
Geo!. Ser., v. 18, p. 49-115.
Gonzalez de Juana. C N. G. Munoz J., and M. Vig-
nali C, 1968, On the geology of eastern Paria (Ven-
ezuela) : 4th Caribbean Geol. Conf. Trans, p. 25-29.
Isacks, B., J. Oliver, and L. R. Sykes, 1968, Seismology
and the new global tectonics: Jour. Geophys. Re-
search, v. 73, p. 5855-5899.
Koldewijn, B. W., 1958, Sediments of the Paria-Trini-
dad shelf; v. 3 of Reports of the Orinoco Shelf expe-
dition: The Hague, Mouton and Co., 109 p.
Maloney, N. J., 1967, Geomorphology of the continen-
tal margin of Venezuela, Pt. 2, Continental terrace off
Carupano: Bol. Inst. Ocean., Univ. Oriente
(Cumana, Venezuela), v. 6, p. 147-155.
Maxwell, J. C, and Gabriel Dengo, 1951, Carupano
area and its relation to the tectonics of northeastern
Venezuela: Am. Geophys. Union Trans., v. 32, no.
2, p. 259-267.
Officer, C. B., J. I. Ewing, J. F. Hennion, D. G. Hark-
rider, and D. E. Miller, 1959, Geophysical investi-
gations in the eastern Caribbean: Summary of 1955
and 1956 cruises, in L. H. Ahrens et al., eds., Physics
and chemistry of the earth, v. 3: New York, Perga-
mon Press, p. 17-109.
Weeks, L. A., R. K. Lattimore, R. N. Harbison, B. G.
Bassinger, and G. F. Merrill, 1971, Structural rela-
tions among Lesser Antilles, Venezuela, and Trini-
dad-Tobago: Am. Assoc. Petroleum Geologists Bull.,
v. 55, no. 10, p. 1741-1752.
59
Reprinted from Nature Physical Science 232 , No. 31,
97-98 .
Deformation of the Sea Floor off the
North-west Coast of the United States
GEORGE PETER & OMAR E. DeWALD
NOAA, Atlantic Oceanographic and Meteorological Laboratories, Miami, Florida 33130
A new fracture zone separating the
Tufts Abyssal Plain from the moun-
tainous topography of the Explorer and
Juan de Fuca ridges has been discovered
on the basis of the magnetic anomaly
offsets. North-east-south-west compres-
sion is the likely cause for the rotation,
strike-slip faulting, and deformation of
the small crustal blocks of the area.
Thirteen east-west tracklines run by NOAA ships during the
past few years off the coasts of Oregon and Washington enabled
us to identify the magnetic anomaly lineations and to establish
their offset pattern west of the Juan de Fuca and Gorda ridges.
The magnetic lineation pattern obtained (Fig. 1) reveals a new
NW-SE trending fault zone which cuts the magnetic anomalies
west of the Juan de Fuca Ridge, and explains the abrupt drop
of the sea floor and the disappearance of the rough topography
associated with the Juan de Fuca Ridge west of the proposed
fault (Fig. 2). The establishment of the anomaly pattern from
the Juan de Fuca Ridge to anomaly 7 (ref. 1) closes the gap
that existed between the well known pattern near the coast and
in the central north-east Pacific2-3.
It is usually considered that magnetic anomaly lineations
Fig. 1 Map of the sea floor magnetic anomaly lineations off
the coasts of Washington and Oregon. Zip patterns demon-
strate the correlation of the magnetic anomalies across the
various fault offsets. Numbers (I) refer to key magnetic anoma-
lies. Number 1 (from north to south) is associated with the
centre parts of the Explorer, Juan de Fuca, and Gorda ridges.
Fig. 2 Map of the magnetic anomaly offsets (dashed lines)
superimposed on a sketch of the bathymetry of the sea floor
west of Washington and Oregon. Zip patterns-show the idealized
crestal areas of the mid-oceanic ridge segments; dark patches
show the major seamounts. The shelf edge is depicted by the
100 fathom isobath (1 fathom=1.83 m). For clarity, contour
lines (200 fathom contour intervals) are shown only in depths
greater than 1,600 fathoms. Bathymetry is after Chase el a/.14.
The new names, Juan de Fuca, Explorer, and Cobb fault zones,
were approved by the Board on Geographic Names.
originate from the upper, basaltic part of the oceanic crust and
represent strips of rocks which were formed at the centre of
mid-oceanic ridges under the influence of the periodically
reversing magnetic field of the Earth". As the oceanic crust is
younger and has a much simpler tectonic history than the
continental crust5, the magnetic lineations acquired by the
oceanic crust at the time of its genesis have been preserved
through geologic time. Magnetic anomaly maps, therefore,
show the offsets of former mid-oceanic ridges and the offsets
or deformation pattern of the oceanic crust acquired after its
formation.
The Juan de Fuca and Gorda ridges represent short segments
of a former mid-oceanic ridge6 which in large part has been
obliterated as it migrated eastward and collided with the North
American continent17. The origin of the two ridges and the
reason for their north-easterly trend have long been a matter
of controversy. Various authors have discussed whether the
ridges separated and tilted north-east in adjustment to a change
in the direction of sea floor spreading7-8, or whether they
became offset and rotated as a result of a strike-slip faulting".
We believe that the new data (Fig. 3) suggest a solution to this
problem.
The magnetic anomaly offset pattern (Fig. I) follows the
interpretation of Pavoni'0 and Peter and Lattimore9, and is
based on the magnetic anomaly map of Mason and Raff2
1 —"" 1
2, ^^\/j\^Aj^
3 /w^n^/\WYW
« A^yv^MAW^/lAJ^W
s M/VMTv^>Vv{yV\/V^lj|
6 v^a^-a^AaA^W|/^^vAAMA/v-
7 \fxy^Mft iVt^Wv/^
8 M^/wvyvy\A>ft^^
9 V^^r^fJ^A^M^^^
Fig. 3 o, Tracklines used for the westward extension of former magnetic anomaly maps. 6, Selected east-west magnetic anomaly
profiles showing identification and correlation of the magnetic anomalies. The location of the profiles is shown in a.
south of the Blanco fracture zone, east of the Juan de Fuca
Ridge, and east of 134° W in the area north of48°N. In the
remaining part of Fig. 1 the magnetic lineations were established
on the basis of east-west tracklines which, with the exception
of a few cross lines, extend approximately along each degree
latitude. A more detailed survey, therefore, may show this area
structurally more complex than indicated by this figure.
The new magnetic anomaly data show that anomaly 6 has
only minor offsets south of the Sedna fracture zone. The
Surveyor fracture zone ends directly west of anomaly 6, and the
Blanco fracture zone terminates at the southern tip of the Juan
de Fuca Ridge. The magnetic anomaly pattern is continuous
west of the Gorda Ridge, but anomaly 5 and a number of
anomalies between 5 and 6 are missing west of the Juan de Fuca
Ridge. The disappearance of the anomalies occurs along a
north-west line which correlates with a sharp 300 fathom
(550 m) change in the relief of the sea floor (Fig. 2). To the
west of this line lies the Tufts Abyssal Plain with a gentle topo-
graphic gradient rising eastward; to the east lies the moun-
tainous topography of the Juan de Fuca Ridge. We suggest
that this demarcation line trending north-west separating the
magnetic lineations and cutting the topography of the Juan de
Fuca Ridge at an oblique angle represents a fracture zone, and
we named it the Juan de Fuca fracture zone.
The origin of the Juan de Fuca fracture zone is most likely
related to the Late Tertiary deformation11 that affected this
entire area. It appears in light of the new data that if the
Explorer, Juan de Fuca, and Gorda ridges were continuous at
the time of the formation of anomaly 5, approximately 10 m.y.
ago3, then they must have been in alignment with the segment
of anomaly 5 located west of the Gorda Ridge, where the
anomaly sequence is uninterrupted. The missing anomalies and
the well defined fault-border of the crustal fragments indicate
that the deformation involved the rotation, strike-slip faulting,
and overthrust of small crustal plates north of the Blanco and
Juan de Fuca fault zones, rather than a gradual realignment of
the ridges under the influence of a change in the direction of the
sea floor spreading. If the magnetic anomalies that were offset
by strike-slip faults east of the Juan de Fuca Ridge are aligned,
a north-south crustal shortening of 120 km is indicated. The
offset of anomaly 5 and the missing anomalies suggest a 200 km
westerly displacement and consequent destruction of the crust
along the Juan de Fuca and Blanco fracture zones. Part of the
north-south compression has been transmitted to the area of
the Gorda Ridge, where the deformation of anomaly 3 near the
coastline indicates a north-south compression of 150 km.
North-south compression indicated by the deformation
pattern of the magnetic anomalies is in agreement with the
relative plate motions derived for the area east of the Juan de
Fuca and Gorda ridges7-12. The scatter of earthquakes13 east
of the Gorda Ridge also supports the proposed compression of
that area, but to the north the distribution of the earthquakes
indicates that at the present time the deformation is con-
centrated along the Explorer and Blanco fault zones. A more
detailed discussion of the plate motions of the area will be
presented in another article now in preparation.
We thank B. H. Erickson, NOAA, Pacific Oceanographic
Laboratories, for providing most of the magnetic anomaly
profiles.
Received July 20, 1971.
1 Pitman, W. C, III, Herron, E. M., and Heirtzler, J. R., J. Geo-
phys. Res., 73, 2069(1968).
2 Raff, A. D., and Mason, R. G., Bull. Geol. Soc. Amer., 72, 1267
(1961); Mason, R. G., and Raff, A. D., Bull. Geol. Soc. Amer ,
72, 1259(1961).
3 Pitman, W. C, III, and Hayes, D. E , J. Geophys. Res., 73,
6571 (1968).
* Vine, F." J., and Matthews, D. H., Nature, 199, 947 (1963);
Vine, F. J., Science, 154, 1405 (1966); Cox, A., Doell, R. R.,
and Dalrymple, G. B., Science, 144, 1537 (1964).
5 Hess, H. H., in Submarine Geology and Geophysics (vol. 17,
Colston papers) (edit, by Whittard, W. F., and Bradshaw, R.),
317 (Butterworths, London, 1965); Dietz, R. S., Amer. J. Sci.,
264, 177(1966).
6 Wilson, J. T., Science, 150, 482 (1965); Menard, H. W., Marine
Geology of the Pacific, 111 (McGraw-Hill, New York, 1964).
7 Atwater, T., Bull. Geol. Soc. Amer., 81, 3513 (1970).
8 Menard, H. W., and Atwater, T., Nature, 219, 463 (1968); ibid.,
222, 1037 (1969).
9 Peter, G., and Lattimore, R., J. Geophys. Res., 74, 586 (1969).
10 Pavoni, N., Pure Appl. Geophys., 63, 172 (1966).
11 McManus, D. A., Marine Geol., 3, 429 (1965); Wise, D. V.,
Bull. Geol. Soc. Amer., 74, 357 (1963).
12 Silver, E. A., Science, 166, 1265 (1969).
13 Tobin, D. G.,and Sykes, L. R.,7. Geophys. Res., 73, 3821 (1968).
14 Chase, T. E., Menard, H. W., and Mammerickx, J., The Institute
of Marine Resources (University of California, 1970).
Primed in Grcal Briiam by Flarepath Printers Limned. Watling Sireel. Colney Streel. St. Albans. Herts
60
Reprinted from The Sea, Vol. 4, Pt. 2, 191-222.
5. MAGNETIC STRUCTURE OF THE ALEUTIAN TRENCH
AND NORTHEAST PACIFIC BASIN
(June 1968)
George Peter, Barrett H. Erickson, and Paul J. Grim
1. Introduction
The large number of detailed magnetic surveys and exploratory tracklines
made during the last decade have contributed significantly to the development
of new ideas and to the understanding of the structure and evolution of the
oceanic crust. Particularly significant among the methods of study of crustal
structure was the Scripps Institution of Oceanography — U.S. Coast and
Geodetic Survey magnetic-bathymetric survey project off the west coast of the
United States (Mason, 1958; Mason and Raff, 1961; Vacquier et al., 1961;
Raff and Mason, 1961). It was found that the magnetic anomalies in this area
form parallel, north-south trending lineations which are frequently offset as if
by lateral faults. Offsets of the magnetic lineations were found to be associated
with fracture zones such as the Mendocino; investigation of other offsets led
to the discovery of other major fracture zones with well-developed topographic
expression. Like the magnetic lineations themselves, the minor offsets appear to
lack topographic or even sub-bottom expression; these features, however,
generally are considered to reflect internal structure of the oceanic crust or
upper mantle. The pattern of the magnetic anomaly lineations therefore can
be called the magnetic structure.
Throughout the world, similar magnetic-anomaly lineations have been found
to be disposed symmetrically along either side of the axis of the mid-oceanic
rises (Vine, 1966; Pitman et al., 1968; Dickson et al, 1968; Le Pichon and
Heirtzler, 1968; Heirtzler et al., 1968). The axial symmetry of these magnetic-
anomaly lineations and their correlation (within a central crestal zone) with
dated magnetic-polarity reversals on land and with the magnetic reversals
found in deep-sea cores have given strong support to the hypothesis of crustal
evolution through sea-floor spreading (Dietz, 1961; Hess, 1962; Vine and
Matthews, 1963; Heirtzler et al., 1966; Ninkovich et al., 1966; Vine, 1966;
Cox et al., 1964; Opdyke et al., 1966; Dickson and Foster, 1966).
Detailed studies by McManus (1965), Loncarevic et al. (1966), van Andel
et al. (1967), and van Andel and Bowin (1968) have provided insight into the
hitherto unknown, complex geology of the crests of the mid-oceanic rises.
Although this new information does not directly contradict the hypothesis of
sea-floor spreading, it has raised serious questions as to its applicability.
Important limitations can be placed on the mechanism of sea-floor spreading
by the Y-shaped ridge-junction discovered near the Galapagos Islands (Herron
and Heirtzler, 1967; Raff, 1968), by the sediment distribution over mid-oceanic
ridges (Ewing and Ewing, 1967), and by the undisturbed sediments in "trans-
form fault" zones and trenches (Ludwig et al., 1966; van Andel et al., 1967;
Scholl et al., 1968).
191
192
PETER, ERICKSON, AND GRIM
[chap. 4
The purpose of this paper is to describe the magnetic structure of the North-
east Pacific and the Aleutian Arc, and to discuss the questions that can be
raised in regard to the application of the sea-floor spreading hypothesis within
this area. All available data from the Northeast Pacific have been compiled.
Magnetic and bathymetric maps for the central Northeast Pacific and the
Aleutian Arc that have significant bearing on the discussion are presented, and
their implications in regard to crustal genesis are discussed in some detail.
The specific areas under consideration (Fig. 1) represent part of the total
systematic coverage under ESSA — Coast and Geodetic Survey project SEAMAP
(Peter and Stewart, 1965; Peter, 1965; Elvers et al., 1967). Tracks for these
surveys comprise a grid of north-south lines approximately spaced at 18 km
intervals; irregularly spaced cross-lines were run as checks. Magnetic and
bathymetric data were collected with a Varian proton-precession magnetometer
and a Precision Depth Recorder, respectively. Accuracies of these measurements
are discussed in Peter et al. (1965) and Elvers et al. (1967).
Primary control of the survey was obtained from LORAN-C. Lines run
relatively close to the LORAN-C net provided positions along the tracklines
with an estimated accuracy of + 1 km. The uncertainty in position increases
to the south, although no obvious discrepancies were noted north of 38°N.
Between 35°30'N and 38°N, one trackline was rejected and three others were
adjusted in a north-south direction by 5 km, based on systematic discrepancies
of the magnetic and bathymetric values among adjacent tracklines.
The density of tracklines and the prominence of the lineations are adequate
to show all essential details on the magnetic-anomaly contour maps. The
trackline density and the contour interval selected are sufficient to delineate
the major topographic features. The shortcomings of the 18-km grid, however,
are clearly evident in areas of irregular topography or elongated, smaller
seamounts and ridges.
150" 170°E 170°W 150" 130"
Fig. 1. Map of North Pacific Ocean: areas of detailed coverage shown in center (A, B, C).
60
Reprinted from The Sea, Vol. 4, Pt. 2, 191-222.
5. MAGNETIC STRUCTURE OF THE ALEUTIAN TRENCH
AND NORTHEAST PACIFIC BASIN
(June 1968)
George Peter, Barrett H. Erickson, and Paul J. Grim
1. Introduction
The large number of detailed magnetic surveys and exploratory tracklines
made during the last decade have contributed significantly to the development
of new ideas and to the understanding of the structure and evolution of the
oceanic crust. Particularly significant among the methods of study of crustal
structure was the Scripps Institution of Oceanography — U.S. Coast and
Geodetic Survey magnetic-bathymetric survey project off the west coast of the
United States (Mason, 1958; Mason and Raff, 1961; Vacquier et al., 1961;
Raff and Mason, 1961). It was found that the magnetic anomalies in this area
form parallel, north-south trending lineations which are frequently offset as if
by lateral faults. Offsets of the magnetic lineations were found to be associated
with fracture zones such as the Mendocino; investigation of other offsets led
to the discovery of other major fracture zones with well-developed topographic
expression. Like the magnetic lineations themselves, the minor offsets appear to
lack topographic or even sub-bottom expression; these features, however,
generally are considered to reflect internal structure of the oceanic crust or
upper mantle. The pattern of the magnetic anomaly lineations therefore can
be called the magnetic structure.
Throughout the world, similar magnetic-anomaly lineations have been found
to be disposed symmetrically along either side of the axis of the mid-oceanic
rises (Vine, 1966; Pitman et al., 1968; Dickson et al, 1968; Le Pichon and
Heirtzler, 1968; Heirtzler et al., 1968). The axial symmetry of these magnetic-
anomaly lineations and their correlation (within a central crestal zone) with
dated magnetic-polarity reversals on land and with the magnetic reversals
found in deep-sea cores have given strong support to the hypothesis of crustal
evolution through sea-floor spreading (Dietz, 1961; Hess, 1962; Vine and
Matthews, 1963; Heirtzler et al., 1966; Ninkovich et al., 1966; Vine, 1966;
Cox et al., 1964; Opdyke et al., 1966; Dickson and Foster, 1966).
Detailed studies by McManus (1965), Loncarevic et al. (1966), van Andel
et al. (1967), and van Andel and Bowin (1968) have provided insight into the
hitherto unknown, complex geology of the crests of the mid-oceanic rises.
Although this new information does not directly contradict the hypothesis of
sea-floor spreading, it has raised serious questions as to its applicability.
Important limitations can be placed on the mechanism of sea-floor spreading
by the Y-shaped ridge-junction discovered near the Galapagos Islands (Herron
and Heirtzler, 1967; Raff, 1968), by the sediment distribution over mid-oceanic
ridges (Ewing and Ewing, 1967), and by the undisturbed sediments in "trans-
form fault" zones and trenches (Ludwig et al., 1966; van Andel et al., 1967;
Scholl et al., 1968).
191
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THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN
193
2. Central Northeast Pacific
A. Bathymetry
In area A (Figs. 1, 2a), there are three distinct bathymetric provinces
separated by major fracture zones. South of the Mendocino Fracture Zone, the
sea floor is comparatively smooth and has an average depth of 3100 fathoms
(5670 m). This area falls under the classification of an abyssal-hill province
(Hurley, 1960; Menard, 1964); there is a general east- west trend in the bottom
topography which strongly contrasts with the irregular abyssal-hill topography
north of the Mendocino Fracture Zone. Two east-west troughs with associated
ridges on their northern side cut the ocean floor at 36°10'N and 37°20'N. The
troughs and ridges have a relief of approximately 300 fathoms (550 m). A third
trough at 37°45'N is bordered by ridges on both sides.
The Mendocino and Pioneer fracture zones cannot be separated. Complex
elongated ridges and valleys with steep walls that resemble horsts and
grabens extend from 38°N to 39°30'N within this zone (Fig. 3). The central
40°00' 4 TOO' 4I°40'
2500
3000
2500
3000
2500
3000
2500
3000
2500
3000
2500
3000
2500
3000
2500
3000
50
100 km
Fig. 3. PDR tracing of north-south trackline along 156°40'W. Depth is in fathoms
(1 fm = 1.83 m).
194 PETER, ERICKSON, AND GRIM [CHAP. 5
valley of the Mendocino Fracture Zone (Menard, 1964) is the deepest part of
the sea floor here. At the western end of Fig. 2a the greatest depth measured
was 3525 fathoms (6450 m). In this area all the valleys and ridges of the
Mendocino Fault Zone strike 070°.
Between the Mendocino and Surveyor fracture zones (Peter, 1966; Fig. 2a)
the abyssal hills are more prominent and there are numerous small seamounts.
The sea floor has an average depth of 3000 fathoms (5490 m); this is 100 fathoms
(180 m) higher than the sea floor south of the Mendocino Fracture Zone, and
200 fathoms (360 m) lower than the base of the Mendocino ridges.
The Surveyor Fracture Zone has a strike parallel to the Mendocino Fracture
Zone and is located at 42°45'N (Fig. 2a). Topographically, it is a 350-fathom
(650 m) high ridge, bounded on the northern side by a 200-fathom (360 m)
deep trough. Elongated ridges and a generally irregular topography north of
the trough appear to be related to the fracture zone. From this area northward
to the Aleutian Trench the sea floor is smooth and rises gently to the north.
B. Magnetic Anomalies
The displacement of magnetic anomaly lineations (Mason, 1958; Vacquier
et al., 1961) provides a method for the determination of the offsets along the
submarine fracture zones. Peter (1966) previously discussed the offsets along the
fracture zones of this area. Anomalies 27, 28, and 29 to the north of the Surveyor
Fracture Zone and 25 and 26 to the south of it (labelled in Fig. 4) are identified
from the spectrum of the world-wide magnetic-anomaly lineations (Pitman
et al., 1968) in Fig. 2b. Although it has been found that east of this area the
offsets of the magnetic-anomaly lineations and bottom topography generally
agree in displacement (Menard, 1964), it has not been determined whether or
not a particular type of bottom topography is characteristic of a specific group
of magnetic lineations. It is generally agreed that there is no correlation between
the individual magnetic-anomaly lineations and the bottom topography.
Correlation is not found even between the magnetic data and the rugged
topography of the second layer (Drake et al., 1963). Nevertheless these observa-
tions only stress the lack of direct, one-to-one correlation; Peter (1966) reported
that the minor steplike elevation changes and broad (200-300 km) undulations
in the sea-floor topography appear to line up with the strike of the magnetic-
anomaly lineations.1
In the area of the Surveyor Fracture Zone, the absence of correlation between
the magnetic lineations and the sea-floor topography is well illustrated. Sound-
ing and magnetic profiles suggest that this fracture zone forms a border between
the smooth, south-southwest dipping, sea floor to the north and the generally
horizontal, abyssal-hill province to the south. Yet the magnetic anomalies
1 Recent studies by Talwani et al. (1968) in the area of the Reykjanes Ridge have shown
that within a positive or negative magnetic anomaly lineation the variation of the ampli-
tude of the anomaly is caused, in general, by changes of the bottom topography. Deep-tow
magnetometer observations indicate correlation between trends of the magnetic anomalies
and small-scale bottom irregularities (Spiess et al., 1968).
Hill I L
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r-t—Hi '
nij
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-.
bb
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J L_
196 PETER, ERICKSON, AND GRIM [CHAP. 5
(offset by 300 km in a right lateral sense) cross this fracture zone and continue
through the two entirely different bathymetric provinces without apparent
change in character.
A detailed study of the Murray Fracture Zone indicates that there are
elongated magnetic anomalies over the horst-graben pattern of the topography
(Malahoff, 1968); in contrast to this, over this area of the Mendocino Fracture
Zone magnetic anomalies are absent over even the sharpest ridges. There is a
broad, magnetic low over the central part of the fracture zone, but it appears
to strike east-west rather than to follow the strike of the topography.
South of the Mendocino Fracture Zone (Figs. 2a, b) the magnetic field is
smooth (with the exception of three elongated anomalies over the troughs and
ridges described earlier). The magnetic anomalies are strikingly different over
each of these features. Over the northernmost feature a positive anomaly is
present, over the central feature there is a prominent negative anomaly, and
over the southernmost trough and ridge the anomaly consists of both negative
and positive parts, disposed in accordance with induced magnetization in the
northern hemisphere. None of the anomalies, however, is suggestive of induced
magnetization due to the earth's present magnetic field. If simple vertical-sided
bodies are assumed as sources, the direction of the dip of the magnetization
vector, as judged by the model studies of Heirtzler et al. (1962), is different for
each of these features.
3. Abyssal Plain and Trench Southwest of Kodiak
A. Bathymetry
The Aleutian Abyssal Plain (Hurley, 1960) lies between the Aleutian Trench
and the Surveyor Fracture Zone (Figs, lb, and 5). The sea floor is essentially
flat, with a small southward dip of 2 m/km. A number of knolls and seamounts
that vary in heights from a few hundred to over one thousand meters are
distributed irregularly throughout the area. The general fabric of the sea-floor
topography trends northeast-southwest in the southeastern part of Fig. 5, and
northwest-southeast in the southwestern part. At 51°N weak east- west trends
are observed; these give way to the northeast-southwest trends at the southern
wall of the Aleutian Trench. There is no outer ridge associated with the Aleutian
Trench in this area; only a small swell separates the abyssal plain and the
trench.
Depths in the trench vary from 3000 fathoms (5480 m) on the east to 3800
fathoms (6960 m) on the west. Although the southern wall of the trench is
relatively smooth, the northern wall is irregular with a few benches and welts
which persist for great distances (Peter et al., 1965).
B. Magnetic Anomalies
In area A and most of area B (Fig. 1) the magnetic lineations generally
strike N18°W. Between 47 °N and 51°30'N these lineations progressively bend
196 PETER, ERICKSON, AND GRIM [CHAP. 5
(offset by 300 km in a right lateral sense) cross this fracture zone and continue
through the two entirely different bathymetric provinces without apparent
change in character.
A detailed study of the Murray Fracture Zone indicates that there are
elongated magnetic anomalies over the horst-graben pattern of the topography
(Malahoff, 1968); in contrast to this, over this area of the Mendocino Fracture
Zone magnetic anomalies are absent over even the sharpest ridges. There is a
broad, magnetic low over the central part of the fracture zone, but it appears
to strike east-west rather than to follow the strike of the topography.
South of the Mendocino Fracture Zone (Figs. 2a, b) the magnetic field is
smooth (with the exception of three elongated anomalies over the troughs and
ridges described earlier). The magnetic anomalies are strikingly different over
each of these features. Over the northernmost feature a positive anomaly is
present, over the central feature there is a prominent negative anomaly, and
over the southernmost trough and ridge the anomaly consists of both negative
and positive parts, disposed in accordance with induced magnetization in the
northern hemisphere. None of the anomalies, however, is suggestive of induced
magnetization due to the earth's present magnetic field. If simple vertical-sided
bodies are assumed as sources, the direction of the dip of the magnetization
vector, as judged by the model studies of Heirtzler et al. (1962), is different for
each of these features.
3. Abyssal Plain and Trench Southwest of Kodiak
A. Bathymetry
The Aleutian Abyssal Plain (Hurley, 1960) lies between the Aleutian Trench
and the Surveyor Fracture Zone (Figs, lb, and 5). The sea floor is essentially
flat, with a small southward dip of 2 m/km. A number of knolls and seamounts
that vary in heights from a few hundred to over one thousand meters are
distributed irregularly throughout the area. The general fabric of the sea-floor
topography trends northeast-southwest in the southeastern part of Fig. 5, and
northwest-southeast in the southwestern part. At 51°N weak east- west trends
are observed ; these give way to the northeast-southwest trends at the southern
wall of the Aleutian Trench. There is no outer ridge associated with the Aleutian
Trench in this area; only a small swell separates the abyssal plain and the
trench.
Depths in the trench vary from 3000 fathoms (5480 m) on the east to 3800
fathoms (6960 m) on the west. Although the southern wall of the trench is
relatively smooth, the northern wall is irregular with a few benches and welts
which persist for great distances (Peter et al., 1965).
B. Magnetic Anomalies
In area A and most of area B (Fig. 1) the magnetic lineations generally
strike N18°W. Between 47°N and 51°30'N these lineations progressively bend
. 5. Bathymotric map of area B (Fig. 1). Contour interval 50 fms (1 fm = 1.83 m),
except in areas of large gradients in which the interval is increased (from Elvers et al.,
1967).
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN
197
+500 -500
I 1 1
GAMMAS
Fig. 6. Illustration of the offset of the magnetic -anomaly lineations across the Amlia and
Adak fracture zones (location of profiles shown in Fig. 12) (from Grim and Erickson,
1969).
sharply westward, and their general strike becomes N83°W (Fig. 7). Anomaly
32B (see Fig. 4 for identification) bends first, at the south-west part of Fig. 7;
anomaly 25 is the last lineation that clearly bends westward. The east-west
lineation along 53°30'N and the south-east limb that projects from it may be
anomaly 24. The new strike represents an abrupt change in orientation of 65°
for all these anomalies.
The control for the magnetic map is shown in Fig. 8, and discussed in detail
by Elvers et al. (1967). To demonstrate the continuity of the anomalies around
the bend, a number of north -south magnetic lines from this area are compared
to east-west lines in Fig. 9. It is shown that along the profiles the character of
the anomalies changes abruptly at the bend. The entire group of lineations is
present on the westernmost profile (Fig. 9, profile 1).
One of the most pronounced differences between the east-west and north-
south portions of the lineations is the higher amplitude of the anomalies along
the east-west segments. Model studies (Heirtzler et al., 1962) indicate that the
change in orientation of the lineations with respect to magnetic north (which
changes approximately from 30 to 70° across the bend) is not sufficient to
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN
197
Fig. 6. Illustration of the offset of the magnetic-anomaly lineations across the Amlia and
Adak fracture zones (location of profiles shown in Fig. 12) (from Grim and Erickson,
1969).
sharply westward, and their general strike becomes N83°W (Fig. 7). Anomaly
32B (see Fig. 4 for identification) bends first, at the south-west part of Fig. 7;
anomaly 25 is the last lineation that clearly bends westward. The east-west
lineation along 53°30'N and the south-east limb that projects from it may be
anomaly 24. The new strike represents an abrupt change in orientation of 65°
for all these anomalies.
The control for the magnetic map is shown in Fig. 8, and discussed in detail
by Elvers et al. (1967). To demonstrate the continuity of the anomalies around
the bend, a number of north-south magnetic lines from this area are compared
to east-west lines in Fig. 9. It is shown that along the profiles the character of
the anomalies changes abruptly at the bend. The entire group of lineations is
present on the westernmost profile (Fig. 9, profile 1).
One of the most pronounced differences between the east-west and north-
south portions of the lineations is the higher amplitude of the anomalies along
the east-west segments. Model studies (Heirtzler et al., 1962) indicate that the
change in orientation of the lineations with respect to magnetic north (which
changes approximately from 30 to 70° across the bend) is not sufficient to
Rig. 7. Magnetic total intensity anomaly map of area B (Fig. 1). Contour interval is 100
gammas (from Fivers ot al., 1967).
198
PETER, ERICKSON, AND GRIM
[CHAP. 5
160
Fig. 8. Trackline chart of area B (Fig. 1). Small course changes are not shown (accuracy
+ 3 km).
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN
199
32B
32A
31 30
29 28 27
26 25
46l
48fc
50c
52^
i
26 25
148 c
1
146°
__l
144'
L_
142'
L_
E
200
0
200
r200
- 0
—200
140°
Fig. 9. Illustration of the westward bend of the magnetic -anomaly lineations. Selected
north-south profiles (upper half) are compared to two east-west profiles (lower half)
run along 35°30'N and 36°30'N. Location of N-S profiles is shown in Fig. 8.
account for the increase in amplitude of the positive anomalies. The change in
orientation in certain parts of the area would provide an adequate explanation
for the change in amplitude of the negative lineations. In other parts, however,
the change in amplitude is either greater or much less than that which would be
expected from the model studies.
The decrease of distance between anomalies 26 and 27 after these lineations
bend westward, is also quite prominent. By contrast, the distance between 31
and 32B increases considerably. The decreased distance between anomalies
26 and 27 seems to be at the expense of the broad, generally negative area
directly east of 27; the extra distance between anomalies 31 and 32B apparently
is taken up by two additional, small lineations (Fig. 6c).
200 PETER, ERICKSON, AND GRIM [CHAP. 5
A narrow, positive and negative lineation also is developed north of the
east-west segment of anomaly 25. If the prominent east-west lineation along
53°30'N is anomaly 24, the distance between 24 and 25 is greatly increased after
the westward bend. Furthermore, if the northwest-southeast trending, positive
anomaly at 52°N, 156°W, is part of anomaly 24, then there is an apparent break
in this lineation at 52°30'N. A similar break of anomaly 32A is seen just before
it bends westward. A more detailed survey would be necessary to adaquately
determine the smaller internal fractures and the discontinuities of these
lineations.
4. Aleutian Trench and Outer Ridge (164°W to 180°W)
A. Bathymetry
Area C (Fig. 1) includes the Aleutian Trench and outer ridge. The weakly
developed, east-west trending ridges on the outer swell southwest of Kodiak
continue westward and their relief increases progressively. By 172°W a typical
outer ridge of moderate relief is present (Fig. 10).
At 172°40'W, a north-south depression cuts through the outer ridge. West of
this depression there are a number of seamounts and the relief of the outer
ridge is greater than it is to the east. The seamounts on the western side of this
depression mark the location of the north-south trending Amlia Fracture Zone
(Grim and Erickson, 1969; Hayes and Heirtzler, 1968). No indication of this
fracture zone is seen in the trench; however, the change in trend of the Aleutian
Arc may be related to it.
Another depression, with a less pronounced relief and a somewhat irregular
shape, crosses the southern part of the outer ridge at 177°20'W. This depression
marks the general location of the Adak Fracture Zone (Grim and Erickson,
1969). There is no appreciable difference in the topography of the outer ridge on
opposite sides of this fracture zone, nor is there any evidence of a fracture zone
on the trench floor. The offset of the depression between the Aleutian Terrace
and the Aleutian Arc (Nichols and Perry, 1966), however, may be related to
this feature. This offset — approximately 30 km — appears to be expressed as a
reduction of the width of the Aleutian Terrace.
Adak Canyon to the north is approximately in line with the Adak Fracture
Zone, and is probably another expression of it. The canyon separates strikingly
different topography on either side. A generally smooth shelf on the east
changes to chaotic topography, riddled with numerous smaller canyons, on
the west. The eastern wall of Adak Canyon trends north-south; it is quite steep
and has the appearance of a fault scarp.
B. Magnetic data
Westward extension of the magnetic anomaly lineations is shown in Fig. 11.
Correlation of the magnetic lineations across the Amlia and Adak fracture zones
is demonstrated in Fig. 6 (location of profiles is shown in Fig. 12).
o
o
o
o
J2
O
I
u
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o
+-<
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ft
08
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202
PETER, ERICKSON, AND GRIM
[CHAP. 4
-}-450
165°
Fig. 12. Trackline chart of area C (Fig. 1) (after Grim and Erickson, 1969).
The anomalies terminate abruptly at the axis of the trench; traces of
anomalies 24, 25, and 26, however, appear to cross the trench and extend over
the Aleutian Terrace (Fig. 6a, profiles P, Q, and R). The east- west trend of
the isogamma lines north of the trench between the Amlia and Adak fracture
zones may also represent vestiges of the east- west magnetic lineations.
Generally, the magnetic field is smooth over the trench, but short- wavelength
anomalies are found in shallow water near the islands where the tracklines
cross the top of the Aleutian Ridge. Hayes and Heirtzler (1968) report that no
traces of the lineations can be found in the Bering Sea north of the Aleutian
Islands.
The location of the Amlia and Adak fracture zones was determined by the
offset of magnetic lineations. The Amlia Fracture Zone offsets most lineations
in a left-lateral sense by 230 km. The offset of anomalies 32A and 32B is only
140 km. The difference in offset is the result of two small anomalies (Fig. 6c,
box) that are developed between anomalies 31 and 32 A east of the Amlia
Fracture Zone.
Anomalies 25 and 26 are not seen on profiles N and M (Fig. 6c); they seem to
disappear where they cross the axis of the Aleutian Trench. Similarly, anomalies
27 and 28 disappear in the trench east of the Amlia Fracture Zone. Anomalies
29 through 32B do not cross the trench. These anomalies have the same
Fig. 11. Magnetic total-intensity anomaly map of areas B and C (Fig. 1). Contour interval
ia 100 gammaa.
202
PETER, ERICKSON, AND GRIM
[CHAP. 4
-J- 45°
165°
Fig. 12. Trackline chart of area C (Fig. 1) (after Grim and Erickson, 1969).
The anomalies terminate abruptly at the axis of the trench; traces of
anomalies 24, 25, and 26, however, appear to cross the trench and extend over
the Aleutian Terrace (Fig. 6a, profiles P, Q, and R). The east-west trend of
the isogamma lines north of the trench between the Amlia and Adak fracture
zones may also represent vestiges of the east-west magnetic lineations.
Generally, the magnetic field is smooth over the trench, but short-wavelength
anomalies are found in shallow water near the islands where the tracklines
cross the top of the Aleutian Ridge. Hayes and Heirtzler (1968) report that no
traces of the lineations can be found in the Bering Sea north of the Aleutian
Islands.
The location of the Amlia and Adak fracture zones was determined by the
offset of magnetic lineations. The Amlia Fracture Zone offsets most lineations
in a left-lateral sense by 230 km. The offset of anomalies 32 A and 32B is only
140 km. The difference in offset is the result of two small anomalies (Fig. 6c,
box) that are developed between anomalies 31 and 32 A east of the Amlia
Fracture Zone.
Anomalies 25 and 26 are not seen on profiles N and M (Fig. 6c); they seem to
disappear where they cross the axis of the Aleutian Trench. Similarly, anomalies
27 and 28 disappear in the trench east of the Amlia Fracture Zone. Anomalies
29 through 32B do not cross the trench. These anomalies have the same
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN 203
amplitude on both sides of the Amlia Fracture Zone; anomalies 25 through 28,
which disappear in the trench, have a uniformly lower amplitude west of the
Amlia Fracture Zone.
The offset of the magnetic anomalies across the Adak Fracture Zone is 30 km
left-lateral. Figure 6b clearly shows the offset of anomalies 25 and 26. Data
from Hayes and Heirtzler (1968) further support this offset, although these
authors offer a different interpretation of the fracture pattern of this area.
The offset at 178°30'E was interpreted from data published by Hayes and
Heirtzler (1968). The offset at 176°30'E was adopted from their interpretation.
5. Magnetic Structure of the Northeast Pacific Ocean
A. General Pattern
The Northeast Pacific constitutes an especially satisfactory area for the study
of the geophysical implications of the magnetic anomalies because of the
excellent survey coverage. An interpretation of the magnetic data available at
the time of the writing of this article is assembled in Fig. 4. Most data are
taken from published maps and profiles, unpublished data are presented through
the courtesy of R. H. Higgs, U.S. Naval Oceanographic Office, and W. C.
Pitman III and D. E. Hayes, Lamont-Doherty Geological Observatory.
The magnetic-anomaly lineations are numbered according to the system of
Pitman et al. (1968). For most of the area shown in Fig. 4, the magnetic lines
were mapped by detailed systematic surveys (18 km grid or closer); where
the pattern of lineations was established from a few isolated tracklines, these
tracks are indicated by black circles. For the schematic representation of the
fracture zones, heavy lines are used. Dashed lines represent the possible exten-
sion of the anomalies and the fracture zones in areas in which control is poor
or not available.
The magnetic lineations of the Northeast Pacific can be separated into the
following three groups or "magnetic structural provinces":
1. The coastal pattern ("crestal anomalies" of Heirtzler and Le Pichon,
1965) is found east of anomaly 7 (or east of anomaly 10 between the Pioneer
and Murray fracture zones) and is cut by numerous northwest-southeast and
northeast-southwest faults.
2. The central pattern, between anomalies 7 and 21 (10 and 21 between the
Pioneer and Murray fracture zones) consists only of north -south trending
lineations. This pattern is cut by east-west faults that apparently are confined
to these lineations.
3. The western pattern extends from anomaly 21 through anomaly 32B. It
strikes northwest-southeast and bends abruptly as it approaches the Aleutian
Trench. This pattern is also cut by fault zones that are nearly perpendicular to
the lineations.
The orthogonal relationship between the faults and the lineations of the
central and western patterns is especially striking in the case of the Surveyor
204 PETER, EKICKSON, AND GRIM [CHAP. 5
and the Mendocino fault zones; these clearly change trend toward the south-
west at the beginning of the general area of the western pattern (Fig. 4).
Differences between the three patterns are further illustrated in Table I.
The distance between a chosen lineation of the coastal group and one of the
Table I
Anomalies
Latitude
Distance (km)
5-10
52°N
775
48°N
675
46°N
525
41°N
880
10-20
56°N
440
52°N
575
48°N
685
45°N
740
41°N
840
35°N
870
30°N
1570
25-32B
45°N
590
41°N
585
35°N
590
central group is highly irregular. The central anomalies gradually widen to the
south; the distances among the western lineations are generally unchanged. In
Table I, anomalies 10 and 20 were chosen for the measurements because they
have been observed in the northern part of the area shown in Fig. 4, as well as
in the area between the Pioneer and Murray fracture zones.
Although there are small internal changes, the overall width of the western
lineations is the same even after they bend westward. At the Amlia Fracture
Zone, however, the distance between anomalies 25 and 32B has decreased to
460 km. Westward of the Amlia Fracture Zone this distance appears to remain
constant.
The large increase in the distance between anomalies 10 and 20 at 32°N is
the result of the disturbed zone south of the Murray Fracture Zone that is
described by Raff and Mason (1961).
Lineations 22 through 24 are somewhat irregular. As in the central group,
the distances separating them increase to the south, but they strike parallel
to the western group. These anomalies, therefore, can be considered to form a
transitional zone between the central and western patterns. Definition of the
exact nature of this transition zone must await further studies.
B. Coastal Pattern
The coastal pattern is the most complex of the three provinces. Part of the
area mapped by Mason and Raff (1961) was resurveyed by Lattimore et al.
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN 205
(1968) with a less dense line spacing. The similarity of the results from the two
surveys proves that the complex, faulted, magnetic pattern, in fact represents
complex tectonic activity in the coastal areas, and is not simply a function of
the more detailed coverage as might be expected.
North of the Mendocino Fracture Zone the fault pattern is actually much
more complex than can be shown in Fig. 4. There are a large number of faults
between Vancouver Island and anomaly 5 along the trends shown here.
Numerous small, east-west faults east of the Juan de Fuca Ridge, and northeast-
southwest and northwest-southeast offsets in the Gorda Ridge area, were
depicted by Pavoni (1966). Most of the faults shown here were also indicated by
Raff and Mason (1961) and others.
The dashed arrow that indicates right-lateral motion along the Mendocino
Fracture Zone at its eastern end (Fig. 4) represents the eastward movement of
the Gorda block (area between the Mendocino and Blanco fracture zones —
westward limit is approximately 135°W) which caused the separation of the
Juan de Fuca and Gorda ridges postulated by Peter and Lattimore (1969).
They assumed that the northeast-southwest trending magnetic lineations of
this area originally were oriented north-south in conformance with the overall
pattern of lineations, and that the Juan de Fuca and Gorda ridges at one time
were part of a continuous ridge.
The offsets of anomalies 3 and 3' east of the Juan de Fuca Ridge argue
against an original transform-fault relationship along the Blanco Fracture Zone
(i.e., original offset of the two ridges) because no comparable ridge crest is
present from which anomaly 3' could have originated by spreading (Pavoni,
1966; Peter and Lattimore, 1969). A relative eastward motion of the Gorda
block is postulated in preference to an overall westward displacement of the
crustal blocks north of the Blanco Fracture Zone. If realignment of the anomaly
bands is made with respect to the anomalies of the Gorda block, a number of
lineations east of the Juan de Fuca Ridge would fall under the Washington-
Oregon coast, with the ridge crest and central anomalies located under Van-
couver Island. Unless the continent was farther eastward at that time, these
anomalies would have had to emerge from under the continent. If they were
under the continent, they probably would have been "erased." This phenom-
enon seems to occur today along the margins of the continents.
The coastal anomaly group is not seen between the Mendocino and Pioneer
fracture zones. Anomaly 9 [and possibly 8 (not shown)] occurs adjacent to the
continental slope.
None of the prominent (numbered) anomalies of the coastal group are present
between the Pioneer and Murray fracture zones. The somewhat distorted
anomaly 10 of the central group sharply abuts the northeast-southwest trend-
ing, short-wavelength lineations that presumably belong to the coastal group.
The absence of anomalies 9, 8, and 7 is a curious phenomenon which seems to
occur nowhere else in the Northeast Pacific.
The northwest-southeast fault at 35°N and 123°W is quite clear on the
magnetic-anomaly map of Mason and Raff (1961); the exact identity of the
206 PETER, ERICKSON, AND GRIM [CHAP. 5
coastal group of lineations is not known (triple line and double line), therefore
their offset cannot be determined.
Magnetic expression of the Murray Fracture Zone toward the east ends
between anomalies 9 and 7. Data are too scarce to present a good case for offset
of the coastal anomalies along the extension of the Murray Fracture Zone.
Small, left-lateral offsets inferred within the coastal pattern (Fig. 4), however,
seem to align with left-lateral faults on the Channel Islands.
Anomalies 9, 8, and 7 are present south of the Murray Fracture Zone.
Unfortunately, available data do not extend to the coastline, so only the edge
of the coastal pattern is shown in Fig. 4.
C. Central Pattern
The "central pattern" has been surveyed in detail only in the area between
the Pioneer and Murray fracture zones. However, since there are numerous
tracklines over this pattern throughout the Northeast Pacific the north-south
trend of the magnetic anomalies and the location of the east-west fracture
zones (with the exception of the two northern ones) are sufficiently established.
Many of the east-west fracture zones are clearly restricted to the central
pattern. Major fracture zones, like the Surveyor, Mendocino, Pioneer, and the
Murray, seem to cross the western pattern as well. According to Menard (1967),
some of these extend across the greater part of the Pacific basin. Even among
these major fracture zones, the Surveyor and the Murray appear to terminate
on the east at the eastern edge of the central pattern. The same may hold for
the Mendocino and Pioneer fracture zones; this cannot be determined because
south of these faults the eastern edge of the central pattern is not reached before
the magnetic pattern and the faults reach the continental slope. The east- west
fault at 37°N (Bassinger et al., 1969) ends east of anomaly 13, where two north-
east-southwest faults seem to offset the magnetic anomalies.
The generally smaller offset of anomaly 7 at the eastern edge of the central
pattern and the offsets of anomaly 6 are shown in Fig. 4 as hypothetical
northwest-southeast faults. The interpretation of the offsets by these northwest-
southeast faults, with the exception of the fault at 49°N and 135°W, is not
necessary if differential movements (crustal compression or extension) are
postulated at the eastern termination of the east-west faults.
From detailed surveys (Vacquier et al., 1961 ; Lattimore et al., 1968) the east-
west fault at 37°N is known to terminate at 127°W against a northeast-south-
west fault that, in turn, apparently cuts the crustal block between the Pioneer
and Murray fracture zones. Some of the magnetic lineations are clearly offset
across the east- west fault; others seem to bend and give the impression of
plastic drag (Fig. 13, from Bassinger et al., 1969). Although the sediment
cover is only 200 m, there is no topographic expression of this fault (L. A.
Weeks, personal communication).
The western end of the east-west fault is not known. The offset of anomaly 21,
designated as the westernmost of the central pattern, is generally the same as
the rest of the lineations. A further puzzle is that no obvious topographic
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN
Fig. 13. Magnetic total- intensity anomaly map with interpretation of the magnetic
offsets. Area is located between the Pioneer and Murray fracture zones (from Bassinger
et al., 1969).
evidence exists where the faults either disappear or run into faults of different
motions at the edges of the central pattern.
D. Western Pattern
The essential characteristics of the western magnetic pattern are described
in the discussion of the magnetic maps for areas A, B, and C of Fig. 1. Thus only-
possible modes of origin of the bend in the magnetic lineations [or, as called by
Elvers et al. (1967), the "Great Magnetic Bight"] are presented here.
Some of the possible explanations for the existence of the bend in the
lineations are the following:
1 . The magnetic lineations, as discrete geological structures within the earth's
rigid crust, were straight at one time. Subsequently the crust was broken up and
bent westward.
2. The magnetic lineations were straight at one time. When they were bent
westward, the crustal material responsible for the lineations behaved like
pliable plastic so that crustal break did not occur.
208
PETER, ERICKSON, AND GRIM
[CHAP. 5
3. The magnetic anomalies were formed [as postulated by the Vine and
Matthews (1963) hypothesis] along two separate, mid-oceanic ridge axes (one
trending northwest-southeast, the other east-west) both of which have been
obliterated since their formation.
4. The magnetic anomalies were formed [as postulated by the Vine and
Matthews ( 1 963) hypothesis] along an approximately northwest-southeast and an
east-west trending, mid-oceanic ridge axis, located along anomaly 32B (Pitman
and Hayes, 1 968). As the younger lineations were formed these ridge crests migra-
ted northward and eastward, leaving behind the successively younger crustal
elements represented by the magnetic lineations north and east of 32B. The two
ridge crests disappeared under the Aleutian Arc and the North American
Continent.
5. The anomaly lineations represent a global stress or fracture pattern in
the crust (possibly intruded by mantle rocks), so that the magnetic pattern
(including the bend) formed "in place" (Mason, 1958; Raff and Mason, 1961;
Peter, 1965 and 1966; Elvers et al., 1967).
6. The magnetic-anomaly lineations are related to geological entities located
in the upper mantle and in the lower part of the oceanic crust. The magnetic
bend may have formed as differentiated mantle kept filling a void created by
crustal fracture. The shape of the crustal fracture and the direction of the
tension that caused the fracture have determined the shape of the bend.
Arguments can be raised against both the plastic (case 2) and the rigid (case 1)
behavior of the magnetic lineations. The relative straightness for thousands of
kilometers, the usual fracture type offsets [although draglike phenomena are
observed in places (Bassinger et al., 1969)], and the small internal fractures
within individual blocks seem to support the idea that the anomalies are
caused by rigid geological bodies. Yet, as Fig. 14 illustrates, the bend could
not have occurred by rotation of two rigid crustal blocks. Part A (Fig. 14)
represents a crustal block with two magnetic lineations. Parts B and C demon-
strate that if the crust is bent as a rigid block, either crustal opening or crustal
compression must occur. In the area of the bend, neither topographic nor
magnetic data support such a possibility.
■4— h
(a) (b) (c) (d)
Fig. 14. Development of crustal opening and compression in case of rotation of rigid blocks.
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN 209
Part D shows that overthrust of blocks must occur if the anomalies "spread"
at right angles away from two segments of a ridge that forms an angle (case 3).
For this case, one may consider the right edge of drawing D as the spreading
source; the overlapping part is shown by dashed lines.
Case 5 is unlikely in view of the well demonstrated axial symmetry and
global occurrence of the magnetic lineations.
The "migrating ridge" hypothesis (case 4) of Pitman and Hayes (1968) is a
possible explanation for the formation of the bend. This, together with the last
explanation above (No. 6) is treated in detail in connection with the discussion
on the origin of the magnetic lineations.
6. Magnetic Structure — Origin of Magnetic Lineations
A. Proposed Hypotheses
A comprehensive summary on the possible geological origin of the magnetic
lineations was given by Bullard and Mason (1963) in Volume 3 of The Sea.
Some of their observations have a direct bearing on the origin of the magnetic
lineation pattern and are shown in Table II.
Table II
1. There is no correlation between bottom topography and magnetic lineations.
2. There is no difference in seismic velocities between areas of positive and negative
lineations.
3. Oceanic crust appears to be rigid; there are large displacements without distortion of
the lineations.
4. Orthogonal relationship between the magnetic lineations and major fracture zones
may indicate common origin.
5. Anomaly sharpness indicates that the upper surface of magnetic body is not deeper
than 1 km below sea floor.
6. Pattern disappears below continents; anomalies erased by combined effect of tempera-
ture and pressure.
7. Fracture zones are younger than the magnetic pattern.
Bullard and Mason (1963) listed three possible explanations for the origin
of the lineations: (a) isolated magnetic bodies (such as lava flows) within the
second layer; (b) elevated folds or fault blocks in the main crustal layer; and
(c) zones of intrusion of mantle material.
The most commonly accepted explanation for the origin of the lineations is
the Vine and Matthews (1963) hypothesis which is a corollary to the sea-floor
spreading concept of Hess (1962, 1965) and Dietz (1961). According to this
hypothesis, at the axis of the mid-oceanic ridges the crust is broken apart by
convection currents and the basaltic material that fills the break acquires a
magnetization in the direction of the existing magnetic field of the earth as it
cools through the Curie point. As the earth's magnetic field periodically reverses
210 PETER, ERICKSON, AND GRIM [CHAP. 5
polarity (Cox et al., 1964), a sequence of normally and reversely magnetized
rocks, symmetrical about the ridge axis, comes into existence and slowly
spreads away from the ridge crest.
As another corollary of the sea-floor spreading hypothesis, Wilson (1965[a],
1965[b]) suggested that offsets of mid-oceanic ridges do not represent actual
displacements, but that the opening in the crust (along which the mid-oceanic
ridges and magnetic lineations subsequently formed) was offset originally. He
postulated that, as the sea floor spreads away from the ridge crests, the motion
along the planes which connect the offset portion of the ridge crests is actually
opposite in direction to that which would be indicated by strike-slip faulting.
He called this motion transform faulting and used it to explain both the earth-
quake activity concentrated along the planes which join the offset ridge
crests, and the relative absence of earthquakes along the extensions of the
faults that lie beyond the ridges that they join.
B. Sea- floor Spreading
Some of the data in direct support of the original sea-floor spreading and
transform -fault concepts are listed in Table III; data opposed to these hypoth-
eses are summarized in Table IV. Comparison of these two tables indicates
Table III
1. Magnetic lineations are generally parallel to mid-oceanic ridges.
2. Magnetic lineations are symmetrical about the axis of mid-ocean ridges.
3. The same spectrum of lineations and axial symmetry is present in association with all
tectonically active mid-oceanic ridges.
4. The sequence of positive and negative lineations which extend from the ridge-axis to a
distance approximately 160 km, agrees with the sequence of normal and reverse
polarities of the earth's magnetic field in the past fovir million years. (Measured on
dated volcanic rocks on land and on deep-sea sediment cores.)
5. Earthquake mechanism studies corroborate the motion required by transform faulting.
6. The age of sediments (based on available samples) indicates general increase from the
ridge crest to the flanks.
that an important part of the facts that argue against sea-floor spreading are
based on sediment structure and distribution, and on sea-floor topography. If
the main source of the magnetic lineations lies within a 1- or 2 -km thick basaltic
layer which overlies the main " serpentinite " crustal layer (Vine and Wilson,
1965; Vine, 1966), offsets of the magnetic pattern, of either the transcurrent or
transform kind, should be reflected in the sediment structure. In the Northeast
Pacific, where the sediment overlying the second layer is relatively thin
[145-680 m thick according to Hamilton (1967)] these offsets should be indicated
on the sea floor.
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN 211
Table IV
1. Over 1 km of undisturbed, horizontally bedded sediments were found in the trough of
the Vema Fracture Zone which is considered to be an active transform fault.
2. Numerous magnetic offsets, some "dated" by the magnetic time scale as less than two
million years old, show no disturbance of either sea-floor topography or sub-buttom
sediments.
3. Most trenches studied are either unfilled or filled with undisturbed sediments.
4. The topography and petrology of the upper flanks of the ridges are of a different origin
from those of the ridge-crest.
5. Magnetic lineations cross morphologic province boundaries without ajjparent change
in character.
6. Magnetic anomalies over the ridge-crests differ in amplitude and wavelength from those
over the flanks.
7. The magnetic structure of the Northeast Pacific indicates three phases of tectonic
activity.
8. Most faults of the Northeast Pacific do not meet the definition of transform faults.
If the offsets either preceded the sediment deposition or started very recently
the above arguments are not necessarily valid . However, according to Vine ( 1 966 ) ,
motion along the offsets (such as transform faults) has been uniform since the
Cretaceous. Based on this assumption, a geomagnetic time scale has been
proposed in which anomaly 32B is "dated" as 72 million years old (Vine, 1966,
Heirtzler et al., 1968).
East of the Juan de Fuca Ridge a northeast-southwest strike-slip fault
offsets a group of magnetic-anomaly lineations by 100 km (Fig. 4). According
to the geomagnetic time scale, the youngest lineation offset (anomaly 3) is two
million years old, therefore a 5 cm/yr motion is required along the fault during
Late Pliocene and Pleistocene (Peter and Lattimore, 1968). Seismic-reflection
studies of this area indicated no sediment disturbance in the area of this fault
(Hamilton and Menard, 1968).
On the basis of these arguments it appears that the "marine" geomagnetic
time scale is questionable, and/or the magnetic lineations are likely to originate
below the second layer so that their offset is not necessarily reflected in the
upper part of the crustal column.
Near the axis of mid-oceanic ridges the geomagnetic time scale is supported
by a number of observations (Table III), therefore its validity may be accepted
within the "coastal pattern." A pause in sea-floor spreading, and consequently
a rejection of the time scale outside the area of the ridge crests ("coastal
pattern' j, was suggested by E\, ing and Ewing (1967) on the basis of the abrupt
increase m sediment thickness at the edge of the ridge crests. The three different
patterns in the magnetic structure (Fig. 4) strongly support the idea of three
separate episodes of tectonic activity, and since the length of the pauses cannot
be determined, the extrapolation of the geomagnetic time scale outside the
crestal area of mid-oceanic ridges is not justified.
212 PETER, ERICKSON, AND GRIM [CHAP. 5
The suggestion that the magnetic anomalies originate below the second layer
is contrary to the conclusion reached by Bullard and Mason (1963) who state
that the upper surface of the magnetic bodies should be no deeper than 1 km
below the sea floor. Additionally, deep-towed magnetometer data indicate
large-amplitude, short-wavelength anomalies near the sea floor (Mudie and
Harrison. 1067; Spiess et al.. 1968; and Spiess and Mudie, Part I, Chapter 7).
In order to satisfy all observations it is suggested that small intrusives (dikes)
in the second layer could be responsible for the short-wavelength, large
amplitude anomalies, and that the major bodies (as possible sources of these
intrusives) may lie deeper.
The existence of a magnetically quiet zone at continental margins and
trenches may be interpreted as support of this suggestion. Model computations,
like those reported by Hayes and Heirtzler (1968), indicate that if the magnet-
ized bodies are part of the second layer, the down-bow of the crust indicated
by seismic data at the Aleutian Islands is not sufficient to account for the
abrupt elimination of the anomalies over the Aleutian Trench. If, however, the
magnetic bodies lie in the lower part of the crust or in the upper mantle as
suggested here, the 3-6-km crustal down- warp may be sufficient to either carry
the temperature of the magnetic bodies above the Curie point or cause sufficient
metamorphism that their magnetization is erased (Bullard and Mason, 1963;
Table II).
The crossing of the magnetic lineations over major morphologic provinces
without a change in character, the apparent "drag" effect on certain lineations
(mapped across fault A in Fig. 13), the relatively young offset of the
magnetic lineations east of the Juan de Fuca Ridge without deformation of
sediments, the irregular junction of the "central pattern" with the neighboring
magnetic patterns (Fig. 4), and the abrupt termination of large east- west faults
without sub-bottom or bottom topographic expression all support the prob-
ability of a deeper source of the magnetic lineations whereby the magnetic
offsets do not necessarily indicate the offset of the entire crustal column. This
interpretation suggests that in certain cases small offsets of the deeper magnetic
layer can be compensated for within the overlying crustal layers in such a
manner that noticeable offsets do not necessarily occur near the top of the
second layer. The combination of offsets and drags of the lineations across
fault A in Fig. 13 may be the result of the interaction between the deeper crustal
layers that represent the proposed compensation.
Seismic refraction measurements in the Northeast Pacific (Shor, 1962;
Shor et al., 1968) indicate normal oceanic crust in the areas of the "central"
and "western" magnetic patterns; over the Gorda and Juan de Fuca ridges
(i.e., over the "coastal pattern") the crustal velocity is slightly higher, the
mantle velocity is below normal, and the ridges appear to represent the surface
expression of the upraised crust and mantle. Shor et al. (1968) concluded that
the structure of the Juan de Fuca and Gorda ridges is the same as that of the
East Pacific Rise. Gravity anomalies over oceanic ridges [summarized by
Worzel (1965)] further reflect unique crustal structure. As Heirtzler and Le
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN 213
Pichon (1965) noted, short-wavelength magnetic anomalies seem to be associ-
ated with the anomalous-mantle zone in the area of the ridge crests. It can be
concluded, therefore, that the "coastal pattern" in the Northeast Pacific is
associated with the anomalous crustal structure, and that it alone represents
segments of the present East Pacific Rise.
Although uplifted by the present East Pacific Rise, the normal oceanic crust
to the west does not appear to be a part of it structurally (Fig. 4). Both
reference to the areas of the central and western magnetic patterns as "ridge
flank," and the extension of the East Pacific Rise to the edge of all lineations
(anomaly 32B) as proposed by many investigators, are unwarranted. It is
suggested that the change of the magnetic lineations from broad, even-
amplitude anomalies to short-wavelength anomalies at the edge of the "coastal
pattern," is related to a change in crustal structure, rather than to more
frequent reversals of the earth's field alone as Vine (1966) proposed.
A modification of the sea-floor spreading hypothesis, namely, the possibility
that the ridge crest itself migrates, was raised by Pitman and Hayes
(1968). These authors proposed that a Y-shaped junction of ridge crests
initially existed southwest of the present bend in the anomaly lineations.
Convection currents that upwelled along this junction carried the ridge crests
along with them (northward and eastward) until the convection pattern was
"stifled" by the Aleutian Trench. If the corollary assumptions of this hy-
pothesis are valid, a simplified magnetic pattern (Pitman and Hayes, 1968;
Fig. 4) may be explained. Modifications are necessary, however, to incorporate
the detail shown in Fig. 4.
Morgan (1968) suggested that the earth's surface is broken up into large
rigid blocks bounded by rises, trenches, or faults, and that these blocks rotate
about each other with respect to several "poles." The mid-oceanic rises are not
associated with deep-seated convection currents, but instead represent new
crust created where two blocks separate. Dikes a few kilometers in width and,
perhaps 100 km deep are formed in this way and magnetized according to the
existing polarity of the earth's field. With continued tension, the dikes are
split down the middle, new material is injected, and a symmetrical pattern
of magnetic anomalies is created. Although Morgan's (1968) hypothesis may not
account for all the detail of the magnetic structure derived here for the North-
east Pacific, his suggestion that the ridge crests are independent of the
location of the convection cell is a significant departure from the original
sea-floor spreading hypothesis.
C. Transform faults
Beyond question, many of the faults in the "coastal pattern" are not trans-
form faults; many make a small angle with the ridge crests and some are
bounded by other faults. Especially in the area of the Juan de Fuca Ridge,
fault patterns are clearly incompatible with the concept of transform-faulting
(see Morgan, 1968, Fig. 2). By definition, a transform fault must cross all
magnetic lineations; none of the faults in the "coastal pattern" and only a few
214 PETER, ERICKSON, AND GRIM [CHAP. 5
in the "central pattern" meet this criterion. The Murray and Surveyor fracture
zones clearly stop near the eastern edge of the "central pattern"; the other
east-west faults of the "central pattern" do not extend into the westernmost
lineations. The Pioneer and Mendocino fracture zones appear to cross the
"western" and "central" patterns but terminate near the continental margin
before the "coastal pattern" develops. The proposition that the Mendocino and
Murray fracture zones may be transform faults (Wilson, 1965[a]; Vine, 1966)
is also open to question on the basis of their linear extent across the entire
Pacific basin (Menard, 11)67).
If transform faults (cutting all three magnetic patterns) did exist in the
area of Fig. 4, the "coastal pattern" could have evolved into the "central
pattern" and this, in turn, into the "western pattern" through lateral spread-
ing. The bend in the "western pattern," the development of extra lineations
in part of the east-west segment of the "western pattern," and the fact that the
"central pattern" does not bend, together with the arguments derived earlier,
require modification of the sea-floor spreading hypothesis and its twro corollaries
—the Vine and Matthews (1963) and the transform-fault hypotheses (Wilson,
1965[a], 1965[b]) — in their application to the East Pacific area. Present-day,
transform -fan It motions (Sykes, 1967) do not necessarily prove that the ridge
crests were originally offset. Once the offset has taken place (e.g., by transcurrent
faulting) active growth of the individual ridges would produce relative motion
along the fault plane connecting the ridge crests that is in accord with
transform-fault motion.
D. Interpretation
In previous portions of this paper, it is suggested that the main source of
the magnetic lineations may lie below the second layer. It has been demon-
strated that — because of the absence of the required overlap of lineations — the
bend in the magnetic anomaly bands could not have originated by crustal
spreading from two stationary ridge crests. The characteristic internal fault
system of the three magnetic patterns could not be derived from one another
through simple lateral spreading, and it has been suggested that the three
patterns probably are associated with three episodes of tectonic activity. The
interpretation of the genesis of the lineations and their offset pattern must
combine these deductions with the world-wide occurrence of the magnetic
lineations in association with mid-oceanic ridges, and their general symmetry
with respect to the ridge crests.
These latter observations suggest that there is a definite relationship between
the magnetic lineations and the ridges. Two reasonable explanations may be
offered for the axial symmetry of the magnetic anomaly bands: (a) an "active"
system of intrusives at the ridge crest that forces the crust aside [Vine and
Wilson (1965) suggest that this takes place in the second layer]; and (b) a
"passive" system of intrusives that are simply filling a void created by the
opening of the crust. In the first explanation the ridge crest is directly tied to
the up welling and dynamic motion of the convection currents. The second
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN
215
explanation is based on crustal tension alone, that is, there is no restriction on
the mechanism that may cause the crustal tension. Among possible mechanisms
are polar shift, earth-expansion, and the suggestion of Morgan (1968) that
tension is produced by rotation of large crustal blocks.
Since the existence of the bend in the "western pattern" demands that the
lineations cannot be pushed aside by subsequently formed younger lineations
(Fig. 14d), the ridge crest is considered here not as a dynamic, moving part of
the oceanic crust but as a passive part formed as the result of crustal tension.
The mid-oceanic ridges are seen as "scars" in the earth's crust. The anomalous
mantle and crustal structure below the ridge crest is believed to be caused by
differentiation and volcanic processes occurring in response to the fracturing
of the crust. It is only in the sense of "cause and effect" that the proposed
"passive ridge-crest" hypothesis is different from the process of crustal
generation described by Hess (1965).
If the earth's crust as a whole is under tension (earth-expansion), fracturing
of the crust, differentiation processes in the upper mantle, and the filling of the
void created by fracturing with differentiated mantle rocks and volcanics
could account for both the existence of mid-oceanic ridges and the axial
symmetry of the magnetic lineations. Figure 15b illustrates the formation of
the magnetic bend according to this hypothesis: as the crust on the two sides
of the fracture is pulled apart, differentiated mantle material fills the gap and
becomes "welded" to the crust. Continued tension breaks this "dike" in the
center where it is hottest and may be only partially solidified at depth (Morgan,
1968). With further tension, under the influence of a periodically reversing
magnetic field (Vine and Matthews, 1963), magnetic lineations could be formed
symmetrically about the center of the crustal break.1
/
v////////////////////////////,
fa)
(b)
(c)
Fig. 15. Development of Y-shaped ridge junction, magnetic bend, and ridge offset through
crustal tension.
1 Symmetrical lineations can be produced not only by normally and reversely magnetized
blocks, but also by nonmagnetic blocks intermixed with magnetized blocks in the formation
cycle. This may be an especially attractive assumption for the older lineations.
216 PETER, ERICKSON, AND GRIM [CHAP. 5
If, in Fig. 15b, one side of the fracture is stationary and only the other side
is being pulled away, the appearance is that of a "migrating ridge" such as
described by Pitman and Hayes (1068) and Morgan (1968). Crustal tension in
three directions (or in two directions away from a stationary block) is shown in
Fig. 15a; this case is applicable to the Y-shaped ridge junction reported near
the Galapagos Islands by Herron and Heirtzler (1067) and Raff (1068).
It should be noted that with a "passive" ridge crest the problem of lateral
compression seen in connection with spreading (Fig. 14d) does not exist since
the lineations are not spreading away from a ridge crest; they are "welded" to
the lower crust and upper mantle, which are under tension and pulling apart.
Thus the lineations, together with the receding crust, are moving away from
the center of the ridge and give the impression of a spreading ridge. Both
"active" and "passive" ridge crest hypotheses imply that the lineations are
progressively older away from the center of the ridge crest.
Figure 15c illustrates how crustal tension can cause the "transform-fault"
motion between the offset portions of ridge crests that Sykes (1067) noted.
Application of the observations in the preceding paragraphs to the specific
case of the Northeast Pacific suggests that the "western pattern" is related to
an early phase of tectonic activity, that is, to a predecessor of the East Pacific
Rise. During this period, the inferred crustal opening probably followed the
tectonic grain of the North American Cordillera with its westward bend in
Alaska (Fig. 15b). Development of the "western pattern" was followed by a
pause in the tectonic activity; during this time the opening healed over com-
pletely. Renewed crustal tension, probably with a predominant east-west
component, may have been manifested in a crustal break along a "zig-zag"
pattern (Fig. 15c). The intrusives represented by the anomalies of the "central
pattern" would have formed in north-south openings in the crust. These
openings may have been connected by east-west planes of dislocation that could
be described as transform faults. During the second period of quiescence, these
fractures healed over so that with renewal of east-west tensional forces the crust
yielded along a slightly different pattern. The present East Pacific Rise is
related to this last phase of tectonic activity. The pattern, which probably
originally conformed to the north-south orientation of the "central pattern,"
apparently was broken up by northeast-southwest and northwest-southeast
fractures subsequent to its formation. If the inferences of McManus (1065) and
Peter and Lattimore (1060) are assumed, this breaking-up occurs as the result
of the Late Tertiary to Recent coastal orogeny.
The deep source of the magnetic lineations postulated in this paper permits
some faulting of the magnetic lineations without the disruption of bottom
topography or the sedimentary section. Thus the occurrence of undisturbed
sediments east of the Juan de Fuca Ridge that Hamilton and Menard (1068)
reported does not present a contradiction to the proposed interpretation. The
passive ridge hypothesis, coupled with earth-expansion, is especially attractive
when one considers the undisturbed sediments and the lack of obvious com-
pressional phenomena on the ocean floor at the continental margins.
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN 217
7. Magnetic Structure — Origin of Aleutian Trench
A. Proposed Hypotheses
In this section the previously derived interpretation is applied to the problems
of the origin of the Aleutian Trench as seen from the point of view of the two
major hypotheses: the tensional- and compressional-origin hypotheses.
The hypotheses are not reviewed in detail. A comprehensive treatise on the
tensional hypothesis was given by Worzel (1965); a summary of data on
trenches with emphasis on their compressional, convection-current origin was
given by Fisher and Hess (1963).
According to the tensional hypothesis, the trenches are considered to be
down-faulted parts of the oceanic crust. The negative, isostatic anomalies that
characterize the trench areas are explained in terms of mutual interaction of
the island arc, trench, and outer-ridge systems. Shor (1965) suggested that the
Aleutian Trench formed as a direct result of the loading of the island arc on the
oceanic crust; the isostatic imbalance of the trench is attributed to the elastic
behavior of the oceanic crust.
The argument for the compressional origin is also based on the negative
isostatic anomalies associated with the trenches. According to this theory,
static-mass imbalances in the area of the trench should be compensated for
in a relatively short time; since the negative isostatic anomalies indicate that
this has not occurred it is presumed that a dynamic force, such as compression
caused by convection currents or drag induced by them, is preventing the
trench from adjusting to isostatic equilibrium.
B. Interpretation
The mechanical conditions that might be expected to exist if the oceanic
crust is moving under a curved trench driven by convection currents have been
illustrated by Fisher and Hess (1963; Fig. 16). Geological structural trends
similar to f-f, illustrated in Fig. 16, should conform to the arcuate shape of
the trench on both sides. The east-west trends of the magnetic-anomaly
lineations in the vicinity of the Aleutian Trench are in sharp conflict with these
logical expectations. The apparent north-south (as opposed to radial) trend of
the fracture zones associated with the Aleutian Trench further implies structural
independence.
Data collected in the area of the Aleutian Trench indicate that (a) traces of
some magnetic lineations extend over the Aleutian Terrace; (b) those lineations
that intersect the trench east of the Amlia Fracture Zone have reduced
amplitudes west of the fracture zone; and (c) the fracture zones have no
obvious topographic expression in the trench floor, but they may be related
to changes in trend on the Aleutian Ridge.
If it is assumed that the sea floor is rigid and that it has been carried
deep below the trench and island arc by a descending convection current,
vestiges of the lineations and general, weak east-west trends of the anomalies
218
PETER, ERICKSON, AND GRIM
[CHAP. 5
Fig. 16. Postulated mechanical situation in which the crust moves into a curved trench
(from Fisher and Hess, 1963).
should not exist over the Aleutian Terrace; instead, the anomaly trends
either should follow the curvature of the island arc or should not be seen
at all.
The fact that anomalies 25 through 28 (the only ones that intersect the trench
east of the Amlia Fracture Zone) are much reduced in amplitude west of the
fracture strongly suggests that the reduction in amplitude is related to the
trench formation. If the island arc and trench were superimposed on an exist-
ing, unfaulted magnetic pattern, then such loading might depress the lower
part of the crust below the Curie point isotherm, or to such a temperature that
metamorphism would cause alteration of mineralogy. In this manner part of
the magnetization could have been erased. Before complete suppression of the
anomalies took place, transcurrent faulting could have carried the crust away
from the influence of the island arc, thus preserving the lineations in their
diminished form. If, on the other hand, the Amlia Fracture Zone is assumed to
be a transform fault and the only movement of the sea floor was northward,
there is no explanation for the uniformly reduced amplitude of that particular
group of anomalies.
Northward movement of the sea floor would also require that the sea-floor
topography of the outer ridge be carried into the trench; the drift of guyots
into the Aleutian Trench has been proposed by Menard and Dietz (1951), and
the drift of guyots from the Darwin Rise to the Gulf of Alaska by Hess (1965).
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN 219
Yet, the high relief of the outer ridge does not continue onto the south wall of
the Aleutian Trench.
If the structures that cause the magnetic anomaly lineations lie mainly in
the lower part of the crust and upper mantle, the relatively "quiet" magnetic
zone of the trenches and continental margins is to be expected because crustal
down-bow may be sufficient to carry the lower crust-upper mantle into such
temperatures that its magnetization is erased.
Vine (1966) and others suggested that the fracture pattern off the Washington-
Oregon coast is the result of the westward drift of the North American con-
tinent and the change in the direction of sea-floor spreading during the Pliocene.
It was further assumed that as a result of this new direction of spreading the
crust of the entire North Pacific ocean has been moving northwestward, and
causing the formation of the Aleutian Trench. Recent studies of earthquake
first motions by Isacks et al. (1968) support this interpretation, and together
with the distribution of sediments in the North Pacific (Ewing et al., 1968),
imply that the Aleutian Trench may be as young as Late Tertiary.
If the Aleutian Trench is Tertiary or younger, and the western half of the
Aleutian Arc is dominated by strike-slip faulting (Isacks et al., 1968), then the
existence of a well-developed trench along the western half of the arc may be
questioned because no appreciable underthrusting could have taken place in
the last ten million years.
Pitman and Hayes (1968) have proposed that the Aleutian Trench was
formed by the underthrusting of a northward moving sea floor which ended
in the Paleocene; Ewing and Ewing (1967) suggested that there was a 10-million-
year pause before the renewal of sea-floor spreading in the Pliocene. These
suggestions raise the question of whether or not the elapsed time before the
latest phase of spreading would have been sufficient for isostatic rebound of
the trench, if the cause of trench formation is underthrusting.
Whether there has been an "early" trench or not, however, the north-
westward motion of the sea-floor in the last 10 million years should have
created measurable differences in the development of the two halves of the
Aleutian Trench.
These considerations, together with the magnetic structure of the Aleutian
Arc and the Northeast Pacific, complement our earlier conclusions and suggest
that the Aleutian Trench has been formed as the result of crustal downfault or
down-bow rather than underthrust of the ocean floor.
Acknowledgments
The U.S. Coast and Geodetic Survey ships Pioneer and Surveyor collected
the systematic SEAMAP data. For additional data and manuscripts not
published at the time of writing this paper, we are indebted to R. H. Higgs,
U.S. Naval Oceanographic Office, and W. C. Pitman, III, D. E. Hayes, and
J. I. Ewing, Lamont-Doherty Geological Observatory. Several colleagues, es-
pecially O. E. DeWald and the late A. B. McCollum deserve credit for their help
in working on SEAMAP data.
220 PETER, ERICKSON, AND GRIM [CHAP. 5
We are grateful to R. K. Lattimore and H. B. Stewart, Jr. for many helpful
discussions and critical review of the manuscript.
References
Bassinger, B. G., O. E. DeWald, and G. Peter, 1969. Interpretation of the magnetic
anomalies off central California. J . Geophys. Res., 74, 1484-1487.
Bullard, E. C, and R. G. Mason, 1963. "The magnetic field over the oceans," in The Sea,
Vol. 3, M. N. Hill, Ed., Wiley Interscience, New York, pp. 175-217.
Cox, A., R. R. Doell, and G. B. Dalrymple, 1964. Reversals of the Earth's magnetic field.
Science, 144, 1537-1543.
Dickson, G. O., and J. Foster, 1966. The magnetic stratigraphy of a deep sea core from the
North Pacific Ocean. Earth Planet. Sci. Letters, 1, 458-462.
Dickson, G. O., W. C. Pitman, III, and J. R. Heirtzler, 1968. Magnetic anomalies in the
South Atlantic and ocean floor spreading. J. Geophys. Res., 73, 2087-2100.
Dietz, R. S., 1961. Continent and ocean basin evolution by spreading of the sea floor.
Nature, 190, 854-857.
Drake, C. L., J. R. Heirtzler, and J. Hirshman, 1963. Magnetic anomalies off eastern
North America. J. Geophys. Res., 68, 5259-5275.
Elvers, D. J., C. C. Mathewson, R. E. Kohler, and R. L. Moses, 1967. "Systematic ocean
surveys by the USC & GSS Pioneer 1961-1963," ESSA, Operational Data Report,
C & GS DR-1, 19 pp.
Ewing, J., and M. Ewing, 1967. Sediment distribution on the mid-ocean ridges with respect
to spreading of the sea floor. Science, 156, 1590-1592.
Ewing, J., M. Ewing, T. Aitken, and W. Ludwig, 1968. "North Pacific sediment layers
measured by seismic profiling," in The Crust and Upper Mantle of the Pacific Area,
Geophys. Monograph, 12, American Geophysical Union, Washington, D.C., pp. 147-
173.
Fisher, R. L., and H. H. Hess, 1963. "Trenches," in The Sea, Vol. 3, M. N. Hill, Ed.,
WTiley Interscience, New York, pp. 411-436.
Grim, P. J., and B. H. Erickson, 1969. Fracture zones and magnetic anomalies south of
the Aleutian Trench. J. Geophys. Res., 74, 1488-1494.
Hamilton, E. L., 1967. Marine geology of the abyssal plains in the Gulf of Alaska. J.
Geophys. Res., 72, 4189-4213.
Hamilton, E. L., and H. W. Menard, 1968. Undistorted turbidites on the Juan de Fuca
Ridge (abstract) Trans. Amer. Geophys. Un., 49, 208.
Hayes, D. E., and J. R. Heirtzler, 1968. Magnetic anomalies and their relation to the
Aleutian Island arc. J. Geophys. Res., 73, 4637-4646.
Heirtzler, J. R., G. Peter, M. Talwani, and E. Zurflueh, 1962. "Magnetic anomalies caused
by two dimensional structure; their computation by digital computers, and their
interpretation," Tech. Rept. 5, Cv-6-62. Nonr-Geology, Columbia University, New
York.
Heirtzler, J. R., and X. Le Pichon, 1965. Crustal structure of the mid-ocean ridges, 3.
Magnetic anomalies over the mid-Atlantic Ridge. J. Geophys. Res., 70, 4013-4033.
Heirtzler, J. R., X. Le Pichon, and J. G. Baron, 1966. Magnetic anomalies over the
Reykjanes Ridge. Deep-Sea Res., 13, 427-443.
Heirtzler, J. R., G. O. Dickson, E. M. Herron, W. C. Pitman, III, and X. Le Pichon,
1968. Marine magnetic anomalies, geomagnetic field reversals, and motions of the
ocean floor and continents. J. Geophys. Res., 73, 2119-2136.
Herron, E. M., and J. R. Heirtzler, 1967. Sea-floor spreading near Galapagos. Science,
158, 775-779.
Hess, H. H., 1962. "History of ocean basins," in Petrologic studies: A Volume in Honor of
A. F. Buddington, Geol. Soc. Amer., New York, pp. 599-620.
THE ALEUTIAN TRENCH AND NORTHEAST PACIFIC BASIN 221
Hess H. H., 1965. Mid-oceanic ridges and tectonics of the sea-floor. Colston Papers, 17,
317-332.
Hurley, R. J., 1960. The geomorphology of the abyssal plains in the Northeast Pacific
Ocean (unpublished manuscript), Scripps Inst. Oceanography, San Diego, 105 pp.
Isacks, B., J. Oliver, and L. R. Sykes, 1968. Seismology and the new global tectonics.
J. Geophys. Res., 73, 5855-5899.
Lattimore, R. K., B. G. Bassinger, and O. E. DeWald, 1968. Magnetic map from the coast
of California to 133°W longitude. Misc. Geol. Inv. Map. I-531A, U.S. Geol. Surv.,
Washington, D.C.
Le Pichon, X., and J. R. Heirtzler, 1968. Magnetic anomalies in the Indian Ocean and
sea-floor spreading. J. Geophys. Res., 73, 2101-2117.
Loncarevic, B. D., C. S. Mason, and D. H. Matthews, 1966. Mid-Atlantic ridge near 45°
North, I, The Median Valley. Can. J. Earth Sci., 3, 327-349.
Ludwig, W. J., J. I. Ewing, M. Ewing, S. Murauchi, N. Den, S. Asano, H. Hotta, M.
Hayakawa, T. Asanuma, K. Ichikawa, and I. Noguchi, 1966. Sediments and structure
of the Japan trench. J. Geophys. Res., 71, 2121-2137.
Malahoff, A., 1968. Detailed geophysical studies of the Murray Fracture Zone (abstract).
Trans. Amer. Geophys. Un. 49, 213.
Mason, R. G., 1958. A magnetic survey off the west coast of the United States between
latitudes 32° and 36°N, longitudes 121° and 128°W. Geophys. J., 1, 320-329.
Mason, R. G., and A. D. Raff, 1961. A magnetic survey off the west coast of North America,
32°N to 42°N. Bull. Geol. Soc. Amer., 72, 1259-1265.
McManus, D. A., 1965. Blanco fracture zone, Northeast Pacific Ocean. Marine Geol., 3,
429-455.
Menard, H. W., 1964. Marine Geology of the Pacific, McGraw-Hill, New York, 271 pp.
Menard, H. W., 1967. Extension of northeastern Pacific fracture zones. Science, 155,
72-74.
Menard, H. W., and R. S. Dietz, 1951. Submarine geology of the Gulf of Alaska. Bull. Geol.
Soc. Amer., 62, 1263-1285.
Morgan, W. J., 1968. Rises, trenches, great faults, and crustal blocks. J . Geophys. Res., 73,
1959-1982.
Mudie, J. D., and C. G. Harrison, 1967. Deep-tow profiles across Mason-Raff lineations
(abstract). Trans. Amer. Geophys. Un., 48, 133.
Nichols, H., and R. B. Perry, 1966. Bathymetry of the Aleutian Arc, Alaska. Six maps by
U.S. Coast and Geodetic Survey, ESS A.
Ninkovich, D., N. Opdyke, B. C. Heezen, and J. H. Foster, 1966. Paleomagnetic stratig-
raphy, rates of deposition and tephrachronology in North Pacific deep-sea sediments.
Earth Planet. Sci. Letters, 1, 476-492.
Opdyke, N. D., B. Glass, J. D. Hays, and J. Foster, 1966. Paleomagnetic study of
Antarctic deep-sea cores. Science, 154, 349-357.
Pavoni, N., 1966. Tectonic interpretation of the magnetic anomalies southwest of
Vancouver Island. Pure Appl. Geophys., 63, 172-209.
Peter, G., 1965. "Preliminary results of a systematic geophysical survey south of the
Alaska Peninsula," in Continental Margins and Island Arcs, Geol. Surv. Canada
Papers, 66-15, pp. 223-237.
Peter, G., 1966. Magnetic anomalies and fracture pattern in the Northeast Pacific Ocean.
J. Geophys. Res., 71, 5365-5374.
Peter, G., and H. B. Stewart, Jr., 1965. Ocean Surveys: the systematic approach. Nature,
206, 1017-1018.
Peter, G., D. Elvers, and M. Yellin, 1965. Geological structure of the Aleutian Trench
southwest of Kodiak Island. J. Geophys. Res., 70, 353-366.
Peter, G., and R. Lattimore, 1969. Magnetic structure of the Juan de Fuca-Gorda ridge
area. J. Geophys. Res., 74, 586-593.
222 PETER, ERICKSON, AND GRIM [CHAP. 5
Pitman, W. C, III, and D. E. Hayes, 1968. Sea-floor spreading in the Gulf of Alaska
(abstract). Trans. Amer. Geophys. Un., 49, 208.
Pitman, W. G, III, E. M. Herron, and J. R. Heirtzler, 1968. Magnetic anomalies in the
Pacific and sea-floor spreading. J. Geophys. Res., 73, 2069-2085.
Raff, A. D., 1968. Sea-floor spreading, another rift. J. Geophys. Res., 73, 3699-3705.
Raff, A. D., and R. G. Mason, 1961. Magnetic survey off the west coast of North America,
40°N to 52£°N. Bull. Geol. Soc. Amer., 72, 1259-1265.
Scholl, D. W., and R. von Huene, 1968. Spreading of the ocean floor: Undeformed sedi-
ments in the Peru-Chile Trench. Science, 159, 869-871.
Shor, G. G., 1962. Seismic refraction studies off the coast of Alaska. Bull. Seism. Soc. Amer.,
52, 37-55.
Shor, G. G., 1965. Structure of the Aleutian Ridge, Aleutian Trench, and Bering Sea
(abstract). Trans. Amer. Geophys. Un., 46, 196.
Shor, G. G., P. Dehlinger, H. K. Kirk, and W. S. French, 1968. Seismic refraction studies
off Oregon and northern California. J. Geophys. Res., 73, 2175-2194.
Spiess, F. N., B. P. Luyendyk, and J. D. Mudie, 1968. Geological observations of abyssal
hills using a deeply towed instrument package (abstract). Trans. Amer. Geophys.
Un., 49, 213-214.
Sykes, L. R., 1967. Mechanism of earthquakes and nature of faulting on the mid-oceanic
ridges. J. Geophys. Res., 72, 2131-2153.
Talwani, M., C. Windisch, and M. Langseth, 1968. Recent geophysical studies on the
Reykjanes Ridge (abstract). Trans. Amer. Geophys. Un., 49, 201.
Vacquier, V., A. D. Raff, and R. E. Warren, 1961. Horizontal displacement in the floor
of the Pacific Ocean. Bull. Geol. Soc. Amer., 72, 1267-1270.
van Andel, Tj. H., J. B. Corliss, and V. T. Bowen, 1967. The intersection between the Mid-
Atlantic Ridge and the Vema fracture zone in the North Atlantic. J. Marine Res.,
25, 343-351.
van Andel, Tj. H., and C. O. Bowin, 1968. Mid-Atlantic ridge between 22° and 23° North
latitude and the tectonics of mid-ocean rises. J. Geophys. Res., 73, 1279-1298.
Vine, F. J., 1966. Spreading of the ocean floor: New evidence. Science, 154, 1405-1415.
Vine, F. J., and D. H. Matthews, 1963. Magnetic anomalies over oceanic ridges. Nature,
199, 947-949.
Vine, F. J., and J. T. Wilson, 1965. Magnetic anomalies over a young oceanic ridge off
Vancouver Island. Science, 150, 485-489.
Wilson, J. T., 1965[a]. A new class of faults and their bearing on continental drift. Nature,
207, 343-345.
Wilson, J. T., 1965[b]. Transform faults, oceanic ridges, and magnetic anomalies southwest
of Vancouver Island. Science, 150, 482-485.
Worzel, J. L., 1965. Deep structure of coastal margins and mid-oceanic ridges. Colston
Papers, 17, 335-359.
61
Reprinted from Deep-Sea Research 18_, 321-327.
Bathymetry off central northwest Africa*
Peter A. RoNAf
{Received 13 July, 1970; revised and accepted 3 September 1970)
Abstract — A preliminary bathymetric chart of an area about 106 km2 extending from Cap Blanc,
Mauritania, to the abyssal hills near 30°W, was constructed from about 8000 km of sounding tracks
recorded by the USNS Gibbs in 1968 plus other earlier soundings. Major unnamed U-shaped sub-
marine canyons attain widths of 85 km and a relief of 700 m where they cross the continental slope
and upper continental rise between 20° and 25°N; narrow V-shaped canyons attain widths of 10 km
and a relief of 300 m between 18° and 20°N.
Comparison of bottom morphology with patterns of atmospheric and oceanic circulation suggests
that wind transport of sediment derived from North Africa is a major process in shaping the Cape
Verde Plateau.
INTRODUCTION
About 8000 km of sounding tracks recorded by the USNS /. W. Gibbs in 1968 were
combined with earlier soundings to construct a preliminary bathymetric chart which
delineates the northern edge of the Cape Verde Plateau, major submarine canyons,
and specific topographic features between the continental shelf and the abyssal hills
near 30°W (Fig. 1). Previous bathymetric charts, based on a low density of sounding
tracks, outline an unusually wide continental rise off central northwest Africa con-
tiguous with the Cape Verde Plateau (Fig. 2) (U.S.N. Oceanographic Office, 1952,
1961; International Hydrographic Bureau, 1958; Heezen and Tharp, 1968).
Navigation on the Gibbs was performed by Omega with an estimated positional
accuracy of ± 5 nm (Zuccaro and Rona, 1968). Soundings were made with a
12 kHz 60° full beam width Edo UQN sonar transducer and recorded on a Raytheon
192 Precision Fathometer Recorder.
submarine canyons
Submarine canyons of major dimensions, either absent or less completely shown
on prior charts, occur on the continental slope and upper continental rise between
18° and 26°N (Fig. 1). Seismic reflection profile A-A' parallel with the lower con-
tinental slope (Fig. 3) records U-shaped canyons with axes at 180, 225, 350 and 470 km
which range in shoulder-to-shoulder width between 35 and 85 km and in floor-to-
shoulder relief between about 350 and 780 m (Table 1). Each is underlain by a succes-
sion of buried troughs to at least 1-5 km (1*5 sec) acoustic penetration. These are
directly below the canyon axis at 470 km and are offset 10-20 km south of the axes
at 225, and 340 km. The sediment-water interface of the intercanyon areas (divides
♦The field work was supported by the Office of Naval Research under Contract Nonr-266 (84).
Reproduction in whole or in part is permitted for any purpose of the United States Government.
tNOAA Atlantic Oceanographic and Meteorological Laboratories, 901 South Miami Avenue,
Miami, Florida 33130.
321
322
Peter A. Ron a
30° W
20°W
-|0°N
Fig. 2. Regional bathymetric chart showing the relation of the area in Fig. 1 (outlined) to the
Cape Verde Plateau (U.S.N. Oceanographic Office, 1961 ; Dietz et al., 1969). Directions of
ocean surface currents (arrows) and a current velocity contour (< 25 cm/sec) (U.S.N. Oceano-
graphic Office, 1965, Figs. 1-5) are indicated. Envelopes are shown of most frequent dust
fall occurrence (ship) (after Folger, 1970, Fig. 1) and of a dust storm photographed by ESSA 5
satellite on 7 June, 1967 (satellite) (Prospero et al., 1970, Figs. 3 and 4). The locations of sedi-
ment cores (A153-158, A180-47, V17-158) (Ericson et al, 1961) and of an atmospheric dust
sample collected aboard H.M.S. Vidal on 17 January, 1965 are also shown (Folger, 1970).
Table 1 . Submarine canyons which cross the continental slope off Cap Blanc, Mauri-
tania measured from precision echo-sounding records made with a 12 kHz 60° total
beam width sonar transducer.
Canyon shoulder-to-
Maximum
shoulder distances
Width
Width
Depth N.
Depth S.
Depth
floor-to-
along profile A- A'
shoulders
floor
shoulder
shoulder
floor
shoulder
(Fig. 3) (km)
(km)
(km)
(m)
(m)
(m)
relief {m)
144-145
1
0-5
2200
2190
2225
35
145-205
60
15
2190
1770
2550
780
206-208
2
0-5
1790
1765
1915
150
210-245
35
10
1750
1775
2100
350
230-232
2
1
2120
2100
2210
110
265-305
40
5
1710
1885
1950
240
305-385
80
25
1885
1855
2550
695
390-425
35
10
1860
1605
2020
415
425-510
85
25
1605
1720
2290
685
470-473
3
0-5
2240
2230
2350
120
520-523
3
2
1815
1790
1900
110
531-534
3
1
1885
1900
2050
165
538-540
2
1
1945
1945
2160
215
541-542
1
0-5
1980
1940
2140
200
556-566
10
9
1805
1810
1875
70
582-585
3
1
1805
1825
1990
185
604-611
7
1
1765
1875
2065
300
622-623
1
0-5
1935
1950
2080
145
628-630
2
1
1925
1960
2070
145
649-5-6500
0-5
0-25
1960
1920
2080
160
651-652
1
0-5
1935
1960
2060
125
Bathymetry off central northwest Africa
323
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324
Peter A. Rona
between canyons including walls) are convex-up and are generally underlain by
sub-parallel convex-up strata. Smaller narrow V-shaped canyons are situated on
the crests of intercanyon areas at 145 and 207 km and are nearly centered within
U-shaped canyons at 231 and 471 km. A succession of narrow (< 10 km wide),
steep-walled, roughly V-shaped canyons with flat floors is present off Cap Timiris
between 510 and 630 km.
SEAMOUNTS
Major seamounts known off Cap Blanc are Echo Bank and Papp Seamount
based on soundings and nomenclature of the British National Institute of Oceano-
graphy (International Hydrographic Bureau, 1968) and Tropical Bank (Inter-
national Hydrographic Bureau, 1958) contoured from Gibbs sounding tracks
(Fig. 1). Tropical Bank consists of two distinct peaks at nearly equivalent depths
aligned NW-SE with a common base deeper than about 2000 m below sea level,
rather than a single peak as previously shown (U.S.N. Hydrographic Office, 1952).
The 9-km wide summit of the southeastern peak* is nearly flat with local protuber-
ances, possibly coral, which rise up to about 25 m above the 999-m summit (Fig. 4).
This is less than the previous minimum depths of 1696 m (U.S.N. Hydrographic
Office, 1952) and 1055 m (Internationa.. Hydrographic Bureau, 1958). A bench
about 0-5 km wide indents the northeast side at about 1050 m below sea level.
NE OKM
Fig. 4. Minimum depth bathymetric profile across the summit of Carmenchu Peak on Tropical
Bank. A bench faces northeast at about 1050 m below sea level. Vertical exaggeration is
about 20 : 1.
DISCUSSION
Knowledge of geological processes considered important in the shaping of the
more thoroughly investigated continental margin off eastern North America is
helpful in the interpretation of the morphology on the northwest African continental
margin. Submarine canyons on the continental slope off Cape Hatteras are inferred
*I propose to name this southeastern summit of Tropical Bank ' Carmenchu Peak ', in honor
of Me. del Carmen Piernavieja y Oramas of Las Palmas, Canary Islands, Spain.
Bathymetry off central northwest Africa 325
to have developed by depositional upbuilding of the walls (intercanyon areas), while
the channels were maintained over sites of original incision by sediment transport
processes (Rona, 1970). Some of the original incisions off Cap Blanc appear to
have been structurally controlled at the intersections of oceanic fracture zones with
the continental margin (Rona, 1969). As off Cape Hatteras, the canyons off Cap
Blanc are underlain by buried troughs and the intercanyon areas by convex-up strata
sub-parallel with the sediment-water interface. The similarity in the formations
implies that similar processes have been active in the development of canyons on the
continental slopes on both sides of the Atlantic. The scale differs, the canyons on
the continental slope off Cap Blanc attaining about twice the relief and several times
the width of those off Cape Hatteras (Table 1 ; Rona et al, 1967). As canyon relief
is inferred to be constructural, the differences in relief indicate that higher rates of
sediment accumulation have prevailed off Cap Blanc.
The Cape Verde Plateau forms a roughly triangular salient encompassing the
Cape Verde archipelago with base extending along the continental shelf from about
12° to 22°N and apex reflected as far as 1000 km seaward to the 4575-m isobath
(Figs. 1 and 2). Continental rise isobaths inflect around the northern and southern
flanks of the Cape Verde Plateau delineating a broad central ridge between Cap Blanc
and Dakar which converges toward the Cape Verde Islands. Seismic reflection
profiles reveal sediment in excess of 2 km (2 sec) with the acoustic character of
stratified lutite (silt and clay size) beneath this ridge (Fig. 3 ; Lowrie and Escowitz,
1969, Kane 9 D,E,F). The smoothness of the residual magnetic field along the
continental slope (Fig. 3) also indicates the presence of a thick sedimentary column.
The 700-m relief of Cayar Canyon where it crosses the continental slope off Dakar
(Fig. 2) (Dietz et al, 1968) is comparable to that of canyons off Cap Blanc (Table 1),
suggesting that relatively high rates of sediment accumulation have affected the entire
landward margin of the Cape Verde Plateau. Post-glacial rates of accumulation of
lutite cored from the wall of Cayar Canyon are 20 cm/ 1 000 y (Ericson et al, 1961,
core A 180-47, Table 5).
Wind-borne dust has frequently been observed off northwest Africa from sea-
level to several kilometers above sea-level by ships (Folger, 1970), aircraft (Prospero
and Carlson, 1970), and satellites (Prospero et a/., 1970). A striking spatial cor-
relation exists between the shapes and areas of the envelope of most frequent dust
falls and the Cape Verde Plateau (Fig. 2). This correlation suggests a possible genetic
relation between the pattern and volume of eolian sediment transport and sediment
deposition on the Cape Verde Plateau. On the basis of similarities of composition,
texture, and consideration of air parcel trajectories of the prevailing trade winds,
silt and clay-sized material has been traced from North African soils to the dust
envelope off northwest Africa (Folger, 1970; Prospero et al, 1970), to surface sea
water samples (Folger, 1970), and finally to deep-sea sediments (Folger, 1970).
The ratios of clay minerals measured in tops of sediment cores from the Cape Verde
Plateau (Biscaye, 1965, cores A153-158, V17-158) are similar to those collected from
the adjacent atmosphere (Fig. 2) (Folger, 1970, Fig. 9, Table 3). Cores recovered
from the Cape Verde Plateau contain lutite (Ericson et al, 1961, A180-51, 53, 56)
with the exception of those from the floor of Cayar Canyon which contain sand
(A180-49, 50), probably derived from the adjacent shelf where sand predominates
(McMaster and Lachance, 1968).
326 Peter A. Rona
Oceanographic conditions immediately underlying the dust envelope favor the
persistence of the fallout pattern as particles settle from the sea surface, through
the water column, to the bottom. The velocity of surface currents, affecting perhaps
the upper 200 m, is less than 25 cm/sec in an area over the Cape Verde Plateau (Fig.
2). The deep thermohaline circulation is predicted to be weak and diffuse on the
eastern boundary of the North Atlantic (Wust, 1957; Defant, 1961) and direct
observations indicate negligible near bottom currents at present (Lowrie et ah, 1970).
The irregular topographic relief of the Cape Verde archipelago would further act to
trap sediment on the bottom. The amount of atmospheric fallout might be expected
to decrease away from the sediment source, which corresponds with the seaward
narrowing and apparent thinning of the sedimentary apron that forms the Cape
Verde Plateau. The northeast orientation of the bench observed on Tropical Bank
(Fig. 4) indicates that the bench was cut by surf driven from the present prevailing
wind direction and suggests that an eolian sediment transport system may have been
in effect long enough to shape the Cape Verde Plateau and prograde the continental
rise.
Acknowledgements — William P. Osborn, formerly with Hudson Laboratories of Columbia
University, assisted with the bathymetric chart. Henry S. Fleming of U.S. Naval Research
Laboratory gave helpful encouragement. Dr. A. S. Laughton of the British National Institute of
Oceanography provided charts of Echo Bank and Papp Seamount. Conversations with Drs. Louis
W. Butler and George H. Keller of NOAA were valuable. Dr. Robert S. Dietz and Paul
J. Grim of NOAA constructively criticized the manuscript. Ernest L. Bergeron, Consular Agent of
the U.S., facilitated matters when the Gibbs made port in the Canary Islands. Captain Raymond
E. Salman and the officers and crew of the USNS /. W. Gibbs provided splendid co-operation.
REFERENCES
Biscaye P. E. (1965) Mineralogy and sedimentation of recent deep-sea clay in the Atlantic
Ocean and adjacent seas and oceans. Bull. Geol. Soc. Am., 76, 803-831.
Defant A. (1961) Physical Oceanography. Macmillan, New York, Vol. 1, 729 pp.
Dietz R. S., H. J. Knebel and L. H. Somers (1968) Cayar submarine canyon. Bull. Geol.
Soc. Am., 79, 1821-1828.
Ericson D. B., M. Ewtng, G. Wollin and B. C. Heezen (1961) Atlantic deep-sea sediment
cores. Bull. Geol. Soc. Am., 72, 193-286.
Folger D. W. (1970) Wind transport of land-derived mineral, biogenic, and industrial
matter over the North Atlantic. Deep-Sea Res., 17, 337-352.
Heezen B. C. and M. Tharp (1968) Physiographic diagram of the North Atlantic Ocean.
Spec. Pap. Geol. Soc. Am., 65, revised.
International Hydrographic Bureau (1958) Carte Generate Bathymetrique des Oceans,
4th edition, Monaco.
International Hydrographic Bureau (1968) Sheets 103, 104, 128, 129 for the Carte
Generate Bathymetrique des Oceans, Monaco.
Lowrie A. and E. Escowitz, editors (1969) Kane 9. U.S.N. Oceanogr. Off. Global Ocean
Floor Analysis Res. Data, Ser. 1, 1-971.
Lowrie A., W. Jahn and J. Egloff (1970) Bottom current activity in the Cape Verde and
Canaries Basin, Eastern Atlantic. Trans. Am. geophys. Un., 51, 336.
Matthews D. J. ( 1 939) Tables of the velocity of sound in pure water and sea water. Admiralty,
Hydrographic Department, London, 52 pp.
McMaster R. L. and T. P. Lachance (1970) Northwestern African continental shelf sedi-
ments. Marine Geol., 7, 57-67 (1969).
Prospero J. M. and T. N. Carlson (1970) Radon-222 in the North Atlantic trade winds:
Its relationship to dust transport from Africa. Science, 167, 974-977.
Prospero J. M., E. Bonatti, C. Schubert and T. N. Carlson (1970) Dust in the Caribbean
atmosphere traced to an African dust storm. Earth Planet. Sci. Letters, in press.
Bathymetry off central northwest Africa 327
Rona P. A. (1969) Seismic reflection profiles from northwest African continental margin
between Canary and Cape Verde islands (abs.). Trans. Am. geophys. Un., 50, 21 1.
Rona P. A. (1970) Submarine canyon origin on upper continental slope off Cape Hatteras.
/. Geo!., 78, 141-152.
Rona P. A., E. D. Schneider and B. C. Heezen (1967) Bathymetry of the continental rise
off Cape Hatteras. Deep-Sea Res., 4, 625-633.
U.S.N. Hydrographic Office (1952) Bottom Contour Chart 0305 N, 1st edition.
U.S.N. Oceanographic Office (1961) The world. H. O. Misc., 15, 254-257.
U.S.N. Oceanographic Office (1965) Oceanographic atlas of the North Atlantic Ocean,
Section I Tides and Currents. USNOO Pub. 700. 75 pp.
Wust G. (1957) Stromgeschwindigkeiten und Strommengen in den Tiefen des Atlantischen
Ozeans. Wiss. Ergebn. dt. Atlant. Exped. ' Meteor ', 6 (2), 261-^20.
Zuccaro A. and P. A. Rona (1968) Omega navigation performance off northwest Africa
during operation no. 267, April 23-May 28, 1968. Tech. Rept. Columbia Univ. Hudson
Lab., 153, 36 pp. (unpublished manuscript).
62
Reprinted from Geotimes
deep-sea salt diapirs
The case for deep-sea salt diapirs is
alive and well in spite of reports to the
contrary. Leg 14 of the Deep Sea
Drilling Project (February 1971 Geo-
times) obtained evidence from 2 drill-
ing sites off northwest Africa support-
ing the existence of deep-sea salt de-
posits. At both Sites 139 and 140, in
water depths of 3,047 and 4,483 m,
on the middle and lower continental
rise, the sediments showed marked sa-
linity gradients (38 to 75 ppt in 665 m
penetration at Site 139; the salinity of
sea water is generally about 35 ppt).
These 2 sites are situated where I have
interpreted the presence of possible
salt diapirs from geophysical data
and regional geologic considerations
(Rona, 1969, Nature, v. 224, p. 141-
143: American Association of Petro-
leum Geologists Bulletin, v. 54, p. 129-
157). The diffusion rates of ions in
saturated unconsolidated sediments
are so high ( Vi to %o of diffusion rates
in free solution according to Manheim
(1970, Earth and planetary science
letters 9, p. 307-309) that a signifi-
8 GEOTIMES May 1971
cant source concentration at depth is
required to maintain the observed sa-
linity gradients. The salinity gradients
observed off northwest Africa are com-
parable to those in sediments over salt
deposits in the Gulf of Mexico (Man-
heim & Sayles, 1970, Science, v. 170,
p. 57-61).
The Leg 14 report emphasizes the
drilling of a basalt body at Site 141,
200 km north of the Cape Verde
Islands, that was interpreted as a salt
diapir (Schneider & Johnson, 1970,
AAPG Bulletin, v. 54, p. 2,151-2,169,
figure 8). The hypothesis of deep-sea
salt diapirs should not be judged on
evidence from this single site but
should await more evidence including
publication of the Leg 14 salinity
studies. The model which I postulated
of the early Atlantic as an evaporite
basin restricted by the Late Triassic/
Jurassic positions of the drifting con-
tinents remains reasonable.
Peter A. Rona
NOAA, Atlantic Oceanographic &
Meteorologic Laboratories
Miami, Fla.
63
Reprinted from Nature 231 , 179-180.
Depth Distribution in Ocean
Basins and Plate Tectonics
In this article I shall show that relationships between the
movement of lithospheric plates1-3 and the depths of the sea
floor are leading towards a quantitative theory of the distri-
bution of oceanic depths, and that some predictions can be
made. Several principal lithospheric plates have now been
recognized; their relative motion over the mantle is described
by a rotation of one plate relative to an adjacent plate4-6.
The rotation requires two parameters to locate the pole of
relative rotation, and one to specify the magnitude of the
angular velocity. The direction of spreading is along small
circles concentric about the pole of rotation and the velocity
of spreading varies as the sine of the distance (measured in
degrees of arc) from that pole, to a maximum at a distance of
90° along the equator of rotation. The angular velocity of
rotation is the same everywhere. In the Atlantic Ocean the
fracture zones between about 60° N and 10° S are very nearly
small circles centred about a pole near the southern tip of
Greenland (62 ±5° N, 36 ±2° W), and the spreading rates
approximately agree with the velocities required for the
opening of the North Atlantic about this pole1,3.
Examination of the topography of the sea floor and spreading
rates in the central region of the world system of mid-ocean
ridges shows that the width of the ridge7, the local topography8,
and the thickness of layer 2 of the oceanic crust8 seem to be
related to the spreading rate in the following way. (1) Slow
spreading (1-2 cm yr-1) away from the ridge centre is asso-
ciated with a narrow ridge, a central rift, adjacent rift moun-
tains and a thick layer 2. (2) Fast spreading (3-4.5 cm yr-1)
is associated with a wide ridge, subdued topography (no
central rift) and a thin layer 2. (3) The volume of lava dis-
charged in layer 2 per unit time and unit length along the
crest of the whole active system is relatively constant regardless
of the spreading rate. Thus, topography and the thickness
of layer 2 can be predicted if the rate of spreading is known.
An examination of topographic profiles perpendicular to
various sections of the world mid-ocean ridge system supports
the inference that topography is a function of spreading rate9.
The relationship between the slope of ridge flanks and the
spreading rate from the ridge crest to magnetic anomaly No. 5
at a distance corresponding to 107 yr was formulated from
this series of profiles so that, by knowing the spreading rate,
the slope can be calculated9. The faster the spreading rate
within an episode of spreading, the lower the topographic
slope and roughness, measured over a distance corresponding
to the crust generated during that episode. The decrease in
180
0
1,000
2,000
3,000
4,000
5,000
6,000
7,000
I ' I ■
ft ~*~ ' X
I «•»!
Latitude (north)
Fig. 1 Depth distribution at the inner margin of the High Fractured Plateau province and marginal basins1 ' of the northern Mid-Atlantic
Ridge (R, I-IV" ; E, I, J10). A vertical bar indicates variations where the topography is too irregular to determine a unique depth. The
dashed line is part of a sine curve varying from maximum elevation (zero depth) at the latitude of the North Atlantic pole of rotation
(62° N, ref. 1) to minimum elevation (maximum depth) at the equator of rotation, 90° to the south.
topographic slope with increasing spreading rates is a result
of the greater length of layer 2 crust generated per unit time,
as well as an almost linear decrease in the absolute elevation
of the crest of the ridge associated with the thinning of layer 2.
From the lithospheric plate motions1 ~3 and the relationships
between spreading rate and sea floor topography7-9, it follows
that the depth of a mid-ocean ridge crest increases from a
maximum elevation (zero reference depth) near the pole of
rotation with the sine of the distance from the pole, and the
slope of its adjacent flanks decreases with the reciprocal of the
sine of the distance from the pole of rotation of the two litho-
spheric plates the boundaries of which form the ridge. The
limiting case of zero slope and zero elevation (maximum depth)
along the equator of rotation never occurs because it would
require an infinite rate of sea floor spreading.
Sufficient data exist to test this hypothesis over about 40°
of latitude in the North Atlantic. The depths of the Mid-
Atlantic Ridge, measured at the inner margin of the High
Fractured Plateau province, decrease between 49° and 12° N
and this decrease may be approximated by a sine curve originat-
ing at the latitude of the pertinent North Atlantic pole of
rotation (62° N) (Fig. 1, and see ref. 1). The variation in
depths about the sine curve is a result of the irregular topo-
Distar.ce from rift valley of Mid- Atlantic Ridge (km)
0 100 200 300
s.ooo-1
Fig. 2 Half-profiles perpendicular to the crest of the Mid-
Atlantic Ridge. The High Fractured Plateau and Flank pro-
vinces are represented by straight line segments fitted through
the mean topographical values with slopes as indicated'0.
The topographic step between provinces is evidence of a lapse
in sea floor spreading which occurred simultaneously ending
about 107 yr ago10.
graphy of the ridge crest transected by numerous fracture
zones. The southward decrease in crestal elevation and slope
of the ridge flanks is apparent in profiles perpendicular to the
ridge axis (Fig. 2). To measure depth and slope, the irregular
topography of the High Fractured Plateau and Flank provinces
was fitted with straight line segments through the mean topo-
graphical values. The depth of both provinces progressively
increases and the slope decreases with distance from the pole
of rotation. A marked topographic step between the High
Fractured Plateau and the Flank provinces is evidence of a
discontinuity in sea floor spreading, when the ridge subsided
during a spreading lapse ending about 107 yr ago10 (a dis-
continuity of zero spreading would result in a vertical topo-
graphic step of infinite slope). The progressive southward
increase in the width of the High Fractured Plateau province
is consistent with the increase of spreading rates with distance
from the pole of rotation.
The maximum depth along the axes of the basins on the
east and west margins of the Mid-Atlantic Ridge increases
away from the pole of rotation, measured between 55° N and
12° N (Fig. 1). The axes of maximum depth can be approxi-
mated by sine functions, with the exception of an anomalous
decrease in depth along the part of the western basin adjacent
to the Lesser Antilles island arc, where special structural
conditions prevail. The increase in depth at the axes of the
marginal basins is less than that at the ridge crest, so that their
respective sine curves converge towards the equator of rotation.
The observation that the increase in depth at the ridge crest
and at the axes of the marginal basins can both be described by
sine functions, originating near a pole of rotation and con-
verging towards the equator of rotation, indicates that depth
distribution is maintained as the sea floor spreads bilaterally
away from the crestal region and subsides on the ridge flanks.
The hypothesis presented here helps to explain the correspond-
ence between depth and latitude in the oceans, because the
poles of lithospheric plate rotation tend to lie near the Earth's
rotational axis.
I thank D. C. Krause for a constructive review.
Peter A. Rona
National Oceanic and Atmospheric Administration,
Atlantic Oceanographic and Meteorological Laboratories,
Miami, Florida 33130
Received April 16, 1971.
1 Morgan, W. J., J. Geophys. Res., 73, 1959 (1968).
2 McKenzie, D. P., and Parker, R. L., Nature, 216, 1276 (1967).
3 Le Pichon, X., J. Geophys. Res., 73, 3661 (1968).
4 Holmes, A., Trans. Geol. Soc. Glasgow, 18-3, 559 (1931).
5 Hess, H. H., Petrologic Studies: A Volume in Honour of A. F
Buddington, 599 (Geol. Soc. Amer., 1962).
6 Dietz, R. S., Nature, 190, 854 (1961).
7 Vogt, P. R., and Ostenso, N. A., Nature, 215, 810 (1967).
8 Menard, H. W., Science, 157, 923 (1967).
9 Le Pichon, X., and Langseth, jun., M. G., Tectonophysics, 8, 319
(1969).
10 Schneider, E. D., and Vogt, P. R., Nature, 217, 1212 (1968).
11 Heezen, B. C, Tharp, M., and Ewing, M., Special Paper 65
(Geol. Soc. Amer., 1959).
Reprinted from Geology Bulletin No. 5, 25-29
MARINE GEOPHYSICAL OBSERVATIONS OF
THE EASTERN PUERTO RICO-VIRGIN ISLANDS REGION
by
Robert B. Starr and Robert G. Bassinger
Atlantic Oceanographic Laboratories, Environmental Science Services Administration, Miami, Florida 33130
Abstract
During early May 1966, a combined bathymetric,
seismic reflection profile, and total magnetic field inten-
sity investigation was conducted of the area south and east
from Puerto Rico to the Virgin Islands, using precise Hi-
Fix navigation control. Except for the exceptionally
shallow, flat area of the Puerto Rico-northern Virgin
Islands platform, the bathymetry indicates a very irregular
submarine topography of basins and block faults. The
disturbed magnetic signature over the platform indicates
at- or near-surface sources. South of the platform three
basins with appreciably different depths were delineated.
Sub-buttom reflectors within these basins indicate evi-
dence of recent deformation. Bordering these basins to the
south, a broad ridge with peaks at least as shallow as 500
fathoms, except for the shoaler Grappler Bank, extends
west from St. Croix. A minor magnetic expression was
evident over the ridge, but none was noted for Grappler
Bank.
Introduction
The Puerto Rico-Virgin Islands shelf and St. Croix
Ridge with the intervening Virgin Islands Trough1 are at
the eastern end of the Greater Antilles sector of the An-
tilles Arc. The area and tracklines are shown in Figure 1 .
This study was conducted from the USC&GSS
"Whiting" in 1966. Observations consist of 1,1 80 nautical
miles of hydrographic soundings, continuous seismic re-
flection profiling, and total magnetic-field intensity
observations at a nominal line spacing of 4.6 nautical
miles. Ship's position was determined with Hl-FIX elec-
tronic navigation. Additional lines of hydrography and
magnetics were obtained by the USC&GSS "Explorer" in
1965 and one line of hydrography and seismic reflection
profiling by the USNS "Lynch" in 1 967.
Results
Bathymetry
For convenience of discussion, the bathymetry of
the Puerto Rico-Virgin Islands region may be divided into
five provinces on the basis of their morphology. From
north to south these are ( 1 ) south slope of the Puerto Rico
Trench (north slope of the shelf), (2) Puerto Rico-Virgin
Islands shelf, (3) Virgin Islands Trough, (4) St. Croix
Ridge, and (5) north margin of the Venezuelan Basin.
These provinces have an east-west trend throughout the
study area.
1 The names "Virgin Islands Trough" vice "Virgin Islands Basin,"
"Grappler Seamount" vice "Grappler Bank," "St. Croix Ridge,"
"Whiting Basin," and "Whiting Seamount" were approved by the
U.S. Board of Geographic Names, September 19, 1968.
The upper portion of the south slope of the Puerto
Rico Trench (Fig. 2) consists of a short, steep scarp of
about 20° terminating between depths of 80 and 940
fathoms. At this point the slope abruptly changes to a 3°
gradient which it maintains to the limit of the tracklines. A
"V"-shaped depression in this slope at about 65°05'W
suggests a submarine canyon.
The Puerto Rico-Virgin Islands shelf is nearly a
featureless plain except for the islands and isolated banks
and reefs. The northern half, however, averages approxi-
mately 15 fathoms deeper than the shallower southern
half. From our traverse west of Culebra Island, this depth
difference appears to be associated with a fault. Donnelly
(1965) relates this declivity between St. Thomas and
Culebra to post-Pleistocene faulting.
From the character of the sounding records the
steep walls of the Virgin Islands Trough appear to be much
rougher than mapped, with spurs intersecting a bottom of
discontinuous, relatively flat areas. Southeast of Puerto
Rico a small basin (Whiting Basin) is defined by the
1 ,000-fathom isobath. This basin is separated from the
trough by a north-south ridge connecting the Puerto
Rico-Virgin Islands shelf with Whiting Seamount. East of
the basin the trough deepens to a small plain at 2,200
fathoms which is partially separated from the main floor
of the trough (PI. 1). The main floor is outlined by the
2,400 fathom isobath (PI. 1 and Fig. 2).
The St. Croix Ridge extends westward from St.
Croix to Investigator Bank. West to 65°35'W, the ridge
consists of an irregular row of discontinuous highs with
northeast-trending spurs. Our soundings indicate that the
deepest passage over the ridge occurs between 65°25'W
and 65°30'W, and appears to be a little over 1,000
fathoms.
West of 65°35'W,the St. Croix Ridge has a different
character from that to the east. It consists of three inter-
connected peaks: Whiting Seamount, Grappler Seamount,
and Investigator Bank. Summits of these are much
shallower than the crest of the ridge in the east ; the top of
Grappler Seamount is only 35 fathoms, for instance, and
no consistent trend of the isobaths is apparent.
The north slope of the Venezuelan Basin appears to
have a uniform gradient. Except for minor irregularities,
the slope averages between 4° and 7°. It decends from the
St. Croix Ridge to somewhat over 2,700 fathoms in the
southeastern part of the area (PI. 1 ).
Sub-Bottom Profiling Results
Seismic reflection results shown in the cross-section
(Fig. 2) are form lines showing approximate penetration
based on the instrument calibration velocity of 4,800 fps.
The quality of the reflection records varied widely
throughout the area. Penetration of the south slope of the
Puerto Rico Trench was excellent. Several reflectors were
observed, decreasing in number and thickness downslope
(Fig. 2).
Trans. Fifth Carib. GeoL Cont, GeoL Bull. No.
Queens College Press, May 1971.
26
On the shallow Puerto Rico-Virgin Islands shelf, the
hard bottom and multiple reflectors limited the profiler
results. However, on the lines northeast of Vieques Island,
sufficient penetration was obtained to identify southeast-
dipping strata as far as three miles offshore ( Fig. 3). South-
east of St. Thomas, an anticline was crossed with its limbs
dipping northeast and southwest (Fig. 4). In addition,
numerous small scarps were crossed. Similar features have
been interpreted by Donnelly ( 1 965) as fault scarps.
No significant sub-bottom reflectors were recorded
along the walls of the Virgin Islands Trough owing pos-
sibly to the lack of sediment on the steep walls. The
bottom of the trough, however, consists of good reflec-
tors. These reflectors are flat lying or dip to the south
away from a low, northeast-trending ridge which crosses
the floor of the trough at 65°05'W. The contacts of the
sediments of the trough bottom with the walls are in all
cases abrupt and discontinuous. The walls appear to be
fault scarps and the trough a graben (Fig. 2) as earlier
suggested by Meyerhoff( 1927) and Whetten ( 1 966).
On the St. Croix Ridge, the eastern sector has
southerly dipping strata on the northern ends of the spurs,
but no reflectors were apparent on the main crest of the
ridge (Fig. 2) or on the seamounts of the western sector.
The profiler record of the top of Grappler Seamount is
similar to that of the Puerto Rico-Virgin Islands shelf.
No discernible sedimentary strata were found on the
northern slope of the Venezuelan Basin. However, the
basin itself provided some of the deepest reflected pene-
trations recorded (up to 0.7 sec). On the reflection
records the boundary between the basin and the north
slope can be placed at an apparent fault scarp (Fig. 2). The
abrupt discontinuous contact of the basin sediments with
the north slope, and the slump structures with multiple
slip planes on some of the sections indicate this boundary
to be a fault line. A fault at this general location has been
inferred by Meyerhoff (1927) and Donnelly ( 1 964).
Magnetics
Over the southern slope of the Puerto Rico Trench
and the northern edge of the Puerto Rico-Virgin Islands
shelf the magnetic anomalies are of long wave length and
small amplitude (PI. 2 and Fig. 2). This suggests that the
sources of the anomalies are broad relative to their thick-
ness and are probably at a moderate depth.
The magnetic pattern of the Puerto Rico-Virgin
Islands shelf proper consists of belts of high amplitude,
short wave-length anomalies (Fig. 2) which are more or
less parallel to the margins of the shelf. Some of these
anomalies are directly associated with known intrusivesin
the islands and most of them probably reflect the occur-
rence of near-surface intrusive bodies (Renard, 1967).
The linear magnetic low in the wall of the Virgin
Islands Trough (PI. 2) which coincides with the break in
the slope east of Vieques Island suggests the possibility of
a fault. This could be an extension of the major east-west
fault zone of northern Puerto Rico (Briggs and Akers,
1965;Mattson, 1966).
East of 65°35'W a slight, linear, east-west magnetic
high with a corresponding magnetic low to the north is
apparently associated with the St. Croix Ridge. A promi-
nent low immediately southeast of St. Croix may be
related to the coastal plain graben found there (Ceder-
strom, 1950; Whetten, 1966). The western sector of the
ridge has noticeable anomalies which correlate with
Whiting and Grappler seamounts. To the south, the
northern edge of the Venezuelan Basin appears to have a
relatively featureless magnetic pattern.
References
1. Briggs, R.P., and Akers, J. P., 1965, Hydrogeologic
map of Puerto Rico and adjacent islands: U.S. Geol.
Survey Hydrol. Inv. Atlas HA-1 97.
2. Cederstrom, D.J., 1950, Geology and ground-water
resources of St. Croix, Virgin Islands: U.S. Geol.
Survey Water Supply Paper 1067, 117 p.
3. Donnelly, T.W., 1964, Evolution of eastern Greater
Antillean island arc: Am. Assoc. Petroleum Geolo-
gists Bull., v. 48, p. 680-696.
4. 1965, Sea-bottom morphology
suggestive of Post-Pleistocene tectonic activity of the
eastern Greater Antilles: Geol. Soc. America Bull., v.
76, p. 1291-1294.
5. Mattson, P.H., 1966, Geological characteristics of
Puerto Rico: p. 124-138 in Continental margins and
island arcs, ed. Poole, W. H.: Geol. Survey Canada
Paper 66-15, Ottawa, Queens Printer, 486 p.
6. Meyerhoff, H.A., 1927, The physiography of the
Virgin Islands, Culebra, and Vieques: N.Y. Acad. Sci.
Scientific Survey of Porto Rico and the Virgin
Islands, v. 4, pt. 2, p. 145-219.
7. Renard, V., 1967, Virgin bank: Correlation of mag-
netism and gravity with geology: Ph.D. Thesis, Rice
University, 1 1 1 p.
Whetten, J.T.,
Virgin Islands:
177-239.
1966, Geology of St. Croix, U.S.
Geol. Soc. Am. Memoir 98, p.
*•••.,.. .100
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USC a GSS EXPLORER 1965
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USNS LYNCH 1967
FIGURE 1- Location and track chart.
28
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PUERTO RICO -VIRGIN ISLANDS RECION
BATHYMETR1C MAP
CONTOUR INTERVAL: 100 FATHOMS
(Corrected for Sound Velocity)
STAM AND IASSINGER PIATE
PUERTO RICO- VIRGIN ISLANDS REGION
TOTAL MAGNETIC FIELD INTENSITY t
IN GAMMAS
(Corrected to 1966 .31
CONTOUR INTERVAL 60 GAMMAS
SUM AND lASSMGa. PLATE 2
Reprinted from Marine Geophysical Researchers 1_,
145-161.
CONTINENTAL TERRACE AND DEEP PLAIN
OFFSHORE CENTRAL CALIFORNIA
L.AUSTIN WEEKS* and ROBERT K. LATTIMORE
Environmental Science Services Administration, Atlantic Oceanographic and
Meteorological Laboratories, Miami, Fla. 33130, U.S.A.
(Received 21 April, 1970)
Abstract. Seismic-reflection profile investigations of the California continental terrace and Deep
Plain, between 35 °N and 39 °N, support the hypothesis that the continental shelf and slope consist
of alternating blocks of Franciscan and granitic-metamorphic basement overlain by varying thick-
nesses of younger sediments. North of 37 °N, the seismic profiles confirm the distribution of turbidites
shown by other workers. A significant proportion of the sediments on the middle and lower con-
tinental rise, south of 37 °N, appears to be unrelated to the present Monterey deep-sea canyon system.
Near 39 °N the ridge which forms the topographic axis of the Delgada deep-sea fan consists of a
thin cover of acoustically-transparent sediment unconformably overlying a thick sequence of turbi-
dites; the southern part of this ridge is composed of well-defined short reflectors of highly variable
dip. The ridge is incised by a steep-walled, flat-floored valley which follows a nearly straight course
across its eastern flank. Among possible explanations for this pattern is uplift of the sea floor beneath
the ridge.
Our data and investigations of others indicate that acoustic basement north of 38°40'N is at least
0.5 sec (two-way travel time) shoaler than it is south of Pioneer Ridge; when present, the ridge may
represent as much as 0.5 sec additional basement relief. This structural pattern probably does not
extend east of 127°40'W, although the magnetic expression of the ridge persists to 127°W.
Disappearance of the distinctive abyssal hills topography from west to east within the area of
investigation usually can be attributed to burial by turbidites. Normal 'pelagic' sediments form a
veneer, rarely more than 0.15 sec thick, which conforms with the basement topography; some loca-
lities are devoid of discernible sediment.
1. Introduction
The first regional investigation of the sea floor off central California was part of a
study of the entire California coastal margin by Shepard and Emery (1941); along
with maps and descriptions of the shelf and slope, their paper includes hypotheses on
the evolution of the more important physiographic features. Menard (1955) gave the
name, "Deep Plain of the northeastern Pacific", to the area bounded by the Mendoci-
no and Murray fracture zones (Figure 1), and described the area in the context of the
tectonic framework of the entire northeastern Pacific basin.
Systematic marine geomagnetic observations in the area bounded by the Mendocino
and Murray fracture zones have been reported by Mason (1958), Vacquier et al. (1961),
Mason and Raff (1961) and others. A detailed bathymetric map of the continental
margin, prepared by H. W. Menard, was published in Heezen and Menard (1963,
Figure 12) and in more complete form in Winterer et al. (1968, Figure 7). Soundings
and bottom samples taken across Santa Lucia Bank and the shelf offshore San Fran-
* Present address: 13720 SW 78th Ct., Miami, Fla. 33158, U.S.A.
Marine Geophysical Researches 1 (1971) 145-161. All Rights Reserved
Copyright © 1971 by D. Reidel Publishing Company, Dordrecht - Holland
65
146
L.AUSTIN WEEKS AND ROBERT K.LATTIMORE
cisco as part of a regional investigation of the continental slope have been reported
by Uchupi and Emery (1963). Curray (1965) has described seismic-reflection profiles
of the continental shelf and slope between Santa Lucia Bank and Cape Mendocino.
In addition to these regional investigations, there is an extensive literature dealing
with individual features within the Deep Plain.
Fig. 1.
In 1965 and 1966, as part of the Environmental Science Services Administration -
U.S. Coast and Geodetic Survey contribution to the international Upper Mantle
Project, systematic marine geological and geophysical studies were made of the area
between 35° and 39° North Latitude, extending from the California coast to 133°
West Longitude - the offshore extension of the U.S. Trancontinental Geophysical
Survey (TGS) (U.S. Upper Mantle Committee, 1965, p. 115). The TGS investigations
included continuous geomagnetic measurements, soundings, and gravity observations
along east-west lines spaced at 18-km intervals (Lattimore et al., 1968a, b) as well as
the collection of deep-sea cores and heat-flow measurements (Burns and Grim, 1967).
The results of the TGS seismic-reflection profile reconnaissance, made by USC&GSS
Surveyor in April and May, 1966, are presented in this report.
CONTINENTAL TERRACE AND DEEP PLAIN OFFSHORE CENTRAL CALIFORNIA 147
2. Methods
Continuous seismic-reflection profiles were made along a series of east-west lines,
spaced at 50-60 km intervals, extending from the California coast to the base of the
continental slope; at 36 °N and 39 °N, the lines were extended to 130°W (Figure 2).
Additional traverses were run to construct a northeast-southwest profile which inter-
sects the continental slope near Pioneer Seamount, and a northwest-southeast profile
running roughly along the 4000-m isobath. The seismic profiles were made with a
20,000-joule Rayflex 'arcer' fired at 4-sec intervals; the return signal was subjected to
a 70-120 Hz-bandpass filter. Normal survey speed was about 12 km/hr but the vessel's
speed was slowed as necessary to obtain acceptable records in heavy seas.
Ship's position was determined with the U.S. Navy Satellite Navigation System,
fixes being obtained at irregular intervals averaging once every two hours. This con-
trol was supplemented with LORAN and other conventional means of determining
position. The probable error in any smooth-plotted ship's position is estimated to be
less than 2 km.
The deepest continuous reflector on the seismic records usually was selected as the
top of the basement. Beneath the sediments of the upper continental rise and in other
localities where there was no distinctive reflector, the top of the basement was picked
at a level below which there were no returns suggestive of bedding, so long as this
level was well within the limits of penetration of the signal. 'Basement' thus represents
only the shoalest acoustically-opaque rock and the nature and lithology of the base-
ment would be expected to vary from place to place. In the continental rise, the top
of the basement seems to be generally equivalent with the top of the seismic second
layer as determined by refraction measurements (Mason, 1958, p. 328 and Figure 2;
Menard, 1964, Figure 3.3; Winterer et «/., 1968, Figure 6).
3. Results and Discussions
As has been noted, the deep-sea portion of the area of the Transcontinental Geophys-
ical Survey investigation falls within the "Deep Plain of the northeastern Pacific"
(Menard, 1955, p. 1158). Generally, the Deep Plain is about 1.5 km deeper than the
Ridge-and-Trough Province north of the Mendocino Escarpment, and about a half-
kilometer deeper than the Baja California Seamount Province south of the Murray
Fracture Zone (Menard, 1960, Figure 2); its main characteristic is that it is relatively
featureless in comparison with the two provinces which adjoin it.
The results of the TGS seismic reflection observations are presented as interpreta-
tive line drawings in Figure 2. The locations of the illustrated profiles are shown on
the accompanying bathymetric map (Figure 2) which has been redrawn from one
prepared by the authors for the Transcontinental Geophysical Survey report (Latti-
more et ah, 1968b).
Because of the size of the area of study and the diversity of geologic features within
it, it is convenient to divide the TGS area into five provinces, and to include in the
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CONTINENTAL TERRACE AND DEEP PLAIN OFFSHORE CENTRAL CALIFORNIA 151
discussion of each province a review of the results and conclusions of earlier investi-
gators. The five areas are: (1) continental terrace (shelf and slope); (2) continental rise
south of 37 °N; (3) Delgada deep-sea fan; (4) Pioneer Ridge; and (5) abyssal hills
(Figure 1 ).
A. CONTINENTAL TERRACE
North of Cordell Bank, the TGS investigation and the study reported by Curray
(1965) show that the continental shelf is composed of a thick sequence of moderately
to intensely deformed strata, in some localities overlain by beds which are gently
arched and cut by faults of small vertical displacement (see Curray, 1965, Figure 2).
The continental slope is made up of a series of fault blocks, in which evidence of
stratification can be found in the surface sediments down to depths of approximately
1800 m (A A', Figure 2).
The area from Cordell Bank south to Pioneer Seamount, which for convenience
will be referred to as the Farallon platform, is characterized by an unusually wide
shelf (in comparison with the shelf to the north and south) and by relatively minor
incision of the shelf by sea valleys. The width and morphology undoubtedly are
attributable to the presence of relatively resistant rock beneath the edge of the shelf
and the upper slope (BB', Figure 2; Curray, 1965, Figure 3). A thick section of folded
strata lies to landward of this resistant block ; the present sea floor has been cut across
both units, presumably by Pleistocene wave erosion (Curray, 1965, p. 798).
Between Pioneer Seamount and Monterey Canyon, the edge of the continental shelf
is made up of at least a half-second of folded sedimentary rocks but a well-defined
basement block, cut by faults, can be recognized under the middle continental slope
at depths of 800 m or more (CC, DD', Figure 2; Curray, 1965, Figure 4).
From Monterey Canyon south to 35 °N, the edge of the shelf consists of no more
than a half-second of folded sedimentary rock (EE\ FF', GG', Figure 2). These strata
are overlain by younger sediments which thicken landward (to at least 0.7 sec at
36 °N) and have been tilted and faulted. Off Point Sur (EE', Figure 2), at a depth of
1000 m (approximately 1.5 sec), folded strata which make up the edge of the shelf are
in fault contact with a basement block that forms the middle continental slope. Off
Cape San Martin (FF', Figure 2) and on Santa Lucia Bank (GG', Figure 2), the base-
ment can be traced from beneath the edge of the shelf toward the shoreline; both
basement and some of the overlying sediments are cut by faults. The continental slope
is made up of fault-blocks of basement rock, in some places thinly covered by sedi-
ments.
The presence of basement beneath the outer continental shelf and upper slope was
first established by Curray (1965), who concluded that basement rocks comprise an
essentially continuous ridge extending from 35°30'N to 39°30'N, with the possible
exception of a zone north of Point Arena (Curray, 1965, p. 799 and Figure 1). Page
(1966) suggested that, like the Coast Ranges, the California shelf and slope may be
made up of blocks of a granitic-metamorphic complex alternating with blocks under-
lain by Franciscan rocks. The Franciscan includes a flysch sequence ranging in age
152 L. AUSTIN WEEKS AND ROBERT K. LATTIMORE
from Late Jurassic to Late Cretaceous; the granites are overlain unconformably by
Upper Cretaceous and Paleocene strata (Taliaferro, 1951, p. 117). Page (1966, Figure
1 ) also proposed that the Salinian block - granodiorite basement bounded roughly by
the Nacimiento and San Andreas faults - extends beneath the continental shelf
northwest of Monterey Bay. South of Monterey Bay and west of the Nacimiento
fault, sediments of the shelf are underlain by the Franciscan core complex (Page,
1966, Figure 6). The results of our investigations are entirely consistent with the
hypothesis of Page (1966). Furthermore, because the trends of the Salinian block are
slightly to the west of the shoreline, Franciscan basement would be expected to occur
west of the shelf break, north of 36°30'N (Figure 3); the presence of faulted basement
blocks beneath the slope at 36°50'N (DD', Figure 2) and 37°20'N (CC\ Figure 2)
has been noted.
B. CONTINENTAL RISE SOUTH OF 37 °N
The thalwegs of the more important sea valleys on the lower continental slope and
continental rise, inferred by the authors from the TGS fathograms, are shown on the
bathymetric map (Figure 2).
The existence of a tight meander in the Monterey deep-sea valley system, at 36°15'N,
122°50'W (map, Figure 2), was first established by Shepard (1966, Figure 1); he also
showed that the valley which drains southward from the meander just east of 123°W
does not breach the wall of the main canyon. South of 36 °N, what is presumed to be
the main channel of the Monterey system trends somewhat east of south toward the
flank of Davidson Seamount, as has been shown by Dill et al. (1954, Figure 2); a
secondary valley branches off to the southwest. South of 35°30'N the main channel
also swings southwestward and breaks up into a number of distributary channels.
Although the TGS investigation included east-west bathymetric profiles at approx-
imately 18-km intervals, Pioneer Canyon could not be traced beyond the base of the
continental slope. The depressions delineated by the 3800-, 4000-, and 4200-m
isobaths between 36 °N and 37 °N (Figure 2) are marked by a number of valleys;
although some of these are fairly well-developed, no single valley could be traced
from one bathymetric profile to the next.
Throughout the area south of 37'30'N, two distinct types of internal structure can
be recognized in the sediments of the continental rise. The first is characterized by
near-horizontal, continuous reflectors which are independent of structural relief of
the basement or underlying strata, and usually form a smooth sea-floor profile, con-
cordant with the regional gradient. On the upper and middle continental rise, these
sediments form floodplain-like deposits which rise tens or even hundreds of meters
above the regional level of the sea floor, and extend laterally from the axes of deep-sea
valleys for a hundred kilometers or more. Such deposits often are impounded by local
topographic highs (124°25'W, 126°50'W, FF', Figure 2). In the transition zone be-
tween the typical profile of the abyssal hills and the smooth profile of the continental
rise, continuous reflectors can be seen to fill-in between the hills, forming broad, flat-
floored valleys (127°20'W, 127°50'W, BB', Figure 2); disappearance of the abyssal
CONTINENTAL TERRACE AND DEEP PLAIN OFFSHORE CENTRAL CALIFORNIA
153
Fig. 3.
hills topography from west to east across the lower continental rise usually can be
attributed to burial by this type of sediment. There is little doubt that these strata are
turbidites (Hamilton, 1967, Figure 10a).
The second type of sedimentary structure is characterized by 'soft' reflectors, often
154 L.AUSTIN WEEKS AND ROBERT K.LATTIMORE
with variable dip, which commonly extend for no more than 2-3 km along the profile.
Sea-floor outcrops of these strata frequently coincide with reversals or marked changes
in the regional depth gradient (124°30'W-125°W, HH', Figure 2) and often with a
zone of 'rough' topography (124°40'W-125°W, FF'; 37°N, JJ', Figure 2). Perhaps
the most significant characteristic of these reflectors is that they are to some degree
conformable with structural relief of the basement. An extensive blanket of sediments
containing zones of these discontinuous-conformable reflectors occurs south of 37 °N
at depths greater than 4000 m(124°15'W-124°25'W, DD', 124o30'VV-125°30'W, HH',
Figure 2); the zones range in thickness from 0.4 sec upwards. The presence of isolated
valleys in this area has been noted; despite the presence of such valleys, however, it is
impossible to relate these strata to any known major deep-sea channel system. South
of 36°15'N, similar deposits extend landward to the 3800-m isobath (JJ', Figure 2);
the seismic profiles show that they are overlain by near-horizontal, floodplain-like
turbidites which are associated with the Monterey deep-sea valley system. In some
localities, well-bedded, horizontal strata fill in valleys and other depressions in the
discontinuous-conformable sediments.
From consideration of their areal distribution, conformability, and relationship
with the overlying turbidites, it seems likely that strata containing the discontinuous-
conformable reflectors are composed predominantly of deposits formed in the deep
ocean by some means other than turbidite sedimentation. If these deposits can be
attributed to normal ('hemipelagic') sedimentary processes operating in the deep
ocean, the sediment column in any given locality would consist of varying admixtures
of 'normal' allogenic-abyssal and turbidite sediments; distinctive internal structures
would be expected only if one process or the other were predominant. A second pos-
sibility is that the discontinuous-conformable strata originally were horizontal, and
have been involved in post-depositional tectonic activity.
Regardless of the origin of the discontinuous-conformable reflectors, their nature
and distribution militate against their having been derived from the present Monterey
deep-sea valley system. These investigations suggest that deposits clearly associated
with the Monterey system actually may comprise only a relatively small part of the
blanket of sediments on the middle and lower continental rise between 35 °N and 37 °N.
C. DELGADA DEEP-SEA FAN
The topographic axis of the Delgada deep-sea fan is a broad, roughly symmetrical
ridge which originates at the base of the continental slope north of Delgada Canyon
(Shepard and Emery, 1941, Chart IV) and extends southwest to about 38°15'N
(Figure 2). Two deep-sea valleys lie southeast of this ridge, between its axis and the
base of the continental slope. Both valleys run generally south-southwest from where
they enter the area (39 °N) to about 38 °N, where they swing southwest and apparently
break up into a number of smaller distributary channels; one of these channels can
be traced as far as 37 °N, 126°30'W (Figure 2).
Between 39 °N and 38°10'N the westernmost of the two deep-sea valleys follows a
nearly straight course across the eastern flank of the axial ridge, and its valley seems
CONTINENTAL TERRACE AND DEEP PLAIN OFFSHORE CENTRAL CALIFORNIA 155
to have been incised into the ridge. South of 38°15'N, where the relief of the ridge
disappears, the channel begins to meander and constructional levees are present. This
valley is considered to be a member of the Delgada Canyon system (Figure 1).
Between 39 N and 38 °30'N, the eastern channel apparently occupies a broad, shal-
low valley, 10 km or more across, with relief on the order of 30 m. At depths greater
than 3800 m, this channel has a well-defined V-shape with relief of 40 m or more.
Bathymetric profiles between 38°20'N and 37°50'N show an asymmetric valley whose
cross-sections are consistent with the meandering course shown on the map (Figure 2);
levees first appear south of 38°10'N, at depths of about 3900 m.
Of the several sedimentary 'units' which can be distinguished in the Delgada deep-
sea fan, by far the most important in terms of volume are the turbidites. These deposits
cover the upper continental rise between 37°30'N and 39 °N (BB', AA', Figure 2) and
extend into the abyssal hills as far west as 128°W (BB', Figure 2), in some localities
beyond 128°30'W (Ewing et a/., 1968, Figure 7). As far south as 36 °N, turbidite
strata west of 126°30'Wmay be part of the Delgada deep-sea fan (FF', HH', Figure 2).
As has been shown by Menard (1964, plate) a tongue of turbidites, 20-40 km wide,
extends along the base of Pioneer Ridge at least as far west as 133°W. Stratified,
horizontal sediments were noted on seismic-reflection profile crossings of Pioneer
Ridge between 132°W and 133°W, and Naugler and Perry (personal communication)
describe a typical turbidite sequence from a core at 38°30'N, 132°W.
At 38°50'N (AA', Figure 2), the western slope of the ridge which forms the topo-
graphic axis of the fan consists of 0.1-0.2 sec of sediments lying unconformably upon
a thick sequence of near-horizontal strata that appear to be continuous with the tur-
bidites at the base of the continental slope. Extensive areas of the western slope are
characterized by a 'hummocky, terrain in which low (15-25 m) hills, sinusoidal in
section, occur at regular 1-2 km intervals along the profile. An example of this topo-
graphy can be seen in Profile AA' (Figure 2), where the hummocks are developed in
near-surface sediments which lie unconformably on the turbidites. Within the uppor-
most 0.1-0.2 sec of these sediments only a single reflector can be discerned - a nearly
continuous surface which is parallel with the present sea floor and which follows the
relief of the individual hummocks. The hummocky structure and the absence of
horizontal reflectors make it extremely unlikely that the near-surface sediments are
turbidites; probably, they are normal deep-ocean allogenic deposits, or 'pelagic'
sediments in the broad sense.
The southern end of the ridge consists of 0.4-0.6 sec of sediments in which the
reflectors are discontinuous and highly contorted (37°55'N-38°30'N, JJ', Figure 2).
These chaotic reflectors apparently have been observed also by Truchan et al. (1967,
p. 126) as "'cross reflections' exhibiting large apparent dips" covering an area from
the Delgada Channel (probably the eastern valley) to 38°30'N and 125°35'W. Land-
ward of this valley, these authors noted, the sub-bottom strata are nearly horizon-
tal.
The 'cross reflections' differ in several important respects from the discontinuous-
conformable reflectors described in the preceding section. Although short, the 'cross
156 L.AUSTIN WEEKS AND ROBERT K.LATTIMORE
reflections' are distinct and well defined. In contrast with the soft, discontinuous
reflectors, which may show sub-parallel orientation and commonly reflect basement
relief, the 'cross reflections' may be highly angular with respect to one another, and
usually are independent of relief of the basement. Significantly, the 'cross reflections'
are clearly associated with a major deep-sea valley system, as has been established by
Truchan et al. (1967, p. 126) and is illustrated in Profile JJ' (Figure 2).
The relation of the 'cross reflections' to sea floor stream channels, and their internal
structure and independence of basement relief suggest that the southern part of the
axial ridge (JJ', Figure 2) is composed of fossil channel levee and scour-and-fill
deposits. The suggestion that these are slump deposits or submarine landslides derived
from the shelf to the east is unsatisfactory in view of their distance from the base of
the continental slope, their areal extent (Truchan et al., 1967, p. 126) and the present
gradient of the ridge, which is a maximum of 20 m/km.
To summarize the preceding paragraphs, near 39 °N the ridge which forms the
topographic axis of the Delgada deep-sea fan consists of a succession of turbidites
overlain unconformably by 'normal' allogenic-abyssal sediments. To the south, both
give way to the 'cross reflections' which may have formed by reworking of older sedi-
ments. The eastern slope of the ridge is deeply incised by a stream valley that follows
a fairly straight course across it, forming an acute angle with the axis of the ridge near
38°15'N (Figure 2). Clearly, this pattern of sedimentation and valley morphology
cannot be explained in terms of a static environment; some element of tectonic activity
must be invoked to explain it.
Uplift of the continental shelf north of 39 °N might have increased the gradient of
an existing drainage system to the point that its valley would have been incised into
the axial ridge; the deepened channels would have contained all sediment moved
through the drainage system, so that 'normal' allogenic-abyssal sediments could have
accumulated on the flanks of the ridge undiluted by turbidite deposits. An equally
acceptable, alternate explanation for the incised valley and the accumulation of
'normal' deep-ocean sediments is uplift of the sea floor beneath the ridge, proper. If it
may be further postulated that this uplift began in the north and progressed south-
ward, several other major features of the area also are accounted for. The course of
any major deep-sea valleys, prior to the uplift, may have been normal to the continental
slope, and a thick sequence of turbidites built seaward across the continental rise.
Uplift of the ridge, progressing from north to south, would have diverted the channels
southward, exposing older sediments to erosion and reworking. Beyond the area of
uplift the channels, once again under influence of the regional topographic gradient,
would swing westward and erosional relief of the valleys would disappear. The south-
eastward migration of the channels across the southern half of the ridge would account
for formation of the 'cross reflections' and, particularly, for the fact that they seem to
occur only to seaward of the distributary valleys (Truchan et al., 1967, p. 126). The
wedge of turbidites shown in Profile AA' (Figure 2) is simply an erosional remnant
covered by subsequent normal deep-ocean sediments. Tectonic activity associated
with uplift of the ridge also would account for displacements of the basement, often
CONTINENTAL TERRACE AND DEEP PLAIN OFFSHORE CENTRAL CALIFORNIA 157
accompanied by distortion of overlying continuous reflectors, which are found in the
middle continental rise north of 37J30'N.
The ridges which extend westward from the base of the continental slope at approx-
imately 37°15'N and 37°30'N (Figure 2) enclose a basin which may be receiving
little if any terrigenous sand (Uchupi and Emery, 1963, p. 427; Wilde, 1965, Figures
9-11) despite proximity to the drainage system which empties into the Pacific through
the Golden Gate. Just north of the ridge at 37°05'N, the sediments are no thicker
than 0.3 sec (HH', Figure 2). Along the axis of the basin, at 37°20'N, a seismic record
of marginal quality (not shown) suggests a maximum of 0.6 sec and a minimum of
0.2 sec of sediment overlying an extremely irregular basement surface. At least the
upper 0.2-0.3 sec of these sediments are turbidites.
D. BASEMENT TRENDS IN THE CONTINENTAL RISE
The ridges which extend westward from the base of the continental slope at 37°05'N
and 37°30'N are only two of at least five topographic features with marked east-west
orientation which occur on the upper continental rise north of 37 °N (Figure 2).
Profile HH' (Figure 2) suggests that the ridge at 37°05'N reflects basement structure;
the presence of knolls on the distal ends of the ridges at 37°45'N and 38°10'N supports
the conclusion that the ridges are primarily basement structures.
Although there is no correlation between these east-west trends and the magnetic-
anomaly pattern north of 37 °N (see Mason and Raff, 1961, Figure 2 ; Lattimore et al.
1968a), the ridges all seem to end at about 124°40'W, which coincides with the axis
of the easternmost 'typical' deep-ocean magnetic anomaly lineation. This anomaly,
whose north-south trend truncates the anomalies of the upper continental rise between
36 °N and 38°30'N, also coincides with the western flank of another low ridge (defined
by the 4000-m isobath) that extends due south from approximately 37 °N to 36°30'N
(Figure 2). From Profiles HH' and J J' (Figure 2), it may be seen that at least the north-
ern tip of this north-south ridge reflects structural relief of the basement.
These observations suggest that there is, in fact, a relationship between the magnetic
anomalies and the structure of the upper continental rise; for example, the crust may
change from typical oceanic to intermediate at 124°40'W.
E. PIONEER RIDGE
The TGS seismic-reflection investigation of Pioneer Ridge was limited to a profile
along the ridge at 38°50'N (AA', Figure 2) and two north-south crossings west of
130 °W (not shown). These profiles, together with those of Ewing et al. (1968, Figure 7)
and Winterer et al. (1968, Figures 2-5), yield some idea of the gross structure of this
feature. West of 126°W, the general level of the basement north of 38°40'N is about
0.5 sec higher than beneath the continental rise and abyssal hills to the south (compare
AA' and BB', Figure 2; Winterer et al., 1968, Figures 2a-2c). The ridge which usually
occurs on the southern margin of this uplifted block, west of 127°30'W, represents an
additional 400 m or 0.5 sec of basement relief.
West of 127°30'W the basement associated with Pioneer Ridge can be described in
158 L. AUSTIN WEEKS AND ROBERT K. LATTIMORE
terms of short-wavelength features of low, regular amplitude, which are morphologi-
cally similar to the structure of the abyssal hills (AA\ Figure 2; Winterer et al, 1968,
Figure 2d). East of 127°W, relief of the basement appears to be irregular and of
greater amplitude, and the pattern more nearly resembles the basement structure
found beneath the middle and upper continental rise (Figure 2).
Although the 'magnetic structure' of Pioneer Ridge extends at least as far east as
127°W (Mason and Raff, 1961, PI. 1) topographic relief on the ridge does not
extend beyond 127°40'W (Figure 2) and it is obvious from the profiles shown by
Winterer et al. (1968, Figure 2) that the gross structure of the feature changes marked-
ly, near the meridian. The bathymetric data compiled from the TGS investigation
suggest that the low ridge at 126°W, defined by the 4000-m isobath, has an east-
northeast trend (Figure 2), but the map prepared by Menard (Winterer et al., 1968,
Figure 7) shows this ridge as being oriented almost east-west, and Winterer et al. present
data in support of the idea that the feature is a continuation of the Pioneer trend.
Profile AA' (Figure 2) shows that terrigeneous sediments, mostly turbidites, extend
along the north slope of Pioneer Ridge for about 300 km west of the base of the con-
tinental slope. At 127°W, 0.2 sec of horizontally-stratified deposits overlie thinner,
acoustically-transparent beds which are conformable with the bedrock topography.
West of 127°30'W acoustically transparent sediments predominate. Between 127°30'W
and 128°30'W such deposits average 0.3 sec in thickness, or about double the average
thickness of pelagic sediments on the abyssal hills south of the ridge. The north-south
profile of Ewing et al. (1968, Figure 7) shows that at 128°30'W these same sediments
thicken to the north. These data support the hypothesis of Winterer et al. (1968, p.
518) that sediments in the northern part of the Delgada fan may be at least partially
derived from north of the Mendocino Escarpment.
F. ABYSSAL HILLS
At a distance of 400-500 km from the base of the continental slope the distinctive,
parabolic profiles of the abyssal hills emerge from beneath a waning cover of terri-
genous sediments. Within the abyssal hills province, maximum relief is found in ridges
and seamounts along the northern and eastern margins; these stand 600 m or so
above the surrounding sea floor (Figure 2). Otherwise, the entire province east of
1 33 °W falls in the 4600-5400 m depth range (Lattimore et al, 1 968). Relief on individ-
ual hills seldom exceeds a few hundred meters, and width along the base generally
is 2.5 km or less. Slope gradients approaching 10 per cent are not uncommon.
The basement structure of the abyssal hills typically is covered by a conformable
mantle of acoustically-transparent sediments, undoubtedly equivalent to the 'pelagic'
sediments of Hamilton (1967, p. 4202). This mantle rarely is more than 0.15 sec thick,
and zones in the southwestern part of the study area are completely devoid of per-
ceptible sediments (FF', Figure 2).
As may be expected, turbidites do not vanish abruptly from the sediment column.
Almost every east-west profile contains a transition zone, up to 1 50 km wide, in which
basement features covered with a conforming mantle of acoustically-transparent
CONTINENTAL TERRACE AND DEEP PLAIN OFFSHORE CENTRAL CALIFORNIA 1 59
sediments rise above horizontal, stratified sediments filling adjacent lows (FF',
Figure 2). Flat-floored valleys suggesting turbidite sedimentation are common through-
out the area of investigation.
4. Summary
The Transcontinental Geophysical Survey seismic-reflection profiles support the
hypothesis that the gross patterns of the geology of the Coast Ranges of California
are present beneath the continental shelf and slope. In particular, the broad, fiat con-
tinental shelf from Pigeon Point north to Cordell Bank may be attributed to the
occurrence of a crystalline ridge along the edge of the shelf; Page (1966, Figure 1)
has suggested that this is an extension of the Salinian block that forms the basement
beneath the Coast Ranges south of Monterey Bay. The more deeply-incised continen-
tal shelf and less precipitous upper continental slope south of Monterey Canyon are
believed to reflect the presence of the Franciscan basement complex overlain by a
sequence of folded and faulted sedimentary rocks, as also suggested by Page (1966,
Figure 6). Basement blocks beneath the middle and lower continental slope, north
of 37 °N, may be a continuation of the Franciscan complex.
On the continental rise south of 37 °N, the course of the Monterey deep-sea valley
has been traced south and southwest from the meander at 36°15'N, 122°50'W, mapped
by Shepard (1966, Figure 1). Pioneer Canyon could not be traced beyond the base of
the continental slope.
Turbidites on the continental rise are characterized by near-horizontal, continuous
reflectors; they tend to be concordant with the regional topographic gradient and
independent of structural relief on the strata or basement beneath them. On the upper
rise, south of 37 °N, these sediments form floodplain-like deposits clearly associated
with the distributary system of the Monterey deep-sea valley.
Below 3800-4000 m a significant proportion of the sediment column is characterized
by 'soft', discontinuous reflectors which tend to be conformable with structural relief
of the basement and cannot be related to any known deep-sea valley system; in places,
these strata are overlain unconformably by horizontally-stratified turbidites. While
the origin of these discontinuous-conformable reflectors is uncertain, it is clear that
they are not related to the present Monterey deep-sea valley system.
Turbidite deposits which are related to the Delgada deep-sea fan comprise the
continental rise north of 37°30'N; turbidites cover abyssal hills east of 128°W, and
extend south of 36°.N. A tongue of turbidite strata extends along the base of Pioneer
Ridge at least as far west as 133°W, as shown by Menard (1964, plate). Our investiga-
tions show that turbidites occur also north of Pioneer Ridge, between 126°50'W and
127°20'W.
Near 39 °N the ridge which forms the topographic axis of the Delgada deep-sea
fan consists of a sequence of turbidites overlain unconformably by 0.1-0.2 sec of
normal allogenic-abyssal or 'pelagic' sediments. The southern end of this ridge is
made up of 'cross reflections', probably the same as those observed by Truchan et al.
(1967), which we interpret as having resulted from submarine scour-and-fill or rework-
1 60 L. AUSTIN WEEKS AND ROBERT K. LATTIMORE
ing of older sediments. The ridge is incised by a valley with steep walls and a flat floor,
which follows a nearly straight course southwestward across it. Although the struc-
ture of this ridge implies a change in the sedimentary environment in response to
tectonic activity, several alternative explanations can be offered which are consistent
with the available data. The preferred explanation is that the ridge has undergone
uplift progressing from north to south.
A pattern of abrupt changes in depth-to-basement, which is associated with the
sedimentary ridge, could be related to epeirogenic activity. An alternate explanation
is offered by Winterer et al. (1968, pp. 510-514), namely, that the structure of Pioneer
Ridge extends into or beneath the sedimentary ridge.
The low east-west ridges on the upper continental rise north of 37 °N are con-
sidered to be indicative of basement structure. While there is no direct correlation be-
tween these trends and the magnetic anomaly pattern (Mason and Raff, 1961, Plate 2;
Lattimore et al., 1968a) neither these trends nor the magnetic anomaly pattern of
the upper continental rise extend west of 124°40'W - the axis of the easternmost
'typical' deep-ocean magnetic anomaly.
A broad picture of the basement structure associated with Pioneer Ridge can be
drawn from our investigations, the profile published by Ewing et al. (1968, Figure 7)
and the report of Winterer et al. (1968). North of 38°40'N the basement stands about
0.5 sec higher than the basement beneath the sea floor to the south. When present, the
topographic ridge which runs along the southern margin of this raised block represents
an additional 0.5 sec of basement relief. That this structural pattern is modified east
of 127°40'W is indicated by the bathymetry as well as by the seismic-reflection inves-
tigations of Winterer et al. (1968, Figure 2). The TGS data neither support nor contra-
dict the inference of Winterer et al. (1968) that the Pioneer trend extends eastward
from 127°40'W beneath the sediments of the Delgada fan. Our data and that of
Ewing et al. (1968) do substantiate the proposal of Winterer et al. that 'pelagic'
sediments on Pioneer Ridge may have been derived partially from north of the Men-
docino Escarpment.
Seismic-reflection observations in the abyssal hills reveal that conformable, acous-
tically-transparent 'pelagic' sediments rarely exceed 0.15 sec in thickness; in the south-
western part of the area they do not appear at all.
Acknowledgements
The authors thank S. P. Perry (ESSA, Pacific Oceanographic Research Laboratories),
J. M. McAlinden and C. X. G. Fefe (U.S. Coast and Geodetic Survey) and F. M.
Edvalson (U.S. Naval Oceanographic Office) for providing supplementary data on
the deep-sea cores and bathymetry within the TGS area. G. F. Merrill and F. P. Sauls-
bury (ESSA, Atlantic Oceanographic and Meteorological Laboratories) supervised
cartography and drafting of the figures. The manuscript was critically reviewed by
L. W. Butler, G. H. Keller, and G. Peter (ESSA, Atlantic Oceanographic and Meteo-
rological Laboratories).
CONTINENTAL TERRACE AND DEEP PLAIN OFFSHORE CENTRAL CALIFORNIA 161
References
Bums, R. E. and Grim, P. J.: 1967, 'Heat Flow in the Pacific Ocean off Central California', J.
Geophys. Res. 72, 6239-47.
Curray, J. R.: 1965, 'Structure of the Continental Margin off Central California', N. Y. Acad. Sci.
Trans., Ser. II 27, 794-801.
Dill, R. F., Dietz, R. S., and Stewart, H.: 1954, 'Deep-Sea Channels and Delta of the Monterey
Submarine Canyon', Bull. Geol. Soc. Am. 65, 191-94.
Ewing, J., Ewing, M., Aitken, T., and Ludwig, W. J. : 1968, 'North Pacific Sediment Layer Measured
by Seismic Profiling'; 147-173 in Knopoff, L., Drake, C. L. and Hart, P. J. (eds.), 'Crust and
Upper Mantle of the Pacific Area', Am. Geophys. Un. Geophys. Mon. 12, 522 p.
Hamilton, E. L.: 1967, 'Marine Geology of Abyssal Plains in the Gulf of Alaska', J. Geophys. Res.
72, 4189-4213.
Heezen, B. C. and Menard, H. W.: 1963, 'Topography of the Deep-Sea Floor'; 233-280 in Hill,
M. N. (ed.) The Sea 3, New York, Interscience, 963 p.
Lattimore, R. K., Bassinger, B. G., and DeWald, O. E.: 1968, 'Transcontinental Geophysical Survey
(35°-39°N) - Magnetic map from the Coast of California to 133°W Longitude', U.S. Geol. Surv.
Misc. Geol. Inv., Map I-531-A.
Lattimore, R. K., Bush, S. A., and Bush, P. A.: 1968, 'Transcontinental Geophysical Survey
(35°-39°N)- Gravity and Bathymetric Map from the Coast of California to 133°W Longitude',
U.S. Geol. Surv. Misc. Geo!. Inv., Map I-531-B.
Mason, R. G.: 1958, 'Magnetic Survey off the West Coast of the United States between Latitudes
32° and 36 °N and Longitudes 121° and 128°W, Geophys. J. Roy. Astron. Soc. 1, 320-29.
Mason, R. G. and Raff, A. D.: 1961, 'Magnetic Survey off the West Coast of North America, 32 °N
Latitude to 42 °N Latitude', Bull. Geol. Soc. Am. 72, 1259-66.
Menard, H. W. : 1955, 'Deformation of the Northeastern Pacific Basin and the West Coast of North
America', Bull. Geol. Soc. Am. 66, 1149-98.
Menard, H. W : 1960, 'Possible Pre-Pleistocene Deep-Sea Fans off Central California', Bull. Geol.
Soc. Am. 71, 1271-78.
Menard, H. W.: 1964, Marine Geology of the Pacific, McGraw-Hill, New York, N.Y., 271 p.
Page, B. M.: 1966, 'Geology of the Coast Ranges of California', 255-76, in Bailey, E. H. (ed.),
'Geology of Northern California', Bull. Calif. Div. Mines and Geology 190, 508 p.
Shepard, F. P. and Emery, K. O.: 1941, 'Submarine Topography off the California Coast: Canyons
and Tectonic Interpretation', Geol. Soc. Am. Spec. Paper 31, 171 p.
Shepard, F. P.: 1966, 'Meander in Valley Crossing a Deep-Ocean Fan', Science 154, 385-86.
Taliaferro, N. L.: 1951, 'Geology of the San Francisco Bay Counties', 117-50, in 'Geologic Guide-
book of the San Francisco Bay Counties', Bull. Calif. Div. Mines 154, 392 p.
Truchan, M., Windisch, C. C, and Hamilton, G. R.: 1967, 'Detailed Bathymetric and Seismic
Reflection Survey of a Portion of the Delgada Deep-Sea Fan and its Channel' (abs.), Am. Geophys.
Un. Trans. 48, 126-27.
Uchupi, E. and Emery, K. O.: 1963, 'The Continental Slope between San Francisco, California and
Cedros Island, Mexico', Deep-Sea Res. 10, 397^147.
U.S. Upper Mantle Committee: 1965, United States program for the international Upper Mantle
Project: Progress report - 1965: Washington, D.C., Nat. Acad. Sci. - Nat. Res. Council.
Vacquier, V., Raff, A. D., and Warren, R. E.: 1961, 'Horizontal Displacements in the Floor of the
Northeastern Pacific Ocean', Bull. Geol. Soc. Am. 72, 1251-58.
Wilde, P.: 1965, 'Recent Sediments of the Monterey Deep-Sea Fan', Univ. California (Berkeley),
Hydraulic Eng. Lab. Tech. Rept. HEL-2-13.
Winterer, E. L., Curray, J. R., and Peterson, M. N. A.: 1968, 'Geologic History of the Intersection
of the Pioneer Fracture Zone with the Delgada Deep-Sea Fan, Northeast Pacific', Deep-Sea Res.
15, 509-20.
66
Reprinted from The American Association of Petroleum
Geologists Bulletin 55_, No. 10, 1741-1752 .
Structural Relations Among Lesser Antilles, Venezuela, and Trinidad-Tobago1
L. AUSTIN WEEKS,3 R. K. LATTIMORE,' R. N. HARBISON,8
B. G. BASSINGER," and G. F. MERRILL3
Miami, Florida 33158
Abstract More than 2,500 n. mi (4,630 km) of seismic
reflection profiling, gravity, magnetics, and bathymetric
data were collected in the southeastern Caribbean by the
ESSA Coast and Geodetic Survey ship Discoverer in
1968-1969.
A review of the structural geology of the southeastern
Caribbean and the South American continent in conjunc-
tion with the ESSA data supports a relatively simplistic
explanation for the geologic structure. The Barbados
Ridge is a greatly fractured anticlinorium, supported by
"basement" rocks, and consisting of two parallel arches
with a central syncline. The Lesser Antilles volcanic arc,
the Tobago trough, and the Barbados anticlinorium are
traceable into the Venezuelan and Trinidadian shelves
(South American continent).
An analogy between the Caribbean and Indonesian
island arcs shows the validity of the concept of continua-
tion of continental mobile belts into island arc systems.
The mobile belt and the island arc system are analogous
manifestations of orogeny in different crustal types. Evi-
dence is against wrench faulting, with its implication of
vast horizontal movements of individual blocks. The island
arc structural belts and the mobile belts of the continent
are interrelated, gradational, and interlocked.
Introduction
In 1968 the ESSA ship Discoverer began a
continuing geophysical study of the southern
Lesser Antilles, the Venezuelan and Trinida-
dian shelves, and the Barbados Ridge.
The primary purpose of this study is to de-
termine the structural configuration of the
Lesser Antilles island arc system and its rela-
tion to the South American continent. Previ-
ously, the senior writer and others conducted a
similar study in the Andaman Sea during the
International Indian Ocean Expedition in 1964
(Peter et al, 1966; Weeks et al, 1967). Simi-
larities between the Andaman-Nicobar Islands
and the Lesser Antilles led to a similar though
expanded study of the Caribbean eastern mar-
gin.
This paper is a synthesis of the ESSA data
1 Manuscript received, August 24, 1970; accepted,
December 3, 1970.
2 Consultant, 13720 SW 78th Court.
'National Oceanic and Atmospheric Administration
(NOAA), Atlantic Oceanographic and Meteorological
Laboratories.
© 1971. The American Association of Petroleum Geologists.
All rights reserved.
presented in the preceding papers in this Bulle-
tin by Lattimore et al. (1971) and Bassinger et
al. (1971), and of the known structural geol-
ogy of the island arc system and the northeast-
ern part of the South American continent. A
structural analogy between the Lesser Antilles
and Indonesian arcs is presented.
Ths 1969 study area was bounded by long.
58°30'-63°W and lat. 10°-12°30'N. Within
that area more than 2,500 n. mi (4,630 km)
were covered by seismic reflection profiling,
gravimeter, magnetometer, and echo sounding
observations. Additional gravimetric, magnetic,
and bathymetric data were collected along vari-
ous transects of the area. Figure 1 shows ba-
thymetry and track lines within the study area.
Structural Belts
An interpretative cross section across the
Lesser Antilles island arc system from the Ven-
ezuela basin through the Aves Ridge, Lesser
Antilles, Barbados anticlinorium, and interven-
ing troughs (Grenada Trough, Tobago Trough,
Central syncline) is shown in Figure 2. The
vertical scale is exaggerated to show the struc-
tural features more clearly.
Venezuela Basin
The west end of the section (Fig. 2) starts in
the eastern Venezuela basin, on the west flank of
the Aves Ridge. According to Edgar (1968;
Fig. 3 this report), there are about 2 km (1V4
mi) of sediments, of velocity less than 5 km/
sec (3.1 mi/sec), within the central part of the
Venezuela basin, thickening to about 5 km (3.1
mi) on the western flank of the Aves Ridge.
Sediments are thinnest within the central part
of the basin and thicken toward the flanks of
the basin in all directions. Ewing et al. (1967)
showed that the sediments of the Venezuela ba-
sin are flat and undisturbed, indicating a lack
of deformation or tectonic activity within the
block. The basin as a unit has had a relatively
stable tectonic history with only minor defor-
mation around the edges of the plate. It is seis-
mically inactive. Ewing et al. (1967) con-
cluded that stability of the Caribbean subbasins
1741
1742
Weeks, Lattimore, Harbison, Bassinger and Merri'I
t
WOlf Wild
lOGIS 1SV3
3NH3NAS 1V11N23
10018 1S3M
3NI1DNAS OOVSOi 1
3NHDI1NV OeviOlN
!
t
I
fc.S
£5
" 3
1.S
~ c
<u cs
> o
u —
>
H >
73 c3
C
"c7S c
i
•< «
1) G
S .2
►J —
w (J
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ca
O.T3
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B O
1744
Weeks, Lattimore, Harbison, Bassinger and Merritl
Fig. 3. — Lamont refraction data. Isopachs of less than
5 km/sec-layers are in 1-km intervals.
seems to preclude sea-floor spreading or hori-
zontal movement, implying rather a dominant
role of vertical movements instead.
Aves Ridge
The Aves Ridge is considered to be part of
the island arc system, as its gross characteristics
relate more to the arc than to the Venezuela
basin. Sediments on the east flank of the ridge
plunge unconformably beneath younger turbi-
dites of the Grenada Trough (Edgar, 1968).
The unconformable relation between older
folded beds and younger relatively flat-lying de-
posits is characteristic of the basinal areas of
the double island arc system (Fig. 2). In addi-
tion, the Carib beds of the Venezuela basin are
not identified east of the western flank of the
Aves Ridge. These sediments are the deep-wa-
ter deposits identified over much of the Carib-
bean west of the Aves Ridge (Ewing et al.,
1967).
Bunce et al. (1970) showed a generalized
crustal structure section from the Venezuela
basin to the Atlantic Ocean. The crust thickens
considerably in the eastern Venezuela basin,
under the Aves Ridge and the rest of the island
arc system, and does not thin again until the
Atlantic Ocean is reached. Aves Ridge is, there-
fore, part of the thickened crust of the island
arc system. Depth to mantle is roughly the
same in the eastern Venezuela basin and the
Atlantic Ocean, just east of the Barbados Ridge
or anticlinorium.
The Aves Ridge is aseismic, nearly neutral in
gravity, and approximately enclosed by the
1,000-fm (1,830 m) isobath. The only segment
of the ridge above sea level is Aves Island, a
small, low 3-m (9.9 ft) maximum feature cov-
ered by calcareous sediments. Bedding strikes
N70E, and dips toward the north and south
(Maloney et al., 1968). This strike is subparal-
Iel with strikes normal to the arc system found
in Barbados and Grenada (Lesser Antilles).
Dredging on the ridge has produced basalt
(Hurley, 1966), glassy flows and brecciated
rocks of possible eruptive origin (Marlowe,
1968), and much granite (recent cruise of R/V
Eastward). The latter cruise dredged over 2
tons of light-colored granitic rocks from more
than 50 locations along the ridge.
Aves Island has been decreasing slowly in
size since the last century, and a slow epeiro-
genic subsidence of the whole ridge may be in-
dicated. Such subsidence after positive eleva-
tion in tectonic trends is quite widespread (e.g.,
Weeks et al., 1967).
Grenada Trough
East of the Aves Ridge is the Grenada
Trough (Fig. 2). Sedimentation in the Grenada
Trough is distinct from that in the Venezuela
basin. From the Grenada Trough eastward,
flank sediments off the positive areas dip be-
neath the relatively flat sediments of the inter-
vening Grenada and Tobago Troughs (negative
areas within Barbados anticlinorium). The
deeper parts of the Grenada Trough are east of
the structural axis of the basin; therefore,
asymmetry is eastward, toward the Atlantic
Ocean. The unconformity between flank sedi-
ments dipping into the trough and the younger
flat-lying beds is typical of the negative areas in
the arc system. Edgar (1968; Fig. 3, this re-
port) shows 4-7 km (2.5-4.4 mi) of sedi-
ments, a greater thickness than in the Venezu-
ela basin.
Volcanic Arc
The volcanic arc of the Lesser Antilles forms
a long graceful curve, convex toward the At-
lantic. The arc is also asymmetric, with topo-
graphic slopes steeper on the west.
Volcanic activity in the Lesser Antilles has
continued into recent geologic time, whereas it
ceased in the Greater Antilles (except Hispanio-
la [MacDonald and Melson, 1969] during the
Eocene (MacGillavry, 1970). MacGillavry
considered that this cannot be explained by a
quiescent episode of ocean-floor spreading. Ac-
cording to Lewis (1968, p. 44-45) the "Basal-
tic rocks occurring in the Lesser Antilles are
directly comparable to chemical composition
and mineralogy with basalts from other circum-
Lesser Antilles, Venezuela, and Trinidad-Tobago
1745
oceanic islands and from orogenic belts on
the continental margins. Basalts of this type,
characterized by a high alumina and low alkali
content, are distinct from olivine tholeiites of
the ocean basins and from alkali basalts of the
intraoceanic islands."
Earle (1924, 1928), describing the southern
Antilles, mentioned folding in Grenada that is
approximately east-west, similar to strikes found
on Aves Island, Barbados, and Trinidad. More
recently, Martin-Kaye and Saunders (1962)
described an upper Eocene sedimentary series
(Tufton Hall Formation) in northern Grenada.
The series consists of several hundred feet of
folded, repetitively bedded graywacke and
shale, with a fauna suggesting deposition at
bathyal depth. It is tempting to correlate these
deposits with the lower Scotland Group of Bar-
bados (Baadsgaard, 1960), also considered to
have been deposited at bathyal depth and
folded with a pronounced northeast-southwest
strike. Marine limestone at 180 m (600 ft) of
elevation attests to later epeirogenic uplift in
Grenada.
The most volcanically active segment of the
arc is near the center, as the most recent vol-
canism is restricted to that part. The synchro-
nous eruption of Soufriere (St. Vincent) and
Pelee (Martinique) in 1902 indicates a deep
common origin.
Seismically, the Lesser Antilles overlie a
zone of intermediate depth earthquakes (Sykes
and Ewing, 1965). Most of the hypocenters are
confined to a zone about 50 km (31 mi) wide,
dipping about 60 °W.
Tobago Trough
East of the volcanic arc is the Tobago
Trough, whose surface is about 500 fm (915 m)
shallower than the Grenada Trough (Fig. 2).
The trough is elliptical, asymmetrical toward
the east, with the deeper parts near the Barba-
dos anticlinorium (Fig. 1). The topographic
axis is east of the structural axis, which contin-
ues southwest, depressing the Paria shelf (Figs.
1, 3). The total area of the Tobago Trough,
even including the part on the Paria shelf, is
less than half that of the Grenada Trough. This
is a result of its termination on the north by a
structural feature, herein termed the "St. Lucia-
Barbados cross-warp" (Fig. 5).
The ESSA data indicate that younger, rela-
tively flat-lying sediments unconformably over-
lie folded sediments which plunge under the
Tobago Trough from both sides. Major contri-
bution of sediment is from the south and per-
ANDAMAN SEA
, MOBILE BELTS
(Continent)
5 4 3 2 1
CARIBBEAN SEA
Fig. 4. — Double island arc system structural belts
as seen in Andaman Sea (Indonesian Arc) and Eastern
Caribbean (Lesser Antilles). See Table 1 for descrip-
tion of specific belts. Belts: 1. stable platform; 2. back-
deep; 3. inner volcanic arc; 4. interdeep; 5. outer sedi-
mentary arc and/or foredeep (trench).
haps southeast, with smaller amounts from the
Lesser Antilles. Sediment thickness exceeds 10
km (6.2 mi, Fig. 3). Minimum thickness of
sediments of similar velocities is 4 km (2.5 mi)
at the southwest end of the Paria shelf, just off
the Araya-Paria Peninsulas (Pilar block),
reaching the maximum of more than 10 km
(6.2 mi) on the northeast, just west of, and in-
cluding Barbados. Tobago Trough sediments
are now more than five times as thick as those
in the Venezuela basin, having thickened grad-
ually eastward across the island arc system
(Fig. 3).
Barbados Anticlinorium
The Barbados anticlinorium was described
earlier as a double ridge with a central syncline
or trough. The Central syncline surface is
somewhat above the general level of the To-
bago Trough. However, the Tobago Trough is
larger than the Central syncline in areal extent
and volume. Sediment isopachs based on re-
fraction data are oriented approximately east-
west, with thickening northward toward Barba-
dos (Fig. 3).
The inference of a southern source of supply
for Barbados and the Tobago Trough is strong.
East-west structural lineations in the Pilar
block, and in some structures on Barbados it-
self, parallel the isopachs in every respect.
The seismic profiles suggest that the base-
ment of the West ridge (Barbados anticlino-
1746
Weeks, Lattimore, Harbison, Bassinger and Merrill
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ea .y «-
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Lesser Antilles, Venezuela, and Trinidad-Tobago
1747
rium) plunges northward under the island of
Barbados, a plausible phenomenon in view of
the northward thickening of sediments (Fig. 3).
The folded sediments of the East ridge and of
the generally higher West ridge also plunge un-
der the younger flat-lying sediments of the Cen-
tral syncline.
Thus, the section from the Venezuela basin
across the Barbados anticlinorium (Fig. 2)
shows essentially a typical double island arc
system. At the west is the Venezuela basin; at the
east, the Atlantic basin; the apex is at the inner
volcanic arc of the Lesser Antilles. Even where
the outer sedimentary arc ceases to exist north
of the Barbados anticlinorium, alternation of
positive and negative structures prevails. Basins
and ridges are approximately equidistant in
their spacing. The Barbados anticlinorium is at
about the same distance from the Lesser An-
tilles as the Aves Ridge. One cannot but believe
that an overall pattern of structural "waves" is
involved in the development of this double arc.
Island Arc Structure, Development,
and Analogies with Indonesian Arc
A structural development very similar to that
of the Caribbean island arc was noted in the
Indonesian island arc by Weeks et al. (1967)
and a direct comparison can be made (Fig. 4).
The Indonesian arc in the Andaman Sea area
and the Lesser Antilles arc of the eastern Ca-
ribbean are both double arc systems, in that
both inner volcanic and outer sedimentary arcs
are represented. The terminology used by the
senior Writer in the Andaman Sea, following
that of van Bemmelen (1949), is equally appli-
cable to the eastern Caribbean (Fig. 4; Table
1). Its advantage lies in its simplicity of terms,
which are self-explanatory.
Both the Indonesian and Lesser Antilles is-
land arc systems are characterized by inner vol-
canic arcs, outer sedimentary arcs, backdeeps,
interdeeps, and foredeeps — present or former
Abbreviations :
CR = Curacao ridge
G =Grenada Is.
LR =Los Roques Is.
SL-B =St. Lucia-Barbados cross-warp
0=Orchila Is.
B = Barbados Is.
C = Caracas
To =Tobago Is.
Bl =Blanquilla Is.
NTA = North Tobago anticline
LH =Los Hermanos Is.
ETS =East Tobago syncline
A =Aves Is.
WR =West ridge
M =Margarita Is.
CS =Central syncline
LF=Los Frailes Is.
ER =East ridge
LT = Los Testigos Is.
trenches (Fig. 4). Table 1 lists the similarities
in structure and gravity of the several arcuate
belts in both the Andaman Sea and the eastern
Caribbean.
The pattern of development in an island arc
system is one of growth toward the ocean plate,
not only normal to the arc but, in certain re-
spects, also axially. Growth in both directions,
normal and axial to the arc, occurs over a con-
siderable period of time, or a diastrophic cycle.
The cycle includes periods of orogeny and
epeirogeny, as well as relaxation and/ or exten-
sional collapse. In the sense that double arcs
are continuations of continental orogenic belts,
the axial growth is quite evident, but axial
growth within the outer island arc-foredeep
belts of the system proper is becoming increas-
ingly apparent. Axial growth explains the dual
roles and interrelations between the outer sedi-
mentary arc and the foredeep or trench (belt 5,
Fig. 4).
The development of the outer sedimentary
arc is of greatest interest in defining the interre-
lations not only of the outer sedimentary arc
with the foredeep or trench, but also of the
outer arc-foredeep with the orogenic belt of the
continent. It is the key to the interlocking rela-
tion between the continental crust and the in-
termediate or oceanic crust. It is a mutual rela-
tion that is gradational in nature — axially,
rather than normal to the arc system.
The writers believe that a double island arc
system is a continuation of a continental mobile
belt. In the Indonesian arc the orogenic belt of
the Himalayas-Arakan Yoma (western Burma)
continues by gradation into the Indian Ocean
via the Andaman-Nicobar-Mentawai islands, or
the outer sedimentary arc. At the distal end of
the outer island arc the foredeep or trench be-
comes prominent (belt 5, Fig. 4). As shown in
Table 1, the outer island arc is most completely
developed where the foredeep is not and, con-
versely, the foredeep is best developed where
the outer island arc is not. It is apparent that
one cannot develop except at the expense of the
other; hence, they must be mutually interre-
lated and gradational. The outer arc is the posi-
tive manifestation of the foredeep (negative
feature). Both the foredeep and the outer island
arc contain sedimentary rocks. Abyssal deposits
of Barbados, the Oceanic Group (Baadsgaard,
1960), are testimony to the earlier foredeep na-
ture of the outer arc in that area. In addition,
the Eocene deposits in Barbados are flyschlike
turbidites laid down under submarine condi-
tions. The Eocene sediments of the Andaman-
1748
Weeks, Lattimore, Harbison, Bassinger and Merril
Table 1. Double Island Arc System Belts (See Fig. 4)
Area
E. Caribbean
Andaman Sea
1 . Stable platform
(a) plate from which arc system radiates
(b) formerly involved in arc system, but now stable area
2 . Backdeep
(a) basin behind, or on concave side of inner volcanic arc
(b) part of arc system farthest from ocean plate
3. Inner volcanic arc
(a) positive gravity
(b) intermediate earthquake belt
(c) older feature than outer sedimentary arc
(d) asymmetry toward ocean plate
4. Interdeep
(a) between outer sedimentary arc and inner volcanic arc
(b) absent where no outer arc present
5 . Outer sedimentary arc
(a) negative gravity
(b) occurs near continental end of island arc
(c) found where trench is absent or buried
(d) youngest feature of arc system
(e) asymmetry toward ocean plate
(f) folded, faulted, and thrusted
(g) shallow earthquake belt
(h) structural history closely related to forcdeep
6 . Foredeep (or Trench)
(a) frontal to outer arc, where present, or to inner volcanic arc
(b) negative gravity, where outer arc absent
(c) trench where frontal to inner volcanic arc
(d) youngest part of arc system
(e) occurs along axis of outermost arc system farthest from
continent
(f) least expression where frontal to outer arc (older); most
expression where frontal to inner volcanic arc (younger)
(g) shallow earthquake belt
Venezuela basin piate and
Aves Ridge
Grenada Trough on concave
side of inner volcanic arc
Lesser Antilles
Tobago Trough
Barbados anticlinorium
Depressed structural belt just
in front of Barbados
anticlinorium
Malay Peninsula
Andaman Sea area on concave
side of inner volcanic arc
Barisan Range (Sumatra)-
Narcondam and Barren
Islands
Negative structural belt between
Andaman-Nicobar Islands and
Barisan-Narcondam-Barren arc
Andaman-Nicobar-Mentawai
Islands
Depressed structural belt just
in front of Andaman-Nicobar-
Mentawai Islands
Nicobar outer arc grade from coarse terrestrial
deposits on the continental end of the belt near-
est Burma to marine carbonates on the distal
end of the outer arc. Infill and attendant facies
changes take place from the continental end of
the arc to the distal end. Hurley (1966), refer-
ring to his work in the Aleutian Trench,
pointed out a similar situation there.
In Indonesia the continuation of the conti-
nental orogenic belt through the outer sedimen-
tary arc is uninterrupted. However, in the
southeastern Caribbean the Pilar block acted in
some degree as a rigid wall. Toward the eastern
end of the Pilar block, rigidity appears to de-
crease, and it is there that the outer sedimen-
tary arc manifests itself. The analogy between
the Indonesian arc and eastern Caribbean is
still good, if one accepts the fact that the Pilar
block is an exception to the general rule. This
block is an old geologic feature which has be-
come involved in a much younger orogenic
belt-island arc development, and therefore it
has acted as a partial deterrent to the more nor-
mal gradation, such as that in Indonesia and
elsewhere.
The outer arc-foredeep relation is not contin-
uous in the axial sense, but more en echelon,
with some overlap of two structures (belt 5,
Fig. 4). In both Indonesia and the eastern Ca-
ribbean it can be seen that the distal end of the
outer sedimentary arc lies within or concave to
the foredeep (Fig. 4). There is evidence of a
buried foredeep lying outside the Andaman-Ni-
cobar chain (Weeks et al., 1967), a great dis-
tance from its more obvious expression as the
Java trench. The en echelon expression or par-
tial overlap of the two features is explained by
the fact that the arc system is growing not only
axially but also normal to the arc. Infill and ele-
vation of the foredeep into an outer arc from
the continental end are closely related to its con-
current development normal to the arc and to-
ward the ocean basin. Undoubtedly, the devel-
opment normal to the arc demands a much
greater period of geologic time than axial infill
and elevation. Hence, the two are still mutually
Lesser Antilles, Venezuela, and Trinidad-Tobago
1749
interrelated, but development in two directions
creates the en echelon or overlap effect.
The en echelon effect of complete island arc
systems is very evident in the western Pacific-
Asian region. Arcs overlap, are concentric with
each other, bifurcate, and may even be super-
imposed. Tectonic trends on the Asian conti-
nent exhibit remarkable proximity in some
arcs, without major fracturing.
In summary, the double arc grows in two di-
rections— normal (toward the ocean basin),
and axial to the arc. Axial growth is from the
continental end (mobile belt) of the outer arc
toward its distal equivalent, the foredeep. The
foredeep is, therefore, a younger structure than
the outer sedimentary arc. Normal to the arc,
the youngest feature is the outer arc or fore-
deep (belt 5, Fig. 4), and the oldest features
are the backdeep and stable plate (belts 1, 2;
Table 1, Fig. 4).
Tectonic Map and Interpretation
A tectonic map of the southeastern Carib-
bean and adjacent areas is shown in Figure 5.
It is based on marine data from ESSA and
other sources, and on the geology of the conti-
nent and certain islands.
The simplistic approach in the tectonic map
reflects the view that the geologic history of this
area can be explained without recourse to vast
horizontal wrench faults or differential plate
movements. Continuation of double island arc
system belts into continents has been substanti-
ated (Indonesian, Aleutian, Scotian, and Antil-
lean). The arc belts have in places modified the
structural trends of the continental margin, as
on the Paria shelf.
It was noted in reviewing the geologic litera-
ture that the prevalence of cross trends in the
arc system appeared to be the rule rather than
the exception. These trends are more or less at
right angles or normal to the arcs, and include
not only faults but folds and even thrust faults.
A summary of the cross trends found in the lit-
erature includes the following.
1. A fracture zone at the southeastern limit
of the Los Roques Trench, north of the Nether-
lands Antilles, curves sharply across the inter-
rupted arc of the Aves Ridge-Netherlands An-
tilles. The axis of the Eastern Venezuela basin
makes a double change in trend just south of
the southeastern terminus of the Los Roques
Trench, and suggests the existence of a cross
trend of some type, approximately at right an-
gles to the coast near Barcelona, Venezuela.
2. Northwest-striking cross fractures, nor-
mal to the arc, occur in the Los Testigos Is-
lands, which the ESSA data show to be a con-
tinuation of the Lesser Antilles inner volcanic
arc. The islands consist of granites and volcanic
rocks, Testigo Grande being a granitic intrusive
body, bordered by younger volcanic rocks
(Maloney, 1967). The Los Frailes Islands,
along the same arc between Margarita and the
Testigos, are a northwest-trending en echelon
set of islands parallel with the eastern coast of
Margarita.
3. The Los Hermanos Islands, just east of
La Blanquilla Island, are oriented somewhat
normal to the trend connecting the Blanquilla-
Hermanos platform and the Aves Ridge. A sea-
mount, 13 n. mi (24 km) southwest of La
Blanquilla, also is oriented northwest-southeast,
normal to the major trend. A basin between the
seamount and the island of La Blanquilla like-
wise has a northwest-southeast orientation
(Maloney, 1966, 1968).
4. Aves Island, the only part of the ridge
above sea level, is arched with an axis approxi-
mately N70°E, and dips north and south (Ma-
loney et al., 1968). This general east-west ori-
entation has been noted by prior workers.
5. The folds and thrusts exposed in eastern
Barbados are oriented more or less east-west,
normal to the outer island arc trend. The St.
Lucia-Barbados cross-warp, whatever its true
nature, also is normal to the arc trend.
6. In Grenada, the southernmost island of
the Lesser Antilles, several anticlines and syn-
clines have fold axes in an approximately east-
west direction. These folds cross the arc trend,
and are similar to those in Barbados.
7. Tobago Island consists of isoclinally
folded schist and phyllite in the northern third
of the island. These trends are east-northeast,
contrary to the northeast strike of the island.
Undoubtedly many other examples exist, but
those listed are sufficient to emphasize the fact
that cross fractures and/ or folds are far from
uncommon.
The type of movement that has occurred
along the El Pilar fault zone is very important
in solving the tectonics of the region. The writ-
ers consider movement along the El Pilar and
the northern fault zones to have been primarily
vertical, and if any horizontal movement has
occurred, it is relatively minimal. Vast horizon-
tal movement of the magnitude of hundreds of
miles is not supportable by field data.
1. Work by Potter (1968) shows that much
of the literature has been theoretical, based on
previous lack of field investigations. His map-
1750
Weeks, Lattimore, Harbison, Bassinger and Merrill
ping in the Northern Range of Trinidad has
provided data for examining movement on the
El Pilar fault. Evidence is good for vertical dis-
placement of up to 6,000 ft (1,830 m) on the
El Pilar and on the Brasso Seco faults, but
there is no evidence for lateral movement. In
addition. Potter noted that lateral movement
since late Pliocene is not suggested by the posi-
tions of buried Plio-Pleistocene alluvial fans.
2. ESSA data from the Dragon's Mouth east
to 59°W merely indicate a very clean high-an-
gle to vertical break, between the Pilar block
and the sediments on the south (Bassinger et
al., 1971 ). Lack of a wide gouge zone, expecta-
ble in a wrench fault, is quite conclusive. Al-
though the near-vertical trace of the fault at the
surface is indicated, it is not unlikely that the
plane of the fault at depth may become shal-
lower and dip north, as shown in published
cross sections of Trinidad's structure (Kugler,
1961). At least this type of fault is consistent
with other field data in Trinidad. The ESSA
data further indicate the possibility that the El
Pilar fault either becomes deeply buried or
ceases to be a fracture east of 58°30'W.
3. Detailed field work along the El Pilar
fault by Metz (1964) in the central Araya-Pa-
ria Peninsulas provides the evidence against
large-scale strike-slip displacement, (a) The
Cutacual Formation (Lower Cretaceous), only
locally developed, crops out on both sides of
the fault; this facies does not occur elsewhere,
and therefore cannot have been displaced; (b)
the same light-colored facies of the San Anto-
nio Formation (Upper Cretaceous) also is
found on either side of the fault, suggesting de-
position in the same lithic province; and (c)
the east-northeast-trending belt of the upper
Cantil Formation (Lower Cretaceous) contin-
ues across the fault into the metamorphic belt
on the north. Metz considered that, if any
wrench faulting has taken place, it is minor,
and recently (personal commun) Metz has
even further reduced his estimate of wrench
movement to 5 km (3.1 mi) or less.
4. The El Pilar and the now discounted
Southern Caribbean faults have been consid-
ered as logical zones for possible right-lateral
wrench movement. However, as Mencher
(1963, p. 84, 85) pointed out in reference to
the El Pilar, the actual field evidence for such
extensive faulting and movement in Venezuela
is limited and very little surface evidence of the
fault exists in Trinidad. The age of the origin
of the fault is uncertain, but some of the move-
ment must be post-Cretaceous, as Cretaceous
rocks are affected, but Miocene to Holocene
sediments overlapping the fault are not.
Mencher concluded that, if such faults were
not pre-Tertiary, they could not have played an
important part in much of the tectonic history
of Venezuela.
It is concluded that the El Pilar is no more
than a vertical displacement fault, possibly a
high-angle thrust at the surface, which contin-
ues east to about 58°30'W. It may continue
even farther, but is either deeply buried or be-
comes inactive toward the east. If the El Pilar
changes its east-west trend and becomes the
frontal fault of the Barbados anticlinorium, it
would indicate a reactivation of the fault as
part of the arc system. This also would mean
that the mobile belt continued around the east-
ern end of the Pilar block.
An analysis of the tectonic map (Fig. 5)
shows two overall trends which have interacted.
The old east-west trend, exemplified by the Pi-
lar block and El Pilar fault, has somewhat
modified and directed the arcward continuation
of the continental mobile belt, with a trend
more north than due east, into the island arc
system. The fold and fault trends south of the
Pilar block have an east-northeast trend and
terminate against the block. The trends on the
north have a similar east-northeast trend and
terminate against the block at their southwest-
ern ends; some are subparallel with the block.
The general strike of the folds is, therefore, ap-
proximately the same north and south of the
block. Only at the extreme west end of the Pi-
lar block do trends continue around it, and it is
possible that the same is true at the east end of
the block.
Several extensional collapse features along
the Pilar block are indicated, particularly in the
Cariaco basin and the Dragon's Mouth. The
abrupt turn in the southeastern part of the Los
Roques Trench, the collapse of the Cariaco ba-
sin, and the abrupt twists in the axis of the
Eastern Venezuela basin near 65 °W long, sug-
gest the presence of a possible tectonic cross
feature. West of 66°W long, the strike of the
coastal features is compatible with the merger
of the continental orogenic belt-island arc sys-
tem. The trends interrupted by the southeastern
end of the Los Roques Trench continue west
for some distance before merging with the oro-
genic belts of western Venezuela and Colombia
(west of Fig. 5). The Pilar block seems to lose
its identity, or to become involved in the trend
of the merged orogenic systems from Caracas
westward.
Lesser Antilles, Venezuela, and Trinidad-Tobago
1751
Fold and fault patterns south of the Pilar
block indicate the probability that three seg-
ments of the block once stood higher in eleva-
tion, resulting in gravity-slide thrusting toward
the southeast. These three areas are the Caracas
(Caribbean Ranges), Cariaco (Araya-Paria
Peninsulas), and North Range (Trinidad)
areas. Sliding toward the southeast, normal to
the folding, is suggested most strongly south of
these three localities. Considerable thrusting is
found in northern Guarico state, Venezuela,
south of Caracas; the Serrania del Interior,
south of Cariaco; and throughout Trinidad,
south of the Northern Range. Wrench faults, of
limited displacement, such as the Los Bajos
fault of southwestern Trinidad, also occur in
the Serrania del Interior, possibly merging into
southeastward-directed thrusts at their limits.
These faults are found south of the potentially
higher areas. The high areas were undoubtedly
much reduced by erosion prior to development
of more recent phases of the arc system off-
shore.
Summary
The results obtained during this study, in
conjunction with the known structural geology
of the region, show the following.
1. Sediments flanking the positive ridges of
the southeast Caribbean island arc system are
overlain unconformably by relatively undis-
turbed beds in the intervening troughs. In the
Tobago Trough and the Central syncline (Bar-
bados anticlinorium), an unconformity sepa-
rates the folded strata of the positive elements
from the flat-lying younger beds of the negative
elements. Considerable elevation of the outer
parts of the arc has occurred since folding
ceased, as shown by the presence of reefs on
Barbados at an elevation of 1,100 ft (336 m)
above sea level. A period of folding was
followed by one of epeirogeny.
2. Several cross features, normal to the
trend of the arc system, appear to be quite
common. Collapsed areas, such as in the Drag-
on's Mouth and the zone between the Grenada
platform (Lesser Antilles) and Testigos-Mar-
garita platform, occur within the area of study.
3. The Barbados anticlinorium, or outer sed-
imentary arc of the island arc system, is a fea-
ture consisting of two positive elements (West
and East ridges), separated by a negative ele-
ment (Central syncline). "Basement" rocks
support the two ridges and lie more than 1.5
sec of acoustic penetration below the Central
syncline. Other subsidiary or modifying fea-
tures, such as the North Tobago anticline and
the East Tobago syncline, belong to the folded
and faulted outer sedimentary arc.
4. The Lesser Antilles, or inner volcanic arc,
is traceable onto the Paria shelf, continuing
into the Testigos-Margarita platform. The con-
tinuation is confirmed by seismic reflection pro-
filer and gravity data, but not by the bathyme-
try.
5. The Tobago Trough extends across the
Paria shelf, depressing it with a large volume of
sediments. The trend appears to end subparallel
with the Pilar block. This observation is sup-
ported by seismic-reflection profiling, bathyme-
try inside the 100-fm (183 m) isobath, and re-
fraction data. Evidence for a southern source
of sediments both for the trough and Barbados
is very strong.
6. Evidence shows that the Pilar block is an
old structure which has partly modified the
junction of the island arc system with the conti-
nent. The block is essentially a horst, bounded
on the north and south by fault zones. The
northern fault zone is traceable from the west-
ern end of the Araya Peninsula to the edge of
the eastern Trinidadian shelf, where it cannot
be distinguished from the fracture system at the
junction of the East ridge and the Pilar block.
In all likelihood, the fault zone north of the Pi-
lar block consists of a series of en echelon frac-
tures. Although the individual faults may strike
east-northeast, the fault zone strikes essentially
east-west. The El Pilar is traceable farther east,
because a "basemenf'-sediment contact is easy
to detect seismically. It is traceable east to
58°30'W, although there is considerable ques-
tion as to whether it continues as a fault, be-
cause it may be deeply buried by sediments
from the south.
Both the El Pilar and northern fault zones
may cross the Cariaco basin and be present
north and south of the coastal ranges near Ca-
racas. This would be the most logical projec-
tion, and Figure 5 reflects this inference.
7. The evidence in the southeastern Carib-
bean does not support the concept of wrench
faulting, with its implication of vast horizontal
movements of individual blocks. The Southern
Caribbean fault, long hypothesized as the
southern margin of the Caribbean plate, simply
does not exist. Nor is the EI Pilar a wrench
fault, inasmuch as most field data show its
movements to have been vertical with only a
small wrench component.
8. The structural geology of the region can
be explained in a simplistic manner. The island
1752
Weeks, Lattimore, Harbison, Bassinger and Merrill
arc structural belts and the mobile belts of the
continent are interrelated, gradational, and in-
terlocked.
9. An analogy between the southeastern Ca-
ribbean and the Andaman Sea arcs shows the
logic in an extension of a continental mobile
belt into an island arc system. Except for the
modifying influence of the Pilar block, the two
island arc systems are surprisingly similar.
References Cited
Baadsgaard, P. H., 1960, Barbados, W. L: exploration
results 1950-1958, in Structure of the earth's crust
and deformation of rocks: 21st Internat. Geol.
Cong. Rept., Copenhagen, pt. 18, p. 21-27.
Bassinger, B. G., R. N. Harbison, and L. A. Weeks,
1971, Marine geophysical study northeast of Trini-
dad-Tobago: Am. Assoc. Petroleum Geologists
Bull., v. 55, no. 10, p. 1730-1740.
Bunce, E. T., J. D. Phillips, R. L. Chase, and C. O.
Bowin, 1970, The Lesser Antilles arc and the eastern
margin of the Caribbean Sea: Woods Hole Oceanog.
Inst. Contrib. 2288, 36 p.; in press, in A. E. Max-
well, ed., The sea, v. 4: New York, Wiley Tntersci-
ence.
Earle, K. W., 1924, Geological survey of Grenada and
the (Grenada) Grenadines: St. George's, Grenada,
Govt. Printing Office, 9 p.
1928, Report on the geology of Saint Vincent
and the neighbouring Grenadines: Kingston, Ja-
maica, Govt. Printing Office, 65 p.
Edgar, N. T., 1968, Seismic refraction and reflection in
the Caribbean Sea: Ph.D. thesis, Columbia Univ.,
163 p.
J. I. Ewing, and J. Hennion, 1971, Seismic re-
fraction and reflection in Caribbean Sea: Am. Assoc.
Petroleum Geologists Bull., v. 55, no. 6, p. 833-870.
Ewing, J. I., M. Talwani, M. Ewing, and T. Edgar,
1967, Sediments of the Caribbean: Internat. Conf.
Tropical Oceanog. Proc, Miami Univ., 1965, p. 88-
102.
Hurley, R. J., 1966, Geological studies of the West In-
dies: Canada Geol. Survey Paper 66-15, p. 139—
150.
Kugler, H. G., 1961, Geological map of Trinidad and
geological sections through Trinidad: pub. for Petro-
leum Assoc. Trinidad, Zurich, Orell Fussli, and Lon-
don, E. Strand.
Lattimore, R. K., L. A. Weeks, and L. W. Mordock,
1971, Marine geophysical reconnaissance of con-
tinental margin north of Paria Peninsula, Venezuela:
Am. Assoc. Petroleum Geologists Bull., v. 55, no. 10,
p. 1719-1729.
Lewis, J. F., 1968, Composition, origin and differentia-
tion of basalt magma in the Lesser Antilles (abs.),
in Abstracts of papers: 5th Caribbean Geol. Conf.,
Virgin Islands, July 1-5, 1968, p. 44-45.
MacDonald, W. D., and W. G. Melson, 1969, A late
Cenozoic volcanic province in Hispaniola: Carib-
bean Jour. Sci., v. 9, nos. 3-4, p. 81-90.
MacGillavry, H. J., 1970, Geological history of the Ca-
ribbean: Nederlandse Akad. Wetensch. Proc, ser. B,
v. 73, no. 1, p. 64-96.
Maloney, N. J., 1966, Geomorphology of continental
margin of Venezuela, pt. 1, Cariaco basin: Univ.
Oriente, Inst. Oceanog. Bol., v. 5, no. 1, 2, p. 38-53.
1967, Geomorphology of continental margin of
Venezuela, pt. 2, Continental terrace off Carupano:
Univ. Oriente, Inst. Oceanog. Bol., v. 6, no. 1, p.
147-155.
C. Shubert, J. I. Marlowe, and A. T. S. Ramsay,
1968, Geology of Aves Island, Venezuela (abs.), in
Abstracts of papers: 5th Caribbean Geol. Conf., Vir-
gin Islands, July 1-5, 1968, p. 50-51.
1968, Geology of La Blanquilla Island with
notes on Los Hermanos Islands, eastern Venezuela
(abs.), in Abstracts of papers: 5th Caribbean Geol.
Conf., Virgin Islands, July 1-5, 1968, p. 49-50.
Marlowe, J. I., 1968, Geological reconnaissance of
parts of Aves Ridge (abs.), in Abstracts of papers:
5th Caribbean Geol. Conf., Virgin Islands, July 1-5,
1968, p. 51-52.
Martin-Kaye, P. H. A., and J. B. Saunders, 1962, An
upper Eocene formation in Grenada, West Indies
(abs.): 3d Caribbean Geol. Conf. Prog., Kingston,
Jamaica, p. 29-30.
Mencher, E., 1963, Tectonic history of Venezuela, in
Backbone of the Americas: Am. Assoc. Petroleum
Geologists Mem. 2, p. 73-87.
Metz, H. L., 1964, Geology of the El Pilar fault zone,
state of Sucre, Venezuela: Ph.D. thesis, Princeton
Univ., 102 p.
Peter, G., L. A. Weeks, and R. E. Bruns, 1966, A re-
connaissance geophysical survey in the Andaman Sea
and across the Andaman-Nicobar Island arc: Jour.
Geophys. Research, v. 71, p. 495-509.
Potter, H. C, 1968, Faulting in the Northern Range of
Trinidad (abs.): 23d Internat. Geol. Cong. Rept.,
Prague, p. 95.
Sykes, L. R., and M. Ewing, 1965, The seismicity of
the Caribbean region: Jour. Geophys. Research, v.
70, p. 5065-5074.
Tomblin, J. F., 1968, Geochemistry and genesis of
Lesser Antillean volcanic rocks (abs.), in Abstracts
of papers: 5th Caribbean Geol. Conf., Virgin Is-
lands, July 1-5, 1968, p. 74-75.
van Bemmelen, R. W., 1949, The geology of Indonesia,
v. 1A: The Hague, Govt. Printing Office, 732 p.
Weeks, L. A., R. N. Harbison, and G. Peter, 1967, Is-
land arc system in Andaman Sea: Am. Assoc. Petro-
leum Geologists Bull., v. 51, no. 9, p. 1803-1815.
67
Reprinted from Proceedings of the Miami Workshop
on Remote Sensing, March 29-31, 1971, 133-148.
STUDIES OF
OF SOLAR
CLOUD AND SATELLITE PARAMETERIZATION
IRRADIANCE AT THE EARTH'S SURFACE
Ki rby J . Hanson
National Oceania and Atmospheric Administration
Atlantic Oceano graphic and Meteorological Laboratories
Miami, Florida
INTRODUCTION
Whe
uate the
this can
during t
During t
(mostly
cent of
however ,
surface
figures
at Swan
on the d
only 1 . 2
the type
for para
n cloud
i r r a d i
be see
he four
hese mo
cirrus)
that re
the at
is very
1 and 2
I si and
ay with
percen
of cl o
meteri z
s are
ance
n fro
-mon t
nths
, but
c e i v e
tenua
1 ow .
whi c
( C a r i
deep
t of
u d i n e
i ng s
thin
by on
m sol
h per
the a
yet
d on
ti on
An
h sho
bbean
trop
the c
ss as
urf ac
(sue
ly a
ar i r
iod f
verag
the s
cl ear
is la
examp
w the
)• T
i cal
1 ear-
wel 1
e i rr
h as c i
smal 1 a
r a d i a n c
rom Sep
e s ky c
o 1 a r i r
days .
rge and
le of t
sol ar
he inte
con vect
day val
as the
adi ance
rrus ) t
moun t .
e data
tember-
overage
r a d i a n c
When c
the i r
his is
i r r a d i a
prated
ion ( 0 c
ue (Oct
amount
hey te
An ex
at Can
Decemb
was 1
e was
1 ouds
radian
i 1 lust
nee on
daily
tober
ober A
is i m
nd to atten
ample of
ton I s 1 and
er, 1960.
0/10th
85-90 per-
are thick ,
ce at the
rated in
two days
i r r a d i a n c e
30 ) was
) . Thus ,
portan t
133
(1968) to apply to Canton Island:
1. Q = Q
Q = Q,
Q = Q,
Q = Q,
Q = Q,
Q - Q,
Q ■ Q
(1 .0-0. 71 C) (Kimball . 1928)
(0.803-0. 304C-0.458C2) (Back, 1956)
(1-0.655C) (Savino-Angstrom
(Budyko, 1956))
(1-0.39C-0.38C2) (Berliand, 1960)
(l-0.0006Ct3) (Laevastu, 1960)
(1-0. 0895C+0. 00252a' ) (Tabata, 1964)
A
0. 884-0. 552C )
op
(Quinn, 1969)
where :
Q
Q,
!A
op
a1
total incoming solar irradiance,
total incoming solar irradiance with a clear sky,
total solar irradiance on a horizontal surface at
the top of the atmosphere,
proportion of sky covered with clouds (0-1.0),
cloud cover in tenths (1-10),
cloud amount in Oktas (1-8),
proportion of sky covered with opaque clouds (0-1.0),
midmonth solar altitude in degrees.
Oct. U, 1^66 - 670(cal/cm2)
Oct. 30, l<) 66 - 8(cal/cm2)
II 12 13 14
True Solar Time ( Hrs.)
Figure 1
Solar irradiance curves for Swan Island. Values are
integrated daily total irradiance (cal/cm2 ) .
134
OCTOBER 4, 7966
OCTOBER 30. 1966
Figure 2. Satellite photos of Central Amerioa3 the Gulf
of Mexico, and the western Caribbean. Swan
Island is located at l7°Ni 84°W. The photos
correspond to the two days (radiation curves)
shown in figure 1.
These empirical equations have been araphed and illustrated in
figure 3 to show the wide range of transmi ttance values for a
particular value of cloud cover. Moreover, the functional re-
lationships differ depending on the proposed formula used: in
four cases a linear relationship has been found, but in others
second- and third-order polynomials are illustrated.
Another difficulty with parameterization using cloudiness
is that the result depends on the time scale over which the
cloud and irradiance data are averaged. An example of this is
shown in figures 4 and 5. In both illustrations, curves 3 and
5 are shown as limiting curves. Mean atmospheric transmi ttance
and mean cloudiness averaged over daily periods are shown in
figure 4, and averaged over annual periods are shown in
135
Cloudiness (tenths)
Figure 3. Atmospheric transmittance vs. cloudiness by var-
ious authors (see text) as summarized by Quinn
(1968).
10
I I
1
l i 1 - — i 1
s Total Sky Cover
/ Miami Fla
"^^_
\
\
X
\
""-«
i> , Opaque Sky Cover
^;*1^/ Miami, fla
-
\.
'
\
■s \ \
\\ \
\\ \
\ \ \ .
\
\3
\
N
10
Cloudiness (tenths)
Figure 4. Atmospheric transmittanoe vs. cloudiness for Miami,
Florida, based on daily values of irradiance and
cloudiness .
136
Cloudiness (tenths)
Figure 5. Atmospheric transmittance vs. cloudiness for
Miami, Florida, based on annual values of
irradianoe and cloudiness .
figure 5. The transmittance values are obtained as the ratio
of the solar irradiance at the earth's surface to the extra-
terrestrial irradiance. Both figures 4 and 5 are based on
data from Miami, Florida. From these figures it is clear that
the time scale of averaging the data changes both the position
and the shape of the parameterization curve. This may offer a
partial explanation for the wide variety of curves in figure 3
which undoubtedly are based on a variety of time scales.
It is apparent from more than 40 years of effort by many
investigators that there are certain shortcomings in quantify-
ing solar irradiance from cloudiness. This paper is
to look at the accuracies of simple parameterization
ques (which include surface-observed cloudiness) and
pare these with parameterization accuracies based on
tive satellite data.
an attempt
techni -
to com-
quanti ta-
2. PARAMETERIZATION METHODS
There are many applications for calculated values of
solar irradiance at the earth's surface and, presumably, each
137
of these applications has a certain requirement for accuracy.
Thus, it is important to be able to state quantitatively the
predictability of surface irradiance. The followinq sections
discuss the use of simple techniques for calculating surface
irradiance as well as the use of quantitative satellite data
for this purpose.
2.1 Long-Term Mean Irradiance
The most simple technique for determining the surface
irradiance is to use the long-term (climatic) mean irradiance
T
the cl
Fl ori d
standa
for bo
tabl e
di ance
are av
v i a t i o
on an
nearly
standa
for sh
the eq
strong
0 test
i mati c
a , and
rd dev
th 1 oc
1 , sho
to be
eraged
fi is 3
hourly
an or
rd dev
orter
uatori
ly att
the v
mean ,
15 ye
i a t i o n
ati ons
w (as
depen
. On
. 5 per
basis
der of
i a t i o n
time s
al dry
e n u a t i
a r i a b i
we ha
ars f r
of th
. The
expect
dent o
a y ear
cent o
the s
magni
value
cal es )
zone
na cl o
lity
ve ta
om Ca
e i rr
resu
ed) t
n the
ly ba
f the
tanda
tude
s are
beca
(2° S
u d i n e
of observ
ken 18 ye
nton Isla
ad i ance o
Its, in t
he standa
time sea
sis at Mi
observed
r d d e v i a t
1 arger .
somewhat
use Canto
. lat. ) a
ss .
ed i r
ars o
nd an
n var
he le
rd de
1 e ov
ami ,
i rra
ion i
For C
smal
n Isl
nd is
radian
f data
d cal c
i o u s t
ft-han
v i a t i o
er whi
the st
di ance
s 30.5
anton
ler (p
and is
less
ce da
from
ul ate
ime s
d col
n of
ch th
andar
, whe
perc
Isl an
a r t i c
1 oca
af fee
ta from
Miami ,
d the
cales
umns of
i r r a -
e data
d de-
re as ,
ent --
d, the
ul arly
ted in
ted by
These values in the left
hand
ii
section of table
1 might
be termed the "natural variance" of irradiance that occurs
on various time scales. In this respect they represent an
upper limit -- against which various parameterization tech-
niques should show improvement.
2.2 Surface-Observed Cloudiness
A commonly observed meteorological parameter is total
sky cover, which is the amount of sky obscured by clouds of
any discernable thickness. Because it is commonly available,
we have used this parameter to determine a functional rela-
tionship between cloudiness and irradiance and have calcu-
lated the variance of observed irradiance values from function
generated irradiance values. (This is commonly called "vari-
ance of the residuals after regression".) The same Miami
138
05
o
K
0)
o
a
<K
Sh
co
CO
co
o
O
o
•<^
«
0)
a
g
+s
0)
Eh
1
u
<u
4J
<u
E
w
u
CO
Ph 0)
3
CJ tH
4J CO
ID
w
•H >
QJ
0) -X
tH
4-)
•u ,~>
tH -a
•H
CO e^
ai a)
C
4J v-'
4J N
Cj
to
CO H
CO
E
o
>-l
m
T3
<L>
N
•H
0)
4J
<u
E
CO
co
13
o
.H
u
E
o
1-1
CO
U • *
E w i^
r-i M ^
CO
CM
O • -X
4J tH ^
c: co s^
O
s ^
B-«
cu
c
E O
o
•
■K
^ C
4-1
r-i
/■-s
CU co
c
CO
B-S
•U «H
CO
M
V^
i -a
u
W) co
C U
o ^
tH M
•H
E. c
E
•
*
O CO
cO
CO
/— ^
U CU
•H
tH
s^s
«w S
•r-l
^-1
fe
^
cu
O iH
E cfl
•H O
H co
CO
CN
I • I
en
—< CM
tH CO
r^
r-
C7%
CO
CO
o^
CO
CN
m
o
<n
en
CN
CTv
O
CO
tH
C
en
O CO
^<J 4J >^
0) C co
CU O CU
IS X! >*
CN
4-1
u
CO
•H
m
4J
4JU
CJ sf
sr co
cm m
• •
1 1 co
4J
tH tH CO
v_^ v_^ Q
O O
M M ^-s
Ptf
II D M
CU
Pi
o
c
0!
H M g
*» *K
•H
/-s ^-n M
X)
O O M
co
r^ r^.
I-j
C\ C7> CO
u
HrHD
r-i
^-1
C
^ XI H
CO
*J Wg
CU
CO CO
>:
V-i ^ |
d d
<+-<
CU CU v£>
o
4-1 4-) vO
«i tn cm
4J
CO CO tH
c
03 K
cu
M
o
•> « CU
M
X X C!
CU
O O p
CU
O C_) >-)
■K --i N ro
139
and Canton Island data were used, and the results are shown in
tne middle section of table 1. It can be seen that standard
deviation increased with shorter time scales, and the values
are less than those determined from the climatic mean. The
major improvement in predictability (over the climatic mean)
is in the shorter time scales. For example, for Miami, the
standard deviation decreases from 27.3 to 17.7 percent on the
daily ti me scale.
Thus, it appears that simple cloud parameterization of
irradiance is most useful for applications which require cal-
culations on time scales of a week or less.
2.3 Satellite-Observed Irradiance
Based on the principle of conservation of energy, it is
possible to calculate the absorption of radiation by the at-
mosphere as a residual, in cases where satellite and surface
irradiance measurements are available (Hanson et al . 1967).
However, in the present case it is not atmospheric absorption
that is desired, but irradiance at the surface. Thus, the
residual calculation is surface irradiance -- which requires
satellite irradiance measurements and a quantitative estimate
of atmospheric absorption.
We have used this method to establish the accuracy with
which surface irradiance may be determined. The result, with
dependent data, shows that for the United States on a monthly
scale (June, 1966) the standard deviation of surface irra-
diance is 3.2 percent (table 1). This is smaller by a factor
of three than the standard deviation of the irradiance from
the long-term mean. This satellite data technique is yet to
be tested with independent data.
The method used in this technique is to determine the
atmospheric absorption of irradiance (I„) as a residual in
lo = ^"^g + h + h
(1)
where
I = incident extraterrestrial solar irradiance,
I = solar irradiance at earth's surface,
L = irradiance reflected to space,
a = surface reflectance (albedo).
140
Dividing ( 1 ) by I gives
where
1 = qa + qr + qg(1"a)
(2)
qa = W
the fraction of incident sunlight absorbed
i n the atmosphere ,
^r " V:o
the fraction of incident sunlight reflected
to space ,
«g = I/[o'
the fraction of incident sunlight transmitted
by the atmosphere to the earth's surface.
The right-hand term in (2) is the fraction of the incident
irradiance which is absorbed at the earth's surface; this will
be denoted as q
Then
1 = q + q + q
^a ^r Me
(3)
Equation (3) simply shows the partitioning of solar radiation
which is incident on the earth's outer atmosphere.
The following sections show how the individual irradiance
terms were determined.
2.3.1 Irradiance at Upper Boundary
In this study, the irradiance, I , was calculated from
i0 = y>vr)2 cos^
(4)
The solar constant, I , was taken as 2.0 cal/cm2 min, r and
r are the mean and actual earth-sun distances, and c, is the
time- integrated solar zenith angle at the subsatellite point
2.3.2 Irradiance at the Earth's Surface
The irradiance, I , was obtained from measurements by the
National Weather Service network of pyranometer stations which
141
measure the broadband (0.3-2.5 urn) solar irradiance. These
data are avaiable from the National Climatic Center (NOAA,
1966). Corrections have been made to the measurements in
order to account for degradation of the sensors at some sta-
tions. The background information for determining those cor-
rections was obtained from Stark (1971). Surface reflectance,
a, values for the United States were obtained from the summer
season surface reflectances reported by Kung et al . (1964).
The resulting surface absorption of irradiance, q , over the
United States is shown in the lower portion of figure 6 and
is expressed as the fraction of incident extraterrestrial
irradiance.
2.3.3 Irradiance at the Upper Boundary
The upwelling irradiance at satellite height, IR, was
observed by the MRIR (broadband solar) sensor on NIMBUS II.
The irradiance was determined from MRIR radiance data by
methods described by Raschke and Bandeen (1970). The earth's
reflectance at satellite height, q , is given in the upper
half of figure 6. There is a high negative correlation be-
tween q and q , as is evident in figure 6.
2.3.4 Irradiance in the Atmosphere
a res
Values of atmospheric absorption, I.
i dual using (1) and the values of a,
were cal cul a ted as
I , I , and ID from
U 0 K
the sources indicated above. The resulting q values are
a
shown in the upper half of fiaure 7. The distribution of q
shows high absorption in the east -- particularly the south-
east -- as expected from water-vapor distribution. This
latter value is shown in the lower part of figure 7 and has
been calculated from mean monthly temperature and water-
vapor (vertical) distributions. Optical depth of water
vapor, u, was calculated from:
u =
1
Tw dp
(5)
where g is the acceleration of gravity at the earth's surface
w is the mixing ratio of water vapor, and p is pressure. The
integration was carried out to approximately 300 mb . Optical
pathlength values, t, (in lower fig. 7) have been determined
142
Figure 6. Distributions of fractional reflectance 3
q j of earth/atmosphere and fractional
absorption of the earth ' s surf ace 3 q 3
for June, 1966.
143
Fractional Absorption
Atmosphere
ne, 1966
^"^-Vvp? cp \ .
Figure 7. Distributi
on of fractional absorption by the
atmosphere, q ^ and optical pathlength of
water vapor for June, 1966.
144
from these u values, from the change in optical pathlength
due to varying solar zenith angles, 5, and from the effect
of diffuse radiation beneath clouds. The latter effect was
introduced in the following way:
t = (l-c)(.86u* + .14(1. 66u)) + c(1.66u)
(6)
where c is the mean monthly cloudiness and u* is the opti
cal pathlength with clear skies,
i* =
u sec i>
(7)
A diffusivity factor of 1.66 has been used as the optical
pathlength under diffuse light conditions due to clouds.
The resulting t values, mapped in figure 7, show a
pattern very similar to the atmospheric absorption, q .
a
There are low values for optical pathlenqth in the western
United States and higher values in the east and southeast.
In comparing these two distributions, it appears that qa
a
values in the northeastern quarter of the United States are
higher than expected from water vapor along -- and may be a
result of industrial or other pollution. The strong depend
ence of q on t is clear from figure 7.
a
In figure 8, the dependence of q 3 on t is shown in a
a
scatter diagram. The qa values are related to t by
a
117 + .031t* In t
(8)
where the constants have been determined by least squares
fit. The variance of the residuals from the function values
is .00101. Thus, the standard deviation of the residuals is
3.2 percent.
In this case we have determined I„ as a residual in
(1). However, it is also possible to use the measurement of
I n and a knowledge of I and In (calculated from (8)) in
K 3 O A
order to parameterize I over the United States. This has
been done, and the calculated I values and observed (dependent
145
0.50
<
40
- 0 30
20
U.S. Network
June . 1966
2 3 4 5
Optical Pathlength of Water Vapor (cm)
Figure 8. Fractional absorption of solar radiation
by the atmosphere q 3 vs. optical path-
length of water vapor based on the U.S.
network of pyranometer and radiosonde
stations and on NIMBUS II broadband solar
(MRIR) data for June 1966.
data) values of I have a standard deviation of 3.2 percent
9
The significance of this fact, as shown in table 1, is that
the satellite parameterization of I shows improvement by
factors of 2 and 3 over the other two techniques.
SUMMARY
This study has shown that there are difficulties and
shortcomings with relatively simple techniques for parameter-
izing solar irradiance from (1) long-term climatic radiation
data, and (2) cloud observations from the earth's surface.
One difficulty is that there is a wide range in the results
of empirically determined irradiance values (from cloudiness)
depending on the equation used (i.e., the author selected).
A second difficulty is that both the form and the constants
of the empirical equation depend on the time scale over which
the data are averaged.
146
In an attempt to determine the accuracy of these two
parameterization techniques, we have used 18 years of data
from Miami, Florida, and 15 years from Canton Island. The
result (table 1) shows that the longer time scales have the
smallest errors. The use of surface-observed cloudiness to
parameterize the surface irradiance shows only slight im-
provement over the natural variance that occurs. On shorter
time scales, the improvement is somewhat more significant
than on the longer time scale. The use of satellite data
for parameterizing surface irradiance on a monthly time
scale shows improvement by a factor of about 3 over the
natural variance that occurs.
REFERENCES
Beriland, T.G. (I960), Metodika Kl imatol ogi cheski kh Raschetov
Summarnoi Radiatsii (Method of CI i matol ogi cal Calculation
of Global Radiation), Meteor, i Gidrol. 6, 9-12.
Black, J.N. (1956), The distribution of solar radiation over
the earth's surface, Archiv. Meteorol . Geophys. Bioklim.
B7, 165-189.
Budyko, M.I. (1956), The Heat Balance of the Earth's Surface,
Gi drometeorol ogi cheskoe Izdatel'stvo Leningrad (transl.
by Office of Tech. Services, U.S. Dept. of Commerce,
Washington, D.C., 1958, 259 pp).
Cox, S., and S. Hastenrath (1970), Radiation measurements
over the equatorial central Pacific, Monthly Weather Rev.
98, 823-832.
Hanson, K.J., T.H. Vonder Haar, and V. Suomi (1967), Reflec-
tion of sunlight to space and absorption by the earth and
atmosphere over the United States during the spring 1962,
Monthly Weather Rev. 95_, 353-362.
Kimball, H.H. (1928), Amount of solar radiation that reaches
the surface of the earth on the land and on the sea, and
methods by which it is measured, Monthly Weather Rev. 56 ,
393-398.
Laevastu, T. (1960), Factors affecting the temperature of
the surface layer of the sea, Soc. Sci . Fennica, Commen-
tationes Phys. Math. 25, 1-135.
147
NOAA (1966), CI imatologi cal Data - National Summary, Natl.
Climatic Data Center, Asheville, N.C.
Quinn, W.H. (1969), A study of several approaches to com-
puting surface insolation over tropical oceans, J. Appl.
Meteorol . 8, 205-212.
Raschke, E., and W. Bandeen (1970), The radiation balance
of the planet earth from radiation measurements of the
satellite NIMBUS II, J. Appl. Meteorol. 9, 215-238.
Tabata, S. (1964), Insolation in relation to cloud amount
and sun's altitude, Univ. of Tokyo, Geophysics Notes
17, 202-210.
148
68
Reprinted from Journal of Geophysical Research 76,
No. 18, 4172-4180 .
Airborne Measurements of the Total Heat Flux from the Sea
during Bomex
E. D. McAlister
University of California at San Diego
Scripps Institute of Oceanography, La Jolla, California 92037
William McLeish
Environmental Science Services Administration
Atlantic Oceanographic and Meteorologic Laboratories, Miami, Florida 33130
Ernst A. Corduan
University of California at San Diego
Scripps Institute of Oceanography, La Jolla, California 92037
Airborne measurements of the total heat flux from the sea were successfully made during
the Barbados oceanographic and meteorological experiment in May 1969. The values found
at night ranged from 0.05 to 0.45 cal cm"2 min"1 and are half-hour averages over contiguous
strips of ocean 1.6 km long and 75 meters wide. These are the first airborne measurements of
this oceanic factor and the method used is new.
A total of 1021 calories of solar energy is
stored during the daylight hours of one aver-
age day in the top 30 meters of the world's
oceans. This energy is released during a 24-hour
cycle and thus is important to the dynamics
of the ocean. It represents the total energy
available to the marine atmosphere from below
and so has a direct bearing on meteorological
predictions. No direct method of measurement
of this total heat loss has previously been dem-
onstrated.
For the past several years at Scripps Insti-
tution of Oceanography, the authors have at-
tempted to fill this need by developing an air-
borne infrared-optical method. The principle of
this method depends on the physical properties
of water, namely its absorption coefficient for
infrared radiation and its molecular heat con-
ductivity. The system developed measures the
vertical temperature gradient in the top 0.1 mm
of the sea surface wherein the heat flow is dom-
inated by molecular conduction [McAlister and
McLeish, 1969]. The total heat flow may be
determined from this temperature gradient and
the heat conductivity of sea water. A two-wave-
Copyright © 1971 by the American Geophysical Union.
length infrared radiometer was developed for
this purpose.
The use of an airborne digital data reduction
system was of major importance in this system.
This combined with continuous calibration of
detector sensitivity allowed measurement of
water temperature to 0.01 °C and the tempera-
ture difference between the two depths to
0.003°C. It is believed that the accuracy in
reading water temperature is set by the mer-
cury thermometer used in calibration, which
could be read to 0.01 °C.
This accuracy is reached only after determin-
ing atmospheric losses caused by absorption,
scattering, and emission by flying at different
altitudes and extrapolating the data to zero
altitude, i.e., the sea surface. The radiation
from the sky is continuously measured and
used to remove reflected sky radiation from
the beam coming from immediately below the
water surface. Details of the two-wavelength
radiometer, the digital data recorder, calibra-
tion, operation, calculation procedures, and the
effect of sea state are described in McAlister
and McLeish [1970]. The calculation pro-
cedure is repeated here and one day's records
are analyzed later to illustrate the calculation
4172
Heat Flux
4173
of total heat flux and sea-surface temperature.
The infrared radiance from the water sur-
face at night Iw is the sum of two parts: h(l
— r) from immediately below the water sur-
face and Is ■ r from the sky by reflection
from the water surface, i.e.,
Iw = Iu(l - r) + ls-r (1)
where Iv and Ia are the underwater and sky
radiation intensities and r is the reflectivity of
the water surface. The radiometer compares
this total with that from the reference black-
body IB- The radiometer uses two wavelength
bands, 3.4 to 4.1 /x (channel 1) and 4.5 to
5.1 /jl (channel 2), which effectively isolate radia-
tion coming from depths of 0.0075 cm and
0.0025 cm in the water. The reflectivity for the
wavelengths used in channel 1 is rt — 0.0268
and in channel 2 the reflectivity is r2 = 0.0210.
In channel 1 the comparison of intensity from
the water with that from the reference black-
body is
(la, ~ Is)
_ (Iw, - IBl) ~ (h, - h,)-r, ^ A ,y
(1 - r,)
and in channel 2 it is
(la. ~ h,)
(Jw, - //»,) - (Is, - js^tll _ A (3)
(1 - r2)
The difference in intensity coming from the two
depths is then
Iv, ~ la, = A, - A2 (4)
The temperature difference in the water at the
two depths is therefore
AT = (Al - A2)C
(5)
where
C
((TBl) - (TBJ)/((IBl) - </*.» (6)
and (IB,), (Ib,), (TBi), and (TBa) are the aver-
age intensities and temperatures for the two
reference blackbodies during the time interval
of interest. This approximate relation holds
with sufficient accuracy when water temperature
and the blackbody temperatures are no more
than 2° or 3°C apart. After AT is evaluated for a
particular exercise the total heat flux is calculated
by multiplying the coefficient of heat conduc-
tivity of sea water by the vertical temperature
gradient.
The actual temperature at the two depths
cannot be obtained as accurately as the dif-
ference in temperatures, equation 5. This is
because the temperature of the water surface
flown over does change a few hundredths of
a degree centigrade during the half hour or
more of time necessary to obtain several read-
ings at three or more altitudes. Also, since the
difference in radiation intensity coming from
the two depths (equation 4) changes very little
(a small fraction of 1%) for a 0.1 °C change
in water temperature (say, from 300.0°K to
300.1 °K) the temperature difference as ob-
tained from equation 5 is accurate.
The Trials at Barbados
During May of 1969 at Barbados scientists
from several oceanographic institutions made
use of Scripps' Floating Instrument Platjorm
(Flip) to measure the latent heat flux, sen-
sible heat flux, and the factors influencing the
magnitude of these heat losses. This offered an
opportunity for comparison with values meas-
ured simultaneously by the total heat flow
radiometric system.
The equipment and crew were flown to Bar-
bados in Scripps' DC-3 aircraft. The system
was assembled and recalibrated to verify its
condition after the flight from San Diego.
Flip was stationed 200 miles east of Barba-
dos. Flights near it were made when weather
and operating conditions permitted. These flights
were at night to avoid solar interference with
readings from the shorter wavelength channel
(3.5 to 4.1 fi). Safety regulations that were
adopted required a lateral separation of 300
meters from Flip. Consequently a racetrack
course was flown, the downwind leg being 300
meters north of Flip and the upwind leg 300
meters south.
Data was tape recorded during 24 sec of
each leg, which gave information on a 1.6-km
strip on the sea which averaged 75 meters in
width. 26,000 readings of 10 parameters were
recorded during each pass. The flights were
made at 50, 100, and 150 meters altitude to
correct for atmospheric attenuation [McAUster
and McLeish, 1970]. Usually 16 to 24 passes
by Flip were made during a period of from
4174 McAlister, McLeish, and Corduan
TABLE 1. Computer printout of 30- sec averages
DEC. SEAU) b« III SKYI1) BB 121 Sfi4(?1 66 II) SKY m BB 121 I8e(ll 168(21
DEC. 9 1091. 0<i 1898,94 2841.34 1851.90 1923.30 1942.14 2654.62 1678.42 212. IT 1407.33
AVG.
TEMP. 9 27.995 27.291 28.262
AVC.
DEC. 10 1665.97 1997.00 277?. 4fc le49.28 1947.44 1971.23 2617.25 1907.40 275.59 1466.70
SVG.
TEMP. 10 28.060 27.340 28.309
AVC.
DEC. 11 1876.61 1185.20 2635.95 1837.71 1940.77 1961.43 2671.24 1898.28 258.95 1454.42
AVG.
TEMP. 11 28.002 27.327 28.299
A VS.
DEC. 12 1853.44 lt61.10 2761. B9 1816.11 19C6.32 1933.50 ?5tl.22 1871.03 258.75 1438.78
AVG.
TEMP. 12 28.029 27.327 28.287
AVG.
DEC. 13 1863.76 1871.05 2806.24 lR26.e7 le93.78 1920.17 75^6. 86 1859.41 278.99 1437.53
AVG.
TEMP. 13 28.053 27.343 28.286
AVG.
OEC. 14 1958.30 116'j.42 27H4.56 1421.71 1977. 5e 1994.48 2603.85 1933.22 317.16 1462.60
AVG.
TEMP. 14 28.010 27.373 28.306
AVG.
OEC. 15 1900.21 1907.02 2861.19 1862. <3 1936.15 1954.25 26H4.4A 1893.82 244.26 1382.84
AVG.
TEMP. 15 29.011 27.316 28.243
AVG.
DEC. 16 1853.96 1858.08 2793.82 1814.4? 1903. C9 1921.34 2614.61 1861.69 341.23 1461.46
AVG.
TEMP. 16 28.019 27.392 26.305
AVG.
DEC. 17 1878.85 1887.36 2828.32 1843. CO 1110. ec 1933.83 2641.84 1873.75 275.55 1389.29
AVG.
TEMP. 17 28.050 27.340 28.246
AVG.
OfcC. 1H 1342.90 1354.76 2693.51 1M2.C2 ie53.85 1923.75 2511.77 1863.65 217.09 1331.49
AVG.
TEMP. 18 28.045 27.295 28.203
AVG.
DEC. 19 1913.10 1925.65 2532.79 1883.36 1945.05 1972.99 2426.26 1913.70 309.50 1412.35
AVG.
TEMP. 19 27.997 27.367 28.266
AVG.
DEC. 20 1945.03 1953.21 2828.69 1909.44 1941.08 1958.49 2632.18 1899.71 282.05 1396.89
AVG.
TEMP. 20 28.021 27.345 28.254
AVG.
OEC. 21 1888.39 1893.17 2848.46 1849.59 1912.94 1928.09 2656.76 1868.22 265.53 1375.34
AVG.
TEMP. 21 27.981 27.332 28.237
AVG.
OEC. 22 2048.00 2048.00 2048.00 2048. CO 2048.00 2048.00 2048.00 2048.00 2048.00 2048.00
AVG.
TEAR. 22 28.725 28.725 28.763
Heat Flux
4175
40 minutes to 1 hour. These provide an aver-
age value of total heat flux from the strip of
ocean 1.6 km long and 75 meters wide.
Flights were made when weather permitted
a night rendevous with Flip. The Flip was be-
ing towed to a new location from May 20 to
23, consequently no flights were made then.
From May 19 to May 29, seven flights were
made as shown in Table 3. The flight on May
29 was made in cooperation with ESSA planes.
Flip was departing Barbados on this date.
During all of these flights there were scattered
low clouds, 300 to 600 meters and a secondary
layer at middle altitudes. These cloud condi-
tions were uniform for all of the flights. Dark-
ness prevented detailed cloud description.
TABLE 2. Computer printout of radiation intensity differences
CHANNEL 1
CHANNEL 2
R1C. (S(D-BB(l)l - ((SKYI2I-BBI III*. 02681
(S(2)-BB(ll 1 - ((3KYI2I-
2
-33.22*2
2
-3*. 1212
3
-35.2994
3
-36.252-.
4
-33. 423*
4
-34.3258
5
-35.7298
5
-36.6945
6
-35.4512
6
-36.4084
7
-37.5697
7
-38.5841
a
-35.6011
8
-3-6.5623
9
-33.1563
9
-34.0515
10
-34.4929
10
-35.4242
11
-32.0701
11
-32.9360
12
-32.4824
12
-33.3594
13
-32.3531
13
-33.2266
1<V
-30.0462
1*
-30.8574
15
-32.4354
15
-33.3111
16
-29.1973
16
-29.9862
17
-33.7277
17
-34.6334
18
-34.3385
18
-35.2656
19
-28.8214
19
-29.5995
20
-31.6429
20
-32.4972
21
-30.3818
21
■531.2021
47.7200
45.6900
44.ieco
45.21C0
44.4900
43.6500
44.3600
43.5eC0
-21.7335
-25.5144
-33.3133
-24.48S9
-38.4351
-27.0927
-42.2011
-30.8148
-43.10E0
-31.4974
-46.0594
-34.9672
-35.0295
-26.1607
-33.8021
-25.3289
-37.3564
-28.3480
-35.5660
-27.1464
-40.7821
-30.2761
-<.0.60C5
-29.9654
-29.6968
-22.2458
-33.4340
-24.9850
-32.8087
-24.3693
-37.flle2
-28.3429
-42.24e4
-30.59e4
-37.4587
-27.12CO
-31.5575
-23.8523
-30.4521
-22.4997
29
. 57C0
56
.5000
58
.7800
60
.OBCO
59
.9300
6 0.
. 38CO
b!
■ 48C0
63
.7200
63,
,e300
65,
. 15C0
6?
,4700
60,
, 76C0
61 ,
,26C0
60.
,4300
S>J.
6500
60.
caco
59,
S0CO
'.9.
2900
58.
7800
59.
8700
BBUI)'.0210>
ALT. IN
Ai"Ao
METERS
1 2
^.7966
150
-8.6068
-.8118
-11.7626
-.8548
100
-7.2331
-.8818
-5.8796
-.8967
50
-4.9110
-.9231
-3.6169
-.9484
150
-10.4016
-.9717
-8.7227
-.9686
100
-7.0762
-.9720
-5.7875
-.9599
50
-3.0833
-.9431
-3.2612
-.9330
150
-8.6116
-.9275
-8.3261
-.9132
100
-5.6169
-.9081
-6.2955
-.9086
50
-4.6672
-.8996
-2.4795
-.9090
1 CA
-8.6449
-.9050
■8.7024
4176
McAlister, McLeish, and Corduan
Experimental Results
The operation of the system is illustrated by
a set of computer print-outs of magnetic tape
records obtained during the Barbados exercises
(Bomex) on May 26, 1969, and interpretation
of these records. As mentioned previously the
losses in the atmospheric path to the sea are
determined by two flights, each at three alti-
tudes: 50 meters, 100 meters and 150 meters.
These are made in a series of flights in a
racktrack course around Scripps vessel Flip.
Successive flights of 26 sec (yielding data for
^1.6 km of sea surface) were made upwind
300 meters north of Flip and then downwind
300 meters south of Flip. On May 26, from
1743 to 1838 LT 20 fly-bys were made and
the computer print-out of the average of a
part of the 100-entry record is shown in Table
1, along with the blackbody temperatures and
the water surface temperature from channel 1.
Note that the water temperature is between
the blackbody temperatures. Each one of the
entries in this table is the average of 2600 in-
dividual readings. Notice the small variations in
temperature of the blackbodies and of the
water at a 0.075-mm depth, the latter being
the average temperature for a 1.6-km path
on the sea surface. (Details of these tempera-
ture calculations are given later.)
The computer (CDC 3600) is programmed
to calculate A^ and A2> the right-hand members
of equations 2 and 3. Some of the steps in this
calculation are printed out by the computer
in Table 2. The first column is the record (flight)
number, the second column is IVl — IBl, the
third column is IBl — IB,. The fourth column
is IUt — IBl (channel 2), the fifth column is
IBi — IBa (channel 2), the sixth column is
TB, — TBl in degrees centigrade, the seventh
column is flight altitude, and finally in column
8 is Ai — A2 in intensity units.
The first number in column 2 is the numer-
ator of equation 2. The next number down (also
record 2) is the above number divided by (1 —
rj which makes it Aa. Numbers in the third
and fifth column are the intensity differences
in channels 1 and 2 for the temperature differ-
ences (column 6) between the two blackbodies.
The first number in column 4 is the numerator
of equation 3. The next number down this
column is the first one divided by (1 — r2)
and multiplied by the sensitivity ratio of col-
umn 3 over column 5. This number is A2.
Column 7 is the altitude of the flight in meters.
Column 8 is Ax — Aa (equation 4) for the dif-
ferent altitudes of flight, column 7. A progres-
sive change in intensity difference from the two
water depths (column 8) is apparent as the
sea surface is approached in equal steps of 50
meters. These values of Ai — A2 are plotted
against altitude in Figure 1. Each value plotted
here is an average and is derived from 5200
readings in the two channels. The circled points
are average values for the different flight alti-
tudes and are derived from some 21,000 read-
ings for the 150-meter altitude and 16,000
readings for the 100- and 50-meter altitudes.
The intercept at zero altitude shows a dif-
ference of 0.75 intensity units. Using equation
6, C (the calibration constant) is calculated
from the average of the numbers in column 6
divided by the average of the numbers in
column 3. This ratio is 0.0208 °C per intensity
unit in channel 1 for the exercise. The average
temperature difference between the depths of
0.025 mm and 0.075 mm during this time in-
terval is obtained from equation 5 and has a
value of 0.75 X 0.0208 = 0.016°C.
The heat flow equation
Q = K AT/d per unit area
gives the amount of heat energy flowing up-
wards as
0.086 X 0-016
0.0050
= 0.27 cal cm min"
LU UJ
O Q
Z ID
£ l 10 -
50 IOO
ALTITUDE - METERS
150
Fig. 1, Intensity difference received at altitude
versus altitude.
Heat Flux
4177
This then is the average value of heat flux
from the sea surface for the period 1743 to
1838 LT on May 26, 1969, near the latitude and
longitude of Flip, 13.57 N and 56.33 W.
Table 3 shows the average sea-surface tem-
perature and average heat flux obtained for the
useful flights made at Barbados. Column 3
shows average values of wind speed at a 2-meter
altitude as measured on Flip and kindly sup-
plied by K. Davidson, University of Michigan.
These are averages over the time intervals indi-
cated in column 2. The sea-surface tempera-
tures shown are average values for the time
interval indicated. The average deviation in
temperature is shown below each value. The
average temperature for individual fly-bys of
five of these exercises are shown in Tables 4
and 5.
The heat flux result for the May 26 exercise
(calculated as shown above) is the second entry
in Table 3. The May 27 results are calculated in
detail in McAlister and McLeish [1970, page
2702]. The results for May 24 and May 29 are
obtained in exactly the same way from tape
records for these dates. The May 29 exercise
was flown nearer to Barbados and also nearer
to vessels participating in Bomex. The strong
radar pulses from these vessels interacted with
our electronic system a good part of the time
so that only fragmentary records were obtained.
These fragments, however, did enable a value
of 0.4 cal cm"2 min"1 to be calculated.
The comments column in Table 3 gives some
indication of weather conditions, especially for
the first three exercises listed. The negative
results for May 25 were caused by radar inter-
ference nearly 100% of the time. On May 19 the
wind was very gusty, so much so that the air-
craft could not maintain a constant altitude,
and there was no way to correct for this. In
the early exercise on May 24 the power supply
for the electronic system became so 'noisy' that
no useful data could be obtained. The aircraft
returned to Barbados, the power supply was
repaired, and a late flight on that date gave the
results shown in the first entry in Table 3. The
TABLE 3. Total Heat Flux Results
Date (1969)
Local Time
Sea Surface
Wind Speed Temperature
cm sec"1* °Ct
Heat Flux
Results t
cal cm-2 min-
Comments
May 24
1827-1858
612
27.77
±0.02
0.05
Intermittent rain
May 26
1740-1838
890
28.06
±0.02
0.27
Rain nearby
May 27
0446-0552
830
27.71
±0.02
0.45
Best weather
May 29
1724-1834
—
28.44
0.4
Radar interference
90% data lost
May 25
1746-1838
650
27.61
±0.13
Negative
Radar interfer-
ence
May 19
1804-1855
795
27.96
±0.02
Negative
Heavy weather.
Altitudes uncer-
tain
May 24
0654-0724
770
28.08
±0.05
Negative
Internal interfer-
ence from power
supply
May 28
0553-0623
830
27.84
±0.07
Negative
Gusty winds;
spray below 75
meters
* Data from Flip.
t Average over a 1.6-km strip 75 meters wide.
4178
McAlister, McLeish, and Corduan
May 28 exercise gave no heat flux results be-
cause of wind-blown spray encountered at the
75-meter altitude. This prevented an accurate
extrapolation of data to the sea surface.
The comparison of heat flux results shown in
Table 3 with simultaneous measurements by
others on Flip did not materialize. The only
comparison that can be made was to data ob-
tained on Flip the week before, which ranged
in value from 0.15 to 0.40 cal cm"2 min"1. This
range compares favorably with values in Table
3, but the measurements were not simultaneous.
The May 29 value of 0.4 cal cm"2 min"1 may be
compared to a simultaneously obtained value
of 0.3 cal cm"2 min"1 reported in a private com-
munication by Dr. B. Bean of ESSA. Laboratory
measurements in a wind-water tunnel [Mc-
Alister and McLeish, 1969] show an experi-
mental error in heat flux for this system of
±8%.
Sea-Surface Temperatures
McAlister and McLeish [1970] showed that
the use of an airborne digital data recorder, con-
TABLE 4. Sea-Surface Temoeratures
TABLE 5. Sea-Surface Temperatures
May 19, 1969
14.43 N, 57.32 W
May 24, 1969
13.57 N, 56.30 W
Surface Surface
Local Time Temp. °C Local Time Temp. °C
1804
06
08
12
14
16
18
20
25
27
30
32
35
.'57
41
43
45
47
50
53
1855
27.94
0.95
0.95
0.94
0.98
28.00
27.96
0.98
28.01
27.95
0.98
0.98
0.97
0.94
0.95
0.96
0.94
0.94
0.95
0.90
27.92
27.96 ± 0.02
0700
04
OS
12
17
20
22
24
0728
1827
31
33
40
43
45
47
50
53
55
1858
.05
28.05
0.09
0.16
0.20
0.05
0.04
0.06
0.07
27.99
28.08 ±
27.79
0.77
0.84
0.78
0.75
0.78
0.78
0.77
0.69
0.74
27.75
27.77 ± .02
May 26, 1969
13.57.3 N, 56.33 W
May 27, 1969
13.58 N, 56.37 W
Surface Surface
Local Time Temp. °C Local Time Temp. °C
1743
46
49
52
55
57
1801
03
06
09
13
16
20
22
26
28
32
35
1838
28.09
0.07
0.11
0.08
0.10
0.10
0.04
0.08
0.03
0.04
0.06
0.05
0.05
0.04
0.07
0.06
0.01
0.06
28.02
28.06 ± 0
.02
0446
49
52
55
59
0502
06
08
11
14
17
20
24
27
30
33
37
40
43
46
49
0552
27.70
0.70
0.70
0.67
0.69
0.72
0.69
0.69
0.70
0.73
0.75
0.75
0.74
0.73
0.72
0.74
0.71
0.73
0.70
0.74
0.70
27.71
27.71 ± 0.02
tmuous calibration of detector sensitivity, and
the data reduction methods employed provided
an accuracy in temperature measurement of
0.01 °C. These factors also allowed measure-
ment of the temperature difference between the
two water depths to 0.003°C. This accuracy is
reached in a 30-sec averaging period, i.e., while
the aircraft is flying 1.6 km at constant altitude
over the ocean. (Thermistor drift found after
6-months use caused an error of 0.004 in tem-
perature values.)
In Table 1 there are two rows for each fly-by
(record number). The lower one is labeled
AVG. TEMP, (average temperature) and the
two temperatures on the right are of black-
bodies 1 and 2 obtained from the numbers
immediately above and calibration charts. The
average sea-surface temperature for that 1.6
km of flight is shown to the left. These sea-
surface temperatures are obtained as follows:
for record 21 in Table 2 we find the entry
(lower one) 31.202 which is a value for the
right-hand member of equation 2, i.e., the
Heat Flux
4179
radiation intensity difference between the sea
readings and the readings on blackbody 1. The
radiometer sensitivity for record 21 is the ratio
of the temperature difference between the two
blackbodies and their intensity reading differ-
ence in column 3, i.e., 0.905/43.58 or 0.0208°C
per unit intensity. The product 0.0208 X
31.202 = 0.649°C is the temperature difference
between the sea and blackbody 1 . Table 1 shows
an average temperature for blackbody 1 of
27.332°C. So 0.649 + 27.332 or 27.981°C is
the average sea-surface temperature for that
record, which is printed out by the computer
in Table 1 for record 21. The average sea-sur-
face temperature for each record in Table 1 is
calculated by the computer in the same way.
The effect of surface roughness and waves
(i.e., sea state) on these temperature readings
is discussed by McAlister and McLeish [1970]
on page 2701. Here the studies of others and the
25° beamwidth of the radiometer that was used
lead to the conclusion that as a first approxi-
mation the ocean is 'essentially flat' even up to
high wind speeds. This can be visualized by
noting that the radiometer beam averages the
intensity received over one or two wavelengths
of ocean waves so the effect of positive and
negative slopes tends to cancel. If the relation
between reflectivity and angle of incidence were
linear, the effect of equal elements of positive
and negative wave slopes would exactly cancel
under conditions where the effective sky radia-
tion is constant with angle from the zenith. For
a range of ±15° the reflectivity versus angle
is nearly linear (departs a maximum of three
parts in 100 from linear). Also for a uniform
overhead sky its radiation is quite uniform out
to 30° from zenith. Thus the assumption of a
'flat' ocean is a good first approximation, the
limits of which will have to be set by consider-
able experience. The distribution of wave slopes
(including capillaries) is somewhat different
downwind compared to upwind so that a definite
lack of symmetry exists. The procedure followed
in these airborne measurements of making an
equal number of flights upwind and downwind
is believed to cancel out this wind effect. Evi-
dence for this belief can be seen in Figure 1
where the experimental points are seen to cluster
in a group above the line and another group
below this line. In Table 2 the even flights are
upwind and the odd flights are downwind. Of
these ten pairs of flights six gave results where
upwind and downwind were on opposite sides
of the line drawn, two were nearly equal in
value while two were opposed to the first six.
This shows evidence of a cancellation of the
wind effect as mentioned above.
With this in mind it is interesting to examine
the sea surface temperatures off Barbados for
the time periods shown in Table 3. Five of these
flights are shown in Tables 4 and 5. Each entry
in these tables gives the time of the start of
each 30-sec pass and the average sea surface
temperature for the strip flown over. These
values were obtained from the 3.5 to 4.1 fi
channel where atmospheric absorption is least.
Plotting the values as a function of altitude
of observation, an absorption correction of
+ 0.012°C for each 50-meter increase in alti-
tude was found. This correction was used to
obtain values shown in Tables 4 and 5.
Most of the time Flip was being held against
wind and current by a tug so there was little
overlap in the one-mile strips of ocean from
one pass to the next. In other words, each pass
was most of the time over a new strip of ocean
but these strips were not far apart. The latitude
and longitude for each exercise are shown in
these tables.
Examination of entries in these tables reveals
an interesting constancy in average tempera-
ture of these one-mile strips of ocean surface
under Barbados conditions. Surface tempera-
ture changes from one day to the next were
noted but for periods of an hour at night the
temperature stays remarkably constant. The
average deviation in temperature is shown and
for four of the five periods it is only ±0.02°C.
No previous measurements of sea-surface tem-
perature have been made which show the accu-
racy and area coverage (a 1.6-km strip) that are
reported in Tables 4 and 5. This type of temper-
ture measurement should be better for correla-
tion with oceanic and meteorologic factors than
isolated bucket temperature measurements.
Tests are in progress to study the possibility
of shipborne use of the heat flow system. Here,
so near the sea surface, atmospheric attenuation
is quite small and correctable from meteorologi-
cal data. A protective housing and stabilized
platform have been made. This usage, if found
possible, would enable longer time surveys at
much less expense.
4180 McAlister, McLeish, and Corduan
Limitations of the Present System Summary
The present procedure of flying at three alti-
tudes to obtain corrections for atmospheric
attenuation is very time consuming. A modifica-
tion of the radiometer's optical system to view
the ocean at 20° and 60° from the vertical
would provide two optical path lengths to the
sea from one altitude. With adequate system
sensitivity they should be sufficient for attenua-
tion corrections. This would be a major re-
design of the optical system.
Daytime operation with the present wave-
lengths used in channel 1 is not possible because
of solar energy reflected from the sea. Design
of a system for day and night operation is diffi-
cult but not impossible.
Sky conditions very different from those found
at Barbados have been encountered near San
Diego which interfere with the operation and
linearity of the preamplifier system. These con-
ditions are a clear cold night sky with small
scattered low clouds. Under these conditions
the clear sky signal, (/8ky — IB), may be 20
times that from the water, (Iw — IB), and it
may vary ±50% from second to second. Lab-
oratory tests duplicating these conditions show
the amplifier system to become erratic and to
depart from linearity in measuring intensity
differences. The sky conditions at Barbados for
all exercises showed a maximum variation in sky
signal of 5%. Further tests of the amplifier sys-
tem show that it departs from linearity when
the clear sky to cloud signal variation reaches
±15%.
An initial solution of this electronic problem
is under study. This is to attenuate the sky
signal about an order of magnitude by intro-
ducing a fixed impedance to the feedback loop
input of the preamplifiers when the rotating
mirror brings the sky radiation onto each de-
tector. Airborne tests of this solution are en-
couraging. Here it is necessary to write a new
program for the tape records to bring the sky
signal back to its unattenuated value before
proceeding with the calculations. If this does
not solve the scattered cloud problem then an
improved preamplification system will be neces-
sary. This would be a major undertaking.
Participation in the Bomex trials during May
1969 resulted in airborne measurements of the
total heat flow from the sea. The values found
at night ranged from 0.05 cal cm"2 min"1 on
May 24 to 0.45 cal cm-2 min-1 on May 27.
Measurements of heat flux made from Flip the
week before in the same location show a range
from 0.15 to 0.40 cal cm"2 min-1. Thus the range
of values found by conventional methods from
Flip and the airborne system agrees well but
the measurements were not simultaneous. Lab-
oratory tests of the airborne system show an
error of ±8%.
A new order of accuracy in measurement
of sea surface temperature has been demon-
strated. It surpasses the accuracy of oceano-
graphic mercury thermometry for sea surface
temperature.
A redesign of the optical system is possible to
shorten the time for one measurement. Also, a
preamplifier improvement to include a wider
range of sky conditions is under test.
These tests at Barbados have demonstrated
the feasibility of airborne measurement of total
heat flux with the present system. A thorough
'at sea' calibration is still lacking and further
redesign is necessary before this development
can be considered complete.
Acknowledgments. We are indebted to Bomex
management organization and its operations team
for fitting our needs so smoothly into a very com-
plex exercise.
This research was supported by the Office of
Naval Research, codes 461 and 481, Naval Ocean-
ographic Office code 7007, and National Science
Foundation, Atmospheric Sciences Section, under
grants GA-1491 and GA 11975.
References
McAlister, E. D., and W. McLeish, Heat transfer
in the top millimeter of the ocean, J. Geophys.
Res., 74, 3408, 1969.
McAlister. E. D.. and W. McLeish, A radiometric
system for airborne measurement of the total
heat flow from the sea, Appl. Opt., 9, 2697, 1970.
(Received October 10, 1970;
revised March 18, 1971.)
Reprinted from Journal of Atmospher ic Sciences 2 8 ,
No. 3, 429-435.
69
Measurements of Microwave Emission from a Foam-Covered, Wind-Driven Sea
W. NORDBERG, J. CONAWAY, DUNCAN B. ROSS1 AND T. WlLHEIT
Goddard Space Flight Center, Greenbell, Md.
(Manuscript received 13 October 1970. in revised form 11 January 1971)
ABSTRACT
Measurements were made from aircraft of the 1.55-cm microwave emission from the North Sea and North
Atlantic at surface wind speeds ranging from less than 5 to 25 m sec-1. Brightness temperatures in the nadir
direction increased almost linearly with wind speed from 7 to 25 m sec-1 at a rate of about 1.2C (m sec-1)-1.
At 70° from nadir the rate was 1.8C (m sec-1)-1. This increase was directly proportional to the occurrence of
white water on the sea surface. At wind speeds <7 m sec-1, essentially no white water was observed and
brightness temperatures in the nadir direction were ~120K; at wind speeds of 25 m sec-1 white water cover
was on the order of 30% and average brightness temperatures at nadir were ~142K. Maximum brightness
temperatures for foam patches large enough to fill the entire radiometer beam were 220K.
1. Introduction
Considerable interest has been devoted to the quanti-
tative measurement of sea surface roughness, on a
global scale, from spacecraft and to the possible deriva-
tion of surface winds from these measurements (NAS
Summer Study, 1969). For this reason, we measured
the microwave emission at 1.55 cm over the North
Atlantic and the North Sea in March 1969 over a wide
range of sea surface, wind and cloud conditions in order
to establish a quantitative relationship between the
emission and the sea state and to delineate parameters
such as surface winds, foam cover, wave height and
cloud cover that would affect this relationship.
Earlier measurements (Nordberg el al., 1969) over
the Salton Sea have shown that the microwave emis-
sion, observed at all nadir angles from 0° to 50° and
at a wavelength of 1.55 cm, is considerably greater
from a rough water surface than from a smooth one.
Stogryn (1967) had predicted that increases in micro-
wave emission from rough water could be observed
only at nadir angles >30°. However, Stogryn's calcula-
tions were addressed primarily to the effect of the large-
scale wave geometry on the emission and did not, for
example, account for foam and spray. We have there-
fore conducted these observations at high wind speeds
and extensive foam cover to investigate further this
discrepancy between theory and earlier observations.
2. Description of experiment
Measurements were made from the NASA Convair
990 airborne observatory. Primary instruments carried
by the aircraft were as follows :
1 Present affiliation : NOAA Air-Sea Interaction Laboratory,
Miami, Fla.
1) A radiometer measuring horizontally polarized
radiation at 1.55 cm wavelength within a 2.8° diameter
field of view which was scanned perpendicularly to the
aircraft's flight path over a nadir angle range of ±50°.
The same instrument was used in the Salton Sea obser-
vations; it was built by the Space Division of Aerojet
General Corporation (Oister and Falco, 1967).
2) A laser geodolite of the Spectra-Physics Corpora-
tion to measure the ocean wave height spectrum.
3) An infrared radiometer, similar to the Medium
Resolution Infrared Radiometer (MRIR) flown on
Nimbus satellites (Nimbus III User's Guide, 1969),
to determine the sea surface temperature from emission
measurements at wavelengths between 10.6 and 11.6
(j.m.
4) Standard airborne navigation systems, both
Doppler and inertial, with which wind speed and direc-
tion at the aircraft altitude were measured.
5) A Vinton 70-mm camera, pointing at nadir with
a square field of view of about 68°, to photograph sea
surface and cloud conditions.
In addition, the aircraft carried standard instrumen-
tation for altitude, attitude, speed, and ambient tem-
perature measurements and auxiliary cameras. A non-
scanning, nadir viewing, 3-cm microwave radiometer
with a field of view of about 13°X 13° was provided by
the Jet Propulsion Laboratory for comparison with the
1.55-cm measurements.
The aircraft was based at Shannon, Ireland. Two
flights, averaging 5 hr each, were made over the North
Sea, and four flights, equally long, covered a region of
the North Atlantic between Iceland and Ireland. In
general, passes were made over each area of interest at
several altitudes between 120 and 12,000 m to differ-
entiate the effects of atmospheric and surface emission.
430
JOURNAL OF THE ATMOSPHERIC SCIENCES
Volume 2
Table 1. Summary of meteorological conditions and microwave emission temperatures for six overwater flights.
Case
Date (March 69)
Time (GMT)
Location
A
10
1321
Atlantic
Off Shannon
B
13
1247
Atlantic
Ship J
C
13
1117
Atlantic
Ship I
D
10
1430
Atlantic
Ship I
E
19
1023
North Sea
57°N 3°E
F
14
1453
North Sea
59°N 1°30'E
Wind speed (m sec-1)
<5
6
13
16
17
25
Significant wave height (m)
<1
6.0|
3.9
5.0
4.0
7.8
Foam cover (%)
Whitecaps
Streaks
Total
—
—
4.2
3.5
7.7
5.6
6.9
12.5
6.0
17.4
23.4
5.0
27.0
32.0
Temperature (°C)
Sea surface
Air surface
9
10 (est.)
10
11
9
7
9
5
2
2
4
2
Cloud altitude (m)
Base
Top
2000
2300
clear
clear
300
2100
800
2000
600
2000
150
5000
Brightness temperature (CK)
High altitude*
Low altitude
128**
120
118
127
138
132
138
132
148
142
* Measured within 30 min of time shown.
** Over Irish Sea at 1212 GMT.
f All swell, no wind waves.
Surface wind speeds ranged from calm to 25 m sec-1.
They were obtained from surface anemometer obser-
vations and/or by extrapolation of the aircraft measured
ambient wind speeds at the lowest flight altitudes under
the assumption that wind speed decreased exponen-
tially toward the surface (Ross et al., 1970). Where both
were available no significant discrepancy was noted.
This assumption was applied to all cases shown in
Table 1, except case E. In that case, examination of
reduced geostrophic winds and ship reports led us to
assume that the wind speed increased from the height
of the aircraft to the surface. We are very much in-
debted to Prof. Vincent Cardone of New York Uni-
versity for pointing this out to us. A similar increase
in wind speed with decreasing altitude was observed
during the Salton Sea flight. However, in the absence
of surface observations, it was not deemed appropriate
to depart from the winds observed at 200 m, the mini-
mum aircraft altitude, for our approximation of the sur-
face winds. In this case, it is recognized that the true
surface wind speed could be considerably higher. For
the Atlantic Ocean and North Sea observations, the
accuracy of the surface wind speed determinations is
judged to be within 3 m sec-1.
Cloud conditions, observed visually and photo-
graphically from the aircraft, ranged from clear to
stralocumulus overcasts with moderate rain, over the
numerous sea surface targets selected for the flights.
The 10-11 jum equivalent blackbody temperatures
were taken to be equal to the sea surface temperature
when measured with the infrared radiometer at the
lowest altitudes. Temperatures ranged from 10C at 50N
over the Atlantic to 2C over the coldest part of the
North Sea.
Sea state varied from calm, with no whitecaps, tc
significant wave heights of ~8 m with over 30%
coverage by foam with extensive streaking. Significant
wave heights were determined by analysis of the wave
spectra observed with the laser geodolite. The foam
coverage was determined from photographs of the sea
surface with a digital densitometer. The method con-
sists of numerically computing the areas on the photo-
graphs above and below a chosen brightness threshold
such that whitecaps, foam streaks and undisturbed sea
can be differentiated quantitatively. These parameters
are listed in Table 1. Due largely to the subjective
nature of the choice of the thresholds, the accuracy of»
this method is limited to about 15% of the value ob-
tained. Percentages for each case are averages resulting
from several consecutive photographs due to the vari-
ation in the foam cover between individual frames.
Whenever possible, sea state, temperatures and winds
measured with the aircraft were compared with the
observations obtained from ocean vessels I and J
(59N, 19W and 53N, 20°30'W, respectively) and with
analyses made by the Irish Meteorological Service at
Shannon Airport. There was never any significant dis-
crepancy among these data. A complete log of all
llights, including environmental and meteorological
observations was compiled by Griffie et al. (1969). The
specific conditions for which microwave measurements
are reported here arc summarized in Table 1.
3. Results
Brightness temperatures measured at 1.55 cm during
six low-altitude passes over the Atlantic and North Sea
at wind speeds ranging from less than 5 to about 25
m sec-1 were selected to illustrate their dependence on
April 1971
1320
-+
NORDBERG, CONAWAY, ROSS AND WILHEIT
19 MAR
1429 1432 10
l-
431
19 MAR
1323 1116
13 MAR
1119
1432 1020
1023 1449
I-
14 MAR
1452 1455
TIME (GMT)
1427 1430
14 MARCH
Fig. 1. Instantaneous brightness temperatures measured in the nadir direction vs time. Plot (a) corre-
sponds to case A in Table 1, plots (b)-(e) to cases C-F. All brightness temperatures in (a)-(e) were
observed from heights of > — 'ISO m. Brightness temperatures in (f) were observed from a height ~5500 m
over approximately the same location as (e).
wind speed and foam cover (Fig. 1). The recorded
radiometer output was converted to radiances taking
into account the calibrations performed on board the
aircraft during each scan with two reference loads, one
stabilized at 330K and another terminated in a liquid
nitrogen dewar. Antenna and radiometer character-
istics, including effects of radiation received by the
antenna through side lobes outside the 2.8° diameter
instantaneous field of view which were measured in the
laboratory and against a known sky background prior
to and after the expedition, were also taken into ac-
count in this conversion. The resulting radiances are
expressed as brightness temperatures (°K) and are
plotted in Fig. 1 for the nadir viewing positions only.
The radiometer field of view scanned from 50° left of
nadir to 50° right of nadir, once every 2 sec. Thus, the
traces shown in Fig. 1 consist of one data point per
2 sec. They cover time segments corresponding to the
sea, cloud and wind conditions listed in Table 1.
The plotted brightness temperatures (Tb) result
from three radiation components received by the
radiometer — radiation emitted to the aircraft by the
sea surface, radiation emitted to the aircraft by clouds
and atmospheric water vapor, and atmospheric radia-
tion reflected toward the aircraft by the sea surface :
TB = eTWTH+(l-€)TSTH+ I TA(h)(dT/dh)dh, (1)
where Tw is the water surface temperature, Ts the sky
brightness temperature, TA the atmosphere tempera-
ture, r the atmosphere transmissivity, e the surface
emissivity, h height above surface, and H aircraft
altitude. The first, second and third terms of (1) cor-
respond to surface emission, reflected atmospheric
radiation, and atmospheric emission, respectively.
The cases listed in Table 1 were chosen such that
atmospheric conditions, including cloud cover, were
generally similar. In each of these cases, there was no
measurable precipitation from the prevailing broken
stratocumulus clouds. Somewhat denser cloud cover
encountered during higher wind speeds was almost
compenstated for by the lower atmospheric tempera-
tures prevailing in these cases. For example, we have
computed that the reflected radiation component for
cases A and B of Table 1 (thin clouds but warm
atmosphere) contributed ~9.5C to the measured
brightness temperature, while for cases E and F
(thicker clouds, but cold atmosphere) this contribution
was ~11C. Thus, for the conditions listed in Table 1,
the reflected component due to T s can be assumed to
be nearly constant, with variations certainly remaining
smaller than 3C. Also, the directly received emitted
atmospheric radiation was negligible when the aircraft
was at low altitudes (150-200 m), since there were no
clouds below the aircraft, and the transmissivity was
very near unity between the aircraft and the surface. In
those cases, the integral term in Eq. (1) approaches zero.
Measurements of TB were also made from high
altitudes (> 5000 m) for the same conditions and gener-
432
JOURNAL OF THE ATMOSPHERIC SCIENCES
Volume 2
i r
X ATLANTIC, NORTH SEA
• SALTON SEA «
10 20
WIND SPEED (m/sec)
30
Fig. 2. Brightness temperature differences between observations
made at wind speeds <5 m sec-1 and higher wind speeds as a
function of wind speed.
ally within less than 30 min of the times listed in Table
1. Brightness temperatures were 6-8C higher (depend-
ing on sea surface roughness) than corresponding bright-
ness temperatures observed at the low altitudes. In
each case, these increases relative to the low-altitude
passes account quite precisely for the emitted atmo-
spheric radiation term and for the decrease of th from
unity to about 0.95. The comparison between low- and
high-altitude observations confirms our assertion that
the measurements shown in Fig. 1 were obtained under
comparable atmospheric and cloud conditions.
At this wavelength, the measured brightness temper
atures are essentially independent of the sea surface
temperatures within the observed range, because e
varies inversely with the surface temperature such that
iTw in Eq. (1) is nearly constant. Differences between
the measured brightness temperatures for the various
cases of Table 1 are then almost entirely due to dif-
ferences in sea surface roughness. Brightness tempera-
ture differences between the lowest wind condition
(case A) and each of the other cases were computed
and plotted vs surface wind speeds in Fig. 2. A system-
atic increase in emission with increasing wind speed is
clearly evident. The rate of increase is ~1.2C (m
sec-1)-1. A qualitatively similar result was obtained
from the data taken over the Salton Sea in 1968.
This previously unpublished datum is from the same
series of measurements discussed by Nordberg et al.
(1969). The apparent quantitative disagreement with
the 1.2C rate of increase for the North Atlantic and
North Sea measurements is not deemed significant
because of the large wind speed uncertainty in the
Salton Sea case.
Measurements for the nadir direction only were
plotted in Figs. 1 and 2. At larger nadir angles, up to
70°, we have observed proportionally larger rates of
increase. Fig. 3 shows brightness temperatures as a
function of nadir angle for a low and for the highest
wind speeds listed in Table 1. Although the radiomete
antenna scanned only to nadir angles up to 50°, wi
were able to observe radiation from nadir angles up t<
80° during banking of the aircraft. The two solid curve:
in Fig. 3 were obtained by smoothing brightness tern
perature averages at each nadir angle for periods o
10-20 sec during which the aircraft bank angle wai
held constant at 30°. The brightness temperature rat<
of change with wind speed increased from 1.2C (rr
sec-1)-1 at nadir to ~ 1.8C (m sec-1)-1 at 70° from nadir
This is qualitatively in accord with observations b\|
Hollinger (1970), who reported an increase from 0.8C
(m sec-1)-1 at 30° from nadir to 1.4C (m sec-1)-1 al
70° from nadir, for a much lower wind speed range.
The dashed curve in Fig. 3 was computed for the
atmospheric and sea surface temperature conditions
observed for case B, but for a specular sea surface. The
absolute brightness temperatures measured at nadir
for case B were ~ 15C lower than the computed tem-
peratures (dashed curve). We believe that this dis-
crepancy is largely due to errors in the absolute calibra-,
tion of the radiometer and indicates that all brightness
2 130
120
z 110
I
o
80 -
-20
20 40
NADIR ANGLE (degrees)
Fig. 3. Brightness temperatures averaged for 10-29 sec time
periods, for each antenna scan angle during 30° aircraft banks, vs
nadir angle for case B of Table 1 (lower curve) and case F of
Table 1 (upper curve). Absolute brightness temperatures were
normalized to computations for smooth sea (dashed curve) at
nadir. The dashed curve shows computed brightness temperatures
for atmospheric and sea surface temperatures encountered in case
B but for a smooth, specular sea surface.
April 1971
NORDBERG, CONAWAY, ROSS AND WILHEIT
433
temperatures measured with this instrument should be
corrected by about + ISC. This correction was made for
the brightness temperatures plotted for cases B and F
in Fig. 3. The relative calibration of the instrument was
maintained at about ±1.5C throughout all flights.
Comparison of the slope of the dashed curve with the
slope of curve B shows that the decrease of brightness
temperatures with nadir angle is much steeper for
a theoretical, specular and smooth water surface than
for real water surfaces, even at low wind speeds.
This suggests that the small-scale roughness intro-
duced even by very low winds causes a considerable
brightness temperature increase at large nadir angles.
The slopes of curves B and F differ much less than those
of curve B and the smooth water curve. This suggests
that the rate of brightness temperature increase with
nadir angle diminishes at the higher wind speeds. How-
ever, there remains a brightness temperature increase
of at least 22C with wind speed at all nadir angles, as
shown by the offset of curve F compared to curve B.
This offset could be caused by the greater emission
from white water such as foam and spray which would
produce nearly the same brightness temperature in-
crease at all nadir angles, depending only on the amount
of foam cover.
Fig. 2 shows that a nearly linear brightness temper-
ature increase with wind speed occurs above a threshold
of ~7 m sec-1. The measurements at 6 m sec-1 (case B)
show no increase of Tb over the measurements at less
than 5 m sec-1 (case A). There is no evidence of any
brightness temperature difference between cases A and
B despite the fact that the sea surface was very smooth
for case A while extremely large swells (6 m) but no
whitecaps were observed for case B. Monahan (1969a)
has reported an abrupt increase in whitecap coverage
and spray density at 7 m sec-1 and Cardone (1969) has
computed that the energy available for whitecap pro-
duction at wind speeds <7 m sec-1 is practically
negligible. This suggests that the increase of microwave
emission with wind speed, shown in Fig. 2, is related
mainly to the occurrence of white water (foam and
spray). At lower wind speeds, where foam does not
occur, the brightness temperature measured at all nadir
directions is independent of wind speed. Foam has been
suspected previously as a cause for increased microwave
emission (Williams, 1969; Droppleman, 1970).
Further evidence of the dependence of the micro-
wave emission on foam cover can be found in the rapid
brightness temperature fluctuations with time, shown
in Figs, lc-le. In Fig. Id, for example, the average
brightness temperature is ~132K, but, instantaneous
spikes frequently reach 140K and two spikes exceed
155K. Fig. le, which corresponds to winds of 25 m
sec-1, shows many more of these spikes. In this case,
the average brightness temperature is ~142K, but
instantaneous spikes exceeding 150K occur about every
30 sec. Several of these spikes range between 175 and
Fig. 4. Photographs with a 70-mm camera taken in the nadir
direction at surface wind speeds of 16 m sec-1 (a) and 25 m sec-1
(b), corresponding to cases D and F, respectively, in Table 1.
190K. From the photographs there is a strong implica-
tion that these spikes are caused by foam patches on the
sea surface.
We have analyzed the instantaneous brightness tem-
peratures measured at all scan angles over a period of
20 min, approximately centered on the time corre-
sponding to Fig. le. to determine the amplitude and
frequency of brightness temperature spikes. We found
that the maximum amplitude was ~220K for seven
spikes which occurred during that period. One such
spike was clearly coincident with the immense foam
patch photographed in Fig. 4b. The radiometer scanned
the scenes shown in Fig. 4 from left to right, with the
434
JOURNAL OF THE ATMOSPHERIC SCIENCES
Volume 28
I 1 I l
• 5ALT°N SEA 1 FROM J
X ATLANTIC - NORTH SEA { PH°T°S /
D SINGLE FOAM PATCHES /
/
+ WHITECAP MODEL /
CARDONE (1969) /
<\/
ox-
0
y
40 60
% FOAM COVER
100
Fig. 5. Brightness temperature differences between observations
made at wind speeds less than 5 m sec-1 and at higher wind speeds
as a function of foam cover as estimated from photographs, from
the analytical model of Cardone, and from single foam patches
covering the entire microwave radiometer beam.
aircraft having flown from bottom to top. Since the
position of the scans on the photographs are not known
exactly, and since at low altitudes scans were not con-
tiguous, the foam patches may not always have filled
the antenna field of view entirely. We assume that this
occurred only when the maximum brightness tempera-
tures of 220K were measured.
The photographs of Fig. 4 were taken over sea states
corresponding to the brightness temperature measure-
ments in Figs, lc and le, respectively. Aircraft altitudes
ranged from 120 to 450 m. Fig. 4b was observed
from 120 m and extends over about 200 m from top
to bottom. The foam estimates (Table 1) were made
from time series of photographs similar to those shown
in Fig. 4. The increasing amounts of both foam patches
and streaking with wind speed are quite apparent from
Table 1. We assume that such streaking and foam
patches, which were small relative to the radiometer
field of view, raised the measured brightness tempera-
tures uniformly throughout each scan, but that the
largest patches of foam produced the temperature
spikes which were more than 70C above the average.
It is, therefore, very important that estimates of foam
coverage, as they relate to the microwave emission,
include the effect of both foam patches and streaking.
This has been attempted with the estimates of total
foam cover listed in Table 1.
The brightness temperature spikes seen in Figs. Id
and le were not observed when the aircraft was at
higher altitudes, where each foam patch covered an
area much smaller than that resolved by the instantan-
eous field of view of the radiometer. Fig. If shows
brightness temperatures measured from 5500 m in the
vicinity where the photograph of Fig. 4b and the
measurements shown in Fig. le were made. No large
spikes are evident in this case. At the aircraft height of
120 m (Fig. le) each scan spot covered an area with a
diameter of ~ 7 m, while at the aircraft height of 5500 m
(Fig. If) the diameter of the area covered was ■ — -275 m.
In the latter case, brightness temperatures show a
much smoother pattern with no significant spikes be-
cause the characteristic diameter and spacing of the
largest foam patches were less than ~ 100 m (Fig. 4b)
and individual patches were not resolved by the
radiometer.
Brightness temperature differences were plotted vs
foam coverage in Fig. 5, as determined from the photo-
graphs (solid line). There is a similar increase of bright-
ness temperature with foam cover, as there is with wind
speed. However, the rate of increase obtained from the
small-scale, single foam patch measurements, each repre-
senting 100% foam cover (dashed line), is considerably
greater than the rate determined from the large-scale
observations derived from the photographs for less
than 40% foam cover (solid line). There are two possible
explanations for this discrepancy :
1) The estimates of streaking which account for a
large portion of the white water coverage as determined
from the photographs (Table 1) are subjective, though
internally consistent. Thus, foam cover as determined
from the photographs may have been overestimated.
This is also suggested by the fact that if foam cover is
taken from Cardone's (1969) model, corrected for salt
water after Monahan (1969b), brightness temperature
increases are consistent with the rate obtained for 100%
foam cover (dashed line) which is independent of the
estimates made from the photographs. The uncertainty
of estimating Whitewater coverage from photographs
and the possibility of overestimating foam cover has
been pointed out recently by Blanchard (1971).
2) Another possibility is that the total white water
estimates made from the photographs are correct but
that the effect of the streaks on the microwave emission
is smaller than the effect of the whitecaps which
produce the 100% foam cover spikes. In this case, the
agreement with Cardone's model would be purely coin-
cidental. Further microwave measurements under con-
trolled conditions of foam and streaking should resolve
this point.
It is noteworthy that the Salton Sea measurements
made on 5 June 1968 are generally consistent with the
North Sea and Atlantic measurements with regard to
brightness temperature dependence on both wind speed
and on foam cover.
Preliminarv results from the 3-cm radiometer, flown
simultaneously with the other instruments, indicate
that the brightness temperature increase at this wave-
length is about 8C for a wind speed increase from calm
to 13 m sec-1. Beyond 13 m sec-1 there is only a negligi-
ble increase in brightness temperature. However,
because of calibration uncertainties, the 3-cm measure-
ments cannot be considered as firm as those at 1.55
April 1971
NORDBERG, CONAWAY, ROSS AND WILHEIT
435
cm. We are indebted to Messrs. F. Barath and J.
Blinn of the Jet Propulsion Laboratory and A. Edgerton
of Aerojet General Corporation for making this, as yet
unpublished, information available to us.
4. Conclusions
There is a definite increase in the thermal emission
at 1.55 cm from the sea surface with increasing wind
speed. On the average, this increase amounts to about
22C in the nadir direction and 32C at 70° from nadir
for a wind speed increase from 7 to 25 m sec-1. For
very low wind speeds, up to about 7 m sec-1 when
foam cover is negligible, there is no increase in bright-
ness temperatures. Compared to calm sea states,
brightness temperatures are ~100C higher when foam
patches covering the radiometer field of view are ob-
served. We conclude that the increased emission
at 1.55 cm from a wind-driven sea surface is primarily
due to white water cover, while the effect of the wave
slope geometry is negligible. The microwave emission
at 1.55 cm from the sea surface is therefore a sensitive
indicator of white water coverage and of wind speed
at all nadir angles, at least to 50°.
We believe that an important parameter involved in
the interaction between air and the sea surface, namely,
the energy expended in the production of white water,
can be inferred from microwave brightness tempera-
ture measurements provided that: 1) the consistent
relationship between white water occurrence and wind
speed reported here is confirmed; and 2) microwave
measurements are made at various wavelengths, both
polarizations, and over a large range of nadir angles to
separate the various effects of foam cover, cloud cover,
and atmosphere and sea surface temperatures on the
microwave emission.
Results from the observations reported here might
provide a basis to test further developments or re-
visions of analytical models relating microwave emis-
sion to sea surface roughness.
Acknowledgments. There were several dozen indi-
viduals without whom these observations would not
have been possible. We are unable to name all of them,
but we acknowledge their dedicated contributions
gratefully. We are especially indebted to the NASA
pilots and flight crew of the CV 990 observatory for
carrying out the demanding flight operations that were
required for these observations, to Mr. Earl Peterson
of the NASA Ames Research Center for organizing
the expedition, and the Irish Meteorological Service
for providing excellent weather forecasts and analyses
to support our flight operations.
REFERENCES
Blanchard, D. C, 1971: Whitecaps at sea. /. Atmos. Sci., 27
(in press).
Cardone, V. J., 1969: Specification of the wind field distribution
in the marine boundary layer for wave forecasting. Geo-
physical Science Lab., New York University, Rept. TR69-1.
Droppleman, J. D., 1970: Apparent microwave emissivity of sea
foam. J. Geophys. Res., 75, 696-698.
Griflee, L., J. Ledgerwood, D. Hill and W. E. Marlatt, 1969:
Support data for NASA Convair 990 meteorological flight IV.
Dept. Atmos. Sci., Colorado State University, Ft. Collins,
83, pp.
Hollinger, J. P., 1970: Passive microwave measurements of the
sea surface. /. Geophys. Res., 75, 5209-5213.
Monahan, E. C, 1969a: Freshwater whitecaps. J. Atmos. Sci., 26,
1026-1029.
, 1969b: Laboratory comparisons of freshwater and salt
water whitecaps. /. Geophys. Res., 74, 6961-6966.
NAS Summer Study, 1966. Useful applications of earth-oriented
satellites. Summer study on space applications, National
Academy of Sciences, Washington, D. C.
Nimbus III User's Guide, 1969: Staff Members, Nimbus Project,
NASA, Goddard Space Flight Center, Greenbelt, Md.
Nordberg, W., J. Conaway and P. Thaddeus, 1969: Microwave
observations of sea state from aircraft. Quart. J. Roy. Meteor.
Soc, 95, 408.
Oister, G, and C. V. Falco, 1967: Microwave radiometer design
and development. Final Rept., Contract NAS5-9680, Aerojet-
General Corp., Space Division, El Monte, Calif.
Ross, D. R. V. Cardone and J. Conaway, 1970: Laser and micro-
wave observations of sea surface conditions for fetch limited
35 to 50 knot winds. IEEE Trans. Geoscience Electronics,
GE-8 (in press).
Stogryn, A., 1967: The apparent temperature of the sea at micro-
wave frequencies. IEEE Trans. Antennas Propagation, AP-15,
278.
Williams, G. F., Jr., 1969: Microwave radiometry of the ocean
and the possibility of marine wind velocity determination
from satellite observations. J. Geophys. Res., 74, 4591-4594.
70
Reprinted from IEEE Transactions on Geoscience
Electronics GE-9 , No. 4, 197-198.
Introductory Remarks.
SEA-AIR INTERACTION INSTRUMENTATION
Problems of the interaction between the atmosphere and the
ocean have confronted man ever since he left his homestead in the
urge to expand his horizon and to conquer new frontiers. In his
search for food and the riches of his environment, he had to master
the winds, waves, and ocean currents; and these factors are primarily
the result of air-sea interaction. More recently, the less obvious, but
perhaps in many respects equally important, aspects of air-sea in-
teraction have been stressed, namely, the influence of the ocean on
the atmosphere in producing weather and climates. This is reflected
in the present effort to gain a better understanding of the processes
occurring at the sea surface and in the adjoining boundary layers in
order to better parameterize the major exchanges of momentum,
heat, and moisture.
The importance of the oceans to the global environment lies in
the fact that more than two-thirds of the surface of this planet is
covered by water with its very special and unique physical properties.
This has profound effects on the atmosphere, since most of the energy
received from the sun is absorbed by the water. Again, most of this
absorbed energy in the water is released in the form of latent heat
during the evaporation process. Thus the ocean provides a large
portion of the moisture supply to the atmosphere and heats the
atmosphere when the latent heat of evaporation is freed upon con-
densation of water vapor in the atmosphere. This heat represents the
main fuel which drives the atmospheric circulation. It is therefore no
surprise that large-scale experiments, such as the 1969 Barbados
Oceanographic and Meteorological Experiment (BOMEX), have
been conducted recently to investigate air-sea interaction processes.
Others are planned for the future, such as those within the framework
of the Global Atmospheric Research Program (GARP), which are
designed to investigate how air-sea processes relate to large- and
small-scale convective atmospheric systems.
Recently, advances have been made in several problem areas.
Numerical atmospheric circulation models have been successfully
coupled through air-sea interaction with ocean circulation models.
Correlations between positive sea surface temperature anomalies in
the Northern Pacific and dry and cold winters in the Eastern portion
of the United States have been found, suggesting a strong large-
scale interaction between ocean and atmospheric circulation patterns.
Obviously, such large-scale investigations require data coverage
on the global scale. Although the general climatological coverage has
been obtained from data collected during the last hundred years by
merchant and other ships, vast areas outside the regular shipping
lanes are poorly covered. With the development of indirect sensing
techniques and man-made satellites and the considerable effort spent
in technology, global coverage for observing ocean surface parameters
such as temperatures, salinity, waves, winds, tides, and ocean cur-
rents appears possible. Present planning for oceanographic satellites
is concentrated on the feasibility of obtaining many of these pa-
rameters from space.
On the other hand, direct and indirect sensing techniques to be
employed from surface platforms also need further development in
order to provide ground truth ,i\»\ to investigate the important
processes that govern air sea exchanges. A most pressing need exists
to obtain a better understanding of planetary boundary layer dy-
namics. Here, Doppler radar and acoustic sounding techniques seem
to be the most promising tools for studying the three-dimensional
structure of the boundary layer of the air. Some pertinent work on
related problems may be found in the Prodizedings of the IEEE
(Special Issue on Remote Environmental Sensing, April 1969).
This issue, then, is organized in three parts: direct sensing of the
boundary layer structure, remote sensing of the sea surface parame-
ters, and laboratory studies of the water surface perturbed by waves
and foam.
The paper by Garstang el al. provides an excellent summary and
description of the marine atmospheric boundary layer and some of
the transfer processes germane to the subcloud layer. Although some
previous boundary layer observations exist, mainly over land and
made from high towers, the technique described in this paper is a
ship-deployed instrumented platform capable of providing unique
time-series data from the atmospheric boundary layer over the ocean.
Somewhat more limited in its use (nearshore areas) is a tracking
system, described in the paper by Dunkel el al., which permits wind
profiles to be observed in the atmospheric boundary layer using
rapid releases of pilot balloons. This system has been successfully
198
IEI E TRANSACTIONS ON GEOSCIENCE ELECTRONICS, OCTOBER 1471
applied in an experiment just concluded over the Grand Bahama
Banks. Some 400 wind profiles have been obtained in conjunction
with other pertinent observations.
The next two papers deal with remote sensing of ocean waves.
In his paper, league describes a technique by which long wavelength
directional wave spectra can be observed for an area of several hun-
dred kilometers offshore using LORAN A transmissions. This tech-
nique may prove a convenient way to monitor offshore wave condi-
tions. The paper by Chadwick and Cooper shows that with presently
available radar technology it should be possible to estimate wave
heights, at least from aircraft. Through functional relationships
between wind speed, letch, and duration, possibly wind speed could
be estimated by this technique.
Finally, a very important problem in the application of indirect
microwave teciniques is the knowledge of the emissivity of foam
and bubbles, which are generated extensively by breaking waves
and strong winds. Williams, in his paper, presents results of labora-
tory experiments that will be helpful in the interpretation of micro-
wave data.
In closing, I would like to emphasize that the collection of papers
in this issue represents a small sample of present scientific endeavors
in the field of air-sea interaction. It is gratifying to see that a sig-
nificant effort is now being made to bring to bear the advances in
technology of the last 10 or 20 yeats in helping to solve our environ-
mental problems.
Fe:odor Ostapoff, Guesl Editor
Feodor Ostapoff was born in Danzig on March 19, 1925. He studied physics, mathematics, and chemistry
at the University of Marburg, Marburg, Germany, and received the German equivalent of the B.S. degiee
in physics in 1949. He studied physical oceanography at the University of Kiel, Kiel, Germany, and re-
ceived the M.S. degree in physical oceanography from New York University, New York, N. Y., in 1957.
In 1959 he joined the U. S. Weather Bureau as a Research Scientist and was engaged in Antarctic
research. Since 1964 he was heavily involved in the coordination and implementation of the Federal air-
sea interaction program, especially after the formation of the Environmental Science Services Administra-
tion. This program culminated in the Barbados Oceanographic and Meteorological Experiment in 1969,
which he helped plan and organize. Presently he holds the position of Director of the Sea-Air Interaction
Laboratory of the National Oceanographic and Atmospheric Administration.
Mr. Ostapoff is a member of the American Geophysical Union and American Meteorological Society,
serving on the Committee on the Interaction of the Sea and Atmosphere. He is also a member of Sigma
Xi. He also serves the Cooperative Investigations of the Caribbean and Adjacent Region (CICAR), an
international program with some 15 nations participating and sponsored by the Intergovernmental
Oceanographic Commission of UNESCO, as Assistant International Coordinator (Meteorology) ap-
pointed by the World Meteorological Organization.
71
Repr inted from Proceedings of the Symposium on
Investigations and Resources of the Caribbean
Sea and Adjacent Regions , 137 -145 .
OCEAN-ATMOSPHERE INTERACTION IN THE CARIBBEAN SEA
VIEWED FROM THE O C E A NOG R A P HI C SIDE
Feodor Ostapoff
1. INTRODUCTION
The title of my paper is rather broad and while
listening to my colleagues yesterday and today it
became obvious that many aspects of ocean-atmo-
sphere interactions have been discussed directly
or indirectly.
Perhaps the most direct visual evidence of
the effects of the atmosphere on the sea surface
are the waves and wavelets which have been the
subject of intense study for the past 200 years.
The same driving forces establish the general
circulation of the ocean. As early as 1686,
Halley concluded that the surface circulation of
the ocean is wind driven. Today the theory of
wind driven ocean circulation has advanced to a
considerable degree of sophistication. In addi-
tion the ocean is heated and cooled at the surface,
in other words , its heat sources and sinks are
essentially at the same geopotential , forming dis-
tinct water mass characteristics. The strength
of the heat and salinity sources and sinks is de-
termined by climatic conditions on the globe.
Once the water masses are formed at the sea
surface due to heating, cooling, evaporation and
precipitation, ice formation and melting, they will
seek their equilibrium position in the ocean ac-
cording to their density. Combination of the wind
driven mode and the internal pressure distribution
then spreads these water masses with their speci-
fic characteristics through the oceans, modifying
them through turbulent mixing. Thus, Wiist and
Gordon (1964) identify in the Caribbean Sea four
"core layers" : the sub-tropical underwater, the
sub-Antarctic intermediate water, the North
Atlantic deep water, the Caribbean bottom water.
In this sense then, we must recognize an ocean-
atmosphere interaction process in the Caribbean
Sea. Although direct effects forming the water
masses occur in remote areas perhaps tens or
hundreds of years earlier, these are the large-
scale (in time and space) interactions.
Figure 1 (after Wyrtki , 1967) illustrates the
distribution of the main water masses at the sea
surface and boundaries between these water
masses. Clearly, the area of our topic is influ-
enced by a very complicated and complex mecha-
nism .
At the other end of the spectrum , we recog-
nize small-scale interactions - perhaps it would be
better to call them "first order" interactions -
which act locally and are highly variable. Consi-
derable research has been done in this field during
the past few decades. The importance of this re-
search lies in the fact that neither of the large-
scale phenomena can be fully understood without
an intimate knowledge of the first order interac-
tion, nor can specific characteristics such as the
sea surface temperature and salinity, the mixed
layer depth and the thermocline be treated theo-
retically in a satisfactory way. Let us first
briefly discuss these first order interactions.
2. BASIC PROCESSES ACROSS THE SEA
SURFACE AND THEIR SIGNIFICANCE
The exchange across the sea surface involves a
number of important quantities.
They can be classified in three main catego-
ries, as shown in Figure 2.
(1) Momentum exchange
(2) Heat exchange
(3) Mass exchange
Momentum exchange is one of the most impor-
tant interaction quantities from the oceanographic
point of view, as discussed above. While the mo-
mentum loss by the atmosphere is of perhaps neg-
ligible consequence to the atmospheric circulation,
it represents the major force which generates and
maintains surface waves and drives local and
major ocean currents. Indeed, the early results
in ocean dynamics are based on the momentum
exchange process. In this connexion we need only
mention Ekman's work.
The total heat exchange can be differenti-
ated depending on the process involved. First
of all, 80% of the short-wave radiation received
from the sun at the ocean surface is absorbed in
the top layer of the ocean. Long-wave radiation
is emitted from the ocean's surface a. absorbed
partially in the atmosphere. Sensible h.-at is ex-
changed by conduction due to the difference in
temperatures between the two media. But most
importantly, the ocean is cooled by evaporation of
water, resulting in latent heat exchange. This
138
Feodor Ostapoff
Figure 1. Distribution of the main water masses at the sea surface and boundaries between these water
masses.
process and the associated water transport from
the ocean to the air is of utmost importance from
the energetic point of view to the generation and
maintenance of the atmospheric circulation, in-
cluding hurricanes and tropical storms. Evapo-
ration and precipitation, of course, determine also
to a large extent the salinity distribution in the
ocean.
The most important masses exchanged at the
surface are water vapour (in conjunction with the
exchange of latent heat) , the return of water in the
form of rain (thereby releasing latent heat in the
atmosphere) , salt and gases. The latter are again
instrumental in important physical processes in
the atmosphere.
In view of the complexity and the numerous
modes of interaction, we will discuss in the fol-
lowing only a few of the important oceanographic
processes which seem particularly suited for study
in the Caribbean Sea - our main topic today.
3.
PRECIPITATION AND THE PRESSURE
FIELD IN THE OCEAN
An often neglected but apparently important effect
is that of precipitation which, in these latitudes,
is more localized and more intense than in other
parts of the world ocean.
Last summer, the USC&GS ship "Discoverer"
(Figure 3) occupied a station some 60 miles east
of Barbados for about 2 months, more or less
continuously. Three-hourly surface salinities
(bucket) were observed and six -hourly STD lower-
ings were made. During a heavy rain shower, the
surface salinity dropped abruptly by 0.7 to 1 part
per thousand for about 24 hours, while the 10 me-
tre salinity followed a longer-term trend (Figure 4).
The implication for dynamic height calcula-
tions , the basis for all geostrophic calculations ,
seems considerable.
Let us perform a hypothetical experiment in
our minds as follows : we calculate dynamic
depths for one of the regular stations which were
obtained during the expedition. Then we replace
the surface salinity value by a value of one part
per thousand less than the original observation.
Using standard oceanographic procedures, and not
knowing how deep this lens is , the calculation was
made for the usual standard depths of 0 , 25, 50,
MOMENTUM HEAT
MASS
Figure 2. Air-sea interactions.
Ocean-atmosphere interaction in the Caribbean sea
139
Figure 3.
S o/oo
17 AUGUST 196S
Figure 4. Surface bucket salinities (solid line)
and 10 meter salinities (circles) 60 miles east
of Barbados.
75, 100 metres etc. Comparing the two calcula-
tions, one finds at 25 metres a difference of 2 dyn.
cm. between the two "stations". Moreover, if the
two "stations" were 30 miles apart (and such
variability in rain may very well occur in those
latitudes) an additional "current" of about 2 knots
would result in these low latitudes.
4. THE EFFECT OF HURRICANES ON TEM-
PERATURE STRUCTURES IN THE TOP
LAYERS OF THE OCEANS
Next, I wish to discuss the effects of hurricanes
on the ocean, a very pertinent subject if we con-
sider the Caribbean Sea. Possibly, an opportunity
will present itself to continue research along those
lines .
In 1964, when Hurricane Hilda cross the Gulf
of Mexico an opportunity arose to study the direct
effects of a hurricane on the thermal structure of
the open ocean. Leipper (1967) had surveyed the
area prior to the passage of the hurricane. When
the hurricane traversed the area a new expedition
140
Feodor Ostapoff
§f »r
»r M'
HILDA CRUISE DATA
MERCHANT SHIPS DATA-
INADEQUATE DATA
Figure 5. Sea-surface temperature, after Hilda. October 1-13 inclusive. Including Cruise Hilda and
BCF data (shaded area > 28° ; stippled area < 25°). [After Leipper, 1967]
was quickly organized and remarkable data
obtained.
Figure 5 shows the sea surface temperature
distribution after Hilda. The general surface
temperature prior to Hilda was about 29°C. A
lowering of about 6°C was observed. Even more
remarkable are the vertical temperature profiles.
An example is given in Figure 6.
If upwelling due to divergence induced by the
wind stress is the process responsible for lower-
ing the surface temperature , then the water may
have come to the surface from about 60-80 metre
depths.
Figure 7 shows the density distribution along
the same cross section as in Figure 6.
The gross features of upwelling can easily be
explained by Ekman's wind drift theory. The
transport in the Ekman layer is outward from the
centre of the storm , producing divergence from
the centre up to the distance of maximum winds
and convergence further out. Therefore, upward
motion is indicated left and right of the eye with
maximum vertical velocity at the radius of maxi-
mum winds and downward motion at the outer
fringes of the storm (about twice the radius of
maximum wind stress). Now, since the storm is
radially symmetric, the hurricane should leave
one cold water trace at the surface. However, in
low latitudes and with an east-west propagation of
the storm two upwelled regions may be generated
Ocean-atmosphere interaction in the Caribbean sea
141
POSITION OF HURRICANE EYE
STA. NO. 15
V VWv
Figure 6. Depth of isotherms in section across
path, after Hilda. [After Leipper, 1967]
due to the difference in Coriolis parameter (every-
thing else being equal). For a storm of 30 miles
radius of maximum winds, the Coriolis parameter
could change almost by 10%. Such an effect has
not been clearly observed yet, but all our mea-
surements were taken in the Gulf of Mexico. A
more elaborate transient .(although with a station-
ary storm) numerical model has been developed
by J.J. O'Brien and R.O. Reid (1967) and J.J.
O'Brien (1967) which agrees with major parts of
the observations.
Present technology permits the rapid collec-
tion of sea surface temperatures from aircraft
using infra-red radiation thermometers. Fur-
thermore, expendable bathythermometers have
been developed for use from aircraft. Indeed,
expendable salinity -temperature probes are in the
offing.
Examples of radiation temperature observa-
tion in the wake of Hurricane Betsy in 1965 are
given in Figures 8 and 9. These data were ob-
tained by J. McFadden (1967) from ESSA research
aircraft. While data obtained from a ship must be
\ %%> *"
-i 1 1 1 i i_
-j i i i_
NAUTICAL MILES
Figure 7. Depth of contours of density anomaly
0", across path, after Hilda [After Leipper,
1967J
composite in nature (anywhere from 8 to 14 days)
the aircraft can span the same area within a few
hours. With the additional technique of sampling
temperature and salinity vertically a powerful
research tool becomes available. Not only can
the detailed structure of the ocean be explored on
a synoptic basis , but this technique also enables
study of the important question of the relative
permanence of the observed changes.
This could be accomplished by repeated flights
over the hurricane path to obtain a time history of
the event. The Caribbean Sea may be ideally
suited to investigate these questions and bring us
closer to understanding strong interactions and
the response of the ocean to these interactions.
5. MODELLING OF EXCHANGE PROCESSES
Finally , I wish to touch briefly on a recent effort
in modelling exchange processes. This work is
being carried out primarily by J. Pandolfo with
support of the Sea Air Interaction Laboratory.
The model represents a complex local simu-
lation of the atmosphere -ocean planetary boundary
layer (Pandolfo and Brown, 1967; Pandolfo and
Atwater , 1968) which extends from depths of a
few hundred metres (say 400 m) in the ocean
layer to heights of about a kilometre in the atmo-
spheric layer. The principal processes are the
eddy fluxes , mixing due to wind induced waves at
the sea surface and radiative heating, which de-
pends on cloud cover.
At the sea surface the following conditions are
imposed: continuity of eddy shearing stress, con-
tinuity in the velocities in both media , continuity
in temperature , saturation of the air by water
vapour , and a balance between evaporation and
142
Feodor Ostapoff
e- -JP
-30
26* +30°
-24*
90*
38'
+ MERCHANT SHIP DATA
(Within 12 hr. of flight time)
86* 84* JJ 82*
t K
30'-
28*-
26'-
24*-
l80?v
Figure 8. Sea-surface
temperature distribu-
tion 10-11 September
1965. [After McFadden,
19671
28°
26*
-24*
90*
v \ » ' '' \ 1
V*3\ ( /' /JM. ) I -
+ MERCHANT SHIP DATA
(Within 12 hr. of flight time)
88* 86* 84*
30»-
28*-
26*
74*-
Figure 9. Sea-surface
temperature distribu-
tion 15 September 1965.
[After McFadden, 1967]
Ocean-atmosphere interaction in the Caribbean sea
143
T'C
+ 2
^*^
/
MODEL
1100 1600 2100 0200
Figure 10. [After Pandolfo, 1968
MODEL
^x x DEFANT
1100 1600 2100 0200 0700 LT
Figure 11. [After Pandolfo, 1968]
salinity. Conditions at the top and bottom of the
model are prescribed.
A few examples may illustrate the presently
available results although the full power of the
model has not yet been explored.
The agreement between the two curves is
quite satisfactory. In particular the occurrence
of the maximum and minimum agrees very well,
both in the salinity and temperature curves.
(Figures 10 and 11). It is noteworthy that the
salinity maximum follows the temperature maxi-
mum by about 3 hours. Also, the small secon-
dary salinity maximum is reproduced in agree-
ment with observations. This secondary maxi-
mum is related to maximum vertical mixing in
the ocean, which occurs at the same time.
The observed diurnal salinity amplitude is
about five times larger than the computed value.
This indicates a deficiency in the model, possibly
due to the fact that at this time precipitation had
not been incorporated.
The vertical temperature and salinity distri-
bution is shown in Figure 12. The initial temper-
ature and salinity profiles were assumed linear.
Again the calculated temperature profile com-
pares quite favourably with observations obtained
this summer (1968) on the Discoverer. The Dis-
coverer data shows a mixed top layer of 15 to 17
metres. The model calculates a mixed layer
depth of 20 metres. The temperature difference
between 20 metres and 100 metres amounts to
4.5°C. Observations showed a difference of 3°C.
The salinity profile disagrees with observations ,
not so much in the mixed layer as in the complete
lack of the salinity maximum at about 100 metres.
Clearly a single station model incorporating local
processes cannot simulate such phenomena as
water mass advection.
The vertical current distribution at one par-
-10
-20
-30
-40
I "50
-60
-70
-80
-90
O Temperature
X Salinity
-i 1 1 i x-o
A
X -t
X
X -6)
X o
xo
•o
s<o/0o>
35.400 35.420 35.440 35.460 35.480 35.^00
-100 I dt 1 1 1 1
294
295
296 297
T(°K)
298
299
300
Figure 12. Oceanic temperature and salinity
profiles at one time step in the run JB1 ; 0530
LST. [After Pandolfo, 1968]
144
Feodor Ostapoff
l (cm sec ')
Figure 13. Wind current hodographs at one time
step in the simulation run JB1 ; 0930 LST.
[After Pandolfo, 1968]
ticular time step in the integration is shown in
Figure 13. Variations with inertial periods are
superimposed on the current vector.
The mean angle between surface current
direction and the surface wind direction is about
30°.
This model is being further developed, prin-
cipally to expand areawise and to include advec-
tive processes in the ocean and the atmosphere.
An observational programme could be carried out
during Cicar to utilize the model in further
understanding changes occurring in the near sur-
face layers of the ocean.
6. CLOSING REMARKS
In closing, I would like to emphasize that I have
only touched briefly on a few problems which may
40 be interesting or important to oceanographers if
we concern ourselves with the air -sea interaction
problem in relationship to oceanography.
Many problems of interaction are of a funda-
mental nature and can be studied anywhere in the
world ocean. However, we must still distinguish
between climatic regimes which may favour one
7~ exchange process over the other, making the
v choice of an experimental area an important one
g if we want to isolate and study one aspect of inter -
— action. This is certainly true as far as our sister
science, meteorology is concerned, where con-
vective processes are a predominant process in
low latitudes while air mass modification may be
studied better in regions where drastic differen-
ces in air masses occur. In oceanography con-
vective mixing may be the predominant process
of high latitudes where deep water masses are
formed.
The Caribbean Sea has been studied exten-
sively if we consider large-scale exchanges from
the meteorological point of view. Essentially,
the meteorological island network surrounding
the Caribbean Sea has been utilized b,y applying
continuity considerations. We need to mention
only the works by J. Colon (1963), Malkus (1962),
Hastenrath (1967) and Rasmusson (1967 and 1968).
Evidently, this work could continue in support of
the planned Cigar activities. Within this frame-
work specific problems may be studied for which
the Caribbean Sea may present itself as a natural
laboratory.
In closing I would like to quote a few words
from J. Malkus (1962) which may be worth rem-
embering when planning our future work. She
writes : "Rarely, but often enough to be of ines-
timable value, nature herself performs an ex-
periment under partially controlled conditions ,
as we have seen in some of the trade wind cases;
one of the main skills of the earth scientist lies
in being able to recognize and exploit these, using
them to guide his measurement programmes and
as a framework within which to relate the
results . "
REFERENCES
Colon, F.A. 1963. Seasonal variations in heat
flux from the sea surface to the atmosphere
over the Caribbean Sea. Journ. Geoph.
Res. , 68, 5, p. 1421-1430.
Defant , A. 1961. Physical Oceanography , New
York, Pergamon Press, 2 vols.
Hastenrath, S.L. 1967. Diurnal fluctuations of
the atmospheric moisture flux in the Carib-
bean and Gulf of Mexico area. Journ. Geoph.
Res. , 72, p. 4119-4130.
Leipper , D.F. 1967. Observed ocean conditions
and Hurricane Hilda , 1964. Journ. Atmos.
Sci. , 24, p. 182-196.
Malkus, J.S. 1962. Large-scale interactions ,
The Sea (ed. M.N. Hill), V, 1 , p. 88-294,
Interscience Publ. , New York, J. Wiley &
Sons.
McFadden , J.D. 1967. Sea surface tempera-
tures in the wake of Hurricane Betsy (1965).
Monthly Weath. Rev. , p. 299-302.
Ocean-atmosphere interaction in the Caribbean sea
145
O'Brien, J.J.: Reid, R.O. 1967. The non-linear
response of a two layer , baroclinic ocean to
a stationary, axially symmetric hurricane,
Part I. Upwelling induced by momentum
transfer. , Journ. Atmos. Sci. , p. 197-207.
O'Brien, J.J. 1967. The non-linear response
of a two layer, baroclinic ocean to a station-
ary, axially symmetric hurricane: Part II.
Upwelling and mixing induced by momentum
transfer. Journ. Atmos. Sci. , p. 208-215.
Pandolfo, J.P.: Atwater , M. A. 1968. Varia-
tions of diurnal and inertial period in a phy-
sical-numerical model of the atmosphere-
ocean planetary boundary layer. Final Re-
port, 7046-321 , Contract E-120-67(N).
Hartford, Conn. , The Travelers Research
Center , Inc. ,
Pandolfo, J.P. : Brown, P.S. Jr. , 1967.
Inertial oscillations in an Ekman layer con-
taining a horizontal discontinuity surface.
Journ . Mar. Res. , 25, p. 10-28.
Rasmusson, E.M. 1967. Atmospheric water
vapour transport and the water balance of
North America : Parti. Characteristics of
the water vapour flux field. Monthly Weath.
Rev. , 95, p. 403-426.
Rasmusson, E.M. 1968. Atmospheric water
vapour transport and the water balance of
North America : Part II. Large-scale water
balance investigations. Monthly Weath. Rev.
96, p. 720-734.
Wust, G. : Gordon, A. 1964. Stratification and
circulation in the Antillean -Caribbean basins.
Part I. Spreading and mixing of the water
types. New York and London, Columbia
University Press, 201 p.
Wyrtki, K. 1967. Water masses in the oceans
and adjacent seas, in: International Dic-
tionary of Geophysics (gen .
Pergamon Press.
ed. K. Runcorn).
72
U.S. DEPARTMENT OF COMMERCE
National Oceanic and Atmospheric Administration
Environmental Research Laboratories
NOAA Technical Memorandum ERL AOML-15
TESTS OF MODIFIED RADIOSONDE HYGRISTOR DUCT
Willard W. Shinners
Gerald E. Putland
Peter B. Connors
Atlantic Oceanographic and Meteorological Laboratories
Miami, Florida
December 1971
TABLE OF CONTENTS
PAGE
1 . I NTRODUCT I ON
2 . AIR FLOW TESTS
3 . FL I GHT TESTS
k. CONCLUSION
5. REFERENCES
1
3
5
6
10
TESTS OF MODIFIED RADIOSONDE HYGRISTOR DUCT
Willard W. Shinners, Gerald E. Putland, and Peter B. Connors
To evaluate a modified configuration of the National
Weather Service's radiosonde humidity duct, wind
tunnel and flight tests were made by the Sea-Air
Interaction Laboratory. Results indicate the new
design to be greatly improved over the previous
type with respect to ventilation and radiational
heating.
1 . INTRODUCTION
The VIZ Corporation provided the NOAA Sea Air Interac-
tion Laboratory several newly designed hygristor housings or
ducts for wind tunnel and flight tests similar to the origi-
nal tests by SAIL reported in NOAA Technical Report 19^-AOML ^
"Some Tests on the Radiosonde Humidity Error." The 1970
report indicated the ventilation in the area of the hygristor
was reduced about 70% from ambient air flow, and the trans-
1 ucency and reflective characteristics of the plastic duct
permitted considerable solar heating of the hygristor
resulting in significant humidity errors.
The newly designed duct provides a much larger opening
or air scoop than the prior design. The air passes through
a restricted section holding the hygristor, and as a result
the air movement is accelerated. Air entering the scoop of
2 2
58 cm area passes through the restricted area of 23 cm
cross-section with over 100% increase in speed from the scoop
area to the exit of the hygristor chamber (fig. 1). A black
covering under the top and at the bottom of the hygristor
section is highly effective in reducing direct and reflected
solar heating of the hygristor.
Figure 1. New design of NWS hygristor duct. Cover removed
2. AIR FLOW TESTS
Tests were conducted in SAIL's wind-water tunnel facility,
(NOAA Tech. Memo ERL AOML-12). The facility provides an air
chamber 70 by 90 cm in c ross -sec t i on and 610 cm in length.
Air flow was 5-2 mps - about the rate of ascent of a radio-
sonde. A Pitot tube and a The rmo-Sys terns , Inc., hot wire
(constant temperature anemometer) model 1050 was used to
monitor air flow rates.
The duct with a carbon hygristor in place was placed in
the wind tunnel and a series of readings at 1 -cm spacing were
made along line A-B (fig. 1). The probe was even with the
top of the side wall of the scoop. Table 1 lists these
values .
Table 1. Air flow at air scoop entrance
mps
Cm Left
5 k
Center
1 0 1
Cm Ri ght
k 5
1.9 2.0 2.0 2.1 2.1 2.1 2.2 2.2 2.2 2.2 2.0
■B
The data give an average value of 2.1 mps for air enter-
ing the air scoop along A-B. This is kQ% of the ambient 5-2
mps flow rate in the tunnel. Measurements were made up-wind
from the duct air scoop at a distance of 7-6 cm, where a
speed of 3-6 mps was recorded. At a distance of 15-2 cm
upwind the speed was h.k mps.
Measurement of the air flow right at the hygristor posed
a problem due to the probe support and connecting cables.
Since the cross sectional area is nearly constant and uniform
in dimensions from the air scoop to the discharge orifice, the
assumption was made that the air speed at the hygristor would
be essentially the same as in the discharge area. Measure-
ments were made at 1 cm intervals from the center line along
line C-D. Table 2 presents average values.
Table 2. Air flow in discharge orifice
Cm Left
5 k
Center
1 0
Cm Right
3 4 5
mps 5-3 5-4 5-4 5-0 4.4 4.8 4.1 5-2 5-0 5.0 4.9
The mean value across the discharge orifice was 5.0 mps,
over SS% of ambient flow in the wind tunnel.
Since lee or down-wind turbulence could affect the air
flow through and past the duct, a 403 mc radiosonde, without
the thermistor out-rigger or strap was included for a second
series of measurement.
Values in Table 3 were obtained 2 cm above the air scoop
at 2-cm intervals along line A-B.
Table 3- Air flow 2 cm above air scoop with radiosonde
Cm Left Center Cm Right
4 2 0 2 4
A B
mps 2.9 2.6 2.4 2.4 2.6
A mean value of 2.6 mps is obtained from the above data.
The higher value at 2 cm above the orifice is consistent with
the increase in speed-up wind.
Measurements across the exit orifice provide the
f o 1 1 ow i ng :
Table 4
Wind speed at discharge orifice -duct with radiosonde
Cm Left Center Cm Right
4 2 0 2 4
C D
mps 5.4 4.6 4.2 5-0 5-4
A mean value of k .9 mps results for flow through the
duct. A recheck of air flow up-wind of the duct resulted in
identical values to those obtained prior to the inclusion of
the full radiosonde in the tests. The 0.1 mps difference
(5-0 and k .S mps) does not appear significant, and the exper-
imental procedure followed does not indicate a change in ven-
tilation rate when the duct and radiosonde are combined (i.e.,
without the thermistor or webbed strap in place).
3. FLIGHT TESTS
To determine the effectiveness of the new duct under
operational conditions, several flights were made at Miami.
Releases were made close to solar noon In order to expose
the duct to maximum radiotonal effect. Air mass characteris-
tics were typica of the trade winds, with a warm moist layer
the first several hundred meters, then an inversion and rela-
tively dry air above. Two radiosondes were flown on the same
train, one with the older duct configuration and one with the
new design. A further comparison was made with the vertical
duct used by SAIL (Ostapoff, et al., 1970) and the new design.
Figure 2 thru 6 present the comparative relative humidity
values as obtained by the dual flights.
Figure 2 indicates differences as high as 20% in rela-
tive humidity with the difference varying up to 830 mb . The
sonde with the new duct showed lower relative humidity above
this level. Scattered clouds and the resultant shading may
account for the variability at the lower level. The reversal
above 825 nib, where the standard sonde indicated higher hu-
midity, has been observed before (Brousaides and Morrissey,
1971); however, a confirmed explanation is not available.
A maximum difference of 32% in RH at 835 mb appears in
figure 3 with the newly designed duct configuration giving a
97% RH value. Figures k and 5 are typical of comparative
flights in which solar heating was substantially reduced and
ventilation of the hygristor improved relative to the
standard sonde.
Figure 6 presents curves for the new NWS duct and a
vertical tube used by SAIL (Ostapoff, et al., 1970). The
sondes were observed to swing through a large arc during the
first few minutes of flight, and it is suspected that some
solar heating as well as reduced ventilation in the tube may
account for the differences in RH during the early part of
the f 1 i ght .
k. CONCLUSION
Based on these wind tunnel and flight tests, the new
National Weather Service radiosonde duct virtually eliminates
the solar heating problem found in the previous duct config-
uration. The problem of thermal lag should also be reduced
to a considerable extent with the increased ventilation rate.
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5. REFERENCES
Broussaides, F. J., and Morrissey, J. F. (1971), Improved
measurements with a redesigned radiosonde humidity duct,
Bulletin AMS , 2, No . 3 .
McLeish, Wm . , Berles, R., Everard, W., and Putland, G. (1971),
The SAIL 6-m wind-water tunnel facility, NOAA TM ERL
AOML- 1 2 .
Ostapoff, F., Shinners, W., Augstein, E. (1970), Some tests
on the radiosonde humidity error, NOAA TR ERL I9A-AOML k.
10
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