/HFd

O1
ceanus

Spring 1956, Vol. IV, No. 3

WOODS HOLE OCEANOGRAPHIC INSTITUTION WOODS HOLE, MASSACHUSETTS

EDITOR: JAN HAHN

Published quarterly and distributed to the Asso-
ciates of the Woods Hole Oceanographic
Institution and others interested
in Oceanography

Woods Hole Oceanographic Institution

WOODS HOLE, MASSACHUSETTS

HENRY B. BIGELOW
Chairman of the ISoard of Trustees

RAYMOND STEVENS
"President of the Corporation

EDWARD H. SMITH ALFRED C. REDFIELD
"Director Associate ^Director

COLUMBUS O'D. ISELIN

BOSTWICK H. KETCHUM

Senior Oceanographers

Meteorological Issue

WE HOPE TO WITNESS THE
START OF A HURRICANE

Columbus O'D. he/in

BUBBLES, SALT DUST AND RAINDROPS

A. H. Woodcock

WEATHER AND INSURANCE

TRADE WINDS AND
TRADE WIND CLOUDS

THE FINGERPRINTS OF A STORM

Thomas F. Malone

Joanne S. Malkus

Duncan C. Blanchard

On the cover: Our artist's conception of
a North Atlantic hurricane's generating
area and its path of destruction.

EDITORIAL

Spring 1956, Vol. IV, No. 3

I

N this issue our contributors are not only "talking about the wea-
ther" but also explain how something may be done about it.

In a recent letter to a Boston newspaper a correspondent ac-
cused "scientists in general" of tampering with the weather, there-
by causing heavy floods, snowstorms and general misery suffered
by him this winter. As you will notice from the following articles,
there still remain a few things to be learned before anyone can
"tamper" with the weather and we certainly expect that if this
day ever comes such tampering will be of general benefit. How
this will be possible remains to be seen. One man's joy in rain
is another man's spoiled holiday. One man's joy in sunshine is
another's ruined vegetable patch. The person who will finally
have to make the decisions will be in an unenviable position.

Simplified view of the general horizontal and vertical circulation in the atmos-
phere. Cumulus clouds forming in the Trade Wind cell. See article on page 8.

Educational Opportunities

J.O acquaint faculties and students interested in oceanography
with the facilities at Woods Hole, the 1956 Annual Announcement
was distributed recently to several hundred educational institu-
tions. A copy was also sent to each Associate, individual and
corporation, that they may be advised of the Institution's educa-
tional program. The Announcement also explains the opportuni-
ties open to undergraduate and graduate students to do research
at the Institution and explains the Fellowships and Grants award-
ed each year.

The Woods Hole Oceanographic Institution has been official-
ly recognized as an institution of higher education by a recent
ruling of the Office of Education of the United States Department
of Health, Education, and Welfare.

Tuna Tagging

1— /ART type tags, harpoons
and instructions are ready for
distribution for this year's co-
operative tagging program.
The equipment is available
free of charge and it is our
hope that the sport fishermen
among our readers will en-
courage their friends and
clubs to make this an out-
standing tagging season.
News from the Pacific gives

Life Membership

us hope that we may also ob-
tain some returns this year.
One of only 82 big-eye tuna,
tagged by ships of the Pacific
Oceanic Fisheries Investiga-
tions 400 miles northeast of
Midway Island, was caught
again ten months later 690
miles north of Oahu Island in
the Hawaiian Group. The
tuna had travelled 800 miles
and grown ten pounds.

J.HE Executive Committee of the Associates of the Woods Hole
Oceanographic Institution has recommended, and the Trustees
have authorized, the establishment of Life Membership to those
interested in the study of the ocean and wishing to further the
scientific and educational aims of the Institution. This mem-
bership has been placed at $1,000.00

We are most pleased to report as the first Life Member:

Mr. Harry Alfandre
Montau/c Point, L. I.

We Hope To Witness The Start

Of A Hurricane

.HE cumulus cloud is the
work horse of tropical mete-
orology. It is the vital and
critical link in the transfer
of heat and water vapor from
the sea surface to the atmos-
phere. Huge areas of the tro-
pics are covered by cumulus
clouds which are often ar-
ranged in long bands sepa-
rated by areas of less dense
cloud cover. The life cycle
of an individual cumulus
cloud is usually less than
half an hour, but few people
have the patience to watch
one for long, especially when
thousands of them are in
sight. Since the Wyman-
Woodcock expedition of 1945
in a Navy PBY plane, sever-
al members of our staff have
continued to be interested in
the dynamics and physical
chemistry of warm cumulus
clouds, the characteristic
cloud of the marine tropics,
an area which covers about

by C. O'D. Iselin

Basic atmospheric and oceanic

information will be gathered

by our new ship.

40% of the earth's surface.

Anyone reading "Tropical
Meteorology" by Herbert
Riehl, the newest and most
complete discussion of the
warm end of the great at-
mospheric heat engine, is
struck by the many signifi-
cant contributions of our
staff. Dr. Joanne Malkus has
continued and developed the
pioneer studies of Mr. Henry
Stommel on the dynamics of
large scale convection in and
beneath clouds. Mr. Andrew
Bunker has made most of the
measurements of turbulence
both within the clouds and
in the clear areas surround-
ing them. Mr. Alfred Wood-
cock is our expert on the role
of giant condensation nuclei
in the initiation of rain. Mr.
Duncan Blanchard has as-
sisted him in studies of the
details of the formation of
sea-salt nuclei and recently
has begun a study of the as-

sociated electrical phenomena
present near the sea surface
and within the clouds. Mr.
Theodore Spencer has pro-
duced most of the instru-
ments to observe these phen-
omena.

The expeditions gathering
the basic atmospheric infor-
mation have for various rea-
sons mostly taken place dur-
ing the winter season. This is
also true of the cruises of our
ships. Thus we have gained a
relatively clear winter pic-
ture, both of the oceanogra-
phy of the surface layer of the
tropical North Atlantic, in-
cluding the Caribbean Sea,
and of the physical charac-
teristics of the lower layer of
the winter atmosphere. In the
tropics this is the orderly sea-
son. Although many variable
phenomena are at work, the
system as a whole is in bal-
ance. The winds blow stead-
ily from the east. The sky is
covered rather uniformly
with relatively small clouds.
While showers occur, espe-
cially during the afternoon, a
disturbance as violent as a
small thunderstorm is rare
until the equator is approach-
ed. Storms are nonexistent.
In winter, then, small scale,
convective processes over the
tropical Atlantic are rather
orderly and uniformly distri-
buted. No large scale, organ-
ized convective phenomena,
such as a hurricane, appears.

For obvious reasons, last
autumn we began to think
about the oceanography and
meteorology leading up to the
formation of a hurricane. Be-
tween us, we soon evolved a
plausible physical model of
the birth of a hurricane, but

we found that we had practi-
cally no data that could be
used to support or to refute
this model. We had kept our
ships out of the tropics during
the summer season and so
have nearly all other oceano-
graphers. Our data on tropi-
cal clouds are similarly limit-
ed. Since hurricanes form
along a rather narrow band
of the marine tropics, center
ing 5° to 8° away from the
equator, perhaps oceanogra-
phers could make a signifi-
cant contribution to their un-
derstanding, for they are a
uniquely marine phenomena.

New vessel.

A general plan of attack
rather quickly evolved, but
we had no really suitable
ship. One reason that we had
not sent the "Atlantis" south
during the summer is that in
so small a steel ship the heat
and humidity below decks are
almost unbearable. Another is
that she is somewhat slow to
be dodging even newly form-
ed hurricanes. However, in Oc-
tober we received word that
the U. S. Coast Guard had
decided that three of its 125'
cutters could be disposed of.
The Director vigorously fol-
lowed up this lead and, after
plowing through a mountain
of red tape, by January we
were the proud owners of an
excellent vessel whose en-
gines had only been used dur-
ing three, ice free seasons in
the Great Lakes. The "Craw-
ford" is now1 at Munro's Ship-
yard in East Boston being
converted for scientific work.
It is hoped that by early June
she will be ready for sea and

it is planned that her first
five months as a research ves-
sel will be devoted to hurri-
cane research. Some initial
financial support has been
promised by the U.S. Weather
Bureau and it is hoped that
more will follow.

Although a departure from
our main theme, a brief dis-
cussion of the conversion of
the "Crawford" may be of in-
terest to the sailors among our
readers. In January the Ex-
ecutive Committee authorized
the expenditure of $100,000
for this conversion and the
firm of M. Rosenblatt and Son
was asked to undertake a fea-
sibility study of some rather
novel ideas which might
make the "Crawford" a really
superior research vessel. For
some time the design of the
"ideal" oceanographic vessel
has been under discussion and
preliminary study. Within the
Navy a preliminary design
has been prepared. This is
for a vessel of 1000 tons dis-
placement and the gross
weight of the "Crawford" is
less than one third of this.
Nevertheless, it seemed possi-
ble that two of the chief fea-
tures of the Navy's proposed
design might be incorporated
into the "Crawford" namely
both passive and active anti-
rolling tanks, and a bow jet
pump propulsion unit for
holding the vessel head to the
seas without forward motion
so as to facilitate lowering in-
struments to great depths.

Our naval architects have
recommended against these
particular features in a ves-
sel so small as the "Craw-
ford". Anti-rolling tanks would
take up too much of the space

necessary for living quarters
and instead they have advised
in favor of an active rudder,
a German development which
is installed on their newest
research vessel. Fortunately
other more important fea-
tures of the conversion could
be achieved within the limits
of displacement and funds
available. The endurance of
the 'Crawford" is being in-
creased to 30 days and 6000
miles. Her living quarters are
being re-arranged and air con-
ditioned, and a large deck
laboratory is being added.
Although we will still have to
put up with a certain amount
of roll while on station, in all
other respects she should
make an economical and com-
fortable vessel for prolonged
field work in the tropics.

Birth of a Hurricane.

What is this physical mode
of the birth of a hurricane
that we plan to test out with
the "Crawford" during the
next several summers? First
of all, it is supposed that the
situation becomes particularly
ripe for the formation of a
hurricane after a period of
abnormally light winds across
the northern half of the trade
wind belt. Light winds in
theory result in several im-
portant effects. As far as the
sea is concerned, heat accu-
mulates near the surface. So
far as is known, hurricanes
only form in areas where the
sea surface temperatures are
higher than 27°C. Light
winds, according to Mr. Wood-
cock's studies would also re-
sult in the production of too
few of the larger condensation

The Crawford at Woods
Hole, now being converted
to a research vessel, will
start soon on the first
cruise ever made by a
scientific ship to study the
birth of a hurricane.

nuclei and consequently few
of the lower clouds would
rain out. Thus the humidity
of the lower layer of the at-
mosphere can build up to ab-
normal levels. A large sup-
ply of especially warm and
humid air over the sea is the
first requirement of a hurri-
cane, for this becomes an un-
stable situation. Our model
goes on to suppose that at this
point a large scale wave-like
disturbance occurs in the
light easterly winds. As this
wave travels westward, local-
ly at its crest the winds pick
up so that white caps are pres-
ent. A supply of larger con-
densation nuclei is then avail-
able to the low level convec-
tive processes. Clouds can be-
gin to rain out and the ener-
gy of latent heat accelerates
the convection. Locally the
surface winds further in-
crease, bringing more moist
air and a really adequate sup-
ply of salt particles to the re-
gion of most active convec-
tion. The clouds increase in
height and remain active for
a long time so that the low

level wind flow becomes or-
ganized over a considerable
area, as when the whirl forms
over the drain in a wash ba-
sin. From there on the dis-
turbance can be clearly rec-
ognized as a hurricane. Its
duration and intensity will
depend only on the quantity
and moisture content of the
warm, low level air available
to it.

Prevent hurricanes?

There is nothing radically
novel about this model and so
far as it is known it fits the
facts. What is exciting is that
if the picture presented here
is found to be basically true,
it is conceivable that the for-
mation of, hurricanes could be
prevented. What is necessary
is to maintain random con-
vective activity during the
build up period, to bleed off
energy at scattered points be-
fore any large scale pattern
of flow can become organized.
Mr. Woodcock's studies sug-
gest several techniques by
which this might be accom-

6

plished. It is too early to at-
tempt accessing the engineer-
ing problems involved. If we
are lucky, perhaps the "Craw-
ford" will return in Septem-
ber with the necessary data.
In any case, it seems quite
possible that if detailed stu-
dies at sea can be continued
during several seasons, a weak
link in the chain of events can
be found. What makes the
difference between hurricanes
and no hurricanes is clearly
something quite subtle. It is
believed that hurricanes start
as weak disturbances. This
is the time for man to try to
attack them. By the time they
become recognized on the
weather maps the energy has
become organized and it is too
late. At any rate, we mean
to have a good try.

Observations.

To study at first hand the
details of the environment in
which they form will be a
new approach to hurricane
research. Meteorologists work
from weather maps, which
are particularly deficient in
reliable observations from
mid-ocean areas in the tropics.
To attack the observational
part of the problem with aer-
oplanes, as a well organized

Weather Bureau team will be
doing simultaneously, may
leave a critical question unan-
swered. If our model of the
situation is correct, it is vital
to be able to measure small
changes in surface wind velo-
city. Low level winds are
extremely difficult to observe
accurately from a plane. Thus
we believe that the "Craw-
ford" may provide the key in-
formation that will bring suc-
cess to the very major re-
search effort that was trig-
gered off by the North Atlan-
tic hurricanes of the past two
seasons. Once full under-
standing has been gained, the
question of whether or not
weather modification at sea
will become practical depends
mainly on how weak the weak
link in the chain of events
turns out to be.

Columbus O'D. Iselin,

Oceanographer, was director of
this Institution from 1940 to 1950.
He started his \ career as a Harvard
student by malcing a survey of the
Labrador Current with his schoo-
ner "CHANCE." Now teaching a
half course in oceanography at
Harvard University he also serves
as advisor and consultant to many
government departments. He is a
member of the National Academy
of Sciences and received an Hon-
orary Doctorate from Brown Uni-
versity in 1947.

Trade Winds and

* Trade Wind Clouds

J.HE visitor to the islands
in the tropics is struck by
two outstanding features of
the weather: The first is the
regularity and monotony of
the east wind, which even at
night does not stop from rat-
tling the palm leaves. The
second is the beautiful and
exotic array of clouds.

The trade winds, covering
about 40% of the earth's sur-
face, are the world's most ex-
tensive and most steady wind
system. For comparison, the
middle latitude westerlies
with whose variability we are
well acquainted cover about
30% to 35% of the earth's sur-
face.

Meteorologically, the trade
winds and the trade cumuli
are most important. Trade
cumuli are not just a feature
of sunny days, as are their
relatives in our temperate lat-
itudes, but appear around the
clock, and are as much visi-

BY JOANNE S. MALKUS

Trade Wind Clouds form a
link in providing the energy
for all the wind systems of
the globe.

ble in full moonlight as in the
baking noonday sun. Even in
the turbulent gray cauldron
of a tropical storm the trade
cumuli are found below the
overcast, made ragged by the
high winds, but still with
patches of sea visible between
them. The tropical storm,
however, though spectacular
and in its intense versions hid-
eously destructive, is a rare
phenomenon, much less com-
mon than the larger frontal
storm of middle latitudes.
Trade-wind weather is far
more faithfully characterized
by the first illustration than
by the last, and its outstand-
ing feature is sultry monot-
ony.

Because of the rarity of
storms, rainfall in the trade-
wind region, in latitudes 10° -
30° North and South, is un-
reliable. Most tropical islands
are water-starved communi-
ties. Even the casual visitor

8

to the Virgin Islands, for ex-
ample, is impressed by the
large concrete catch-basins
scarring the hills, and the
strict economy of water use
by the local inhabitants. Stu-
dy of the life cycle of the
trade cumulus is thus of econ-
omic importance. It is of
practical value to discover
what causes these clouds to
form and develop, how small
cloud droplets grow into much
larger raindrops within them,
and in particular why some
clouds grow to enormous pro-
portions and others are cut
off after a few hundred feet.

Woods Hole Studies

The meteorology group of
the Woods Hole Oceanogra-
phic Institution has been in-
volved in the study of these
clouds since the close of World
War II. Theoretical and ex-
perimental work on cloud and
precipitation growth has been
carried out at the Woods Hole
Laboratory and frequent field
trips to the Caribbean area
have been made. During the
field trips a meteorologically-
instrumented PBY aircraft,
loaned to the Institution by
the U. S. Navy, has been flown
into clouds of assorted sizes,
and cross sections of their
temperatures, humidities, and
draft structure were drawn.

In comparing these detailed
studies of individual clouds
with larger-scale investiga-
tions of the circulations and
features of low-latitude mete-
orology as a whole, some sur-
prising and important connec-
tions have been brought to
light. It now appears as if the
humble trade winds clouds

Dr. Malkus well known in me-
teorological circles, recently re-
turned from England where
she spent a year as Honorary
Lecturer in the Meteorological
Department of the Imperial
College. She has made frequent
flights on board the PBY am-
phibious plane which we have
on loan from the U.S. Navy.

form a vital link in the mech-
anism driving the trade-wind
circulation and thus in provid-
ing the energy for all the
wind systems of the globe.

To understand this, it is
necessary to give a brief de-
scription of low-latitude air
motions.* The atmospheric
circulation from latitudes 0°
to 30° on either side of the
equator consists fundamen-
tally of a meridional cell,
with rising motion over the
heated equatorial doldrums
and sinking motion in the
subtropical high pressure
belt which circles the globe
at about latitude 30°. The
division between vertical as-
cent and descent lies about
halfway between these
bounds, or around 15°. The
motion near the surface of
the earth is thus equator-
ward at low levels and pole-
ward higher up. Because of
the earth's rotation, the low-
level equatorward-moving
air is deflected to its own
right (looking downwind) in
the northern hemisphere and
to its left in the southern.
This combination of effects
produces the "trades," north-
easterly winds in latitudes
10° -30° North and south
easterly winds in correspond-

Irregular clusters of Trade
Cumulus clouds are com-
monly found over the sea,
separated by slightly larger
clear areas.

ing south latitudes. At high-
er elevations the easterlies
weaken, and are overlaid by
westerlies in some areas. As
mentioned earlier, the low-
level easterlies are a re-
markably steady wind sys-
tem, far more constant than
any winds of the temperate
zone. This fact is brought
home forcibly to the visitor
to the tropics when he sees
the airports there — which
are built with only one run-
way, facing east-west.

Heat engine

Now it turns out, as a re-
sult of recent researches, that
trade winds and their main-
tenance are intimately relat-
ed to the presence and ac-
tivity of the clouds. To ex-
plain this we may regard the
tropical circulation cell just
described as a large, and
very inefficient, heat engine
which exhibits many of the
properties of a man-made
servomechanism. To carry
the analogy a bit further, the
clouds may be conceived as
the fuel pump for the engine,
in that they carry up heat
from the warm tropical seas
and distribute it through a
vertical depth of air so that
it may be used in maintain-
ing the pressure gradients
which drive the easterlies
against friction. The servo-

Definite lines of clouds are

sometimes formed, generally,

though not always, parallel

to the wind.

control comes in because the
clouds are forever operating
against resistances or brakes.
It so happens that if the
clouds are weakened, the
overall air currents change
in just such a way as to re-
lease these brakes slightly
and clouds are permitted to
surge forth with renewed
vigor restoring the heating
and thereby the air currents
to their original condition.
Thus there appears to be a
"stable coupling" between
the small-scale phenomena,
namely the clouds, and the
much larger-scale air cur-
rents, namely the easterly
trades themselves. It is an
interesting confirmation of
these ideas (which have re-
cently been worked out quan-
titatively) that above the
height reached by the cloud
tops, or about 10,000 ft., the
steadiness of the flow van-
ishes, and the upper level

10

In the turbulent gray caul-
dron of a tropical storm the
cumuli, made ragged by the
high winds, are still found
below the overcast. I

~

P

Small cotton puffs in the
foreground stand out in con-
trast with the giant towers
in the background, reaching
an elevation of 50,000 feet.

winds of the tropics are as
variable as those of our own
latitudes.

Hurricanes and Brakes

Of course, we know that
the servomechanism some-
times gets out of control in
localized regions. Especially
in the more westerly por-
tions of the trad e-wind
oceans the fuel pumps occa-
sionally work too energeti-
cally over a small area and
the earth's rotation helps
convert some of the energy
released by precipitating
clouds into a wave-like dis-
turbance, or in severe cases
into a whirling hurricane
vortex. Devastating though
these may be to man and his
artifacts, the atmosphere rec-
ognizes tropical storms only
as rare and insignificant
backfires which contribute
negligibly to the energy con-
versions normally going on

in a smoothly operating en-
gine. Ordinarily the brakes
against convection are work-
ing so effectively that most
potential storms in the tro-
pics perish in anonymous in-
fancy.

It is thus of importance for
multifold reasons to learn
more of the "brakes" or re-
sistances operating against
cumulus cloud development.
It now appears that these re-
sistances are not only inhi-
bitors of precipitation and
storm growth, but play a
regulatory role upon the rate
at which energy is fed into
the large-scale circulations.
Much of the work of the
Woods Hole meteorology
group has therefore been fo-
cused upon this aspect of the
problem. It has been learned
that these resistances are
primarily of three kinds:

(1) Sinking motion in the en-

vironment, which chang-
es the air structure so
that the clouds are pre-
vented from forming.

(2) A force analogous to aer-
odynamic drag which re-
duces the momentum of
a rising lump of buoyant
air or cloud tower.

(3) Turbulent mixing of the
cloudy air with the drier
environment. This eats
away the cloud's energy
supply, which has been
found to be the heat re-

11

leased by condensation of
water vapor into liquid
water.

Using these concepts it has
been found possible to con-
struct a theory of a cloud near
the middle or well-developed
stage of its life history. This
model has compared well with
the cloud cross-sections ob-
tained by the PBY aircraft.
Recently, preliminary efforts
have been made to construct
the theory of the origin of a
cumulus and to learn how a
lump of warm buoyant air or-

ganizes its motions in the
early stages. Laboratory and
further field studies are being
carried out to check and
guide the theory. Simultane-
ously, investigations of the
raindrop-forming and growth
process are being continued at
Woods Hole. It is believed
that such studies must pre-
cede, and fundamentally un-
derlie, any possible efforts to
understand, predict, or control
the behavior of rainfall, trop-
ical storms, or larger-scale
circulations in the trades.

ASSOCIATES NEWS

Annual New York Dinner

President Raymond Stev-
ens, in a letter to your Presi-
dent McLean, stated that:
"The showing of The Silent
World was in my opinion one
of the best things that has
happened to the Woods Hole
Oceanographic Institution in
a long time. I am sure that
everyone interested in the
Institution is grateful."

Mid-Winter Lectures

Through your sponsorship
we have had this winter at
Woods Hole the extreme
pleasure of listening to eight
noted Harvard and M.I.T.

savants speaking on their re-
spective interests which
ranged from galaxies to or-
ganic evolution and from
anthropology to the science
of human behavior. Capacity
audiences listened every Fri-
day afternoon to the lectur-
ers whose attendance was
obtained through the co-op-
eration of our Trustee, Dr.
Harlow Shapley.

Associates Fellowships

Announcements of two As-
sociate Fellowships for 1956-
57 went out early this year
to attract two college gradu-
ates. It will be remembered

12

that Mr. Roderic B. Park
now at the California Insti-
tute of Technology was ap-
pointed last year, and that a
total of three Fellowships are
to be awarded each year.
Successful candidates will be
reappointed for the normal
three-year period of gradu-
ate education leading to a
doctorate.

New Corporate Associates

In Memoriam

With deep regret we
learned of the death in Jan-
uary of Associate Mr. Charles
W. Brown, Jr. Mr. Brown
was an ardent participant in
our game fish studies. To-
gether with his son and
guests on board the sport-
fisherman KETCHUM III,
he tagged and released many
tuna during the summer of
1955.

American Export Lines, Inc. New York, N. Y.

Esso Shipping Company New York, N. Y.

Marine Office of America New York, N. Y.

Newport News Shipbuilding Company Foundation

Newport News, Va.

BY THOMAS F. MALONE

—

*

More scientific research offers hope of reducing hurricane losses to own-
ers and insurance companies.

o

NE of the primary func- are health and longevity,

tions of an insurance com-
pany is to protect the values
which make our domestic
and economic life sound and
secure. Among the many

fires, accidents — and wea-
ther. Notable progress has
been made in studying and
improving health conditions
and extending life expect-

factors affecting those values ancy, and in analyzing and

13

minimizing fires and acci-
dents. Increasing attention
is now being given to the
weather factor. There are
two reasons for this: the in-
creasing complexity of our
civilization which makes it
more susceptible to the vicis-
situdes of weather, and the
expansion of the protection
principle of insurance to take
care of losses occasioned by
weather occurences in which
this principle is applicable. It
follows that the insurance in-
dustry has a rather vital
stake in meteorology. It is
of some interest to examine
some aspects of the meteoro-
logical problem in which in-
surance is involved.

Better predictions

The most obvious instanc-
es, and certainly the most
dramatic, are the major wea-
ther catastrophes, the hurri-
cane and the tornado. Losses
from these two weather
phenomena mount to mil-
lions of dollars each year. Al-
though there are not at hand,
now or in the foreseeable fu-
ture, means to eliminate
these losses completely, more
precise predictions would be
of inestimable aid in reduc-
ing these losses. Improve-
ments in prediction tech-
niques and warning systems
made in recent years have
already reduced the intensi-
ty and frequency of such
losses. Similar arguments ap-
ply to the more frequent but
less spectacular weather oc-
currences. In this sense, the
insurance industry has a vital
interest in the prediction
problem in meteorology, in

more precise predictions of
wind, rain, hail, tidal height,
temperature, and so forth. A
word of caution is in order
here, in the interpretation of
the term "more precise." Ab-
solute precision in weather
prediction may well turn out
to be incompatible with the
fundamental nature of the
meteorological problem. It
is likely that, as pointed out
by a distinguished English
meteorologist* in a presi-
dential address before the
Royal Meteorological Socie-
ty: "Our answers must al-
ways be expressed as proba-
bilities."

Whatever form improved
short-range predictions may
take in the future, they will
be of direct and immediate
interest to the insurance in-
dustry. In a broader sense,
the probabilistic nature of the
meteorological problem is in-
extricably linked to the in-
terest of insurance people in
weather matters. It is pre-
cisely because it is not possi-
ble to anticipate weather oc-
currences weeks, months, and
years in advance that insur-
ance is desirable covering
losses due to weather. How-
ever, such insurance, if it is
soundly conceived, must be
underwritten with some
awareness of the probability
that a given weather event
will occur. Here, the interest
of the insurance industry
veers from what has already
been referred to as the pre-
diction problem and focuses
on the climatic aspects. In a
sense, the shift in interests

*Sir Graham Sutton, April 28, 1954.

14

involves only semantics, be-
cause climatic data are used
to predict the future from a
consideration of the past.
Here, the attempt is, or
should be, to determine the
probability or likelihood that
damaging hail will fall on a
particular tract of land, that
wind in excess of a critical
value will cause damage to a
radio or television tower or
to a home or business build-
ing, that the distribution of
winds in the atmosphere
would distribute uncon-
trolled radioactive particles
in a particular pattern of fall-
out, or that a combination of
wind and waves at sea would
cause loss of life and prop-
erty to shipping operations
or to off-shore oil drilling and
exploration work. Such
knowledge is required in the
setting of rates on an equita-
ble basis so as to provide
sound and continuing pro-
tection.

Climatic trends

It is apparent that more
than a simple knowledge of
past climatic conditions is
required. Interrelationships
between climatic elements
and the interaction between
the atmosphere and its bound-
ary, both land and ocean,
must be known and appre-
ciated. Moreover, cognizance
must be taken of long-term
(i.e., of the order or decades
and centuries) climatic trends
whenever they can be shown
to be real and of significance.
Estimates of unusual or ex-
treme values must frequently
be made from distributions

Dr. Malone is Director of the
Travelers Weather Research
Center, The Travelers Insur-
ance Co., Hartford, Conn. He
has had a distinguished career
in the field of meteorology and
is a partner of Weather Train-
ing Supplies, furnishing educa-
tional material to schools and
universities.

which leave something to be
desired in the way of com-
pleteness. Critical values of
weather elements must be
determined, either empirical-
ly or theoretically, From a
correlation of comparatively
short period of insurance ex-
perience and weather data it
is frequently possible to ex-
trapolate the insurance ex-
perience over a longer time
and thus provide a broader
base for underwriting. Fi-
nally, the most sophisticated
treatment of climatic data
may be of no avail unless it is
possible to apply it in actual
practice according to accep-
table standards for sound in-
surance procedures.

In summary, the insurance
industry is interested in the
climatic aspects of meteoro-
logy in order to arrive at a
procedure of underwriting
which will permit extending
the protective features of in-
surance on a realistic and
sustained basis. It is inter-
ested in the prediction prob-
lem insofar as this can be
utilized in an effective man-
ner to minimize the losses to
the insurer and hence the
costs to the insured. To meet
the challenge suggested by
these dual interests, meteoro-
logy and its sister field of
oceanography have much to
offer and a great deal yet to do.

15

The Associates Distinguished Lecturer

.HE Associates of the
Woods Hole Oceanographic
Institution, by sponsoring the
distinguished lectureship ser-
ies for the past three sum-
mers at Woods Hole, have
contributed significantly to
the educational opportunities
for the staff and students at
the Institution.

Announcements will soon
be distributed to colleges and
universities that the Associ-
ates' lecturer for 1956 at
Woods Hole will be Professor
B. Kullenberg, Associate Pro-
fessor of Oceanography of
the University of Goteborg,
Sweden. Dr. Kullenberg also
will be available as a consul-
tant, and may participate in
some phases of the Institu-
tion's research.

Einar Borge Kullenberg
was born May 11, 1906, at
Uppokra, Sweden and edu-
cated at the University of

Lund taking his B.A. in 1928
and his Ph.D. in 1938. He is
married and has two chil-
dren. Dr. Kullenberg's pro-
fessional career includes four
years as a demonstrater at
the Institute of Experimental
Physics, University of Lund;
thirteen years on the staff of
the Swedish Hydrographical
Biological Commission at
Stockholm, and since 1939
has been a member of the
staff at the Oceanographic
Institute at Goteborg. In 1942
he was appointed Lecturer in
Oceanography on the faculty
of the University of Gote-
borg, and in 1948 an Associ-
ate Professor.

Dr. Kullenberg's activities
include membership in Swe-
den's delegation to the Inter-
national Council for the Ex-
ploration of the Sea, member
of Goteborg's Academy of
Arts and Sciences, and of the
Royal Swedish Academy of
Sciences. His scientific pub-
lications include articles on
inertial currents in the sea,
internal waves, water ex-
changes of harbor and chan-
nels, marine sediments, and
the techniques of core samp-
ling. The Kullenberg piston
corer, for which he is proba-
bly best known, was used ef-
fectively on the round-the-
world Swedish Deep-Sea Ex-
pedition of 1947-48, when
cores of sediment as long as

16

66 feet were obtained. He has
unusual ingenuity in the de-
sign of oceanographic instru-
ments.

Dr. Kullenberg is a cul-
tured scholar of social poise
and gifted as a raconteur. He
likes chess and often plays it
blind. The summer of 1954,

he was one of the eminent
scientists attending the dedi-
cation ceremonies of the Lab-
oratory of Oceanography at
Woods Hole where again he
will find many friends and
admirers waiting to extend
to him a warm welcome.

E. H. S.

Research in marine meteorology at the
Institution is supported by contracts with
the Office of Naval Research, U.S. Navy,
the US. Weather Bureau, and the support
of basic research by the associates.

BUBBLES

SALTDUST

and

BY A. H. WOODCOCK

RAINDROPS

Salt particles from the sea play a role in rain formation.

E

VERYONE knows that
winds blowing over the sea
carry water vapor from the
ocean areas to the land areas
of the earth, and that this
water vapor eventually falls
as rain or snow. But, it is
less well-known that these
winds also transport an av-
erage of about 30 pounds of
sea salts per cubic mile of air,
and that this salt seems to be
important if not essential in
rain formation.

On a clear, dark night the
visible "dust beam" from a
flashlight reveals the pres-

ence of this salt as minute
particles, shining star-like as
they are tumbled about in
marine air-streams. Spider
webs are often strung with
tiny salt crystals, some of
which are just large enough
to be seen with a good hand
lens. On still nights these
crystals often collect water,
and the morning sun will re-
veal a "jeweled web." The
number of salt particles at
cloud-base altitudes is almost
equal to the number found
relatively near the surface.
At these higher levels, clean

17

glass slides exposed to the
air from an airplane soon be-
come "fogged' 'with the crys-
tals or droplets which rap-
idly collect on the surface.
After a short flight the lead-
ing edge of the propeller tip
will often taste salty when
touched with the tip of the
tongue.

Origin of salt.

Knowledge of the nature of
these atmospheric salt nuclei
and of their origin is impor-
tant as an aid in the search
for understanding of a great
many geophysical problems,
the most important of which
are the problems of the for-
mation of rain and the role
of airborne salts in the cycles
of geochemistry.

The breaking waves caused
by winds on the open sea
force much air beneath the
surface in the form of small
bubbles. These bubbles range
in size from less than one-
thousandth of an inch up to
about one-tenth of an inch
in diameter. With ultra-
slow-motion photography we
have established one way in
which bubbles of this size
produce droplets when they
burst at the surface of the
sea. Several droplets are
produced by each bubble and
many of them remain air-
borne. As the water evapo-
rates they leave a minute
crystalline residue. Thus
winds passing over the sea
acquire a burden of salt dust
simultaneously with the ad-
dition of water vapor. Well-
mixed marine air, which has
passed over hundreds of
miles of sea surface will com-
monly contain from 10 to

100 of these salt particles
per cubic inch, from the sea
surface up to the bases of the
local cumulus clouds.

Other natural phenomena
which produce great num-
bers of small bubbles in sea
water, and hence add to the
salt-nuclei population of the
air, are melting snow, sleet
and hail, and impinging rain-
drops. For instance, individ-
ual snowflake clusters re-
lease as many as 500 bubbles
as they melt in the surface
waters of the sea. Most of
the bubbles produced in the

<"BBB5HPr

High speed photograph, made in
our laboratory, of droplets pro-
duced by an air bubble bursting
at a water surface.

sea in this manner are of mi-
croscopic size.

When droplets are ejected
into the air from the burst-
ing bubbles, they commonly
carry with them a strong
positive charge. This charge
on the droplets has been mea-
sured in this laboratory by
Mr. D. C. Blanchard. " His
preliminary results indicate
that the electrical current
flow due to the transfer of
charged droplets from the sea
surface to the atmosphere
may contribute largely to the
well-known electrical inter-

18

change between the earth
and the atmosphere. Hence
it is possible that these
charged nuclei are important
in the generation of thunder-
storm electricity.

Sampling salt.

Here at Woods Hole we
have also developed tech-
niques for sampling and
weighing air-borne salt parti-
cles. As everyone knows,
table salt (NaCl) crystals
tend to become wet when the
weather is humid. In fact,
at a relative humidity of 80%
a single small crystal will,
if left exposed for a sufficient
time, collect enough water
from the air to completely
dissolve and to form a drop-
let. At a given humidity and
temperature the amount of
water collected in this way
by a mass of NaCl is directly
related to its weight, and this
is also true for a particle of
sea salt. This fact was uti-
lized in weighing indirectly
the minute sea-salt crystals
sampled in the free air. The
method has been tested by
direct but more laborious
chemical methods.

When a small glass slide 1
mm wide was exposed from
an aircraft at a speed of 70
mph, it was found that prac-
tically all of the salt nuclei
larger than about one micron
or 0.00025 inches in radius,
impinged upon and adhered
to the glass surface. These
salt particles are crystalline
at a low relative humidity
and become liquid droplets
at high humidities. Under a
microscope, measurements of
the diameter of the droplets
enable us to compute the vol-

Mr. A. H. Woodcock has

been with the Institution since
1931. Serving originally as
ship's technician on the Atlan-
tis his curiosity and power of
observation led to new knowl-
edge about the behavior of air
over the sea. These and the
studies mentioned in his article
have received international at-
tention.

ume of each, and from this
volume the weights of salt in
solution.

Rain formation.

Samples taken from air-
craft have shown that the
salt particles from the sea
are carried by the winds to
great heights, and there seems
to be a physical connection
between the salt in these
particles and the salt in rain
water. One of the most excit-
ing aspects of the study of
atmospheric salt particles
concerns the role of these
particles in raindrop forma-
tion. Over a period of about
five years, evidence has been
slowly accumulating that
each large salt particle be-
comes the nucleus upon
which raindrops form in ma-
rine air. The evidence sup-
porting this idea was ac-
quired by comparing the
number and weight of the
salt nuclei in a volume of
relatively clear air with the
number of raindrops, and the
weight of salt dissolved in
them, in an equal volume of
rainy air. These comparisons
are too complex to present in

19

detail here. However, the
result implies that droplets
containing each salt particle
grow to raindrop size through
coalescence with much more
numerous and relatively non-
saline cloud droplets.

Measurements of the
weights of salt in oceanic air
are also useful in attempting
to explain world-wide occur-
rence of chloride in precipi-
tation and river waters.
Comparisons of the weights
of chloride suspended in ma-
rine winds and the weights
of chloride carried onto the
continents by rains, wind im-
pingement, etc., have suggest-
ed that all of the chlorides
found in river waters may
come from the sea, via the at-
mosphere. If, however, all
of the salts found in rain wa-
ters and in the airborne par-
ticles do in fact come from
the sea, how is one to explain
the often observed discrep-
ancies in the ratios of these
various salts as compared to
the ratios of these salts in
the sea?

Further problems.

Progress in understanding
is often dependent upon
learning enough to be able
to frame detailed questions
which are realistic, and which
are sufficiently limited in
scope to be answered within
a reasonable time and with
the available facilities.

Recent studies have en-
abled us to frame detailed
and more nearly ideal ques-
tions concerning a number of
problems in cloud physics and
geochemistry. The future
work required to answer
some of the most important of

these questions should, it
seems to me, involve a study
of the detailed mechanics of
the production of droplets by
bursting bubbles of the vari-
ous sizes found in the sea, and
the chemistry of the drop-
lets so produced. Special at-
tention should be given to
the affects of various surface
film conditions of the sea up-
on the chemical make-up of
the droplets. The results of
this study may be of great
interest to geochemists and
to agriculturalists.

Other efforts, aimed at fur-
ther understanding of the
rain-forming role of the sea-
salt nuclei, should involve
tracing the physical and
chemical events within and
near individual cumulus
clouds before, during and af-
ter the time of occurrence of
rain showers.

The present time is one of
accelerated interest in the
role of the oceans in weather
processes. The outlook is for
increased research effort in
marine meteorology. I feel
that it is important at this
stage to emphasize the rela-
tively small scale studies of
the interrelationships of sea
surface conditions, air-borne
salts, and the conditions in
and around individual cumu-
lus clouds. These studies may
provide useful evidence and
understanding of the compli-
cated sequence of events
leading up to rain formation.
Such understanding should
be of basic aid in defining the
larger problems of rain for-
mation in the groups of
clouds in marine storms such
as hurricanes. Knowledge of
the details of the natural

20

rainforming process should, artificially altering this pro-
and probably will, lead to cess.
new ideas and methods for

The Fingerprints

J.HE sudden downpour of a
violent summer thunderstorm,
the light steady rains from a
grey overcast sky and the
gusty wind-swept rains of the
northeaster, all are familiar to
us. We are quite aware of the
different cloud formations,
overcasts and general wind
conditions that accompany
these rains. But what of the
rain itself? Does one ever
think of differences in the
nature of the rain in each of
these storms?

Most of us merely classify
the rain as light, medium,
heavy or perhaps the well-
known ultimate in intensity;
cats and dogs. After all, this
is a sufficient classification for
most purposes. But, when we
examine the raindrops them-
selves, there begins to emerge
a rather unique feature, inde-
pendent of the rate of rainfall,
which may enable us to asso-
ciate a particular rain with a
certain type of storm. This is
the size and number of rain-
drops present in a given space
in a rain, a feature which the
cloud physicists call the basic
structure of the raindrop size
distribution. It has been found

BY DUNCAN C. BLANCHARD

Laboratory photograph of raindrop

disintegrating in upward moving

airstream.

that a particular type of rain-
storm will often have its own
characteristic drop size dis-
tribution and it is beginning

21

to appear that a storm may
be typed by this distribution.
This may be called the finger-
print of a storm. Existing
evidence indicates that these
fingerprints in oceanic rains
at least, may be controlled by
the minute salt particles that
rise from the surface of the
sea. Mr. Woodcock, in an-
other article in this issue of
Oceanus, has described how
these particles originate.

Measuring drops.

The science of meteorology
had existed for a long time
before anyone gave thought
to measuring the sizes of rain-
drops. The simple techniques
that were used during some
of the first attempts are still
used today. The first meas-
urements probably were
made by the Englishman
Lowe in 1892 and his observa-
tions of raindrop splashes on
pieces of slate were the pre-
lude to increased interest in
the subject. A few years
later Wiesner in Germany
introduced a sampling tech-
nique, still widely used, which
consists of allowing a small
sample of rain to fall upon
an ordinary chemical filter
paper which has been lightly
dusted with a water soluble
dye. The size of the rain
spots, easily visible now by
virtue of the dye, can be re-
lated to the raindrop size. A
novel and ingenious flour
method for determing rain-
drop size was discovered in
1904 by a Vermont farmer
named Bentley. This method
consists of allowing the rain
to fall into a pan containing
a layer of sifted flour. The
pan and contents, with the

raindrops now forming soft
dough pellets, are baked in a
warm oven until the pellets
are hard. The size of the pel-
lets can then be related to
the original raindrop size. I
have used Bentley's flour pel-
let method and find it quite
satisfactory. Indeed, a lack
of cooking skill is no great
handicap. It is interesting to
note that Bentley was not a
professional meteorologist but
was engaged in these inter-
esting scientific adventures
in his spare time.

Radar echoes

The measurements of rain-
drop size were accelerated
during and since World War
II, when it was found that
rain produced an excellent
radar echo. Meteorologists
were quick to take advantage
of the opportunity offered by
this new technique. Both
theory and experiment proved
that the reflection of a radar
signal from a raindrop was
proportional to the 6th power
of the raindrop diameter. For
example, a given raindrop
would reflect a radar signal
64 times as well as a drop half
its size or 729 times as well as
a drop one third its size. This
measure of the ability of a
collection of raindrops to pro-
duce a radar echo was called
the radar reflectivity or sim-
ply Z. This seemed to be the
ideal meteorological tool.
Higher rates of rainfall meant
more and larger raindrops and
consequently a much greater
value of Z. After obtaining
by experiment the relation-
ship between Z and the rate
of rainfall it would appear
that with the aid of radar a

22

Duncan C. Blanchard is

associated with Mr. Woodcock's
meteorological group. Trained
in engineering and physics, he
worked with Drs Langmuir and
Vincent Schaefer at General
Electric Research Laboratory,
Schenectady, N. Y.

meteorologist could determine
how hard it was raining in a
storm many miles distant.

Now, all this is based on the
assumption that for a given
rate of rainfall the raindrop
size distribution is always the
same and thus only one value
of Z can exist for any given
rainfall rate. But what would
happen if, in two rains of the
same intensity or rate of
rainfall, the drops were large
and scarce in the first rain
and small and plentiful in
the second. A little thought
will show that a much great-
er radar echo will most likely
come from the rain with the
large raindrops. A single
drop of 5 mm diameter pro-
duces the same echo as about
16,000 raindrops of 1 mm di-
ameter. The differences in
the raindrop size distribution
that tend to confuse the esti-
mates of the intensity of rain-
fall on a radar screen un-
doubtedly lie in the mechan-
ism responsible for the very
origin of the rain itself.

Let us look at a striking
example of how two differ-
ent rains, having exactly the
same rate of rainfall, will
give vastly different finger-
prints or raindrop size distri-
butions which apparently are
a direct result of the manner
in which the embryo drops
are formed. During recent
experiments on the island of
Hawaii, A. H. Woodcock and
the author obtained measure-

ments of the raindrop size
distribution in many types of
rain. During one rain falling
at the rate of 0.1 inch per
hour we found few and big
drops while in another rain
we found the opposite; many,
but small drops. This latter
rain is typical of the rains of
Hawaii, where the clouds do
not penetrate to any great
heights in the atmosphere
and the raindrops, whose fi-
nal size is somewhat depend-
ent on the cloud thickness,
are relatively small. On this
basis then it is somewhat my-
terious to find Hawaiian rains
showing sparse numbers of
big drops. Is this drop dis-
tribution a reflection of some
other origin of the rain, pos-
sibly entirely different from
the process that produces
many but small drops? This
puzzling question was some-
what clarified when we looked
at the weather condition
that produced the few but
large drops. The measure-
ments were obtained late one
evening at an elevation of
about 7,000 feet on the vol-
cano of Mauna Kea. The fol-
lowing morning, after the
rain had ceased and clouds
swept away, the entire top of
Mauna Kea was covered with
a blanket of snow which ex-
tended nearly down to the
elevation where the raindrop
samples were made.

I think we are now in a
position to give a reasonable
explanation of why we found
the few but large drops. The
raindrops evolved from snow-
flakes which formed high
within the great cloud system
that existed over Mauna Kea
that night. When these rath-

23

er sparsely distributed snow-
flakes fell down into re-
gions above freezing they
melted into small raindrops
which continued to "feed" on
the much smaller cloud drop-
lets, like a large snowball
growing as it plummets down
a snow covered slope, until
their arrival at the ground
was characterized by large
drops.

And so it appears that
someday we may have hopes
of identifying what type of
rain-forming process is going
on in the clouds by the size
distribution of the raindrops
that fall out. It will be excit-

ing if we are definitely able
to show that the distribution
of raindrops in oceanic rains
reflects the manner in which
salt particles are produced
by the sea. We will certainly
have to find out how nature
produces rain before we are
able to duplicate the process
ourselves. The problem is
difficult and far from solved.
We must learn more about
how the drops behave in their
flight from cloud to earth.
The eventual answer may en-
able us to type or fingerprint
a storm with certainty by
measuring the size of rain-
drops.

Currents and Tides

"The effects of atomic ex-
plosions on the atmosphere
and the sea" were presented
to the staff by Dr. Yasua Mi-
yake of the Meteorological
Research Institute in Tokyo,
who visited us in February.
The essence of his talk was
reported in TIME of March
20th, 1956.

Among recent distinguished
visitors to the Institution
were: Dr. G. E. R. Deacon,
Director of the National In-
stitute of Oceanography in
Great Britain, an old friend
of many staff members; Dr.
G. I. Taylor of Cambridge
University, pioneer into the
properties of rotating fluids;
and Dr. Jacques Picard, co-
inventor of the Bathyscaphe
TRIESTE.

Honorary degrees were
awarded on March 13 by the
University of Oslo, Norway,
to Dr. A. C. Redfield, Senior
Oceanographer and to Dr.
Laurence Irving, Associate in
Physiology. The University
of Oslo presents such awards
once in five years to distin-
guished foreigners.

On the instigation of phy-
sical oceanographer Allyn C.
Vine, the science teachers of
our local High School spent
an instructive evening at the
Institution. Many staff mem-
bers explained their respec-
tive fields, while a spirited
open meeting discussed how
this Institution and the staff
might aid in local science
education.

24

LIBRARY

WH 17YS X

ASSOCIATES

OF THE

WOODS HOLE OCEANOGRAPHIC INSTITUTION

GERARD SWOPE, JR., Chairman

N. B. McLEAN, President

JOHN A. GIFFORD, Secretary

RONALD A. VEEDER, Executive Assistant

EXECUTIVE COMMITTEE

CHARLES F. ADAMS, JR. N. B. McLEAN

BENJAMIN H. ALTON
WINSLOW CARLTON
RACHEL L. CARSON
POMEROY DAY
JOHN A. GIFFORD
GEORGE F. JEWETT

HENRY S. MORGAN
FRANK PACE, JR.
MALCOLM S. PARK
GERARD SWOPE, JR.
THOMAS J. WATSON, JR.
JAMES H. WICKERSHAM

CORPORATE COMMITTEE

Chairman: CHARLES F. ADAMS, JR.
President, Raytheon Manufacturing Company

ROBERT M. AKIN, JR.

F. M. BUNDY

W. VAN ALAN CLARK

POMEROY DAY

M. C. GALE

CAPTAIN PAUL HAMMOND

F. L. LaQUE

T. V. MOORE

FRANK PACE, JR.

MILES F. YORK

President, Hudson Wire Company
President, Gorton Pew Fisheries
Chairman, Avon Products, Inc.
Partner, Robinson, Robinson and Cole
President, Monarch Buick Company
Hammond, Kennedy & Legg Company
Vice President, International Nickel Company
Esso Research and Engineering Company

Exec. Vice President, General Dynamics
Corporation

President, Atlantic Mutual Insurance Company

(Dffiriu

RAYMOND STEVENS, President
ADMIRAL ED. H. SMITH, Director
EDWIN D. BROOKS, JR., Treasurer

Published by

WOODS HOLE OCEANOGRAPHIC INSTITUTION

WOODS HOLE, MASSACHUSETTS