TR-272 TECHNICAL REPORT saogne a ls Tae H Ol S VARIATIONS IN THE THERMAL STRUCTURE | jocUMENT | AND WIND FIELD OCCURRING IN THE COLLECTION y WESTERN INDIAN OCEAN DURING THE Loner MONSOONS JOHN G. BRUCE AUGUST 1981 Approved for public release; distribution unlimited i PREPARED BY COMMANDING OFFICER, - . NAVAL OCEANOGRAPHIC OFFICE (6 NSTL STATION, BAY ST. LOUIS, MS 39522 PREPARED FOR 7-91, COMMANDER NAVAL OCEANOGRAPHY COMMAND NSTL STATION, BAY ST. LOUIS, MS 39529 FOREWORD A series of temperature sections from expendable bathythermographs over a 4's year period off the Somali and Arabian coasts described in this report shows the complex eddy structure formed each year during the southwest monsoon. These eddies may be three to five times the diameter of Gulf Stream rings. Strong near-surface fronts associated with the boundaries of the larger eddies are formed. This report gives an idea of the extreme frontal variability that occurs seasonally in this region and information about the strong wind system driving the circulation. Co Hes BASSETT Captain, USN Commanding Officer ET ~, ~\ WHO] ON \ f COLLECTION / a \ \ \ } UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) REPORT DOCUMENTATION PAGE T. REPORT NUMBER 2, GOVT ACCESSION NO. TR-272 4. TITLE (and Subtitle VARIATIONS IN. THE THERMAL STRUCTURE AND WIND FIELD OCCURRING IN THE WESTERN INDIAN OCEAN DURING THE MONSOONS READ INSTRUCTIONS BEFORE COMPLETING FORM 5. TYPE OF REPORT & PERIOD COVERED 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(s) 8. CONTRACT OR John G. Bruce UR y UME 12. REPORT DATE 2 August 1981 aie ee 15. SECURITY CLASS. (of this report) 10. PROGRAM AREA & WO 9. PERFORMING ORGANIZATION NAME AND ADDRESS iL Naval Oceanographic Office (Code 9100) NSTL. Station Bay Sit, Louis, MS 89522 11. CONTROLLING OFFICE NAME AND ADDRESS 14. MONITORING AGENCY NAME & ADDRESS(if different from Controlling Office) UNCLASSIFIED {Sa, DECLASSIFICATION/ DOWNGRADING SCHEDULE 16. DISTRIBUTION STATEMENT (of this Report) Approved for public release; distribution unlimited. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, if different from Report) 17. 18. SUPPLEMENTARY NOTES 19. KEY WORDS (Continue on reverse side if neceasary and identify by block number) 20. ABSTRACT (Continue on reverse side if necessary and identify by block number) : : The changes occurring in the temperature field in the Somali Basin and off the Arabian coast have been monitored from October 1975 through December 1979 by a time series of temperature sections obtained along the tanker sea lane offshore between 29S and 22°N. The development and decay of the large eddy (up to rougnly 600 km in diameter) in the northern Somali Basin and its smaller associated eddies were observed each southwest monsoon. Strong norizontal thermal gradients particularly in the upper 200 m occur at the eddy boundaries; . yO . 2 . 5 1 and currents in this region can attain velocities of up to 7 knots. (con'd DD jan, 1473 EDITION OF 1 Nov 65 Is OBSOLETE UNCLASSIFIED S/N 0102-014- 6601 | SECURITY CLASSIFICATION OF THIS PAGE (When Data Entered) HOOT UNCLASSIFIED LECURITY CLASSIFICATION OF THIS PAGE(When Data Entered) 20. ‘Abstract (cond) Monthly wind stress contoured for the western Indian Ocean clearly shows the southwest monsoon from May through September (with values over 4 dynes cm~* during July) to be considerably stronger than the northeast monsoon with a maximum in January. Maps of wind stress curl during the southwest monsoon show a large region of negative curl (over -4 x 1078 dynes cm73) to the north- east off the Somali coast, whereas a region of high positive curl occurs off the Arabian peninsula and in a small band off the Somali gast coast north of 5°N. Sverdrup mass transports of up to 40 x 107 2 g sec’- to the north off the Somali coast are in rough agreement with observed values. we UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered) CONTENTS Page INTRODUCTION ] BACKGROUND AND RESULTS ] WIND FIELD IN THE WESTERN INDIAN OCEAN 5 WIND DATA 6 WESTERN INDIAN OCEAN WIND STRESS FIELD 6 CURL OF WIND STRESS DURING MONSOONS 8 TOTAL MERIDIONAL TRANSPORT 9 CONCLUSIONS 10 REFERENCES 12 FIGURES Figure la. 14 Figure 1b. 15 Figure 2. 16-69 Figure 3. 70 Figure 4. 71 Figure 5, 72-125 Figure 6 126 Figure 7 127 Figure 8. 128 Figure 9. 129 Figure 10. 130 Figure 11. 131 Figure 12. 132 Figure 13. 133 Figure 14. 134-157 Figure 15. 158 Figure 16. 159 Figure 17. 160 Figure 18. 161 Figure 19. 162 Figure 20. 163 Figure 21. 164 Figure 22. 165 Figure 23. 166 Figure 24, 167 PUCWIRE Zoe 168 Figure 26. 169 Figure 27. 170 Figure 28. val TABLE Table 1. Number of Observations in Subdivisions I/ Wi ACKNOWLEDGEMENTS The author would like to express particular thanks to the EXXON Corpora- tion for allowing us the use of their tankers. Without their generous cooperation this experiment would have been impossible. Special thanks are also due the University of Cape Town Oceanographic Department, particularly JovK. Mallory, ES. W. Simpson; ’andsl) Wolhuter. Data’ required far con= structing the wind stress maps were kindly furnished by the late A. Bunker. The author is indebted to Tochiko Turner for considerable help in data analysis and to Linda-Anne Stanley for typing and help in putting this report together. Support during the experiment was to the Woods Hole Oceanographic Institution from the Office of Naval Research under contract NO0014-14-C- 0262, NR-083-004 and NOO014-79-C-0071, NR-083-004. The National Science Foundation furnished support also during tne initial stage of the experiment under grant ATM 74-2226 AQOl. iv 1. INTRODUCTION A program of XBT measurements in the northwestern and equatorial Indian Ocean has continued from the end of the southwest monsoon in 1975 through 1979. A series of temperature sections has been accumulated which, combined with other surveys in the area, has given a considerable amount of information about this region. The long-range scientific objectives have been to attempt an understanding of the circulation characteristics particularly in the Somali Basin and off the Arabian coast, in order to examine the time variations and horizontal scale of the eddy circulation associated with the commencement of the dominant southwest monsoon, the variation during an entire season and also that from year to year. It is important to know whether certain preferred modes exist in the current patterns, the decline of the flow upon cessation of the monsoon winds, the changes in the heat content of the mixed layer, the variations in the region of strong upwelling off the Somali and Arabian coasts, and the changes occurring in the near-equatorial dynamic topography as a result of the Somali circulation. These studies in the western Indian Ocean are important to the Navy because considerable information about the unusually strong horizontal tempera- ture gradients which develop during northern summer off the Somali and Arabian coasts within a relatively short period (two to three months for full strength) has been obtained. The surface currents associated with these gradients are on the order of twice those found in the Gulf Stream, and volume transports in the upper 200 m exceed that of the Gulf Stream. Variation in acoustic patterns Should be expected in this area. This program was set up for monitoring the thermal structure in the northwestern Indian Ocean by means of XBT observations from tankers and other available ships. It is a cooperative effort originated and managed by the Woods Hole Oceanographic Institution and shared during 1979 by the U. S. Naval Oceanographic Office. The University of Cape Town, South Africa, has coopera- ted with and aided the observational program. This study has been part of INDEX (Indian Ocean Experiment), a program designed for examining the circula- tion dynamics by a series of oceanographic studies associated with the First GARP Global Experiment (FGGE). 2. BACKGROUND AND RESULTS A series of temperature sections along the tanker sea lane (figure la) off the East African and Arabian coasts has allowed the observqtion of the seasonal development of large eddies which occur during the period of strong southwest monsoon winds in the northwestern Indian Ocean. For five consecutive years (1975-1979), a large eddy described by Bruce (1968) was formed in the northern Somali Basin between approximately 4°N and 12°N. This eddy appears to be the first to form in the region upon commencement of the southwest monsoon; it is considerably larger and more energetic than other eddies formed there during the year; and it has been observed to remain in this location at least three months after cessation of the southwest monsoon. It is first discernable from sections in late May or early June in the near surface waters (0-100 m) and continues to intensify until late September or early October at the end of the southwest monsoon. The fully developed eddy is clearly evident as indicated by the depressed isotherms of the temperature sections in figure 1. The horizontal dimensions across the prime eddy are 400 to 600 km with variations occurring during a single monsoon season (Bruce, 1970) as well as yearly differences which will be described here. An eddy of smaller horizontal dimensions which appears to be associated with the prime eddy was found each year (1979-1979) off Socotra between 12°N to 150N. During some years such as 1976 and 1979 [also 1970 (Bruce, 1973)] an eddy was observed south of about 5°N and adjacent to the southern boundary of the prime eddy and to the east African coast. Observations during several surveys within the last fifteen years indicate that the northeastward current flowing alongshore (Somali Current) is clearly part of the eddy field found each southwest monsoon off the Somali coast (Swallow and Bruce, 1966; Bruce, 1968, 1973). The current diverges from the coast turning eastward about 9°N to 10°N each year and during some years also at 3°N to 5°N forming a southern eddy. Farther offshore (550E to 580E), it turns southward and then back toward the shore. All past measurements known to the author indicate that during the southwest monsoon, a clockwise "warm" eddy (prime eddy) of this general description occurs within the Somali Basin. Pronounced upwelling with surface temperatures as low as 13°C (Warren Gig ill.» 1966) is found in the region where the strong coastal current turns offshore. The program has utilized ships of opportunity (EXXON tankers) en route along the sea lane between the Persian Gulf and South Africa. These obtained a temperature-depth (0-450 m) section with expendable bathythermograph probes (XBTs) on an average of approximately every three weeks along essentially the same track. The track location is extremely fortuitous in that it passes directly through the central region of the eddy field and thus provides an excellent means of monitoring the growth and decay of the eddies formed during each southwest monsoon. The measurements were obtained by special observers who were placed aboard at Cape Town, South Africa, and made a round trip to the Persian Gulf, thus obtaining two sections per trip. Altogether 55 sections were completed (figure 2). The closely spaced stations (20-30 km apart) necessary to observe the small scale features of the temperature structure essentially require a full time observer who was also needed to maintain good quality control of the data and record, at each station, wind velocity, ship's set by currents, surface salinity samples, etc. With each of the sections shown in figure 1 (which represents the fully developed southwest monsoon eddy system) is given a schematic representation of the circulation pattern of the near-surface water (upper 150 m). This estimate is aided by previous surveys in this area (Bruce, 1968, 1970) during which time the structure of the eddies to the east and west of the tanker track was observed. The complete time sequence showing the changes occurring in the thermal structure of the eddy field is given in figure 2. In late March and April no large scale horizontal gradients generally are evident in the upper thermocline, whereas in the late June - early July sections the prime eddy is clearly discernible roughly between 5°N to 10°N. Then during July and August (the periods of maximum wind strength) the development inten- sifies with a deepening of the mixed layer in the central regions of the prime eddy (centered approximately 8°N) and the Socotra eddy (12°N to 14°N). By December a relaxation of the eddy field is evident. During some years, how- ever, the prime eddy is still discernible in the upper layer as late as January (i.e., January 1976). Although a large eddy is found each year within the northern Somali Basin, there are some differences from year to year. Probably the most evident is the formation of a southern loop or eddy in 1976 and 1979. The pattern at that time was similar to that found in 1970 (Bruce, 1973). The coastal surface current turned offshore about 5°N to the south of the prime eddy. Normally in the case of a single large eddy as observed during 1976 and 1977 the strong upwelling associated with the divergence of the coastal current from the coast occurs at approximately 9°N to 11°N. When the southern circulation or eddy forms and becomes well developed, strong upwelling also occurs at 4°N to 6°N. Although this circulation is termed an eddy, some of the flow extends south of the equator and may in fact not all return to the coastal current regime. Judging from XBT data from 1975 through July 1979, it appeared that once the general pattern of circulation becomes established during the monsoon, it then tends to continue throughout the duration of the monsoon. For example, between late May and mid-October 1976 (see figure 2), all eight tanker XBT sections obtained throughout this period indicate that both the southern eddy and prime eddy were present. However, this might not always hold true. During late August 1979 (figure 2), a northward shift in the northern boundary of the southern eddy near 5°N occurred. This shift occurred in the following manner: during the early stages of the development of the 1979 southwest monsoon eddies, a large southern eddy and the northern prime eddy were both clearly established by June in the Somali Basin. This circulation resulted in the current turning offshore and forming a wedge of cold upwelled water in two locations: 4°N to 5°N, and 9°N to 10°N. The general location and size of the eddies tended to remain approximately the same through early August. The ESSO HONOLULU XBT section, 14-18 July 1979 (figure 2), is representative of the temperature structure along the tanker sea lane. The strong gradients above 150 m depth near 4°N occur at the northern edge of the southern eddy. The cold near-surface water advected offshore by the anticyclonic eddy extends through the section here. It may be seen that the southern eddy is relatively shallow whereas the northern prime eddy (4°N to 10°N) exhibits horizontal temperature gradients at least to 400-500 m depth. The upwelled cold water also extends offshore through the section near 10°N. As found in each previous southwest monsoon during which data in this region have been collected (Bruce, 1979), the Socotra eddy also occurred in 1979 (10°N to 149N). Because of the relatively fresh (35.135.3 9/00) near-surface water entrained in the system of eddies from the Somali coastal current, a surface salinity map serves as a remarkably good method for examining the circulation pattern. By mid-August the northern front and cold wedge associated with the southern eddy began a northward translation at a rate of 15-30 cms™'. By late August the southern eddy apparently had merged with the northern prime eddy as indicated by the temperature section taken 25-31 August 1979 from the ESSO CARRIBBEAN (figure 2) and a map of sur- face salinity (figure 3) obtained during the survey aboard USNS WILKES. The satellite imagery of sea surface temperature also indicated this translation during August. The coalescence of the southern eddy with the northern prime eddy is somewhat similar to that observed during August and September 1970 by Bruce (1973), although for 1979 the data was obtained more frequently during the occurrence. Data collected from WILKES during August and September included 415 XBTs and 27 STD stations. In addition to observing the snift of the southern eddy, the prime or northern eddy was surveyed. Also a more detailed study of the Socotra eddy was obtained than nas been made to date. In 1975, 1977, and 1978, whereas a well-developed southern eddy was not evident, still there appear to be variations in the near-surface (0-100 m) structure that suggest that some offshore flow might occur between 3°N and 5°N. For example, along the 19-23 October 1975 section (figure 1b) at 4°N to SON, there are small scale temperature gradients which suggest a weak eastward flow in the upper 100 m. It seems possible that the returning onshore flow (2°N to 5°N) of tne prime eddy or northern eddy might well affect changes in the alongshore current flow. Similar observations are described in laboratory scale models for fluidics research (Carbonare et al., 1970). A small southern eddy was found during the early stage of the southwest monsoon 1978 (Bruce et al., 1980) although it did not appear to attain the size or strong horizontal gradients occurring during 1976 or 1979. The time series of sections following the development of the eddy struc- ture through the early stages of the southwest monsoon (March through June) indicate that the prime eddy first forms between 5°N to 10°N in the Somali Basin, with the center at approximately 8°N, 53°E. The data do not suggest that the northern eddy is formed at the equator and then translates northeast- ward along the coast as postulated by the numerical models of Cox (1976), and Hurlburt and Thompson (1976). The strong signal during the southwest monsoon in the surface dynamic topography (79N to 10°N) of the sea surface within the prime eddy is evident in figure 4 and tne complete series in figure 5. The same temperature-salinity relationship for the Somali Basin during the southwest monsoon (a mean tempera- ture-salinity curve determined by values obtained from previous surveys during the southwest monsoon period) was used for all the determinations Shown. The density gradients that occur in the Somali eddies, as in the Gulf Stream, are largely a function of temperature. The pronounced downward slope of the surface dynamic topography to the north in figure 4 occurs between 8°N to 12°N with values on the order of 2 x 1073 dynes g7! (about the same as found across the Gulf Stream at 36°N). The volume transport of the prime eddy to the east offshore amounts to 38 to 42 x 10© m3 sec-! (0-400 dbar, rel. 400 dbar) with a comparable return flow inshore to the south between 4°N to SON. To the north of the prime eddy, the Socotra eddy occurs each of the five observation years with transports on the order of 9 to 15 x 10© m3 secu!. The temperature sections and surface dynamic topography show that this eddy during 1979 (center of eddy along sections is about 12°N) was well developed from July through October (figures 2 and 5). The surface temperature (figure 6) and salinity (figure 7) characteristics of the western Indian Ocean, particularly in the region of the Somali Basin, are changed considerably during the southwest monsoon as a result of several factors: 1) the advection into the basin by the Somali Current of relatively coo] and fresh South Equatorial Current water, 2) high evaporation, 3) advec- tion of upwelled water (also relatively fresh and cool) off the Somali Coast, 4) vertical mixing resulting from the very large wind stress at the sea Surface during the southwest monsoon, and 5) horizontal mixing within the anticyclonic eddies. Within the upper 100 m (approximation of the mixed layer oa ae the tanker sea lane between 2°N and 12°N during the monsoon roe. (approximately three months) there was a heat loss of approximately 3 x to 5 x 10'© cal/cm as determined from the XBT temperature stations ane 8). Now the area of the region influenced by entrainment within the eddy circulation where relatively good mixing is found (Bruce, 1968) extends feagLe 400 km offshore. Thus the total heat loss of the area would be about cal if the tanker section is assumed to be representative of the area. The rate of heat loss during the southwest monsoon is the same order of magni- tude as that found in the western North Atlantic on an annual average (Bunker and Worthington, 1976), although in the Somali region the loss occurs only over the monsoon period and is regained again in the interim northern fall and Spring warming period between the northeast and southwest monsoons. Although there is a heat loss in the upper 100 m during the southwest monsoon, at the same time because of the deepening of the isotherms below the prime eddy there is a heat gain in the layers deeper than the mixed layer (figures 9, 10 and 11). Thus the amount of actual heat lost to the atmosphere would be reduced by the transfer of heat to deeper layers. After the south- west monsoon as the eddy slowly weakens, as shown by the series of XBT temperature sections, heat is released from these layers for three to four months after the monsoon. There is evidence from the sections that the prime eddy in fact might have been maintained from 1975 to 1976 (in particular see 22-27 January 1976, figure 2) through the northeast monsoon as suggested from earlier measurements by Bruce and Volkmann (1969); however, it is not clear that the continuity occurred during other years. The data indicate that the temperature of the mixed layer of the equatorial water in the Somali Basin as well changes at the time the eddy field is built up. Between 19N to 1°S during the southwest monsoon the near-surface water along the tanker lane (48°E to 50°E) becomes cooler resulting in a correspond- ing drop in sea surface dynamic height (relative to 400 dbar) on the order of 0.10 to 0.15 dynamic meters (figure 12). In figure 2 the reduction of tempera- ture in the mixed layer can be seen to occur after the spring warming period each year. During the warming period the layer normally reacnes 28°C to 30°C. By July and August after the eddy field has developed the temperature drops to about 25°C to 26°C in this region. After the cessation of the southwest monsoon by November the layer had again warmed (27°C to 28°C). These changes are clearly shown in the surface temperature values given in figure 6. It seems that this change might well influence the strength and/or direction of the equatorial undercurrent because a local slope of the sea surface which is negative westward might occur. Taft and Knauss (1967) found no evidence of the undercurrent on the western side of the Indian Ocean during the months of the southwest monsoon. It should be noted that although there are only sur- face salinity observations from tnese XBT sections, it turns out that the hydrographic data from this equatorial region indicate that the probable seasonal salinity variations would produce changes in the sea surface dynamic height of only about 0.01 dynamic meters. 3. WIND FIELD IN THE WESTERN INDIAN OCEAN Recent interest in the effect of monsoonal winds on the circulation of the Indian Ocean has resulted in several programs of oceanographic measurement both of the Somali current and equatorial dynamics in the western and central Indian Ocean. As part of the oceanographic participation (INDEX, Indian Ocean Experiment) during FGGE, the eddy structure and current system off the Somali coast was studied during the 1979 southwest monsoon (May-September) with particular emphasis on the commencing stage of the monsoon. Since consider- able data have been made available from the National Climatic Center (NCC) on past wind measurements throughout this region, it is felt that some discussion of these observations would be worthwhile. 4. WIND DATA Using the NCC ship observations from the TDF-11 tapes, Bunker (1976) prepared a program for calculating sea surface energy fluxes. From these determinations the values of wind stress over the western Indian Ocean kindly were made available by him. Using these values, maps of monthly averages of Ty and ty were contoured in order to observe the patterns occurring during the southwest (May through September) and northeast (December through February) monsoons. The values of Cp in the equation tr = ely Uso (o is air density, Ujg is average wind speed at 10 mor ship's anemometer level) were selected by Bunker (1979, table 2) using various classes of air-sea temperature differences and wind speed ranges from the work of several investigators. Monthly averages for the period 1922-1972 were obtained for subdivisions of the Marsden squares as shown in figure 13 which gives the center of gravity of the observation positions. The total number of observations for each subdivision is given in table 1. The remoteness of some regions of the Indian Ocean results in a number of lesser traveled sea lanes as may be seen by comparing the volume of observations in table 1 with that of the North Atlantic in Bunker (1976, figure 3). The subdivisions of the Marsden squares have been adjusted in an attempt to include sufficient monthly observations to be significant. Averages for periods greater than a month would be of considerably less value in depict- ing the relatively rapid seasonal changes occurring during the monsoons. 5. WESTERN INDIAN OCEAN WIND STRESS FIELD The maps of wind stress (figure 14) have been contoured with the same interval, 0.2 dynes cm-2, for all months with Ty and Ty positive to the east and north respectively. Perhaps the most outstanding characteristic of the montnly maps is the large difference in magnitude of the wind stress field between the two monsoons. The southwest monsoon reaches its greatest strength during July and the northeast monsoon during January. In the early stage of the southwest monsoon the components become positive by May off the Somali coast around 5°N to 10°N with the largest values (> 1 dyne cm-2) near 8°N. This region is where the first evidence of upwelling at the sea surface is observed from tne maps of Wyrtki (1971) with near coastal temperatures falling below 279C. The June and July averages indicate the rapid development of the areas of high positive stress values, particularly off northeast Somali at about 10°N to 12°N. June averages greater than 2 dynes cm extend over half the distance to the Indian coast and meridionally between 5°N to 15°9N. 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The general pattern of the contours is similar for August and September, however, with a continued weakening of stress to 0.2 dynes cm-2 or less by October. There are apparently fluctuations of a shorter duration than could be Shown by monthly averages during the build-up of the southwest monsoon wind field. Schott and Fernandez-Partagas (1980) have found that the wind for May and June 1979 varies over a period of a few days in both speed and direction. The variations were evident in three-day averaged ship observations as well as records from shore stations and cloud-level winds from satellite data. The first evidence of wind reversal and the commencing of the northeast monsoon is also indicated off the Somali coast about 69N to 10°9N during Novem- ber. By January at the maximum strength of this monsoon values of -1.0 dynes cm72 occur, these being along the Somali coast approximately between O°N and 10°N. The wind stress then diminishes by March. April and October, the months falling between monsoons, have relatively low values over most of the northwestern Indian Ocean. 6. CURL OF WIND STRESS DURING MONSOONS The increase of the curl of the wind stress during the commencement of the southwest monsoon starting in May and reaching maximum values in July is shown in the maps of figures 15, 16, and 17. The curl maps were constructed using the severuelincs of the wind stress field given in figure 14 with a grid spacing of 2 for both latitude and longitude. The most negative values first appear in the Somali Basin (5°N to 8°N, 530E) by May and increase through July. They tend to lie in a band extending from the central Somali Basin on toward the northeast to about 65°E. Values during July of -6 x 10-8 dynes cm-3 in the region, 5°N to 10°N, 540E to 599E, occur approximately where the thermocline deepens in the central part of the large Somali anticyclonic eddy observed each southwest monsoon (Bruce, 1968, 1979). There is insufficient data concerning the prevalence and Structure of the eddy field to the northeast of the Somali Basin, 10°N to 15°N, 60°E to 65°E, where the curl values up to -10 x 10°78 dynes cm-3 are Shown for July, to estimate the probable location of these mid-ocean eddies. However, there is evidence from the near-surface dynamic topography that they occur here (Bruce, 1968). Also from Robinson et al. (1979) (figures 18 and 19) the depth to the top of the thermocline reaches a maximum during the southwest monsoon in the region of large negative curl values and tne patterns of the maps of curl and thermocline depth are somewhat similar. A region of positive curl to the north of this band is found off the Arabian coast (values over 10 x 1078 dynes cm’) and extends down to the southwest just off the Somali coast to about 49N. The region where the Somali current turns offshore has been observed to be between about 4°N to 9°N (Bruce, 1979) within the area of positive curl. Here upwelling and the upward vertical velocity reaches a maximum in_the near_surface water (calculated by Swallow and Bruce (1966) to be 7 x 1073 cm sec-! while the thickness of the mixed layer decreases. During the period of maximum strength of the northeast monsoon in January, the values of curl are substantially less than those of July. Over much of the Somali Basin the curl becomes positive (figure 20) up to >1 x 10-8 dynes cm-3 with a small area about 10°N just off the Somali coast which is >2 x 10° dynes cm7>3. In the region to the north of the contour of zero curl between the Somali east coast and the Indian west coast (which has positive curl during the southwest monsoon), the curl during the northeast monsoon becomes negative. A similar reversal of sign occurs to the south of the zero contour. Although in general there is a change of sigh of the curl between monsoons, the magnitude of the values in most regions is considerably less during the northeast monsoon. 7. TOTAL MERIDIONAL TRANSPORT From the July and January values of curl (representing the maximum values for each monsoon) the meridional mass transport (Sverdrup transport), M, = a | curl t can be determined (Stommel, 1965). M, is the sum of the geostrophic and Ekman transports. Values were summed over areas of 2° latitude and longi- tude (figures 21 and 22) from the eastern boundary (transport function consi- dered zero here), i.e., the west coast of India and Sri Lanka and from 80°E for the region south of Sri Lanka down to 29N, toward the west approaching the Somali and Arabian Coasts. In the Somali Basin during July the transport is greater than 30 x 1912 g sec-! and in two regions near 69N and 12°N greater than 40 x 102 g sec! to the south. For continuity this would require a northward current of equal magnitude along the Somali coast and off the island of Socotra (12°N, 54°E). The transport around 69N jis in SCIrCeN ene with direct measurements here which amount to 40 to 50 x 1012 g sec-! (Swallow and Bruce, 1966) (figure 22), however, a more northerly section (up to 8° 40'N) of direct measurements where the current_turns offshore during the same cruise had a transport over 60 x 1012 g sec-!. It was also found that in the North Atlantic the computations of transport failed to account for the large observed transports in the Gulf Stream after it leaves the coast (Leetmaa and Bunker, 1978). The Somali Basin, as in this area of the Atlantic, has a strong eddy field which in part might account for the greater transport. The northwestern Indian Ocean is subjected to large seasonal changes in wind stress, particularly with the onset and build-up of the southwest monsoon, and it is not clear whether the mean stress curl for a period as short as a month would account for the trans- port which is a function of both barotropic and baroclinic processes (Hantel, 1971). However, once the onset of the monsoons has occurred, the wind direc- tion tends to be relatively steady compared to most ocean regions, thus conceivably a shorter response time would be required in this part of the Indian Ocean as suggested by the agreement with direct current observations. A lag of the order of magnitude of a month between the build-up in the wind stress field (greatest in July) and the oceanic response is indicated in figures 6 and 7 where the greatest monthly mean depths of the top of the thermocline are attained during August (Robinson et al., 1979). The_fact that there are two areas in figure 21 with transports greater than AO) 3 OLS g sec7| Suggests the formation of two eddies. Such a circulation has been observed each southwest monsoon during the period 1975-1979 (Bruce, 1979): a large eddy off the Somali coast and a somewhat smaller one to the east of Socotra. Note that the mass transport calculations suggest that the Socotra eddy is the larger. Observations also show that during certain years (as 1970, 1976, 1979) (Bruce, 1973, 1979; Brown et al., 1980; Duing et al., 1980) a portion of the Somali current may turn offshore about 4°N to 6°N forming a separate near-equatorial eddy or loop. There is no indication of this mode of circulation in the mass transport map. To the east of the Somali Basin obseryations from earlier hydrographic surveys (sections along 59N and 10°N) (Bruce, 1968) give evidence for the occurrence of other eddies formed during the southwest monsoon. The geostro- phic velocity and transport across these sections are shown in figures 23, 24, 25, and 26. Drawing from these data and previous studies of the southwest monsoon circulation (Bruce, 1968; Duing, 1970) a schematic drawing indicating a pee ae circulation pattern of the eddy field which occurs is given in figure he Off the Arabian coast during July (figure 21) a southward transport would be required. From hydrographic observations (Bruce, 1968) it is not clear that Such might be the case. The section along 15°N during early August 1963 (Bruce, 1968) indicates a northward geostrophic near-surface current_along the coast with a transport amounting to approximately 12 x 10!2 g sec-!. Pilot charts and the Dutch atlas (1952) show a northward current along the coast. During January the Sverdrup transport (figure 22) values are relatively weak compared with that of July. A southward transport along the Somali coast south of about 5°N amounting to greater than 10 x 10/2 go! sec would be re- quired. This flow is in good agreement with the pilot charts (H.0. Pub. 566) which show southward coastal currents ranging up to 125 cm sec-!. The meri- dional geostrophic transport across a 5°N section just after the northeast monsoon (figure 28) gives relatively low values compared with the transports during the southwest monsoon (figure 24) as well as indicating a small north- ward transport off the Somali coast. 8. CONCLUSIONS From the evidence on hand to date, it appears that both the northern (or "prime" ) eddy in the Somali Basin and the eddy east of Socotra are probably generated each southwest monsoon. These eddies have been observed for five consecutive years (1975 through 1979) by XBT temperature sections along the tanker sea lane. They have also been present during all known earlier surveys (Bruce, 1979). During some years (1970, 1976, 1979) the Somali current has been found to turn offshore between about 49N to 6°N forming a southern loop or eddy. When this circulation pattern is established, a region of cold upwelled water occurs both at the location where the northern eddy turns offshore (approximately 80N to 109N) and where the southern turnoff is observed (approxi- mately 4°N to 6°N) along the coast. During late August and early September during 1970 and 1979 the southern eddy was observed to flow into and coalesce with the northern one. During the southwest monsoon the strong signal in the sea surface dynamic topography of the northern eddy develops each year. The slope on_the northern edge of the.eddy (8°N to 120N) amounts to about 2 x 107-2 dynes g-! (comparable 10 to the Gulf Stream at 36°N). The volume transport offshore during the south- west monsoon can reach 38 to 42 x 106 m3 sec’! (0-400 dbar, rel. 400 dbar). In the mixed layer (upper 100 m) along the XBT section (2°N to 12°N) heat js gained in late Spring until the commencement of the southwest monsoon, after which a rapid heat loss occurs. At the same time the loss takes place in the mixed layer, however, there is a comparable gain in heat in the 100 to 200 m layer caused by a deepening of the isotherms, thus the heat loss for 0 to 200 m appears to be small, if any, during the southwest monsoon. After the southwest monsoon at the end of the year both layers show a heat loss. The surface dynamic topography of western Indian Ocean equatorial water (489E to 50°E) shows strong seasonal signals: an increase in dynamic height during each interim between monsoons (at the times the Wyrtkie jet should occur) and a decrease during the northwest and southwest monsoons. The patterns of the monthly averages of the wind stress show the magnitude of values during the southwest monsoon (July, off Socotra, > 4 dynes cm™ ) are large relative to that of the northeast monsoon (January, off northern Somalia, > 1 dynes cm-2). Sverdrup mass transport determinga from velWes of curl of the wind stress shows agreement (values up to 40 x 10'© g sec’! to the north) with observations during the southwest monsoon off the Somali coast (6°N). During the northeast monsoon the Sverdrup transport requires a_,southward flow along the Somali coast south of about 5°N (up to 10 x 10!2 g7! sec). am REFERENCES Brown, 0.B., J.G. Bruce, and R.H. Evans, Evolution of sea surface temperature in the Somali Basin during the southwest monsoon of 1979, Science, 209, 595-597, 1980. Bruce, J.G., Comparison of near-surface dynamic topography during the two mon- soons in the western Indian Ocean, Deep-Sea Research, 15, 665-678, 1968. Bruce, J.G., Notes on the Somali Current system during the soutnwest monsoon, Journal of Geophysical Research, 75, 4170-4173, 1970. Bruce, J.G., Large-scale variations of the Somali Current during tne southwest monsoon, 1970, Deep-Sea Research, 20, 837-846, 1973. Bruce, J.G., Eddies off the Somali Coast during the southwest monsoon, Journal of Geophysical Research, 84, 7742-7748, 1979. Bruce, J.G., D.R. Quadfasel, and J.C. Swallow, Somali eddy formation during the commencement of the southwest monsoon, 1978, Journal of Geophysical Research, 85, 6654-6660, 1980. Bruce, J.G. and G.H. Volkmann, Some measurements of current off the Somali coast during the northwest monsoon, Journal of Geophysical Research, 74, 1958-1967, 1969. Bunker, A.F. and L.V. Worthington, Energy exchange charts of the Nortn Atlantic Ocean, Bulletin of the American Meteorological Society, 57, 670-678, 19/6. Carbonaro, M., P.E. Colin, and D. Olivari, The deflection of a jet by a cross- flowing stream and its application to anemometry, The von Karman Institute for Fluid Dynamics, Rhode-Saint-Genese, Belgium, 1970. Cox, M.D., Equatorially trapped waves and the generation of the Somali Current, Deep-Sea Research, 23 (12), 1139-1152, 1976. Duing, W., The monsoon regime of the currents in the Indian Ocean, East-West Center Books, Honolulu, 1970. Duing, W., R.L. Molinari, J.C. Swallow, Somali current: Evolution of surface current, Science, 209, 588, 1980. Hantel, M., Wind stress curl - the forcing function for ocean motions. Studies in Physical Oceanography, Gordon and Breach, New York, 124-136, 1971. Hurlburt, H.E. and J.D. Thompson, A numerical model of the Somali current, Journal of Physical Oceanography, 6 (5), 646-664, 1976. Koninklijk Nederlands Meteorologisch Instituut, Indische Oceaan, Oceanografische in Meteorologische gegevens, (Dutch Atlas), 2nd Ed., Publ. No. 135, Vol. I, WESe SA Does Voll 25 2H Chatres, U9S2. Leetmaa, A. and A.F. Bunker, Updated charts of the mean annual wind stress, convergences in the Ekman layers, and Sverdrup transports in the North Atlantic, Journal of Marine Science, 36 (2), 311-322, 1978. Robinson, M.K., R.A. Bauer, and E.H. Schroeder, Atlas of North Atlantic - Indian Ocean monthly mean temperatures and mean salinities of the surface layer, Naval Oceanographic Office Ref. Pub. 18, Dept. of the Navy, Washington, DC, 1979. Schott, F. and J. Fernandez-Partagas, The onset of the summer monsoon during the FGGE 1979 experiment off the East African coast: a comparison of wind data collected by different means, Journal of Geophysical Research, in press, 1980. Stommel, H., The Gulf Stream, University of California Press, Berkeley, 248 pp., 1965. Swallow, J.C. and J.G. Bruce, Current measurements off the Somali Coast during the southwest monsoon of 1964, Deep-Sea Research, 13, 861-888, 1966. Taft, B.A. and J.A. Knauss, Tne equatorial undercurrent of the Indian Ocean as observed by the Lusiad expedition, Bulletin of Scripps Institution of Oceanography, 9, 19-26, 1967. U.S. Navy Hydrographic Office, Atlas of surface currents, Indian Ocean, H.O. PUD NOs B05 S/S. Warren, B.A., H. Stommel and J.C. Swallow, Water masses and patterns of flow in the Somali Basin during the southwest monsoon of 1964, Deep-Sea Research, isp SZ5=E005 1905. Wyrtki, K., Oceanographic Atlas of the International Indian Ocean Expedition, The National Science Foundation, Washington, D.C., 531 pp., 1971. is ARABIA 20°N 10° O°? 40° 50° 60°E Figure 1a. Sea lane used by tankers en route between Persian Gulf and Atlantic ports along which XBT sections are obtained. ESSO KAWASAKI 19-23 0CT. 1975 5 10 20 n pip DEPTH (METERS) ESSO JAPAN 18-25 AUGUST 1976 STATION NO. 100 30 DEPTH (METERS) LATITUDE ESSO KAGOSHIMA 29 AUG. — 3SEPT. 1977 STATION NO. DEPTH (METERS) LATITUDE Figure 1b - 1g. Temperature (°C) sections along the (a) tanker sea lane from XBTs for three successive southwest monsoons: (b), (c) 1975, (d), (e) 1976, and (f), (g) 1977. 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Ol 02k ON NOLLVLS 8261 0430 62-be2 N3AAVHSWISH IM OSSS 54 BSSOP CARIBBEAN 22> 2A VANMSI7 9 STATION NO. 60 48 50 30 40 20 10 O fe) (oe) oO N ne) (SYHILIW) HLd IC 50 400 qo 6° 8° 10° 122 14° 16° a= = 2OP > a 22N LATITUDE Bo Figure 2. (cont.) (‘\uod) *z aunbil4 OM LILY) Noc2 002 Bk 09h ot och oO} 08 09 ov of J Sed 002 (SYFILIW) HLdICG Ook 4s) OL 08 98 88 G66 20i 80 Sly Si 92) ON NOILVLS 626lmadaae Ihe NVaedievo OSsa 56 (\u09) *Z eunbi4 IGNLILG 7 20g ll o9| ob! och oOl 08 09 ov of 00 = Sod UU U avy Zz, ot oe 09 OS Ov o¢ Oz Ok ON NOILVLS 626) HOYVW OS HVAIYNG 1V 006 00b S mM 00f & = S a 002 q 2D 00} 0 oy AL DURIYAH 24-30 MARCH 1979 STATION NO. 58 WAY TIONS Figure 2. (cont.) ESSO CARIBBEAN 18-24 APRIL 1979 STATION WO. 40 Zl SO 20 = oO w!} O 9) na) K 6) ° _| (10 te ee A Bs Re 72 Ke & Re c ( Ly Ds py-= ee g N ne) (SHILIW) HLdIC LATITUDE Figure 2. (cont.) (uo9) *Z aunbl4 SAOMLAL Za Nodd 00d o8l oD ot och oOh o8 o9 oV od oO Sod OOF [e) (e) ne) fe) fe) N (SHILIN) HLdIC OO! vg SIS) LE ih. 82 08 G8 28 OO} 80} Obl Sik 2th Ok 92h ON NOILVLS 6261 AVW O|-9 ~NV3AGEINVO OSSs3 60 (.u09) *Z aunbi.} AO LL, ock oO} o8 09 ob od 30) Sad Ov og OZ Ol | ON NOILVLS 6261 SNNf Ol-G HVAIYNG 1V 00S 00b S mM 00 & = S a ooz G NS foley 0 61 AL DURIYAH 28 JUNE -3 JULY 1979 STATION WO. 90 126 100 (e) (e) (e) Oo a) ne) (SYILIW) HLd IC 62 o° Boo ae 6 NC IS ES aN 2S LATITUDE Figure 2. (cont.) 1979 14-18 JULY ESSO HONOLULU STATION NO. 100 (2) (2) (e) oO N ino) (SYILIW) HLdIG 63 400 500 2 LATITUDE Figure 2. (cont.) Nodd Od 8l 91 (yuo) Z aunbi4 AIONLILV 7 ocl Ol 08 09 Oe ON NO/LVLS 6261 ONV ZL-Ol oV of oO S od NVA8gluvod OSS4 (e) a (SYHFLIW) HLIFC 64 (\u0d) °Z aunbil4 IDNLILV 7 Nood 00d o8l o9| ot | odl oO l o8 o9 oV od oO Sod OOS OOv (2) Oo mM (SHILIW) HLdIC Ool OL dg) 16 OO! Oll 02k Sel ON NOILVLS SAE Siw MeeGe — Nhysisielshyo) OSSal 65 (\uod) Z aunbi4 FICNLILY 7 Noc2@ 002 o8t 09h ott och 0 OI o8 09 ov oc 00 = Sod OOv (2) oO ino) fe) fe) N (SYILIW) HLAIG OO} 09 OS Ov Of Se Cz O} ; ON NOLLVLS 6261 100 12-2) NSOVHN3d09 OSS 66 00d och (\u09) ‘Zz aunbil4 SOUL I oOh o8 o9 ON NOILVLS 626) AON OAMOL OSSA (SYILIW) HLAIG 67 obl (\uo9) *z aunbi4 IGNLILV 7 och —o OL o8 09 ON NOILVLS 6264 9430 v- AON 82 oV od oO Sod Od} NS9VHN3d09 OSS4 OOS OOv (e) oO no) fe) fo) aN) (SYILIW) HLd IC OO} 68 (uod) Z aunbi4 FIONLILV 7 Nodd 007d o8h ot obl och oOh 08 oD oV od oO Sod OOS OOv ; OO€ y x =N = = 002 q 2) OO} O v9 OL og =¢8 06 OO} Ol Oz} 921 ON NOILVLS 626) 040 €I-2 OANOL OSSS 69 = socoTRA /7= 5 eee, 10° SOMALIA Be fo) SURFACE SALINITY, %o 0 1SPAUGESSsSEPm iGo USNS WILKES 50m 55° COge Figure 3. Surface salinity (°/o9), 18 August - 3 September 1979, from USNS WILKES. 70 STATION NUMBER S110 15 20 20 30 oS) 4o) 45 90 14 ere /\ —a— (9-22 OCT. 1975 aa ESSO KAWASAKI a | @ —e— {0-13 SEPT. 1976 ne ° ESSO GENEVA 183 me Tad —e— 30 AUG - 2 SEPT 1977 i / \ ESSO KAGOSHIMA / — A @ A \ Hoh \ % A B B12 J . \ a Nae / : & : ‘ S e a Nn Se) / \ ie St pr \ | x yo i , S rN a / e | a G r r S 1.0 mn f “a y 4 C1 = Joon @ oo a ae a y ry 4. | a |e ie: 4 4 a rN ogb Cl \, Via! ant Ba _) B WN io ‘aye { e. 08 Plc agels I \ U1 2 hee 2°N 4° 6° 8° 10° 12° 14° 16°N LATITUDE Figure 4. Sea surface dynamic height relative to 400 dbar during the southwest monsoons 1975, 1976, and 1977 constructed from XBT stations along the tanker sea lane (Figure 1a). For each year the strong signal of the prime eddy occurs from 8°N to 10°N with a deep trough to the north (17°N to 12°N) between it and the Socotra eddy 12°N to 14°N. Mean temperature-salinity relationship determined from previous data in this region (same temperature-salinity distribution used for all stations) was used with XBT temperatures to determine the specific volume values needed to produce these curves. 7| SAAIND BSay} BoNpold 0} Papaau sanjer BWNIOA dyIDadS ay) aUILIA}9p 0} Saunyesadwia} |X YM pasn sem (SuOI}e}s |Je JO} pasn uOINUISIP AyuIes-einyesadwa} wes) UoIGaL 94} Ul BJep SNo|Aasd Woy paulUua}ap diysuoNejas Ayuies-ainyesadwia} ueaW) *Z euNBi4 ul UMOYS SUOI}D—S aunjesadiua} Woy (| ain6y) aue| eas saxue} Buoje yore suegp OOP 0} aANeja! 1yGIey d1WeUAp a9deLNS eas ‘cg aunbi4 SONL/LV 7 NZ to Sh toGih srotzenoctercCle olily sto Olle oOsm™sc0) god 0) vo9 nme toa) uote mot mmtoCm Nolmano Ol sa Sal 80 60 OnENS 3 SS 3 ur bt 5. ch (400P OOP '|24) JOVSYNS V3S 40 LHOISH DINVNAG Ch YAGOLIO ge-Gl IMVSVMV OSS4 72 (\u09) g aunbi4 FONLILY 7 (404P OO 124) 3ov4uNS vas 40 LHOISH OINVNAG GZ6r YFEWSAON £-Y5EOL90 FE IMVSVMYY OSS4 [>.90S,W Of) Ww AQ 73 (\u09) °g aunfil4 SONLILY 7 Novih soOlrcGilao iH estoctantoGln toliien 80 0)l 0 Oo Clsmto/4 temo seta Gieeerc Zetocmetees Comal eee OME Ga [>.725,W Of) Ws AQ (4094p OOb 124) Jovsuns vas 40 LHOISH QIWVNAG 926} AYVANVE 92-2 VOIUdV OSS4 74 (}u09) “Gg eunbi4 FONLILV 7 Nodt ot oSh ovh oft och ott ot 06 08 od 9 oS oV of oC Nob oO T =e =a (409P OOb 124) Jov4suns vas 40 LHOISH DIWVNAG 9/6) AYVNYEA4 6-S WOKE OSSs Sob 8'0 60 [>.995,W Of) AQ G li gh 75 (\uo09) “g aunbi4 FONLILY 7 06 o8 od. oJ OG rolemue | ac) = Nolasco) (409P OOb 124) Jov4NNS V3S 40 LHOISH JINVNAG SAS MNslely G2 ie NSAVHSW 14H TIM OSS3 W OF) Ww AG IAS 76 (uoo) “G aunbi4 FONLILV 7 No Gb ch aa deh eh ohh Ob co cB of GD dG dp od a Nor oO Sol (>_995,W Of) Ww Aq (40qP OOF 124) JOVSYNS VAS 40 LHOISH DIWVNAG 9/61 AVW 8-7 NSAVHSW 14H WM OSS4 ah NoZt o9F oGt obh oft od (\uod) *g aunbi4 FONLILY 7 ol CO oo a Choa dS ar at = eG Ne a Sl 60 a [>.985,W OF) AQ Sli (4094p OOb 124) J0v4uNS V3S 40 LHOISH DINVNAG 926h AVW S¢-€e A INIONOH OSS4 eh 78 (uo9) *g aunbi4 FONLILY 7 Nodt oS oSt oh of h och obt oOh 06 08 od oy) 0G oD of od Nok oO Sol (>. I95, W) Ow 4G (409P OO 124) JOVAYNNS VAS 40 LHOISH JIWVNAG 926+ ANA 2-7 NIN IONOH OSS4 79 (\uod) °g aunbi4 FONLILY 7 Novis xcOls _995,W Of) AQ ch (404P QOv ‘|24) / 4Ov4YNS V3S 40 LHOISH OIWVNAG i 926 LSNOAW v2- 02 a \ Nvdwr OSS3 8] @—______» (\uod) “g aunbil4 FONL/LV 7 oOt 06 08 od Oe Gia +x alee Chemeaas ee SE 5 One Sak 80 oe 60 ae) neg at é ° OnmNS @ 3 SS 3 wr ies / ts @-@ Zt (40qP OO 124) 3J0VSYNS V3AS 40 LHOISH SINVNAG Cy S7Oh-dssWaltaes ShsOh VAANS9 OSSS 82 (\uo9) ‘g aunbi4 FONLILV 7 NoZt 9) cGSh oh off och off cOF 106 8 of 0% oS oF of of Noh. 00 Sol 80 60 @ | @ (>. I95, W Of) W AG ct (40q4P OOb 124) JOVAUNS VAS JO LHOISH DINVNAG . YAANI9 OSS4 83 (uo) *g aunbi4 FONLILYT Neoe 0h . 99S,W Op) Ws AQ 86 NoLt oD oSh oVb (1u09) *g aunbi4 JIONL/LV 7 06 08 od 09 0G oV of od Nok 00 (4DgP OOF 124) 30v4yNS VW3asS 40 LHOISH JINVNAG 9261 YAEGW350SC ¢c-8h VAANAD OSS4 Sol [7.985 W Of) AQ 87 (uod) *g aunbi4 FIONLILY 7 NoZt ot oSt oVh oft ok obt ot 06 08 od. 9 oS oD of ot Nob oO Sok he 60 ‘ ° 01S Aer J\ ee 3 i See d @@ S o 3 US bt § ch (40qP OOr ‘|94) 3JOvVsuNS V3S 40 LHOISH SINVNAG 7 JJ6h HOMWW b- AMvnNuga4 82. |! VAAN39 OSS4 88 Nod} oD oSt ovh oft och =i — aca —acalt cs) (1u09) °c ainbi4 FONLILY 7 SW Op) Ww AQ (792 (4094p OOb ‘124) J0v4UNS Vas 40 LHOI3H DIWVNAG ACV GINS eval : YVAANAD OSS4 89 (\uo9) *g aunfi4 FSONLILV 7 Nal eh dS a? cle “aah llr Ol oS de oe GS) dS tt EG Neti dO) Sol [>.90S,W Op) Ws AQ (409P OOb 194) JOVSYNS VAS 40 LHOISH IIWVNAG 216+ AVW 8-9 IIVMVH OSS4 90 (\uod) “sg aunbi4 FONLILY 7 Nolb o9b oSt oth oft och obk ocOt 06 o8 of 09 oS of of of Not oc Sob W OY Ww G (7. 995, (40qP OOP '194) JIVSYNS VAS 40 LHOISH SINVNAG 226r ANN’ GS-AVW 62 IIVMVH OSS4 9] (\uod) °g aunbi4 JFONLILV 7 New Oly tcGlam ctenctlacscche cht cOlm 001s totes tote 00ns oS oY ayo a oCmea Notyoaca() ° (4094p OOb 13%) J0v4ynNS vas 40 LHOISH DINVNAG 226+ ANAC 9t-th IMNVSVMVX OSSJ 60 Oh aa eh 92 (\uo9) *g aunbi4 JIONLILY 7 NoZt o9b oSt ob oft och off ocOt 06 oc8 of 09 oF oF of 06 Not oc Sob W OF w AG IAS 7 fe. (404P OOP 194) JOVSYNS VAS 40 LHSISH DINVNAG LM NUME alNINE Os IMVSVMV OSS4 93 (\uo9) “g aunbi4 JSONLILV 7 Newt Ol cGh = oth c@h toCh= tolls cOl; to) = t0b me odeaos 8'0 @ (7.995, Of) AQ GI (409P OOP 124) OWANNS VAS 40 LH9I3H DINVNAG DAG SARE Base 1” GI4aVW OSS3 94 (\uod) “Gg aunbil4 JIONL/LY 7 Ned cS AS a? dal clr oll? OP oS oo lo OD) SC SiC) (404P OOv 194) JOVSYNS VAS JO LHOISH SIWVNAG a LAS? ISN Is Wie xe GIYGVW OSS4 WO, WY MG IAS 7 (ps 95 (\uo9) °¢ aunbi4 JONLILV 7 New 09h “eShoucv) oth dla cll oO 00s cOmemocmnro L261 . —2@ 0G oP «of ~=— oS Nob =o (409P OOb 12) 30V4YNS V3S 40 LHOI3H DINVNAG lieisls G SLSMONW Ge VWIHSOOVY OSS4 [>_995,W Op) AQ ch 96 (uod) *g aunbi4 FONLILY 7 06 =o od 09 0G oD of od Not o0) (409P OOb 12) 30v4uNS Vas 40 1H9I3H DIWVNAG 226+ YAGWALdAS Ye-te VWIHSOOVY OSS4 Sob IaS,W Op) 4g es 97 Nodh oDb oSt obb oft och ott ot (\uod) “g aunbi4 FONLILV 7 06 08 od 9 oS oV of od Not oO (409P OOb 124) 30v4UNS W3S 40 LHOISH DINVNAG 226) YSEW5INIC C-YAEWSAON 8d N4AAVHSW 13H TIM OSS3 SW OV) Ww 4G # (2 98 (\uo9) *g aunbi4 IONLILYV 7 Nodt ot oSt oVh of th och ott oO 06 08 od o9 0G oD of of Nok oO Sol (7.995, W Op) ‘W Aq (40qP OOb 194) JOVAUNS VAS 40 LHSISH OJINVNAG 226) YSEW450SC LI-Sh N4AVHSW 14H TIM OSS3 99 Dy m (10 m@ sec 4 ESSO PACIFIC 27-31 MARCH 1978 ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) A \ ef 0.9 0.8 0.7 0. Seg O° {°N 2°N 4°N 6°N BON ON neo N nto Niemen Gul LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 100 Dy m (10 mé sec’) ESSOMPAGI AC SOI ARRILN8 ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.9 0.8 ON 0.6 PS Oren 2n SOND lOcNing a (22N 142NF 1G3N 4°N 6°N LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 101 Dy m (10 m® sec 9 ESSO_ OSAKA 19-23 MAY 1978 DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 08 cg O° {°N 2°N 4°N 6°N 8°N 10 LATITUDE ALONG TANKER Figure 5. (cont.) 102 °N {2°N —14°N SEA LANE 16°N Dy. m (10 mé sec 4 AL DURIYAH Slo JUNEF 1978 ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.9 0.8 0.7 0 05 O° 1°N 2°N 4°N 6°N CPN IOAN ZAIN BRIN lea LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 103 ESSO ATLANTIC OT ON UU g78 DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.6 f250 OwnieNi2oN 4°N 6°N OoNi a lOSNI CoN ten FoNbin meoaN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 104 Dy. m (10 m@ sec4) ESSO ATLANTIC 26> on JULY 198 ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.9 0.8 0.7 0.6 igo OmHteNy 2oN 4°N 6°N SrNG a (OSNE I2oNe atGoNGe ern LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 105 Dy. m (10 mé sec4) ESSO NEDERLAND 24-27 AUGUST 1978 'SF DYNAMIC HEIGHT OF SEA SURFACE a, (rel. 400 dbar) * 0.9 0.8 0.7 08 65 O° {°N 2°N 4°N 6°N BONT a OCNE M22Nt atScN Ss siGeN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 106 ESSO TOKYO 27-80 SePvehielen ys DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.8 0.7 0.6 FS ©? anh Zein : 4°N 6°N N {0°N 12°N — 14°N 16°N LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 107 Dy. m (10 m@ sec 4) ESSO TOKYO < 9-14 OCTOBER 1978 ¢* DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.6 ies OrtSNecoN 4°N 6° 8°N ION. HI23Ne Ol4SN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 108 16°N Dy m (10 mé sec 4) 0.6 FS. OP APN Ze ESSO WILHELMSHAVEN 21-25 NOVEMBER 1978 DYNAMIC HEIGHT OF Sef SUR EAGE (rel. 400 dbar) N 4°N 6°N BEN) OSNT M2eN) MIGSND PtGIN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 109 Dy m (10 m@ sec 4 ESSO WILHELMSHAVEN 26-29 DECEMBER 1978 ‘ST DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) (OLS) 0.8 0.7 0.6 RS, Oe TN) Zen SIN ZANT IN 16°N 4°N 6°N SN Ao) LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 110 Dy. m (10 m@ sec4 0.9 0.8 0.7 0.6 ESSO CARIBBEAN 23-26 JANUARY 1979 ‘ST DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) ESMOSMISNZEN % OsNEIZcNN 14SNie GEN 4°N 6°N Sant aaa! LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) Wi Dy. m (10 m@ sec4) 0.9 0.8 0.7 0.6 APS 0? EN 2N 4° ESSO CARIBBEAN 7-10 FEBRUARY 1979 DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) %e e a e \ Se ‘e ‘oe vy \,° we i ~e N 6°N CoNigee | OSNiomen 2c NemmaicecN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) We 16°N Dy. m. (10 mé sec 4) ESSO DURIYAH 9-9 MARCH 1979 ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.9 0.8 0.7 0.6 FSO? AN 22 fo) 4°N 6°N ND AIOGN OU 22N) GSN al6aN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 113 Dy. m (10 mé sec 4) ESSO DURIYAH 26-29 MARCH 1979 DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.6 {FSi Osaate Nie CiN fe} 4°N 6°N Noire LOaiN Steen 2g Nemo Go Niece On LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 114 ESSO CARIBBEAN IS=CIPAP RIE NOG ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) @. r * : ; / Vy Pe of SNe ny al al oe 1.0 o 0.8 0.7 0.6 FS CN ZN GN eel 2oN GON) StGsN 4°N 6°N SoNE nO LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) WS by. m (10 mésec9. ESSO CARIBBEAN TO MAY 199 ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.9 0.8 ON, 06 og 0° 1°N 2°N ss 4°N GON Bo Nia OtNisns (2oNeoONig WEEN LATITUDE "ALONG TANKER SEA LANE Figure 5. (cont.) Dy, m (10 m@sec4) AL DURIYAH 9-8 JUNE 1979 DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 06 fog O° {°N 2°N 4°N 6°N CoN lOSNieeaIZoNT at SoNE IGN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) Wid Dy m (10 m@ sec) AL DURIYAH 28 JUN- 3 JUL 1979 ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.9 0.8 0.7 0.6 Se ON OoNicy 122Ni WaoNe IGEN 4°N 6°N SINGa al LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 118 Dy m. (10 m@ sec’ 4) ESSO_ HONOLULU Gaile wuily iis ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.9 0.8 0.7 0.6 FS OP Naan ° 4°N 6°N IN = SCAN IZSIN BIND teak LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 119 Dy, m (10 m@ sec 4) ESSO CARIBBEAN iis "AUGUST 1979 ‘SF DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.8 0.7 06 tog O° {°N 2°N 4°N 6°N SaNey Ose HiCaNmen gi taNees aIGnN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 120 Dy, m (10 msec) ESSO CARIBBEAN Ciao AUGUSTEII9 ‘ST DYNAMIC HEIGHT OF SEA SURFACE / (rel. 400 dbar) g 0.9 0.8 0.7 0.6 PSO? MEN EN SIN 1OSNeS 2oNiee IGSNES GSN 4°N 6°N LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 12] Dy m (10 mé sec) TAPS OMPN 2°N ESSO COPENHAGEN IS=2] OCTOBER 1979 DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 4°N 6°N 8°N —_{0°N LATITUDE ALONG TANKER Figure 5. (cont.) 22 12°N—14°N SEA LANE 16°N Dy. m (10 m@ sec 4) E990) (Ose) 23-26 NOVEMBER 1979 DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) PS OP EN BN 4°N 6°N SN WORN | IAN AN LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 2S 16°N Dy. m (10 msec 9 ESSO COPENHAGEN 23 NO 8 DEG irs DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.6 (eS) OFMIENT2aN BNE {ZONE sta SN erly 4°N 6°N CaNe 0; LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 124 ESSO TOKYO Jo DeCeislety AS ‘ST DYNAMIC HEIGHT OF SEA SURFACE (rel. 400 dbar) 0.8 0.7 0. fog O° {°N 2°N ° fe} 4°N 6°N NOP ZN) IND tet LATITUDE ALONG TANKER SEA LANE Figure 5. (cont.) 125 6 ‘6261 48quia9aq 0} G/6|}. 18q0}99 S}SBO9 URIGeJY PUR I|EWOS HO NoZZ 0} Sog (@} aunbi4) aue) eas Jay4ue} Huoje suoNdas 1gX Woy (9,) aunyesadwa} aeLNS “9 aunbi4 126 "6261 Jaquiadag 0} 7/6} Areniqa4 ‘sjseoo ueiqesy PUB I|BWOS JO NoZZ 0} Soz (2}. aunbil4) aue] eas Jayue} Huoje suojdes 1qX YM SNoauesodwa}U0d (/,) AyuNes adeyNS ‘7 ainBIy 127 ONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJFMAMJJASOND 1976 USOT 1978 1979 Figure 8. Heat content (cal) for 0 - 100 m layer between 2°N to 12°N from XBT temperature sections (Figure 2) along tanker sea lane (Figure 1a). 128 fA |] OND JFMAMJJASONDJFMAMJJASONDJFMAMJJASONDJUFMAMJJASOND 1976 1977 1978 1979 Figure 9. Heat content (cal) for 100 - 200 m layer between 2°N to 12°N from XBT temperature sections (Figure 2) along tanker sea lane (Figure 1a). 129 646) Jaquacag 0} G/6|. 19q0}99 ‘s}se09 URIGeIY PUR I|EWOS HO NozZ 0} Soz (24 ainBi4) aue) eas sayue} Buoje suoNoes 1qxX Woy yJdap W QOZ Ie (Dp) aunyeradwa) ‘OL aunbiy 2£6/ Vv RE ea eS) SS ep clio (6 \ te Ff 5 ¥SE fp O al Ca 130 5 ‘6Z6L Jaqwacag 0} S/6|. 18q0}90 ‘s}seo9 URIGeIY PUR IJEWOS 0 NoZZ 0} Soz (2) aunBiy) aue| eas Jayue) Huoje suoljoes 1gX WOY WWAaLJOS! 4,0z Jo (W) ydag “11 auNbi4 S26) aw of 9 8! 002 13] i) ‘6261 Jaquisoaq 0} G26} 19q0}99 Woy 3p6p Ajayewixoudde ye Joyenba ay) Hulsso19 (2} aun6y) aue| eas sayue} Buje eyep 1X WO ‘Sol 0} No} UaaMjaq SUOI}e}S Woy pabesaAe JegN OOF 0} aANe|a/ }yBIay dIWeUAP adeuNs jeLOyeNby “Z| auNbi4 626/ &ZE6/ 226} 9L6h GZL6/ IO SWPP TU PIN OS Wes PY TE eK NN O-S VP Pie Mes) PIG IT OS Wow ~ WV W4Pril|aNn oO . Vineslinae age eae calielie eT blO 80 en r) 7 i} S eo" / ' RS CaN e os ' 2 ‘ 1S ‘ leas oe IN R Ge PIX 60 & ! \ e \ 1 \ \ J) e \ e~ 3S ‘ | \ @, EAN e \ U \ / i D \ (es . ' i BA) IP | \ i \ ! ) / \ ! \ ! \ @ >= ee . Fee a a \ Siena eet : y Nee! \ ji Neel ay Cy fi Nee ie arte 1 u | \ / e \ @ © i ‘ 1 ee) / ‘4 \ r ‘e© j \ | x Ne, : 1 vn a! \ / \e \ D \ V4 wy) \ e@ eel \ @ t \ 7 ey cI 1 TN ee ry e Y SNe) Ose \e! Jor ea ) yo ‘eo ’ / ~e e-0 Vy ed 'e/ \ / ‘ ‘e Nee eo’ 400G- o8h ‘Sot 0} Nob XOUddV 4QP OOb 184° LHOISH OINVNAG 3dvsYNS 1e2 Tyerilgrel cee line eleces lem ae] Ue lr ls=ttlelee lea ZOe T Test aaa la Yor B T Ur T T T T Vege | samen T TAR Njeses fae |e | oe 7 @ 28 | 7 Aut ES - Ee ( ra al GE i BG ieee pal pe) 4 SS aaa a | a) RY ICT WELLS ORL TTT OE Wal A oo aye | 2 a ea rare ae SN (=e el (a I OE : e9 e {0 O'8) Je ° 10 9 e10 10° JL — 41 iL Lf 1 1 Lt LN ee L/L Lt fe) fe) (eo) ce} ° 40 D0 60 70 8OE Figure 13. Subdivisions of Marsden squares within which monthly averages of wind stress were calculated for Figure 14. Dot gives center of gravity of observations. Number of observations for each subdivision is given in Table 1. iss fe) 30 Tas pitenlinall pg Gan nema! ab yal y a Steg ea ses) a sao Pn ae eer eon OU LU Us es UE \ | A | | ol @) y AG? os 20 } : EN 0 00 [ aa. oe ee "©" JANUARY | 7 Ue T, (dynes /cm2) 2 | 0 | | ‘ | 10° ° ° ° aie ° ° 40 5O 60 70 8OE Figure 14. Monthly averages of zonal, Ty, and meridional,t,,, wind stress for the western Indian Ocean. The contour increment of 0.2 dynes cm-2 is the same for all monthly maps. Values are positive to east and north. 134 7) amiga LLG Te PU aU ae fe aL ee ° | y -10 5 JANUARY Giggs iY - Ty (dynes/cm ) 9° (Ce : 4 i. —- | 9 AO) | L z| f aN or, 40° [ + eee = ptt A te 1 Se Lemos tal i 40 5O 60 7@ SOs Figure 14. (cont.) 138 30 Tana inclqea aang lrnanlacD saall Licensor in Upon cam ta ane nana pL Inala sale ale alae ay Vigan | tend ome a T = & A of ‘ - “FEBRUARY - T, (dynes/cm2) es el ce ener Va 60° Figure 14. (cont.) 136 30 iTpamaa T Tat ae T T T T T T T a ea Tia Troma aa T \ SS ees | SF [ | ol 0 200 z ; 2 : < S p wy ‘a Or r IN WL » FEBRUARY 02) KE | - 1, (dynes/cmé) NS [ 08 0° [ ’ [ 202 | | L eee ] 00 ] gp eee TOO ARRON See rere | AO: 50° 60° OM 80°E Figure 14. (cont.) ° 10 Lap aUcan Uae) (Pal gel a Maa US pela eli alt Trovtentt pinnae y 00 | _ o >) al K 00 (== “MARCH | T (dynes /cm@ Figure 14. (cont.) 138 30 T Ticaaaa (eva es Geel (ae yoy LS Uy T Tea Una eal aes Tia Tee lee (ee T Teal T BOP se aa ‘ | rcs - Vet 10" MARCH | Wi “Ty tah os eee ° 0! O O Oe | oe) | Cre L S 3 1 r TS 4O. 4 o < ey 40° [ ne Ne See SEE ane aw a ee a 40° 507 60° Figure 14. (cont.) 39 ZO MES e eu cg Mie tal sae eee licen Nic car een ocala | cock Mineo mmcel paeea loos Voce J; ar Teal Ge lem [ape scl ae ie eel) gm eo ° Be y ZOOM F 00 j ve | Sy ||$= Su) oes | Fa NE r i ae Zo, gz bf (. { ne) [ i - APRIL | T%} (dynes/cm®) | ] O° Q> | | ia ee a) 4 60° iO 80°E Figure 14. (cont.) 140 T Tal Talreal el eeal T ve 00 | gl g J ol | 3 ; | 0: | OQ | Z) S ‘ gb ar ; y | | i <0 | SS | | va 90 { 40 fb 4 "APRIL x Ty (dynes/cm®) | 90 O° CO | Le | HOM f S Ll 1G le Awl 5 1 1 it it it i 1 1 z JL 1 EE 1 5 1 1 1 1 LL ——e iS 5 40 50 60 70 8OE Figure 14. (cont.) 14] Toone asa lierina acme nal) at | : a y [ oF Ny O ag t : 0 S a 04 i 0. \ iS lr EDT be ae | ee 10 aay | Ch Se L 4 ae (dynes fem?) 0) hae | 0.6 08/| ra oe | Oa : Sf | oO So ae L ‘oO Opies ak Noe tes Vee Qh NE pe a I ea ma) 40° 50° 60° 70° 80°E Figure 14. (cont.) 142 ' MAY Ty (dynes/cm®) 4 60° Om 80°E Figure 14. (cont.) 143 Figure 14. (cont.) 144 | JUNE Figure 14. (cont.) 145 L avo” | B® Yj L G EK 0 A 02 ; JULY ; Ty (dynes/cm*) Me ee ae ee Figure 14. (cont.) 147 ZO) ie ~ AUGUST | T(dynes/cm®) [ 80°E Figure 14. (cont.) 148 “AUGUST - Ty (dynes/cm Figure 14. (cont.) 149 AO 50° 60° Ou 10 “SEPTEMBER - T(dynes/cm ) L 40° 50° 60° On 80°E Figure 14. (cont.) 150 “SEPTEMBER - Ty(dynes/cm®) 50° 60° Figure 14. (cont.) 15] 20 UII le SAT Loe Te eae AE at E fe) Oo Oo ae [eee _ OCTOBER aS (dynes/cm® ) 60° TO Figure 14. (cont.) 152 ° By OCTOBER Ty (dynes/cm®) {0 60° TO" 80°F Figure 14. (cont.) 18 O “ “NOVEMBER ye T (dynes/cm®) aft [eae ee ee ee eee ee eerie ° ° fe) 40 5,0 60 Figure 14. (cont.) 154 NO OS ae ~ NOVEMBER Ty(dynes/cm®) oo “36° 60° WeSC SOE Figure 14. (cont.) 159 ~ DECEMBER tlesien?) G9 Figure 14. (cont.) 156 ‘DECEMBER Ty(dynes/cm 40° 50° 60° On 80°E Figure 14. (cont.) 157 MAY evi ian Po ees ve lon dynes cm) aw 40° 50° 60°F Figure 15. Curl of the wind stress for May in 10-8 dynes cm-3 from monthly averages (Figure 14) off Somali and Arabian coasts during commencing stage of southwest monsoon. 158 si JUNE a code Leh le \ 10°dynes CUS 10° 40° 50° 60°E Figure 16. Curl of the wind stress for June in 10-8 dynes cm-3 from monthly averages (Figure 14) off Somali and Arabian coasts. 159 JULY | UME ee, oN 10° dynes cm? O O O ) O 40 90 60 10 80m Figure 17. Curl of the wind stress for July in 10-8 dynes cm-3 from monthly averages (Figure 14) in the western Indian Ocean during the maximum of the southwest monsoon. 160 40° S05 60° 70° 80° 30°N 20° o° 50° 60° BO°E Figure 18. July mean depths (m) to the top of the thermocline (after Robinson et al., 1979). 161 40° 50° 60° COP 80° 30°N 20° IOP O° 40° 50° 60° 70° BO°E Figure 19. August mean depth (m) to the top of the thermocline (after Robinson et al., 1979). 162 30°N JANUARY curl T in 20° 108 dynes cm™3 10° fo) 40° 90 60° GO; S07 Figure 20. Curl of the wind stress for January in 10-8 dynes cm-3 from monthly averages (Figure 14) in the western Indian Ocean during the maximum of the northeast monsoon. 163 3O°N JULY of mass transport in 20 10'4q sec! OP 1OKS | 7 40° 90° 60° (> OME Figure 21. Mean July Sverdrup mass transport in 1012 g sec-1, positive to north. 164 30°N JANUARY mass transport in 20° S “10!2g sect 10° 40° 50K 60° Oe 0 Figure 22. Mean January Sverdrup mass transport in 1012 g sec+1, positive to the north. 165 SOAIPIE 0} “Yd| * 00d oS9 . “UOOSUOW JSAMUINOS jo ed 49}}e| HuNp (jyBU ‘adojs IsaM }SB09 IPOS U9BM}9q) ULBDQ UeIPU] AY} U! UOI}DIS NoG SSOIDE JegD OOO! 0} 9ANe|a1 Ayoojan diydousoay ‘Ez aunbi4 JONLIINOT LSVF 009 €96! 1d3S 22-€l ‘I SILNVIIV NoGS ‘31M4OUd ALIOONSA i LN3YYND DIHdOULSOAD LN3NOdWOD HLNOS ~~~ LNANOdWOD HLYON ~~ 23s NI ALIQOT3A ral T €2b bel S2h YIGWIN NOILVLS 00S 921 beh 2eh A Eeh vel 002 oof oO SYFILIW NI HLdIO 166 no 5 "120 IU a 60° 65° 125 0° I LONG. (EAST) 5 STATION # t z WU 240;- 120 }-— Le o—$—= ——— — — bWOS (29572) zp Af 100};- 120;— 220;-- SS ES) Figure 24. Geostrophic volume transport, 0 - 1000 dbar relative to 1000 dbar, across 5°N section (Figure 23) in the Indian Ocean. Area of columns represents transport, value for each group in 106 m3 sec-1. 167 ‘uOOSUOW }SaMU}NOS ay} HuUNp (\ybu ‘adojs JSAM SAAIPedde] PuUe ‘Ya| ‘JSLOD ||PWOS U9BM}aq) UBBIO UPIPU| AY} U! UON}DAS NoQ|. SSOIIE JegD OOO} 0} aAnejas AyoojaA dIydoNsoay “sz aunBi4 JONLIINOT LSVF 002 oS9 009 €961 1d3S S— ONV 62 ‘IT SILNVILV NoOl ‘3MNSOYd ALIOOTSA AN3YYND DIHdOY1SO39 | LN3SNOdWOD HLNOS ~~ LNANOdWOD HLYON —— ‘29S 335 NI ALIOOT3A SYILIW NI HLdIO 86 26 YIGWNIN NO/LVLS 168 "1-08S eW Ul LOdSuUeL} Sjuasaide! UWUN}OD jo Realy "Ued9Q URIPU| BY} UI (GZ aINHi4) UONDAS NoO| SSO1DE ‘WeGP OOO! 0} SANEIAJ Jeqp OO! - 0 ‘Uodsue awWNjoA dI1ydoNsoeD ‘gz ainbi4 JONLIINOT LSVF o0d oS9 009 SS Bch Oz) 08 LY S S x= WY pe =~ 0-8 G sR Ov = : x 08 €96l ‘Ld3S S —“ONV 62 ‘ IE SILNVILV 2G Ni LYOdSNWYL 3WNTOA Uh GO\-88 SNOLLVLS DIHdVYSOYCAH [fous NOILOSS N-O!l ONOW Zp Af O09} cial l bOh cOh OO|\ 86 96 v6 c6 06 88 SNOILVLS 169 30°N aa" |p 10° 10% AMO 05 60° HOF SION Figure 27. Schematic diagram giving probable circulation pattern of anticyclonic eddies formed during the southwest monsoon in the western Indian Ocean. 170 9 SEs © ty 0 SD o_O mo) x (vo) 9 _ © wo inp) (Co) 8 GZ ee Y : WW WM. fo) ° eS V CS & . Ww (Z es Sy ELIE D ILL kph “| VLLLLLLLLLLLLLLLLLLLLLLLLLLLLLLL Ss wo + Se ee ro) fo) fo) fo) Oo oO ro) O ro) 6) e (oo) o t+ nN N + © (oo) << HLYON <———— —_— > HILNOs IW (285/2W) zp af Figure 28. Geostrophic volume transport, 0 - 1000 dbar relative to 1000 dbar, across 5°N section in the Indian Ocean during April 1975 (ATLANTIS Il, Cruise 15). Area of column represents transport in 106 m3 sec-1. f LS? a ai ae i : ‘ SN N yp ; 4 } * a N ; x ‘ ee ee i i y * 2 k 1 1 is fericg hi ie es : 5 ari his Sat 5 ie 5 i | reat, ih She OP iag rad if dn Uy ‘f } ee earl ( so i ¢ t ie : a) Ly | ¥. a ' i { : ; ee ' i ’ “f i: 1 vs A; ; sist { wala ste Fen ane i di ; ' i ite " 5 . we i * +x fia i y \ J ie eo) PG a ary Uhh hus ae ’ ‘ y & i ote FD if ir $ ; ntl om . ib Yoeght > ha oy aabeeesnp Speer oa Miidloaye ainperce iv ote wlan re wi fe Fpl he ai Mai innalclea an Fea BY an Mea io aH i t ae He th pai ae Boi ' i ; x tan Lee) Ly Pl h i Leh Nine, i) | } crete : , ; Te ines yea H ; or ; . i P ; Bs nite i “ a " * if irs i'n iy EH ite Per Urinna Men ines eer Ti Cie beans, Oe ee eee DISTRIBUTION LIST Activity CNO(OP 095, OP 0952) COMNAVOCEANCOM UNSECDEF (R&E) NAVWARCOL CNR (Code 480) NISC NORDA NRL NUSC (Newport) NUSC (New London) NAVPGSCOL NOSC ASN (R&D) Total No. of Copies Ss ss ss ss ss Ss Ss Ss 0). 8 wa TR-272 VARIATIONS IN THE THERMAL STRUCTURE AND WIND FIELD OCCURRING IN THE WESTERN INDIAN OCEAN DURING THE MONSOONS