Showing papers on "Monsoon published in 1977"

Some Aspects of the Life History, Structure and Movement of Monsoon Depressions

Abstract: Monsoon depression is one of the most important synoptic scale disturbances on the quasi-stationary planetary scale monsoon trough over the Indian region during the summer monsoon season (June to September) Salient features of the climatology of the depressions with regard to frequency of cyclogenesis, life expectancy, horizontal scale and tracks are discussed Rainfall aspects of the depressions are discussed in some detail and the role of local, dynamical and sub-synoptic scale factors are brought out Work done on the life history such as formation, intensification and maintenance of depressions has been reviewed based on synoptical and theoretical approaches Structure of the depression based on composited, synoptical and dynamical studies is discussed Wind circulation, thermal and moisture patterns, vertical motion field, vorticity budget etc, of a recent case study are brought out in some detail The problem of movement of the depression against the low level basic westerly wind is briefly discussed and the results of several numerical and climatological prediction models are presented

Relationships Between Sea Surface Temperature and Wind Speed Over the Central Arabian Sea, and Monsoon Rainfall Over India

Abstract: Sixty years (1901–60) of mean monthly sea surface temperature (SST) and surface wind speed observations over the central Arabian Sea have been correlated with the observed mean monthly rainfall over India during the peak monsoon months of July and August. It is found that correlation coefficients between SST during July and rainfall over central and western India during August are positive and significant. Correlation coefficients between surface wind speed during July and rainfall during July are also found to be positive, but correlation coefficients between surface wind speed during July and rainfall during August are either negative or insignificant. Spatial homogeneity and statistical significance of correlation coefficients lends support to the hypothesis of a possible relationship between SST over central Arabian Sea and rainfall over central and western India. Although we do not know the time scales of interaction between the Arabian sea and the Indian monsoon, the observations suggest th...

Palaeoclimates of Central Sahara during the early Holocene

Abstract: In the Central Sahara lying approximately between 27° N and 18° N, rains were primarily due to tropical depressions in the early Holocene up to about 6500 BP. Then the monsoon rains of Sahelian type dominated up to about 4400 BP.

Observational Aspects of the Low-level Cross-equatorial Jet Stream of the Western Indian Ocean

Abstract: Studies of all available upper wind data up to 3 km over eastern Africa and the western Indian Ocean reveal a major low-level air current circulating at about 1.5 km in the western periphery of the monsoon regime. The current originates in the southern hemisphere and penetrates progressively further north in spring until it reaches its maximum development in July. The major current is composed of systems of low-level jet streams which can be located on a daily basis, always in the same geographical areas, with speeds reaching 25–50 ms−1 at heights of only 1–1.5 km. Because the current is topographically-locked over eastern Africa the massive flow of air from one hemisphere to the other can be monitored and some relationships with the rainfall of parts of western India can be deduced.

Downstream Amplification and Formation of Monsoon Disturbances

Abstract: In this paper we present many examples (based on 43 years of data) of a phenomenon of downstream amplification over the monsoonal belt. The specific finding here is the following sequence of events: 1) During northern summer pressure drops in the vicinity of the North Vietnam coast (near 20°N) as a typhoon or a tropical storm arrives; 2) during the ensuing week pressure rises over Indochina and Burma by some 5–7 mb; and 3) during the following week a monsoon disturbance forms near the northern part of the Bay of Bengal. On an x-t (or Hovmoller) diagram this sequence of low-high-low formation is similar to the downstream amplification phenomenon of the middle latitudes. The following are some interesting differences: over the middle latitudes the eastward propagating phase velocity is of the order of 10° longitude day−1, while the eastward propagating group velocity (the speed of propagation of the amplification) is around 30° longitude day−1. The tropical counterparts are westward propagating, an...

Onset of the Southwest Monsoon over the Arabian Sea from Marine Reports of Surface Winds: Structure and Variability

Abstract: The time and type of onset of the southwest monsoon over the Arabian Sea is studied using ship reports of surface wind tabulated by 1° squares daily along two densely occupied shipping lanes. It is found that several types of onset occur, and that the mean time of onset, suitably defined, changes very little from year to year.

Effects of a variety of Indian Ocean surface temperature anomaly patterns on the summer monsoon circulation: Experiments with the NCAR general circulation model

Abstract: The time mean response of the summer monsoon circulation, as simulated by the 2.5° latitude-longitude resolution, July version of the National Center for Atmospheric Research (NCAR) General Circulation Model (GCM), to a variety of Indian Ocean surface temperature anomaly patterns is examined. In separate experiments, prescribed changes in surface temperature are imposed in the Western Arabian Sea, the Eastern Arbian Sea or the Central Indian Ocean. The influence of these anomaly patterns on the simulated summer monsoon circulation is evaluated in terms of the geographical distribution of the prescribed change response for any field of interest. This response is defined as the grid point difference between a 30-day mean from a prescribed change experiment and the ensemble average of the 30-day means from the control population for which the same set of climatological ocean surface temperatures are used in each simulation. The statistical significance of such a prescribed change response is estimated by relating the normalized response (defined as the ratio of the prescribed change response to the standard deviation of 30-day means as estimated from the finite sample of control cases) to the classical Student'st-statistic. Using this methodology, the most prominent and statistically significant features of the model's response are increased vertical velocity and precipitation over warm anomalies and typically decreased vertical velocity and precipitation in some preferred region adjacent to the prescribed change region. In the case of cold anomalies, these changes are of opposite sign. However, none of the imposed anomaly patterns produces substantial or statistically significant precipitation changes over large areas of the Indian sub-continent. The only evidence of a major nonlocal effect is found in the experiment with a large positive anomaly (+3°C) in the Central Indian Ocean. In this instance, vertical velocity and precipitation are reduced over Malaysia and a large area of the Equatorial Western Pacific Ocean. Thus, while these anomaly experiments produce only a local response (for the most part), it is hoped, as one of the purposes of the planned Monsoon Experiment (MONEX), that the necessary data will be provided to produce detailed empirical evidence on the extent to which Indian Ocean surface temperature anomalies correlate with precipitation anomalies over the Indian subcontinent—a correlation which generally does not appear in these GCM results.

Some Aspects of the Monsoon Circulation and Monsoon Rainfall

Abstract: The south Asian summer monsoon from June to September accounts for the greater part of the annual rainfall over most of India and southeast Asia. The evolution of the summer and winter monsoon circulations over India is examined on the basis of the surface and upper air data of stations across India. The salient features of the seasonal reversals of temperature and pressure gradients and winds and the seasonal and synoptic fluctuations of atmospheric humidity are discussed. The space-time variations of rainfall are considered with the help of climatic pentad rainfall charts and diagrams. The rainfall of several north and central Indian stations shows a minimum around mid-August and a maximum around mid-February which seem to be connected with the extreme summer and winter positions of the ITCZ and the associated north-south shifts in the seasonal circulation patterns. Attention is drawn to the characteristic features of the monsoon rainfall that emerge from a study of daily and hourly rainfall of selected stations. Diurnal variations of temperature, pressure, wind and rainfall over the monsoon belt are briefly treated.

Synoptic Features and Structures of some Equatorial Vortices Over the South China Sea in the Malaysian Region During the Winter Monsoon, December 1973

Abstract: In December 1973, Peninsular Malaysia and Sarawak2) experienced a few periods of heavy rain caused by westward moving equatorial vortices from the South China Sea. In this report, the synoptic characteristics associated with the development and intersification of these vortices are shown. Structure of one of the disturbances was examined. Disturbances in the trades associated with lateral shear were found to be important for the genesis of the equatorial vortices. However, the intensification of these disturbances depended on the interaction with the cold monsoon surge.

The East Coast, Madagascar and the Indian Ocean

Abstract: The eastern coast of Africa looks out over the Indian Ocean, which, though vast, is comparatively easily navigated. Consequently there has been much contact over the past two thousand years among the peoples who inhabit its shores. This, coupled with similar climatic and ecological conditions in most of the surrounding coastal lands, has resulted in a considerable degree of cultural homogeneity, particularly marked in the western part of the ocean. Communication between the African coast and the interior was, on the other hand, difficult. Voyages in this part of the Indian Ocean would have been facilitated by the pattern of the monsoon regime, the winds blowing from a north-easterly direction towards East Africa for half the year, and from the south-west for the other half. This renders voyages by sailing ship from the Persian Gulf and north-western India particularly easy; those from Aden and the Yemen are rather more difficult. To the south, the South Equatorial Current facilitates voyages from the Far East to Africa, and the return is assisted by the monsoonal drift setting to the east between that current and India, together with predominantly westerly winds in this region. The main motive for voyages to East Africa was trade, but the pressure of population in the arid lands bordering the northern margin of the Indian Ocean provided a stimulus to migration. In the traditions of the coast, religious persecution figures as the reason for migrants leaving their homelands in the Persian Gulf, but it is probable that the attractions of well-watered lands, coupled with the prospect of wealth and a comfortable life in an agreeable environment, played at least as great a part.

Orographic effects on the southwest monsoon: A review

Abstract: An overview of the problem of orographic effects on the southwest monsoon using the contributions of all the available analytical and numerical models is attempted. A quasi-geostrophic model is applied to deduce the effect of the topographic complex on the Indian peninsula. This model suggests that the southward bending of the low-level isobars on the peninsula can be ascribed to the topographically-induced southward velocity. This southward velocity triggers a Rossby wave to the east of the peninsula which is manifested as a trough on the southern Bay of Bengal.

Further studies of plankton ecosystems in the eastern Indian Ocean. V. Ecology of the Copepoda

Abstract: Seasonal changes in 82 species of epiplanktonic copepods along a longitudinal section in the eastern Indian Ocean (meridian 110°) were studied so that the main structural features of the pelagic ecosystem could be identified. Counts were made of 46 species of Eucalanidae, Euchaetidae, and Sapphirinidae, and the presence or absence of the remainder was recorded. This mixture of qualitative and quantitative data was used to identify the major niche complexes ('biocenoses') and habitat complexes (geocenoses') in the study area. Many species were ubiquitous. The greatest proportion of endemic species occurred in a narrow fringe to the south of Java; these included neritic species such as Acartia erythraea and Eucalanus dentatus, upwelling species such as Calanoides carinatus, and other species of less certain origin (e.g. Eucalanus crassus, Euchaeta concinna, and Candacia catula). The best indicator of tropical water was Candacia pachydactyla, and the best indicator of its mixtures with subtropical water was Euchneta wolfendeni. Whereas presence-absence data were sufficient to group many tropical species which had a limited range, numerical data were needed to classify subtropical species such as Eucalanus subtenuis, Euchaeta longicornis, and Copilia mediterranea. Diurnally separate, as well as seasonally separate, biocenoses could be recognized; these were characterized, in particular, by species of the genus Pleuromamma. The agglomerative program MULTCLAS, using quantitative as well as qualitative data, defined plankton geocenoses more clearly than did the simple divisive program DIVINF using qualitative (presence-absence) data alone. Six systems could be recognized. Their latitudinal and seasonal distribution, and their temperature-salinity properties showed that two were tropical, two were subtropical, and two were tropical-subtropical mixtures. The tropical geocenoses were early and late phases of the 'Java Dome', a south-east monsoon upwelling system. The subtropical geocenoses corresponded to the central water mass and the west wind drift transition zone. The tropical-subtropical mixtures were seasonal phases, the south-east monsoon phase being generally richer than its successor, due probably to lateral advection from the north, possibly from coastal upwelling off the north-west Australian shelf. The west wind drift transition zone had unusual biological properties due, apparently, to its characteristic turbulence and deep mixed layer. Using the scaled exponent of the Shannon-Wiener entropy function H, a diversity maximum was located at about 20oS. in the tropical convergence. Eucalanus subtenuis was responsible for diversity minima in the subtropics. A variety of species was responsible for diversity minima in the tropics, in particular Rhincalanus cornutus and Euchaeta russelli, the latter swarming in the upper layers in midsummer and reducing diversity to practically zero.

Some aspects of the life history, structure and movement of monsoon depressions

Abstract: Monsoon depression is one of the most important synoptic scale disturbances on the quasi-stationary planetary scale monsoon trough over the Indian region during the summer monsoon season (June to September). Salient features of the climatology of the depressions with regard to frequency of cyclogenesis, life expectancy, horizontal scale and tracks are discussed. Rainfall aspects of the depressions are discussed in some detail and the role of local, dynamical and sub-synoptic scale factors are brought out. Work done on the life history such as formation, intensification and maintenance of depressions has been reviewed based on synoptical and theoretical approaches. Structure of the depression based on composited, synoptical and dynamical studies is discussed. Wind circulation, thermal and moisture patterns, vertical motion field, vorticity budget etc., of a recent case study are brought out in some detail. The problem of movement of the depression against the low level basic westerly wind is briefly discussed and the results of several numerical and climatological prediction models are presented.

Mid-tropospheric cyclones of the summer monsoon

Abstract: Mid-tropospheric cyclones are often observed on daily and monthly mean maps over southern Asia during the summer southwest monsoon season Although they are important activators of monsoon rains over certain regions, only a few observational studies are available, and even fewer theoretical and numerical studies have been performed This article attempts to summarize the present observational knowledge about mid-tropospheric cyclones and reviews current ideas on the formation, maintenance and dissipation of these systems A recent numerical simulation of a mid-tropospheric cyclone is described In general, latent heat release plays the dominant role in the dynamics of the cyclone Much is still to be learned about mid-tropospheric cyclones and several promising areas of future research are suggested

Meteorological Phenomena of the Arabian Sea

Abstract: : This document, the product of extensive literature research, provides a single and comprehensive reference text for the operational forecaster in the Arabian Sea and Gulfs of Aden and Oman. It contains extensive climatological information, descriptions of significant meteorological phenomena and relevant forecasting aids, discussions of meteorological conditions affecting various regional ports, and a representative assortment of typical weather sequences depicted by both satellite imagery and conventional data. General information on the large-scale Asian monsoon and its relationship to the Arabian Sea region is presented. Also discussed are the significant meteorological phenomena associated with time and space variations in the Arabian Sea monsoon; forecasting aids and typical weather sequences are provided. Seasonal progressions of weather events are discussed; variations from normal conditions are described in first-hand reports from observers in the field. (Author)

The Simulation of the Asian Summer Monsoon by General Circulation Models

Abstract: The monsoon simulations of four general circulation models are illustrated. Additional results from the Meteorological Office model showing factors that are important in determining its simulation are presented. The large-scale flow patterns of all the models reproduce the large-scale flow fairly realistically, but more detailed characteristics and, in particular, the rainfall, are poorly represented.

Diagnosis of the Satellite-Observed Radiative Heating in Relation to the Summer Monsoon

Abstract: Seasonal and monthly global patterns of outgoing longwave radiation, albedo, absorbed solar radiation, and net radiation have been derived from scanning radiometer observations aboard the NOAA polar orbiting satellites since June 1974. These patterns, along with patterns of interannual differences in seasonal and monthly heating, are examined for the three summers of 1974–76 over the Eastern Hemisphere in relation to the variations in the summer monsoon and the major circulation features. During portions of the summer of 1975 the monsoon was more active than in 1974 and 1976, as evidenced by increased albedo and decreased longwave radiation over large sections of India, the Indian Ocean, Southeast Asia, and the Western Pacific. The roles of clouds, snow cover, and other surface characteristics in modulating the radiation balance and circulation are discussed. The pre-monsoon radiative heating in spring is examined with respect to monsoon onset and intensity in the three years.

Further studies of plankton ecosystems in the eastern Indian Ocean. III. Numerical abundance and biomass

Abstract: The numerical abundance of 13 zooplankton taxa in the eastern Indian Ocean (meridian 110oE.) was examined in relation to some factors likely to control their distribution. Regression analysis showed that season, latitude (and their interaction), and time of day were frequently significant sources of variance. Decapoda, Amphipoda, fish eggs and larvae, Coelenterata and, sometimes, Copepoda and Euphausiacea were more abundant by night than by day. Numbers were generally high in late winter (June-September) and low in early summer, with a secondary peak, in some cases, in early autumn (March). Numbers were generally high at low latitudes (9-15oS.) and low at high latitudes (25-32oS.), one exception being fish eggs and larvae whose centre of abundance lay at 24-25oS. Seasonal periodicity was frequently in phase along the study section, numerical abundance reaching a peak 1-2 months after a general phytoplankton bloom at the onset of the south-east monsoon. There is no ready explanation why the subtropical regime should be in synchrony with that prevailing in the tropics, no subtropical source of nutrient enrichment being known which could match, for example, the Java Dome. An explanation for the observed tropical-subtropical synchrony was therefore sought in terms of interzonal advection. Data from a variety of sources showed that between May and August there was considerable enrichment not only at the Java Dome but also on the north-west Australian shelf. The area between North-West Cape and Port Hedland is the place where (plankton-feeding) humpback whales are known to gather. Sperm whales, on the other hand, congregate 1100-1300 km further to the south- west where the waters are rich in micronekton. The mass transport of upper waters during the south- east monsoon season suggests that these phenomena constitute a trophic sequence. The second zooplankton peak, in March, is the result of a summer algal bloom generated, perhaps, by remineralization of organic matter produced during the previous south-east monsoon season.

Moisture flux across the west coast of India and rainfall during the southwest monsoon

Abstract: For the nine years 1964-1972 the correlation coefficient between the net moisture flux across the west coast of India south of Bombay and the monsoon rainfall (June to September) was 0.87 for coastal rains and 0.85 for rains east of the Western Ghats region bounded by lines joining Bombay, Nagpur and Trlvandrum, both coefficients being significant at 1 % level. North of Bombay the correlation was -0.14

Further studies of plankton ecosystems in the eastern Indian Ocean. II. Seasonal variations in water mass distribution (upper 150 m) along 110°E. (August 1962-August 1963)

Abstract: From temperature-salinity relations, with approximate corrections for localized heat exchange, and from evaporation-precipitation records, in an upper mixed layer of 50 m (tropical) and of 75 m (subtropical region), the variations throughout the year of the principal surface and subsurface water masses along 110°E. have been examined. In winter-spring the west-flowing South Equatorial Current and the east-drifting subtropical waters maintain a tropical convergence around 20°S. Doming of deeper tropical waters creates a nutrient-enriched near-surface zone to the north of this South Equatorial Current. In summer-autumn the east-flowing Monsoon Current creates a more sluggish uplift of deeper waters around 20°. These deeper waters, however, contain little of the deeper nutrient-rich tropical waters. Around 30-35°S. nutrient-richer deeper water is carried into near-surface layers by doming within cyclonic eddies or by horizontal entrainment from the south. A number of other surface water bodies of tropical origin occur irregularly throughout the year at the northern end of the 110°E. section.

Spectrum Analysis Relevant to Indian Monsoon

Abstract: Recent investigations on Indian monsoon by the method of spectrum analysis are reviewed from the viewpoint of various aspects of its application. The assessment is also made on their results and discussions. Through these processes, it emerged that there exist at least two kinds of quasi-periodic variations in the summer monsoonal fluctuation over India and adjacent regions. One appears as a spectral peak around the 5-day period and another is around the 15-day period.

Some aspects of break and active monsoon over southern Asia during summer

Abstract: North of 10° N, at least three synoptic phases of the summer monsoon can be identified. Two of these phases—the break and active monsoon—are extremes. Patterns of cloudiness and rainfall for these two phases differ substantially. These indicate differences in the geographic location and intensity of tropospheric energy sources. Tropospheric circulations over the equatorial Indian Ocean during break and active monsoon also differ. A break is often accompanied by the development of a trough in the lower troposphere northeast of Gan; this appears to enhance rainfall over southeast India. Although cause and effect are difficult to separate using scanty aerological data, synoptic variation over the equatorial Indian Ocean east of 60°–65° E may influence rainfall over western and southern India. DOI: 10.1111/j.2153-3490.1977.tb00743.x

Mass-spring-damper system as the mathematical model for the pattern of sand movement for an eroding beach around Digha, West Bengal, India

Abstract: Patterns of sand movement based on the results of repeated seasonal surveys have been analysed in the foreshore region of an actively eroding beach around Digha, West Bengal, India. Two-dimensional trend surface analyses on the seasonal changes in the patterns of erosional and depositional envelopes between beach zones revealed a cyclicity in the offshore-onshore movement of sediment. An intefering effect of two sets of movements was clear. A major transfer of sediments towards offshore with gradual lowering of the beach and fluctuations in the direction of alongshore current were recognised. Offshore transfer of sediments started in the early summer months (February to June) characterised by short period waves and strong onshore winds. During monsoon (July to September) further removal of beach sediments either towards offshore or towards alongshore was registered. In winter months (October to January) long period swells and mild offshore winds nourished the beach possibly at the expense of the offshore reservoir of sands. Occasional storm surges causing extensive collapse of coastal dunes gave rise to deviations from this general cyclicity. The net seasonal material balance calculation for any set of complementary erosional and depositional zones was worked out. The pattern of volume change during different seasons displayed a clear tendency to settle down gradually with time. The impact loadings of cyclonic storms interfered and reinforced the oscillation. The overall nature of sand movement in this foreshore was fitted roughly into a mathematical model of an underdamped second order mass-spring-damper system.

Deposition of tar balls (oil residue) on beaches along the west coast of India

Abstract: Much of the world's transport of petroleum is carried along the shipping route in the Arabian Sea, not too far away from India. Hence oil spills seem to be common in the sea which ultimately find their way as deposits on the beaches of west coast of India in the form of tar balls. Based on the data for the years 1975 and 1976, the total tar ball deposition on the west coast of India is approximately 1000 and 750 tonnes respectively. A reduction of approximately 25% in 1976 is attributed to the reopening of the Suez Canal which has reduced the tanker traffic across the Arabian Sea. The deposition is heaviest during the monsoon months after which it ceases in the northern part of the west coast but, though minimal, is found throughout the year on the southern coast

Radon daughter's radioactivity levels over the Arabian Sea as indicators of air mass mixing

Abstract: Measurements on radon daughter's activities over the Arabian Sea were carried out during the period 19 May to 9 July, 1973, under the joint Indo-USSR MONEX-73 project. The data were collected on board the ships of the Indian Navy cruising between 19–21°N within longitudes 60–73°E and the two USSR vessels Okean and Prilive cruising between latitudes 0–10°N and 10–18°N, respectively. The results show that there is a significant increase in radon daughter's activity at about 19–21°N, the average level being of the order of about 8 pCi m−3 as compared to 1–2 pCi m−3 at lower latitudes. This is explained, on the basis of synoptic charts and available sounding data, as being due to the normal wind and pressure pattern prevailing during the monsoon months which results in the transport of continental air from Arabia and Pakistan and its mixing with the maritime monsoon air mass of Southern Hemispheric origin. The significant increase in radon activity on some days of the cruise was mainly due either to ...

The Propagation of Tropical Disturbances over the Indian Ocean during the Summer Monsoon

Abstract: Daily nephanalysis of NOAA 4 satellite visible images over the Indian Ocean during the 1975 summer monsoon was used to construct time-longitude sections of cloud cover during a month and a half. Tropical disturbances traveled over the Indian Ocean during the summer monsoon—eastward moving to the north of the equator and westward moving to the south. Conventional meteorological data recorded as island stations agree well with these results; the passage of the disturbances over these stations was associated with a decrease of pressure and sometimes a noticeable change in surface wind direction. Using low-level superpressure balloon data, balloon trajectories and cloud brightness were compared. The influence of the tropical disturbances on the low-level air flow circulation over the Indian Ocean is shown. The possible link between these traveling disturbances and pulsations in the Indian summer monsoon circulation is also investigated.

Summer winds around the southern Red Sea

Abstract: Daily synoptic maps for May–September 1966 have shown the presence of a persistent wind shift or convergence zone, the Afar Convergence Zone (ACZ), between northwesterlies over the southern Red Sea and south-westerlies over the Gulf of Aden. This ACZ (a) oscillates north-south over periods of a few days, depending on the strength of the north-westerlies but not of the south-westerlies; (b) slopes upwards to the south and moves diurnally over the Afar lowalands, like the Inter-Tropical Convergence Zone (ITCZ) over West Africa; (c) has little horizontal contrast in dewpoint, like the ITCZ over East Africa; (d) resembles both the ITCZ and a lee convergence, where two branches of the south-west monsoon meet after flowing around the Ethiopian highlands.

Large‐scale eddies in the Somali Current

Abstract: Velocity records from a subsurface mooring in the Somali Current exhibit direction reversals during a time when the SW Monsoon is still steadily blowing. The records are interpreted in terms of large-scale eddies which seem to be generated near the equator and propagate slowly northward along the coast of Somalia. The Somali Current constitutes the most important branch of the complex East African Current System. It is generated by the Summer Monsoon and flows along the coast of East Africa, from the latitude of Mombasa to the island of Socotra, corresponding to a distance of about 2200 km. Translated to the path of the Gulf Stream, this corresponds to the distance between Yucatan and Cape Hatteras. Despite the fact that this current has been immensely important to seafarers for nearly 2000 years, it is one of the least explored boundary current systems in the Northern Hemisphere. In contrast to the Gulf Stream, which shows only insignificant seasonal variations, the Somali Current reverses its direction following the seasonal change of the monsoon winds. A first long-term current meter record from the region indicates that the classical picture of a straightforward oceanic response to the forcing of the windstress may be greatly oversimplified. It is shown that some of the key features of the record are not related to fluctuations of the wind field, but more likely to large-scale eddies propagating northward along the coast.

On the Role of the Asian Monsoon in the Angular Momentum and Kinetic Energy Balances of the Tropics

Abstract: The balance conditions of relative angular momentum and time-mean kinetic energy and their annual variations are studied for the Northern Hemisphere tropical belt. The belt is divided into two roughly equal size parts, the monsoon and the extramonsoon regions. The data used consist of all available daily rawinsonde reports from the world aerological network for the two 5-year periods 1958–63 and 1968–73.