中国近海及其附近海域若干涡旋研究综述Ⅱ.东海和琉球群岛以东海域

综述东海和琉球群岛以东海域若干气旋型和反气旋型涡旋的研究.对东海陆架、200m以浅海域,主要讨论了东海西南部反气旋涡、济州岛西南气旋式涡和长江口东北气旋式冷涡.东海两侧和陆坡附近出现了各种不同尺度的涡旋,其动力原因之一是与东海黑潮弯曲现象有很大关系,其次也与地形、琉球群岛存在等有关.东海黑潮有两种类型弯曲:黑潮锋弯曲和黑潮路径弯曲.黑潮第一种弯曲出现了锋面涡旋,评述了锋面涡旋的存在时间尺度与空间尺度和结构等;也指出了黑潮第二种弯曲,即路径弯曲时在其两侧出现了中尺度气旋式和反气旋涡,讨论了它们的变化的特性.特别讨论了冲绳北段黑潮弯曲路径和中尺度涡的相互作用,着重指出,当气旋式涡在冲绳海槽北段成长,并充分地发展,其周期约在1~3个月时,它的空间尺度成长到约为200km(此尺度相当于冲绳海槽的纬向尺度)时,黑潮路径从北段转移到南段.也分析了东海黑潮流量和其附近中尺度涡的相互作用.最后指出在琉球群岛以东、以南海域,经常出现各种不同的中尺度反气旋式和气旋式涡,讨论了它们在时间与空间尺度上变化的特征.     

The ‘suitcase hypothesis’: Can entrainment of meroplankton by eddies provide a pathway for gene flow between Madagascar and KwaZulu-Natal,South Africa?

Similarities in the marine fauna found off the coasts of southern Madagascar and KwaZulu-Natal Province (KZN), South Africa, led to the development of the ‘suitcase project,’ with the aim of establishing whether eddies that form off southern Madagascar may package and transport biological material across the Mozambique Channel, facilitating connectivity and gene flow. Meroplankton (larval stages of fishes and benthic invertebrates) were collected on the Madagascan shelf and along a transect through a cyclonic eddy in the Mozambique Channel. The samples were analysed using microscopy and DNA barcoding, seeking to identify species known to be common to both the southeast coast of Madagascar and the east coast of South Africa and thereby to reveal potential indicators of connectivity between these regions. The greatest zooplankton biovolume in the upper 200 m occurred on the shelf, followed by in the western part of the eddy and in the region outside the eddy to the west, and was lowest in the region outside the eddy to the east. The meroplankton were dominated by taxa of coastal origin and these were also most abundant on the shelf and in the western part of the eddy, with the lowest abundances in the region outside the eddy to the east. The findings show greater zooplankton biovolumes and larval abundances and the presence of reef-associated larval assemblages on the Madagascan shelf and along the transect through the cyclonic eddy, providing support for the suitcase hypothesis that planktonic organisms are entrained within eddies as they propagate south-westwards of the Madagascan shelf.     

Shelf currents,lee-trapped and transient eddies on the inshore boundary of the Agulhas Current,South Africa: their relevance to the KwaZulu-Natal sardine run

The existence and strength of the annual KwaZulu-Natal (KZN) sardine run has long been a conundrum to fishers and scientists alike ― particularly that the sardine Sardinops sagax migrate along the narrow Transkei shelf against the powerful, warm Agulhas Current. However, examination of ship-borne acoustic Doppler current profiler (S–ADCP) data collected during two research surveys in 2005 indicated that northward-flowing coastal countercurrents exist at times between the Agulhas Bank and the KZN Bight, near Port Alfred, East London, Port St Johns and Durban. The countercurrent near Port Alfred extended as far east as the Keiskamma River, within an upwelling zone known to exist there. An ADCP mooring at a depth of 32 m off Port Alfred indicated that the countercurrent typically lasted a few days, but at times remained in the same direction for as long as 10 days. Velocities ranged between 20 and 60 cm s^?1 with maximum values of ～80 cm s^?1. The S–ADCP data also highlighted the existence of cyclonic flow in the Port St Johns–Waterfall Bluff coastal inset, with a northward coastal current similarly ranging in velocity between 20 and 60 cm s^?1. CTD data indicated that this was associated with shelf-edge upwelling, with surface temperatures 2–4 °C cooler than the adjacent core temperature (24–26 °C) of the Agulhas Current. Vertical profiles of the S–ADCP data showed that the countercurrent, about 7 km wide, extends down the slope to at least 600 m, where it appeared to link with the deep Agulhas Undercurrent at 800 m. S–ADCP and sea surface temperature (SST) satellite data confirmed the existence of the semi-permanent, lee-trapped, cyclonic eddy off Durban, associated with a well-defined northward coastal current between Park Rynie and Balito Bay. Analysis of three months (May–July 2005) of satellite SST and ocean colour data showed the shoreward core-boundary of the Agulhas Current (24 °C isotherm) to commonly be close to the coast along the KZN south coast, as well as between the Kei and Mbhashe rivers on the Transkei shelf. The Port St Johns–Waterfall Bluff cyclonic eddy was also frequently visible in these satellite data. Transient cyclonic eddies, which spanned 150–200 km of shelf, appeared to move downstream in the shoreward boundary of the Agulhas Current at a frequency of about once a month. These seemed to be break-away Durban eddies. Data collected by ADCP moorings deployed off Port Edward in 2005 showed that these break-away eddies and the well-known Natal Pulse are associated with temporary northward countercurrents on the shelf, which can last up to six days. It is proposed that these countercurrents off Port Alfred, East London and Port St Johns assist sardine to swim northwards along the Transkei shelf against the Agulhas Current, but that their progress north of Waterfall Bluff is dependent on the arrival of a transient, southward-moving, break-away Durban cyclonic eddy, which apparently sheds every 4–6 weeks, or on the generation of a Natal Pulse. This passage control mechanism has been coined the ‘Waterfall Bluff gateway’ hypothesis. The sardine run survey in June–July 2005 was undertaken in the absence of a cyclonic eddy on the KZN south coast, i.e. when the ‘gate’ was closed.     

Observed Variability of Thermohaline Fields,Currents and Eddies in the Western Bay of Bengal During BOBMEX-99

Field measurements during the Bay of Bengal Monsoon Experiment (BOBMEX-99), data from a deep sea moored buoy, and satellite altimeter were used to describe variability in the hydrographic and meso-scale features in the Bay of Bengal (BoB) during the summer monsoon of 1999. The thermohaline fields showed two regions of upsloping of isopleths centered at 82°E and 84.75°E, ～110 km and 450 km away from the coast, respectively, followed by downsloping. The upsloping/downsloping of isopleths and the alternating currents was part of cyclonic and anti-cyclonic circulation patterns in the western BoB. In this region, both wind and current were important in the dynamics of coastal upwelling. The observations showed a relationship between the propagating waves and eddy on variability of thermohaline fields. On an annual cycle, four Kelvin waves were observed in the BoB, but only the downwelling Kelvin wave formed during October entered the Arabian Sea. During the monsoon season, four eddies were formed in the western BoB, of which the anticyclonic eddy centered at 15°N, 84°E and the cyclonic eddy centered at 17.5°N, 84.5°E were prominent. The baroclinic instability caused by the opposing currents along the east coast and the wind stress curl favored the formation of eddies. Okhubo-Weiss and Isern-Fontanet parameter confirmed the presence of eddies in the BoB.     

The transition zone of the Canary Current upwelling region

Like all the major upwelling regions, the Canary Current is characterised by intense mesoscale structure in the transition zone between the cool, nutrient-rich waters of the coastal upwelling regime and the warmer, oligotrophic waters of the open ocean. The Canary Island archipelago, which straddles the transition, introduces a second source of variability by perturbing the general southwestward flow of both ocean currents and Trade winds. The combined effects of the flow disturbance and the eddying and meandering of the boundary between upwelled and oceanic waters produce a complex pattern of regional variability. On the basis of historical data and a series of interdisciplinary field studies, the principal features of the region are described. These include a prominent upwelling filament originating near 28°N off the African coast, cyclonic and anti-cyclonic eddies downstream of the archipelago, and warm wake regions protected from the Trade winds by the high volcanic peaks of the islands. The filament is shown to be a recurrent feature, apparently arising from the interaction of a topographically trapped cyclonic eddy with the outer edge of the coastal upwelling zone. Its role in the transport and exchange of biogenic material, including fish larvae, is considered. Strong cyclonic eddies, observed throughout the year, drift slowly southwestward from Gran Canaria. One sampled in late summer was characterised by large vertical isopycnal displacements, apparent surface divergence and strong upwelling, producing a fourfold increase in chlorophyll concentrations over background values. Such intense eddies can be responsible for a major contribution to the vertical flux of nitrogen. The lee region of Gran Canaria is shown to be a location of strong pycnocline deformation resulting from Ekman pumping on the wind shear boundaries, which may contribute to the eddy formation process.     

北太平洋中尺度涡时空特征分析

利用1993~2011年19 a的AVISO卫星高度计资料研究了北太平洋(10°~60°N,120°E~100°W)中尺度涡的时空分布特征,结果表明:北太平洋每年约产生1 800余个涡旋,其中气旋涡稍多。北太平洋东部沿岸、西北沿岸、黑潮延伸体北侧、副热带逆流区是中尺度涡的高发区,春、冬季是涡旋的高发季节。涡极性分布以35°N为界,北部多反气旋涡,南部多气旋涡。涡旋半径以100 km左右为主,并且基本随纬度升高而减小,涡旋数量随着周期增长而急剧下降。反气旋涡的平均半径和周期均大于气旋涡。利用Argo浮标剖面资料分析的6个个例涡旋的垂直结构显示,每个涡旋都有其独特的冷暖核结构,深度不同。研究结果对于分析北太平洋涡动能分布及传输具有一定的参考价值。     

Statistical characteristics and mechanisms of mesoscale eddies in the North Indian Ocean

The statistical characteristics and mechanisms of mesoscale eddies in the North Indian Ocean are investigated by adopting multi-sensor satellite data from 1993 to 2019. In the Arabian Sea(AS), seasonal variation of eddy characteristics is remarkable, while the intraseasonal variability caused by planetary waves is crucial in the Bay of Bengal(BOB). Seasonal variation of the eddy kinetic energy(EKE) is distinct along the west boundary of AS,especially in the Somali Current region. In the BOB, lar...     

Oceanic Odyssey of a satellite-tracked drifter: North Pacific variability delineated by a single drifter trajectory

A near-surface satellite-tracked drifter launched off the east coast of the Kuril Islands on September 4,1993 began a 2.5-year Odyssey across the North Pacific Ocean. During its travels, the drifter encountered numerous energetic oceanographic regimes as it moved from the region of the Kuril-Kamchatka Trench to the continental margin of the Kuril Islands, through Friza Strait into the Sea of Okhotsk, seaward again through Bussol’ Strait, and then eastward across the North Pacific. Oceanic features detected along the basin-wide trajectory include a quasi-permanent anticyclonic eddy over the Kuril-Kamchatka Trench, open-ocean wind-driven inertial oscillations, coastal-trapped diurnal shelf waves, semidiurnal tidal currents, transient cyclonic and anticyclonic eddies, through-strait flows, and wave-like mesoscale meanders. The single drifter track delineates the dynamically-rich variability of upper ocean currents, emphasizes the marked difference in flow dynamics between boundary and open ocean regions, and provides a time-scale for the movement of surface waters across the entire North Pacific.     

2000年8月南海中部与南部海洋温、盐与环流特征

根据2000年8—9月份南海中部与南部航次的温、盐资料,采用P—矢量诊断方法,结合ADCP测流资料和同期伪风应力资料以及TOPEX／Poseidon高度计资料,研究了2000年夏季风持续强迫之后南海大尺度环流与中尺度涡旋的空间结构。结果表明,南海夏季温度和盐度水平分布随深度有显著的变化：中层(250—400m左右)温、盐水平分布与其它各层的温度和盐度分布相比有很大的差异。用诊断方法计算得到的环流场与用TOPEX／Poseidon海面高度计资料计算得到的地转流场比较一致,即流场内部有多个中尺度的涡旋,主要有越南东南外海反气旋涡、中沙群岛东南反气旋涡以及南沙群岛东北角的气旋涡等,这说明南海中部与南部盛夏环流具有较强的地转分量和显著的多涡结构,并且这些中尺度涡在垂向上存在速度场的切变。     

The influence of mesoscale physical processes on the larval fish community in the Canaries CTZ, in summer

We have studied the relation between the hydrography, the composition and horizontal structure of the larval fish community, and the horizontal distribution patterns of larval fish abundances in an area characterised by strong mesoscale oceanographic activity, located between the Canary Islands and the African coast (the Canaries Coastal Transition Zone), during August 1999. Upwelling, upwelling filaments, cyclonic and anticyclonic eddies and island wakes are typical mesoscale features of the northwest African coast in summer. A single upwelling filament off Cabo Juby was joined in mid-August by a second that originated about 100 km to the north. The two filaments flowed together and merged 100 km offshore. The merged filament was partially entrained around a cyclonic eddy, trapped between the Canary Islands and the African coast, and interacted with cyclonic and anticyclonic eddies shed from Gran Canaria. Mesoscale oceanographic features strongly influenced the horizontal distributions of fish larvae. Eddies acted as a mechanism of concentration, while upwelling filaments were dispersive, transporting larvae from the African neritic zone into oceanic areas and towards the Canary archipelago. This transport was the major cause of the predominance of neritic larvae in the composition of the larval fish community of the area. The results also suggest: (1) that anchovy larvae are good indicators of the offshore displacement of upwelled water; (2) that the alternation between anchovy and sardine as species dominant in the larval fish community of the area during summer depends upon the water temperature in the African upwelling region, anchovy dominating at higher temperature; (3) that a coupling of anchovy and sardine spawning with the mesoscale oceanographic structure formed by the upwelling filaments and trapped eddy overcomes the negative effect that Ekman transport has on their populations.     

Variability in the Canary Islands area of filament-eddy exchanges

The physical background to a suite of biological studies carried out in the Canary Islands upwelling region is presented. The area is unique in that the coastal transition zone is spanned by an archipelago of islands that shed mesoscale eddies of diameter 50–100 km into the alongshore flow. A recurrent filament and eddy system was sampled intensively to study the changing properties of waters as they are advected towards the open ocean in the filament and to investigate the exchanges between filament and eddies. The system was more complex than previously revealed. In early August, a single filament extended offshore from near Cape Juby. Two weeks later, a second filament had developed slightly farther north and extended offshore to merge with the first at 100 km offshore. The merged filament was entrained around a recurrent, topographically trapped cyclonic eddy and interacted with transient cyclonic and anticyclonic eddies shed from the island of Gran Canaria. Between the two filaments and the coast, a pair of counter-rotating eddies re-circulated water parcels for several weeks. Surface layer drifters cycled around this near-shore re-circulation several times before following convoluted paths that demonstrate significant exchange between continental shelf and open ocean waters.     

Drifting and Meandering of Olive Ridley Sea Turtles in the Bay of Bengal: Role of Oceanic Rossby Waves

Olive Ridley turtles in the Bay of Bengal are previously thought to migrate southward from their nesting ground, along the east coast of India (Orissa coast), towards Sri Lanka. Surprisingly, three of the four Platform Transmitter Terminal (PTT) attached turtles in April-June 2001 meandered off the east coast of India for about two months. It is found that these turtles meandered at the peripherals of cold core cyclonic eddy surrounded by warm core eddies on either side. Concentrations of prey for the turtles in those frontal regions are known to be abundant. Only one of the four PTT attached turtles migrated to the south along the frontal regions in the direction of geostrophic currents. It is found that the locations of these thermal fronts in the Bay of Bengal are primarily determined by the Oceanic Rossby waves and local Ekman pumping.     

Dynamics and role of the Durban cyclonic eddy in the KwaZulu-Natal Bight ecosystem

The semi-permanent Durban Eddy is a mesoscale, lee-trapped, cold-core cyclonic circulation that occurs off the east coast of South Africa between Durban in the north and Sezela, some 70 km to the south. When present, strong north-eastward countercurrents reaching 100 cm s^–1 are found inshore. It is hypothesised that the cyclone is driven by the strong south-westward flowing Agulhas Current offshore of the regressing shelf edge near Durban. Analysis of ADCP data and satellite imagery shows the eddy to be present off Durban approximately 55% of the time, with an average lifespan of 8.6 days, and inter-eddy periods of 4 to 8 days. After spin-up the eddy breaks loose from its lee position and propagates downstream on the inshore boundary of the Agulhas Current. The eddy is highly variable in occurrence, strength and downstream propagation speeds. There is no detectable seasonal cycle in eddy occurrence, with the Natal Pulse causing more variability than any seasonal signal. A thermistor array deployed in the eddy centre, together with ship CTD data, indicates upward doming of the thermal structure in the eddy core associated with cooler water and nutrients being moved higher in the water column, stimulating primary production. Together with the use of satellite imagery, our findings indicate a second mechanism of upwelling, viz. divergent upwelling in the northern limb of the eddy. Satellite-tracked surface drifters released in the eddy demonstrated the potential for nutrient-rich eddy water to be transported northwards along the inshore regions of the KwaZulu-Natal (KZN) Bight, thus contributing to the functioning of the bight ecosystem, as well as southwards along the KZN and Transkei coasts – both by the eddy migrating downstream and by eddy water being recirculated into the inshore boundary of the Agulhas Current itself.     

Cyclonic eddies reveal Oegopsida squid egg balloon masses in the Agulhas Current,South Africa

In 2005, 2006, 2007 and 2011, distinct Oegopsida squid egg masses were observed by scuba divers on the narrow southern KwaZulu-Natal (KZN) shelf in depths of 35–50 m off the coastal resorts of Park Rynie, Pumula and Port Edward, South Africa. In 2006, larvae in the egg balloons were sampled. DNA barcoding (i.e. cytochrome c oxidase subunit 1 sequencing) linked the larvae to the genus Lycoteuthis, a group commonly found on the continental slope of the Agulhas Bank and the west coast of South Africa. In all cases, the sightings were concomitant with low water temperatures of 14–18 °C, indicative of shelf edge upwelling. Historical ship-collected CTD data show these cooler waters to originate from a depth of 100–180 m on the KZN continental slope. Complementary satellite imagery revealed the cooler water and discoveries of the egg balloons to be coincident with cold core cyclonic eddies embedded in the shoreward boundary of the Agulhas Current. The temperature data suggest that these egg balloons, in the absence of cyclonic eddy activity, would normally be found in the current on a density surface at a depth of ～130 m where velocities are typically around 100 cm s^–1.     

Influence of Mesoscale Eddies on Variations of the Kuroshio Path South of Japan

The influences of mesoscale eddies on variations of the Kuroshio path south of Japan have been investigated using time series of the Kuroshio axis location and altimeter-derived sea surface height maps for a period of seven years from 1993 to 1999, when the Kuroshio followed its non-large meander path. It was found that both the cyclonic and anticyclonic eddies may interact with the Kuroshio and trigger short-term meanders of the Kuroshio path, although not all eddies that approached or collided with the Kuroshio formed meanders. An anticyclonic eddy that revolves clockwise in a region south of Shikoku and Cape Shionomisaki with a period of about 5–6 months was found to propagate westward along about 30°N and collide with the Kuroshio in the east of Kyushu or south of Shikoku. This collision sometimes triggers meanders which propagate over the whole region south of Japan. The eddy was advected downstream, generating a meander on the downstream side to the east of Cape Shionomisaki. After the eddy passed Cape Shionomisaki, it detached from the Kuroshio and started to move westward again. Sometimes the eddy merges with other anticyclonic eddies traveling from the east. Coalescence of cyclonic eddies, which are also generated in the Kuroshio Extension region and propagate westward in the Kuroshio recirculation region south of Japan, into the Kuroshio in the east of Kyushu, also triggers meanders which mainly propagate only in a region west of Cape Shionomisaki. This revised version was published online in July 2006 with corrections to the Cover Date.     

Western Arctic primary productivity regulated by shelf-break warm eddies

The response of phytoplankton to the Beaufort shelf-break eddies in the western Arctic Ocean is examined using the eddy-resolving coupled sea ice–ocean model including a lower-trophic marine ecosystem formulation. The regional model driven by the reanalysis 2003 atmospheric forcing from March to November captures the major spatial and temporal features of phytoplankton bloom following summertime sea ice retreat in the shallow Chukchi shelf and Barrow Canyon. The shelf-break warm eddies spawned north of the Barrow Canyon initially transport the Chukchi shelf water with high primary productivity toward the Canada Basin interior. In the eddy-developing period, the anti-cyclonic rotational flow along the outer edge of each eddy moving offshore occasionally traps the shelf water. The primary production inside the warm eddies is maintained by internal dynamics in the eddy-maturity period. In particular, the surface central area of an anti-cyclonic eddy acquires adequate light, nutrient, and warm environment for photosynthetic activity partly attributed to turbulent mixing with underlying nutrient-rich water. The simulated biogeochemical properties with the dominance of small-size phytoplankton inside the warm eddies are consistent with the observational findings in the western Arctic Ocean. It is also suggested that the light limitation before autumn sea ice freezing shuts down the primary production in the shelf-break eddies in spite of nutrient recovery. These results indicate that the time lag between the phytoplankton bloom in the shelf region following the summertime sea ice retreat and the eddy generation along the Beaufort shelf break is an important index to determine biological regimes in the Canada Basin.     

Numerical Study of the Upper-Layer Circulation in the South China Sea

Upper-layer circulation in the South China Sea has been investigated using a three-dimensional primitive equation eddy-resolving model. The model domain covers the region from 99° to 122°E and from 3° to 23°N. The model is forced by the monthly averaged European Centre for Medium-Range Weather Forecasts (ECMWF) model winds and the climatological monthly sea surface temperature data from National Oceanographic Data Center (NODC). Inflow and outflow through the Taiwan Strait and the Sunda shelf are prescribed monthly from the Wyrtki estimates. Inflow of the Kuroshio branch current in the Luzon Strait is assumed to have a constant volume transport of 12 Sv (1 Sv = 10⁶ m³/s), and the outflow from the open boundary to the east of Taiwan is adjusted to ensure the net volume transport through all open boundaries is zero at any instant. The model reveals that a cyclonic circulation exists all year round in the northern South China Sea. During the winter time this cyclonic eddy is located off the northwest of Luzon, coinciding with the region of positive wind stress curl in this season. This cyclonic eddy moves northward in spring due to the weakening of the northeast winds. The cyclonic circulation becomes weak and stays in the continental slope region in the northern South China Sea in the summer period. The southwest wind can raise the water level along the west coast of Luzon, but there is no anticyclonic circulation in the northern South China Sea. After the onset of the northeast monsoon winds in fall, the cyclonic eddy moves back to the region off the west coast of Luzon. In the southern South China Sea and off the Vietnam coast, the model predicts a similar flow structure as in the previous related studies. This revised version was published online in July 2006 with corrections to the Cover Date.     

Mesoscale eddies off Peru in altimeter records: Identification algorithms and eddy spatio-temporal patterns

Relatively little is known about coherent vortices in the eastern South-Pacific along the Peruvian coast, even with regard to basic facts about their frequency of occurrence, longevity and structure. This study addresses these issues with nearly 15 years of relatively high-resolution satellite altimetry measurements.We first compare two distinct automated methods for eddy identification. The objective validation protocol shows that the rarely-used geometrical or “winding-angle method”, based on the curvature of the streamline functions, is more accurate than the commonly-used “Okubo–Weiss algorithm”, which defines a vortex as a simple connected region with values of Okubo–Weiss parameter weaker than a given threshold.We then investigate vortices off Peru using more than 20,000 mesoscale eddies identified by the winding-angle method. Coherent eddies, characterized by a high ratio of vorticity to deformation rate, are typically formed along the coast and propagate westward at 3–6 cm s⁻¹. The vortices have a mean radius of 80 km, increasing northward, and are most frequently observed off of Chimbote (9°S) and south of San Juan (15°S). The mean eddy lifetime is about 1 month, but if eddies survive at least 2 months, the probability for surviving an additional week (or month) is constant at 90% (or 67%). Anticyclonic eddies tend to propagate northwestward whereas cyclonic vortices migrate southwestward. In general, cyclones and anticyclones are similar, except for eddies surviving at least 6 months. In this case, after a similar 3–4 months of radius and amplitude growth, amplitudes (or sizes) decay particularly rapidly for anticyclonic (or cyclonic) eddies. In terms of intensity, cyclonic eddies show a rapid decay during the first 3 months before arriving at a quasi-constant value, whereas anticyclones exhibit steady decline. Finally, eddy temporal variations were examined at seasonal and interannual scales in the “coastal” region favorable to the formation of energetic mesoscale structures. On seasonal scales, eddy activity is maximal in fall and minimum in spring. At interannual scales, the eddy activity index was maximal during the strong El Niño of 1997–1998 but another strong maximum of eddy activity also occurred late in 2004. These temporal variations are probably associated with the intensification of the upwelling thermal front and with the passage of coastal-trapped waves which generate baroclinic instabilities. Further investigation of the mechanisms involved on the eddy genesis is needed.     

Prognostic numerical analysis of currents in the black sea with high horizontal resolution

We present the results of numerical prognostic experiments performed with a resolution of 1.64 km in the horizontal coordinates. Unlike the calculations performed with coarser resolution, we reveal the following dynamic specific features: The Rim Current is traced down to 400 m as a continuous jet directed along the continental slope. Mesoscale anticyclonic eddies are regularly formed along the east part of the Anatolian coast and affect the formation of the Batumi anticyclone. The Sevastopol, Sinop, Kizilirmak, and Caucasian anticyclonic eddies are quasiperiodic. A region of cyclonic rotation of waters is formed between the newly formed Sevastopol anticyclone and the previous eddy.     

Three dimensional diagnostic modeling study of the South China Sea circulation before onset of summer monsoon in 1998

The wind data from NCEP and hydrographic data obtained from April 22–May 24, 1998 have been used to compute the circulation in the South China Sea (SCS) using three dimensional diagnostic models. The main numerical results with SSHA derived from T/P altimeter are as follows: most of intruded Kuroshio bypasses. However, a part of Kuroshio intrudes westward above 300 m levels. This intruded westward flow is narrowly confined to the continental slope south of China, in agreement with the findings of Qu et al. (2000). The basin-scale cyclonic gyre dominates in the northern SCS and consists of two cyclonic eddies, C2 and C3, above 300 m levels. However, it is separated into two parts by an anti-cyclonic eddy, W4, below 300 m. The basin-scale anti-cyclonic gyre dominates in the central SCS and consists of three anti-cyclonic eddies, W1, W2 and W3, above 300 m levels. However, below 300 m it consists of the anti-cyclonic eddies W1, W2 and W4 and extends northward to near 20°N. A northward coastal jet is present near the coast of Vietnam at depths above 300 m, and develops northward further to about a distance of 3°15′ N than that in cruise 2. The most important dynamical mechanism is due to the joint effect of the baroclinity and relief. The second dynamical mechanism is due to the interaction between the wind stress and relief. The topography effect is more important than the β effect. The Sverdrup relation cannot be satisfied in the SCS.