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1.
孟加拉湾上层环流研究综述 总被引：2，自引：0，他引：2
综述了孟加拉湾上层环流研究的主要成果并指出,研究海区环流与季风转换不完全同步。在西南季风期间,南、北海区各有一气旋式环流;在秋季季风过渡期间,出现海湾尺度的气旋式环流;在东北季风期间,气旋式环流减弱北移,南部则为一反气旋式环流控制;春季与秋季的情形相反,整个湾出现一海湾尺度的反气旋式环流。研究海区环流的变异主要受季风、赤道远地作用和浮力通量等复杂外源作用的影响。东印度沿岸流的季节变化与季风转换也不同步,局地风、内部Ekman抽吸、远地沿岸风及赤道远地作用的影响对沿岸流周年变化有重要作用。孟加拉湾上层环流年际变化显著,此年际变化主要受赤道风场的影响。 相似文献
2.
应用1993～2003年TOPEX/Poseidon卫星测高数据结合历史水文资料,反演了孟加拉湾海面动力地形的平均周年变化,探讨了孟加拉湾上层环流季节特征和演变规律.结果显示,虽然孟加拉湾的大气环流受季风支配年周期波动显著,但表层环流形态的周年演变却呈3个不同的阶段.1～4月间(东北季风后期)湾内受一个海盆尺度的强大反气旋式环流的支配,湾口为西向流;5月西南季风骤起,印度季风漂流越过印度半岛南端出现在湾口,湾内反气旋环流弱化,在其南北两侧各出现一气旋式涡,构成5～9月间南北相间的三涡结构;10月东北季风再起,湾口漂流再次转向,10～12月间湾内则为海盆尺度的弱气旋式环流.受上述环流格局影响,位于西边界的印度沿岸流亦呈相应的3个阶段变化.分析表明,孟加拉湾风应力旋度的变化是造成湾内环流3个阶段演变的主要原因.本地风场和来自赤道海域的外强迫的共同驱动形成了孟加拉湾环流周年演变的独特规律. 相似文献
3.
A coupled single-layer/two-layer model is employed to study the South China Sea (SCS) upper circulation and its response before and after the onset of summer monsoon. It is found that, in summer, due to the β effect and the first baroclinic mode of the wind-driven current, a northward western boundary jet current is formed along the Indo-China Peninsula coast, and it leaves the coast at about 13° N and diffuses towards northeast; next to the Indo-China Peninsula, a large anticyclonic 相似文献
4.
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. 相似文献
5.
基于1979—2018年欧洲中期天气预报中心(ECMWF)近海面10 m风场资料,采用增长型分层自组织映射(GHSOM)神经网络方法,对南海海表面风场(SSW)的季节变化和年际异常变化进行了分析,结果表明：(1)GHSOM网络训练原始风场数据第一层结果揭示了4个特征模态,高度概括了南海近海面风场的季节变化特征;第二层结果提取了风场的月变化特征。(2)GHSOM网络训练异常风场数据第一层结果揭示了4类异常风场特征模态：反气旋式异常、气旋式异常、西南风异常和东北风异常模态。其中反气旋式异常和气旋式异常模态呈现出不对称现象,即反气旋式异常风场的振幅大于气旋式异常风场;且这两个模态与ENSO事件密切相关,它们的时间序列与Niño 3.4指数序列存在显著的延迟相关。同时,东北风异常风场模态的发生频率大于西南风异常模态。向下扩展的第二层结果揭露了异常风场模态更多的细节特征。 相似文献
6.
Tetsuya Takahashi Hideaki Nakata Keiji Hirano Kazumi Matsuoka Mitsunori Iwataki Hitoshi Yamaguchi Tomoyuki Kasuya 《Journal of Oceanography》2009,65(1):113-120
Wind-induced circulation and the distribution of hypoxia corresponding to the upwelling of oxygen-depleted water (called “Aoshio”
in Japan and “Sumishio” locally in Omura Bay) in Omura Bay, Japan, was examined field observations and by three-dimensional
modeling. During the calm weather in summer, well-mixed strait water, in rich oxygen at the mouth of the bay intruded into
the middle layer of the bay, southward and northward along the west and east coast, respectively, forming basin-scale cyclonic
circulation. A stagnant water mass was formed below the center of this cyclonic circulation, and it became hypoxic water.
As a result of the prevailing strong southeast (northeast) wind, the bottom hypoxia moved in a southeasterly (northeasterly)
direction. This induces the upwelling of hypoxic water, accompanied by mass mortality of marine organisms. 相似文献
7.
Chunjian Sun Xidong Wang Anmin Zhang Lianxin Zhang Caixia Shao Guosong Wang 《海洋学报(英文版)》2022,41(5):27-40
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... 相似文献
8.
A recurring spring mesoscale eddy in the western South China Sea (SCS) is studied using remote sensing data and historical in situ observations. The feature first appears east of the central Vietnam coast in February as a high sea-level anomaly, grows rapidly to a well-developed anticyclonic eddy by March, matures in April, and decays in May. Besides the warm-core feature, it also has an inherent low-salinity property, so it is named "spring mesoscale high (SMH)". Though with clear interannual variation in terms of intensity and spatial coverage, the SMH always emerges in the region between 110 E and 114 E and between 12 N and 16 N. The formation of SMH is ascribed to the combined effects of wind forcing and releasing of potential energy set up by winter monsoon. In particular, the wind-stress curl plays an important role in its development, maintenance, and dissipation. 相似文献
9.
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. 相似文献
10.
Interannual variability of the Kuroshio intrusion in the South China Sea 总被引：13，自引：1，他引：13
Michael J. Caruso Glen G. Gawarkiewicz Robert C. Beardsley 《Journal of Oceanography》2006,62(4):559-575
The interannual variability of intrusions of the Kuroshio into the South China Sea (SCS) is investigated using satellite remote
sensing data supported by in-situ measurements. The mesoscale circulation of the SCS is predominantly wind-forced by the northeast
winter and southwest summer monsoons. Although the region has been studied extensively, considerable uncertainty remains about
the annual and interannual mesoscale nature of the circulation. The frequency and characteristics of Kuroshio intrusions and
their effect on circulation patterns in the northeast SCS are also not well understood. Satellite observations of Sea Surface
Temperature (SST) from the Tropical Rainfall Measuring Mission (TRMM) and the Advanced Very High Resolution Radiometer (AVHRR)
and Sea Surface Height Anomalies (SSHA) from TOPEX/ Poseidon for the period 1997–2005 are used here to analyze the annual
and interannual variability in Kuroshio intrusions and their effects on the region. Analysis of SST and SSHA shows the formation
and characteristics of intrusions vary considerably each year. Typically, the intrusion occurs in the central region of Luzon
Strait and results in an anticyclonic circulation in the northeastern SCS. However, in some years, the intrusion is located
in the northern portion of Luzon Strait and a cyclonic intrusion results. Wind stress and wind stress curl derived from the
National Aeronautics and Space Administration (NASA) QuikSCAT satellite scatterometer are used to evaluate the relationship
between wind stress or wind stress curl and the presence of winter Kuroshio intrusions into the SCS. 相似文献
11.
On the total geostrophic circulation of the pacific ocean: flow patterns, tracers, and transports 总被引：3，自引：0，他引：3
Joseph L. Reid 《Progress in Oceanography》1997,39(4):263-352
The large-scale circulation of the Pacific Ocean consists of two great anticyclonic gyres that contract poleward at increasing depth, two high-latitude cyclonic gyres, two westward flows along 10° to 15° north and south that are found from the surface to abyssal depths, and an eastward flow that takes place just north of the equator at the surface and at about 500m, but lies along the equator at all other depths.This pattern is roughly symmetric about the equator except for the northward flow across the equator in the west and the southward flow in the east.As no water denser than about 26.8 in σ0 is formed in the North Pacific, the denser waters of the North Pacific are dominated by the inflow from the South Pacific. Salinity and oxygen in the deeper water are higher in the South Pacific and the nutrients are lower. These characteristics define recognizable paths as they move northward across the equator in the west and circulate within the North Pacific. Return flow is seen across the equator in the east. Part of it turns westward and then southward with the southward limb of the extended cyclonic gyre, and part continues southward along the eastern boundary and through the Drake Passage.The important differences from earlier studies are that the equatorial crossings and the deep paths of flow are defined, and that there are strong cyclonic gyres in the tropics on either side of the equator. 相似文献
12.
Patterns of upper layer circulation variability in the South China Sea from satellite altimetry using the self-organizing map 总被引：2，自引：2，他引：0
Patterns of the South China Sea (SCS) circulation variability are extracted from merged satellite altimetry data from October 1992 through August 2004 by using the self-organizing map (SOM). The annual cycle, seasonal and inter-annual variations of the SCS surface circulation are identified through the evolution of the characteristic circulation patterns. The annual cycle of the SCS gener- al circulation patterns is described as a change between two opposite basin-scale SW-NE oriented gyres embedded with eddies: low sea surface height anomaly (SSHA) (cyclonic) in winter and high SSHA (anticyclonic) in summer half year. The transition starts from July--August (January--February) with a high (low) SSHA tongue east of Vietnam around 12°～14° N, which de- velopa into a big anticyclonic (cyclonic) gyre while moving eastward to the deep basin. During the transitions, a dipole structure, cyclonic (anticyclonic) in the north and anticyclonic (cyclonic) in the south, may be formed southeast off Vietnam with a strong zonal jet around 10°～12° N. The seasonal variation is modulated by the interannual variations. Besides the strong 1997/1998 e- vent in response to the peak Pacific El Nino in 1997, the overall SCS sea level is found to have a significant rise during 1999～ 2001, however, in summer 2004 the overall SCS sea level is lower and the basin-wide anticyclonic gyre becomes weaker than the other years. 相似文献
13.
We have constructed a fine-resolution model with realistic bathymetry to study the spatial and temporal variations of circulation in the Taiwan Strait (TS). The TS model with a resolution of 3～10 km derives its open boundary conditions from a larger-scale model. The QSCAT/NCEP winds and AVHRR SST provide forcing at the sea surface. Because of the high resolution in model grids and forcing, the model achieves a previously unavailable level of agreement with most observations. On biweekly time scales surface-trapped current reversals often lead to Strait transport reversals if the northeasterly wind bursts in winter are sufficiently strong. On seasonal time scales the northward current is the strongest in summer since both summer monsoon and pressure gradient force are northward. The summer northward current appears to be relatively unimpeded by the Changyun Rise (CYR) and bifurcates slightly near the surface. With the arrival of the northeast monsoon in fall, downwind movement of China Coastal Water (CCW) is blocked by the northward current near 25.5°N and 120°E. In winter, the northward current weakens even more as the northeasterly monsoon strengthens. The CCW moves downwind along the western boundary; the CYR blocks part of the CCW and forces a U-shaped flow pattern in the northern Strait. Past studies have failed to reveal an anticyclonic eddy that develops on the northern flank of CYR in winter. On interannual time scales a weakened northeast monsoon during El Niño reduces advection of the cold CCW from the north and enhances intrusion of warm water from the south, resulting in warming in the TS. 相似文献
14.
R.R. Rao M.S. Girish Kumar M. Ravichandran A.R. Rao V.V. Gopalakrishna P. Thadathil 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(1):1-13
The observed variability of the Kelvin waves and their propagation in the equatorial wave guide of the Indian Ocean and in the coastal wave guides of the Bay of Bengal (BoB) and the southeastern Arabian Sea (AS) on seasonal to interannual time scales during years 1993–2006 is examined utilizing all the available satellite and in-situ measurements. The Kelvin wave regime inferred from the satellite-derived sea surface height anomalies (SSHA) shows a distinct annual cycle composed of two pairs of alternate upwelling (first one occurring during January–March and the second one occurring during August–September) and downwelling (first one occurring during April–June and the second one occurring during October–December) Kelvin waves that propagate eastward along the equator and hit the Sumatra coast and bifurcate. The northern branches propagate counterclockwise over varied distances along the coastal wave guide of the BoB. The potential mechanisms that contribute to the mid-way termination of the first upwelling and the first downwelling Kelvin waves in the wave guide of the BoB are hypothesized. The second downwelling Kelvin wave alone reaches the southeastern AS, and it shows large interannual variability caused primarily by similar variability in the equatorial westerly winds during boreal fall. The westward propagating downwelling Rossby waves triggered by the second downwelling Kelvin wave off the eastern rim of the BoB also shows large interannual variability in the near surface thermal structure derived from SODA analysis. The strength of the equatorial westerlies driven by the east–west gradient of the heat sources in the troposphere appears to be a critical factor in determining the observed interannual variability of the second downwelling Kelvin wave in the wave guides of the equatorial Indian Ocean, the coastal BoB, and the southeastern AS. 相似文献
15.
Naoto Ebuchi 《Journal of Oceanography》2006,62(2):171-183
Seasonal and interannual variations in the East Sakhalin Current (ESC) are investigated using ten-year records of the sea
level anomaly (SLA) observed by the TOPEX/POSEIDON (T/P) altimeter. The T/P SLA clearly documents seasonal and interannual
variations in the ESC along the east coast of Sakhalin Island, although sea ice masks the region from January to April. Estimates
of surface current velocity anomaly derived from T/P SLA are in good agreement with drifting buoy observations. The ESC is
strong in winter, with a typical current velocity of 30–40 cm s−1 in December, and almost disappears in summer. Southward flow of the ESC is confined to the shelf and slope region and consists
of two velocity cores. These features of the ESC are consistent with short-term observations reported in previous studies.
Analysis of the ten-year records of T/P SLA confirms that the structure of the ESC is maintained each winter and the seasonal
cycle is repeated every year, although the strength of the ESC shows large interannual variations. Seasonal and interannual
variations in the ESC are discussed in relation to wind-driven circulation in the Sea of Okhotsk, using wind stress and wind
stress curl fields derived from European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis data and a scatterometer-derived
wind product. Seasonal and interannual variations of the anticyclonic eddy in the Kuril Basin are also revealed using T/P
SLA. 相似文献
16.
Propagation of Rossby Waves over Ridges Excited by Interannual Wind Forcing in a Western North Pacific Model 总被引：1，自引：4，他引：1
Numerical experiments with a multi-level general circulation model have been performed to investigate basic processes of westward
propagation of Rossby waves excited by interannual wind stress forcing in an idealized western North Pacific model with ocean
ridges. When the wind forcing with an oscillation period of 3 years is imposed around 180°E and 30°N, far from Japan, barotropic
waves excited by the wind can hardly cross the ridges, such as the Izu-Ogasawara Ridge. On the other hand, a large part of
the first-mode baroclinic waves are transmitted across the ridges, having net mass transport. The propagation speed of the
first-mode baroclinic wave is accelerated (decelerated) when an anticyclonic (cyclonic) circulation is formed at the sea surface,
due to a deeper (shallower) upper layer, and to southward (slightly northward) drift of the circulation. Thus, when the anticyclonic
circulation is formed on the northern side of the cyclonic one, they propagate almost together. The second-mode baroclinic
waves converted from the first-mode ones on the ridges arrive south of Japan, although their effects are small. The resulting
volume transport variation of the western boundary current (the Kuroshio) reaches about 60% of the Sverdrup transport variability
estimated from the wind stress. These characteristics are common for the interannual forcing case with a longer oscillation
period. In the intraseasonal and seasonal forcing cases, on the other hand, the transport variation is much smaller than those
in the interannual forcing cases.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
17.
18.
Response of surface subtidal current to wind and outflow plume in the bay-shape estuary, which had been artificially made by the Samangeum reclamation dike with two sluices in the west coast of Korea, was examined using the ocean radar-derived current data obtained in the summer 2010. The southerly wind was dominant due to Asian summer monsoon and the outflow plume water was discharged by the gate operation of the Shinsi and Garyeok sluices separated by 11 km into the study area that are opened in a southwestward direction. The monthly-mean flow pattern consisted of the westward outflow currents around the two sluices, the along-dike currents between the two sluices and the northward currents in the outer bay. Based upon the complex correlations of subtidal current to wind and outflow jets we explained that the northward mean current in the outer bay be formed by both the southerly wind-driven current and the geostrophic current by mean pressure setup due to the Ekman transport and plume water accumulation in the inner bay, and the along-dike mean current may be induced by the southerly wind that generates on-dike currents in the central region of study area and leads to pressure setup toward the dike between the two sluices. Combination of outflow jets, wind and coastline configuration affects variations of subtidal surface current in the inner bay. Variability of subtidal current in the outer bay is dominated by wind variation. The southerly wind produced the northward current in the outer bay though the outflow plumes from the two sluices turned clockwise from the inner to the outer bay due to the geostrophic balance when the wind was calm. The wind factor was from 2% to 7% depending on the amount of freshwater outflow and wind speed. Occasionally, when plume water discharges were large and the southerly wind was stronger than 5 m/s, a large eddy with a closed loop current was produced off the Shinsi sluice. 相似文献
19.
In this study, El Niño Southern Oscillation (ENSO)-induced interannual variability in the South China Sea (SCS) is documented using outputs from an eddy-resolving data-assimilating model. It is suggested that during an El Niño (La Niña) event, off-equatorial upwelling (downwelling) Rossby waves induced by Pacific equatorial wind anomalies impinge on the Philippine Islands and excite upwelling (downwelling) coastal Kelvin waves that propagate northward along the west coast of the Philippines after entering the SCS through the Mindoro Strait. The coastal Kelvin waves may then induce negative (positive) sea level anomalies in the southeastern SCS and larger (smaller) volume transport through the Mindoro and Luzon Straits during an El Niño (La Niña) event. 相似文献
20.
利用2002—2015年ARGO网格化的温度、盐度数据, 结合卫星资料揭示了赤道东印度洋和孟加拉湾障碍层厚度的季节内和准半年变化特征, 探讨了其变化机制。结果表明, 障碍层厚度变化的两个高值区域出现在赤道东印度洋和孟加拉湾北部。在赤道区域, 障碍层同时受到等温层和混合层变化的影响, 5—7月和11—1月受西风驱动, Wyrtki急流携带阿拉伯海的高盐水与表层的淡水形成盐度层结, 同时西风驱动的下沉Kelvin波加深了等温层, 混合层与等温层分离, 障碍层形成。在湾内, 充沛的降雨和径流带来的大量淡水产生很强的盐度层结, 混合层全年都非常浅, 障碍层季节内变化和准半年变化主要受等温层深度变化的影响。上述两个区域障碍层变化存在关联, 季节内和准半年周期的赤道纬向风驱动的波动过程是它们存在联系的根本原因。赤道东印度洋地区的西风(东风)强迫出向东传的下沉(上升)的Kelvin波, 在苏门答腊岛西岸转变为沿岸Kelvin波向北传到孟加拉湾的东边界和北边界, 并且在缅甸的伊洛瓦底江三角洲顶部(95°E, 16°N)激发出向西的Rossby波, 造成湾内等温层深度的正(负)异常, 波动传播的速度决定了湾内的变化过程滞后于赤道区域1~2个月。 相似文献