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1.
In this study, we develop a variable-grid global ocean general circulation model(OGCM) with a fine grid(1/6)°covering the area from 20°S–50°N and from 99°–150°E, and use the model to investigate the isopycnal surface circulation in the South China Sea(SCS). The simulated results show four layer structures in vertical: the surface and subsurface circulation of the SCS are characterized by the monsoon driven circulation, with basin-scaled cyclonic gyre in winter and anti-cyclonic gyre in summer. The intermediate layer circulation is opposite to the upper layer, showing anti-cyclonic gyre in winter but cyclonic gyre in summer. The circulation in the deep layer is much weaker in spring and summer, with the maximum velocity speed below 0.6 cm/s. In fall and winter, the SCS deep layer circulation shows strong east boundary current along the west coast of Philippine with the velocity speed at 1.5 m/s, which flows southward in fall and northward in winter. The results have also revealed a fourlayer vertical structure of water exchange through the Luzon Strait. The dynamics of the intermediate and deep circulation are attributed to the monsoon driving and the Luzon Strait transport forcing. 相似文献
2.
Direct measurements of surface and mid-depth circulationin the Shikoku Basin by Argo profiling floats 总被引：1，自引：0，他引：1
The circulation in the Shikoku Basin plays a very important role in the pathway of the Kuroshio and the water exchange in the subtropical gyre in the North Pacific Ocean. The Argo profiling floats deployed in the Shikoku Basin are used to study the circulations and water masses in the basin. The trajectories and parking depth velocity fields derived from all Argo floats show an anticyclonic circulation at 2 000 m in the Shikoku Basin. There are inhanced eddy activities in the Shikoku Basin, which have large influence on the Shikoku Basin circulation patterns. The characteristics of temperature-salinity curves indicate that there are North Pacific Ocean tropical water (NPTW), North Pacific Ocean subtropical mode water (NPSTMW) and North Pacific Ocean intermediate water (NPIW) in the Shikoku Basin. The NPTW is only exists south of 32°N. In the middle part of the basin, which is 28°~31°N,133°~135°E, there is a confluence region. Water masses coming from the Kuroshio mix with the water in the Shikoku Basin. 相似文献
3.
The structure of the annual-mean shallow meridional overturning circulation(SMOC) in the South China Sea(SCS) and the related water movement are investigated,using simple ocean data assimilation(SODA) outputs.The distinct clockwise SMOC is present above 400 m in the SCS on the climatologically annual-mean scale,which consists of downwelling in the northern SCS,a southward subsurface branch supplying upwelling at around 10°N and a northward surface flow,with a strength of about 1×10~6 m~3/s.The formation mechanisms of its branches are studied separately.The zonal component of the annual-mean wind stress is predominantly westward and causes northward Ekman transport above 50 m.The annual-mean Ekman transport across 18°N is about 1.2×10~6 m~3/s.An annual-mean subduction rate is calculated by estimating the net volume flux entering the thermocline from the mixed layer in a Lagrangian framework.An annual subduction rate of about 0.66×10~6m~3/s is obtained between 17° and 20°N,of which 87% is due to vertical pumping and 13% is due to lateral induction.The subduction rate implies that the subdution contributes significantly to the downwelling branch.The pathways of traced parcels released at the base of the February mixed layer show that after subduction water moves southward to as far as 11°N within the western boundary current before returning northward.The velocity field at the base of mixed layer and a meridional velocity section in winter also confirm that the southward flow in the subsurface layer is mainly by strong western boundary currents.Significant upwelling mainly occurs off the Vietnam coast in the southern SCS.An upper bound for the annual-mean net upwelling rate between 10° and 15°N is 0.7×10~6m~3/s,of which a large portion is contributed by summer upwelling,with both the alongshore component of the southwest wind and its offshore increase causing great upwelling. 相似文献
4.
On the basis of the salinity distribution of isopycnal(σ_0=27.2 kg/m~3) surface and in salinity minimum, the Antarctic Intermediate Water(AAIW) around South Australia can be classified into five types corresponding to five regions by using in situ CTD observations. Type 1 is the Tasman AAIW, which has consistent hydrographic properties in the South Coral Sea and the North Tasman Sea. Type 2 is the Southern Ocean(SO) AAIW, parallel to and extending from the Subantarctic Front with the freshest and coldest AAIW in the study area. Type 3 is a transition between Type 1 and Type 2. The AAIW transforms from fresh to saline with the latitude declining(equatorward). Type 4, the South Australia AAIW, has relatively uniform AAIW properties due to the semienclosed South Australia Basin. Type 5, the Southeast Indian AAIW, progressively becomes more saline through mixing with the subtropical Indian intermediate water from south to north. In addition to the above hydrographic analysis of AAIW, the newest trajectories of Argo(Array for real-time Geostrophic Oceanography) floats were used to constructed the intermediate(1 000 m water depth) current field, which show the major interocean circulation of AAIW in the study area. Finally, a refined schematic of intermediate circulation shows that several currents get together to complete the connection between the Pacific Ocean and the Indian Ocean. They include the South Equatorial Current and the East Australia Current in the Southwest Pacific Ocean, the Tasman Leakage and the Flinders Current in the South Australia Basin, and the extension of Flinders Current in the southeast Indian Ocean. 相似文献
5.
Understanding of the temporal variation of oceanic heat content(OHC) is of fundamental importance to the prediction of climate change and associated global meteorological phenomena. However, OHC characteristics in the Pacific and Indian oceans are not well understood. Based on in situ ocean temperature and salinity profiles mainly from the Argo program, we estimated the upper layer(0–750 m) OHC in the Indo-Pacific Ocean(40°S–40°N, 30°E–80°W). Spatial and temporal variability of OHC and its likely physical mechanisms are also analyzed. Climatic distributions of upper-layer OHC in the Indian and Pacific oceans have a similar saddle pattern in the subtropics, and the highest OHC value was in the northern Arabian Sea. However, OHC variabilities in the two oceans were different. OHC in the Pacific has an east-west see-saw pattern, which does not appear in the Indian Ocean. In the Indian Ocean, the largest change was around 10°S. The most interesting phenomenon is that, there was a long-term shift of OHC in the Indo-Pacific Ocean during 2001–2012. Such variation coincided with modulation of subsurface temperature/salinity. During 2001–2007, there was subsurface cooling(freshening)nearly the entire upper 400 m layer in the western Pacific and warming(salting) in the eastern Pacific. During2008–2012, the thermocline deepened in the western Pacific but shoaled in the east. In the Indian Ocean, there was only cooling(upper 150 m only) and freshening(almost the entire upper 400 m) during 2001–2007. The thermocline deepened during 2008–2012 in the Indian Ocean. Such change appeared from the equator to off the equator and even to the subtropics(about 20°N/S) in the two oceans. This long-term change of subsurface temperature/salinity may have been caused by change of the wind field over the two oceans during 2001–2012, in turn modifying OHC. 相似文献
6.
副热带东北太平洋混合层深度及其对潜沉的影响 总被引：1，自引：0，他引：1
The present climate simulations of the mixed layer depth(MLD) and the subduction rate in the subtropical Northeast Pacific are investigated based on nine of the CMIP5 models. Compared with the observation data,spatial patterns of the MLD and the subduction rate are well simulated in these models. The spatial pattern of the MLD is nonuniform, with a local maximum MLD(140 m) region centered at(28°N, 135°W) in late winter. The nonuniform MLD pattern causes a strong MLD front on the south of the MLD maximum region, controls the lateral induction rate pattern, and then decides the nonuniform distribution of the subduction rate. Due to the inter-regional difference of the MLD, we divide this area into two regions. The relatively uniform Ekman pumping has little effect on the nonuniform subduction spatial pattern, though it is nearly equal to the lateral induction in values. In the south region, the northward warm Ekman advection(–1.75×10~(–7) K/s) controls the ocean horizontal temperature advection(–0.85×10~(–7) K/s), and prevents the deepening of the MLD. In the ensemble mean, the contribution of the ocean advection to the MLD is about –29.0 m/month, offsetting the sea surface net heat flux contribution(33.9 m/month). While in the north region, the southward cold advection deepens the MLD(21.4 m/month) as similar as the heat flux(30.4 m/month). In conclusion, the nonuniform MLD pattern is dominated by the nonuniform ocean horizontal temperature advection. This new finding indicates that the upper ocean current play an important role in the variability of the winter MLD and the subduction rate. 相似文献
7.
Hydrographic observations collected by conductivity-temperature-depth(CTD) and instrumented elephant seals on the Prydz Bay continental shelf during 2012 and 2013 are used to characterize the intrusion of modified circumpolar deep water.As a regular occurrence,modified circumpolar deep water(MCDW) intrudes onto the shelf mainly between 150–300 m layer of 73°–75°E and then turns southeast affected by the cyclonic gyre of the Prydz Bay.The southernmost point of the warm water signal is captured on the east front of Amery Ice Shelf during March 2012.In terms of vertical distribution,MCDW occupies the central layer of 200 m with about 100 m thickness in the austral summer,but when to winter transition,the layer of MCDW deepens with time on the central shelf. 相似文献
8.
北太平洋副热带东部模态水现在和未来的模拟分析 总被引：2，自引：1，他引：1
The present climate simulation and future projection of the Eastern Subtropical Mode Water(ESTMW) in the North Pacific are investigated based on the Geophysical Fluid Dynamics Laboratory Earth System Model(GFDL-ESM2M). Spatial patterns of the mixed layer depth(MLD) in the eastern subtropical North Pacific and the ESTMW are well simulated using this model. Compared with historical simulation, the ESTMW is produced at lighter isopycnal surfaces and its total volume is decreased in the RCP8.5 runs, because the subduction rate of the ESTMW decreases by 0.82×10-6 m/s during February–March. In addition, it is found that the lateral induction decreasing is approximately four times more than the Ekman pumping, and thus it plays a dominant role in the decreased subduction rate associated with global warming. Moreover, the MLD during February–March is banded shoaling in response to global warming, extending northeastward from the east of the Hawaii Islands(20°N, 155°W) to the west coast of North America(30°N, 125°W), with a maximum shoaling of 50 m, and then leads to the lateral induction reduction. Meanwhile, the increased northeastward surface warm current to the east of Hawaii helps strengthen of the local upper ocean stratification and induces the banded shoaling MLD under warmer climate. This new finding indicates that the ocean surface currents play an important role in the response of the MLD and the ESTMW to global warming. 相似文献
9.
南海北部陆坡区内孤立波的垂向热量输送 总被引：1，自引：0，他引：1
An integrated analysis of internal solitary wave(ISW) observations obtained from two moorings over the continental slope in the northern South China Sea(SCS) leads to an assessment of the vertical heat transport of the ISWs. The clusters of ISW packets are phase-locked to the fortnightly cycle of the semidiurnal tide. The ISWs appear during large semidiurnal tides, and there is a period of 5–6 d when no ISWs are observed. The effect of the ISWs on the continental slope heat budget is observed. The ISWs can modify a local temperature field in which the temperature in the upper layer can be changed by O(100) °C after the ISWs passed the mooring. Both ISWinduced diffusion and ISW-induced advection contribute to the temperature variation. The estimates imply an average vertical heat flux of 0.01 to 0.1 MW/m~2 in the ISWs in the upper 500 m of the water column. The vertical heat transport ranges from 0.56 to 2.83 GJ/m~2 with a mean value of 1.63 GJ/m~2. The observations suggest that the vertical heat transport is proportional to the maximum vertical displacement. 相似文献
10.
In this study, high-resolution temperature and salinity data obtained from three Sea-Wing underwater gliders were used together with satellite altimeter data to track the vertical thermohaline structure of an anticyclonic eddy that originated from the loop current of the Kuroshio southwest of Taiwan, China. One of the gliders crossed the entire eddy and it observed a remarkable warm anomaly of as much as 3.9℃ extending to 500 dbar from the base of the mixed layer. Conversely, a positive salinity anomaly was found to be above 200 dbar only in the anticyclonic eddy, with a maximum value of >0.5 in the mixed layer. Below the mixed layer, water of higher salinity (>34.7) was found, which could have been preserved through constrained vertical mixing within the anticyclonic eddy. The salinity in the upper layer of the anticyclonic eddy was much similar to that of the northwestern Pacific Ocean than the northern South China Sea, reflecting Kuroshio intrusion with anticyclonic eddy shedding from the loop current. 相似文献
11.
Mizuki Tsuchiya 《Progress in Oceanography》1986,16(4)
There are three major permanent thermostads with roughly the same potential densities in the upper layer of the Atlantic Ocean. One is the thermostad of the 13°C Water in the equatorial Atlantic. The original type of the 13°C Water is formed in the thermocline in the eastern sector of the South Atlantic subtropical gyre by vertical mixing of dense, low-salinity water from the winter outcrop farther south and overlying less dense, high-salinity water. There might also be a lateral contribution of relatively high-salinity water from the Indian Ocean. The original 13°C Water thus formed is transported northwestward along the northern edge of the subtropical gyre and fed into the North Brazilian Current, which flows equatorward along the coast of Brazil. In the region of the equator, the Equatorial Undercurrent and the subsurface North and South Equatorial countercurrents branch off from the North Brazilian Current and carry the 13°C Water eastward to the thermostad region. Vertical mixing does not explain the development of the thermostad, but is found to be essential in determining the ultimate characteristics of the 13°C Water. The other two thermostads are those of the 18°C Water in the Sargasso Sea and the Subantarctic Mode Water in the western South Atlantic. Unlike the 13°C Water, both of these mode waters are formed as thermostads in the surface layer by winter convection, but vertical mixing in the subtropical gyres may play a role in determining their characteristics. All the three thermostads appear to be required to balance the system of flows in opposing directions. 相似文献
12.
《Deep Sea Research Part I: Oceanographic Research Papers》1999,46(11):1895-1921
An analysis of the water mass structure of the Atlantic Ocean central layer is conducted by applying optimum multiparameter (OMP) analysis to an expansive historical data set. This inverse method utilises hydrographic property fields to determine the spreading and mixing of water masses in the permanent thermocline. An expanded form of OMP analysis is used, incorporating Redfield ratios and pseudo-age to correct for the non-conservative behaviour of oxygen and nutrients over large oceanic areas.Three water masses are considered to contribute to the central layer of the Atlantic Ocean. One of these is formed in each hemisphere of the Atlantic Ocean and the other advects around the southern tip of Africa from its formation region in the Indian Ocean. The Atlantic Ocean is analysed on a fine three-dimensional grid so that at every grid point the relative contributions of each water mass and the pseudo-age are determined.The model is remarkably successful in verifying many accepted circulation features in the Atlantic Ocean, including the large-scale circulations of the subtropical gyres, the zonal flows of equatorial currents at the equator, and a cross-equatorial flow of the water masses formed in the southern hemisphere near the western boundary. The inter-hemisphere flow is so important that almost half of the thermocline waters in the Caribbean Sea and the Gulf of Mexico are supplied by the two water masses formed in the South Atlantic and Indian Oceans. This provides support for an upper-layer replacement path for the formation of North Atlantic Deep Water. Further east, the sharp front at about 15°N between North and South Atlantic Central Waters is clearly discriminated throughout the thermocline. The central waters of the South Atlantic thermocline are found to be highly stratified, with central water formed in the Indian Ocean underlying the South Atlantic Central Water. At around 5°N a strong upwelling zone is identified in which the central water formed in the Indian Ocean penetrates towards the surface. The pseudo-age results allow pathways for the flow of water masses to be inferred, and clearly identify circulation features such as the subtropical gyres, the Equatorial Undercurrent, and the shadow zones in the eastern equatorial regions of the Atlantic Ocean. Water mass renewal in these shadow zones occurs on considerably longer time scales than for the well-ventilated subtropical gyres. 相似文献
13.
亚南极模态水(sub-Antarctic mode water,SAMW)的潜沉过程与全球变暖减缓现象密切相关。为了增进对亚南极模态水长期变化特征的认识,使用一个高分辨率长时间序列的海洋模式数据对SAMW的潜沉率变化趋势的空间分布进行了系统地分析。结果显示,在1958~2016年间,SAMW的潜沉量在南太平洋和南印度洋在长时间段上存在着相反的趋势变化,即在南太平洋增大,在南印度洋减少,这与已有研究结果相符。但进一步的分析发现,SAMW潜沉量的空间分布存在着明显的差异。在南印度洋,其北部潜沉区的潜沉率仅有很微弱的上升趋势,而位于南部潜沉区的潜沉率则有明显的下降趋势。与此同时,在南太平洋中,其西部潜沉区的潜沉率趋势非常小,而东部潜沉区的水的潜沉有明显上升的长期趋势。总体而言,密度较大的SAMW潜沉水团比密度较小的潜沉水团表现出更显著的长期变化的趋势。南部变化趋势明显的潜沉水量大概占总潜沉水量的60%,由此可知SAMW的总体趋势更多地来自其南部密度更大的潜沉区的贡献。进一步的分析表明,SAMW潜沉区的混合层的长期变化趋势与潜沉率的长期变化趋势之间存在较为一致的空间分布。其中,在南太平洋,东侧潜沉区的混合层的长期增大趋势,主要由于风应力增大的作用,而西侧潜沉区的混合层的长期减小趋势,则主要因为海表浮力强迫的控制;在南印度洋,南侧潜沉区的潜沉率长期减小趋势更多的是受到浮力强迫的影响,而西北部的潜沉率长期增加趋势则主要由风应力增强导致的。 相似文献
14.
《Deep Sea Research Part I: Oceanographic Research Papers》2007,54(5):710-731
The distribution and optical absorption characteristics of chromophoric dissolved organic matter (CDOM) were systematically investigated along three meridional transects in the North Atlantic Ocean and Caribbean Sea conducted as part of the 2003 US CLIVAR/CO2 Repeat Hydrography survey. Hydrographic transects covered in aggregate a latitudinal range of 5° to 62° north along longitudes 20°W (line A16N, Leg 1), 52°W (A20), and 66°W (A22). Absorption spectra of filtered seawater samples were collected and analyzed for depths ranging from the surface to ∼6000 m, sampling all the ocean water masses in the western basin of the subtropical North Atlantic and several stations on the North and South American continental slopes. The lowest surface abundances of CDOM (< 0.1 m−1 absorption coefficient at 325 nm) were found in the central subtropical gyres while the highest surface abundances (∼0.7 m−1) were found along the continental shelves and within the subpolar gyre, confirming recent satellite-based assessments of surface CDOM distribution. Within the ocean interior, CDOM abundances were relatively high (0.1–0.2 m−1 absorption coefficient at 325 nm) except in the subtropical mode water, where a local minimum exists due to the subduction of low CDOM surface waters during mode water formation. In the subthermocline water masses of the western basin, changes in CDOM abundance are not correlated with increasing ventilation age as assessed using chlorofluorocarbon (CFC) concentrations and the atmospheric CFC history. But dissolved organic carbon (DOC) mass-specific absorption coefficients of CDOM increase with increasing ventilation age in the deep sea, indicating that CDOM is a refractory component of the DOC pool. The overall CDOM distribution in the North Atlantic reflects the rapid advection and mixing processes of the basin and demonstrates that remineralization in the ocean interior is not a significant sink for CDOM. This supports the potential of CDOM as a tracer of ocean circulation processes for subducted water masses. 相似文献
15.
Eitarou Oka Shota Katsura Hiroyuki Inoue Atsushi Kojima Moeko Kitamoto Toshiya Nakano Toshio Suga 《Journal of Oceanography》2017,73(4):479-490
The 137°E repeat hydrographic section for 50 winters during 1967–2016 has been analyzed to examine interannual to interdecadal variations and long-term changes of salinity and temperature in the surface and intermediate layers of the western North Pacific, with a particular focus on freshening in the subtropical gyre. Rapid freshening on both isobars and isopycnals began in the mid-1990s and persisted for the last 20 years in the upper main thermocline/halocline in the western subtropical gyre. In addition, significant decadal variability of salinity existed in the subtropical mode water (STMW), as previously reported for the shallower layers. An analysis of the 144°E repeat hydrographic section during 1984–2013 supplemented by Argo profiling float data in 2014 and 2015 revealed that the freshening trend and decadal variability observed at 137°E originated in the winter mixed layer in the Kuroshio Extension (KE) region and was transmitted southwestward to 137°E 1–2 years later in association with the subduction and advection of STMW. The mechanism of these changes and variations in the source region was further investigated. In addition to the surface freshwater flux in the KE region pointed out by previous studies, the decadal KE variability in association with the Pacific Decadal Oscillation likely contributes to the decadal salinity variability through water exchange between the subtropics and the subarctic across the KE. Interdecadal change in both the surface freshwater flux and the KE state, however, failed to explain the rapid freshening for the last 20 years. 相似文献
16.
Response of the North Pacific subtropical countercurrent and its variability to global warming 总被引：1，自引：0，他引：1
Response of the North Pacific subtropical countercurrent (STCC) and its variability to global warming is examined in a state-of-the-art
coupled model that is forced by increasing greenhouse gas concentrations. Compared with the present climate, the upper ocean
is more stratified, and the mixed layer depth (MLD) shoals in warmer climate. The maximum change of winter MLD appears in
the Kuroshio–Oyashio extension (KOE) region, where the mean MLD is the deepest in the North Pacific. This weakens the MLD
front and reduces lateral induction. As a result of the reduced subduction rate and a decrease in sea surface density in KOE,
mode waters form on lighter isopycnals with reduced thickness. Advected southward, the weakened mode waters decelerate the
STCC. On decadal timescales, the dominant mode of sea surface height in the central subtropical gyre represents STCC variability.
This STCC mode decays as CO2 concentrations double in the twenty-first century, owing both to weakened mode waters in the mean state and to reduced variability
in mode waters. The reduced mode-water variability can be traced upstream to reduced variations in winter MLD front and subduction
in the KOE region where mode water forms. 相似文献
17.
《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(9):1571-1590
Water mass formation rates were calculated for subtropical underwater (STUW) in the North and South Pacific by two partially independent methods. One is based on the World Ocean Circulation Experiment (WOCE)/TOGA drifter array over two periods: 1988–1992, and 1992–1996. Drifter velocities were used to calculate two components of the subduction rate, lateral induction and vertical pumping. The second method used CFC-12 data (1987–1994) from WOCE and Pacific Marine Environmental Laboratory to calculate ages on σθ surfaces. Subduction rates were estimated from the inverse age gradient. The two subduction rate methods are independent, but they share a common identification of STUW formation area based on satellite-derived surface temperature maps. Using both methods, one can put bounds on the formation rates: 4–5 Sv in the North and 6–7 Sv in the South Pacific. The drifter calculated STUW subduction rates for 1988–1992 and 1992–1996 are 21 and 13 m/yr in the North Pacific and 25 and 40 m/yr in the South. The CFC-12 calculated STUW subduction rate in the North Pacific is 26 m/yr, and 32 m/yr in the South. The South Pacific rates exceed those in the North Pacific. Consistent differences between the two methods support earlier studies, they conclude that mixing contributes to STUW formation in addition to the larger-scale circulation effects. The drifter and tracer rates agree well quantitatively, within 22%, except for the second period in the North Pacific and there are some differences in spatial patterns. Tracer rates integrate over time, and drifters allow analysis of interannual variability. The decrease in subduction rate between periods in the North Pacific is due to negative lateral induction entraining STUW into the mixed layer. The increase in the South Pacific rate is due to an increase in the vertical pumping. Although Ekman pumping is in phase in the North and South, the subduction rate is out of phase. These results confirm that subduction depends on the large-scale circulation and a combination of the outcrop pattern and air–sea fluxes. Temporal differences in rates and partitioning between the hemispheres are consistent with interannual changes in gyre intensity and current positions. 相似文献
18.
基于参与第六次耦合模式比较计划（CMIP6）的8个地球系统耦合模式所输出的历史模拟结果,本文通过与观测对比,评估了CMIP6模式对东南印度洋亚南极模态水的模拟能力,并预估了在中等强迫情景和高强迫情景下,该模态水潜沉率、体积及性质的变化趋势。结果表明:与Argo观测相比,CMIP6模式中南印度洋混合层偏深且上层海洋的位势密度偏小,因此其模拟的东南印度洋亚南极模态水潜沉率偏大而位势密度偏小。不同CMIP6模式之间模拟的东南印度洋亚南极模态水潜沉区存在差异,混合层侧向输入是导致这一差异的主要原因。此外,在历史模拟和两种情景试验中,东南印度洋亚南极模态水均呈现出潜沉率和体积减小、温度升高、盐度和密度降低的趋势。其中,在高强迫情景下,变化趋势最大,中等强迫情景次之,历史模拟中的变化趋势最小。这表明,辐射强迫越强,东南印度洋海表温度升高和淡水输入增加的趋势越大,导致混合层变浅及其南北梯度减小的趋势越快,东南印度洋亚南极模态水潜沉率、体积和性质变化的趋势也随之增大。 相似文献
19.
基于近40 a NCEP/NCAR再分析月平均高度场、风场、涡度场、垂直速度场以及NOAA重构的海面温度(sea surface temperature,SST)资料和美国联合台风预警中心(Joint Typhoon Warning Center,JTWC)热带气旋最佳路径资料,利用合成分析方法,研究了前期春季及同期夏季印度洋海面温度同夏季西北太平洋台风活动的关系。结果表明:1)前期春季印度洋海温异常(sea surface temperature anomaly,SSTA)尤其是关键区位于赤道偏北印度洋和西南印度洋地区对西北太平洋台风活动具有显著的影响,春季印度洋海温异常偏暖年,后期夏季,110°～180°E的经向垂直环流表现为异常下沉气流,对应风场的低层低频风辐散、高层辐合的形势,这种环流形势使得低层水汽无法向上输送,对流层中层水汽异常偏少,纬向风垂直切变偏大,从而夏季西北太平洋台风频数偏少、强度偏弱,而异常偏冷年份则正好相反。2)春季印度洋异常暖年,西北太平洋副热带高压加强、西伸;而春季印度洋异常冷年,后期夏季西北太平洋副热带高压减弱、东退,这可能是引起夏季西北太平洋台风变化的另一原因。 相似文献
20.
Sang-Han Lee Pavel P. Povinec Janine Gastaud Beniamino Oregioni Laurent Coppola Catherine Jeandel 《Journal of Oceanography》2009,65(3):397-406
Anthropogenic 90Sr, 239,240Pu and 241Am were used as tracers of water mass circulation in the Crozet Basin of the South Indian Ocean, represented by three main
water fronts—Agulhas (AF), Subtropical (STF) and Subantarctic (SAF). Higher 90Sr concentrations observed north of 43°S were due to the influence of AF and STF, which are associated with the south branch
of the Subtropical gyre, which acts as a reservoir of radionuclides transported from the North to the South Indian Ocean.
On the other hand, the region south of 43°S has been influenced by SAF, bringing to the Crozet Basin Antarctic waters with
lower radionuclide concentrations. The 238Pu/239,240Pu activity ratios observed in water and zooplankton samples indicated that, even 35 years after the injection of 238Pu to the Indian Ocean from the burn-up of the SNAP-9A satellite, the increased levels of 238Pu in surface water and zooplankton are still well visible. The radionuclide concentrations in seawater and their availability
to zooplankton are responsible for the observed 210Po, 239,240Pu and 241Am levels in zooplankton. 相似文献