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1.
波浪诱导的水体输运会对海洋产生大尺度影响。结合波浪大尺度效应的研究现状和印度洋涌浪分布的事实,利用ECMWF-CERA20的波浪、海表面温度(SST)及风场数据,采用多种统计分析方法,研究了波浪输运与赤道印度洋SST的潜在关系。结果显示:中高纬度波浪输运异常的低频信号在空间、周期上与赤道SST异常均有高度相似性;Stokes漂流纬向、经向异常呈现出南—北、东—西的振荡,其第二模态时间序列与印度洋偶极子(Indian Ocean Dipole,IOD)指数存在强相关性并在La Ni a次年的负IOD事件中达到最高:相关系数在ACC区域纬向异常超前6个月时接近0.6,中纬度区域经向异常在超前3个月时达到0.7。在La Ni a次年的负IOD中,波浪经向输运异常的相位(超前三个月)与赤道SST异常相位呈全年反相位,经向浪致输运异常造成的东—西热量输运差异对赤道SST异常分布有不可忽略的贡献。  相似文献   

2.
近年来厄尔尼诺期间北赤道流输运的年际变化   总被引：1，自引：0，他引：1  
为了研究近年来厄尔尼诺期间北赤道流输运的年际变化,本文利用海洋客观分析数据MOAA GPV(Grid Point Value of the Monthly Objective Analysis)以及P-vector方法计算了北太平洋绝对地转流,探讨了2001~2013年期间厄尔尼诺与北赤道流输运之间的关系。在此期间发生的4次厄尔尼诺事件中,北赤道流输运在2002~2003、2006~2007、2009~2010年的厄尔尼诺成熟期都出现了明显的增强,但是在2004~2005年的厄尔尼诺成熟期并没有明显的增强。进一步分析发现,在2002~2003年、2006~2007年、2009~2010年的厄尔尼诺成熟期,10°N以南的热带西北太平洋区域出现了负的海面高度异常和气旋式环流异常,这主要是由热带环流区域出现的西风异常和正的Ekman抽吸通过Rossby波西传到热带西太平洋区域所致;但是在2004~2005年厄尔尼诺成熟期,海面温度异常的分布明显不同,西风异常和正的Ekman抽吸异常明显北移,导致负的海面高度异常和气旋式环流异常出现在了10°N以北的西北太平洋区域,使得北赤道流输运在2004~2005年的厄尔尼诺成熟期没有明显的增强。  相似文献   

3.
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   

4.
Wind-stress products supplied by satellite scatterometers carried the European Remote-sensing Satellite (ERS) and QuikSCAT (QSCAT), together with numerical weather predictions from the European Centre for Medium Range Weather Forecasting (ECMWF) and the National Centre for Environmental Prediction (NCEP) were used to estimate wind-driven transports of the North Pacific subtropical gyre. At 30°N, we compared the wind-driven transports with geostrophic transports calculated from World Ocean Database 2005. The wind-driven transports for QSCAT and NCEP are in good agreement with the geostrophic transport within reasonable error, except for a regional difference in the eastern part of the section. The difference in the eastern part suggests an anti-cyclonic deviation of the geostrophic transport, resulting from an anti-cyclonic anomalous flow in the surface layer. It is suggested that this anomalous flow is the Eastern Gyral, produced by the thermohaline process associated with the formation of the Eastern Subtropical Mode Water. To investigate the validity of QSCAT and NCEP data, we examined whether or not the Sverdrup transports for these products are consistent with the transport of the western boundary current estimated by past studies. The net southward transport, given by the sum of the Sverdrup transport for QSCAT and NCEP and the thermohaline transport, agrees well with the net northward transport of the western boundary current. From this result, together with the fact that the wind-driven transports for these products are in good agreement with the geostrophic transport, we conclude that the Sverdrup balance can hold in the North Pacific subtropical gyre.  相似文献   

5.
The volume transport of the Kuroshio, the western boundary current of the North Pacific subtropical gyre, varies vigorously due to merging of disturbances propagating from the entire North Pacific. Taking into account the recirculation in the Shikoku Basin by the zonal observation line at 30°N to the west of the Izu–Ogasawara Ridge, we estimated the volume transport in the top 1,000 m layer toward the Kuroshio Extension region. The volume transport of the local recirculation gyre in the Shikoku Basin increases associated with the westward extension of the gyre, particularly in the period of the large meandering path of the Kuroshio south of Japan. Meanwhile, most of the transport variations toward the Kuroshio Extension region correspond to those of the Kuroshio transport on the continental slope south of Japan, which vary independently of those of the recirculation gyre.  相似文献   

6.
The Alaskan Stream is the westward boundary current of the North Pacific subarctic gyre. In the central region of the North Pacific, the Alaskan Stream serves as a connection between the Alaskan gyre, Western subarctic gyre and Bering Sea gyre. Its volume transport is very important in estimating the magnitude of the subarctic circulation in the North Pacific. In order to clarify its seasonal and interannual variation, we conducted observations along a north-south section at 180° during June from 1990 to 1997. Moorings were deployed from 1995 to 1997. Hydrographic casts were made at intervals of 37 km to a depth of 3000 m. Moorings were set between CTD stations, with Moor1 (Moor2) at the center (southern edge) of the Alaskan Stream. Geostrophic volume transport (referred to 3000 m) revealed large interannual variability in the Alaskan Stream. Average volume transport over the 8 years was 27.5 × 106 m3s-1 with a standard deviation of 6.5 × 106 m3s-1. Maximum transport was 41.0 × 106 m3s-1 (1997) and minimum was 21.7 × 106 m3s-1 (1995). Stable westward flows were observed at Moor1 1500 m (259°, 11.7 cm s-1) and 3000 m (240°, 3.7 cm s-1, 1996–1997 year average). The ratio of eddy to mean kinetic energy (KE/ ) was very small (<0.6) throughout the year. A relatively weak and unstable westward flow was observed at Moor2 at 3000 m depth. Conversely, the average flow direction at Moor2 5000 m was eastward.  相似文献   

7.
《Ocean Modelling》2011,40(3-4):220-232
We investigate an ambiguity in the current understanding of the Gulf Stream (GS) transport in response to the North Atlantic Oscillation (NAO). While some investigations (discussed herein) suggest enhanced transport during low NAO phases, other studies suggest enhanced transport in high NAO phases. NAO-induced variability in the western North Atlantic is studied by using a 1/6°-resolution basin-scale Regional Ocean Modeling System (ROMS) model. Results indicate that the western boundary current limb of the GS, upstream of Cape Hatteras, exhibit enhanced transport during low-NAO phases. However, further downstream of Cape Hatteras, after the GS separates from the coast, diminished GS transport is seen during low-NAO phases. The converse is true for high NAO phases for both segments of the GS system. Model results show the Deep Western Boundary Current (DWBC), the northern recirculation gyre and the southern recirculation gyre intensify (weaken) during the high (low) NAO periods.  相似文献   

8.
Three eddy-permitting (1/4°) versions and one eddy-resolving (1/12°) version of the OCCAM ocean model are used to simulate the World Ocean circulation since 1985. The first eddy-permitting simulation has been used extensively in previous studies, and provides a point of reference. A second, improved, eddy-permitting simulation is forced in the same manner as the eddy-resolving simulation, with a dataset based on a blend of NCEP re-analysis and satellite data. The third eddy-permitting simulation is forced with a different dataset, based on the ERA-40 re-analysis data. Inter-comparison of these simulations in the North Atlantic clarifies the relative importance of resolution and choice of forcing dataset, for simulating the mean state and recent variability of the basin-scale circulation in that region. Differences between the first and second eddy-permitting simulations additionally reveal an erroneous influence of sea ice on surface salinity, dense water formation, and the meridional overturning circulation. Simulations are further evaluated in terms of long-term mean ocean heat transport at selected latitudes (for which hydrographic estimates are available) and sea surface temperature errors (relative to observations). By these criteria, closest agreement with observations is obtained for the eddy-resolving simulation. In this simulation, there is also a weak decadal variation in mid-latitudes, with heat transport strongest, by around 0.2 PW, in the mid-1990s. In two of the eddy-permitting simulations, by contrast, heat transport weakens through the study period, by up to 0.4 PW in mid-latitudes. The most notable changes of heat transport in all simulations are linked to a weakening of the subpolar gyre, rather than changes in the meridional overturning circulation. It is concluded that recent changes in the structure of mid-latitude heat transport in the North Atlantic are more accurately represented if eddies are explicitly resolved.  相似文献   

9.
Analysis of Argo float trajectories at 1 000 m and temperature at 950 m in the North Atlantic between November 2003 and January 2005 demonstrates the existence of two different circulation modes with fast transition between them. Each mode has a pair of cyclonic - anticyclonic gyres. The difference is the location of the cyclonic gyre. The cyclonic gyre stretches from southeast to northwest in the first mode and from the southwest to the northeast in the second mode. The observed modes strongly affect the heat and salt transport in the North Atlantic. In particular, the second mode slows down the westward transport of the warm and saline water from the Mediterranean Sea.  相似文献   

10.
金啟华  王辉  姜华  何春  刘珊 《海洋学报》2012,34(1):64-70
利用SODA资料和ECCO资料计算得到的北太平洋副热带海洋环流强度,和国家气候中心整编的中国160站逐月降水资料,结合NCEP/NCAR再分析资料和Hadley中心海表面温度资料,分析了1970－2007年海洋环流强度异常同期的大尺度大气环流异常特征及对中国东部夏季降水的影响。结果表明:海洋环流强度变化与长江中下游地区降水存在密切的反相关。环流强度异常可以通过影响西太平洋副热带高压的南北位置异常进而影响长江中下游降水。海洋环流偏弱时,副高位置偏南,长江中下游地区受气旋性环流异常影响,来自副高西北侧的强西南水汽输送至此,在该地区形成强水汽辐合中心,同时伴随上升运动加强和对流的加强,进一步导致该地区降水偏多;当海洋环流偏强时,西太平洋副高位置偏北,长江中下游地区受反气旋性环流异常影响,伴随辐散下沉及水汽辐散,导致该地区降水偏少;海洋环流强度异常导致的中纬度海区海表面温度异常,可能是导致副高南北位置异常的主要原因。  相似文献   

11.
The role of Mediterranean Overflow Water (MOW) in creating subsurface salinity anomalies within the Rockall Trough, a gateway to high latitude areas of deep convection, has been examined closely in recent years. Eulerian investigations of high latitude property fields have suggested that these subsurface anomalies are likely the result of variability in the zonal extent of the eastern limb of the subpolar gyre: when expanded into the eastern North Atlantic, the gyre is presumed to limit the extent to which MOW is able to penetrate northward to subpolar latitudes. However, though the depth of the subsurface salinity anomalies in the Rockall Trough supports the hypothesis that the intermittent presence of MOW is involved in creating the anomalies, MOW pathways to the Rockall Trough have not yet been established. Here, Lagrangian trajectories from floats released in the eastern North Atlantic between 1996 and 1997 and synthetic trajectories launched within an eddy-resolving ocean general circulation model are used to demonstrate that two main density neutral transport pathways lead to the Rockall Trough. One pathway involves the transport of relatively fresh waters as part of the North Atlantic Current and the other involves the transport of relatively salty waters from the eastern reaches of the subtropical North Atlantic. The results from this study indicate that changes in these pathways over time can explain the subsurface salinity variability in the Rockall Trough.  相似文献   

12.
太平洋东边界波浪输运   总被引：4，自引：0，他引：4  
通过计算2000年涌浪指标(swell index)的全球分布,发现太平洋东边界赤道附近区域存在涌浪池.利用ECMWF再分析波浪资料,计算出2000年全球月平均波浪体积输运.比较2000年全球月平均波浪体积输运和2000年QUICKSCAT月平均风场,发现在赤道太平洋东边界涌浪池区域内的波浪输运方向和风向存在很大的差别,两者方向相差大约90°.这进一步验证了该地区涌浪池存在的真实性.研究发现,赤道太平洋东边界涌浪主要来源于北太平洋和南太平洋的西风带对应的海区.在涌浪池区域内分别在2.5°S和2.5°N取两条边界(边界起点为125°W,终点为美洲大陆西边界),计算通过这两条边界进入赤道区域涌浪的Stokes体积净输运量.结果表明,不同月份通过南、北两条边界波浪的净输运量与当月南、北太平洋西风带的风浪强度密切相关.同时指出了,涌浪的体积输运将会对大洋环流系统产生潜在的重要影响.  相似文献   

13.
破波带内外都有质量输移流存在,其对破波带内污染物输移有怎样的影响,需要进一步深入研究。本文基于实验以及考虑质量输移流的对流扩散数学模型研究了平直斜坡上破波带内质量输移流对污染物输移影响。数学模型包括波浪模型、近岸流模型以及对流扩散模型。首先建立了破波带内污染物输移数学模型,其中波浪场基于波能守恒方程来计算,波导流场基于Longuet-Higgins提出的辐射应力模拟,污染物对流扩散方程中考虑了质量输移流的影响,并利用算例验证该数学模型。其次简要介绍了平直斜坡上破波带内污染物输移实验,并分析了污染物输移特性。连续投放污染物会形成污染带,本文分析了两种波况下不同时刻污染带与岸线夹角的变化,以及污染物在垂直岸线和沿岸线方向的输移速度,结果表明对两种波况来说在初始10-40s污染团向岸线方向输移速度分别约为0.05m/s、0.017m/s,之后速度分别减小为0.001m/s、0.011m/s。数值模拟结果与实验结果比较表明：考虑质量输移流的模拟结果与实验更为吻合。因而,通过实验以及数模研究表明破波带内质量输移流对破波带内污染物在垂直岸线方向的输移有重要影响,而对沿岸方向的输移则影响较小。  相似文献   

14.
The Meteorological Research Institute's ocean general circulation model (MRI-OGCM) has been used to investigate the temperature variability of the North Pacific Subtropical Mode Water (NPSTMW) over a time series longer than 5 years via the spin-up of the subtropical gyre. Besides an interannual variation, the wintertime sea surface temperature in the area where the NPSTMW is formed, and the temperature of the NPSTMW itself, both change remarkably in a >5-year time scale. An analysis of heat budgets showed that the long-term changes in NPSTMW temperature are due mainly to a leading advection of heat by the Kuroshio Extension and compensating surface heat flux. As a result of a dynamical adjustment to the wind stress fields, the transports of the Kuroshio and the Kuroshio Extension increased in the mid 1970s with a lag of 3 years after the wind stress curl in the central North Pacific. The increased heat advection by the Kuroshio Extension induces a warming in the mixed layer in the NPSTMW formation area, followed by a warming of the NPSTMW itself. Both these warming actions increase the heat release to the atmosphere. These results imply that the surface heat flux over the Kuroshio Extension area varies in response to the change in the ocean circulation through the spin-up of the subtropical gyre. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

15.
Various statistical methods (empirical orthogonal function (EOF), rotated EOF, singular value decomposition (SVD), principal oscillation pattern (POP), complex EOF (CEOF) and joint CEOF) were applied to low-pass filtered (>7 years) sea surface temperature (SST), subsurface temperature and 500 hPa geopotential height in order to reveal standing and propagating features of decadal variations in the North Pacific. Four decadal ocean-atmosphere covariant modes were found in this study. The first mode is the well-known ENSO-like mode associated with the “Pacific-North American” atmospheric pattern, showing SST variations reversed between the tropics and the extratropics. In the western tropical Pacific, subsurface temperature variations were found to be out of phase with the SST variations. The other three modes are related to the oceanic general circulation composed of the subtropical gyre, the Alaskan gyre and the subpolar gyre, respectively. The 1988/89 event in the northern North Pacific was found to be closely associated with the subtropical gyre mode, and the atmospheric pattern associated with this mode is the Arctic Oscillation. An upper ocean heat budget analysis suggests that the surface net heat flux and mean gyre advection are important to the Alaskan gyre mode. For the subpolar gyre mode, the mean gyre advection, local Ekman pumping and surface net heat flux play important roles. Possible air-sea interactions in the North Pacific are also discussed. The oceanic signals for these decadal modes occupy a thick layer in the North Pacific, so that accumulated heat content may in turn support long-term climate variations. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

16.
Baroclinic variations of the southward flow in the interior region of the North Pacific subtropical gyre are presented with five hydrographic sections from San Francisco to near Japan during 2004–2006. The volume transport averaged temperature of the interior flow, which varies vigorously by a maximum of 0.8°C, is negatively correlated with the transport in the layer of density 24.5–26.5σ θ, associated with changes in the vertical current structure. Transport variation in this density layer is thus mainly responsible for the thermal impact of the interior flow on the heat transport of the subtropical gyre.  相似文献   

17.
利用海浪模式WWIII(Wave Watch III)2008年的模拟结果对海面Stokes漂流、Stokes输运、Stokes深度以及全球Langmuir数的年平均分布特征和季节平均分布特征分别进行了详细的研究与分析。结果表明,海面Stokes漂流和Stokes输运均呈现高纬度偏大的特征,以南极绕极流海域最为突出。全球大部分海域Stokes漂流影响深度在20 m以内,呈现大洋东部偏大,西部偏小的分布特征。全球大部分海域的混合作用是剪切不稳定性和Langmuir湍效应并存的状态,甚至有些海域是以Langmuir湍效应为主。因此,在进行大尺度的海洋数值模拟时,应该考虑波浪导致的混合效应。  相似文献   

18.
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   

19.
Ocean temperature responses to Typhoon Mstsa in the East China Sea   总被引：1，自引：1，他引：0  
The MASNUM wave-tide-circulation coupled model, with 21 layers in the vertical and （1/8） °horizontal resolution, was employed to investigate the oceanic responses to Typhoon Mstsa which traversed the East China Sea （ECS） during the period of 4 - 6 August, 2005. Numerical experiment results are analyzed and compared with observation. The responses of the sea surface temperature （SST）, in a focused area of （27° -29°N, 121° - 124°E）, include heating and cooling stages. The heating is mainly due to warm Kuroshio water transportation and downwelling due to the water accumulation. In the cooling stage, the amplitude of the simulated cold wake （ -3℃ ）, located on the right side of this typhoon track, is compared quite well with that of the satellite observed SST data. The wave-induced mixing（Bv） plays a key role for the SST cooling. Bv still plays a leading role, which accounts for 36%, for the ocean temperature drop in the upper ocean of 0 - 40 m, while the upwelling is responsible for 84% of the cooling for the lower layer of 40 - 70 m. The mixed layer depth （MLD） increased quickly from 28 to 50 m in the typhoon period. However, the simulated MLD without the wave-induced vertical mixing, evolution from 13 to 32 m, was seriously underestimated. The surface wave is too important to be ignored for the ocean responses to a typhoon.  相似文献   

20.
基于德国Max-Planck气象研究所的最新大气海洋环流模式(ECHAM5/MPI-OM),对控制试验(control run)下热盐环流(THC)年际及年代际变化进行了分析,揭示了年代际变率的产生机制。研究表明:(1)THC年际振荡的主导周期是4 a,年代际振荡的主导周期是24 a,THC的年代际振荡信号最强,是第一主成分。(2)THC的年代际振荡机制为:首先从大西洋径向翻转环流(MOC)强度最小开始,由于MOC强度处于较弱状态,从低纬度向高纬度输送的热量偏少,副极地海区海表温度出现负异常,持续5 a之后,北大西洋副极地海区海表温度达到最大负异常。此时副极地流环中心(北大西洋)的表层海水变冷,密度增加,海表面下降,产生从副极地流环边缘指向副极地流环的中心的压强梯度力,根据地转平衡关系,北大西洋副极地海区的上层海洋会出现一个气旋式的环流异常(副极地流环得到加强),北大西洋暖流(NAC)同时得到加强。在副极地海区海表温度达到最大负异常的3 a之后,副极地流环和NAC达到最强。由此,作为NAC延伸的法鲁海峡入流水增强,更多的高盐法鲁海峡入流水进入格陵兰-冰岛-挪威海(GIN)海域,使GIN海域层结稳定性减弱。1 a后,GIN海域深层对流增强,格陵兰-苏格兰海脊溢流水增加。在GIN海域深层对流达到最强的3 a之后,MOC强度达到最大。整个状态翻转过程完成的时间大约为12 a,THC年代际振荡的整个周期大约是24 a。  相似文献   

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