共查询到20条相似文献，搜索用时 15 毫秒
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热带西太平洋大气气候基本态与厄尔尼诺期间赤道附近西风异常 总被引：6，自引：1，他引：6
利用合成分析的方法分析了自1961年以来观测到的8次厄尔尼诺事件中赤道西太平洋地区西风异常与大气气候基本态的关系,结果发现厄尔尼诺年赤道西太平洋地区西风异常具有和大气气候基本态相一致的季节变化特征.利用一个简单热带海-气耦合模式较好地模拟出了观测到的厄尔尼诺年赤道西太平洋地区西风异常的变化特征.对模式结果的分析表明,大气气候基本态对厄尔尼诺年赤道西太平洋地区西风异常的形成起重要作用,它是通过影响大气模式中的加热场来影响赤道西太平洋地区西风异常.大气模式中赤道太平洋地区的加热场的形成具有阶段性和地区性,在厄尔尼诺事件的初始阶段,大气气候基本态是大气模式中的加热场形成的主要因子,而在厄尔尼诺事件的发展和成熟阶段,赤道中东太平洋地区的海表温度异常(SSTA)是加热场形成的主要因子.模式模拟结果对大气气候基本态依赖的敏感性试验说明,在大气模式加热场中含有大气气候基本态的模拟中,沿中西太平洋赤道附近的纬向风异常表现出和观测类似的传播特征. 相似文献
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SST年循环对El Niño事件局地海气过程的影响 总被引：2，自引：0，他引：2
利用Hadley中心逐月海表温度、欧洲中心ERA-40的10 m风场及CMAP降水资料探讨了年循环对热带太平洋El Niño海气相互作用过程的影响。尽管El Niño对应的海表温度异常主要出现在赤道东太平洋,经向上呈南北对称分布,然而其对应的大气响应在El Niño年衰减阶段却有着强的向南移动特征。在El Niño发展年的11月之前,强的西风和降水异常主要出现在赤道中太平洋;在12月份之后,赤道上的西风和降水异常迅速南移至5°S,随后西风一直维持在该位置直至衰亡。同时,西太平洋负降水和反气旋异常向北移动。这种SST异常与其大气响应的经向移动不一致,主要是由热带中太平洋气候态SST的季节性南移导致的。由于对流与海温之间存在非线性关系,即当总SST超过一定的阈值,对流降水才会迅速增强;因此相应的对流响应也随着总海温的南移而南移,风场响应也同时南移。此外,南半球增强的对流会通过经向环流进一步抑制北半球的降水,从而使西太平洋负降水和反气旋异常增强并北移。通过分析有/无年循环的两组数值试验结果验证了上述结论,即有年循环的试验较真实地模拟出了观测中异常西风南移和西北太平洋反气旋异常的出现;无年循环试验尽管能模拟出El Niño年赤道中太平洋的西风异常,但其却没有南北向的移动,西北太平洋的反气旋也没有出现。因此,热带中太平洋气候态暖海温的季节循环对El Niño事件大气响应有着至关重要的作用。 相似文献
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ENSO variability and the eastern tropical Pacific: A review 总被引：3，自引：0，他引：3
El Niño-Southern Oscillation (ENSO) encompasses variability in both the eastern and western tropical Pacific. During the warm phase of ENSO, the eastern tropical Pacific is characterized by equatorial positive sea surface temperature (SST) and negative sea level pressure (SLP) anomalies, while the western tropical Pacific is marked by off-equatorial negative SST and positive SLP anomalies. Corresponding to this distribution are equatorial westerly wind anomalies in the central Pacific and equatorial easterly wind anomalies in the far western Pacific. Occurrence of ENSO has been explained as either a self-sustained, naturally oscillatory mode of the coupled ocean–atmosphere system or a stable mode triggered by stochastic forcing. Whatever the case, ENSO involves the positive ocean–atmosphere feedback hypothesized by Bjerknes. After an El Niño reaches its mature phase, negative feedbacks are required to terminate growth of the mature El Niño anomalies in the central and eastern Pacific. Four requisite negative feedbacks have been proposed: reflected Kelvin waves at the ocean western boundary, a discharge process due to Sverdrup transport, western Pacific wind-forced Kelvin waves, and anomalous zonal advections. These negative feedbacks may work together for terminating El Niño, with their relative importance being time-dependent.ENSO variability is most pronounced along the equator and the coast of Ecuador and Peru. However, the eastern tropical Pacific also includes a warm pool north of the equator where important variability occurs. Seasonally, ocean advection seems to play an important role for SST variations of the eastern Pacific warm pool. Interannual variability in the eastern Pacific warm pool may be largely due to a direct oceanic connection with the ENSO variability at the equator. Variations in temperature, stratification, insolation, and productivity associated with ENSO have implications for phytoplankton productivity and for fish, birds, and other organisms in the region. Long-term changes in ENSO variability may be occurring and are briefly discussed. This paper is part of a comprehensive review of the oceanography of the eastern tropical Pacific. 相似文献
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A possible role of the South China Sea in ENSO cycle 总被引：5，自引：4，他引：5
A data-based hypothesis on the role of the South China Sea (SCS) in ENSO cycle is proposed: during El Nino, there are westerly wind anomaly over the western equatorial Pacific and positive SST anomaly in the eastern equatorial Pacific. Meanwhile anomalous convection moves to the central Pacific with anomalous sinking over Indonesian Archipelago. The latter can cause southerly wind anomaly over the north of South China Sea (NSCS) and makes the NSCS warmer. The warm NSCS can attract the anomalous convection to it in some degree. This attraction is in favor for producing easterly wind anomaly over the western equatorial Pacific, so it helps to form a cycle. 相似文献
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The relative importance of tropical pelagic algal blooms in not yet fully appreciated and the way they are induced not well understood. The tropical Atlantic supports pelagic blooms together equivalent to the North Atlantic spring bloom. These blooms are driven by thermocline tilting, curl of wind stress and eddy upwelling as the ocean responds to intensified basin-scale winds in boreal summer. The dimensions of the Pacific Ocean are such that seasonal thermocline tilting does not occur, and nutrient conditions are such that tilting might not induce bloom, in any case. Divergence at the equator is a separate process that strengthens the Atlantic bloom, is more prominent in the eastern Pacific, and in the Indian Ocean induces a bloom only in the western part of the ocean. Where western jet currents are retroflected from the coast off Somalia and Brazil, eddy upwelling induces prominent blooms. In the eastward flow of the northern equatorial countercurrents, positive wind curl stress induces Ekman pumping and the induction of algal blooms aligned with the currents. Some apparent algal bloom, such as that seen frequently in CZCS images westwards from Senegal, must be due to interference from airborne dust. 相似文献
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为研究赤道太平洋海表二氧化碳分压(pCO2sw)年际变化的机制,基于中科院海洋所宋金明研究团队于2021年发布的中国首套全球海表二氧化碳分压数据产品,使用相关性分析、经验正交函数(empirical orthogonal function, EOF)分析和奇异值分解(singular value decomposition, SVD)等方法,研究了2005～2019年赤道太平洋pCO2sw气候态分布及其去趋势后的年际异常的时空演变特征;结合pCO2sw与多种参数的相关性和厄尔尼诺-南方涛动(El Ni?o-Southern Oscillation, ENSO)过程探讨了赤道中西太平洋pCO2sw年际异常中心形成的原因。研究结果显示,热带太平洋pCO2sw季节变化、年际异常及其EOF第一模态特征向量沿赤道均出现两个中心,其中一个在赤道中西太平洋日界线附近,另一个在赤道中东... 相似文献
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John P. Ryan Paulo S. Polito Peter G. Strutton Francisco P. Chavez 《Progress in Oceanography》2002,55(3-4)
Unusual large-scale accumulations of phytoplankton occurred across 10,000 km of the equatorial Pacific during the 1998 transition from El Niño to La Niña. The forcing and dynamics of these phytoplankton blooms were studied using satellite-based observations of sea surface height, temperature and chlorophyll, and mooring-based observations of winds, hydrography and ocean currents. During the bloom period, the thermocline (nutricline) was anomalously shallow across the equatorial Pacific. The relative importance of processes that enhanced nutrient flux into the euphotic zone differed between the western and eastern regions of the blooms. In the western bloom region, the important vertical processes were turbulent vertical mixing and wind-driven upwelling. In contrast, the important processes in the eastern bloom region were wave-forced shoaling of nutrient source waters directly into the euphotic zone, along-isopycnal upwelling, and wind-driven upwelling. Advection by the Equatorial Undercurrent spread the largest bloom 4500 km east of where it began, and advection by meridional currents of tropical instability waves transported the bloom hundreds of kilometers north and south of the equator. Many processes influenced the intricate development of these massive biological events. Diverse observations and novel analysis methods of this work advance the conceptual framework for understanding the complex dynamics and ecology of the equatorial Pacific. 相似文献
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对一个6层5°×4°网格的全球海洋模式作了一些改进,建立了10层5°×4°网格的全球海洋模式,进行了季节变化数值模拟,积分250a,取得稳定的结果.除了高纬度海洋外,模拟的季节变化与实际观测十分接近.在此基础上,作了热带太平洋海温场对热带季风异常响应的3组敏感性实验,第1组为赤道西太平洋异常西风向东传播的试验;第2组为整个赤道太平洋风应力振荡异常试验;第3组为赤道西太平洋异常西风、东风交替向东传播的敏感性试验.模拟结果表明:(1)第1组风应力敏感性实验结果揭示出,西太平洋西风异常的向东传播的风应力异常可以产生类似厄尔尼诺的赤道东太平洋变暖;(2)第2组试验结果表明,热带太平洋风应力的局地振荡首先在中太平洋东西部激发出海温扰动,然后海温扰动分别向东太平洋和西太平洋传播,从而引起东、西太平洋海温的异常;(3)第3组试验验证风应力QBO可以产生海洋中类似的QBO振荡. 相似文献
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应用TAO(Tropical Atmosphere Ocean project)热带太平洋实测海温和风场资料,分析研究了2010/2011年La Nia事件的变化特征,讨论了此次过程中赤道太平洋次表层异常海温的变化特征及其传播过程,以及上层海温场的异常变化机理。结果表明,2010/2011年的La Nia事件与传统事件不同,是一次明显的中部型La Nia事件(简称CPP La Nia),其爆发过程主要存在两个不同机制的响应过程:一是西太平洋暖池(WPWP)区域次表层异常冷海温通过赤道潜流的作用沿温跃层东传,导致赤道东太平洋上层海洋温度场出现异常降温:二是赤道中东太平洋出现强的距平东风,通过上升流作用,导致冷海温上传影响中太平洋上层异常海温场。前者是导致La Nia事件的必要条件,后者则是形成此次中部型La Nia事件的关键过程。由分析结果还表明,日界线以东赤道太平洋纬向风变化对中西太平洋上层海温场变化有重要影响,是导致此次中部型事件爆发的重要机制。文章进一步分析了此次中部型La Nia事件过程中热带垂直环流的变化,结果表明经向和纬向大气环流都表现出明显的异常。 相似文献
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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
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本文使用SODA(simple ocean data assimilation)海洋同化资料,系统分析了厄尔尼诺-南方涛动(El Ni?o-Southern Oscillation,ENSO)循环中冷暖位相期间热带太平洋上层海洋环流的演变规律,探讨了形成海洋环流异常的新机制。结果表明,在厄尔尼诺成熟期,热带中东太平洋赤道潜流最弱,赤道两侧出现反气旋性环流异常;西太平洋赤道外热带海域出现气旋性环流异常,该区南、北赤道流、棉兰老流、黑潮、新几内亚沿岸潜流及南赤道逆流增强;北赤道逆流区出现异常气旋性环流串,北赤道逆流接近正常。在厄尔尼诺衰退期和拉尼娜发展期,热带中西太平洋赤道潜流达到极强,赤道两侧出现气旋性环流异常;西太平洋赤道外热带海域异常环流减弱,该处主要流场的强度减弱或处于正常状态;北赤道逆流区反转为异常西向流。结果表明, ENSO循环期间的上层海洋环流异常受到热带太平洋温跃层深度异常产生的压强梯度力异常调控,在赤道外热带海洋温跃层深度异常和科里奥利力共同作用产生大尺度海洋环流异常,而在赤道海域,海洋温跃层深度异常和Gill效应造成赤道潜流异常以及关于赤道对称的气旋或反气旋性环流异常。 相似文献
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The present study investigates the way an ocean filled with homogeneous warm water is cooled by prescribing cold water formation inside the ocean in the southern part of the southern hemisphere using multi-level numerical models. Cooling of the whole ocean starts with introduction of the cold water from the formation region into the deepest part of the ocean in the equatorial and eastern boundary regions by Kelvin wave-type density currents. The cold water along the eastern boundary extends westward as a Rossby wave-type density current setting up an interior poleward flow, and hits the western boundary to form a northward flowing boundary current in the northern hemisphere. Only then does the western boundary current cross the equator. Cooling of the rest of the ocean basin is accomplished by upwellings in the interior and also along the coasts. During this introduction the cold water is mixed with surrounding warm waters, and the thermocline, rather than forming just below the top level where heating is imposed, tends to spread down to deeper depths. Consequently the circulation at a steady state has a significant vertical structure such that the maximum upwelling in the interior occurs in the mid-depths, and only the deeper part of the deep ocean yields the Stommel and Arons circulation pattern. In the equatorial region higher vertical mode motions dominate, and a set of alternating zonal jets forms along the equator. 相似文献
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James R. Christian Ragu Murtugudde 《Deep Sea Research Part II: Topical Studies in Oceanography》2003,50(22-26):2947
A three-dimensional ocean biogeochemical model of the tropical Atlantic Ocean was run for more than half a century (1949–2000) in order to characterize the ocean biogeochemical response to variable forcing over this period. The seasonal cycle in the equatorial upwelling zone agrees reasonably well with observations and other published simulations but underestimates phytoplankton biomass under strong upwelling conditions. Away from the equator, modelled nutrient flux and biological production are maximal in each hemisphere's winter season, and appear to be proximately forced by evaporative cooling and wind stirring rather than by Ekman upwelling. The fraction of the total variance associated with the seasonal cycle is considerably smaller for modelled biogeochemical fields than for sea-surface temperature over this long simulation, and much of the biogeochemical variance is associated with interdecadal changes. The model results suggest that the tropical Atlantic became more productive following the Pacific climate shift of 1976 and remained so until about 1989. Summer surface nitrate concentrations during the 1990s were lower than those in the 1980s. The relationship between the equatorial and off-equatorial regimes may have changed following the 1976 event, with equatorial variability dominating the basin-wide variance patterns after 1976. 相似文献
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G. Reverdin P. Delcluse C. Lvy P. Andrich A. Morlire J.M. Verstraete 《Progress in Oceanography》1991,27(3-4)
Isotherm vertical displacements within the thermocline and surface currents were investigated in the tropical Atlantic Ocean from 12°N to 12°S in 1982–1984, the period of the FOCAL-SEQUAL experiment. The study is based on a numerical simulation of an oceanic general circulation model tuned for the study of the equatorial regions, and on the analysis of the large scale thermocline displacements and currents using observed temperature profiles. Ground truth is provided by temperature and currents from moorings, records from inverted echo sounders and tide gauges as well as from drifting buoys. Comparison of the analysis with the ground truth shows that some important aspects of the low frequency variability are “captured” by the analysis when the data base is large enough.On large scales, the simulation generally resembles the analysis. Along the equator, the upwelling signal propagates eastward. The seasonal set-up of the westerly winds is associated with large westward currents, and a following overshoot of the zonal dynamic topography. Otherwise, the zonal dynamic topography is in near-equilibrium with the winds. The North Equatorial Countercurrent is portrayed comparably in the analysis and the simulation, where, after starting as a narrow eastward flow near 5°N, it extends northward through the northern summer. Interannual variations are found both in the analysis and the simulation. In particular, the thermocline flattened early in 1984.However, the simulation differs in significant respects from the real world: the equatorial undercurrent is too weak in the east and the model produces too much variability south of the equator. The 20°C isotherm is too shallow above the core of the thermocline, and the surface layer is too stratified. Because the surface layer is where the wind stress, main forcing of the model is applied, major effort will have to be devoted to parameterizing the near-surface downward mixing of momentum, heat and fresh water. 相似文献
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利用最近20 a的大气海洋资料,分析了厄尔尼诺事件与赤道太平洋西风异常以及赤道太平洋次表层海温之间的关系.结果表明,赤道西太平洋(5°S～5°N,120°～160°E)和赤道中东太平洋(5°S～5°N,160°E～160°W)西风异常都存在着与厄尔尼诺周期一致的年际变化,但前者还包含有显著的2～3个月季节内振荡.赤道西太平洋次表层冷暖水东移也呈现年和年际时间尺度的振荡周期.在厄尔尼诺发生前,赤道西太平洋次表层海水出现持续性增暖,赤道西太平洋西风异常频率加快,强度增强.随后赤道中太平洋(160°E～160°W)出现持续性(3个月以上)强西风异常(即西风爆发),并进一步向东扩展,同时次表层暖水沿着赤道波导东移到赤道东太平洋混合层,导致赤道东太平洋海表大面积异常增暖,形成一次厄尔尼诺现象.最后,模式模拟了1980～1984年赤道太平洋海温的变化,进一步证实了赤道纬向西风异常对暖水东移起着重要的作用. 相似文献
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印度洋上层海气相互作用对印度洋和太平洋气候系统有重要影响。目前针对印度洋气候态环流特征已有较为全面的研究,但针对印度洋环流的年际变化及其季节性差异的特征分析和具体作用机制,仍缺乏深入的研究。本文利用1979—2007年Simple Ocean Data Assimilation(SODA)再分析资料研究了赤道印度洋表层辐合辐散的年际变异及其季节依赖性。结果表明,以赤道为中心,印度洋上层异常海流,在经向上形成显著的辐合(辐散)现象,究其原因主要是赤道纬向风异常形成的Ekman流所导致。进一步分析表明,热带印度洋异常纬向风的成因与太平洋-印度洋的热力强迫过程作用有关,并且不同的热力强迫过程呈现出显著的季节差异性。此热力强迫过程,具体可分为3种类型:第一类是太平洋纬向海表热力差异的遥强迫作用,主要发生在冬末春初,热带太平洋的纬向热力差异通过调节Walker环流,在印度洋激发出一个异常的次级环流,对应的大气低层形成纬向风异常;第二类是东-西印度洋海表热力差异的局地强迫作用导致的局地环流,使赤道印度洋上空形成纬向风异常,此过程在春末夏初较为显著;第三类是太平洋-印度洋热力差协同作用的结果,使赤道印度洋盛行异常的纬向风,此过程在秋季起主导作用。 相似文献
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Using a gridded array for real-time geostrophic oceanography(Argo) program float dataset, the features of upperocean salinity stratification in the tropical Pacific Ocean are studied. The salinity component of the squared Brunt-V?is?l? frequency N~2( N_S~2) is used to represent salinity stratification. Layer-max N_S~2(LMN), defined as the N_S~2 maximum over the upper 300 m depth, and halocline depth(HD), defined as the depth where the N_S~2 maximum is located, are used to specifically describe the intensity of salinity stratification. Salinity stratification in the Topical Pacific Ocean has both spatial and temporal variability. Over the western and eastern equatorial Pacific, the LMN has a large magnitude with a shallow HD, and both have completely opposite distributions outside of the equatorial region. An obvious seasonal cycle in the LMN occurs in the north side of eastern equatorial Pacific and freshwater flux forcing dominates the seasonal variations, followed by subsurface forcing.At the eastern edge of the western Pacific warm pool around the dateline, significant interannual variation of salinity stratification occurs and is closely related to the El Ni?o Southern Oscillation event. When an El Ni?o event occurs, the precipitation anomaly freshens sea surface and the thermocline shoaling induced by the westerly wind anomaly lifts salty water upward, together contribute to the positive salinity stratification anomaly over the eastern edge of the warm pool. The interannual variations in ocean stratification can slightly affect the propagation of first baroclinic gravity waves. 相似文献