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1.
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
2.
Statistical analysis about ENSO index represented by SSTA in Nino3 with several datasets shows obviously decadal changes in the dominant period and amplitude of ENSO. Correlation analysis about the composite El Nino events before and after 1976 exhibits obviously decadal changes in the propagation and intensity of the oceanic anomaly related to the variation of SSTA in Nino3. In the composite El Nino before 1976, the coherence is relatively weak between the oceanic anomaly in the tropical Pacific and the SSTA in the Nino3 region; the area with significant correlation coefficient is relatively small; the oceanic anomaly related to Nino3 SSTA propagates faster. The above changes correspond well to the decadal changes of ENSO cycles. Some preliminary explanations are given based on the analysis of the decadal changes in the thermocline. The tropical thermocline shoals after 1976 except in the equatorial far East Pacific and the inclination of the tropical thermocline deep west and shallow east patterns wea 相似文献
3.
A class of E1 Niйo atmospheric physics oscillation model is considered. The E1 Niйo atmospheric physics oscillation is an abnormal phenomenon involved in the tropical Pacific ocean-atmosphere interactions. The conceptual oscillator model should consider the variations of both the eastern and western Pacific anomaly patterns. An E1 Niйo atmospheric physics model is proposed using a method for the variational iteration theory. Using the variational iteration method, the approximate expansions of the solution of corresponding problem are constructed. That is, firstly, introducing a set of functional and accounting their variationals, the Lagrange multiplicators are counted, and then the variational iteration is defined, finally, the approximate solution is obtained. From approximate expansions of the solution, the zonal sea surface temperature anomaly in the equatorial eastern Pacific and the thermocline depth anomaly of the sea-air oscillation for E1 Niйo atmospheric physics model can be analyzed. E1 Niйo is a very complicated natural phenomenon. Hence basic models need to be reduced for the sea-air oscillator and are solved. The variational iteration is a simple and valid approximate method. 相似文献
4.
MENGXiangfeng WUDexing HURuijin 《海洋学报(英文版)》2004,23(3):415-426
Statistical analysis about ENSO index represented by SSTA in Nino3 with several datasets shows obviously decadal changes in the dominant period and amplitude of ENSO. Correlation analysis about the composite E1 Nino events before and after 1976 exhibits obviously decadal changes in the propagation and intensity of the oceanic anomaly related to the variation of SSTA in Nino3. In the composite E1 Nino before 1976, the coherence is relatively weak between the oceanic anomaly in the tropical Pacific and the SSTA in the Nino3 region; the area with significant correlation coefficient is relatively small; the oceanic anomaly related to Nino3 SSTA propagates faster. The above changes correspond well to the decadal changes of ENSO cycles. Some preliminary explanations are given based on the analysis of the decadal changes in the thermocline. The tropical thermocline shoals after 1976 except in the equatorial far East Pacific and the inclination of the tropical thermocline deep west and shallow east patterns weakens. Much of the oceanic anomaly from the relative higher latitude contributes to the slow propagation of the oceanic anomaly in the North Pacific. The air-sea coupling in the tropical Pacific intensifies after 1976 corresponding to decadai change of the ENSO amplitude. Decadai adjustment of the thermocline may have influenced the propagation and intensity of the oceanic anomaly related to the ENSO and intensity of air-sea interaction in the tropical Pacific, and changed the dominant period of ENSO and its amplitude. 相似文献
5.
Large-scale water transport is one of the key factors that affect sea surface temperature anomaly(SSTA) in the eastern equatorial Pacific(EEP).The relationship between the wave transport in the tropical Pacific and the SSTA in the EEP is examined by different methods,including band-pass filtering,period analysis,correlation analysis,significant analysis,and empirical orthogonal function(EOF) analysis.We have found that the eastward shift of the wave transport anomaly in the tropical Pacific,with a period of 2 a and enhancing the transport of warm waters from the western Pacific warm pool,precedes the increase of sea surface temperature(SST) in the EEP.The wave transport and the SSTA in the EEP have a maximum correlation of 0.65 with a time-lag of 6 months(transport variation precedes the temperature).The major periods(3.7 a and 2.45 a) of the wave transport variability,as revealed by the EOF analysis,appear to be consistent with the SSTA oscillation cycle in the EEP.Based on the first occurrence of a significant SSTA in the Ni?o 3 region(5°S–5°N,90°–150°W),two types of warm events are defined.The wave transport anomalies in two types present predominantly the west anomaly in the tropical Pacific,it is that the wave transport continues transport warm water from west to east before the onset of the warm event.The impact of wave-induced water transport on the SSTA in the EEP is confirmed by the heat flux of the wave transport.The wave transport exerts significant effect on the SSTA variability in the EEP and thus is not neglectable in the further studies. 相似文献
6.
The relationship between SST in the Eastern Pacific and equatorial wind fields in the Western Pacific is analysed by using COADS.It is pointed out that in the year before El Nino , the continuative easterly anomalies and the meridional anomalies blowing from the Equator to both sides in the Equatorial Western Pacific cause the sea level in the Western Pacific to rise higher than in the Eastern Pacific and the sea level at the Equator to drop lower than on both sides of it. In the El Nino year, the westerly anomalies and the meridional anomalies blowing from both sides to the Equator bring warm water to build up around the Equator. At such times Kelvin waves are generated and they play an important role in raising SST in the Eastern Pacific. It is also emphatically pointed out that in the El Nino year the two maxima of the equatorial westerly anomalies, the two cross-equatorial air flows from the Northern Hemisphere to the Southern one and the two maxima of the near-equatorial tropical cyclones in the Eq 相似文献
7.
The results of the tropical Pacific response to the sudden onset of the equatorial wind stress anomalies are discussed. The ocean model is a barotropic, non-linearized one that includes reduced-gravity and an equation for the temperature of the ocean mixed-layer. The experiments are based on a state of equilibrium reached through a long running under the action of annual mean wind stress. There are two kinds of westward wind intensity regions: the whole tropical Pacific and the western tropical Pacific, which are all between latitude 6. 8癗 and 6. 8癝.In these cases, the results show that the positive sea surface temperature (SST) anomalies in the Eastern Pacific and the negative SST anomalies in the Western Pacific are produced, and the positive SST anomalies propagate eastward, just as those observed during the actual El Nino phenomena. The propagations of the Kelvin waves and Rossby waves in the ocean are discussed.Another experiment is also carried out in simulating the process of the decay of El Ni 相似文献
8.
The El Ni?o Southern Oscillation(ENSO) is a natural phenomenon that relates to the fluctuation of temperatures over the Pacific Ocean. The ENSO significantly affects the ocean dynamics including upwelling event and coastal front. A recent study discovered the seasonal upwelling in the east coast of Peninsular Malaysia(ECPM), which is significant to the fishery industry in this region. Thus, it is vital to have a better understanding of the influence of ENSO towards the coastal upwelling and thermal front in the ECPM. The sea surface temperature(SST) data achieved from moderate resolution imaging spectroradiometer(MODIS) aboard Aqua satellite are used in this study to observe the SST changes from 2005 to 2015. However, due to cloud cover issue, a reconstruction of data set is applied to MODIS data using the data interpolating empirical orthogonal function(DINEOF) to fill in the missing gap in the dataset based on spatial and temporal available data. Besides, a wavelet transformation analysis is done to determine the temperature fluctuation throughout the time series. The DINEOF results show the coastal upwelling in the ECPM develops in July and reaches its peak in August with a clear cold water patch off the coast. There is also a significant change of SST distribution during the El Ni?o years which weaken the coastal upwelling event along the ECPM. The wavelet transformation analysis shows the highest temperature fluctuation is in 2009–2010 which indicates the strongest El Ni?o throughout the time period. It is suggested that the El Ni?o is favourable for the stratification in water column thus it is weakening the upwelling and thermal frontal zone formation in ECPM waters. 相似文献
9.
Positive SST anomalies usually appear in remote ocean such as the China seas during an ENSO event.By analyzing the monthly data of HadISST from 1950 to 2007,it shows that the interannual component of SST anomalies peak approximately 10 months after SST anomalies peak in the eastern equatorial Pacific.As the ENSO event progresses,the positive SST anomalies spread throughout the China seas and eastward along the Kuroshio extension.Atmospheric reanalysis data demonstrate that changes in the net surface heat flux entering into the China seas are responsible for the SST variability.During El Ni o,the western north Pacific anticyclone is generated,with anomalous southwester lies prevailing along the East Asian coast.This anticyclone reduces the mean surface wind speed which decreases the surface heat flux and then increases the SST.The delays between the developing of this anticyclone and the south Indian Ocean anticyclone with approximately 3–6 months cause the 2–3 months lag of the surface heat flux between the China seas and the Indian Ocean.The northwestern Pacific anticyclone is the key process bridging the warming in the eastern equatorial Pacific and that in the China seas. 相似文献
10.
Lin Xuechun 《海洋学报(英文版)》1990,9(4):527-538
In this paper, the response of the atmospheric 3-5 year cycle to Northern Pacific SST is discussed, The results are as follows:1. From the simultaneous temporal correlations between the Equatorial Eastern Pacific SST, the westerly dirft area's SST and the Northern Pacific SST at all gridpoints, we find that there are three correlative regions in the Northern Pacific SST field, they are the westerly drift area, the Equatorial Eastern Pacific and the Alaska Bay , and their structures are very similar to the PNA pattern in the atmosphere The difference PTI between the Equatorial Eastern Pacific SST anomaly and the westerly drift area's SST anomaly can indicate the change of the PNA pattern of the Northern Pacific SST anomaly. It can represent SST change of 65 % areas over the Northern Pacific and can keep watch on El Nino and un-El Nino.2. Simultaneous temporal correlative field between PTI and filtered 500hPa (there is 3-5 year cycle only ) of the Northern Hemisphere presents clear PNA structure. The resp 相似文献
11.
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
12.
2002/03年厄尔尼诺事件,是暖海温中心出现在赤道中太平洋区域的一种新型厄尔尼诺,即中太平洋型厄尔尼诺。本文基于一个厄尔尼诺预测系统,利用三组回报试验来详细区分海洋表层和次表层初始状态对预报2002/03年中太平洋型厄尔尼诺事件的作用,并由此来探寻对预报厄尔尼诺演变过程最有利的初始条件。回报试验分为三组:(1)仅同化海表温度观测(sea surface temperature;简称SST)来优化海洋表层初始状态(Assim_SST);(2)仅同化海表高度观测(sea level;简称SL)来更新海洋次表层初始状态(Assim_SL);(3)同时同化SST和SL观测来一起更新海洋表层和次表层初始状态(Assim_SST+SL)。回报试验结果表明,三种不同的初始条件都可以使模式提前一年成功地预报2002/03年厄尔尼诺事件,并且"Assim_SST+SL"回报试验的效果最好。三组回报试验结果间的对比表明:海洋表层和次表层初始状态均对成功地预报该事件有重要作用,但其作用分别集中在事件发展的不同阶段。精确的海洋表层初始状态更容易激发模式预报出一次厄尔尼诺事件,而更合理的海洋次表层初始状态则能有效地提高厄尔尼诺事件预报的强度。 相似文献
13.
14.
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
15.
本文利用HYCOM （Hybrid Coordinate Ocean Model）再分析数据对北赤道流（NEC）、棉兰老流（MC）以及黑潮（KC）所构成的NMK环流系统在2015/2016年超强厄尔尼诺事件期间的变化特征及其影响机制进行了研究，并与其他厄尔尼诺期间的变化特征进行了对比。结果表明，在2015/2016年超强厄尔尼诺事件期间，NEC和MC输运均显著增强，最大值分别达到66 Sv （1 Sv=106 m3/s）和49.4 Sv，北赤道流分叉纬度最北可达16°N，KC输运没有明显增强。NMK环流系统的年际变化主要与此次厄尔尼诺事件期间热带西北太平洋15°N以南、160°E以西海域出现的气旋式环流异常有关。该环流异常出现自厄尔尼诺事件的前期阶段，并于爆发阶段达到顶峰，主要是由15°N以南区域出现的强西风异常所引起的。进一步分析表明，此次厄尔尼诺事件期间NEC、MC输运和NBL的平均值均大于1992— 2014年间所有厄尔尼诺事件的平均状况，但与1997/1998年超强厄尔尼诺事件期间的平均值相近。 相似文献
16.
为研究在厄尔尼诺现象演变过程中海气相互作用的性态特征,该文再次应用拓展伴随模态分析于简易海洋同化数据(SODA data).结果表明:通过相互作用形成厄尔尼诺/拉尼娜现象的海洋与大气具有明显不同的性态,气候系统中并不存在一个相对独立的热带太平洋大气变异,但是的确存在一个相对独立的热带太平洋海洋变异;原因在于大气是底部界面受热而海洋是顶部界面受热,从而导致前者具有较后者强烈得多的斜压不稳定性和能够覆盖大部分热带太平洋的赤道辐合带; 再次证实了正是直接来自中纬度海域的西风爆发和海面风辐聚导致赤道太平洋上层海水的东向移动和经向辐聚造就了厄尔尼诺所特有的增温信号. 相似文献
17.
利用一个斜压两层海洋模式解析地研究了赤道东、西太平洋对信风张弛的响应特征.研究表明:当赤道上空偏东信风张弛或转为西风时,由于打破了海洋原来的平衡关系,结果在赤道东、西太平洋的温跃层附近产生了扰动并开始传播.西太平洋温跃层附近的扰动向东传播的速度远大于东太平洋扰动向西传播的速度,而且与东太平洋温跃层扰动向西传播的狭窄范围和小振幅相比,西太平洋温跃层扰动向东传播的范围和强度均很大.这与最近几次强厄尔尼诺增暖事件暖水从赤道西太平洋向赤道中、东太平洋的迅速传播特征是一致的. 相似文献
18.
为研究东部型和中部型两类厄尔尼诺(El Ni?o)事件与中国近海海表温度(sea surface temperature,SST)变化间的联系,基于中国科学院大气物理研究所连续80年(1940—2019年)的SST再分析数据,采用EOF分解、合成分析等方法做了初步分析,发现中国近海及毗邻海域近80年SST变化与全球变暖密切相关。并且两类El Ni?o事件对中国近海SST变化的影响存在显著差异。东部型El Ni?o事件发展过程中,中国近海及毗邻海域SST在发展年主要为负异常,衰退期为正异常;中部型ElNi?o事件发展过程中, SST变化区域差异大,发展年日本附近海域为正异常, 28°N以南为弱的负异常。两类El Ni?o事件引发西太平洋风场反气旋涡的时间、位置与强度等的不同,是造成中国近海风场与海表温度异常(sea surface temperature anomaly, SSTA)差异的主要原因。 相似文献
19.
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