东太平洋暖池及经向风异常在ENSO事件发生、发展过程中的作用

The Impact of Eastern Pacific Warm Pool and Meridional Wind Anomaly on the Genesis and Development of ENSO Event

利用1982~1999期间LDEO海表温度资料和NCEP/NCAR再分析风场资料,分析东太平洋暖池及经向风异常与ENSO事件的可能关系。结果表明,东太平洋暖池气候平均海表温度存在明显的季节变化特征,且与ElNio事件春季发生、夏季发展、秋季达到成熟及冬季衰亡的成长过程非常相似。经向风异常及其散度与ENSO事件密切相关。综合考虑,提出了东太平洋暖池及经向风异常(北风距平及经向风距平散度辐合)对ENSO事件发生、发展作用的概念模型:北风距平爆发通过产生北风吹洋流的作用,将东太平洋暖池暖水由北向南输送至赤道附近,从而有利于Nio3区海表温度上升;几乎与此同时,东太平洋暖池赤道上经向风距平散度辐合不仅能导致暖水在赤道附近堆积,而且辐合的风场对赤道附近的冷上升流有抑制作用,从而有利于Nio3区海表温度的增加,上述增温因素的叠加作用有(不)利于El Nio(La Nia)事件的发生、发展。进一步分析表明,东太平洋暖池及经向风异常仅对El Nio(La Nia)事件发生、发展起促进(抑制)作用而不起决定作用。将东太平洋暖池、经向风异常与西太平洋暖池、西风距平结合起来一并考虑,完善了El Ni^no事件发生、发展机制。最后,初步分析1980、1990年代El Nio事件特性差异的可能原因。

By means of LDEO sea surface temperature （SST） and NCEP/NCAR reanalysis wind from 1982 to 1999, the relations of the eastern Pacific warm pool （EPWP） and abnormal meridional wind to ENSO events are analyzed. The results show that the EPWP climatologic SST has a clear intraseasonal variability, which is very similar to El Nifio event growth process, i. e. , occurring in spring, developing in summer, maturing in autumn and decaying in winter, meanwhile, the meridional wind anomaly and its divergence both are closely related to ENSO events. Based on synchronous considerations, a concept model of the EPWP and the meridional wind anomaly （north wind anomaly and convergence of meridional wind anomaly divergence） affecting the genesis and development of ENSO events is suggested, specifically, the north wind anomaly transports EPWP warm water to the equatorial neighborhood by producing southward ocean current, which, in turn, is instrumental to Nino3 SST increase, almost in the meantime, EPWP equatorial abnormal meridional wind convergence not only causes the warm water from north bank to pile up near the equator but also suppresses the cold upwelling around the equator, which, in turn, are favorable to Nino3 SST increase. Such factors are （not） favourable to genesis and development of （La Nina） El Nino events. Further analysis indicates that EPWP and abnormal meridional wind only play a motivating （suppressing） not decisional role in the genesis and development of El Nino （La Nina） events. Considering EPWP and abnormal meridional wind with inclusion of the western Pacific warm pool and abnormal west wind perfects further genesis mechanism for El Nino events. Finally, the characteristics difference of El Nino events occurring between in the 1980s and in the 1990s is simply examined.