两类ENSO事件赤道太平洋次表层海温异常的演变特征

Evolution characteristics of the subsurface temperature anomaly in the equatorial Pacific to two pattern ENSO events

基于美国马里兰大学提供的海洋同化(SODA)月平均资料,用个例和合成分析方法,剖析了两类ENSO事件赤道太平洋海温异常演变特征。结果指出,东部型ENSO事件的初始海温异常源来自赤道西太平洋次表层,海温异常中心沿气候温跃层向东向上传送,至赤道东太平洋表层形成ENSO事件。东部型ENSO冷暖事件互为初始场,在形成某一位相的ENSO事件的过程中也同时为相反位相的ENSO事件准备条件。中部型ENSO事件的初始海温异常源出现在赤道中太平洋次表层,海温异常中心沿气候温跃层向东向上传送至赤道中东太平洋表层形成ENSO事件。中部型ENSO事件多在前次事件减弱中断后出现。

The observed facts and the researched results show that the ENSO events in the ocean have two different patterns： the Eastern pattern and the Central pattern, and the variation of the ENSO has important relations to the Central Pattern. To understand the mechanism of the ENSO cycle, based on the SODA data set by the University of Maryland, the evolution characteristics of the subsurface temperature anomaly in the equatorial Pacific of the two pattern ENSO events are analyzed by the case study and the composite method. The results show that, the initial source of the subsurface temperature anomaly in the Eastern pattern ENSO events comes from the western Pacific, and that of the Central pattern ENSO events occurs in the central Pacific, then the center of the subsurface temperature anomaly moves upward and eastward along the climate thermocline driven by air-sea interaction, and theENSO events happen when they reach the sea surface of the eastern Pacific. The results also show that, due to the warm and cold phase of the Eastern pattern ENSO events, one phase is the initial field of another, while one phase of ENSO events forms, another phase will follow meantime, thereby the ENSO cycle completes. But the Central pattem ENSO events develop under the weak ENSO state with long-time succession, and they disturb the regularity of the ENSO cycle and may cause the break of the ENSO cycle.