热带太平洋ENSO事件和印度洋的DIPOLE事件

THE ENSO EVENTS IN THE TROPICAL PACIFIC AND DIPOLE EVENTS IN THE INDIAN OCEAN

在热带太平洋和印度洋的次表层构造了一个气候上的海温距平极值曲面(接近由20℃定义的温跃层曲面),分析了1960～2000年海温距平在这一曲面上演变的统计行为,指出,在这个曲面上分析海温距平的演变要比分析海表温度距平的演变规律更清楚,例如热带太平洋的ENSO事件,海温距平信号在赤道和南北10°左右的纬带附近呈逆时针方向传播,在传播过程中其强度产生变化甚至变号;在热带印度洋的Dipole若在最大海温距平曲面上来分析,则西、东印度洋的海温距平在统计上呈负相关(真正物理意义下的Dipole),而不像用海表温度距平分析那样只在西、东温度距平梯度上呈现年际的正、负号变化.进一步的分析表明,ENSO和Dipole的发展,在统计上呈现出时滞的相互关系,一般赤道东太平洋的海温距平变化在前(一个季度左右),联系这两者变化之间的纽带是赤道太平洋和印度洋的一对反相转动的Walker环流的耦合演变.

A curved surface （close to that of the thermocline as defined by 20℃ ） of climatically maximum sea-temperature anomaly was created at the subsurface of the tropical Pacific and Indian Ocean, based on which the evolving sea-temperature anomaly at this curved surface from 1960 to 2000 was statistically analyzed. It is noted that the evolving sea temperature anomaly at this curved surface can be better analyzed than the evolving sea surface one. For example, during the ENSO event in the tropical Pacific, the sea-temperature anomaly signals propagate counter-clockwise within the range of 10 degree north and south latitudes along the equator, and while moving, the signals change in intensity or even type. If Dipole is used in the tropical Indian Ocean, for analyzing the curved surface of maximum sea-temperature anomaly, the sea-temperature anomalies of the eastern and western Indian Ocean would be negatively correlated in statistical sense （Dipole in real physical sense）, which is unlike the sea surface temperature anomaly based analysis that demonstrates that the inter-annual positive and negative changes only occur on the gradients of the western and eastern temperature anomalies. A further analysis shows that the development of ENSO and Dipole has a time lag features statistically, with the sea-temperature anomaly in the eastern equatorial Pacific changing earlier （by three months or so）. And the linkage between these two changes is a pair of coupled evolving Walker circulations that move reversely in the equatorial Pacific and Indian oceans.