两类厄尔尼诺事件期间热带大气GILL响应分析

分析了1979-2018年两类厄尔尼诺事件期间月平均热带太平洋海面温度(sea surface temperature,SST)异常、对流降水异常、大气环流异常等特征,发现东部型、中部型厄尔尼诺期间海洋及大气加热场并不是赤道对称,赤道以南热源强度大于赤道以北.大气对热源的响应表现在:1)低层在大气热源西侧出现南、北半球...

GILL response analysis of tropical atmosphere during two types of El Nino events

The characteristics of the monthly mean sea surface temperature(SST)anomaly,convective precipitation anomaly,and atmospheric circulation anomaly over the tropical Pacific during the two types of El Nino events from 1979 to 2018 are analyzed.It is found the oceanic and atmospheric heating fields during the eastern Pacific and central Pacific El Nino events are not equatorially symmetrical,and the intensity of heating sources south of the equator is greater than that north of the equator.The responses of the atmosphere to the heating source are as follows.1)In the lower level,there are cyclonic circulation anomalies corresponding to the tropics in the Southern Hemisphere and the Northern Hemisphere in the west of the atmospheric heating source,but the vorticity of cyclones south of the equator is greater than that north of the equator.The locations of vorticity centers during the two type of El Nino events are different.In the upper level,the equatorial central-eastern Pacific presents equatorially symmetric anticyclone circulation control.2)In the lower level,westerly wind anomalies appear in the west of the heating source and easterly wind anomalies in the east.The intensity and range of westerly wind anomalies are obviously greater than those of easterly wind anomalies,and the intensity of westerly wind anomalies during the eastern Pacific El Nino events is greater than that during the central Pacific El Nino events.While in the upper level,the zonal wind blows in the opposite direction compared with the lower level.3)In the lower level,the ascending motion anomalies during the eastern Pacific and central Pacific El Nino events are located in the equatorial central-eastern Pacific and the equatorial central Pacific,respectively,and the descending motion anomalies occur in the east and west of the heating sources and tropical areas to the north of 5°N and to the south of 5°S.For the eastern Pacific El Nino events,the intensity of ascending motion anomalies reaches its maximum in the middle level,while for the central Pacific El Nino events,the intensity reaches its maximum in the upper level.4)In the lower level,the geopotential height shows negative anomaly in the central-eastern Pacific and positive anomaly in the western Pacific during the eastern Pacific and central Pacific El Nino events.In the upper level,the whole equatorial central-eastern Pacific shows positive geopotential height anomaly,and there are positive geopotential height anomaly centers on both sides of the equator,corresponding to the vorticity centers of anticyclone circulations and the descending motion anomaly centers.5)Except for the range of westerly wind anomalies greater than that of the easterly wind anomalies,other corresponding features are basically consistent with the theoretical calculation modes of the equatorially asymmetric heating source GILL response.