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、北半球热带相对应的气旋环流异常,但是赤道以南气旋的涡度大于赤道以北,且两类厄尔尼诺事件期间涡度中心的位置不同;到高层赤道中东太平洋呈现赤道对称的反气旋环流控制。2)低层热源的西侧出现西风异常,东侧为东风异常,西风异常的强度与范围明显大于东风异常,且东部型西风异常的强度大于中部型;而到高层,纬向风的风向和低层正好相反。3)低层东部型、中部型厄尔尼诺上升运动异常分别位于赤道中东太平洋和赤道中太平洋,下沉运动出现在热源东西两侧及赤道两侧5°N以北、5°S以南的热带地区;东部型到中层上升运动异常强度达到最大,而中部型到高层上升运动异常强度达到最大。4)低层东部型、中部型厄尔尼诺期间位势高度在中东太平洋为负异常,西太平洋为正异常;到高层,整个赤道中东太平洋地区均为位势高度正异常,并且在赤道两侧分别出现位势高度正异常中心,与反气旋环流涡度中心及下沉运动异常中心相对应。5)除西风异常范围大于东风异常,其他特征与赤道非对称热源GILL响应的理论计算模态基本一致。
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 Niño events from 1979 to 2018 are analyzed. It is found the oceanic and atmospheric heating fields during the eastern Pacific and central Pacific El Niño 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 Niño 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 Niño events is greater than that during the central Pacific El Niño 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 Niño 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 Niño events, the intensity of ascending motion anomalies reaches its maximum in the middle level, while for the central Pacific El Niño 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 Niño 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.