夏季南亚高压年际变化及其与ENSO的关系

Interannual Variation of Summer South Asia High and Its Association with ENSO

采用1948～2006年NCEP/NCAR月平均再分析资料,探讨了夏季南亚高压年际变化及其与ENSO事件的关系,结果表明:在ENSO事件暖(冷)位相衰减期的夏季,印度洋和亚洲大陆南侧海温为正(负)异常,对应热带印度洋地区低层为上升(下沉)气流而其东侧西太平洋和西侧非洲西部为下沉(上升)气流的异常纬向环流,低层850hPa上从西太平洋到非洲赤道南北两侧依次各存在一异常反气旋-气旋-反气旋(气旋-反气旋-气旋)环流,高层200hPa异常流场的分布与850hPa基本相反,使得南亚高压强度发生显著变化,强度增强(减弱)、面积扩大(缩小)、东西向扩展(收缩)、脊线北侧气压梯度增大(减小)、南侧气压梯度减小(增大)。

Based on the NCEP/NCAR monthly reanalysis data, this paper studies the interannual change of summer South Asia high （SSAH） and its relationship to ENSO events. Results show： During the summer decaying stage of ENSO warm （cool） phase, the positive （negative） SST anomaly in the Indian Ocean and its adjacent ocean regions to the south of Asia causes the zonal abnormal circulation in the tropical region with upward （downward） motion in the Indian Ocean and subsidence （ascent） in the eastern Pacific and western Africa, accompanied by two anomalous anti- cyclones-cyclones-anticyclones （cyclones-anticyclones-cyclones） on the south and north sides of the equator at the lower level （850 hPa）, and anomalous cyclone-anticyclone-cyclone （anticyclone-cyclone-anticyclone） at the upper level （200 hPa） from the western Pacific westward to Africa; the SSAH becomes stronger （weaker） with its area enlarging （reducing）, its east and west borders extending outward （retracting inward）, and pressure-gradient force enhancing （reducing） on the south side/reducing （enhancing） on the north side of high ridge. Based on the above a- nalysis, it is found that the SST anomaly in the Indian Ocean and its adjacent ocean to the south of Asia plays an im- portant role in the interannual abnormality of SSAH during the summer decaying stage of ENSO.