热带环流演变与南海季风爆发

Tropical Circulation Evolution and the Onset of the South China Sea Monsoon

利用 1 95 8～ 1 997年的 NCEP/ NCAR再分析资料 ,分析了南、北半球中低纬环流的气候特征 ,并讨论了南海夏季风爆发与大尺度环流的关系。研究发现阿拉伯海经向环流管的上升气流和南半球纬向环流管的上升气流在 5月份同时到达南海 ,经向环流管低层的偏西风和纬向环流管低层的偏南风共同组成西南风 ,于是 5月份西南季风在南海地区首先爆发。此外 ,由于青藏高原地形及各经度海陆分布的影响 ,造成太阳辐射加热不均 ,是热带夏季风爆发的直接原因 。

By using the NCEP/NCAR reanalysis data averaged over 40 years from 1958 to 1997,the climatic characteristics of the tropical circulation in the two Hemispheres are analyzed.The relations between the onset of the South China Sea (SCS) monsoon and the large scale circulation are discussed.It is indicated that the updrafts of the Arabian Sea meridional cell tube and the south zonal cell tube arrive in the SCS at the same time in May,which brings strong convective precipitation.Meanwhile,the westerly of the meridional cell tube and the southerly of the south zonal cell tube combine together to form the southwesterly at the low levels,resulting in the onset of the SCS monsoon.The influences of the Tibetan Plateau and the land sea distribution at different longitudes cause the heating differences of solar radiation,which is the direct cause of the summer monsoon onset,as well as,the cause of the earlier onset in the SCS than in the Indian region.