南海夏季风爆发的EOF分析

本文利用1983～1992年的NCEP资料．对南海夏季风爆发做经验正交函数分解，分析了主要模态的时空变换特征。结果表明：太阳辐射北移，是南海夏季风爆发的最重要的因素。南海夏季风爆发前后，在典型季风区850hPa上东西风有一次重大调整。南半球中高纬西风带槽脊振幅的增强和北半球副热带系统经向环流的加大是南海夏季风爆发的重要原因。西太平洋副高的迅速减弱东撤，导致南海夏季风的爆发。

EOF EXPANSION OF SUMMER MONSOON ONSET OVER THE SOUTH CHINA SEA

Using the NECP data from 1983 to 1992, the spatial and the temporal variation characteristics of main models of the summer monsoon onset process in the South China Sea(SCS) have been studied by the method of EOF expansion. It has been found that the northward shift of solar radiation is the most important factor of the monsoon onset. There is very evident adjustment of wind field at 850 hPa associated with the Asian summer monsoon onset in typical monsoon area. Amplification of westerlies trough and ridge in Southern Hemisphere mid-high latitude and augmentation of subtropical system meridional circulation in Northern Hemisphere are significant role of the Asian summer monsoon onset. The western Pacific Ocean high pressure abated rapidly and retreated east about 5 days before the monsoon erupts, which caused the southwest monsoon onset.