中文摘要：

利用1998—2006年共9年4—6月的TRMM卫星2A25资料,选取南海中北部地区（110～120°E,10～20°N）为关键区域,分别对比分析了夏季风爆发前后南海地区降水特性的差异。结果表明：⑴南海夏季风爆发后,对流和层云的降水比面积均有明显增加,且层云的降水比面积增加幅度更大。夏季风爆发后的对流降水比降水量减小,而层云降水比降水量增加。⑵南海夏季风爆发后,强降水所占的比重比爆发前有所增加,而弱降水所占比重减小。⑶南海夏季风的爆发使南海地区降水场的水平分布发生变化,降水中心发生偏移。⑷夏季风爆发后,南海地区降水的垂直结构也相应发生变化。降水率随高度的变化率加大,释放出更多的潜热,并通过正反馈机制使得对流降水变得更加深厚,层云降水的冻结层高度也得到一定的提升。

英文摘要：

Choosing the central and northern part of South China Sea（110～120 °E,10～20 °N） as the area of research and the 27th pentad as the occurrence time of the South China Sea（SCS） monsoon onset,the temporal and spatial variations of precipitation for the area during the SCS monsoon onset period were analyzed by using precipitation radar data derived from the Tropical Rainfall Measuring Mission（TRMM） satellite between April and June over the nine years from 1998 to 2006.The conclusions are as follows.（1） The specific area of both convective and stratiform rain increased significantly after the monsoon onset,with the latter having a larger magnitude.The specific rainfall in convective rain decreased while that in stratiform rain increased.（2） Results also show significant increases of heavy rain and decreases of weak rain after the monsoon onset.（3） The horizontal distribution of rainfall over the SCS and the mean precipitation profiles changed after the monsoon onset.（4） During the monsoon onset period,the variability of rainrate increased more significantly with the altitude,which led to more latent heat emission,and the convective rain also became deeper.The bright band altitude of stratiform became higher at the same time.