华南前汛期雨季开始期的降水及环流特征

PRECIPITATION AND CIRCULAION FEATURES DURING LATE-SPKING TO EARLY-SUMMER FLOOD RAIN IN SOUTH CHINA

根据较客观的分析，给出了历年华南与前汛期雨季开始期的划分结果。然后分析了华南雨季开始期的降水特征、雨季开始期前后５００ｈＰａ平均环流的差异以及开始期内各种降水分布型的５００ｈＰａ环流特征。结果表明，华南前汛期雨季开始期前后，５００ｈＰａ平均环流发生明显变化。开始期前，环流场有利于华南升温增湿。开始期后，环流场有利于冷空气向华南输送。在雨季开始期，华南地区的降水具有６种主要分布型，各型具有不同的环流特征。在不同环流形势下水汽输送及冷空气的强弱不同，从而造成不同的降水分布。

Presented is classification of the starting times for late-spring to early summer floedrain in South Chiiia in the light of more objective analysis of long-term dataset,followed by exam-ining the rainfall characteristics at the starting time,the difference in 500hPa mean circulation be-fore and after the start and the circulation features in relation to different rainfall patterns.Evi-dence suggests that the mean circtilation undergoes marked change before and after,i.e.,the pre-start circulation field favors the rise in temperature and humidity while the post-start field pro-motes cold air invasion into South China;at the beginning of the wet sea:on precipitation exhibitssix dominant patterns,each corresponding to a particular circulation pattern;for different circula-tion situations moisture transfer and cold air display discrepancy in vigor,giving rise tto diversityof rainfall.