华南前汛期持续暴雨环流特征分析

Analysis on circulation characters of persistent heavy rain in the first flood season in South China

利用华南279站日雨量及NCEP再分析等资料,分析1961—2008年前汛期82次持续暴雨过程。结果表明:持续暴雨以3～5 d为主,多出现在5月末到6月,年均1.71次。按500 hPa华南附近主要低值系统划分,前汛期持续暴雨分为东亚槽底型(EAT)、南方低槽型(TSC)、孟加拉湾槽前型(TBB)、西风波动型(FWB)和热带风暴型(LTS)五类。EAT型出现次数最多,LTS型最少;各型平均持续时间,TBB型最长,FWB型最短。各型暴雨过程平均500 hPa西太平洋副热带高压均较强,华南或直接受低值系统或主要受西南气流影响。各型主要降水中心均在广东,但TBB型在福建也出现较强降雨中心。各型持续暴雨期间在江淮等地受850 hPa相对冷区与冷平流控制,而华南主要受暖平流影响;影响华南地区的850 hPa暖平流,TSC型最强,FWB型、TBB型次之,EAT型、LTS型最弱。各型暴雨期间,华南均为整层积分水汽辐合区,其中,LTS型、TSC型与TBB型水汽辐合较明显;华南沿海可降水量(PW)中心值从大到小依次是,LTS型、EAT型、TBB型、FWB型与TSC型。

Based on the daily precipitation data from 279 stations in South China and NCEP daily reanalysis datasets, this paper analyzed 82 persistent heavy rain events in the first flood season of South China from 1961 to 2008. The results indicate that the persistent heavy rain last- ed for 3-5 days predominates all the events, occurred mainly from the end of May to June, and happened 1.71 times annually. According to main low pressure systems at 500 hPa around South China, 82 persistent heavy rain events in the first flood season are divided into five types, namely the East Asia bottom-trough-type （EAT）, the low trough over South China-type （TSC）, the prior-trough over the Bay of Bengal-type （TBB）, the fluctuation in westerly belt-type （FWB）, and landing tropical storms-type （LTS） respectively. Among them, the occurrence frequen- cy of EAT is the most but that of LTS is the least; the mean duration of TBB is the longest but that of FWB is the shortest. The mean intensity of subtropical high over the Western Pacific is high in all types, and South China is influenced either by low vortex or trough directly or by south- west airflow mainly. The main rainfall centers of all types drop in Guangdong Province, but an obvious rainfall center of TBB appears in Fujian Province also. The duration of all types is controlled by both relative cold sector and cold advection in the Yangtze-Huaihe River region at 850 hPa, but is mainly influenced by warm advection in the area of South China. For warm advection at 850 hPa influencing South China, TSC is the strongest, followed by FWB and TBB, and EAT and LTB are the weakest. In all types water vapor convergence zone integrated from surface to 300 hPa is situated in South China, and among them water vapor convergence zone is obvious in LST, TSC and TBB. The order of the large pre- cipitable water （PW） center values in the coastal areas of South China from big to small is LTS, EAT, TBB, FWB and TSC.