近55年广东“龙舟水”异常特征及成因分析

ANALYSIS ON CHARACTERISTICS AND ABNORMAL CAUSES OF DRAGON-BOAT PRECIPITATION IN GUANGDONG IN THE PAST 55 YEARS

利用1961—2015年广东86个气象观测站的日降水资料和NCEP/NCAR逐日再分析资料(分辨率为1°×1°),采用EOF分析、相关分析和合成分析等方法研究了广东"龙舟水"的时空分布特征和异常成因。结果表明,广东"龙舟水"最主要的分布型是除雷州半岛外具有"空间一致型"分布。广东"龙舟水"的变化趋势不明显,但具有显著的年际和年代际变化。在"龙舟水"期间(5月21日—6月20日),降水异常多年的对流层高层副热带西风急流偏强;中层极涡明显偏强,东亚大槽北段减弱、南段加强,西太平洋副热带高压偏弱、偏东;低层南海北部-华南的偏南气流偏强。"龙舟水"异常少年则相反。

Using the daily precipitation data of 86 meteorological observational stations during 1961--2015 in Guangdong and the NCEP/NCAR daily reanalysis data（resolution 1 ° × 1°）, the spatial temporal features and cause of Dragon-boat precipitation in Guangdong are studied by using statistical diagnostic methods, such as EOF analyses,correlation analysis and composite analysis. The results show that the main distribution pattern of Dragon-boat precipitation is consistent. In Guangdong, except the Leizhou Peninsula, the change tendency of Dragon-boat precipitation in Guangdong in the last 55 years is not obvious, and there are significant inter-annual and inter-decadal variations of Dragon-boat precipitation. During more Dragon-boat precipitation （May 21 to June 20） in Guangdong, in the upper troposphere, a subtropical westerly jet stream is stronger compared with the mean. In mid troposphere, the polar vortex is stronger, and an East Asian trough is weaker in the northern section and stronger in the southern section. Northwest Pacific subtropical high is weaker and shifts eastwards. Southerly air stream from northern South China Sea to south China is stronger in lower troposphere, but is the opposite in the years of less Dragon-boat precipitation in Guangdong.