Anomalies Of Extreme Precipitation During The Meiyu Period Of JiangHuai Valleys And Its General Circulation Characteristics

Give five characteristic parameters describing extreme precipitation. Based on the extreme precipitation analyses during the Meiyu period, the JiangHuai valleys is divided objectively into north and south regions. Based on that, this paper is particularly concerned with the extreme precipitation anomalies during the MeiYu period of each regions in JiangHuai valleys and its corresponding general circulation anomalies characters. The main conclusions are as followed :(1) The extreme precipitation above rainstorm is mainly centralized in Meiyu period in both of the north and south regions. The anomalies of extreme precipitation in Meiyu period is also maximal. The north regions' extreme precipitation is more centralized than the south region. The peaks of extreme precipitation anomalies in south region of JiangHuai valleys appear in June, but the north region's of JiangHuai valleys is July.(2) The contribution of extreme precipitation to the total precipitation in MeiYu period is very large in both of the north and south regions. The percentage of contribution is about 40%, which that of the south region's is a little higher than that of the north region. So the anomalies of the total precipitation in MeiYu period is mainly caused by the extreme precipitation anomalies.(3) The extreme precipitation is singularly large in the former 1950s and the 1990s, especially the 1990s is the most extreme precipitation periods in nearly 50 years.(4) In the recent 50 years, the extreme precipitation of the north region in JiangHuai valleys shows a faint increase tendency, but that of the south region in JiangHuai valleys is large, especially the increase tendency of the rainstorm frequence is remarkable.(5) In the north region of JiangHuai valleys, the rainstorm, rainstorm days, and the rainstorm concentration ratio in MeiYu period mainly show periodic variations ofquasi-five years and 2-3 years, the rainstorm intensity shows periodic variation of quasi-seven years, the rainstorm contribution ratio shows periodic variation of 6 years and 3 years. In the south region of JiangHuai valleys, all the five extreme precipitation characteristic parameters show periodic variations of quasi-five years and 2-3 years.(6) There exists close relationship between the MeiYu period extreme precipitation in JiangHuai valleys and the anomalies of subtropical summer monsoon, the anomalies of cold air from north. The south region's extreme precipitation anomalies in MeiYu period is closely correlate with Sub-tropical anticyclone. But the correlation of the north region's extreme precipitation anomalies in MeiYu period and the Sub-tropical anticyclone is not obvious.