The Statistical Analysis of the Persistent Heavy Rain in the Last 50 Years over China and Their Backgrounds on the Large Scale Circulation
近50年我国持续性暴雨的统计分析及其大尺度环流背景

Based on the daily precipitation datasets at 730 stations in China from 1951 to 2005,two objective methods are adopted to depict the variations and characteristics of the persistent heavy rain in the last 50 years over China.One is the definition of the local persistent heavy rain,and the other is the definition of the regional persistent heavy rain.The local persistent heavy rain means that sequential heavy rain(the daily precipitation amount exceeds 50 mm) occur at a certain station at least 3 days.The regional persistent heavy rain denotes that the extent in which the total precipitation amount exceeds 100 mm during 3 days at certain region achieves the threshold,as such the extent in which the daily precipitation amount exceeds 25 mm in the same region achieves this threshold.According to the first definition,the results show that the local persistent heavy rain occurs in South China and to the southern parts of the Yangtze River mostly in the last 50 years,and the maximum instances of the local persistent heavy rain occur in June.According to the second definition,the results show that there are four kinds of regional persistent heavy rain primarily,namely the Bohai Sea-western Liaoning Province type,the northern meridional type,the southern front type,and tropical depression type in South China.Three types in the regions of the Yangtze River-Huaihe River,the southern parts of the Yangtze River and South China are included in the southern front type.All types of regional heavy rain searched from the historical observational data are analyzed using the intercomparison method among these cases of the same type.The seasonal and interannual variations of the regional persistent heavy rain are compared and these backgrounds on the large scale circulation of the different types are also studied.