近50年我国持续性暴雨的统计分析及其大尺度环流背景

根据1951～2005年中国大陆730个台站的逐日降水资料和持续性暴雨发生的特点, 提出了采用局地持续性暴雨和区域持续性暴雨事件的两种客观定义来描述和统计近50年我国持续性暴雨时空特征及其变化。单站逐日降水量连续三天或三天以上均大于等于50 mm为一次局地持续性暴雨；区域持续性暴雨指在一定区域范围内连续三天降水量总和大于等于100 mm且每天降水量大于等于25 mm的面积超过某一阈值 (详细定义见正文）。根据局地持续性暴雨定义, 指出: 近50年中国局地持续性暴雨事件主要发生在江南和华南地区, 发生季节以6月为最多；根据区域持续性暴雨定义, 统计分析了四类典型的区域持续性暴雨类型, 分别是: 渤海辽西型、北方经向型、南方锋面型和华南低压型。其中南方锋面型又可根据持续性暴雨易发生的地理位置分为江淮型、江南型和华南型三种。对这六类区域持续性暴雨的历史个例进行同比分析, 研究了不同类型持续性暴雨发生的季节性和年际变化,以及它们在大尺度环流背景方面的共性特征。

The Statistical Analysis of the Persistent Heavy Rain in the Last 50 Years over China and Their Backgrounds on the Large Scale Circulation

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.