华东地区夏季不同等级降水变化特征分析

采用华东地区78个气象站点逐日降水资料,根据日降水量的5个等级划分,应用线性趋势分析、相关分析等分析了不同等级降水频率和降水量的空间分布及其变化趋势。结果表明:(1)夏季不同等级降水频率在整个华东地区具有明显的地区差异,区域平均的降水频率由大到小依次为小雨、微量降水、中雨、大雨、暴雨。(2)平均的夏季总降水量呈南多北少的分布,各等级降水对总降水量的贡献率由大到小依次为暴雨、大雨、中雨、小雨,暴雨对夏季总降水量的贡献在某些年份可达50%以上。(3)区域平均的夏季降水日数呈下降趋势,但总降水量却有明显的增大趋势。(4)区域平均的某等级降水频率正异常时,华东地区各地该等级降水频率,亦多表现为正异常,尤其中雨以上等级降水频率异常符号在整个华东地区更为一致。(5)华东区域微量降水和小雨发生频率分别与其他等级降水存在显著的反相关关系,而中雨、大雨、暴雨三者发生频率之间无显著相关。

Climatic characteristics of graded summer precipitation over East China

Using the daily precipitation data from 78 meteorological stations over East China, the spatial distribution and temporal variation trend of the rainfall frequency and total amount have been analyzed under 5 different grades according to rainfall daily amount with linear trend and correlation analysis. The results show that summer daily rainfall frequency under different grades has spatial differences over East China. Areal average frequencies of event occurrence in an apparent descending order are light rain, micro rain, moderate rain, heavy rain, and torrential rain. The mean climatology of summer total rainfall presents the distribution of larger rainfall amount in the south and less in the north. Impressively,the contribution of precipitation under different grades is contrary to the total precipitation. Contribution of torrential rain to the total rainfall is almost up to 50% in some years. Regional mean occurrence frequency of occurrence and amount of summer rainfall change yearly with a significant long-term trend, the number of rainy-day in summer is decreasing while the regional mean total precipitation is increasing during the studying period. When regional mean precipitation frequency anomaly for a certain grade is positive, the composite precipitation frequency for this grade also tends to be positive all over East China, especially for the rainfall heavier than moderate rain. Significant negative correlations are found between micro rain (light rain) and other precipitation grades over East China. However,no significant relationship exists among moderate rain, heavy rain and torrential rain.