兰州地区降水量正态分布特征

Normal Distribution Characteristics of Precipitation in Lanzhou Region

在对降水资料的分析过程中，要求资料的时间序列呈正态分布。利用兰州地区的兰州、皋兰、榆中和永登4个站点1960～2009年的降水量资料，采用“偏度-峰度系数＋W检验”方法，基于SPSS软件，对兰州地区的年、季和月降水量正态特征进行分析。结果表明，兰州地区4个气象站的年降水量均呈正态性分布；兰州、皋兰和永登3站的夏、秋2季降水量为正态性分布，而榆中站只有秋季降水量为正态性分布，且秋季降水量的正态性最好，冬季最差；大多数月降水量不服从正态分布，但对降水序列进行平方根处理后，其正态性得到明显的改善。

It is generally known that the research on precipitation depends on normal distribution of the time-series data.Based on the observational precipitation data at 4 weather stations in Lanzhou,Gaolan,Yuzhong and Yongdeng of Lanzhou region from 1960 to 2009,the normality of the monthly,seasonal and annual precipitations were analyzed by using strictly the “skewness and sharpness coefficient ＋W test ”methods.The results showed that the annual precipitation of each station obeyed normal distribution in Lanzhou region.The seasonal precipitation in Lanzhou,Gaolan and Yongdeng was subject to normal distribution in summer and autumn,but that in Yuzhong was only subject to normal distribution in autumn,and the normality of precipitation in autumn was the best and the worst in winter in Yuzhong.In addition,most of the monthly precipitations at 4 stations didn’t conform normal distribution,however, the normality of their square root had been improved significantly.