中国三峡地区汛期降水量的正态性研究

THE STUDY OF NORMALITY ON SUMMER PRECIPITION IN SANXIA AREA OF CHINA

中文关键词:  正态  非线性  主分量

英文关键词:Normality  Nonlinear transformation  Principal components of precipitation

中文摘要:

      为了分析三峡地区降水量序列的正态性和谱结构,对降水量的常见各种变换进行试验性研究。试验包括单站降水量、降水量的平方根、立方根和Γ分布概率值等非线性变换,以及级别变换。研究区域多站平均降水量、区域降水量的主分量、区域降水量的非线性变换后的主分量和区域降水量的级别变换后的主分量等序列。研究发现三峡地区单站降水量的各种变换不改变序列原始谱结构,仅影响概率分布的偏度和峰度,使其较好地遵从正态分布,其中以Γ分布的变换以及级别变换在分布的偏度上为最好。 区域降水量的各种变换的综合指数(区域平均值和主分量)正态性及谱结构分析表明,除区域平均值变换后不改变原单站序列的谱结构外,主分量的综合指数能改变原单站序列的谱结构,同时也影响概率分布的偏度和峰度,使其能较好地遵从正态分布。其中以降水量的立方根和Γ分布概率变换以及级别变换,在分布的偏度上有较好的效果。

英文摘要:

      In short-range climatic prediction, the transformations for summer precipitation usually have been made in single station or in stations in some area in China. There are linear transformations, such as anomaly, anomaly percent,and normalized for single station. Otherwise, the average and principal component analysis based on stations in the area has been usually made. Sometime the nonlinear transformations are also used on the preapitation series for impnwing the prediction, for example, square root, cubice root, or class transformation and so on. In order to investigate spectral structure and normality on summer precipitation in the original and transformed series, the data of summer (June to August) precipitation in Sanxia in China during the period 1952-1997 are selected in this paper. The transformations of precipitation are completed by nonlinear transformation. Those are square root,cubic root,probability (by Gamma distribution),class and rank transformation. Otherwise,the average, principal comonent of the variables in the 16 stations in the area is also analyzed. The method of power spectral analysis is used for the series. The parameters of skewness and kurtosis in distribution are calculated for the variables.