基于Copula函数和SPEI的广东北江流域干旱频率分析

Drought Frequency Analysis of the Beijiang River Basin in Guangdong Based on Copula Function and SPEI

选取广东北江流域18测站近50年日均温、日降水数据,计算出标准化降水蒸散指数(SPEI),通过游程理论确定干旱历时、烈度、烈度峰值等干旱变量;选用11种概率分布函数对干旱烈度和烈度峰值进行拟合,采用线性矩法估计参数,通过Kolmogorov-Smirnov方法进行拟合优度检验,确定出最佳的概率分布函数,并在此基础上对干旱变量10年一遇设计值进行空间分析。通过Genest-Rivest方法及尾部相关性分析,本文选取具有上尾相关性的GH Copula作为干旱变量的联接函数,并采用相关性指标法估计参数;进而对流域干旱变量联合概率分布进行研究,以期为分析区域水量平衡及防灾减害的干旱风险管理提供科学依据。

Daily precipitation and mean temperature data of 18 meteorological stations over the Beijiang River Basin of Guangdong for the last fifty years were analyzed to classify anomalously dry conditions u- sing the standardized precipitation and evapotranspiration index （SPEI）. In this study, drought variables （drought duration, drought severity and drought severity peak） were identified using run-length theory, 11 probability distribution functions were adopted to analyze the probability behaviors of drought severity and drought severity peak at 18 meteorological stations. The L-moment technique is used to estimate the parameters of the probability functions, the Kolmogorov-Smirnov method （K-S） is accepted to evaluate the goodness-of-fit of the probability functions and evaluate the ten-year return periods values. Based on the Genest-Rivest method and the tail dependency of random variable, GH copula that has up tail de- pendency is used for drought variable connect function. The Kendall rank correlation coefficient method is used to estimate the parameters of GH copula function. Then we comprehensively analyze the spatial vari- ability of joint probability distribution of two indices. The spatial variability of probability distribution of one drought variable and joint distribution of two drought variables can provide the scientific basis for a-nalysis of the local water volume balance and reduce drought disaster risk.