基于三维Copula函数的河南郑州市干旱频率分析

Analysis of drought frequency in Zhengzhou City based on three-dimensional Copula Function

为研究河南郑州市气象干旱特征的一般规律,观测百余年来郑州市标准化降水蒸散指数的变化状况,收集了郑州市1901-2015年月际标准化降水蒸散指数,并运用Mann-Kendall检验法对郑州区域标准化降水指数的变化趋势以及突变情况进行检验。基于月际标准化降水蒸散指数以及游程理论对干旱事件进行识别,分离出干旱历时、干旱烈度以及干旱烈度峰值3个干旱特征变量。选取了3种二维对称Copula函数和3种三维对称Copula函数对干旱特征变量进行拟合并计算联合重现期和同现重现期。经拟合检验,二维Frank Copula函数和三维Frank Copula函数对干旱特征变量的联合分布拟合效果最佳。

In order to study the general rule of meteorological drought characteristics and to observe the variation of standardized precipitation evapotranspiration index in Zhengzhou over the past hundred years,the monthly standardized precipitation evapotranspiration index from 1901 to 2015 in Zhengzhou was collected,and the variation trend and abrupt change of regional standardized precipitation index were tested by Mann-Kendall test method. Based on the monthly standardized precipitation evapotranspiration index and the run-length theory,the drought events were identified,and three characteristic variables of drought duration,drought intensity and drought intensity peak were separated. Three two-dimensional symmetric Copula functions and three threedimensional symmetric Copula functions were selected to fit the characteristic variables of drought and calculate the joint return periods and co-occurrence return periods of drought characteristic variables. Through the fitting test,the joint distribution fitting of two-dimensional Frank Copula function and three-dimensional Frank Copula function demonstrate the best fitting effect on the joint distribution of drought characteristic variables.