基于Copula的澜沧江流域气象干旱风险分析

基于云南省澜沧江流域9个气象站点在1953—2015年逐月降水、蒸散发序列，构建标准化降水蒸散发指数SPEI，采用游程理论分离干旱特征变量，利用Copula函数建立联合分布函数，分析干旱发生概率及其重现期. 结果表明:1）当发生相同程度历时、强度的干旱事件时，澜沧江流域北部区域的发生频率高于南部；2）不同地区的联合重现期等值线变化趋势不同，实际重现期介于联合重现期与同现重现期之间，联合重现期与同现重现期的值可作为预测实际重现期的区间范围；3）通过重现期确定不同程度干旱对应的区间范围；4）流域内轻微干旱风险概率为5.50%~11.05%、中度干旱风险概率为17.43%~39.31%、重度干旱风险概率为12.89%~17.83%、特大干旱风险概率为7.20%~14.00%. 研究结果可为澜沧江流域干旱风险应对提供有益参考. 

Risk of meteorological drought in Lancang River Basin as analyzed by Copula

Drought risk assessment, quantitative analysis of drought in particular, is useful for drought prevention. Monthly precipitation and evapotranspiration sequences from 9 meteorological stations in the Lancang River Basin of Yunnan Province were used to construct standardized precipitation evapotranspiration index (SPEI). According to runoff theory, drought characteristic variables were separated, Copula function was used to establish joint distribution function to analyze drought occurrence probability and return period. With identical duration and intensity of drought events, frequency of occurrence was found higher in the northern part of Lancang River Basin than the southern part. Trend of contour change in joint return period was found to vary from region to region. Actual return period was found to be between joint return period and co-occurrence period. Values of joint return period and co-occurrence return period were within the range of predicted actual return period. Range of corresponding drought was determined by return period. Probability of mild drought in the basin was found to be 5.50% - 11.05%, moderate drought 17.43% - 39.31%, severe drought 12.89% - 17.83%, extreme drought 7.20% - 14.00%. These data would provide some useful reference for drought risk response in the basin.