基于Copula函数的珠江流域旱涝组合事件概率特征研究

Study on the Characteristic of Multiply Events of Drought and Flood Probability in the Pearl River Basin Based on Copula Function

以珠江流域高要、石角和博罗3个代表性站点1956—2000年月流量数据为基础资料,选取4种边缘分布函数拟合各站点春、夏、秋、冬四季的径流距平百分率序列,并利用线性矩法来估计参数,在此基础上采用3种Copula函数拟合春-夏、夏-秋、秋-冬、冬-春径流距平百分率序列,然后计算出各站点连旱连涝和旱涝交替这两类旱涝组合事件发生的概率,结果表明:基于Copula函数建立的联合分布模型可以较好地描述季节间连旱连涝和旱涝交替这两类旱涝组合事件发生的概率;东江、西江与北江3个地区中北江流域的极端旱涝灾害最为频繁,平均每0.98 a发生一次连旱连涝的事件,每3.17 a发生一次旱涝交替的灾害;在珠江流域春-夏、夏-秋、秋-冬、冬-春4个时段中,以夏-秋极端旱涝问题最为严重,发生旱涝组合事件的平均概率为27.52%。

Based on the monthly flow data of 1956-2000 at Gaoyao, Shijiao and Buoluo hydrological stations in the Pearl River basin, the sequences of percentage of runoff anomalies （Spring/Summer/Autumn/Winter） were fitted by 4 marginal distribution functions. Making use of the L - moment method, the parameters of the 4 models were estimated. Three kinds of Copula functions （ Gumbel - Hougaard, Clayton, Frank and AMH） were used to fit the sequences of percentage of runoff anomalies for spring - summer, summer - autumn, autumn - winter and winter - spring and the probahility of multiple events of continuous drought and flood as well as alteruating one were calculated. The results show that： Joint distribution of the model set up based on copula function can well describe the probability of multiple events of drought and flood between seasons. The extreme drought and flood disasters occurmost frequently in the NorthRiver basin among the Pearl River Basin. Continuous drought and flood occurs every 0.98 years on average and the ahernating oneoeeurs evey 7 3.17 years in the NorthRiver basin. The most serious problem of extreme drought and flood occurs in summer - autmnn, which theprobability is around 27.52% on average.