基于Copula函数的韩江流域旱涝组合事件概率特征研究

Probability of Drought-Flood Combinations in Hanjiang Basin:Based on Copula Function

以韩江流域潮安、横山和溪口3个代表性站点1959—2000年日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,并利用线性矩法估计参数,在此基础上采用4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2类旱涝组合事件发生的概率,结果表明:1)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2类旱涝组合事件发生的概率;2)潮安与溪口站夏-秋、秋-冬时段平均每4年发生一次连旱连涝的事件,春-夏、冬-春时段发生连旱和先旱后涝的概率均在10%左右;横山站秋冬季节平均每1.28年就发生一次连续干旱的事件。

Based on the daily flow data of 1959—2000 at Chao＇an,Hengshan and Xikou hydrological stations in the Hanjiang Basin, sequences of percentage of runoff anomalies（ Spring / Summer / Autumn / Winter） were fitted by 4 marginal distribution functions. By L-moment method,the parameters of the 4 models were estimated. Four 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 probability of multiple events of continuous drought and flood as well as alternating ones were calculated. The results show that： 1） 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. 2） Long drought and long flood occur every four yearson average during summer- autumn and autumn- winter at Chao＇an and Xikou,while the probability of long drought and drought before water logging is around 10% during spring- summer and winter-spring. Besides,long drought occurs every 1. 28 years on average during autumn- winter in Hengshan.