西江水文干旱历时与强度的遭遇概率分析

Probability of hydrologic drought duration and intensity of Xijiang River

利用西江下游马口水文站1959 2009年月径流量数据计算径流干旱指数,经游程理论提取了水文干旱特征值.应用Copula函数分析水文干旱强度和历时之间的联合概率分布.对构建的干旱历时和强度联合分布模式进行分析,结果表明:(1)径流干旱历时和强度之间具有高关联性,秩相关系数达0.617;(2)三参数Weibull分布较好地描述了干旱历时和强度的边缘分布特征;(3)经拟合优度检验结果优选的干旱历时和强度之间的较优连接函数为Archimedean类的Gumbel-Hougaard Copula函数;(4)5～10年重现期和20年重现期的水文干旱分别达到了重旱级别和特旱级别;(5)干旱历时和强度之间的遭遇概率可为特定干旱历时与水文干旱级别或特定干旱强度与干旱历时之间的对应关系提供概率意义上的干旱特征诊断与预测.

Astreamflow drought index was calculated by using monthly runoff from 1959 to 2009 at Makou hydrologic station in the lower reaches of the Xijiang River. The hydrologic drought duration and intensity was characterized through run theory, which were used to construct the bivariate joint distribution model in this paper. The results of drought duration and imensity joint distribution model show that： （1） There is high correlation coefficiem of 0. 617 between streamflow drought duration and intensity; （2） The marginal distributions of drought duration and intensity can he better represented by three-parameter WeihuU distribution ; （3） The Gumhel-Hougaard copula which belongs to Archimedean Copula family was selected for constructing the joint distribution model of hydrological drought duration and intensity by using goodness-of-fit test;（4 ） The 5-10 years return period and twenty years return period of hydrologic drought can reach to heavy drought level and extreme drought level, respectively ; （ 5 ） The encounter probabili- ties can be provided for diagnosis and prediction of drought characteristics for the correspondence between specific drought duration and hydrological drought levels or between specific drought intensity and drought duration in the probability sense.