基于Copula的干旱频率分析方法在唐乃亥流域中的应用

Application of Drought Frequency Analysis Method Based on Copula inTangnaihai Watershed

以黄河源区唐乃亥水文站以上流域为研究对象,选取唐乃亥站45年(1956年~2000年)的逐月天然径流资料,运用游程理论识别出干旱历时和干旱烈度序列,在假定干旱历时服从指数分布、干旱烈度服从二参数Gamma分布条件下,用χ2检验其合理性,最后用copula函数构建干旱历时和干旱烈度的联合分布函数,优选出最适合唐乃亥站的联合分布函数,并计算干旱重现期。结果表明:Gumbel-Copula函数是用于研究唐乃亥站以上流域水文干旱特征的最佳分布概率函数,干旱联合重现期平均值为11个月。

The monthly natural runoff data of 45 years(from 1956 to 2000)were analyzed from Tangnaihai hydrological station in the source region of the Yellow River.The duration and intensity of drought were identified using the Run-length theory.The rationality was checked usingχ2 under the assumption that drought duration followed the exponential distribution and drought intensity followed the two-parameter gamma distribution.Finally,the copula function was used to construct the joint distribution function of drought duration and drought intensity.The most suitable joint distribution function was selected and the drought recurrence period was calculated.The results showed that the Gumbel-Copula function was the best distribution probability function used to study the hydrological and drought characteristics of the basins above the Tangnaihai station,and the average drought recurrence period is 11 months.