Abstract:

Based on the monthly precipitation of 613 meteorological stations in China during 1961-2010, the standardized precipitation index (SPI) was caculated, firstly. Then, the drought events were selected by using the run length theory, and the probability distribution fucnctions of drought intensity and drought duriation were tested by using K-S test. And on this basis the joint probability distribution function of dought intensity and drought duriation was established by using the Compula function, and the influence of the revised and unrevised drought duration distribution function on different types drought joint probability and recurrence peroid was contrastively analyzed. The results show that the drought intensity variable conformed to Gamma disttibution, while the drought duriation didn’t completely accord with the exponential function. Therefore, it was necessary to revise the drought duration distribution function so as to pass the K-S test. Under the revised drought duration distribution function condition, the joint probability of most drought types decreased, while that of a few increased, and the joint return peroid of different types drought increased. The difference of the maximum and minimum joint return peroid wasn’t obvious as the intensity of drought increased under the same drought duration, but that obviously enlarged as the drought duration increased under the same drought intensity.

Key words: drought, run length theory, Copula function, revision

摘要：

利用中国613个站点1961～2010年逐月降水数据，基于游程理论从月标准化降水指数（SPI）序列中分离出干旱事件，并通过K-S检验方法对其干旱强度和干旱历时2个特征量的分布函数进行检验。在此基础上，利用Copula函数建立2个特征量的二维联合概率分布函数，对比分析干旱历时分布函数修订前后对不同类型干旱联合概率及重现期的影响。结果表明：干旱强度特征量符合Gamma分布，而干旱历时特征量并非完全符合指数分布，因此需对干旱历时分布函数进行必要的修订。在干旱历时分布函数修订情况下，大部分干旱类型的联合概率减小，少部分干旱类型的联合概率增大；且不同类型干旱的联合重现期增大。在干旱历时尺度相同时，随着干旱强度的增加，最大和最小联合重现期的差异无明显变化；但在干旱强度相同时，最大和最小联合重现期的差异随着干旱历时的增加而明显增大。

关键词: 干旱, 游程理论, Copula函数, 修订