中文摘要：

基于中国西南地区（四川省、云南省、贵州省和重庆市）89个站点1961--2010年的逐月标准化降水指数序列，利用游程理论和Copula函数建立干旱历时和干旱强度的概率模型，基于该模型讨论了干旱事件样本量对分布参数、干旱类型的出现概率及联合重现期的影响．结果表明：分布参数稳定对样本量的要求较大，部分区域样本量要求大于50，并且各参数对样本量的要求不一致，又以干旱强度分布的参数对样本量的要求最大：干旱事件样本量为10个左右求得的干旱类型出现概率和联合重现期与样本量为40求得的结果己无明显差异，以计算结果作为标准可大幅降低统计模型建立对样本量的要求，进而表明起止时间不一致和具有缺测数据的站点仍可建立干旱历时和干旱强度的分布函数；气候变暖对模型建立所需的最少样本量影响不大，样本量波动在±5之间，即统计模型具有一定的稳定性，同时气候态的划分降低了分布检验对样本量的需求，易于模型的建立．

英文摘要：

Based on the standardized precipitation index data of 89 meteorological stations in southwest China （Sichuan Province, Yunnan Province, Guizhou Province, Chongqing） during 1961-2010, probability model containing drought duration and drought severity is established by using the theory of run and the Copula function. The influences of the drought sample number on the distribution parameters, the probability and drought return period are discussed. The result shows that the stability of distribution parameters needs larger sample number. The sample number is greater than 50 in some regions and the requirements for sample number of each parameter is not consistent. The sample number of severity distribution parameters is largest. The probability and return period obtained in the case where the sample number is about 10 have no significant difference （the significant level is 0.05） from those in the case where the sample number is 40 in most of region. With the results used as the standard, statistical model can greatly reduce the requirements for the sample number. And then it demonstrates that the distribution function of drought duration and drought severity can still be established in the lack of measurement data and the inconsistency between starting and ending time. Climate warming has no influence on the minimum of sample number. The fluctuation is mostly between -5 to 5. Statistical model has a certain stability. Meanwhile, the division of climate state reduces the need for distribution test sample number and makes it easier to build model.