北京降雨过程分型特征及短历时降雨重现期研究

摘要

利用北京观象台1961-2004年44 a逐分钟自记降雨资料,采用模糊识别法和统计分析法对北京市降雨过程进行雨型分型,并对5、10、15、20、30、45、60、90、120、180 min共10种不同短历时年最大降雨极值的概率分布利用指数分布、耿贝尔分布和皮尔逊Ⅲ型概率分布函数进行拟合.在此基础上,推算各历时降雨重现期极值.结果表明,暴雨天数年代际差异较大,暴雨量主要集中在50~100 mm范围内;不同月份雨型分布不一致,6月多双峰型,7-9月多单峰型雨型;总体上,北京降雨过程多为单峰型,占80%以上.最大降雨量主要出现在午后至傍晚和凌晨;北京短历时降雨极值的概率分布多数不服从指数分布而服从皮尔逊Ⅲ型分布;重现期降雨极值随历时增加而增大,2 a至100 a重现期内10 min降雨极值取值为10.4~22.6 mm,60 min降雨极值取值为22.3~59.2 mm,180 min取值为53.0~89.8 mm.%Using the rainfall autographic records with 1-minute interval at Beijing Observatory from 1961 to 2004, we have performed the classification of short-duration rainfall pattern with fuzzy identification method and statistical analysis method. The Exponential distribution, Gumbel distribution and Pearson-Ⅲ distribution are also fitted to infer the short-duration rainfall extremes, such as 5-min, 10-min, 15-min, 20-min, 30-min, 45-min, 60-min, 90-min, 120-min and 180-min extremes, based on the establishment of the probability distribu-tion pattern under different return period scenarios, respectively. Results indicate that the amounts of rainfall mainly concentrate on 50-100 mm, but inter-decadal variations of torrential rain days are evident. The monthly temporal patterns are different so that the bimodal type is dominant in June while the unimodal type is mainly temporal pattern from July to September. The dominant temporal patterns of the short-du-ration rainfall process at Beijing Observatory are unimodal type, which account for more than 80%of all short-duration rainfall process. The maximum precipitation occurs in the two periods from afternoon to evening and before dawn. Pearson-Ⅲdistribution is an adequate fit to the probability distribution of the short-period precipitation probability at Beijing Observatory according to the comparison among the fittings of Exponential distribution, Gumbel distribution and Pearson-Ⅲdistribution. The maximum amount of precipitation under different return peri-od increases with return period. That is the rainfall amounts of 10-min, 60-min and 180-min from 2 years to 100 years return period are lim-ited in 10.4-22.6 mm, 22.3-59.2 mm and 53.0-89.8 mm, respectively. All these results will provide a more scientific support to prevent ur-ban waterlogging deposition and drainage system planning.