系列长度和最大值处理方式对降雨量重现期估算的影响

Impact of Series Length and Maximum Processing on Estimation of Rainfall Return Period

以2017年无定河流域"7.26"暴雨为例。根据李家河和丁家沟水文站1960~2017年的58年降雨量资料,计算分析了系列长度对变差系数的影响;采用三种方式处理"7.26"暴雨值,对李家河和丁家沟两个站的降雨进行频率分析,估算了暴雨区各站"7.26"降雨量的重现期。结果表明:(1)系列长度达到30~35a及以上时,年内六种不同时间尺度的变差系数均趋于稳定。(2)"7.26"降雨量对重现期的影响非常明显。李家河"7.26"暴雨的最大24h降雨量是系列最大值,建立频率曲线时,若考虑该值,重现期约为90年一遇,若不考虑该值,重现期约为五百年一遇;丁家沟"7.26"暴雨的最大24h降雨量不是系列最大值,无论该值是否参与建立频率曲线,其重现期均为20~30年一遇。(3)建议在分析暴雨重现期时,不仅要考虑单站最大降雨量,而且要移植邻近区域大暴雨值。

This paper took Wudinghe "7.26" rainstorm as an example.According to the rainfall data from the Lijiahe and Dingjiagou stations in the Wudinghe basin during 1960-2017,the influence of series length on variation coefficient were calculated and analyzed.Three different types were applied to deal with "7.26" rainstorm.The rainfall frequency curve of the two stations were established and the rainfall recurrence period at each station were calculated.The results show that:(1) When series length reaches30-35 years,variation coefficients of different time scales tend to be stable.(2) The influence of "7.26" rainstorm on the rainfall return period is obvious.The maximum 24 h rainfall of the "7.26" rainstorm at the Lijiahe station is the largest one in the series.If considering the maximum 24 h rainfall in establishing frequency curve,the return period is about 90 years,otherwise it is about 500 years.However,it is not the largest one at the Dingjiagou station in the series.The recurrence interval is 20-30 years whatever it is involved in establishing the frequency curve.(3) It is suggested that not only the maximum rainfall at one station should be considered,but also the adjacent extra-large torrential rain should be transplanted into the analysis of rainfall return period.