不同选样方法对Pilgrim&Cordery设计暴雨雨型的对比研究

采用宜昌市主城区国家基本站长序列的逐分钟降雨过程资料,利用PilgrimCordery法(简称"PC法")比较通过自然降雨过程和最大历时过程两种降雨场次样本选样方法推求的设计暴雨雨型,并分析结果差异。结果表明:基于自然降雨过程和最大历时过程选样,利用PC法推求的宜昌市主城区短历时设计暴雨雨型基本都为单峰型,且雨峰均出现在整场降雨过程的前1/3时段。两种选样方法推求的短历时设计暴雨雨型的雨量分配比例存在较大差异,自然降雨过程选样推求的雨型雨峰峰值占总雨量的比例相较于最大历时过程的数值偏大,更为突出。实际工程设计中,设计师应当根据最大历时过程的选样规则进行推求,结合一定重现期下各个历时的降雨量值,进而得到各历时时程分配的具体雨强;计算得到宜昌市主城区重现期2a历时60、120、180 min的雨峰时段雨强分别为1.16、0.86、0.72 mm/min。

Contrastive Study of the Pilgrim & Cordery Design Storm Pattern on Different Sampling Methods

In this paper,the long sequences rainfall data of national stations over the main urban area of Yichang are used to investigate the design hyetograph,which are analyzed by Pilgrim & Cordery(P & C) method on two sampling methods of the natural rainfall process and the biggest diachronic process.The results show that on the base of the sampling methods of the natural rainfall process and the biggest diachronic process,the design hyetograph of short durations on Yichang by P & C method presents single peak pattern uniformly,and the rainfall peak are located in the pre 1/3 of the whole rainfall process.The performance of the rainfall distribution proportions on the short duration design hyetograph by two sampling methods is not consistent.The rainfall rate on the rainfall peak of the natural rainfall process appears larger and more outstanding than the biggest diachronic process.In practical engineering design,the designer should choose the biggest diachronic process and combine the precipitation of each rainfall duration over a return period to calculate the specific rainfall intensity.The rainfall intensity of rainfall peak on 60,120,180 min over 2 years return period of Yichang are 1.16,0.86,0.72 mm/min.