黄土高原侵蚀性降雨特征分析

侵蚀性降雨是黄土高原地区剧烈土壤水蚀的原动力。利用黄土高原6个水土保持试验站20年以上的断点雨强资料和30年的气象站逐日降水观测资料,分析了侵蚀性降雨的发生频率、次降雨量、次降雨历时、次降雨侵蚀力以及降雨时程分布的统计特征:(1)黄土高原6个站侵蚀性降雨平均发生频率分别为7.0~13.4天/年,各站侵蚀性降雨的场雨量均值介于19.17~25.38mm,但变异性很大。各站次降水量、降雨历时和次降雨侵蚀力的频率分布都近似为指数分布。(2)根据本文设定的雨峰标准,黄土高原单峰降水占总降水次数的65%,双峰降水占30%,三峰降水占5%。峰值雨强的频率分布函数大致为Gamma分布中的一种,或者是偏正态分布,侵蚀性降水多为前锋型。上述结果可作为降水过程的随机模拟理论依据,也可以为全面深入研究土壤水蚀机理提供参考。

Statistic Analysis of Erosive Rainfall on the Loess Plateau

Erosive rainfall is one of the main reasons for serious water erosion on the loess plateau.Previous studies were limited in extreme storms,seasonal and annual distribution and spatial distribution of storms while few researches were done on statistic analysis of erosive rainfall,especially the rainfall process.The purpose of this research is to analyzethe statistic characteristics of erosive rainfall on the loess plateau.Observationdata of rainfall processover 20 years and observed daily rainfall of 30 years from 6 soil and water conservation experimental stations were used to analyzethe statistic regulation of erosive rainfall including occurring frequency,daily rainfall amounts,rainfall duration,event erosivity,and rainfall process.Results were as follows:(1) Averagely,erosive rainfall occurred7.0～13.4 days per year among the six stations.Means of daily rainfall amounts of the six stations were from 19.17 to 25.38mm with large variance.Statistic distribution of daily rainfall amounts,duration and event erosivity were all similar to exponentialdistribution.(2) According to the suggested criterionfor rainfall peak,65% of the rainfall on the loess plateau had single peak,30% had two peaks and 5% had three peaks.Statistic distribution of the peak intensity was one of the Gamma distribution or skewed normal distribution.Most of the erosive rainfall events presented their peaks in the early part of the process.The resultscan be basis to statistic model of rainfall process as well as reference for understanding the mechanic of water erosion on loess plateau.