基于日雨量的长武县53年来降雨量及侵蚀力演变趋势分析

用长武县1957—2009年日雨量数据,对该地区侵蚀性降雨量及降雨侵蚀力不同时间尺度变化趋势及其协同性进行系统分析,为该区水土流失治理及生态环境建设提供科学支持。结果表明:(1)长武县53a来多年平均降雨量577.8mm,侵蚀性降雨量340.7mm,降雨侵蚀力1 691.2(MJ.mm)/(hm2.h)。3要素变异系数、集中程度逐渐增大,变异系数分别为22.5%,34.4%,43.2%。分别有76.1%,83.4%和85.8%的量集中于夏、秋两季,53.2%,65.5%,70.1%的量集中于7—9月。(2)53a来年降雨量和年侵蚀性降雨均呈不显著减少趋势,受极端降雨事件发生次数增多的影响,降雨侵蚀力呈不显著增加趋势。季节间的变化格局类似,夏、秋两季均呈不显著的增、减趋势,春、冬两季均呈显著减、增趋势。4月、6月呈显著的减、增趋势。(3)对全年降雨量、侵蚀性降雨量及降雨侵蚀力年际变化的贡献程度,季节尺度上均受夏、秋两季尤其夏季影响较大,月尺度上则以7—9月尤其8月影响较大。影响程度在3要素间逐渐增强。53a来3要素的演变特征既有差异,又有巨大协同性。

Trend Analysis of Precipitation and Its Erosivity over Last 53 Years Based on the Daily Rainfall in Changwu County

The daily observation data from 1957 to 2009 were used to systematically analyze the trend of precipitation,erosive precipitation and the precipitation erosivity in Changwu County.The results showed that:(1) the mean annual precipitation was 577.8 mm and the erosive precipitation was 340.7 mm,and for precipitation erosivity 1 691.2(MJ·mm)/(hm·h).Their coefficients of variations were 22.5%,34.4%,43.2% respectively.And the proportion of 76.1%,83.4% and 85.8% concentrated in summer and autumn,53.2%,65.5% and 70.1% focused on the period from July to September;(2) over the last 53 years,precipitation and erosive precipitation were detected with an insignificant negative trend and for precipitation erosivity,it was slightly positive trend,the seasonal change patterns among the three elements were similar,for all three elements,there were slightly positive trend both in summer and winter and slightly negative trend both in autumn and spring,for April it was significant negative trend and positive trend for June;(3) the trends of precipitation,erosive precipitation and precipitation erosivity were equally influenced greatly by the change of summer and autumn especially in summer,in monthly scale,by the changes from July to September especially in August.The impact,whatever from two seasons or three months,was intensified gradually among three elements.The results indicated that the changes of three elements differentiated but showed great same phase over the last 53 years.