渭河流域降雨结构时空演变特征

为研究气候变化背景下渭河流域降水结构的时空变化,利用渭河流域71个气象站1981—2012年汛期(5—9月)逐时降水资料,选取降水发生率和降水贡献率两个指标,结合线性倾向率和非参数Mann-Kendall检验法探讨了流域降水结构的变化趋势及不同降水历时和不同降水等级的空间变化特征。结果表明:(1)渭河流域各历时降水发生率随历时增加呈指数形式快速递减,降水贡献率随历时增长先快速增大,后波动减小。流域上游短历时降水发生率和贡献率较高,而流域中下游长历时降水发生率和贡献率较高。(2)渭河流域1~6h的短历时和48h以上长历时降水发生率和贡献率均表现为减小趋势,7~24h历时降水发生率和贡献率为增加趋势,这种变化趋势在流域的中下游更加显著。(3)渭河流域降水发生率随降水等级的增加呈指数下降,小雨发生率最高,而暴雨的发生率最低。比较而言,流域上游小雨和中雨的发生率和贡献率较高,而流域中下游大雨和暴雨发生率和贡献率较高,特别是在渭河干流,暴雨贡献率在25%以上。(4)渭河流域小雨级别的降水事件发生率和贡献率均表现为显著的下降趋势,而暴雨级别降水发生率和贡献率表现为增加趋势,这种变化趋势将可能使流域防洪形势趋于严峻。

Spatiotemporal Variability Characteristics of Precipitation Pattern in Weihe River Basin

In order to study the temporal and spatial variation of precipitation pattern in Weihe River Basin under the background of climate change,the change trend of precipitation pattern and the spatial variation characteristics of different precipitation durations and different precipitation grades were discussed by using the incidence rate,contribution rate of precipitation and the method of linear tendency rate and non-parametric Mann-Kendall test.The data included hourly precipitation covering 1981-2012 in 71 meteorological stations in the Weihe River basin.The results show that:(1) the precipitation occurrence rate decreases rapidly with the increase of precipitation time;the contribution rate of precipitation increases rapidly with the increase of precipitation time,and then decreases in Weihe River Basin;the short duration precipitation has a high occurrence rate and the contribution rate in the upper reaches of the river basin,and the duration precipitation occurrence rate and contribution rate are higher in the middle and lower reaches of the river basin;(2) the long duration precipitation rate and contribution rate show the decreasing trend from 1 to 6 h of short duration and more than 48 hours in Weihe River Basin,and the increasing trend in 7 to 24 h,This trend is more significant in the middle and lower reaches of the basin;(3) the precipitation rate decreases exponentially with the increase of precipitation grades,the occurrence rate of sprinkle is the highest,and the rainstorm is the lowest in Weihe River Basin;the occurrence rate and contribution rate of sprinkle and moderate rain are higher in upstream,and heavy rain and rainstorm are higher in the middle and lower basin,especially in the mainstream of Weihe River,the rainstorm contribution rate is more than 25％;(4) the occurrence rate and contribution rate of sprinkle show a significant downward trend and the rainstorm performs an increasing trend in Weihe River Basin,this trend will likely make the watershed flood control situation tends severe.