泾河南小河沟流域自然降雨特性

Characteristics of Natural Rainfall of Nanxiaohegou Basin in Jinghe River

采用德国HSC-OTT Persivel32激光雨滴谱探测仪监测南小河沟流域自然降雨的雨滴谱,分析不同雨型自然降雨雨滴特征及其分布规律,并分析了降雨特性各要素间的相互关系。结果表明:(1)该区自然降雨雨滴直径集中在0.3~1.5mm,与黄土高原利用传统的滤纸色斑法测定结果基本一致,但略小于东北和闽南地区。当雨强I<10mm/h时,雨滴中数直径随雨强的增大而增大;当I≥10mm/h时,雨滴中数直径骤然下降,这在一定程度上和雨强增大后大雨滴破裂有关。该地区雨谱随雨强的变化可用Best分布拟合。(2)普通型降雨雨滴数量随直径的分布曲线较平缓,其动能与雨强呈线性相关;而短阵型降雨的雨滴数量随直径的分布曲线较陡峭,其动能与雨强呈幂函数关系。两种雨型的降雨动能均随雨强的增大而增大,但短阵型降雨动能增大的更快,因此短阵型降雨的侵蚀力更大。

By using HSC-OTT Persivel32 laser raindrop spectrum detector（Germany）,raindrop size distribution under natural rainfall was detected in Nanxiaohegou basin of Jinghe River, and the characteristics and distribution of raindrops in different kinds of natural rainfall were analyzed.The relationships among the elements of rainfall characteristics were analyzed as well.Results showed that：（1）The raindrop diameter of natural rainfall was concentrated at 0.3-1.5 mm in the study area, and this result was basically identical with that on the Loess Plateau which determined by the method of traditional filter paper splash.But the raindrop diameter was smaller than those in Northeast and Minnan region.The median raindrop diameter（D（50））increased with the increase of rainfall intensity when rainfall intensity（I）was less than10 mm/h.When rainfall intensity was greater than or equal to 10mm/h,the median raindrop diameter（D（50））dropped abruptly,to some extent,it was related to rupture of large raindrops after the increase of rainfall intensity.The variation of rain spectrum with rain intensity in this area could be fitted by Best distributed.（2）The distribution curve of raindrops number with the diameter was flat in common rainfall, and its kinetic energy was linearly correlated with rainfall intensity,while the distribution curve of raindrop number with diameter in short formation rainfall was steeper, and its kinetic energy and rain intensity were power function.The rainfall kinetic energy increased with the increasing of rain intensity in both kinds of rainfall,but the kinetic energy of short formation rainfall increased faster,therefore short formation rains were more erosive.