北京低边界层雨滴谱的垂直分布特征

基于安装在气象铁塔不同高度的3台Parsivel激光雨滴谱仪, 研究2020年6—8月北京地区31次降雨过程低边界层的雨滴谱垂直分布特征及其对雷达测量降雨的影响。结果表明, 在雨滴从280 m下落到140 m的过程中, 雨滴破碎占据主导地位, 大尺度雨滴减少, 小尺度雨滴大量增加; 从140 m下落到地面的过程中, 雨滴合并占据主导地位, 大尺度和小尺度雨滴均减少, 中等尺度雨滴增加; 对流型降雨中, 随着高度降低, 大尺度雨滴迅速减少, 雨滴破碎对雨滴谱分布的影响较大。北京地区对流型降雨的雨滴谱特征介于海洋型与大陆型之间。由于雨滴谱的分布随高度变化, 不同降雨特征量也随高度发生非线性变化, 因此使用地面的降雨测量结果对气象雷达进行校准以及联合反演降雨会产生Z-R错配误差, 这种误差在稳定型降雨和弱降雨中更显著。

Vertical Distribution Characteristics of Raindrop Size Distribution at Lower Atmospheric Boundary Layer in Beijing

Based on three laser optical Parsivel disdrometers installed at different heights on meteorological tower, the vertical distribution characteristics of raindrop size distribution (DSD) and the influences on rainfall measurement by radar in the lower atmospheric boundary layer were investigated, during 31 precipitation episodes in Beijing from June to August 2020. The results show that the break-up process is dominant from 280 m to 140 m, which leads to the decrease of large scale raindrops and the increase of small scale raindrops. Whereas, from 140 m to ground, the collision-coalescence process is dominant on the falling path of raindrops, which leads to the decrease of large and small scale raindrops and the increase of medium scale raindrops. Because of the great influence on DSD by break up, large scale raindrops in convection rain decrease rapidly with height. The DSD of convective rain in Beijing is different from oceanic-like cluster and continental-like cluster. Due to the change of DSD with height, characteristic parameters of rainfall vary nonlinerly. A Z-R mismatch error would be caused when using ground precipitation data for correction of the meteorological radar rainfall estimation, which is heavier in stratiform and light rain.