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

TANG Jishun1,2, LIU Xiaoyang1,†, LIU Junhui1, LI Aiguo3, WANG Pengfei4

1. Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing 100871; 2. 91197 PLA Troop, Qingdao 266405; 3. Tower Division, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100020; 4. Beijing Intell-sun Technology Limited, Beijing 100020; † Corresponding author, E-mail: xyl@pku.edu.cn

Abstract 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. Key words raindrop size distribution; vertical distribution; Parsivel; precipitation; Z-R mismatch error

雨滴数浓度随雨滴直径的变化关系称为雨滴谱, 是基础性的降雨微物理量。通过雨滴谱, 可以计算得到雨强(R)、雷达反射率因子(Z)和液态水含

量(LWC)等降雨特征量, 建立用于雷达定量测量降雨的Z-R关系(Z=arb, a和b为系数)[1]。利用电磁波通过降雨时产生的散射和吸收特性, 雨滴谱的三参