Microphysical characteristics of precipitating cumulus cloud based on airborne Ka-band cloud radar and droplet measurements

Abstract

Based on cloud-probe data and airborne Ka-band cloud radar data collected in Baoding on 5 August 2018, the microphysical structural characteristics of cumulus (Cu) cloud at the precipitation stage were investigated. The cloud droplets in the Cu cloud were found to be significantly larger than those in stratiform (STF) cloud. In the Cu cloud, most cloud particles were between 7 and 10 μm in diameter, while in the STF cloud the majority of cloud particles grew no larger than 2 μm. The sensitivity of cloud properties to aerosols varied with height. The cloud droplet effective radius showed a negative relationship with the aerosol number concentration (Na) in the cloud planetary boundary layer (PBL) and upper layer above the PBL. However, the cloud droplet concentration (Nc) varied little with decreased Na in the high liquid water content region above 1500 m. High Na values of between 300 and 1853 cm−3 were found in the PBL, and the maximum Na was sampled near the surface in August in the Hebei region, which was lower than that in autumn and winter. High radar reflectivity corresponded to large FCDP (fast cloud droplet probe) particle concentrations and small aerosol particle concentrations, and vice versa for low radar reflectivity. Strong updrafts in the Cu cloud increased the peak radius and Nc, and broadened cloud droplet spectrum; lower air temperature was favorable for particle condensational growth and produced larger droplets.摘要在积云中, 大多数云粒子的直径在7到10微米之间, 而在层云中, 大多数云粒子的直径不超过2微米. 云滴有效半径与云中行星边界层(PBL)及PBL上层的气溶胶数浓度(Na)呈负相关. 在1500米以上的高液态水含量区域, 云滴浓度(Nc)变化不大, Na含量降低. 高雷达反射率对应于大的FCDP云粒子浓度和小的气溶胶粒子浓度. 积云中的强上升气流增加了云滴的峰值半径和数浓度, 拓宽了云滴谱; 较低的空气温度有利于粒子的凝结增长, 并产生较大的液滴.