Measurement report: Aircraft observations of aerosol and microphysical quantities of stratocumulus in autumn over Guangxi Province, China: Diurnal variation, vertical distribution and aerosol-cloud relationship

Abstract. Aerosols and clouds play important roles in the global climate system, and aerosol-cloud interactions have a significant impact on the radiation balance, water cycle, and energy cycle of the earth-atmosphere system. To understand the effect of aerosols on the vertical distribution of stratocumulus microphysical quantities in southwest China, the daily variation characteristics and formation mechanism of the vertical profiles of stratocumulus microphysical characteristics in this region were described by using the data of 9 cloud-crossing aircraft observations over Guangxi from October 10 to November 3, 2020. The influence of aerosol number concentration on cloud microphysical quantity was analyzed by combining the source of air mass and individual cases. Aerosol number concentration (Na) and cloud droplet concentration (Nc) both decreased gradually with the increase of altitude below 1500m, and did not change with the height between 1500 m and 3300 m. The inversion layer at the top of the boundary layer (PBL) hindered the increase in the cloud droplet particle size. The lower layer of the stratocumulus cloud in Guangxi was mainly small particle-size cloud droplet (effective diameter of cloud droplet, E_d<15 μm), and the middle and upper layer cloud droplet was large particle-size cloud droplet (E_d>20 μm). The vertical distribution of cloud microphysical quantity had apparent diurnal variation. When aerosols in the boundary layer were transported to the upper air (14:00 to 20:00), the number of cloud droplets (Nc) in the lower layer decreased, and the small particle-size cloud droplets (E_d <20 μm) in the middle layer and upper layer increased. When aerosols were transported to the boundary layer (10:00 to 13:00), the number of small particle-size cloud droplets in the lower layer of the cloud increased. The characteristics of cloud microphysical quantity were also affected by the source of air mass and the boundary layer. Under the influence of land air mass or in the boundary layer, the aerosol number concentration (Na) and Nc were high, and the cloud droplet number concentration spectrum was unimodal. Na and Nc were low under the influence of marine air mass or above the boundary layer, and the cloud droplet number concentration spectrum was bimodal. The relationship between stratocumulus and aerosol in this region is consistent with the Twomey effect. E_d and Na remain negatively correlated in different liquid water content ranges, and FIE ranged from 0.07 to 0.58.