Spatial Distribution and Impacts of Aerosols on Clouds Under Meiyu Frontal Weather Background Over Central China Based on Aircraft Observations

An airborne field campaign was conducted from 10 June to 10 July 2018 in Hubei Province over central China as a part of the State Key Natural Science Foundation Project referred to as Integrative Monsoon Frontal Rainfall Experiment (IMFRE). Comprehensive observations of atmospheric aerosols and cloud characteristics in this region were collected and analyzed. In this study, data from six flights on nonprecipitating days were selected to investigate the spatial distribution of aerosols and microphysical properties of clouds. The profiles of aerosol number concentrations (N_a) were 1 order of magnitude lower than those over the North Plain of China, due to the different atmospheric backgrounds, local emission, and long-range transport. The highest N_a occurred at the altitude of the temperature inversion layer (TIL), indicating that N_a profiles were significantly affected by the TIL structure. Relative humidity (RH) had an effect on the aerosol size distribution where high RH values corresponded well with large values of particle mean diameter (MD). Compared with the vertical distributions of N_a and MD, their horizontal directions had minor changes, except for the MD at 4,000 m in one case. Of the three flights that penetrated through the stratiform clouds, the probability distribution functions of cloud droplet number concentration (N_c), effective radius (r_e), and liquid water content (LWC), showed the same features with a single peak mode. Since the nucleation of aerosol in-cloud caused the decrease of aerosol concentration, the maximum aerosol activation ratio almost reached 74%. The average spectrum of cloud droplets showed a multimodal distribution and their microphysical properties were analyzed in this study.