Distinct Microphysical Characteristics of Precipitating and Non-Precipitating Parts of a Stratus Cloud From In Situ Aircraft Observations

Abstract

Cloud microphysical properties play a crucial role in stratus cloud behavior, with notable differences between precipitating and non-precipitating parts. This study presents aircraft-based observations on 8 May 2020 over a coastal region in China, to investigate the microphysical characteristics of a liquid stratus cloud. Significant differences in aerosols number concentration (N_a), cloud droplet concentration (N_c), and drizzle droplet concentration (N_d) are observed, with lower number concentrations in the precipitating part for all three. The effective radius (r_e) of cloud droplets is smaller, while drizzle droplets exhibit a larger r_e in the precipitating part. In the non-precipitating part, drizzle droplet r_e decreases with altitude, while in the precipitating part, it remains constant due to larger droplets falling out. Aerosol size distribution analysis implies that precipitation mainly scavenges aerosols with sizes smaller than 0.3 μm. Cloud particle size distributions are bimodal, with a broader spectrum in the precipitating part, especially in lower layers. Additionally, drizzles contribute approximately 20% to the total liquid water content in the non-precipitating part, and 70% in the precipitating part. Our findings highlight distinct differences in cloud microphysical properties of the stratus cloud between precipitating and non-precipitating parts, with drizzle playing a critical role in cloud microphysics and precipitation formation.