ACPD Atmospheric Chemistry and Physics Discussions ACPD Atmos. Chem. Phys. Discuss. 1680-7375 Göttingen, Germany 10.5194/acpd-13-25481-2013 An explicit study of aerosol mass conversion and its parameterization in warm rain formation of cumulus clouds Sun J. 3 4 2 1 Fen J. 3 Ungar R. K. 4 Key Laboratory of Cloud-Precipitation Physics and Severe Storms (LACS),Institute of Atmospheric Physics, Chinese Academy of Sciences, China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science and Technology, China Meteorological Service of Canada, Environment Canada, Canada Verification and Incident Monitoring Radiation Protection Bureau, Health Canada, Canada 02 10 2013 13 10 25481 25536 Copyright: © 2013 J. Sun et al. 2013 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://acp.copernicus.org/preprints/13/25481/2013/acpd-13-25481-2013.html The full text article is available as a PDF file from https://acp.copernicus.org/preprints/13/25481/2013/acpd-13-25481-2013.pdf

The life time of atmospheric aerosols is highly affected by in-cloud scavenging processes. Aerosol mass conversion from aerosols embedded in cloud droplets into aerosols embedded in raindrops is a pivotal pathway for wet removal of aerosols in clouds. The aerosol mass conversion rate in the bulk microphysics parameterizations is always assumed to be linearly related to the precipitation production rate, which includes the cloud water autoconversion rate and the cloud water accretion rate. The ratio of the aerosol mass concentration conversion rate to the cloud aerosol mass concentration has typically been considered to be the same as the ratio of the precipitation production rate to the cloud droplet mass concentration. However, the mass of an aerosol embedded in a cloud droplet is not linearly proportional to the mass of the cloud droplet. A simple linear relationship cannot be drawn between the precipitation production rate and the aerosol mass concentration conversion rate. In this paper, we studied the evolution of aerosol mass concentration conversion rates in a warm rain formation process with a 1.5-dimensional non-hydrostatic convective cloud and aerosol interaction model in the bin microphysics. We found that the ratio of the aerosol mass conversion rate to the cloud aerosol mass concentration can be statistically expressed by the ratio of the precipitation production rate to the cloud droplet mass concentration with an exponential function. We further gave some regression equations to determine aerosol conversions in the warm rain formation under different threshold radii of raindrops and different aerosol size distributions.

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