Investigating the Influence of Rainfall Frequency on Aerosol Removal and Aerosol Radiative Effects in Conventional and Multiscale Modeling Framework Configurations of CESM

Aerosols particles can have significant impacts both on climate, though absorption and scattering of incoming solar radiation, and human health when inhaled. These effects vary based on the characteristics of the aerosol particles, and can be influenced by their emissions, transport, and removal in the atmosphere. Most aerosol emissions are prescribed in Earth System Models (ESMs), but the resulting concentrations can vary significantly across different ESMs due to the representation of removal processes, particularly precipitation and wet deposition. In this study, we examine the characteristics of simulated particulate matter in the Community Earth System Model (CESM2.1.0) in two configurations with very different treatments of convection and precipitation processes, the standard parameterized configuration (CAM) and the multiscale modeling framework configuration (MMF), in which 4 km cloud resolving models replace conventional parameterizations to explicitly represent convection. To understand the effects of resolved convection on precipitation, aerosol, and ultimately the global radiative budget, we compare the results to observations from the TRMM, MODIS, and CERES satellite missions’ data. The MMF approach has been shown to better capture the frequency and intensity of rain events compared to observations, reducing the overestimation of light precipitation frequency in CAM, which has a strong impact on the removal of aerosol particles. By improving the frequency of precipitation, we find that the subsequent removal of aerosol particles is also improved and better matches observations in the MMF. Additionally, through a comparison between the MMF and CAM, we identify that the spatial patterns of black carbon, primary organic matter, sulfate production and secondary organic aerosol distribution are influenced by multiscale modeling processes which impact production and removal rates. Overall, this leads to an increased burden of anthropogenic aerosol particles in the MMF, which has important implications for the global energy balance and radiative budget at the top of the atmosphere.