The Impact of Resolution on Precipitation Characteristics and Aerosol Removal over North America in E3SMv2

Atmospheric aerosol particles have varied impacts global radiation, and fine aerosol particles smaller than 2.5 µm in diameter (PM2.5) are known to pose hazards to human health when inhaled. These particles are removed from the atmosphere primarily through the process of wet deposition, which is largely controlled by the frequency of precipitation. This study evaluates differences in aerosol concentration that result from precipitation sensitivities and other impacts from higher model resolution. The Energy Exascale Earth System Model version 2 (E3SMv2) is used to examine the role of resolution on wet deposition of aerosols. The model is run both with uniform grid spacing and with a four times refinement of all components (atmosphere, land, river, etc.) over North America, referred to as the North American Regionally Refined Model (NARRM). The finer resolution of NARRM over the North American Continent has shown improvements in precipitation and clouds when compared to the lower resolution configuration. With these improvements in annual average and frequency of precipitation, wet deposition rates are altered with mixed results depending on the size of particle as defined by the Modal Aerosol Module (MAM4). Over the continental United States, the higher resolution NARRM model shows a decrease in rainfall frequency but stronger intensity. Furthermore, the NARRM model more accurately captures seasonal precipitation, all characteristics of precipitation which affect the removal of aerosols in the atmosphere and the subsequent regional patterns of removal. These rainfall rate changes are critical for understanding and better representing the dynamics of aerosol removal, both by mode and species across the United States, and serve in our ability to model air quality risk as well as impacts on global radiation.