Impacts of spatial heterogeneity of anthropogenic aerosol emissions in a high-resolution Earth system model

Emissions of anthropogenic aerosol particles and their precursors are often prescribed in global aerosol models. Most of these emissions are spatially heterogeneous at model grid scales. When remapped from low-resolution data, the spatial heterogeneity in emissions can be lost, leading to large errors in the simulation. It can also cause the conservation problem if non-conservative remapping is used. The default emission treatment in Energy Exascale Earth System Model (E3SM) suffers from both problems. In this study, an improved treatment is implemented in E3SM to retain the emission heterogeneity at finer resolution (<100 km) and mass conservation. We have compared the improved treatment to the default treatment in the global uniform standard-resolution (1deg) simulations and Regionally Refined Model (RRM) simulations with high resolution (~0.25 deg) over North America. Global annual/seasonal mean aerosol quantities (e.g., surface concentration, burden, and optical depth) show small differences (~1%). However, much larger differences exist at regional/local scales. Compared to the more accurate new treatment, the default treatment significantly underestimates these aerosol quantities at locations with high emissions, while overestimating them at locations with relatively low emission near sharp emission gradients. These findings suggest the new emission treatment can better represent the spatial emission distribution in simulations (especially for RRM) and help improve the simulated aerosol lifecycle and the aerosol impact on climate.