Regional-scale aerosol models experience structural uncertainty due to multiple factors, including the selection of aerosol representation and the resolution of spatial heterogeneity. In this work we investigate the uncertainty due to these two factors on the prediction of cloud condensation nuclei (CCN). We use the particle-resolved model PartMC coupled to the Weather Research and Forecasting (WRF) model configured for large-eddy simulations (LES). The resulting modeling framework allows for unprecedented spatial resolution gas phase and aerosol evolution and includes the processes of gas phase chemistry, particle coagulation, and gas-particle partitioning. The model domain has horizontal dimensions of 20 km by 20 km with a grid spacing of 100 m, and 200 vertical log-spaced pressure layers. Periodic boundary conditions are chosen, and meteorological initial conditions are set by large-scale forcing profiles. Numerous idealized profiles are simulated for aerosol and gas species and are selected to investigate a range of spatiotemporally varying emission scenarios. To quantify the importance of the particle-resolved treatment and high spatial resolution on estimating CCN activity, CCN concentrations are compared against results from simulations with similar configurations using the modal MAM3 model at coarser grid resolutions (1 km, 4 km, 12 km). This work is a first step in quantifying structural uncertainties imposed by the choice of aerosol representation and spatial resolution and their interaction. Future work will apply this modeling approach to more geographically representative emissions profiles to investigate a broader range of sources and spatial configurations.

Particle-resolved LES simulations to evaluate the impact of spatial heterogeneity on CCN activity

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