Application of high-resolution large-eddy simulation in atmospheric chemistry studies for urban and fire environments

Mesoscale atmospheric chemical transport models, while widely used for studying atmospheric chemistry, face significant challenges in capturing fine-scale processes in complex environments such as urban areas and wildfire smoke plumes. The coarse spatial resolution of these models limits their ability to resolve turbulent transport, sharp concentration gradients, and nonlinear chemical interactions driven by subgrid-scale dynamics. To address these limitations, we apply the high-resolution Weather Research and Forecasting model with Large Eddy Simulation and Chemistry (WRF-LES-Chem) to two distinct cases: (1) investigating ozone formation in the Houston urban domain in Texas, U.S., characterized by complex emission sources and intricate coastal boundary layer processes, and (2) understanding in-plume chemistry during the Williams Flats Fire, a severe wildfire event in Washington State, U.S., where intense emissions and plume dynamics drive rapid chemical transformations. Our simulations demonstrate the advantages of high-resolution modeling in resolving small-scale chemical and meteorological interactions, improving the representation of observed diurnal and spatial variations in highly reactive chemicals, ozone, and secondary organic aerosols (SOA), and providing deeper insight into the role of radical chemistry in controlling ozone formation regimes and SOA formation. These applications highlight the importance of LES-Chem approaches in advancing air quality predictions and understanding atmospheric chemistry in dynamic and heterogeneous environments.