Impact of the Multi-Layer Urban Schemes on the Feedback between Heat Waves and Urban Air Quality in the Chicago Metropolitan Area

Heat waves can negatively impact the air quality, especially in urban areas with urban heat island effect. However, current modeling studies on air quality lack accurate representation of urban processes. To address this knowledge gap, we adopted two versions of coupled Building Effect Parameterizations and Building Energy Model (BEP/BEM) into the WRF-Chem model to investigate how multi-layer urban scheme affects the interaction between heat waves and urban air quality during the Aug 23—24, 2023 heatwave in the Chicago metropolitan area. Specifically, we examined the default BEP/BEM implementation and a modified BEP/BEM parameterization scheme derived from high-fidelity Computational Fluid Dynamics simulations. We compare the concentrations of PM2.5, CO, NO2 and O3 among the coupled model simulations, WRF-Chem simulations without urban parameterizations and observations from EPA AirNow observations, the Community Research on Climate and Urban Science measurement (CROCUS) measurements and the Measurement of Pollution in the Troposphere (MOPITT) remote sensing data. Our study shows that with the integration of the BEP/BEM model, the accuracy of the air pollutant concentration predictions significantly improved due to a better representation in air flow stagnation and urban heat, compared to that without the BEP/BEM model. Accurate representation of urban processes is essential for predicting air quality at the urban scale.