High-Resolution Numerical Simulations of Urban Air Quality Using Computational Fluid Dynamics Model: Applications in Madrid, Spain

This paper presents a high-spatial-resolution 3D system to simulate air quality in urban environments by coupling the WRF/Chem regional model with the PALM4U computational fluid dynamics model, together with an emission model using the SUMO microscopic traffic model. The system has been applied to two experiments in the city of Madrid, Spain. The first study quantifies the impact of four high-rise buildings on pollutant dispersion. The second evaluates the effect of changing tree types (broad-leaf vs. needle-leaf) in the Retiro Park on NO2 and O3 concentrations. Both simulations adopt a multiscale approach, using detailed 3D urban morphology, traffic flow data and meteorological conditions. In the first experiment, high-rise buildings caused local variations in NO2 and O3 of up to 15% and 20%, respectively. In the second experiment, replacing broad-leaf trees with needle-leaf trees led to a mean NO2 reduction of 1.69% across 90.67% of the study area. This research demonstrates the value of integrated CFD modeling for planning urban mitigation strategies and optimizing air quality in complex urban environments.