Mobile Sensing for Assessing Urban Microclimate (UMC) and Urban Heat Island (UHI) Effects on Air Quality

During the intense heatwaves of late summer 2024, Washington, DC’s urban landscape revealed the powerful influence of urban morphology on microclimates and air quality. This study investigates how building height-to-width (H/W) ratios impact the urban heat island (UHI) effect, using a combination of field measurements and CFD simulations to understand the dynamics. Street-level data collected from late August to November 2024 across three sites in Washington DC. show that high H/W ratios 2.5–3.0, significantly increased temperatures 30.12–32.10°C and reduced wind speeds 0.02–3.20 m/s, leading to elevated pollutant concentrations, with PM2.5 averaging 2.19 µg/m³. Meanwhile, lower H/W ratios less than 1.5 demonstrated better air circulation and lower pollution levels. The CFD simulations are in good agreement with the experimental data yielding an RMSE of 0.75 for temperature, thus demonstrating its utility for forecasting UHI effects under varying urban layouts. These results demonstrate the potential of CFD in not only modeling but also predicting UHI dynamics, providing valuable tools for urban planners to mitigate heat and improve air quality through strategic design decisions.