Simulations of a High Ozone Episode and Heatwave Day Using a Coupled Multi‐Layer Urban Canopy and Chemistry Model

Abstract Coastal cities face critical challenges in managing ozone pollution because of high population density and complex interactions between urbanization and coastal meteorology. Using New York City (NYC) as a case study, this work examines how urban surfaces influence heatwaves, sea‐breeze circulations, and boundary‐layer dynamics, and how these processes shape nitrogen dioxide () distributions and ozone formation. Observations from the 2018 Long Island Sound Tropospheric Ozone Study (LISTOS), collected with an airborne high‐resolution ultraviolet–visible spectrometer, provide tropospheric column densities for evaluating the Weather Research and Forecasting model coupled with Chemistry (WRF‐Chem) in multiple urban canopy configurations. Results show that the early‐morning urban heat island effect accelerated sea‐breeze initiation, concentrating over the city. Building‐induced drag reduced wind speeds, altered advection patterns, and prolonged precursor residence times, enhancing photochemistry. These processes elevated ozone both within NYC and downwind. The findings demonstrate how the interplay of urban heat islands, building drag, and coastal circulations governs ozone pollution in coastal cities, providing a framework for improving air‐quality modeling and mitigation strategies.