A Wall of Smoke: Understanding the Drivers of the June 2023 Canadian Wildfire Smoke Event for New York City

Abstract The 2023 Canadian wildfire season was notable for its extent and the dense smoke it produced. Motivated by the resulting record‐breaking air quality hazard in the New York City region, we use in situ observations, satellite retrievals, reanalysis data, and trajectory analysis to explore how the smoke aerosol emitted from the Quebec fires came to influence PM 2.5 concentrations 1,000 km downstream in New York City. Using emissions estimates from the Regional Advanced Baseline Imager + VIIRS Emissions data set and injection height estimates from the Integrated Monitoring and Modeling System, we relate the emissions timing of the fires with the broader synoptic context and surface PM 2.5 concentrations. The smoke aerosols were predominantly confined to the boundary layer and lower troposphere throughout the event. The daily cycle of fire emission intensity contributed to sub‐daily variations in PM 2.5 concentrations in New York City downstream. Using data from the NYS Mesonet Profiler Network, radiosondes, and ERA5 reanalysis, we clarify the critical role played by a strong, quasi‐stationary extratropical cyclone east of the fires: this cyclone's unusually slow, westward propagation helped organize the plume and advect its smoke from Quebec to New York City for three consecutive days.