The role of transport in New York’s air quality impacts from the 2023 Canadian wildfires

In 2023, Canada experienced its most severe wildfire season on record, burning over 7.8 million hectares and releasing unprecedented carbon emissions surpassing the country’s previous record by several fold. These fires produced dense plumes that were transported into the Northeastern United States (US), including New York City (NYC), contributing to extreme air pollution in the area. This study investigates whether atmospheric transport from Canada to NYC during the 2023 wildfire season was unusual compared to previous years, considering the important role that transport consistently plays in carrying smoke over long distances, or whether the meteorological conditions were different than previous years, which led to the poor air quality in NYC. We use community atmospheric model (CAM) simulations driven by reanalysis winds for the period 1985–2023, along with daily PM _2.5 observations from the US environmental protection agency (EPA), to simulate long-range aerosol transport under base and high emission scenarios and analyze pollutant transport and concentrations over NYC. Results show that although long-range transport was necessary to bring smoke to NYC, the transport patterns in 2023 were not significantly different from those in previous years. Instead, the record-breaking PM _2.5 levels were mainly caused by the extraordinary magnitude of fire emissions. The model accurately captured the spatial distribution of smoke. These findings thus emphasize anomalously high fire emissions, rather than transport or meteorology, played a more crucial role in driving the air quality impacts of this event over the Northeastern US.