Long-range transport of Siberian biomass burning emissions to North America during FIREX-AQ

Biomass burning from wildfires is a significant global source of aerosol and trace gases which impact air quality, tropospheric and stratospheric composition, and climate. During the summer of 2019, wildfire activity in central and eastern Siberia occurred during the Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) campaign conducted in the United States between July 24 and September 6, 2019. Ground-based lidar observations from the Autonomous Mobile Ozone Lidar for Tropospheric Experiments (AMOLITE) system in Alberta, Canada retrieved frequent ozone (O3) and aerosol lamina in the free troposphere during the campaign. Simulated data from NASA's GEOS Composition Forecast (GEOS-CF) coupled chemistry meteorology model, TROPOspheric Monitoring Instrument (TROPOMI), and ground-based in situ measurements were applied to define the trans-Pacific and trans-Arctic transport pathways of Siberian biomass burning emissions resulting in the enhanced O3 and aerosol lamina observed by AMOLITE in western Canada. Siberian wildfires had some influence on North American air quality resulting in enhancements of surface carbon monoxide (CO) and fine particulate matter (PM2.5) concentrations in western Canada; however, minimal increases in surface-level O3 were measured as well as modeled by GEOS-CF. The impact in western Canada was larger in the free troposphere, demonstrated by GEOS-CF modeled and AMOLITE observed O3 lamina >20 ppb above background values and coincident model-predicted PM2.5 lamina >30 μg m−3. This study demonstrated that the Siberian biomass burning emissions in the summer of 2019 impacted tropospheric composition in western Canada, and potentially could have influenced areas in the vicinity of FIREX-AQ airborne and ground-based measurements in the United States, and should be considered in future studies.