Estimations of CO and NO2 emissions and the burning combustion efficiency for fire activities over North America using TROPOspheric Monitoring Instrument (TROPOMI) measurements

Fire activities have significant impacts on air quality by emitting various trace gases (e.g. carbon monoxide (CO) and nitrogen oxides (NO_x)) and fine particulate matter (PM_2.5) into the atmosphere. Fire emissions are critical inputs of chemical transport models (CTMs), which are used to understand, and even predict, the influence of fires on the atmosphere and air quality. Most of the current fire emission inventories use ground and space-borne measurements of fire radiance to estimate trace gas and particle emissions from fire activities depending on prescribed emission factors. In this study, the total-column CO and nitrogen dioxide (NO₂) measurements from the TROPOspheric Monitoring Instrument (TROPOMI) satellite are used to quantify the CO and NO₂ fire emissions over North America in 2020. We use high resolution total-column CO and NO₂ measurements from TROPOMI and atmospheric transport and chemical loss processes to derive estimates of CO and NO₂ fire emissions (E_CO and E_NO2). We further use the emission ratio (E_NO2/E_CO) as a proxy for biomass burning combustion efficiency. Preliminary results show that, although the TROPOMI-based emissions have a weak linear relationship compared to the U.S. EPA’s 2020 draft National Emission Inventory (EPA NEI), which is based on a “bottom-up” approach to derive biomass burning emissions, the TROPOMI-based biomass burning combustion efficiency has a relatively high correlation coefficient. Compared to other satellite-based, “top-down” biomass burning inventory approaches (e.g. the Blended Global Biomass Burning Emissions Product (GBBEPx) and the Global Fire Assimilation System (GFAS)), there are weaker linear relationships and relatively low correlation coefficients in terms of biomass burning emissions and combustion efficiency. Also, the TROPOMI-based burning combustion efficiency is able to reflect the fire type of different regions, which could be a useful input for CTMs.