Estimation of biomass burning emission of NO₂ and CO from 2019-2020 Australia fires based on satellite observations

The bushfires that occurred in Australia in late 2019 and early 2020 were unprecedented in terms of their scale, intensity, and impacts. Using nitrogen dioxide (NO2) and carbon monoxide (CO) data measured by the Tropospheric Monitoring Instrument (TROPOMI), together with fire counts and fire radiative power (FRP) from MODIS, we analyzed the temporal and spatial variation of NO2 and CO column densities over three selected areas covering savanna and temperate forest vegetation. The delta NO2/delta CO emission ratio and emission factor were also estimated. The delta NO2/delta CO emission ratio was found to be 1.57 +/- 1.71 for temperate forest fire and ranged from 2.0 +/- 2.36 to 2.6 +/- 1.92 for savanna fire. For savanna and temperate forest fires, satellite-derived NOx emission factors were found to be 1.48 and 2.39 gkg(-1), respectively, whereas the CO emission factors are 107.39 and 126.32 gkg(-1), respectively. This study demonstrates that the large-scale emission ratio from the TROPOMI satellite for different biomass burnings can help identify the relative contribution of smoldering and flaming activities in a large region and their impacts on the regional atmospheric composition and air quality. This method can be applied to study the emissions from other large fires, or even the burning of fossil fuel in megacities, and their impact on air quality.