Spaceborne detection of XCO2 enhancement induced by Australian mega-bushfires

The 2019–20 Australian mega-bushfires, which raged particularly over New South Wales and Victoria, released large amounts of toxic haze and CO 2 . Here, we investigate whether the resulting CO 2 enhancement can be directly detected by satellite observations, based on National Aeronautics and Space Administration’s Orbiting Carbon Observatory-2 (OCO-2) column-averaged CO 2 (XCO 2 ) product. We find that smoke from wildfires can greatly obscure satellite observations, making the available XCO 2 mainly locate over outer fringes of plumes downwind of the major mega-bushfires in eastern Australia in three orbit observations during November–December 2019, with their enhancements of approximately 1.5 ppm. This fire-induced CO 2 enhancement is further confirmed using an atmospheric transport model, Goddard Earth Observing System-Chem, forced by satellite observation-derived fire product Global Fire Emissions Database, version 4.1 and wind observations, with comparable simulated XCO 2 enhancements. Model simulation also suggests that the sensitivity of the downwind maximum XCO 2 enhancement is 0.41 ± 0.04 ppm for 1 TgC d −1 fire emissions. In sum, though detectable to some extent, it remains a challenge to get the accurate maximum XCO 2 enhancements due to the gaps in XCO 2 detections obscured by smoke. Understanding the capability of OCO-2 XCO 2 detection is prerequisite for monitoring and constraining wildfire CO 2 emissions by inversions.