摘要：The 2019-20 Australian mega-bushfires, which raged particularly over New South Wales and Victoria, released large amounts of toxic haze and CO2. Here, we investigate whether the resulting CO2 enhancement can be directly detected by satellite observations, based on National Aeronautics and Space Administration's Orbiting Carbon Observatory-2 (OCO-2) column-averaged CO2 (XCO2) product. We find that smoke from wildfires can greatly obscure satellite observations, making the available XCO2 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 CO2 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 XCO2 enhancements. Model simulation also suggests that the sensitivity of the downwind maximum XCO2 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 XCO2 enhancements due to the gaps in XCO2 detections obscured by smoke. Understanding the capability of OCO-2 XCO2 detection is prerequisite for monitoring and constraining wildfire CO2 emissions by inversions.
