Spaceborne detection of XCO₂ enhancement induced by Australian mega-bushfires

Abstract

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.

The Carbon Cycle of Southeast Australia During 2019–2020: Drought, Fires, and Subsequent Recovery

“…It is also notable that the largest biomass burning enhancements of $${\mathrm{X}}_{{\text{CO}}_{2}}$$ were not observable by OCO‐2 or TCCON sites due to the presence of co‐emitted aerosols (J. Wang et al., 2020). Rapid deployment of aircraft campaigns that observe the chemical composition of the biomass burning plumes would help mitigate these sampling biases.…”

Detecting the Responses of CO2 Column Abundances to Anthropogenic Emissions from Satellite Observations of GOSAT and OCO-2

“…XCO 2 observations from OCO-2 have also been used to identify enhanced plume signals and estimate anthropogenic emissions from individual point sources such as power plants and volcanoes [30][31][32]. For Australian mega bushfires, fire-induced XCO 2 enhancement detected by three orbits of observations from OCO-2 during November-December in eastern Australia is approximately 1.5 ppm [33]. Global XCO 2 anomalies derived from satellite observations agree well with the spatial patterns of emission inventories and model simulations [34][35][36].…”

Modulation of Land Photosynthesis by the Indian Ocean Dipole: Satellite‐Based Observations and CMIP6 Future Projections

“…More recently, an extreme IOD event occurred in 2019, which was the strongest pIOD in the past two decades. It took large responsibility for the out-of-control mega-bushfires over the eastern Australia in 2019-2020 (Nolan et al, 2020;Phillips & Nogrady, 2020;Wang et al, 2020). Inspired by this extreme event, here we demonstrate the different impacts of IOD and ENSO on terrestrial gross primary productivity (GPP) and investigate the impacts of the recent extreme pIOD, mainly based on climate observations and a newly satellite-based GPP product.…”

“…For a typical example in 2019, a very weak El Niño event occurred. This event obviously cannot explain the warm and severe drought conditions over the eastern Australia, making the devastating bushfires (Boer et al, 2020;Nolan et al, 2020;Wang et al, 2020) and GPP reductions (Figure 3d). Taking both of ENSO and IOD events into account, we can better understand or even predict the variations of these regional ecosystems and carbon cycle.…”