First satellite measurements of carbon dioxide and methane emission ratios in wildfire plumes

Using methane and carbon dioxide atmospheric mixing ratios retrieved using SWIR spectra from the Greenhouse Gases Observing SATellite (GOSAT), we report the first wildfire plume CH₄ to CO₂ emission ratios (ER_CH4/CO2) determined from space. We demonstrate the approach's potential using forward modeling and identify a series of real GOSAT spectra containing wildfire plumes. These show significantly changed total-column CO₂ and CH₄ mixing ratios, and from these we calculate ER_CH4/CO2 for boreal forest, tropical forest, and savanna fires as 0.00603, 0.00527, and 0.00395 mol mol^-1, respectively. These ERs are statistically significantly different from each other and from the "normal" atmospheric CH₄ to CO₂ ratio and generally agree with past ground and airborne studies.