Satellite‐derived methane emissions from inundation in Bangladesh

Abstract The uncertainty in methane (CH 4 ) source strength of rice fields and wetlands is particularly high in South Asia CH 4 budgets. We used satellite observations of CH 4 column mixing ratios from Atmospheric Infrared Sounder (AIRS), Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), and Greenhouse Gases Observing Satellite (GOSAT) to estimate the contribution of Bangladesh emissions to atmospheric CH 4 concentrations. Using satellite‐derived inundation area as a proxy for source area, we developed a simple inverse advection model that estimates average annual CH 4 surface fluxes to be 4, 9, and 19 mg CH 4 m −2 h −1 in AIRS, SCIAMACHY, and GOSAT, respectively. Despite this variability, our flux estimates varied over a significantly narrower range than reported values for CH 4 surface fluxes from a survey of 32 studies reporting ground‐based observations between 0 and 260 mg CH 4 m −2 h −1 . Upscaling our satellite‐derived surface flux estimates, we estimated total annual CH 4 emissions for Bangladesh to be 1.3 ± 3.2, 1.8 ± 2.0, 3.1 ± 1.6 Tg yr −1 , depending on the satellite. Our estimates of total emissions are in line with the median of total emission values for Bangladesh reported in earlier studies.