Satellite-based modeling of wetland methane emissions on a global scale (SatWetCH4 1.0)

Abstract. Wetlands are major contributors to global methane emissions. However, their budget and temporal variability remain subject to large uncertainties. This study develops the Satellite-based Wetland CH₄ model (SatWetCH4), which simulates global wetland methane emissions at 0.25°x0.25° and monthly temporal resolution, relying mainly on remote sensing products. In particular, a new approach is derived to assess the substrate availability, based on Moderate-Resolution Imaging Spectroradiometer data. The model is calibrated using eddy covariance flux data from 58 sites, allowing for independence from other estimates. At the site level, the model effectively reproduces the magnitude and seasonality of the fluxes in the boreal and temperate regions, but shows limitations in capturing the seasonality of tropical sites. Despite its simplicity, the model provides global simulations over decades and produces consistent spatial patterns and seasonal variations comparable to more complex Land Surface Models. In addition, our study highlights uncertainties and issues in wetland extent datasets and the need for new seamless satellite-based wetland extent products. In the future, there is potential to integrate this one-step model into atmospheric inversion frameworks, thereby allowing optimization of the model parameters using atmospheric methane concentrations as constraints, and hopefully better estimates of wetland emissions.