Multi-species inversion of CH4, CO and H2 emissions from surface measurements

International audience; In order to study the spatial and temporal variations of the emissions of greenhouse gases and of their precursors , we developed a data assimilation system and applied it to infer emissions of CH 4 , CO and H 2 for one year. It is based on an atmospheric chemical transport model and on a simplified scheme for the oxidation chain of hydrocarbons , including methane, formaldehyde, carbon monoxide and molecular hydrogen together with methyl chloroform. The methodology is exposed and a first attempt at evaluating the inverted fluxes is made. Inversions of the emission fluxes of CO, CH 4 and H 2 and concentrations of HCHO and OH were performed for the year 2004, using surface concentration measurements of CO, CH 4 , H 2 and CH 3 CCl 3 as constraints. Independent data from ship and aircraft measurements and satellite retrievals are used to evaluate the results. The total emitted mass of CO is 30% higher after the inversion , due to increased fluxes by up to 35% in the Northern Hemisphere. The spatial distribution of emissions of CH 4 is modified by a decrease of fluxes in boreal areas up to 60%. The comparison between mono-and multi-species inversions shows that the results are close at a global scale but may significantly differ at a regional scale because of the interactions between the various tracers during the inversion.