Joint CO-CO2 inversion setup for investigating the effect of drought on the carbon cycle

Abstract : Droughts impact the carbon cycle by enhancing biomass burning, and by reducing the carbon uptake by the biosphere. Droughts are expected to increase under future climate change. Therefore a good understanding of the feedback processes between droughts and the carbon cycle is important for accurately predicting future carbon dioxide (CO2) levels in the atmosphere. An important tracer for biomass burning is carbon monoxide (CO). By combining the information from both CO and CO2 satellite data in an inverse modelling setup, it is possible to separately constrain the biomass burning and biosphere atmospheric fluxes of CO2. Within the TM5-4DVAR inverse modelling system, we implemented a joint CO-CO2 inversion setup. The simulated CO and CO2 concentrations were fully coupled, for instance by modelling the CO2 production from oxidation of CO. The biomass burning CO emissions to the atmosphere are further constrained using satellite CO observations from IASI and MOPITT. We use available information on temporally and spatially varying CO:CO2 emission ratios to calculate the direct biomass burning CO2 flux based on derived CO emissions. The CO2 exchange between the biosphere and atmosphere is then inferred using GOSAT satellite measurements. Our inversion setup provides a powerful tool for investigating the ecosystem sensitivity to droughts. We will present first results of the coupled system, focusing on the regional effect of the 2010 drought event in Russia.