Theme coordinator: Peter Rayner, Laboratoire des Sciences du Climat et de l’Environnement
This theme develops the component to monitor the concentrations of greenhouse gases and their surface sources and sinks, and to attribute these sources and sinks to controlling processes. Carbon dioxide and methane are added as variables in the ECMWF meteorological model, using prescribed surface fluxes. Radiance measurements from satellite-borne infrared sounding instruments and retrievals of gas concentrations from measurements at shorter wavelengths are used in four-dimensional variational data assimilation. The analysed concentrations are then used with surface flask measurements to infer global time-evolving distributions of surface fluxes. Terrestrial ecosystem models, independent satellite retrievals, carbon-model simulations and in-situ aircraft observations are utilized to evaluate and interpret the results. Insights into the effects of processes such as transport, anthropogenic activity and biomass burning are expected.
The system currently assimilates radiance data from the AIRS and IASI instruments, and retrievals of methane from SCIAMACHY. It will exploit new data to be received from the dedicated GOSAT and OCO greenhouse-gas missions. The figure shows distributions of carbon dioxide for August 2003 from a model simulation (left) and from a prototype assimilation of radiance information from AIRS (right).