A new 4-dimensional variational assimilation system applied to ENVISAT MIPAS observations

A four-dimensional variational (4D-var) data assimilation system intended for operational application to stratospheric trace gas observations is being developed. The Kernel of this new system is a novel stratospheric global chemistry circulation model (GCCM) and its adjoint version. The German Weather Service's global forecast model (GME) with its icosahedral discretisation scheme serves as an online meteorological driver for the GCCM. As a first application of the new system, ENVISAT MIPAS data has been assimilated for a selected period. It can be demonstrated that the assimilation procedure gains a considerable improvement over legacy model runs, as the discrepancies between observations and the model are significantly reduced, while chemical consistency is maintained by the computationally costly, but efficient 4D-var technique.