1A NEW 4-DIMENSIONAL VARIATIONAL ASSIMILATION SYSTEM APPLIED TO ENVISAT MIPAS OBSERVATIONS

A four-dimensional variational (4D-var) data assimila-tion system intended for operational application to strato-spheric trace gas observations is being developed. The Kernel of this new system is a novel stratospheric global chemistry circulation model (GCCM) and its adjoint ver-sion. 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 MI-PAS 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