[6-1] Invited

Variational and EnKF assimilation systems at ECMWF

M. Bonavita (ECMWF)

The Ensemble Kalman Filter has currently reached a level of maturity which makes it competitive with standard 4DVar for use in global operational NWP. The choice between the two techniques is thus more dependent on considerations of computational efficiency and scalability than accuracy. On the other hand hybrid data assimilation systems which combine aspects of the variational and EnKF methodologies have been shown to be able to provide further improvements. These hybrid systems can be set up in a variety of ways. In this talk I will describe two examples of hybrid ensemble data assimilation systems that have been implemented at ECMWF and provide results of their performance in a quasi-operational set-up.