Title: Towards a longer 4D-Var assimilation window

Authors: Yannick Tremolet (ECMWF)

For a linear system, weak constraints 4D-Var with a long enough assimilation window is equivalent to a full rank kalman smoother. Good results have been obtained with simple systems that confirm that the analysis can be improved with a long assimilation window. However, there are still difficulties in using long assimilation widows for operational systems.

In this talk, we will present results obtained with the full ECMWF system with 24-hour and 48-hour assimilation windows. The formulation of the weak constraint term, the model error covariance matrix and the cycling with overlapping windows will be discussed.

GMAO Head: Michele Rienecker Global Modeling and Assimilation Office NASA Goddard Space Flight Center

Curator: Nikki Privé Last Updated: May 27 2011