Recently the NCEP's regional four-dimensional variational (4DVAR) data assimilation system has been updated to accommodate the need for operational implementation. Few important changes are:The performance of a new 4DVAR system will be shown.
- minimization space is defined in coarser resolution,
- system can employ a combination of fine and coarse resolution forecast models, and corresponding adjoints,
- only the nonlinear models are used in forward integration, and
- background and model error covariances are anisotropic and non-homogeneous.
Key words: variational, four-dimensional, data assimilation, regional