Use and impact of ATOVS in the DMI-HIRLAM regional weather model

The HIRLAM (HIgh Resolution Limited Area Model) 3D-VAR (three dimensional variational) data assimila-tion system (Gustafsson et al., 2001; Lindskog et al., 2001) has been used operationally at DMI since October 2001. A major reason for changing from the former OI (Optimum Interpolation) data assimilation system was to be able to make better use of satellite radiance data. At DMI experiments with use of locally receive