Assimilating ambiguous QuikScat scatterometer observations in HIRLAM 3-D-Var at the Norwegian Meteorological Institute

The Norwegian Meteorological Institute has implemented ambiguous QuikScat observations in the HIRLAM threedimensional variational data assimilation system, by approximating the method that will achieve the best mean squared error verification results according to the Bayesian decision theory. A four-month long impact study of this implementation during the 2003/2004 winter showed that assimilating QuikScat observations had a small positive effect on the average mean sea level pressure forecasting skill.