Prior to the assimilation, a global check on instrument performance is performed on 6-hourly data batches. This QC is based on the value of the residual cost function from the 50-km inversion. It is a purely self-consistency check, and therefore, does not rely on any ECMWF fields.
The assimilation of QuikSCAT data has a positive impact on forecast performance, especially on the southern hemisphere. The benefit of QuikSCAT on ECMWF's analyses and forecasts will be discussed.
On average, the analysis of tropical cyclones has been improved. However, this is not true for all cases. Too much good quality data around tropical cyclones is rain flagged, leaving only moderate wind speedsfar from the centre. Experiments using different rain-contamination QC schemes retaining more data in the vicinity of tropical cyclones will be presented. In addition, the impact of using only one wind solution in a purely quadratic cost function required by a new 4D-Var minimization method will be discussed.
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