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SDP 2.0 validation

J Vogelzang

The SeaWinds Data Processor (SDP) generates ocean vector wind fields from the measurements of the SeaWinds scatterometer carried by QuikScat. SDP is a free software package developed in the framewotk of the Satellite Application Facility for Numerical weather prediction (NWP SAF) sponsored by EUMETSAT. A full description of SDP can be found in [SCAT group, 2007].
SDP 2.0 will replace SDP 1.5 medio 2008. The main differences between the two versions are:
 The default resolution of SDP 2.0 will be 25 km (was 100 km);
 The dimensions and cell size of the batch grid are now adjustable with the only restriction that they are even (they were fixed to dimension 32  32 points with a free edge of 5 points and a cell size of 100 km  100 km);
 SDP 2.0 also processes the outer swath (wind vector cells 1-10 and 67-76);
 Improved rain flag handling.
From SDP 1.0 to 1.5, the following lessons were learned [Vogelzang, 2006, 2007]:
 At 25 km resolution, the Multiple Solution Scheme (MSS) must be used in order to suppress the noise in the retrieved wind fields, notably in the nadir swath;
 At 25 km resolution and with MSS, the Gross Error Probabilities should preferably be switched off.
 The free edge of 500 km (5 batch grid points) around the observations is rather small, since in the Tropics the background error correlation length equals 600 km.
Therefore these settings will be used as default by SDP 2.0.

The possibility to change the batch grid size and dimension offers a whole range of new settings for 2DVAR. The optimum settings will be determined in this report. Further, the quality of the outer swath wind vectors will be assessed by statistical analysis of the differences with ECMWF background fields, rain flagging and MLE values, and a-priori probabilities.

Bibliografische gegevens

J Vogelzang. SDP 2.0 validation
2008, EUMETSAT, 2008

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