CFOSAT and WindRad Rotating Fan-beam SCATterometer Simulation and Wind Retrieval Performance Evaluation

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CFOSAT-Windrad-simulation_OSISAF

In the frame of the NWP SAF and of the OSI SAF, the scatterometer team at KNMI assessed the performance of CFOSAT and WindRad Rotating Fan-beam Scatterometer Simulation and Wind Retrieval.

Here below, Zhen Li explains briefly what was done and what was found during this study.

What did we do?

  • Built a simulation framework for all existing rotating-beam scatterometer types (rotating fan-beam and rotating pencil-beam).

  • Evaluated the wind retrieval performance of SCAT (CFOSAT), WindRad and SeaWinds under the same simulation framework.

  • Analyzed the pros and cons among SCAT, WindRad and SeaWinds.

  • The developed simulation package allows us to further investigate the true resolution of the instruments before their launch and also to determine the non-overlap of the views in a WVC, which contributes to the geophysical noise.

What did we find?

  • The wind retrieval quality strongly depends on the location of the WVCs across the swath, and the sweet swath shows the most favourable geometries for wind retrieval (Figure 1).

  • Among the more unfavourable outer and nadir swath regions, SCAT and SeaWinds perform best in the nadir swath, while WindRad rather substantially improves the outer swath wind retrieval.

  • WindRad’s nadir swath region with lower wind retrieval quality is larger than its outer swath region, while SCAT and SeaWinds have a relatively large outer swath region with degraded quality (Figure 2).

  • The outer swath of SCAT implies both wind speed and wind direction retrieval problems, while for WindRad only wind speed retrieval is affected.

  • The increased number of views in the nadir and sweet swath for WindRad does not lead to an improved wind retrieval, but it shows a saturation effect and stays relatively similar to SCAT.

Report on this study :

CFOSAT and WindRad Rotating Fan-beam SCATterometer Simulation and Wind Retrieval Performance Evaluation