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

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