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NWP Ocean Calibration for the CFOSAT wind scatterometer and wind retrieval evaluation
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  • Zhen Li,
  • Zhen Li,
  • Ad Stoffelen,
  • Anton Verhoef,
  • Jeroen Verspeek
Zhen Li
Royal Netherlands Meteorogical Institute

Corresponding Author:[email protected]

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Zhen Li
Royal Netherlands Meteorogical Institute
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Ad Stoffelen
Royal Netherlands Meteorogical Institute
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Anton Verhoef
Royal Netherlands Meteorogical Institute
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Jeroen Verspeek
Royal Netherlands Meteorogical Institute
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Abstract

The unique rotating fan-beam feature of SCAT onboard CFOSAT leads to varying geometries across the swath and furthermore leads to varying wind retrieval performance across the swath. The Wind Vector Cells (WVCs) across the swath are classified into outer, sweet and nadir. The sweet WVCs contain the most diverse geometries, which lead to the best wind retrieval performance. In the outer WVCs the azimuth and incidence angle diversity is very limited and the number of views is smallest, which makes the wind retrieval the most ambiguous and difficult to improve. Secondly, in order to improve the wind retrieval, two kinds of NWP Ocean Calibration (NOC) are applied. One is a NOC as a function of incidence angle (NOCinc). The other one is a newly developed NOC as a function of incidence angle and antenna azimuth angle (NOCant), which takes the rotation angle into account. The NOCant correction results in better fits of the Geophysical Model Function than the NOCinc correction does, except for the outer WVCs, where the limited diversity of views determines retrieval quality. The results show that NOCant correction improves the wind speed Probability Distribution Function per WVC and reduces the average wind direction bias and the relative wind direction (relative to the satellite motion direction) biases, as compared to NOCinc correction. In conclusion, the rotating fan-beam feature of SCAT leads to unique and various data characteristics across the swath. Overall the performance of the proposed NOCant correction is better than NOCinc and improves the wind statistics.
Oct 2021Published in Earth and Space Science volume 8 issue 10. 10.1029/2020ea001606