Evaluation of CFOSAT Scatterometer Wind Data in Global Oceans

The China-France Oceanography SATellite (CFOSAT), launched on 29 October 2018, is a joint mission developed by China and France. To evaluate the CFOSAT wind product, L2B swath data with a spatial resolution of 25 x 25 km were compared with in situ measurements between December 2018 and December 2020. The in situ measurements were collected from 217 buoys. All buoy winds were adjusted to 10 m height using a simple logarithmic correction method. The temporal and spatial separations between the CFOSAT and in situ measurements were restricted to less than 30 min and 0.25 degrees. The results indicate that the CFOSAT wind retrievals agree well with the buoy measurements. The root mean square errors (RMSEs) of wind vectors were 1.39 m s(-1) and 34.32 degrees and negligible biases were found. In the near shore under rain-free conditions, the RMSEs were enhanced to 1.42 m s(-1) and 33.43 degrees. Similarly, the RMSEs were reduced to 1.16 m s(-1) and 30.41 degrees offshore after the rain effect was removed. After winds less than 4 m s(-1) were removed, the RMSE of wind directions was reduced to 19.69 degrees. The effects of significant wave height, air-sea temperature difference, sea surface temperature, atmospheric pressure and ocean surface current on the wind residuals were assessed. The performance of wind retrievals under the passage of tropical cyclones was evaluated. The evaluation results show that the CFOSAT wind retrievals satisfy the accuracy requirements of scientific research, although some improvements are needed to enhance the performance.