Validation and accuracy analysis of wind products from scatterometer onboard the HY-2B satellite

The Chinese marine dynamic environment satellite HY-2B was launched in October 2018 and carries a Ku-band scatterometer. This paper focuses on the accuracies of HY-2B scatterometer wind data during the period from November 2018 to May 2021. The HY-2B wind data are validated against global moored buoys operated by the U.S. National Data Buoy Center and Tropical Atmosphere Ocean, numerical model data by the National Centers for Environmental Prediction, and the Advanced Scatterometer data issued by the Remote Sensing System. The results showed that the wind speeds and directions observed by the HY-2B scatterometer agree well with these buoy wind measurements. The root-mean-squared errors (RMSEs) of the HY-2B wind speed and direction are 0.74 m/s and 11.74°, respectively. For low wind speeds (less than 5 m/s), the standard deviation of the HY-2B-derived wind direction is higher than 20°, which implies that the HY-2B wind direction for low wind speeds is less accurate than that for moderate to high wind speed ranges. The RMSE of the HY-2B wind speed is slightly larger in high latitude oceans (60°–90°S and 60°–90°N) than in low latitude regions. Furthermore, the dependence of the residuals on the cross-track location of wind vector cells and the stability of the HY-2B scatterometer wind products are discussed. The wind stability assessment results indicate that a clear yearly oscillation is observed for the HY-2B wind speed bias which is due to seasonal weather variations. In general, the accuracy of HY-2B winds meets the operational precision requirement and is consistent with other wind data.