Validation and intercomparison of HY-2A/MetOp-A/Oceansat-2 scatterometer wind products

Abstract

Sea surface winds are of great significance in scientific research. In the last few years, three series of scatterometers were launched to measure these winds, including the Advanced Scatterometer (ASCAT) aboard Meteorological Operational Satellite A (MetOp-A) and MetOp-B, Oceansat-2 Scatterometer (OSCAT), and HY-2A Scatterometer (HY-2A SCAT). Based on buoy wind data, validation and intercomparison of these scatterometers were performed. Scatterometer-derived wind and buoy wind data were collected only if the spatial difference was less than 0.1 degree and temporal difference less than 5 min. After discarding wind direction data outside five times the standard deviation, ASCAT wind products showed high accuracy in both wind speed and direction, with root-mean-square error (RMSE) 0.86 m/s and 17.97 degrees, respectively. HY-2A SCAT nearly meets the mission requirement, with RMSE for wind speed 1.23 m/s and 22.85 degrees for wind direction. OSCAT had poor performance when compared with the others. RMSE for wind speed was 1.54 m/s and 39.86 degrees for wind direction, which greatly exceeds the mission requirement of 20 degrees. In addition, the RMSE for wind direction shows a high-low pattern on buoy wind speed. However, a wind speed range from 14 to 15 m/s was found to be abnormal, and the reason remains unclear. There was no systematic dependency of both wind speed and direction residuals on buoy wind speed and cross-track location of the wind vector cells across the entire range. No seasonal variation was found for any scatterometer.