Novel Validation and Calibration Strategy for Total Precipitable Water Products of Fengyun-2 Geostationary Satellites

The latest batch of the Chinese Fengyun-2 (FY-2) geostationary satellites (i.e., FY-2F, FY-2G, and FY-2H) provides total precipitable water (TPW) products at high spatial and temporal resolutions. However, due to the lack of accuracy and performance evaluation for these products, a vast amount of valuable TPW data remains unused in atmospheric science research. To address this issue, this study aimed to propose and apply a validation strategy that incorporated a hemispheric vertical correction model (VCM) to obtain reliable evaluation results. With the help of reliable radiosonde and the state-of-the-art fifth generation of the European Center for Medium-Range Weather Forecasts (ECMWF) reanalysis data (ERA5), this study was the first to assess the quality of the full-disk TPW products retrieved via the three FY-2 satellites from January 2019 to December 2020. In addition, this study analyzed the water vapor content, latitude, and elevation dependencies of FY-2 TPW retrieval error and explored the potential for improving the quality of each satellite TPW product through a linear calibration in the three test areas of northern and southern temperate zones and tropics. The results of this study were threefold. First, the accuracy of FY-2F and FY-2H TPW was superior to that of FY-2G. The root mean square error (RMSE) values of FY-2F, FY-2G, and FY-2H were 3.84, 4.46, and 3.73 mm and 2.30, 2.55, and 2.14 mm relative to the radiosonde and ERA5 data, respectively. Second, the TPW retrieval error of the FY-2 satellites decreased with the increasing latitude or decreasing elevation. Overall, FY-2G underestimated TPW, whereas FY-2F and FY-2H only underestimated TPW under wet conditions (i.e., TPW > 55 mm). Finally, the calibration potential of FY-2F and FY-2H was higher than that of FY-2G, and the bias, slope, and potential index (PI) values of FY-2G were lower than those of FY-2H and FY-2F in all the three test areas.