Evaluation of Wet Tropospheric Delay for HY-2C Altimeter Based on GNSS and ERA5 Data

HY-2C satellite equipped with a three-channel Calibrated Microwave Radiometer (CWR) for Wet Tropospheric Delay (WTD) correction for satellite altimetry was launched by China on 21 September 2020. WTD is one of the range errors in satellite measurements of Sea Surface Height (SSH), so verifying the accuracy of CMR WTD inversion is important to obtain high precision SSH. However, there are few researches on the evaluation of BY -2C CWR WTD at present. The objective of this study is to evaluate the accuracy of HY-2C CMR WTD using Global Navigation Satellite Systems (GNSS) and ECMWF Reanalysis vS (ERAS) data. The results of the evaluation in the coastal ocean show that there are some anomalies in CMR WTD and anomaly rate is about 3% for distances to the coast from 40 to 200 km. The results of the evaluation in the open ocean show that there are some anomalies with spare spatial distribution and anomaly rate is about 1% over the open ocean beyond 40km offshore. The accuracy of HY-2C CMR WTD are evaluated in this study, and the abnormal data in BY -2C CMR WTD products over the ocean especially in coastal ocean that need to be improved.