Performance of Haiyang-2 Derived Gravity Field Products in Bathymetry Inversion

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Haiyang-2A (HY-2A), China’s first altimetry satellite mission, was launched more than ten years ago, and its follow-up satellites, HY-2B, HY-2C, and HY-2D, have also been launched. More attention has been paid to the evaluation of these satellite observations in marine gravity field inversion. However, this is not the case for bathymetry inversion. This study is aimed at evaluating the performance of HY-2 gravity field products in bathymetry recovery. Not only gravity anomaly, but also deflection of the vertical from the HY-2 series’ observations is also used. The results show that the bathymetry derived from the deflection of the vertical from HY-2A has a precision of around 128~130 m, and the north-south component performs better than the east-west component. Three versions of the gravity anomaly are used in bathymetry inversion, i.e., HY2ONLY_GRA, WHU16_GRA, and NSOASS22_GRA, and three bathymetry models are derived correspondingly, named as HY2ONLY_BAT, NSOASS22_BAT, and WHU16_BAT, respectively. The results show that HY2ONLY_BAT has a precision of 82.93 m, which is a little poorer than WHU16_BAT; NSOAS22_BAT has the best performance in bathymetry inversion among the three versions of the gravity anomaly. It indicates that HY-2 observations can also contribute to bathymetry inversion compared to current altimetry datasets, since the main difference between WHU16_GRA and NSOASS22_GRA is the use of HY-2 observations. According to spatial analysis results, considerable improvements appear in the west of the Pacific and Indian oceans, and most of the improvements are within 20 m. Meanwhile, the improvements are stronger in the regions with depths ranging between 2600~5500 m. Correlation analysis demonstrates that NSOASS22_BAT is very close to SIO V19.1 and DTU21BAT, which once again indicates the excellent performance of NSOASS22_BAT.