Preliminary Results of Marine Gravity Anomaly and Bathymetry From SWOT Wide-Swath Altimeter Data

In this article, we assess the accuracy of the surface water and ocean topography (SWOT) mission for deriving marine gravity anomalies and bathymetry in the Philippine Sea using wide-swath L3 Ka-band radar interferometer data. Our evaluation includes determining the deflection of vertical (DOV) using the least-squares collocation method, recovering gravity anomalies with the inverse Vening–Meinesz formula, and predicting bathymetry through the gravity-geological method. The accuracy of the east–west DOV component has improved but remains lower than that of the north–south component. SWOT-derived (from 14-cycle data) gravity anomalies exhibit stronger signals in the short-wave ranges (< 20 km), with a precision of 2.37 mGal compared to shipborne measurements. The SWOT-derived bathymetry shows an accuracy of 124.02 m, representing an 8.36-m improvement compared to the conventional SIO altimeter-based model. We show that 14 cycles (10 months) of SWOT data provide more detailed information than 30 years of traditional nadir altimetry in both gravity anomaly and bathymetry. We have optimized the SWOT data processing strategy to enable the retrieval of high-quality marine gravity anomalies. With advancements in data processing and the accumulation of observations, the SWOT mission is progressing toward its marine geophysics objectives.