Enhancing SWOT Geoid Resolution in Regions Characterized by Complex Oceanic Dynamics via the mrCOSTS Method

Abstract

The advanced 2-D sea surface height (SSH) observations from the surface water and ocean topography (SWOT) satellite have achieved a global average geoid resolution better than 13 km, as estimated from spectral analysis of adjacent single-cycle observations. However, in regions with complex oceanic dynamics (the ocean off southwestern Argentina and east of Japan), SWOT observations show significant temporal variability across cycles. This variability greatly hampers the satellite’s ability to detect and precisely measure steady-state marine geoid signals. Even with multicycle data stacking, resolution remains poor in some regions, sometimes underperforming conventional satellite altimetry. To solve this issue, this study employs a multiresolution coherent spatio-temporal scale separation (mrCOSTS) method to analyze sea surface height anomaly (SSHA) data from 26 SWOT cycles, aiming to isolate stable signal components and reconstruct the geoid. The approach notably improves geoid resolution in regions with intricate ocean features, with the maximum enhancement reaching up to 76%. This resolution reflects the spatial scales of features reproducibly resolved by two independent SWOT geoid estimates, rather than a direct improvement in absolute marine geoid accuracy. The method effectively suppresses ocean dynamic signals while preserving the static oceanic component, and it also contributes to improving the recovery of the marine gravity field in regions characterized by complex ocean dynamics. Furthermore, in regions with relatively high resolution, the method achieves additional subtle improvements, which are of considerable significance for obtaining a stable static field.