Advancing Internal Tide Correction for SWOT Cal/Val: The Role of Ocean Forecasts

Abstract Internal tides are sub‐surface inertia‐gravity waves that generate significant sea surface height signals detectable with satellite altimetry. The Surface Water and Ocean Topography (SWOT) mission provides an exciting opportunity to characterize these signals with unprecedented spatial detail. Separating tidal and non‐tidal oceanic signals is necessary for achieving the SWOT mission's objective of advancing our understanding of mesoscale and submesoscale processes. In this study, we evaluate the performance of a data‐assimilative HYbrid Coordinate Ocean Model (HYCOM) forecast system in resolving both phase‐locked and non‐phase‐locked internal tides during the SWOT Cal/Val period. We compare HYCOM's effectiveness to the High‐Resolution Empirical Tide model (HRET22), which is currently used for internal tide corrections but only accounts for the phase‐locked component. HYCOM achieves an average of 5% greater reduction in phase‐locked internal tide variance and a 24.6% greater total variance reduction compared to HRET22 by also accounting for non‐phase‐locked internal tides. At the frequency, HYCOM reduces up to 73% of total internal tide variance in SWOT observations, including substantial contributions from the non‐phase‐locked component. Despite these advances, persistent residuals remain in energetic, topographically complex areas, pointing to the continued need for improved modeling and data assimilation. These findings demonstrate the crucial role of forecast models in advancing internal tide mapping and significantly improving altimetric data correction in the era of SWOT oceanography.