Abstract
The equidistant nodes orthogonal polynomial fitting (ENOPF) method proves effective and efficient to extract tidal information from satellite data, yet its dependency on accurate satellite data limits performance in coastal areas with sparse coverage, where extracting reliable harmonic constants is challenging. By using a 2D adjoint tidal model and integrating X-TRACK data with simulated data via equidistant nodes orthogonal polynomial fitting, we extracted harmonic constant of four major tidal constituents (M2, S2, K1, and O1) with high resolution on the South China Sea. We divided the study area into five sub-areas, and mitigated systematic errors through varied weight coefficients for different data sources. For M2 and S2 constituents, ENOPF had the smallest errors overall, while FES2014 and EOT20 performed best for K1 and O1 constituents. Although ENOPF was slightly less accurate overall, its coastal performance improved significantly with the 2D adjoint model. The cotidal charts from ENOPF were consistent with other models, though some distortion at the junction of Area I and Area V indicated a need for better splicing methods. Distortions in O1 constituent simulations were likely due to strong internal tide signals. The findings provide a reliable high-resolution tidal dataset for the South China Sea, supporting accurate tidal corrections for sea level anomaly studies.
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