An equidistant nodal orthogonal polynomial fitting model for the central Pacific Ocean basin derived from satellite altimeter data: eight major tidal harmonic constants

Abstract. High-precision tidal harmonic constants serves as an important foundation for numerical ocean tidal modeling and studies of tidal dynamics. Prior studies have validated the applicability and efficacy of the equidistant node orthogonal polynomial for the fitting of tidal harmonic constants. In this study, observational records acquired from the TOPEX/Poseidon, Jason-1, Jason-2, and Jason-3 satellite altimetry missions are employed to conduct a systematic tidal harmonic analysis over the Central Pacific Basin. The dataset generated by the Equidistant Node Orthogonal Polynomial Fitting (ENOPF) model for the Central Pacific Basin (170° E–230° W, 30° S–30° N) was used to construct cotidal charts for the eight major tidal constituents (M₂, S₂, N₂, K₂, K₁, O₁, P₁, Q₁). The dataset has a spatial resolution of 3′ × 3′, and its tidal amplitude and phase lags are quantitatively compared with outputs from the Finite Element Solutions 2014 (FES2014), FES2022b, Empirical Ocean Tide 20 (EOT20), Tidal Prediction eXtended OSU 10 (TPXO10), and Technical University of Denmark 16 (DTU16) tide models. The results show that, relative to the comparative models, the vector error (VE), mean absolute error of amplitude (ΔH), and mean absolute error of phase lag (ΔG) computed with satellite altimeter data and tide gauges exhibit superior performance using ENOPF dataset. For example, for the M₂, S₂, K₁, and O₁ tidal constituents, the vector errors between the ENOPF-derived dataset and data from satellite altimeters were 0.91, 0.44, 0.41, and 0.21 cm. Furthermore, the ENOPF method offers a simpler and faster method for improving resolution; subsequently, by extracting the polynomial coefficients, a more detailed dataset with resolution of 1′ × 1′ can be constructed. This high-precision tidal harmonic constant dataset for the Central Pacific Basin offers significant application advantages, providing more reliable data support and technical references for tidal dynamics, ocean circulation, and marine engineering projects in the region.