Fitting Cotidal Charts of Eight Major Tidal Components in the Bohai Sea, Yellow Sea Based on Chebyshev Polynomial Method

Abstract

High-precision tidal harmonic constants are necessary for studies involving tides. This study proposes a new method combined with the adjoint assimilation model and the Chebyshev polynomial fitting (CPF) method to obtain the tidal harmonic constants in the shallow-water region of the Bohai and Yellow Sea (BYS). Based on the CPF method, the full-field harmonic constants and reliable cotidal charts of the eight major constituents (M2, S2, K1, O1, N2, K2, P1 and Q1) were fitted from the X-TRACK products briefly and this method was effectively for coastal conditions. Compared with the observations of the X-TRACK products and tidal gauges, for the M2 constituent, the TPXO9, Finite Element Solutions 2014 (FES2014), National Astronomical Observatory 99b (NAO.99b) and Empirical Ocean Tide 20 (EOT20) models yield the root-mean-square errors (RMSEs) of 18.50, 7.31, 18.73 and 13.32 cm, respectively, while the CPF method yields an RMSE of 10.74 cm. These results indicate that the CPF method could maintain high resolution and obtain accurate cotidal charts consistent with the simulations of the four models in shallow-water regions.

Two-Dimensional Numerical Simulation of Tide and Tidal Current of Eight Major Tidal Constituents in the Bohai, Yellow, and East China Seas

“…However, as a fitting method, the results of the CPF method are inevitably affected by the low accuracy and limited quantity of observations near the coast, resulting in deviations from actual conditions. This is also reflected in the cotidal charts drawn by Wang et al [19]. As the open boundary is adjacent to the open ocean, the CPF method can be effectively utilized [16].…”

“…Cotidal charts of various constituents near the Hawaiian were derived by fitting T/P altimeter data using Chebyshev polynomials fitting (CPF) [16][17][18]. The CPF method for processing altimeter data to obtain tidal harmonic constants has also been applied to the Bohai and Yellow Seas [19]. However, altimeter sampling exhibits spatial discontinuity, particularly in marginal seas with convoluted coastlines where data are dispersed and scarce.…”

“…The CPF method is used to directly fit the harmonic constants of satellite altimeter data to obtain OBCs. The CPF method has been validated for calculating the harmonic constants of eight major constituents and has demonstrated excellent performance in the area near Hawaii (open sea) and Bohai and Yellow Seas (marginal seas) [16,19]. The altimeter data are assimilated by the adjoint method to estimate BFCs.…”

Application of Trigonometric Polynomial Fitting Method in Simulating the Spatial Distribution of PM2.5 Concentration in South-Central China

“…The primary advantage of the RBF method lies in its ability to effectively extract pertinent information from discrete point data, resulting in a smoother and more natural magnified image. The radial basis function (RBF) interpolation method is known for its computational efficiency, making it a favorable choice when compared to other interpolation methods [32][33][34]. One of its valuable features is the ability to address the limitation of uniform grids by distributing discrete nodes in irregular regions for constructing the grid model.…”

“…Orthogonal polynomial fitting is a highly precise and efficient technique for modeling intricate data, which has been extensively applied in various fields including artificial intelligence, image processing, and marine science [31][32][33][34][35][36]. Li et al [31] utilized the Chebyshev polynomial fitting technique to derive the temporal-spatial distribution of PM 2.5 in central and southern regions of China, followed by analysis thereof.…”