Global Tide Assimilated Simulation Based On19-year Satellite Altimetric Data Method

The assimilation of two kind of global tide model is employed in building andimproving the domestic global tide model, which also contributes to the simulatedaccuracy in coastal waters of China. These two model are empirical model obtainedfrom harmonic analysis for altimetric data from TOPEX/POSEIDON satellite seriesand hydrodynamic model, which is based on finite volume method with unstructuredmesh grids, respectively. Two simple assimilation strategy, successive correctionanalysis and Nudging method, are chosen for this study. For empirical model, theintercomparison of harmonic constants obtained from both descending and ascendingtracks at crossover points reveals that the increase of record length will improve theprecision of harmonic analysis. The relative deviations for diurnal tidal constituent K1and O1decrease by7%when use the data over19years in comparison to the resultobtained from T/P data only. The comparisons between harmonic constants obtainedfrom363tidal gauge stations and that from different groups of satellite data indicatethat increase of record length contributes to the decline of amplitude error. But theinvolve of Jason-1and Jason-2leads to an increase of3°in phase-lag error for K1and O1constituents. This paper analyzes the reason of this error variation throughidealized experiment. Through introducing the tidal force term of M₂constituent andthe self-attraction effect, the main tidal pattern of M₂in oceans are obtained from thehydrodynamic model, although the accuracy turns out to be lower than other mainglobal tide models and the empirical one when compared with the harmonic constantsfrom273tide gauges. But the results are credible in coastal water of China except thelow amplitude around BFC coast, which are confirmed from the comparison betweenthe hydrodynamic and empirical model and the cotidal charts in this area. Theassimilations based on these two models, when their accuracy emerges, are finishedby the methods of successive correction and Nudging after several experiments. These two assimilation methods both improve the model accuracy. The simulated accuracyfor amplitude of M₂constituent improves by3cm in oceans and4cm in coastal waterof China and by6°for phase-lag in oceans through successive correction analysis.Nudging method reflects the assimilated effort to the tidal current through adjustingthe surface elevation, which has the similar effect of accuracy improvement withsuccessive correction in coastal waters of China. The results from assimilatedhydrodynamic model are better than Huaming Yu （2011） and other previous workwith the amplitude RMS of3cm and phase-lag of6°for M₂constituent.