AN INVESTIGATION OF OCEAN TIDES DERIVED FROM ALONG-TRACK ALTIMETRY

With the availability of a long data record of accurate sea surface he ight measurements, it is now possible to estimate the ocean tide along the ground track of TOPEX/POSEIDON (T/P). This has been done from ove r 4.5 years of data using both response and harmonic analyses. These e stimates agree well with each other, and with other gridded models ove r both long and short wavelengths in deep water, for those tidal compo nents whose alias frequencies are separable by the Rayleigh criterion. Comparisons of along-track (AT) estimates to-current tide models show shorter wavelength features not present in dynamical and empirical gl obal models. AT estimates follow the general trends of empirical model s far from sharp topographical changes, but near sharp changes, they t end to follow dynamical model results. Error estimates show that the T /P data are not significantly worse in shallow water than in deep wate r, suggesting that there is accurate information about tides in shallo w water in the T/P data. Tides at crossover locations are improved by computing estimates with both ascending and descending track data. Pos sible techniques to improve AT tidal estimates between crossover point s are discussed. AT tidal estimation can be useful for studying local regions where resolution is more important than regular spacing, for s tudying tidal interactions over sharp topography, and for extending ti dal models from deep to shallow waters through assimilation into a dyn amical model.