Abstract. Over 20 global ocean tide models have been developed since 1994, primarily as a consequence of analysis of the precise altimetric measurements from TOPEX/POSEIDON and as a result of parallel developments in numerical tidal modeling and data assimilation. This paper provides an accuracy assessment of 10 such tide models and discusses their benefits in many fields including geodesy, oceanography, and geophysics. A variety of tests indicate that all these tide models agree within 2-3 cm in the deep ocean, and they represent a significant improvement over the classical Schwiderski 1980 model by approximately 5 cm rms. As a result, two tide models were selected for the reprocessing of TOPEX/POSEIDON Geophysical Data Records in late 1995. Current ocean tide models allow an improved observation of deep ocean surface dynamic topography using satellite altimetry. Other significant contributions include theft applications in an improved orbit computation for TOPEX/POSEIDON and other geodetic satellites, to yield accurate predictions of Earth rotation excitations and improved estimates of ocean loading corrections for geodetic observatories, and to allow better separation of astronomical tides from phenomena with meteorological and geophysical origins. The largest differences between these tide models occur in shallow waters, indicating that the current models are still problematic in these areas. Future improvement of global tide models is anticipated with additional high-quality altimeter data and with advances in numerical techniques to assimilate data into high-resolution hydrodynamic models.

Abstract. Atmospherically forced, high-frequency oceanic variability is investigated using different configurations of an ocean general circulation model. At periods less than 20 days, the dynamic response of the sea surface to pressure loading exceeds that due to wind stress, and is mostly barotropic. Energy at these periods aliases into satellite altimeter measurements of sea surface height (SSHT). The global variance of collinear (•10 day) differences of this modelled aliased SSHT is between (2 cm) 2 and (3.5 cm) 2 , depending on the model configuration used. The local variance can reach (14cm) 2 at some high latitude locations. We use the ocean model predictions to remove the high-frequency signals from TOPEX/Poseidon (T/P) observations. We obtain a global variance reduction in collinear differences of up to (2cm) 2, about 7% of the T/P signal. Our model has difficulty in predicting the variability at periods less than 5 days.

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In this second part, we explore the implications of the tides derived from the high‐resolution, data‐assimilative, nonlinear barotropic global ocean tidal model described by Kantha (this issue) in altimetric analysis and geophysical applications. It is shown that when applied to the task of removing tidal sea surface height from TOPEX altimetric records, the model performance is comparable to other global tidal models in the open ocean as measured by the reduction in crossover variances. The performance is slightly better than that of the only other high‐resolution global tidal model from Grenoble (Le Provost et al., 1994). The results are however mixed in regions shallower than 1000 m and in semienclosed seas such as the Bering Sea, with the model performance slightly worse overall than the Grenoble model. Computations of total power input (and hence total tidal dissipation rate) are shown to be in excellent agreement with recent analyses of TOPEX data and geophysical observations. In addition, distributions of the tidal power input, tidal dissipation, and the power fluxes in the global oceans are shown for the two primary constituents, M2 and K1. Load tides in solid Earth due to ocean tidal loading fluctuations are also computed for the major semidiurnal and diurnal constituents. The load tides are shown to be large in the shallow seas adjacent to the coasts with high tides such as the Patagonian shelf, because of the higher resolution of this global tide model. This has potential implications in geophysical applications.

Abstract. With the availability of a long data record of accurate sea surface height measurements, it is now possible to estimate the ocean tide along the ground track of TOPEX/POSEIDON (T/P). This has been done from over 4.5 years of data using both response and harmonic analyses. These estimates agree well with each other, and with other gridded models over both long and short wavelengths in deep water, for those tidal components 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 global models. AT estimates follow the general trends of empirical models far from sharp topographical changes, but near sharp changes, they tend to follow dynamical model results. Error estimates show that the T/P data are not significantly worse in shallow water than in deep water, suggesting that there is accurate information about tides in shallow water in the T/P data. Tides at crossover locations are improved by computing estimates with both ascending and descending track data. Possible techniques to improve AT tidal estimates between crossover points are discussed. AT tidal estimation can be useful for studying local regions where resolution is more important than regular spacing, for studying tidal interactions over sharp topography, and for extending tidal models from deep to shallow waters through assimilation into a dynamical model.