ACCURACY ASSESSMENT OF RECENT OCEAN TIDE MODELS

Over 20 global ocean tide models have been developed since 1994, prima rily as a consequence of analysis of the precise altimetric measuremen ts from TOPEX/POSEIDON and as a result of parallel developments in num erical tidal modeling and data assimilation, This paper provides an ac curacy assessment of 10 such tide models and discusses their benefits in many fields including geodesy, oceanography, and geophysics. A vari ety of tests indicate that all these tide models agree within 2-3 cm i n the deep ocean, and they represent a significant improvement over th e classical Schwiderski 1980 model by approximately 5 cm rms. As a res ult, two tide models were selected for the reprocessing of TOPEX/POSEI DON Geophysical Data Records in late 1995. Current ocean tide models a llow an improved observation of deep ocean surface dynamic topography using satellite altimetry. Other significant contributions include the ir applications in an improved orbit computation for TOPEX/POSEIDON an d other geodetic satellites, to yield accurate predictions of Earth ro tation excitations and improved estimates of ocean loading corrections for geodetic observatories, and to allow better separation of astrono mical tides from phenomena with meteorological and geophysical origins . The largest differences between these tide models occur in shallow w aters, indicating that the current models are still problematic in the se 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 model s.