RESUMEN
Comparisons of TOPEX/POSEIDON tidal solutions derived from the data of the first year of this altimetric mission with the best previous models and with in situ data show very substantial improvements. Typically, the gain in accuracy for the major lunar tidal component M(2) is 30 percent in root-mean-square differences with reference to a standard ground truth data set from 78 stations distributed over the world ocean. This is a major step, obtained because of the high quality of these altimetric data. The combination of these data with recent numerical models through assimilation methods is pointing toward solutions at the ultimate limits of practical accuracy.
RESUMEN
Recent space-geodetic observations have revealed daily and subdaily variations in the Earth's rotation rate. Although spectral analysis suggests that the variations are primarily of tidal origin, comparisons to previous theoretical predictions based on various ocean models have been less than satisfactory. This disagreement is partly caused by deficiencies in physical modeling. Rotation predictions based on a reliable tidal-height model, with corresponding tidal currents inferred from a modified form of Laplace's momentum equations, yield predictions of tidal variations in Universal Time that agree with very long baseline interferometer observations to 2 microseconds. This agreement resolves a major discrepancy between theory and observation and establishes the dominant role of oceanic tides for inducing variation in the Earth's rotation at these frequencies.
