Diurnal/semidiurnal oceanic tidal angular momentum: Topex/Poseidon models in comparison with Earth’s rotation rate

Abstract. The oceanic tidal angular momentum (OTAM) has been demonstrated to be the primary cause for the diurnal and semidiurnal variations in the Earth's rotational rate, or AUT1. Three ocean tide models derived from the Topex/Poseidon altimetry mission are employed to yield predictions of AUT1 for eight major diurnal/semidiurnal fides. The predictions are compared with geodetic determinations ofAUT1 from the very-long-baseline interferometry data both for long-term observations and during intensive campaigns. The agreement is good, with discrepancies typically within 2-3 gs. Systematic discrepancies observed for the well-determined M 2 tide clearly reveal the contribution of the Earth's spin libration