An alternative model for short period ocean tidal variations of Earth rotation (SPOT)

Within project SPOT (Short Period Ocean Tidal variations in Earth rotation) we develop an alternative high frequency Earth rotation model based on empirical ocean tide models. The main purpose of the SPOT model is its application to space geodetic observations such as GNSS and VLBI. We consider an empirical ocean tide model, which does not require hydrodynamic ocean modeling to determine ocean tidal angular momentum. We use here the EOT11a model of Savcenko & Bosch (2012). The effect of minor tides, for which recent studies show significant differences between admittance theory, hydrodynamic modeling and estimation from satellite altimetry is investigated. As empirical tide models do not provide ocean tidal currents, which are required for the computation of oceanic relative angular momentum, we implement an approach first published by Ray (2001) to estimate ocean tidal current velocities. The approach itself is validated by application to tidal heights from hydrodynamic ocean tide models, which also provide tidal current velocities. Based on the tidal heights and the associated current velocities the oceanic tidal angular momenta are calculated. For the computation of the related short period variations of Earth rotation, we have re-examined the Euler-Liouville equation for an elastic Earth model with a liquid core. The focus here is on the consistent calculation of the elastic Love numbers and associated Earth model parameters, which are considered in the Euler-Liouville equation for diurnal and sub-diurnal periods in the frequency domain. The SPOT model is compared with the IERS2010 conventional model for a first evaluation and the new model is validated using VLBI data.