Preliminary results of the newly developed model for short period ocean tidal variation of Earth rotation (SPOT)

Abstract:

Within project SPOT (Short Period Ocean Tidal variations in Earth
rotation) we develop a new 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).
We investigate the effect of minor tides, for which recent studies show
significant differences between admittance theory, hydrodynamic modeling
and estimation from satellite altimetry. 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 preliminary SPOT
model is compared in the time domain with the IERS2010 conventional model for a first
evaluation. In addition, the effects of various Earth models and tidal models are quantified.