Quantifying FES2004 S-2 tidal model from multiple space-geodesy techniques, GPS and GRACE, over North West Australia

S. A. Melachroinos 1 J. M. Lemoine P. Tregoning R. Biancale
LEGOS - Laboratoire d'études en Géophysique et océanographie spatiales
Abstract : Unmodeled sub-daily ocean S-2 tide signals that alias into lower frequencies have been detected in the analysis of gravity recovery and climate experiment (GRACE) space gravity fields of GRGS. The most significant global S-2 aliased signal occurs off the northwest coast of Australia in a shallow continental shelf zone, a region with high tidal amplitudes at a period of 161 days. The GRACE S-2 aliased equivalent water height grids are convolved with Green's functions to produce GRACE aliased tidal loading (GATL) vertical displacements. The analysis of hourly global positioning system (GPS) vertical coordinate estimates at permanent sites in the region confirms the presence of spectral power at the S-2 frequency when the same ocean tide model (FES2004) was used. Thus, deficiencies in the FES2004 ocean tide model are detected both directly and indirectly by the two independent space geodetic techniques. Through simulation, the admittance (ratio of amplitude of spurious long-wavelength output signal in the GRACE time-series to amplitude of unmodeled periodic signals) of the GRACE unmodeled S-2 tidal signals, aliased to a 161-day period, is found to have a global average close to 100%, although with substantial spatial variation. Comparing GATL with unmodeled S-2 tidal sub-daily signals in the vertical GPS time-series in the region of Broome in NW Australia suggests an admittance of 110-130%.
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S. A. Melachroinos, J. M. Lemoine, P. Tregoning, R. Biancale. Quantifying FES2004 S-2 tidal model from multiple space-geodesy techniques, GPS and GRACE, over North West Australia. Journal of Geodesy, Springer Verlag, 2009, 83 (10), pp.915-923. ⟨10.1007/s00190-009-0309-2⟩. ⟨hal-00991083⟩



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