Validation of long-period oceanic tidal models with superconducting gravimeters

Long gravity records from 18 superconducting gravimeters (SG) are used to estimate ocean tide loading for the monthly (Mm) and fortnightly (Mf) tidal waves. The estimates are compared with predicted ocean loading computed from various global tidal models. Despite their long-term sensitivity, the SG non-tidal noise continuum in the near-monthly band is large and renders the Mm estimates too imprecise for validating the different models. For most SG we are able to demonstrate that recent Mf tidal hydrodynamical models that assimilate satellite altimeter data are in significantly better agreement with SG tidal records than an equilibrium tidal model or the old Schwiderski [Schwiderski, E.W., 1980. On charting global ocean tides. Rev. Geophys. Space Phys. 18 (1), 243-268] model.