Qualitative comparisons of global ocean tide models by analysis of intersatellite ranging data



[1] Four global ocean tide models are compared in terms of their contribution to Gravity Recovery and Climate Experiment (GRACE) satellite-to-satellite tracking residuals. The residuals are computed relative to a comprehensive model of Earth's time-varying gravity, including allowance for mass motions in the atmosphere, ocean, terrestrial hydrology, and mantle, in addition to tides. For each analyzed tide model, 4 years of GRACE range rate data are processed. Range and range acceleration residuals are tidally analyzed by geographic location. All four global tide models are shown to be error prone in various ways, leaving tidally coherent residuals especially in polar regions but also in some lower-latitude regions. Considerable power in the solar semidiurnal S2 tide in low latitudes suggests errors in our adopted model of atmospheric tides, which is based on 3 hourly European Centre for Medium-Range Weather Forecasts operational analyses. Anomalies in the μ2 tidal constituent over some shallow seas suggest the presence of unmodeled nonlinear compound tides, in this case 2MS2. Similarly, anomalies in the nonlinear M4 tide are seen if this constituent is omitted from the models. Errors in assumed seawater density may be contributing to some residuals.