Aurore Sibois

Evaluating predicted diurnal and semidiurnal tidal variations in polar motion with GPS‐based observations

We evaluate models for the predicted diurnal and semidiurnal tidal variations in polar motion using observations based upon the Global Positioning System (GPS). The GPS-based observations are composed of 10 year continuous time series of polar motion estimates with 15 min temporal resolution. Predicted effects account for the contributions from ocean tide angular momentum and libration. We consider two models for the predicted ocean tide effects, both of which have their heritage with the so-called TPXO hydrodynamic models of the ocean tide heights and currents that assimilate satellite altimetry, for example, Egbert et al. (1994) and Egbert and Erofeeva (2002). When considering libration effects we use the model from Mathews and Bretagnon (2003). Of the models considered in this study, the best consistency with the GPS-based observations is achieved with predictions from the most recent (version 8) TPXO-based model for ocean tide effects together with the model for libration effects. This combination demonstrates closure of the budget between predicted and GPS-based observations at the level of less than 10, 2, and 5 µas in prograde diurnal, prograde semidiurnal, and retrograde semidiurnal tidal variations in polar motion, respectively. The observations also demonstrate inconsistency between the older TPXO-based model for ocean tide effects and the libration model, both of which are currently recommended by the International Earth Rotation Service.

Analysis of decade-long time series of GPS-based polar motion estimates at 15-min temporal resolution

We present results from the generation of 10-year-long continuous time series of the Earth’s polar motion at 15-min temporal resolution using Global Positioning System ground data. From our results, we infer an overall noise level in our high-rate polar motion time series of 60

Observed features of GPS Block IIF satellite yaw maneuvers and corresponding modeling

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Recent Advances in Realizing the Terrestrial Reference System from GPS

μas (RMS). However, a spectral decomposition of our estimates indicates a noise floor of 4

GRACE-Based Estimates of GPS Satellite Antenna Phase Variations: Impact on Determining the Scale of the Terrestrial Reference Frame

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Realizing a terrestrial reference frame using the Global Positioning System: GPS-BASED REFERENCE FRAME

μas at periods shorter than 2 days, which enables recovery of diurnal and semidiurnal tidally induced polar motion. We deliberately place no constraints on retrograde diurnal polar motion despite its inherent ambiguity with long-period nutation. With this approach, we are able to resolve damped manifestations of the effects of the diurnal ocean tides on retrograde polar motion. As such, our approach is at least capable of discriminating between a historical background nutation model that excludes the effects of the diurnal ocean tides and modern models that include those effects. To assess the quality of our polar motion solution outside of the retrograde diurnal frequency band, we focus on its capability to recover tidally driven and non-tidal variations manifesting at the ultra-rapid (intra-daily) and rapid (characterized by periods ranging from 2 to 20 days) periods. We find that our best estimates of diurnal and semidiurnal tidally induced polar motion result from an approach that adopts, at the observation level, a reasonable background model of these effects. We also demonstrate that our high-rate polar motion estimates yield similar results to daily-resolved polar motion estimates, and therefore do not compromise the ability to resolve polar motion at periods of 2–20 days.