Ocean tide effects on GRACE gravimetry

Abstract

Initial studies of the effects of ocean tides on the GRACE gravity field are. Based on the predicted accuracy estimates associated with GRACE errors in the ocean tide modeling are evaluated using gravity anomalies filtered at harmonic degrees 50 and 80 respectively. The results of the analysis show that the ocean tides and the ocean tide loading are important to consider in analysis of GRACE data. Furthermore, the loading is important to consider. The current ocean tide models are not accurate enough to correct GRACE data. Furthermore, the atmospheric tides may give significant errors in the ocean tide model if altimetry corrected for inverted barometer effects is used.

To study the temporal characteristics of the ocean tidal constituents when sampled by GRACE, preliminary alias frequencies have been derived assuming a sampling of one sidereal day. Those results show that the ocean tide errors will not cancel in the GRACE monthly averaged temporal gravity fields at harmonic degrees 1–50. The S2 and the K1 terms have alias frequencies much longer than 30 days, so that they remain almost unreduced in the monthly averages.