A method of analyzing GRACE satellite-to-satellite ranging data is presented which accentuates signals from diurnal ocean tides and dampens signals from long-period non-tidal phenomena. We form a time series of differences between two independent monthly mean gravity solutions, one set computed from range-rate data along strictly ascending arcs and the other set computed from data along descending arcs. The solar and lunisolar diurnal tides having alias periods longer than a few months, such as K1, P1, and S1, present noticeable variations in the monthly ascending and descending ‘difference’ solutions, while the climate-related signals are largely cancelled. By computing tidal arguments evaluated along the actual GRACE orbits, we decompose and estimate residual tidal signals with respect to our adopted prior model GOT4.7. The adjustment in the tidal height is small yet significant, yielding maximum amplitudes of 4 cm mostly under the Antarctic ice shelves and ~1 cm in general at spatial scales of several hundred kilometer. Moreover, the results suggest there are possible 1-cm errors in the tide model even over oceans well-covered by decades of radar altimetry missions. Independent validation of such small adjustments covering wide areas, however, is difficult, particularly with limited point measurements such as tide gauge.
Ocean tides Time-variable gravity Aliasing
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Egbert GD, Erofeeva SY (2002) Efficient inverse modeling of barotropic ocean tides. J Atmos Ocean Technol 19(2): 183–204CrossRefGoogle Scholar
Egbert G, Erofeeva S, Han S-C, Luthcke S, Ray R (2009) Assimilation of GRACE tide solutions into a numerical hydrodynamic inverse model. Geophys Res Lett 36: L20609. doi:10.1029/2009GL040376CrossRefGoogle Scholar
Han D, Wahr J (1995) The viscoelastic relaxation of a realistically stratified Earth, and a further analysis of post glacial rebound. Geophys J Int 120: 287–311CrossRefGoogle Scholar
Han S-C, Jekeli C, Shum C (2004) Time-variable aliasing effects of ocean tides, atmosphere, and continental water mass on monthly mean GRACE gravity field. J Geophys Res 109: B04403. doi:10.1029/2003JB002501CrossRefGoogle Scholar
Han S-C, Shum C, Matsumoto K (2005) GRACE observations of M2 and S2 ocean tides below the Filchner-Ronne and Larsen Ice Shelves, Antarctica. Geophys Res Lett 32: L20311. doi:10.1029/2005GL024296CrossRefGoogle Scholar
Han S-C, Rowlands DD, Luthcke SB, Lemoine FG (2008) Localized analysis of satellite tracking data for studying time-variable Earth’s gravity fields. J Geophys Res 113: B06401. doi:10.1029/2007JB005218CrossRefGoogle Scholar
Heiskanen WA, Moritz H (1967) Physical geodesy. W.H. Freeman, San FranciscoGoogle Scholar
Knudsen P, Andersen O (2002) Correcting GRACE gravity fields for ocean tide effects. Geophys Res Lett 29: 1–4CrossRefGoogle Scholar
Lefèvre F (2002) Modélisation de la marée océanique à l’échelle globale par la méthode des éléments finis avec assimilation de données altimétriques, CLS-DOS-NT-01.416/SALP-RP-MA-E2-21060-CLS. Ramonville Saint-AgneGoogle Scholar
Schrama EJO, Wouters B, Lavallée DA (2007) Signal and noise in Gravity Recovery and Climate Experiment (GRACE) observed surface mass variations. J Geophys Res 112: B08407. doi:10.1029/2006JB004882CrossRefGoogle Scholar
Seidelmann PK (1992) Explanatory supplement to the astronomical almanac. University Science Book, Mill ValleyGoogle Scholar
Shum CK et al (1997) Accuracy assessment of recent ocean tide models. J Geophys Res 102(C11): 25,173–25,194CrossRefGoogle Scholar