Ocean Tides in GRACE Monthly Averaged Gravity Fields

  • Per Knudsen
Part of the Space Sciences Series of ISSI book series (SSSI, volume 17)


The GRACE mission will map the Earth’s gravity fields and its variations with unprecedented accuracy during its 5-year lifetime. Unless ocean tide signals and their toad upon the solid earth are removed from the GRACE data, their long period aliases obscure more subtle climate signals which GRACE aims at. In this analysis the results of Knudsen and Andersen (2002) have been verified using actual post-launch orbit parameter of the GRACE mission. The current ocean tide models are not accurate enough to correct GRACE data at harmonic degrees lower than 47, The accumulated tidal errors may affect the GRACE data up to harmonic degree 60. A study of the revised alias frequencies confirm that the ocean tide errors will not cancel in the GRACE monthly averaged temporal gravity fields. The S2 and the K2 terms have alias frequencies much longer than 30 days, so they remain almost unreduced in the monthly averages. Those results have been verified using a simulated 30 days GRACE orbit. The results show that the magnitudes of the monthly averaged values are slightly higher than the previous values. This may be caused by insufficient sampling to fully resolve and reduce the tidal signals at short wavelengths and close to the poles.


GRACE satellite mission ocean tides gravity 


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  1. Bettadpur, S„ Gruber, Th.. and Watkins, M.: 1999. ‘GRACE Science Data System Design’, Supplement to EOS Transactions, AGU Fall Meeting 80 (46). F254.Google Scholar
  2. Eanes, R.. and Bettadpur, S.: 1995. ‘The CSR 3.0 global ocean tide model, CSR-TM- 95–06’. Technical Memorandum. Center for Space Research. December 1995.Google Scholar
  3. Katila, W.M.: 1966, ‘Theory of Satellite Orbits’, Blaisdcll Publishing Co., Waltham, Mass, 124 pp.Google Scholar
  4. Knudsen, P.; 1994, ‘Separation of residual ocean tide signals in a collinear analysis of GEOSAT altimetry“, Bull. Geod. 68. 7–18.CrossRefGoogle Scholar
  5. Knudsen. P., and Andersen. O.: ‘Correcting GRACE gravity fields for ocean tide efleets’. Geophys.Res. Let. 29(8). 19–1–19–4.Google Scholar
  6. Knudsen, P., Andersen, O. B., Khan, S. A., and H0yer. J.L.: 2000. ‘Ocean Tide Effects on GRACE Gravimeiry’. I AG Symposia, Gravity Geoid and Geodytiamics 2000, Vol. 123, Springer-Verlag, pp. 159–164.Google Scholar
  7. Matsumoto. K.. Takanezawa, T.. and Ooe. M.: 2000, ‘Ocean Tide Models Developed by Assimilating TOPEX/POSEIDON Altimeter Data into Hydrodymimical Model: A Global Model and a Regional Model Around Japan’, Journal of Oceanography 56. 567–581.CrossRefGoogle Scholar
  8. Ray, R, D.. Eancs. R. J.. Egbert. G. D., and Pavlis. N. K,: 2001. “Error spectrum for the global Mi ocean tide’, Geophys. Res. Lett. 28. 21–24.CrossRefGoogle Scholar
  9. Tapley, B. D.: 1997, ‘The gravity recovery and climate experiment (GRACE)’, Supplement to EOS Trans. AGU 78 (46), pp. 163.Google Scholar
  10. Telford, W. M.. Gcldart. L. P.. Sheriff, R.E.. Keys, D, A.: 1976. Applied Geophysics. Cambridge University Press, 270Google Scholar
  11. Wahr, J., Molenaar, M., and Bryan, F.: 1998, ‘Time variablity of the Earth’s gravity field: Hydrolog-ical and oceanic effects and their possible detection using GRACE“. J. Geophys. Res. I03 (B12), 30205–30229.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media Dordrecht 2003

Authors and Affiliations

  • Per Knudsen
    • 1
  1. 1.Kort & MatrikelstyrelsenGeodetic DepartmentDenmark

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