1. Global Ocean Tide Models – Assesment of Errors and their Impact on GRACE gravity fields Roman Savcenko and Wolfgang Bosch Deutsches Geodätisches Forschungsinstitut (DGFI) München Email: savcenko@dgfi.badw.de

2. Joint International GSTM and DFG SPP Symposium, October 15-17,2007, Potsdam 2 MotivationMotivation The errors in global tide models are one of the possible causes of meridional striping in GRACE satellite-only gravity fields. The errors in global tide models are one of the possible causes of meridional striping in GRACE satellite-only gravity fields. Due to sampling characteristics of GRACE it is impossible to estimate the whole residual tide signal from GRACE data. Due to sampling characteristics of GRACE it is impossible to estimate the whole residual tide signal from GRACE data. The analysis of multi-mission-altimeter data can help to correct the global tide models in order to improve the GARCE de-aliasing. The analysis of multi-mission-altimeter data can help to correct the global tide models in order to improve the GARCE de-aliasing.

3. Joint International GSTM and DFG SPP Symposium, October 15-17,2007, Potsdam 3 Residual tides and their effect on the gravity potential in GRACE orbit The residual amplitudes of semidiurnal tidal constituents can extend 15 cm level. The residual amplitudes of semidiurnal tidal constituents can extend 15 cm level. The residual signal can exhibit the large-scale character. The residual signal can exhibit the large-scale character. Caused by alias effects the residual tidal signals cause the meridional striping and large- scale errors in the gravity field estimation. Caused by alias effects the residual tidal signals cause the meridional striping and large- scale errors in the gravity field estimation. Residual tides [cm] Potential differences [m 2 /s 2 ] / GRACE ephemeris August 2003