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Dynamic and residual ocean tide analysis for improved GRACE de-aliasing (DAROTA)

Precise models of ocean tides are crucial because (i) the effect of ocean tides has to be removed from CHAMP and GRACE observations in order to obtain gravity field models describing the Earth gravity and (ii) altimetric sea surface heights should be must be reduced for ocean tides in order to be comparable with each other and to be assimilated into numerical models. Deficiencies of ocean tides over continental shelves and in polar oceans are well known – even for the most recent tide models. The present project therefore focuses on two strategies:

  1. Empirical improvements to the widely used state-of-the-art ocean tide model FES2004 by (a) determining residuals for major tidal constituents with a spatial resolution as short as 300 km from GRACE data only (long wavelength) and (b) applying response and harmonic analysis to multi-mission altimeter data to estimate in particular for shallow water areas corrections for the dominant tidal constituents and non-linear effects like M4 (short wavelength). Both corrections will be validated and combined to an upgraded FES2004 model subsequently used for a more precise de-aliasing of the GRACE gravity field models and for improved corrections of altimetry data.
  1. Hydrodynamic modelling to further enhance the Hamburg Tide Model. Revising expertise these investigations shall provide a quantitative dynamical tide modelling with assimilation in open ocean and shallows sea, capable to overcome the deficiencies of current tide models.

Results: EOT10a - a new global ocean tide model

Residual amplitudes of EOT10a with respect to FES2004

The EOT10a was obtained by means of residual harmonic analysis of multi-mission altimeter data with respect to FES2004 and consists of four diurnal tides (K1, O1, P1, Q1, and S1), five semi-diurnal tides (M2, S2, N2, K2, and 2N2), long period tides (Mm and Mf), and non-linear tide constituent M4. The grids with spatial resolution of 7.5’x7.5’ are available under ftp://ftp.dgfi.badw.de/pub/EOT10a/.

 

 

Project information

Funding: DFG

Period: 01/2007-02/2013

Project partners: Institut für Theoretische Geodäsie und Satellitengeodäsie (ITSG) / TU Graz and German Research Center of Geosciences (GFZ)

Responsible persons at DGFI: Wolfgang Bosch, Roman Savcenko

 

 

Selected publications

Mayer-Gürr T., Savcenko R., Bosch W., Daras I., Flechtner F., Dahle C.: Ocean tides from satellite altimetry and GRACE. Journal of Geodynamics 59-60: 28-38, DOI:10.1016/j.jog.2011.10.009, 2012
Richter A., Mendoza L., Perdomo R., Hormaechea J.L., Savcenko R., Bosch W., Dietrich R.: Pressure tide gauge records from the Atlantic shelf off Tierra del Fuego, southernmost South America. Continental Shelf Res., volume 42, pages 20-29, DOI:10.1016/j.csr.2012.03.016, 2012
Bosch W., Savcenko R., Flechtner F., Dahle C., Mayer-Gürr T., Stammer D., Taguchi E., Ilk K.-H.: Residual ocean tides signals from satellite altimetry, GRACE gravity fields, and hydrodynamic modelling. Geophys. J. Int., DOI:10.1111/j.1365-246X.2009.04281.x, 2009
Bosch W., Savcenko R.: EOT08a - ein neues Gezeitemodell. INTERGEO, Geodätische Woche, Bremen, Germeny, 2008-10-02 (Poster)
Mayer-Gürr T., Savcenko R.: Improving ocean tide models by a joint estimation using GRACE and altimeter data. GGEO 2008 Symposium, Chania, Greece, 2008-06-26 (Poster)
Savcenko R., Bosch W.: EOT08a - Empirical Ocean Tide Model from Multi-Mission Satellite Altimetry. DGFI Report 81, Deutsches Geodätisches Forschungsinstitut (DGFI), München, 2008
Bosch W.: Multi-Mission Altimetry: Joint estimation of relative range biases, radial errors and sea state biases for contemporary missions. ENVISAT Symposium 2007, Montreux, Schweiz, 2007-04-25 (Poster)
Savcenko R., Bosch W.: Empirical ocean tide analysis of cross-calibrated multi-mission altimeter data. IUGG XXIV General Assembly, Perugia, Italy, 2007-07-05 (Poster)
Savcenko R., Bosch W.: Assessment of errors in global ocean tide models and their impact on GRACE gravity fields. A. Joint International GSTM and DFG SPP Symposium, Potsdam, Germany, 2007-10-15/17 (Poster)
Savcenko R., Bosch W.: Residual tide analysis in shallow water - contributions of ENVISAT and ERS altimetry. In: Huguette Lacoste (ed): ENVISAT Symposium 2007, ESA SP636, 2007

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