1:45 PM - 2:00 PM
[G02-5-02] Geomed2: gravimetric versus combined geoid model
Computation of the geoid of the Mediterranean Sea is challenging due to the combination of poor marine gravity data coverage and their non-homogeneous quality with gravity and geoid slopes that reach significant values with high variability. The GEOMED 2 project aims at the determination of a high-accuracy and resolution marine geoid model based on the availability of improved models for gravity, thanks to GRACE and GOCE in particular, for land topography and bathymetry, and the compilation of a cleaned-up gravity database of the Mediterranean area based on BGI and SHOM data. GEOMED 2 uses land and marine gravity data, the latest satellite-only and combined GOCE/GRACE based Global Geopotential Models and a combination of MISTRALS, EMODnet and SRTM/bathymetry terrain models in the geoid computation. Marine gravity data is not available for large parts of the Mediterranean and consequently a gravimetric geoid solution will be significantly less accurate there. Gravity inferred from altimetry data, or a mean sea surface corrected for mean dynamic topography, can be used to fill the gaps. However, ocean dynamic signal always contaminates the derived gravity or synthetic geoid, which is why a gravimetric solution is preferred.
The effect on the geoid solution of using several altimeter-based models, such as DTU10, DTU13 and DTU16 gravity and mean sea surface, a new DTU model for the Mediterranean, as well as the CNES-CLS15 mean sea surface, in weighted combinations with the gravimetric data will be evaluated and quantified. To that purpose, test models will be constructed and compared to the gravimetric geoid solution. The (localized) uncertainty due to the data gaps, and the subsequent uncertainty in the ocean mean dynamic topography and geostrophic currents, can be estimated via the results of all comparisons. The processing methodology is based on the remove-compute-restore method and the fast collocation method has been used to construct all test models.
The effect on the geoid solution of using several altimeter-based models, such as DTU10, DTU13 and DTU16 gravity and mean sea surface, a new DTU model for the Mediterranean, as well as the CNES-CLS15 mean sea surface, in weighted combinations with the gravimetric data will be evaluated and quantified. To that purpose, test models will be constructed and compared to the gravimetric geoid solution. The (localized) uncertainty due to the data gaps, and the subsequent uncertainty in the ocean mean dynamic topography and geostrophic currents, can be estimated via the results of all comparisons. The processing methodology is based on the remove-compute-restore method and the fast collocation method has been used to construct all test models.