CoAuthors

Riccardo Barzaghi (Politecnico di Milano, Italy); George Vergos (Aristotle University of Thessaloniki, Greece); Marie-Françoise Lequentrec-Lalancette (SHOM, France); Ole Andersen (DTU Space, Denmark)

The objective of the GEOMED2 project is to compute an updated estimate of the geoid of the Mediterranean. The gravimetric geoid computation is based on ship and land gravity data collected in the area (29°;48°) latitude and (-10°;41°) longitude covering the entire Mediterranean basin. Outlier rejection and bias correction (with respect to the EIGEN-6C4 model) have been carefully performed on the entire database. Wavelengths of the gravity field down to 40 km have been modelled using the EIGEN-6C4 model in the gravity data reduction; gravity data reduced with satellite-only derived models led to significantly less accurate geoids. Reduction for the terrain effect also has been accounted for using the SRTM Digital Terrain Model that has been complemented with bathymetric data. A problem we encountered in this project is the at best negligible bathymetry reduction of the gravity data over sea (as opposed to reduction of topographic masses over land, which is essential), and tests without terrain effect over sea will equally be done.
Different methods will be considered to compute the geoid. Collocation, Fast Collocation, and Stokes/FFT will be used and differences among the different geoid solutions will be analyzed. Based on a set of quality tests, one of the geoid solutions will be selected for the next stage of the project: the estimation of a new, more detailed SST model, both over open-sea and in coastal zones, which will be enhanced with drifter data to develop a new current model for the Mediterranean Sea.