On the Correlation Between MDT and Geoid Models
Förste, Christoph¹; Abrykosov, Oleh²; Rio, Marie-Hélène³; Mulet, Sandrine³; Bruinsma, Sean⁴; Knudsen, Per⁵; Anderson, Ole^5
1GFZ German Research Centre for Geosciences, GERMANY; ²GFZ, GERMANY; ³CLS, FRANCE; ⁴CNES/GRGS, FRANCE; ⁵DTU Space, DENMARK

Geoid models are used together with an altimetric Mean Sea Surface (MSS) to compute the ocean Mean Dynamic Topography (MDT) and the associated mean geostrophic currents. The geoid model selected in the calculation of the MDT can either be based on satellite data only, or on a combination of satellite data and surface data in order to enhance the spatial resolution. Over the ocean, the surface data consists of a synthetic geoid computed as altimetric MSS minus model MDT. Therefore, when a combined geoid model is used in a MDT calculation and subsequent geostrophic current derivation, correlation may be present between the MDTs and between the currents. However, to the authors’ knowledge, this has never been thoroughly analyzed. We will present the results of a twin experiment where two combined geoid models are computed by using over the ocean synthetic geoids obtained from two different Mean Dynamic Topographies. These two combined geoids are then subtracted from the MSS to estimate two new MDTs, which will be compared to the ones used for the synthetic geoid model computation. The comparisons are done after spatial filtering of the MDTs in order to analyze differences and possible correlation as a function of scale. In this way, the implications of using a satellite-only or a combined model in oceanography will be answered definitively.