Rigorous fusion of gravity field,altimetry and stationary ocean models

Many characteristics of the ocean circulation are reflected in the mean dynamic topography (MDT). Therefore observing the MDT provides valuable information for evaluating or improving ocean models. Using this information is complicated by the inconsistent representation of MDT in observations and ocean models. This problem is addressed by a consistent treatment of satellite altimetry and geoid height information on an ocean model grid. The altimetric sea surface is expressed as a sum of geoid heights represented by spherical harmonic functions and the mean dynamic topography parameterized by a finite element method. Within this framework the inversion and smoothing processes are avoided that are necessary in step-by-step approaches, such that the normal equations of the MDT can be accumulated in a straightforward way. Conveniently, these normal equations are the appropriate weight matrices for model-data misfits in least-squares ocean model inversions. Two prototypes of these rigorously combined MDT models, with an associated complete error description including the omission error, are developed for the North Atlantic Ocean and assimilated into a 3D-inverse ocean model. The ocean model solutions provide evidence that satellite observations and oceanographic data are consistent within prior errors.