Combination of multi-satellite altimetry data with CHAMP and GRACE EGMs for geoid and sea surface topography determination

Abstract

Since the launch of the first altimetric missions a wealth of data for the sea surface has become available and utilized for geoid and sea surface topography modeling. The data from the gravity field dedicated satellite missions of CHAMP and GRACE provide a unique opportunity for combination studies with satellite altimetric observations. This study focuses on the combination of data from GEOSAT, ERS1/2, Topex/Poseidon, JASON-1 and ENVISAT with Earth Gravity Models (EGMs) generated from CHAMP and GRACE data to study the mean sea surface (MSS)/marine geoid in the Mediterranean Sea. Various combination methods, i.e., weighted least squares and least squares collocation are investigated and conclusions on the most appropriate combination strategy are drawn. Then, a remove-compute-restore scheme is followed to estimate the MSS model. Comparisons with other MSS models referenced to EGM96 and CHAMP/GRACE EGMs are performed in terms of the geoid height values at various control points. Finally, a sea surface topography model for the eastern part of the Mediterranean Sea is determined by a combination of the altimetric geoid and the CHAMP/GRACE EGM. The latter is validated against a sea surface topography model derived from altimetric data, in-situ oceanographic observations and an ocean general circulation model. © Springer-Verlag Berlin Heidelberg 2007.