Geocentre motion from the DORIS space system and laser data to the Lageos satellites:: comparison with surface loading data

Surface mass redistribution within the Earth system, especially in the atmosphere, oceans, continents and ice sheets, causes the position of the centre of mass to vary in a reference frame attached to the solid Earth. Space techniques are now precise enough to measure the centre of mass motion. Here we present a determination of the centre of mass coordinates at regular monthly intervals using DORIS data on SPOT-2, SPOT-3 and Topex-Poseidon (1993-1997) and laser data on Lageos-1 and Lageos-2 (1993-1996). The amplitude and phase of the space-geodesy-derived annual cycle for each coordinate are further compared to estimates based on surface mass redistribution at the Earth surface derived from various climatic data sources: surface pressure, soil moisture, snow depth and ocean mass variations.