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 atmo sphere, oceans, continents and ice sheets, causes the position of the centr e of mass to vary in a reference frame attached to the solid Earth. Space t echniques are now precise enough to measure the centre of mass motion. Here we present a determination of the centre of mass coordinates at regular mo nthly 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 a nd phase of the space-geodesy-derived annual cycle for each coordinate are further compared to estimates based on surface mass redistribution at the E arth surface derived from various climatic data sources: surface pressure, soil moisture, snow depth and ocean mass variations.