Geophysical interpretation of observed geocenter variations

Geocenter variations are caused by mass redistribution within the Earth sys tem, especially the atmosphere, oceans, and continental water. Using surfac e pressure fields, and soil moisture and snow depth fields of the NCEP-NCAR . Climate Data Assimilation System I (CDAS-1), we estimate contributions fr om variations in atmospheric surface pressure and continental water storage to the Earth's geocenter (center of mass) variation. In addition, sea surf ace anomalies determined by the TOPEX/POSEIDON altimeter are used to invest igate geocenter variations resulting from ocean mass redistribution. These sea surface height data were corrected using a simplified steric model. A c omparison with observed geocenter variations derived from Lageos 1 and 2 sa tellite laser ranging data indicates that the atmosphere, oceans, and conti nental hydrological cycle all provide significant contributions at differen t frequencies. Geocenter variations estimated in this paper are in reasonab ly good agreement with results given by Dong et al. [1997] for atmospheric and ocean contributions, but not for the estimates of continental hydrologi cal contributions.