We report results on the use of CHAMP observations for Earth's mean and time-varying gravity field solutions and the associated geophysical interpretation. 1.5 years of CHAMP data from May 2001 through February 2003 are used for monthly gravity solutions as well as a mean solution based on 6 months of data, employing the energy conservation principle and an efficient conjugate gradient inversion technique. The mean CHAMP gravity field model, OSU03a, is evaluated using other gravity fields model and various data including GPS leveling and Arctic 5′×5′ gravity anomalies. It is shown that OSU03a agrees well with EIGEN2 (CHAMP) model, and both models exhibit improvement over the polar regions. The estimated 3×3 CHAMP time-varying gravity field model, with the exception of J
order tesseral coefficients, are compared with available solutions using satellite laser ranging (SLR) for the semi-annual and annual components. It is shown that CHAMP temporal gravity solution agrees well with the SLR solutions as well as various geophysical fluid models, including atmosphere, hydrology, and ocean. The correlation coefficients between CHAMP and SLR solutions are 0.6∼0.8, with RMS at 0.7∼0.8 mm.