HR: 08:45h
AN: G31A-04    [PDF]
TI: Static and time-variable Earth gravity fields from CHAMP and GRACE
AU: * Han, S
EM: han.104@osu.edu
AF: Laboratory for Space Geodesy and Remote Sensing Research, The Ohio State University, 2070 Neil Avenue, Columbus, OH 43210-1275 United States
AU: Shum, C
EM: ckshum@osu.edu
AF: Laboratory for Space Geodesy and Remote Sensing Research, The Ohio State University, 2070 Neil Avenue, Columbus, OH 43210-1275 United States
AU: Jekeli, C
EM: jekeli.1@osu.edu
AF: Laboratory for Space Geodesy and Remote Sensing Research, The Ohio State University, 2070 Neil Avenue, Columbus, OH 43210-1275 United States
AU: Kuo, C
EM: kuo.70@osu.edu
AF: Laboratory for Space Geodesy and Remote Sensing Research, The Ohio State University, 2070 Neil Avenue, Columbus, OH 43210-1275 United States
AU: Braun, A
EM: braun.118@osu.edu
AF: Byrd Polar Research Center, The Ohio State University, 1090 Carmack Rd, Scott Hall, Columbus, OH 43210-1002
AB: We investigate the use of CHAMP observations for Earth's mean and time-varying gravity solutions and their geophysical interpretation. 1.5 years of CHAMP data (dynamic RSO orbits and accelerometer) were processed for monthly gravity solutions in spherical harmonics complete to degree 90, using the energy conservation principle and an efficient conjugate gradient inversion with an approximate error covariance matrix. With the exception of several months (because of the bad ground track coverage), monthly gravity solutions are computed for the time period from May 2001 through February 2003. The mean CHAMP gravity field solution (including 1 year of data) is evaluated using other gravity field solutions and various data. The estimated 2nd and 3rd degree/order of the time-varying components of the CHAMP gravity field are modeled with secular, annual, and semi-annual parameters, and compared with available solutions using satellite laser ranging (SLR). Although the second tesseral and the third zonal coefficient observed by CHAMP show unrealistically large variations, other estimates agree well with SLR solutions. The temporal geoid changes from the CHAMP solutions have correlations of 0.6~0.8 and RMS differences of 0.8~0.7 mm, when compared with the CSR's SLR solutions. The CHAMP temporal gravity field solutions are compared with combinations of various geophysical fluid models, including atmosphere, hydrology, ocean, cryosphere, and in situ data. Finally, we investigate some local methods to recover the continental surface water from GRACE mission. Our proposed methods are basically based on the local modeling of the water contents using GRACE potential difference [Jekeli, 1999 and Han, 2003]. They will enhance the spatial resolution as well as the accuracy of the estimates. The results based on the one year simulation of GRACE orbit and range-rate indicate that the local method can improve higher degree/order spectral contents compared to the global spherical harmonic approach.
DE: 1214 Geopotential theory and determination
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 1241 Satellite orbits
SC: Geodesy [G]
MN: 2003 Fall Meeting