HR: 16:30h
AN: G24A-03 INVITED     [Abstracts]
TI: A Comparison of GRACE and GPS Annual Signals over Europe: Why don't they agree?
AU: * van Dam, T
EM: tvd@ecgs.lu
AF: European Center for Geodynamics and Seismology, 19 Rue Josy Welter, Walferdange, L-7256 Luxembourg
AU: Wahr, J
EM: wahr@lemond.colorado.edu
AF: CIRES and Department of Physics, University of Colorado, 216 UCB, Boulder, CO 80309 United States
AB: We compare observations of annual surface displacements from GPS with surface displacements predicted from GRACE gravity observations. The results indicate that the signals are highly correlated in amplitude and phase. However, of the 41 sites analyzed, we find that we are only able to reduce the scatter on 13 time series by removing the GRACE predicted annual signal. There are three possibilities why the RMS is not reduced: 1) the annual signal from the GRACE data does not represent the true environmental annual signal, i.e. the observations are inaccurate; 2) the annual signal in the GPS heights is driven by shorter wavelength environmental variability than is not captured by the GRACE data; or 3) In addition to the environment, other sources contribute to and dominate the annual signal in the GPS measurements. In this talk, we investigate and report on each of these possibilities, and discuss the potential for using GPS to learn about the water storage signal at short wavelengths.
DE: 1211 Non-tectonic deformation
DE: 1217 Time variable gravity (7223, 7230)
DE: 1225 Global change from geodesy (1222, 1622, 1630, 1641, 1645, 4556)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
SC: Geodesy [G]
MN: Fall Meeting 2005