HR: 0800h
AN: G31C-0808    [Abstracts]
TI: Mass redistribution from inversion of global GPS timeseries and global time-varying gravity: inverse methodology, estimability and truncation
AU: Kusche, J
EM: j.kusche@lr.tudelft.nl
AF: DEOS, Delft University of Technology, Kluyverweg 1, Delft, 2629 HS Netherlands
AU: * Schrama, E J
EM: e.j.o.schrama@lr.tudelft.nl
AF: DEOS, Delft University of Technology, Kluyverweg 1, Delft, 2629 HS Netherlands
AB: Monitoring global mass redistributions through their integrated gravitational attraction is the primary aim of the GRACE mission. There are, however, indications that is possible to achieve this independently through geometrically measuring the elastic response of the Earth to the loading effect of these (hydrological and oceanic) masses, eg with the IGS network. In any case, the analyst is forced to constrain any solved-for mass configuration either by low-degree truncation, by spatial averaging, and/or regularization operations. Combining satellite gravity and geometrical displacements in a joint inversion might help in improving the reliability of estimates, but in particularly it offers prospects for cross-validation and for a more realistic quality assessment. We lay out a concept for such a joint inversion. For the time being, we have analyzed global GPS time series publicly made available as IGS combination solutions. One can easily show that parametrization issues (truncation, spatial aliasing due to inhomogeneous station distribution) affect the estimation of low-degree mass redistributions like geocenter motion and seasonal $J_2$ changes from these data. We show how a biased estimation technique that applies only physically motivated constraints over oceanic areas renders the truncation problem in a less serious one. Linear combinations of spherical harmonic coefficients beyond degree 4 contain significant information. We quantify what the effect of adding GRACE monthly solutions in a joint inversion would be, dependend on their quality.
DE: 1214 Geopotential theory and determination
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 1243 Space geodetic surveys
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting