HR: 1340h
AN: G53A-0121    [Abstracts]
TI: Choice of Basis Functions for the Representation of Seasonal Surface Loading Signals in Geodetic Time Series
AU: * Clarke, P J
EM: Peter.Clarke@newcastle.ac.uk
AF: Newcastle University, School of Civil Engineering and Geosciences, Newcastle, NE1 7RU United Kingdom
AU: Lavallee, D A
AF: Newcastle University, School of Civil Engineering and Geosciences, Newcastle, NE1 7RU United Kingdom
AU: Blewitt, G
AF: Newcastle University, School of Civil Engineering and Geosciences, Newcastle, NE1 7RU United Kingdom
AU: Blewitt, G
AF: University of Nevada, Reno, Mackay School of Earth Science and Engineering, Mail Stop 178, Reno, NV 89557 United States
AU: van Dam, T
AF: European Center for Geodynamics and Seismology, 19 Rue Josie Welter, Walferdange, LUX L-7256
AB: We discuss the relative merits of different techniques and basis functions for (i) the forward modelling of geodetic monument displacements due to surface loading, and (ii) inverse modelling of surface load parameters given geodetic displacements. Forward modelling is frequently performed using gridded datasets and a Green's function approach, but in this method it is difficult to account properly for the effects of geocenter motion on the reference frame. In forward modelling, spherical harmonic representation does not suffer from this drawback, but fine-scale (higher-degree) inversion is unstable due to the continent-rich, ocean-poor distribution of geodetic displacement data. A further problem, which affects both of these methods but is readily correctable using the spherical harmonic approach, is the appropriate treatment of mass conservation and of the oceanic equilibrium-tide response to the total gravitational field. We show how a modified set of basis functions derived from mass-conserving, tidally-equilibrated, area-masked spherical harmonics can be used in the inverse procedure. Although this approach is more stable at higher degrees, the basis functions are no longer orthonormal, even for a global dataset. We compare our method with other local representations such as spherical wavelets.
DE: 1836 Hydrologic budget (1655)
DE: 1223 Ocean/Earth/atmosphere interactions (3339)
DE: 1247 Terrestrial reference systems
DE: 1294 Instruments and techniques
DE: 1655 Water cycles (1836)
SC: Geodesy [G]
MN: 2004 AGU Fall Meeting