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Choice of optimal averaging radii for temporal GRACE gravity solutions, a comparison with GPS and satellite altimetry


King, MA and Moore, P and Clarke, P and Lavallee, D, Choice of optimal averaging radii for temporal GRACE gravity solutions, a comparison with GPS and satellite altimetry, Geophysical Journal International, 166, (1) pp. 1-11. ISSN 0956-540X (2006) [Refereed Article]

DOI: doi:10.1111/j.1365-246X.2006.03017.x


One of the initial challenges of the Gravity Recovery and Climate Experiment (GRACE) mission is to validate the accuracy of the time-variable gravity fields. These gravity fields contain both spatially correlated (systematic) and random noise and hence spatial averaging needs to be implemented. Before the fields may be interpreted, optimum averaging radii need to be determined through comparison with independent data. We compare time-series of vertical solid earth deformations computed from 22 approximately monthly GRACE gravity fields (covering 2002.3 until 2004.6) with vertical displacements measured using a global GPS network of 63 sites, about half of which are located on small islands. The GPS data were processed using a Precise Point Positioning approach using fiducial free orbits and attempting to minimize propagated systematic errors. The optimum mean correlations were obtained at 500 km averaging radii for continental sites (R = 0.55), > =2000 km for island sites (R = 0.3). Subtracting the GRACE displacement time-series from the GPS ones revealed a mean variance reduction of ∼14 per cent. To supplement the GPS data at the island sites, we also computed displacements based on TOPEX/POSEIDON (T/P) sea surface height data between 2002.3 and 2004.0 corrected for steric effects. Correlations reached a maximum at 2000 km with a correlation of 0.38, increasing to 0.47 after the removal of six outlying sites. Overall, we conclude that optimum averaging radii are ∼500 km for continental sites and >=2000 km over the oceans, but that the measurement precision of GPS and T/P may be inflating these values. © 2006 The Authors Journal compilation © 2006 RAS.

Item Details

Item Type:Refereed Article
Keywords:Crustal deformation; Global Positioning System (GPS); Gravity; Hydrology; Satellite Geodesy; crustal deformation; geodesy; GPS; gravity field; satellite altimetry; TOPEX-Poseidon
Research Division:Earth Sciences
Research Group:Physical geography and environmental geoscience
Research Field:Physical geography and environmental geoscience not elsewhere classified
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:King, MA (Professor Matt King)
ID Code:81910
Year Published:2006
Web of Science® Times Cited:37
Deposited By:Geography and Environmental Studies
Deposited On:2013-01-11
Last Modified:2013-01-11

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