Modeling and Observation of Loading Contribution to Time-Variable GPS Sites Positions
We investigate loading consequences on the time-variable GPS station positions of one hundred stations around the world during the 2001–2006 time period. We model the three dimensional site displacements using a Love number formalism to describe the elastic deformation of a spherical Earth model submitted to atmospheric, oceanic and hydrological loadings.
We produce site position time series using the GPS analysis software GAMIT/GLOBK with or without inserting a combination of loading models and study their impact on 3D site positions. First of all, we compare the variability of modeled and observed site positions without integrating loading. We secondly study the variability reduction in the GPS site positions provided by the loading when integrating it in the GAMIT Software as an a priori contribution to the station motion model.
We conclude that the seasonal variability of site vertical displacement is quite well explained by our model at several locations, mainly located at mid-latitudes in the northern hemisphere, while it is much less understood near coastal areas.
KeywordsEarth/Atmosphere/Ocean/Hydrosphere interactions Loading Earth’s deformation GPS Time-variable sites positions Vertical positioning
The authors thank Matthew Rodell and Florent Lyard for providing their insights and datasets. We thank IGS, ECMWF, NCEP for providing data and products, and GAMITeers, T. Herring, R. King and P. Tregoning, for continuously improving and implementing new methods inside GAMIT/GLOBK.
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