Atmospheric pressure loading in GPS positions: dependency on GPS processing methods and effect on assessment of seasonal
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ORIGINAL ARTICLE
Atmospheric pressure loading in GPS positions: dependency on GPS processing methods and effect on assessment of seasonal deformation in the contiguous USA and Alaska Hilary R. Martens1 · Donald F. Argus2 · Cody Norberg3 · Geoffrey Blewitt4 · Thomas A. Herring5 · Angelyn W. Moore2 · William C. Hammond4 · Corné Kreemer4 Received: 10 April 2020 / Accepted: 29 September 2020 / Published online: 18 November 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The Global Positioning System (GPS) has revolutionized the ability to monitor Earth-system processes, including Earth’s water cycle. Several analysis centers process GPS data to estimate ground-antenna positions at daily temporal resolution. Differences in processing strategies can lead to inconsistencies in coordinate-position estimates and therefore influence the analysis of crustal displacement associated with variations in atmospheric and hydrologic mass loading. Here, we compare five GPS data products produced by three processing centers: the Nevada Geodetic Laboratory, Jet Propulsion Laboratory, and UNAVCO Consortium. We find that 5 to 30% of the scatter in residual GPS time series (commonly considered noise) can be explained by atmospheric loading in the contiguous USA and Alaska, but that the percentages vary widely by data product. Positions derived using high-resolution troposphere models (e.g., ECMWF) exhibit significantly lower scatter after correcting for atmospheric loading than positions estimated using constant or slowly varying troposphere models (e.g., GPT2w). The data products also exhibit differences in seasonal deformation (commonly attributed, in large part, to fluctuations in hydrologic mass loading): median vector differences in estimated seasonal amplitude range from 0.4–1.0 mm in the vertical component and 0.1–0.3 mm in the horizontal components, or about 10–40% of the mean amplitudes of seasonal oscillation. Newer products exhibit lower total scatter and stronger correlations than older products. Network-coherent differences in estimates of seasonal deformation reveal reference-frame inconsistencies between data products. We also cross-check two independent models of atmospheric pressure loading: ESMGFZ and LoadDef. Keywords Elastic Earth deformation · Atmospheric pressure loading · Troposphere delays · GPS processing · GNSS processing · Hydrologic loading · Seasonal Earth deformation
1 Introduction
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Hilary R. Martens [email protected]
1
Department of Geosciences, University of Montana, Missoula, USA
2
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA
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Department of Physics and Astronomy, University of Montana, Missoula, USA
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Nevada Geodetic Laboratory, Nevada Bureau of Mines and Geology, University of Nevada, Reno, USA
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Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, USA
The Global Positioning System (GPS) records displacements of Earth’s surface associated with a variety of natural pr
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