Abstract
A good understanding of the accuracy of the Global Positioning System (GPS) surface displacements provided by different processing centers plays an important role in load deformation analysis. We estimate the noise level in both vertical and horizontal directions for four representative GPS time series products, and compare GPS results with load deformation derived from the Gravity Recovery and Climate Experiment (GRACE) gravity measurements and climate models in Europe. For the extracted linear trend signals, the differences among different GPS series are small in all the three (east, north, and up) directions, while for the annual signals the differences are large. The mean standard deviations of annual amplitudes retrieved from the four GPS series are 3.54 mm in the vertical component (69% of the signal itself) and ~ 0.3 mm in the horizontal component (30% of the signal itself). The Scripps Orbit and Permanent Array Center (SOPAC) and MEaSUREs series have the lowest noise level in vertical and horizontal directions, respectively. Through consistency/discrepancy analysis among GPS, GRACE, and model vertical series, we find that the Jet Propulsion Laboratory (JPL) and Nevada Geodetic Laboratory (NGL) series show good consistency, the SOPAC series show good agreements in annual signal with the GRACE and model, and the MEaSUREs series show substantially large annual amplitude. We discuss the possible reasons for the notable differences among GPS time series products.
Highlights
Note that for sites with large differences among the four products, the mean values of annual amplitudes and phases can hardly reflect the real deformation signals, and are only calculated as a value for joint analysis combined with the standard deviations (SD)
To examine the detailed information of the arrows, we show in Figure 5 the zoomed-in figures of the annual amplitudes and phases at the selected 9 sites, whose annual variations are significant and representative of the study region
We carried out a detailed comparison of Global Positioning System (GPS) surface displacement time series products from four institutions in Europe, and analyzed their influences on load deformation study
Summary
Surface load deformations are caused by mass redistributions in the geophysical fluids system, including the atmosphere, ocean, terrestrial water, ice sheets and glaciers, etc. With gradually increasing precision of the Global Positioning System (GPS), one of the most representative Global Navigation Satellite System (GNSS), surface deformation can be fairly accurately observed. GPS measurements were combined with data from other geodetic techniques (e.g., satellite gravimetry, altimetry) to study large scale surface loads, such as global water cycling, and polar ice melting [1,2]. With dense and continuous observation sites, GPS can be used as an effective constraint or even an independent means to quantify the magnitude and spatial distribution of surface load [3,4]
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