Abstract
We investigated the effect of mass loading (atmospheric, oceanic and hydrological loading (AOH)) on Global Positioning System (GPS) height time series from 30 GPS stations in the Eurasian plate. Wavelet coherence (WTC) was employed to inspect the correlation and the time-variable relative phase between the two signals in the time–frequency domain. The results of the WTC-based semblance analysis indicated that the annual fluctuations in the two signals for most sites are physically related. The phase asynchrony at the annual time scale between GPS heights and AOH displacements indicated that the annual oscillation in GPS heights is due to a combination of mass loading signals and systematic errors (AOH modelling errors, geophysical effects and/or GPS system errors). Moreover, we discuss the impacts of AOH corrections on GPS noise estimation. The results showed that not all sites have an improved velocity uncertainty due to the increased amplitude of noise and/or the decreased spectral index after AOH corrections. Therefore, the posterior mass loading model correction is potentially feasible but not sufficient.
Highlights
The strong annual oscillations in Global Positioning System (GPS) observations are known to be driven by the redistribution of environmental mass loading [1,2]
Van Dam et al [14] corrected 51 GPS sites in Europe with AOH derived from Gravity Recovery and Climate Experiment (GRACE) and found that only 10 GPS stations have a reduction in their root mean square (RMS) values
The results indicated that 64% of the stations underwent a decrease in their RMS values, the reasons for the inconsistency between the mass loading displacements and GPS observations were not discussed in detail
Summary
The strong annual oscillations in Global Positioning System (GPS) observations are known to be driven by the redistribution of environmental mass loading [1,2]. Distributed surface mass variabilities can be estimated to a certain extent using the method of a mass loading model and Gravity Recovery and Climate Experiment (GRACE) technology [12,13]. Van Dam et al [14] corrected 51 GPS sites in Europe with AOH derived from GRACE and found that only 10 GPS stations have a reduction in their root mean square (RMS) values. Compared to GRACE, the mass loading model can estimate the small-scale variability [15]. Jiang et al [16] adjusted 233 globally distributed GPS sites by AOH derived from the mass loading model, provided by the Global Geophysical Fluid Center (GGFC)
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