The quest for a consistent signal in ground and GRACE gravity time series
Résumé
Recent studies show that terrestrial and space based observations of gravity agree overEurope. In this paper, we compare time series of terrestrial gravity (including thecontribution due to surface displacement) as measured by superconducting gravimeters(SGs), space based observations from GRACE, and predicted changes in gravity derived fromtwo global hydrological models at 10 SG stations in Central Europe. Despite the fact that allobservations and models observe a maximum in the same season due to water storagechanges, there is little agreement the SG time series even when they are separated bydistances smaller than the spatial resolution of GRACE. We also demonstrate that GRACE andthe SG observations and the water storage models do not display significant correlation atseasonal periods nor at inter-annual periods. These findings are consistent with the fact thatthe SGs are sensitive primarily to mass changes in the few hundred meters surrounding thestation. Even if the hydrological models were perfect, we show that we could not correct theSGs for these local effects that would allow comparisons with GRACE.
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