Assessing the precision in loading estimates by geodetic techniques in Southern Europe

Abstract

This paper investigates the precision of the estimation of geophysical fluid load deformation computed from GRACE space gravity, GPS vertical displacement and geophysical fluids models [Global Circulation Models (GCMs) for ocean, atmosphere and hydrology], using the three-cornered hat method. This method allows the estimation of the variance of the errors of each technique, when the same quantity is monitored by three instruments with independent errors. Applied on a network of stations, several points of view can be considered: the technique level (in order to determine the error of each technique: GRACE, GPS and GCMs), the solution level (allowing to compare the precision of the same technique when different strategies/models are used), and the station level (in order to emphasize local anomalies and geographical patterns). In particular, our results show a precision of the loading vertical displacement at the level of 1 mm when using GRACE or the fluid models, and of 2 mm using GPS. We do not find significant differences between the precision of different solutions of the same techniques, even when there are strong differences in the data processing.

Impact of the North Atlantic Oscillation on Southern Europe Water Distribution: Insights from Geodetic Data

“…The preprocessing information directly relevant to our study is described below; the reader is referred to Valty et al (2013) for more information.…”

“…The possible discontinuities related to earthquakes or equipment changes have been removed. As the signature of the surface load is cleaner in the vertical component of the station displacements (Tregoning et al 2009;Valty et al 2013), our study is limited to that component. The origin of the frame in which these vertical displacements are expressed is Earth's center of figure ).…”

“…The water mass load at Earth's surface changes both the gravity and Earth's shape, as the ground bends under the load. At annual (Tregoning et al 2009;Tesmer et al 2011) and also interannual time scales (Valty et al 2013), the water mass distribution is the major source of time variation of Earth's gravity as seen by satellites and of Earth's shape. This makes geodetic data a great tool for understanding the global-and regional-scale water mass redistributions.…”

Uncertainties of the Gravity Recovery and Climate Experiment time-variable gravity-field solutions based on three-cornered hat method

“…The three-cornered hat (TCH) method can offer an alternative approach to quantify the uncertainty of each GRACE processing center. Originally applied to assessing the relative precision of oscillators and timing devices, 34 this method has recently been applied to the fields of geodesy [35][36][37][38] and hydrology. 39,40 The TCH method is based on a difference approach relying on the removal of common signals from the observations (i.e., the truth), then providing the uncertainties that reflect the measurement errors.…”

Estimating observation and model error variances using multiple data sets

“…Gray and Allan (1974) The THC method has been used to estimate the stability of GNSS clocks using the measured frequencies from multiple clocks (Ekstrom and Koppang, 2006;Griggs et al, 2014Griggs et al, , 2015Luna et al, 2017). Valty et al (2013) used the TCH method to estimate the geophysical load deformation computed from GRACE satellites, GPS vertical displacement measurements, and global general circulation (GCM) models. 20…”