Abstract
It is of great interest to numerous geophysical studies that the time series of global gravity field models derived from Gravity Recovery and Climate Experiment (GRACE) data remains uninterrupted after the end of this mission. With this in mind, some institutes have been spending efforts to estimate gravity field models from alternative sources of gravimetric data. This study focuses on the gravity field solutions estimated from Swarm global positioning system (GPS) data, produced by the Astronomical Institute of the University of Bern, the Astronomical Institute (ASU, Czech Academy of Sciences) and Institute of Geodesy (IfG, Graz University of Technology). The three sets of solutions are based on different approaches, namely the celestial mechanics approach, the acceleration approach and the short-arc approach, respectively. We derive the maximum spatial resolution of the time-varying gravity signal in the Swarm gravity field models to be degree 12, in comparison with the more accurate models obtained from K-band ranging data of GRACE. We demonstrate that the combination of the GPS-driven models produced with the three different approaches improves the accuracy in all analysed monthly solutions, with respect to any of them. In other words, the combined gravity field model consistently benefits from the individual strengths of each separate solution. The improved accuracy of the combined model is expected to bring benefits to the geophysical studies during the period when no dedicated gravimetric mission is operational.
Highlights
The Earth’s Magnetic Field and Environment Explorers, launched in November 2013, aim at improving the knowledge of the geomagnetic field (Haagmans 2004; Friis-Christensen et al 2006, 2008; Olsen et al 2013)
We have shown that the Swarm gravity field models represent the same geophysical signals as Gravity Recovery and Climate Experiment (GRACE) with root mean square (RMS) differences ranging from 2 to 4 mm geoid height and a spatial resolution up to degree 12
In this study, we have compared the gravity field models produced from Swarm High– low satellite-to-satellite tracking (hl-SST) data and from GRACE K-band ranging (KBR) data
Summary
The Earth’s Magnetic Field and Environment Explorers (more commonly known as the Swarm satellites), launched in November 2013, aim at improving the knowledge of the geomagnetic field (Haagmans 2004; Friis-Christensen et al 2006, 2008; Olsen et al 2013). The main source of highly accurate gravimetric data describing the temporal changes in Earth’s gravity field is the GRACE mission (Tapley et al 2004), launched in March 2002. From these data, monthly gravity field models describing the global mass variations at scales. This study proposes to determine the quality of the monthly gravity field models estimated from Swarm data from all three satellites. We determine the maximum spatial resolution of these models on a monthly basis and identify the geographical regions where the temporal variations of Earth’s gravity field are in good agreement with what is observed by GRACE. The handling of tidal and nontidal Atmosphere and Ocean processes is shown
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