Achievements of the First 4 Years of the International Geodynamics and Earth Tide Service (IGETS) 2015–2019

Boy, Jean-Paul; Barriot, Jean‐Pierre; Förste, Christoph; Voigt, Christian; Wziontek, Hartmut

doi:10.1007/1345_2020_94

Cited by 18 publications

(14 citation statements)

References 21 publications

(19 reference statements)

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“…The time-series from nine Superconducting Gravimeter sites (Bad Homburg, Cantley, Canberra, Membach, Metsahovi, Moxa, Strasbourg, Sutherland and Wettzell), with duration of 14-20 yr (from 1996-2001 to 2015-2016), were pre-processed to remove large earthquakes, to fill small gaps and glitches in a classical way (Hinderer et al 2007) and decimated to 1 hr in order to perform a tidal analysis. Superconducting Gravimeter Level 1 data products were downloaded from IGETS 2 (Boy et al 2020). The new version of the ETERNA3.4 software developed by (Wenzel 1996), ET34-ANA-V60, improved by Schüller (2015), was used.…”

Section: Gravimetric Factors Estimationmentioning

confidence: 99%

Contribution of a joint Bayesian inversion of VLBI and gravimetric data to the estimation of the free inner core nutation and free core nutation resonance parameters

Ziegler

Lambert

Huda

et al. 2020

Geophysical Journal International

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SUMMARY The rotational motions of the internal Earth layers induce resonances in the Earth nutations and tidal gravimetric response to external luni-solar gravitational forcings. The characterization of these resonances is a mean of investigating the deep Earth properties since their amplitudes and frequencies depend on a few fundamental geophysical parameters. In this work, we focus on the determination of the free core nutation and free inner core nutation periods and quality factors from the Bayesian inversion of VLBI and gravimetric data. We make a joint inversion of data from both techniques and show that, even if the results are only slightly different from the inversion of VLBI data alone, such approach may be valuable in the future if the accuracy of gravimetric data increases. We also briefly discuss the polar motion resonance, which is related to the Chandler Wobble as seen from the diurnal frequency band. Our overall estimates of the FCN period and quality factor, TFCN = (−430.2, −429.8) solar days and QFCN = (15 700, 16 700), respectively, are in good agreement with other studies, albeit slightly different for unclear reasons. Despite some concerns about the detection and characterization of the FICN, it seems that we could also successfully estimate its period, TFICN = (+600, +1300) solar days, and give a loose estimate of the upper bound on its quality factor.

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Section: Gravimetric Factors Estimationmentioning

confidence: 99%

Contribution of a joint Bayesian inversion of VLBI and gravimetric data to the estimation of the free inner core nutation and free core nutation resonance parameters

Ziegler

Lambert

Huda

et al. 2020

Geophysical Journal International

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“…Non-local hydrological gravity variations include both attraction effects and surface loading, while for local to catchment scales only the attraction effects from mass redistributions is considered. The non-local hydrology is provided by the EOST Loading Service(Boy, 2015) using the Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2;Gelaro et al, 2017) with spatial resolutions of 0.5° and 0.625° in latitude and longitude, respectively, and 1-hour temporal resampling.https://doi.org/10.5194/hess-2021-78 Preprint. Discussion started: 8 March 2021 c Author(s) 2021.…”

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confidence: 99%

Introduction of a Superconducting Gravimeter as Novel Hydrological Sensor for the Alpine Research Catchment Zugspitze

Voigt

Schulz

Koch

et al. 2021

Preprint

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Abstract. The Zugspitze Geodynamic Observatory Germany has been set up with a worldwide unique installation of a superconducting gravimeter at the summit of Mount Zugspitze. With regard to hydrology, this karstic high-alpine site is largely dominated by high precipitation amounts and a long seasonal snow cover period with significant importance for water supply to its forelands, while it shows a high sensitivity to climate change. However, regarding the majority of alpine regions worldwide there is only weak knowledge on temporal water storage variations due to only sparsely distributed hydrological and meteorological point sensors and the large variability and complexity of alpine signals. This underlines the importance of well-equipped areas such as Mount Zugspitze serving as natural test laboratories for an improved monitoring, understanding and prediction of alpine hydrological processes. The observatory superconducting gravimeter OSG 052 supplements the existing sensor network as a novel hydrological sensor system for the direct observation of the integral gravity effect of total water storage variations in the alpine research catchment Zugspitze. Besides the experimental setup and the available datasets, the required gravimetric prerequisites are presented such as calibration, tidal analysis and signal separation of the superconducting gravimeter observations from the first 2 years. The snowpack is identified as primary contributor to seasonal water storage variations and thus to the gravity residuals with a signal range of up to 750 nm/s2 corresponding to 1957 mm snow water equivalent measured at a representative station at the end of May 2019. First hydro-gravimetric sensitivity analysis are based on simplified assumptions of the snowpack distribution within the area around Mount Zugspitze. These reveal a snow-gravimetric footprint of up to 4 km distance around the gravimeter with a dominant gravity contribution from the snowpack in the Partnach spring catchment. This study already shows that the hydro-gravimetric approach can deliver important and representative integral insights into this high-alpine site. This work is regarded as a concept study showing preliminary gravimetric results and sensitivity analysis for upcoming long-term hydro-gravimetric research projects.

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“…For stations operating a SG, it is recommended to perform absolute gravity observations every two years for the determination of the SG instrumental drift. Stations of the International Geodynamics and Earth Tide Service (IGETS) (Boy et al 2020) with long-term SG records should become an essential part of the IGRF. -Comparison stations are reference stations as described above with extended facilities to check the compatibility of instruments, either based on continuous gravity monitoring or by simultaneous measurements of at least two absolute gravimeters.…”

Section: Infrastructurementioning

confidence: 99%

Status of the International Gravity Reference System and Frame

Wziontek

Bonvalot

Falk

et al. 2021

J Geod

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The increasing importance of terrestrial gravimetry in monitoring global change processes, in providing a reference for satellite measurements and in applications in metrology necessitates a stable reference system reflecting the measurement accuracy achievable by modern gravimeters. Therefore, over the last decade, the International Association of Geodesy (IAG) has developed a system to achieve accurate, homogeneous, long-term global recording of Earth’s gravity, while taking advantage of the potential of today’s absolute gravity measurements. The current status of the International Gravity Reference System and Frame is presented as worked out by the IAG Joint Working Group 2.1.1 “Establishment of a global absolute gravity reference system” during the period 2015–2019. Here, the system is defined by the instantaneous acceleration of free-fall, expressed in the International System of Units (SI) and a set of conventional corrections for the time-independent components of gravity effects. The frame as the systems realization includes a set of conventional temporal gravity corrections which represent a uniform set of minimum requirements. Measurements with absolute gravimeters, the traceability of which is ensured by comparisons and monitoring at reference stations, provide the basis of the frame. A global set of such stations providing absolute gravity values at the microgal level is the backbone of the frame. Core stations with at least one available space geodetic technique will provide a link to the terrestrial reference frame. Expanded facilities enabling instrumental verification as well as repeated regional and additional comparisons will complement key comparisons at the level of the International Committee for Weights and Measures (CIPM) and ensure a common reference and the traceability to the SI. To make the gravity reference system accessible to any user and to replace the previous IGSN71 network, an infrastructure based on absolute gravity observations needs to be built up. This requires the support of national agencies, which are encouraged to establish compatible first order gravity networks and to provide information about existing absolute gravity observations.

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Achievements of the First 4 Years of the International Geodynamics and Earth Tide Service (IGETS) 2015–2019

Cited by 18 publications

References 21 publications

Contribution of a joint Bayesian inversion of VLBI and gravimetric data to the estimation of the free inner core nutation and free core nutation resonance parameters

Contribution of a joint Bayesian inversion of VLBI and gravimetric data to the estimation of the free inner core nutation and free core nutation resonance parameters

Introduction of a Superconducting Gravimeter as Novel Hydrological Sensor for the Alpine Research Catchment Zugspitze

Status of the International Gravity Reference System and Frame

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