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  • English  (12)
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  • 1
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    Landscape-scale water balance monitoring with an iGrav superconducting gravimeter in a field enclosure (2017)
    In:  Hydrology and Earth System Sciences
    Details
    Publication Date: 2020-02-12
    Description: In spite of the fundamental role of the landscape water balance for the Earth's water and energy cycles, monitoring the water balance and its components beyond the point scale is notoriously difficult due to the multitude of flow and storage processes and their spatial heterogeneity. Here, we present the first field deployment of an iGrav superconducting gravimeter (SG) in a minimized enclosure for long-term integrative monitoring of water storage changes. Results of the field SG on a grassland site under wet–temperate climate conditions were compared to data provided by a nearby SG located in the controlled environment of an observatory building. The field system proves to provide gravity time series that are similarly precise as those of the observatory SG. At the same time, the field SG is more sensitive to hydrological variations than the observatory SG. We demonstrate that the gravity variations observed by the field setup are almost independent of the depth below the terrain surface where water storage changes occur (contrary to SGs in buildings), and thus the field SG system directly observes the total water storage change, i.e., the water balance, in its surroundings in an integrative way. We provide a framework to single out the water balance components actual evapotranspiration and lateral subsurface discharge from the gravity time series on annual to daily timescales. With about 99 and 85 % of the gravity signal due to local water storage changes originating within a radius of 4000 and 200 m around the instrument, respectively, this setup paves the road towards gravimetry as a continuous hydrological field-monitoring technique at the landscape scale.
    Language: English
    Type: info:eu-repo/semantics/article
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  • 2
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    Landscape-scale water balance monitoring with an iGrav superconducting gravimeter in a field enclosure (2017)
    In:  Geophysical Research Abstracts Vol. 19, EGU2017-13940
    Details
    Publication Date: 2020-02-12
    Description: In spite of the fundamental role of the landscape water balance for the Earth’s water and energy cycles, monitoring the water balance and its components beyond the point scale is notoriously difficult due to the multitude of flow and storage processes and their spatial heterogeneity. Here, we present the first deployment of an iGrav superconducting gravimeter (SG) in a minimized field enclosure on a grassland site for integrative monitoring of water storage changes. Results of the field SG were compared to data provided by a nearby SG located in the controlled environment of an observatory building. For wet-temperate climate conditions, the system proves to provide gravity time series that are similarly precise as those of the observatory SG. At the same time, the field SG is more sensitive to hydrological variations than the observatory SG. We demonstrate that the gravity variations observed by the field setup are almost independent of the depth below the terrain surface where water storage changes occur (contrary to SGs in buildings), and thus the field SG system directly observes the total water storage change, i.e. the water balance, in its surroundings in an integrative way.We provide a framework to single out the water balance components actual evapotranspiration and lateral subsurface discharge from the gravity time series on annual to daily time scales.With about 99% and 85% of the gravity signal originating within a radius of 4000 and 200 meter around the instrument, respectively, this setup paves the road towards gravimetry as a continuous hydrological field monitoring technique at the landscape scale.
    Language: English
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  • 3
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    Hydrometeorological and gravity data from the Argentine-German Geodetic Observatory in La Plata (2018)
    GFZ Data Services
    Details
    Publication Date: 2020-02-12
    Description: The data set contains hydrological, meteorological and gravity time series collected at Argentine-German Geodetic Observatory (AGGO) in La Plata, Argentina. The hydrological series include soil moisture, temperature, electric conductivity, soil parameters, and groundwater variation. The meteorological time series comprise air temperature, humidity, pressure, wind speed, solar short- and long-waver radiation, and precipitation. The observed hydrometeorological parameters are extended by modelled value of evapotranspiration and water content variation in the zone between deepest soil moisture sensor and the groundwater level. Gravity products include large-scale hydrological, oceanic as well as atmospheric effects. These gravity effects are furthermore extended by local hydrological effects and gravity residuals suitable for comparison and evaluation of the model performance. Provided are directly observed values denoted as Level 1 product along with pre-processed series corrected for known issues (Level 2). Level 3 products are model outputs acquired using Level 2 data. The maximal temporal coverage of the data set ranges from May 2016 up to November 2018 with some exceptions for sensors and models set up in May 2017. The data set is organized in a database structure suitable for implementation in a relational database management system. All definitions and data tables are provided in separate text files allowing for traditional use without database installation.
    Language: English
    Type: info:eu-repo/semantics/workingPaper
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  • 4
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    Report on the Data Base of the International Geodynamics and Earth Tide Service (IGETS) (2016)
    GFZ German Research Centre for Geosciences
    In:  Scientific Technical Report STR - Data
    Details
    Publication Date: 2020-11-05
    Description: The International Geodynamics and Earth Tide Service (IGETS) was established in 2015 by the International Association of Geodesy (IAG). IGETS continues the activities of the Global Geodynamics Project (GGP, 1997-2015) to provide support to geodetic and geophysical research activities using superconducting gravimeter data within the context of an international network. The primary objective of IGETS is to provide a service to monitor temporal variations of the Earth’s gravity field through long-term records from ground gravimeters, tiltmeters, strainmeters and other geodynamic sensors. IGETS also continues the activities of the International Center for Earth Tides, in particular, in collecting, archiving and distributing Earth tide records from long series of the various geodynamic sensors. This report is a compilation of data descriptions originating to a large part from GGP but including updates and extensions for IGETS.
    Language: English
    Type: info:eu-repo/semantics/report
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  • 5
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    The Nordic Comparison of Absolute Gravimeters – NKG-CAG-2022 (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-07-04
    Description: In the year 2022, the Nordic Comparison of Absolute Gravimeters NKG-CAG-2022 took place at the Onsala Space Observatory of Chalmers University in Sweden. The comparison enabled participants, especially of the Nordic Countries, to obtain traceability to the SI units for their absolute gravimeters and compare their instruments to make sure they are compatible. This is important for the Fennoscandian post-glacial rebound studies carried out with these instruments.The comparison was arranged as an additional comparison according to the CCM-IAG Strategy for Metrology in Absolute Gravimetry. It was organized under the umbrella of the Nordic Geodetic Commission by the Chalmers University, Lantmäteriet and the Finnish Geospatial Research Institute, that acted as the pilot laboratory for metrology. 15 instruments of 12 organizations participated in the comparison between 10.5.2022 and 7.7.2022.The instruments measured at three sites and temporal changes in gravity were monitored with the SG054 superconducting gravimeter at Onsala. After the comparison results of 13 instruments and 11 organizations were received. Of the instruments, 6 were FG5X gravimeters, 4 FG5 gravimeters, 2 A10 gravimeters and 1 AQG atom gravimeter. The link to the latest international and European comparisons of absolute gravimeters (CCM.G-K2.2017 and EURAMET.M.G-K3) was provided by the FG5-215H and FG5X-221, that participated in those comparisons and are from a National Metrological Institute or Designated Institute. We will present the results of the comparison.
    Language: English
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  • 6
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    Evaluation of the AQG-B10 absolute quantum gravimeter for field measurements (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-06-28
    Description: Falling corner cube gravimeters (FCCG) pose the current state-of-the-art instruments for absolute terrestrial gravimetry. However, already in the early 1990s, experimental quantum gravimeters have been demonstrated: a fundamentally different principle for measuring gravity based on probing the free-fall trajectory of ultracold atoms via quantum matter wave interference. In recent years, the community's interest in quantum gravimeters has strongly increased as they have progressed from experimental prototypes towards commercially available instruments intended for end-users in geodetic applications.The commercially available iXblue Absolute Quantum Gravimeter (AQG) B-series instrument is a field-compatible successor to the A-series AQG, which is restricted to indoor use. Here, we present our first results of evaluating the AQG-B10 instrument for lab and field operation in BKG’s routine measurement campaigns. We assess the instrument precision, stability, accuracy and reproducibility based on comparison measurements at the Geodetic Observatory Wettzell employing a continuous gravity reference function. This reference is derived from the combination of measurements with the Micro-g LaCoste FG5 FCCG, currently dominating absolute gravimetry, with highly precise superconducting gravimeters, and is linked to the EURAMET.M.G-K3 regional comparison of absolute gravimeters. Moreover, we compare the AQG-B10 to the Micro-g LaCoste A10 FCCG, the current state-of-the-art instrument for absolute field measurements.
    Language: English
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  • 7
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    Update of the Atmospheric attraction computation service (Atmacs) for high-precision terrestrial gravity observations (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-11-15
    Description: The Atmospheric attraction computation service (Atmacs) provides atmospheric corrections for terrestrial high-precision gravity time series based on operational weather models of the German Weather Service (DWD). In Atmacs, Newtonian attraction and deformation contributions to loading are computed separately. The attraction component benefits from the discrete 3D distribution of air mass around the station, while deformation effects are derived from surface atmospheric pressure changes assuming that the oceans behave as a perfect Inverse Barometer (IB).Several improvements in the modelling approach of Atmacs are presented. A revision of the IB hypothesis implementation revealed that the attraction component over oceans is overestimated. A modification of the IB implementation not only resolves this issue but further enhances the compatibility between the atmospheric modelling and ocean models. This allows to complement Atmacs with non-tidal ocean loading (NTOL) effects, here based on the Max-Plank-Institute for Meteorology Ocean Model (MPIOM). These updates allow for a consistent combination of atmospheric and ocean models and a more efficient reduction of the gravity time series.Finally, we evaluate atmospheric corrections derived from both meteorological models currently used by Atmacs: the global and the European solutions of the Icosahedral Nonhydrostatic (ICON) model. In the case of the regional model, non-regional contributions are accounted from the global solution. This comparison is performed for several stations located in Europe, with emphasis on the estimation of tidal parameters and the reduction of gravity residuals.
    Language: English
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  • 8
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    Status of the International Geodynamics and Earth Tide Services (IGETS) (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-08-29
    Description: The International Geodynamics and Earth Tide Services is one of the newer IAG services under the umbrella of the International Gravity Field Service (IGFS). Its primary objective is to support the monitoring of temporal gravity field variations at the Earth’s surface through long-term records from superconducting and mechanical gravimeters, tiltmeters and other geodynamic sensors. Its main products are the raw and processed data from a worldwide set of superconducting gravimeters (SG), hosted at the main Data Center located at the German Research Centre for Geosciences (GFZ) in Potsdam (Germany). We present here the status of IGETS, the data availability and the different data products: - Level-1: raw gravity and pressure sampled at 1 or 2 seconds and filtered at 1 minute. - Level-2: gravity and pressure data corrected for instrumental perturbations, ready for tidal analysis. - Level-3: gravity residuals after geophysical corrections. The University of French Polynesia (UPF) in Tahiti and the Ecole et Observatoire des Sciences de la Terre (EOST) in Strasbourg (France) are the two current Analysis Centers in charge of producing these higher order level data. While Level-1 products require special knowledge in data pre-processing, the Level-2 and -3 products are intended for analysis and interpretation. In particular, level-2 products are dedicated to the analysis of Earth tides, while level-3 products directly allow further interpretation of small signals after the removal of known components, like water storage changes.
    Language: English
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  • 9
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    International Gravimetric Bureau (BGI): database, services and products (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-09-06
    Description: As a scientific service of the International Gravity Field Service of IAG, the BGI is in charge of the collection, validation and distribution of gravity measurements acquired at the Earth’s surface. The BGI maintains four global databases of relative gravity measurements (derived from land and marine surveys), of absolute gravity measurements (AGrav database maintained by the BKG in Germany) and of reference gravity stations. In addition, BGI and its supporting organizations contribute to research and educational activities including the development of global and regional gravity products, tools and software. We present the main services provided to the gravity data users and the latest novelties, in particular the automatic attribution of doi (Digital Object Identifier) for all incoming datasets, products and software to facilitate the traceability and referencing to the authors.
    Language: English
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  • 10
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    Proposal for the International Terrestrial Gravity Reference System and Frame of IAG (2023)
    In:  XXVIII General Assembly of the International Union of Geodesy and Geophysics (IUGG)
    Details
    Publication Date: 2023-09-12
    Description: Over the past several years, a definition for a modern International Terrestrial Gravity Reference System (ITGRS) has been developed by the IAG Joint Working Group 2.1.1. Now a resolution will be proposed to IAG to adopt the ITGRS. The ITGRS is based on the instantaneous acceleration of free-fall, expressed in the International System of Units (SI). Consequently, the International Terrestrial Gravity Reference Frame (ITGRF) will be its realization and will be based on measurements with absolute gravimeters at an accuracy level of a few microGal〈sup〉 〈/sup〉(1 µGal = 10〈sup〉-8〈/sup〉 m/s〈sup〉2〈/sup〉). Conventional models for the correction of time dependent effects in these measurements are proposed which are compatible with previous standards. An adequate infrastructure then allows for replacement of IGSN71 which no longer meet the today’s requirements. The details of the concept are outlined and summarized, specifically the proposal to include constant components of temporal gravity corrections as part of the system definition and the importance of instrument comparisons at different levels to ensure a common reference level and the traceability to the SI. Reference stations to monitor the stability of absolute gravimeters will play a key role in the ITGRF. Colocation with space geodetic techniques will provide a link to the International Terrestrial Reference Frame and to GGOS. Establishing compatible first order gravity networks and sharing information on absolute gravity observations will provide access to users but will require support and collaboration with national authorities worldwide.
    Language: English
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