hig.sePublications
Change search
Link to record
Permanent link

Direct link
Publications (10 of 17) Show all publications
Bagherbandi, M., Shirazian, M., Amin, H. & Horemuz, M. (2023). Time transfer and significance of vertical land motion in relativistic geodesy applications: a review paper. Frontiers in Earth Science, 11, Article ID 1139211.
Open this publication in new window or tab >>Time transfer and significance of vertical land motion in relativistic geodesy applications: a review paper
2023 (English)In: Frontiers in Earth Science, E-ISSN 2296-6463, Vol. 11, article id 1139211Article, review/survey (Refereed) Published
Abstract [en]

Determination of the Earth’s gravity field and geopotential value is one of the fundamental topics in physical geodesy. Traditional terrestrial gravity and precise leveling measurements can be used to determine the geopotential values at a local or regional scale. However, recent developments in optical atomic clocks have not only rapidly improved fundamental science but also contributed to applied research. The latest generation of optical clocks is approaching the accuracy level of 10−18 when facilitating atomic clock networks. These systems allow examining fundamental theories and many research applications, such as atomic clocks applications in relativistic geodesy, to precisely determine the Earth’s gravity field parameters (e.g., geopotential values). According to the theory of relativistic geodesy, the frequency difference measured by an optical clock network is related to the gravity potential anomaly, provided that the effects of disturbing signals (i.e., tidal and non-tidal contributions) are filtered out. The relativistic geodesy principle could be used for a practical realization of global geodetic infrastructure, most importantly, a vertical datum unification or realization of height systems. This paper aims to review the background of relativistic (clock-based) geodesy and study the variations of optical atomic clock measurements (e.g., due to hydrology loading and land motion).

Place, publisher, year, edition, pages
Frontiers, 2023
Keywords
relativistic geodesy, geodetic reference system, optical atomic clocks, time transfer, frequency analysis, geodetic height systems, datum unification
National Category
Infrastructure Engineering Other Engineering and Technologies not elsewhere specified Signal Processing
Identifiers
urn:nbn:se:hig:diva-42070 (URN)10.3389/feart.2023.1139211 (DOI)001020785200001 ()2-s2.0-85164145319 (Scopus ID)
Available from: 2023-06-11 Created: 2023-06-11 Last updated: 2023-08-28Bibliographically approved
Bagherbandi, M., Amin, H., Wang, L. & Shirazian, M. (2022). Mantle Viscosity Derived From Geoid and Different Land Uplift Data in Greenland. Journal of Geophysical Research - Solid Earth, 127(8), Article ID e2021JB023351.
Open this publication in new window or tab >>Mantle Viscosity Derived From Geoid and Different Land Uplift Data in Greenland
2022 (English)In: Journal of Geophysical Research - Solid Earth, ISSN 2169-9313, E-ISSN 2169-9356, Vol. 127, no 8, article id e2021JB023351Article in journal (Refereed) Published
Abstract [en]

The Earth's mass redistribution due to deglaciation and recent ice sheet melting causes changes in the Earth's gravity field and vertical land motion in Greenland. The changes are because of ongoing mass redistribution and related elastic (on a short time scale) and viscoelastic (on time scales of a few thousands of years) responses. These signatures can be used to determine the mantle viscosity. In this study, we infer the mantle viscosity associated with the glacial isostatic adjustment (GIA) and long-wavelength geoid beneath the Greenland lithosphere. The viscosity is determined based on a spatio-spectral analysis of the Earth's gravity field and the land uplift rate in order to find the GIA-related gravity field. We used different land uplift data, that is, the vertical land motions obtained by the Greenland Global Positioning System (GPS) Network (GNET), gravity recovery and climate experiment (GRACE) and glacial isostatic adjustment (GIA) data, and also combined them using the Kalman filtering technique. Using different land uplift rates, one can obtain different GIA-related gravity fields. As shown in this study, the mantle viscosities of 1.9 × 1022 Pa s and 7.8 × 1021 Pa s for a depth of 200–700 km are obtained using ICE-6G (VM5a) model and the combined land uplift model, respectively, and the GIA-related gravity potential signal

Place, publisher, year, edition, pages
AGU, 2022
Keywords
glacial isostatic adjustment, mantle viscosity, spectral analysis, land uplift, GPS sites, GRACE, Greenland
National Category
Geophysics Geology Climate Research Other Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:hig:diva-39745 (URN)10.1029/2021jb023351 (DOI)000841308700001 ()2-s2.0-85136902508 (Scopus ID)
Available from: 2022-08-19 Created: 2022-08-19 Last updated: 2022-09-15Bibliographically approved
Bagherbandi, M., Amin, H., Wang, L. & Shirazian, M. (2022). Mantle viscosity derived from geoid and different land uplift data in Greenland. In: : . Paper presented at The EGU General Assembly 2022, Vienna, Austria, 23-27 May 2022. Copernicus GmbH
Open this publication in new window or tab >>Mantle viscosity derived from geoid and different land uplift data in Greenland
2022 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

The Earth’s mass redistribution due to deglaciation and recent ice sheet melting causes changes in the Earth’s gravity field and vertical land motion in Greenland. The changes are because of ongoing mass redistribution and related elastic (on a short time scale) and viscoelastic (on time scales of a few thousands of years) responses. These signatures can be used to determine the mantle viscosity. In this study, we infer the mantle viscosity associated with the glacial isostatic adjustment (GIA) and long-wavelength geoid beneath the Greenland lithosphere. The viscosity is determined based on a spatio-spectral analysis of the Earth’s gravity field and the land uplift rate in order to find the GIA-related gravity field. We used and evaluated different land uplift data, i.e. the vertical land motions obtained by the Greenland Global Positioning System (GPS) Network (GNET), GRACE and Glacial Isostatic Adjustment (GIA) data. In addition, a  combined land uplift rate using the Kalman filtering technique is presented in this study. We extract the GIA-related gravity signals by filtering the other effects due to the deeper masses i.e. core-mantle (related to long-wavelengths) and topography (related to short-wavelengths). To do this, we applied correlation analysis to detect the best harmonic window. Finally, the mantle viscosity using the obtained GIA-related gravity field is estimated. Using different land uplift rates, one can obtain different GIA-related gravity fields. For example, different harmonic windows were obtained by employing different land uplift datasets, e.g. the truncated geoid model with a harmonic window between degrees 10 to 39 and 10 to 25 showed a maximum correlation with the GIA model ICE-6G (VM5a) and the combined land uplift rates, respectively. As shown in this study, the mantle viscosities of 1.6×1022 Pa s and 0.9×1022 Pa s for a depth of 200  to 650  km are obtained using ICE-6G (VM5a) model and the combined land uplift model, respectively, and the GIA-related gravity potential signal.

Place, publisher, year, edition, pages
Copernicus GmbH, 2022
National Category
Geophysics Climate Research Geology
Identifiers
urn:nbn:se:hig:diva-38903 (URN)10.5194/egusphere-egu22-13323 (DOI)
Conference
The EGU General Assembly 2022, Vienna, Austria, 23-27 May 2022
Available from: 2022-06-11 Created: 2022-06-11 Last updated: 2023-03-08Bibliographically approved
Allah Tavakoli, Y., Amin, H., Bagheri, H. & Bagherbandi, M. (2022). On an approach to surface mass change detection from satellite gravimetry, a case study of barystatic sea-level, ice-sheet mass and basin mass changes.
Open this publication in new window or tab >>On an approach to surface mass change detection from satellite gravimetry, a case study of barystatic sea-level, ice-sheet mass and basin mass changes
2022 (English)In: Article in journal (Refereed) Submitted
National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:hig:diva-39413 (URN)
Available from: 2022-07-03 Created: 2022-07-03 Last updated: 2022-07-04Bibliographically approved
Amin, H. (2022). Study on the Earth’s Surface Mass Variations using Satellite Gravimetry Observations. (Doctoral dissertation). Gävle: Gävle University Press
Open this publication in new window or tab >>Study on the Earth’s Surface Mass Variations using Satellite Gravimetry Observations
2022 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Our complex planet is continuously undergoing temporal and spatial changes. In this context, ongoing processes in the Earth subsystems (geosphere, biosphere, cryosphere, hydrosphere, and atmosphere) cause changes in the gravity field of the Earth across a wide range of temporal and spatial scales. Accordingly, by both spatially and temporally tracing our planet’s ever-changing gravity field, scientists can better constrain the underlying processes contributing to such dynamic changes of mass distribution within the Earth system. Monitoring the Earth’s gravity field and its temporal variations is essential, among others, for tracking disasters and specifying land areas with a high risk of flooding, earthquakes, and droughts, movements of tectonic plates, and providing accurate positioning through satellite positioning technology. On short-term timescales, temporal variations in the Earth’s gravity field are mainly caused by the movement of water in its various forms. Accordingly, sea-level variations and ice-sheet and glacier changes, which are known as critical indicators of global warming and climate change, can be accurately monitored by tracking the Earth’s gravity field changes. Since there is a close link between water redistribution and the Earth’s energy cycle, climate system, food security, human and ecosystem health, energy generation, economic and societal development, and climate extremes (droughts and floods), it is essential to accurately monitor water mass exchange between the Earth system components. Among all observational techniques, satellite gravimetry has provided an integrated global view of ongoing processes within the Earth system. The current generation of satellite gravimetry missions (the Gravity Recovery and Climate Experiment (GRACE) mission and its successor, GRACE Follow-On) has dramatically revolutionized our understanding of dynamic processes in the Earth’s surface and, consequently, has significantly improved our understanding of the Earth’s climate system. By considering different aspects of studying the Earth’s gravity field, this thesis brings new insights to the determination and analysis of the mass change in the Earth system. First, by studying the shortcomings of the common techniques of estimating the geoid potential, a new approach is examined that simultaneously estimates the geoid potential, W0, and the geometrical parameters of the reference Mean Earth Ellipsoid (MEE). In this regard, as the geoid needs to be considered as a static equipotential surface, the sensitivity of the estimations to the time dependent Earth’s gravity field changes is studied. Secondly, relying on the GRACE monthly gravity fields and the complementary observational techniques, and by pushing the limit of GRACE, mass redistribution over land and ocean is investigated. Within the ocean, satellite altimetry and Argo products are utilized along with the GRACE monthly solutions for quantifying the global barystatic sea-level change and assessing the closure of the global mean sea level budget. Over land, a region with relatively high temporal mass change (oil and water extraction) is chosen in which by taking advantage of having in-situ observations and hydrological models, the ability of GRACE products in quantifying the changes in groundwater storage is studied. In this frame, for both the ocean and land studies, different aspects of the processing of GRACE monthly gravity fields are investigated and GRACE inherent errors are addressed appropriately to arrive at reliable and accurate estimates of the Earth’s surface mass change. As the final contribution in this thesis, a rigorous analytical model for detecting surface mass change from the time-variable gravity solutions is proposed and examined in different case studies of surface mass change. Since the launch of the GRACE twin satellites, the GRACE(-FO) time-varying gravity fields are conventionally converted into the surface mass change using a spherical analytical model that approximates the Earth by a sphere. More recently, the analytical mass change detection model has been improved by considering an ellipsoid as the shape of the Earth, which improved the previous estimations of surface mass change, especially over high latitudes with relatively large mass change signals. However, by taking into account the real shape of the Earth and considering more realistic assumptions, a new analytical solution for the problem of surface mass change detection from the time-varying gravity fields is proposed in this thesis. It is shown that the simplistic spherical and ellipsoidal geometries are no longer tenable and the new model surpasses the common spherical approach and its ellipsoidal version.

Abstract [sv]

Pågående processer i jordens olika delar (geosfären, biosfären, kryosfären, hydrosfären och atmosfären) orsakar massförändringar som bland annat ger sig till känna i form av variationer i jordens tyngdkrafts-/gravitationsfält över ett brett spektrum av tidsmässiga och rumsliga skalor. Följaktligen, genom att studera detta ständigt föränderliga fält i tid och rum, kan forskare utröna de underliggande orsakerna till de dynamiska förändringarna av massfördelningarna i dessa processer. Övervakning av jordens gravitationsfält och dess tidsmässiga variationer är nödvändig bland annat för att spåra katastrofer och specificera landområden med hög risk för översvämningar, jordbävningar och torka, rörelser av tektoniska plattor och tillhandahålla exakt positionering genom satellitpositioneringsteknik. På kortsiktiga tidsskalor orsakas tidsmässiga variationer i jordens gravitationsfält främst av vattenrörelser i dess olika former. Följaktligen kan havsnivå-, istäcke- och glaciärförändringar, som är kända som kritiska indikatorer på global uppvärmning och klimatförändringar, övervakas exakt genom övervakning av tyngdkraftfältets förändringar. Eftersom det finns en intim koppling mellan omfördelningen av jordens vattenmassor och energicykel, klimatsystem, livsmedelssäkerhet, människors och ekosystems hälsa, energiproduktion, ekonomisk och samhällelig utveckling och extremer i klimatet (torka och översvämningar), är det viktigt att noggrant övervaka vattnets massutbyte mellan jordsystemets olika komponenter. Bland alla observationstekniker ger satellitgravimetri en global integrerad översikt av pågående massförändringar. De nuvarande satellitsystemen, dedikerade för gravimetri-uppdrag (Gravity Recovery and Climate Experiment (GRACE) satellitprojektet och dess efterträdare, GRACE Follow-On), har dramatiskt revolutionerat vår förståelse av de dynamiska processerna på jordytan, och de har följaktligen avsevärt förbättrat vår förståelse av jordens klimatsystem. Genom att pröva olika aspekter av att studera jordens gravitationsfält ger denna avhandling nya möjligheter att studera jordsystemets massvariationer. Först, genom att studera bristerna i de vanliga teknikerna för att uppskatta ett potentialvärde för geoiden, undersöks ett nytt tillvägagångssätt som samtidigt uppskattar ett värde på geopotentialen, W0, och de geometriska parametrarna för en global referensellipsoid (Mean Earth Ellipsoid, MEE). Eftersom geoiden i detta sammanhang måste betraktas som en statisk ekvipotentialyta, så beräknar vi även noggranheten hos uppskattningarna för de tidsberoende förändringar av jordens gravitationsfält. För det andra, att förlita sig på GRACE månatliga gravitationsfält och de kompletterande observationsteknikerna, och genom att tänja på gränsen för GRACE, undersöks massutbytet mellan land och hav. I havsområden används satellitaltimetri- och Argo-data tillsammans med GRACE månatliga gravitationsfält för att kvantifiera den globala havsnivåförändringen och bedöma slutningsfelet i den globala medelhavsnivå-budgeten. I en annan studie väljer vi en region på land med relativt stor massförändring i tiden p.g.a. olje och vattenutvinning, där vi drar fördel av in-situ observationer och hydrologiska modeller, för att analysera förmågan hos GRACE att kvantifiera förändringar i grundvattennivån. För både havs- och landstudierna undersöks olika aspekter att bearbeta GRACE månatliga data , samt lämpliga åtgärder att korrigera fel för att ernå tillförlitliga och noggranna uppskattningar av massförändringar vid jordytan. Som det sista bidraget i denna avhandling föreslås en rigorös analytisk modell för detektering av massförändringarna i tiden, som undersöks i olika fallstudier av massförändringar. Data från GRACE(-FO) som varierar i tiden omvandlas konventionellt till ytmass-förändringar med hjälp av en sfärisk analytisk modell, som approximerar jorden med en sfär. Nyligen har den analytiska modellen för detektering av massförändringar förbättrats genom att approximera jordens form med en ellipsoid, vilket förbättrade de tidigare uppskattningarna av massförändringar, särskilt för höga latituder med relativt stora massförändringar. Men genom att gå ännu längre och ta hänsyn till jordens verkliga form och överväga mer realistiska antaganden, föreslås i denna avhandling en ny analytisk lösning för problemet. Det har visat sig att de förenklade sfäriska och ellipsoida geometrierna inte längre är försvarbara och den nya modellen överträffar det vanliga sfäriska tillvägagångssättet och dess ellipsoida version.

Place, publisher, year, edition, pages
Gävle: Gävle University Press, 2022. p. 92
Series
Doctoral thesis ; 30
Keywords
geodetic reference system, geoid potential, global vertical datum, climate change, global warming, mass change, ice melting, sea-level change, remote sensing, satellite gravimetry, geodetiska referenssystem, geopotential, globala vertikala datum, klimatförändring, global uppvärmning, massförändring, issmältning, havsnivåförändring, fjärranalys, satellitgravimetri
National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:hig:diva-39412 (URN)978-91-88145-91-8 (ISBN)
Public defence
2022-09-23, 13:111, 10:00 (English)
Opponent
Supervisors
Available from: 2022-09-02 Created: 2022-07-03 Last updated: 2022-09-02
Amin, H., Sjöberg, L. E. & Bagherbandi, M. (2020). A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters. In: : . Paper presented at EGU General Assembly 2020, Vienna, Austria, 3-8 May.
Open this publication in new window or tab >>A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters
2020 (English)Conference paper, Oral presentation with published abstract (Other (popular science, discussion, etc.))
Abstract [en]

According to the classical Gauss–Listing definition, the geoid is the equipotential surface of the Earth’s gravity field that in a least-squares sense best fits the undisturbed mean sea level. This equipotential surface, except for its zero-degree harmonic, can be characterized using the Earth’s Global Gravity Models (GGM). Although nowadays, the satellite altimetry technique provides the absolute geoid height over oceans that can be used to calibrate the unknown zero-degree harmonic of the gravimetric geoid models, this technique cannot be utilized to estimate the geometric parameters of the Mean Earth Ellipsoid (MEE). In this study, we perform joint estimation of W0, which defines the zero datum of vertical coordinates, and the MEE parameters relying on a new approach and on the newest gravity field, mean sea surface, and mean dynamic topography models. As our approach utilizes both satellite altimetry observations and a GGM model, we consider different aspects of the input data to evaluate the sensitivity of our estimations to the input data. Unlike previous studies, our results show that it is not sufficient to use only the satellite componentof a quasi-stationary GGM to estimate W0. In addition, our results confirm a high sensitivity of the applied approach to the altimetry-based geoid heights, i.e. mean sea surface and mean dynamic topography models. Moreover, as W0 should be considered a quasi-stationary parameter, we quantify the effect of time-dependent Earth’s gravity field changes as well as the time-dependent sea-level changes on the estimation of W0. Our computations resulted in the geoid potential W0 = 62636848.102 ± 0.004 m2s-2 and the semi-major and –minor axes of the MEE,a = 6378137.678 ± 0.0003 m and b = 6356752.964 ± 0.0005 m, which are 0.678 and 0.650 m larger than those axes of the GRS80 reference ellipsoid, respectively. Moreover, a new estimation for the geocentric gravitational constant was obtained as GM = (398600460.55 ± 0.03) × 106 m3s-2.

National Category
Earth and Related Environmental Sciences
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-31485 (URN)
Conference
EGU General Assembly 2020, Vienna, Austria, 3-8 May
Available from: 2020-01-18 Created: 2020-01-18 Last updated: 2021-08-11Bibliographically approved
Amin, H., Bagherbandi, M. & Sjöberg, L. E. (2020). Quantifying barystatic sea-level change from satellite altimetry, GRACE and Argo observations over 2005–2016. Advances in Space Research, 65(8), 1922-1940
Open this publication in new window or tab >>Quantifying barystatic sea-level change from satellite altimetry, GRACE and Argo observations over 2005–2016
2020 (English)In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 65, no 8, p. 1922-1940Article in journal (Refereed) Published
Abstract [en]

Time-varying spherical harmonic coefficients determined from the Gravity Recovery and Climate Experiment (GRACE) data provide a valuable source of information about the water mass exchange that is the main contributor to the Earth’s gravity field changes within a period of less than several hundred years. Moreover, by measuring seawater temperature and salinity at different layers of ocean depth, Argo floats help to measure the steric component of global mean sea level (GMSL). In this study, we quantify the rate of barystatic sea-level change using both GRACE RL05 and RL06 monthly gravity field models and compare the results with estimates achieved from a GMSL budget closure approach. Our satellite altimetry-based results show a trend of 3.90 ± 0.14 mm yr−1 for the GMSL rise. About 35% or 1.29 ± 0.07 mm yr−1 of this rate is caused by the thermosteric contribution, while the remainder is mainly due to the barystatic contribution. Our results confirm that the choice of decorrelation filters does not play a significant role in quantifying the global barystatic sea-level change, and spatial filtering may not be needed. GRACE RL05 and RL06 solutions result in the barystatic sea-level change trends of 2.19 ± 0.13 mm yr−1 and 2.25 ± 0.16 mm yr−1, respectively. Accordingly, the residual trend, defined as the difference between the altimetry-derived GMSL and sum of the steric and barystatic components, amounts to 0.51 ± 0.51 and 0.45 ± 0.44 mm yr−1 for RL05 and RL06-based barystatic sea-level changes, respectively, over January 2005 to December 2016. The exclusion of the halosteric component results in a lower residual trend of about 0.36 ± 0.46 mm yr−1 over the same period, which suggests a sea-level budget closed within the uncertainty. This could be a confirmation on a high level of salinity bias particularly after about 2015. Moreover, considering the assumption that the GRACE-based barystatic component includes all mass change signals, the rather large residual trend could be attributed to an additional contribution from the deep ocean, where salinity and temperature cannot be monitored by the current observing systems. The errors from various sources, including the model-based Glacial Isostatic Adjustment signal, independent estimation of geocenter motion that are not quantified in the GRACE solutions, as well as the uncertainty of the second degree of zonal spherical harmonic coefficients, are other possible contributors to the residual trend.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Climate change, Sea-level budget, Decorrelation, Barystatic sea-level change, Steric sea-level change
National Category
Earth and Related Environmental Sciences
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-31978 (URN)10.1016/j.asr.2020.01.029 (DOI)000533504300004 ()2-s2.0-85079432165 (Scopus ID)
Note

Funding: CSIRO, NASA, NOAA

Available from: 2020-03-02 Created: 2020-03-02 Last updated: 2022-07-03Bibliographically approved
Gido, N. A. A., Amin, H., Bagherbandi, M. & Nilfouroushan, F. (2020). Satellite monitoring of mass changes and ground subsidence in Sudan’s oil fields using GRACE and Sentinel-1 data. In: : . Paper presented at EGU General Assembly 2020, Vienna, Australia, 3-8 May.
Open this publication in new window or tab >>Satellite monitoring of mass changes and ground subsidence in Sudan’s oil fields using GRACE and Sentinel-1 data
2020 (English)Conference paper, Oral presentation with published abstract (Other (popular science, discussion, etc.))
Abstract [en]

Monitoring environmental hazards, due to natural and anthropogenic causes, is one of the important issues, which requires proper data, models, and cross-validation of the results. The geodetic satellite missions, e.g. the Gravity Recovery and Climate Experiment (GRACE) and Sentinel-1, are very useful in this aspect. GRACE missions are dedicated to model the temporal variations of the Earth’s gravity field and mass transportation in the Earth’s surface, whereas Sentinel-1 collects Synthetic Aperture Radar (SAR) data which enables us to measure the ground movements accurately. Extraction of large volumes of water and oil decreases the reservoir pressure, form compaction and consequently land subsidence occurs which can be analyzed by both GRACE and Sentinel-1 data. In this paper, large-scale groundwater storage (GWS) changes are studied using the GRACE monthly gravity field models together with different hydrological models over the major oil reservoirs in Sudan, i.e. Heglig, Bamboo, Neem, Diffra and Unity-area oil fields. Then we correlate the results with the available oil wells production data for the period of 2003-2012. In addition, using the only freely available Sentinel-1 data, collected between November 2015 and April 2019, the ground surface deformation associated with this oil and water depletion is studied. Due to the lack of terrestrial geodetic monitoring data in Sudan, the use of GRACE and Sentinel-1 satellite data is very valuable to monitor water and oil storage changes and their associated land subsidence over our region of interest. Our results show that there is a significant correlation between the GRACE-based GWS change and extracted oil and water volumes. The trend of GWS changes due to water and oil depletion ranged from -18.5 to -6.2mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 SAR data analysis using Persistent Scatterer Interferometry (PSI) method shows high rate of subsidence i.e. -24.5, -23.8, -14.2 and -6 mm/year over Heglig, Neem, Diffra and Unity-area oil fields respectively. The results of this study can help us to control the integrity and safety of operations and infrastructure in that region, as well as to study the groundwater/oil storage behavior.

National Category
Earth and Related Environmental Sciences
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-31486 (URN)
Conference
EGU General Assembly 2020, Vienna, Australia, 3-8 May
Available from: 2020-01-18 Created: 2020-01-18 Last updated: 2020-11-23Bibliographically approved
Gido, N. A. A., Amin, H., Bagherbandi, M. & Nilfouroushan, F. (2020). Satellite Monitoring of Mass Changes and Ground Subsidence in Sudan’s Oil Fields Using GRACE and Sentinel-1 Data. Remote Sensing, 12(11), Article ID 1792.
Open this publication in new window or tab >>Satellite Monitoring of Mass Changes and Ground Subsidence in Sudan’s Oil Fields Using GRACE and Sentinel-1 Data
2020 (English)In: Remote Sensing, E-ISSN 2072-4292, Vol. 12, no 11, article id 1792Article in journal (Refereed) Published
Abstract [en]

Monitoring environmental hazards, owing to natural and anthropogenic causes, is an important issue, which requires proper data, models, and cross-validation of the results. The geodetic satellite missions, for example, the Gravity Recovery and Climate Experiment (GRACE) and Sentinel-1, are very useful in this respect. GRACE missions are dedicated to modeling the temporal variations of the Earth’s gravity field and mass transportation in the Earth’s surface, whereas Sentinel-1 collects synthetic aperture radar (SAR) data, which enables us to measure the ground movements accurately. Extraction of large volumes of water and oil decreases the reservoir pressure and form compaction and, consequently, land subsidence occurs, which can be analyzed by both GRACE and Sentinel-1 data. In this paper, large-scale groundwater storage (GWS) changes are studied using the GRACE monthly gravity field models together with different hydrological models over the major oil reservoirs in Sudan, that is, Heglig, Bamboo, Neem, Diffra, and Unity-area oil fields. Then, we correlate the results with the available oil wells production data for the period of 2003–2012. In addition, using the only freely available Sentinel-1 data, collected between November 2015 and April 2019, the ground surface deformation associated with this oil and water depletion is studied. Owing to the lack of terrestrial geodetic monitoring data in Sudan, the use of GRACE and Sentinel-1 satellite data is very valuable to monitor water and oil storage changes and their associated land subsidence over our region of interest. Our results show that there is a significant correlation between the GRACE-based GWS anomalies (ΔGWS) and extracted oil and water volumes. The trend of ΔGWS changes due to water and oil depletion ranged from –18.5 ± 6.3 to –6.2 ± 1.3 mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 SAR data analysis using the persistent scatterer interferometry (PSI) method shows a high rate of subsidence, that is, –24.5 ± 0.85, –23.8 ± 0.96, –14.2 ± 0.85, and –6 ± 0.88 mm/year over Heglig, Neem, Diffra, and Unity-area oil fields, respectively. The results of this study can help us to control the integrity and safety of operations and infrastructure in that region, as well as to study the groundwater/oil storage behavior.

Place, publisher, year, edition, pages
MDPI, 2020
Keywords
groundwater; GRACE; hydrological model; oil depletion; land subsidence; InSAR
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:hig:diva-32371 (URN)10.3390/rs12111792 (DOI)000543397000097 ()2-s2.0-85086427019 (Scopus ID)
Available from: 2020-06-03 Created: 2020-06-03 Last updated: 2023-08-28Bibliographically approved
Amin, H., Sjöberg, L. & Bagherbandi, M. (2019). A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters. Journal of Geodesy, 93(10), 1943-1961
Open this publication in new window or tab >>A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters
2019 (English)In: Journal of Geodesy, ISSN 0949-7714, E-ISSN 1432-1394, Vol. 93, no 10, p. 1943-1961Article in journal (Refereed) Published
Abstract [en]

The geoid, according to the classical Gauss–Listing definition, is, among infinite equipotential surfaces of the Earth’s gravity field, the equipotential surface that in a least squares sense best fits the undisturbed mean sea level. This equipotential surface, except for its zero-degree harmonic, can be characterized using the Earth’s global gravity models (GGM). Although, nowadays, satellite altimetry technique provides the absolute geoid height over oceans that can be used to calibrate the unknown zero-degree harmonic of the gravimetric geoid models, this technique cannot be utilized to estimate the geometric parameters of the mean Earth ellipsoid (MEE). The main objective of this study is to perform a joint estimation of W0, which defines the zero datum of vertical coordinates, and the MEE parameters relying on a new approach and on the newest gravity field, mean sea surface and mean dynamic topography models. As our approach utilizes both satellite altimetry observations and a GGM model, we consider different aspects of the input data to evaluate the sensitivity of our estimations to the input data. Unlike previous studies, our results show that it is not sufficient to use only the satellite-component of a quasi-stationary GGM to estimate W0. In addition, our results confirm a high sensitivity of the applied approach to the altimetry-based geoid heights, i.e., mean sea surface and mean dynamic topography models. Moreover, as W0 should be considered a quasi-stationary parameter, we quantify the effect of time-dependent Earth’s gravity field changes as well as the time-dependent sea level changes on the estimation of W0. Our computations resulted in the geoid potential W0 = 62636848.102 ± 0.004 m2 s−2 and the semi-major and minor axes of the MEE, a = 6378137.678 ± 0.0003 m and b = 6356752.964 ± 0.0005 m, which are 0.678 and 0.650 m larger than those axes of GRS80 reference ellipsoid, respectively. Moreover, a new estimation for the geocentric gravitational constant was obtained as GM = (398600460.55 ± 0.03) × 106 m3 s−2.

Keywords
Geodetic reference system, Geoid potential W0, Global vertical datum, Mean Earth ellipsoid, Reference ellipsoid
National Category
Climate Research Geophysics Other Earth and Related Environmental Sciences
Research subject
Sustainable Urban Development
Identifiers
urn:nbn:se:hig:diva-30666 (URN)10.1007/s00190-019-01293-3 (DOI)000495245100009 ()2-s2.0-85073812763 (Scopus ID)
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2022-07-03Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7899-5421

Search in DiVA

Show all publications