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EN
Gravity Recovery and Climate Experiment (GRACE) mission data is widely used in various fields of science. GRACE explored changes of the gravity field regularly from April 2002 to June 2017. In the following research, we examine variance of signal contained in two different formats of GRACE data: standard spherical harmonics and mass concentration blocks (so-called “mascons”) solutions, both provided in the most recent releases. For spherical harmonics-based solution, we use monthly gravity field solutions provided up to degree and order (d/o) 96 by three different computing centers, i.e. the NASA’s Jet Propulsion Laboratory (JPL), the German Research Center for Geosciences (GFZ) and the Center for Space Research (CSR). For the mass concentration blocks, we use values of total water storage provided by the CSR, JPL and the Goddard Space Flight Center (GSFC) computing centers, which we convert to spherical harmonic coefficients up to d/o 96. We show that using the anisotropic DDK3 filter to smooth the north-south stripes present in total wate storage obtained from standard spherical harmonics solution leaves more information than common isotropic Gaussian filter. In the case of mascons, GSFC solution contains much more information than the CSR and JPL releases, relevant for corresponding d/o. Differences in variance of signal arise from different background models as well as various shape and size of mascons used during processing of GRACE observations.
EN
Global satellite gravity measurements provide unique information regarding gravity field distribution and its variability on the Earth. The main cause of gravity changes is the mass transportation within the Earth, appearing as, e.g. dynamic fluctuations in hydrology, glaciology, oceanology, meteorology and the lithosphere. This phenomenon has become more comprehensible thanks to the dedicated gravimetric missions such as Gravity Recovery and Climate Experiment (GRACE), Challenging Minisatellite Payload (CHAMP) and Gravity Field and Steady-State Ocean Circulation Explorer (GOCE). From among these missions, GRACE seems to be the most dominating source of gravity data, sharing a unique set of observations from over 15 years. The results of this experiment are often of interest to geodesists and geophysicists due to its high compatibility with the other methods of gravity measurements, especially absolute gravimetry. Direct validation of gravity field solutions is crucial as it can provide conclusions concerning forecasts of subsurface water changes. The aim of this work is to present the issue of selection of filtration parameters for monthly gravity field solutions in RL06 and RL05 releases and then to compare them to a time series of absolute gravimetric data conducted in quasi-monthly measurements in Astro-Geodetic Observatory in Józefosław (Poland). The other purpose of this study is to estimate the accuracy of GRACE temporal solutions in comparison with absolute terrestrial gravimetry data and making an attempt to indicate the significance of differences between solutions using various types of filtration (DDK, Gaussian) from selected research centres.
EN
The role of continental water in polar motion excitation can be illustrated by determining Hydrological Angular Momentum calculated from terrestrial water storage (TWS). In this paper we compare global and regional changes in TWS computed using Coupled Model Intercomparison Project Phase 5 climate models, Global Land Data Assimilation System (GLDAS) land hydrology models and observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. We also compare hydrological excitation functions derived from models with those obtained from the GRACE mission and the hydrological signal in observed polar motion excitation (the so-called geodetic residuals). The results confirm that GLDAS models of seasonal and non-seasonal TWS change are more consistent with GRACE data than climate models; on the other hand, none of the considered models are fully consistent with GRACE data or geodetic residuals. In turn, GRACE observations are most consistent with the non-seasonal hydrological signal in observed excitation. A detailed study of the contribution of different TWS components to the hydrological excitation function shows that soil moisture dominates.
EN
The aim of this study was to examine the relationship between vertical movements of the Earth’s crust and variation in geoid height. Data from the Gravity Recovery and Climate Experiment (GRACE), precise levelling, tidal gauge observations and Global Navigation Satellite Systems (GNSS) stations for the Sudetes area were used. The GRACE data provided the possibility of the analysis of geopotential changes. The geoid heights were calculated for the period from April 2002 to March 2016, using data from GeoForschungsZentrum (GFZ) GRACE Level-2 Product Release 05 in the form of spherical harmonic coefficients, truncated at degree and order (d/o) 60. Different filters were used. The calculated geoid change over time has the approximate value of 0.16 mm/y. This value was compared to the expected change in geoid height, determined on the basis of the Earth’s crustal movements.
EN
Annual cycles in the geocenter motion time series are primarily driven by mass changes in the Earth’s hydrologic system, which includes land hydrology, atmosphere, and oceans. Seasonal variations of the geocenter motion have been reliably determined according to Sun et al. (J Geophys Res Solid Earth 121(11):8352-8370, 2016) by combining the Gravity Recovery And Climate Experiment (GRACE) data with an ocean model output. In this study, we reconstructed the observed seasonal geocenter motion with geophysical model predictions of mass variations in the polar ice sheets, continental glaciers, terrestrial water storage (TWS), and atmosphere and dynamic ocean (AO). The reconstructed geocenter motion time series is shown to be in close agreement with the solution based on GRACE data supporting with an ocean bottom pressure model. Over 85% of the observed geocenter motion time series, variance can be explained by the reconstructed solution, which allows a further investigation of the driving mechanisms. We then demonstrated that AO component accounts for 54, 62, and 25% of the observed geocenter motion variances in the X, Y, and Z directions, respectively. The TWS component alone explains 42, 32, and 39% of the observed variances. The net mass changes over oceans together with self-attraction and loading effects also contribute significantly (about 30%) to the seasonal geocenter motion in the X and Z directions. Other contributing sources, on the other hand, have marginal (less than 10%) impact on the seasonal variations but introduce a linear trend in the time series.
EN
The dedicated gravity satellite missions, in particular the GRACE (Gravity Recovery and Climate Experiment) mission launched in 2002, provide unique data for studying temporal variations of mass distribution in the Earth’s system, and thereby, the geometry and the gravity fi eld changes of the Earth. The main objective of this contribution is to estimate physical height (e.g. the orthometric/normal height) changes over Central Europe using GRACE satellite mission data as well as to analyse them and model over the selected study area. Physical height changes were estimated from temporal variations of height anomalies and vertical displacements of the Earth surface being determined over the investigated area. The release 5 (RL05) GRACE-based global geopotential models as well as load Love numbers from the Preliminary Reference Earth Model (PREM) were used as input data. Analysis of the estimated physical height changes and their modelling were performed using two methods: the seasonal decomposition method and the PCA/ EOF (Principal Component Analysis/Empirical Orthogonal Function) method and the differences obtained were discussed. The main fi ndings reveal that physical height changes over the selected study area reach up to 22.8 mm. The obtained physical height changes can be modelled with an accuracy of 1.4 mm using the seasonal decomposition method.
EN
Temporal mass variations in the Earth system, which can be detected from the Gravity Recovery and Climate Experiment (GRACE) mission data, cause temporal variations of geoid heights. The main objective of this contribution is to analyze temporal variations of geoid heights over the area of Poland using global geopotential models (GGMs) developed on the basis of GRACE mission data. Time series of geoid height variations were calculated for the chosen subareas of the aforementioned area using those GGMs. Thereafter, these variations were analyzed using two different methods. On the basis of the analysis results, models of temporal geoid height variations were developed and discussed. The possibility of prediction of geoid height variations using GRACE mission data over the area of Poland was also investigated. The main findings reveal that the geoid height over the area of Poland vary within 1.1 cm which should be considered when defining the geoid model of 1 cm accuracy for this area.
EN
We use GRACE gravity data released by the Center for Space Research (CSR) and the Groupe de Recherches en Geodesie Spatiale (GRGS) to detect the water storage changes over the Tibetan Plateau (TP). A combined filter strategy is put forward to process CSR RL05 data to remove the effect of striping errors. After the correction for GRACE by GLDAS and ICE-5G, we find that TP has been overall experiencing the water storage increase during 2003-2012. During the same time, the glacier over the Himalayas was sharply retreating. Interms of linear trends, CSR’s results derived by the combined filter are close to GRGS RL03 with the Gaussian filter of 300-km window. The water storage increasing rates determined from CSR’s RL05 products in the interior TP, Karakoram Mountain, Qaidam Basin, Hengduan Mountain, and middle Himalayas are 9.7, 6.2, 9.1, –18.6, and –20.2 mm/yr, respectively. These rates from GRGS’s RL03 products are 8.6, 5.8, 10.5, –19.3 and –21.4 mm/yr, respectively.
EN
Two integral transformations between the stress function, differentiation of which gives the meridian and prime vertical components of the sub-crustal stress due to mantle convection, and the satellite-to-satellite tracking (SST) data are presented in this article. In the first one, the SST data are the disturbing potential differences between twin-satellites and in the second one the line-of-sight (LOS) gravity disturbances. It is shown that the corresponding integral kernels are well-behaving and therefore suitable for inversion and recovery of the stress function from the SST data. Recovery of the stress function and the stress components is also tested in numerical experiments using simulated SST data. Numerical studies over the Himalayas show that inverting the disturbing potential differences leads to a smoother stress function than from inverting LOS gravity disturbances. Application of the presented integral formulae allows for recovery of the stress from the satellite mission GRACE and its planned successor.
EN
In this study, a scheme to estimate oceanic and hydrological effects in the GRACE (Gravity Recovery and Climate Experiment) data is presented. The aim is to reveal tectonic signals for the case of the Sumatra earthquake on 26 December 2004. The variations of hydrological and oceanic effects are estimated with the aid of data set of GRACE, altimetry, World Ocean Atlas, and the GLDAS model for a period of January 2003 to December 2006. The time series of computed gravity changes over Sumatra region show some correlations to the deformation resulting from the earthquake occurred in December 2004. The maximum and minimum impacts of hydrological and oceanic effects on gravity changes are about 3 μGal in radial direction and –5 μGal in northward direction. The maximum and minimum amounts of gravitational gradient changes after the correction are 0.2 and –0.25 mE, which indicates the significant influences of hydrological and oceanic sources on the desired signal.
EN
The impact of continental hydrological loading from land water, snow and ice on polar motion excitation, calculated as hydrological angular momentum (HAM), is difficult to estimate, and not as much is known about it as about atmospheric angular momentum (AAM) and oceanic angular momentum (OAM). In this paper, regional hydrological excitations to polar motion are investigated using monthly terrestrial water storage data derived from the Gravity Recovery and Climate Experiment (GRACE) mission and from the five models of land hydrology. The results show that the areas where the variance shows large variability are similar for the different models of land hydrology and for the GRACE data. Areas which have a small amplitude on the maps make an important contribution to the global hydrological excitation function of polar motion. The comparison of geodetic residuals and global hydrological excitation functions of polar motion shows that none of the hydrological excitation has enough energy to significantly improve the agreement between the observed geodetic excitation and geophysical ones.
EN
Since the launch of the GRACE (Gravity Recovery And Climate Experiment) satellite mission in 2002, significant progress in the knowledge regarding the temporal variations of the Earth’s gravity field has been achieved. The main objectives of this contribution are to define a suitable filter to reduce the noise contained in the latest release, i.e. RL05, of GRACE-based GGMs as well as to select the most suitable GRACE-based GGM time series for estimating mass variations in the Earth system over Poland. The performance of the Gaussian filter with different radii and the de-correlation filters (DDK1–DDK5) applied to reduce the noise contained in those GGMs was examined. First, they were investigated globally. Then, they were examined over the area of Poland, in particular, over two basins, i.e. the Vistula river basin and the Odra river basin. Moreover, both the internal and external accuracy of RL05 GRACE-based GGMs were assessed. Error degree variances of geoid heights were calculated on the basis of these models. Equivalent water thickness variations obtained from GRACE-based GGMs were compared with the corresponding ones obtained from the hydrology model. The obtained results were analysed and discussed. Finally the filtering method and the GGM time series most suitable for estimating mass variations in the Earth system over Poland were selected.
PL
Satelitarna misja GRACE (Gravity Recovery And Climate Experiment zapoczątkowana w 2002 roku znacząco przyczyniła się do rozwoju wiedzy o zmianach w czasie pola siły ciężkości Ziemi. Głównym celem niniejszego opracowania jest zdefiniowanie odpowiedniego filtru do redukcji szumu zawartego w ostatniej wersji, tj. wersji 5. globalnych modeli geopotencjału opracowanych na podstawie danych z misji GRACE, jak również wybór najbardziej odpowiedniego szeregu czasowego globalnych modeli geopotencjału wyznaczonych na podstawie danych z misji GRACE, do określenia zmian rozkładu mas w systemie Ziemia dla obszaru Polski. W szczególności badano wpływ filtrów Gaussa o różnych promieniach oraz filtrów dekorelacyjnych (DDK1–DDK5) na redukcję szumu zawartego w globalnych modelach geopotencjału. Na początku wpływ użycia filtru był badany w ujęciu globalnym. Następnie wpływ ten został zbadany dla obszaru Polski – oddzielnie dla dorzeczy Wisły i Odry. Ponadto, została oszacowana zarówno wewnętrzna, jak i zewnętrzna dokładność wersji 5. globalnych modeli geopotencjału opracowanych na podstawie danych z misji GRACE. Obliczono wariancje błędów wysokości geoidy dla poszczególnych stopni badanych modeli. Zmiany ekwiwalentnej warstwy wody wyznaczone z globalnych modeli geopotencjału opracowanych na podstawie danych z misji GRACE zostały porównane z odpowiednimi zmianami otrzymanymi z modelu hydrologicznego. Wyniki poddano analizie i dyskusji. Ostatecznie wybrano metodę filtracji oraz szereg czasowy globalnych modeli geopotencjału najbardziej odpowiednie do oszacowania zmian rozkładu mas w systemie Ziemia dla obszaru Polski.
EN
The Level-2 monthly GRACE gravity field models issued by Center for Space Research (CSR), GeoForschungs Zentrum (GFZ), and Jet Propulsion Laboratory (JPL) are treated as observations used to extract the equivalent water height (EWH) with the robust independent component analysis (RICA). The smoothing radii of 300, 400, and 500 km are tested, respectively, in the Gaussian smoothing kernel function to reduce the observation Gaussianity. Three independent components are obtained by RICA in the spatial domain; the first component matches the geophysical signal, and the other two match the north-south strip and the other noises. The first mode is used to estimate EWHs of CSR, JPL, and GFZ, and compared with the classical empirical decorrelation method (EDM). The EWH STDs for 12 months in 2010 extracted by RICA and EDM show the obvious fluctuation. The results indicate that the sharp EWH changes in some areas have an important global effect, like in Amazon, Mekong, and Zambezi basins.
EN
We can estimate the Equivalent Water Thickness (EWT) from results of observations of the Earth gravity field from the Gravity Recovery and Climate Experiment (GRACE) gravimetric mission. However the maps of EWT obtained from raw gravimetric data contain typical stripes. To eliminate these disturbances we need to filter the raw data to improve the signal to noise ratio. The distribution of EWT obtained from the GRACE mission can be used to determine the gravimetric excitation function. In this paper it was investigated the filter influence on the EWT distribution and the amplitude of the gravimetric excitation functions. We use the EWT data sets derived from Stokes coefficients made accessible and filtered by the International Centre for Global Earth Models (ICGEM). The data sets available on ICGEM website were imported from three research centers GFZ, JPL and CSR. The anisotropic filter, with three degrees of smoothing DDK3, DDK2 and DDK1 is described in (Kusche et al., 2009).
15
Content available remote Verification of localized GRACE solutions by the Polish quasigeoid
EN
The GRACE-based model GGM02S is a global gravity model expressed in spherical harmonics. As the model is a global solution, a certain smoothing of the available gravity field information is unavoidable. For regional geoid determination of the irregularities of residual gravity field should be included. The paper presents the global GRACE gravity field solution, regionally improved by adding a residual field, which is represented by radial base functions. The GRACE observations over the territory of Poland are analysed and a regionally improved GRACE geoid from this data is derived. This improved regional geoid is compared with the Polish quasigeoid and differences between the global and regionally improved GRACE GGM02S solutions are discussed. The study shows that the error of the official GRACE GGM02s solution was reduced by 50% due to regional refinement.
PL
Model GGM02S wyznaczony na podstawie danych z misji GRACE jest globalnym modelem grawimetrycznym opartym na harmonikach sferycznych. Ponieważ model ten jest globalnym rozwiązaniem, nieuniknione jest pewne wygładzenie informacji grawimetrycznych. Dla wyznaczenia lokalnego modelu geoidy konieczne jest uwzględnienie informacji o zmienności lokalnego pola grawitacyjnego. W pracy przedstawiono globalne rozwiązanie GRACE, poprawione przez dodanie informacji o lokalnym polu grawitacyjnym, określonym za pomocą radialnych funkcji bazowych. Obserwacje GRACE z obszaru Polski zostały przeanalizowane i na ich podstawie został wyznaczony ulepszony lokalny model geoidy. Model ten porównano z istniejącym modelem quasigeoidy dla Polski "quasigeoida 2001", oraz przeanalizowano różnice uzyskane pomiędzy globalnym a lokalnie wzmocnionym rozwiązaniem GRACE GGM02S. Badania wykazały, że zastosowanie modelowania regionalnego zmniejsza o 50% błąd oficjalnego rozwiązania GRACE GGM02S.
EN
Only with satellites it is possible to cover the entire Earth densely with gravity field related measurements of uniform quality within a short period of time. How-ever, due to the altitude of the satellite orbits, the signals of individual local masses are strongly damped. Based on the approach of Petrovskaya and Vershkov we determine the gravity gradient tensor directly from the spherical harmonic coefficients of the recent EIGEN-GL04C combined model of the GRACE satellite mission. Satellite gradiometry can be used as a complementary tool to gravity and geoid information in interpreting the general geophysical and geodynamical features of the Earth. Due to the high altitude of the satellite, the effects of the topography and the internal masses of the Earth are strongly damped. However, the gradiometer data, which are nothing else than the second order spatial derivatives of the gravity potential, efficiently counteract signal attenuation at the low and medium frequencies. In this article we review the procedure for estimating the gravity gradient components directly from spherical harmonics coefficients. Then we apply this method as a case study for the interpretation of possible geophysical or geodynamical patterns in Iran. We found strong correlations between the cross-components of the gravity gradient tensor and the components of the deflection of vertical, and we show that this result agrees with theory. Also, strong correlations of the gravity anomaly, geoid model and a digital elevation model were found with the diagonal elements of the gradient tensor.
17
Content available remote Kalkulacja kosztów użytkowania infrastruktury transportu drogowego w Polsce
PL
Problemy związane z realizacją polityki zrównoważonego rozwoju transportu oraz niedoinwestowanie infrastruktury transportowej sprawiły, że niezbędna jest w Europie reforma systemu obciążeń za korzystanie z infrastruktury transportowej. Aby prowadzić działania w kierunku większej zgodności kosztów użytkowania infrastruktury z faktycznie ponoszonymi opłatami, należy znaleźć metodę obciążania użytkowników w sposób optymalny. Teoretycy generalnie zgadzają się, że taką metodą jest rachunek oparty na kalkulacji krótkookresowych kosztów krańcowych. W odniesieniu do infrastruktury poszczególnych gałęzi transportu oznacza to konieczność podjęcia badań w kierunku wyliczenia tych kosztów w poszczególnych krajach / regionach. Celem niniejszego artykułu jest prezentacja wyników prac prowadzonych w zespole Katedry Badań Porównawczych Systemów Transportowych Uniwersytetu Gdańskiego w ramach projektu badawczego Unii Europejskiej GRACE. Opracowano model ekonometryczny i dokonano wyliczenia kosztu krańcowego dróg krajowych w Polsce, wskazując równocześnie na problemy związane z dostępnością danych, co jest charakterystyczną cechą wszystkich gospodarek przechodzących proces transformacji oraz dokonując interpretacji uzyskanych wyników.
EN
In recent years Europe faces increasing problems in introduction of balanced growth strategy in transport. One of main reasons for that is under investment of transport infrastructure which in turn leads to urgent need of rebuilding of infrastructure use charges and revenues system. Key problem in that field could be identified as need to develop honest system linking cost incurred with charges paid. Currently the schemes based on marginal cost estimates are believed to be optimal solution. This paper deals with the problem of road infrastructure use costs calculation. First Polish study in that regard has been recently conducted by Department of Comparative Analysis of Transportation Systems at the University of Gdansk under EU-based project GRACE. Econometric modelling has been used to relate traffic impacts on costs of infrastructure use. Based on the results cost levels have been calculated. Conclusive results are compared with other relevant studies in EU countries and differences are identified and discussed.
EN
Marine geoid modelling in the Atlantic coastal region of Argentina is problematic. Firstly, because of the insufficient amount of available shipborne gravity data, which renders a purely gravimetric solution not feasible. Second1y, because of the very strong ocean currents, that affect the quality of satellite altimetry data, so that a purely altimetric model is too noisy, even after low-pass filtering the Sea Surface Heights (SSHs) to remove (part of) the influence of the oceanographic signals. Thus, the recommended solution is to employ a combination method and the use of all the available gravity and altimetry data together. This is a suitable solution since (i) combination methods such as least squares collocation and Input Output System Theory (IOST) inherently low-pass filter and weigh the data, and (ii) will make use of the altimetric heights to fill the gaps of the shipborne gravity data. FolIowing this idea, purely altimetric, gravimetric and combined (using the IOST method) marine geoid models have been estimated for Argentina, employing all available shipborne gravity data, satellite altimetry SSHs and the latest Earth Gravity Models (EGMs) developed from CHAMP and GRACE missions. The new EGMs are especially usefuI to assess the quality of the new geoid models, especially against EGM96, which was used in an older ERSI-onIy solution for the same area. From the comparison of the estimated geoid models with respect to stacked TOPEX/Poseidon SSHs, the authors found that the altimetric model provides the best agreement while the combined one improves the accuracy [...] of the gravimetric solution.
PL
Z modelowaniem geoidy morskiej na obszarze Atlantyku w pobliżu wybrzeży Argentyny wiąże się wiele problemów. Po pierwsze, brak wystarczającej ilości morskich danych grawimetrycznych uniemożliwia modelowanie na tym obszarze czysto grawimetrycznej geoidy. Z drugiej strony, występowanie w tym rejonie bardzo silnych prądów oceanicznych zakłóca dane altimetryczne; czysto altimetryczny model geoidy jest obarczony zbyt dużym szumem, nawet po zastosowaniu wysokości poziomu morza (SSHs), przefiltrowanych przy użyciu nisko-pasmowego filtru, do usunięcia (częściowego) wpływu sygnałów oceanograficznych. Proponowane kombinowane rozwiązanie polega zatem na łącznym wykorzystaniu wszystkich dostępnych danych grawimetrycznych i altimetrycznych. Zastosowana w nim kombinacja metod takich jak metoda kollokacji i teoria wejścia-wyjścia systemów (IOST) umożliwia filtrowanie danych przy użyciu nisko-pasmowego filtru oraz ich odpowiednie wagowanie. W rozwiązaniu tym wykorzystywane są także dane altimetryczne do wypełnienia luk w morskich danych grawimetrycznych. Wszystkie dostępne morskie dane grawimetryczne, dane altimetryczne (SSHs) i najnowsze modele geopotencjału wyznaczone z wykorzystaniem danych z misji CHAMP i GRACE zostały użyte do wyznaczenia czysto altimetrycznego, grawimetrycznego i kombinowanego (z użyciem metody IOST) modeli geoidy morskiej dla Argentyny. Nowe modele geopotencjału, odgrywają istotną rolę w podniesieniu jakości modeli geoidy, w szczególności w odniesieniu do modelu EGM96, który był wykorzystany przy opracowaniu poprzedniego modelu geoidy morskiej na tym samym obszarze przy wykorzystaniu jedynie danych altimetrycznych z satelity ERS l. Z porównania opracowanych przez autorów modeli geoidy z SSHs otrzymanymi z misji TOPEX/Poseidon wynika, że modele altimetryczne charakteryzują się najlepszą zgodnością, zaś model kombinowany charakteryzuje się większą dokładnością aniżeli model czysto grawimetryczny.
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