WorldWideScience

Sample records for monthly grace gravity

  1. Ocean tides in GRACE monthly averaged gravity fields

    DEFF Research Database (Denmark)

    Knudsen, Per

    2003-01-01

    aims at. In this analysis the results of Knudsen and Andersen (2002) have been verified using actual post-launch orbit parameter of the GRACE mission. The current ocean tide models are not accurate enough to correct GRACE data at harmonic degrees lower than 47. The accumulated tidal errors may affect......The GRACE mission will map the Earth's gravity fields and its variations with unprecedented accuracy during its 5-year lifetime. Unless ocean tide signals and their load upon the solid earth are removed from the GRACE data, their long period aliases obscure more subtle climate signals which GRACE...... the GRACE data up to harmonic degree 60. A study of the revised alias frequencies confirm that the ocean tide errors will not cancel in the GRACE monthly averaged temporal gravity fields. The S-2 and the K-2 terms have alias frequencies much longer than 30 days, so they remain almost unreduced...

  2. Validation of the EGSIEM combined monthly GRACE gravity fields

    Science.gov (United States)

    Li, Zhao; van Dam, Tonie; Chen, Qiang; Weigelt, Matthias; Güntner, Andreas; Jäggi, Adrian; Meyer, Ulrich; Jean, Yoomin; Altamimi, Zuheir; Rebischung, Paul

    2016-04-01

    Observations indicate that global warming is affecting the water cycle. Here in Europe predictions are for more frequent high precipitation events, wetter winters, and longer and dryer summers. The consequences of these changes include the decreasing availability of fresh water resources in some regions as well as flooding and erosion of coastal and low-lying areas in other regions. These weather related effects impose heavy costs on society and the economy. We cannot stop the immediate effects global warming on the water cycle. But there may be measures that we can take to mitigate the costs to society. The Horizon2020 supported project, European Gravity Service for Improved Emergency Management (EGSIEM), will add value to EO observations of variations in the Earth's gravity field. In particular, the EGSIEM project will interpret the observations of gravity field changes in terms of changes in continental water storage. The project team will develop tools to alert the public water storage conditions could indicate the onset of regional flooding or drought. As part of the EGSIEM project, a combined GRACE gravity product is generated, using various monthly GRACE solutions from associated processing centers (ACs). Since each AC follows a set of common processing standards but applies its own independent analysis method, the quality, robustness, and reliability of the monthly combined gravity fields should be significantly improved as compared to any individual solution. In this study, we present detailed and updated comparisons of the combined EGSIEM GRACE gravity product with GPS position time series, hydrological models, and existing GRACE gravity fields. The GPS residuals are latest REPRO2 station position residuals, obtained by rigorously stacking the IGS Repro 2 , daily solutions, estimating, and then restoring the annual and semi-annual signals.

  3. Regularized GRACE monthly solutions by constraining the difference between the longitudinal and latitudinal gravity variations

    Science.gov (United States)

    Chen, Qiujie; Chen, Wu; Shen, Yunzhong; Zhang, Xingfu; Hsu, Houze

    2016-04-01

    The existing unconstrained Gravity Recovery and Climate Experiment (GRACE) monthly solutions i.e. CSR RL05 from Center for Space Research (CSR), GFZ RL05a from GeoForschungsZentrum (GFZ), JPL RL05 from Jet Propulsion Laboratory (JPL), DMT-1 from Delft Institute of Earth Observation and Space Systems (DEOS), AIUB from Bern University, and Tongji-GRACE01 as well as Tongji-GRACE02 from Tongji University, are dominated by correlated noise (such as north-south stripe errors) in high degree coefficients. To suppress the correlated noise of the unconstrained GRACE solutions, one typical option is to use post-processing filters such as decorrelation filtering and Gaussian smoothing , which are quite effective to reduce the noise and convenient to be implemented. Unlike these post-processing methods, the CNES/GRGS monthly GRACE solutions from Centre National d'Etudes Spatiales (CNES) were developed by using regularization with Kaula rule, whose correlated noise are reduced to such a great extent that no decorrelation filtering is required. Actually, the previous studies demonstrated that the north-south stripes in the GRACE solutions are due to the poor sensitivity of gravity variation in east-west direction. In other words, the longitudinal sampling of GRACE mission is very sparse but the latitudinal sampling of GRACE mission is quite dense, indicating that the recoverability of the longitudinal gravity variation is poor or unstable, leading to the ill-conditioned monthly GRACE solutions. To stabilize the monthly solutions, we constructed the regularization matrices by minimizing the difference between the longitudinal and latitudinal gravity variations and applied them to derive a time series of regularized GRACE monthly solutions named RegTongji RL01 for the period Jan. 2003 to Aug. 2011 in this paper. The signal powers and noise level of RegTongji RL01 were analyzed in this paper, which shows that: (1) No smoothing or decorrelation filtering is required for RegTongji RL

  4. AIUB-RL02: an improved time-series of monthly gravity fields from GRACE data

    Science.gov (United States)

    Meyer, U.; Jäggi, A.; Jean, Y.; Beutler, G.

    2016-05-01

    The new release AIUB-RL02 of monthly gravity models from GRACE GPS and K-Band range-rate data is based on reprocessed satellite orbits referring to the reference frame IGb08. The release is consistent with the IERS2010 conventions. Improvements with respect to its predecessor AIUB-RL01 include the use of reprocessed (RL02) GRACE observations, new atmosphere and ocean dealiasing products (RL05), an upgraded ocean tide model (EOT11A), and the interpolation of shallow ocean tides (admittances). The stochastic parametrization of AIUB-RL02 was adapted to include daily accelerometer scale factors, which drastically reduces spurious signal at the 161 d period in C20 and at other low degree and order gravity field coefficients. Moreover, the correlation between the noise in the monthly gravity models and solar activity is considerably reduced in the new release. The signal and the noise content of the new AIUB-RL02 monthly gravity fields are studied and calibrated errors are derived from their non-secular and non-seasonal variability. The short-period time-variable signal over the oceans, mostly representing noise, is reduced by 50 per cent with respect to AIUB-RL01. Compared to the official GFZ-RL05a and CSR-RL05 monthly models, the AIUB-RL02 stands out by its low noise at high degrees, a fact emerging from the estimation of seasonal variations for selected river basins and of mass trends in polar regions. Two versions of the monthly AIUB-RL02 gravity models, with spherical harmonics resolution of degree and order 60 and 90, respectively, are available for the time period from March 2003 to March 2014 at the International Center for Global Earth Models or from ftp://ftp.unibe.ch/aiub/GRAVITY/GRACE (last accessed 22 March 2016).

  5. EGSIEM: Combination of GRACE monthly gravity models on normal equation level

    Science.gov (United States)

    Meyer, Ulrich; Jean, Yoomin; Jäggi, Adrian; Mayer-Gürr, Torsten; Neumayer, Hans; Lemoine, Jean-Michel

    2016-04-01

    One of the three geodetic services to be realized in the frame of the EGSIEM project is a scientific combination service. Each associated processing center (AC) will follow a set of common processing standards but will apply its own, independent analysis method. Therefore the quality, robustness and reliability of the combined monthly gravity fields is expected to improve significantly compared to the individual solutions. The Monthly GRACE gravity fields of all ACs are combined on normal equation level. The individual normal equations are weighted depending on pairwise comparisons of the individual gravity field solutions. To derive these weights and for quality control of the individual contributions first a combination of the monthly gravity fields on solution level is performed. The concept of weighting and of the combination on normal equation level is introduced and the formats used for normal equation exchange and gravity field solutions is described. First results of the combination on normal equation level are presented and compared to the corresponding combinations on solution level. EGSIEM has an open data policy and all processing centers of GRACE gravity fields are invited to participate in the combination.

  6. Monthly gravity field recovery from GRACE orbits and K-band measurements using variational equations approach

    Directory of Open Access Journals (Sweden)

    Changqing Wang

    2015-07-01

    Full Text Available The Gravity Recovery and Climate Experiment (GRACE mission can significantly improve our knowledge of the temporal variability of the Earth's gravity field. We obtained monthly gravity field solutions based on variational equations approach from GPS-derived positions of GRACE satellites and K-band range-rate measurements. The impact of different fixed data weighting ratios in temporal gravity field recovery while combining the two types of data was investigated for the purpose of deriving the best combined solution. The monthly gravity field solution obtained through above procedures was named as the Institute of Geodesy and Geophysics (IGG temporal gravity field models. IGG temporal gravity field models were compared with GRACE Release05 (RL05 products in following aspects: (i the trend of the mass anomaly in China and its nearby regions within 2005–2010; (ii the root mean squares of the global mass anomaly during 2005–2010; (iii time-series changes in the mean water storage in the region of the Amazon Basin and the Sahara Desert between 2005 and 2010. The results showed that IGG solutions were almost consistent with GRACE RL05 products in above aspects (i–(iii. Changes in the annual amplitude of mean water storage in the Amazon Basin were 14.7 ± 1.2 cm for IGG, 17.1 ± 1.3 cm for the Centre for Space Research (CSR, 16.4 ± 0.9 cm for the GeoForschungsZentrum (GFZ and 16.9 ± 1.2 cm for the Jet Propulsion Laboratory (JPL in terms of equivalent water height (EWH, respectively. The root mean squares of the mean mass anomaly in Sahara were 1.2 cm, 0.9 cm, 0.9 cm and 1.2 cm for temporal gravity field models of IGG, CSR, GFZ and JPL, respectively. Comparison suggested that IGG temporal gravity field solutions were at the same accuracy level with the latest temporal gravity field solutions published by CSR, GFZ and JPL.

  7. Analysis of star camera errors in GRACE data and their impact on monthly gravity field models

    NARCIS (Netherlands)

    Inacio, P.M.G.; Ditmar, P.G.; Klees, R.; Hashemifarahani, H.

    2015-01-01

    Star cameras (SCs) on board the GRACE satellites provide information about the attitudes of the spacecrafts. This information is needed to reduce the K-band ranging data to the centre of mass of the satellites. In this paper, we analyse GRACE SC errors using two months of real data of the primary an

  8. An improved GRACE monthly gravity field solution by modeling the non-conservative acceleration and attitude observation errors

    Science.gov (United States)

    Chen, Qiujie; Shen, Yunzhong; Chen, Wu; Zhang, Xingfu; Hsu, Houze

    2016-06-01

    The main contribution of this study is to improve the GRACE gravity field solution by taking errors of non-conservative acceleration and attitude observations into account. Unlike previous studies, the errors of the attitude and non-conservative acceleration data, and gravity field parameters, as well as accelerometer biases are estimated by means of weighted least squares adjustment. Then we compute a new time series of monthly gravity field models complete to degree and order 60 covering the period Jan. 2003 to Dec. 2012 from the twin GRACE satellites' data. The derived GRACE solution (called Tongji-GRACE02) is compared in terms of geoid degree variances and temporal mass changes with the other GRACE solutions, namely CSR RL05, GFZ RL05a, and JPL RL05. The results show that (1) the global mass signals of Tongji-GRACE02 are generally consistent with those of CSR RL05, GFZ RL05a, and JPL RL05; (2) compared to CSR RL05, the noise of Tongji-GRACE02 is reduced by about 21 % over ocean when only using 300 km Gaussian smoothing, and 60 % or more over deserts (Australia, Kalahari, Karakum and Thar) without using Gaussian smoothing and decorrelation filtering; and (3) for all examples, the noise reductions are more significant than signal reductions, no matter whether smoothing and filtering are applied or not. The comparison with GLDAS data supports that the signals of Tongji-GRACE02 over St. Lawrence River basin are close to those from CSR RL05, GFZ RL05a and JPL RL05, while the GLDAS result shows the best agreement with the Tongji-GRACE02 result.

  9. Seasonal Gravity Field Variations from GRACE and Hydrological Models

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Hinderer, Jacques; Lemoine, Frank G.

    2004-01-01

    This study present an investigation of the newly released 18 monthly gravity field solutions from the GRACE twin space-crafts with emphasis on the global scale annual gravity field variations observed from GRACE and modeled from hydrological models as annual changes in terrestrial water storage....... Four global hydrological models covering the same period in 2002–2003 as the GRACE observations were investigated to for their mutual consistency in estimates of annual variation in terrestrial water storage and related temporal changes in gravity field. The hydrological models differ by a maximum of 2...... variation in gravity from GRACE is around 0.4 µGal (0.9 cm water layer thickness) on 2000 km length scales. This makes the GRACE observations of terrestrial water storage on global annual scales more accurate than present-day hydrological models....

  10. Global inter-annual gravity changes from GRACE: Early results

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Hinderer, J.

    2005-01-01

    with an accuracy of 0.4 muGal corresponding to 9 mm water thickness on spatial scales longer than 1300 km. Four of the most widely used global hydrological models have been investigated for their spatial comparison with GRACE observations of inter-annual gravity field variations due to changes in continental water...... storage. The Global Land Data Assimilation System model has a spatial correlation coefficient with GRACE observations of 0.65 over the northern hemisphere. This demonstrates that the observed gravity field changes on these scales are largely related to changes in continental water storage.......Fifteen monthly gravity field solutions from the GRACE twin satellites launched more than two years ago have been studied to estimate gravity field changes between 2002 and 2003. The results demonstrate that GRACE is capable of capturing the changes in ground water on inter-annual scales...

  11. GRACE Gravity Field Product Description and Mission Profile

    Science.gov (United States)

    Bettadpur, S.; Flechtner, F.; Watkins, M. M.

    2003-12-01

    A time sequence of approximately monthly estimates of the Earth's gravity field, derived from the Gravity Recovery And Climate Mission (GRACE) science data, have been recently made available to the user community. In addition to these monthly estimates, a long-term mean gravity field has also been made available. These gravity field products are generated by the GRACE Science Data System team elements at the UT-CSR, Jet Propulsion Laboratory and at GFZ-Potsdam. In this presentation, we briefly describe the gravity field processing standards and methodology in use at UT-CSR. The traditional linearized least-squares implementation of gravity field determination from GRACE tracking data is reviewed with particular attention the to a-priori gravitational force models in use. The evolution of GRACE mission since its launch in March 2002 is then discussed. The main mission events, and the flight dynamic profile (pointing, inter-satellite separation, ground-track evolution, etc) are presented - with the purpose of aiding the interpretation and assessment of the gravity field product quality. The presentation closes with the description of the likely future evolution of the flight profile.

  12. Seasonal Gravity Field Variations from GRACE and Hydrological Models

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Hinderer, Jacques; Lemoine, Frank G.

    2004-01-01

    This study present an investigation of the newly released 18 monthly gravity field solutions from the GRACE twin space-crafts with emphasis on the global scale annual gravity field variations observed from GRACE and modeled from hydrological models as annual changes in terrestrial water storage....... Four global hydrological models covering the same period in 2002–2003 as the GRACE observations were investigated to for their mutual consistency in estimates of annual variation in terrestrial water storage and related temporal changes in gravity field. The hydrological models differ by a maximum of 2...... µGal or nearly 5 cm equivalent water storage in selected regions. Integrated over all land masses the standard deviation among the annual signal from the four hydrological models are 0.6 µGal equivalent to around 1.4 cm in equivalent water layer thickness. The estimated accuracy of the annual...

  13. Tongji-GRACE01: A GRACE-only static gravity field model recovered from GRACE Level-1B data using modified short arc approach

    Science.gov (United States)

    Chen, Qiujie; Shen, Yunzhong; Zhang, Xingfu; Chen, Wu; Hsu, Houze

    2015-09-01

    The modified short arc approach, where the position vector in force model are regarded as pseudo observation, is implemented in the SAtellite Gravimetry Analysis Software (SAGAS) developed by Tongji university. Based on the SAGAS platform, a static gravity field model (namely Tongji-GRACE01) complete to degree and order 160 is computed from 49 months of real GRACE Level-1B data spanning the period 2003-2007 (including the observations of K-band range-rate, reduced dynamic orbits, non-conservative accelerations and altitudes). The Tongji-GRACE01 model is compared with the recent GRACE-only models (such as GGM05S, AIUB-GRACE03S, ITG-GRACE03, ITG-GRACE2010S, and ITSG-GRACE2014S) and validated with GPS-leveling data sets in different countries. The results show that the Tongji-GRACE01 model has a considered quality as GGM05S, AIUB-GRACE03S and ITG-GRACE03. The Tongji-GRACE01 model is available at the International Centre for Global Earth Models (ICGEM) web page (http://icgem.gfz-potsdam.de/ICGEM/).

  14. Progress towards CSR RL06 GRACE gravity solutions

    Science.gov (United States)

    Save, Himanshu

    2017-04-01

    The GRACE project plans to re-processes the GRACE mission data in order to be consistent with the first gravity products released by the GRACE-FO project. The next generation Release-06 (RL06) gravity products from GRACE will include the improvements in GRACE Level-1 data products, background gravity models and the processing methodology. This paper will outline the planned improvements for CSR - RL06 and discuss the preliminary results. This paper will discuss the evolution of the quality of the GRACE solutions, especially over the past few years. We will also discuss the possible challenges we may face in connecting/extending the measurements of mass fluxes from the GRACE era to the GRACE-FO era due quality of the GRACE solutions from recent years.

  15. The potential of ground gravity measurements to validate GRACE data

    Directory of Open Access Journals (Sweden)

    D. Crossley

    2003-01-01

    Full Text Available New satellite missions are returning high precision, time-varying, satellite measurements of the Earth’s gravity field. The GRACE mission is now in its calibration/- validation phase and first results of the gravity field solutions are imminent. We consider here the possibility of external validation using data from the superconducting gravimeters in the European sub-array of the Global Geodynamics Project (GGP as ‘ground truth’ for comparison with GRACE. This is a pilot study in which we use 14 months of 1-hour data from the beginning of GGP (1 July 1997 to 30 August 1998, when the Potsdam instrument was relocated to South Africa. There are 7 stations clustered in west central Europe, and one station, Metsahovi in Finland. We remove local tides, polar motion, local and global air pressure, and instrument drift and then decimate to 6-hour samples. We see large variations in the time series of 5–10µgal between even some neighboring stations, but there are also common features that correlate well over the 427-day period. The 8 stations are used to interpolate a minimum curvature (gridded surface that extends over the geographical region. This surface shows time and spatial coherency at the level of 2– 4µgal over the first half of the data and 1–2µgal over the latter half. The mean value of the surface clearly shows a rise in European gravity of about 3µgal over the first 150 days and a fairly constant value for the rest of the data. The accuracy of this mean is estimated at 1µgal, which compares favorably with GRACE predictions for wavelengths of 500 km or less. Preliminary studies of hydrology loading over Western Europe shows the difficulty of correlating the local hydrology, which can be highly variable, with large-scale gravity variations.Key words. GRACE, satellite gravity, superconducting gravimeter, GGP, ground truth

  16. Reducing errors in the GRACE gravity solutions using regularization

    Science.gov (United States)

    Save, Himanshu; Bettadpur, Srinivas; Tapley, Byron D.

    2012-09-01

    The nature of the gravity field inverse problem amplifies the noise in the GRACE data, which creeps into the mid and high degree and order harmonic coefficients of the Earth's monthly gravity fields provided by GRACE. Due to the use of imperfect background models and data noise, these errors are manifested as north-south striping in the monthly global maps of equivalent water heights. In order to reduce these errors, this study investigates the use of the L-curve method with Tikhonov regularization. L-curve is a popular aid for determining a suitable value of the regularization parameter when solving linear discrete ill-posed problems using Tikhonov regularization. However, the computational effort required to determine the L-curve is prohibitively high for a large-scale problem like GRACE. This study implements a parameter-choice method, using Lanczos bidiagonalization which is a computationally inexpensive approximation to L-curve. Lanczos bidiagonalization is implemented with orthogonal transformation in a parallel computing environment and projects a large estimation problem on a problem of the size of about 2 orders of magnitude smaller for computing the regularization parameter. Errors in the GRACE solution time series have certain characteristics that vary depending on the ground track coverage of the solutions. These errors increase with increasing degree and order. In addition, certain resonant and near-resonant harmonic coefficients have higher errors as compared with the other coefficients. Using the knowledge of these characteristics, this study designs a regularization matrix that provides a constraint on the geopotential coefficients as a function of its degree and order. This regularization matrix is then used to compute the appropriate regularization parameter for each monthly solution. A 7-year time-series of the candidate regularized solutions (Mar 2003-Feb 2010) show markedly reduced error stripes compared with the unconstrained GRACE release 4

  17. Studies of GRACE Gravity Field Inversion Techniques

    Science.gov (United States)

    Wang, L.; Shum, C.; Duan, J.; Schmidt, M.; Yuan, D.; Watkins, M. M.

    2008-12-01

    The geophysical inverse problem using satellite observations, such as GRACE, to estimate gravity change and mass variations at the Earth's surface is a well-known ill-posed problem. Different methods using different basis function (representing the gravity field) for different purposes (global or regional inversion) have been employed to obtain a stable solution, such as Bayesian estimation with prior information, the repro-BIQUUE of variance components and iterative least-squares estimation with simultaneous updating of a prior covariance, and to achieve enhanced spatial resolutions. The gravity field representation methods include spherical harmonics, regional gridded data (including mascons), and various wavelet representations (Poisson wavelets, Blackman band-limited regional wavelets with global representation). Finally, the use of data types (KBR range, range-rate, range-rate-rate) and data-generation methods (e.g., nonlinear orbit determination and geophysical inverse approach, energy conservation principle, etc) could also reflect relative inversion accuracy and the content of signal spectra in the resulting solution. In this contribution, we present results of a simulation experiment, which used various solution techniques and data types to attempt to quantify the relative advantage and disadvantage of each of the techniques.

  18. Correcting GRACE gravity fields for ocean tide effects

    DEFF Research Database (Denmark)

    Knudsen, Per; Andersen, Ole Baltazar

    2002-01-01

    subtle climate signals which GRACE aims at. The difference between two existing ocean tide models can be used as an estimate of current tidal model error for the M-2,S-2,K-1, and O-1 constituents. When compared with the expected accuracy of the GRACE system, both expressed as spherical harmonic degree...... variances, we find that the current ocean tide models are not accurate enough to correct GRACE data at harmonic degrees lower that 35. The accumulated tidal errors may affect the GRACE data up to harmonic degree 56. Furthermore, the atmospheric (radiation) tides may cause significant errors in the ocean......[1] The GRACE mission will be launch in early 2002 and will map the Earth's gravity fields and its variations with unprecedented accuracy during its 5-year lifetime. Unless ocean tide signals and their load upon the solid earth are removed from the GRACE data, their long period aliases obscure more...

  19. Radial and tangential gravity rates from GRACE in areas of glacial isostatic adjustment

    Science.gov (United States)

    van der Wal, Wouter; Kurtenbach, Enrico; Kusche, Jürgen; Vermeersen, Bert

    2011-11-01

    In areas dominated by Glacial Isostatic Adjustment (GIA), the free-air gravity anomaly rate can be converted to uplift rate to good approximation by using a simple spectral relation. We provide quantitative comparisons between gravity rates derived from monthly gravity field solutions (GFZ Potsdam, CSR Texas, IGG Bonn) from the Gravity Recovery and Climate Experiment (GRACE) satellite mission with uplift rates measured by GPS in these areas. The band-limited gravity data from the GRACE satellite mission can be brought to very good agreement with the point data from GPS by using scaling factors derived from a GIA model (the root-mean-square of differences is 0.55 mm yr-1 for a maximum uplift rate signal of 10 mm yr-1). The root-mean-square of the differences between GRACE derived uplift rates and GPS derived uplift rates decreases with increasing GRACE time period to a level below the uncertainty that is expected from GRACE observations, GPS measurements and the conversion from gravity rate to uplift rate. With the current length of time-series (more than 8 yr) applying filters and a hydrology correction to the GRACE data does not reduce the root-mean-square of differences significantly. The smallest root-mean-square was obtained with the GFZ solution in Fennoscandia and with the CSR solution in North America. With radial gravity rates in excellent agreement with GPS uplift rates, more information on the GIA process can be extracted from GRACE gravity field solutions in the form of tangential gravity rates, which are equivalent to a rate of change in the deflection of the vertical scaled by the magnitude of gravity rate vector. Tangential gravity rates derived from GRACE point towards the centre of the previously glaciated area, and are largest in a location close to the centre of the former ice sheet. Forward modelling showed that present day tangential gravity rates have maximum sensitivity between the centre and edge of the former ice sheet, while radial gravity

  20. Evaluation of GRACE data using terrestrial gravity observations

    Science.gov (United States)

    Abe, Maiko; Kroner, Corinna; Foerste, Christoph; Weise, Adelheid; Guentner, Andreas; Creutzfeldt, Benjamin; Jahr, Thomas; Jentzsch, Gerhard; Wilmes, Herbert; Wziontek, Hartmut

    2010-05-01

    The GRACE twin satellite mission has been running since March, 2002 and now seven years of time-dependent global gravity field solutions are available. The sensitivity of the GRACE data is that they can detect variation in continental hydrology in the range of several μGal. However, there is still argument how to filter and rescale the GRACE gravity data. During the recent past, different filtering methods have been developed. GRACE solutions provided by different institutions show 15 % discrepancies in the annual cycle for the Amazon area (Bruinsma et al. 2009). Other types of observations, such as superconducting gravimeter (SG) combined with repeated absolute gravity (AG) measurements, offer the opportunity to evaluate the filtered and rescaled satellite data. By these constraints for post-processing treatment of GRACE solutions can be derived as well as information on the significance of GRACE-based temporal gravity changes will be gained. For this assessment it is necessary to bridge the gap in the spatial and temporal resolution of the terrestrial and satellite-based time series. Empirical Orthogonal Functions (EOFs) are used to overcome the different resolutions. For comparisons of the signal content, coherence and principal component analyses of the data sets are carried out. In this study, GFZ, JPL, CSR, and CNES/CRGS RL-2 GRACE solutions are used and for the filtering techniques a non-isotropic filter presented by Kusche (2007, 2009) and Gaussian filter for various radii are compared. From coherence analyses between SG and GRACE time series, good coherence is found for the periods of longer than semi-annual.

  1. Near real-time GRACE gravity field solutions for hydrological monitoring applications

    Science.gov (United States)

    Kvas, Andreas; Gouweleeuw, Ben; Mayer-Gürr, Torsten; Güntner, Andreas

    2016-04-01

    Within the EGSIEM (European Gravity Service for Improved Emergency Management) project, a demonstrator for a near real-time (NRT) gravity field service which provides daily GRACE gravity field solutions will be established. Compared to the official GRACE gravity products, these NRT solutions will increase the temporal resolution from one month to one day and reduce the latency from currently two months to five days. This fast availability allows the monitoring of total water storage variations and of hydrological extreme events as they occur, in contrast to a 'confirmation after occurrence' as is the situation today. The service will be jointly run by GFZ (German Research Centre for Geosciences) and Graz University of Technology, with each analysis center providing an independent solution. A Kalman filter framework, in which GRACE data is combined with prior information, serves as basis for the gravity field recovery in order to increase the redundancy of the gravity field estimates. The on-line nature of the NRT service necessitates a tailored smoothing algorithm as opposed to post-processing applications, where forward-backward smoothing can be applied. This contribution gives an overview on the near real-time processing chain and highlights differences between the computed NRT solutions and the standard GRACE products. We discuss the special characteristics of the Kalman filtered gravity field models as well as derived products and give an estimate of the expected error levels. Additionally, we show the added value of the NRT solutions through comparison of the first results of the pre-operational phase with in-situ data and monthly GRACE gravity field models.

  2. New Views of Earth's Gravity Field from GRACE

    Science.gov (United States)

    2003-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Map 1Map 2Gravity and the Earth's Shape Gravity is the force that is responsible for the weight of an object and is determined by how the material that makes up the Earth is distributed throughout the Earth. Because gravity changes over the surface of the Earth, the weight of an object changes along with it. One can define standard gravity as the value of gravity for an perfectly smooth 'idealized' Earth, and the gravity 'anomaly' is a measure of how actual gravity deviates from this standard. Gravity reflects the Earth's surface topography to a high degree and is associated with features that most people are familiar with such as large mountains and deep ocean trenches.Progress in Measuring the Earth's Gravity Field Through GRACE Prior to GRACE, the Earth's gravity field was determined using measurements of varying quality from different satellites and of incomplete coverage. Consequently the accuracy and resolution of the gravity field were limited. As is shown in Figure 1, the long wavelength components of the gravity field determined from satellite tracking were limited to a resolution of approximately 700 km. At shorter wavelengths, the errors were too large to be useful. Only broad geophysical features of the Earth's structure could be detected (see map 1).In contrast, GRACE, by itself, has provided accurate gravity information with a resolution of 200 km. Now, much more detail is clearly evident in the Earth's geophysical features (see map 2). High resolution features detected by GRACE that are representative of geophysical phenomena include the Tonga/Kermadec region (a zone where one tectonic plate slides under another), the Himalayan/Tibetan Plateau region (an area of uplift due to colliding plates), and the mid-Atlantic ridge (an active spreading center in the middle of the Atlantic ocean where new crust is being created). Future GRACE gravity models are

  3. GRACE Orbit and Gravity Field Recovery at GFZ Potsdam - First Experiences and Perspectives

    Science.gov (United States)

    Reigber, C.; Flechtner, F.; Koenig, R.; Meyer, U.; Neumayer, K.; Schmidt, R.; Schwintzer, P.; Zhu, S.

    2002-12-01

    Since the launch of the two GRACE satellites on March 17, 2002, both satellites follow each other in a distance of about 220 km in an almost polar, circular and 500 km high orbit. For orbit and long-wavelength gravity field recovery the GRACE mission concept follows CHAMP's configuration, i.e., GPS satellite-to-satellite tracking and accelerometry on each of the two satellites. The essentially new element is the K-band microwave link measuring the relative distance of one satellite with respect to the other in both directions with an ultra-high precision (few æm). To fully exploit this high precision, the requirements on the performance and precision of the accelerometers to measure non-gravitational orbit perturbations are one order of magnitude more stringent than on CHAMP. The goal of GRACE is a distinct progress in global gravity field recovery from space with respect to accuracy and spatial as well as temporal resolution. First experiences of the GFZ project team with the instrument and sensor performance on the GRACE satellites, the parametrization of the data in precise orbit determination and first tentative gravity field solutions are discussed and compared with CHAMP related results. GRACE data processing at GFZ Potsdam is part of the GRACE level-2 product generation and validation, which is shared with UTEX/CSR and NASA/JPL. On level-1, GFZ Potsdam is responsible for providing high frequency atmosphere and ocean mass variation models to avoid alias effects in GRACE's envisaged sequence of monthly gravity field solutions. Gravity de-aliasing products quality will be discussed.

  4. Towards combined global monthly gravity field solutions

    Science.gov (United States)

    Jaeggi, Adrian; Meyer, Ulrich; Beutler, Gerhard; Weigelt, Matthias; van Dam, Tonie; Mayer-Gürr, Torsten; Flury, Jakob; Flechtner, Frank; Dahle, Christoph; Lemoine, Jean-Michel; Bruinsma, Sean

    2014-05-01

    Currently, official GRACE Science Data System (SDS) monthly gravity field solutions are generated independently by the Centre for Space Research (CSR) and the German Research Centre for Geosciences (GFZ). Additional GRACE SDS monthly fields are provided by the Jet Propulsion Laboratory (JPL) for validation and outside the SDS by a number of other institutions worldwide. Although the adopted background models and processing standards have been harmonized more and more by the various processing centers during the past years, notable differences still exist and the users are more or less left alone with a decision which model to choose for their individual applications. This procedure seriously limits the accessibility of these valuable data. Combinations are well established in the area of other space geodetic techniques, such as the Global Navigation Satellite Systems (GNSS), Satellite Laser Ranging (SLR), and Very Long Baseline Interferometry (VLBI). Regularly comparing and combining space-geodetic products has tremendously increased the usefulness of the products in a wide range of disciplines and scientific applications. Therefore, we propose in a first step to mutually compare the large variety of available monthly GRACE gravity field solutions, e.g., by assessing the signal content over selected regions, by estimating the noise over the oceans, and by performing significance tests. We make the attempt to assign different solution characteristics to different processing strategies in order to identify subsets of solutions, which are based on similar processing strategies. Using these subsets we will in a second step explore ways to generate combined solutions, e.g., based on a weighted average of the individual solutions using empirical weights derived from pair-wise comparisons. We will also assess the quality of such a combined solution and discuss the potential benefits for the GRACE and GRACE-FO user community, but also address minimum processing

  5. Towards near-real time daily GRACE gravity field solutions for global monitoring of hydrological extremes

    Science.gov (United States)

    Gouweleeuw, B.; Kvas, A.; Gruber, C.; Schumacher, M.; Mayer-Gürr, T.; Flechtner, F.; Kusche, J.; Guntner, A.

    2016-12-01

    Water storage anomalies from the Gravity Recovery and Climate Experiment (GRACE) satellite mission (2002-present) have been shown to be a unique descriptor of large-scale hydrological extreme events. However, possibly due to its coarse temporal (weekly to monthly), spatial (> 150.000 km2) resolution and the latency of standard products of about 2 months, the comprehensive information from GRACE on total water storage variations has rarely been evaluated for near-real time flood or drought monitoring or forecasting so far. The Horizon 2020 funded EGSIEM (European Gravity Service for Improved Emergency Management) project is scheduled to launch a near-real time test run of GRACE gravity field data, which will provide daily solutions with a latency of 5 days. This fast availability allows the monitoring of total water storage variations related to hydrological extreme events as they occur, as opposed to a 'confirmation after occurrence', which is the current situation. A first hydrological evaluation of daily GRACE gravity field solutions for floods in the Ganges-Brahmaputra Delta in 2004 and 2007 confirms their potential for gravity-based large-scale flood monitoring. This particularly applies to short-lived, high-volume floods, as they occur in Bangladesh with a 4-5 year return period. The subsequent assimilation of daily GRACE data into a (global) hydrological model - carried out jointly within the framework of the Belmont Forum funded BanD-AID project - decomposes total water storage into its individual components (e.g., surface water), increases the spatial resolution and opens up the possibility of flood early warning and forecasting.

  6. Evaluation of recent GRACE monthly solution series with an ice sheet perspective

    Science.gov (United States)

    Horwath, Martin; Groh, Andreas

    2016-04-01

    GRACE monthly global gravity field solutions have undergone a remarkable evolution, leading to the latest (Release 5) series by CSR, GFZ, and JPL, to new series by other processing centers, such as ITSG and AIUB, as well as to efforts to derive combined solutions, particularly by the EGSIEM (European Gravity Service for Improved Emergency Management) project. For applications, such as GRACE inferences on ice sheet mass balance, the obvious question is on what GRACE solution series to base the assessment. Here we evaluate different GRACE solution series (including the ones listed above) in a unified framework. We concentrate on solutions expanded up to degree 90 or higher, since this is most appropriate for polar applications. We empirically assess the error levels in the spectral as well as in the spatial domain based on the month-to-month scatter in the high spherical harmonic degrees. We include empirical assessment of error correlations. We then apply all series to infer Antarctic and Greenland mass change time series and compare the results in terms of apparent signal content and noise level. We find that the ITSG solutions show lowest noise level in the high degrees (above 60). A preliminary combined solution from the EGSIEM project shows lowest noise in the degrees below 60. This virtue maps into the derived ice mass time series, where the EGSIEM-based results show the lowest noise in most cases. Meanwhile, there is no indication that any of the considered series systematically dampens actual geophysical signals.

  7. Evaluation of GRACE daily gravity solutions for hydrological extremes in selected river basins

    Science.gov (United States)

    Gouweleeuw, Ben; Güntner, Andreas; Gain, Animesh; Gruber, Christian; Flechtner, Frank; Kvas, Andreas; Mayer-Gürr, Torsten

    2016-04-01

    Water storage anomalies from the Gravity Recovery And Climate Experiment (GRACE) satellite mission (2002-present) have been shown to be a unique descriptor of large-scale hydrological extreme events. However, possibly due to its coarse temporal (monthly to weekly) and spatial (> 150.000 km2) resolution, the comprehensive information from GRACE on total water storage variations has rarely been evaluated for flood or drought monitoring or forecasting so far. In the context of the Horizon 2020 funded European Gravity Service for Improved Emergency Management (EGSIEM) project, we evaluate two approaches to solve the spatio-temporal variations of the Earth's gravity field as daily solutions through comparison to selected historical extreme events in medium-large river basins (Ganges-Brahmaputra, Lower Mekong, Danube, Elbe). These comparisons show that highs and lows of GRACE-derived total water storage are closely related to the occurrence of hydrological extremes and serve as an early indicator of these events. The degree to which the daily GRACE solutions contain high-frequent temporal hydrological information, e.g. individual flood peaks, is related to the size of the extreme event.

  8. GRACE gravity field modeling with an investigation on correlation between nuisance parameters and gravity field coefficients

    Science.gov (United States)

    Zhao, Qile; Guo, Jing; Hu, Zhigang; Shi, Chuang; Liu, Jingnan; Cai, Hua; Liu, Xianglin

    2011-05-01

    The GRACE (Gravity Recovery And Climate Experiment) monthly gravity models have been independently produced and published by several research institutions, such as Center for Space Research (CSR), GeoForschungsZentrum (GFZ), Jet Propulsion Laboratory (JPL), Centre National d’Etudes Spatiales (CNES) and Delft Institute of Earth Observation and Space Systems (DEOS). According to their processing standards, above institutions use the traditional variational approach except that the DEOS exploits the acceleration approach. The background force models employed are rather similar. The produced gravity field models generally agree with one another in the spatial pattern. However, there are some discrepancies in the gravity signal amplitude between solutions produced by different institutions. In particular, 10%-30% signal amplitude differences in some river basins can be observed. In this paper, we implemented a variant of the traditional variational approach and computed two sets of monthly gravity field solutions using the data from January 2005 to December 2006. The input data are K-band range-rates (KBRR) and kinematic orbits of GRACE satellites. The main difference in the production of our two types of models is how to deal with nuisance parameters. This type of parameters is necessary to absorb low-frequency errors in the data, which are mainly the aliasing and instrument errors. One way is to remove the nuisance parameters before estimating the geopotential coefficients, called NPARB approach in the paper. The other way is to estimate the nuisance parameters and geopotential coefficients simultaneously, called NPESS approach. These two types of solutions mainly differ in geopotential coefficients from degree 2 to 5. This can be explained by the fact that the nuisance parameters and the gravity field coefficients are highly correlated, particularly at low degrees. We compare these solutions with the official and published ones by means of spectral analysis. It is

  9. Gravity Variation in Siberia: GRACE Observation and Possible Causes

    Directory of Open Access Journals (Sweden)

    Benjamin Fong Chao

    2011-01-01

    Full Text Available We report the finding, from the GRACE observation, of an increasing trend in the gravity anomaly in Siberia at the rate of up to 0.5 ugal yr-1 during 2003/1 - 2009/12, in the backdrop of a negative anomaly of magnitude on the order of ~-10 mgal. In consideration of the non-uniqueness of the gravitational inverse problem, we examine in some detail the various possible geophysical causes to explain the increasing gravity signal. We find two geophysical mechanisms being the most plausible, namely the melting of permafrost and the GIA post-glacial rebound. We conclude that these two mechanisms cannot be ruled out as causes for the regional gravity increase in Siberia, based on gravity data and in want of ancillary geophysical data in the region. More definitive identification of the contributions of the various causes awaits further studies.

  10. Estimating signal loss in regularized GRACE gravity field solutions

    Science.gov (United States)

    Swenson, S. C.; Wahr, J. M.

    2011-05-01

    Gravity field solutions produced using data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are subject to errors that increase as a function of increasing spatial resolution. Two commonly used techniques to improve the signal-to-noise ratio in the gravity field solutions are post-processing, via spectral filters, and regularization, which occurs within the least-squares inversion process used to create the solutions. One advantage of post-processing methods is the ability to easily estimate the signal loss resulting from the application of the spectral filter by applying the filter to synthetic gravity field coefficients derived from models of mass variation. This is a critical step in the construction of an accurate error budget. Estimating the amount of signal loss due to regularization, however, requires the execution of the full gravity field determination process to create synthetic instrument data; this leads to a significant cost in computation and expertise relative to post-processing techniques, and inhibits the rapid development of optimal regularization weighting schemes. Thus, while a number of studies have quantified the effects of spectral filtering, signal modification in regularized GRACE gravity field solutions has not yet been estimated. In this study, we examine the effect of one regularization method. First, we demonstrate that regularization can in fact be performed as a post-processing step if the solution covariance matrix is available. Regularization then is applied as a post-processing step to unconstrained solutions from the Center for Space Research (CSR), using weights reported by the Centre National d'Etudes Spatiales/Groupe de Recherches de geodesie spatiale (CNES/GRGS). After regularization, the power spectra of the CSR solutions agree well with those of the CNES/GRGS solutions. Finally, regularization is performed on synthetic gravity field solutions derived from a land surface model, revealing that in

  11. Analysis of Hydrology Induced Gravity Variations Observed by GRACE --- and Other Applications of Spherical Wavelets

    Science.gov (United States)

    Michel, V.

    2005-12-01

    A spherical wavelet analysis of monthly GRACE gravity data is presented. We observe strong correlations to gravity variations predicted by some common hydrology models, in particular in the Amazon, Zambezi and Ganges area. A time series analysis of the predicted gravity due to surface density changes in comparison to spherical wavelet coefficients of the GRACE potential demonstrates the advantages of spherical wavelets. Whereas a spherical harmonics expansion always implicitly includes a global averaging process, wavelets represent localizing basis functions that are much better able to analyze regional variations of a considered data set. Moreover, it is demonstrated that the spherical wavelet approach due to W. Freeden and U. Windheuser can be extended to a larger set of problems including the modelling of functions on balls, i.e. not only on the spherical surface. Examples of applications, such as the volume density recovery from simulated SGG gravity data (cf. planned satellite mission GOCE) are demonstrated. References: M.J. Fengler, W. Freeden, A. Kohlhaas, V. Michel, T. Peters: Wavelet Modelling of Regional and Temporal Variations of the Earth's Gravitational Potential Observed by GRACE, Schriften zur Funktionalanalysis und Geomathematik, 21 (2005), preprint, article submitted to Journal of Geodesy, 2005. V. Michel: Regularized Wavelet--based Multiresolution Recovery of the Harmonic Mass Density Distribution from Data of the Earth's Gravitational Field at Satellite Height, Inverse Problems, 21 (2005), 997-1025.

  12. Correlation between annual gravity changes monitored by GRACE and background seismicity rates

    Science.gov (United States)

    Mitsui, Y.; Yamada, K.

    2016-12-01

    GRACE(Gravity Recovery and Climate Experiment) has monitored global gravity changes after 2002.Indeed the gravity changes include signals of mass redistribution by M9-classmega-earthquakes (Han et al., 2006; Matsuo and Heki, 2011) and uplift by a deep earthquake (Tanaka et al., 2015),but most of them represent water mass movements (ex. Wahr et al., 2004). Water mass movements around the surfacemay affect earthquake occurrences via surface loads or pore pressure increases (ex. Ellsworth, 2013).Thus we examine the relation between temporal gravity changes and earthquake occurrences in a global scale. We use the GRACE level-3 data (for land) analyzed by UTCSR. The observation period is from April, 2002to January, 2015. The sampling interval is about 1 month. For deficient data, we linearly interpolate themfrom the last and next data. Then we estimate linear trends and amplitudes of annual changes. We also use seismicity catalogue data from USGS and select earthquakes over M4 and whose focal depths areshallower than 30 km. In order to exclude effects of aftershocks of large earthquakes, we extractbackground seismicity µ in the ETAS model (Ogata, 1988). We need sufficient numbers of earthquakesin each spatial grid for stable estimation. Therefore we first separate the surface of the Earth intolarge spatial grids and next select grids where mean values of the earthquake numberswere over three per month. We estimated the background seismicity rates, the linear gravity trends, andthe amplitudes of the annual gravity changes in the selected grids. We find that the correlation coefficient between the background seismicity rate and the annual gravity change is about 0.60 (p-value is 0.002), whereas that of the linear gravity trend between the background seismicity rateis about -0.03. This result implies that annual water movements truly affected the earthquake occurrences, butsecular movements did not.

  13. High-Resolution Gravity and Time-Varying Gravity Field Recovery using GRACE and CHAMP

    Science.gov (United States)

    Shum, C. K.

    2002-01-01

    This progress report summarizes the research work conducted under NASA's Solid Earth and Natural Hazards Program 1998 (SENH98) entitled High Resolution Gravity and Time Varying Gravity Field Recovery Using GRACE (Gravity Recovery and Climate Experiment) and CHAMP (Challenging Mini-satellite Package for Geophysical Research and Applications), which included a no-cost extension time period. The investigation has conducted pilot studies to use the simulated GRACE and CHAMP data and other in situ and space geodetic observable, satellite altimeter data, and ocean mass variation data to study the dynamic processes of the Earth which affect climate change. Results from this investigation include: (1) a new method to use the energy approach for expressing gravity mission data as in situ measurements with the possibility to enhance the spatial resolution of the gravity signal; (2) the method was tested using CHAMP and validated with the development of a mean gravity field model using CHAMP data, (3) elaborate simulation to quantify errors of tides and atmosphere and to recover hydrological and oceanic signals using GRACE, results show that there are significant aliasing effect and errors being amplified in the GRACE resonant geopotential and it is not trivial to remove these errors, and (4) quantification of oceanic and ice sheet mass changes in a geophysical constraint study to assess their contributions to global sea level change, while the results improved significant over the use of previous studies using only the SLR (Satellite Laser Ranging)-determined zonal gravity change data, the constraint could be further improved with additional information on mantle rheology, PGR (Post-Glacial Rebound) and ice loading history. A list of relevant presentations and publications is attached, along with a summary of the SENH investigation generated in 2000.

  14. GRACE Data-based High Accuracy Global Static Earth's Gravity Field Model

    Directory of Open Access Journals (Sweden)

    CHEN Qiujie

    2016-04-01

    Full Text Available To recover the highly accurate static earth's gravity field by using GRACE satellite data is one of the hot topics in geodesy. Since linearization errors of dynamic approach quickly increase when extending satellite arc length, we established a modified dynamic approach for processing GRACE orbit and range-rate measurements in this paper, which treated orbit observations of the twin GRACE satellites as approximate values for linearization. Using the GRACE data spanning the period Jan. 2003 to Dec. 2010, containing satellite attitudes, orbits, range-rate, and non-conservative forces, we developed two global static gravity field models. One is the unconstrained solution called Tongji-Dyn01s complete to degree and order 180; the other one is the Tongji-Dyn01k model computed by using Kaula constraint. The comparisons between our models and those latest GRACE-only models (including the AIUB-GRACE03, the GGM05S, the ITSG-Grace2014k and the Tongji-GRACE01 published by different international groups, and the external validations with marine gravity anomalies from DTU13 product and height anomalies from GPS/levelling data, were performed in this study. The results demonstrate that the Tongji-Dyn01s has the same accuracy level with those of the latest GRACE-only models, while the Tongji-Dyn01k model is closer to the EIGEN6C2 than the other GRACE-only models as a whole.

  15. 3-D GRACE gravity model for the 2011 Japan earthquake

    Science.gov (United States)

    Sastry, Rambhatla G.; Sonker, Mahendra K.

    2017-02-01

    The GRACE mission has contributed to the seismic characterization of major earthquakes in offshore regions of the world. Here, we isolate satellite gravity signal (μGal range) for the Japan Earthquake of 2011 using a difference method. Contrary to the existing gravity models, we propose a unit vertical pyramid based five-layer 3-D thrust fault model, which extends to the hypocenter and honors the ocean water layer and sea floor upheaval also. Our model partly uses existing seismological information (hypocenter depth of 32 km, rupture length of 300 km and vertical slip of 4 m), provides a snapshot of episodic subduction of the Pacific Plate below the Atlantic Plate and its gravity response closely matches the observed gravity (RMS error of 3.4012×10-13μGal), fully accounting for co-seismic mass redistribution including sea surface deformation. Our inferred rupture length, rupture velocity, average seismic moment magnitude and momentum, respectively, are 300 km, 4.49 km/s, 1.152×1021-1.8816×1021 N m and 2.319×106 GNs, which fairly agree with the literature. Further, our model inferred momentum at the sea floor corresponds to an area pulse that led to Tsunami generation.

  16. 3-D GRACE gravity model for the 2011 Japan earthquake

    Indian Academy of Sciences (India)

    Rambhatla G Sastry; Mahendra K Sonker

    2017-02-01

    The GRACE mission has contributed to the seismic characterization of major earthquakes in offshore regions of the world. Here, we isolate satellite gravity signal (μGal range) for the Japan Earthquake of 2011 using a difference method. Contrary to the existing gravity models, we propose a unit vertical pyramid based five-layer 3-D thrust fault model, which extends to the hypocenter and honors the ocean water layer and sea floor upheaval also. Our model partly uses existing seismological information (hypocenter depth of 32 km, rupture length of 300 km and vertical slip of 4 m), provides a snapshot of episodic subduction of the Pacific Plate below the Atlantic Plate and its gravity response closely matches the observed gravity (RMS error of 3.4012×10−13μGal), fully accounting for co-seismic mass redistribution including sea surface deformation. Our inferred rupture length, rupture velocity, average seismic moment magnitude and momentum, respectively, are 300 km, 4.49 km/s, 1.152×1021 −1.8816×1021 N m and 2.319×106 GNs, which fairly agree with the literature. Further, our model inferred momentum at the sea floor corresponds to an area pulse that led to Tsunami generation.

  17. GRACE RL03-v2 monthly time series of solutions from CNES/GRGS

    Science.gov (United States)

    Lemoine, Jean-Michel; Bourgogne, Stéphane; Bruinsma, Sean; Gégout, Pascal; Reinquin, Franck; Biancale, Richard

    2015-04-01

    Based on GRACE GPS and KBR Level-1B.v2 data, as well as on LAGEOS-1/2 SLR data, CNES/GRGS has published in 2014 the third full re-iteration of its GRACE gravity field solutions. This monthly time series of solutions, named RL03-v1, complete to spherical harmonics degree/order 80, has displayed interesting performances in terms of spatial resolution and signal amplitude compared to JPL/GFZ/CSR RL05. This is due to a careful selection of the background models (FES2014 ocean tides, ECMWF ERA-interim (atmosphere) and TUGO (non IB-ocean) "dealiasing" models every 3 hours) and to the choice of an original method for gravity field inversion : truncated SVD. Identically to the previous CNES/GRGS releases, no additional filtering of the solutions is necessary before using them. Some problems have however been identified in CNES/GRGS RL03-v1: - an erroneous mass signal located in two small circular rings close to the Earth's poles, leading to the recommendation not to use RL03-v1 above 82° latitudes North and South; - a weakness in the sectorials due to an excessive downweighting of the GRACE GPS observations. These two problems have been understood and addressed, leading to the computation of a corrected time series of solutions, RL03-v2. The corrective steps have been: - to strengthen the determination of the very low degrees by adding Starlette and Stella SLR data to the normal equations; - to increase the weight of the GRACE GPS observations; - to adopt a two steps approach for the computation of the solutions: first a Choleski inversion for the low degrees, followed by a truncated SVD solution. The identification of these problems will be discussed and the performance of the new time series evaluated.

  18. Estimation of regional mass anomalies from Gravity Recovery and Climate Experiment (GRACE) over Himalayan region

    Science.gov (United States)

    Agrawal, R.; Singh, S. K.; Rajawat, A. S.; Ajai

    2014-11-01

    Time-variable gravity changes are caused by a combination of postglacial rebound, redistribution of water and snow/ice on land and as well as in the ocean. The Gravity Recovery and Climate Experiment (GRACE) satellite mission, launched in 2002, provides monthly average of the spherical harmonic co-efficient. These spherical harmonic co-efficient describe earth's gravity field with a resolution of few hundred kilometers. Time-variability of gravity field represents the change in mass over regional level with accuracies in cm in terms of Water Equivalent Height (WEH). The WEH reflects the changes in the integrated vertically store water including snow cover, surface water, ground water and soil moisture at regional scale. GRACE data are also sensitive towards interior strain variation, surface uplift and surface subsidence cover over a large area. GRACE data was extracted over the three major Indian River basins, Indus, Ganga and Brahmaputra, in the Himalayas which are perennial source of fresh water throughout the year in Northern Indian Plain. Time series analysis of the GRACE data was carried out from 2003-2012 over the study area. Trends and amplitudes of the regional mass anomalies in the region were estimated using level 3 GRACE data product with a spatial resolution at 10 by 10 grid provided by Center for Space Research (CSR), University of Texas at Austin. Indus basin has shown a subtle decreasing trend from 2003-2012 however it was observed to be statistically insignificant at 95 % confidence level. Ganga and Brahmaputra basins have shown a clear decreasing trend in WEH which was also observed to be statistically significant. The trend analysis over Ganga and Brahamputra basins have shown an average annual change of -1.28 cm and -1.06 cm in terms of WEH whereas Indus basin has shown a slight annual change of -0.07 cm. This analysis will be helpful to understand the loss of mass in terms of WEH over Indian Himalayas and will be crucial for hydrological and

  19. Large-scale Hydrology Inferred From Grace Estimates of Time-variable Gravity

    Science.gov (United States)

    Swenson, S.; Wahr, J.; Milly, P. C. D.

    In recent years, a number of techniques for remotely sensing the Earth's surface have been developed, including active and passive radiometers, synthetic aperture radar, and radar and laser altimeters. These instruments have produced measurements of a wide range of phenomena at temporal and spatial scales that are not feasible by in-situ methods. Surface soil moisture, one of the principal components of terrestrial water storage, can be measured by microwave techniques; however, only the moisture in the top few centimeters of soil can be detected. Sub-surface soil moisture and groundwater are thus far undetectable by radiation based remote sensing techniques. Measurements of changes in surface gravity are indicative of changes in the sur- rounding water column. U.S. Geological Survey scientists use repeat surface gravity measurements to monitor groundwater recharge. Surface in-situ measurement is not a practical approach for water storage estimation at large length scales, because of the high spatial variability of terrestrial water storage. Satellite-based gravity mea- surement, however, promises to provide estimates of continental groundwater change, averaged over regions of a few hundred km and larger. The GRACE satellite mission, scheduled for launch at the end of 2001, is expected to deliver global estimates of the Earth's gravity field approximately every 30 days. After removing the effects of the at- mosphere and oceans, GRACE gravity solutions can be inverted to determine changes in continental water storage. We describe methods of extracting the water storage signal from simulated hydrolog- ical gravity solutions constructed using a land surface model based on monthly global precipitation records. Spatial averaging kernels were created to isolate the gravity sig- nal of individual drainage basins without contamination from surrounding hydrologi- cal or oceanic gravity signals. We then estimated the probable accuracy of averaging kernels for basins of

  20. HUST-Grace2016s: A new GRACE static gravity field model derived from a modified dynamic approach over a 13-year observation period

    Science.gov (United States)

    Zhou, Hao; Luo, Zhicai; Zhou, Zebing; Zhong, Bo; Hsu, Houze

    2017-08-01

    The modified dynamic approach, where the observation vector and design matrix of observation equation are simultaneously filtered by empirical parameters, is implemented in this study. Using approximately 13 years (spanning from January 2003 to April 2015) of Gravity Recovery and Climate Experiment (GRACE) Level 1B data published by JPL and kinematic orbits published by ITSG, we developed a new GRACE static gravity field model called HUST-Grace2016s complete to degree and order 160. To evaluate the quality of our model, other GRACE-only gravity field models including AIUB-GRACE03S, GGM05S, ITG-Grace2010s, ITSG-Grace2014s and Tongji-GRACE01, are introduced for comparison. The difference degree amplitudes in terms of geoid height of our HUST-Grace2016s relative to GOCO05c are smaller than 1 mm and 1 cm before degree 100 and degree 138, respectively. In terms of global gravity anomalies and geoid heights relative to GOCO05c, the RMS values of our model up to degree 140 are 4.31 cm and 0.87 mGal respectively, which are smaller compared to AIUB-GRACE03S, GGM05S and Tongji-GRACE01. In addition, validated with GPS-leveling data in North America and the Netherlands, the standard deviation values of our HUST-Grace2016s model are 46.56 cm and 24.80 cm respectively, which also performs better than AIUB-GRACE03S, GGM05S and Tongji-GRACE01.

  1. Arctic Ocean gravity, geoid and sea-ice freeboard heights from ICESat and GRACE

    DEFF Research Database (Denmark)

    Forsberg, René; Skourup, Henriette

    2005-01-01

    Gravity Project in combination with GRACE gravity field models to derive an improved Arctic geoid model. This model is then used to convert ICESat measurements to sea-ice freeboard heights with a coarse lowest-level surface method. The derived freeboard heights show a good qualitative agreement...... all major tectonic features of the Arctic Ocean, and has an accuracy of 6 mGal compared to recent airborne gravity data, illustrating the usefulness of ICESat data for gravity field determination....

  2. GRACE Gravity Satellite Observations of Terrestrial Water Storage Changes for Drought Characterization in the Arid Land of Northwestern China

    Directory of Open Access Journals (Sweden)

    Yanping Cao

    2015-01-01

    Full Text Available Drought is a complex natural hazard which can have negative effects on agriculture, economy, and human life. In this paper, the primary goal is to explore the application of the Gravity Recovery and Climate Experiment (GRACE gravity satellite data for the quantitative investigation of the recent drought dynamic over the arid land of northwestern China, a region with scarce hydrological and meteorological observation datasets. The spatiotemporal characteristics of terrestrial water storage changes (TWSC were first evaluated based on the GRACE satellite data, and then validated against hydrological model simulations and precipitation data. A drought index, the total storage deficit index (TSDI, was derived on the basis of GRACE-recovered TWSC. The spatiotemporal distributions of drought events from 2003 to 2012 in the study region were obtained using the GRACE-derived TSDI. Results derived from TSDI time series indicated that, apart from four short-term (three months drought events, the study region experienced a severe long-term drought from May 2008 to December 2009. As shown in the spatial distribution of TSDI-derived drought conditions, this long-term drought mainly concentrated in the northwestern area of the entire region, where the terrestrial water storage was in heavy deficit. These drought characteristics, which were detected by TSDI, were consistent with local news reports and other researchers’ results. Furthermore, a comparison between TSDI and Standardized Precipitation Index (SPI implied that GRACE TSDI was a more reliable integrated drought indicator (monitoring agricultural and hydrological drought in terms of considering total terrestrial water storages for large regions. The GRACE-derived TSDI can therefore be used to characterize and monitor large-scale droughts in the arid regions, being of special value for areas with scarce observations.

  3. Greenland Ice Sheet Mass Loss from GRACE Monthly Models

    DEFF Research Database (Denmark)

    Sørensen, Louise Sandberg; Forsberg, René

    2010-01-01

    model ICE-5G and on ground measurements made in Scandinavia. We find that the PGR signal corresponds to a mass change signal of approximately -4 Gt per year. We conclude that there are large differences between these estimated mass change models. We find a total mass loss of 189, 146 and 67 Gt......The Greenland ice sheet is currently experiencing a net mass loss. There are however large discrepancies between the published qualitative mass loss estimates, based on different data sets and methods. There are even large differences between the results based on the same data sources...... these monthly global gravity models, we first calculate the gravity trend from these. When isolating the gravity trend signal, which is caused by the ice mass change, we first subtract the signal produced by the postglacial rebound (PGR) in Greenland. This is done by a simple method based on the ice history...

  4. EGSIEM combination service: combination of GRACE monthly K-band solutions on normal equation level

    Science.gov (United States)

    Meyer, Ulrich; Jean, Yoomin; Arnold, Daniel; Jäggi, Adrian

    2017-04-01

    The European Gravity Service for Improved Emergency Management (EGSIEM) project offers a scientific combination service, combining for the first time monthly GRACE gravity fields of different analysis centers (ACs) on normal equation (NEQ) level and thus taking all correlations between the gravity field coefficients and pre-eliminated orbit and instrument parameters correctly into account. Optimal weights for the individual NEQs are commonly derived by variance component estimation (VCE), as is the case for the products of the International VLBI Service (IVS) or the DTRF2008 reference frame realisation that are also derived by combination on NEQ-level. But variance factors are based on post-fit residuals and strongly depend on observation sampling and noise modeling, which both are very diverse in case of the individual EGSIEM ACs. These variance factors do not necessarily represent the true error levels of the estimated gravity field parameters that are still governed by analysis noise. We present a combination approach where weights are derived on solution level, thereby taking the analysis noise into account.

  5. Global gravity field models from the GPS positions of CHAMP, GRACE and GOCE satellites

    Science.gov (United States)

    Bezděk, A.; Sebera, J.; Klokočník, J.; Kostelecký, J.

    2012-04-01

    of the sample autocorrelation function and partial autocorrelation function of the residuals shows that their dependence structure might be represented by the autoregressive model. This indeed appears to be the case, upon applying the estimated autoregressive model, the residuals become uncorrelated and the geopotential harmonic coefficients improve by a factor of 2-3. We applied the presented method to orbits of CHAMP and GRACE covering 7 years (2003-2009) and to two months of GOCE (Nov/Dec 2009). The obtained long-term static gravity field models are of similar or better quality compared to other published solutions. We also tried to extract the time variable gravity signal from the CHAMP and GRACE orbits. Based on the data covering several years, we obtained the average annual continental hydrology signal, where the main geographical areas with important hydrological variations are evident.

  6. Improved source parameter constraints for five undersea earthquakes from north component of GRACE gravity and gravity gradient change measurements

    Science.gov (United States)

    Dai, Chunli; Shum, C. K.; Guo, Junyi; Shang, Kun; Tapley, Byron; Wang, Rongjiang

    2016-06-01

    The innovative processing of Gravity Recovery And Climate Experiment (GRACE) data using only the north component of gravity change and its corresponding gravity gradient changes allows the enhancement of the spatial resolution for coseismic deformation signals. Here, we report the study of five undersea earthquakes using this technique: the 2004 Sumatra-Andaman earthquake, the 2007 Bengkulu earthquake, the 2010 Maule, Chile earthquake, the 2011 Tohoku earthquake, and the 2012 Indian Ocean earthquakes. By using the high spherical harmonic degree (up to degree 96) data products and the associated GRACE data processing techniques, the retrieved north component of gravity change is up to - 34 ± 1.4 μGal for the 2004 Sumatra-Andaman earthquake, which illustrates by far the highest amplitude of the coseismic signal retrieved from satellite gravimetry among previous studies. We creatively apply the localized spectral analysis as an efficient method to empirically determine the practical spherical harmonic truncation degree. By combining least squares adjustment with the simulated annealing algorithm, point source parameters are estimated, which demonstrates the unique constraint on source model from GRACE data compared to other data sources. For the 2004 Sumatra-Andaman earthquake, GRACE data produce a shallower centroid depth (9.1 km), as compared to the depth (28.3 km) from GPS data. For the 2011 Tohoku earthquake, the GRACE-estimated centroid location is southwest of the GPS/seismic solutions, and the slip orientation is about 10° clockwise from the published GPS/seismic slip models. We concluded that these differences demonstrate the additional and critical offshore constraint by GRACE on source parameters, as compared to GPS/seismic data.

  7. Measuring the Value of Earth Observation Information with the Gravity Research and Climate Experiment (GRACE) Satellite

    Science.gov (United States)

    Bernknopf, R.; Kuwayama, Y.; Brookshire, D.; Macauley, M.; Zaitchik, B.; Pesko, S.; Vail, P.

    2014-12-01

    Determining how much to invest in earth observation technology depends in part on the value of information (VOI) that can be derived from the observations. We design a framework and then evaluate the value-in-use of the NASA Gravity Research and Climate Experiment (GRACE) for regional water use and reliability in the presence of drought. As a technology that allows measurement of water storage, the GRACE Data Assimilation System (DAS) provides information that is qualitatively different from that generated by other water data sources. It provides a global, reproducible grid of changes in surface and subsurface water resources on a frequent and regular basis. Major damages from recent events such as the 2012 Midwest drought and the ongoing drought in California motivate the need to understand the VOI from remotely sensed data such as that derived from GRACE DAS. Our conceptual framework models a dynamic risk management problem in agriculture. We base the framework on information from stakeholders and subject experts. The economic case for GRACE DAS involves providing better water availability information. In the model, individuals have a "willingness to pay" (wtp) for GRACE DAS - essentially, wtp is an expression of savings in reduced agricultural input costs and for costs that are influenced by regional policy decisions. Our hypothesis is that improvements in decision making can be achieved with GRACE DAS measurements of water storage relative to data collected from groundwater monitoring wells and soil moisture monitors that would be relied on in the absence of GRACE DAS. The VOI is estimated as a comparison of outcomes. The California wine grape industry has features that allow it to be a good case study and a basis for extrapolation to other economic sectors. We model water use in this sector as a sequential decision highlighting the attributes of GRACE DAS input as information for within-season production decisions as well as for longer-term water reliability.

  8. Gravity Recovery and Climate Experiment (GRACE) detection of water storage changes in the Three Gorges Reservoir of China and comparison with in situ measurements

    Science.gov (United States)

    Wang, Xianwei; de Linage, Caroline; Famiglietti, James; Zender, Charles S.

    2011-12-01

    Water impoundment in the Three Gorges Reservoir (TGR) of China caused a large mass redistribution from the oceans to a concentrated land area in a short time period. We show that this mass shift is captured by the Gravity Recovery and Climate Experiment (GRACE) unconstrained global solutions at a 400 km spatial resolution after removing correlated errors. The WaterGAP Global Hydrology Model (WGHM) is selected to isolate the TGR contribution from regional water storage changes. For the first time, this study compares the GRACE (minus WGHM) estimated TGR volume changes with in situ measurements from April 2002 to May 2010 at a monthly time scale. During the 8 year study period, GRACE-WGHM estimated TGR volume changes show an increasing trend consistent with the TGR in situ measurements and lead to similar estimates of impounded water volume. GRACE-WGHM estimated total volume increase agrees to within 14% (3.2 km3) of the in situ measurements. This indicates that GRACE can retrieve the true amplitudes of large surface water storage changes in a concentrated area that is much smaller than the spatial resolution of its global harmonic solutions. The GRACE-WGHM estimated TGR monthly volume changes explain 76% (r2 = 0.76) of in situ measurement monthly variability and have an uncertainty of 4.62 km3. Our results also indicate reservoir leakage and groundwater recharge due to TGR filling and contamination from neighboring lakes are nonnegligible in the GRACE total water storage changes. Moreover, GRACE observations could provide a relatively accurate estimate of global water volume withheld by newly constructed large reservoirs and their impacts on global sea level rise since 2002.

  9. High resolution time-lapse gravity field from GRACE for hydrological modelling

    DEFF Research Database (Denmark)

    Krogh, Pernille Engelbredt

    Calibration of large scale hydrological models have traditionally been performed using point observations, which are often sparsely distributed. The Gravity Recovery And Climate Experiment (GRACE) mission provides global remote sensing information about mass fluxes with unprecedented accuracy......-catchments, derived for the river basin from a digital elevation model. The hydrological model is initially calibrated to discharge and mass variations in a 1.251.5 grid every ten days from five years of GRACE mascon only solutions, using a joint sequential calibration function. Coupling of the mascon method...... with the hydrological model is done by chaining of partial derivatives, so that the normal equation system is solved for model parameters instead of mascon parameters. The mass variations from GRACE are relative, meaning that the origin is arbitrary, while the terrestrial water storage variations from model...

  10. Arctic Ocean gravity, geoid and sea-ice freeboard heights from ICESat and GRACE

    DEFF Research Database (Denmark)

    Forsberg, René; Skourup, Henriette

    2005-01-01

    ICESat laser measurements provide a high-resolution mapping of the sea-ice surface of the Arctic Ocean, which can be inverted to determine gravity anomalies and sea-ice freeboard heights by a "lowest-level'' filtering scheme. In this paper we use updated terrestrial gravity data from the Arctic...... all major tectonic features of the Arctic Ocean, and has an accuracy of 6 mGal compared to recent airborne gravity data, illustrating the usefulness of ICESat data for gravity field determination....... Gravity Project in combination with GRACE gravity field models to derive an improved Arctic geoid model. This model is then used to convert ICESat measurements to sea-ice freeboard heights with a coarse lowest-level surface method. The derived freeboard heights show a good qualitative agreement...

  11. Application of GRACE to the assessment of model-based estimates of monthly Greenland Ice Sheet mass balance (2003-2012)

    Science.gov (United States)

    Schlegel, Nicole-Jeanne; Wiese, David N.; Larour, Eric Y.; Watkins, Michael M.; Box, Jason E.; Fettweis, Xavier; van den Broeke, Michiel R.

    2016-09-01

    Quantifying the Greenland Ice Sheet's future contribution to sea level rise is a challenging task that requires accurate estimates of ice sheet sensitivity to climate change. Forward ice sheet models are promising tools for estimating future ice sheet behavior, yet confidence is low because evaluation of historical simulations is challenging due to the scarcity of continental-wide data for model evaluation. Recent advancements in processing of Gravity Recovery and Climate Experiment (GRACE) data using Bayesian-constrained mass concentration ("mascon") functions have led to improvements in spatial resolution and noise reduction of monthly global gravity fields. Specifically, the Jet Propulsion Laboratory's JPL RL05M GRACE mascon solution (GRACE_JPL) offers an opportunity for the assessment of model-based estimates of ice sheet mass balance (MB) at ˜ 300 km spatial scales. Here, we quantify the differences between Greenland monthly observed MB (GRACE_JPL) and that estimated by state-of-the-art, high-resolution models, with respect to GRACE_JPL and model uncertainties. To simulate the years 2003-2012, we force the Ice Sheet System Model (ISSM) with anomalies from three different surface mass balance (SMB) products derived from regional climate models. Resulting MB is compared against GRACE_JPL within individual mascons. Overall, we find agreement in the northeast and southwest where MB is assumed to be primarily controlled by SMB. In the interior, we find a discrepancy in trend, which we presume to be related to millennial-scale dynamic thickening not considered by our model. In the northwest, seasonal amplitudes agree, but modeled mass trends are muted relative to GRACE_JPL. Here, discrepancies are likely controlled by temporal variability in ice discharge and other related processes not represented by our model simulations, i.e., hydrological processes and ice-ocean interaction. In the southeast, GRACE_JPL exhibits larger seasonal amplitude than predicted by the

  12. Detection of co-seismic earthquake gravity field signals using GRACE-like mission simulations

    Science.gov (United States)

    Sharifi, Mohammad Ali; Shahamat, Abolfazl

    2017-05-01

    After launching the GRACE satellite mission in 2002, the earth's gravity field and its temporal variations are measured with a closer inspection. Although these variations are mainly because of the mass transfer of land water storage, they can also happen due to mass movements related to some natural phenomena including earthquakes, volcanic eruptions, melting of polar ice caps and glacial isostatic adjustment. Therefore this paper shows which parameters of an earthquake are more sensitive to GRACE-Like satellite missions. For this purpose, the parameters of the Maule earthquake that occurred in recent years and Alaska earthquake that occurred in 1964 have been chosen. Then we changed their several parameters to serve our purpose. The GRACE-Like sensitivity is observed by using the simulation of the earthquakes along with gravity changes they caused, as well as using dislocation theory under a half space earth. This observation affects the various faulting parameters which include fault length, width, depth and average slip. These changes were therefore evaluated and the result shows that the GRACE satellite missions tend to be more sensitive to Width among the Length and Width, the other parameter is Dip variations than other parameters. This article can be useful to the upcoming scenario designers and seismologists in their quest to study fault parameters.

  13. Modelling the Earth's static and time-varying gravity field using a combination of GRACE and GOCE data

    NARCIS (Netherlands)

    Farahani, H.H.

    2013-01-01

    The main focus of the thesis is modelling the static and time-varying parts of the Earth's gravity field at the global scale based on data acquired by the Gravity Recovery And Climate Experiment (GRACE) and Gravity field and steady-state Ocean Circulation Explorer (GOCE). In addition, a new

  14. Modelling the Earth's static and time-varying gravity field using a combination of GRACE and GOCE data

    NARCIS (Netherlands)

    Farahani, H.H.

    2013-01-01

    The main focus of the thesis is modelling the static and time-varying parts of the Earth's gravity field at the global scale based on data acquired by the Gravity Recovery And Climate Experiment (GRACE) and Gravity field and steady-state Ocean Circulation Explorer (GOCE). In addition, a new methodol

  15. Identifying presence of correlated errors in GRACE monthly harmonic coefficients using machine learning algorithms

    Science.gov (United States)

    Piretzidis, Dimitrios; Sra, Gurveer; Karantaidis, George; Sideris, Michael G.

    2017-04-01

    A new method for identifying correlated errors in Gravity Recovery and Climate Experiment (GRACE) monthly harmonic coefficients has been developed and tested. Correlated errors are present in the differences between monthly GRACE solutions, and can be suppressed using a de-correlation filter. In principle, the de-correlation filter should be implemented only on coefficient series with correlated errors to avoid losing useful geophysical information. In previous studies, two main methods of implementing the de-correlation filter have been utilized. In the first one, the de-correlation filter is implemented starting from a specific minimum order until the maximum order of the monthly solution examined. In the second one, the de-correlation filter is implemented only on specific coefficient series, the selection of which is based on statistical testing. The method proposed in the present study exploits the capabilities of supervised machine learning algorithms such as neural networks and support vector machines (SVMs). The pattern of correlated errors can be described by several numerical and geometric features of the harmonic coefficient series. The features of extreme cases of both correlated and uncorrelated coefficients are extracted and used for the training of the machine learning algorithms. The trained machine learning algorithms are later used to identify correlated errors and provide the probability of a coefficient series to be correlated. Regarding SVMs algorithms, an extensive study is performed with various kernel functions in order to find the optimal training model for prediction. The selection of the optimal training model is based on the classification accuracy of the trained SVM algorithm on the same samples used for training. Results show excellent performance of all algorithms with a classification accuracy of 97% - 100% on a pre-selected set of training samples, both in the validation stage of the training procedure and in the subsequent use of

  16. Monitoring groundwater storage change in Mekong Delta using Gravity Recovery and Climate Experiment (GRACE) data

    Science.gov (United States)

    Aierken, A.; Lee, H.; Hossain, F.; Bui, D. D.; Nguyen, L. D.

    2016-12-01

    The Mekong Delta, home to almost 20 million inhabitants, is considered one of the most important region for Vietnam as it is the agricultural and industrial production base of the nation. However, in recent decades, the region is seriously threatened by variety of environmental hazards, such as floods, saline water intrusion, arsenic contamination, and land subsidence, which raise its vulnerability to sea level rise due to global climate change. All these hazards are related to groundwater depletion, which is the result of dramatically increased over-exploitation. Therefore, monitoring groundwater is critical to sustainable development and most importantly, to people's life in the region. In most countries, groundwater is monitored using well observations. However, because of its spatial and temporal gaps and cost, it is typically difficult to obtain large scale, continuous observations. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) satellite gravimetry mission has delivered freely available Earth's gravity variation data, which can be used to obtain terrestrial water storage (TWS) changes. In this study, the TWS anomalies over the Mekong Delta, which are the integrated sum of anomalies of soil moisture storage (SMS), surface water storage (SWS), canopy water storage (CWS), groundwater storage (GWS), have been obtained using GRACE CSR RL05 data. The leakage error occurred due to GRACE signal processing has been corrected using several different approaches. The groundwater storage anomalies were then derived from TWS anomalies by removing SMS, and CWS anomalies simulated by the four land surface models (NOAH, CLM, VIC and MOSAIC) in the Global Land Data Assimilation System (GLDAS), as well as SWS anomalies estimated using ENVISAT satellite altimetry and MODIS imagery. Then, the optimal GRACE signal restoration method for the Mekong Delta is determined with available in-situ well data. The estimated GWS anomalies revealed continuously decreasing

  17. Spectral assessment of isostatic gravity models against CHAMP, GRACE, GOCE satellite-only and combined gravity models

    Science.gov (United States)

    Tsoulis, Dimitrios; Patlakis, Konstantinos

    2014-08-01

    The availability of digital elevation databases representing the topographic and bathymetric relief with global homogeneous coverage and increasing resolution permits the computation of crust-related Earth gravity models, the so-called topographic/isostatic Earth gravity models (henceforth T/I models). Although expressing the spherical harmonic content of the topographic masses, the interpretation purpose of T/I models has not been given the attention it deserves, apart from the fact that they express some degree of compensation to the observed spectrum of the topographic heights, depending on the kind of the applied compensation mechanism. The present contribution attempts to improve the interpretation aspects of T/I Earth gravity models. To this end, a rigorous spectral assessment is performed to a standard Airy/Heiskanen T/I model against different CHAllenging Minisatellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), Gravity field and steadystate Ocean Circulation Explorer (GOCE) satellite-only, and combined gravity models. Different correlation bandwidths emerge for these four groups of satellite-based gravity models. The band-limited forward computation of the models using these bandwidths reproduces nicely the main features of the applied T/I model.

  18. Can the Gravity Recovery and Climate Experiment (GRACE) mission detect hydrological droughts?

    Science.gov (United States)

    Agustin Brena Naranjo, Jose; Pedrozo Acuña, Adrian

    2016-04-01

    Detecting and characterizing hydrological droughts at the global scale is a difficult task as several thousands of mid-to-large catchments remain ungauged or have limited discharge records. In water-limited regions, research on hydrological drought is even more complex because of the dominant streamflow perennial regime that characterizes small order watersheds. Over the last decade, the emergence of global remote sensing products has remarkably improved the capability to observe different climate and land surface processes that affect catchment discharge. Among several observational satellites that provide continuous data on terrestrial hydrology, the Gravity Recovery and Climate Experiment (GRACE) is perhaps the only tool able to retrieve information about large-scale water storage variations across the world's terrestrial surface. This work tests the hypothesis that water storage deficits derived from GRACE are inextricably linked to below-than-average baseflow values extracted from streamflow records. This study case analyzed several regions in Mexico and USA with different hydro-climate regimes. Drought conditions using total water storage variations and observed streamflow records from 2003 until 2013 were computed and compared. Results indicate that although the GRACE mission is moderately/highly correlated to streamflow and baseflow time series, discrepancies in the magnitude of hydrological deficit exist and can be attributed to active versus passive catchment storage issues. Finally, the suitability of creating an improved product to monitor hydrological drought by merging in situ with remote sensed information will be discussed.

  19. Improved drought indicators based on Gravity Recovery and Climate Experiment (GRACE), water balance components and soil moisture

    Science.gov (United States)

    Saemian, Peyman; Tourian, Mohammad J.; Sneeuw, Nico

    2017-04-01

    Drought, as a natural recurring hazard, can occur in virtually all climate zones. In recent years, severe large scale droughts have been detected in all continents including large areas in Europe. A change in water storage, which is the combination of groundwater, snow, and soil moisture, can indicate deficiencies in water storage in general. Such deficiencies may be related to any of its components or even a combination of them. We present here a new water storage deficiency index that has been developed using the terrestrial water storage (TWS) change from the Gravity Recovery and Climate Experiment (GRACE) and global water balance components data (Precipitation, Evapotranspiration and Runoff). First, for each monthly time series of TWS we calculate differences of water storage from a climatology that has been obtained from the long term water balance components time series. We then turn the differences into meaningful indices with the help of soil moisture data that characterizes agricultural drought. Our indexes identifies variation in water storage in general and characterizes groundwater drought including onset, severity, and duration of drought periods. Our results highlight the ability of GRACE TWS in combination with global water balance fluxes as an invaluable source to detect and monitor groundwater and groundwater drought which is a vital step for the planning and management of water resources both at local and global scales.

  20. Comparison and validation of combined GRACE/GOCE models of the Earth's gravity field

    Science.gov (United States)

    Hashemi Farahani, H.; Ditmar, P.

    2012-04-01

    Accurate global models of the Earth's gravity field are needed in various applications: in geodesy - to facilitate the production of a unified global height system; in oceanography - as a source of information about the reference equipotential surface (geoid); in geophysics - to draw conclusions about the structure and composition of the Earth's interiors, etc. A global and (nearly) homogeneous set of gravimetric measurements is being provided by the dedicated satellite mission Gravity Field and Steady-State Ocean Circulation Explorer (GOCE). In particular, Satellite Gravity Gradiometry (SGG) data acquired by this mission are characterized by an unprecedented accuracy/resolution: according to the mission objectives, they must ensure global geoid modeling with an accuracy of 1 - 2 cm at the spatial scale of 100 km (spherical harmonic degree 200). A number of new models of the Earth's gravity field have been compiled on the basis of GOCE data in the course of the last 1 - 2 years. The best of them take into account also the data from the satellite gravimetry mission Gravity Recovery And Climate Experiment (GRACE), which offers an unbeatable accuracy in the range of relatively low degrees. Such combined models contain state-of-the-art information about the Earth's gravity field up to degree 200 - 250. In the present study, we compare and validate such models, including GOCO02, EIGEN-6S, and a model compiled in-house. In addition, the EGM2008 model produced in the pre-GOCE era is considered as a reference. The validation is based on the ability of the models to: (i) predict GRACE K-Band Ranging (KBR) and GOCE SGG data (not used in the production of the models under consideration), and (ii) synthesize a mean dynamic topography model, which is compared with the CNES-CLS09 model derived from in situ oceanographic data. The results of the analysis demonstrate that the GOCE SGG data lead not only to significant improvements over continental areas with a poor coverage with

  1. Changes in water storage in Australia as resolved using GRACE gravity field solutions

    Science.gov (United States)

    Fleming, Kevin; Awange, Joseph; Anjasmara, Ira; Kuhn, Michael; Featherstone, Will; Sarukkalige, Priyantha

    2010-05-01

    The GRACE gravity field solutions have been used in several studies to provide some constraint on how terrestrial water storage in Australia is changing, especially given the recent drought that has afflicted much of the country for most of the past decade. In this study we look at four regions of Australia, and compare/contrast how GRACE describes the behaviour of the terrestrial water storage. These areas are the Murray-Darling River Basin (MDRB) in the southeast corner of Australia, one of the primary agricultural regions that have been seriously afflicted by the drought, monsoonal Northern Australia, which has seen an increase in terrestrial water storage, the southwest corner of Western Australia (SWWA), another area of regional agricultural importance and the Lake Eyre district, an area that is usually extremely dry, but experiences occasional flooding. We make use of the mascon solutions from the Goddard Space Science Laboratory, and apply principle component analysis to identify the most important spatial and temporal trend variability in the GRACE solutions. These are in turn compared to other datasets, namely ground truth data such as groundwater levels and river gauges from various government agencies (e.g. the Western Australian Department of Water), as well as precipitation data from the Tropical Rainfall Measuring Mission. Loss of mass, interpreted as a decrease in stored terrestrial water, is identified from the GRACE time series for the MRDB and SWWA, while an increase is seen in the monsoonal north, with significant mass fluctuations noted around Lake Eyre which are correlated with flooding events in other parts of Australia, e.g. Queensland.

  2. Seasonal changes in the European gravity field from GRACE: A comparison with superconducting gravimeters and hydrology model predictions

    DEFF Research Database (Denmark)

    Hinderer, J.; Andersen, Ole Baltazar; Lemoine, F.

    2006-01-01

    This paper is devoted to the investigation of seasonal changes of the Earth's gravity field from GRACE satellites and the comparison with surface gravity measurements in Europe from the Global Geodynamics Project (GGP) sub-network, as well as with recent hydrology models for continental soil......-derived and ground gravity changes due to continental hydrology is studied and we also compute the theoretical ratio of gravity versus radial displacement (in mu Gal/mm) involved in the hydrological loading process. The 'mean' value (averaged in time and in space over Europe) from hydrologic forward modeling...... is found to be close to - 1.0 mu Gal/mm and we show that this value can be explained by a strong low degree (n = 5-6) peak in the hydrology amplitude spectrum. The dominant time-variable signal from GRACE is found to be annual with an amplitude and a phase both of which are in fair agreement...

  3. Seasonal changes in the European gravity field from GRACE: A comparison with superconducting gravimeters and hydrology model predictions

    DEFF Research Database (Denmark)

    Hinderer, J.; Andersen, Ole Baltazar; Lemoine, F.

    2006-01-01

    is found to be close to - 1.0 mu Gal/mm and we show that this value can be explained by a strong low degree (n = 5-6) peak in the hydrology amplitude spectrum. The dominant time-variable signal from GRACE is found to be annual with an amplitude and a phase both of which are in fair agreement......This paper is devoted to the investigation of seasonal changes of the Earth's gravity field from GRACE satellites and the comparison with surface gravity measurements in Europe from the Global Geodynamics Project (GGP) sub-network, as well as with recent hydrology models for continental soil......-derived and ground gravity changes due to continental hydrology is studied and we also compute the theoretical ratio of gravity versus radial displacement (in mu Gal/mm) involved in the hydrological loading process. The 'mean' value (averaged in time and in space over Europe) from hydrologic forward modeling...

  4. Electrostatic Accelerometer for the Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Lebat, V.; Foulon, B.; Christophe, B.

    2013-12-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, that will produce an accurate model of the Earth's gravity field variation providing global climatic data during five year at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Non-uniformities in the distribution of the Earth's mass cause the distance between the two satellites to vary. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics and the Front-End Electronic Unit) and the Interface Control Unit. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained in a center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench and with drops in ZARM catapult. Besides, a thermal stability is needed for the accelerometer core and front-end electronics to avoid bias and scale factor variation, and reached by a thermal box designed by Astrium, spacecraft manufacturer. The accelerometers are designed to endure the launch vibrations and the thermal environment at

  5. Trends in gravity changes from 2009 to 2013 derived from ground-based gravimetry and GRACE data in North China

    Directory of Open Access Journals (Sweden)

    Chongyang Shen

    2015-11-01

    Full Text Available North China is a key region for studying geophysical progress. In this study, ground-based and Gravity Recovery and Climate Experiment (GRACE gravity data from 2009 to 2013 are used to calculate the gravity change rate (GCR using the polynomial fitting method. In general, the study area was divided into the Shanxi rift, Jing-Jin-Ji (Beijing-Tianjin-Hebei Province, and Bohai Bay Basin (BBB regions. Results of the distribution of the GCR determined from ground-based gravimetry show that the GCR appears to be “negative-positive-negative” from west to east, which indicates that different geophysical mechanisms are involved in the tectonic activities of these regions. However, GRACE solutions are conducted over a larger spatial scale and are able to show a difference between southern and northern areas and a mass redistribution of land water storage.

  6. Application of the Convolution Formalism to the Ocean Tide Potential: Results from the Gravity and Recovery and Climate Experiment (GRACE)

    Science.gov (United States)

    Desai, S. D.; Yuan, D. -N.

    2006-01-01

    A computationally efficient approach to reducing omission errors in ocean tide potential models is derived and evaluated using data from the Gravity Recovery and Climate Experiment (GRACE) mission. Ocean tide height models are usually explicitly available at a few frequencies, and a smooth unit response is assumed to infer the response across the tidal spectrum. The convolution formalism of Munk and Cartwright (1966) models this response function with a Fourier series. This allows the total ocean tide height, and therefore the total ocean tide potential, to be modeled as a weighted sum of past, present, and future values of the tide-generating potential. Previous applications of the convolution formalism have usually been limited to tide height models, but we extend it to ocean tide potential models. We use luni-solar ephemerides to derive the required tide-generating potential so that the complete spectrum of the ocean tide potential is efficiently represented. In contrast, the traditionally adopted harmonic model of the ocean tide potential requires the explicit sum of the contributions from individual tidal frequencies. It is therefore subject to omission errors from neglected frequencies and is computationally more intensive. Intersatellite range rate data from the GRACE mission are used to compare convolution and harmonic models of the ocean tide potential. The monthly range rate residual variance is smaller by 4-5%, and the daily residual variance is smaller by as much as 15% when using the convolution model than when using a harmonic model that is defined by twice the number of parameters.

  7. Understanding data noise in gravity field recovery on the basis of inter-satellite ranging measurements acquired by the satellite gravimetry mission GRACE

    NARCIS (Netherlands)

    Ditmar, P.; Teixeira da Encarnacao, J.; Hashemi Farahani, H.

    2012-01-01

    Spectral analysis of data noise is performed in the context of gravity field recovery from inter-satellite ranging measurements acquired by the satellite gravimetry mission GRACE. The motivation of the study is two-fold: (i) to promote a further improvement of GRACE data processing techniques and

  8. Electrostatic Accelerometer for the Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, Eddy; Boulanger, Damien; Christophe, Bruno; Foulon, Bernard; Liorzou, Françoise; Lebat, Vincent

    2014-05-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, that will produce an accurate model of the Earth's gravity field variation providing global climatic data during five year at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link, and optionally a laser link, measuring the inter-satellites distance variation. Non-uniformities in the distribution of the Earth's mass cause the distance between the two satellites to vary. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained in a center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The Preliminary Design Review was achieved successfully on November 2013. The FEEU Engineering Model is under test. Preliminary results on electronic unit will be compared with the expected performance. The integration of the SUM Engineering Model and the first ground levitation of the proof-mass will be presented. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with

  9. CO-SEISMIC GRAVITY GRADIENT CHANGES OF THE 2006–2007 GREAT EARTHQUAKES IN THE CENTRAL KURIL ISLANDS FROM GRACE OBSERVATIONS

    Directory of Open Access Journals (Sweden)

    A. Rahimi

    2017-09-01

    Full Text Available GRACE satellites (the Gravity Recovery And climate Experiment are very useful sensors to extract gravity anomalies after earthquakes. In this study, we reveal co-seismic signals of the two combined earthquakes, the 2006 Mw8.3 thrust and 2007 Mw8.1 normal fault earthquakes of the central Kuril Islands from GRACE observations. We compute monthly full gravitational gradient tensor in the local north-east-down frame for Kuril Islands earthquakes without spatial averaging and de-striping filters. Some of gravitational gradient components (e.g. ΔVxx, ΔVxz enhance high frequency components of the earth gravity field and reveal more details in spatial and temporal domain. Therefore, co-seismic activity can be better illustrated. For the first time, we show that the positive-negative-positive co-seismic ΔVxx due to the Kuril Islands earthquakes ranges from − 0.13 to + 0.11 milli Eötvös, and ΔVxz shows a positive-negative-positive pattern ranges from − 0.16 to + 0.13 milli Eötvös, agree well with seismic model predictions.

  10. Long Range River Discharge Forecasting Using the Gravity Recovery and Climate Experiment (GRACE) Satellite to Predict Conditions for Endemic Cholera

    Science.gov (United States)

    Jutla, A.; Akanda, A. S.; Colwell, R. R.

    2014-12-01

    Prediction of conditions of an impending disease outbreak remains a challenge but is achievable if the associated and appropriate large scale hydroclimatic process can be estimated in advance. Outbreaks of diarrheal diseases such as cholera, are related to episodic seasonal variability in river discharge in the regions where water and sanitation infrastructure are inadequate and insufficient. However, forecasting river discharge, few months in advance, remains elusive where cholera outbreaks are frequent, probably due to non-availability of geophysical data as well as transboundary water stresses. Here, we show that satellite derived water storage from Gravity Recovery and Climate Experiment Forecasting (GRACE) sensors can provide reliable estimates on river discharge atleast two months in advance over regional scales. Bayesian regression models predicted flooding and drought conditions, a prerequisite for cholera outbreaks, in Bengal Delta with an overall accuracy of 70% for upto 60 days in advance without using any other ancillary ground based data. Forecasting of river discharge will have significant impacts on planning and designing intervention strategies for potential cholera outbreaks in the coastal regions where the disease remain endemic and often fatal.

  11. Coseismic and post-seismic signatures of the Sumatra 2004 December and 2005 March earthquakes in GRACE satellite gravity

    Science.gov (United States)

    Panet, I.; Mikhailov, V.; Diament, M.; Pollitz, F.; King, G.; de Viron, O.; Holschneider, M.; Biancale, R.; Lemoine, J.-M.

    2007-01-01

    The GRACE satellite mission has been measuring the Earth's gravity field and its temporal variations since 2002 April. Although these variations are mainly due to mass transfer within the geofluid envelops, they also result from mass displacements associated with phenomena including glacial isostatic adjustment and earthquakes. However, these last contributions are difficult to isolate because of the presence of noise and of geofluid signals, and because of GRACE's coarse spatial resolution (>400 km half-wavelength). In this paper, we show that a wavelet analysis on the sphere helps to retrieve earthquake signatures from GRACE geoid products. Using a wavelet analysis of GRACE geoids products, we show that the geoid variations caused by the 2004 December (Mw = 9.2) and 2005 March (Mw = 8.7) Sumatra earthquakes can be detected. At GRACE resolution, the 2004 December earthquake produced a strong coseismic decrease of the gravity field in the Andaman Sea, followed by relaxation in the area affected by both the Andaman 2004 and the Nias 2005 earthquakes. We find two characteristic timescales for the relaxation, with a fast variation occurring in the vicinity of the Central Andaman ridge. We discuss our coseismic observations in terms of density changes of crustal and upper-mantle rocks, and of the vertical displacements in the Andaman Sea. We interpret the post-seismic signal in terms of the viscoelastic response of the Earth's mantle. The transient component of the relaxation may indicate the presence of hot, viscous material beneath the active Central Andaman Basin. ?? 2007 The Authors Journal compilation ?? 2007 RAS.

  12. A GRACE-based water storage deficit approach for hydrological drought characterization

    OpenAIRE

    Thomas, AC; Reager, JT; Famiglietti, JS; M. Rodell

    2014-01-01

    We present a quantitative approach for measuring hydrological drought occurrence and severity based on terrestrial water storage observations from NASA's Gravity Recovery and Climate Experiment (GRACE) satellite mission. GRACE measurements are applied by calculating the magnitude of the deviation of regional, monthly terrestrial water storage anomalies from the time series' monthly climatology, where negative deviations represent storage deficits. Monthly deficits explicitly quantify the volu...

  13. Robust estimation of error covariance functions in GRACE gravity field determination

    Science.gov (United States)

    Behzadpour, Saniya; Mayer-Gürr, Torsten; Flury, Jakob

    2016-04-01

    The accurate modelling of the stochastic behaviour of the GRACE mission observations is an important task in the time variable gravity field determination. After fitting a model in the least-squares sense, it is necessary to determine whether all the necessary model assumptions, i.e., independence, normality, and homoscedasticity of the residuals, are valid before performing inference. Checking the model assumptions for the range rate residuals, it has been concluded that one of the major problems in the range rate observations is the outliers in the data. One way to deal with this problem is to implement a robust estimation procedure to dampen the effect of observations that would be highly influential if least squares were used. In addition to insensitivity to outliers, such a procedure tends to leave the residuals associated with outliers large, therefore making the identification of outliers much easier. Implementation of this procedure using robust error covariance functions, comparison of different robust estimators, e.g., Huber's and Tukey's estimators, and assessing the detected outliers with respect to temporal and spatial patterns are discussed.

  14. Estimation of mass change trends in the Earth’s system on the basis of GRACE satellite data, with application to Greenland

    NARCIS (Netherlands)

    Siemes, C.; Ditmar, P.; Riva, E.M.; Slobbe, D.C.; Liu, X.L.; Farahani, H.

    2012-01-01

    The Gravity Recovery and Climate Experiment (GRACE) satellite mission measures the Earth’s gravity field since March 2002. We propose a new filtering procedure for post-processing GRACE-based monthly gravity field solutions provided in the form of spherical harmonic coefficients. The procedure is tu

  15. Correlating GRACE with Standardized Precipitation Indices and Precipitation Gauges for the High Plains Aquifer

    Science.gov (United States)

    Miller, K. A.; Clancy, K.

    2016-12-01

    The NASA and German Aerospace Center Gravity Recovery and Climate Experiment (GRACE) detects monthly changes in the gravity of the earth assumed to be water storage using the distance between two satellites, GRACE A and GRACE B, as a phase change. We will use level 3 GRACE Tellus data from the NASA Jet Propulsion Laboratory Physical Oceanography Distributed Active Archive Center (PO.DAAC). The data have a resolution of 9 km2 and are available for 2002 to 2015. We examine GRACE data for the High Plains aquifer (Texas, Oklahoma, Wyoming, Nebraska, Kansas, New Mexico, Colorado and South Dakota) and compare changes to monthly averaged precipitation gauges, standardized precipitation indices for one, three, six, and twelve-months. We hypothesize that GRACE data will correlate best with 1) three-month standardized precipitation indices; 2) regions with natural land cover; 3) and in years where precipitation is at or above average.

  16. A source model for the great 2011 Tohoku earthquake (Mw=9.1) from inversion of GRACE gravity data

    Science.gov (United States)

    Cambiotti, G.; Sabadini, R.

    2012-06-01

    The co-seismic slip distribution of the 2011 Tohoku megathrust earthquake is constrained from GeoForschungsZentrum (GFZ) Gravity Recovery and Climate Experiment (GRACE) Level 2 data time series and our self-gravitating, compressible 1-D Earth model. After spatial localization of space gravity data in the surrounding of the U.S. Geological Survey (USGS) epicenter by means of orthogonal Slepian functions, we estimate the long-wavelength co-seismic gravity signature. The pattern is bipolar: the positive pole off-shore in the Pacific ocean (+3.6μGal) and the negative pole in the northern Japan and Japan sea (-8.6μGal). Inversion of the GRACE data resolves average features of finite fault models: the total seismic moment (5.3±1×1022Nm, corresponding to MW=9.1 in agreement with the centroid-moment-tensor solution), the rake angle (87°±9°), and the mean position of the slip distribution on the fault plane. We obtain that the mean depth of the rupture is 17.1±5km, just below the Moho discontinuity, although we cannot exclude that the rupture also extended to shallower crustal layers and deeper within the lithospheric mantle due to the poor resolution of the along-dip dimension of the fault.

  17. Hydrological Excitation of Polar Motion Derived from GRACE Gravity Field Solutions

    Directory of Open Access Journals (Sweden)

    L. Seoane

    2011-01-01

    Full Text Available The influence of the continental water storage on the polar motion is not well known. Different models have been developed to evaluate these effects and compared to geodetic observations. However, previous studies have shown large discrepancies mainly attributed to the lack of global measurements of related hydrological parameters. Now, from the observations of the GRACE mission, we can estimate the polar motion excitation due to the global hydrology. Data processing of GRACE data is carried out by several centers of analysis, we focus on the new solution computed by the Groupe de Recherche de Géodésie Spatiale. At annual scales, excitations derived from GRACE data are in better agreement with geodetic observations than models estimates. The main contribution to the hydrological excitation comes from the monsoon climates regions where GRACE and models estimates are in a very good agreement. Still, the effect of the north high latitudes regions, where the principal areas of snow cover are found, cannot be neglected. At these regions, GRACE and models estimated contributions to polar motion excitations show significant discrepancies. Finally, GRACE-based excitations reveal the possible influence of water storage variations in exciting polar motion around the frequency of 3 cycles per year.

  18. A Test of General Relativity Using the LARES and LAGEOS Satellites and a GRACE Earth's Gravity Model

    CERN Document Server

    Ciufolini, Ignazio; Pavlis, Erricos C; Koenig, Rolf; Ries, John; Gurzadyan, Vahe; Matzner, Richard; Penrose, Roger; Sindoni, Giampiero; Paris, Claudio; Khachatryan, Harutyun; Mirzoyan, Sergey

    2016-01-01

    We present a test of General Relativity, the measurement of the Earth's dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS and LAGEOS 2 laser-ranged satellites together with the Earth's gravity field model GGM05S produced by the space geodesy mission GRACE. We measure $\\mu = (0.994 \\pm 0.002) \\pm 0.05$, where $\\mu$ is the Earth's dragging of inertial frames normalized to its General Relativity value, 0.002 is the 1-sigma formal error and 0.05 is the estimated systematic error mainly due to the uncertainties in the Earth's gravity model GGM05S. Our result is in agreement with the prediction of General Relativity.

  19. Tests Results of the Electrostatic Accelerometer Flight Models for Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, E.; Boulanger, D.; Christophe, B.; Foulon, B.; Lebat, V.; Huynh, P. A.; Liorzou, F.

    2015-12-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, which will produce an accurate model of the Earth's gravity field variation providing global climatic data during five years at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Earth's mass distribution non-uniformities cause variations of the inter-satellite distance. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit - ICU. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained at the center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the output measurement of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench on ground and with drops in ZARM catapult. The Critical Design Review was achieved successfully on September 2014. The Engineering Model (EM) was integrated and tested successfully, with ground levitation, drops, Electromagnetic Compatibility and thermal vacuum. The integration of the two Flight Models was done on July 2015. The

  20. Status of Electrostatic Accelerometer Development for Gravity Recovery and Climate Experiment Follow-On Mission (GRACE FO)

    Science.gov (United States)

    Perrot, Eddy; Boulanger, Damien; Christophe, Bruno; Foulon, Bernard; Liorzou, Françoise; Lebat, Vincent; Huynh, Phuong-Anh

    2015-04-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory), is an Earth-orbiting gravity mission, continuation of the GRACE mission, which will produce an accurate model of the Earth's gravity field variation providing global climatic data during five years at least. The mission involves two satellites in a loosely controlled tandem formation, with a micro-wave link measuring the inter-satellites distance variation. Earth's mass distribution non-uniformities cause variations of the inter-satellite distance. This variation is measured to recover gravity, after subtracting the non-gravitational contributors, as the residual drag. ONERA (the French Aerospace Lab) is developing, manufacturing and testing electrostatic accelerometers measuring this residual drag applied on the satellites. The accelerometer is composed of two main parts: the Sensor Unit (including the Sensor Unit Mechanics - SUM - and the Front-End Electronic Unit - FEEU) and the Interface Control Unit - ICU. In the Accelerometer Core, located in the Sensor Unit Mechanics, the proof mass is levitated and maintained at the center of an electrode cage by electrostatic forces. Thus, any drag acceleration applied on the satellite involves a variation on the servo-controlled electrostatic suspension of the mass. The voltage on the electrodes providing this electrostatic force is the measurement output of the accelerometer. The impact of the accelerometer defaults (geometry, electronic and parasitic forces) leads to bias, misalignment and scale factor error, non-linearity and noise. Some of these accelerometer defaults are characterized by tests with micro-gravity pendulum bench on ground and with drops in ZARM catapult. The Critical Design Review was achieved successfully on September 2014. The Engineering Model (EM) was integrated and tested successfully, with ground levitation, drops, Electromagnetic Compatibility and thermal vacuum. The integration of the first Flight Model has begun on December 2014

  1. Groundwater storage changes in the Tibetan Plateau and adjacent areas revealed from GRACE satellite gravity data

    Science.gov (United States)

    Xiang, Longwei; Wang, Hansheng; Steffen, Holger; Wu, Patrick; Jia, Lulu; Jiang, Liming; Shen, Qiang

    2016-09-01

    Understanding groundwater storage (GWS) changes is vital to the utilization and control of water resources in the Tibetan Plateau. However, well level observations are rare in this big area, and reliable hydrology models including GWS are not available. We use hydro-geodesy to quantitate GWS changes in the Tibetan Plateau and surroundings from 2003 to 2009 using a combined analysis of satellite gravity and satellite altimetry data, hydrology models as well as a model of glacial isostatic adjustment (GIA). Release-5 GRACE gravity data are jointly used in a mascon fitting method to estimate the terrestrial water storage (TWS) changes during the period, from which the hydrology contributions and the GIA effects are effectively deducted to give the estimates of GWS changes for 12 selected regions of interest. The hydrology contributions are carefully calculated from glaciers and lakes by ICESat-1 satellite altimetry data, permafrost degradation by an Active-Layer Depth (ALD) model, soil moisture and snow water equivalent by multiple hydrology models, and the GIA effects are calculated with the new ICE-6G_C (VM5a) model. Taking into account the measurement errors and the variability of the models, the uncertainties are rigorously estimated for the TWS changes, the hydrology contributions (including GWS changes) and the GIA effect. For the first time, we show explicitly separated GWS changes in the Tibetan Plateau and adjacent areas except for those to the south of the Himalayas. We find increasing trend rates for eight basins: + 2.46 ± 2.24 Gt/yr for the Jinsha River basin, + 1.77 ± 2.09 Gt/yr for the Nujiang-Lancangjiang Rivers Source Region, + 1.86 ± 1.69 Gt/yr for the Yangtze River Source Region, + 1.14 ± 1.39 Gt/yr for the Yellow River Source Region, + 1.52 ± 0.95 Gt/yr for the Qaidam basin, + 1.66 ± 1.52 Gt/yr for the central Qiangtang Nature Reserve, + 5.37 ± 2.17 Gt/yr for the Upper Indus basin and + 2.77 ± 0.99 Gt/yr for the Aksu River basin. All these

  2. A new degree-2190 (10 km resolution) gravity field model for Antarctica developed from GRACE, GOCE and Bedmap2 data

    Science.gov (United States)

    Hirt, Christian; Rexer, Moritz; Scheinert, Mirko; Pail, Roland; Claessens, Sten; Holmes, Simon

    2016-02-01

    The current high-degree global geopotential models EGM2008 and EIGEN-6C4 resolve gravity field structures to ˜ 10 km spatial scales over most parts of the of Earth's surface. However, a notable exception is continental Antarctica, where the gravity information in these and other recent models is based on satellite gravimetry observations only, and thus limited to about ˜ 80-120 km spatial scales. Here, we present a new degree-2190 global gravity model (GGM) that for the first time improves the spatial resolution of the gravity field over the whole of continental Antarctica to ˜ 10 km spatial scales. The new model called SatGravRET2014 is a combination of recent Gravity Recovery and Climate Experiment (GRACE) and Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite gravimetry with gravitational signals derived from the 2013 Bedmap2 topography/ice thickness/bedrock model with gravity forward modelling in ellipsoidal approximation. Bedmap2 is a significantly improved description of the topographic mass distribution over the Antarctic region based on a multitude of topographic surveys, and a well-suited source for modelling short-scale gravity signals as we show in our study. We describe the development of SatGravRET2014 which entirely relies on spherical harmonic modelling techniques. Details are provided on the least-squares combination procedures and on the conversion of topography to implied gravitational potential. The main outcome of our work is the SatGravRET2014 spherical harmonic series expansion to degree 2190, and derived high-resolution grids of 3D-synthesized gravity and quasigeoid effects over the whole of Antarctica. For validation, six data sets from the IAG Subcommission 2.4f "Gravity and Geoid in Antarctica" (AntGG) database were used comprising a total of 1,092,981 airborne gravimetric observations. All subsets consistently show that the Bedmap2-based short-scale gravity modelling improves the agreement over satellite

  3. Monitoring Continental Water Mass Variations by GRACE

    Science.gov (United States)

    Mercan, H.; Akyılmaz, O.

    2015-12-01

    The low-low satellite-to-satellite tracking mission GRACE (Gravity Recovery And Climate Experiment), launched in March 2002, aims to determine Earth's static gravity field and its temporal variations. Geophysical mass changes at regional and global scale, which are related with terrestrial water bodies, ocean and atmosphere masses, melting and displacements of ice sheets and tectonic movements can be determined from time-dependent changes of the Earth's gravity field. In this study, it is aimed to determine total water storage (TWS) (soil moisture, groundwater, snow and glaciers, lake and river waters, herbal waters) variations at different temporal and spatial resolution, monitoring the hydrologic effect causing time-dependent changes in the Earth's gravity field by two different methods. The region between 30°-40° northern latitudes and 36°-48° eastern longitudes has been selected as a study area covering the Euphrates - Tigris basin. TWS maps were produced with (i) monthly temporal and 400 km spatial resolution, based on monthly mean global spherical harmonic gravity field models of GRACE satellite mission (L2), and with (ii) monthly and semi-monthly temporal and spatial resolution as fine as 200 km based on GRACE in-situ observations (L1B). Decreasing trend of water mass anomalies from the year 2003 to 2013 is proved by aforesaid approaches. Monthly TWS variations are calculated using two different methods for the same region and time period. Time series of both solutions are generated and compared.

  4. GRACE, time-varying gravity, Earth system dynamics and climate change

    NARCIS (Netherlands)

    Wouters, B.; Bonin, J.A.; Chambers, D.P.; Riva, R.E.M.; Sasgen, I.; Wahr, J.

    2014-01-01

    Continuous observations of temporal variations in the Earth's gravity field have recently become available at an unprecedented resolution of a few hundreds of kilometers. The gravity field is a product of the Earth's mass distribution, and these data—provided by the satellites of the Gravity Recover

  5. Kalman Filtered Daily GRACE Gravity Field Solutions in Near Real-Time- First Steps

    Science.gov (United States)

    Kvas, Andreas; Mayer-Gurr, Torsten

    2016-08-01

    As part of the EGSIEM (European Gravity Service for Improved Emergency Management) project, a technology demonstrator for a near real-time (NRT) gravity field service will be established. In preparation of the operational phase, several aspects of the daily gravity field processing chain at Graz University of Technology have been inspected in order to improve the gravity field solutions and move towards NRT. The effect of these adaptions is investigated by comparison with post-processing and forward-only filtered solutions and evaluated using in-situ data.

  6. NASA 3D Models: GRACE

    Data.gov (United States)

    National Aeronautics and Space Administration — GRACE (Gravity Recovery and Climate Experiment), twin satellites launched in March 2002, are making detailed measurements of Earth's gravity field which will lead to...

  7. NASA 3D Models: Grace

    Data.gov (United States)

    National Aeronautics and Space Administration — GRACE (Gravity Recovery and Climate Experiment), twin satellites launched in March 2002, are making detailed measurements of Earth's gravity field which will lead to...

  8. The unexpected signal in GRACE estimates of C_{20}

    Science.gov (United States)

    Cheng, Minkang; Ries, John

    2017-08-01

    For science applications of the gravity recovery and climate experiment (GRACE) monthly solutions, the GRACE estimates of C_{20} (or J2) are typically replaced by the value determined from satellite laser ranging (SLR) due to an unexpectedly strong, clearly non-geophysical, variation at a period of ˜ 160 days. This signal has sometimes been referred to as a tide-like variation since the period is close to the perturbation period on the GRACE orbits due to the spherical harmonic coefficient pair C_{22}/S_{22} of S2 ocean tide. Errors in the S2 tide model used in GRACE data processing could produce a significant perturbation to the GRACE orbits, but it cannot contribute to the ˜ 160-day signal appearing in C_{20}. Since the dominant contribution to the GRACE estimate of C_{20} is from the global positioning system tracking data, a time series of 138 monthly solutions up to degree and order 10 (10× 10) were derived along with estimates of ocean tide parameters up to degree 6 for eight major tides. The results show that the ˜ 160-day signal remains in the C_{20} time series. Consequently, the anomalous signal in GRACE C_{20} cannot be attributed to aliasing from the errors in the S2 tide. A preliminary analysis of the cross-track forces acting on GRACE and the cross-track component of the accelerometer data suggests that a temperature-dependent systematic error in the accelerometer data could be a cause. Because a wide variety of science applications relies on the replacement values for C_{20}, it is essential that the SLR estimates are as reliable as possible. An ongoing concern has been the influence of higher degree even zonal terms on the SLR estimates of C_{20}, since only C_{20} and C_{40} are currently estimated. To investigate whether a better separation between C_{20} and the higher-degree terms could be achieved, several combinations of additional SLR satellites were investigated. In addition, a series of monthly gravity field solutions (60× 60) were

  9. Use of GRACE data to detect the present land uplift rate in Fennoscandia

    Science.gov (United States)

    Shafiei Joud, Mehdi S.; Sjöberg, Lars E.; Bagherbandi, Mohammad

    2017-05-01

    After more than 13 yr of GRACE monthly data, the determined secular trend of gravity field variation can be used to study the regions of glacial isostatic adjustment (GIA). Here we focus on Fennoscandia where long-term terrestrial and high-quality GPS data are available, and we study the monthly GRACE data from three analysis centres. We present a new approximate formula to convert the secular trend of the GRACE gravity change to the land uplift rate without making assumptions of the ice load history. The question is whether the GRACE-derived land uplift rate by our method is related to GIA. A suitable post-processing method for the GRACE data is selected based on weighted RMS differences with the GPS data. The study reveals that none of the assumed periodic changes of the GRACE gravity field is significant in the estimation of the secular trend, and they can, therefore, be neglected. Finally, the GRACE-derived land uplift rates are obtained using the selected post-processing method, and they are compared with GPS land uplift rate data. The GPS stations with significant differences were marked using a statistical significance test. The smallest rms difference (1.0 mm a-1) was obtained by using GRACE data from the University of Texas.

  10. ITSG-Grace2016 data preprocessing methodologies revisited: impact of using Level-1A data products

    Science.gov (United States)

    Klinger, Beate; Mayer-Gürr, Torsten

    2017-04-01

    For the ITSG-Grace2016 release, the gravity field recovery is based on the use of official GRACE (Gravity Recovery and Climate Experiment) Level-1B data products, generated by the Jet Propulsion Laboratory (JPL). Before gravity field recovery, the Level-1B instrument data are preprocessed. This data preprocessing step includes the combination of Level-1B star camera (SCA1B) and angular acceleration (ACC1B) data for an improved attitude determination (sensor fusion), instrument data screening and ACC1B data calibration. Based on a Level-1A test dataset, provided for individual month throughout the GRACE period by the Center of Space Research at the University of Texas at Austin (UTCSR), the impact of using Level-1A instead of Level-1B data products within the ITSG-Grace2016 processing chain is analyzed. We discuss (1) the attitude determination through an optimal combination of SCA1A and ACC1A data using our sensor fusion approach, (2) the impact of the new attitude product on temporal gravity field solutions, and (3) possible benefits of using Level-1A data for instrument data screening and calibration. As the GRACE mission is currently reaching its end-of-life, the presented work aims not only at a better understanding of GRACE science data to reduce the impact of possible error sources on the gravity field recovery, but it also aims at preparing Level-1A data handling capabilities for the GRACE Follow-On mission.

  11. Gravity

    CERN Document Server

    Gamow, George

    2003-01-01

    A distinguished physicist and teacher, George Gamow also possessed a special gift for making the intricacies of science accessible to a wide audience. In Gravity, he takes an enlightening look at three of the towering figures of science who unlocked many of the mysteries behind the laws of physics: Galileo, the first to take a close look at the process of free and restricted fall; Newton, originator of the concept of gravity as a universal force; and Einstein, who proposed that gravity is no more than the curvature of the four-dimensional space-time continuum.Graced with the author's own draw

  12. Amazing grace: Vancouver's supervised injection facility granted six-month lease on life.

    Science.gov (United States)

    Small, Dan

    2008-01-24

    scientific evidence, and lead the way towards to provision of a permanent medical exemption for injection facilities from Canada's Controlled Drugs and Substances Act (CDSA). In so doing, the Prime Minister would be on the brink of grace and would rescue a life saving health program from perpetual political interference.

  13. Variations of geoid undulations from satellite data of GRACE for Israel and surrounding countries

    Science.gov (United States)

    Kostelecky, Jan; Klokocnik, Jaroslav; Bezdek, Ales

    2017-04-01

    Since 2002, the US-German GRACE satellite mission (Gravity Recovery and Climate Experiment) has been providing a precise survey of the Earth's time-variable gravity field, with unprecedented temporal and spatial sampling. GRACE time-variable gravity field is a tool for measuring temporal and spatial variations of the mass redistribution within the Earth system. Time variability of the gravity field is presented here as "monthly gravity field models" of the geoid undulations. We show their regional variations in Israel and surrounding countries which have seasonal and secular character, connected with desiccation of underground water in the area. During 13 year interval of the data from GRACE, the secular decrease of the level of the waters in this area became evident. This result supports warnings coming from other data and points to the existence of a great danger not only for this area.

  14. A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model. Measurement of Earth's dragging of inertial frames

    Energy Technology Data Exchange (ETDEWEB)

    Ciufolini, Ignazio [Universita del Salento, Dipartimento Ingegneria dell' Innovazione, Lecce (Italy); Sapienza Universita di Roma, Scuola di Ingegneria Aerospaziale, Rome (Italy); Paolozzi, Antonio; Paris, Claudio [Sapienza Universita di Roma, Scuola di Ingegneria Aerospaziale, Rome (Italy); Museo della Fisica e Centro Studi e Ricerche Enrico Fermi, Rome (Italy); Pavlis, Erricos C. [University of Maryland, Joint Center for Earth Systems Technology (JCET), Baltimore County (United States); Koenig, Rolf [GFZ German Research Centre for Geosciences, Helmholtz Centre Potsdam, Potsdam (Germany); Ries, John [University of Texas at Austin, Center for Space Research, Austin (United States); Gurzadyan, Vahe; Khachatryan, Harutyun; Mirzoyan, Sergey [Alikhanian National Laboratory and Yerevan State University, Center for Cosmology and Astrophysics, Yerevan (Armenia); Matzner, Richard [University of Texas at Austin, Theory Center, Austin (United States); Penrose, Roger [University of Oxford, Mathematical Institute, Oxford (United Kingdom); Sindoni, Giampiero [Sapienza Universita di Roma, DIAEE, Rome (Italy)

    2016-03-15

    We present a test of general relativity, the measurement of the Earth's dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS, and LAGEOS 2 laser-ranged satellites together with the Earth gravity field model GGM05S produced by the space geodesy mission GRACE. We measure μ = (0.994 ± 0.002) ± 0.05, where μ is the Earth's dragging of inertial frames normalized to its general relativity value, 0.002 is the 1-sigma formal error and 0.05 is our preliminary estimate of systematic error mainly due to the uncertainties in the Earth gravity model GGM05S. Our result is in agreement with the prediction of general relativity. (orig.)

  15. A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model: Measurement of Earth's dragging of inertial frames.

    Science.gov (United States)

    Ciufolini, Ignazio; Paolozzi, Antonio; Pavlis, Erricos C; Koenig, Rolf; Ries, John; Gurzadyan, Vahe; Matzner, Richard; Penrose, Roger; Sindoni, Giampiero; Paris, Claudio; Khachatryan, Harutyun; Mirzoyan, Sergey

    2016-01-01

    We present a test of general relativity, the measurement of the Earth's dragging of inertial frames. Our result is obtained using about 3.5 years of laser-ranged observations of the LARES, LAGEOS, and LAGEOS 2 laser-ranged satellites together with the Earth gravity field model GGM05S produced by the space geodesy mission GRACE. We measure [Formula: see text], where [Formula: see text] is the Earth's dragging of inertial frames normalized to its general relativity value, 0.002 is the 1-sigma formal error and 0.05 is our preliminary estimate of systematic error mainly due to the uncertainties in the Earth gravity model GGM05S. Our result is in agreement with the prediction of general relativity.

  16. Contributions of GRACE to Climate Monitoring

    Science.gov (United States)

    Rodell, Matthew; Famiglietti, James; Chambers, Don P.; Wahr, John

    2011-01-01

    The NASA/German Gravity Recovery and Climate Experiment (GRACE) was launched in March 2002. Rather than looking downward, GRACE continuously monitors the locations of and precise distance between twin satellites which orbit in tandem about 200 km apart. Variations in mass near Earth's surface cause heterogeneities in its gravity field, which in turn affect the orbits of satellites. Thus scientists can use GRACE data to map Earth's gravity field with enough accuracy to discern month to month changes caused by ocean circulation and redistribution of water stored on and in the land. Other gravitational influences, such as atmospheric circulation, post-glacial rebound, and solid earth movements are either independently determined and removed or are negligible on a monthly to sub-decadal timescale. Despite its coarse spatial (>150,000 sq km at mid-latitudes) and temporal (approx monthly) resolutions, GRACE has enabled significant advancements in the oceanic, hydrologic, and cryospheric science, and has great potential for climate monitoring, because it is the only global observing system able to measure ocean bottom pressures, total terrestrial water storage, and ice mass changes. The best known GRACE results are estimates of Greenland and Antarctic ice sheet loss rates. Previously, scientists had estimated ice mass losses using ground and satellite based altimetry and surface mass balance estimates based on snowfall accumulation and glacier discharge. While such measurements are still very useful for their spatial detail, they are imperfectly correlated with large-scale ice mass changes, due to snow and ice compaction and incomplete spatial coverage. GRACE enables scientists to generate monthly time series of Greenland and Antarctic ice mass, which have confirmed the shrinking of the polar ice sheets, one of the most obvious and indisputable manifestations of climate change. Further, GRACE has located and quantified hot spots of ice loss in southeastern Greenland and

  17. Measuring water accumulation rates using GRACE data in areas experiencing glacial isostatic adjustment: The Nelson River basin

    Science.gov (United States)

    Lambert, A.; Huang, J.; Kamp, G.; Henton, J.; Mazzotti, S.; James, T. S.; Courtier, N.; Barr, A. G.

    2013-12-01

    Recovery and Climate Experiment (GRACE) satellite-derived total water storage can be obscured by glacial isostatic adjustment. In order to solve this problem for the Nelson River drainage basin in Canada, a gravity rate map from 110 months (June 2002 to October 2011) of GRACE gravity data was corrected for glacial isostatic adjustment using an independent gravity rate map derived from updated GPS vertical velocities. The GPS-based map was converted to equivalent gravity rate using a transfer function developed from GPS and absolute-g data at colocated sites. The corrected GRACE gravity rate map revealed a major positive anomaly within the drainage basin, which was independently shown by hydrological data to be due to changes in water storage. The anomaly represents a cumulative increase at its center of about 340 mm of water, reflecting a progression from extreme drought to extremely wet conditions.

  18. Advanced Stellar Compass, Electrical Interface Control Document for Grace

    DEFF Research Database (Denmark)

    Madsen, Peter Buch; Jørgensen, Finn E; Jørgensen, John Leif;

    1999-01-01

    The Space Instrumentation Group has made an Electrical Interface Control Document for the GRACE (Gravity Recovery and Climate Experiment Mission) satellite, witch describes the electrical interface between the Star Imager and the Computer (IPU) on the GRACE Satellite....

  19. Investigating different filter and rescaling methods on simulated GRACE-like TWS variations for hydrological applications

    Science.gov (United States)

    Zhang, Liangjing; Dahle, Christoph; Neumayer, Karl-Hans; Dobslaw, Henryk; Flechtner, Frank; Thomas, Maik

    2016-04-01

    Terrestrial water storage (TWS) variations obtained from GRACE play an increasingly important role in various hydrological and hydro-meteorological applications. Since monthly-mean gravity fields are contaminated by errors caused by a number of sources with distinct spatial correlation structures, filtering is needed to remove in particular high frequency noise. Subsequently, bias and leakage caused by the filtering need to be corrected before the final results are interpreted as GRACE-based observations of TWS. Knowledge about the reliability and performance of different post-processing methods is highly important for the GRACE users. In this contribution, we re-assess a number of commonly used post-processing methods using a simulated GRACE-like gravity field time-series based on realistic orbits and instrument error assumptions as well as background error assumptions out of the updated ESA Earth System Model. Two non-isotropic filter methods from Kusche (2007) and Swenson and Wahr (2006) are tested. Rescaling factors estimated from five different hydrological models and the ensemble median are applied to the post-processed simulated GRACE-like TWS estimates to correct the bias and leakage. Since TWS anomalies out of the post-processed simulation results can be readily compared to the time-variable Earth System Model initially used as "truth" during the forward simulation step, we are able to thoroughly check the plausibility of our error estimation assessment and will subsequently recommend a processing strategy that shall also be applied to planned GRACE and GRACE-FO Level-3 products for hydrological applications provided by GFZ. Kusche, J. (2007): Approximate decorrelation and non-isotropic smoothing of time-variable GRACE-type gravity field models. J. Geodesy, 81 (11), 733-749, doi:10.1007/s00190-007-0143-3. Swenson, S. and Wahr, J. (2006): Post-processing removal of correlated errors in GRACE data. Geophysical Research Letters, 33(8):L08402.

  20. Development of daily "swath" mascon solutions from GRACE

    Science.gov (United States)

    Save, Himanshu; Bettadpur, Srinivas

    2016-04-01

    The Gravity Recovery and Climate Experiment (GRACE) mission has provided invaluable and the only data of its kind over the past 14 years that measures the total water column in the Earth System. The GRACE project provides monthly average solutions and there are experimental quick-look solutions and regularized sliding window solutions available from Center for Space Research (CSR) that implement a sliding window approach and variable daily weights. The need for special handling of these solutions in data assimilation and the possibility of capturing the total water storage (TWS) signal at sub-monthly time scales motivated this study. This study discusses the progress of the development of true daily high resolution "swath" mascon total water storage estimate from GRACE using Tikhonov regularization. These solutions include the estimates of daily total water storage (TWS) for the mascon elements that were "observed" by the GRACE satellites on a given day. This paper discusses the computation techniques, signal, error and uncertainty characterization of these daily solutions. We discuss the comparisons with the official GRACE RL05 solutions and with CSR mascon solution to characterize the impact on science results especially at the sub-monthly time scales. The evaluation is done with emphasis on the temporal signal characteristics and validated against in-situ data set and multiple models.

  1. Remote Sensing of Terrestrial Water Storage with GRACE and Future Gravimetry Missions

    Science.gov (United States)

    Rodell, Matt; Watkins, Mike; Famiglietti, Jay

    2011-01-01

    The Gravity Recovery and Climate Experiment (GRACE) has demonstrated that satellite gravimetry can be a valuable tool for regional to global water cycle observation. Studies of ice sheet and glacier mass losses, ocean bottom pressure and circulation, and variability of water stored on and in the land including groundwater all have benefited from GRACE observations, and the list of applications and discoveries continues to grow. As the mission approaches its tenth anniversary of launch on March 12,2012, it has nearly doubled its proposed lifetime but is showing some signs of age. In particular, degraded battery capacity limits the availability of power in certain orbital configurations, so that the accelerometers must be turned off for approximately one month out of six. The mission managers have decided to operate the spacecrafts in a manner that maximizes the remaining lifetime, so that the longest possible climate data record is available from GRACE. Nevertheless, it is not unlikely that there will be a data gap between GRACE and the GRACE Follow On mission, currently proposed for launch in 2016. In this presentation we will describe recent GRACE enabled science, GRACE mission health, and plans for GRACE Follow On and other future satellite gravimetry missions.

  2. Quasi-Stationary SST Estimation in the Eastern Mediterranean Sea Using Marine Gravity, GOCE/GRACE Gravity Information and Recent Altimetry Missions Through the Multiple Input/Multiple Output System Theory

    Science.gov (United States)

    Andritsanos, Vassilios D.; Tziavos, Ilias N.

    2016-08-01

    The Multiple Input / Multiple Output System (MIMOS) Theory is used in the spectral combination of marine and satellite data for Quasi-stationary Sea Surface Topography (QSST) estimation. 15 years (2000 - 2015) of altimetric data from ERS2, GEOSAT FOLLOW-ON, ENVISAT and SARAL / Altika satellites are optimally combined with in situ marine gravity observations. The repeated character of the altimetric missions provides more than one sample of Sea Surface Height (SSH) data sets, and the approximation of the input signal and output error power spectral densities is feasible using this successive information. The assimilation of low frequency global gravity information from GOCE/GRACE satellites is considered in data reductions. The geodynamically active area of the Eastern Mediterranean Sea is chosen as test area and the evolution of yearly SST is presented.

  3. 42 CFR 136a.33 - Grace period.

    Science.gov (United States)

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Grace period. 136a.33 Section 136a.33 Public Health... HEALTH AND HUMAN SERVICES INDIAN HEALTH Transition Provisions § 136a.33 Grace period. (a) Upon the... of the new eligibility regulations) shall retain their eligibility for a six month grace period...

  4. Comparison of in situ bottom pressure data with GRACE gravimetry in the Crozet-Kerguelen region

    NARCIS (Netherlands)

    Rietbroek, R.; LeGrand, P.; Wouters, B.; Lemoine, J.M.; Ramillien, G.; Hughes, C.W.

    2006-01-01

    Two time series of deep ocean bottom pressure records (BPRs) in between the Crozet Islands and Kerguelen are compared with GRACE (Gravity Recovery And Climate Experiment) equivalent water heights. An analysis of the correlation is performed for four time series: 1) monthly averages of the equivalent

  5. Comparison of in situ bottom pressure data with GRACE gravimetry in the Crozet-Kerguelen region

    NARCIS (Netherlands)

    Rietbroek, R.; LeGrand, P.; Wouters, B.; Lemoine, J.M.; Ramillien, G.; Hughes, C.W.

    2006-01-01

    Two time series of deep ocean bottom pressure records (BPRs) in between the Crozet Islands and Kerguelen are compared with GRACE (Gravity Recovery And Climate Experiment) equivalent water heights. An analysis of the correlation is performed for four time series: 1) monthly averages of the equivalent

  6. Observed changes in the Earth's dynamic oblateness from GRACE data and geophysical models.

    Science.gov (United States)

    Sun, Y; Ditmar, P; Riva, R

    A new methodology is proposed to estimate changes in the Earth's dynamic oblateness ([Formula: see text] or equivalently, [Formula: see text]) on a monthly basis. The algorithm uses monthly Gravity Recovery and Climate Experiment (GRACE) gravity solutions, an ocean bottom pressure model and a glacial isostatic adjustment (GIA) model. The resulting time series agree remarkably well with a solution based on satellite laser ranging (SLR) data. Seasonal variations of the obtained time series show little sensitivity to the choice of GRACE solutions. Reducing signal leakage in coastal areas when dealing with GRACE data and accounting for self-attraction and loading effects when dealing with water redistribution in the ocean is crucial in achieving close agreement with the SLR-based solution in terms of de-trended solutions. The obtained trend estimates, on the other hand, may be less accurate due to their dependence on the GIA models, which still carry large uncertainties.

  7. Estimation of fault parameters using GRACE observations and analytical model. Case study: The 2010 Chile earthquake

    Science.gov (United States)

    Fatolazadeh, Farzam; Naeeni, Mehdi Raoofian; Voosoghi, Behzad; Rahimi, Armin

    2017-07-01

    In this study, an inversion method is used to constrain the fault parameters of the 2010 Chile Earthquake using gravimetric observations. The formulation consists of using monthly Geopotential coefficients of GRACE observations in a conjunction with the analytical model of Okubo 1992 which accounts for the gravity changes resulting from Earthquake. At first, it is necessary to eliminate the hydrological and oceanic effects from GRACE monthly coefficients and then a spatio-spectral localization analysis, based on wavelet local analysis, should be used to filter the GRACE observations and to better refine the tectonic signal. Finally, the corrected GRACE observations are compared with the analytical model using a nonlinear inversion algorithm. Our results show discernible differences between the computed average slip using gravity observations and those predicted from other co-seismic models. In this study, fault parameters such as length, width, depth, dip, strike and slip are computed using the changes in gravity and gravity gradient components. By using the variations of gravity gradient components the above mentioned parameters are determined as 428 ± 6 Km, 203 ± 5 Km, 5 Km, 10°, 13° and 8 ± 1.2 m respectively. Moreover, the values of the seismic moment and moment magnitude are 2. 09 × 1022 N m and 8.88 Mw respectively which show the small differences with the values reported from USGS (1. 8 × 1022N m and 8.83 Mw).

  8. Study of Sub-basin Scale Groundwater Variations in Asia Using GRACE, Satellite Altimetry and in-situ Data

    Science.gov (United States)

    Yamamoto, K.; Fukuda, Y.; Taniguchi, M.

    2008-12-01

    A project to assess the effects of human activities on the subsurface environment in Asian developing cities is now in progress (Research Institute for Humanity and Nature., 2008). In the project, precise in situ gravity and landwater observations combined with GRACE (Gravity Recovery and Climate Experiment) satellite gravity data is proposed to evaluate local groundwater level changes of the developing urban areas in Asia. It is necessary for precise and accurate estimation of the local groundwater variations to separate local groundwater level changes from regional or global scale landwater variations. GRACE data is useful to estimate large scale landwater variations. Using GRACE Level 2 monthly gravity field solutions, we previously recovered landwater mass variation around Bangkok, in Thailand, which is one of the test areas of the project and located on the downstream of Chao Phraya river basin in the Indochina Peninsula. However, it is difficult to distinguish landwater signal of Chao Phraya river basin itself with the neighboring 3 large river basins because of the limitation of the spatial resolution of the GRACE monthly solutions. In this study, we recovered mass variation of Chao Phraya river basin using GRACE"fs along track range rate data instead of the monthly solutions. We used the method developed by Chen et al (2007), which uses GRACE"fs line-of-sight range acceleration measurements. We also tested the recoveries of landwater mass variations in other small scale river basins including Jakarta, Seoul and Taipei, which are also study areas of the project. Using the sub-basin scale landwater mass variation recovered by GRACE, we estimated groundwater level change in the project study areas by combing with in situ landwater and gravity observations. Satellite altimetry data is also used to separate groundwater variation from other landwater components as a constraint of river water storage variations.

  9. Sensitivity of GRACE-derived estimates of groundwater-level changes in southern Ontario, Canada

    Science.gov (United States)

    Hachborn, Ellen; Berg, Aaron; Levison, Jana; Ambadan, Jaison Thomas

    2017-06-01

    Amidst changing climates, understanding the world's water resources is of increasing importance. In Ontario, Canada, low water conditions are currently assessed using only precipitation and watershed-based stream gauges by the Conservation Authorities in Ontario and the Ministry of Natural Resources and Forestry. Regional groundwater-storage changes in Ontario are not currently measured using satellite data by research institutes. In this study, contributions from the Gravity Recovery and Climate Experiment (GRACE) data are compared to a hydrogeological database covering southern Ontario from 2003 to 2013, to determine the suitability of GRACE total water storage estimates for monitoring groundwater storage in this location. Terrestrial water storage data from GRACE were used to determine monthly groundwater storage (GWS) anomaly values. GWS values were also determined by multiplying groundwater-level elevations (from the Provincial Groundwater Monitoring Network wells) by specific yield. Comparisons of GRACE-derived GWS to well-based GWS data determined that GRACE is sufficiently sensitive to obtain a meaningful signal in southern Ontario. Results show that GWS values produced by GRACE are useful for identifying regional changes in groundwater storage in areas with limited available hydrogeological characterization data. Results also indicate that GRACE may have an ability to forecast changes in groundwater storage, which will become useful when monitoring climate shifts in the near future.

  10. Comparison of GRACE data and groundwater levels for the assessment of groundwater depletion in Jordan

    Science.gov (United States)

    Liesch, Tanja; Ohmer, Marc

    2016-09-01

    Gravity Recovery and Climate Experiment (GRACE) derived groundwater storage (GWS) data are compared with in-situ groundwater levels from five groundwater basins in Jordan, using newly gridded GRACE GRCTellus land data. It is shown that (1) the time series for GRACE-derived GWS data and in-situ groundwater-level measurements can be correlated, with R 2 from 0.55 to 0.74, (2) the correlation can be widely ascribed to the seasonal and trend component, since the detrended and deseasonalized time series show no significant correlation for most cases, implying that anomalous signals that deviate from the trend or seasonal behaviour are overlaid by noise, (3) estimates for water losses in Jordan based on the trend of GRACE data from 2003 to 2013 could be up to four times higher than previously assumed using estimated recharge and abstraction rates, and (4) a significant time-lagged cross correlation of the monthly changes in GRACE-derived groundwater storage and precipitation data was found, suggesting that the conventional method for deriving GWS from GRACE data probably does not account for the typical conditions in the study basins. Furthermore, a new method for deriving plausible specific yields from GRACE data and groundwater levels is demonstrated.

  11. On the capability of Swarm for surface mass variation monitoring: Quantitative assessment based on orbit information from CHAMP, GRACE and GOCE

    Science.gov (United States)

    Baur, Oliver; Weigelt, Matthias; Zehentner, Norbert; Mayer-Gürr, Torsten; Jäggi, Adrian

    2014-05-01

    In the last decade, temporal variations of the gravity field from GRACE observations have become one of the most ubiquitous and valuable sources of information for geophysical and environmental studies. In the context of global climate change, mass balance of the Arctic and Antarctic ice sheets gained particular attention. Because GRACE has outlived its predicted lifetime by several years already, it is very likely that a gap between GRACE and its successor GRACE follow-on (supposed to be launched in 2017, at the earliest) occurs. The Swarm mission - launched on November 22, 2013 - is the most promising candidate to bridge this potential gap, i.e., to directly acquire large-scale mass variation information on the Earth's surface in case of a gap between the present GRACE and the upcoming GRACE follow-on projects. Although the magnetometry mission Swarm has not been designed for gravity field purposes, its three satellites have the characteristics for such an endeavor: (i) low, near-circular and near-polar orbits, (ii) precise positioning with high-quality GNSS receivers, (iii) on-board accelerometers to measure the influence of non-gravitational forces. Hence, from an orbit analysis point of view the Swarm satellites are comparable to the CHAMP, GRACE and GOCE spacecraft. Indeed and as data analysis from CHAMP has been shown, the detection of annual signals and trends from orbit analysis is possible for long-wavelength features of the gravity field, although the accuracy associated with the inter-satellite GRACE measurements cannot be reached. We assess the capability of the (non-dedicated) mission Swarm for mass variation detection in a real-case environment (opposed to simulation studies). For this purpose, we "approximate" the Swarm scenario by the GRACE+CHAMP and GRACE+GOCE constellations. In a first step, kinematic orbits of the individual satellites are derived from GNSS observations. From these orbits, we compute monthly combined GRACE+CHAMP and GRACE

  12. Seasonal water storage change of the Yangtze River basin detected by GRACE

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    US-Germany co-sponsered satellite gravimetry mission GRACE (Gravity Recovery And Climate Experiment), launched in March 2002, has been producing monthly time series of Earth gravity models up to degree and order of 120. The GRACE mission consists of two identical satellites flying on an almost polar orbit with an altitude of about 300-500 km and satelite-to-satellite ranging of about 220 km. Thanks to the payloads of space-borne GPS receivers, accelerometers and high-precision K-band satelite-to-satellite ranging mesurements, GRACE gravity models are expected to achieve more than one order of magnitude of improvement over previous models at spatial scales of a few hundred kilometers or larger. Recovery of surface mass re-distribution based on GRACE's time-varying gravity models is applied to studies in solid Earth geophysics, oceanography, climatology and geodesy. At secular time scales, GRACE is expected to provide valuable information on global ice changes, whose variations have profound influences on global climate, and in particular, on sea level changes. At seasonal time scales, GRACE is expected to reveal surface water changes with an accuracy of less than 1 cm, or ocean bottom pressure changes with an accuracy of less than 1 mbar (1 mbar =102 Pa). These surface mass redistribution measurements would impove our understanding of the global and regional mass and energy cycles that are critical to human life. Using 15 GRACE monthly gravity models covering the period from April 2002 to December 2003, this study compares seasonal water storage changes recovered from GRACE data and hydrology models at global and regional scales, with particular focus on the Yangtze River basin of China. Annual amplitude of 3.4 cm of equivalent water height change is found for the Yangtze River basin with maximum in Spring and Autumn, agreeing with two state-of-the-art hydrology models. The differences between GRACE results and model predictions are less than 1-2 cm. We conclude

  13. Changes in gravitational parameters inferred from time variable GRACE data-A case study for October 2005 Kashmir earthquake

    Science.gov (United States)

    Hussain, Matloob; Eshagh, Mehdi; Ahmad, Zulfiqar; Sadiq, M.; Fatolazadeh, Farzam

    2016-09-01

    The earth's gravity changes are attributed to the redistribution of masses within and/or on the surface of the earth, which are due to the frictional sliding, tensile cracking and/or cataclastic flow of rocks along the faults and detectable by earthquake events. Inversely, the gravity changes are useful to describe the earthquake seismicity over the active orogenic belts. The time variable gravimetric data are hardly available to the public domain. However, Gravity Recovery and Climatic Experiment (GRACE) is the only satellite mission dedicated to model the variation of the gravity field and an available source to the science community. Here, we have tried to envisage gravity changes in terms of gravity anomaly (Δg), geoid (N) and the gravity gradients over the Indo-Pak plate with emphasis upon Kashmir earthquake of October 2005. For this purpose, we engaged the spherical harmonic coefficients of monthly gravity solutions from the GRACE satellite mission, which have good coverage over the entire globe with unprecedented accuracy. We have analysed numerically the solutions after removing the hydrological signals, during August to November 2005, in terms of corresponding monthly differentials of gravity anomaly, geoid and the gradients. The regional structures like Main Mantle Thrust (MMT), Main Karakoram Thrust (MKT), Herat and Chaman faults are in closed association with topography and with gravity parameters from the GRACE gravimetry and EGM2008 model. The monthly differentials of these quantities indicate the stress accumulation in the northeast direction in the study area. Our numerical results show that the horizontal gravity gradients seem to be in good agreement with tectonic boundaries and differentials of the gravitational elements are subtle to the redistribution of rock masses and topography caused by 2005 Kashmir earthquake. Moreover, the gradients are rather more helpful for extracting the coseismic gravity signatures caused by seismicity over the area

  14. Assimilation of GRACE Terrestrial Water Storage into a Land Surface Model: Evaluation 1 and Potential Value for Drought Monitoring in Western and Central Europe

    Science.gov (United States)

    Li, Bailing; Rodell, Matthew; Zaitchik, Benjamin F.; Reichle, Rolf H.; Koster, Randal D.; van Dam, Tonie M.

    2012-01-01

    A land surface model s ability to simulate states (e.g., soil moisture) and fluxes (e.g., runoff) is limited by uncertainties in meteorological forcing and parameter inputs as well as inadequacies in model physics. In this study, anomalies of terrestrial water storage (TWS) observed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission were assimilated into the NASA Catchment land surface model in western and central Europe for a 7-year period, using a previously developed ensemble Kalman smoother. GRACE data assimilation led to improved runoff correlations with gauge data in 17 out of 18 hydrological basins, even in basins smaller than the effective resolution of GRACE. Improvements in root zone soil moisture were less conclusive, partly due to the shortness of the in situ data record. In addition to improving temporal correlations, GRACE data assimilation also reduced increasing trends in simulated monthly TWS and runoff associated with increasing rates of precipitation. GRACE assimilated root zone soil moisture and TWS fields exhibited significant changes in their dryness rankings relative to those without data assimilation, suggesting that GRACE data assimilation could have a substantial impact on drought monitoring. Signals of drought in GRACE TWS correlated well with MODIS Normalized Difference Vegetation Index (NDVI) data in most areas. Although they detected the same droughts during warm seasons, drought signatures in GRACE derived TWS exhibited greater persistence than those in NDVI throughout all seasons, in part due to limitations associated with the seasonality of vegetation.

  15. Regional patterns of ocean mass change from GRACE satellite data

    Science.gov (United States)

    Riva, R. E.; Bamber, J. L.; Lavallee, D. A.; Wouters, B.; Hashemi Farahani, H.; Ditmar, P.; Van Der Wal, W.

    2011-12-01

    The Gravity Recovery and Climate Experiment (GRACE) satellites provide a direct measure of mass exchange between continents and oceans over time. Here, we make use of 8 years (2003-2010) of optimally filtered monthly GRACE-based solutions produced at TUDelft to determine trends in the mass of land ice and continental water stocks. We pay particular attention to accounting for the main error sources in the estimation of the land load: the model of glacial isostatic adjustment, signal leakage caused by a limited spatial resolution, and geocentre motion. Through gravitational coupling, load changes over land induce a redistribution of ocean water, which is characterized by complex patterns with peak values in coastal areas. We focus on a few selected regions where those sea-level changes are going to have a particularly high impact on human activities and settlements.

  16. California Drought Recovery Assessment Using GRACE Satellite Gravimetry Information

    Science.gov (United States)

    Love, C. A.; Aghakouchak, A.; Madadgar, S.; Tourian, M. J.

    2015-12-01

    California has been experiencing its most extreme drought in recent history due to a combination of record high temperatures and exceptionally low precipitation. An estimate for when the drought can be expected to end is needed for risk mitigation and water management. A crucial component of drought recovery assessments is the estimation of terrestrial water storage (TWS) deficit. Previous studies on drought recovery have been limited to surface water hydrology (precipitation and/or runoff) for estimating changes in TWS, neglecting the contribution of groundwater deficits to the recovery time of the system. Groundwater requires more time to recover than surface water storage; therefore, the inclusion of groundwater storage in drought recovery assessments is essential for understanding the long-term vulnerability of a region. Here we assess the probability, for varying timescales, of California's current TWS deficit returning to its long-term historical mean. Our method consists of deriving the region's fluctuations in TWS from changes in the gravity field observed by NASA's Gravity Recovery and Climate Experiment (GRACE) satellites. We estimate the probability that meteorological inputs, precipitation minus evaporation and runoff, over different timespans will balance the current GRACE-derived TWS deficit (e.g. in 3, 6, 12 months). This method improves upon previous techniques as the GRACE-derived water deficit comprises all hydrologic sources, including surface water, groundwater, and snow cover. With this empirical probability assessment we expect to improve current estimates of California's drought recovery time, thereby improving risk mitigation.

  17. Mortality and cardiovascular morbidity within 30 days of discharge following acute coronary syndrome in a contemporary European cohort of patients: How can early risk prediction be improved? The six-month GRACE risk score.

    Science.gov (United States)

    Raposeiras-Roubín, Sergio; Abu-Assi, Emad; Cambeiro-González, Cristina; Álvarez-Álvarez, Belén; Pereira-López, Eva; Gestal-Romaní, Santiago; Pedreira-López, Milagros; Rigueiro-Veloso, Pedro; Virgós-Lamela, Alejandro; García-Acuña, José María; González-Juanatey, José Ramón

    2015-06-01

    Given the increasing focus on early mortality and readmission rates among patients with acute coronary syndrome (ACS), this study was designed to evaluate the accuracy of the GRACE risk score for identifying patients at high risk of 30-day post-discharge mortality and cardiovascular readmission. This was a retrospective study carried out in a single center with 4229 ACS patients discharged between 2004 and 2010. The study endpoint was the combination of 30-day post-discharge mortality and readmission due to reinfarction, heart failure or stroke. One hundred and fourteen patients had 30-day events: 0.7% mortality, 1% reinfarction, 1.3% heart failure, and 0.2% stroke. After multivariate analysis, the six-month GRACE risk score was associated with an increased risk of 30-day events (HR 1.03, 95% CI 1.02-1.04; p<0.001), demonstrating good discrimination (C-statistic: 0.79 ± 0.02) and optimal fit (Hosmer-Lemeshow p=0.83). The sensitivity and specificity were adequate (78.1% and 63.3%, respectively), and negative predictive value was excellent (99.1%). In separate analyses for each event of interest (all-cause mortality, reinfarction, heart failure and stroke), assessment of the six-month GRACE risk score also demonstrated good discrimination and fit, as well as adequate predictive values. The six-month GRACE risk score is a useful tool to predict 30-day post-discharge death and early cardiovascular readmission. Clinicians may find it simple to use with the online and mobile app score calculator and applicable to clinical daily practice. Copyright © 2014 Sociedade Portuguesa de Cardiologia. Published by Elsevier España. All rights reserved.

  18. Landwater variation in four major river basins of the Indochina peninsula as revealed by GRACE

    Science.gov (United States)

    Yamamoto, K.; Fukuda, Y.; Nakaegawa, T.; Nishijima, J.

    2007-04-01

    We estimated mass variations in four major river basins the Mekong, Irrawaddy, Salween and Chao Phraya river basins of the Indochina Peninsula using the newly released GRACE (Gravity Recovery and Climate Experiment) monthly gravity field solutions of UTCSR RL02 (University of Texas at Austin, Center for Space Research Release 02), JPL RL02 (Jet Propulsion Laboratory Release 02) and GFZ RL03 (GeoForschungsZentrum Potsdam Release 03). The estimated variations were compared with that calculated from a numerical model. The results show that there is a good agreement between the GRACE estimations and the model calculation for the Mekong and Irrawaddy basins, while the aggreement for the Salween and Chao Phraya basins is poor, mainly due to the spatial scale of the areas concerned. The comparison over the combined area of the four river basins shows fairly good agreement, although there are small quantitative discrepancies. The amplitudes of the annual signals of the GRACE solutions are 0.9- to 1.4-fold larger than that of the hydrological model, and the phases are delayed about 1 month compared with the model signal. The phase differences are probably due to improper treatments of the groundwater storage process in the hydrological model, suggesting that the GRACE data possibly provide constraints to the model parameters.

  19. Sediment-Mass Accumulation Rate and Variability in the East China Sea Detected by GRACE

    Directory of Open Access Journals (Sweden)

    Ya-Chi Liu

    2016-09-01

    Full Text Available The East China Sea (ECS is a region with shallow continental shelves and a mixed oceanic circulation system allowing sediments to deposit on its inner shelf, particularly near the estuary of the Yangtze River. The seasonal northward-flowing Taiwan Warm Current and southward-flowing China Coastal Current trap sediments from the Yangtze River, which are accumulated over time at rates of up to a few mm/year in equivalent water height. Here, we use the Gravity Recovery and Climate Experiment (GRACE gravity products from three data centres to determine sediment mass accumulation rates (MARs and variability on the ECS inner shelf. We restore the atmospheric and oceanic effects to avoid model contaminations on gravity signals associated with sediment masses. We apply destriping and spatial filters to improve the gravity signals from GRACE and use the Global Land Data Assimilation System to reduce land leakage. The GRACE-derived MARs over April 2002–March 2015 on the ECS inner shelf are about 6 mm/year and have magnitudes and spatial patterns consistent with those from sediment-core measurements. The GRACE-derived monthly sediment depositions show variations at time scales ranging from six months to more than two years. Typically, a positive mass balance of sediment deposition occurs in late fall to early winter when the southward coastal currents prevail. A negative mass balance happens in summer when the coastal currents are northward. We identify quasi-biennial sediment variations, which are likely to be caused by quasi-biennial variations in rain and erosion in the Yangtze River basin. We briefly explain the mechanisms of such frequency-dependent variations in the GRACE-derived ECS sediment deposition. There is no clear perturbation on sediment deposition over the ECS inner shelf induced by the Three Gorges Dam. The limitations of GRACE in resolving sediment deposition are its low spatial resolution (about 250 km and possible contaminations by

  20. Groundwater Storage Changes: Present Status from GRACE Observations

    Science.gov (United States)

    Chen, Jianli; Famigliett, James S.; Scanlon, Bridget R.; Rodell, Matthew

    2016-03-01

    Satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) provide quantitative measurement of terrestrial water storage (TWS) changes with unprecedented accuracy. Combining GRACE-observed TWS changes and independent estimates of water change in soil and snow and surface reservoirs offers a means for estimating groundwater storage change. Since its launch in March 2002, GRACE time-variable gravity data have been successfully used to quantify long-term groundwater storage changes in different regions over the world, including northwest India, the High Plains Aquifer and the Central Valley in the USA, the North China Plain, Middle East, and southern Murray-Darling Basin in Australia, where groundwater storage has been significantly depleted in recent years (or decades). It is difficult to rely on in situ groundwater measurements for accurate quantification of large, regional-scale groundwater storage changes, especially at long timescales due to inadequate spatial and temporal coverage of in situ data and uncertainties in storage coefficients. The now nearly 13 years of GRACE gravity data provide a successful and unique complementary tool for monitoring and measuring groundwater changes on a global and regional basis. Despite the successful applications of GRACE in studying global groundwater storage change, there are still some major challenges limiting the application and interpretation of GRACE data. In this paper, we present an overview of GRACE applications in groundwater studies and discuss if and how the main challenges to using GRACE data can be addressed.

  1. Groundwater Storage Changes: Present Status from GRACE Observations

    Science.gov (United States)

    Chen, Jianli; Famiglietti, James S.; Scanlon, Bridget R.; Rodell, Matthew

    2015-01-01

    Satellite gravity measurements from the Gravity Recovery and Climate Experiment (GRACE) provide quantitative measurement of terrestrial water storage (TWS) changes with unprecedented accuracy. Combining GRACE-observed TWS changes and independent estimates of water change in soil and snow and surface reservoirs offers a means for estimating groundwater storage change. Since its launch in March 2002, GRACE time-variable gravity data have been successfully used to quantify long-term groundwater storage changes in different regions over the world, including northwest India, the High Plains Aquifer and the Central Valley in the USA, the North China Plain, Middle East, and southern Murray-Darling Basin in Australia, where groundwater storage has been significantly depleted in recent years (or decades). It is difficult to rely on in situ groundwater measurements for accurate quantification of large, regional-scale groundwater storage changes, especially at long timescales due to inadequate spatial and temporal coverage of in situ data and uncertainties in storage coefficients. The now nearly 13 years of GRACE gravity data provide a successful and unique complementary tool for monitoring and measuring groundwater changes on a global and regional basis. Despite the successful applications of GRACE in studying global groundwater storage change, there are still some major challenges limiting the application and interpretation of GRACE data. In this paper, we present an overview of GRACE applications in groundwater studies and discuss if and how the main challenges to using GRACE data can be addressed.

  2. Groundwater storage changes from GRACE satellite in the Southern Gobi Region of Mongolia

    Science.gov (United States)

    Nemer, B.; Yanping, C.; Bayanzul, B. B.; Altangerel, E. E.

    2014-12-01

    Groundwater is an important resource in the Southern Gobi Region of Mongolia because rainfall and surface water availability are severely limited and the demands are expected to increase rapidly with the development of mining and new population centers. Groundwater systems are more complex and yet its distribution and quantity are poorly known. The purpose of the research is to evaluate the potential utility of GRACE (Gravity Recovery and Climate Experiment) satellites to monitor groundwater storage in the arid area. Regional groundwater storage changes in SGR are estimated using monthly GRACE total water storage change data. Groundwater storage change estimates are compared to groundwater level measurements of 66 shallow dug wells and 72 deep boreholes for the period 2004-2012. Groundwater storage decreases during the cold season and increases during the warm season. Seasonal groundwater change calculated from GRACE total water storage is highly correlated to groundwater level measurements in shallow aquifers. There is no correlation between groundwater storage changes derived from GRACE and deep aquifer. The result indicates that GRACE can be used to monitor large area where groundwater observation is limited, especially unconfined shallow aquifers.

  3. Detection of human-induced evapotranspiration using GRACE satellite observations in the Haihe River basin of China

    Science.gov (United States)

    Pan, Yun; Zhang, Chong; Gong, Huili; Yeh, Pat J.-F.; Shen, Yanjun; Guo, Ying; Huang, Zhiyong; Li, Xiaojuan

    2017-01-01

    Regional evapotranspiration (ET) can be enhanced by human activities such as irrigation or reservoir impoundment. Here the potential of using Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage data in water budget calculations to detect human-induced ET change is investigated over the Haihe River basin of China. Comparison between GRACE-based monthly ET estimate (2005-2012) and Global Land Data Assimilation System (GLDAS)-modeled ET indicates that human-induced ET due to intensive groundwater irrigation from March to May can only be detected by GRACE. GRACE-based ET (521.7 ± 21.1 mm/yr), considerably higher than GLDAS ET (461.7 ± 29.8 mm/yr), agrees well with existing estimates found in the literature and indicates that human activities contribute to a 12% increase in ET. The double-peak seasonal pattern of ET (in May and August) as reported in published studies is well reproduced by GRACE-based ET estimate. This study highlights the unique capability of GRACE in detecting anthropogenic signals over regions with large groundwater consumption.

  4. Say Good-Bye Gracefully.

    Science.gov (United States)

    Armstrong, Coleen

    1994-01-01

    Advises retiring administrators to exercise a bit of dignity and common sense in their remaining months on the job. Administrators should show consideration regarding retirement plans, fight laziness, conduct training sessions for other administrators, accept others' foolish behavior gracefully, and be generous with parting insights. (MLH)

  5. High-resolution CSR GRACE RL05 mascons

    Science.gov (United States)

    Save, Himanshu; Bettadpur, Srinivas; Tapley, Byron D.

    2016-10-01

    The determination of the gravity model for the Gravity Recovery and Climate Experiment (GRACE) is susceptible to modeling errors, measurement noise, and observability issues. The ill-posed GRACE estimation problem causes the unconstrained GRACE RL05 solutions to have north-south stripes. We discuss the development of global equal area mascon solutions to improve the GRACE gravity information for the study of Earth surface processes. These regularized mascon solutions are developed with a 1° resolution using Tikhonov regularization in a geodesic grid domain. These solutions are derived from GRACE information only, and no external model or data is used to inform the constraints. The regularization matrix is time variable and will not bias or attenuate future regional signals to some past statistics from GRACE or other models. The resulting Center for Space Research (CSR) mascon solutions have no stripe errors and capture all the signals observed by GRACE within the measurement noise level. The solutions are not tailored for specific applications and are global in nature. This study discusses the solution approach and compares the resulting solutions with postprocessed results from the RL05 spherical harmonic solutions and other global mascon solutions for studies of Arctic ice sheet processes, ocean bottom pressure variation, and land surface total water storage change. This suite of comparisons leads to the conclusion that the mascon solutions presented here are an enhanced representation of the RL05 GRACE solutions and provide accurate surface-based gridded information that can be used without further processing.

  6. Estimating geocenter motion and barystatic sea-level variability from GRACE observations with explicit consideration of self-attraction and loading effects

    Science.gov (United States)

    Bergmann-Wolf, Inga; Dobslaw, Henryk

    2016-04-01

    Estimating global barystatic sea-level variations from monthly mean gravity fields delivered by the Gravity Recovery and Climate Experiment (GRACE) satellite mission requires additional information about geocenter motion. These variations are not available directly due to the mission implementation in the CM-frame and are represented by the degree-1 terms of the spherical harmonics expansion. Global degree-1 estimates can be determined with the method of Swenson et al. (2008) from ocean mass variability, the geometry of the global land-sea distribution, and GRACE data of higher degrees and orders. Consequently, a recursive relation between the derivation of ocean mass variations from GRACE data and the introduction of geocenter motion into GRACE data exists. In this contribution, we will present a recent improvement to the processing strategy described in Bergmann-Wolf et al. (2014) by introducing a non-homogeneous distribution of global ocean mass variations in the geocenter motion determination strategy, which is due to the effects of loading and self-attraction induced by mass redistributions at the surface. A comparison of different GRACE-based oceanographic products (barystatic signal for both the global oceans and individual basins; barotropic transport variations of major ocean currents) with degree-1 terms estimated with a homogeneous and non-homogeneous ocean mass representation will be discussed, and differences in noise levels in most recent GRACE solutions from GFZ (RL05a), CSR, and JPL (both RL05) and their consequences for the application of this method will be discussed. Swenson, S., D. Chambers and J. Wahr (2008), Estimating geocenter variations from a combination of GRACE and ocean model output, J. Geophys. Res., 113, B08410 Bergmann-Wolf, I., L. Zhang and H. Dobslaw (2014), Global Eustatic Sea-Level Variations for the Approximation of Geocenter Motion from GRACE, J. Geod. Sci., 4, 37-48

  7. Flood potential index over China based on GRACE

    Science.gov (United States)

    Zhou, Xudong

    2016-04-01

    As an important element relating to wet status over a region, the terrestrial water storage (TWS) has a tight connection with the potential of flood occurrence. However, few of the flood indicators have taken TWS into consideration because it is difficult to measure in large regional scale. After 2002, Gravity Recovery And Climate Experiment (GRACE) mission became a helpful tool to fill the gap in regional water storage estimation. Over the GRACE record period, the repeated maxima in water storage anomaly suggest an active storage capacity for a given grid. When the additional precipitation exceeds the water deficit in the vertical space, it is marked as potential saturation runoff. Hence, in this paper, a normalized gridded index indicating the flood potential was developed over China based on the monthly storage deficit simulated by the terrestrial water storage anomaly (TWSA) from GRACE, precipitation from GPCC as well as the simulated potential water release. The results indicate that the average release water rates show large variation over China mainland, with larger rate in south and the lower around the north-west deserts. The monthly rate of release water in most of grids are well correlated with the precipitation feed especially in summer. This provides us the chance in estimating the monthly natural release water with the average precipitation in corresponding month. To highlight the flood potential application, the monthly map during the 2013 floods and 2009-2010 droughts are presented. The flood potential index can effectively indicate the floods in specific regions with higher values. Moreover, we can detect the spatial extend and temporal development of the droughts if the index in the region keeps in a lower level. As the advantages, this flood potential index captures the spatial structures while the common hydrological drought index is more regionally. Meanwhile, compared to the widely used meteorological drought index, the index here is more

  8. A comment on ''A test of general relativity using the LARES and LAGEOS satellites and a GRACE Earth gravity model'', by I. Ciufolini et al

    Energy Technology Data Exchange (ETDEWEB)

    Iorio, Lorenzo [Ministero dell' Istruzione Univ. della Ricerca (M.I.U.R.), Bari (Italy)

    2017-02-15

    Recently, Ciufolini et al. reported on a test of the general relativistic gravitomagnetic Lense-Thirring effect by analyzing about 3.5 years of laser ranging data to the LAGEOS, LAGEOS II, LARES geodetic satellites orbiting the Earth. By using the GRACE-based GGM05S Earth's global gravity model and a linear combination of the nodes Ω of the three satellites designed to remove the impact of errors in the first two even zonal harmonic coefficients J{sub 2}, J{sub 4} of the multipolar expansion of the Newtonian part of the Earth's gravitational potential, they claimed an overall accuracy of 5% for the Lense-Thirring caused node motion. We show that the scatter in the nominal values of the uncancelled even zonals of degree l = 6, 8, 10 from some of the most recent global gravity models does not yet allow to reach unambiguously and univocally the expected ∼1% level, being large up to

  9. Introducing GRACE Follow-On mock data challenge project

    Science.gov (United States)

    Darbeheshti, Neda; Naeimi, Majid; Hewitson, Martin; Heinzel, Gerhard; Flury, Jakob

    2016-04-01

    GRACE Follow-On satellites will be launched in 2017. Equipped with the additional Laser Ranging Instrument (LRI) sensor, GRACE Follow-On is expected to reach even better spatial and temporal resolution for the Earth's gravity field. GRACE Follow-On mock data challenge project is part of the geo-Q project at Leibniz Universität Hannover and plans several runs of data challenges for GRACE Follow-On. The challenges are coordinated from simple gravity field recovery in 2015 to more advanced forms when LRI noise model will be added in 2016 challenge. The aim of these challenges is to engage different research centers around the world to test their methods for gravity field recovery from simulated data which will lead to develop data analysis tools and capabilities for GRACE follow-On data. In this contribution we introduce the mock data challenge project for GRACE and GRACE Follow-On. The highlights and objectives of the challenges will be given, with the details about the webpage and data exchange for the participants.

  10. Seasonal crustal vertical deformation induced by environmental mass loading in mainland China derived from GPS, GRACE and surface loading models

    Science.gov (United States)

    Gu, Yanchao; Yuan, Linguo; Fan, Dongming; You, Wei; Su, Yong

    2017-01-01

    Obvious seasonal crustal vertical deformation largely related to mass redistribution on the Earth's surface can be captured by Gravity Recovery and Climate Experiment (GRACE), simulated by surface loading models (SLMs), and recorded by continuous Global Positioning System (GPS). Vertical deformation time series at 224 GPS stations with more than four-year continuous observations are compared with time series obtained by GRACE and SLMs with the aim of investigating the consistency of the seasonal crustal vertical deformation obtained by different techniques in mainland China. Results of these techniques show obvious seasonal vertical deformation with high consistency at almost all stations. The GPS-derived seasonal vertical deformation can be explained, to some content, by the environmental mass redistribution effect represented by GRACE and SLMs. Though the mean weighted root mean square reduction is 34% after removing the environmental mass loading from the monthly GPS height time series (up to 47% for the mean annual signals), systematic signals are still evident in the residual time series. The systematic residuals are probably attributed to GPS related errors, such as draconitic errors, while the leakage errors in the GRACE data processing and unmodeled components in land water storage should be considered in some regions. Additionally, the obvious seasonal residual perturbations in Southwest China may be related to the leakage errors in the GRACE data processing and large uncertainty in the land water storage in SLMs, indicating that GPS observations may provide more realistic mass transport estimates in Southwest China.

  11. Resolving mass flux at high spatial and temporal resolution using GRACE intersatellite measurements

    DEFF Research Database (Denmark)

    Rowlands, D. D.; Luthcke, S. B.; Klosko, S. M.

    2005-01-01

    The GRACE mission is designed to monitor mass flux on the Earth's surface at one month and high spatial resolution through the estimation of monthly gravity fields. Although this approach has been largely successful, information at submonthly time scales can be lost or even aliased through...... resolution. Using 4° × 4° blocks at 10-day intervals, we estimate the mass of surplus or deficit water over a 52° × 60° grid centered on the Amazon basin for July 2003. We demonstrate that the recovered signals are coherent and correlate well with the expected hydrological signal....

  12. Validating hydro-meteorological fluxes using GRACE-derived water storage changes - a global and regional perspective

    Science.gov (United States)

    Eicker, Annette; Springer, Anne; Kusche, Jürgen; Jütten, Thomas; Diekkrüger, Bernd; Longuevergne, Laurent

    2016-04-01

    Atmospheric and terrestrial water budgets, which represent important boundary conditions for both climate modeling and hydrological studies, are linked by evapotranspiration (E) and precipitation (P). These fields are provided by numerical weather prediction models and atmospheric reanalyses such as ERA-Interim and MERRA-Land; yet, in particular the quality of E is still not well evaluated. Via the terrestrial water budget equation, water storage changes derived from products of the Gravity Recovery and Climate Experiment (GRACE) mission, combined with runoff (R) data can be used to assess the realism of atmospheric models. While on short temporal scales (inter-annual down to sub-seasonal) the modeled fluxes agree remarkably well with GRACE water storage changes, the models exhibit large biases and fail to capture the long-term flux trends in P-E-R corresponding to GRACE accelerations (Eicker et al. 2016). This leads to the assumption that despite the short time span of available gravity field observations, GRACE is able to provide new information for constraining the long-term evolution of water fluxes in future atmospheric reanalyses. In this contribution we will investigate the agreement of GRACE water storage changes with P-E-R flux time series from different (global and regional) atmospheric reanalyses, land surface models, as well as observation-based data sets. We will perform a global analyses and we will additionally focus on selected river basins. The investigations will be carried out for various temporal scales, focussing on the short-term fluxes (month-to-month variations), for which models and GRACE agree well with correlations of the de-trended and de-seasoned fluxes time series reaching up to 0.8 and more. We will furthermore extent the study towards even higher temporal frequencies, investigating whether the modeled and observed fluxes show sub-monthly variability that can be detected in daily GRACE time series. Eicker, A., E. Forootan, A. Springer

  13. Estimation of soil loss by water erosion in the Chinese Loess Plateau using Universal Soil Loss Equation and GRACE

    Science.gov (United States)

    Schnitzer, S.; Seitz, F.; Eicker, A.; Güntner, A.; Wattenbach, M.; Menzel, A.

    2013-06-01

    For the estimation of soil loss by erosion in the strongly affected Chinese Loess Plateau we applied the Universal Soil Loss Equation (USLE) using a number of input data sets (monthly precipitation, soil types, digital elevation model, land cover and soil conservation measures). Calculations were performed in ArcGIS and SAGA. The large-scale soil erosion in the Loess Plateau results in a strong non-hydrological mass change. In order to investigate whether the resulting mass change from USLE may be validated by the gravity field satellite mission GRACE (Gravity Recovery and Climate Experiment), we processed different GRACE level-2 products (ITG, GFZ and CSR). The mass variations estimated in the GRACE trend were relatively close to the observed sediment yield data of the Yellow River. However, the soil losses resulting from two USLE parameterizations were comparatively high since USLE does not consider the sediment delivery ratio. Most eroded soil stays in the study area and only a fraction is exported by the Yellow River. Thus, the resultant mass loss appears to be too small to be resolved by GRACE.

  14. Assimilation of gridded terrestrial water storage observations from GRACE into a land surface model

    Science.gov (United States)

    Girotto, Manuela; De Lannoy, Gabriëlle J. M.; Reichle, Rolf H.; Rodell, Matthew

    2016-05-01

    Observations of terrestrial water storage (TWS) from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have a coarse resolution in time (monthly) and space (roughly 150,000 km2 at midlatitudes) and vertically integrate all water storage components over land, including soil moisture and groundwater. Data assimilation can be used to horizontally downscale and vertically partition GRACE-TWS observations. This work proposes a variant of existing ensemble-based GRACE-TWS data assimilation schemes. The new algorithm differs in how the analysis increments are computed and applied. Existing schemes correlate the uncertainty in the modeled monthly TWS estimates with errors in the soil moisture profile state variables at a single instant in the month and then apply the increment either at the end of the month or gradually throughout the month. The proposed new scheme first computes increments for each day of the month and then applies the average of those increments at the beginning of the month. The new scheme therefore better reflects submonthly variations in TWS errors. The new and existing schemes are investigated here using gridded GRACE-TWS observations. The assimilation results are validated at the monthly time scale, using in situ measurements of groundwater depth and soil moisture across the U.S. The new assimilation scheme yields improved (although not in a statistically significant sense) skill metrics for groundwater compared to the open-loop (no assimilation) simulations and compared to the existing assimilation schemes. A smaller impact is seen for surface and root-zone soil moisture, which have a shorter memory and receive smaller increments from TWS assimilation than groundwater. These results motivate future efforts to combine GRACE-TWS observations with observations that are more sensitive to surface soil moisture, such as L-band brightness temperature observations from Soil Moisture Ocean Salinity (SMOS) or Soil Moisture Active Passive

  15. Ocean contribution to seismic gravity changes: the sea level equation for seismic perturbations revisited

    NARCIS (Netherlands)

    Broerse, D.B.T.; Riva, R.E.M.; Vermeersen, B.

    2014-01-01

    During megathrust earthquakes, great ruptures are accompanied by large scale mass redistribution inside the solid Earth and by ocean mass redistribution due to bathymetry changes. These large scale mass displacements can be detected using the monthly gravity maps of the GRACE satellite mission. In r

  16. Ocean contribution to seismic gravity changes: the sea level equation for seismic perturbations revisited

    NARCIS (Netherlands)

    Broerse, D.B.T.; Riva, R.E.M.; Vermeersen, B.

    2014-01-01

    During megathrust earthquakes, great ruptures are accompanied by large scale mass redistribution inside the solid Earth and by ocean mass redistribution due to bathymetry changes. These large scale mass displacements can be detected using the monthly gravity maps of the GRACE satellite mission. In

  17. Precise Relative Orbit Determination of Twin GRACE Satellites

    Institute of Scientific and Technical Information of China (English)

    ZHAO Qile; HU Zhigang; GUO Jing; LI Min; GE Maorong

    2010-01-01

    When formation flying spacecrafts are used as platform to gain earth oriented observation, precise baselines between these spacecrafts are always essential. Gravity recovery and climate experiment (GRACE) mission is aimed at mapping the global gravity field and its variation. Accurate baseline of GRACE satellites is necessary for the gravity field modeling. The determination of kinematic and reduced dynamic relative orbits of twin satellites has been studied in this paper, and an accuracy of 2 mm for dynamic relative orbits and 5 mm for kinematic ones can be obtained, whereby most of the double difference onboard GPS ambiguities are resolved.

  18. A 1985-2015 data-driven global reconstruction of GRACE total water storage

    Science.gov (United States)

    Humphrey, Vincent; Gudmundsson, Lukas; Isabelle Seneviratne, Sonia

    2016-04-01

    After thirteen years of measurements, the Gravity Recovery and Climate Experiment (GRACE) mission has enabled for an unprecedented view on total water storage (TWS) variability. However, the relatively short record length, irregular time steps and multiple data gaps since 2011 still represent important limitations to a wider use of this dataset within the hydrological and climatological community especially for applications such as model evaluation or assimilation of GRACE in land surface models. To address this issue, we make use of the available GRACE record (2002-2015) to infer local statistical relationships between detrended monthly TWS anomalies and the main controlling atmospheric drivers (e.g. daily precipitation and temperature) at 1 degree resolution (Humphrey et al., in revision). Long-term and homogeneous monthly time series of detrended anomalies in total water storage are then reconstructed for the period 1985-2015. The quality of this reconstruction is evaluated in two different ways. First we perform a cross-validation experiment to assess the performance and robustness of the statistical model. Second we compare with independent basin-scale estimates of TWS anomalies derived by means of combined atmospheric and terrestrial water-balance using atmospheric water vapor flux convergence and change in atmospheric water vapor content (Mueller et al. 2011). The reconstructed time series are shown to provide robust data-driven estimates of global variations in water storage over large regions of the world. Example applications are provided for illustration, including an analysis of some selected major drought events which occurred before the GRACE era. References Humphrey V, Gudmundsson L, Seneviratne SI (in revision) Assessing global water storage variability from GRACE: trends, seasonal cycle, sub-seasonal anomalies and extremes. Surv Geophys Mueller B, Hirschi M, Seneviratne SI (2011) New diagnostic estimates of variations in terrestrial water storage

  19. Estimation of GRACE water storage components by temporal decomposition

    Science.gov (United States)

    Andrew, Robert; Guan, Huade; Batelaan, Okke

    2017-09-01

    The Gravity Recovery and Climate Experiment (GRACE) has been in operation since 2002. Water storage estimates are calculated from gravity anomalies detected by the operating satellites and although not the true resolution, can be presented as 100 km × 100 km data cells if appropriate scaling functions are applied. Estimating total water storage has shown to be highly useful in detecting hydrological variations and trends. However, a limitation is that GRACE does not provide information as to where the water is stored in the vertical profile. We aim to partition the total water storage from GRACE into water storage components. We use a wavelet filter to decompose the GRACE data and partition it into various water storage components including soil water and groundwater. Storage components from the Australian Water Resources Assessment (AWRA) model are used as a reference for the decompositions of total storage data across Australia. Results show a clear improvement in using decomposed GRACE data instead of raw GRACE data when compared against total water storage outputs from the AWRA model. The method has potential to improve GRACE applications including a means to test various large scale hydrological models as well as helping to analyse floods, droughts and other hydrological conditions.

  20. Recent Advances in the GRACE Data Assimilation System (Invited)

    Science.gov (United States)

    Zaitchik, B. F.; Rodell, M.; Kumar, S.; Reichle, R. H.; Bolten, J. D.; Bergaoui, K.

    2013-12-01

    Anomalies in Terrestrial Water Storage (TWS) derived from the Gravity Recovery and Climate Experiment (GRACE) mission have been used effectively to study hydrologic variability and trends at basin scale across diverse climatic and geologic conditions. Many hydrology and water resources applications, however, require water storage estimates at higher spatial resolution, greater temporal frequency, and with greater physical specificity (e.g., groundwater versus soil moisture versus snow) than GRACE alone can offer. The GRACE Data Assimilation System (GRACE-DAS) was developed to merge GRACE information on large-scale TWS anomalies with physically-based advanced Land Surface Models in order to improve model simulation of water storage while disaggregating and downscaling the raw GRACE TWS estimate. The primary assimilation algorithm is a variant of the ensemble Kalman Smoother. In recent years the system has been applied to studies of water resources and drought monitoring over four different continents. These experiences have led to refinements in the assimilation system that include modifications to land surface model parameters and the treatment of irrigation withdrawals, adjustments in the assimilation algorithm for snow updates, and, most recently, the implementation of a gridded observation assimilation capability that allows for a more flexible application of the system. This presentation will provide an overview of current GRACE-DAS capabilities, report on recent innovations in the modeling system, and describe future directions in GRACE data assimilation research and applications.

  1. Grace Nash: Nine Decades of Graceful Teaching.

    Science.gov (United States)

    Cole, Judith

    2000-01-01

    Provides information on the life of Grace Nash, an influential educator and pioneer of Orff Schulwerk in the United States, focusing on issues such as her young life, experience as a prisoner-of-war, development of her interest in the Orff, Kodaly, and Laban methods, and her own work. Offers selected resources. (CMK)

  2. Economy and Grace

    DEFF Research Database (Denmark)

    Pedersen, Else Marie Wiberg

    2015-01-01

    Luther develops his idea the grace of God in tandem with his idea of economy, and a society characterized by ethical and social values such as love of neighbour and caring for the poor. Hence, the reformer's search for a gracious God is developed along with his criticism of the current indulgence...... doctrine and the emerging 'oeconomia moderna'. Thus, building on a simul gratia et oeconomia, grace and economy simultaneously, Luther's reformation theology can be perceived as te intersection of an economy of grace and a horizontal social economy (works of love) in quotidian life that together constitute...

  3. An Improved GRACE Terrestrial Water Storage Assimilation System For Estimating Large-Scale Soil Moisture and Shallow Groundwater

    Science.gov (United States)

    Girotto, M.; De Lannoy, G. J. M.; Reichle, R. H.; Rodell, M.

    2015-12-01

    The Gravity Recovery And Climate Experiment (GRACE) mission is unique because it provides highly accurate column integrated estimates of terrestrial water storage (TWS) variations. Major limitations of GRACE-based TWS observations are related to their monthly temporal and coarse spatial resolution (around 330 km at the equator), and to the vertical integration of the water storage components. These challenges can be addressed through data assimilation. To date, it is still not obvious how best to assimilate GRACE-TWS observations into a land surface model, in order to improve hydrological variables, and many details have yet to be worked out. This presentation discusses specific recent features of the assimilation of gridded GRACE-TWS data into the NASA Goddard Earth Observing System (GEOS-5) Catchment land surface model to improve soil moisture and shallow groundwater estimates at the continental scale. The major recent advancements introduced by the presented work with respect to earlier systems include: 1) the assimilation of gridded GRACE-TWS data product with scaling factors that are specifically derived for data assimilation purposes only; 2) the assimilation is performed through a 3D assimilation scheme, in which reasonable spatial and temporal error standard deviations and correlations are exploited; 3) the analysis step uses an optimized calculation and application of the analysis increments; 4) a poor-man's adaptive estimation of a spatially variable measurement error. This work shows that even if they are characterized by a coarse spatial and temporal resolution, the observed column integrated GRACE-TWS data have potential for improving our understanding of soil moisture and shallow groundwater variations.

  4. Antarctic contribution to sea level rise observed by GRACE with improved GIA correction

    Science.gov (United States)

    Ivins, Erik R.; James, Thomas S.; Wahr, John; Schrama, Ernst J. O.; Landerer, Felix W.; Simon, Karen M.

    2013-06-01

    Antarctic volume changes during the past 21 thousand years are smaller than previously thought, and here we construct an ice sheet history that drives a forward model prediction of the glacial isostatic adjustment (GIA) gravity signal. The new model, in turn, should give predictions that are constrained with recent uplift data. The impact of the GIA signal on a Gravity Recovery and Climate Experiment (GRACE) Antarctic mass balance estimate depends on the specific GRACE analysis method used. For the method described in this paper, the GIA contribution to the apparent surface mass change is re-evaluated to be +55±13 Gt/yr by considering a revised ice history model and a parameter search for vertical motion predictions that best fit the GPS observations at 18 high-quality stations. Although the GIA model spans a range of possible Earth rheological structure values, the data are not yet sufficient for solving for a preferred value of upper and lower mantle viscosity nor for a preferred lithospheric thickness. GRACE monthly solutions from the Center for Space Research Release 04 (CSR-RL04) release time series from January 2003 to the beginning of January 2012, uncorrected for GIA, yield an ice mass rate of +2.9± 29 Gt/yr. The new GIA correction increases the solved-for ice mass imbalance of Antarctica to -57±34 Gt/yr. The revised GIA correction is smaller than past GRACE estimates by about 50 to 90 Gt/yr. The new upper bound to the sea level rise from the Antarctic ice sheet, averaged over the time span 2003.0-2012.0, is about 0.16±0.09 mm/yr.

  5. Monitoring and comparison of terrestrial water storage changes in the northern high plains using GRACE and in-situ based integrated hydrologic model estimates

    Science.gov (United States)

    Seyoum, Wondwosen M.; Milewski, Adam M.

    2016-08-01

    Enhanced measurement of the variation of the terrestrial water cycle are imperative to better understand the dynamics, water availability, and evaluate impacts of global changes on the water cycle. This study quantified storage in the various terrestrial water compartments using an integrated hydrologic model (IHM) - MIKE SHE that simulates the entire terrestrial water cycle and the Gravity Recovery and Climate Experiment (GRACE) satellite data in the intensively irrigated Northern High Plains (area ∼ 250,000 km2). The IHM, mainly constructed using in-situ data, was evaluated using field measured groundwater level, stream flow, and soil moisture data. The model was first used to calculate the incremental water storage for each water balance component (e.g. storage in the saturated zone) and then the GRACE equivalent terrestrial water storage anomaly. In the study area, storage in the saturated zone is the major component of the terrestrial water storage (TWS) anomaly. The GRACE-derived TWS anomaly and the anomaly simulated from the model are generally in agreement on a monthly scale with few discrepancies. Generally, both GRACE and the IHM results displayed a statistically significant increasing trend in the total TWS and groundwater storage anomalies from 2002-2013 over the Northern High Plains. This study demonstrates the applicability of an integrated hydrologic model to monitor TWS variations in a large area, and GRACE data and IHMs are capable of reproducing observed trends in TWS.

  6. Improving Budyko curve-based estimates of long-term water partitioning using hydrologic signatures from GRACE

    Science.gov (United States)

    Fang, Kuai; Shen, Chaopeng; Fisher, Joshua B.; Niu, Jie

    2016-07-01

    The Budyko hypothesis provides a first-order estimate of water partitioning into runoff (Q) and evapotranspiration (E). Observations, however, often show significant departures from the Budyko curve; moreover, past improvements to Budyko curve tend to lose predictive power when migrated between regions or to small scales. Here to estimate departures from the Budyko curve, we use hydrologic signatures extracted from Gravity Recovery And Climate Experiment (GRACE) terrestrial water storage anomalies. The signatures include GRACE amplitude as a fraction of precipitation (A/P), interannual variability, and 1-month lag autocorrelation. We created a group of linear models embodying two alternate hypotheses that departures can be predicted by (a) Taylor series expansion based on the deviation of physical characteristics (seasonality, snow fraction, and vegetation index) from reference conditions and (b) surrogate indicators covarying with E, e.g., A/P. These models are fitted using a mesoscale USA data set (HUC4) and then evaluated using world data sets and USA basins migrated to a global data set, type b models performed better than type a. This contrast in transferability is argued to be due to data set limitations and catchment coevolution. The GRACE-based correction performs well for USA basins >1000 km2 and, according to comparison with other global data sets, is suitable for data fusion purposes, with GRACE error as estimates of uncertainty.

  7. Monitoring groundwater drought with GRACE data assimilation

    Science.gov (United States)

    Li, B.; Rodell, M.; Beaudoing, H. K.; Getirana, A.; Zaitchik, B. F.

    2015-12-01

    Groundwater drought is a distinct class of drought, not a sub-class of meteorological, agricultural and hydrological drought and has profound impacts on natural environments and societies. Due to a deficiency of in situ measurements, we developed a groundwater drought indicator using groundwater change estimates derived by assimilating GRACE derived terrestrial water storage (TWS) anomalies into the NASA Catchment land surface model. Data assimilation enables spatial and temporal downscaling of coarse GRACE TWS observations (monthly and ~150,000 km2 effective spatial resolution) and extrapolation to near-real time. In this talk, we will present our latest progress on using GRACE satellite data for groundwater drought monitoring in the U.S. and globally. Characteristics of this groundwater drought indicator will be discussed, including its relationship with other types of drought and how they are influenced by model physics and climate conditions. Results are evaluated using in situ groundwater observations.

  8. Multi-scale gravity field modeling in space and time

    Science.gov (United States)

    Wang, Shuo; Panet, Isabelle; Ramillien, Guillaume; Guilloux, Frédéric

    2016-04-01

    The Earth constantly deforms as it undergoes dynamic phenomena, such as earthquakes, post-glacial rebound and water displacement in its fluid envelopes. These processes have different spatial and temporal scales and are accompanied by mass displacements, which create temporal variations of the gravity field. Since 2002, the GRACE satellite missions provide an unprecedented view of the gravity field spatial and temporal variations. Gravity models built from these satellite data are essential to study the Earth's dynamic processes (Tapley et al., 2004). Up to present, time variations of the gravity field are often modelled using spatial spherical harmonics functions averaged over a fixed period, as 10 days or 1 month. This approach is well suited for modeling global phenomena. To better estimate gravity related to local and/or transient processes, such as earthquakes or floods, and adapt the temporal resolution of the model to its spatial resolution, we propose to model the gravity field using localized functions in space and time. For that, we build a model of the gravity field in space and time with a four-dimensional wavelet basis, well localized in space and time. First we design the 4D basis, then, we study the inverse problem to model the gravity field from the potential differences between the twin GRACE satellites, and its regularization using prior knowledge on the water cycle. Our demonstration of surface water mass signals decomposition in time and space is based on the use of synthetic along-track gravitational potential data. We test the developed approach on one year of 4D gravity modeling and compare the reconstructed water heights to those of the input hydrological model. Perspectives of this work is to apply the approach on real GRACE data, addressing the challenge of a realistic noise, to better describe and understand physical processus with high temporal resolution/low spatial resolution or the contrary.

  9. Cubesat Gravity Field Mission

    Science.gov (United States)

    Burla, Santoshkumar; Mueller, Vitali; Flury, Jakob; Jovanovic, Nemanja

    2016-04-01

    CHAMP, GRACE and GOCE missions have been successful in the field of satellite geodesy (especially to improve Earth's gravity field models) and have established the necessity towards the next generation gravity field missions. Especially, GRACE has shown its capabilities beyond any other gravity field missions. GRACE Follow-On mission is going to continue GRACE's legacy which is almost identical to GRACE mission with addition of laser interferometry. But these missions are not only quite expensive but also takes quite an effort to plan and to execute. Still there are few drawbacks such as under-sampling and incapability of exploring new ideas within a single mission (ex: to perform different orbit configurations with multi satellite mission(s) at different altitudes). The budget is the major limiting factor to build multi satellite mission(s). Here, we offer a solution to overcome these drawbacks using cubesat/ nanosatellite mission. Cubesats are widely used in research because they are cheaper, smaller in size and building them is easy and faster than bigger satellites. Here, we design a 3D model of GRACE like mission with available sensors and explain how the Attitude and Orbit Control System (AOCS) works. The expected accuracies on final results of gravity field are also explained here.

  10. The effect of signal leakage and glacial isostatic rebound on GRACE-derived ice mass changes in Iceland.

    Science.gov (United States)

    Sørensen, Louise Sandberg; Jarosch, Alexander H.; Aðalgeirsdóttir, Guðfinna; Barletta, Valentina R.; Forsberg, René; Pálsson, Finnur; Björnsson, Helgi; Jóhannesson, Tómas

    2017-01-01

    Monthly gravity field models from the GRACE satellite mission are widely used to determine ice mass changes of large ice sheets as well as smaller glaciers and ice caps. Here, we investigate in detail the ice mass changes of the Icelandic ice caps as derived from GRACE data. The small size of the Icelandic ice caps, their location close to other rapidly changing ice covered areas, and the low viscosity of the mantle below Iceland, makes this especially challenging. The mass balance of the ice caps is well constrained by field mass balance measurements, making this area ideal for such investigations. We find that the ice mass changes of the Icelandic ice caps derived from GRACE gravity field models are influenced by both the large gravity change signal resulting from ice mass loss in southeast Greenland, as well as by mass redistribution within the Earth mantle due to glacial isostatic adjustment since the Little Ice Age (˜1890 AD). To minimize the signal that leaks towards Iceland from Greenland, we employ an independent mass change estimate of the Greenland Ice Sheet derived from satellite laser altimetry. We also estimate the effect of post Little Ice Age glacial isostatic adjustment, from knowledge of the ice history and GPS network constrained crustal deformation data. We find that both the leakage from Greenland and the post Little Ice Age glacial isostatic adjustment are important to take into account, in order to correctly determine Iceland ice mass changes from GRACE, and when applying these an average mass balance of the Icelandic ice caps of -11.4 ± 2.2 Gt/yr for the period 2003-2010 is found. This number corresponds well with available mass balance measurements.

  11. Radio Graceful Hamming Graphs

    Directory of Open Access Journals (Sweden)

    Niedzialomski Amanda

    2016-11-01

    Full Text Available For k ∈ ℤ+ and G a simple, connected graph, a k-radio labeling f : V (G → ℤ+ of G requires all pairs of distinct vertices u and v to satisfy |f(u − f(v| ≥ k + 1 − d(u, v. We consider k-radio labelings of G when k = diam(G. In this setting, f is injective; if f is also surjective onto {1, 2, . . . , |V (G|}, then f is a consecutive radio labeling. Graphs that can be labeled with such a labeling are called radio graceful. In this paper, we give two results on the existence of radio graceful Hamming graphs. The main result shows that the Cartesian product of t copies of a complete graph is radio graceful for certain t. Graphs of this form provide infinitely many examples of radio graceful graphs of arbitrary diameter. We also show that these graphs are not radio graceful for large t.

  12. GRACE-derived terrestrial water storage depletion associated with the 2003 European heat wave

    DEFF Research Database (Denmark)

    Andersen, Ole Baltazar; Seneviratne, S.I.; Hinderer, J.

    2005-01-01

    datasets agree well with the GRACE measurements despite the disparity of the employed information; the difference between datasets tends to be within GRACE margin of error. The April-to-August terrestrial water storage depletion is found to be significantly larger in 2003 than in 2002 from both models......The GRACE twin satellites reveal large inter-annual terrestrial water-storage variations between 2002 and 2003 for central Europe. GRACE observes a negative trend in regional water storage from 2002 to 2003 peaking at -7.8 cm in central Europe with an accuracy of 1 cm. The 2003 excess terrestrial...... water storage depletion observed from GRACE can be related to the record-breaking heat wave that occurred in central Europe in 2003. We validate the measurements from GRACE using two independent hydrological estimates and direct gravity observations from superconducting gravimeters in Europe. All...

  13. Repairing filtering induced damage to the GRACE time-series at catchment scale

    Science.gov (United States)

    Dutt Vishwakarma, Bramha; Sneeuw, Nico; Devaraju, Balaji

    2016-04-01

    The gravity field products from Gravity Recovery And Climate Experiment (GRACE) satellites are usable only after filtering. Filtering suppresses noise, but also changes the signal. There are methods to minimize the signal change, and most of them depend on a hydrological model to compute leakage, scale factor or bias for improving the time-series signal. Using a model to suppress the uncertainty introduced by filtering is not without problems of its own, because it brings in the uncertainty in the model, that varies spatially and temporally. We provide a mathematical relation between leakage, true signal and filtered signal. We find that not only the amplitude but also the phase of the total water storage time-series is affected due to filtering. For certain catchments the phase change can be equivalent to a shift of half a month or nearly a month. We propose a data driven approach to negate the effects of filtering on catchment scale signal. We demonstrate our method in a closed loop simulation environment and compare it to other widely used approaches for 24 catchments. The method proposed is independent of the filter type and works exceptionally well for catchments above the filter resolution. We apply our approach to GRACE products and discuss its limitations.

  14. A Class of Graceful Trees

    Institute of Scientific and Technical Information of China (English)

    孟凡洪; 苏耕; 杨继

    2000-01-01

    The present paper shows the coordinates of a tree and its vertices, defines a kind of Trees with Odd-Number Radiant Type (TONRT), deals with the gracefulness of TONRT by using the edge-moving theorem, and uses graceful TONRT to construct another class of graceful trees.

  15. Gravity field models derived from Swarm GPS data

    Science.gov (United States)

    Teixeira da Encarnação, João; Arnold, Daniel; Bezděk, Aleš; Dahle, Christoph; Doornbos, Eelco; van den IJssel, Jose; Jäggi, Adrian; Mayer-Gürr, Torsten; Sebera, Josef; Visser, Pieter; Zehentner, Norbert

    2016-07-01

    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.

  16. HlSST and SLR - bridging the gap between GRACE and GRACE Follow-on

    Science.gov (United States)

    Weigelt, Matthias; Jäggi, Adrian; Meyer, Ulrich; Arnold, Daniel; Grahsl, Andrea; Sosnica, Krysztof; Dahle, Christoph; Flechtner, Frank

    2017-04-01

    GRACE is undoubtedly one of the most important sources to observe mass transport on global scales. Numerous applications have shown the validity and impact of using its data. Within the EGSIEM project GRACE gravity field solutions from various processing centers are processed and combined to further increase the spatial and temporal resolution. However, it is expected that GRACE will not continue to observe mass variations from space till its successor GRACE Follow-on will be operational. Thus there is a need for an intermediate technique that will bridge the gap between the two missions and will allow 1) for a continued and uninterrupted time series of mass observations and 2) to compare, crossvalidate and link the two time series. Here we will focus on the combination of high-low satellite-to-satellite tracking (hlSST) of low-Earth orbiting satellites by GNSS in combination with SLR. SLR is known to provide highest quality time-variable gravity for the very low degrees (2-5). HlSST provides a higher spatial resolution but at a lower precision in the very low degrees. Thus it seems natural to combine these two techniques and their benefit has already been demonstrated in the past. Here we make use of the lessons learned within the EGSIEM project and focus on various aspects of combination such as the optimal strategy and relative weighting schemes. We discuss also the achievable spatial and temporal resolutions of different satellite scenarios, such as e.g. using Swarm satellites in combination with Sentinel and/or single GRACE satellites, and present the potential and limitations for geophysical applications.

  17. Seasonal Mass Changes in the Red Sea Observed By GPS and Grace

    Science.gov (United States)

    Alothman, A. O.; Fing, W.; Fernandes, R. M. S.; Bos, M. S.; Elsaka, B.

    2014-12-01

    The Red Sea is a semi-enclosed basin and exchanges water with the Gulf of Aden through the strait of Bab-el-Mandeb at the southern part of the sea. Its circulation is affected by the Indian Monsoon through its connection via the Gulf of Aden. Two distinctive (in summer and in winter) seasonal signals represent the water exchange. To understand the seasonal mass changes in the Red Sea, estimates of the mass changes based on two geodetic techniques are presented: from the Gravity Recovery and Climate Experiment (GRACE) and from the Global Navigation Satellite System (GNSS). The GRACE solutions were truncated up to spherical harmonic degree and order degree 60 to estimate the average monthly mass change in the atmosphere and ocean from models (several hours). GNSS solution is based on observations from four stations along the Red Sea that have been acquired in continuous mode starting in 2007 (having at least 5 years' data-span). The time series analysis of the observed GNSS vertical deformation of these sites has been analyzed. The results revealed that the GNSS observed vertical loading agrees with the atmospheric loading (ATML) assuming that the hydrological signal along the costs of the Red sea is negligible. Computed values of daily vertical atmospheric loading using the NCEP surface pressure data (Inverted Barometer IB) for the 4 stations for 2003 until 2013 are provided. Comparison of the GRACE and GNSS solutions has shown significant annual mass variations in the Red Sea (about 15 cm annual amplitude). After removing the atmospheric effect (ATML), the ocean loading can be observed by GNSS and GRACE estimates in the Red Sea.

  18. A quantitative approach for hydrological drought characterization in southwestern China using GRACE

    Science.gov (United States)

    Chao, Nengfang; Wang, Zhengtao; Jiang, Weiping; Chao, Dingbo

    2016-06-01

    A quantitative approach for hydrological drought characterization, based on non-seasonal water storage deficit data from NASA's Gravity Recovery and Climate Experiment (GRACE) satellite mission, is assessed. Non-seasonal storage deficit is the negative terrestrial water storage after deducting trend, acceleration and seasonal signals, and it is designated as a drought event when it persists for three or more continuous months. The non-seasonal water storage deficit is used for measuring the hydrological drought in southwestern China. It is found that this storage-deficit method clearly identifies hydrological drought onset, end and duration, and quantifies instantaneous severity, peak drought magnitude, and time to recovery. Moreover, it is found that severe droughts have frequently struck southwestern China in the past several decades, among which, the drought of 2011-2012 was the most severe; the duration was 10 months, the severity was -208.92 km3/month, and the time to recovery was 17 months. These results compare well with the National Climate Center of China drought databases, which signifies that the GRACE-based non-seasonal water storage deficit has a quantitative effect on hydrological drought characterization and provides an effective tool for researching droughts.

  19. Grace by Body Clues.

    Science.gov (United States)

    Adams, Marianne

    2001-01-01

    Describes the author's journey in the expressive arts, including dance, poetry, healing, and interdisciplinary expressive arts. Offers poems that illustrate how she grapples with professional identity, deeply personal life issues, and early formative memories. Shows how she is beginning to experience the arts as a place of acceptance and grace.…

  20. Stumble into Grace

    Science.gov (United States)

    Rogers, Jennifer

    2015-01-01

    Jennifer Rogers writes with apt and lyrical snippets from her perspective as a Montessori parent and from her long history as a primary guide. This short piece examines the word "grace" from multiple facets and serves as a meditation that uplifts and reminds us "that the life of a child is a gift."

  1. Status of the GRACE Follow-On Mission (Invited)

    Science.gov (United States)

    Watkins, M. M.; Flechtner, F.; Tapley, B. D.

    2010-12-01

    NASA has included a GRACE Follow-On mission in its proposed budget for fiscal year 2011. As of the time of this abstract submission (September 2, 2010), although the FY11 NASA budget has not been approved by Congress, we continue to anticipate a new start for the mission in FY11. We also anticipate and welcome a continuation of the GRACE partnership with German colleagues at GFZ and DLR. The proposed mission goal is focused on continuation of the critical global mass flux time series initiated by GRACE, and therefore launching as soon as practical is a high priority. The GRACE mission is well into its extended mission, and we will summarize the latest satellite status and expected lifetime. To minimize the development time of a Follow-On mission while minimizing cost and technical risk, a high inheritance "rebuild" of GRACE is the mission baseline, taking advantage of lessons learned from GRACE. We have conducted a study of the systematic errors from the GRACE thermal control system, the satellite seismicity (particularly the nadir radiator), and the attitude control hardware and software in order to feed forward selected modest cost design improvements which provide high science value to the Follow-On. We have also developed basic plans to incorporate, on a "tech demo" basis, an experimental laser interferometer system derived from technology developed by the Earth Science Technology Office Instrument Incubator program, and in conjunction with German developments led by AEI/U. Hannover. This system could provide important experience and risk reduction for future gravity mapping missions targeted for improved accuracy and spatial resolution. In this talk, we will provide the latest technical and programmatic status of this developing project to continue and extend the successful science from the GRACE mission.

  2. Rapid variability of Antarctic Bottom Water transport into the Pacific Ocean inferred from GRACE

    Science.gov (United States)

    Mazloff, Matthew R.; Boening, Carmen

    2016-04-01

    Air-ice-ocean interactions in the Antarctic lead to formation of the densest waters on Earth. These waters convect and spread to fill the global abyssal oceans. The heat and carbon storage capacity of these water masses, combined with their abyssal residence times that often exceed centuries, makes this circulation pathway the most efficient sequestering mechanism on Earth. Yet monitoring this pathway has proven challenging due to the nature of the formation processes and the depth of the circulation. The Gravity Recovery and Climate Experiment (GRACE) gravity mission is providing a time series of ocean mass redistribution and offers a transformative view of the abyssal circulation. Here we use the GRACE measurements to infer, for the first time, a 2003-2014 time series of Antarctic Bottom Water export into the South Pacific. We find this export highly variable, with a standard deviation of 1.87 sverdrup (Sv) and a decorrelation timescale of less than 1 month. A significant trend is undetectable.

  3. Evaluating water storage variations in the MENA region using GRACE satellite data

    KAUST Repository

    Lopez, Oliver

    2013-12-01

    Terrestrial water storage (TWS) variations over large river basins can be derived from temporal gravity field variations observed by the Gravity Recovery and Climate Experiment (GRACE) satellites. These signals are useful for determining accurate estimates of water storage and fluxes over areas covering a minimum of 150,000 km2 (length scales of a few hundred kilometers) and thus prove to be a valuable tool for regional water resources management, particularly for areas with a lack of in-situ data availability or inconsistent monitoring, such as the Middle East and North Africa (MENA) region. This already stressed arid region is particularly vulnerable to climate change and overdraft of its non-renewable freshwater sources, and thus direction in managing its resources is a valuable aid. An inter-comparison of different GRACE-derived TWS products was done in order to provide a quantitative assessment on their uncertainty and their utility for diagnosing spatio-temporal variability in water storage over the MENA region. Different processing approaches for the inter-satellite tracking data from the GRACE mission have resulted in the development of TWS products, with resolutions in time from 10 days to 1 month and in space from 0.5 to 1 degree global gridded data, while some of them use input from land surface models in order to restore the original signal amplitudes. These processing differences and the difficulties in recovering the mass change signals over arid regions will be addressed. Output from the different products will be evaluated and compared over basins inside the MENA region, and compared to output from land surface models.

  4. Evaluating Water Storage Variations in the MENA region using GRACE Satellite Data

    Science.gov (United States)

    Lopez, O.; Houborg, R.; McCabe, M. F.

    2013-12-01

    Terrestrial water storage (TWS) variations over large river basins can be derived from temporal gravity field variations observed by the Gravity Recovery and Climate Experiment (GRACE) satellites. These signals are useful for determining accurate estimates of water storage and fluxes over areas covering a minimum of 150,000 km2 (length scales of a few hundred kilometers) and thus prove to be a valuable tool for regional water resources management, particularly for areas with a lack of in-situ data availability or inconsistent monitoring, such as the Middle East and North Africa (MENA) region. This already stressed arid region is particularly vulnerable to climate change and overdraft of its non-renewable freshwater sources, and thus direction in managing its resources is a valuable aid. An inter-comparison of different GRACE-derived TWS products was done in order to provide a quantitative assessment on their uncertainty and their utility for diagnosing spatio-temporal variability in water storage over the MENA region. Different processing approaches for the inter-satellite tracking data from the GRACE mission have resulted in the development of TWS products, with resolutions in time from 10 days to 1 month and in space from 0.5 to 1 degree global gridded data, while some of them use input from land surface models in order to restore the original signal amplitudes. These processing differences and the difficulties in recovering the mass change signals over arid regions will be addressed. Output from the different products will be evaluated and compared over basins inside the MENA region, and compared to output from land surface models.

  5. Ocean calibration approach to correcting for spurious accelerations for data from the GRACE and GRACE Follow-On missions

    CERN Document Server

    Bender, Peter L

    2015-01-01

    The GRACE mission has been providing valuable new information on time variations in the Earth's gravity field since 2002. In addition, the GRACE Follow-On mission is scheduled to be flown soon after the end of life of the GRACE mission in order to minimize the loss of valuable data on the Earth's gravity field changes. In view of the major benefits to hydrology and oceanography, as well as to other fields, it is desirable to investigate the fundamental limits to monitoring the time variations in the Earth's gravity field during GRACE-type missions. A simplified model is presented in this paper for making estimates of the effect of differential spurious accelerations of the satellites during times when four successive revolutions cross the Pacific Ocean. The analysis approach discussed is to make use of changes in the satellite separation observed during passages across low latitude regions of the Pacific and of other oceans to correct for spurious accelerations of the satellites. The low latitude regions of t...

  6. Observing coseismic gravity change from the Japan Tohoku-Oki 2011 earthquake with GOCE gravity gradiometry

    NARCIS (Netherlands)

    Fuchs, M.J.; Bouman, J.; Broerse, D.B.T.; Visser, P.N.A.M.; Vermeersen, L.L.A.

    2013-01-01

    The Japan Tohoku-Oki earthquake (9.0 Mw) of 11 March 2011 has left signatures in the Earth's gravity field that are detectable by data of the Gravity field Recovery and Climate Experiment (GRACE) mission. Because the European Space Agency's (ESA) satellite gravity mission Gravity field and

  7. Observing coseismic gravity change from the Japan Tohoku-Oki 2011 earthquake with GOCE gravity gradiometry

    NARCIS (Netherlands)

    Fuchs, M.J.; Bouman, J.; Broerse, T.; Visser, P.; Vermeersen, B.

    2013-01-01

    The Japan Tohoku-Oki earthquake (9.0 Mw) of 11 March 2011 has left signatures in the Earth's gravity field that are detectable by data of the Gravity field Recovery and Climate Experiment (GRACE) mission. Because the European Space Agency's (ESA) satellite gravity mission Gravity field and steady-st

  8. Observing coseismic gravity change from the Japan Tohoku-Oki 2011 earthquake with GOCE gravity gradiometry

    NARCIS (Netherlands)

    Fuchs, M.J.; Bouman, J.; Broerse, D.B.T.; Visser, P.N.A.M.; Vermeersen, L.L.A.

    2013-01-01

    The Japan Tohoku-Oki earthquake (9.0 Mw) of 11 March 2011 has left signatures in the Earth's gravity field that are detectable by data of the Gravity field Recovery and Climate Experiment (GRACE) mission. Because the European Space Agency's (ESA) satellite gravity mission Gravity field and steady-st

  9. Test environments for the GRACE follow-on laser ranging interferometer

    Science.gov (United States)

    Görth, A.; Sanjuan, J.; Gohlke, M.; Rasch, S.; Abich, K.; Braxmaier, C.; Heinzel, G.

    2016-05-01

    In the year 2017 a follow-on mission to the very successful joint German/US mission GRACE (Gravity Recovery And Climate Experiment) will be launched. As of this day the two GRACE satellites have successfully been mapping the spatial and temporal varitations of the gravitational field of the Earth by satellite-to-satellite tracking for over a decade. The main science instrument on GRACE and its successor mission GRACE Follow-On which is used to measure the inter-satellite distance changes is a microwave link sensor. However, an additional instrument, the laser ranging interferometer (LRI), will be implemented into the architecture of the GRACE Follow-On satellites as a technology demonstrator. In this paper we will give a brief overview of a fiber-based test environment which is currently used during the assembly, integration and test of the LRI flight hardware.

  10. Non-Linear Non Stationary Analysis of Two-Dimensional Time-Series Applied to GRACE Data Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovative two-dimensional (2D) adaptive analysis will be tested NASA's Gravity Recovery and Climate Experiment (GRACE) mission database in phase I in...

  11. Non-Linear Non Stationary Analysis of Two-Dimensional Time-Series Applied to GRACE Data Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed innovative two-dimensional (2D) empirical mode decomposition (EMD) analysis was applied to NASA's Gravity Recovery and Climate Experiment (GRACE)...

  12. Evaluating Greenland glacial isostatic adjustment corrections using GRACE, altimetry and surface mass balance data

    NARCIS (Netherlands)

    Sutterley, T.C.; Velicogna, I.; Csatho, B.; van den Broeke, M.R.; Rezvan-Behbahani, S.; Babonis, G.

    2014-01-01

    Glacial isostatic adjustment (GIA) represents a source of uncertainty for ice sheet mass balance estimates from the Gravity Recovery and Climate Experiment (GRACE) timevariable gravity measurements. We evaluate Greenland GIA corrections from Simpson et al (2009 Quat. Sci. Rev. 28 1631–57), A et al (

  13. Distributed fault slip model for the 2011 Tohoku-Oki earthquake from GNSS and GRACE/GOCE satellite gravimetry

    NARCIS (Netherlands)

    Fuchs, Martin Johann; Hooper, Andrew; Broerse, Taco|info:eu-repo/dai/nl/411299344; Bouman, Johannes

    2016-01-01

    The Gravity Recovery and Climate Experiment (GRACE) mission (launched 2002) and the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) mission (March 2009 to November 2013) collected spaceborne gravity data for the preseismic and postseismic periods of the 2011 Tohoku-Oki earthquake. I

  14. Distributed fault slip model for the 2011 Tohoku-Oki earthquake from GNSS and GRACE/GOCE satellite gravimetry

    NARCIS (Netherlands)

    Fuchs, Martin Johann; Hooper, Andrew; Broerse, Taco; Bouman, Johannes

    The Gravity Recovery and Climate Experiment (GRACE) mission (launched 2002) and the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) mission (March 2009 to November 2013) collected spaceborne gravity data for the preseismic and postseismic periods of the 2011 Tohoku-Oki earthquake.

  15. Distributed fault slip model for the 2011 Tohoku-Oki earthquake from GNSS and GRACE/GOCE satellite gravimetry

    NARCIS (Netherlands)

    Fuchs, Martin Johann; Hooper, Andrew; Broerse, Taco; Bouman, Johannes

    2016-01-01

    The Gravity Recovery and Climate Experiment (GRACE) mission (launched 2002) and the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) mission (March 2009 to November 2013) collected spaceborne gravity data for the preseismic and postseismic periods of the 2011 Tohoku-Oki earthquake. I

  16. Assimilation of GRACE Terrestrial Water Storage Observations into a Land Surface Model for the Assessment of Regional Flood Potential

    Science.gov (United States)

    Reager, John T.; Thomas, Alys C.; Sproles, Eric A.; Rodell, Matthew; Beaudoing, Hiroko K.; Li, Bailing; Famiglietti, James S.

    2015-01-01

    We evaluate performance of the Catchment Land Surface Model (CLSM) under flood conditions after the assimilation of observations of the terrestrial water storage anomaly (TWSA) from NASA's Gravity Recovery and Climate Experiment (GRACE). Assimilation offers three key benefits for the viability of GRACE observations to operational applications: (1) near-real time analysis; (2) a downscaling of GRACE's coarse spatial resolution; and (3) state disaggregation of the vertically-integrated TWSA. We select the 2011 flood event in the Missouri river basin as a case study, and find that assimilation generally made the model wetter in the months preceding flood. We compare model outputs with observations from 14 USGS groundwater wells to assess improvements after assimilation. Finally, we examine disaggregated water storage information to improve the mechanistic understanding of event generation. Validation establishes that assimilation improved the model skill substantially, increasing regional groundwater anomaly correlation from 0.58 to 0.86. For the 2011 flood event in the Missouri river basin, results show that groundwater and snow water equivalent were contributors to pre-event flood potential, providing spatially-distributed early warning information.

  17. Statistically optimal estimation of degree-1 and C20 coefficients based on GRACE data and an ocean bottom pressure model

    Science.gov (United States)

    Sun, Yu; Ditmar, Pavel; Riva, Riccardo

    2017-09-01

    In this study, we develop a methodology to estimate monthly variations in degree-1 and C20 coefficients by combing Gravity Recovery and Climate Experiment (GRACE) data with oceanic mass anomalies (combination approach). With respect to the method by Swenson et al., the proposed approach exploits noise covariance information of both input data sets and thus produces stochastically optimal solutions supplied with realistic error information. Numerical simulations show that the quality of degree-1 and -2 coefficients may be increased in this way by about 30 per cent in terms of RMS error. We also proved that the proposed approach can be reduced to the approach of Sun et al. provided that the GRACE data are noise-free and noise in oceanic data is white. Subsequently, we evaluate the quality of the resulting degree-1 and C20 coefficients by estimating mass anomaly time-series within carefully selected validation areas, where mass transport is small. Our validation shows that, compared to selected Satellite Laser Ranging (SLR) and joint inversion degree-1 solutions, the proposed combination approach better complements GRACE solutions. The annual amplitude of the SLR-based C10 is probably overestimated by about 1 mm. The performance of the C20 coefficients, on the other hand, is similar to that of traditionally used solution from the SLR technique.

  18. Assimilation of GRACE Terrestrial Water Storage Observations into a Land Surface Model for the Assessment of Regional Flood Potential

    Science.gov (United States)

    Reager, John T.; Thomas, Alys C.; Sproles, Eric A.; Rodell, Matthew; Beaudoing, Hiroko K.; Li, Bailing; Famiglietti, James S.

    2015-01-01

    We evaluate performance of the Catchment Land Surface Model (CLSM) under flood conditions after the assimilation of observations of the terrestrial water storage anomaly (TWSA) from NASA's Gravity Recovery and Climate Experiment (GRACE). Assimilation offers three key benefits for the viability of GRACE observations to operational applications: (1) near-real time analysis; (2) a downscaling of GRACE's coarse spatial resolution; and (3) state disaggregation of the vertically-integrated TWSA. We select the 2011 flood event in the Missouri river basin as a case study, and find that assimilation generally made the model wetter in the months preceding flood. We compare model outputs with observations from 14 USGS groundwater wells to assess improvements after assimilation. Finally, we examine disaggregated water storage information to improve the mechanistic understanding of event generation. Validation establishes that assimilation improved the model skill substantially, increasing regional groundwater anomaly correlation from 0.58 to 0.86. For the 2011 flood event in the Missouri river basin, results show that groundwater and snow water equivalent were contributors to pre-event flood potential, providing spatially-distributed early warning information.

  19. GRACE-based validation of terrestrial water storage variations as simulated by 4 different hydrological models under WFDEI atmospheric forcing

    Science.gov (United States)

    Zhang, Liangjing; Dobslaw, Henryk; Stacke, Tobias; Güntner, Andreas; Dill, Robert; Thomas, Maik

    2016-04-01

    Since its launch in 2002, the Gravity Recovery and Climate Experiment (GRACE) mission provides a unique way to monitor the terrestrial water storage (TWS) variations at large spatial scale (>300km) by measuring month-to-month changes of the Earth's gravity field. We apply TWS variations estimated from GRACE to assess the ability of four hydrological and land surface models to simulate the continental branch of the global water cycle. Based on four different validation metrics that focus on variability on sub-seasonal to inter-annual time scales, we demonstrate that for the 31 largest discharge basins worldwide all model runs agree with the observations to a very limited degree only, together with large spreads among the models themselves. In particular, we focus on selected basins with very different climatic conditions and discuss time series of individual water storage components such as surface water, soil moisture, and snow depth. Since we are applying a common atmospheric forcing data-set to all models considered, we conclude that the discrepancies found are not due to differences in the forcing, but are mainly related to the model structure and parametrization. By investigating the relative performance of these different models, we attempt to give directions for further development of global numerical models in the areas of large-scale hydrology and land-atmosphere interactions.

  20. Advances in precision orbit determination of GRACE satellites

    Science.gov (United States)

    Bettadpur, Srinivas; Save, Himanshu; Kang, Zhigui

    The twin Gravity Recovery And Climate Experiment (GRACE) satellites carry a complete suite of instrumentation essential for precision orbit determination (POD). Dense, continuous and global tracking is provided by the Global Positioning System receivers. The satellite orientation is measured using two star cameras. High precision measurements of non-gravitational accel-erations are provided by accelerometers. Satellite laser ranging (SLR) retroreflectors are used for collecting data for POD validation. Additional validation is provided by the highly precise K-Band ranging system measuring distance changes between the twin GRACE satellites. This paper presents the status of POD for GRACE satellites. The POD quality will be vali-dated using the SLR and K-Band ranging data. The POD quality improvement from upgraded modeling of the GPS observations, including the transition to the new IGS05 standards, will be discussed. In addition, the contributions from improvements in the gravity field modeling -partly arising out of GRACE science results -will be discussed. The aspects of these improve-ments that are applicable for the POD of other low-Earth orbiting satellites will be discussed as well.

  1. Grace in Sikhism

    OpenAIRE

    Weber, Edmund

    2010-01-01

    As in all other religions there are two contrary streaming in Sikhism too. One teaches that meaning and value of human existence depends on the human works which we call the operative model. The other streaming preaches that the Holy’s grace is the substance of men’s ultimate destination, and it alone gives meaning to their existence; this position we call the receptive model. As the third streaming we can identify the doctrine of conditioned gratification which means that the humans get Divi...

  2. Diagnosing Land Water Storage Variations in Major Indian River Basins using GRACE observations

    Science.gov (United States)

    Soni, Aarti; Syed, Tajdarul H.

    2015-10-01

    Scarcity of freshwater is one of the most critical resource issue the world is facing today. Due to its finite nature, renewable freshwater reserves are under relentless pressure due to population growth, economic development and rapid industrialization. Assessment of Terrestrial Water Storage (TWS), as an unified measure of freshwater reserve, is vital to understand hydrologic and climatic processes controlling its availability. In this study, TWS variations from Gravity Recovery and Climate Experiment (GRACE) satellites are analyzed in conjuction with multi-platform hydrologic observations for the period of 2003-2012. Here, the primary objective is to quantify and attribute the observed short-term variability of TWS and groundwater storage in the largest river basins of India (Ganga, Godavari, Krishna and Mahanadi). Alongside commendable agreement between TWS variations obtained from GRACE and water balance computation, results highlight some of the important deficiencies between the two. While monthly changes in TWS are highly correlated with precipitation, monthly TWS anomalies reveal a 1-2 month lag in their concurrence. Analysis of groundwater storage estimates demonstrate significant decline in the Ganga basin (- 1.28 ± 0.20 mm/month) but practically no change in the Mahanadi basin. On the contrary, groundwater storage in Godavari and Krishna basins reveal notable increase at the rate of 0.74 ± 0.21 mm/month and 0.97 ± 0.21 mm/month respectively. Subsequently, in order to assess the influence of quasi-periodic, planetary scale, variations in the Earth's climate system, groundwater storage anomalies are evaluated with reference to ENSO variability. Results manifest that in all the basins, with the exception of Ganga, groundwater storage is dominantly influenced by ENSO, with large decrease (increase) during El Niño (La Niña) events. In the Ganga basin, groundwater storage variations refer to possible amalgamation of human intervention and natural climate

  3. Use of GRACE data to monitor climate change-induced variations in water storage availability in the African continent

    Science.gov (United States)

    Ahmed, M. E.; Sultan, M.; Wahr, J. M.; Yan, E.; Milewski, A.; Mohsen, F.; Chouinard, K.

    2011-12-01

    The Gravity Recovery and Climate Experiment (GRACE) data provides direct measurements of temporal mass variations; the latter is largely controlled by variations in water volumes in various reservoirs such as surface water (e.g., lakes and streams), groundwater (e.g., shallow and deep aquifers) and in the soil profile. Climatic changes impact the amounts of precipitation and its partitioning into each of these reservoirs. We explored the use of GRACE data for monitoring climate change-induced variations in water availability in the African continent over a period of nine years and used the identified trends to predict water storage availability across the continent over the next decade. Monthly GRACE gravity field solutions (Center of Space Research [CSR] RL04) in form of Spherical Harmonic Coefficients (SHC's) that span the period from April 2002 through November 2010 were processed (temporal mean was removed, de-striped, smoothed [250 km; Gaussian], and converted to 0.5 x 0.5 deg. equivalent water thicknesses). Several relevant GRACE bi-products (e.g., standard deviation, annual trend) were generated over time periods of six, seven, eight, and nine years and compared (in a GIS environment) with relevant co-registered data sets and derived products (e.g., precipitation, topography, geology, VNIR Landsat, NDVI, stream network distribution, water bodies distribution, watershed boundaries, and Community Climate System Model [CCSM-3] products). Spatial correlations of the co-registered data sets revealed the following: (1) persistent and increasingly pronounced linear annual trends (+ve: increasing mass; -ve: decreasing mass) over periods of six to nine years with the most pronounced trends detected over domains of high signal to noise ratios; (2) +ve trends over the source areas for the Blue Nile basin (4.2 mm/yr) and over the source areas of the Congo basin (7 mm/yr) and over the Zambezi basin (24 mm/yr), whereas -ve trends were detected over Central Africa (-7 mm

  4. Assessing sequential data assimilation techniques for integrating GRACE data into a hydrological model

    KAUST Repository

    Khaki, M.

    2017-07-06

    The time-variable terrestrial water storage (TWS) products from the Gravity Recovery And Climate Experiment (GRACE) have been increasingly used in recent years to improve the simulation of hydrological models by applying data assimilation techniques. In this study, for the first time, we assess the performance of the most popular data assimilation sequential techniques for integrating GRACE TWS into the World-Wide Water Resources Assessment (W3RA) model. We implement and test stochastic and deterministic ensemble-based Kalman filters (EnKF), as well as Particle filters (PF) using two different resampling approaches of Multinomial Resampling and Systematic Resampling. These choices provide various opportunities for weighting observations and model simulations during the assimilation and also accounting for error distributions. Particularly, the deterministic EnKF is tested to avoid perturbing observations before assimilation (that is the case in an ordinary EnKF). Gaussian-based random updates in the EnKF approaches likely do not fully represent the statistical properties of the model simulations and TWS observations. Therefore, the fully non-Gaussian PF is also applied to estimate more realistic updates. Monthly GRACE TWS are assimilated into W3RA covering the entire Australia. To evaluate the filters performances and analyze their impact on model simulations, their estimates are validated by independent in-situ measurements. Our results indicate that all implemented filters improve the estimation of water storage simulations of W3RA. The best results are obtained using two versions of deterministic EnKF, i.e. the Square Root Analysis (SQRA) scheme and the Ensemble Square Root Filter (EnSRF), respectively improving the model groundwater estimations errors by 34% and 31% compared to a model run without assimilation. Applying the PF along with Systematic Resampling successfully decreases the model estimation error by 23%.

  5. Assessing sequential data assimilation techniques for integrating GRACE data into a hydrological model

    Science.gov (United States)

    Khaki, M.; Hoteit, I.; Kuhn, M.; Awange, J.; Forootan, E.; van Dijk, A. I. J. M.; Schumacher, M.; Pattiaratchi, C.

    2017-09-01

    The time-variable terrestrial water storage (TWS) products from the Gravity Recovery And Climate Experiment (GRACE) have been increasingly used in recent years to improve the simulation of hydrological models by applying data assimilation techniques. In this study, for the first time, we assess the performance of the most popular data assimilation sequential techniques for integrating GRACE TWS into the World-Wide Water Resources Assessment (W3RA) model. We implement and test stochastic and deterministic ensemble-based Kalman filters (EnKF), as well as Particle filters (PF) using two different resampling approaches of Multinomial Resampling and Systematic Resampling. These choices provide various opportunities for weighting observations and model simulations during the assimilation and also accounting for error distributions. Particularly, the deterministic EnKF is tested to avoid perturbing observations before assimilation (that is the case in an ordinary EnKF). Gaussian-based random updates in the EnKF approaches likely do not fully represent the statistical properties of the model simulations and TWS observations. Therefore, the fully non-Gaussian PF is also applied to estimate more realistic updates. Monthly GRACE TWS are assimilated into W3RA covering the entire Australia. To evaluate the filters performances and analyze their impact on model simulations, their estimates are validated by independent in-situ measurements. Our results indicate that all implemented filters improve the estimation of water storage simulations of W3RA. The best results are obtained using two versions of deterministic EnKF, i.e. the Square Root Analysis (SQRA) scheme and the Ensemble Square Root Filter (EnSRF), respectively, improving the model groundwater estimations errors by 34% and 31% compared to a model run without assimilation. Applying the PF along with Systematic Resampling successfully decreases the model estimation error by 23%.

  6. Testing the use of standardised indices and GRACE satellite data to estimate the European 2015 groundwater drought in near-real time

    Science.gov (United States)

    Van Loon, Anne F.; Kumar, Rohini; Mishra, Vimal

    2017-04-01

    In 2015, central and eastern Europe were affected by a severe drought. This event has recently been studied from meteorological and streamflow perspective, but no analysis of the groundwater situation has been performed. One of the reasons is that real-time groundwater level observations often are not available. In this study, we evaluate two alternative approaches to quantify the 2015 groundwater drought over two regions in southern Germany and eastern Netherlands. The first approach is based on spatially explicit relationships between meteorological conditions and historic groundwater level observations. The second approach uses the Gravity Recovery Climate Experiment (GRACE) terrestrial water storage (TWS) and groundwater anomalies derived from GRACE-TWS and (near-)surface storage simulations by the Global Land Data Assimilation System (GLDAS) models. We combined the monthly groundwater observations from 2040 wells to establish the spatially varying optimal accumulation period between the Standardised Groundwater Index (SGI) and the Standardized Precipitation Evapotranspiration Index (SPEI) at a 0.25° gridded scale. The resulting optimal accumulation periods range between 1 and more than 24 months, indicating strong spatial differences in groundwater response time to meteorological input over the region. Based on the estimated optimal accumulation periods and available meteorological time series, we reconstructed the groundwater anomalies up to 2015 and found that in Germany a uniform severe groundwater drought persisted for several months during this year, whereas the Netherlands appeared to have relatively high groundwater levels. The differences between this event and the 2003 European benchmark drought are striking. The 2003 groundwater drought was less uniformly pronounced, both in the Netherlands and Germany. This is because slowly responding wells (the ones with optimal accumulation periods of more than 12 months) still were above average from the wet

  7. Geocenter motion due to surface mass transport from GRACE satellite data

    Science.gov (United States)

    Riva, R. E. M.; van der Wal, W.; Lavallée, D. A.; Hashemi Farahani, H.; Ditmar, P.

    2012-04-01

    Measurements of mass redistribution from satellite gravimetry are insensitive to geocenter motions. However, geocenter motions can be constrained by satellite gravity data alone if we partition mass changes between land and oceans, under the assumption that the ocean is passive (i.e., in gravitational equilibrium with the land load and the solid earth). Here, we make use of 8 years (2003-2010) of optimally filtered monthly GRACE-based solutions produced at TU Delft to determine changes in the land load and the corresponding geocenter motion, through an iterative procedure. We pay particular attention to correcting for signal leakage caused by the limited spatial resolution of GRACE. We also investigate how the choice of a model of glacial isostatic adjustment (GIA) affects the estimated geocenter motion trend due to present-day surface mass transport. Finally, we separate the contribution of ice masses from that of land hydrology and show how they have a different sensitivity to the chosen GIA model and observational time-span.

  8. Simulation of realistic instrument noise for GRACE follow-on.

    Science.gov (United States)

    Ellmer, Matthias; Mayer-Gürr, Torsten

    2014-05-01

    Computer simulations have been an indispensable tool in assessing and predicting the performance of gravity recovery satellite missions, both present and future. Future satellite missions like GRACE follow-on will measure Earth's gravity with a much higher precision than their predecessors. This increased precision makes it necessary to reevaluate the applicability of current simulation strategies to future gravity missions. In past simulation efforts, effects that are known to be relevant factors for mission performance are often approximated or modeled incompletely. One such effect is the noise applied to simulated observables like precise orbits or K-Band ranges. These noisy observables are generated by adding simple white noise of a specific power to noise-free raw measurements. The noisy observables are then used in closed-loop simulations to quantify the performance of specific instruments, or a mission scenario as a whole. This work presents strategies to generate more realistic noise for satellite missions as implemented in the GROOPS (Gravity Recovery Object Orientated Programming System) software package. A generic interface for different noise generators is implemented in GROOPS. This interface is used to add different types of noise, such as white noise, colored or correlated noise, or noise with a given power spectral density to generated observables. It is thus possible to study the effect of the chosen noise model on the generated observable, and conversely the recovered gravity field as a whole. A better knowledge of the noise characteristics of the instruments on GRACE and GRACE follow-on will allow us to improve our understanding of their complex interactions. It will also allow us to improve our processing strategies for both simulated and real data, and will thus lead to a more precise and better understood recovered gravity field.

  9. LISA Experience from GRACE-FO Optical Payload (LEGOP)

    Science.gov (United States)

    McKenzie, Kirk

    arm-locking to be used on LISA. We will modify the LISA arm- locking controller for GRACE-FO mission parameters and perform a hardware-in-the- loop simulation. GRACE-FO is the planned follow-on to the Gravity Recovery and Climate Experiment (GRACE) mission. In addition to the microwave link used to sense micron-level changes in the separation between a pair of satellites in a following orbit, GRACE-FO will include a 2-way laser link as a technology demonstrator package. LISA is a planned gravitational wave observatory consisting of three drag-free spacecraft arranged in an equilateral triangle with 5 million km separation in a heliocentric orbit. LISA will have three 2-way laser links to allow LISA to observe low frequency astrophysical and cosmological sources. Demonstration of inter-spacecraft interferometry using GRACE-FO has the potential to retire several of the highest-risk procedures for LISA and complements the drag-free performance technology demonstration of the LISA Pathfinder mission. Similarities between the GRACE-FO and LISA flight systems means we will not need to develop or deploy any new hardware to achieve this goal. Rather, we propose to develop algorithms that could be deployed on the existing GRACE-FO control and diagnostics system.

  10. An Economy of Grace

    Directory of Open Access Journals (Sweden)

    Victor Tan Chen

    2017-03-01

    Full Text Available This essay is adapted from a plenary talk the author gave at the “Growing Apart: The Implications of Economic Inequality” interdisciplinary conference at Boston College on 9 April 2016, as well as portions of his book Cut Loose: Jobless and Hopeless in an Unfair Economy, a sociological ethnography based on interviews and observations of unemployed autoworkers in Detroit, Michigan, and Windsor, Canada, during and after the Great Recession. The essay discusses four themes from this research. First, it provides a sociological understanding of how long-term unemployment and economic inequality are experienced by today’s less advantaged workers. Second, it illustrates how social policy can improve their circumstances. Third, it examines the limits of policy, and how dealing with inequality also requires changing the broader culture. Fourth, it makes the case for one possible approach to bring about that cultural change: a morality of grace.

  11. Monitoring Global Freshwater Resources with GRACE

    Science.gov (United States)

    Rodell, Matt; Famiglietti, Jay; Velicogna, Isabella; Swenson, Sean; Chambers, Don

    2011-01-01

    Freshwater resources include surface waters, groundwater, and seasonal snowpack. Given adequate ground based measurements, all of these can be monitored effectively, however, outside of the developed world such measurements often are not systematic and the data not centralized, and as a result reports of freshwater availability may be largely anecdotal. Even in the developed world it can be difficult to quantify changes in groundwater storage over large scales. Owing to its global coverage, satellite remote sensing has become a valuable tool for freshwater resources assessment. In particular, the Gravity Recovery and Climate Experiment (GRACE) has demonstrated an unequaled ability to monitor total terrestrial water storage including groundwater at regional to continental scales. In this presentation we will identify apparent trends in terrestrial water storage observed by GRACE over the past nine years and attempt to explain their origins and predict whether they are likely to continue. Trends in certain regions where groundwater extraction has significantly depleted aquifers, including northern India and California, will be discussed in detail.

  12. Identifying water mass depletion in Northern Iraq observed by GRACE

    Directory of Open Access Journals (Sweden)

    G. Mulder

    2014-10-01

    Full Text Available Observations acquired by Gravity Recovery And Climate Experiment (GRACE mission indicate a mass loss of 31 ± 3 km3 or 130 ± 14 mm in Northern Iraq between 2007 and 2009. This data is used as an independent validation of a hydrologic model of the region including lake mass variations. We developed a rainfall–runoff model for five tributaries of the Tigris River, based on local geology and climate conditions. Model inputs are precipitation from Tropical Rainfall Measurement Mission (TRMM observations, and potential evaporation from GLDAS model parameters. Our model includes a representation of the karstified aquifers that cause large natural groundwater variations in this region. Observed river discharges were used to calibrate our model. In order to get the total mass variations, we corrected for lake mass variations derived from Moderate Resolution Imaging Spectroradiometer (MODIS in combination with satellite altimetry and some in-situ data. Our rainfall–runoff model confirms that Northern Iraq suffered a drought between 2007 and 2009 and is consistent with the mass loss observed by GRACE over that period. Also, GRACE observed the annual cycle predicted by the rainfall–runoff model. The total mass depletion seen by GRACE between 2007 and 2009 is mainly explained by a lake mass depletion of 74 ± 4 mm and a natural groundwater depletion of 37 ± 6 mm. Our findings indicate that man-made groundwater extraction has a minor influence in this region while depletion of lake mass and geology play a key role.

  13. Source Parameter Inversion for Recent Great Earthquakes from a Decade-long Observation of Global Gravity Fields

    Science.gov (United States)

    Han, Shin-Chan; Riva, Ricccardo; Sauber, Jeanne; Okal, Emile

    2013-01-01

    We quantify gravity changes after great earthquakes present within the 10 year long time series of monthly Gravity Recovery and Climate Experiment (GRACE) gravity fields. Using spherical harmonic normal-mode formulation, the respective source parameters of moment tensor and double-couple were estimated. For the 2004 Sumatra-Andaman earthquake, the gravity data indicate a composite moment of 1.2x10(exp 23)Nm with a dip of 10deg, in agreement with the estimate obtained at ultralong seismic periods. For the 2010 Maule earthquake, the GRACE solutions range from 2.0 to 2.7x10(exp 22)Nm for dips of 12deg-24deg and centroid depths within the lower crust. For the 2011 Tohoku-Oki earthquake, the estimated scalar moments range from 4.1 to 6.1x10(exp 22)Nm, with dips of 9deg-19deg and centroid depths within the lower crust. For the 2012 Indian Ocean strike-slip earthquakes, the gravity data delineate a composite moment of 1.9x10(exp 22)Nm regardless of the centroid depth, comparing favorably with the total moment of the main ruptures and aftershocks. The smallest event we successfully analyzed with GRACE was the 2007 Bengkulu earthquake with M(sub 0) approx. 5.0x10(exp 21)Nm. We found that the gravity data constrain the focal mechanism with the centroid only within the upper and lower crustal layers for thrust events. Deeper sources (i.e., in the upper mantle) could not reproduce the gravity observation as the larger rigidity and bulk modulus at mantle depths inhibit the interior from changing its volume, thus reducing the negative gravity component. Focal mechanisms and seismic moments obtained in this study represent the behavior of the sources on temporal and spatial scales exceeding the seismic and geodetic spectrum.

  14. Comparison of observed and modeled seasonal crustal vertical displacements derived from multi-institution GPS and GRACE solutions

    Science.gov (United States)

    Gu, Yanchao; Fan, Dongming; You, Wei

    2017-07-01

    Eleven GPS crustal vertical displacement (CVD) solutions for 110 IGS08/IGS14 core stations provided by the International Global Navigation Satellite Systems Service Analysis Centers are compared with seven Gravity Recovery and Climate Experiment (GRACE)-modeled CVD solutions. The results of the internal comparison of the GPS solutions from multiple institutions imply large uncertainty in the GPS postprocessing. There is also evidence that GRACE solutions from both different institutions and different processing approaches (mascon and traditional spherical harmonic coefficients) show similar results, suggesting that GRACE can provide CVD results of good internal consistency. When the uncertainty of the GPS data is accounted for, the GRACE data can explain as much as 50% of the actual signals and more than 80% of the GPS annual signals. Our study strongly indicates that GRACE data have great potential to correct the nontidal loading in GPS time series.

  15. Broadband assessment of degree-2 gravitational changes from GRACE and other estimates, 2002-2015

    Science.gov (United States)

    Chen, J. L.; Wilson, C. R.; Ries, J. C.

    2016-03-01

    Space geodetic measurements, including the Gravity Recovery and Climate Experiment (GRACE), satellite laser ranging (SLR), and Earth rotation provide independent and increasingly accurate estimates of variations in Earth's gravity field Stokes coefficients ΔC21, ΔS21, and ΔC20. Mass redistribution predicted by climate models provides another independent estimate of air and water contributions to these degree-2 changes. SLR has been a successful technique in measuring these low-degree gravitational changes. Broadband comparisons of independent estimates of ΔC21, ΔS21, and ΔC20 from GRACE, SLR, Earth rotation, and climate models during the GRACE era from April 2002 to April 2015 show that the current GRACE release 5 solutions of ΔC21 and ΔS21 provided by the Center for Space Research (CSR) are greatly improved over earlier solutions and agree remarkably well with other estimates, especially on ΔS21 estimates. GRACE and Earth rotation ΔS21 agreement is exceptionally good across a very broad frequency band from intraseasonal, seasonal, to interannual and decadal periods. SLR ΔC20 estimates remain superior to GRACE and Earth rotation estimates, due to the large uncertainty in GRACE ΔC20 solutions and particularly high sensitivity of Earth rotation ΔC20 estimates to errors in the wind fields. With several estimates of ΔC21, ΔS21, and ΔC20 variations, it is possible to estimate broadband noise variance and noise power spectra in each, given reasonable assumptions about noise independence. The GRACE CSR release 5 solutions clearly outperform other estimates of ΔC21 and ΔS21 variations with the lowest noise levels over a broad band of frequencies.

  16. Inter-comparison of GRACE data over India

    Science.gov (United States)

    Banerjee, Chandan; Kumar, D. Nagesh

    2016-05-01

    The advent of satellite remote sensing and its use in hydrology has facilitated a huge leap in the understanding of the various water resources, its interaction with ecological systems and anthropogenic creations. Recently, NASA and German Aerospace Research Agency-DLR launched the Gravity Recovery and Climate Experiment (GRACE) satellite mission consisting of two satellites. They measure the time varying gravity which gives changes in the distribution of mass on the surface of the earth which after removing atmospheric and oceanic effects is majorly caused by changes in Terrestrial Water Storage (TWS) changes. GRACE data is generally available as spherical harmonic coefficients, which is difficult for hydrologists to understand and interpret. JPL's TELLUS website is now providing gridded global data set in the form of mass anomaly derived from the Level-2 data sets of spherical harmonic coefficients of 3 sources, viz. CSR, GFZ and JPL. Before using these data sets for solving hydrological problems, it is important to understand the differences and similarities between these data sets as direct calibration of GRACE data is not possible. In this study we do an inter-comparison of the Level-3 Release 05 data sets over India. We compare the data sets using Pearson, Spearman and Kendall correlation. CSR and GFZ data sets appear to be closest to each other whereas JPL and GFZ data sets are most different from each other.

  17. Minimizing the effects of filtering on catchment scale GRACE solutions

    Science.gov (United States)

    Dutt Vishwakarma, Bramha; Devaraju, Balaji; Sneeuw, Nico

    2016-08-01

    The Gravity Recovery and Climate Experiment (GRACE) satellite mission has provided time variable gravity information since its launch in 2002. Due to short-wavelength noise, the total water storage variations over a catchment observed from GRACE are usable only after filtering. Filtering smooths both the signal and the noise, inevitably changing the nature of the estimated total water storage change. The filtered estimates suffer from attenuation and leakage, which changes the signal characteristics. Several studies have mainly focused on correcting the changed amplitude with the aid of hydrological models. In this study, it is demonstrated that in addition to the amplitude loss, also significant phase change in the time series of total water storage over a region can occur. The phase change due to leakage from nearby catchments can be around 20° to 30° for catchments with moderate size, which makes it difficult to retrieve signal by only scaling. We propose a strategy to approach the true time series with improved phase and amplitude. The strategy is independent of any hydrological model. It is first demonstrated in a closed-loop environment over 32 catchments, where we show that the performance of our method is consistent and better than other model-dependent approaches. Then we also discuss the limitations of our approach. Finally we apply our method to the GRACE level 2 products for 32 catchments.

  18. Global evaluation of new GRACE mascon products for hydrologic applications

    Science.gov (United States)

    Scanlon, Bridget R.; Zhang, Zizhan; Save, Himanshu; Wiese, David N.; Landerer, Felix W.; Long, Di; Longuevergne, Laurent; Chen, Jianli

    2016-12-01

    Recent developments in mascon (mass concentration) solutions for GRACE (Gravity Recovery and Climate Experiment) satellite data have significantly increased the spatial localization and amplitude of recovered terrestrial Total Water Storage anomalies (TWSA); however, land hydrology applications have been limited. Here we compare TWSA from April 2002 through March 2015 from (1) newly released GRACE mascons from the Center for Space Research (CSR-M) with (2) NASA JPL mascons (JPL-M), and with (3) CSR Tellus gridded spherical harmonics rescaled (sf) (CSRT-GSH.sf) in 176 river basins, ˜60% of the global land area. Time series in TWSA mascons (CSR-M and JPL-M) and spherical harmonics are highly correlated (rank correlation coefficients mostly >0.9). The signal from long-term trends (up to ±20 mm/yr) is much less than that from seasonal amplitudes (up to 250 mm). Net long-term trends, summed over all 176 basins, are similar for CSR and JPL mascons (66-69 km3/yr) but are lower for spherical harmonics (˜14 km3/yr). Long-term TWSA declines are found mostly in irrigated basins (-41 to -69 km3/yr). Seasonal amplitudes agree among GRACE solutions, increasing confidence in GRACE-based seasonal fluctuations. Rescaling spherical harmonics significantly increases agreement with mascons for seasonal fluctuations, but less for long-term trends. Mascons provide advantages relative to spherical harmonics, including (1) reduced leakage from land to ocean increasing signal amplitude, and (2) application of geophysical data constraints during processing with little empirical postprocessing requirements, making it easier for nongeodetic users. Results of this product intercomparison should allow hydrologists to better select suitable GRACE solutions for hydrologic applications.

  19. Graceful Exit and Energy Conditions in String Cosmology

    CERN Document Server

    Brustein, Ram; Brustein, Ram; Madden, Richard

    1997-01-01

    String cosmology solutions are examined in a generalized phase-space including sources representing arbitrary corrections to lowest order string-dilaton-gravity effective action. We find a set of necessary conditions for a graceful exit transition from a dilaton-driven inflationary phase to a radiation dominated era. We show that sources allowing such a transition have to violate energy conditions similar to those appearing in singularity theorems of general relativity. Since familiar classical sources, excepting spatial curvature, obey these energy conditions we conclude that a generic graceful exit in string cosmology requires a new effective phase of matter. Our results clarify and generalize previous analyses and enable us to critically reexamine proposed non-singular cosmologies.

  20. 77 FR 73452 - Grace Period Study

    Science.gov (United States)

    2012-12-10

    ... Patent and Trademark Office Grace Period Study ACTION: Proposed collection; comment request. SUMMARY: The...Collection@uspto.gov . Include ``0651- 00xx Grace Period Study comment'' in the subject line of the message... United States' grace period, which permits exceptions to absolute novelty, figures centrally in the...

  1. Tests of daily time variable Earth gravity field solutions for precise orbit determination of altimetry satellites

    Science.gov (United States)

    Rudenko, Sergei; Gruber, Christian

    2016-04-01

    This study makes use of current GFZ monthly and daily gravity field products from 2002 to 2014 based on radial basis functions (RBF) instead of time variable gravity field modeling for precise orbit determination of altimetry satellites. Since some monthly solutions are missing in the GFZ GRACE RL05a solution and in order to reach a better quality for the precise orbit determination, daily generated RBF solutions obtained from Kalman filtered GRACE data processing and interpolated in case of gaps have been used. Moreover, since the geopotential coefficients of low degrees are better determined using SLR observations to geodetic satellites like Lageos, Stella, Starlette and Ajisai than from GRACE observations, these terms are co-estimated in the RBF solutions by using apriori SLR-derived values up to degree and order 4. Precise orbits for altimetry satellites Envisat (2002-2012), Jason-1 (2002-2013) and Jason-2 (2008-2014) are then computed over the given time intervals using this approach and compared with the orbits obtained when using other models such as EIGEN-6S4. An analysis of the root-mean-square values of the observation fits of SLR and DORIS observations and the orbit arcs overlaps will allow us to draw a conclusion on the quality of the RBF solution and to use these new trajectories for sea level trend estimates and geophysical application.

  2. Analysis of Terrestrial Water Storage Changes from GRACE and GLDAS

    Science.gov (United States)

    Syed, Tajdarul H.; Famiglietti, James S.; Rodell, Matthew; Chen, Jianli; Wilson, Clark R.

    2008-01-01

    Since March 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided first estimates of land water storage variations by monitoring the time-variable component of Earth's gravity field. Here we characterize spatial-temporal variations in terrestrial water storage changes (TWSC) from GRACE and compare them to those simulated with the Global Land Data Assimilation System (GLDAS). Additionally, we use GLDAS simulations to infer how TWSC is partitioned into snow, canopy water and soil water components, and to understand how variations in the hydrologic fluxes act to enhance or dissipate the stores. Results quantify the range of GRACE-derived storage changes during the studied period and place them in the context of seasonal variations in global climate and hydrologic extremes including drought and flood, by impacting land memory processes. The role of the largest continental river basins as major locations for freshwater redistribution is highlighted. GRACE-based storage changes are in good agreement with those obtained from GLDAS simulations. Analysis of GLDAS-simulated TWSC illustrates several key characteristics of spatial and temporal land water storage variations. Global averages of TWSC were partitioned nearly equally between soil moisture and snow water equivalent, while zonal averages of TWSC revealed the importance of soil moisture storage at low latitudes and snow storage at high latitudes. Evapotranspiration plays a key role in dissipating globally averaged terrestrial water storage. Latitudinal averages showed how precipitation dominates TWSC variations in the tropics, evapotranspiration is most effective in the midlatitudes, and snowmelt runoff is a key dissipating flux at high latitudes. Results have implications for monitoring water storage response to climate variability and change, and for constraining land model hydrology simulations.

  3. Sea‐level fingerprint of continental water and ice mass change from GRACE

    NARCIS (Netherlands)

    Riva, R.E.M.; Bamber, J.L.; Lavallée, D.A.; Wouters, B.

    2010-01-01

    The Gravity Recovery and Climate Experiment satellites (GRACE) provide, for the first time, a method to directly measure mass exchange between the land and oceans over time. The dominant components of this exchange are due to continental ice loss/gain and land hydrology. Here, we determine the secul

  4. Mass changes from GRACE data in Argentina. A preliminary qualitative analysis

    DEFF Research Database (Denmark)

    Pereira, Alexandre De Lemos; Pacino, M. C.; Forsberg, René

    2012-01-01

    detected the significant mass changes of the area, thought there are some discrepancies between the four GRACE processing centers. Gravity trend as well as amplitude maps of these variations for the period 2002- 2008 show important features in three zones: Patagonia, La Plata basin, and the Andes Mountain...

  5. The method of tailored sensitivity kernels for GRACE mass change estimates

    Science.gov (United States)

    Groh, Andreas; Horwath, Martin

    2016-04-01

    To infer mass changes (such as mass changes of an ice sheet) from time series of GRACE spherical harmonic solutions, two basic approaches (with many variants) exist: The regional integration approach (or direct approach) is based on surface mass changes (equivalent water height, EWH) from GRACE and integrates those with specific integration kernels. The forward modeling approach (or mascon approach, or inverse approach) prescribes a finite set of mass change patterns and adjusts the amplitudes of those patterns (in a least squares sense) to the GRACE gravity field changes. The present study reviews the theoretical framework of both approaches. We recall that forward modeling approaches ultimately estimate mass changes by linear functionals of the gravity field changes. Therefore, they implicitly apply sensitivity kernels and may be considered as special realizations of the regional integration approach. We show examples for sensitivity kernels intrinsic to forward modeling approaches. We then propose to directly tailor sensitivity kernels (or in other words: mass change estimators) by a formal optimization procedure that minimizes the sum of propagated GRACE solution errors and leakage errors. This approach involves the incorporation of information on the structure of GRACE errors and the structure of those mass change signals that are most relevant for leakage errors. We discuss the realization of this method, as applied within the ESA "Antarctic Ice Sheet CCI (Climate Change Initiative)" project. Finally, results for the Antarctic Ice Sheet in terms of time series of mass changes of individual drainage basins and time series of gridded EWH changes are presented.

  6. Predictive modeling of cholera using GRACE and TRMM satellite data

    Science.gov (United States)

    Jutla, A.; Akanda, A. S. S.; Colwell, R. R.

    2015-12-01

    Cholera outbreaks can be classified in three forms- epidemic (sudden or seasonal outbreaks), endemic (recurrence and persistence of the disease for several consecutive years) and mixed-mode endemic (combination of certain epidemic and endemic conditions) with significant spatial and temporal heterogeneity. Endemic cholera is related to floods and droughts in regions where water and sanitation infrastructure are inadequate or insufficient. With more than a decade of terrestrial water storage (TWS) data obtained from Gravity Recovery and Climate Experiment (GRACE), understanding dynamics of river discharge is now feasible. We explored lead-lag relationships between TWS in the Ganges-Brahmaputra-Meghna (GBM) basin and endemic cholera in Bangladesh. Since bimodal seasonal peaks in cholera in Bangladesh occur during the spring and autumn season, two separate models, between TWS and disease time series (2002 to 2010) were developed. TWS, hence water availability, showed an asymmetrical, strong association with spring (τ=-0.53; pcholera prevalence up to five to six months in advance. One unit (cm of water) decrease in water availability in the basin increased odds of above normal cholera by 24% [confidence interval (CI) 20-31%; pcholera in the autumn by 29% [CI:22-33%; pcholera is related with warm temperatures and heavy rainfall. Using TRMM data for several locations in Asia and Africa, probability of cholera increases 18% [CI:15-23%; p<0.05] after heavy precipitation resulted in a societal conditions where access to safe water and sanitation was disrupted. Results from mechanistic modeling framework using systems approach that include satellite based hydroclimatic information with tradition disease transmission models will also be presented.

  7. Validation of MPI-ESM Decadal Hindcast Experiments with Terrestrial Water Storage Variations as Observed by the GRACE Satellite Mission

    Directory of Open Access Journals (Sweden)

    Liangjing Zhang

    2016-12-01

    Full Text Available Time-variations in the gravity field as observed by the GRACE mission provide for the first time quantitative estimates of the terrestrial water storage (TWS at monthly resolution over one decade (2002–2011. TWS from GRACE is applied here to validate three different ensemble sets of decadal hindcasts performed with the coupled climate model MPI-ESM within the German research project MiKlip. Those experiments differ in terms of the applied low (LR and medium (MR spatial resolution configuration of MPI-ESM, as well as by the applied ensemble initialization strategy, where ocean-only (b0 is replaced by atmosphere and ocean (b1 anomaly initialization. Moderately positive skill scores of the initialized hindcasts are obtained both with respect to the zero anomaly forecast and the uninitialized projections in particular for lead year 1 in moderate to high latitudes of the Northern Hemisphere. Skill scores gradually increase when moving from b0-LR to b1-LR, and less prominent also for b1-LR to b1-MR, thereby documenting improvements of the MPI-ESM decadal climate prediction system during the most recent years.

  8. Terrestrial Gravity Fluctuations

    Science.gov (United States)

    Harms, Jan

    2015-12-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10-23 Hz-1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of

  9. Terrestrial Gravity Fluctuations.

    Science.gov (United States)

    Harms, Jan

    2015-01-01

    Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW) detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10(-23) Hz(-1/2) above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of

  10. Terrestrial Gravity Fluctuations

    Directory of Open Access Journals (Sweden)

    Jan Harms

    2015-12-01

    Full Text Available Different forms of fluctuations of the terrestrial gravity field are observed by gravity experiments. For example, atmospheric pressure fluctuations generate a gravity-noise foreground in measurements with super-conducting gravimeters. Gravity changes caused by high-magnitude earthquakes have been detected with the satellite gravity experiment GRACE, and we expect high-frequency terrestrial gravity fluctuations produced by ambient seismic fields to limit the sensitivity of ground-based gravitational-wave (GW detectors. Accordingly, terrestrial gravity fluctuations are considered noise and signal depending on the experiment. Here, we will focus on ground-based gravimetry. This field is rapidly progressing through the development of GW detectors. The technology is pushed to its current limits in the advanced generation of the LIGO and Virgo detectors, targeting gravity strain sensitivities better than 10^–23 Hz^–1/2 above a few tens of a Hz. Alternative designs for GW detectors evolving from traditional gravity gradiometers such as torsion bars, atom interferometers, and superconducting gradiometers are currently being developed to extend the detection band to frequencies below 1 Hz. The goal of this article is to provide the analytical framework to describe terrestrial gravity perturbations in these experiments. Models of terrestrial gravity perturbations related to seismic fields, atmospheric disturbances, and vibrating, rotating or moving objects, are derived and analyzed. The models are then used to evaluate passive and active gravity noise mitigation strategies in GW detectors, or alternatively, to describe their potential use in geophysics. The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our

  11. Accuracy Analysis for SST Gravity Field Model in China

    Institute of Scientific and Technical Information of China (English)

    LUO Jia; LUO Zhicai; ZOU Xiancai; WANG Haihong

    2006-01-01

    Taking China as the region for test, the potential of the new satellite gravity technique, satellite-to-satellite tracking for improving the accuracy of regional gravity field model is studied. With WDM94 as reference, the gravity anomaly residuals of three models, the latest two GRACE global gravity field model (EIGEN_GRACE02S, GGM02S) and EGM96, are computed and compared. The causes for the differences among the residuals of the three models are discussed. The comparison between the residuals shows that in the selected region, EIGEN_GRACE02S or GGM02S is better than EGM96 in lower degree part (less than 110 degree). Additionally, through the analysis of the model gravity anomaly residuals, it is found that some systematic errors with periodical properties exist in the higher degree part of EIGEN and GGM models, the results can also be taken as references in the validation of the SST gravity data.

  12. Evaluating flood potential with GRACE in the United States

    Science.gov (United States)

    Molodtsova, Tatiana; Molodtsov, Sergey; Kirilenko, Andrei; Zhang, Xiaodong; VanLooy, Jeffrey

    2016-04-01

    Reager and Famiglietti (2009) proposed an index, Reager's Flood Potential Index (RFPI), for early large-scale flood risk monitoring using the Terrestrial Water Storage Anomaly (TWSA) product derived from the Gravity Recovery and Climate Experiment (GRACE). We evaluated the efficacy of the RFPI for flood risk assessment over the continental USA using multi-year flood observation data from 2003 to 2012 by the US Geological Survey and Dartmouth Flood Observatory. In general, we found a good agreement between the RFPI flood risks and the observed floods on regional and even local scales. RFPI demonstrated skill in predicting the large-area, long-duration floods, especially during the summer season.

  13. GRACE Assimilation into Hydrological Model Improves Representation of Drought-induced Groundwater Trend over Murray-Darling Basin, Australia

    Science.gov (United States)

    Schumacher, Maike; Forootan, Ehsan; Van Dijk, Albert I. J. M.; Müller Schmied, Hannes; Crosbie, Russell S.; Kusche, Jürgen; Döll, Petra

    2016-04-01

    The Murray-Darling Basin, one of the largest and driest river basins over the world, experienced a long-term drought (over 2003-2009), the so-called Millennium Drought. As a result, the terrestrial water storage in the region decreased, which was attributed to dry meteorological conditions and extensive irrigation for agriculture. We used simulations of the WaterGAP Global Hydrology Model (WGHM) driven by monthly climate fields from the Climate Research Unit's Time Series (CRU TS 3.2) and precipitation data from the Global Precipitation Climatology Center (GPCC) to estimate linear trends in soil, surface and groundwater compartments, as well as total water storage changes (TWSC). However, the model was not able to capture the effect of the Millennium Drought on the storage compartments likely due to missing processes in dry regions or climate forcing uncertainties. Particularly, TWSC simulated by standard WGHM did not reproduce the negative trend during 2003-2009. Therefore, in this study, we investigate whether assimilating TWSC from the Gravity Recovery And Climate Experiment (GRACE) satellite mission into WGHM enables a more realistic representation of the Millennium Drought on the basin hydrology. Firstly, the quality of monthly GRACE TWSC and its post-processing over the Murray-Darling Basin was assessed. An improved calibration and data assimilation (C/DA) approach (Schumacher et al., JoG-2016) was then applied to integrate GRACE TWSC along with its full error covariance information into WGHM during 2003-2009. Independent observations of soil moisture, groundwater and surface water extent were used to validate the model outputs after C/DA. Our investigations indicate that the integration of GRACE data indeed introduces a negative trend to TWSC simulations of WGHM, which occurred predominantly in the south (Murray Basin). The trend was found to be associated with the changes in groundwater storage, which was confirmed through validation with in

  14. Natural and human-induced terrestrial water storage change: A global analysis using hydrological models and GRACE

    Science.gov (United States)

    Felfelani, Farshid; Wada, Yoshihide; Longuevergne, Laurent; Pokhrel, Yadu N.

    2017-10-01

    Hydrological models and the data derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have been widely used to study the variations in terrestrial water storage (TWS) over large regions. However, both GRACE products and model results suffer from inherent uncertainties, calling for the need to make a combined use of GRACE and models to examine the variations in total TWS and their individual components, especially in relation to natural and human-induced changes in the terrestrial water cycle. In this study, we use the results from two state-of-the-art hydrological models and different GRACE spherical harmonic products to examine the variations in TWS and its individual components, and to attribute the changes to natural and human-induced factors over large global river basins. Analysis of the spatial patterns of the long-term trend in TWS from the two models and GRACE suggests that both models capture the GRACE-measured direction of change, but differ from GRACE as well as each other in terms of the magnitude over different regions. A detailed analysis of the seasonal cycle of TWS variations over 30 river basins shows notable differences not only between models and GRACE but also among different GRACE products and between the two models. Further, it is found that while one model performs well in highly-managed river basins, it fails to reproduce the GRACE-observed signal in snow-dominated regions, and vice versa. The isolation of natural and human-induced changes in TWS in some of the managed basins reveals a consistently declining TWS trend during 2002-2010, however; significant differences are again obvious both between GRACE and models and among different GRACE products and models. Results from the decomposition of the TWS signal into the general trend and seasonality indicate that both models do not adequately capture both the trend and seasonality in the managed or snow-dominated basins implying that the TWS variations from a

  15. Evaluating terrestrial water storage variations from regionally constrained GRACE mascon data and hydrological models over Southern Africa – Preliminary results

    DEFF Research Database (Denmark)

    Krogh, Pernille Engelbredt; Andersen, Ole Baltazar; Michailovsky, Claire Irene B.;

    2010-01-01

    A concentration of surface mass has a distinct, localized signature in Gravity Recovery and Climate Experiment (GRACE) K-band range rate (KBRR) data. This fact is exploited in the regional solutions for mass concentration parameters (mascons) made at the Goddard Space Flight Center (GSFC). In thi......A concentration of surface mass has a distinct, localized signature in Gravity Recovery and Climate Experiment (GRACE) K-band range rate (KBRR) data. This fact is exploited in the regional solutions for mass concentration parameters (mascons) made at the Goddard Space Flight Center (GSFC...

  16. Graceful Exit in String Cosmology

    CERN Document Server

    Brustein, Ram; Brustein, Ram; Madden, Richard

    1998-01-01

    The graceful exit transition from a dilaton-driven inflationary phase to a decelerated Friedmann-Robertson-Walker era requires certain classical and quantum corrections to the string effective action. Classical corrections can stabilize a high curvature string phase while the evolution is still in the weakly coupled regime, and quantum corrections can induce violation of the null energy condition, allowing evolution towards a decelerated phase.

  17. Changes of Groundwater Storage in the Heihe River Basin Derived from GRACE Gravity Satellite Data%利用GRACE重力卫星数据反演黑河流域地下水变化

    Institute of Scientific and Technical Information of China (English)

    曹艳萍; 南卓铜; 胡兴林

    2012-01-01

    Water scarcity is becoming an increasingly severe problem in arid and semiarid regions because of limitation of available surface water resources and over exploitation of groundwater.As a typical inland river basin in the arid and semiarid regions of Northwest China,the Heihe River basin is facing the same trouble of water resources.Because there is limited and unevenly distributed groundwater monitoring wells within the basin,monitoring groundwater change is hard.In this paper,it is intended to derive temporal and spatial groundwater variation in the Heihe River basin for the period of 2003—2008 from GRACE recovery satellite data,which will be useful for better understanding groundwater resources changing characteristics in the basin.The study also offers a feasible approach to monitor groundwater variation of a river basin only with a small number of(or even without site) groundwater data.To verify the approach,only the groundwater data in the upper and middle reaches of the river was used.The correlation between the derived groundwater variation and the measured one is relatively high,which consequently shows the applicability of GRACE in the river basin to some extent.Based upon preliminary verifications,the method is applied to the entire Heihe River basin.It is found that the groundwater amount decreased,with a small magnitude,in the entire basin during 2003—2004.In 2005 summer groundwater increasing reached a highest rate,and then the increasing magnitude began to decrease,and no more increase in 2008.Spatially,in the upper reaches of the river,groundwater showed decline in 2003—2004,with a slight increase in 2005,no increase in 2006 and a small increase in 2007—2008.In the middle reaches of the river,groundwater slightly increased in 2005,and then declined in the following three years.In the lower reaches of the river,groundwater kept increase in the total 6 study years.%干旱区地表水资源有限,地下水资源被超采利用,黑河流域

  18. Quantifying renewable groundwater stress with GRACE

    Science.gov (United States)

    Richey, Alexandra S.; Thomas, Brian F.; Lo, Min‐Hui; Reager, John T.; Voss, Katalyn; Swenson, Sean; Rodell, Matthew

    2015-01-01

    Abstract Groundwater is an increasingly important water supply source globally. Understanding the amount of groundwater used versus the volume available is crucial to evaluate future water availability. We present a groundwater stress assessment to quantify the relationship between groundwater use and availability in the world's 37 largest aquifer systems. We quantify stress according to a ratio of groundwater use to availability, which we call the Renewable Groundwater Stress ratio. The impact of quantifying groundwater use based on nationally reported groundwater withdrawal statistics is compared to a novel approach to quantify use based on remote sensing observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. Four characteristic stress regimes are defined: Overstressed, Variable Stress, Human‐dominated Stress, and Unstressed. The regimes are a function of the sign of use (positive or negative) and the sign of groundwater availability, defined as mean annual recharge. The ability to mitigate and adapt to stressed conditions, where use exceeds sustainable water availability, is a function of economic capacity and land use patterns. Therefore, we qualitatively explore the relationship between stress and anthropogenic biomes. We find that estimates of groundwater stress based on withdrawal statistics are unable to capture the range of characteristic stress regimes, especially in regions dominated by sparsely populated biome types with limited cropland. GRACE‐based estimates of use and stress can holistically quantify the impact of groundwater use on stress, resulting in both greater magnitudes of stress and more variability of stress between regions. PMID:26900185

  19. Status and Assessments of CSR GRACE Level-2 Data Products

    Science.gov (United States)

    Bettadpur, Srinivas; Kang, Zhigui; Nagel, Peter; Pastor, Rick; Poole, Steve; Ries, John; Save, Himanshu

    2015-04-01

    The joint NASA/DLR GRACE mission has successfully operated for more than 13 years, and has provided a remarkable record of global mass flux due to a large variety of geophysical and climate processes at various spatio-temporal scales. The University of Texas Center for Space Research (CSR) hosts the mission PI, and is responsible for delivery of operational (presently denoted as Release-05 or RL05) gravity field data products. In addition, CSR generates and distributes a variety of other gravity field data products, including products generated from the use of satellite laser ranging data. This poster will provide an overview of all these data products, their relative quality, potential applications, and future plans for their development and delivery.

  20. Evapotranspiration Estimation over Yangtze River Basin from GRACE satellite measurement and in situ data

    Science.gov (United States)

    Li, Qiong; Luo, Zhicai; Zhong, Bo; Wang, Haihong; Zhou, Zebing

    2016-04-01

    As the critical component of hydrologic cycle, evapotranspiration (ET) plays an important role in global water exchanges and energy flow across the hydrosphere, atmosphere and biosphere. Influenced by the Asian monsoon, the Yangtze River Basin (YRB) suffer from the several severe floods and droughts over the last decades due to the significant difference between temporal and spatial distribution terrestrial water storages. As an indispensable part, it is practically important to assessment ET in the YRB accompany with increased population and rapid economic and agriculture development. Average ET over the YRB is computed as the residual of terrestrial water budget using the Gravity Recovery and Climate Experiment (GRACE) satellite-based measurements and the ground-based observations. The GRACE-based ET were well coincidence with the ET from MODIS, with the correlation coefficient of 0.853, and the correlation coefficient is 0.696 while comparing with the ET ground-based observation. The mean monthly average of ET from these various estimates is 56.9 mm/month over the whole YRB, and peak between June and August. Monthly variations of ET reach a maximum in Wujiang with 69.11 mm/month and a minimum in Jinshajiang with 39.01 mm/month. Based on the correlation between ET and independent estimates of near-surface temperature and soil moisture, it is showed that as the temperature increased, the ET of the seven sub-catchment were rising except for the Poyang Lake and Donting Lake. And we also can infer that the midstream of YRB is significant correlated with ESON especially in the Hanjiang basin. The Surface Humidity Index over the YRB was gradually decreased and its variations in each sub-catchment showed a significant decreasing trend in Jinshajiang and Mingjiang. This research has important potential for use in large-scale water budget assessments and intercomparison studies. Acknowledgements: This research is supported by the National Natural Science Foundation of

  1. Accounting for spatial correlation errors in the assimilation of GRACE into hydrological models through localization

    Science.gov (United States)

    Khaki, M.; Schumacher, M.; Forootan, E.; Kuhn, M.; Awange, J. L.; van Dijk, A. I. J. M.

    2017-10-01

    Assimilation of terrestrial water storage (TWS) information from the Gravity Recovery And Climate Experiment (GRACE) satellite mission can provide significant improvements in hydrological modelling. However, the rather coarse spatial resolution of GRACE TWS and its spatially correlated errors pose considerable challenges for achieving realistic assimilation results. Consequently, successful data assimilation depends on rigorous modelling of the full error covariance matrix of the GRACE TWS estimates, as well as realistic error behavior for hydrological model simulations. In this study, we assess the application of local analysis (LA) to maximize the contribution of GRACE TWS in hydrological data assimilation. For this, we assimilate GRACE TWS into the World-Wide Water Resources Assessment system (W3RA) over the Australian continent while applying LA and accounting for existing spatial correlations using the full error covariance matrix. GRACE TWS data is applied with different spatial resolutions including 1° to 5° grids, as well as basin averages. The ensemble-based sequential filtering technique of the Square Root Analysis (SQRA) is applied to assimilate TWS data into W3RA. For each spatial scale, the performance of the data assimilation is assessed through comparison with independent in-situ ground water and soil moisture observations. Overall, the results demonstrate that LA is able to stabilize the inversion process (within the implementation of the SQRA filter) leading to less errors for all spatial scales considered with an average RMSE improvement of 54% (e.g., 52.23 mm down to 26.80 mm) for all the cases with respect to groundwater in-situ measurements. Validating the assimilated results with groundwater observations indicates that LA leads to 13% better (in terms of RMSE) assimilation results compared to the cases with Gaussian errors assumptions. This highlights the great potential of LA and the use of the full error covariance matrix of GRACE TWS

  2. Construction of Earth's gravitational field model from CHAMP, GRACE and GOCE data

    Directory of Open Access Journals (Sweden)

    Xiaogang Liu

    2015-07-01

    Full Text Available The basic principle of spectral combination method is discussed, and the general expressions of the spectral weight and spectral combination of the united-processing of various types of gravimetric data are shown. What's more, based on degree error RMS of potential coefficients, the detailed expressions of spectral combination formulae and the corresponding spectral weights in the Earth's gravitational field model(EGM determination using GOCE + GRACE and CHAMP + GRACE + GOCE are derived. The fundamental situation that ulux-champ2013s, tongji-GRACE01, go-cons-gcf-2-tim-r5 constructed respectively by CHAMP, GRACE, GOCE data and go-cons-gcf-2-dir-r5 constructed by syncretic processing of GRACE, GOCE and LAGEOS data are explained briefly, the degree error RMS, cumulative geoid height error and cumulative gravity anomaly error of these models are calculated. A syncretic model constructed from CHAMP, GRACE and GOCE data, which is expressed by champ + grace + goce, is obtained based on spectral combination method. Experimentation results show that the precision of CHAMP data model is the lowest in satellite-only models, so it is not needed in the determination of syncretic models. The GRACE data model can improve the GOCE data model in medium-long wavelength, so the overall precision of syncretic model can be improved. Consequently, as many types of gravimetric data as possible should be combined together in the data processing in order to strengthen the quality and reliability with widening scope and improve the precision and spatial resolution of the computational results.

  3. Establishing the Framework for Land Data Assimilation of GRACE Terrestrial Water Storage Information

    Science.gov (United States)

    Sakumura, C.; Bettadpur, S. V.; Yang, Z. L.; Save, H.; McCullough, C.

    2015-12-01

    Assimilation of terrestrial water storage (TWS) data from the Gravity Recovery and Climate Experiment (GRACE) mission into current land surface models can correct model deficiencies due to errors in the model structure, atmospheric forcing datasets, parameters, etc. However, the assimilation process is complicated by spatial and temporal resolution discrepancies between the model and observational datasets, characterization of the error in each, and limitations of the algorithms used to calculate and update the model state. This study aims to establish a framework for hydrological data assimilation with GRACE. GRACE is an independent and accurate but coarse resolution terrestrial water storage dataset. While the models cannot attain the accuracy of GRACE, they are effective in interpretation and downscaling of the product and providing continuity over space and time. Accurate assimilation of GRACE TWS into LSMs thus will take the best characteristics of each and create a combined product that outperforms each individual source. More specifically, this framework entails a comprehensive analysis of the deficiencies and potential improvements of the satellite data products, the assimilation procedures and error characterization, and assimilation effectiveness. A daily sliding window mascon GRACE TWS product, presented previously, was developed to reduce smoothing in time and space during assimilation into the Community Land Model 4.0. The Ensemble Kalman Filter assimilation algorithms are analyzed and adapted for use with the new products, GRACE error information, and model characteristics. Additional assimilation tools such as Gaspari-Cohn localization and ensemble inflation are implemented and tuned for the model and observation properties. Analysis of the observational data, model data, sensitivity and effectiveness of the assimilation routines, and the assimilated results is done through regional comparison with independent in-situ datasets and external model

  4. Contribution of satellite laser ranging to combined gravity field models

    Science.gov (United States)

    Maier, A.; Krauss, S.; Hausleitner, W.; Baur, O.

    2012-02-01

    In the framework of satellite-only gravity field modeling, satellite laser ranging (SLR) data is typically exploited to recover long-wavelength features. This contribution provides a detailed discussion of the SLR component of GOCO02S, the latest release of combined models within the GOCO series. Over a period of five years (January 2006 to December 2010), observations to LAGEOS-1, LAGEOS-2, Ajisai, Stella, and Starlette were analyzed. We conducted a series of closed-loop simulations and found that estimating monthly sets of spherical harmonic coefficients beyond degree five leads to exceedingly ill-posed normal equation systems. Therefore, we adopted degree five as the spectral resolution for real data analysis. We compared our monthly coefficient estimates of degree two with SLR and Gravity Recovery and Climate Experiment (GRACE) time series provided by the Center for Space Research (CSR) at Austin, Texas. Significant deviations in C20 were noted between SLR and GRACE; the agreement is better for the non-zonal coefficients. Fitting sinusoids together with a linear trend to our C20 time series yielded a rate of (-1.75 ± 0.6) × 10-11/yr; this drift is equivalent to a geoid change from pole to equator of 0.35 ± 0.12 mm/yr or an apparent Greenland mass loss of 178.5 ± 61.2 km3/yr. The mean of all monthly solutions, averaged over the five-year period, served as input for the satellite-only model GOCO02S. The contribution of SLR to the combined gravity field model is highest for C20, and hence is essential for the determination of the Earth's oblateness.

  5. Combining satellite radar altimetry, SAR surface soil moisture and GRACE total storage changes for model calibration and validation in a large ungauged catchment

    DEFF Research Database (Denmark)

    Milzow, Christian; Krogh, Pernille Engelbredt; Bauer-Gottwein, Peter

    2010-01-01

    hundred meters; and (iii) Temporal changes of the Earth’s gravity field recorded by the Gravity Recovery and Climate Experiment (GRACE) caused by total water storage changes in the catchment. The SSM data are compared to simulated moisture conditions in the top soil layer. They cannot be used for model...

  6. Simulation of the time-variable gravity field by means of coupled geophysical models

    Directory of Open Access Journals (Sweden)

    Th. Gruber

    2011-07-01

    Full Text Available Time variable gravity fields, reflecting variations of mass distribution in the system Earth is one of the key parameters to understand the changing Earth. Mass variations are caused either by redistribution of mass in, on or above the Earth's surface or by geophysical processes in the Earth's interior. The first set of observations of monthly variations of the Earth gravity field was provided by the US/German GRACE satellite mission beginning in 2002. This mission is still providing valuable information to the science community. However, as GRACE has outlived its expected lifetime, the geoscience community is currently seeking successor missions in order to maintain the long time series of climate change that was begun by GRACE. Several studies on science requirements and technical feasibility have been conducted in the recent years. These studies required a realistic model of the time variable gravity field in order to perform simulation studies on sensitivity of satellites and their instrumentation. This was the primary reason for the European Space Agency (ESA to initiate a study on "Monitoring and Modelling individual Sources of Mass Distribution and Transport in the Earth System by Means of Satellites". The goal of this interdisciplinary study was to create as realistic as possible simulated time variable gravity fields based on coupled geophysical models, which could be used in the simulation processes in a controlled environment. For this purpose global atmosphere, ocean, continental hydrology and ice models were used. The coupling was performed by using consistent forcing throughout the models and by including water flow between the different domains of the Earth system. In addition gravity field changes due to solid Earth processes like continuous glacial isostatic adjustment (GIA and a sudden earthquake with co-seismic and post-seismic signals were modelled. All individual model results were combined and converted to gravity field

  7. Characterization of spatio-temporal patterns for various GRACE- and GLDAS-born estimates for changes of global terrestrial water storage

    Science.gov (United States)

    Yang, Tao; Wang, Chao; Yu, Zhongbo; Xu, Feng

    2013-10-01

    Since the launch in March 2002, the Gravity Recovery and Climate Experiment (GRACE) satellite mission has provided us with a new method to estimate terrestrial water storage (TWS) variations by measuring earth gravity change with unprecedented accuracy. Thus far, a number of standardized GRACE-born TWS products are published by different international research teams. However, no characterization of spatio-temporal patterns for different GRACE hydrology products from the global perspective could be found. It is still a big challenge for the science community to identify the reliable global measurement of TWS anomalies due to our limited knowledge on the true value. Hence, it is urgently necessary to evaluate the uncertainty for various global estimates of the GRACE-born TWS changes by a number of international research organizations. Toward this end, this article presents an in-depth analysis for various GRACE-born and GLDAS-based estimates for changes of global terrestrial water storage. The work characterizes the inter-annual and intra-annual variability, probability density variations, and spatial patterns among different GRACE-born TWS estimates over six major continents, and compares them with results from GLDAS simulations. The underlying causes of inconsistency between GRACE- and GLDAS-born TWS estimates are thoroughly analyzed with an aim to improve our current knowledge in monitoring global TWS change. With a comprehensive consideration of the advantages and disadvantages among GRACE- and GLDAS-born TWS anomalies, a summary is thereafter recommended as a rapid reference for scientists, end-users, and policy-makers in the practices of global TWS change research. To our best knowledge, this work is the first attempt to characterize difference and uncertainty among various GRACE-born terrestrial water storage changes over the major continents estimated by a number of international research organizations. The results can provide beneficial reference to usage of

  8. Analysis of GRACE attitude variations based on characteristics of the AOCS sensors and actuators

    Science.gov (United States)

    Bandikova, Tamara; Flury, Jakob; Ko, Ung-Dai

    Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided the infor-mation about variations in the Earth's gravity field with unprecedented accuracy. Although this mission is in operation for more than 8 years, the onboard sensor behavior is not yet fully understood. The focus of this study is on GRACE satellite dynamics and the operation of attitude determination and control sensors. The goal is to better understand the onboard pro-cesses leading to certain systematic attitude variations which might influence the gravity field solution. Systematic patterns in long-time series of relative and absolute attitude variations of both GRACE spacecrafts during the different AOCS operational modes are investigated. They are put into connection with attitude determination sensors such as star camera and inertial measurement unit, to attitude control systems i.e. magnetic torquers and cold gas thrusters, and to other onboard sensors and satellite environment. Besides, some of the parameters used for the gravity field determination such as KBR geometric correction are analyzed with respect to the above mentioned attitude variations. The emphasis is put on the analysis of the star camera operation and on fuel consumption which are both very crucial topics not only for current but also for the future satellite missions.

  9. Grace and Courtesy in the Elementary Community

    Science.gov (United States)

    Huneke-Stone, Elise

    2015-01-01

    Don't be fooled by Elise Huneke-Stone's disarming beginning where she implies that grace and courtesy is not normally associated with the elementary. She goes on to elaborate that grace and courtesy is indeed everywhere: in project-based learning, understanding of moral precepts, social and intellectual independence, in the utilization of empathy,…

  10. Water storage variations in the Poyang Lake Basin estimated from GRACE and satellite altimetry

    Institute of Scientific and Technical Information of China (English)

    Yang Zhou; Shuanggen Jin; Robert Tenzer; Jialiang Feng

    2016-01-01

    The Gravity Recovery and Climate Experiment (GRACE) satellite mission provides a unique opportunity to quantitatively study terrestrial water storage (TWS) variations. In this paper, the terrestrial water storage variations in the Poyang Lake Basin are recovered from the GRACE gravity data from January 2003 to March 2014 and compared with the Global Land Data Assimilation System (GLDAS) hydrological models and satellite altimetry. Further-more, the impact of soil moisture content from GLDAS and rainfall from the Tropical Rainfall Measuring Mission (TRMM) on TWS variations are investigated. Our results indi-cate that the TWS variations from GRACE, GLDAS and satellite altimetry have a general consistency. The TWS trends in the Poyang Lake Basin determined from GRACE, GLDAS and satellite altimetry are increasing at 0.0141 km3/a, 0.0328 km3/a and 0.0238 km3/a, respectively during the investigated time period. The TWS is governed mainly by the soil moisture content and dominated primarily by the precipitation but also modulated by the flood season of the Yangtze River as well as the lake and river exchange water.

  11. An analytical method for error analysis of GRACE-like missions based on spectral analysis

    CERN Document Server

    Cai, Lin; Li, Qiong; Luo, Zhicai; Hsu, Houtse

    2016-01-01

    The aim of this paper is to present an analytical relationship between the power spectral density of GRACE-like mission measurements and the accuracies of the gravity field coefficients mainly from the point of view of theory of signal and system, which indicates the one-to-one correspondence between spherical harmonic error degree variances and frequencies of the measurement noise. In order to establish this relationship, the average power of the errors due to gravitational acceleration difference and the relationship between perturbing forces and range-rate perturbations are derived, based on the orthogonality property of associated Legendre functions and the linear orbit perturbation theory, respectively. This method provides a physical insight into the relation between mission parameters and scientific requirements. By taking GRACE-FO as the object of research, the effects of sensor noises and time variable gravity signals are analyzed. If LRI measurements are applied, a mission goal with a geoid accuracy...

  12. Mass evolution of Mediterranean, Black, Red, and Caspian Seas from GRACE and altimetry: accuracy assessment and solution calibration

    Science.gov (United States)

    Loomis, B. D.; Luthcke, S. B.

    2017-02-01

    We present new measurements of mass evolution for the Mediterranean, Black, Red, and Caspian Seas as determined by the NASA Goddard Space Flight Center (GSFC) GRACE time-variable global gravity mascon solutions. These new solutions are compared to sea surface altimetry measurements of sea level anomalies with steric corrections applied. To assess their accuracy, the GRACE- and altimetry-derived solutions are applied to the set of forward models used by GSFC for processing the GRACE Level-1B datasets, with the resulting inter-satellite range-acceleration residuals providing a useful metric for analyzing solution quality. We also present a differential correction strategy to calibrate the time series of mass change for each of the seas by establishing the strong linear relationship between differences in the forward modeled mass and the corresponding range-acceleration residuals between the two solutions. These calibrated time series of mass change are directly determined from the range-acceleration residuals, effectively providing regionally-tuned GRACE solutions without the need to form and invert normal equations. Finally, the calibrated GRACE time series are discussed and combined with the steric-corrected sea level anomalies to provide new measurements of the unmodeled steric variability for each of the seas over the span of the GRACE observation record. We apply ensemble empirical mode decomposition (EEMD) to adaptively sort the mass and steric components of sea level anomalies into seasonal, non-seasonal, and long-term temporal scales.

  13. Global Mass Flux Solutions from GRACE: A Comparison of Parameter Estimation Strategies - Mass Concentrations Versus Stokes Coefficients

    Science.gov (United States)

    Rowlands, D. D.; Luthcke, S. B.; McCarthy J. J.; Klosko, S. M.; Chinn, D. S.; Lemoine, F. G.; Boy, J.-P.; Sabaka, T. J.

    2010-01-01

    The differences between mass concentration (mas con) parameters and standard Stokes coefficient parameters in the recovery of gravity infonnation from gravity recovery and climate experiment (GRACE) intersatellite K-band range rate data are investigated. First, mascons are decomposed into their Stokes coefficient representations to gauge the range of solutions available using each of the two types of parameters. Next, a direct comparison is made between two time series of unconstrained gravity solutions, one based on a set of global equal area mascon parameters (equivalent to 4deg x 4deg at the equator), and the other based on standard Stokes coefficients with each time series using the same fundamental processing of the GRACE tracking data. It is shown that in unconstrained solutions, the type of gravity parameter being estimated does not qualitatively affect the estimated gravity field. It is also shown that many of the differences in mass flux derivations from GRACE gravity solutions arise from the type of smoothing being used and that the type of smoothing that can be embedded in mas con solutions has distinct advantages over postsolution smoothing. Finally, a 1 year time series based on global 2deg equal area mascons estimated every 10 days is presented.

  14. Using Enhanced Grace Water Storage Data to Improve Drought Detection by the U.S. and North American Drought Monitors

    Science.gov (United States)

    Houborg, Rasmus; Rodell, Matthew; Lawrimore, Jay; Li, Bailing; Reichle, Rolf; Heim, Richard; Rosencrans, Matthew; Tinker, Rich; Famiglietti, James S.; Svoboda, Mark; Wardlow, Brian; Zaitchik, Benjamin F.

    2011-01-01

    NASA's Gravity Recovery and Climate Experiment (GRACE) satellites measure time variations of the Earth's gravity field enabling reliable detection of spatio-temporal variations in total terrestrial water storage (TWS), including groundwater. The U.S. and North American Drought Monitors rely heavily on precipitation indices and do not currently incorporate systematic observations of deep soil moisture and groundwater storage conditions. Thus GRACE has great potential to improve the Drought Monitors by filling this observational gap. GRACE TWS data were assimilating into the Catchment Land Surface Model using an ensemble Kalman smoother enabling spatial and temporal downscaling and vertical decomposition into soil moisture and groundwater components. The Drought Monitors combine several short- and long-term drought indicators expressed in percentiles as a reference to their historical frequency of occurrence. To be consistent, we generated a climatology of estimated soil moisture and ground water based on a 60-year Catchment model simulation, which was used to convert seven years of GRACE assimilated fields into drought indicator percentiles. At this stage we provide a preliminary evaluation of the GRACE assimilated moisture and indicator fields.

  15. Analysis of groundwater anomalies using GRACE over various districts of Jharkhand

    Science.gov (United States)

    Verma, Arpita; Kumar, Anant; Kumar, Sanjay

    2016-05-01

    Groundwater is an important requirement for the massive population of India. Generally the groundwater level is monitored by using monitoring wells. In this study, Gravity Recovery and Climate Experiment (GRACE) Terrestrial Water Storage (TWS), Land surface state variable GLDAS and Soil Moisture (SM) data were tested for estimating ground water information and based on these groundwater assessments were carried out over the years 2003 to 2012 for Jharkhand State. Additionally, Tropical Rainfall Measuring Mission (TRMM) accumulated rainfall data was also used for the year's 2008 to 2012.From the study over 120 months span of various districts the maximum depletion in storage of groundwater averaged over the six districts is +/-5cm/yr in the year 2010 and maximum storage year (in term of Equivalent water thickness) groundwater average over the six districts is +/-4.4cm in the year 2003. The study also utilized ground based Seasonal changes in the groundwater resource over 287 monitoring wells and estimated groundwater data using map analysis over Jharkhand. This study analyzed seasonal water level variations based on groundwater anomaly. Remote sensing generated result compared with well data shows R2 = 0.6211 and RMSE = 39.46 cm at average seasonal cycle. Also information of different time periods of rainfall (i.e., pre-monsoon and post-monsoon) was analyzed. The trend analysis of rainfall and estimated groundwater gives the basic knowledge that groundwater storage loss and gain showed similarities with increase and decrease in rainfall.

  16. Spurious barometric pressure acceleration in Antarctica and propagation into GRACE Antarctic mass change estimates

    Science.gov (United States)

    Kim, Byeong-Hoon; Eom, Jooyoung; Seo, Ki-Weon; Wilson, Clark R.

    2016-08-01

    Apparent acceleration in Gravity Recovery and Climate Experiment (GRACE) Antarctic ice mass time-series may reflect both ice discharge and surface mass balance contributions. However, a recent study suggests there is also contamination from errors in atmospheric pressure de-aliasing fields [European Center for Medium-Range Weather Forecast (ECMWF) operational products] used during GRACE data processing. To further examine this question, we compare GRACE atmospheric pressure de-aliasing (GAA) fields with in situ surface pressure data from coastal and inland stations. Differences between the two are likely due to GAA errors, and provide a measure of error in GRACE solutions. Time-series of differences at individual weather stations are fit to four presumed error components: annual sinusoids, a linear trend, an acceleration term and jumps at times of known ECMWF model changes. Using data from inland stations, we estimate that atmospheric pressure error causes an acceleration error of about +7.0 Gt yr-2, which is large relative to prior GRACE estimates of Antarctic ice mass acceleration in the range of -12 to -14 Gt yr-2. We also estimate apparent acceleration rates from other barometric pressure (reanalysis) fields, including ERA-Interim, MERRA and NCEP/DOE. When integrated over East Antarctica, the four mass acceleration estimates (from GAA and the three reanalysis fields) vary considerably (by ˜2-16 Gt yr-2). This shows the need for further effort to improve atmospheric mass estimates in this region of sparse in situ observations, in order to use GRACE observations to measure ice mass acceleration and related sea level change.

  17. Topological inflation with graceful exit

    CERN Document Server

    Marunović, Anja

    2015-01-01

    We investigate a class of models of topological inflation in which a super-Hubble-sized global monopole seeds inflation. These models are attractive since inflation starts from rather generic initial conditions, but their not so attractive feature is that, unless symmetry is again restored, inflation never ends. In this work we show that, in presence of another nonminimally coupled scalar field, that is both quadratically and quartically coupled to the Ricci scalar, inflation naturally ends, representing an elegant solution to the graceful exit problem of topological inflation. While the monopole core grows during inflation, the growth stops after inflation, such that the monopole eventually enters the Hubble radius, and shrinks to its Minkowski space size, rendering it immaterial for the subsequent Universe's dynamics. Furthermore, we find that our model can produce cosmological perturbations that source CMB temperature fluctuations and seed large scale structure statistically consistent (within one standard...

  18. The impact of (mega)-cities on the earth's gravity

    Science.gov (United States)

    Schnitzer, S.; Estrella, N.; Güntner, A.; Matiu, M.; Peterseim, N.; Menzel, A.

    2013-12-01

    The world population is constantly growing; today over 7 billion people populate the planet. This development has led to a strong urbanization and expanding cities. According to the United Nations, since 2007 more human beings have lived in urban areas than in rural areas, and by 2030 the urban share will be more than 60%. The challenges of fast growing cities lie in urban management, supply to inhabitants of resources (e.g. water, power, food), and strong environmental problems (e.g. pollution), i.e. their ecological footprint. In our study we address the question of another footprint, whether (mega)-cities have an impact on the earth's gravity field. Analyzing the possible triggers will help to understand the multiple footprints of big cities in various regions. We analyze several data sources. The main data sets are a) monthly solutions of the gravity satellite mission GRACE, detecting changes in the earth's gravity field over time, b) data of the hydrological model WGHM, estimating mass changes in terrestrial and ground water storage, c) urban population data of the United Nations, d) land cover information of the European Space Agency, e) different climate data sets and other auxiliary data. The results suggest a non-uniform pattern of gravity changes with variations in trends related to different clustering parameters.

  19. Quantifying Water Stress Using Total Water Volumes and GRACE

    Science.gov (United States)

    Richey, A. S.; Famiglietti, J. S.; Druffel-Rodriguez, R.

    2011-12-01

    Water will follow oil as the next critical resource leading to unrest and uprisings globally. To better manage this threat, an improved understanding of the distribution of water stress is required today. This study builds upon previous efforts to characterize water stress by improving both the quantification of human water use and the definition of water availability. Current statistics on human water use are often outdated or inaccurately reported nationally, especially for groundwater. This study improves these estimates by defining human water use in two ways. First, we use NASA's Gravity Recovery and Climate Experiment (GRACE) to isolate the anthropogenic signal in water storage anomalies, which we equate to water use. Second, we quantify an ideal water demand by using average water requirements for the domestic, industrial, and agricultural water use sectors. Water availability has traditionally been limited to "renewable" water, which ignores large, stored water sources that humans use. We compare water stress estimates derived using either renewable water or the total volume of water globally. We use the best-available data to quantify total aquifer and surface water volumes, as compared to groundwater recharge and surface water runoff from land-surface models. The work presented here should provide a more realistic image of water stress by explicitly quantifying groundwater, defining water availability as total water supply, and using GRACE to more accurately quantify water use.

  20. Fine orbit tuning to increase the accuracy of the gravity-field modelling

    Science.gov (United States)

    Bezdek, A.; Klokocnik, J.; Kostelecky, J.; Floberghagen, R.; Sebera, J.

    2010-12-01

    Fine orbit tuning will be presented as a tool to enhance the accuracy of the gravity-field parameters based on the data from satellite missions around the Earth or other planetary bodies. A slight variation in the satellite altitude of a few hundred metres or kilometres may dramatically change the pattern and density of the groundtracks, thus leading to a significant difference in the quality of the derived gravity-field parameters. This aspect is important not only to missions dedicated to the gravity-field mapping, but it can be applied to any planetary mission, whose orbital data may yield useful information on the particular gravity field. The geometry of satellite groundtracks is closely connected with the term orbital resonance or repeat orbit, which was intensively studied by the satellite geodesy community since the 1970s. In a systematic way, fine orbit tuning was first applied to altimetry missions for oceanographic purposes in the early 1990s, when it became clear that small changes in the satellite altitude might substantially influence the utility of the data from the onboard instruments. The monthly geopotential solutions from the GRACE mission (in orbit since 2002) displayed apparently worse precision in August-September 2004, which was later found to be caused by a sparser groundtrack pattern due to the passage of the GRACE satellites through the 61/4 orbit resonance. The lessons learned from GRACE were applied by ESA to its gravity field mission GOCE (in orbit since 2009). Here, the situation is different, as the GOCE onboard thrusters are capable of maintaining the satellite at a constant altitude. In order to fully use the measurement potential of the first space gradiometer ever flown, in the GOCE mission planning the influence of orbit geometry was taken into account, and a minimum 2-month repeat period for the orbit was specified. We analysed several orbital configurations of GOCE, as possible candidates for the gravity mapping phases. We

  1. GRACE-II Small Satellite Study Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Quantify the science benefits of GRACE-II mission comprised of multiple pairs of smallsats using realistic expected performance of smallsats and a miniaturized...

  2. Hybrid Parallel Computation of Integration in GRACE

    CERN Document Server

    Yuasa, F; Kawabata, S; Perret-Gallix, D; Itakura, K; Hotta, Y; Okuda, M; Yuasa, Fukuko; Ishikawa, Tadashi; Kawabata, Setsuya; Perret-Gallix, Denis; Itakura, Kazuhiro; Hotta, Yukihiko; Okuda, Motoi

    2000-01-01

    With an integrated software package {\\tt GRACE}, it is possible to generate Feynman diagrams, calculate the total cross section and generate physics events automatically. We outline the hybrid method of parallel computation of the multi-dimensional integration of {\\tt GRACE}. We used {\\tt MPI} (Message Passing Interface) as the parallel library and, to improve the performance we embedded the mechanism of the dynamic load balancing. The reduction rate of the practical execution time was studied.

  3. Potential Water Availability Index (PWAI): A New Water Vulnerability Index for Africa Based on GRACE Data

    Science.gov (United States)

    Hasan, E.; Tarhule, A.; Hong, Y.; Moore, B., III

    2016-12-01

    The critical role of water in enabling or constraining human wellbeing and socio-economic activities has led to interest in quantitatively establishing the status or index of water (in)sufficiency over time and space. Introduced in 1989, the first widely accepted index expressed the status of water resources availability in terms of vulnerability, stress, or scarcity. Since then, numerous refinements and modifications to the concept have been published but nearly all adopt the same basic formulation; water status is a function of available water resources and demand or use. However, accurately defining and assessing `available water' has proved problematic especially in data scarce regions, such as Africa. In this paper, we use Total Water Storage (TWS) estimated from NASA's Gravity Recovery and Climate Experiment (GRACE) in lieu of observational hydrologic data, to estimate the Water Scarcity Index (WSI) for Africa at country level. The monthly TWS Positive anomalies represent periods of net system recharge while negative anomalies represent net system loss due to evapotranspiration and anthropogenic withdrawals. The procedure is as follows. First, we calculated the long-term (2002-2014) Internal Water Storage (IWS) for each country using the monthly precipitation data from the Global Precipitation Climatology Centre (GPCC). Next, the yearly cumulative positive and negative anomalies were added to the long-term IWS to obtain volumetric Potential Water Storage (VPWS) per country. By dividing VPWS by population, we obtain estimates of per capita water availability which can be grouped into vulnerability classes using established thresholds. Our VPWS showed very high correlation (R2 =0.94, p=0.0001) with the values of Internal Renewable Water Resources (IRWR) estimated by AQUSTAT. Additionally, the GWSI is highly correlated (R2 =0.94, p=0.0001) with the existing WSI index from the world bank data center. The novelty and contribution of our approach is in using GRACE

  4. The Light and the Grace: Christian Metaphors

    Directory of Open Access Journals (Sweden)

    Iacob COMAN

    2011-01-01

    Full Text Available Our present study continues to provide guidance and meaning for those who are open and have the courage to ask the kind of questions superior to reason. The acceptance of unreasonable realities expresses sometimes the portrait of a non-modern and superstitious man, a portrait dismantled by the contemporary science in order to get the assurance of control over the material and spiritual reality around us. However, the acceptance of unreasonable realities, born by the reason’s questions, expresses in other circumstances the access to super-reason and super-faith. The Light and the Grace from super-existence toward the human nature, and the implications these have, as a divine communication method and metaphors, and as a call to dialogic sharing with the Divine, are the objects of our present study. Super-reason and super-faith can and must characterize also the modern man. The Light and the Grace express both the cause and the means; God who is Light and Grace does communicate Himself in a salvific manner through Light and Grace, and we, as destinations of Light and of Grace can communicate ourselves as Light and Grace to our neighbors.

  5. Predicting Agricultural Drought using NOAH Land Surface Model, MODIS Evapotranspiration and GRACE Terrestrial Water Storage

    Science.gov (United States)

    wu, J.; Zhang, X.

    2013-12-01

    Drought is a major natural hazard in the world which costs 6-8 billion per year in the United States. Drought monitoring and prediction are difficult because it usually develops slowly and it is hard to be recognized until it becomes severe. The severity of agricultural drought was estimated by using Soil Moisture Deficit Index (SMDI) based on soil moisture simulated by Noah land surface model. Based on general water balance and delayed response of soil moisture to the forcing of climate variables, a Multiple Linear Regression (MLR) model for agricultural drought prediction was developed, the inputs of which included data at the previous one and two months of precipitation from Parameter-elevation Regressions on Independent Slopes Model (PRISM), evapotranspiration from MODIS MOD 16 product and terrestrial water storage (TWS) derived from Gravity Recovery and Climate Experiment (GRACE). The stability of the MLR model is tested using different training datasets from 2003 to 2009 with time spans of one year to six years and the results indicated that the model is stable, with very limited changes in estimated parameters between different datasets. A sensitivity analysis shows that evapotranspiration is the most significant variable affecting soil moisture change compared to precipitation and TWS. The predicted SMDI was compared with U.S. drought monitor products to evaluate its performance for the period of 2010-2012 when a severe drought occurred in the U.S. (Fig.1). The predicted SMDI successfully forecasted the severe drought in the southern U.S. in early 2012 and its expansion in the following summer. The MLR model has a high predictive skill with short-term forecast (1-2 months), while less accuracy is observed for the long-term forecast (3-6 months) (Fig.2).

  6. Assimilation of Terrestrial Water Storage from GRACE in a Snow-Dominated Basin

    Science.gov (United States)

    Forman, Barton A.; Reichle, R. H.; Rodell, M.

    2011-01-01

    Terrestrial water storage (TWS) information derived from Gravity Recovery and Climate Experiment (GRACE) measurements is assimilated into a land surface model over the Mackenzie River basin located in northwest Canada. Assimilation is conducted using an ensemble Kalman smoother (EnKS). Model estimates with and without assimilation are compared against independent observational data sets of snow water equivalent (SWE) and runoff. For SWE, modest improvements in mean difference (MD) and root mean squared difference (RMSD) are achieved as a result of the assimilation. No significant differences in temporal correlations of SWE resulted. Runoff statistics of MD remain relatively unchanged while RMSD statistics, in general, are improved in most of the sub-basins. Temporal correlations are degraded within the most upstream sub-basin, but are, in general, improved at the downstream locations, which are more representative of an integrated basin response. GRACE assimilation using an EnKS offers improvements in hydrologic state/flux estimation, though comparisons with observed runoff would be enhanced by the use of river routing and lake storage routines within the prognostic land surface model. Further, GRACE hydrology products would benefit from the inclusion of better constrained models of post-glacial rebound, which significantly affects GRACE estimates of interannual hydrologic variability in the Mackenzie River basin.

  7. Interannual mass variation over Chao Phraya river basin observed by GRACE

    Science.gov (United States)

    Yamamoto, Keiko; Fukuda, Yoichi; Nakaegawa, Toshiyuki; Hasegawa, Takashi; Taniguchi, Makoto

    2010-05-01

    A project to assess the effects of human activities on the subsurface environment in Asian developing cities has been in progress (Research Institute for Humanity and Nature, Japan, 2009). Bangkok, Thailand is one of the study cities in this project. Using GRACE satellite gravity data of 2002 to 2009, we recovered landwater mass variation over the Chao Phraya river basin, where Bangkok is located on the downstream. The result shows that a negative interannual mass trend was observed over the Chao Phraya river basin from 2002 to the beginning of 2005, and after that, no significant trend was observed up to 2009. Over Bangkok and the surrounding area, serious groundwater decrease has been reported because of the previous excessive pumping accompanying development of the city. One of our concerns is whether the GRACE-derived negative trend from 2002 to 2005 has some relationship with the previous groundwater pumping. Thus, we firstly compared the GRACE-derived mass variation with a groundwater storage variation calculated by a regional numerical groundwater model (Yamanaka, personal communication, 2009). The result shows that the model-estimated confined groundwater storage shows positive interannual trend over the GRACE mission time period, which is in contrast to GRACE-derived negative mass change. Further, the magnitude of the confined groundwater storage change is much smaller than that of the GRACE-derived mass change. Thus, it is expected that the negative mass trend was not caused by regional confined groundwater decrease. On the other hand, the terrestrial water storage variation derived from global scale hydrological model shows similar change with the GRACE-derived mass variation. Further, similar mass trend changes at the beginning of 2005 are observed not only over Chao Phraya basin, but over several other areas in the world, e.g. Africa, Antarctica etc. Thus, we supposed that the negative mass change over Chao Phraya basin does not mainly come from

  8. Setup assessment for assimilating GRACE observations into the Australian Water Resource Assessment (AWRA) model

    Science.gov (United States)

    Khaki, Mehdi; Hoteit, Ibrahim; Schumacher, Maike; Van Dijk, Albert; Kuhn, Michael; Awange, Joseph; Forootan, Ehsan

    2016-04-01

    Hydrological models have usually been used to simulate variations in water storage compartments resulting from changes in fluxes (i.e., precipitation, evapotranspiration) considering physical or conceptual frameworks. In an effort to improve the simulation of storage compartments, this research investigated the benefits of assimilating the Gravity Recovery and Climate Experiment (GRACE) derived terrestrial water storage (TWS) anomalies into the AWRA (Australian Water Resource Assessment) model using an ensemble Kalman filter (EnKF) approach in 2009. The Murray-Darling Basin (MDB), which is Australia's biggest river system, was selected to perform the assimilation. Our investigations address (i) the optimal implementation of the EnKF, including sensitivity to ensemble size, localization length scale, observational errors correlations, inflation and stochastic parameterization of forcing terms, and (ii) the best strategy for assimilating GRACE data, which are available at different spatial resolutions (few hundred kilometres). Our motivation to select EnKF was due to its promising performance in previous studies to deal with the nonlinearity and high-dimensionality of hydrological models. However, the small size of ensembles might represent a critical issue for its success, since the statistical state of the system might not be well represented. Therefore, in this study, we analysed the relation between ensemble size and the performance of assimilation process. Previous studies have demonstrated that GRACE can be used to enhance the performance of models. However, it is very difficult to deal with its relatively low spatial resolution. Furthermore, assimilation of GRACE TWS measurements at different spatial resolution may result in different degree of improvements. Therefore, attempts were made here to find an optimal assimilation resolution of GRACE TWS observations into AWRA over MDB. Eventually, a localization approach was applied to modify the error covariance

  9. Reconstructing annual groundwater storage changes in a large-scale irrigation region using GRACE data and Budyko model

    Science.gov (United States)

    Tang, Yin; Hooshyar, Milad; Zhu, Tingju; Ringler, Claudia; Sun, Alexander Y.; Long, Di; Wang, Dingbao

    2017-08-01

    A two-parameter annual water balance model was developed for reconstructing annual terrestrial water storage change (ΔTWS) and groundwater storage change (ΔGWS). The model was integrated with the Gravity Recovery and Climate Experiment (GRACE) data and applied to the Punjab province in Pakistan for reconstructing ΔTWS and ΔGWS during 1980-2015 based on multiple input data sources. Model parameters were estimated through minimizing the root-mean-square error between the Budyko-modeled and GRACE-derived ΔTWS during 2003-2015. The correlation of ensemble means between Budyko-modeled and GRACE-derived ΔTWS is 0.68 with p-value irrigation regions with parsimonious models.

  10. On the analysis of temporal geoid height variations obtained from GRACE-based GGMs over the area of Poland

    Science.gov (United States)

    Godah, Walyeldeen; Szelachowska, Malgorzata; Krynski, Jan

    2017-07-01

    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.

  11. Seasonal Mass Changes and Crustal Vertical Deformations Constrained by GPS and GRACE in Northeastern Tibet

    Directory of Open Access Journals (Sweden)

    Yuanjin Pan

    2016-08-01

    Full Text Available Surface vertical deformation includes the Earth’s elastic response to mass loading on or near the surface. Continuous Global Positioning System (CGPS stations record such deformations to estimate seasonal and secular mass changes. We used 41 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs, in northeastern Tibet. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution around northeastern Tibet. The GPS-derived result is then assessed in terms of the mass changes observed in northeastern Tibet. The GPS-derived common mode vertical change and the stacked Gravity Recovery and Climate Experiment (GRACE mass change are consistent, suggesting that the seasonal surface mass variation is caused by changes in the hydrological, atmospheric and non-tidal ocean loads. The annual peak-to-peak surface mass changes derived from GPS and GRACE results show seasonal oscillations in mass loads, and the corresponding amplitudes are between 3 and 35 mm/year. There is an apparent gradually increasing gravity between 0.1 and 0.9 μGal/year in northeast Tibet. Crustal vertical deformation is determined after eliminating the surface load effects from GRACE, without considering Glacial Isostatic Adjustment (GIA contribution. It reveals crustal uplift around northeastern Tibet from the corrected GPS vertical velocity. The unusual uplift of the Longmen Shan fault indicates tectonically sophisticated processes in northeastern Tibet.

  12. GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage

    Directory of Open Access Journals (Sweden)

    L. Longuevergne

    2012-10-01

    Full Text Available While GRACE (Gravity Recovery and Climate Experiment satellites are increasingly being used to monitor water storage changes globally, the impact of spatial distribution of water storage within a basin is generally ignored but may be substantial. In many basins, water may be stored in reservoirs, lakes, flooded areas, small aquifer systems, and other localized regions with sizes typically below GRACE resolution. The objective of this study was to assess the impact of non-uniform water storage distribution on GRACE estimates as basin-wide averages, focusing on surface water reservoirs. Analysis included numerical experiments testing the effect of mass size and position within a basin, and application to the Lower Nile (Lake Nasser and Tigri–Euphrates (TE basins as examples. Numerical experiments show that by assuming uniform mass distribution, GRACE estimates may under- or over-estimate basin-average water storage by up to a factor of two, depending on reservoir location and extent. Although their spatial extent may be unresolved by GRACE, reservoir storage may dominate in some basins. For example, it accounts for 95% of seasonal variations in the Lower Nile and 10% in the TE basins. Because reservoirs are used to mitigate droughts and buffer against climate extremes, their influence on interannual time scales can be large, for example accounting for 50% of total water storage decline during the 2007–2009 drought in the TE basin. Effects on GRACE estimates are not easily accounted for via simple multiplicative scaling, but in many cases independent information may be available to improve estimates. Accurate estimation of the reservoir contribution is critical, especially when separating groundwater from GRACE total water storage changes. Because the influence of spatially concentrated water storage – and more generally water distribution – is significant, GRACE estimates will be improved when it is possible to combine independent spatial

  13. On super edge-graceful trees of diameter four

    CERN Document Server

    Krop, E; Raridan, C

    2011-01-01

    In "On the super edge graceful trees of even orders," Chung, Lee, Gao, and Schaffer posed the following problem: Characterize trees of diameter 4 which are super edge-graceful. In this paper, we provide super edge-graceful labelings for all caterpillars and even size lobsters of diameter 4 which permit such labelings. We also provide super edge-graceful labelings for several families of odd size lobsters of diameter 4.

  14. Earth's surface fluid variations and deformations from GPS and GRACE in global warming

    CERN Document Server

    Jin, Shuanggen; Feng, Guiping

    2011-01-01

    Global warming is affecting our Earth's environment. For example, sea level is rising with thermal expansion of water and fresh water input from the melting of continental ice sheets due to human-induced global warming. However, observing and modeling Earth's surface change has larger uncertainties in the changing rate and the scale and distribution of impacts due to the lack of direct measurements. Nowadays, the Earth observation from space provides a unique opportunity to monitor surface mass transfer and deformations related to climate change, particularly the global positioning system (GPS) and the Gravity Recovery and Climate Experiment (GRACE) with capability of estimating global land and ocean water mass. In this paper, the Earth's surface fluid variations and deformations are derived and analyzed from global GPS and GRACE measurements. The fluids loading deformation and its interaction with Earth system, e.g., Earth Rotation, are further presented and discussed.

  15. Grace and Courtesy across the Planes of Development

    Science.gov (United States)

    Ludick, Pat

    2015-01-01

    Pat Ludick's commentary on grace and courtesy is established by a philosophical orientation to development: Grace is oriented to the life of the interior that is consciousness and being, and courtesy moves outward to daily living where civility reflects on success with human interactions. Pat's projected grace and courtesy across the planes is…

  16. 3D viscosity maps for Greenland and effect on GRACE mass balance estimates

    Science.gov (United States)

    van der Wal, Wouter; Xu, Zheng

    2016-04-01

    The GRACE satellite mission measures mass loss of the Greenland ice sheet. To correct for glacial isostatic adjustment numerical models are used. Although generally found to be a small signal, the full range of possible GIA models has not been explored yet. In particular, low viscosities due to a wet mantle and high temperatures due to the nearby Iceland hotspot could have a significant effect on GIA gravity rates. The goal of this study is to present a range of possible viscosity maps, and investigate the effect on GRACE mass balance estimates. Viscosity is derived using flow laws for olivine. Mantle temperature is computed from global seismology models, based on temperature derivatives for different mantle compositions. An indication for grain sizes is obtained by xenolith findings at a few locations. We also investigate the weakening effect of the presence of melt. To calculate gravity rates, we use a finite-element GIA model with the 3D viscosity maps and the ICE-5G loading history. GRACE mass balances for mascons in Greenland are derived with a least-squares inversion, using separate constraints for the inland and coastal areas in Greenland. Biases in the least-squares inversion are corrected using scale factors estimated from a simulation based on a surface mass balance model (Xu et al., submitted to The Cryosphere). Model results show enhanced gravity rates in the west and south of Greenland with 3D viscosity maps, compared to GIA models with 1D viscosity. The effect on regional mass balance is up to 5 Gt/year. Regional low viscosity can make present-day gravity rates sensitivity to ice thickness changes in the last decades. Therefore, an improved ice loading history for these time scales is needed.

  17. Comparison of Total Water Storage Anomalies from Global Hydrologic and Land Surface Models and New GRACE Satellite Solutions

    Science.gov (United States)

    Scanlon, B. R.; Zhang, Z.; Sun, A.; Save, H.; Mueller Schmied, H.; Wada, Y.; Doll, P. M.; Eisner, S.

    2016-12-01

    There is Increasing interest in global hydrology based on modeling and remote sensing, highlighting the need to compare output from modeling and remote sensing approaches. Here we evaluate simulated terrestrial Total Water Storage anomalies (TWSA) from global hydrologic models (GHMs: WGHM and PRC-GLOBWB) and global land surface models (LSMs, such as GLDAS NOAH, MOSAIC, VIC, and CLM) using newly released GRACE mascons solutions from the Univ. of Texas Center for Space Research. The comparisons are based on monthly TWS anomalies over 13 years (April 2002 - April 2015) for 176 basins globally. Performance metrics include scatter plots of simulated and GRACE observed TWSA by basin with median slopes for different models indicating bias, correlations (shape and timing of TWS time series), and variability ratio (standard deviation of model TWSA/std. dev. GRACE observed TWSA), with optimal values of 1 indicating perfect agreement. The GRACE data were also disaggregated into long-term trends and seasonal amplitudes. Modeled TWS anomalies are biased low by 20 - 30% relative to GRACE TWSA with similar bias levels for basins in different size classes but greater bias with increasing basin aridity. Discrepancies between models and GRACE TWSA are greatest for long-term trends in TWSA with 60 - 95% underestimation of GRACE TWSA by models. There is good agreement in seasonal amplitudes from models and GRACE ( 0.9 for models with little impact of basin size or climate for most models. These comparisons highlight reliable model performance in terms of seasonal amplitudes in TWSA and underestimation of long-term trends in TWSA and in arid basins.

  18. 78 FR 66617 - National Family Caregivers Month, 2013

    Science.gov (United States)

    2013-11-05

    ... their loved ones before themselves, we must offer our appreciation and flexibility, in our healthcare system, our workplaces, and our communities. This month, as we reflect on the generosity, grace, and...

  19. Development of an Atom Interferometer Gravity Gradiometer for Earth Sciences

    Science.gov (United States)

    Rakholia, A.; Sugarbaker, A.; Black, A.; Kasecivh, M.; Saif, B.; Luthcke, S.; Callahan, L.; Seery, B.; Feinberg, L.; Mather, J.; hide

    2017-01-01

    We report progress towards a prototype atom interferometer gravity gradiometer for Earth science studies from a satellite in low Earth orbit.The terrestrial prototype has a target sensitivity of 8 x 10(exp -2) E/Hz(sup 1/2) and consists of two atom sources running simultaneous interferometers with interrogation time T = 300 ms and 12 hk photon recoils, separated by a baseline of 2 m. By employing Raman side band cooling and magnetic lensing, we will generate atomic ensembles with N = 10(exp 6) atoms at a temperature of 3 nK. The sensitivity extrapolates to 7 x 10(exp -5) E/Hz(sup 1/2) in microgravity on board a satellite. Simulations derived from this sensitivity demonstrate a monthly time-variable gravity accuracy of 1 cm equivalent water height at 200 km resolution, yielding an improvement over GRACE by 1-2 orders of magnitude. A gravity gradiometer with this sensitivity would also benefit future planetary, lunar, and asteroidal missions.

  20. Southern Ocean variability derived from GRACE retrievals, model simulations and in-situ measurements

    Science.gov (United States)

    Böning, C.; Timmermann, R.; Macrander, A.; Schröter, J.; Boebel, O.

    2009-04-01

    The Gravity Recovery and Climate Experiment (GRACE) provides estimates of the Earth's static and time-variant gravity field. Solutions from various processing centres (GFZ, CSR, GRGS, JPL etc.) enable us to determine mass redistributions on the globe. Given that land signals are generally large compared to anomalies over the ocean, an assessment of the latter requires a particularly careful filtering of the data. We utilized the Finite Element Sea-Ice Ocean Model (FESOM) to develop a filtering algorithm which relies on the spatial coherency of ocean bottom pressure (OBP) anomalies. Taking large-scale circulation patterns into account, the new filter yields an improved representation of OBP (i.e. ocean mass) variability in the filtered GRACE data. In order to investigate the representation of Antarctic Circumpolar Current (ACC) variability in the pattern-filtered GRACE retrievals, an analysis of OBP anomalies in FESOM results and in-situ measurements has been performed. A bottom pressure recorder array in the ACC region south of Africa (36°S-58°S, 1°W-7°E) provides data from 2002-2008. Based on anomalies of OBP gradients between individual instruments, these in-situ measurements give an estimate of the overall transport variability as well as of the movement of ACC fronts and transport redistribution between different sectors of the ACC. The validation of simulated and satellite-derived OBP anomaly gradients against these data yields a measure for the representation of this variability in FESOM and GRACE. Furthermore, model simulations are used to assess the relation between transport variations in individual filaments of the Southern Ocean and total transport variability in this and other sectors of the ACC.

  1. Long-term trends of terrestrial water storage in south-east Australia revealed by GRACE and superconducting gravimeter

    Science.gov (United States)

    Hasegawa, Takashi; Fukuda, Yoichi; Yamamoto, Keiko; Nakaegawa, Toshiyuki; Tamura, Yoshiaki; McQueen, Herbert

    2010-05-01

    South-east Australia is experiencing a severe multi-year drought in this decade. In particular, historic drought struck this area in 2006. Australian Bureau of Meteorology reported that the year 2006 was one of the driest years and agriculture suffered extensive damage from the drought. To understand the severity of current water crisis in south-east Australia, monitoring terrestrial water storage (TWS) changes is demanded. For this purpose, we investigated gravity changes associated with the drought in south-east Australia using data from GRACE satellite gravimeter and superconducting gravimeter (SG) at Mt. Stromlo, Canberra, over the period from 2003 to 2008. In 2006 and 2007, GRACE gravity solutions released from CNES/GRGS showed significant TWS decreases at south-east Australia. Areal extent of the TWS decreases showed good consistence with that of rainfall deficiencies. Therefore, it is clear that the TWS decreases estimated from GRACE data are attributed to the 2006 drought. SG data from Canberra also indicated gravity decreases during the 2006 drought period, after correcting for effects of atmosphere, tides, height variations and instrumental drift and steps. Comparison of GRACE and SG data showed good agreements in interannual variations, although some differences were found in seasonal components. Furthermore, both GRACE and SG data indicated that TWS in 2008 still remained at low levels, although annual precipitation returned to average before the drought. It implies TWS is possibly decreasing with longer time scale due to recent climate changes. Finally, the results from GRACE and SG observations were compared with TWS estimates from Noah land surface model, forced by output from the Global Land Data Assimilation System (GLDAS) developed by NASA. The model TWS estimates were the sum of soil moisture (2m column depth) and snow water equivalent. The comparison showed that the model underestimated the TWS decreases due to the 2006 drought. The differences

  2. Antarctic ice-mass balance 2003 to 2012: regional reanalysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment based on GPS uplift rates

    NARCIS (Netherlands)

    Sasgen, I.; Konrad, H.; Ivins, E.R.; van den Broeke, M.R.|info:eu-repo/dai/nl/073765643; Bamber, J.L.; Martinec, Z.; Klemann, V.

    2013-01-01

    We present regional-scale mass balances for 25 drainage basins of the Antarctic Ice Sheet (AIS) from satellite observations of the Gravity and Climate Experiment (GRACE) for time period January 2003 to September 2012. Satellite gravimetry estimates of the AIS mass balance are strongly influenced by

  3. Antarctic ice-mass balance 2003 to 2012: regional reanalysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment based on GPS uplift rates

    NARCIS (Netherlands)

    Sasgen, I.; Konrad, H.; Ivins, E.R.; van den Broeke, M.R.; Bamber, J.L.; Martinec, Z.; Klemann, V.

    2013-01-01

    We present regional-scale mass balances for 25 drainage basins of the Antarctic Ice Sheet (AIS) from satellite observations of the Gravity and Climate Experiment (GRACE) for time period January 2003 to September 2012. Satellite gravimetry estimates of the AIS mass balance are strongly influenced by

  4. GRACE water storage estimates for the Middle East and other regions with significant reservoir and lake storage

    Science.gov (United States)

    Longuevergne, L.; Wilson, C. R.; Scanlon, B. R.; Crétaux, J. F.

    2013-12-01

    While GRACE (Gravity Recovery and Climate Experiment) satellites are increasingly being used to monitor total water storage (TWS) changes globally, the impact of spatial distribution of water storage within a basin is generally ignored but may be substantial. In many basins, water is often stored in reservoirs or lakes, flooded areas, small aquifer systems, and other localized regions with areas typically below GRACE resolution (~200 000 km2). The objective of this study was to assess the impact of nonuniform water storage distribution on GRACE estimates of TWS changes as basin-wide averages, focusing on surface water reservoirs and using a priori information on reservoir storage from radar altimetry. Analysis included numerical experiments testing effects of location and areal extent of the localized mass (reservoirs) within a basin on basin-wide average water storage changes, and application to the lower Nile (Lake Nasser) and Tigris-Euphrates basins as examples. Numerical experiments show that by assuming uniform mass distribution, GRACE estimates may under- or overestimate basin-wide average water storage by up to a factor of ~2, depending on reservoir location and areal extent. Although reservoirs generally cover less than 1% of the basin area, and their spatial extent may be unresolved by GRACE, reservoir storage may dominate water storage changes in some basins. For example, reservoir storage accounts for ~95% of seasonal water storage changes in the lower Nile and 10% in the Tigris-Euphrates. Because reservoirs are used to mitigate droughts and buffer against climate extremes, their influence on interannual timescales can be large. For example, TWS decline during the 2007-2009 drought in the Tigris-Euphrates basin measured by GRACE was ~93 km3. Actual reservoir storage from satellite altimetry was limited to 27 km3, but their apparent impact on GRACE reached 45 km3, i.e., 50% of GRACE trend. Therefore, the actual impact of reservoirs would have been greatly

  5. RELATIONS BETWEEN GRACE-DERIVED WATER STORAGE CHANGE WITH PRECIPITATION AND TEMPERATURE OVER KAIDU RIVER BASIN, CHINA

    Directory of Open Access Journals (Sweden)

    J. Huang

    2016-06-01

    Full Text Available Water is essential for human survival and well-being, and important to virtually all sectors of the economy. In the aridzone of China’s west, water resource is the controlling factor on the distribution of human settlements. Water cycle variation is sensitive to temperature and precipitation, which are influenced by human activity and climate change. Satellite observations of Earth’s time-variable gravity field from the Gravity Recovery and Climate Experiment (GRACE mission, which enable direct measurement of changes of total terrestrial water storage, could be useful to aid this modelling. In this pilot study, TWS change from 2002 to 2013 obtained from GRACE satellite mission over the Kaidu River Basin in Xinjiang, China is presented. Precipitation and temperature data from in-situ station and National Satellite Meteorological Centre of China (NSMC are analysed to examine whether there is a statistically significant correlation between them.

  6. Rockot Launch Vehicle Commercial Operations for Grace and Iridium Program

    Science.gov (United States)

    Viertel, Y.; Kinnersley, M.; Schumacher, I.

    2002-01-01

    The GRACE mission and the IRIDIUM mission on ROCKOT launch vehicle are presented. Two identical GRACE satellites to measure in tandem the gravitational field of the earth with previously unattainable accuracy - it's called the Gravity Research and Climate Experiment, or and is a joint project of the U.S. space agency, NASA and the German Centre for Aeronautics and Space Flight, DLR. In order to send the GRACE twins into a 500x500 km , 89deg. orbit, the Rockot launch vehicle was selected. A dual launch of two Iridium satellites was scheduled for June 2002 using the ROCKOT launch vehicle from Plesetsk Cosmodrome in Northern Russia. This launch will inject two replacement satellites into a low earth orbit (LEO) to support the maintenance of the Iridium constellation. In September 2001, Eurockot successfully carried out a "Pathfinder Campaign" to simulate the entire Iridium mission cycle at Plesetsk. The campaign comprised the transport of simulators and related equipment to the Russian port-of-entry and launch site and also included the integration and encapsulation of the simulators with the actual Rockot launch vehicle at Eurockot's dedicated launch facilities at Plesetsk Cosmodrome. The pathfinder campaign lasted four weeks and was carried out by a joint team that also included Khrunichev, Russian Space Forces and Eurockot personnel on the contractors' side. The pathfinder mission confirmed the capability of Eurockot Launch Services to perform the Iridium launch on cost and on schedule at Plesetsk following Eurockot's major investment in international standard preparation, integration and launch facilities including customer facilities and a new hotel. In 2003, Eurockot will also launch the Japanese SERVI'S-1 satellite for USEF. The ROCKOT launch vehicle is a 3 stage liquid fuel rocket whose first 2 stages have been adapted from the Russian SS-19. A third stage, called "Breeze", can be repeatedly ignited and is extraordinarily capable of manoeuvre. Rockot can place

  7. Towards Improved Snow Water Equivalent Estimation via GRACE Assimilation

    Science.gov (United States)

    Forman, Bart; Reichle, Rofl; Rodell, Matt

    2011-01-01

    Passive microwave (e.g. AMSR-E) and visible spectrum (e.g. MODIS) measurements of snow states have been used in conjunction with land surface models to better characterize snow pack states, most notably snow water equivalent (SWE). However, both types of measurements have limitations. AMSR-E, for example, suffers a loss of information in deep/wet snow packs. Similarly, MODIS suffers a loss of temporal correlation information beyond the initial accumulation and final ablation phases of the snow season. Gravimetric measurements, on the other hand, do not suffer from these limitations. In this study, gravimetric measurements from the Gravity Recovery and Climate Experiment (GRACE) mission are used in a land surface model data assimilation (DA) framework to better characterize SWE in the Mackenzie River basin located in northern Canada. Comparisons are made against independent, ground-based SWE observations, state-of-the-art modeled SWE estimates, and independent, ground-based river discharge observations. Preliminary results suggest improved SWE estimates, including improved timing of the subsequent ablation and runoff of the snow pack. Additionally, use of the DA procedure can add vertical and horizontal resolution to the coarse-scale GRACE measurements as well as effectively downscale the measurements in time. Such findings offer the potential for better understanding of the hydrologic cycle in snow-dominated basins located in remote regions of the globe where ground-based observation collection if difficult, if not impossible. This information could ultimately lead to improved freshwater resource management in communities dependent on snow melt as well as a reduction in the uncertainty of river discharge into the Arctic Ocean.

  8. The absolute gravity measurement by FG5 gravimeter at Great Wall Station, Antarctica

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Gravity measurement is of great importance to the height datum in Antarctica.The absolute gravity measurement was carried out at Great Wall Station, Antarctica, using FG5 absolute gravity instrument.The gravity data was processed with corrections of earth tide, ocean tide, polar motion and the atmospher, and the RMS is within +3 x 10 -s ms-2.The vertical and horizontal gravity gradients were measured using 2 LaCoaste & Romberg (LCR) gravimeters.The absolute gravity measurement provides the fundamental data for the validation and calibration of the satellite gravity projects such as CHAMP, GRACE and GOCE, and for the high accuracy geoid model.

  9. Through the Looking Glass with Grace Hopper.

    Science.gov (United States)

    Blair, Marjorie

    1984-01-01

    Briefly reviews the development of computers in the United States through the eyes of Commodore Grace M. Hopper, USNR, who was one of the first programmers and, at the age of 76, is still lecturing on computers to audiences ranging from military personnel to educators to engineers and computer scientists. (MBR)

  10. Informing Hydrological Drought Response in Headwater Catchments Using Water Storage Estimated From GRACE: Storage-Flow Dynamics

    Science.gov (United States)

    Gaffney, R.; Tyler, S. W.; Harpold, A. A.; Volk, J. M.

    2015-12-01

    Quantifying the relationship between subsurface water storage and streamflow is challenging due to heterogeneity of surface-groundwater interactions in space and time. Hence, point measurements of storage from wells are insufficient to characterize the storage across a catchment, especially in mountainous environments with complex geology. Here, we present a novel approach to quantify the storage-flow relationship for catchments in the Sierra Nevada Mountains. For 23 gages in the Hydro-Climatic Data Network, the 7-day average annual minimum flow (drought flow) was computed for years 2003 to 2015. We then aggregated, for each gage, the associated storage time-series dataset from 1o gridded measurements of monthly Terrestrial Water Storage (TWS) derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission. Despite the significant mismatch between the spatial scales and temporal resolution, we found a strong empirical correlation between TWS and drought flow. From these relationships, we examined how physical characteristics of each catchment (such as size and geology) impact the observed nonlinear relationship between TWS and drought flow. Furthermore, we show how physical characteristics, such as geology/storage capacity, of catchments affect the sensitivity of decreasing flows to multi-year droughts. This research has the potential to help better quantify the streamflow-storage relationship in small mountainous catchments, as well as, classify catchments that may be more vulnerable to decreasing flows with multi-year droughts.

  11. Along-Track Geopotential Difference and Deflection of the Vertical from GRACE Range Rate: Use of GEOGRACE

    Directory of Open Access Journals (Sweden)

    GRACE

    2016-02-01

    Full Text Available We present a theory and numerical algorithm to directly determine the time-varying along-track geopotential difference and deflection of the vertical at the Gravity Recovery and Climate Experiment (GRACE satellite altitude. The determination was implemented using the GEOGRACE computer program using the K-band range rate (KBRR of GRACE from the Level-1B (L1B product. The method treated KBRR, GPS-derived orbit of GRACE and an initial geopotential difference as measurements used in the least-squares estimation of the geopotential difference and its formal error constrained by the energy conservation principle. The computational procedure consisted of three steps: data reading and interpolation, data calibration and estimations of the geopotential difference and its error. The formal error allowed removal of KBRR outliers that contaminated the gravity solutions. We used the most recent models to account for the gravity changes from multiple sources. A case study was carried out over India to estimate surface mass anomalies from GEOGRACE-derived geopotential differences. The 10-day mass changes were consistent with those from the MASCON solutions of NASA (correlation coefficient up to 0.88. Using the geopotential difference at satellite altitude avoids the errors caused by downward continuation, enabling the detection of small-scale mass changes.

  12. Squeezing more information out of time variable gravity data with a temporal decomposition approach

    DEFF Research Database (Denmark)

    Barletta, Valentina Roberta; Bordoni, A.; Aoudia, A.

    2012-01-01

    A measure of the Earth's gravity contains contributions from solid Earth as well as climate-related phenomena, that cannot be easily distinguished both in time and space. After more than 7years, the GRACE gravity data available now support more elaborate analysis on the time series. We propose an...

  13. Use of GRACE Terrestrial Water Storage Retrievals to Evaluate Model Estimates by the Australian Water Resources Assessment System

    Science.gov (United States)

    van Dijk, A. I. J. M.; Renzullo, L. J.; Rodell, M.

    2011-01-01

    Terrestrial water storage (TWS) estimates retrievals from the Gravity Recovery and Climate Experiment (GRACE) satellite mission were compared to TWS modeled by the Australian Water Resources Assessment (AWRA) system. The aim was to test whether differences could be attributed and used to identify model deficiencies. Data for 2003 2010 were decomposed into the seasonal cycle, linear trends and the remaining de-trended anomalies before comparing. AWRA tended to have smaller seasonal amplitude than GRACE. GRACE showed a strong (greater than 15 millimeter per year) drying trend in northwest Australia that was associated with a preceding period of unusually wet conditions, whereas weaker drying trends in the southern Murray Basin and southwest Western Australia were associated with relatively dry conditions. AWRA estimated trends were less negative for these regions, while a more positive trend was estimated for areas affected by cyclone Charlotte in 2009. For 2003-2009, a decrease of 7-8 millimeter per year (50-60 cubic kilometers per year) was estimated from GRACE, enough to explain 6-7% of the contemporary rate of global sea level rise. This trend was not reproduced by the model. Agreement between model and data suggested that the GRACE retrieval error estimates are biased high. A scaling coefficient applied to GRACE TWS to reduce the effect of signal leakage appeared to degrade quantitative agreement for some regions. Model aspects identified for improvement included a need for better estimation of rainfall in northwest Australia, and more sophisticated treatment of diffuse groundwater discharge processes and surface-groundwater connectivity for some regions.

  14. Improved GRACE regional mass balance estimates of the Greenland ice sheet cross-validated with the input-output method

    Science.gov (United States)

    Xu, Zheng; Schrama, Ernst J. O.; van der Wal, Wouter; van den Broeke, Michiel; Enderlin, Ellyn M.

    2016-04-01

    In this study, we use satellite gravimetry data from the Gravity Recovery and Climate Experiment (GRACE) to estimate regional mass change of the Greenland ice sheet (GrIS) and neighboring glaciated regions using a least squares inversion approach. We also consider results from the input-output method (IOM). The IOM quantifies the difference between the mass input and output of the GrIS by studying the surface mass balance (SMB) and the ice discharge (D). We use the Regional Atmospheric Climate Model version 2.3 (RACMO2.3) to model the SMB and derive the ice discharge from 12 years of high-precision ice velocity and thickness surveys. We use a simulation model to quantify and correct for GRACE approximation errors in mass change between different subregions of the GrIS, and investigate the reliability of pre-1990s ice discharge estimates, which are based on the modeled runoff. We find that the difference between the IOM and our improved GRACE mass change estimates is reduced in terms of the long-term mass change when using a reference discharge derived from runoff estimates in several subareas. In most regions our GRACE and IOM solutions are consistent with other studies, but differences remain in the northwestern GrIS. We validate the GRACE mass balance in that region by considering several different GIA models and mass change estimates derived from data obtained by the Ice, Cloud and land Elevation Satellite (ICESat). We conclude that the approximated mass balance between GRACE and IOM is consistent in most GrIS regions. The difference in the northwest is likely due to underestimated uncertainties in the IOM solutions.

  15. Study of landwater variation over Chao Phraya river basin using GRACE, satellite altimetry and in situ data

    Science.gov (United States)

    Yamamoto, K.; Fukuda, Y.; Nakaegawa, T.; Taniguchi, M.

    2009-12-01

    A project to assess the effects of human activities on the subsurface environment in Asian developing cities has been in progress (Research Institute for Humanity and Nature, Japan, 2009). Bangkok, Thailand is one of the study cities in this project. Using GRACE satellite gravity data, we previously recovered landwater mass variation over the Chao Phraya river basin, where Bangkok is located on downstream. However, mainly because of insufficient spatial resolution of the GRACE data then released, it was difficult to distinguish mass variation over the Chao Phraya basin with the ones of the neighboring Mekong, Irrawaddy and Salween river basins. Recently, some new versions of GRACE data sets have been available, and thus we estimated again the mass variations over these basins using version 2 of CNS/GRGS data set. The result shows that mass variations of the each basin could be distinguished due to improvement of the spatial resolution of the data. One of the interesting things is that a negative interannual mass trend is observed only over the Chao Phraya river basin, while the other basins show positive trend values. One of our concerns was which of the landwater components were decreasing. Because GRACE can only detect total terrestrial water storage, we further used satellite altimeter data to separate surface- and groundwater components. EnviSat data were mainly used as satellite altimetry data in this study, because the mission period is overlapping with GRACE mission and the ground track separation is relatively small. River water levels were recovered from satellite altimetry data, and converted to river water storage. Estimated river water storage was subtracted from the GRACE data. Thus, interannual surface- and groundwater trends were discussed separately. Another concern is whether the landwater decrease is caused by meteorological factors or factors of human activities. Thus, we also compared above results with global hydrological simulation model and

  16. GRACE-based estimates of water discharge over the Yellow River basin

    Institute of Scientific and Technical Information of China (English)

    Qiong Li; BO Zhong; Zhicai Luo; Chaolong Yao

    2016-01-01

    As critical component of hydrologic cycle,basin discharge is a key issue for understanding the hydrological and climatologic related to water and energy cycles.Combining GRACE gravity field models with ET from GLDAS models and precipitation from GPCP,discharge of the Yellow River basin are estimated from the water balance equation.While comparing the results with discharge from GLDAS model and in situ measurements,the results reveal that discharge from Mosaic and CLM GLDAS model can partially represent the river discharge and the discharge estimation from water balance equation could reflect the discharge from precipitation over the Yellow River basin.

  17. Have GRACE satellites overestimated groundwater depletion in the Northwest India Aquifer?

    Science.gov (United States)

    Long, Di; Chen, Xi; Scanlon, Bridget R.; Wada, Yoshihide; Hong, Yang; Singh, Vijay P.; Chen, Yaning; Wang, Cunguang; Han, Zhongying; Yang, Wenting

    2016-04-01

    The Northwest India Aquifer (NWIA) has been shown to have the highest groundwater depletion (GWD) rate globally, threatening crop production and sustainability of groundwater resources. Gravity Recovery and Climate Experiment (GRACE) satellites have been emerging as a powerful tool to evaluate GWD with ancillary data. Accurate GWD estimation is, however, challenging because of uncertainties in GRACE data processing. We evaluated GWD rates over the NWIA using a variety of approaches, including newly developed constrained forward modeling resulting in a GWD rate of 3.1 ± 0.1 cm/a (or 14 ± 0.4 km3/a) for Jan 2005-Dec 2010, consistent with the GWD rate (2.8 cm/a or 12.3 km3/a) from groundwater-level monitoring data. Published studies (e.g., 4 ± 1 cm/a or 18 ± 4.4 km3/a) may overestimate GWD over this region. This study highlights uncertainties in GWD estimates and the importance of incorporating a priori information to refine spatial patterns of GRACE signals that could be more useful in groundwater resource management and need to be paid more attention in future studies.

  18. GRACE Mission Design: Impact of Uncertainties in Disturbance Environment and Satellite Force Models

    Science.gov (United States)

    Mazanek, Daniel D.; Kumar, Renjith R.; Seywald, Hans; Qu, Min

    2000-01-01

    The Gravity Recovery and Climate Experiment (GRACE) primary mission will be performed by making measurements of the inter-satellite range change between two co-planar, low altitude, near-polar orbiting satellites. Understanding the uncertainties in the disturbance environment, particularly the aerodynamic drag and torques, is critical in several mission areas. These include an accurate estimate of the spacecraft orbital lifetime, evaluation of spacecraft attitude control requirements, and estimation of the orbital maintenance maneuver frequency necessitated by differences in the drag forces acting on both satellites. The FREEMOL simulation software has been developed and utilized to analyze and suggest design modifications to the GRACE spacecraft. Aerodynamic accommodation bounding analyses were performed and worst-case envelopes were obtained for the aerodynamic torques and the differential ballistic coefficients between the leading and trailing GRACE spacecraft. These analyses demonstrate how spacecraft aerodynamic design and analysis can benefit from a better understanding of spacecraft surface accommodation properties, and the implications for mission design constraints such as formation spacing control.

  19. GRACE leakage error correction with regularization technique: Case studies in Greenland and Antarctica

    Science.gov (United States)

    Mu, Dapeng; Yan, Haoming; Feng, Wei; Peng, Peng

    2017-01-01

    Filtering is a necessary step in the Gravity Recovery and Climate Experiment (GRACE) data processing, but leads to signal leakage and attenuation obviously, and adversely affects the quality of global and regional mass change estimates. We propose to use the Tikhonov regularization technique with the L-curve method to solve a correction equation which can reduce the leakage error caused by filter involved in GRACE data processing. We first demonstrate that the leakage error caused by the Gaussian filter can be well corrected by our regularization technique with simulation studies in Greenland and Antarctica. Furthermore, our regularization technique can restore the spatial distribution of original mass changes. For example, after applying the regularization method to GRAEC data (2003-2012), we find that GRACE mass changes tend to move from interior to coastal area in Greenland, which are consistent with recent other studies. After being corrected for glacial isostatic adjustment (GIA) effect, our results show that the ice mass loss rates were 274 ± 30 and 107 ± 34 Gt/yr in Greenland and Antarctica from 2003 to 2012, respectively. And a 10 ± 4 Gt/yr increase rate in Greenland interior is also detected.

  20. GRACE反演南极冰盖质量变化的高斯与Wiener滤波比较%Comparison of Gaussian and Wiener filter by investigation on mass rates of ice sheet in Antarctic from GRACE

    Institute of Scientific and Technical Information of China (English)

    李军海; 文汉江; 刘焕玲; 朱广彬

    2012-01-01

    本文利用UTCSR 2003年1月到2008年8月间的GRACE Level-2 RL04重力场模型估计了南极冰盖质量变化.计算过程中分别采用高斯和Wiener滤波两种平滑方法,分别采用22、43和65个月重力场模型计算Wiener滤波信号与噪声函数,得出以下结论:在实际的计算过程中需要具体计算Wiener滤波平滑因子值,65个月GRACE重力场模型计算得到的Wiener滤波权值非常接近于平滑半径为540km高斯滤波权值;采用两种不同的滤波方法在相同区域质量变化率基本相同.%Gravity solutions from GRACE level-2 RL04 released by UTCSR for the period January 2003 to August 2008 were used to estimate the rates of Antarctic ice mass change. The Gaussian and Wiener filtering smoothing method were used respectively during the process. The signal and noise function of Wiener filtering were calculated respectively by 22, 43 and 65 months time gravity model, and the result was that the model signal and noise functions relate to the selected time period. Therefore smoothing factor values of Wiener filter need to be calculated during the process. The weights of Gaussian filter and Wiener filter computed by 65 GRACE gravity solutions were computed and it was very close to the Gaussian smoothing radius of 540km. The ice mass rates in the west Antartic Amundsen and the east Antartic Enderby land were computed and the mass rates at the same area were almost the same using the two different filtering methods.

  1. Time-variable gravity fields from satellite tracking

    Science.gov (United States)

    Bettadpur, Srinivas; Cheng, Minkang; Ries, John

    2014-05-01

    At the University of Texas Center for Space Research (CSR), we routinely deliver time-series of Earth's gravity field variations, some of it spanning more than two decades. These time-series are derived - in a consistent manner - from satellite laser ranging (SLR) data, from low-Earth orbiters tracked using GPS, and from low-low satellite to satellite tracking data from GRACE. In this paper, we review the information content in the gravity field time-series derived from each of these methods. We provide a comparison of the time-series at the decadal and annual time-scales, and identify the spatial modes of variability that are well or poorly estimated by each of the observing systems. The results have important bearing on the prospects of extending GRACE time-variable gravity time-series in the event of gaps between dedicated gravity missions, and for extending the time-series into the past. Support for this research from joint NASA/DLR GRACE mission, the NASA MEASURs program, and the NASA ROSES/GRACE Science Team is gratefully acknowledged.

  2. Greenland Ice Sheet seasonal and spatial mass variability from model simulations and GRACE (2003-2012)

    Science.gov (United States)

    Alexander, Patrick M.; Tedesco, Marco; Schlegel, Nicole-Jeanne; Luthcke, Scott B.; Fettweis, Xavier; Larour, Eric

    2016-06-01

    Improving the ability of regional climate models (RCMs) and ice sheet models (ISMs) to simulate spatiotemporal variations in the mass of the Greenland Ice Sheet (GrIS) is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS mass loss, studies focusing on mass variations at sub-annual and sub-basin-wide scales are still lacking. At these scales, processes responsible for mass change are less well understood and modeled, and could potentially play an important role in future GrIS mass change. Here, we examine spatiotemporal variations in mass over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE) satellites for the January 2003-December 2012 period using a "mascon" approach, with a nominal spatial resolution of 100 km, and a temporal resolution of 10 days. We compare GRACE-estimated mass variations against those simulated by the Modèle Atmosphérique Régionale (MAR) RCM and the Ice Sheet System Model (ISSM). In order to properly compare spatial and temporal variations in GrIS mass from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of mass inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of -178.9 ± 4.4 and -239.4 ± 7.7 Gt yr-1 respectively) in GrIS mass over the period examined, but the models appear to underestimate the rate of mass loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS mass loss is occurring. On an ice-sheet-wide scale, the timing of the modeled seasonal cycle of cumulative mass (driven by summer mass loss) agrees with the GRACE-derived seasonal cycle, within limits of uncertainty from the GRACE solution. However, on sub-ice-sheet-wide scales, some areas exhibit significant differences in the timing of peaks in the annual cycle of mass change. At these scales, model biases, or processes not accounted for by models related

  3. Greenland Ice Sheet seasonal and spatial mass variability from model simulations and GRACE (2003–2012

    Directory of Open Access Journals (Sweden)

    P. M. Alexander

    2015-11-01

    Full Text Available Improving the ability of regional climate models (RCMs and ice sheet models (ISMs to simulate spatiotemporal variations in the mass of the Greenland Ice Sheet (GrIS is crucial for prediction of future sea level rise. While several studies have examined recent trends in GrIS mass loss, studies focusing on mass variations at sub-annual and sub-basin-wide scales are still lacking. Here, we examine spatiotemporal variations in mass over the GrIS derived from the Gravity Recovery and Climate Experiment (GRACE satellites for the 2003–2012 period using a "mascon" approach, with a nominal spatial resolution of 100 km, and a temporal resolution of 10 days. We compare GRACE-estimated mass variations against those simulated by the Modèle Atmosphérique Régionale (MAR RCM and the Ice Sheet System Model (ISSM. In order to properly compare spatial and temporal variations in GrIS mass from GRACE with model outputs, we find it necessary to spatially and temporally filter model results to reproduce leakage of mass inherent in the GRACE solution. Both modeled and satellite-derived results point to a decline (of −179 and −240 Gt yr−1 respectively in GrIS mass over the period examined, but the models appear to underestimate the rate of mass loss, especially in areas below 2000 m in elevation, where the majority of recent GrIS mass loss is occurring. On an ice-sheet wide scale, the timing of the modeled seasonal cycle of cumulative mass (driven by summer mass loss agrees with the GRACE-derived seasonal cycle, within limits of uncertainty from the GRACE solution. However, on sub-ice-sheet-wide scales, there are significant differences in the timing of peaks in the annual cycle of mass change. At these scales, model biases, or unaccounted-for processes related to ice dynamics or hydrology may lead to the observed differences. This highlights the need for further evaluation of modelled processes at regional and seasonal scales, and further study of ice sheet

  4. Investigating the Origin of Natural and Anthropogenic Deformation across the Nile Delta Using Radar Interferometry, GRACE, Modeling, and Field data

    Science.gov (United States)

    Gebremichael, E.; Sultan, M.; Becker, R.; El Bastawesy, M.; Cherif, O.; Emil, M.; Ahmed, M.; Fathy, K.; Karki, S.; Chouinard, K.

    2016-12-01

    We applied an integrated approach (radar interferometry, flood simulation, GRACE, GIS) to investigate the nature and distribution of land deformation in the Nile Delta and to identify the natural and anthropogenic controlling factors. Our methodology involved: (1) applying persistent scatterer interferometry (PSI) across the entire Delta (scenes: 108 level 0 scenes; Tracks: 4 tracks; time period: 2003-2010); (2) correcting the interferometry output for various phase contributing errors (e.g., atmosphere, orbit, etc.) and calibrating/validating the output against 3 GNSS GPS stations (2 in Alexandria, 1 in Helwan); (3) conducting spatial correlation (in a GIS environment) of the radar outputs with relevant remote sensing, subsurface, and geologic datasets; (4) simulating flood depth and inundation to investigate the spatial extent and depth of the Holocene sediments using the HEC-RAS software (inputs: DEM and monthly discharge data; period: 1871-1902), (5) identifying subsurface structures by processing 712 gridded field gravity data points in Geosoft Oasis Montaj software (Bouguer anomaly analysis), and (6) analyzing monthly (2002-2015) GRACE-derived TWS solutions (0.5° x 0.5° CSR mascons). Our findings include: (1) three main structural trends (E-W, NW-SE and NE-SW trending) were mapped across the Delta, (2) areas of high subsidence coincide with the distribution of relatively thick recent sediments (<3000 years), probably due to sediment compaction, in three settings: (a) areas susceptible to flooding from the Damietta and Rosetta branches (e.g., east Damietta branch; latitude 30.8° to 31.2°; longitude 31.2° to 31.6°), (b) areas susceptible to sediment deposition at bifurcation locations of primary channels (e.g., near Cairo) and, (c) areas where mapped faults intersect Damietta and Rosetta channels, change their course, and cause ponding of surface water and sediment deposition, (3) extraction of gas from the Abu Madi gas field in north central delta

  5. Landsat and GRACE observations of arid wetland dynamics in a dryland river system under multi-decadal hydroclimatic extremes

    Science.gov (United States)

    Xie, Zunyi; Huete, Alfredo; Ma, Xuanlong; Restrepo-Coupe, Natalia; Devadas, Rakhesh; Clarke, Kenneth; Lewis, Megan

    2016-12-01

    Arid wetlands are important for biodiversity conservation, but sensitive and vulnerable to climate variability and hydroclimatic events. Amplification of the water cycle, including the increasing frequency and severity of droughts and wet extremes, is expected to alter spatial and temporal hydrological patterns in arid wetlands globally, with potential threats to ecosystem services and their functioning. Despite these pressing challenges, the ecohydrological interactions and resilience of arid wetlands to highly variable water regimes over long time periods remain largely unknown. Recent broad-scale drought and floods over Australia provide unique opportunities to improve our understanding of arid wetland ecosystem responses to hydroclimatic extremes. Here we analysed the ecohydrological dynamics of the Coongie Lakes arid wetland in central Australia, one of the world's largest Ramsar-designated wetlands, using more than two decades (1988-2011) of vegetation and floodwater extent retrievals derived from Landsat satellite observations. To explore the impacts of large-scale hydrological fluctuations on the arid wetland, we further coupled Landsat measurements with Total Water Storage Anomaly (TWSA) data obtained from the Gravity Recovery and Climate Experiment (GRACE) satellites. Pronounced seasonal and inter-annual variabilities of flood and vegetation activities were observed over the wetland, with variations in vegetation growth extent highly correlated with flood extent (r = 0.64, p < 0.05) that ranged from nearly zero to 3456 km2. We reported the hydrological dynamics and associated ecosystem responses to be largely driven by the two phases (El Niño and La Niña) of the El Nino-Southern Oscillation (ENSO) ocean-atmosphere system. Changes in flood and vegetation extent were better explained by GRACE-TWSA (r = 0.8, lag = 0 month) than rainfall (r = 0.34, lag = 3 months) over the water source area, demonstrating that TWS is a valuable hydrological indicator for

  6. An interpretation of the interannual mass trend change over the Indochina Peninsula observed by GRACE data

    Science.gov (United States)

    Yamamoto, K.; Fukuda, Y.; Nakaegawa, T.; Hasegawa, T.; Taniguchi, M.

    2010-12-01

    In Research Institute for Humanity and Nature, a project “Human Impacts on Urban Subsurface Environments” to assess impacts of human activities on urban subsurface environment in several Asian developing cities is now in progress. Although one of the main purposes of the project is to investigate local groundwater systems on and around the urban cities, the project also aims to understand large-scale landwater movements including the areas, and Gravity Recovery and Climate Experiment (GRACE) satellite gravity data is used for the purpose. In the previous study (Yamamoto et al., 2010), we recovered the regional-scale interannual landwater mass variation over the Indochina Peninsula, which includes one of the test cities in the project, i.e. Bangkok, Thailand, by using GRACE data. The recovered mass variation showed the change of the interannual trend at around the beginning of 2005: it decreased up to the beginning of 2005, and after that, increased up to 2009. The compared results with observed/modeled hydrological and meteorological data sets showed that the observed trend change did not caused by regional human activities, e.g. excessive groundwater pumping, but caused by global-scale meteorological phenomena. In fact, the interannual mass variation showed high correlation with the climate index represents the intensity of Indian Ocean Dipole (IOD) phenomena. In this study, we investigated the correlation mechanism between the interannual mass change in the Indochina Peninsula and the IOD phenomena, which is the spatial anomaly pattern of sea surface temperature. We firstly made the moisture flux data sets in the GRACE mission duration by using atmospheric objective reanalysis data. The obtained flux pattern was discussed by comparing with the typical flux pattern during the pure IOD years estimated by Ummenhofer et al., 2009. Further, the moisture flux over the Indochina Peninsula was assessed whether the value is quantitatively agreeable by comparing with

  7. A space-time multiscale modelling of Earth's gravity field variations

    Science.gov (United States)

    Wang, Shuo; Panet, Isabelle; Ramillien, Guillaume; Guilloux, Frédéric

    2017-04-01

    The mass distribution within the Earth varies over a wide range of spatial and temporal scales, generating variations in the Earth's gravity field in space and time. These variations are monitored by satellites as the GRACE mission, with a 400 km spatial resolution and 10 days to 1 month temporal resolution. They are expressed in the form of gravity field models, often with a fixed spatial or temporal resolution. The analysis of these models allows us to study the mass transfers within the Earth system. Here, we have developed space-time multi-scale models of the gravity field, in order to optimize the estimation of gravity signals resulting from local processes at different spatial and temporal scales, and to adapt the time resolution of the model to its spatial resolution according to the satellites sampling. For that, we first build a 4D wavelet family combining spatial Poisson wavelets with temporal Haar wavelets. Then, we set-up a regularized inversion of inter-satellites gravity potential differences in a bayesian framework, to estimate the model parameters. To build the prior, we develop a spectral analysis, localized in time and space, of geophysical models of mass transport and associated gravity variations. Finally, we test our approach to the reconstruction of space-time variations of the gravity field due to hydrology. We first consider a global distribution of observations along the orbit, from a simplified synthetic hydrology signal comprising only annual variations at large spatial scales. Then, we consider a regional distribution of observations in Africa, and a larger number of spatial and temporal scales. We test the influence of an imperfect prior and discuss our results.

  8. Seasonal Hydrological Loading in Southern Tibet Detected by Joint Analysis of GPS and GRACE.

    Science.gov (United States)

    Zou, Rong; Wang, Qi; Freymueller, Jeffrey T; Poutanen, Markku; Cao, Xuelian; Zhang, Caihong; Yang, Shaomin; He, Ping

    2015-12-04

    In southern Tibet, ongoing vertical and horizontal motions due to the collision between India and Eurasia are monitored by large numbers of global positioning system (GPS) continuous and campaign sites installed in the past decade. Displacements measured by GPS usually include tectonic deformation as well as non-tectonic, time-dependent signals. To estimate the regional long-term tectonic deformation using GPS more precisely, seasonal elastic deformation signals associated with surface loading must be removed from the observations. In this study, we focus on seasonal variation in vertical and horizontal motions of southern Tibet by performing a joint analysis of GRACE (Gravity Recovery and Climate Experiment) and GPS data, not only using continuous sites but also GPS campaign-mode sites. We found that the GPS-observed and GRACE-modeled seasonal oscillations are in good agreements, and a seasonal displacement model demonstrates that the main reason for seasonal variations in southern Tibet is from the summer monsoon and its precipitation. The biggest loading appears from July to August in the summer season. Vertical deformations observed by GPS and modeled by GRACE are two to three times larger than horizontal oscillations, and the north components demonstrate larger amplitudes than the east components. We corrected the GPS position time series using the GRACE-modeled seasonal variations, which gives significant reductions in the misfit and weighted root-mean-squares (WRMS). Misfit (χ2 divided by degree of freedom) reductions for campaign sites range between 20% and 56% for the vertical component, and are much smaller for the horizontal components. Moreover, time series of continuous GPS (cGPS) sites near the 2015 Nepal earthquakes must be corrected using appropriate models of seasonal loading for analyzing postseismic deformation to avoid biasing estimates of the postseismic relaxation.

  9. On the Odd Gracefulness of Cyclic Snakes With Pendant Edges

    Directory of Open Access Journals (Sweden)

    E. M. Badr

    2013-01-01

    Full Text Available Graceful and odd gracefulness of a graph are two entirely different concepts. A graph may posses one orboth of these or neither. We present four new families of odd graceful graphs. In particular we show an oddgraceful labeling of the linear kC4 − snake e mK1 and therefore we introduce the odd graceful labeling of4 1 kC − snake e mK ( for the general case . We prove that the subdivision of linear 3 kC − snake is oddgraceful. We also prove that the subdivision of linear 3 kC − snake with m-pendant edges is odd graceful.Finally, we present an odd graceful labeling of the crown graph n 1 P e mK .

  10. Uncertainties of the Gravity Recovery and Climate Experiment time-variable gravity-field solutions based on three-cornered hat method

    Science.gov (United States)

    Ferreira, Vagner G.; Montecino, Henry D. C.; Yakubu, Caleb I.; Heck, Bernhard

    2016-01-01

    Currently, various satellite processing centers produce extensive data, with different solutions of the same field being available. For instance, the Gravity Recovery and Climate Experiment (GRACE) has been monitoring terrestrial water storage (TWS) since April 2002, while the Center for Space Research (CSR), the Jet Propulsion Laboratory (JPL), the GeoForschungsZentrum (GFZ), and the Groupe de Recherche de Géodésie Spatiale (GRGS) provide individual monthly solutions in the form of Stokes coefficients. The inverted TWS maps (or the regionally averaged values) from these coefficients are being used in many applications; however, as no ground truth data exist, the uncertainties are unknown. Consequently, the purpose of this work is to assess the quality of each processing center by estimating their uncertainties using a generalized formulation of the three-cornered hat (TCH) method. Overall, the TCH results for the study period of August 2002 to June 2014 indicate that at a global scale, the CSR, GFZ, GRGS, and JPL presented uncertainties of 9.4, 13.7, 14.8, and 13.2 mm, respectively. At a basin scale, the overall good performance of the CSR was observed at 91 river basins. The TCH-based results were confirmed by a comparison with an ensemble solution from the four GRACE processing centers.

  11. Evaluation of Groundwater Storage changes at Konya Closed Basin, Turkey using GRACE-based and in-situ measurements

    Science.gov (United States)

    Kamil Yilmaz, Koray; Saber, Mohamed; Tugrul Yilmaz, Mustafa

    2016-04-01

    The Konya Closed Basin (KCB) located in Central Anatolia, Turkey, is the primary grain producer in Turkey. The lack of sufficient surface water resources and recently changing crop patterns have led to over-exploitation of groundwater resources and resulted in significant drop in groundwater levels. For this reason monitoring of the groundwater storage change in this region is critical to understand the potential of the current water resources and to devise effective water management strategies to avoid further depletion of the groundwater resources. Therefore, the main objective of this study is to examine and assess the utility of the Gravity Recovery and Climate Experiment (GRACE) and the Global Land Data Assimilation System (GLDAS) to monitor and investigate the groundwater storage changes in the Konya Closed Basin. Groundwater storage changes are derived using GRACE and GLDAS data and then are compared with the groundwater changes derived from the observed groundwater levels. The initial results of the comparison indicate an acceptable agreement between declining trends in GRACE-based and observed groundwater storage change during the study time period (2002 to 2015). Additionally, the results indicated that the study region exhibited remarkable drought conditions during 2007-2008 period. This study shows that the GRACE/GLDAS datasets can be used to monitor the equivalent groundwater storage changes which is crucial for long-term effective water management strategies.

  12. Addressing the challenges of GRACE application in basins with hydraulic fracturing activity

    Science.gov (United States)

    Read, L.; Ruybal, C.; Hogue, T. S.; Hinojosa, M. P.

    2016-12-01

    Despite the growing number of studies that employ GRACE to quantify groundwater resources we have found no published studies on whether GRACE is also accounting for subsurface mass redistributions related to energy development activities from oil production, water production, and wastewater injection. Given the similar densities of water and crude oil (water is 1.0g/cc, crude oil is 0.8-0.9g/cc) and the fact that large volumes of oil and water are extracted on a monthly basis for hydraulic fracturing or reinjected as a means of waste disposal, it is important to determine whether GRACE is detecting mass redistributions from energy development to be able to correctly infer changes in water mass. The purpose of this study is to investigate whether GRACE measurements are impacted by energy development activities and offer a methodology for determining whether this activity should be considered when evaluating changes in terrestrial water storage, groundwater storage, or any other prediction involving quantification of groundwater. To address this question we compiled a dataset from the Bakken Play in North Dakota to use as a case study, where oil production was significant and increased exponentially from 2002-2015, and groundwater withdrawals for agriculture were relatively stable and limited. Preliminary results indicate that oil and gas production is of a similar scale and thus important to include when calculating groundwater changes. Broadly, this research addresses the challenges and uncertainties in applying GRACE to quantify groundwater or terrestrial water changes in energy-active basins, namely in accounting for oil reservoir changes, production, and injection rates, as well as the process of data collection in proprietary systems.

  13. Gravity changes in mid-west Greenland from GOCE gravity model and gradient data using ground and airborne gravity

    DEFF Research Database (Denmark)

    Tscherning, Carl Christian; Herceg, Matija; Fredenslund Levinsen, Joanna

    GOCE TRF (terrestrial reference frame) vertical anomalous gradients (Tzz) from two periods have been used to determine gravity anomalies changes in mid-west Greenland, where a large mass-loss has been detected using GRACE (Fig. 1). As additional data were used the GOCE DIR-3 model and ground...... gravity at the coast on solid rock, where no mass loss is expected. The methods of Least-Squares Collocation (LSC) and the Reduced Point Mass (RPM) methods have been used, however only LSC included the ground data....

  14. GRACE captures basin mass dynamic changes in China based on a multi-basin inversion method

    Science.gov (United States)

    Yi, Shuang; Wang, Qiuyu; Sun, Wenke

    2016-04-01

    Complex landform, miscellaneous climate and enormous population have enriched China with geophysical phenomena ranging from water depletion in the underground to glaciers retreat on the high mountains and have aroused large scientific interests. This paper, utilizing gravity observations 2003-2014 from the Gravity Recovery and Climate Experiment (GRACE), intends to make a comprehensive estimation of mass status in 16 drainage basins in the whole region. We proposed a multi-basin inversion method, which is featured by resistance to the stripe noise and ability to alleviate signal attenuation due to truncation and smoothing of GRACE data. The results show both positive and negative trends: there is a tremendous mass accumulation spreading from the Tibetan plateau (12.2 ± 0.6 Gt/yr) to the Yangtze River (7.6 ± 1.3 Gt/yr), and further to the southeast coastal areas, which is suggested to involve an increase in the ground water storage, lake and reservoir water volume and likely materials flowed in by tectonic process; a mass loss is occurring in Huang-Huai-Hai-Liao River Basin (-10.5 ± 0.8 Gt/yr), as well as the Brahmaputra-Nujiang-Lancang River Basin (-15.0 ± 0.9 Gt/yr) and Tienshan Mountain (-4.1 ± 0.3 Gt/yr), which is a result of groundwater pumping and glacier melting. The groundwater depletion area is well consistent with the distribution of land subsidence in North China. In the end, we find intensified precipitation can alter the local water supply and GRACE is proficient to capture this dynamics, which could be instructive for the South-to-North Water Diversion - one China's giant hydrologic project.

  15. Basin mass dynamic changes in China from GRACE based on a multibasin inversion method

    Science.gov (United States)

    Yi, Shuang; Wang, Qiuyu; Sun, Wenke

    2016-05-01

    Complex landforms, miscellaneous climates, and enormous populations have influenced various geophysical phenomena in China, which range from water depletion in the underground to retreating glaciers on high mountains and have attracted abundant scientific interest. This paper, which utilizes gravity observations during 2003-2014 from the Gravity Recovery and Climate Experiment (GRACE), intends to comprehensively estimate the mass status in 16 drainage basins in the region. We propose a multibasin inversion method that features resistance to stripe noise and an ability to alleviate signal attenuation from the truncation and smoothing of GRACE data. The results show both positive and negative trends. Tremendous mass accumulation has occurred from the Tibetan Plateau (12.1 ± 0.6 Gt/yr) to the Yangtze River (7.7 ± 1.3 Gt/yr) and southeastern coastal areas, which is suggested to involve an increase in the groundwater storage, lake and reservoir water volume, and the flow of materials from tectonic processes. Additionally, mass loss has occurred in the Huang-Huai-Hai-Liao River Basin (-10.2 ± 0.9 Gt/yr), the Brahmaputra-Nujiang-Lancang River Basin (-15.0 ± 1.1 Gt/yr), and Tienshan Mountain (-4.1 ± 0.3 Gt/yr), a result of groundwater pumping and glacier melting. Areas with groundwater depletion are consistent with the distribution of cities with land subsidence in North China. We find that intensified precipitation can alter the local water supply and that GRACE can adequately capture these dynamics, which could be instructive for China's South-to-North Water Diversion hydrologic project.

  16. Assessing Groundwater Depletion and Dynamics Using GRACE and InSAR: Potential and Limitations.

    Science.gov (United States)

    Castellazzi, Pascal; Martel, Richard; Galloway, Devin L; Longuevergne, Laurent; Rivera, Alfonso

    2016-11-01

    In the last decade, remote sensing of the temporal variation of ground level and gravity has improved our understanding of groundwater dynamics and storage. Mass changes are measured by GRACE (Gravity Recovery and Climate Experiment) satellites, whereas ground deformation is measured by processing synthetic aperture radar satellites data using the InSAR (Interferometry of Synthetic Aperture Radar) techniques. Both methods are complementary and offer different sensitivities to aquifer system processes. GRACE is sensitive to mass changes over large spatial scales (more than 100,000 km(2) ). As such, it fails in providing groundwater storage change estimates at local or regional scales relevant to most aquifer systems, and at which most groundwater management schemes are applied. However, InSAR measures ground displacement due to aquifer response to fluid-pressure changes. InSAR applications to groundwater depletion assessments are limited to aquifer systems susceptible to measurable deformation. Furthermore, the inversion of InSAR-derived displacement maps into volume of depleted groundwater storage (both reversible and largely irreversible) is confounded by vertical and horizontal variability of sediment compressibility. During the last decade, both techniques have shown increasing interest in the scientific community to complement available in situ observations where they are insufficient. In this review, we present the theoretical and conceptual bases of each method, and present idealized scenarios to highlight the potential benefits and challenges of combining these techniques to remotely assess groundwater storage changes and other aspects of the dynamics of aquifer systems.

  17. Assessing groundwater depletion and dynamics using GRACE and InSAR: Potential and limitations

    Science.gov (United States)

    Castellazzi, Pascal; Martel, Richard; Galloway, Devin L.; Longuevergne, Laurent; Rivera, Alfonso

    2016-01-01

    In the last decade, remote sensing of the temporal variation of ground level and gravity has improved our understanding of groundwater dynamics and storage. Mass changes are measured by GRACE (Gravity Recovery and Climate Experiment) satellites, whereas ground deformation is measured by processing synthetic aperture radar satellites data using the InSAR (Interferometry of Synthetic Aperture Radar) techniques. Both methods are complementary and offer different sensitivities to aquifer system processes. GRACE is sensitive to mass changes over large spatial scales (more than 100,000 km2). As such, it fails in providing groundwater storage change estimates at local or regional scales relevant to most aquifer systems, and at which most groundwater management schemes are applied. However, InSAR measures ground displacement due to aquifer response to fluid-pressure changes. InSAR applications to groundwater depletion assessments are limited to aquifer systems susceptible to measurable deformation. Furthermore, the inversion of InSAR-derived displacement maps into volume of depleted groundwater storage (both reversible and largely irreversible) is confounded by vertical and horizontal variability of sediment compressibility. During the last decade, both techniques have shown increasing interest in the scientific community to complement available in situ observations where they are insufficient. In this review, we present the theoretical and conceptual bases of each method, and present idealized scenarios to highlight the potential benefits and challenges of combining these techniques to remotely assess groundwater storage changes and other aspects of the dynamics of aquifer systems.

  18. Identification of Outliers in Grace Data for Indo-Gangetic Plain Using Various Methods (Z-Score, Modified Z-score and Adjusted Boxplot) and Its Removal

    Science.gov (United States)

    Srivastava, S.

    2015-12-01

    Gravity Recovery and Climate Experiment (GRACE) data are widely used for the hydrological studies for large scale basins (≥100,000 sq km). GRACE data (Stokes Coefficients or Equivalent Water Height) used for hydrological studies are not direct observations but result from high level processing of raw data from the GRACE mission. Different partner agencies like CSR, GFZ and JPL implement their own methodology and their processing methods are independent from each other. The primary source of errors in GRACE data are due to measurement and modeling errors and the processing strategy of these agencies. Because of different processing methods, the final data from all the partner agencies are inconsistent with each other at some epoch. GRACE data provide spatio-temporal variations in Earth's gravity which is mainly attributed to the seasonal fluctuations in water level on Earth surfaces and subsurface. During the quantification of error/uncertainties, several high positive and negative peaks were observed which do not correspond to any hydrological processes but may emanate from a combination of primary error sources, or some other geophysical processes (e.g. Earthquakes, landslide, etc.) resulting in redistribution of earth's mass. Such peaks can be considered as outliers for hydrological studies. In this work, an algorithm has been designed to extract outliers from the GRACE data for Indo-Gangetic plain, which considers the seasonal variations and the trend in data. Different outlier detection methods have been used such as Z-score, modified Z-score and adjusted boxplot. For verification, assimilated hydrological (GLDAS) and hydro-meteorological data are used as the reference. The results have shown that the consistency amongst all data sets improved significantly after the removal of outliers.

  19. Spectral analysis of quasi-stationary sea surface topography from GRACE mission

    Institute of Scientific and Technical Information of China (English)

    ZHANG Zizhan; LU Yang

    2005-01-01

    During the last two decades satellite altimetry has offered an abundance of measurements of the sea surface resulting in the improvement of global mean sea surface height (MSSH) and marine geoid determination. On the other hand, with the launching of new generation gravity satellites, some high accuracy long-wavelength gravity models are available. These breakthroughs give us a great opportunity for new estimation of quasi-stationary sea surface topography (QSST). In this paper, the new gravity model GGM01C derived from GRACE mission is briefly presented, and a new global high precision and high-resolution QSST is determined based on the GGM01C model and the global MSSH. The spectral features of the QSST estimated by GGM01C and EGM96 gravity model to degree/order 200 are discussed by spectral analysis. As a result, the QSST is mainly composed of long waves, medium waves partially and short waves scarcely, its power spectral structures are different between the zonal direction and the meridional direction, there are great differences between the two models, which maybe explain why the ocean currents derived from the two gravity models by Tapley show different patterns.

  20. CSR Gravity Field Data Products

    Science.gov (United States)

    Bettadpur, Srinivas

    2014-05-01

    The joint NASA/DLR GRACE mission has successfully operated for nearly 12 years, and has provided a remarkable record of global mass flux due to a large variety of geophysical and climate processes at various spatio-temporal scales. The University of Texas Center for Space Research (CSR) hosts the mission PI, and is responsible for delivery of operational (presently denoted as Release-05 or RL05) gravity field data products. In addition, CSR generates and distributes a variety of other gravity field data products, including products generated from the use of satellite laser ranging data. This poster will provide an overview of all these data products, their relative quality, potential applications, and future plans for their development and delivery.

  1. Bowie Lecture: Time Variable Gravity Measurements Come of Age

    Science.gov (United States)

    Watkins, M. M.

    2004-12-01

    The Earth and planetary science and geodesy communities have long recognized measurements of the static gravity field as primary for understanding bulk properties and formation histories. Use of the time varying field, however, to measure the cycling of volatiles has been only coarsely demonstrated over the past two decades. The GRACE mission has now realized the promise of those early studies and demonstrated that gravity field measurement is now a valid remote sensing concept for the Earth and eventually other planets in the solar system. We will discuss the latest GRACE results for the measurement of the Earth's water cycle on land, the oceans, and ice sheets, and outline prospects and capabilities of follow-on missions. We will conclude with an overview of the recent exciting results of both current and proposed planetary missions, especially at Mars, for time varying gravity measurements outside the Earth as well.

  2. Antarctic tides from GRACE satellite accelerations

    Science.gov (United States)

    Wiese, D. N.; Killett, B.; Watkins, M. M.; Yuan, D.-N.

    2016-05-01

    The extended length of the GRACE data time series (now 13.5 years) provides the unique opportunity to estimate global mass variations due to ocean tides at large (˜300 km) spatial scales. State-of-the-art global tide models rely heavily on satellite altimetry data, which are sparse for latitudes higher than 66°. Thus, the performance of the models is typically worse at higher latitudes. GRACE data, alternately, extend to polar latitudes and therefore provide information for both model validation and improvement at the higher latitudes. In this work, 11 years of GRACE inter-satellite range-acceleration measurements are inverted to solve for corrections to the amplitudes and phases of the major solar and lunar ocean tidal constituents (M2, K1, S2, and O1) from the GOT4.7 ocean tide model at latitudes south of 50°S. Two independent inversion and regularization methods are employed and compared against one another. Uncertainty estimates are derived by subtracting two independent solutions, each spanning a unique 5.5 years of data. Features above the noise floor in the derived solutions likely represent errors in GOT4.7. We find the GOT4.7 amplitudes to be generally too small for M2 and K1, and too large for S2 and O1, and to spatially correlate with geographic regions where GOT4.7 predicts the largest tidal amplitudes. In particular, we find GOT4.7 errors to be dominant over the Patagonia shelf (M2), the Filchner-Ronne Ice Shelf (M2 and S2), the Ross Ice Shelf (S2), and the Weddell and Ross Seas (K1 and O1).

  3. The design, validation, and performance of Grace

    Science.gov (United States)

    Zhu, Ru

    2016-05-01

    The design, validation and performance of Grace, a GPU-accelerated micromagnetic simulation software, are presented. The software adopts C+ + Accelerated Massive Parallelism (C+ + AMP) so that it runs on GPUs from various hardware vendors including NVidia, AMD and Intel. At large simulation scales, up to two orders of magnitude of speedup factor is observed, compared to CPU-based micromagnetic simulation software OOMMF. The software can run on high-end professional GPUs as well as budget personal laptops, and is free to download.

  4. Investigating the relation between the geometric properties of river basins and the filtering parameters for regional land hydrology applications using GRACE models

    Science.gov (United States)

    Piretzidis, Dimitrios; Sideris, Michael G.

    2016-04-01

    This study investigates the possibilities of local hydrology signal extraction using GRACE data and conventional filtering techniques. The impact of the basin shape has also been studied in order to derive empirical rules for tuning the GRACE filter parameters. GRACE CSR Release 05 monthly solutions were used from April 2002 to August 2015 (161 monthly solutions in total). SLR data were also used to replace the GRACE C2,0 coefficient, and a de-correlation filter with optimal parameters for CSR Release 05 data was applied to attenuate the correlation errors of monthly mass differences. For basins located at higher latitudes, the effect of Glacial Isostatic Adjustment (GIA) was taken into account using the ICE-6G model. The study focuses on three geometric properties, i.e., the area, the convexity and the width in the longitudinal direction, of 100 basins with global distribution. Two experiments have been performed. The first one deals with the determination of the Gaussian smoothing radius that minimizes the gaussianity of GRACE equivalent water height (EWH) over the selected basins. The EWH kurtosis was selected as a metric of gaussianity. The second experiment focuses on the derivation of the Gaussian smoothing radius that minimizes the RMS difference between GRACE data and a hydrology model. The GLDAS 1.0 Noah hydrology model was chosen, which shows good agreement with GRACE data according to previous studies. Early results show that there is an apparent relation between the geometric attributes of the basins examined and the Gaussian radius derived from the two experiments. The kurtosis analysis experiment tends to underestimate the optimal Gaussian radius, which is close to 200-300 km in many cases. Empirical rules for the selection of the Gaussian radius have been also developed for sub-regional scale basins.

  5. Variability of the Antarctic Circumpolar Current derived from GRACE retrievals, model simulations and in-situ measurements

    Science.gov (United States)

    Boening, C.; Timmermann, R.; Macrander, A.; Schroeter, J.; Boebel, O.

    2008-12-01

    The Gravity Recovery and Climate Experiment (GRACE) provides estimates of the Earth's static and time-variant gravity field. Solutions from various processing centres (GFZ, CSR, GRGS, JPL etc.) enable us to determine mass redistributions on the globe. Given that land signals are generally large compared to anomalies over the ocean, an assessment of the latter requires a particularly careful filtering of the data. We utilized the Finite Element Sea-Ice Ocean Model (FESOM) to develop a filtering algorithm which relies on the spatial coherency of ocean bottom pressure (OBP) anomalies. Taking large-scale circulation patterns into account, the new filter yields an improved representation of OBP (i.e. ocean mass) variability in the filtered GRACE data. In order to investigate the representation of Antarctic Circumpolar Current (ACC) variability in the pattern-filtered GRACE retrievals, an analysis of OBP anomalies in FESOM results and in-situ measurements has been performed. Data from a PIES (Pressure sensor equipped Inverted Echo Sounder) array (36°S-55°S, 2°W-13°E) south of Africa provides bottom pressure recorder data from 2002-2008 for the ACC region. Based on anomalies of OBP gradients between individual instruments, these in-situ measurements give an estimate of the overall transport variability as well as of the movement of ACC fronts and transport redistribution between different sectors of the ACC. The validation of simulated and satellite-derived OBP anomaly gradients against these data yields a measure for the representation of this variability in FESOM and GRACE. Furthermore, model simulations are used to assess the relation between transport variations in individual filaments of the Southern Ocean and total transport variability in this and other sectors of the ACC.

  6. Terrestrial water storage changes over the Pearl River Basin from GRACE and connections with Pacific climate variability

    Institute of Scientific and Technical Information of China (English)

    Zhicai Luo; Chaolong Yao; Qiong Li; Zhengkai Huang

    2016-01-01

    Time-variable gravity data from the Gravity Recovery and Climate Experiment (GRACE)satellite mission are used to study terrestrial water storage (TWS) changes over the Pearl River Basin (PRB) for the period 2003-Nov.2014.TWS estimates from GRACE generally show good agreement with those from two hydrological models GLDAS and WGHM.But they show different capability of detecting significant TWS changes over the PRB.Among them,WGHM is likely to underestimate the seasonal variability of TWS,while GRACE detects longterm water depletions over the upper PRB as was done by hydrological models,and observes significant water increases around the Longtan Reservoir (LTR) due to water impoundment.The heavy drought in 2011 caused by the persistent precipitation deficit has resulted in extreme low surface runoff and water level of the LTR.Moreover,large variability of summer and autumn precipitation may easily trigger floods and droughts in the rainy season in the PRB,especially for summer,as a high correlation of 0.89 was found between precipitation and surface runoff.Generally,the PRB TWS was negatively correlated with El Ni(n)o-Southem Oscillation (ENSO) events.However,the modulation of the Pacific Decadal Oscillation (PDO) may impact this relationship,and the significant TWS anomaly was likely to occur in the peak of PDO phase as they agree well in both of the magnitude and timing of peaks.This indicates that GRACE-based TWS could be a valuable parameter for studying climatic influences in the PRB.

  7. Gravity Racers

    Science.gov (United States)

    Wilcox, Dawn Renee; Roberts, Shannon; Wilcox, David

    2010-01-01

    With the 2010 Winter Olympic Games prominent in the media, children were exposed to images of athletes skiing down snow-covered slopes, coasting furiously on bobsleds, and skating gracefully across the ice. Therefore, the authors capitalized on their children's natural curiosity about the world around them by exploring the concept of motion in a…

  8. Gravity Racers

    Science.gov (United States)

    Wilcox, Dawn Renee; Roberts, Shannon; Wilcox, David

    2010-01-01

    With the 2010 Winter Olympic Games prominent in the media, children were exposed to images of athletes skiing down snow-covered slopes, coasting furiously on bobsleds, and skating gracefully across the ice. Therefore, the authors capitalized on their children's natural curiosity about the world around them by exploring the concept of motion in a…

  9. 3 CFR 8407 - Proclamation 8407 of August 31, 2009. National Ovarian Cancer Awareness Month, 2009

    Science.gov (United States)

    2010-01-01

    ... of the United States of America A Proclamation Ovarian cancer remains the leading cause of death from... the disease with grace and dignity. National Ovarian Cancer Awareness Month honors all those affected...

  10. Coseismic Gravity and Displacement Signatures Induced by the 2013 Okhotsk Mw8.3 Earthquake

    Science.gov (United States)

    Zhang, Guoqing; Shen, Wenbin; Xu, Changyi; Zhu, Yiqing

    2016-01-01

    In this study, Gravity Recovery and Climate Experiment (GRACE) RL05 data from January 2003 to October 2014 were used to extract the coseismic gravity changes induced by the 24 May 2013 Okhotsk Mw8.3 deep-focus earthquake using the difference and least square fitting methods. The gravity changes obtained from GRACE data agreed well with those from dislocation theory in both magnitude and spatial pattern. Positive and negative gravity changes appeared on both sides of the epicenter. The positive signature appeared on the western side, and the peak value was approximately 0.4 microgal (1 microgal = 10−8 m/s2), whereas on the eastern side, the gravity signature was negative, and the peak value was approximately −1.1 microgal. It demonstrates that deep-focus earthquakes Mw ≤ 8.5 are detectable by GRACE observations. Moreover, the coseismic displacements of 20 Global Positioning System (GPS) stations on the Earth’s surface were simulated using an elastic dislocation theory in a spherical earth model, and the results are consistent with the GPS results, especially the near-field results. We also estimated the gravity contributions from the coseismic vertical displacements and density changes, analyzed the proportion of these two gravity change factors (based on an elastic dislocation theory in a spherical earth model) in this deep-focus earthquake. The gravity effect from vertical displacement is four times larger than that caused by density redistribution. PMID:27598158

  11. Improving estimates of water resources in a semi-arid region by assimilating GRACE data into the PCR-GLOBWB hydrological model

    Science.gov (United States)

    Tangdamrongsub, Natthachet; Steele-Dunne, Susan C.; Gunter, Brian C.; Ditmar, Pavel G.; Sutanudjaja, Edwin H.; Sun, Yu; Xia, Ting; Wang, Zhongjing

    2017-04-01

    An accurate estimation of water resources dynamics is crucial for proper management of both agriculture and the local ecology, particularly in semi-arid regions. Imperfections in model physics, uncertainties in model land parameters and meteorological data, as well as the human impact on land changes often limit the accuracy of hydrological models in estimating water storages. To mitigate this problem, this study investigated the assimilation of terrestrial water storage variation (TWSV) estimates derived from the Gravity Recovery And Climate Experiment (GRACE) data using an ensemble Kalman filter (EnKF) approach. The region considered was the Hexi Corridor in northern China. The hydrological model used for the analysis was PCR-GLOBWB, driven by satellite-based forcing data from April 2002 to December 2010. The impact of the GRACE data assimilation (DA) scheme was evaluated in terms of the TWSV, as well as the variation of individual hydrological storage estimates. The capability of GRACE DA to adjust the storage level was apparent not only for the entire TWSV but also for the groundwater component. In this study, spatially correlated errors in GRACE data were taken into account, utilizing the full error variance-covariance matrices provided as a part of the GRACE data product. The benefits of this approach were demonstrated by comparing the EnKF results obtained with and without taking into account error correlations. The results were validated against in situ groundwater data from five well sites. On average, the experiments showed that GRACE DA improved the accuracy of groundwater storage estimates by as much as 25 %. The inclusion of error correlations provided an equal or greater improvement in the estimates. In contrast, a validation against in situ streamflow data from two river gauges showed no significant benefits of GRACE DA. This is likely due to the limited spatial and temporal resolution of GRACE observations. Finally, results of the GRACE DA study

  12. Long-term groundwater variations in Northwest India from satellite gravity measurements

    Science.gov (United States)

    Chen, Jianli; Li, Jin; Zhang, Zizhan; Ni, Shengnan

    2014-05-01

    Satellite gravity data from the Gravity Recovery and Climate Experiment (GRACE) provides quantitative measures of terrestrial water storage (TWS) change at large spatial scales. Combining GRACE-observed TWS changes and model estimates of water storage changes in soil and snow at the surface offers a means for measuring groundwater storage change. In this study, we re-assess long-term groundwater storage variation in the Northwest India (NWI) region using an extended record of GRACE time-variable gravity measurements, and a fully unconstrained global forward modeling method. Our new assessments based on the GRACE release-5 (RL05) gravity solutions indicate that during the 10 year period January 2003 to December 2012, the NWI groundwater depletion remains pronounced, especially during the first 5 years (01/2003-12/2007). The newly estimated depletion rates are ~ 20.4 ± 7.1 Gigatonne (Gt)/yr averaged over the 10 year period, and 29.4 ± 8.4 Gt/yr during the first 5 years. The yearly groundwater storage changes in the NWI region are strongly correlated with yearly precipitation anomalies. In 2009, the driest season of the decade, the groundwater depletion reaches nearly 80 Gt, while in the two relatively wet seasons, 2008 and 2011, the groundwater storages even see net increases of about 24 and 35 Gt, respectively. The estimated mean groundwater depletion rates for the first 5 years are significantly higher than previous assessments. The larger depletion rates may reflect the benefits from improved data quality of GRACE RL05 gravity solutions, and improved data processing method, which can more effectively reduce leakage error in GRACE estimates. Our analysis indicates that the neighboring Punjab Province of Pakistan (especially Northern Punjab) apparently also experiences significant groundwater depletion during the same period, which has partly contributed to the new regional groundwater depletion estimates.

  13. Drought Analysis of the Haihe River Basin Based on GRACE Terrestrial Water Storage

    Science.gov (United States)

    Wang, Jianhua; Jiang, Dong; Huang, Yaohuan; Wang, Hao

    2014-01-01

    The Haihe river basin (HRB) in the North China has been experiencing prolonged, severe droughts in recent years that are accompanied by precipitation deficits and vegetation wilting. This paper analyzed the water deficits related to spatiotemporal variability of three variables of the gravity recovery and climate experiment (GRACE) derived terrestrial water storage (TWS) data, precipitation, and EVI in the HRB from January 2003 to January 2013. The corresponding drought indices of TWS anomaly index (TWSI), precipitation anomaly index (PAI), and vegetation anomaly index (AVI) were also compared for drought analysis. Our observations showed that the GRACE-TWS was more suitable for detecting prolonged and severe droughts in the HRB because it can represent loss of deep soil water and ground water. The multiyear droughts, of which the HRB has sustained for more than 5 years, began in mid-2007. Extreme drought events were detected in four periods at the end of 2007, the end of 2009, the end of 2010, and in the middle of 2012. Spatial analysis of drought risk from the end of 2011 to the beginning of 2012 showed that human activities played an important role in the extent of drought hazards in the HRB. PMID:25202732

  14. Glacial density and GIA in Alaska estimated from ICESat, GPS and GRACE measurements

    Science.gov (United States)

    Jin, Shuanggen; Zhang, T. Y.; Zou, F.

    2017-01-01

    The density of glacial volume change in Alaska is a key factor in estimating the glacier mass loss from altimetry observations. However, the density of Alaskan glaciers has large uncertainty due to the lack of in situ measurements. In this paper, using the measurements of Ice, Cloud, and land Elevation Satellite (ICESat), Global Positioning System (GPS), and Gravity Recovery and Climate Experiment (GRACE) from 2003 to 2009, an optimal density of glacial volume change with 750 kg/m3 is estimated for the first time to fit the measurements. The glacier mass loss is -57.5 ± 6.5 Gt by converting the volumetric change from ICESat with the estimated density 750 kg/m3. Based on the empirical relation, the depth-density profiles are constructed, which show glacial density variation information with depths in Alaska. By separating the glacier mass loss from glacial isostatic adjustment (GIA) effects in GPS uplift rates and GRACE total water storage trends, the GIA uplift rates are estimated in Alaska. The best fitting model consists of a 60 km elastic lithosphere and 110 km thick asthenosphere with a viscosity of 2.0 × 1019 Pa s over a two-layer mantle.

  15. Drought Analysis of the Haihe River Basin Based on GRACE Terrestrial Water Storage

    Directory of Open Access Journals (Sweden)

    Jianhua Wang

    2014-01-01

    Full Text Available The Haihe river basin (HRB in the North China has been experiencing prolonged, severe droughts in recent years that are accompanied by precipitation deficits and vegetation wilting. This paper analyzed the water deficits related to spatiotemporal variability of three variables of the gravity recovery and climate experiment (GRACE derived terrestrial water storage (TWS data, precipitation, and EVI in the HRB from January 2003 to January 2013. The corresponding drought indices of TWS anomaly index (TWSI, precipitation anomaly index (PAI, and vegetation anomaly index (AVI were also compared for drought analysis. Our observations showed that the GRACE-TWS was more suitable for detecting prolonged and severe droughts in the HRB because it can represent loss of deep soil water and ground water. The multiyear droughts, of which the HRB has sustained for more than 5 years, began in mid-2007. Extreme drought events were detected in four periods at the end of 2007, the end of 2009, the end of 2010, and in the middle of 2012. Spatial analysis of drought risk from the end of 2011 to the beginning of 2012 showed that human activities played an important role in the extent of drought hazards in the HRB.

  16. Water Storage Changes over the Tibetan Plateau Revealed by GRACE Mission

    Science.gov (United States)

    Guo, Jinyun; Mu, Dapeng; Liu, Xin; Yan, Haoming; Sun, Zhongchang; Guo, Bin

    2016-04-01

    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.

  17. Arm-Locking with the GRACE Follow-On Laser Ranging Interferometer

    CERN Document Server

    Thorpe, James Ira

    2015-01-01

    Arm-locking is a technique for stabilizing the frequency of a laser in an inter-spacecraft interferometer by using the spacecraft separation as the frequency reference. A candidate technique for future space-based gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA), arm-locking has been extensive studied in this context through analytic models, time-domain simulations, and hardware-in-the-loop laboratory demonstrations. In this paper we show the Laser Ranging Interferometer instrument flying aboard the upcoming Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission provides an appropriate platform for an on-orbit demonstration of the arm-locking technique. We describe an arm-locking controller design for the GRACE-FO system and a series of time-domain simulations that demonstrate its feasibility. We conclude that it is possible to achieve laser frequency noise suppression of roughly two orders of magnitude around a Fourier frequency of 1Hz with conservative margins...

  18. A Comparison of Groundwater Storage Using GRACE Data, Groundwater Levels, and a Hydrological Model in Californias Central Valley

    Science.gov (United States)

    Kuss, Amber; Brandt, William; Randall, Joshua; Floyd, Bridget; Bourai, Abdelwahab; Newcomer, Michelle; Skiles, Joseph; Schmidt, Cindy

    2011-01-01

    The Gravity Recovery and Climate Experiment (GRACE) measures changes in total water storage (TWS) remotely, and may provide additional insight to the use of well-based data in California's agriculturally productive Central Valley region. Under current California law, well owners are not required to report groundwater extraction rates, making estimation of total groundwater extraction difficult. As a result, other groundwater change detection techniques may prove useful. From October 2002 to September 2009, GRACE was used to map changes in TWS for the three hydrological regions (the Sacramento River Basin, the San Joaquin River Basin, and the Tulare Lake Basin) encompassing the Central Valley aquifer. Net groundwater storage changes were calculated from the changes in TWS for each of the three hydrological regions and by incorporating estimates for additional components of the hydrological budget including precipitation, evapotranspiration, soil moisture, snow pack, and surface water storage. The calculated changes in groundwater storage were then compared to simulated values from the California Department of Water Resource's Central Valley Groundwater- Surface Water Simulation Model (C2VSIM) and their Water Data Library (WDL) Geographic Information System (GIS) change in storage tool. The results from the three methods were compared. Downscaling GRACE data into the 21 smaller Central Valley sub-regions included in C2VSIM was also evaluated. This work has the potential to improve California's groundwater resource management and use of existing hydrological models for the Central Valley.

  19. Application of the Regional Water Mass Variations from GRACE Satellite Gravimetry to Large-Scale Water Management in Africa

    Directory of Open Access Journals (Sweden)

    Guillaume Ramillien

    2014-08-01

    Full Text Available Time series of regional 2° × 2° Gravity Recovery and Climate Experiment (GRACE solutions of surface water mass change have been computed over Africa from 2003 to 2012 with a 10-day resolution by using a new regional approach. These regional maps are used to describe and quantify water mass change. The contribution of African hydrology to actual sea level rise is negative and small in magnitude (i.e., −0.1 mm/y of equivalent sea level (ESL mainly explained by the water retained in the Zambezi River basin. Analysis of the regional water mass maps is used to distinguish different zones of important water mass variations, with the exception of the dominant seasonal cycle of the African monsoon in the Sahel and Central Africa. The analysis of the regional solutions reveals the accumulation in the Okavango swamp and South Niger. It confirms the continuous depletion of water in the North Sahara aquifer at the rate of −2.3 km3/y, with a decrease in early 2008. Synergistic use of altimetry-based lake water volume with total water storage (TWS from GRACE permits a continuous monitoring of sub-surface water storage for large lake drainage areas. These different applications demonstrate the potential of the GRACE mission for the management of water resources at the regional scale.

  20. GRACE BIOREMEDIATION TECHNOLOGIES - DARAMEND™ BIOREMEDIATION TECHNOLOGY. INNOVATIVE TECHNOLOGY EVALUATION REPORT

    Science.gov (United States)

    Grace Dearborn's DARAMEND™ Bioremediation Technology was developed to treat soils/sediment contaminated with organic contaminants using solid-phase organic amendments. The amendments increase the soil’s ability to supply biologically available water/nutrients to micro...

  1. Global terrestrial water storage capacity and flood potential using GRACE

    National Research Council Canada - National Science Library

    Reager, J. T; Famiglietti, J. S

    2009-01-01

    .... Over the GRACE record length, instances of repeated maxima in water storage anomaly that fall short of variable maxima in cumulative precipitation suggest an effective storage capacity for a given...

  2. Massive Gravity

    National Research Council Canada - National Science Library

    de Rham, Claudia

    2014-01-01

    We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali–Gabadadze–Porrati model (DGP...

  3. Massive gravity

    OpenAIRE

    Claudia de Rham

    2016-01-01

    We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali-Gabadadze-Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware-Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...

  4. Massive Gravity

    OpenAIRE

    de Rham, Claudia

    2014-01-01

    We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali-Gabadadze-Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware-Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...

  5. Massive Gravity

    OpenAIRE

    2014-01-01

    We review recent progress in massive gravity. We start by showing how different theories of massive gravity emerge from a higher-dimensional theory of general relativity, leading to the Dvali–Gabadadze–Porrati model (DGP), cascading gravity, and ghost-free massive gravity. We then explore their theoretical and phenomenological consistency, proving the absence of Boulware–Deser ghosts and reviewing the Vainshtein mechanism and the cosmological solutions in these models. Finally, we present alt...

  6. Spinfoam Gravity

    Science.gov (United States)

    Bianchi, Eugenio

    The following sections are included: * Introduction * Topological Field Theory and Gravity * Classical Spinfoam Gravity: Degrees of Freedom and Foams * Unitary Representations of the Rotation and the Lorentz Group * Boundary Variables and the Loop Quantum Gravity Hilbert Space * Spinfoam Partition Function and the Vertex Amplitude * Cellular Quantum Geometry: A Single Atom of Space * Cellular Quantum Geometry: Coherent Spin-networks * Vertex-amplitude Asymptotics and Regge Gravity * Reconstructing a Semiclassical Spacetime * Conclusions * References

  7. Gravity Anomaly Assessment Using Ggms and Airborne Gravity Data Towards Bathymetry Estimation

    Science.gov (United States)

    Tugi, A.; Din, A. H. M.; Omar, K. M.; Mardi, A. S.; Som, Z. A. M.; Omar, A. H.; Yahaya, N. A. Z.; Yazid, N.

    2016-09-01

    The Earth's potential information is important for exploration of the Earth's gravity field. The techniques of measuring the Earth's gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP), Gravity Recovery and Climate Experiment (GRACE), and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE) has introduced a better way in providing the information on the Earth's gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs) has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth's gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R2) and the root mean square error (RMSE) of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R2 and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

  8. GRAVITY ANOMALY ASSESSMENT USING GGMS AND AIRBORNE GRAVITY DATA TOWARDS BATHYMETRY ESTIMATION

    Directory of Open Access Journals (Sweden)

    A. Tugi

    2016-09-01

    Full Text Available The Earth’s potential information is important for exploration of the Earth’s gravity field. The techniques of measuring the Earth’s gravity using the terrestrial and ship borne technique are time consuming and have limitation on the vast area. With the space-based measuring technique, these limitations can be overcome. The satellite gravity missions such as Challenging Mini-satellite Payload (CHAMP, Gravity Recovery and Climate Experiment (GRACE, and Gravity-Field and Steady-State Ocean Circulation Explorer Mission (GOCE has introduced a better way in providing the information on the Earth’s gravity field. From these satellite gravity missions, the Global Geopotential Models (GGMs has been produced from the spherical harmonics coefficient data type. The information of the gravity anomaly can be used to predict the bathymetry because the gravity anomaly and bathymetry have relationships between each other. There are many GGMs that have been published and each of the models gives a different value of the Earth’s gravity field information. Therefore, this study is conducted to assess the most reliable GGM for the Malaysian Seas. This study covered the area of the marine area on the South China Sea at Sabah extent. Seven GGMs have been selected from the three satellite gravity missions. The gravity anomalies derived from the GGMs are compared with the airborne gravity anomaly, in order to figure out the correlation (R2 and the root mean square error (RMSE of the data. From these assessments, the most suitable GGMs for the study area is GOCE model, GO_CONS_GCF_2_TIMR4 with the R2 and RMSE value of 0.7899 and 9.886 mGal, respectively. This selected model will be used in the estimating the bathymetry for Malaysian Seas in future.

  9. Results from GRACE/SUSY at one-loop

    Indian Academy of Sciences (India)

    J Fujimoto; T Ishikawa; M Jimbo; T Kaneko; T Kon; Y kurihara; M Kuroda; Y Shimizu; Y Yasui

    2007-11-01

    We report the recent development on the SUSY calculations with the help of GRACE system. GRACE/SUSY/1LOOP is the computer code which can generate Feynman diagrams in the MSSM automatically and compute one-loop amplitudes in the numerical way. We present new results of various two-body decay widths and chargino pair production at ILC (international linear collider) at one-loop level.

  10. Detecting seasonal and long-term vertical displacement in the North China Plain using GRACE and GPS

    Directory of Open Access Journals (Sweden)

    L. Wang

    2017-06-01

    Full Text Available In total, 29 continuous Global Positioning System (GPS time series data together with data from Gravity Recovery and Climate Experiment (GRACE are analysed to determine the seasonal displacements of surface loadings in the North China Plain (NCP. Results show significant seasonal variations and a strong correlation between GPS and GRACE results in the vertical displacement component; the average correlation and weighted root-mean-squares (WRMS reduction between GPS and GRACE are 75.6 and 28.9 % respectively, when atmospheric and non-tidal ocean effects were removed, but the annual peak-to-peak amplitude of GPS (1.2–6.3 mm is greater than the data (1.0–2.2 mm derived from GRACE. We also calculate the trend rate as well as the seasonal signal caused by the mass load change from GRACE data; the rate of GRACE-derived terrestrial water storage (TWS loss (after multiplying by the scaling factor in the NCP was 3.39 cm yr−1 (equivalent to 12.42 km3 yr−1 from 2003 to 2009. For a 10-year time span (2003 to 2012, the rate loss of TWS was 2.57 cm yr−1 (equivalent to 9.41 km3 yr−1, which is consistent with the groundwater storage (GWS depletion rate (the rate losses of GWS were 2.49 and 2.72 cm yr−1 during 2003–2009 and 2003–2012 respectively estimated from GRACE-derived results after removing simulated soil moisture (SM data from the Global Land Data Assimilation System (GLDAS/Noah model. We also found that GRACE-derived GWS changes are in disagreement with the groundwater level changes from observations of shallow aquifers from 2003 to 2009, especially between 2010 and 2013. Although the shallow groundwater can be recharged from the annual climate-driven rainfall, the important facts indicate that GWS depletion is more serious in deep aquifers. The GRACE-derived result shows an overall uplift in the whole region at the 0.37–0.95 mm yr−1 level from 2004 to 2009, but the rate of change direction is

  11. Retrieving hydrological signals from current and future gravity field missions

    Science.gov (United States)

    Pail, Roland; Horvath, Alexander

    2017-04-01

    The Global Geodetic Observing System is formed by three pillars: Changes in Earth's shape, gravity field and rotation. Dedicated satellite missions are crucial in the determination and monitoring of the Earth's gravity field. Monitoring the gravity field and studying mass transport phenomena, responsible for the temporal variability of the gravity field, are of high interest. Especially the hydrology is of importance since the mechanisms of water redistribution and unexpected events like floods and droughts can have significant socio-economic impact. The presented study investigates in the possibilities and limits of current space geodetic missions like GRACE to observe such effects. The main target of the study is to determine the potential gain in accuracy as well as spatial and temporal resolution of target signals like hydrological events, whilst operating future mission scenarios. The results from a series of comprehensive simulation runs are presented to demonstrate the benefits to society operating dedicated future space geodetic gravity field missions.

  12. GRACE era variability in the Earth's oblateness: a comparison of estimates from six different sources

    Science.gov (United States)

    Meyrath, Thierry; Rebischung, Paul; van Dam, Tonie

    2017-02-01

    We study fluctuations in the degree-2 zonal spherical harmonic coefficient of the Earth's gravity potential, C20, over the period 2003-2015. This coefficient is related to the Earth's oblateness and studying its temporal variations, ΔC20, can be used to monitor large-scale mass movements between high and low latitude regions. We examine ΔC20 inferred from six different sources, including satellite laser ranging (SLR), GRACE and global geophysical fluids models. We further include estimates that we derive from measured variations in the length-of-day (LOD), from the inversion of global crustal displacements as measured by GPS, as well as from the combination of GRACE and the output of an ocean model as described by Sun et al. We apply a sequence of trend and seasonal moving average filters to the different time-series in order to decompose them into an interannual, a seasonal and an intraseasonal component. We then perform a comparison analysis for each component, and we further estimate the noise level contained in the different series using an extended version of the three-cornered-hat method. For the seasonal component, we generally obtain a very good agreement between the different sources, and except for the LOD-derived series, we find that over 90 per cent of the variance in the seasonal components can be explained by the sum of an annual and semiannual oscillation of constant amplitudes and phases, indicating that the seasonal pattern is stable over the considered time period. High consistency between the different estimates is also observed for the intraseasonal component, except for the solution from GRACE, which is known to be affected by a strong tide-like alias with a period of about 161 d. Estimated interannual components from the different sources are generally in agreement with each other, although estimates from GRACE and LOD present some discrepancies. Slight deviations are further observed for the estimate from the geophysical models, likely to

  13. The average acceleration approach applied to gravity coefficients recovery based on GOCE orbits

    Directory of Open Access Journals (Sweden)

    Huang Qiang

    2012-11-01

    Full Text Available The average acceleration approach was applied to recover a gravity field model Model_ACA from GOCE precise science orbits from September 2 to November 2, 2010, and furthermore a so called sequential least square adjustment was used. The model was compared with other gravity field models based on CHAMP, GRACE and GOCE. The result shows that the model is superior to gravity field based on CHAMP, and with higher accuracy than other international gravity field models based on only GOCE data before 80 degree. The degree geoid height of Model_ACA reaches 3 cm up to 90 degree and order.

  14. Cosmological solutions of emergent noncommutative gravity.

    Science.gov (United States)

    Klammer, Daniela; Steinacker, Harold

    2009-06-01

    Matrix models of the Yang-Mills type lead to an emergent gravity theory, which does not require fine-tuning of a cosmological constant. We find cosmological solutions of the Friedmann-Robertson-Walker type. They generically have a big bounce, and an early inflationlike phase with graceful exit. The mechanism is purely geometrical; no ad hoc scalar fields are introduced. The solutions are stabilized through vacuum fluctuations and are thus compatible with quantum mechanics. This leads to a Milne-like universe after inflation, which appears to be in remarkably good agreement with observation and may provide an alternative to standard cosmology.

  15. Satellite gravity measurement monitoring terrestrial water storage change and drought in the continental United States

    Science.gov (United States)

    Yi, Hang; Wen, Lianxing

    2016-01-01

    We use satellite gravity measurements in the Gravity Recovery and Climate Experiment (GRACE) to estimate terrestrial water storage (TWS) change in the continental United States (US) from 2003 to 2012, and establish a GRACE-based Hydrological Drought Index (GHDI) for drought monitoring. GRACE-inferred TWS exhibits opposite patterns between north and south of the continental US from 2003 to 2012, with the equivalent water thickness increasing from -4.0 to 9.4 cm in the north and decreasing from 4.1 to -6.7 cm in the south. The equivalent water thickness also decreases by -5.1 cm in the middle south in 2006. GHDI is established to represent the extent of GRACE-inferred TWS anomaly departing from its historical average and is calibrated to resemble traditional Palmer Hydrological Drought Index (PHDI) in the continental US. GHDI exhibits good correlations with PHDI in the continental US, indicating its feasibility for drought monitoring. Since GHDI is GRACE-based and has minimal dependence of hydrological parameters on the ground, it can be extended for global drought monitoring, particularly useful for the countries that lack sufficient hydrological monitoring infrastructures on the ground.

  16. The Use of GOCE/GRACE Information in the Latest NGS xGeoid15 Model for the USA

    Science.gov (United States)

    Holmes, S. A.; Li, X.; Youngman, M.

    2015-12-01

    The U.S. National Geodetic Survey [NGS], through its Gravity for the Redefinition of the American Vertical Datum [GRAV-D] program, is flying airborne gravity surveys over the USA and its territories. By 2022, NGS intends that all orthometric heights in the USA will be determined in the field using a reliable national gravimetric geoid model to transform from geodetic heights obtained from GPS. Towards this end, all available airborne data has been incorporated into a new NGS experimental geoid model - xGEOID15. The xGEOID15 model is the second in a series of annual experimental geoid models that incorporates NGS GRAV-D airborne data. This series provides a useful benchmark for assessing and improving current techniques, to ultimately compute a geoid model that can support a national physical height system by 2022. Here, we focus on the combination of the latest GOCE/GRACE models with the terrestrial gravimetry (land/airborne) that was applied for xGeoid15. Comparisons against existing combination gravitational solutions, such as EGM2008 and EIGEN6C4, as well as recent geoid models, such as xGeoid14 and CGG2013, are interesting for what they reveal about the respective use of the GOCE/GRACE satgrav information.

  17. HYDROGRAV - Hydrological model calibration and terrestrial water storage monitoring from GRACE gravimetry and satellite altimetry, First results

    DEFF Research Database (Denmark)

    Andersen, O.B.; Krogh, P.E.; Michailovsky, C.

    2008-01-01

    Space-borne and ground-based time-lapse gravity observations provide new data for water balance monitoring and hydrological model calibration in the future. The HYDROGRAV project (www.hydrograv.dk) will explore the utility of time-lapse gravity surveys for hydrological model calibration and terre......Space-borne and ground-based time-lapse gravity observations provide new data for water balance monitoring and hydrological model calibration in the future. The HYDROGRAV project (www.hydrograv.dk) will explore the utility of time-lapse gravity surveys for hydrological model calibration...... and terrestrial water storage monitoring. Merging remote sensing data from GRACE with other remote sensing data like satellite altimetry and also ground based observations are important to hydrological model calibration and water balance monitoring of large regions and can serve as either supplement or as vital...... change from 2002 to 2008 along with in-situ gravity time-lapse observations and radar altimetry monitoring of surface water for the southern Africa river basins will be presented....

  18. Polar gravity fields from GOCE and airborne gravity

    DEFF Research Database (Denmark)

    Forsberg, René; Olesen, Arne Vestergaard; Yidiz, Hasan

    2011-01-01

    Airborne gravity, together with high-quality surface data and ocean satellite altimetric gravity, may supplement GOCE to make consistent, accurate high resolution global gravity field models. In the polar regions, the special challenge of the GOCE polar gap make the error characteristics...... of combination models especially sensitive to the correct merging of satellite and surface data. We outline comparisons of GOCE to recent airborne gravity surveys in both the Arctic and the Antarctic. The comparison is done to new 8-month GOCE solutions, as well as to a collocation prediction from GOCE gradients...... in Antarctica. It is shown how the enhanced gravity field solutions improve the determination of ocean dynamic topography in both the Arctic and in across the Drake Passage. For the interior of Antarctica, major airborne gravity programs are currently being carried out, and there is an urgent need...

  19. Study on Multi-scale Temporal Gravity Field in the Eastern Margin of Tibetan Plateau Based on Satellite Gravity%基于卫星重力的青藏高原东缘多尺度时变重力场研究

    Institute of Scientific and Technical Information of China (English)

    姜永涛; 张永志; 王帅; 刘国仕

    2014-01-01

    In this paper,we calculate annual satellite gravity changes in the eastern margin of the Tibetan Plateau from 2003 to 2012 by using the Gravity Recovery and Climate Experiment (GRACE)time-variable gravity field models with decorrelated filtering.By contraposing the three strong earthquakes that occurred recently in this region,including the Wenchuan MS8.0,Yushu MS 7.1,and Ya’an MS 7.0 earthquakes,we analyze the changes in satellite gravity field features re-lated to the strong earthquakes with the annual gravity changes before and after each earthquake. For analyzing the relationship between these earthquakes and the gravity change mode in detail, we also caculate the monthly gravity change for the Wenchuan MS 8.0 and Yushu MS 7.1 earth-quakes.Moreover,we use the recently relesed weekly GRACE gravity models to caculate the point-wise gravity change near Longmenshan fault for the Wenchuan MS 8.0 earthquake.The re-gional annual differentiated dynamic gravity changes image indicates that all three earthquakes oc-curred in a period of small gravity change,which means a small migration of crust-mantle material occurred according to the mantle convection theory.The same feature is indicated in the regional annual cumulative dynamic gravity changes image.These gravity changes likely indicate a medi-um-short term earthquake precursor.In the monthly differentiated dynamic gravity changes im-age,the gravity change mode shows significant changes in both the Wenchuan MS 8.0 earthquake and the Yushu MS 7.1 earthquake,which indicates that the gravity gradient change direction al-tered from perpendicular to the plane of a fault to parallel.These change in the gravity change mode may confirm the theory of post-earthquake potential field restoration.The nine points of the weekly gravity change sequences in Longmenshan fault area that occurred during 2008 indicate that a nearly nine-week contrary gravity change trend occurred between the eastern and western areas of the fault

  20. The unrealised ethical potential of the Methodist theology of prevenient grace

    Directory of Open Access Journals (Sweden)

    David N. Field

    2015-03-01

    Full Text Available This article examines the unrealised ethical potential of the theology of prevenient grace. It begins with a brief analysis of John Wesley’s rejection of slavery as rooted in his theology of prevenient grace. This is demonstrated in the next section which analyses Wesley’s notion of prevenient grace. This is followed by a constructive proposal for a contemporary theology of prevenient grace and some ethical implications of this theology, for contemporary social and political ethics, are developed.

  1. A high resolution model of linear trend in mass variations from DMT-2: Added value of accounting for coloured noise in GRACE data

    Science.gov (United States)

    Farahani, Hassan H.; Ditmar, Pavel; Inácio, Pedro; Didova, Olga; Gunter, Brian; Klees, Roland; Guo, Xiang; Guo, Jing; Sun, Yu; Liu, Xianglin; Zhao, Qile; Riva, Riccardo

    2017-01-01

    We present a high resolution model of the linear trend in the Earth's mass variations based on DMT-2 (Delft Mass Transport model, release 2). DMT-2 was produced primarily from K-Band Ranging (KBR) data of the Gravity Recovery And Climate Experiment (GRACE). It comprises a time series of monthly solutions complete to spherical harmonic degree 120. A novel feature in its production was the accurate computation and incorporation of stochastic properties of coloured noise when processing KBR data. The unconstrained DMT-2 monthly solutions are used to estimate the linear trend together with a bias, as well as annual and semi-annual sinusoidal terms. The linear term is further processed with an anisotropic Wiener filter, which uses full noise and signal covariance matrices. Given the fact that noise in an unconstrained model of the trend is reduced substantially as compared to monthly solutions, the Wiener filter associated with the trend is much less aggressive compared to a Wiener filter applied to monthly solutions. Consequently, the trend estimate shows an enhanced spatial resolution. It allows signals in relatively small water bodies, such as Aral sea and Ladoga lake, to be detected. Over the ice sheets, it allows for a clear identification of signals associated with some outlet glaciers or their groups. We compare the obtained trend estimate with the ones from the CSR-RL05 model using (i) the same approach based on monthly noise covariance matrices and (ii) a commonly-used approach based on the DDK-filtered monthly solutions. We use satellite altimetry data as independent control data. The comparison demonstrates a high spatial resolution of the DMT-2 linear trend. We link this to the usage of high-accuracy monthly noise covariance matrices, which is due to an accurate computation and incorporation of coloured noise when processing KBR data. A preliminary comparison of the linear trend based on DMT-2 with that computed from GSFC_global_mascons_v01 reveals, among

  2. Ocean contribution to seismic gravity changes: the sea level equation for seismic perturbations revisited

    Science.gov (United States)

    Broerse, Taco; Riva, Riccardo; Vermeersen, Bert

    2014-11-01

    During megathrust earthquakes, great ruptures are accompanied by large scale mass redistribution inside the solid Earth and by ocean mass redistribution due to bathymetry changes. These large scale mass displacements can be detected using the monthly gravity maps of the GRACE satellite mission. In recent years it has become increasingly common to use the long wavelength changes in the Earth's gravity field observed by GRACE to infer seismic source properties for large megathrust earthquakes. An important advantage of space gravimetry is that it is independent from the availability of land for its measurements. This is relevant for observation of megathrust earthquakes, which occur mostly offshore, such as the M_{text{w}} ˜ 9 2004 Sumatra-Andaman, 2010 Maule (Chile) and 2011 Tohoku-Oki (Japan) events. In Broerse et al., we examined the effect of the presence of an ocean above the rupture on long wavelength gravity changes and showed it to be of the first order. Here we revisit the implementation of an ocean layer through the sea level equation and compare the results with approximated methods that have been used in the literature. One of the simplifications usually lies in the assumption of a globally uniform ocean layer. We show that especially in the case of the 2010 Maule earthquake, due to the closeness of the South American continent, the uniform ocean assumption is not valid and causes errors up to 57 per cent for modelled peak geoid height changes (expressed at a spherical harmonic truncation degree of 40). In addition, we show that when a large amount of slip occurs close to the trench, horizontal motions of the ocean floor play a mayor role in the ocean contribution to gravity changes. Using a slip model of the 2011 Tohoku-Oki earthquake that places the majority of slip close to the surface, the peak value in geoid height change increases by 50 per cent due to horizontal ocean floor motion. Furthermore, we test the influence of the maximum spherical

  3. Measuring the Change in Water Table with Gravity Methods - a Controlled Experiment

    DEFF Research Database (Denmark)

    Lund, S; Christiansen, Lars; Andersen, O. B.;

    2009-01-01

    Gravity changes linearly with the change in soil water content. With the GRACE satellite mission the interest for ground-based gravity methods in hydrology has gained new attention. Time-lapse gravity data have the potential to constrain hydrological model parameters in a calibration scheme...... in water content, a controlled experiment was set up in 30 m by 20 m basin. The water table was lowered 0.69 m within 1½ hours and the corresponding gravity signal measured using two different approaches: a time series measurements at one location and a gravity network measurement including four points....... Both where in agreement with the calculated maximum theoretical gravity change of 27*10^-8 m/s^2. Uncertainties on the change in gravity in the network measurements where 4*10^-8 m/s^2 (one standard deviation). This corresponds to an infinite horizontal slab of water with a thickness of 0.1 m. The time...

  4. 一类优美树%A Class of Graceful Trees

    Institute of Scientific and Technical Information of China (English)

    孟凡洪; 苏耘; 杨继

    2000-01-01

    The present paper shows the coordinates of a tree and its vertices, defines a kind of Trees with Odd-Number Radiant Type (TONRT), deals with the gracefulness of TONRT by using the edge-moving theorem, and uses graceful TONRT to construct another class of graceful trees.

  5. Modes of Arctic Ocean Change from GRACE, ICESat and the PIOMAS and ECCO2 Models of the Arctic Ocean

    Science.gov (United States)

    Peralta Ferriz, C.; Morison, J. H.; Bonin, J. A.; Chambers, D. P.; Kwok, R.; Zhang, J.

    2012-12-01

    EOF analysis of month-to-month variations in GRACE derived Arctic Ocean bottom pressure (OBP) with trend and seasonal variation removed yield three dominant modes. The first mode is a basin wide variation in mass associated with high atmospheric pressure (SLP) over Scandinavia mainly in winter. The second mode is a shift of mass from the central Arctic Ocean to the Siberian shelves due to low pressure over the basins, associated with the Arctic Oscillation. The third mode is a shift in mass between the Eastern and Western Siberian shelves, related to strength of the Beaufort High mainly in summer, and to eastward alongshore winds on the Barents Sea in winter. The PIOMAS and ECCO2 modeled OBP show fair agreement with the form of these modes and provide context in terms of variations in sea surface height SSH. Comparing GRACE OBP from 2007 to 2011 with GRACE OBP from 2002 to 2006 reveals a rising trend over most of the Arctic Ocean but declines in the Kara Sea region and summer East Siberian Sea. ECCO2 bears a faint resemblance to the observed OBP change but appears to be biased negatively. In contrast, PIOMAS SSH and ECCO2 especially, show changes between the two periods that are muted but similar to ICESat dynamic ocean topography and GRACE-ICESat freshwater trends from 2005 through 2008 [Morison et al., 2012] with a rising DOT and freshening in the Beaufort Sea and a trough with decreased freshwater on the Russian side of the Arctic Ocean. Morison, J., R. Kwok, C. Peralta-Ferriz, M. Alkire, I. Rigor, R. Andersen, and M. Steele (2012), Changing Arctic Ocean freshwater pathways, Nature, 481(7379), 66-70.

  6. Improved estimates of global sea level change from Ice Sheets, glaciers and land water storage using GRACE

    Science.gov (United States)

    Velicogna, I.; Hsu, C. W.; Ciraci, E.; Sutterley, T. C.

    2015-12-01

    We use observations of time variable gravity from GRACE to estimate mass changes for the Antarctic and Greenland Ice Sheets, the Glaciers and Ice Caps (GIC) and land water storage for the time period 2002-2015 and evaluate their total contribution to sea level. We calculate regional sea level changes from these present day mass fluxes using an improved scaling factor for the GRACE data that accounts for the spatial and temporal variability of the observed signal. We calculate a separate scaling factor for the annual and the long-term components of the GRACE signal. To estimate the contribution of the GIC, we use a least square mascon approach and we re-analyze recent inventories to optimize the distribution of mascons and recover the GRACE signal more accurately. We find that overall, Greenland controls 43% of the global trend in eustatic sea level rise, 16% for Antarctica and 29% for the GIC. The contribution from the GIC is dominated by the mass loss of the Canadian Arctic Archipelago, followed by Alaska, Patagonia and the High Mountains of Asia. We report a marked increase in mass loss for the Canadian Arctic Archipelago. In Greenland, following the 2012 high summer melt, years 2013 and 2014 have slowed down the increase in mass loss, but our results will be updated with summer 2015 observations at the meeting. In Antarctica, the mass loss is still on the rise with increased contributions from the Amundsen Sea sector and surprisingly from the Wilkes Land sector of East Antarctica, including Victoria Land. Conversely, the Queen Maud Land sector experienced a large snowfall in 2009-2013 and has now resumed to a zero mass gain since 2013. We compare sea level changes from these GRACE derived mass fluxes after including the atmospheric and ocean loading signal with sea level change from satellite radar altimetry (AVISO) corrected for steric signal of the ocean using Argo measurements and find an excellent agreement in amplitude, phase and trend in these estimates

  7. Gravity investigations

    Energy Technology Data Exchange (ETDEWEB)

    Healey, D.L. [Geological Survey, Denver, CO (USA)

    1983-12-31

    A large density contrast exists between the Paleozoic rocks (including the rocks of Climax stock) and less dense, Tertiary volcanic rocks and alluvium. This density contrast ranges widely, and herein for interpretive purposes, is assumed to average 0.85 Mg/m{sup 3} (megagrams per cubic meter). The large density contrast makes the gravity method a useful tool with which to study the interface between these rock types. However, little or no density contrast is discernible between the sedimentary Paleozoic rocks that surround the Climax stock and the intrusive rocks of the stock itself. Therefore the gravity method can not be used to define the configuration of the stock. Gravity highs coincide with outcrops of the dense Paleozoic rocks, and gravity lows overlie less-dense Tertiary volcanic rocks and Quaternary alluvium. The positions of three major faults (Boundary, Yucca, and Butte faults) are defined by steep gravity gradients. West of the Climax stock, the Tippinip fault has juxtaposed Paleozoic rocks of similar density, and consequently, has no expression in the gravity data in that area. The gravity station spacing, across Oak Spring Butte, is not sufficient to adequately define any gravity expression of the Tippinip fault. 18 refs., 5 figs.

  8. Nonlocal gravity

    CERN Document Server

    Mashhoon, Bahram

    2017-01-01

    Relativity theory is based on a postulate of locality, which means that the past history of the observer is not directly taken into account. This book argues that the past history should be taken into account. In this way, nonlocality---in the sense of history dependence---is introduced into relativity theory. The deep connection between inertia and gravitation suggests that gravity could be nonlocal, and in nonlocal gravity the fading gravitational memory of past events must then be taken into account. Along this line of thought, a classical nonlocal generalization of Einstein's theory of gravitation has recently been developed. A significant consequence of this theory is that the nonlocal aspect of gravity appears to simulate dark matter. According to nonlocal gravity theory, what astronomers attribute to dark matter should instead be due to the nonlocality of gravitation. Nonlocality dominates on the scale of galaxies and beyond. Memory fades with time; therefore, the nonlocal aspect of gravity becomes wea...

  9. Ice Mass Change in Greenland and Antarctica Between 1993 and 2013 from Satellite Gravity Measurements

    Science.gov (United States)

    Talpe, Matthieu J.; Nerem, R. Steven; Forootan, Ehsan; Schmidt, Michael; Lemoine, Frank G.; Enderlin, Ellyn M.; Landerer, Felix W.

    2017-01-01

    We construct long-term time series of Greenland and Antarctic ice sheet mass change from satellite gravity measurements. A statistical reconstruction approach is developed based on a principal component analysis (PCA) to combine high-resolution spatial modes from the Gravity Recovery and Climate Experiment (GRACE) mission with the gravity information from conventional satellite tracking data. Uncertainties of this reconstruction are rigorously assessed; they include temporal limitations for short GRACE measurements, spatial limitations for the low-resolution conventional tracking data measurements, and limitations of the estimated statistical relationships between low- and high-degree potential coefficients reflected in the PCA modes. Trends of mass variations in Greenland and Antarctica are assessed against a number of previous studies. The resulting time series for Greenland show a higher rate of mass loss than other methods before 2000, while the Antarctic ice sheet appears heavily influenced by interannual variations.

  10. Analysis of GRACE Range-rate Residuals with Emphasis on Reprocessed Star-Camera Datasets

    Science.gov (United States)

    Goswami, S.; Flury, J.; Naeimi, M.; Bandikova, T.; Guerr, T. M.; Klinger, B.

    2015-12-01

    Since March 2002 the two GRACE satellites orbit the Earth at rela-tively low altitude. Determination of the gravity field of the Earth including itstemporal variations from the satellites' orbits and the inter-satellite measure-ments is the goal of the mission. Yet, the time-variable gravity signal has notbeen fully exploited. This can be seen better in the computed post-fit range-rateresiduals. The errors reflected in the range-rate residuals are due to the differ-ent sources as systematic errors, mismodelling errors and tone errors. Here, weanalyse the effect of three different star-camera data sets on the post-fit range-rate residuals. On the one hand, we consider the available attitude data andon other hand we take the two different data sets which has been reprocessedat Institute of Geodesy, Hannover and Institute of Theoretical Geodesy andSatellite Geodesy, TU Graz Austria respectively. Then the differences in therange-rate residuals computed from different attitude dataset are analyzed inthis study. Details will be given and results will be discussed.

  11. Using tesseroid mascons to improve the estimations of water-mass variations with GRACE

    Science.gov (United States)

    Fereria, Vagner; Heck, Bernhard; Seitz, Kurt; Grombein, Thomas

    2016-04-01

    Observing and monitoring the different components of the hydrological cycle and their dynamics are essential steps to understand and predict natural disasters like floods and droughts, all of which periodically occur worldwide. Nevertheless, in the absence of ground-based measurements as, for example, in Africa and South America, space-borne geodetic sensors offers an opportunity for monitoring the temporal variations of the terrestrial water storage (TWS). However, the TWS fields - inverted from the temporal variations of the gravity field - are generally computed based on a global solution, which has not exploited the fundamental resolution of the satellite gravimetry observations. Thus, in order to overcome the deficiencies of global solutions based on spherical harmonic coefficients, results of TWS can be inverted from a regional recovery approach considering the in-situ measurements of Gravity Recovery and Climate Experiment (GRACE) mission. To this end, an approach based on the tesseroids is proposed to compute the TWS, expressed as equivalent water heights, from the gravitational potential at the altitude of the spacecraft.

  12. Gravitacijske satelitske misije : Satellite gravity missions

    Directory of Open Access Journals (Sweden)

    Medžida Mulić

    2012-12-01

    Full Text Available Sila teže se smatra osnovnom fizikalnom silom u prirodi. Savremene satelitske misije: CHAMP, GRACE i GOCE omogućile su dobivanje globalnih modela polja sile teže s veoma visokom tačnošću, kao i njegovih prostornih i temporalnih varijacija. U ovom radu istaknuti su ciljevi, karakteristike i rezultati navedenih misija, te iznesena očekivanja u budućnosti, kao i njihov značaj i doprinos za geodetsku praksu kao i istraživanja u oblasti geodezije, geofizike i hidrologije. : Gravity is considered as the basic physical force in the nature. Modern satellite missions: CHAMP, GRACE and GOCE allowed modeling of the global gravity field with very high accuracy, as well as its spatial and temporal variations. This paper describes the main objectives, characteristics, the latest results of these missions, as well as the expectations of the future observations, and their importance and contributions for the surveying and geodetic practice, and scientific achievements as well, in geodesy, geophysics and hydrology.

  13. Progress on Antarctic Glacial Isostatic Adjustment and GRACE constraints on ice loss (Invited)

    Science.gov (United States)

    Ivins, E. R.; James, T. S.; Wahr, J. M.; Schrama, E. J.; Simon, K. M.; Landerer, F. W.; Watkins, M. M.; Wiese, D. N.

    2013-12-01

    Preparations for the Intergovermental Panel on Climate Change: Assessment Report 5 (IPCC AR5) has placed pressure on various research groups to accelerate the pace of their work in order to meet the Report deadlines. While this stimulates both positive and negative bi-products, it helped to focus attention to irreconcilable mass balance determinations for the Antarctic Ice Sheet (AIS) using space and airborne data. A glaring ';sore-thumb' for determining AIS trends from Gravity Recovery and Climate Experiment (GRACE) satellite data is the large signal of glacial isostatic adjustment (GIA) that is poorly constrained and possibly of the same magnitude as the present-day mass change. The report published in Science (vol. 338, pp. 1183-89) by S13 [Shepherd et al. 2013] met this challenge head-on by investing heavily in improving the GIA models with new GPS data, and new chronological constraints on ice sheet evolution across the Antarctic continent. This new data has emerged only within the last five years, and it came at a fortuitous time for advancing the IPCC AR5 goals. In this presentation we speak to the improvements developed in a recent JGR Solid Earth publication (14 June 2013). We extend the analysis using all of the official 05 releases of the analysis centers, including the JPL-mascon fields. The total error budgets of GIA correction are poorly determined, in spite of the great model improvements witnessed in the past 5 years. S12 reported the uncertainty for space-based sea level sourcing during 1992-2011 to Antarctica at roughly 0.23 mm/yr. Although GRACE 2002-2013 estimates vary, the uncertainly is about half this value. Here we examine how much of that uncertainty is still caused by GIA models and discuss how new classes of GIA models, and the collection of yet new GPS and ice constraint data for Antarctica, will enhance the value of a GRACE Follow-On mission. However, there will be a limit to constraining GIA, and a limit, therefore, to GIA error due to

  14. Estimating a Global Hydrological Carrying Capacity Using GRACE Observed Water Stress

    Science.gov (United States)

    An, K.; Reager, J. T.; Famiglietti, J. S.

    2013-12-01

    Global population is expected to reach 9 billion people by the year 2050, causing increased demands for water and potential threats to human security. This study attempts to frame the overpopulation problem through a hydrological resources lens by hypothesizing that observed groundwater trends should be directly attributed to human water consumption. This study analyzes the relationships between available blue water, population, and cropland area on a global scale. Using satellite data from NASA's Gravity Recovery and Climate Experiment (GRACE) along with land surface model data from the Global Land Data Assimilation System (GLDAS), a global groundwater depletion trend is isolated, the validity of which has been verified in many regional studies. By using the inherent distributions of these relationships, we estimate the regional populations that have exceeded their local hydrological carrying capacity. Globally, these populations sum to ~3.5 billion people that are living in presently water-stressed or potentially water-scarce regions, and we estimate total cropland is exceeding a sustainable threshold by about 80 million km^2. Key study areas such as the North China Plain, northwest India, and Mexico City were qualitatively chosen for further analysis of regional water resources and policies, based on our distributions of water stress. These case studies are used to verify the groundwater level changes seen in the GRACE trend . Tfor the many populous, arid regions of the world that have already begun to experience the strains of high water demand.he many populous, arid regions of the world have already begun to experience the strains of high water demand. It will take a global cooperative effort of improving domestic and agricultural use efficiency, and summoning a political will to prioritize environmental issues to adapt to a thirstier planet. Global Groundwater Depletion Trend (Mar 2003-Dec 2011)

  15. Evaluation of multiple satellite evaporation products in two dryland regions using GRACE

    KAUST Repository

    Lopez, Oliver

    2015-12-01

    Remote sensing has become a valuable tool for monitoring the water cycle variables in areas that lack the availability of ground-based measurements. Integrating multiple remote sensing-based estimates of evaporation, precipitation, and the terrestrial water storage changes with local measurements of streamflow into a consistent estimate of the regional water budget is a challenge, due to the scale mismatch among the retrieved variables. Evapotranspiration, including soil evaporation, interception losses and canopy transpiration, has received special focus in a number of recent studies that aim to provide global or regional estimates of evaporation at regular time intervals using a variety of remote sensing input. In arid and semi-arid regions, modeling of evaporation is particularly challenging due to the relatively high role of the soil evaporation component in these regions and the variable nature of rainfall events that drive the evaporation process. In this study, we explore the hydrological consistency of remote sensing products in terms of water budget closure and the correlation among spatial patterns of precipitation (P), evaporation (E) and terrestrial water storage, using P-E as a surrogate of water storage changes, with special attention to the evaporation component. The analysis is undertaken within two dryland regions that have presented recent significant changes in climatology (Murray-Darling Basin in Australia) and water storage (the Saq aquifer in northern Saudi Arabia). Water storage changes were derived from the Gravity Recovery and Climate Experiment (GRACE) spherical harmonic (SH) coefficients. Six remote sensing-based evaporation estimates were subtracted from the Global Precipitation Climatology Project (GPCP)-based precipitation estimates and were compared with GRACE-derived water storage changes. Our results suggest that it is not possible to close the water balance by using satellite data alone, even when adopting a spherical harmonic

  16. Artificial Gravity

    CERN Document Server

    Clément, Gilles

    2007-01-01

    Protecting the health, safety, and performance of exploration-class mission crews against the physiological deconditioning resulting from long-term weightlessness during transit and long-term reduced gravity during surface operations will require effective, multi-system countermeasures. Artificial gravity, which would replace terrestrial gravity with inertial forces generated by rotating the transit vehicle or by short-radius human centrifuge devices within the transit vehicle or surface habitat, has long been considered a potential solution. However, despite its attractiveness as an efficient

  17. Globally gridded terrestrial water storage variations from GRACE satellite gravimetry for hydrometeorological applications

    Science.gov (United States)

    Zhang, Liangjing; Dobslaw, Henryk; Thomas, Maik

    2016-07-01

    Globally gridded estimates of monthly-mean anomalies of terrestrial water storage (TWS) are estimated from the most recent GRACE release 05a of GFZ Potsdam in order to provide non-geodetic users a convenient access to state-of-the-art GRACE monitoring data. We use an ensemble of five global land model simulations with different physics and different atmospheric forcing to obtain reliable gridded scaling factors required to correct for spatial leakage introduced during data processing. To allow for the application of this data-set for large-scale monitoring tasks, model validation efforts, and subsequently also data assimilation experiments, globally gridded estimates of TWS uncertainties that include (i) measurement, (ii) leakage and (iii) re-scaling errors are provided as well. The results are generally consistent with the gridded data provided by Tellus, but deviate in some basins which are largely affected by the uncertainties of the model information required for re-scaling, where the approach based on the median of a small ensemble of global land models introduced in this paper leads to more robust results.

  18. Saving Grace - A Climate Change Documentary Education Program

    Science.gov (United States)

    Byrne, J. M.; McDaniel, S.; Graham, J.; Little, L.; Hoggan, J. C.

    2012-12-01

    Saving Grace conveys climate change knowledge from the best international scientists and social scientists using a series of new media formats. An Education and Communication Plan (ECP) has been developed to disseminate climate change knowledge on impacts, mitigation and adaptation for individuals, and for all sectors of society. The research team is seeking contacts with science and social science colleagues around the world to provide the knowledge base for the ECP. Poverty enslaves…and climate change has, and will, spread and deepen poverty to hundreds of millions of people, primarily in the developing world. And make no mistake; we are enslaving hundreds of millions of people in a depressing and debilitating poverty that in numbers will far surpass the horrors of the slave trade of past centuries. Saving Grace is the story of that poverty - and minimizing that poverty. Saving Grace stars the best of the world's climate researchers. Saving Grace presents the science; who, where and why of greenhouse gases that drive climate change; current and projected impacts of a changing climate around the world; and most important, solutions to the climate change challenges we face.

  19. A comparison of coincident GRACE and ICESat data over Antarctica

    NARCIS (Netherlands)

    Gunter, B.; Urban, T.; Riva, R.E.M.; Helsen, M.M.; Harpold, R.; Poole, S.; Nagel, P.; Schutz, B.; Tapley, B.

    2009-01-01

    In this study, we present a comparison of coincident GRACE and ICESat data over Antarctica. The analysis focused on the secular changes over a 4-year period spanning from 2003 to 2007, using the recently reprocessed and publicly available data sets for both missions. The results show that the two in

  20. In between St. Augustine and Luther: Grace and justification

    Directory of Open Access Journals (Sweden)

    Michael M. Ramos

    2014-12-01

    Full Text Available The view presented in this study emphasized grace as a cause of spiritual strength and justification of man. In understanding the deep meaning and nature of grace, this paper analyzes the formations given on the subject by two great minds, St. Augustine and Martin Luther. Because of the great influence of their work on the theology of grace and justification, this paper attempts to seek whether man’s understanding and belief of prudence would mean nothing at all, that any good that he will perform on his behalf would do nothing for his own justification. Thus it raises the question on the purpose of man’s freedom if his proprium is nothing and that divine prudence is the source of everything good. This led to the idea that grace is the primary energy source of man to make good, not by his own, but by divine prudence to obtain justification. Therefore, in this sense there is nothing good in man.

  1. GRACE and the development of an education and training curriculum.

    Science.gov (United States)

    Finch, R G; Blasi, F B; Verheij, T J M; Goossens, H; Coenen, S; Loens, K; Rohde, G; Saenz, H; Akova, M

    2012-09-01

    Antimicrobial resistance is a serious threat and compromises the management of infectious disease. This has particular significance in relation to infections of the respiratory tract, which are the lead cause of antibiotic prescribing. Education is fundamental to the correct use of antibiotics. A novel open access curriculum has been developed in the context of a European Union funded research project Genomics to combat Resistance against Antibiotics in Community-acquired lower respiratory tract infections in Europe (GRACE http://www.grace-lrti.org). The curriculum was developed in modular format and populated with clinical and scientific topics relevant to community-acquired lower respiratory tract infections. This curriculum informed the content of a series of postgraduate courses and workshops and permitted the creation of an open access e-Learning portal. A total of 153 presentations matching the topics within the curriculum together with slide material and handouts and 104 webcasts are available through the GRACE e-Learning portal, which is fully searchable using a 'mindmap' to navigate the contents. Metrics of access provided a means for assessing usage. The GRACE project has permitted the development of a unique on-line open access curriculum that comprehensively addresses the issues relevant to community-acquired lower respiratory tract infections and has provided a resource not only for personal learning, but also to support independent teaching activities such as lectures, workshops, seminars and course work. © 2012 The Authors. Clinical Microbiology and Infection © 2012 European Society of Clinical Microbiology and Infectious Diseases.

  2. DRAGraces: An open source pipeline to extract your GRACES data!

    Science.gov (United States)

    Chené, André-Nicolas

    2017-01-01

    Written in IDL, the DRAGraces pipeline is designed to reduce and extract data from the Gemini high-resolution spectrograph GRACES*. It is barely more than a thousand lines long, and everyone is invited to download, use and modify it as needed (https://github.com/AndreNicolasChene/DRAGRACES/releases/tag/1.0.1).This poster details how to retrieve observed GRACES data from the Gemini Observatory Archive, and explains how to run DRAGraces. It also describes the pipeline's steps, capability and performances. It is recommended to use this code and/or the other open soure pipeline, OPERA, to obtain an optimized extraction of GRACES data, before publication. It is the best way to keep control on all the reduction steps, most importantly calibration.*Gemini Remote Access to CFHT ESPaDOnS Spectrograph (GRACES) is the result of a cooperation between the Canada-France-Hawaii Telescope (CFHT), Gemini, and NRC-Herzberg (Canada). It combines the large collecting area of the Gemini North telescope with the high resolving power and high efficiency of the ESPaDOnS spectrograph at CFHT, to deliver high resolution spectroscopy across the optical region. This is achieved through a 270 m fiber optics feed from the Gemini North telescope to ESPaDOnS.

  3. "Amazing Grace": Literature as a Window on Colonial Slavery.

    Science.gov (United States)

    Basker, James G.

    2003-01-01

    Describes the book, "Amazing Grace: An Anthology of Poems about Slavery 1660-1810." Presents poems, written by 250 writers, that focus on slavery during the 150 year period. Provides examples of materials included in this book and how it can enable students to increase their understanding of slavery. (CMK)

  4. Graceful Degradation: A C2 Design Virtue for Our Times

    Science.gov (United States)

    2013-06-01

    Resistance to change Resistance to uncertainty Redundancy Active... Resistance to change Resistance to uncertainty Redundancy Active Passive Type Action System Resilience Graceful Degradation System...Technology) 2. Software (Doctrine, procedures, instructions) 3. The human interface between hardware & software 2 Robustness Resistance to change

  5. Gravity brake

    Science.gov (United States)

    Lujan, Richard E.

    2001-01-01

    A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.

  6. Gravity waves

    Science.gov (United States)

    Fritts, David

    1987-02-01

    Gravity waves contributed to the establishment of the thermal structure, small scale (80 to 100 km) fluctuations in velocity (50 to 80 m/sec) and density (20 to 30%, 0 to peak). Dominant gravity wave spectrum in the middle atmosphere: x-scale, less than 100 km; z-scale, greater than 10 km; t-scale, less than 2 hr. Theorists are beginning to understand middle atmosphere motions. There are two classes: Planetary waves and equatorial motions, gravity waves and tidal motions. The former give rise to variability at large scales, which may alter apparent mean structure. Effects include density and velocity fluctuations, induced mean motions, and stratospheric warmings which lead to the breakup of the polar vortex and cooling of the mesosphere. On this scale are also equatorial quasi-biennial and semi-annual oscillations. Gravity wave and tidal motions produce large rms fluctuations in density and velocity. The magnitude of the density fluctuations compared to the mean density is of the order of the vertical wavelength, which grows with height. Relative density fluctuations are less than, or of the order of 30% below the mesopause. Such motions may cause significant and variable convection, and wind shear. There is a strong seasonal variation in gravity wave amplitude. Additional observations are needed to address and quantify mean and fluctuation statistics of both density and mean velocity, variability of the mean and fluctuations, and to identify dominant gravity wave scales and sources as well as causes of variability, both temporal and geographic.

  7. Accurate and rapid error estimation on global gravitational field from current GRACE and future GRACE Follow-On missions

    Institute of Scientific and Technical Information of China (English)

    Zheng Wei; Hsu Hou-Tse; Zhong Min; Yun Mei-Juan

    2009-01-01

    Firstly,the new combined error model of cumulative geoid height influenced by four error sources,including the inter-satellite range-rate of an interferometric laser (K-band) ranging system,the orbital position and velocity of a global positioning system (GPS) receiver and non-conservative force of an accelerometer,is established from the perspectives of the power spectrum principle in physics using the semi-analytical approach.Secondly,the accuracy of the global gravitational field is accurately and rapidly estimated based on the combined error model; the cumulative geoid height error is 1.985×10-1 m at degree 120 based on GRACE Level 1B measured observation errors of the year 2007 published by the US Jet Propulsion Laboratory (JPL),and the cumulative geoid height error is 5.825×10-2 m at degree 360 using GRACE Follow-On orbital altitude 250 km and inter-satellite range 50 km.The matching relationship of accuracy indexes from GRACE Follow-On key payloads is brought forward,and the dependability of the combined error model is validated.Finally,the feasibility of high-accuracy and high-resolution global gravitational field estimation from GRACE Follow-On is demonstrated based on different satellite orbital altitudes.

  8. Past terrestrial water storage (1980–2008 in the Amazon Basin reconstructed from GRACE and in situ river gauging data

    Directory of Open Access Journals (Sweden)

    M. Becker

    2011-02-01

    Full Text Available Terrestrial water storage (TWS composed of surface waters, soil moisture, groundwater and snow where appropriate, is a key element of global and continental water cycle. Since 2002, the Gravity Recovery and Climate Experiment (GRACE space gravimetry mission provides a new tool to measure large-scale TWS variations. However, for the past few decades, direct estimate of TWS variability is accessible from hydrological modeling only. Here we propose a novel approach that combines GRACE-based TWS spatial patterns with multi-decadal-long in situ river level records, to reconstruct past 2-D TWS over a river basin. Results are presented for the Amazon Basin for the period 1980–2008, focusing on the interannual time scale. Results are compared with past TWS estimated by the global hydrological model ISBA-TRIP. Correlations between reconstructed past interannual TWS variability and known climate forcing modes over the region (e.g., El Niño-Southern Oscillation and Pacific Decadal Oscillation are also estimated. This method offers new perspective for improving our knowledge of past interannual TWS in world river basins where natural climate variability (as opposed to direct anthropogenic forcing drives TWS variations.

  9. Validation of terrestrial water storage variations as simulated by different global numerical models with GRACE satellite observations

    Science.gov (United States)

    Zhang, Liangjing; Dobslaw, Henryk; Stacke, Tobias; Güntner, Andreas; Dill, Robert; Thomas, Maik

    2017-02-01

    Estimates of terrestrial water storage (TWS) variations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are used to assess the accuracy of four global numerical model realizations that simulate the continental branch of the global water cycle. Based on four different validation metrics, we demonstrate that for the 31 largest discharge basins worldwide all model runs agree with the observations to a very limited degree only, together with large spreads among the models themselves. Since we apply a common atmospheric forcing data set to all hydrological models considered, we conclude that those discrepancies are not entirely related to uncertainties in meteorologic input, but instead to the model structure and parametrization, and in particular to the representation of individual storage components with different spatial characteristics in each of the models. TWS as monitored by the GRACE mission is therefore a valuable validation data set for global numerical simulations of the terrestrial water storage since it is sensitive to very different model physics in individual basins, which offers helpful insight to modellers for the future improvement of large-scale numerical models of the global terrestrial water cycle.

  10. Using GRACE-Derived Water and Moisture Products as a Predictive Tool for Fire Response in the Contiguous United States

    Science.gov (United States)

    Rousseau, N. J.; Jensen, D.; Zajic, B.; Rodell, M.; Reager, J. T., II

    2015-12-01

    Understanding the relationship between wildfire activity and soil moisture in the United States has been difficult to assess, with limited ability to determine areas that are at high risk. This limitation is largely due to complex environmental factors at play, especially as they relate to alternating periods of wet and dry conditions, and the lack of remotely-sensed products. Recent drought conditions and accompanying low Fuel Moisture Content (FMC) have led to disastrous wildfire outbreaks causing economic loss, property damage, and environmental degradation. Thus, developing a programmed toolset to assess the relationship between soil moisture, which contributes greatly to FMC and fire severity, can establish the framework for determining overall wildfire risk. To properly evaluate these parameters, we used data assimilated from the Gravity Recovery and Climate Experiment (GRACE) and data from the Fire Program Analysis fire-occurrence database (FPA FOD) to determine the extent soil moisture affects fire activity. Through these datasets, we produced correlation and regression maps at a coarse resolution of 0.25 degrees for the contiguous United States. These fire-risk products and toolsets proved the viability of this methodology, allowing for the future incorporation of more GRACE-derived water parameters, MODIS vegetation indices, and other environmental datasets to refine the model for fire risk. Additionally, they will allow assessment to national-scale early fire management and provide responders with a predictive tool to better employ early decision-support to areas of high risk during regions' respective fire season(s).

  11. Dynamical effects of General Relativity on the satellite-to-satellite range and range-rate in the GRACE mission

    CERN Document Server

    Iorio, Lorenzo

    2010-01-01

    We numerically investigate the impact of the General Theory of Relativity (GTR) on the satellite-to-satellite range \\rho and range-rate \\dot\\rho of the twin GRACE A/B spacecrafts through their dynamical equations of motion. The present-day accuracies in measuring such observables are \\sigma_\\rho <= 1-10 micron, \\sigma_\\dot\\rho <= 1 micron s^-1. Studies for a follow-on of such a mission points toward a range-rate accuracy of the order of \\sigma_\\dot\\rho = 1 nm s^-1 or better. We also compute the dynamical range and range-rate perturbations caused by the first six zonal harmonic coefficients J_L, L=2,3,4,5,6,7$ of the classical multipolar expansion of the terrestrial gravitational potential in order to evaluate their aliasing impact on the relativistic effects. Conversely, we also quantitatively assessed the possible a-priori \\virg{imprinting} of GTR itself, not solved-for in all the GRACE-based Earth's gravity models produced so far, on the estimated values of the low degree zonals of the geopotential. T...

  12. $BF$ gravity

    CERN Document Server

    Celada, Mariano; Montesinos, Merced

    2016-01-01

    $BF$ gravity comprises all the formulations of gravity that are based on deformations of $BF$ theory. Such deformations consist of either constraints or potential terms added to the topological $BF$ action that turn some of the gauge degrees of freedom into physical ones, particularly giving rise to general relativity. The $BF$ formulations have provided new and deep insights into many classical and quantum aspects of the gravitational field, setting the foundations for the approach to quantum gravity known as spinfoam models. In this review, we present a self-contained and unified treatment of the $BF$ formulations of $D$-dimensional general relativity and other related models, focusing on the classical aspects of them and including some new results.

  13. Quantum gravity

    CERN Document Server

    Kiefer, Claus

    2012-01-01

    The search for a quantum theory of the gravitational field is one of the great open problems in theoretical physics. This book presents a self-contained discussion of the concepts, methods and applications that can be expected in such a theory. The two main approaches to its construction - the direct quantisation of Einstein's general theory of relativity and string theory - are covered. Whereas the first attempts to construct a viable theory for the gravitational field alone, string theory assumes that a quantum theory of gravity will be achieved only through a unification of all the interactions. However, both employ the general method of quantization of constrained systems, which is described together with illustrative examples relevant for quantum gravity. There is a detailed presentation of the main approaches employed in quantum general relativity: path-integral quantization, the background-field method and canonical quantum gravity in the metric, connection and loop formulations. The discussion of stri...

  14. BF gravity

    Science.gov (United States)

    Celada, Mariano; González, Diego; Montesinos, Merced

    2016-11-01

    BF gravity comprises all the formulations of gravity that are based on deformations of BF theory. Such deformations consist of either constraints or potential terms added to the topological BF action that turn some of the gauge degrees of freedom into physical ones, particularly giving rise to general relativity. The BF formulations have provided new and deep insights into many classical and quantum aspects of the gravitational field, setting the foundations for the approach to quantum gravity known as spinfoam models. In this review, we present a self-contained and unified treatment of the BF formulations of D-dimensional general relativity and other related models, focusing on the classical aspects of them and including some new results.

  15. Improved regional sea-level estimates from present day mass fluxes from Ice Sheets, Glaciers and land water using GRACE

    Science.gov (United States)

    Hsu, C. W.; Velicogna, I.

    2016-02-01

    Changes in ice sheets, glaciers and ice caps (GIC) and land water mass cause regional sea level variations that differ significantly from a uniform sea level, with a decrease in sea level near the sources of mass added to the ocean and an increase up to 30% larger than the global mean sea level in the far field. This effect called sea level fingerprints (SLF) are difficult to separate from the variation from ocean dynamics on short time and spatial scales. Most studies removed the uniform sea level to avoid this additional mass flux from atmosphere and land. However, as ice continues to melt, the SLF signal will become significantly different from uniform sea level. This makes removal of uniform mass flux to introduce additional error in the studies of ocean dynamic variation. Here, we employ observations of time variable gravity from GRACE over land, including the mass change of ice sheets, GIC, and land water storage to precisely calculate the SLF for the time period 2002-2015. We compare the results with sea level change from satellite radar altimetry (AVISO) corrected for the steric signal of the ocean from Argo measurements. We find an excellent agreement at the global scale in trend for the entire period between GRACE-derived SLF and AVISO minus Argo estimates. The agreement extends at the spatial scale of oceanic regions. Locally, the GRACE-derived SLF also agrees with in situ ocean bottom pressure recorder. The agreement demonstrates for the first time that SLF are reliable in terms of amplitude (intensity of mass loss), phase (spatial distribution of sources), and trends (increase in mass loss with time) using GRACE. During our observation period, we find that changes in land water mass dominate the seasonal variability of SLF. Greenland controls 42% of the total trend and 39% along the western and eastern US. Antarctica contributes 16% of the total trend and 21% in the western and eastern US. This work was performed at UC Irvine and at Caltech's Jet

  16. Characteristics of gravity signal and loading effect in China

    Directory of Open Access Journals (Sweden)

    Shuang Yi

    2015-07-01

    Full Text Available The complex geographical environment in China makes its gravity signals miscellaneous. This work gives a comprehensive representation and explanation in secular trend of gravity change in different regions, the key features of which include positive trend in inner Tibet Plateau and South China and negative trend in North China plain and high mountain Asia (HMA. We also present the patterns of amplitudes and phases of annual and semiannual change. The mechanism underlying the semiannual period is explicitly discussed. The displacement in three directions expressed in terms of geo-potential spherical coefficients and load Love numbers are given. A case study applied with these equations is presented. The results show that Global Positioning System (GPS observations can be used to compare with Gravity Recovery and Climate Experiment (GRACE derived displacement and the vertical direction has a signal-noise-ratio of about one order of magnitude larger than the horizontal directions.

  17. European Gravity Service for Improved Emergency Management - a new Horizon2020 project to serve the international community and improve the accessibility to gravity field products

    Science.gov (United States)

    Jaeggi, Adrian; Weigelt, Matthias; Flechtner, Frank; Guentner, Andreas; Mayer-Gürr, Torsten; Martinis, Sandro; Bruinsma, Sean; Flury, Jakob; Bourgogne, Stephane

    2015-04-01

    A proposal for a European Gravity Service for Improved Emergency Management (EGSIEM) has been submitted in response to the Earth Observation Call EO-1-2014 of the Horizon 2020 Framework Programme. EGSIEM shall demonstrate that observations of the redistribution of water and ice mass derived from the current GRACE mission, the future GRACE-FO mission, and additional data provide critical and complementary information to more traditional Earth Observation products and open the door for innovative approaches to flood and drought monitoring and forecasting. The EGSIEM project has recently started in January 2015. We present the three key objectives that EGSIEM shall address: 1) to establish a scientific combination service to deliver the best gravity products for applications in Earth and environmental science research based on the unified knowledge of the European GRACE community, 2) to establish a near real-time and regional service to reduce the latency and increase the temporal resolution of the mass redistribution products, and 3) to establish a hydrological and early warning service to develop gravity-based indicators for extreme hydrological events and to demonstrate their value for flood and drought forecasting and monitoring services. All of these services shall be tailored to the various needs of the respective communities. Significant efforts shall be devoted to transform the service products into user-friendly and easy-to-interpret data sets and the development of visualization tools.

  18. The concept of grace in Shakespeare's "Macbeth" and Racine's "Athalie"

    Directory of Open Access Journals (Sweden)

    J. Ferreira-Ross

    1985-03-01

    Full Text Available The design of both Macbeth and Athalie asserts the triumph of the spiritual over the temporal in the sense that both plays demonstrate the way in which the recipients of grace become the means through which divine providence chooses to work. At the opposite end of the scale of grace we find the self-seekers. Like Shakespeare, Racine does not focus on the cause, but on the nature of a corrupt will. In each case the protagonist is shown to possess an overreaching desire for self-aggrandizement and a determination towards the acting out and enforcement of their personal will. Both plays end with a coup de theatre, a kind of dramatic 'trick' which symbolizes the illusory nature of the protagonists' power-seeking.

  19. Preparation of dynamic gravity testing system

    Science.gov (United States)

    Bowin, Carl

    Bowin's interest at WHOI is to obtain the most accurate gravity and gravity gradient measurements possible. The Navy's interest is to have the most accurate navigation possible. Neither can have one without the other. Through Zarak Corporation, Bowin has proposed to the Navy Air System Command to develop a dynamic navigational gravity/gravity gradient (NAV/GRAV) system utilizing superconducting squid gravity and tensor gravity gradient sensors for high precision performance. The proposed system development incorporates that inter-dependency, not only to provide the best estimates of both, but also to provide estimates of the quality of the results obtained. Zarak is pursuing funds for the development of superconducting gravity and gravity gradient sensors. Such sensors, when available, will then be utilized in this palletized system for higher accuracy navigation, gravity and gravity gradient determination. It is desired that initial testing utilize Vibrating String Accelerometers (VSA) gravity sensors and readout systems available at WHOI. This way the development and testing of the NAV/GRAV system can proceed using the VSA sensors while the superconducting gravity sensors are being fabricated. Initial dynamic systems tests will be in a van vehicle for convenience and practicality. The system units will be palletized, and therefore they shall be easily transferable, and thus also be usable in aircraft and ships. It is planned that WHOI will have loan of prototype systems for about two months each year for earth research use.

  20. Characterizing Seasonal Drought, Water Supply Pattern and Their Impact on Vegetation Growth Using Satellite Soil Moisture Data, GRACE Water Storage and Precipitation Observations

    Science.gov (United States)

    A, G.; Velicogna, I.; Kimball, J. S.; Du, J.; Kim, Y.; Njoku, E. G.; Colliander, A.

    2016-12-01

    We combine soil moisture (SM) data from AMSR-E, AMSR-2 and SMAP, terrestrial water storage (TWS) changes from GRACE and precipitation measurements from GPCP to delineate and characterize drought and water supply pattern and its impact on vegetation growth. GRACE TWS provides spatially continuous observations of total terrestrial water storage changes and regional drought extent, persistence and severity, while satellite derived soil moisture estimates provide enhanced delineation of plant-available soil moisture. Together these data provide complementary metrics quantifying available plant water supply and have important implications for water resource management. We use these data to investigate the supply changes from different water components in relation to satellite based vegetation productivity metrics from MODIS, before, during and following the major drought events observed in the continental US during the past 13 years. We observe consistent trends and significant correlations between monthly time series of TWS, SM, and vegetation productivity. In Texas and surrounding semi-arid areas, we find that the spatial pattern of the vegetation-moisture relation follows the gradient in mean annual precipitation. In Texas, GRACE TWS and surface SM show strong coupling and similar characteristic time scale in relatively normal years, while during the 2011 onward hydrological drought, GRACE TWS manifests a longer time scale than that of surface SM, implying stronger drought persistence in deeper water storage. In the Missouri watershed, we find a spatially varying vegetation-moisture relationship where in the drier northwestern portion of the basin, the inter-annual variability in summer vegetation productivity is closely associated with changes in carry-on GRACE TWS from spring, whereas in the moist southeastern portion of the basin, summer precipitation is the dominant controlling factor on vegetation growth.

  1. Long term mass changes and interannual variability in the Canadian Archipelago and Gulf of Alaska from GRACE

    Science.gov (United States)

    Harig, C.; Simons, F. J.

    2015-12-01

    The mass transfer from land ice to the oceans is a major contributor to global sea-level rise. The glaciated regions of the Canadian Archipelago and the Gulf of Alaska are the next largest ice mass loss contributors outside of the Greenland and Antarctic ice sheets. Here we estimate the ice mass change of these regions since 2003 using time-variable gravity data from the GRACE mission. We employ an estimation technique based on spherical Slepian localization functions. These Slepian functions form a sparse set of orthogonal basis functions for a specific region and maximize the signal-to-noise levels of the gravity fields, making them excellent candidates to analyze regional data on the sphere.Between 2003 and 2012 Ellesmere Island lost mass (-38 Gt/yr) at an accelerating rate (-8 Gt/yr2), while Baffin Island lost mass at a lower rate (-22 Gt/yr) with very low acceleration. During this time, interannual variations were well described by an average seasonal cycle. Since 2013 ice mass in Ellesmere and Baffin islands, as well as Greenland, have diverged from their long term mass change trends. During the summer of 2013 these areas had the lowest recorded melt since the start of the GRACE mission. Through the end of 2014, the difference between the observed mass and the extrapolated long term trend for Greenland grew to over 500 gigatons. In contrast to the Canadian Archipelago, the Gulf of Alaska region has average seasonal mass variations four times larger per unit area and greater variability from year to year. Recent years of below average mass loss have lowered the average mass loss rate from previous estimates.

  2. Guo Yan_Gracefulness in the Social Life

    Institute of Scientific and Technical Information of China (English)

    LiuEr

    2004-01-01

    Guo Yan,the Executive Edito of Grace,a mationwide fashion magazine,is often linked with the modifiers such as beautiful,elegant,glanorous,intelligert,smart and wise.Borm and raised in Cjemgdu,Guo Yan graduated from Sichuan Yniversity before she began her Career as a renowned author of prize-Winning short stories and novels.She lives in Chengdu with her husband Yi Dan,a famous uniersity Professor,

  3. Simulating Gravity

    Science.gov (United States)

    Pipinos, Savas

    2010-01-01

    This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…

  4. Simulating Gravity

    Science.gov (United States)

    Pipinos, Savas

    2010-01-01

    This article describes one classroom activity in which the author simulates the Newtonian gravity, and employs the Euclidean Geometry with the use of new technologies (NT). The prerequisites for this activity were some knowledge of the formulae for a particle free fall in Physics and most certainly, a good understanding of the notion of similarity…

  5. Constraints of Melting, Sea-Level and the Paleoclimate from GRACE

    Science.gov (United States)

    Davis, James L.

    2005-01-01

    To gauge the accuracy of the GRACE data, we have undertaken a study to compare deformations predicted by GRACE inferences of seasonal water loading to crustal position variations determined from GRACE data. Two manuscripts that resulted from this study are attached. We found a very high correlation between the GRACE and GPS determinations for South America [Duvis et al., 2004]. We also developed a statistical approach for choosing which Stokes coefficients to include. This approach proves to be somewhat more accurate than the traditional Gaussian filter [Duvis et al., 2005].

  6. Constraints of GRACE on the Ice Model and Mantle Rheology in Glacial Isostatic Adjustment Modeling in North-America

    Science.gov (United States)

    van der Wal, W.; Wu, P.; Sideris, M.; Wang, H.

    2009-05-01

    GRACE satellite data offer homogeneous coverage of the area covered by the former Laurentide ice sheet. The secular gravity rate estimated from the GRACE data can therefore be used to constrain the ice loading history in Laurentide and, to a lesser extent, the mantle rheology in a GIA model. The objective of this presentation is to find a best fitting global ice model and use it to study how the ice model can be modified to fit a composite rheology, in which creep rates from a linear and non-linear rheology are added. This is useful because all the ice models constructed from GIA assume that mantle rheology is linear, but creep experiments on rocks show that nonlinear rheology may be the dominant mechanism in some parts of the mantle. We use CSR release 4 solutions from August 2002 to October 2008 with continental water storage effects removed by the GLDAS model and filtering with a destriping and Gaussian filter. The GIA model is a radially symmetric incompressible Maxwell Earth, with varying upper and lower mantle viscosity. Gravity rate misfit values are computed for with a range of viscosity values with the ICE-3G, ICE-4G and ICE-5G models. The best fit is shown for models with ICE-3G and ICE-4G, and the ICE-4G model is selected for computations with a so-called composite rheology. For the composite rheology, the Coupled Laplace Finite-Element Method is used to compute the GIA response of a spherical self-gravitating incompressible Maxwell Earth. The pre-stress exponent (A) derived from a uni- axial stress experiment is varied between 3.3 x 10-34/10-35/10-36 Pa-3s-1, the Newtonian viscosity η is varied between 1 and 3 x 1021 Pa-s, and the stress exponent is taken to be 3. Composite rheology in general results in geoid rates that are too small compared to GRACE observations. Therefore, simple modifications of the ICE-4G history are investigated by scaling ice heights or delaying glaciation. It is found that a delay in glaciation is a better way to adjust ice

  7. New modes and mechanisms of thermospheric mass density variations from GRACE accelerometers

    Science.gov (United States)

    Calabia, Andres; Jin, Shuanggen

    2016-11-01

    Monitoring and understanding the upper atmosphere processes is important for orbital decay and space physics. Nowadays, Low Earth Orbit (LEO) accelerometers provide a unique opportunity to study thermospheric density variations with unprecedented details. In this paper, thermospheric mass densities variations from Gravity Recovery and Climate Experiment (GRACE) accelerometers are investigated for the period 2003-2016 using the principal component analysis (PCA). The resulting modes are analyzed and parameterized in terms of solar and magnetospheric forcing, local solar time (LST), and annual variations. A better understanding of global thermospheric air density variations is presented, which validates the suitability of our technique and model. The parameterization of the subsolar-point annual variation shows two maxima around June and only one in December. The LST parameterization shows a new fluctuation controlling a middle latitude four-wave pattern, with two maxima at 12 h and 21 h LST and two minima at 1 h and 17 h LST. Our parameterizations are suitable to represent small-scale variations including, e.g., the equatorial mass density anomaly (EMA) and the midnight density maximum (MDM). Finally, the residuals are analyzed in the spectral domain, and additional contributions are found at the frequencies of the radiational tides and at the periods of 83, 93, 152, and 431 days.

  8. Variations in water storage in China over recent decades from GRACE observations and GLDAS

    Science.gov (United States)

    Mo, X.; Wu, J. J.; Wang, Q.; Zhou, H.

    2016-02-01

    We applied Gravity Recovery and Climate Experiment (GRACE) Tellus products in combination with Global Land Data Assimilation System (GLDAS) simulations and data from reports, to analyze variations in terrestrial water storage (TWS) in China as a whole and eight of its basins from 2003 to 2013. Amplitudes of TWS were well restored after scaling, and showed good correlations with those estimated from models at the basin scale. TWS generally followed variations in annual precipitation; it decreased linearly in the Huai River basin (-0.56 cm yr-1) and increased with fluctuations in the Changjiang River basin (0.35 cm yr-1), Zhujiang basin (0.55 cm yr-1) and southeast rivers basin (0.70 cm yr-1). In the Hai River basin and Yellow River basin, groundwater exploitation may have altered TWS's response to climate, and TWS kept decreasing until 2012. Changes in soil moisture storage contributed over 50 % of variance in TWS in most basins. Precipitation and runoff showed a large impact on TWS, with more explained TWS in the south than in the north. North China and southwest rivers region exhibited long-term TWS depletions. TWS has increased significantly over recent decades in the middle and lower reaches of Changjiang River, southeastern coastal areas, as well as the Hoh Xil, and the headstream region of the Yellow River in the Tibetan Plateau. The findings in this study could be helpful to climate change impact research and disaster mitigation planning.

  9. GRAIL gravity field determination using the Celestial Mechanics Approach - status report

    Science.gov (United States)

    Bertone, S.; Arnold, D.; Jäggi, A.; Beutler, G.; Mervart, L.

    2015-10-01

    The NASA mission GRAIL (Gravity Recovery And Interior Laboratory [1]) inherits its concept from the GRACE (Gravity Recovery And Climate Experiment)mission to determine the gravity field of the Moon. The use of inter-satellite Ka-band range-rate (KBRR) observations enables data aquisition even when the spacecraft are not tracked from the Earth [2]. The data allows for a highly accurate estimation of the lunar gravity field on both sides of the Moon, which is crucial to improve the understanding of its internal structure and thermal evolution. In this presentation we dis- cuss our latest GRAIL-based lunar gravity fields generated with the Celestial Mechanics Approach using the Bernese Software.

  10. Stochastic gravity: beyond semiclassical gravity

    Energy Technology Data Exchange (ETDEWEB)

    Verdaguer, E [Departament de Fisica Fonamental and CER en Astrofisica, Fisica de Particules i Cosmologia, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona (Spain)

    2007-05-15

    The back-reaction of a classical gravitational field interacting with quantum matter fields is described by the semiclassical Einstein equation, which has the expectation value of the quantum matter fields stress tensor as a source. The semiclassical theory may be obtained from the quantum field theory of gravity interacting with N matter fields in the large N limit. This theory breaks down when the fields quantum fluctuations are important. Stochastic gravity goes beyond the semiclassical limit and allows for a systematic and self-consistent description of the metric fluctuations induced by these quantum fluctuations. The correlation functions of the metric fluctuations obtained in stochastic gravity reproduce the correlation functions in the quantum theory to leading order in an 1/N expansion. Two main applications of stochastic gravity are discussed. The first, in cosmology, to obtain the spectrum of primordial metric perturbations induced by the inflaton fluctuations, even beyond the linear approximation. The second, in black hole physics, to study the fluctuations of the horizon of an evaporating black hole.

  11. The changing pattern of lake and its contribution to increased mass in the Tibetan Plateau derived from GRACE and ICESat data

    Science.gov (United States)

    Wang, Qiuyu; Yi, Shuang; Sun, Wenke

    2016-10-01

    This paper compares GRACE (Gravity Recovery and Climate Experiment) and ICESat (Ice, Cloud and land Elevation Satellite) observations to confirm whether the observed gravity increase in the Tibetan Plateau (TP) was primarily caused by lake storage gain, and comprehensively analyses the changing pattern of lake level over 2003-2009. An improved automated method was used to obtain lake-level changes and the underestimation of lake water storage was considered due to lake area expansion and lake density. The result demonstrates that GRACE recorded a mass gain (16.43 ± 1.65/11.79 ± 1.25 gt a-1) in the total/inner TP, of which lake storage increase accounts for (8.78 ± 0.75/7.53 ± 0.56 gt a-1) based on ICESat. The northwestern residual may be stored in new lakes and soil moisture as a result of net precipitation gain. According to the character of the lake-level changes, we divide the TP into four subregions. Generally, the changing pattern of lake level concurs with the distribution of precipitation, which is increasing in the inner TP and decreasing in the upstream area of the Indus and Brahmaputra Rivers. An excess of rainfall in the northeastern TP in the summer of 2005 and 2009 caused a simultaneous large increase in water level in many lakes. The correlation of lake changes with precipitation demonstrates that precipitation rather than glacial melt is the main cause of lake-level change in most places. Nonetheless, the meltwater is a considerable supplement for lakes near glaciers such as Selin Co and Nam Co, which partly explains why GRACE indicates a much weaker signal in this region.

  12. Antarctic ice-mass balance 2002 to 2011: regional re-analysis of GRACE satellite gravimetry measurements with improved estimate of glacial-isostatic adjustment

    Directory of Open Access Journals (Sweden)

    I. Sasgen

    2012-09-01

    Full Text Available We present regional-scale mass balances for 25 drainage basins of the Antarctic Ice Sheet (AIS from satellite observations of the Gravity and Climate Experiment (GRACE for the years 2002–2011. Satellite gravimetry estimates of the AIS mass balance are strongly influenced by mass movement in the Earth interior caused by ice advance and retreat during the last glacial cycle. Here, we develop an improved glacial-isostatic adjustment (GIA estimate for Antarctica using newly available GPS uplift rates, allowing us to more accurately separate GIA-induced trends in the GRACE gravity fields from those caused by current imbalances of the AIS. Our revised GIA estimate is considerably lower than previous predictions, yielding an (upper estimate of apparent mass change of 48 ± 18 Gt yr−1. Therefore, our AIS mass balance of −103 ± 23 Gt yr−1 is considerably less negative than previous GRACE estimates. The Northern Antarctic Peninsula and the Amundsen Sea Sector exhibit the largest mass loss (−25 ± 6 Gt yr−1 and −126 ± 11 Gt yr−1, respectively. In contrast, East Antarctica exhibits a slightly positive mass balance (19 ± 16 Gt yr−1, which is, however, mostly the consequence of compensating mass anomalies in Dronning Maud and Enderby Land (positive and Wilkes and George V Land (negative due to interannual accumulation variations. In total, 7% of the area constitute more than half of the AIS imbalance (53%, contributing −151 ± 9 Gt yr−1 to global mean sea-level change. Most of this imbalance is caused by long-term ice-dynamic speed up expected to prevail in the future.

  13. The Performance of Ultra-stable Oscillators for the Gravity Recovery and Interior Laboratory (GRAIL)

    Science.gov (United States)

    2010-11-01

    USO frequency stability requirements with a drift rate requirement of < 7E-11/day, nearly ten times better than the predecessor GRACE requirement...ultra-stable oscillators ( USOs ) to the Jet Propulsion Laboratory (JPL) for the Gravity Recovery and Interior Laboratory (GRAIL) mission. GRAIL is...Along with achieving the drift rate, the delivered USOs showed Allan deviation of < 2 E-13 at 10 and 100 second time intervals, with two units

  14. Over Exploitation of Groundwater in the Centre of Amman Zarqa Basin—Jordan: Evaluation of Well Data and GRACE Satellite Observations

    Directory of Open Access Journals (Sweden)

    Sana’a Al-Zyoud

    2015-11-01

    Full Text Available Jordan faces a sincere water crisis. Groundwater is the major water resource in Jordan and most of the ground water systems are already exploited beyond their estimated safe yield. The Amman Zarqa Basin is one of the most important groundwater systems in Jordan, which supplies the three largest cities in Jordan with drinking and irrigation water. Based on new data the groundwater drawdown in the Amman Zarqa Basin is studied. This basin is the most used drainage area in Jordan. Groundwater drawdown in eight central representative monitoring wells is outlined. Based on almost continuous data for the last 15 years (2000–2015 an average drawdown for the whole basin in the order of 1.1 m·a−1 is calculated. This result is in accordance with results of previous studies in other areas in Jordan and shows that, until now, no sustainable water management is applied. Groundwater management in such a basin presents a challenge for water managers and experts. The applicability of satellite data for estimating large-scale groundwater over exploitation, such as gravity products of the Gravity Recovery and Climate Experiment (GRACE mission, along with supplementary data, is discussed. Although the size of the basin is below the minimum resolution of GRACE, the data generally support the measured drawdown.

  15. Optimizing estimates of annual variations and trends in geocenter motion and J2 from a combination of GRACE data and geophysical models

    Science.gov (United States)

    Sun, Yu; Riva, Riccardo; Ditmar, Pavel

    2016-11-01

    The focus of the study is optimizing the technique for estimating geocenter motion and variations in J2 by combining data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission with output from an Ocean Bottom Pressure model and a Glacial Isostatic Adjustment (GIA) model. First, we conduct an end-to-end numerical simulation study. We generate input time-variable gravity field observations by perturbing a synthetic Earth model with realistically simulated errors. We show that it is important to avoid large errors at short wavelengths and signal leakage from land to ocean, as well as to account for self-attraction and loading effects. Second, the optimal implementation strategy is applied to real GRACE data. We show that the estimates of annual amplitude in geocenter motion are in line with estimates from other techniques, such as satellite laser ranging (SLR) and global GPS inversion. At the same time, annual amplitudes of C10 and C11 are increased by about 50% and 20%, respectively, compared to estimates based on Swenson et al. (2008). Estimates of J2 variations are by about 15% larger than SLR results in terms of annual amplitude. Linear trend estimates are dependent on the adopted GIA model but still comparable to some SLR results.

  16. Improved representations of the Mediterranean Geoid within the GEOMED 2 project. Contributions of local gravity, GOCE and Cryosat2 data

    DEFF Research Database (Denmark)

    Barzaghi, Riccardo; Vergos, George S.; Albertella, Alberta

    )-based techniques have provided the geoid estimation in the frequency domain. In this work, the pre-processing steps consisting in merging and validating all the available gravity observations for the wider Mediterranean are presented and discussed. Furthermore, the latest basin-wide geoid models are estimated from...... of a Mediterranean-wide gravity database. The data employed within GEOMED 2 for the determination of the marine geoid are land and marine gravity data, GOCE/GRACE based Global Geopotential Models and a combination of MISTRAL and SRTM/bathymetry terrain models. The processing methodology will be based on the well...

  17. European Gravity Service for Improved Emergency Management - Status and project highlights

    Science.gov (United States)

    Mayer-Guerr, Torsten; Adrian, Jäggi; Meyer, Ulrich; Jean, Yoomin; Susnik, Andreja; Weigelt, Matthias; van Dam, Tonie; Flechtner, Frank; Gruber, Christian; Güntner, Andreas; Gouweleeuw, Ben; Kvas, Andreas; Klinger, Beate; Flury, Jakob; Bruinsma, Sean; Lemoine, Jean-Michel; Zwenzner, Hendrik; Bourgogne, Stephane; Bandikova, Tamara

    2016-04-01

    The European Gravity Service for Improved Emergency Management (EGSIEM) is a project of the Horizon 2020 Framework Programme for Research and Innovation of the European Commission. EGSIEM shall demonstrate that observations of the redistribution of water and ice mass derived from the current GRACE mission, the future GRACE-FO mission, and additional data provide critical and complementary information to more traditional Earth Observation products and open the door for innovative approaches to flood and drought monitoring and forecasting. In the frame of EGSIEM three key services should established: 1) a scientific combination service to deliver the best gravity products for applications in Earth and environmental science research based on the unified knowledge of the European GRACE community, 2) a near real-time and regional service to reduce the latency and increase the temporal resolution of the mass redistribution products, and 3) a hydrological and early warning service to develop gravity-based indicators for extreme hydrological events and to demonstrate their value for flood and drought forecasting and monitoring services. All of these services shall be tailored to the various needs of the respective communities. Significant efforts shall also be devoted to transform the service products into user-friendly and easy-to-interpret data sets and the development of visualization tools. In this talk the status of the ongoing project is presented and selected results are discussed.

  18. European Gravity Service for Improved Emergency Management - Project Overview and First Results

    Science.gov (United States)

    Jaeggi, A.; Jean, Y.; Weigelt, M. L. B.; Flechtner, F.; Gruber, C.; Guntner, A.; Gouweleeuw, B.; Mayer-Gürr, T.; Kvas, A.; Martinis, S.; Zwenzer, H.; Bruinsma, S.; Lemoine, J. M.; Flury, J.; Bourgogne, S.

    2015-12-01

    The project European Gravity Service for Improved Emergency Management (EGSIEM) of the Horizon 2020 Framework Programme for Research and Innovation of the European Commission has started in January 2015. EGSIEM shall demonstrate that observations of the redistribution of water and ice mass derived from the current GRACE mission, the future GRACE-FO mission, and additional data provide critical and complementary information to more traditional Earth Observation products and open the door for innovative approaches to flood and drought monitoring and forecasting. We give an overview of the project and present first results from the three key objectives that EGSIEM shall address: 1) to establish a scientific combination service to deliver the best gravity products for applications in Earth and environmental science research based on the unified knowledge of the European GRACE community, 2) to establish a near real-time and regional service to reduce the latency and increase the temporal resolution of the mass redistribution products, and 3) to establish a hydrological and early warning service to develop gravity-based indicators for extreme hydrological events and to demonstrate their value for flood and drought forecasting and monitoring services. All of these services shall be tailored to the various needs of the respective communities. Significant efforts shall also be devoted to transform the service products into user-friendly and easy-to-interpret data sets and the development of visualization tools.

  19. GRACE gravity observations constrain Weichselian ice thickness in the Barents Sea

    NARCIS (Netherlands)

    Root, B.C.; Tarasov, L.; Van der Wal, W.

    2015-01-01

    The Barents Sea is subject to ongoing postglacial uplift since the melting of the Weichselian ice sheet that covered it. The regional ice sheet thickness history is not well known because there is only data at the periphery due to the locations of Franz Joseph Land, Svalbard, and Novaya Zemlya surro

  20. GRACE gravity observations constrain Weichselian ice thickness in the Barents Sea

    NARCIS (Netherlands)

    Root, B.C.; Tarasov, L.; Van der Wal, W.

    2015-01-01

    The Barents Sea is subject to ongoing postglacial uplift since the melting of the Weichselian ice sheet that covered it. The regional ice sheet thickness history is not well known because there is only data at the periphery due to the locations of Franz Joseph Land, Svalbard, and Novaya Zemlya surro

  1. Greenland inland ice melt-off: Analysis of global gravity data from the GRACE satellites

    DEFF Research Database (Denmark)

    Nielsen, Allan Aasbjerg; Andersen, Ole Baltazar; Svendsen, Peter L.

    2011-01-01

    August 2010. Results focussing on Greenland show statistically significant mass loss interpreted as inland ice melt-off to the SE and NW with an acceleration in the melt-off occurring to the NW and a possible deceleration to the SE. Also, there are strong indications of a transition taking place...

  2. Greenland inland ice melt-off: Analysis of global gravity data from the GRACE satellites

    DEFF Research Database (Denmark)

    Nielsen, Allan Aasbjerg; Andersen, Ole Baltazar; Svendsen, Peter L.

    2011-01-01

    August 2010. Results focussing on Greenland show statistically significant mass loss interpreted as inland ice melt-off to the SE and NW with an acceleration in the melt-off occurring to the NW and a possible deceleration to the SE. Also, there are strong indications of a transition taking place...

  3. The Gravity Recovery and Interior Laboratory Mission

    Science.gov (United States)

    Lehman, David H.; Hoffman, Tom L.; Havens, Glen G.

    2013-01-01

    The Gravity Recovery and Interior Laboratory (GRAIL) mission, launched in September 2011, successfully completed its Primary Science Mission in June 2012 and is currently in Extended Mission operations. Competitively selected under a NASA Announcement of Opportunity in December 2007, GRAIL is a Discovery Program mission subject to a mandatory project cost cap. The purpose of the mission is to precisely map the gravitational field of the Moon to reveal its internal structure from crust to core, determine its thermal evolution, and extend this knowledge to other planets. The mission uses twin spacecraft flying in tandem to provide the gravity map. The GRAIL Flight System, consisting of the spacecraft and payload, was developed based on significant heritage from previous missions such an experimental U.S. Air Force satellite, the Mars Reconnaissance Orbiter (MRO) mission, and the Gravity Recovery and Climate Experiment (GRACE) mission. The Mission Operations System (MOS) was based on high-heritage multimission operations developed by NASA's Jet Propulsion Laboratory and Lockheed Martin. Both the Flight System and MOS were adapted to meet the unique challenges posed by the GRAIL mission design. This paper summarizes the implementation challenges and accomplishments of getting GRAIL ready for launch. It also discusses the in-flight challenges and experiences of operating two spacecraft, and mission results.

  4. Time-variations of equivalent water heights'from Grace Mission and in-situ river stages in the Amazon basin Variações temporais do equivalente à altura d'água obtidas da Missão Grace e da altura d'água in-situ nos rios da bacia Amazônica

    Directory of Open Access Journals (Sweden)

    Flavio Guilherme Vaz de Almeida

    2012-03-01

    Full Text Available Gravity Recovery and Climate Experiment (GRACE mission is dedicated to measuring temporal variations of the Earth's gravity field. In this study, the Stokes coefficients made available by Groupe de Recherche en Géodésie Spatiale (GRGS at a 10-day interval were converted into equivalent water height (EWH for a ~4-year period in the Amazon basin (from July-2002 to May-2006. The seasonal amplitudes of EWH signal are the largest on the surface of Earth and reach ~ 1250mm at that basin's center. Error budget represents ~130 mm of EWH, including formal errors on Stokes coefficient, leakage errors (12 ~ 21 mm and spectrum truncation (10 ~ 15 mm. Comparison between in situ river level time series measured at 233 ground-based hydrometric stations (HS in the Amazon basin and vertically-integrated EWH derived from GRACE is carried out in this paper. Although EWH and HS measure different water bodies, in most of the cases a high correlation (up to ~80% is detected between the HS series and EWH series at the same site. This correlation allows adjusting linear relationships between in situ and GRACE-based series for the major tributaries of the Amazon river. The regression coefficients decrease from up to down stream along the rivers reaching the theoretical value 1 at the Amazon's mouth in the Atlantic Ocean. The variation of the regression coefficients versus the distance from estuary is analysed for the largest rivers in the basin. In a second step, a classification of the proportionality between in situ and GRACE time-series is proposed.A missão espacial Gravity Recovery and Climate Experiment (GRACE é dedicada às medidas das variações temporais no campo gravitacional da Terra. Neste estudo, os coeficientes de Stokes disponibilizados pelo Groupe de Recherche en Géodésie Spatiale (GRGS com intervalos de 10 dias foram convertidos no equivalente à altura d'água (EWH para um período de 4 anos na bacia Amazônica (de julho de 2002 a maio de 2006

  5. 76 FR 75797 - Transportation Conformity Rule: MOVES Regional Grace Period Extension

    Science.gov (United States)

    2011-12-05

    ... AGENCY 40 CFR Part 93 RIN 2060-AR03 Transportation Conformity Rule: MOVES Regional Grace Period Extension... for regional emissions analyses for transportation conformity determinations (``regional conformity... extending the MOVES regional conformity grace period, published on October 13, 2011 (76 FR 63554). We...

  6. Evaluating Renewable Groundwater Stress with GRACE data in Greece

    Science.gov (United States)

    Lakshmi, V.; Gemitzi, A.

    2016-12-01

    Groundwater is a resilient water source and its importance as a fundamental resource is even greater in times of drought where groundwater stress conditions are greatest for areas like Mediterranean and adverse climate change effects are expected. The present study evaluates Renewable Groundwater Stress (RGS) as the ratio of groundwater use to groundwater availability, quantifying use as the trend in GRACE-derived subsurface anomalies (ΔGWtrend) and renewable groundwater availability as mean annual recharge. Estimates for mean annual recharge were used from groundwater studies conducted for the various regions in Greece, mainly in the form of numerical models. Our results highlighted two RGS regimes in Greece out of the four characteristic stress regimes, i.e. Overstressed, Variable Stress, Human-Dominated Stress and Unstressed, defined as a function of the sign of use and the sign of groundwater availability (positive or negative). Variable Stress areas are found in central Greece (Thessaly region), where intense agricultural activities take place, with negative ΔGWtrend values combined with positive mean annual recharge rates. RGS values range from -0.05 - 0, indicating however a low impact area. Within this region, adverse effects of groundwater overexploitation are already evident, based on the negative GRACE anomalies, recharge however still remains positive, amending the adverse over pumping impacts. The rest of Greek aquifers fall within the unstressed category, with RGS values from 0.02 - 0.05, indicating that the rate of use is less than the natural recharge rate. The highest Unstressed RGS values are observed in Crete Island and in Northeastern Greece. However, the case of Crete is highly uncertain, as precipitation and recharge in this area demonstrate exceptionally high variability and the coarse resolution of GRACE results does not allow for reliable estimates.

  7. The lunar gravity mission MAGIA: preliminary design and performances

    Science.gov (United States)

    Fermi, Marco; Gregnanin, Marco; Mazzolena, Marco; Chersich, Massimiliano; Reguzzoni, Mirko; Sansò, Fernando

    2011-10-01

    The importance of an accurate model of the Moon gravity field has been assessed for future navigation missions orbiting and/or landing on the Moon, in order to use our natural satellite as an intermediate base for next solar system observations and exploration as well as for lunar resources mapping and exploitation. One of the main scientific goals of MAGIA mission, whose Phase A study has been recently funded by the Italian Space Agency (ASI), is the mapping of lunar gravitational anomalies, and in particular those on the hidden side of the Moon, with an accuracy of 1 mGal RMS at lunar surface in the global solution of the gravitational field up to degree and order 80. MAGIA gravimetric experiment is performed into two phases: the first one, along which the main satellite shall perform remote sensing of the Moon surface, foresees the use of Precise Orbit Determination (POD) data available from ground tracking of the main satellite for the determination of the long wavelength components of gravitational field. Improvement in the accuracy of POD results are expected by the use of ISA, the Italian accelerometer on board the main satellite. Additional gravitational data from recent missions, like Kaguya/Selene, could be used in order to enhance the accuracy of such results. In the second phase the medium/short wavelength components of gravitational field shall be obtained through a low-to-low (GRACE-like) Satellite-to-Satellite Tracking (SST) experiment. POD data shall be acquired during the whole mission duration, while the SST data shall be available after the remote sensing phase, when the sub-satellite shall be released from the main one and both satellites shall be left in a free-fall dynamics in the gravity field of the Moon. SST range-rate data between the two satellites shall be measured through an inter-satellite link with accuracy compliant with current state of art space qualified technology. SST processing and gravitational anomalies retrieval shall

  8. Graceful, harmonious and magic type labelings relations and techniques

    CERN Document Server

    López, Susana C

    2017-01-01

    Aimed toward upper undergraduate and graduate students in mathematics, this book examines the foremost forms of graph labelings including magic, harmonious, and graceful labelings. An overview of basic graph theory concepts and notation is provided along with the origins of graph labeling. Common methods and techniques are presented introducing readers to links between graph labels. A variety of useful techniques are presented to analyze and understand properties of graph labelings. The classical results integrated with new techniques, complete proofs, numerous exercises, and a variety of open problems, will provide readers with a solid understanding of graph labelings.

  9. Monthly errors

    Data.gov (United States)

    U.S. Environmental Protection Agency — The 2006 monthly average statistical metrics for 2m Q (g kg-1) domain-wide for the base and MODIS WRF simulations against MADIS observations. This dataset is...

  10. GRACE Data-based Estimation of Spatial Variations in Water Storage over the Central Asia during 2003-2013

    Science.gov (United States)

    Sun, Q.; Tashpolat, T.; Ding, J. L.; Zhang, F.; Mamat, S.

    2014-11-01

    We used the GRACE (Gravity Recovery And Climate Experiment) satellite gravity data obtained from January 2003 to January 2013, with supports of other data, including the TRMM (Tropical Rainfall Measuring Mission) and CMAP (Climate Prediction Center's Merged Analysis of Precipitation) precipitation data, the NDVI (Normalized Difference Vegetation Index) data, and the DEM (Digital Elevation Model) data, to analyze the annual variations in water storage over central Asia. Following conclusions can be drawn from this study. (1) The amplitudes of the annual variations in the water storage exhibit a general E-W increasing trend. (2) The water storage has an increasing trend in the following areas: the Balkhash Basin, the Ob River Basin, and the middle and lower reaches of the Yenisei River Basin. This is caused by the global warming, the melting of permafrost, and the vegetation coverage continued to increase, as well as the improved industrial technologies to reduce water usage, and the other natural and human factors. (3) The water storage has a decreasing trend in the following areas: the Syr Darya River Basin, the Amu Darya River Basin, and the conjunction area between the Euphrates-Tigris Basin and the southwestern shore of the Caspian Sea. (4) The water storage is primarily influenced by the precipitation, the evaporation, the vegetation coverage, and the topography. (5) The water storage maximum normally responds to the precipitation maximum with certain time lags.

  11. Southern Africa Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data base (14,559 records) was received in January 1986. Principal gravity parameters include elevation and observed gravity. The observed gravity values are...

  12. NGS Absolute Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NGS Absolute Gravity data (78 stations) was received in July 1993. Principal gravity parameters include Gravity Value, Uncertainty, and Vertical Gradient. The...

  13. Groundwater Depletion and the Sharp Increase of Seismicity in the Southern States, How GRACE Data Could Help?

    Science.gov (United States)

    Hong, Z.; Hasan, E.; Hong, Y.; Xia, B.; Zhong, H.

    2016-12-01

    This study is a contribution to how NASA's Gravity Recovery and Climate Experiment (GRACE) data may be used to track anthropogenic related change in the groundwater in the Southern Great Plains (SGP) as well recently increased seismicity in the southern states. The SGP contains one of the most important groundwater aquifers in the United States, the Ogallala groundwater aquifer, which has been exploited since 1900. Meanwhile, the recent activities of oil and gas extraction from the unconventional shall reservoir systems has led to significantly increased groundwater withdrawal and injection of wastewater. Consequently, numerous induced fracture related earthquakes have been recorded in Oklahoma and Texas between 2002 and 2016 The current paper investigates the utility of GRACE data along with the Land Water Content (LWC) information from the Global Land Data Assimilation System (GLDAS) to monitor and track the groundwater changes in three southern states of SGP (Oklahoma, Texas and New Mexico). Additionally, the paper investigates links between active seismicity and the injection of the wastewater due to the oil and gas production. Using GRACE data yields unprecedented information about the inter-annual changes in the Total Water Storage (TWS) from 2002 to 2016 over SGP. The LWC data set sums the soil moisture records with the the total canopy water storage to reveal the total land surface water content. The arithmetic difference between the TWS and LWC is the Groundwater Anomaly (GWA) for any particular region. In the current study, the GWA analysis reveals the following: (1) statistically significant drop of the GWA of about - 27 mm from 2002 to 2007 due to natural and anthropogenic causes; (2) the increased precipitation records from 2008 to 2011 over SGP leads to significant recovery in TWS and an increase in the groundwater content of about 40 mm; (3) the period from 2012 to 2015 experienced increased GWA of about - 6 mm for the period. Using the available

  14. Thermospheric density estimation and responses to the March 2013 geomagnetic storm from GRACE GPS-determined precise orbits

    Science.gov (United States)

    Calabia, Andres; Jin, Shuanggen

    2017-02-01

    The thermospheric mass density variations and the thermosphere-ionosphere coupling during geomagnetic storms are not clear due to lack of observables and large uncertainty in the models. Although accelerometers on-board Low-Orbit-Earth (LEO) satellites can measure non-gravitational accelerations and derive thermospheric mass density variations with unprecedented details, their measurements are not always available (e.g., for the March 2013 geomagnetic storm). In order to cover accelerometer data gaps of Gravity Recovery and Climate Experiment (GRACE), we estimate thermospheric mass densities from numerical derivation of GRACE determined precise orbit ephemeris (POE) for the period 2011-2016. Our results show good correlation with accelerometer-based mass densities, and a better estimation than the NRLMSISE00 empirical model. Furthermore, we statistically analyze the differences to accelerometer-based densities, and study the March 2013 geomagnetic storm response. The thermospheric density enhancements at the polar regions on 17 March 2013 are clearly represented by POE-based measurements. Although our results show density variations better correlate with Dst and k-derived geomagnetic indices, the auroral electroject activity index AE as well as the merging electric field Em picture better agreement at high latitude for the March 2013 geomagnetic storm. On the other side, low-latitude variations are better represented with the Dst index. With the increasing resolution and accuracy of Precise Orbit Determination (POD) products and LEO satellites, the straightforward technique of determining non-gravitational accelerations and thermospheric mass densities through numerical differentiation of POE promises potentially good applications for the upper atmosphere research community.

  15. Assessing GOCE Gravity Models using Altimetry and Drifters

    DEFF Research Database (Denmark)

    Knudsen, Per; Andersen, Ole Baltazar

    The improved gravity models provided by the GOCE mission have enhanced the resolution and sharpened the boundaries of those features and the associated geostrophic surface currents reveal improvements for all of the ocean’s current systems. There are still important signals to be recovered...... and issues related to errors in the models have been identified.In this study, a series of newer gravity models including observations from GRACE and GOCE are compared with the DTU15MSS mean sea surface to analyse resolution capacities and to identify issues caused by errors in the models. The comparisons...... are carried out in regional analyses using Fourier techniques to derive the spectral characteristics as well as anisotropic patterns to identify differences and to quantify quality measures associated with the models. In addition, regional analyses are carried out using in-situ observations of the geostrophic...

  16. Viable Mimetic Completion of Unified Inflation-Dark Energy Evolution in Modified Gravity

    CERN Document Server

    Nojiri, S; Oikonomou, V K

    2016-01-01

    In this paper, we demonstrate that a unified description of early and late-time acceleration is possible in the context of mimetic $F(R)$ gravity. We study the inflationary era in detail and demonstrate that it can be realized even in mimetic $F(R)$ gravity where traditional $F(R)$ gravity fails to describe the inflation. By using standard methods we calculated the spectral index of primordial curvature perturbations and the scalar-to-tensor ratio. We use two $F(R)$ gravity models and as it turns out, for both the models under study the observational indices are compatible with both the latest Planck and the BICEP2/Keck array data. Finally, the graceful exit from inflation is guaranteed by the existence of growing curvature perturbations when the slow-roll era ends.

  17. Future missions for observing Earth's changing gravity field: a closed-loop simulation tool

    Science.gov (United States)

    Visser, P. N.

    2008-12-01

    The GRACE mission has successfully demonstrated the observation from space of the changing Earth's gravity field at length and time scales of typically 1000 km and 10-30 days, respectively. Many scientific communities strongly advertise the need for continuity of observing Earth's gravity field from space. Moreover, a strong interest is being expressed to have gravity missions that allow a more detailed sampling of the Earth's gravity field both in time and in space. Designing a gravity field mission for the future is a complicated process that involves making many trade-offs, such as trade-offs between spatial, temporal resolution and financial budget. Moreover, it involves the optimization of many parameters, such as orbital parameters (height, inclination), distinction between which gravity sources to observe or correct for (for example are gravity changes due to ocean currents a nuisance or a signal to be retrieved?), observation techniques (low-low satellite-to-satellite tracking, satellite gravity gradiometry, accelerometers), and satellite control systems (drag-free?). A comprehensive tool has been developed and implemented that allows the closed-loop simulation of gravity field retrievals for different satellite mission scenarios. This paper provides a description of this tool. Moreover, its capabilities are demonstrated by a few case studies. Acknowledgments. The research that is being done with the closed-loop simulation tool is partially funded by the European Space Agency (ESA). An important component of the tool is the GEODYN software, kindly provided by NASA Goddard Space Flight Center in Greenbelt, Maryland.

  18. Second Gravity

    CERN Document Server

    Nash, Patrick Lee

    2010-01-01

    A theory of a new gravitational interaction is described. This theory follows naturally from a new Lagrangian formulation of Maxwell's theory for photons and electrons (and positrons) whose associated Euler Lagrange equations imply the conventional Maxwell equations, but which possesses new \\textbf{\\emph{bosonic}} spinor degrees of freedom that may be associated with a new type of fundamental gravitational interaction. The precise character of this gravitational interaction with a photon vector potential is explicitly defined in terms of a local U(1)-invariant Lagrangian in Eq.[\\ref{Lagrangian3}]. However in Section \\ref{ssec:Simple-Cosmolo-Model}, in order to parallel the well known Friedmann model in cosmology, a phenomenological description of the new gravitational interaction coupled to Newton-Einstein gravity that is sourced by an ideal fluid is discussed. % % To lay the foundation for a description of the new gravitational interaction our new formulation of Maxwell's theory must first be described. It i...

  19. Gravity's Rainbow

    CERN Document Server

    Magueijo, J; Magueijo, Joao; Smolin, Lee

    2004-01-01

    Non-linear special relativity (or doubly special relativity) is a simple framework for encoding properties of flat quantum space-time. In this paper we show how this formalism may be generalized to incorporate curvature (leading to what might be called ``doubly general relativity''). We first propose a dual to non-linear realizations of relativity in momentum space, and show that for such a dual the space-time invariant is an energy-dependent metric. This leads to an energy-dependent connection and curvature, and a simple modification to Einstein's equations. We then examine solutions to these equations. We find the counterpart to the cosmological metric, and show how cosmologies based upon our theory of gravity may solve the ``horizon problem''. We discuss the Schwarzchild solution, examining the conditions for which the horizon is energy dependent. We finally find the weak field limit.

  20. Network Gravity

    CERN Document Server

    Lombard, John

    2016-01-01

    We introduce the construction of a new framework for probing discrete emergent geometry and boundary-boundary observables based on a fundamentally a-dimensional underlying network structure. Using a gravitationally motivated action with Forman weighted combinatorial curvatures and simplicial volumes relying on a decomposition of an abstract simplicial complex into realized embeddings of proper skeletons, we demonstrate properties such as a minimal volume-scale cutoff, the necessity of a positive-definite cosmological constant as a regulator for non-degenerate geometries, and naturally emergent simplicial structures from Metropolis network evolution simulations with no restrictions on attachment rules or regular building blocks. We see emergent properties which echo results from both the spinfoam formalism and causal dynamical triangulations in quantum gravity, and provide analytical and numerical results to support the analogy. We conclude with a summary of open questions and intent for future work in develop...

  1. Newtonian gravity in loop quantum gravity

    OpenAIRE

    Smolin, Lee

    2010-01-01

    We apply a recent argument of Verlinde to loop quantum gravity, to conclude that Newton's law of gravity emerges in an appropriate limit and setting. This is possible because the relationship between area and entropy is realized in loop quantum gravity when boundaries are imposed on a quantum spacetime.

  2. Newtonian gravity in loop quantum gravity

    OpenAIRE

    Smolin, Lee

    2010-01-01

    We apply a recent argument of Verlinde to loop quantum gravity, to conclude that Newton's law of gravity emerges in an appropriate limit and setting. This is possible because the relationship between area and entropy is realized in loop quantum gravity when boundaries are imposed on a quantum spacetime.

  3. Improving the accuracy of GRACE Earth's gravitational field using the combination of different inclinations

    Institute of Scientific and Technical Information of China (English)

    Wei Zheng; Chenggang Shao; Jun Luo; Houze Xu

    2008-01-01

    In this paper,the GRACE Earth's gravitational field complete up to degree and order 120 is recovered based on the combination of different inclinations using the energy conservation principle.The results show that because different inclinations of satellite are sensitive to the geopotential coefficients with different degrees/and orders m.the design of GRACE exploiting 89° inclination can effectively improve the accuracy of geopotential zonal harmonic coefficients.However,it is less sensitive to the geopotential tesseral harmonic coefficients.Accordingly.the second group of GRACE exploiting lower inclination is required to determine high-accurately the geopotential tesseral harmonic coefficients and cover the shortage of the single group of GRACE exploiting 89° inclination.Two groups of GRACE individually exploiting 89°+(82°-84°)inclinations are the optimal combination of the Earth'S gravitational field recovery complete up to degree and order 120.In the degree 120,the joint accuracy of cumulative geoid height based on two groups of GRACE individually exploiting 89° and 83° inclinations is averagely two times higher than the accuracy of a group of GRACE exploiting 89° inclination.

  4. CHAMP gravity field recovery using the energy balance approach

    Directory of Open Access Journals (Sweden)

    Ch. Gerlach

    2003-01-01

    Full Text Available Since the early days of satellite geodesy energy balance based methods for gravity field determination have been considered. If non-conservative forces are known the Hamiltonian along the orbit is a constant of the motion. Thus the gravity field can be determined if position and velocity of the satellite are known and accelerometer measurements are available to model the non-conservative part. CHAMP is the first satellite that provides the user with those three kinds of data nearly continuously. Numerical investigations using real CHAMP data are presented to show the feasibility of the method. Using a semi-analytical approach the gravity field can be determined efficiently by a 2D-Fourier method. Those fast computations also give way to application of the method not only to a full gravity field recovery but also, e.g. for quick-look and validation of SST observations for satellite missions like CHAMP, GRACE or GOCE. The method can also be used for estimation of accelerometer calibration parameters.Key words. gravity field, energy balance, Jacobi-integral, non-conservative forces, accelerometer calibration, CHAMP

  5. Improving estimates of water resources in a semi-arid region by assimilating GRACE data into the PCR-GLOBWB hydrological model

    Science.gov (United States)

    Tangdamrongsub, Natthachet; Steele-Dunne, Susan; Gunter, Brian; Ditmar, Pavel; Sutanudjaja, Edwin; Sun, Yu; Xia, Ting; Wang, Zhongjing

    2016-04-01

    An accurate estimate of water resources is critical for proper management of both agriculture and the local ecology, particularly in semi-arid regions where water is scarce. Imperfections in model physics, uncertainties in model land parameters and meteorological data, and the human impact on land changes often limit the accuracy of hydrological models in estimating water storages. To address this problem, this study investigated the assimilation of Terrestrial Water Storage (TWS) estimates derived from the Gravity Recovery And Climate Experiment (GRACE) data using an Ensemble Kalman Filter (EnKF) approach. The region considered was the Hexi Corridor of Northern China. The hydrological model used for the analysis was PCR-GLOBWB, driven by satellite-based forcing data from April 2002 to December 2010. The performance of the GRACE Data Assimilation (DA) scheme was evaluated in terms of its impact on the TWS as well as on the individual hydrological storage estimates. The capability of GRACE DA to adjust the storage level was apparent not only in the TWS but also in the groundwater component, which had annual amplitude, phase, and long-term trend estimates closer to the GRACE observations. This study also assessed the impact of considering correlated errors in GRACE-based estimates. These were derived based on the error propagation approach using the full error variance-covariance matrices provided as a part of the GRACE data product. The assessment was carried out by comparing the EnKF results after excluding (EnKF 1D) and including (EnKF 3D) error correlations with the in situ groundwater data from 5 well sites, and the in situ streamflow data from two river gauges. Both EnKF 1D and 3D improved groundwater and streamflow estimates compared to the results from the PCR-GLOBWB alone (Ensemble Open Loop, EnOL). Although EnKF 3D was inferior to 1D at some groundwater measurement locations, on average, it showed equal or greater improvement in all metrics. For example

  6. Separating climate-induced mass transfers and instrumental effects from tectonic signal in repeated absolute gravity measurements

    Science.gov (United States)

    Van Camp, M.; Viron, O.; Avouac, J. P.

    2016-05-01

    We estimate the signature of the climate-induced mass transfers in repeated absolute gravity measurements based on satellite gravimetric measurements from the Gravity Recovery and Climate Experiment (GRACE) mission. We show results at the globe scale and compare them with repeated absolute gravity (AG) time behavior in three zones where AG surveys have been published: Northwestern Europe, Canada, and Tibet. For 10 yearly campaigns, the uncertainties affecting the determination of a linear gravity rate of change range 3-4 nm/s2/a in most cases, in the absence of instrumental artifacts. The results are consistent with what is observed for long-term repeated campaigns. We also discuss the possible artifact that can result from using short AG survey to determine the tectonic effects in a zone of high hydrological variability. We call into question the tectonic interpretation of several gravity changes reported from stations in Tibet, in particular the variation observed prior to the 2015 Gorkha earthquake.

  7. Lineal gravity from planar gravity

    CERN Document Server

    Achúcarro, A

    1993-01-01

    We show how to obtain the two-dimensional black hole action by dimensional reduction of the three-dimensional Einstein action with a non-zero cosmological constant. Starting from the Chern-Simons formulation of 2+1 gravity, we obtain the 1+1 dimensional gauge formulation given by Verlinde. Remarkably, the proposed reduction shares the relevant features of the formulation of Cangemi and Jackiw, without the need for a central charge in the algebra. We show how the Lagrange multipliersin these formulations appear naturally as the remnants of the three dimensional connection associated to symmetries that have been lostin the dimensional reduction. The proposed dimensional reduction involves a shift in the three dimensional connection whose effect is to make the length of the extra dimension infinite.

  8. 低轨卫星精密定轨中重力场模型误差的补偿%Reducing Influence of Gravity Model Error in Precise Orbit Determination of Low Earth Orbit Satellites

    Institute of Scientific and Technical Information of China (English)

    郭金来; 胡敏; 赵齐乐; 郭道玉

    2007-01-01

    Based on the orbit integration and orbit fitting method, the influence of the characters of the gravity model, with different precisions, on the movement of low Earth orbit satellites was studied. The way and the effect of absorbing the influence of gravity model error on CHAMP and GRACE satellite orbits, using linear and periodical empirical acceleration models and the so-called "pseudo-stochastic pulses" model, were also analyzed.

  9. Evaluation of the third- and fourth-generation GOCE Earth gravity field models with Australian terrestrial gravity data in spherical harmonics

    Science.gov (United States)

    Rexer, Moritz; Hirt, Christian; Pail, Roland; Claessens, Sten

    2014-04-01

    In March 2013, the fourth generation of European Space Agency's (ESA) global gravity field models, DIR4 (Bruinsma et al. in Proceedings of the ESA living planet symposium, 28 June-2 July, Bergen, ESA, Publication SP-686, 2010b) and TIM4 (Migliaccio et al. in Proceedings of the ESA living planet symposium, 28 June-2 July, Bergen, ESA, Publication SP-686, 2010), generated from the Gravity field and steady-state Ocean Circulation Explorer (GOCE) gravity observation satellite was released. We evaluate the models using an independent ground truth data set of gravity anomalies over Australia. Combined with Gravity Recovery and Climate Experiment (GRACE) satellite gravity, a new gravity model is obtained that is used to perform comparisons with GOCE models in spherical harmonics. Over Australia, the new gravity model proves to have significantly higher accuracy in the degrees below 120 as compared to EGM2008 and seems to be at least comparable to the accuracy of this model between degree 150 and degree 260. Comparisons in terms of residual quasi-geoid heights, gravity disturbances, and radial gravity gradients evaluated on the ellipsoid and at approximate GOCE mean satellite altitude ( km) show both fourth generation models to improve significantly w.r.t. their predecessors. Relatively, we find a root-mean-square improvement of 39 % for the DIR4 and 23 % for TIM4 over the respective third release models at a spatial scale of 100 km (degree 200). In terms of absolute errors, TIM4 is found to perform slightly better in the bands from degree 120 up to degree 160 and DIR4 is found to perform slightly better than TIM4 from degree 170 up to degree 250. Our analyses cannot confirm the DIR4 formal error of 1 cm geoid height (0.35 mGal in terms of gravity) at degree 200. The formal errors of TIM4, with 3.2 cm geoid height (0.9 mGal in terms of gravity) at degree 200, seem to be realistic. Due to combination with GRACE and SLR data, the DIR models, at satellite altitude, clearly

  10. A Model of Graceful Exit in String Cosmology

    CERN Document Server

    Brustein, Ram; Brustein, Ram; Madden, Richard

    1998-01-01

    We construct, for the first time, a model of graceful exit transition from a dilaton-driven inflationary phase to a decelerated Friedman-Robertson-Walker era. Exploiting a demonstration that classical corrections can stabilize a high curvature string phase while the evolution is still in the weakly coupled regime, we show that if additional terms of the type that may result from quantum corrections to the string effective action exist, and induce violation of the null energy condition, then evolution towards a decelerated Friedman-Robertson-Walker phase is possible. We also observe that stabilizing the dilaton at a fixed value, either by capture in a potential minimum or by radiation production, may require that these quantum corrections are turned off, perhaps by non-perturbative effects or higher order contributions which overturn the null energy condition violation.

  11. Current Status of the GRACE Follow-On Mission

    Science.gov (United States)

    Watkins, Michael; Flechtner, Frank; Webb, Frank; Landerer, Felix; Grunwald, Ludwig

    2016-04-01

    The GRACE Follow-On Mission has now advanced to the Assembly and Test Phase with the delivery of essentially all satellite subsystems and science instruments. As of the time of this abstract submission, the team continues to plan launch in 2017. The project team is conducting tests of satellite and instrument operation and performance and putting together updated simulations of expected performance on-orbit, including intersatellite ranging (both microwave and laser), accelerometer, thermal variability and deformation, and other errors. In addition, all required ground analysis software of the Science Data System is in development and testing at JPL, The UTCSR, and GFZ, in preparation for fully integrated end-to-end (international) testing from Level-1 through Level-3 data in the coming year. In this presentation, we will provide the detailed status of project integration and test, the latest simulations of science performance, and schedule for remaining project milestones.

  12. Hydrologic Applications of GRACE Terrestrial Water Storage Data

    Science.gov (United States)

    Rodell, Matthew; Zaitchik, Benjamin F.; Li, Bailing; Bolten, John; Hourborg, Rasmus; Velicogna, Isabella; Famiglietti, Jay

    2009-01-01

    Gravimetry-based terrestrial water storage time series have great potential value for hydrological research and applications, because no other observing system can provide global maps of the integrated quantity of water stored on and below the land surface. However, these data are challenging to use because their spatial and temporal resolutions are low relative to other hydrological observations and because total terrestrial water storage is a measurement unfamiliar to hydrologists. In this presentation we will review techniques for temporal, horizontal, and vertical disaggregation of GRACE terrestrial water storage anomalies, including data assimilation and integration within a land surface model. We will then discuss initial results from three efforts to use the methods for water resources applications. These include drought monitoring across North America, water cycle assessment over the Middle East North African region, and groundwater depletion estimates for northern India.

  13. Inflation with a graceful exit in a random landscape

    Energy Technology Data Exchange (ETDEWEB)

    Pedro, F.G. [Univ. Autonoma de Madrid (Spain). Dept. de Fisica Teorica y Inst. de Fisica Teorica UAM/CSIC; Westphal, A. [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany). Theory Group

    2016-11-15

    We develop a stochastic description of small-field inflationary histories with a graceful exit in a random potential whose Hessian is a Gaussian random matrix as a model of the unstructured part of the string landscape. The dynamical evolution in such a random potential from a small-field inflation region towards a viable late-time de Sitter (dS) minimum maps to the dynamics of Dyson Brownian motion describing the relaxation of non-equilibrium eigenvalue spectra in random matrix theory. We analytically compute the relaxation probability in a saddle point approximation of the partition function of the eigenvalue distribution of the Wigner ensemble describing the mass matrices of the critical points. When applied to small-field inflation in the landscape, this leads to an exponentially strong bias against small-field ranges and an upper bound N<<10 on the number of light fields N participating during inflation from the non-observation of negative spatial curvature.

  14. E-gravity theory

    OpenAIRE

    Linker, Patrick

    2016-01-01

    A couple of quantum gravity theories were proposed to make theoretical predictions about the behavior of gravity. The most recent approach to quantum gravity, called E-theory, is proposed mathematical, but there is not formulated much about what dynamics of gravity this theory proposes. This research paper treats the main results of the application of E-theory to General relativity involving conservation laws and scattering of particles in presence of gravity. Also the low-energy limit of thi...

  15. Water Storage Changes in the Tigris-Euphrates River Basin and the Middle East from GRACE with Implications for Transboundary Water Management

    Science.gov (United States)

    Voss, K.; Famiglietti, J. S.; Lo, M.; De Linage, C.

    2011-12-01

    In this work, we use observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to evaluate freshwater storage trends in the Tigris-Euphrates River Basin from January 2003 to December 2009. GRACE data show an alarming rate of decrease in total water storage of approximately -27.2 ± 0.6 mm/year equivalent water height, equal to a volume of 143.6 km3 during the course of the study period. We use additional remote-sensing information and output from land-surface models to identify that groundwater losses are the major source of this trend. The approach followed here provides an example of 'best current capabilities' in regions like the Middle East, where data access can be severely limited. Results indicate that the Tigris-Euphrates River Basin region lost 15.6 ± 2.9 mm/year of groundwater during the study period, or 82.3 ± 15.4 km3 in volume. Furthermore, results raise important issues regarding water use in transboundary river basins and aquifers, including the necessity of international water use treaties and resolving discrepancies in international water law, while amplifying the need for increased monitoring for core components of the water budget.

  16. Groundwater depletion in the Middle East from GRACE with implications for transboundary water management in the Tigris-Euphrates-Western Iran region

    Science.gov (United States)

    Voss, Katalyn A.; Famiglietti, James S.; Lo, MinHui; de Linage, Caroline; Rodell, Matthew; Swenson, Sean C.

    2013-02-01

    In this study, we use observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to evaluate freshwater storage trends in the north-central Middle East, including portions of the Tigris and Euphrates River Basins and western Iran, from January 2003 to December 2009. GRACE data show an alarming rate of decrease in total water storage of approximately -27.2±0.6 mm yr-1 equivalent water height, equal to a volume of 143.6 km3 during the course of the study period. Additional remote-sensing information and output from land surface models were used to identify that groundwater losses are the major source of this trend. The approach used in this study provides an example of "best current capabilities" in regions like the Middle East, where data access can be severely limited. Results indicate that the region lost 17.3±2.1 mm yr-1 equivalent water height of groundwater during the study period, or 91.3±10.9 km3 in volume. Furthermore, results raise important issues regarding water use in transboundary river basins and aquifers, including the necessity of international water use treaties and resolving discrepancies in international water law, while amplifying the need for increased monitoring for core components of the water budget.

  17. Groundwater Depletion in the Middle East from GRACE with Implications for Transboundary Water Management in the Tigris-Euphrates-Western Iran Region

    Science.gov (United States)

    Voss, Katalyn A.; Famiglietti, James S.; Lo, MinHui; De Linage, Caroline; Rodell, Matthew; Swenson, Sean C.

    2013-01-01

    In this study, we use observations from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to evaluate freshwater storage trends in the north-central Middle East, including portions of the Tigris and Euphrates River Basins and western Iran, from January 2003 to December 2009. GRACE data show an alarming rate of decrease in total water storage of approximately -27.2 plus or minus 0.6 millimeters per year equivalent water height, equal to a volume of 143.6 cubic kimometers during the course of the study period. Additional remote-sensing information and output from land surface models were used to identify that groundwater losses are the major source of this trend. The approach used in this study provides an example of ''best current capabilities'' in regions like the Middle East, where data access can be severely limited. Results indicate that the region lost 17.3 plus or minus 2.1 millimeters per year equivalent water height of groundwater during the study period, or 91.3 plus or minus 10.9 cubic kilometers in volume. Furthermore, results raise important issues regarding water use in transboundary river basins and aquifers, including the necessity of international water use treaties and resolving discrepancies in international water law, while amplifying the need for increased monitoring for core components of the water budget.

  18. 76 FR 63575 - Transportation Conformity Rule: MOVES Regional Grace Period Extension

    Science.gov (United States)

    2011-10-13

    ... [Federal Register Volume 76, Number 198 (Thursday, October 13, 2011)] [Proposed Rules] [Pages...-0393; FRL-9477-9] RIN 2060-AR03 Transportation Conformity Rule: MOVES Regional Grace Period Extension... for regional emissions analyses for transportation conformity determinations (``regional conformity...

  19. SITE TECHNOLOGY CAPSULE: GRACE DEARBORN INC.'S DARAMEND BIOREMEDIATION TECHNOLOGY

    Science.gov (United States)

    Grace Dearborn's DARAMEND Bioremediation Technology was developed to treat soils/sediment contaminated with organic contaminants using solid-phase organic amendments. The amendments increase the soil's ability to supply biologically available water/nutrients to microorganisms and...

  20. An Algorithm for Odd Graceful Labeling of the Union of Paths and Cycles

    Directory of Open Access Journals (Sweden)

    M. Ibrahim Moussa

    2010-03-01

    Full Text Available In 1991, Gnanajothi [4] proved that the path graph Pn with n vertex and n -1edge is odd graceful, andthe cycle graph Cm with m vertex and m edges is odd graceful if and only if m even, she proved thecycle graph is not graceful if m odd. In this paper, firstly, we studied the graph m n C ÈP when m = 4, 6,8,10and then we proved that the graph m n C ÈP is odd graceful if m is even. Finally, we described analgorithm to label the vertices and the edges of the vertex set ( V CmÈPn and the edge set ( E CmÈPn .

  1. RCRA Facility Investigation/Remedial Investigation Report for the Grace Road Site (631-22G)

    Energy Technology Data Exchange (ETDEWEB)

    Palmer, E.

    1998-10-02

    This report summarizes the activities and documents the results of a Resource Conservation and Recovery Act Facility Investigation/Remedial Investigation conducted at Grace Road Site on the Savannah River Site near Aiken, South Carolina.

  2. RFP to work on formation flying capabilities for spacecrafts for the GRACE project

    DEFF Research Database (Denmark)

    Riis, Troels; Thuesen, Gøsta; Kilsgaard, Søren

    1999-01-01

    The National Aeronautics and Space Agency of USA, NASA, are working on formation flying capabilities for spacecrafts, GRACE Project. IAU and JPL are developing the inter spacecraft attitude link to be used on the two spacecrafts.......The National Aeronautics and Space Agency of USA, NASA, are working on formation flying capabilities for spacecrafts, GRACE Project. IAU and JPL are developing the inter spacecraft attitude link to be used on the two spacecrafts....

  3. Prognostic Value of TIMI Score versus GRACE Score in ST-segment Elevation Myocardial Infarction

    Directory of Open Access Journals (Sweden)

    Luis C. L. Correia

    2014-08-01

    Full Text Available Background: The TIMI Score for ST-segment elevation myocardial infarction (STEMI was created and validated specifically for this clinical scenario, while the GRACE score is generic to any type of acute coronary syndrome. Objective: Between TIMI and GRACE scores, identify the one of better prognostic performance in patients with STEMI. Methods: We included 152 individuals consecutively admitted for STEMI. The TIMI and GRACE scores were tested for their discriminatory ability (C-statistics and calibration (Hosmer-Lemeshow in relation to hospital death. Results: The TIMI score showed equal distribution of patients in the ranges of low, intermediate and high risk (39 %, 27 % and 34 %, respectively, as opposed to the GRACE Score that showed predominant distribution at low risk (80 %, 13 % and 7%, respectively. Case-fatality was 11%. The C-statistics of the TIMI score was 0.87 (95%CI = 0.76 to 0.98, similar to GRACE (0.87, 95%CI = 0.75 to 0.99 - p = 0.71. The TIMI score showed satisfactory calibration represented by χ2 = 1.4 (p = 0.92, well above the calibration of the GRACE score, which showed χ2 = 14 (p = 0.08. This calibration is reflected in the expected incidence ranges for low, intermediate and high risk, according to the TIMI score (0 %, 4.9 % and 25 %, respectively, differently to GRACE (2.4%, 25% and 73%, which featured middle range incidence inappropriately. Conclusion: Although the scores show similar discriminatory capacity for hospital death, the TIMI score had better calibration than GRACE. These findings need to be validated populations of different risk profiles.

  4. On Graceful Spider Graphs with at Most Four Legs of Lengths Greater than One

    Directory of Open Access Journals (Sweden)

    A. Panpa

    2016-01-01

    Full Text Available A graceful labeling of a tree T with n edges is a bijection f:V(T→{0,1,2,…,n} such that {|f(u-f(v|:uv∈E(T} equal to {1,2,…,n}. A spider graph is a tree with at most one vertex of degree greater than 2. We show that all spider graphs with at most four legs of lengths greater than one admit graceful labeling.

  5. Towards Designing Graceful Degradation into Trajectory Based Operations: A Human-systems Integration Approach

    Science.gov (United States)

    Edwards, Tamsyn; Lee, Paul

    2017-01-01

    One of the most fundamental changes to the air traffic management system in NextGen is the concept of trajectory based operations (TBO). With the introduction of such change, system safety and resilience is a critical concern, in particular, the ability of systems to gracefully degrade. In order to design graceful degradation into a TBO envrionment, knowledge of the potential causes of degradation, and appropriate solutions, is required. In addition, previous research has predominantly explored the technological contribution to graceful degradation, frequently neglecting to consider the role of the human operator, specifically, air traffic controllers (ATCOs). This is out of step with real-world operations, and potentially limits an ecologically valid understanding of achieving graceful degradation in an air traffic control (ATC) environment. The following literature review aims to identify and summarize the literature to date on the potential causes of degradation in ATC and the solutions that may be applied within a TBO context, with a specific focus on the contribution of the air traffic controller. A framework of graceful degradation, developed from the literature, is presented. It is argued that in order to achieve graceful degradation within TBO, a human-system integration approach must be applied.

  6. Regional GRACE-based estimates of water mass variations over Australia: validation and interpretation

    Directory of Open Access Journals (Sweden)

    L. Seoane

    2013-04-01

    Full Text Available Time series of regional 2°-by-2° GRACE solutions have been computed from 2003 to 2011 with a 10 day resolution by using an energy integral method over Australia [112° E 156° E; 44° S 10° S]. This approach uses the dynamical orbit analysis of GRACE Level 1 measurements, and specially accurate along-track K Band Range Rate (KBRR residuals (1 μm s−1 level of error to estimate the total water mass over continental regions. The advantages of regional solutions are a significant reduction of GRACE aliasing errors (i.e. north–south stripes providing a more accurate estimation of water mass balance for hydrological applications. In this paper, the validation of these regional solutions over Australia is presented as well as their ability to describe water mass change as a reponse of climate forcings such as El Niño. Principal component analysis of GRACE-derived total water storage maps show spatial and temporal patterns that are consistent with independent datasets (e.g. rainfall, climate index and in-situ observations. Regional TWS show higher spatial correlations with in-situ water table measurements over Murray–Darling drainage basin (80–90%, and they offer a better localization of hydrological structures than classical GRACE global solutions (i.e. Level 2 GRGS products and 400 km ICA solutions as a linear combination of GFZ, CSR and JPL GRACE solutions.

  7. Enhanced GPS-based GRACE baseline determination by using a new strategy for ambiguity resolution and relative phase center variation corrections

    Science.gov (United States)

    Gu, Defeng; Ju, Bing; Liu, Junhong; Tu, Jia

    2017-09-01

    Precise relative position determination is a prerequisite for radar interferometry by formation flying satellites. It has been shown that this can be achieved by high-quality, dual-frequency GPS receivers that provide precise carrier-phase observations. The precise baseline determination between satellites flying in formation can significantly improve the accuracy of interferometric products, and has become a research interest. The key technologies of baseline determination using spaceborne dual-frequency GPS for gravity recovery and climate experiment (GRACE) formation are presented, including zero-difference (ZD) reduced dynamic orbit determination, double-difference (DD) reduced dynamic relative orbit determination, integer ambiguity resolution and relative receiver antenna phase center variation (PCV) estimation. We propose an independent baseline determination method based on a new strategy of integer ambiguity resolution and correction of relative receiver antenna PCVs, and implement the method in the NUDTTK software package. The algorithms have been tested using flight data over a period of 120 days from GRACE. With the original strategy of integer ambiguity resolution based on Melbourne-Wübbena (M-W) combinations, the average success rate is 85.6%, and the baseline precision is 1.13 mm. With the new strategy of integer ambiguity resolution based on a priori relative orbit, the average success rate and baseline precision are improved by 5.8% and 0.11 mm respectively. A relative ionosphere-free phase pattern estimation result is given in this study, and with correction of relative receiver antenna PCVs, the baseline precision is further significantly improved by 0.34 mm. For ZD reduced dynamic orbit determination, the orbit precision for each GRACE satellite A or B in three dimensions (3D) is about 2.5 cm compared to Jet Propulsion Laboratory (JPL) post science orbits. For DD reduced dynamic relative orbit determination, the final baseline precision for two

  8. Gravity and InSAR remote sensing of groundwater usage in the Sahel and Horn of Africa

    Science.gov (United States)

    Neely, W.; Borsa, A. A.; Burney, J. A.; Devlin, K.

    2016-12-01

    Changes in the Earth's climatic systems influence agro-ecological conditions on local, regional, and global scales. With the world's highest population growth rate, sub-Saharan Africa faces particularly acute concerns regarding food security and resource management. Historical sources of surface water for agricultural production may become less reliable and/or limited with increased climate variability, and African countries have already begun to depend on more stable sources of groundwater. Expected increases in groundwater usage pose questions about the sustainability of current agricultural practices, which require new sources of information to answer. Due to the logistics and costs to implement in situ networks to monitor regional water security, current remote sensing missions offer an affordable alternative. The Gravity Recovery and Climate Experiment (GRACE) has proven to be effective in quantifying changes in terrestrial water storage (TWS) at the regional scale using near-monthly gravity measurements from orbit. Using over a decade of measurements, we estimate TWS anomalies in Niger and Ethiopia. These anomalies offer a proxy for hydrological stressing, indicating potential targets for additional analysis. We use independent, but complementary, estimates of surface displacements from Interferometric Synthetic Aperture Radar (InSAR) to provide information on local groundwater withdrawal. Using data from ESA's Sentinel 1 mission and JAXA's Advanced Land Observing Satellite (ALOS) missions, we characterize the surface deformation over the past decade in regions of active groundwater pumping using the Small Baseline Subset (SBAS) technique. In particular, we investigate ties of ground motion to known agricultural/industrial land usage near Niamey, Niger and Eastern Oromia, Ethiopia to better understand how human activity affects available groundwater resources.

  9. Antimatter gravity with muonium

    CERN Document Server

    Kaplan, Daniel M; Kirch, Klaus; Mancini, Derrick; Phillips, James D; Phillips, Thomas J; Reasenberg, Robert D; Roberts, Thomas J; Terry, Jeff

    2016-01-01

    The gravitational acceleration of antimatter, $\\bar{g}$, has never been directly measured and could bear importantly on our understanding of gravity, the possible existence of a fifth force, and the nature and early history of the universe. Three avenues appear feasible for such a measurement: antihydrogen, positronium, and muonium. The muonium measurement requires a novel monoenergetic, low-velocity, horizontal muonium beam directed at an atom interferometer. The precision three-grating interferometer can be produced in silicon nitride or ultrananocrystalline diamond using state-of-the-art nanofabrication. The required precision alignment and calibration at the picometer level also appear to be feasible. With 100 nm grating pitch, a 10% measurement of $\\bar{g}$ can be made using some months of surface-muon beam time, and a 1% or better measurement with a correspondingly larger exposure. This could constitute the first gravitational measurement of leptonic matter, of 2nd-generation matter and, possibly, the f...

  10. Signature of range observable in non-dynamical Chern-Simons modified gravity and the measurements with satellite-satellite tracking missions. Theoretical Studies

    CERN Document Server

    Qiang, Li-E

    2014-01-01

    Having great accuracy in the range and range rate measurements, the operating GRACE mission and the planed GRACE Follow On mission can in principle be employed to place strong constraints on certain relativistic gravity theories. In this paper, we work out in details the range observable in the non-dynamical Chern-Simons modified gravity for these Satellite-Satellite Tracking measurements. We find out that an characteristic time accumulating signal appears in the range observable in the non-dynamical Chern-Simons gravity, which has no analogy found in the standard metric theories of gravity. The magnitude of this Chern-Simons range signal will reach to a few times of $(\\frac{\\dot{\\theta}}{100r})meters$ for each free flight of these SST missions, here $\\dot{\\theta}$ measures the length scale of the theory and $r$ denotes the orbital radius of the SST mission. Therefore, with the 12 years data from the GRACE mission and the proper data analysis methods, one expects that the mass scale of the non-dynamical CS gr...

  11. Inflationary cosmology in unimodular F(T) gravity

    Science.gov (United States)

    Bamba, Kazuharu; Odintsov, Sergei D.; Saridakis, Emmanuel N.

    2017-07-01

    We investigate the inflationary realization in the context of unimodular F(T) gravity, which is based on the F(T) modification of teleparallel gravity, in which one imposes the unimodular condition through the use of Lagrange multipliers. We develop the general reconstruction procedure of the F(T) form that can give rise to a given scale-factor evolution, and then we apply it in the inflationary regime. We extract the Hubble slow-roll parameters that allow us to calculate various inflation-related observables, such as the scalar spectral index and its running, the tensor-to-scalar ratio, and the tensor spectral index. Then, we examine the particular cases of de Sitter and power-law inflation, of Starobinsky inflation, as well as inflation in a specific model of unimodular F(T) gravity. As we show, in all cases the predictions of our scenarios are in a very good agreement with Planck observational data. Finally, inflation in unimodular F(T) gravity has the additional advantage that it always allows for a graceful exit for specific regions of the model parameters.

  12. A(i)-系列对虾树的优美性%On Gracefulness of A (i)-series Lobsters

    Institute of Scientific and Technical Information of China (English)

    程辉; 刘文娟; 姚兵

    2011-01-01

    The graceful trees conjecture is a longstanding conjecture. Bermond conjectured that every lobster is graceful in 1979. The gracefulness and odd gracefulness about a class of A ( i )-series lobsters are discussed and relevant conclusion is given.%优美树猜想是一个历史悠久的猜想.1979年,Bermond猜想每一棵对虾树都是优美的.讨论了一类A(i)-系列对虾树的优美性和奇优美性,并给出相应结论.

  13. Performance analysis of satellite constellations for the next generation of gravity missions

    Science.gov (United States)

    Raimondo, J.; Flechtner, F.; Löcher, A.; Kusche, J.

    2011-12-01

    The GOCE and GRACE gravity missions have dramatically improved the knowledge of the Earth's static and time-variable gravity field due to their highly precise on-board instrumentation. This resulted in new information about the mass distribution and transport within or around the Earth system to be used in solid Earth geophysics, oceanography and sea level studies, hydrology, ice mass budget investigations and geodesy. GFZ Potsdam and IGG Bonn, with partners from German industry and universities, have conducted several studies in order to develop a concept for a future gravity mission based on low-low satellite-to-satellite tracking, but realized with laser metrology. In our poster we summarize the performance of different mission scenarios through full-scale simulations and their capacity to reach the science objectives.

  14. Higher-Derivative $f(R,\\Box R, T)$ Theories of Gravity

    CERN Document Server

    Houndjo, M J S; Mazhari, N S; Momeni, D; Myrzakulov, R

    2016-01-01

    In literature there is a model of modified gravity in which the matter Lagrangian is coupled to the geometry via trace of the stress-energy momentum tensor $T=T_{\\mu}^{\\mu}$. This type of modified gravity is called as $f(R,T)$ in which $R$ is Ricci scalar $R=R_{\\mu}^{\\mu}$. We extend manifestly this model to include the higher derivative term $\\Box R$. We derived equation of motion (EOM) for the model by starting from the basic variational principle. Later we investigate FLRW cosmology for our model. We show that de Sitter solution is unstable for a generic type of $f(R,\\Box R, T)$ model. Furthermore we investigate an inflationary scenario based on this model. A graceful exit from inflation is guaranteed in this type of modified gravity.

  15. Assessing Links Between Water and Carbon Storage in Indonesian Peatlands Using Data from the Gravity Recovery and Climate Experiment

    Science.gov (United States)

    Swails, E.; Reager, J. T., II; Randerson, J. T.; Famiglietti, J. S.; Lawrence, D.; Yu, K.

    2014-12-01

    Deforestation and drainage of tropical peat swamp forests for conversion to other uses results in a loss of carbon storage through the clearing and burning of forest vegetation as well as decomposition of peat soils and increased frequency of fires following drainage. We used Gravity Recovery and Climate Experiment (GRACE) terrestrial water storage observations and a global forest cover change product to investigate trends in terrestrial water storage associated with land use conversion in Indonesian peatlands between 2002 and 2012. Our initial analysis indicated that secular trends in GRACE terrestrial water storage were consistent with the spatial distribution of peatlands drained for the establishment of oil palm plantations. A decreasing trend in GRACE terrestrial water storage measurements over the observation period indicated a substantial decrease in water table heights. Combining this information with measurements of bulk density and carbon content of surface peat layers, we estimated potential emissions from carbon stocks now vulnerable to oxidation. Independent measurements of fire carbon emissions were used to estimate the fraction of committed emission that was combusted. Our research represents the first known application of GRACE data to assess loss of soil carbon storage associated with depletion of soil water.

  16. Urine specific gravity test

    Science.gov (United States)

    ... medlineplus.gov/ency/article/003587.htm Urine specific gravity test To use the sharing features on this page, please enable JavaScript. Urine specific gravity is a laboratory test that shows the concentration ...

  17. Idaho State Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (24,284 records) were compiled by the U. S. Geological Survey. This data base was received on February 23, 1993. Principal gravity...

  18. Northern Oklahoma Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (710 records) were compiled by Professor Ahern. This data base was received in June 1992. Principal gravity parameters include latitude,...

  19. Andes 1997 Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Central Andes gravity data (6,151 records) were compiled by Professor Gotze and the MIGRA Group. This data base was received in April, 1997. Principal gravity...

  20. DNAG Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Decade of North American Geology (DNAG) gravity grid values, spaced at 6 km, were used to produce the Gravity Anomaly Map of North America (1987; scale...

  1. Cadiz, California Gravity Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The gravity station data (32 records) were gathered by Mr. Seth I. Gutman for AridTech Inc., Denver, Colorado using a Worden Prospector gravity meter. This data base...

  2. Classical Weyl Transverse Gravity

    CERN Document Server

    Oda, Ichiro

    2016-01-01

    We study various classical aspects of the Weyl transverse (WTDiff) gravity in a general space-time dimension. First of all, we clarify a classical equivalence among three kinds of gravitational theories, those are, the conformally-invariant scalar tensor gravity, Einstein's general relativity and the WTDiff gravity via the gauge fixing procedure. Secondly, we show that in the WTDiff gravity the cosmological constant is a mere integration constant as in unimodular gravity, but it does not receive any radiative corrections unlike the unimodular gravity. A key point in this proof is to construct a covariantly conserved energy-momentum tensor, which is achieved on the basis of this equivalence relation. Thirdly, we demonstrate that the Noether current for the Weyl transformation is identically vanishing, thereby implying that the Weyl symmetry existing in both the conformally-invariant scalar tensor gravity and the WTDiff gravity is a "fake" symmetry. We find it possible to extend this proof to all matter fields,...

  3. A Transportable Gravity Gradiometer Based on Atom Interferometry

    Science.gov (United States)

    Yu, Nan; Thompson, Robert J.; Kellogg, James R.; Aveline, David C.; Maleki, Lute; Kohel, James M.

    2010-01-01

    A transportable atom interferometer-based gravity gradiometer has been developed at JPL to carry out measurements of Earth's gravity field at ever finer spatial resolutions, and to facilitate high-resolution monitoring of temporal variations in the gravity field from ground- and flight-based platforms. Existing satellite-based gravity missions such as CHAMP and GRACE measure the gravity field via precise monitoring of the motion of the satellites; i.e. the satellites themselves function as test masses. JPL's quantum gravity gradiometer employs a quantum phase measurement technique, similar to that employed in atomic clocks, made possible by recent advances in laser cooling and manipulation of atoms. This measurement technique is based on atomwave interferometry, and individual laser-cooled atoms are used as drag-free test masses. The quantum gravity gradiometer employs two identical atom interferometers as precision accelerometers to measure the difference in gravitational acceleration between two points (Figure 1). By using the same lasers for the manipulation of atoms in both interferometers, the accelerometers have a common reference frame and non-inertial accelerations are effectively rejected as common mode noise in the differential measurement of the gravity gradient. As a result, the dual atom interferometer-based gravity gradiometer allows gravity measurements on a moving platform, while achieving the same long-term stability of the best atomic clocks. In the laboratory-based prototype (Figure 2), the cesium atoms used in each atom interferometer are initially collected and cooled in two separate magneto-optic traps (MOTs). Each MOT, consisting of three orthogonal pairs of counter-propagating laser beams centered on a quadrupole magnetic field, collects up to 10(exp 9) atoms. These atoms are then launched vertically as in an atom fountain by switching off the magnetic field and introducing a slight frequency shift between pairs of lasers to create a moving

  4. Phase Residual Estimations for PCVs of Spaceborne GPS Receiver Antenna and Their Impacts on Precise Orbit Determination of GRACE Satellites

    Institute of Scientific and Technical Information of China (English)

    TU Jia; GU Defeng; WU Yi; YI Dongyun

    2012-01-01

    In-flight phase center systematic errors of global positioning system (GPS) receiver antenna are the main restriction for improving the precision of precise orbit determination using dual-frequency GPS.Residual approach is one of the valid methods for in-flight calibration of GPS receiver antenna phase center variations (PCVs) from ground calibration.In this paper,followed by the correction model of spaceborne GPS receiver antenna phase center,ionosphere-free PCVs can be directly estimated by ionosphere-free carrier phase post-fit residuals of reduced dynamic orbit determination.By the data processing of gravity recovery and climate experiment (GRACE) satellites,the following conclusions are drawn.Firstly,the distributions of ionosphere-free carrier phase post-fit residuals from different periods have the similar systematic characteristics.Secondly,simulations show that the influence of phase residual estimations for ionosphere-free PCVs on orbit determination can reach the centimeter level.Finally,it is shown by in-flight data processing that phase residual estimations of current period could not only be used for the calibration for GPS receiver antenna phase center of foretime and current period,but also be used for the forecast of ionosphere-free PCVs in future period,and the accuracy of orbit determination can be well improved.

  5. Determination of gravitational potential distribution over a geocentric quasi- sphere based on links between GRACE- and GNSS-type satellites

    Science.gov (United States)

    Shen, Ziyu; Shen, Wen-Bin

    2017-04-01

    We provide a formulation of determining the Earth's gravitational potential distribution over a geocentric quasi-sphere (QS) that is constructed by a GRACE-type satellite (GTS), based on frequency signal transmission between the GTS and a cluster of GNSS satellites (CGS). By emitting and receiving frequency signals between the GTS and a GNSS satellite, we can determine the gravitational potential at the GTS orbit. For a near-polar GTS with height about 350 km above the geoid, we choose sufficient GNSS satellites to determine the gravitational potential at the GTS position. Simulation results show that the accuracy of the determined gravitational potential distribution over the QS can achieve centimeter level if (1) the accuracy of the given potentials at GDSs is about 1 cm level, and (2) optical atomic clocks with instability of 1*10E-18 are available. Our final purpose is to determine the Earth's external gravity field based on the potential distribution on the QS. This study is supported by National 973 Project China (grant No. 2013CB733301 and 2013CB733305) and NSFCs (grant Nos. 41174011, 41429401, 41210006, 41128003, 41021061)

  6. Physics of Artificial Gravity

    Science.gov (United States)

    Bukley, Angie; Paloski, William; Clement, Gilles

    2006-01-01

    This chapter discusses potential technologies for achieving artificial gravity in a space vehicle. We begin with a series of definitions and a general description of the rotational dynamics behind the forces ultimately exerted on the human body during centrifugation, such as gravity level, gravity gradient, and Coriolis force. Human factors considerations and comfort limits associated with a rotating environment are then discussed. Finally, engineering options for designing space vehicles with artificial gravity are presented.

  7. Terrestrial Gravity Fluctuations

    CERN Document Server

    Harms, Jan

    2015-01-01

    The article reviews the current state of the field, and also presents new analyses especially with respect to the impact of seismic scattering on gravity perturbations, active gravity noise cancellation, and time-domain models of gravity perturbations from atmospheric and seismic point sources. Our understanding of terrestrial gravity fluctuations will have great impact on the future development of GW detectors and high-precision gravimetry in general, and many open questions need to be answered still as emphasized in this article.

  8. Coseismic gravity and displacement changes of Japan Tohoku earthquake (Mw 9.0)

    Institute of Scientific and Technical Information of China (English)

    Xinlin Zhang; Shuhei Okubo; Yoshiyuki Tanaka; Hui Li

    2016-01-01

    The greatest earthquake in the modern history of Japan and probably the fourth greatest in the last 100 years in the world occurred on March 11, 2011 off the Pacific coast of Tohoku. Large tsunami and ground motions caused severe damage in wide areas, particularly many towns along the Pacific coast. So far, gravity change caused by such a great earthquake has been reported for the 1964 Alaska and the 2010 Maule events. However, the spatial-tem-poral resolution of the gravity data for these cases is insufficient to depict a co-seismic gravity field variation in a spatial scale of a plate subduction zone. Here, we report an unequivocal co-seismic gravity change over the Japanese Island, obtained from a hybrid gravity observation (combined absolute and relative gravity measurements). The time in-terval of the observation before and after the earthquake is within 1 year at almost all the observed sites, including 13 absolute and 16 relative measurement sites, which deduced tectonic and environmental contributions to the gravity change. The observed gravity agrees well with the result calculated by a dislocation theory based on a self-gravitating and layered spherical earth model. In this computation, a co-seismic slip distribution is determined by an inversion of Global Positioning System (GPS) data. Of particular interest is that the observed gravity change in some area is negative where a remarkable subsi-dence is observed by GPS, which can not be explained by simple vertical movement of the crust. This indicated that the mass redistribution in the underground affects the gravity change. This result supports the result that Gravity Recovery and Climate Experiment (GRACE) satellites detected a crustal dilatation due to the 2004 Sumatra earthquake by the terrestrial observation with a higher spatial and temporal resolution.

  9. Covariant w∞ gravity

    NARCIS (Netherlands)

    Bergshoeff, E.; Pope, C.N.; Stelle, K.S.

    1990-01-01

    We discuss the notion of higher-spin covariance in w∞ gravity. We show how a recently proposed covariant w∞ gravity action can be obtained from non-chiral w∞ gravity by making field redefinitions that introduce new gauge-field components with corresponding new gauge transformations.

  10. Continental-scale hydrological consistency of evapotranspiration products using GRACE

    Science.gov (United States)

    Lopez, O.; McCabe, M. F.

    2014-12-01

    Multiple remote sensing products based on satellite observations are available at regional and global scales, allowing to obtain an estimation of the individual components of the hydrological cycle. However, using these products to provide closure of the water budget at the basin scale with accuracy remains a challenge. In this work, 12 large continental-scale basins covering a range of various climate types were chosen as regions of interest. Terrestrial water storage changes from GRACE, streamflow data from the Global Runoff Database and precipitation from the Tropical Rainfall Measuring Mission (TRMM) Multi Satellite Precipitation Analysis (TMPA) and Global Precipitation Climatology Project (GPCP), were used as a surrogate evaluation of observed spatio-temporal patterns of multi-model evapotranspiration estimates, derived from a long-term flux product as part of the LandFLUX project. The 10 year period of analysis also allows for the estimation of temporal trends in water storage changes and provides an opportunity to examine the capacity for water budget closure.

  11. GRACES observations of young [alpha/Fe]-rich stars

    CERN Document Server

    Yong, David; Venn, Kim A; Chene, Andre-Nicolas; Keown, Jared; Malo, Lison; Martioli, Eder; Alves-Brito, Alan; Asplund, Martin; Dotter, Aaron; Martell, Sarah L; Melendez, Jorge; Schlesinger, Katharine J

    2016-01-01

    We measure chemical abundance ratios and radial velocities in four massive (i.e., young) [alpha/Fe]-rich red giant stars using high-resolution high-S/N spectra from ESPaDOnS fed by Gemini-GRACES. Our differential analysis ensures that our chemical abundances are on the same scale as the Alves-Brito et al. (2010) study of bulge, thin and thick disk red giants. We confirm that the program stars have enhanced [alpha/Fe] ratios and are slightly metal poor. Aside from lithium enrichment in one object, the program stars exhibit no chemical abundance anomalies when compared to giant stars of similar metallicity throughout the Galaxy. This includes the elements Li, O, Si, Ca, Ti, Cr, Ni, Cu, Ba, La, and Eu. Therefore, there are no obvious chemical signatures that can help to reveal the origin of these unusual stars. While our new observations show that only one star (not the Li-rich object) exhibits a radial velocity variation, simulations indicate that we cannot exclude the possibility that all four could be binarie...

  12. Inflation with a graceful exit in a random landscape

    CERN Document Server

    Pedro, Francisco G

    2016-01-01

    We develop a stochastic description of small-field inflationary histories with a graceful exit in a random potential whose Hessian is a Gaussian random matrix as a model of the unstructured part of the string landscape. The dynamical evolution in such a random potential from a small-field inflation region towards a viable late-time de Sitter (dS) minimum maps to the dynamics of Dyson Brownian motion describing the relaxation of non-equilibrium eigenvalue spectra in random matrix theory. We analytically compute the relaxation probability in a saddle point approximation of the partition function of the eigenvalue distribution of the Wigner ensemble describing the mass matrices of the critical points. When applied to small-field inflation in the landscape, this leads to an exponentially strong bias against small-field ranges and an upper bound $N\\ll 10$ on the number of light fields $N$ participating during inflation from the non-observation of negative spatial curvature.

  13. A mascon approach to assess ice sheet and glacier mass balances and their uncertainties from GRACE data

    NARCIS (Netherlands)

    Schrama, E.J.O.; Wouters, B.; Rietbroek, R.

    2014-01-01

    The purpose of this paper is to assess the mass changes of the Greenland Ice Sheet (GrIS), Ice Sheets over Antarctica, and Land glaciers and Ice Caps with a global mascon method that yields monthly mass variations at 10,242 mascons. Input for this method are level 2 data from the Gravity Recovery an

  14. Estimating the rates of mass change, ice volume change and snow volume change in Greenland from ICESat and GRACE data

    NARCIS (Netherlands)

    Slobbe, D.C.; Ditmar, P.G.; Lindenbergh, R.C.

    2008-01-01

    The focus of this paper is on the quantification of ongoing mass and volume changes over the Greenland ice sheet. For that purpose, we used elevation changes derived from the Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry mission and monthly variations of the Earth’s gravity field

  15. Greenland ice mass balance from GPS, GRACE and ICESat

    DEFF Research Database (Denmark)

    Khan, Shfaqat Abbas; Kjær, Kurt H.; Korsgaard, Niels Jákup

    Greenland, using stereoscopic coverage by aerial photographs recorded in 1985, and subsequent comparative surface elevation data from ICESat (Ice, Cloud and land Elevation Satellite) and ATM (Airborne Topographic Mapper) supplemented with measurements from GPS and the Gravity Recovery and Climate Experiment...

  16. Variable-Gravity Research Facility conceptualization and design study summary

    Science.gov (United States)

    1988-01-01

    It is proposed that three six-month missions be performed at different gravity levels (0.255, 0.39, and 0.64 g) with crews of three individuals to obtain the first approximation of the curves for physiological responses to different levels of gravity. The result data will permit preliminary evaluation of the appropriateness of artificial gravity as a countermeasure for the deconditioning that occurs in 0 g.

  17. Behaviour of the low degree terms of the Earth gravity field over the last 30 years

    Science.gov (United States)

    Biancale, R.; Lemoine, J.-M.; Reinquin, F.; Deleflie, F.; Ramillien, G.; Gégout, P.

    2012-04-01

    The GRACE mission has revealed since 2002 the recent evolution of the Earth's gravity field with a resolution down to 400 km, equivalent to degree and order 50 in spherical harmonics. Precise orbit computation for altimetric satellites can obviously gain by applying these variations, which are classically given, as in recent EIGEN models, as drifts and periodic terms (yearly and semi-yearly). However extrapolating these variations to pre-GRACE periods, mainly the drifts, can be problematic for orbit computation performances on former altimetric satellites. One option is to analyse older satellite data, in particular SLR data on geodetic satellites, in order to assess the very low degree variations of the gravity field and compare it to the GRACE determination. This can be done over the last 30 years, using for instance the Lageos and Lageos-2, Starlette and Stella satellites. The spherical harmonic degrees that can be accessed in this way are degrees 2 to 4. Additional information on degree 2 can be derived from the analysis of the Earth orientation parameters, pole coordinates and length of day (LOD), which have been observed over a long period with great accuracy by astrometric, satellite geodetic and extra-galactic means. Once corrected for atmospheric and oceanic load and velocity variations, the pole coordinates will principally bring information on the C(2,1) and S(2,1) coefficients, while the LOD will principally be connected with the C(2,0). Combining these two approaches allows a better observation of the temporal evolution of the gravity field over a long time span and a more realistic modelling of it for the precise orbit computation of past altimeter missions.

  18. Capital Grace of the Word Incarnate According to Saint Thomas Aquinas

    Directory of Open Access Journals (Sweden)

    Lucia Marie Siemering

    2016-06-01

    Full Text Available The doctrine of capital grace was developed during the Scholastic period and bears on many areas of theology including ecclesiology, Christology, sacraments, and Trinitarian theology with regard to the missions of the Word and the Holy Spirit. Viewed from a Christological standpoint, capital grace sheds light on how Christ in his human nature can be said to be a source of grace to the members of the Church. Following his contemporaries, the young Thomas Aquinas espoused a view in which Christ is a meritorious, ministerial, and dispositive cause of grace according to his human nature, and an efficient cause according to his divinity. After a deeper reading of John Damascene’s treatment of Christ’s humanity being an instrument of his divinity, Thomas was able to articulate a view in which Christ’s human nature is an instrumental efficient cause of grace. This view undergirds Aquinas’s strong conception of Christ as one acting person in two natures.

  19. Quantization of Emergent Gravity

    CERN Document Server

    Yang, Hyun Seok

    2013-01-01

    Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as spacetime admits a symplectic structure, in other words, a microscopic spacetime becomes noncommutative (NC). If gravity emerges from U(1) gauge theory on NC spacetime, this picture of emergent gravity suggests a completely new quantization scheme where quantum gravity is defined by quantizing spacetime itself, leading to a dynamical NC spacetime. Therefore the quantization of emergent gravity is radically different from the conventional approach trying to quantize a phase space of metric fields. This approach for quantum gravity allows a background independent formulation where spacetime as well as matter fields is equally emergent from a universal vacuum of quantum gravity.

  20. Quantization of emergent gravity

    Science.gov (United States)

    Yang, Hyun Seok

    2015-02-01

    Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as space-time admits a symplectic structure, in other words, a microscopic space-time becomes noncommutative (NC). If gravity emerges from U(1) gauge theory on NC space-time, this picture of emergent gravity suggests a completely new quantization scheme where quantum gravity is defined by quantizing space-time itself, leading to a dynamical NC space-time. Therefore the quantization of emergent gravity is radically different from the conventional approach trying to quantize a phase space of metric fields. This approach for quantum gravity allows a background-independent formulation where space-time and matter fields are equally emergent from a universal vacuum of quantum gravity.

  1. High Artic Glaciers and Ice Caps Ice Mass Change from GRACE, Regional Climate Model Output and Altimetry.

    Science.gov (United States)

    Ciraci, E.; Velicogna, I.; Fettweis, X.; van den Broeke, M. R.

    2016-12-01

    The Arctic hosts more than the 75% of the ice covered regions outside from Greenland and Antarctica. Available observations show that increased atmospheric temperatures during the last century have contributed to a substantial glaciers retreat in all these regions. We use satellite gravimetry by the NASA's Gravity Recovery and Climate Experiment (GRACE), and apply a least square fit mascon approach to calculate time series of ice mass change for the period 2002-2016. Our estimates show that arctic glaciers have constantly contributed to the sea level rise during the entire observation period with a mass change of -170+/-20 Gt/yr equivalent to the 80% of the total ice mass change from the world Glacier and Ice Caps (GIC) excluding the Ice sheet peripheral GIC, which we calculated to be -215+/-32 GT/yr, with an acceleration of 9+/-4 Gt/yr2. The Canadian Archipelago is the main contributor to the total mass depletion with an ice mass trend of -73+/-9 Gt/yr and a significant acceleration of -7+/-3 Gt/yr2. The increasing mass loss is mainly determined by melting glaciers located in the northern part of the archipelago.In order to investigate the physical processes driving the observed ice mass loss we employ satellite altimetry and surface mass balance (SMB) estimates from Regional climate model outputs available for the same time period covered by the gravimetry data. We use elevation data from the NASA ICESat (2003-2009) and ESA CryoSat-2 (2010-2016) missions to estimate ice elevation changes. We compare GRACE ice mass estimates with time series of surface mass balance from the Regional Climate Model (RACMO-2) and the Modèle Atmosphérique Régional (MAR) and determine the portion of the total mass change explained by the SMB signal. We find that in Iceland and in the and the Canadian Archipelago the SMB signal explains most of the observed mass changes, suggesting that ice discharge may play a secondary role here. In other region, e.g. in Svalbar, the SMB signal

  2. Peter Berger, Grace Davie & Effie Fokas, Religious America, Secular Europe? A Theme and Variations (Aldershot: Ashgate, 2008), 168 pp

    DEFF Research Database (Denmark)

    Lüchau, Peter

    2012-01-01

    Anmeldelse af bogen: Peter Berger, Grace Davie & Effie Fokas, Religious America, Secular Europe? A Theme and Variations (Aldershot: Ashgate, 2008), 168 pp.......Anmeldelse af bogen: Peter Berger, Grace Davie & Effie Fokas, Religious America, Secular Europe? A Theme and Variations (Aldershot: Ashgate, 2008), 168 pp....

  3. One‑year oral toxicity study on a genetically modified maize MON810 variety in Wistar Han RCC rats (EU 7th Framework Programme project GRACE)

    NARCIS (Netherlands)

    Kleter, G.A.; Kok, E.J.

    2016-01-01

    The GRACE (GMO Risk Assessment and Communication of Evidence; www.grace-fp7.eu) project was funded by the European Commission within the 7th Framework Programme. A key objective of GRACE was to conduct 90-day animal feeding trials, animal studies with an extended time frame as well as analytical, in

  4. Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014

    Science.gov (United States)

    Armitage, Thomas W. K.; Bacon, Sheldon; Ridout, Andy L.; Thomas, Sam F.; Aksenov, Yevgeny; Wingham, Duncan J.

    2016-06-01

    Arctic sea surface height (SSH) is poorly observed by radar altimeters due to the poor coverage of the polar oceans provided by conventional altimeter missions and because large areas are perpetually covered by sea ice, requiring specialized data processing. We utilize SSH estimates from both the ice-covered and ice-free ocean to present monthly estimates of Arctic Dynamic Ocean Topography (DOT) from radar altimetry south of 81.5°N and combine this with GRACE ocean mass to estimate steric height. Our SSH and steric height estimates show good agreement with tide gauge records and geopotential height derived from Ice-Tethered Profilers. The large seasonal cycle of Arctic SSH (amplitude ˜5 cm) is dominated by seasonal steric height variation associated with seasonal freshwater fluxes, and peaks in October-November. Overall, the annual mean steric height increased by 2.2 ± 1.4 cm between 2003 and 2012 before falling to circa 2003 levels between 2012 and 2014 due to large reductions on the Siberian shelf seas. The total secular change in SSH between 2003 and 2014 is then dominated by a 2.1 ± 0.7 cm increase in ocean mass. We estimate that by 2010, the Beaufort Gyre had accumulated 4600 km3 of freshwater relative to the 2003-2006 mean. Doming of Arctic DOT in the Beaufort Sea is revealed by Empirical Orthogonal Function analysis to be concurrent with regional reductions in the Siberian Arctic. We estimate that the Siberian shelf seas lost ˜180 km3 of freshwater between 2003 and 2014, associated with an increase in annual mean salinity of 0.15 psu yr-1. Finally, ocean storage flux estimates from altimetry agree well with high-resolution model results, demonstrating the potential for altimetry to elucidate the Arctic hydrological cycle.

  5. A new mascon approach to assess global ice sheet and glacier mass balances from GRACE.

    Science.gov (United States)

    Schrama, Ernst; Rietbroek, Roelof; Wouters, Bert

    2013-04-01

    Purpose of this paper is to assess the mass balances of the Greenland Ice Sheet (GrIS), Ice Sheets over Antarctica (AIS) and Land Glaciers and Ice Caps (LGIC) with a new method that yields monthly mass variations at 10242 mascons. Input for this algorithm are level 2 data from the GRACE system between 2002.7 and 2012.2. An ensemble of recently updated GIA models based upon new ice history models show for Greenland a mass change of -271 ± 21 Gt/yr which is compatible with mass balances computed from the ICE-5G based GIA models. Whereas the mass balances for the GrIS appear to be insensitive to GIA modeling uncertainties this is not anymore the case for the mass-balance of Antarctica. Ice history models for Antarctica were recently improved and updated historic ice height datasets and GPS time series have been used to generate new GIA models for Antarctica. We investigated the performance of two new GIA models dedicated for Antarctica and found an average mass balance of -91 ± 27 Gt/yr which is approximately 88 Gt/yr less negative than a mass balance derived with the ICE-5g based GIA models. The largest GIA model differences occur on East Antarctica; within the analyzed time window two episodic events occurred in 2009 and 2011 on Dronning Maud land which are related to extreme weather events. The mass balance of land glaciers and ice caps currently stands at -174 ± 8 Gt/yr for which there is no alternative other than to use an ICE-5G based GIA models. We assess the mass-driven part of sea level rise budget at 1.48 ± 0.04 mm/yr which is 0.25 mm/yr less than obtained with traditional GIA models.

  6. Mass balance of Greenland and the Canadian Ice Caps from combined altimetry and GRACE inversion

    DEFF Research Database (Denmark)

    Forsberg, René; Simonsen, Sebastian Bjerregaard; Sørensen, Louise Sandberg

    The combination of GRACE and altimetry data may yield a high resolution mass balance time series of the Greenlandice sheet, highlighting the varying individual mass loss behaviour of major glaciers. By including the Canadian arctic ice caps in the estimation, a more reliable estimate of the mass...... loss of both Greenlandand the Canadian ice caps may be obtained, minimizing the leakage errors otherwise unavoidable by GRACE. Actually, the absolute value of the Greenlandice sheet mass loss is highly dependent on methods and how the effects of Arctic Canadian ice caps are separated in the GRACE...... loss of the ice caps and ice sheet basins for the period 2003-15. This period shows a marked increase of ice sheet melt, especially in NW and NE Greenland, but also show large variability, with the melt anomaly year of 2012 showing a record mass loss, followed by 2013 with essentially no Greenland mass...

  7. Using the Community Land Model to Assess Uncertainty in Basin Scale GRACE-Based Groundwater Estimates

    Science.gov (United States)

    Swenson, S. C.; Lawrence, D. M.

    2015-12-01

    One method for interpreting the variability in total water storage observed by GRACE is to partition the integrated GRACE measurement into its component storage reservoirs based on information provided by hydrological models. Such models, often designed to be used in couple Earth System models, simulate the stocks and fluxes of moisture through the land surface and subsurface. One application of this method attempts to isolate groundwater changes by removing modeled surface water, snow, and soil moisture changes from GRACE total water storage estimates. Human impacts on groundwater variability can be estimated by further removing model estimates of climate-driven groundwater changes. Errors in modeled water storage components directly affect the residual groundwater estimates. Here we examine the influence of model structure and process representation on soil moisture and groundwater uncertainty using the Community Land Model, with a particular focus on basins in the western U.S.

  8. GRace: a MATLAB-based application for fitting the discrimination-association model.

    Science.gov (United States)

    Stefanutti, Luca; Vianello, Michelangelo; Anselmi, Pasquale; Robusto, Egidio

    2014-10-28

    The Implicit Association Test (IAT) is a computerized two-choice discrimination task in which stimuli have to be categorized as belonging to target categories or attribute categories by pressing, as quickly and accurately as possible, one of two response keys. The discrimination association model has been recently proposed for the analysis of reaction time and accuracy of an individual respondent to the IAT. The model disentangles the influences of three qualitatively different components on the responses to the IAT: stimuli discrimination, automatic association, and termination criterion. The article presents General Race (GRace), a MATLAB-based application for fitting the discrimination association model to IAT data. GRace has been developed for Windows as a standalone application. It is user-friendly and does not require any programming experience. The use of GRace is illustrated on the data of a Coca Cola-Pepsi Cola IAT, and the results of the analysis are interpreted and discussed.

  9. Mass balance of Greenland and the Canadian Ice Caps from combined altimetry and GRACE inversion

    DEFF Research Database (Denmark)

    Forsberg, René; Simonsen, Sebastian Bjerregaard; Sørensen, Louise Sandberg

    loss of the ice caps and ice sheet basins for the period 2003-15. This period shows a marked increase of ice sheet melt, especially in NW and NE Greenland, but also show large variability, with the melt anomaly year of 2012 showing a record mass loss, followed by 2013 with essentially no Greenland mass......The combination of GRACE and altimetry data may yield a high resolution mass balance time series of the Greenlandice sheet, highlighting the varying individual mass loss behaviour of major glaciers. By including the Canadian arctic ice caps in the estimation, a more reliable estimate of the mass...... loss of both Greenlandand the Canadian ice caps may be obtained, minimizing the leakage errors otherwise unavoidable by GRACE. Actually, the absolute value of the Greenlandice sheet mass loss is highly dependent on methods and how the effects of Arctic Canadian ice caps are separated in the GRACE...

  10. Monitoring and Characterizing Seasonal Drought, Water Supply Pattern and Their Impact on Vegetation Growth Using Satellite Soil Moisture Data, GRACE Water Storage and In-situ Observations.

    Science.gov (United States)

    A, G.; Velicogna, I.; Kimball, J. S.; Kim, Y.; Colliander, A.; Njoku, E. G.

    2015-12-01

    We combine soil moisture (SM) data from AMSR-E, AMSR-2 and SMAP, terrestrial water storage (TWS) changes from GRACE, in-situ groundwater measurements and atmospheric moisture data to delineate and characterize the evolution of drought and its impact on vegetation growth. GRACE TWS provides spatially continuous observations of total terrestrial water storage changes and regional drought extent, persistence and severity, while satellite derived soil moisture estimates provide enhanced delineation of plant-available soil moisture. Together these data provide complementary metrics quantifying available plant water supply. We use these data to investigate the supply changes from water components at different depth in relation to satellite based vegetation metrics, including vegetation greenness (NDVI) measures from MODIS and related higher order productivity (GPP) before, during and following the major drought events observed in the continental US for the past 14 years. We observe consistent trends and significant correlations between monthly time series of TWS, SM, NDVI and GPP. We study how changes in atmosphere moisture stress and coupling of water storage components at different depth impact on the spatial and temporal correlation between TWS, SM and vegetation metrics. In Texas, we find that surface SM and GRACE TWS agree with each other in general, and both capture the underlying water supply constraints to vegetation growth. Triggered by a transit increase in precipitation following the 2011 hydrological drought, vegetation productivity in Texas shows more sensitivity to surface SM than TWS. In the Great Plains, the correspondence between TWS and vegetation productivity is modulated by temperature-induced atmosphere moisture stress and by the coupling between surface soil moisture and groundwater through irrigation.

  11. Accelerating Cosmology and Phase Structure of F(R) Gravity with Lagrange Multiplier Constraint: Mimetic Approach

    CERN Document Server

    Odintsov, S D

    2015-01-01

    We study mimetic $F(R)$ gravity with potential and Lagrange multiplier constraint. In the context of these theories, we introduce a reconstruction technique which enables us to realize arbitrary cosmologies, given the Hubble rate and an arbitrarily chosen $F(R)$ gravity. We exemplify our method by realizing cosmologies that are in concordance with current observations (Planck data) and also well known bouncing cosmologies. The attribute of our method is that the $F(R)$ gravity can be arbitrarily chosen, so we can have the appealing features of the mimetic approach combined with the known features of some $F(R)$ gravities, which unify early-time with late-time acceleration. Moreover, we study the existence and the stability of de Sitter points in the context of mimetic $F(R)$ gravity. In the case of unstable de Sitter points, it is demonstrated that graceful exit from inflation occurs. We also study the Einstein frame counterpart theory of the Jordan frame mimetic $F(R)$ gravity, we discuss the general propert...

  12. Acceleration of the GrIS mass loss as observed by GRACE

    DEFF Research Database (Denmark)

    Svendsen, Peter Limkilde; Andersen, Ole Baltazar; Nielsen, Allan Aasbjerg

    2012-01-01

    The mass loss of the Greenland Ice Sheet (GrIS) has previously been analysed in a variety of ways, including altimetry, gravimetry and mass budget calculations, establishing a continuing decrease in the ice mass, with a number of studies finding acceleration in the mass loss. Here, we examine...... this acceleration and its statistical significance, using different sets of processed gravimetric data from the GRACE mission. Using an OLS model that takes annual and subannual variation into account, we compare three different GRACE solutions, determining the spatial variability of the acceleration and confidence...

  13. Odd-graceful labeling algorithm and its implementation of generalized ring core network

    Science.gov (United States)

    Xie, Jianmin; Hong, Wenmei; Zhao, Tinggang; Yao, Bing

    2017-08-01

    The computer implementation of some labeling algorithms of special networks has practical guiding significance to computer communication network system design of functional, reliability, low communication cost. Generalized ring core network is a very important hybrid network topology structure and it is the basis of generalized ring network. In this paper, based on the requirements of research of generalized ring network addressing, the author has designed the odd-graceful labeling algorithm of generalized ring core network when n1, n2,…nm ≡ 0(mod 4), proved odd-graceful of the structure, worked out the corresponding software, and shown the practical effectiveness of this algorithm with our experimental data.

  14. GRACE-Based Analysis of Total Water Storage Trends and Groundwater Fluctuations in the North-Western Sahara Aquifer System (NWSAS) and Tindouf Aquifer in Northwest Africa

    Science.gov (United States)

    Lezzaik, K. A.; Milewski, A.

    2013-12-01

    Optimal water management practices and strategies, in arid and semi-arid environments, are often hindered by a lack of quantitative and qualitative understanding of hydrological processes. More