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Sample records for plant grace c-m-g

  1. Capital and operating cost estimates. Volume I. Preliminary design and assessment of a 12,500 BPD coal-to-methanol-to-gasoline plant. [Grace C-M-G Plant, Henderson County, Kentucky

    SciTech Connect

    Not Available

    1982-08-01

    This Deliverable No. 18b - Capital and Operating Cost Estimates includes a detailed presentation of the 12,500 BPD coal-to-methanol-to-gasoline plant from the standpoint of capital, preoperations, start-up and operations cost estimation. The base capital cost estimate in June 1982 dollars was prepared by the Ralph M. Parsons Company under the direction of Grace. The escalated capital cost estimate as well as separate estimates for preoperations, startup and operations activities were developed by Grace. The deliverable consists of four volumes. Volume I contains details of methodology used in developing the capital cost estimate, summary information on a base June 1982 capital cost, details of the escalated capital cost estimate and separate sections devoted to preoperations, start-up, and operations cost. The base estimate is supported by detailed information in Volumes II, III and IV. The degree of detail for some units was constrained due to proprietary data. Attempts have been made to exhibit the estimating methodology by including data on individual equipment pricing. Proprietary details are available for inspection upon execution of nondisclosure and/or secrecy agreements with the licensors to whom the data is proprietary. Details of factoring certain pieces of equipment and/or entire modules or units from the 50,000 BPD capital estimate are also included. In the case of the escalated capital estimate, Grace has chosen to include a sensitivity analysis which allows for ready assessment of impacts of escalation rates (inflation), contingency allowances and the construction interest financing rates on the escalated capital cost. Each of the estimates associated with bringing the plant to commercial production rates has as a basis the schedule and engineering documentation found in Deliverable No. 14b - Process Engineering and Mechanical Design Report, No. 28b - Staffing Plans, No. 31b - Construction Plan, and No. 33b - Startup and Operation Plan.

  2. Process engineering and mechanical design reports. Volume III. Preliminary design and assessment of a 12,500 BPD coal-to-methanol-to-gasoline plant. [Grace C-M-G Plant, Henderson County, Kentucky; Units 26, 27, 31 through 34, 36 through 39

    SciTech Connect

    Stewart, R. M.

    1982-08-01

    Various unit processes are considered as follows: a brief description, basis of design; process selection rationale, a brief description of the process chosen and a risk assessment evaluation (for some cases). (LTN)

  3. W.R. Grace: Plant Uses Six Sigma Methodology and Traditional Heat Balance Analysis to Identify Energy Conservation Opportunities at Curtis Bay Works

    SciTech Connect

    2003-12-01

    The plant-wide energy assessment at W. R. Grace's Curtis Bay Works helped identify four projects with combined potential savings of $840,000 per year. A separate, unique project that would partner W. R. Grace with the City of Baltimore to recover and use landfill gas (methane) to cogenerate steam and electricity was also identified during the assessment. If implemented, the project would recover gas from the landfill to replace 40% of the electricity and 65% of the fuel currently required to produce steam at Curtis Bay Works. Annual savings are estimated at $900,000 to $1.2 million.

  4. W. R. Grace: Plant Uses Six Sigma Methodology and Traditional Heat Balance Analysis to Identify Energy Conservation Opportunities at Curtis Bay Works (Revised)

    SciTech Connect

    Not Available

    2003-12-01

    The plant-wide energy assessment at W. R. Grace's Curtis Bay Works helped identify four projects with combined potential savings of $840,000 per year. A separate, unique project that would partner W. R. Grace with the City of Baltimore to recover and use landfill gas (methane) to cogenerate steam and electricity was also identified during the assessment. If implemented, the project would recover gas from the landfill to replace 40% of the electricity and 65% of the fuel currently required to produce steam at Curtis Bay Works. Annual savings are estimated at $900,000 to $1.2 million.

  5. Grace and Courtesy and Beyond

    ERIC Educational Resources Information Center

    Schaefer, Pat

    2015-01-01

    Taking up the cause of grace and courtesy across the planes of education, Pat Schaefer tells of the grace and courtesy of successive planes within a school culture and gives a glimpse of how the Montessori vision of a new society can look. Grace and courtesy go well beyond the practice of manners and into the topic of deep observation and…

  6. Lessons in Grace.

    ERIC Educational Resources Information Center

    Rishel, Kenn C.; Tingley, Suzanne

    1995-01-01

    While exploring educational leadership concepts, a group of superintendents on retreat found "grace" considerably harder to define than "vision" or "legacy." Inspired by a superintendent's courageous response to imminent dismissal and another's handling of clinical depression, the group first conjured up graceless performances before recollecting…

  7. Grace by Body Clues.

    ERIC Educational Resources Information Center

    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.…

  8. Grace under Pressure

    ERIC Educational Resources Information Center

    Schaeffer, Brett

    2004-01-01

    This article profiles author and activist Grace Llewellyn and her cult classic book, "The Teenage Liberation Handbook: How to Quit School and Get a Real Life and Education." Llewellyn's book, which she published in 1991, created a controversy as it teaches kids everything from how to convince parents to let them leave school to how to pursue their…

  9. Stumble into Grace

    ERIC Educational Resources Information Center

    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."

  10. GRACE star camera noise

    NASA Astrophysics Data System (ADS)

    Harvey, Nate

    2016-08-01

    Extending results from previous work by Bandikova et al. (2012) and Inacio et al. (2015), this paper analyzes Gravity Recovery and Climate Experiment (GRACE) star camera attitude measurement noise by processing inter-camera quaternions from 2003 to 2015. We describe a correction to star camera data, which will eliminate a several-arcsec twice-per-rev error with daily modulation, currently visible in the auto-covariance function of the inter-camera quaternion, from future GRACE Level-1B product releases. We also present evidence supporting the argument that thermal conditions/settings affect long-term inter-camera attitude biases by at least tens-of-arcsecs, and that several-to-tens-of-arcsecs per-rev star camera errors depend largely on field-of-view.

  11. A Touch of Grace

    ERIC Educational Resources Information Center

    Blais, Madeleine

    2009-01-01

    In the two years since her husband's death at the age of 35, Grace Lin has spent much of her time, whether by chance or on purpose, living up to her first name--with excellent results. The petite, self-effacing 35-year-old woman of Taiwanese ancestry lives alone in a two-bedroom apartment in a former schoolhouse in Somerville, Massachusetts. The…

  12. Grace and Courtesy: Empowering Children, Liberating Adults

    ERIC Educational Resources Information Center

    Sackett, Ginni

    2015-01-01

    Ginni Sackett delves into the many implications of grace and courtesy, from social relations and the basis of community to respect for the child's personality. Her point of departure is modern social living with grace and dignity. Hers is an exploration over two generations of seeing grace and courtesy as a comprehensive social view that is the…

  13. Grace by Any Other Name.

    ERIC Educational Resources Information Center

    Atkinson, Robert

    1981-01-01

    Explores how conscious effort often precipitates grace, insight and peak experiences which encourage growth and development. Suggests counselors encourage the expression of attitudes and feelings but refrain from making judgements too quickly and imposing their own moral system on the client. (JAC)

  14. Extending the GRACE Data Record with Gravity Field Solutions Based on a Single GRACE Satellite

    NASA Astrophysics Data System (ADS)

    McCullough, C.; Bettadpur, S. V.; Cheng, M.; Ries, J. C.

    2015-12-01

    Since 2002, the Gravity Recovery and Climate Experiment (GRACE) has enabled unprecedented scientific discovery in a variety of physical Earth sciences. However, with the launch of GRACE Follow-On not taking place until 2017 and the declining health of the current GRACE satellites, it is necessary to cultivate the ability to estimate the Earth's gravity field without the full suite of GRACE measurements. Using a single GRACE satellite, equipped with an accelerometer and a GPS receiver, as well as a compliment of SLR satellites, large-scale features of the Earth's gravity field can be determined. While the accuracy of such solutions are noticeably degraded relative to the nominal GRACE product and smaller-scale features of the Earth's gravity field are impossible to discern without the use of GRACE's satellite-to-satellite (SST) tracking measurements, single satellite solutions do capture continental scale variations in the Earth's gravitational field. These large-scale variations can be used to track global trends such as polar ice loss and water storage, in the event of a gap between GRACE and GRACE Follow-On. In addition, the lessons learned from gravity field solutions computed using only GRACE GPS data provide valuable insight into the optimal combination of GPS data with SST for GRACE Follow-On and other future missions.

  15. Grace and Courtesy in the Elementary Community

    ERIC Educational Resources Information Center

    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,…

  16. Living Grace and Courtesy in the Primary

    ERIC Educational Resources Information Center

    Soholt, Polli

    2015-01-01

    Polli Soholt looks at grace and courtesy from the 3-6 classroom perspective with clear theory explanations as they pertain to the larger classroom culture. She discusses the link between older and young children and the presence of the teacher as a model for grace and takes a brief look to neural science for proof of the existence of social…

  17. Progress towards daily "swath" solutions from GRACE

    NASA Astrophysics Data System (ADS)

    Save, H.; Bettadpur, S. V.; Sakumura, C.

    2015-12-01

    The GRACE mission has provided invaluable and the only data of its kind that measures the total water column in the Earth System over the past 13 years. The GRACE solutions available from the project have been monthly average solutions. There have been attempts by several groups to produce shorter time-window solutions with different techniques. There is also an experimental quick-look GRACE solution available from CSR that implements a sliding window approach while applying variable daily data weights. All of these GRACE solutions require special handling for data assimilation. This study explores the possibility of generating a true daily GRACE solution by computing a daily "swath" total water storage (TWS) estimate from GRACE using the Tikhonov regularization and high resolution monthly mascon estimation implemented at CSR. This paper discusses the techniques for computing such a solution and discusses the error and uncertainty characterization. We perform comparisons with official RL05 GRACE solutions and with alternate mascon solutions from CSR to understand the impact on the science results. We evaluate these solutions with emphasis on the temporal characteristics of the signal content and validate them against multiple models and in-situ data sets.

  18. From GRACE to GRACE Follow-On and Beyond (Vening Meinesz Medal Lecture)

    NASA Astrophysics Data System (ADS)

    Bettadpur, Srinivas

    2016-04-01

    The 15-year long data record of mass flux variability from the US/German Gravity Recovery And Climate Experiment (GRACE) has provided us unprecedented insights into the complete range of Earth System processes. To obtain these insights, the analyst community has revisited the conventional space-geodetic analysis methods in a variety of ways, to work with the precise inter-satellite ranging, accelerometry and GPS tracking data from on-board GRACE. In this talk, we review the methods of modeling and extraction of the gravity field from GRACE data, and put them in the perspective of what we wish to accomplish from the GRACE Follow-On (GRACE-FO) mission. The GRACE-FO mission, once again a US/German collaboration with an intended August 2017 launch, will carry both a microwave as well as a laser interferometer for inter-satellite ranging. We may reasonably expect improved quality of data from GRACE-FO, when compared with GRACE. The user expectations, at the same time, of what may be accomplished from GRACE-FO mass flux variability data have grown. Within this context of growing applications, we review methods that may therefore improve the precision and spatial resolution of the gravity field extracted from future gravity field missions.

  19. Regional Deformation Studies with GRACE and GPS

    NASA Technical Reports Server (NTRS)

    Davis, J. L.; Elosequi, P.; Tamisiea, M.; Mitrovica, J. X.

    2005-01-01

    GRACE data indicate large seasonal variations in gravity that have been shown to be to be related to climate-driven fluxes of surface water. Seasonal redistribution of surface mass deforms the Earth, and our previous study using GRACE data demonstrate that annual radial deformations of +/-13 mm in the region of Amazon River Basin were observed by both GRACE and ten GPS sites in the region. For the GRACE determinations, we estimate in a least-squares solution for each Stokes coefficient parameters that represent the amplitudes of the annual variation. We then filter these parameters based on a statistical test that uses the scatter of the postfit residuals. We demonstrate by comparison to the GPS amplitudes that this method is more accurate, for this region, than Gaussian smoothing. Our model for the temporal behavior of the gravity coefficients includes a rate term, and although the time series are noisy, the glacial isostatic adjustment signal over Hudson s Bay can be observed. .

  20. GRACE Sees Groundwater Losses Around the World

    NASA Video Gallery

    NASA’s Gravity Recovery and Climate Experiment (GRACE) has measured significant groundwater depletion around the world in recent years. These animations show trends in total water storage from Jan....

  1. Groundwater Depletion in India Revealed by GRACE

    NASA Video Gallery

    Scientists using data from NASA’s Gravity Recovery and Climate Experiment (GRACE) have found that the groundwater beneath Northern India has been receding by as much as one foot per year over the p...

  2. Earthquake Signal Visible in GRACE Data

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure1

    This figure shows the effect of the December 2004 great Sumatra earthquake on the Earth's gravity field as observed by GRACE. The signal is expressed in terms of the relative acceleration of the two GRACE satellites, in this case a few nanometers per second squared, or about 1 billionth of the acceleration we experience everyday at the Earth's surface.GRACE observations show comparable signals in the region of the earthquake.

    Other natural variations are also apparent in the expected places, whereas no other significant change would be expected in the region of the earthquake

    GRACE, twin satellites launched in March 2002, are making detailed measurements of Earth's gravity field which will lead to discoveries about gravity and Earth's natural systems. These discoveries could have far-reaching benefits to society and the world's population.

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

    NASA Astrophysics Data System (ADS)

    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/).

  4. Contributions of GRACE to Climate Monitoring

    NASA Technical Reports Server (NTRS)

    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

  5. Grace DAKASEP alkaline battery separator

    NASA Technical Reports Server (NTRS)

    Giovannoni, R. T.; Lundquist, J. T.; Choi, W. M.

    1987-01-01

    The Grace DAKASEP separator was originally developed as a wicking layer for nickel-zinc alkaline batteries. The DAKASEP is a filled non-woven separator which is flexible and heat sealable. Through modification of formulation and processing variables, products with a variety of properties can be produced. Variations of DAKASEP were tested in Ni-H2, Ni-Zn, Ni-Cd, and primary alkaline batteries with good results. The properties of DAKASEP which are optimized for Hg-Zn primary batteries are shown in tabular form. This separator has high tensile strength, 12 micron average pore size, relatively low porosity at 46-48 percent, and consequently moderately high resistivity. Versions were produced with greater than 70 percent porosity and resistivities in 33 wt percent KOH as low as 3 ohm cm. Performance data for Hg-Zn E-1 size cells containing DAKASEP with the properties shown in tabular form, are more reproducible than data obtained with a competitive polypropylene non-woven separator. In addition, utilization of active material is in general considerably improved.

  6. Topological inflation with graceful exit

    NASA Astrophysics Data System (ADS)

    Marunović, Anja; Prokopec, Tomislav

    2016-04-01

    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 deviation) with all available data. In particular, for small and (in our convention) negative nonminimal couplings, the scalar spectral index can be as large as ns simeq 0.955, which is about one standard deviation lower than the central value quoted by the most recent Planck Collaboration.

  7. Add grace to psychiatric practice

    PubMed Central

    Patkar, Shobha V.

    2013-01-01

    Background: The uniqueness of mindset of an individual makes psychiatric practice interesting, sensitive, and at times subjective. The practice in setup of an organization makes the situation more complex in view of administrative regulations, existing work culture, and issues like confidentiality, etc., Dilemmas are often faced while balancing loyalty between an organization and the patients, values of the therapist and the patient, and different dimension of justice coming from different cultural backgrounds of the patients and the treating doctors. A lot of mental work needs to be put in by the practitioner to consistently adhere to medical ethics and professional approach for taking key decisions despite of contradictory external forces from within and without. Aims: I thought of sharing my experiences especially in setup of an organization with my colleagues so that the decision-taking process becomes somewhat easy and balancing for them. Settings and Design: I have to try to interpret my clinical experiences gathered while working with my patients from the Department of Atomic Energy as well as from my private practice. Conclusion: The need of psycho education to self and others from time to time never ceases simply to make the practice more objective, justified, and graceful. PMID:23825861

  8. Laser Frequency Stabilization for GRACE-II

    NASA Technical Reports Server (NTRS)

    Folkner, W. M.; deVine, G.; Klipstein, W. M.; McKenzie, K.; Shaddock, D.; Spero, R.; Thompson, R.; Wuchenich, D.; Yu, N.; Stephens, M.; Leitch, J.; Davis, M.; deCino, J.; Pace, C.; Pierce, R.

    2010-01-01

    The GRACE mission monitors changes in the Earth's gravity field by measuring changes in the distance between spacecraft induced by that changing field. The distance variation is measured with a microwave ranging system with sub-micron accuracy. The ranging measurement accuracy is limited by the signal-to-noise ratio and by the frequency stability of the microwave signal referenced to an ultra-stable oscillator (USO). For GRACE-2 a laser ranging system is envisioned with accuracy better than the GRACE microwave ranging system. A laser ranging system easily provides an improved signal-to-noise ratio over the microwave system. Laser frequency stability better than the GRACE USO stability has been demonstrated in several laboratories using thermally stabilized optical cavities. We are developing a space-qualifiable optical cavity and associated optics and electronics for use on GRACE-2 to provide a stable frequency reference for the laser ranging system. Two breadboard units have been developed and tested for performance and ability to survive launch and orbit environments. A prototype unit is being designed using lessons learned from tests of the breadboard units.

  9. Grace and Courtesy across the Planes of Development

    ERIC Educational Resources Information Center

    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…

  10. 42 CFR 408.8 - Grace period and termination date.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 2 2013-10-01 2013-10-01 false Grace period and termination date. 408.8 Section 408.8 Public Health CENTERS FOR MEDICARE & MEDICAID SERVICES, DEPARTMENT OF HEALTH AND HUMAN SERVICES MEDICARE PROGRAM PREMIUMS FOR SUPPLEMENTARY MEDICAL INSURANCE General Provisions § 408.8 Grace period and termination date. (a) Grace period. (1)...

  11. Monitoring groundwater drought with GRACE data assimilation

    NASA Astrophysics Data System (ADS)

    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.

  12. Mascons, GRACE, and Time-variable Gravity

    NASA Technical Reports Server (NTRS)

    Lemoine, F.; Lutchke, S.; Rowlands, D.; Klosko, S.; Chinn, D.; Boy, J. P.

    2006-01-01

    The GRACE mission has been in orbit now for three years and now regularly produces snapshots of the Earth s gravity field on a monthly basis. The convenient standard approach has been to perform global solutions in spherical harmonics. Alternative local representations of mass variations using mascons show great promise and offer advantages in terms of computational efficiency, minimization of problems due to aliasing, and increased temporal resolution. In this paper, we discuss the results of processing the GRACE KBRR data from March 2003 through August 2005 to produce solutions for GRACE mass variations over mid-latitude and equatorial regions, such as South America, India and the United States, and over the polar regions (Antarctica and Greenland), with a focus on the methodology. We describe in particular mascon solutions developed on regular 4 degree x 4 degree grids, and those tailored specifically to drainage basins over these regions.

  13. Graceful label numbering in optical MPLS networks

    NASA Astrophysics Data System (ADS)

    Arkut, Ibrahim C.; Arkut, Refik C.; Ghani, Nasir

    2000-09-01

    This paper explores the positive effects of the new multi protocol label switching (MPLS) routing platform in IP networks. In particular, novel node numbering algorithms based upon graceful numbering of trees are presented. The first part presents the application of the well-known graceful numbering of spanning caterpillars to the MPLS multicast routing problem. In the second part of the paper, the numbering algorithm is adjusted for the case of unicast routing in the framework of IP-over-WDM optical networks using MPLS, e.g., particularly lambda-labeling and multi protocol lambda switching.

  14. Insights on GRACE (Gender, Race, And Clinical Experience) from the patient's perspective: GRACE participant survey.

    PubMed

    Squires, Kathleen; Feinberg, Judith; Bridge, Dawn Averitt; Currier, Judith; Ryan, Robert; Seyedkazemi, Setareh; Dayaram, Yaswant K; Mrus, Joseph

    2013-06-01

    The Gender, Race And Clinical Experience (GRACE) study was conducted between October 2006 and December 2008 to evaluate sex- and race-based differences in outcomes after treatment with a darunavir/ritonavir-based antiretroviral regimen. Between June 2010 and June 2011, former participants of the GRACE trial at participating sites were asked to complete a 40-item questionnaire as part of the GRACE Participant Survey study, with a primary objective of assessing patients' characteristics, experiences, and opinions about participation in GRACE. Of 243 potential survey respondents, 151 (62%) completed the survey. Respondents were representative of the overall GRACE population and were predominantly female (64%); fewer were black, and more reported recreational drug use compared with nonrespondents (55% vs. 62% and 17% vs. 10%, respectively). Access to treatment (41%) and too many blood draws (26%) were reported as the best and worst part of GRACE, respectively. Support from study site staff was reported as the most important factor in completing the study (47%). Factors associated with nonadherence, study discontinuation, and poor virologic response in univariate analyses were being the primary caregiver for children, unemployment, and transportation difficulties, respectively. Patients with these characteristics may be at risk of poor study outcomes and may benefit from additional adherence and retention strategies in future studies and routine clinical care. PMID:23701200

  15. Assimilation of GRACE Hydrology Data: Recent Progress

    NASA Astrophysics Data System (ADS)

    Rodell, Matthew; Li, Bailing; Zaitchik, Benjamin; Reichle, Rolf; van Dam, Tonie

    2010-05-01

    GRACE is unique among remote sensing systems in its ability to detect changes in total terrestrial water storage (TWS; the sum of groundwater, soil moisture, surface water, and snow). However, three factors have limited the value of GRACE data for hydrological research and applications: (1) low spatial and temporal resolutions relative to other observations; (2) product latency; (3) TWS is an unfamiliar quantity. Land surface models (LSMs) simulate the redistribution of water and energy incident on the land surface, but their accuracy is a function of the quality of the input data used to parameterize and force the models, the model developers' understanding of the physics involved, and the simplifications necessary to depict the Earth system economically. The advantages of GRACE and other observations and LSMs can be harnessed via data assimilation, which synthesizes discontinuous and imperfect observations with our knowledge of physical processes, as represented in a LSM. The model fills observational gaps, provides quality control, and enables data from disparate measurement systems to be merged, while the observations anchor the results in reality. Previously we have demonstrated assimilation of GRACE derived TWS anomalies into the Catchment LSM over the Mississippi River basin, using an Ensemble Smoother approach. We are now improving that capability, extending it to other parts of the world, evaluating the results, and applying the technique for scientific research and socially relevant applications. Here we describe recent progress in these areas.

  16. Psychotherapy as a Rhetoric for Secular Grace.

    ERIC Educational Resources Information Center

    Makay, John J.

    The argument of this paper is that psychotherapy is essentially a rhetorical process that, as an alternative to or substitute for religious rhetoric, seeks to lead people to a secular state of grace. The paper first acknowledges the work of four scholars who have written about the rhetoric of psychotherapy: Erling Eng, Pedro Lain Entralgo, Lloyd…

  17. Through the Looking Glass with Grace Hopper.

    ERIC Educational Resources Information Center

    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)

  18. Arctic Ocean tides from GRACE satellite accelerations

    NASA Astrophysics Data System (ADS)

    Killett, B.; Wahr, J.; Desai, S.; Yuan, D.; Watkins, M.

    2011-11-01

    Models are routinely used to remove the effects of global ocean tides from GRACE data during processing to reduce temporal aliasing into monthly GRACE solutions. These models have typically been derived using data from satellite altimeters such as TOPEX/Poseidon. Therefore the Arctic ocean components of tide models are not constrained by altimetry data, potentially resulting in errors that are likely to alias into monthly GRACE gravity fields at all latitudes. Seven years of GRACE inter-satellite accelerations are inverted to solve for corrections to the amplitude and phase of major solar and lunar ocean tides at latitudes north of 50°N using a mascon approach. The tide model originally applied to our data was FES2004, truncated to maximum degree lmax = 90. Simulations are performed to verify that our inversion algorithm works as designed. Uncertainty estimates are derived from tidal solutions on land, and by subtracting two independent solutions that each use 3.5 years of data. Features above the noise floor in the M2, K1, S2, and O1 solutions likely represent errors in FES2004. Errors due to truncating the spherical harmonic expansion of FES2004 are too small, and errors in the land mask model (needed to transform sea surface heights into mass) only affect coastal areas and do not produce similar relative amplitudes for any examined tides. In the oceans north of 50°N, these residuals tend to reduce the FES2004 amplitudes for M2, K1, S2, and O1. Reductions in the variance of accelerations not used in our inversion suggest that our results can be used to improve GRACE processing.

  19. Hydrology Applications of the GRACE missions

    NASA Astrophysics Data System (ADS)

    Srinivasan, M. M.; Ivins, E. R.; Jasinski, M. F.

    2014-12-01

    NASA and their German space agency partners have a rich history of global gravity observations beginning with the launch of the Gravity Recovery And Climate Experiment (GRACE) in 2002. The science goals of the mission include providing monthly maps of variations in the gravity field, where the major time-varying signal is due to water motion in the Earth system. GRACE has a unique ability to observe the mass flux of water movement at monthly time scales. The hydrology applications of the GRACE mission include measurements of seasonal storage of surface and subsurface water and evapotranspiration at the land-ocean-atmosphere boundary. These variables are invaluable for improved modeling and prediction of Earth system processes. Other mission-critical science objectives include measurements that are a key component of NASA's ongoing climate measuring capabilities. Successful strategies to enhance science and practical applications of the proposed GRACE-Follow On (GRACE-FO) mission, scheduled to launch in 2017, will require engaging with and facilitating between representatives in the science, societal applications, and mission planning communities. NASA's Applied Sciences Program is supporting collaboration on an applied approach to identifying communities of potential and of practice in order to identify and promote the societal benefits of these and future gravity missions. The objective is to engage applications-oriented users and organizations and enable them to envision possible applications and end-user needs as a way to increase the benefits of these missions to the nations. The focus of activities for this applications program include; engaging the science community in order to identify applications and current and potential data users, developing a written Applications Plan, conducting workshops and user tutorials, providing ready access to information via web pages, developing databases of key and interested users/scientists, creating printed materials

  20. Can GRACE detect winter snows in Japan?

    NASA Astrophysics Data System (ADS)

    Heki, Kosuke

    2010-05-01

    Current spatial resolution of the GRACE (Gravity Recovery and Climate Experiment) satellites is 300-400 km, and so its hydrological applications have been limited to continents and large islands. The Japanese Islands have width slightly smaller than this spatial resolution, but are known to show large amplitude seasonal changes in surface masses due mainly to winter snow. Such loads are responsible for seasonal crustal deformation observed with GEONET, a dense array of GPS (Global Positioning System) receivers in Japan (Heki, 2001). There is also a dense network of surface meteorological sensors for, e.g. snow depths, atmospheric pressures, etc. Heki (2004) showed that combined effects of surface loads, i.e. snow (predominant), atmosphere, soil moisture, dam impoundment, can explain seasonal crustal deformation observed by GPS to a large extent. The total weight of the winter snow in the Japanese Islands in its peak season may reach ~50 Gt. This is comparable to the annual loss of mountain glaciers in the Asian high mountains (Matsuo & Heki, 2010), and is above the detection level of GRACE. In this study, I use GRACE Level-2 Release-4 data from CSR, Univ. Texas, up to 2009 November, and evaluated seasonal changes in surface loads in and around the Japanese Islands. After applying a 350 km Gaussian filter and a de-striping filter, the peak-to-peak change of the water depth becomes ~4 cm in northern Japan. The maximum value is achieved in February-March. The region of large winter load spans from Hokkaido, Japan, to northeastern Honshu, which roughly coincides with the region of deep snow in Japan. Next I compiled snow depth data from surface meteorological observations, and converted them to loads using time-dependent snow density due to compaction. By applying the same spatial filter as the GRACE data, its spatial pattern becomes similar to the GRACE results. The present study suggests that GRACE is capable of detecting seasonal mass changes in an island arc not

  1. GRACE: Gravity Recovery and Climate Experiment

    NASA Technical Reports Server (NTRS)

    Ward, A.

    2002-01-01

    While gravity is much weaker than other basic forces in nature, such as magnetism and electricity, its effects are ubiquitous and dramatic. Gravity controls everything from the motion of the ocean tides to the expansion of the entire Universe. To learn more about the mysteries of gravity, twin satellites named GRACE--short for the Gravity Recovery and Climate Experiment--are being launched to make detailed measurements of Earth's gravity field. This experiment could lead to discoveries about gravity and Earth's natural systems, which could have substantial benefits for society and the world's population. The GRACE mission will be the inaugural flight of NASA's Earth System Science Pathfinder Program (ESSP). A component of NASA's Earth Science Enterprise (ESE), the ESSP missions are intended to address unique, specific highly focused scientific issues and provide measurements required to support Earth science research.

  2. GRACE Collaboration in the Swift Era

    NASA Technical Reports Server (NTRS)

    Kouveliotou, C.

    2004-01-01

    I will describe the structure and major discoveries of the Gamma-Ray Afterglow Collaboration at ESO, formed by several European Countries to perform GRB follow up observations using the European Southern Observatory (ESO) ground-based facilities in Chile. I represent the USA-UK node of GRACE. I will also describe a newly funded effort through the Swift GO program aiming at forming a Joint Afterglow NETwork (JANET) using members of the American Association of Variable Star Observers (AAVSO).

  3. 12 CFR 329.104 - Ten-day grace period.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 12 Banks and Banking 4 2010-01-01 2010-01-01 false Ten-day grace period. 329.104 Section 329.104... INTEREST ON DEPOSITS § 329.104 Ten-day grace period. This interpretive rule provides for 10-day grace periods during which interest may be paid on a deposit without violating § 329.2. (a) During the...

  4. 12 CFR 329.104 - Ten-day grace period.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 12 Banks and Banking 4 2011-01-01 2011-01-01 false Ten-day grace period. 329.104 Section 329.104... INTEREST ON DEPOSITS § 329.104 Ten-day grace period. This interpretive rule provides for 10-day grace periods during which interest may be paid on a deposit without violating § 329.2. (a) During the...

  5. Hydrological applications of Gravity Recovery and Climate Experiment (GRACE)

    NASA Astrophysics Data System (ADS)

    Seo, Ki-Weon

    The NASA/DLR Gravity Recovery and Climate Experiment (GRACE) satellite mission was launched March, 2002. GRACE provides monthly Stokes coefficients of spherical harmonics representing the global gravity field and changes over time with unprecedented accuracy. Gravity changes estimated from GRACE include effects from planets, tides, solid Earth deformation, and motion within the fluid envelopes of the atmosphere, hydrosphere, and oceans. After corrections for known or predictable effects, it is possible to isolate changes due to redistribution of water mass, especially related to storage changes in river basins. This study addresses four issues related to hydrological applications of GRACE. The first is to examine optimum filter designs to obtain the maximum spatial resolution from GRACE Stokes coefficients and understand possible GRACE errors associated with the filters. One strategy for the optimum filter design is to adjust the filter on a monthly basis according to signal changes. A time variable filter can perform better than a fixed coefficient filter if good model predictions are available. GRACE aliasing errors are estimated from numerical model fields. Aliasing errors from land and oceans sharply increase up to SH degree 15 and slowly increase thereafter. Atmospheric aliasing errors are significant below SH degree 15. Global water mass loads are recovered from GRACE using various schemes. The largest water mass load changes are observed in low latitude basins such as the Amazon, Congo and Ganges, and show clear seasonal signals. GRACE signals are comparable to GLDAS prediction, providing some validation GRACE result. Gravity potential differences along GRACE ground track are computed from numerical model fields. Using the different time scales between changes in terrestrial water storage and atmospheric surface pressure, the surface pressure field can be removed. This suggests the possibility of improved GRACE dealiasing.

  6. Water Control on Vegetation Growth Pattern in Eurasia from GRACE

    NASA Astrophysics Data System (ADS)

    A, G.; Velicogna, I.; Kimball, J. S.; Kim, Y.

    2014-12-01

    High latitude ecosystem productivity is constrained by cold temperature and moisture limitations to plant growth, while these environmental restrictions may be changing with global warming. Satellite data driven assessments indicate that over the past three decades, rapid warming in the northern high latitudes has resulted in earlier and longer potential growing seasons and widespread greening, due to general relaxation of cold temperature constraints to vegetation productivity. However, warming may have also increased water stress limitations to growth. In this study, we use GRACE (Gravity Recovery and Climate Experiment) derived total water storage (TWS), 2-m air temperature (T) from ERA-interim reanalysis, normalized difference vegetation index (NDVI) data from MODIS (Collection 5) and satellite data driven vegetation gross primary productivity (GPP) estimates as surrogates for vegetation growth, for the period August 2002-December 2013 to evaluate terrestrial water supply controls to vegetation growth changes over the three major river basins of northern Eurasia. We find that during the analyzed period, the apparent growth response follows regional vegetation, moisture and temperature gradients and is spatially complex. In the drier southwest characterized by grassland, vegetation growth is mainly controlled by TWS availability. In the central region, dominated by cold temperature and water limited boreal forest, T is the main control on vegetation growth. In the Lena basin, where vegetation includes both boreal forest and water limited grassland, both T and TWS impact vegetation growth. We suggest that GRACE TWS estimates provide reliable observational constraints on water availability to vegetation that supplement sparse soil moisture observations and satellite precipitation estimates with unknown bias.

  7. Determining dislocation Love numbers using satellite gravity mission GRACE observations

    NASA Astrophysics Data System (ADS)

    junyan, Y.; Sun, W.

    2013-12-01

    Some large megathrust earthquakes can be detected by satellite gravity mission GRACE. The coseismic gravity changes from GRACE measurements can be perfectly explained by spherical dislocation theory. On the contrary, we can use GRACE data to invert earth dislocation Love numbers. This paper proposes a more completed theory and an inversion method to determine dislocation Love numbers using GRACE data. Taking effect of ocean water mass redistribution into consideration, we give an observation equation to model GRACE observations. The ABIC (Akaike Bayes Information Criterion) method is employed to inverse the gravity dislocation Love numbers by the constraint of a prior PREM model. Based on this method, we inverse sphere dislocation Love numbers by using simulated data and GRACE data of 2011 Tohoku earthquake (Mw 9.0) respectively. The results show that sensitivities of Love numbers to the measurement errors are dependent on spherical harmonic degrees. The SNRs (Signal Noise Ratio) of lower degrees are much stronger than the higher ones, and the inverted gravity Love numbers of former are closer to the priori PREM model than the latter. Furthermore, GRACE can be used to invert dislocation Love numbers. However, the unknown Love numbers K12, K32 and K33-K22 cannot be constrained by the PREM Earth model at the same extent due to the orders of magnitude are much different; the K33-K22 agrees the PREM model best. Finally, the gravity changes predicted by inverted Love numbers agree GRACE data well.

  8. Groundwater Storage Changes: Present Status from GRACE Observations

    NASA Astrophysics Data System (ADS)

    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.

  9. Combined GRACE-SLR monthly gravity field solutions

    NASA Astrophysics Data System (ADS)

    Meyer, Ulrich; Sosnica, Krzysytof; Maier, Andrea; Jäggi, Adrian

    2015-04-01

    Monthly gravity field solutions from GRACE GPS and GRACE K-Band data provide remarkable information about the mass transport in the system Earth by capturing the temporal variability of the gravity field at long to medium wavelengths. The GRACE solutions suffer, however, from the poor determination of the C20 coefficient from GRACE K-Band data, which describes the Earth's oblateness. C20 and its temporal variability can, on the other hand, be very well determined using satellite laser ranges (SLR) to spherical geodetic satellites such as LAGEOS and LARES. It is common practice to replace the C20 coefficient in GRACE solutions by SLR-derived values. We perform a meaningful combination of GRACE and SLR solutions at the level of normal equations using the SLR-only monthly gravity fields from the combined analysis of up to nine geodetic satellites that capture the temporal variability to degree 10 of the global spherical harmonic expansion. We present combined monthly GRACE-SLR solutions and compare them to GRACE GPS/K-Band, GRACE GPS-only, and SLR-only solutions. We discuss the relative weighting scheme of the normal equations and evaluate the secular and seasonal periodic time variations of the combined solutions at long wavelengths. We observe a positive influence of the SLR data not only on C20 but also on the formal errors of the other degree-2 spherical harmonic coefficients, which correspond to the excitation of the polar motion. A possible reduction of the influence of aliasing with the S2 tide on some GRACE-derived coefficients using a combination with SLR data will also be addressed. The analysis of SLR-only solutions indicates sensitivity to time variable signal for selected coefficients at even higher degree but special care has to be taken not to corrupt coefficients with the inferior quality in SLR solutions in the combined solutions with GRACE data. In recent years, K-Band tracking between GRACE satellites was deactivated several times resulting in

  10. Improvements in GRACE Gravity Fields Using Regularization

    NASA Astrophysics Data System (ADS)

    Save, H.; Bettadpur, S.; Tapley, B. D.

    2008-12-01

    The unconstrained global gravity field models derived from GRACE are susceptible to systematic errors that show up as broad "stripes" aligned in a North-South direction on the global maps of mass flux. These errors are believed to be a consequence of both systematic and random errors in the data that are amplified by the nature of the gravity field inverse problem. These errors impede scientific exploitation of the GRACE data products, and limit the realizable spatial resolution of the GRACE global gravity fields in certain regions. We use regularization techniques to reduce these "stripe" errors in the gravity field products. The regularization criteria are designed such that there is no attenuation of the signal and that the solutions fit the observations as well as an unconstrained solution. We have used a computationally inexpensive method, normally referred to as "L-ribbon", to find the regularization parameter. This paper discusses the characteristics and statistics of a 5-year time-series of regularized gravity field solutions. The solutions show markedly reduced stripes, are of uniformly good quality over time, and leave little or no systematic observation residuals, which is a frequent consequence of signal suppression from regularization. Up to degree 14, the signal in regularized solution shows correlation greater than 0.8 with the un-regularized CSR Release-04 solutions. Signals from large-amplitude and small-spatial extent events - such as the Great Sumatra Andaman Earthquake of 2004 - are visible in the global solutions without using special post-facto error reduction techniques employed previously in the literature. Hydrological signals as small as 5 cm water-layer equivalent in the small river basins, like Indus and Nile for example, are clearly evident, in contrast to noisy estimates from RL04. The residual variability over the oceans relative to a seasonal fit is small except at higher latitudes, and is evident without the need for de-striping or

  11. Assessing mass change trends in GRACE models

    NASA Astrophysics Data System (ADS)

    Siemes, C.; Liu, X.; Ditmar, P.; Revtova, E.; Slobbe, C.; Klees, R.; Zhao, Q.

    2009-04-01

    The DEOS Mass Transport model, release 1 (DMT-1), has been recently presented to the scientific community. The model is based on GRACE data and consists of sets of spherical harmonic coefficients to degree 120, which are estimated once per month. Currently, the DMT-1 model covers the time span from Feb. 2003 to Dec. 2006. The high spatial resolution of the model could be achieved by applying a statistically optimal Wiener-type filter, which is superior to standard filtering techniques. The optimal Wiener-type filter is a regularization-type filter which makes full use of the variance/covariance matrices of the sets of spherical harmonic coefficients. It can be shown that applying this filter is equivalent to introducing an additional set of observations: Each set of spherical harmonic coefficients is assumed to be zero. The variance/covariance matrix of this information is chosen according to the signal contained within the sets of spherical harmonic coefficients, expressed in terms of equivalent water layer thickness in the spatial domain, with respect to its variations in time. It will be demonstrated that DMT-1 provides a much better localization and more realistic amplitudes than alternative filtered models. In particular, we will consider a lower maximum degree of the spherical harmonic expansion (e.g. 70), as well as standard filters like an isotropic Gaussian filter. For the sake of a fair comparison, we will use the same GRACE observations as well as the same method for the inversion of the observations to obtain the alternative filtered models. For the inversion method, we will choose the three-point range combination approach. Thus, we will compare four different models: (1) GRACE solution with maximum degree 120, filtered by optimal Wiener-type filter (the DMT-1 model) (2) GRACE solution with maximum degree 120, filtered by standard filter (3) GRACE solution with maximum degree 70, filtered by optimal Wiener-type filter (4) GRACE solution with maximum

  12. The design, validation, and performance of Grace

    NASA Astrophysics Data System (ADS)

    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.

  13. Monitoring Global Freshwater Resources with GRACE

    NASA Technical Reports Server (NTRS)

    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.

  14. Variability in deep ocean circulation from GRACE

    NASA Astrophysics Data System (ADS)

    Boening, C.; Watkins, M. M.

    2015-12-01

    Although nearly impossible to observe on a global scale, total water mass transport and inter-basin exchange are central to understanding long-term changes in ocean circulation. Of particular interest are changes in the Meridional Overturning Circulation (MOC) as they pose potential impacts in continental climtae. However, in-situ observations are limited in space and time preventing a holistic view of current variability. The representation of long-term transports in ocean models is highly dependent on the atmospheric forcing fields, which may misrepresent real interannual variability. The bottom pressure observations from the Gravity Recovery And Climate Experiment (GRACE) provide for the first time the ability to observe this global water mass transport. Here, we present the first near-global maps of variability in the depth-independent ocean circulation derived from advanced analysis of GRACE data. We find that significant variability on annual to decadal time scales exists in the deep large-scale circulation, some of which are related to the Southern Annular Mode forcing dominating Southern Ocean variability.

  15. Quantifying renewable groundwater stress with GRACE

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

    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.

  16. Introducing GRACE Follow-On mock data challenge project

    NASA Astrophysics Data System (ADS)

    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.

  17. Basin-Scale Freshwater Storage Trends from GRACE

    NASA Astrophysics Data System (ADS)

    Famiglietti, J.; Kiel, B.; Frappart, F.; Syed, T. H.; Rodell, M.

    2006-12-01

    Four years have passed since the GRACE satellite tandem began recording variations in Earth's gravitational field. On monthly to annual timescales, variations in the gravity signal for a given location correspond primarily to changes in water storage. GRACE thus reveals, in a comprehensive, vertically-integrated manner, which areas and basins have experienced net increases or decreases in water storage. GRACE data (April 2002 to November 2005) released by the Center for Space Research at the University of Texas at Austin (RL01) is used for this study. Model-based data from GLDAS (Global Land Data Assimilation System) is integrated into this study for comparison with the CSR GRACE data. Basin-scale GLDAS storage trends are similar to those from GRACE, except in the Arctic, likely due to the GLDAS snow module. Outside of the Arctic, correlation of GRACE and GLDAS data confirms significant basin-scale storage trends across the GRACE data collection period. Sharp storage decreases are noted in the Congo, Zambezi, Mekong, Parana, and Yukon basins, among others. Significant increases are noted in the Niger, Lena, and Volga basins, and others. Current and future work involves assessment of these trends and their causes in the context of hydroclimatological variability.

  18. Impact of GRACE Error Correlations on Hydrological Data Assimilation

    NASA Astrophysics Data System (ADS)

    Schumacher, Maike; Kusche, Jürgen; Döll, Petra

    2015-04-01

    Recently, ensemble Kalman filters (EnKF) have found increasing application for merging hydrological models with total water storage anomaly (TWSA) fields from the Gravity Recovery And Climate Experiment (GRACE) satellite mission. Previous studies have disregarded the strong effect of GRACE spatial error correlation in their investigations. Here, for the first time, we show that it is important to consider the characteristic error structure by carrying out an in-depth assessment of the impact of spatially correlated GRACE-TWSA errors on the GRACE-adjusted water states. Our investigations include (i) assimilating gridded GRACE-derived TWSA into the WaterGAP Global Hydrology Model (WGHM) and, simultaneously, calibrating its parameters, (ii) introducing GRACE observations with different spatial scales, (iii) modeling observation errors as either white or correlated in the assimilation, and (vi) replacing the original EnKF algorithm with a square root analysis scheme (SQRA) or, alternatively, the Singular Evolutive Interpolated Kalman (SEIK) filter. Results of a synthetic experiment for the Mississippi River Basin indicate that the hydrological parameters were sensitive to TWSA assimilation. We found a significant influence of the spatial error correlation for all implemented filter variants, mainly over subbasins with north-south spatial extensions on the adjusted water states. We conclude that considering the characteristic GRACE error correlations is at least as important as the selection of the resolution of TWSA observations, while the choice of the filter method should be based on the computational simplicity and efficiency.

  19. Integrated instrumentation & computation environment for GRACE

    NASA Astrophysics Data System (ADS)

    Dhekne, P. S.

    2002-03-01

    The project GRACE (Gamma Ray Astrophysics with Coordinated Experiments) aims at setting up a state of the art Gamma Ray Observatory at Mt. Abu, Rajasthan for undertaking comprehensive scientific exploration over a wide spectral window (10's keV - 100's TeV) from a single location through 4 coordinated experiments. The cumulative data collection rate of all the telescopes is expected to be about 1 GB/hr, necessitating innovations in the data management environment. As real-time data acquisition and control as well as off-line data processing, analysis and visualization environment of these systems is based on the us cutting edge and affordable technologies in the field of computers, communications and Internet. We propose to provide a single, unified environment by seamless integration of instrumentation and computations by taking advantage of the recent advancements in Web based technologies. This new environment will allow researchers better acces to facilities, improve resource utilization and enhance collaborations by having identical environments for online as well as offline usage of this facility from any location. We present here a proposed implementation strategy for a platform independent web-based system that supplements automated functions with video-guided interactive and collaborative remote viewing, remote control through virtual instrumentation console, remote acquisition of telescope data, data analysis, data visualization and active imaging system. This end-to-end web-based solution will enhance collaboration among researchers at the national and international level for undertaking scientific studies, using the telescope systems of the GRACE project.

  20. Basin Scale Estimates of Evapotranspiration Using GRACE and other Observations

    NASA Technical Reports Server (NTRS)

    Rodell, M.; Famiglietti, J. S.; Chen, J.; Seneviratne, S. I.; Viterbo, P.; Holl, S.; Wilson, C. R.

    2004-01-01

    Evapotranspiration is integral to studies of the Earth system, yet it is difficult to measure on regional scales. One estimation technique is a terrestrial water budget, i.e., total precipitation minus the sum of evapotranspiration and net runoff equals the change in water storage. Gravity Recovery and Climate Experiment (GRACE) satellite gravity observations are now enabling closure of this equation by providing the terrestrial water storage change. Equations are presented here for estimating evapotranspiration using observation based information, taking into account the unique nature of GRACE observations. GRACE water storage changes are first substantiated by comparing with results from a land surface model and a combined atmospheric-terrestrial water budget approach. Evapotranspiration is then estimated for 14 time periods over the Mississippi River basin and compared with output from three modeling systems. The GRACE estimates generally lay in the middle of the models and may provide skill in evaluating modeled evapotranspiration.

  1. 2. Photocopy of photograph (from the collection of Grace M. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    2. Photocopy of photograph (from the collection of Grace M. Barwise, owner of house in 1972) n.d. VIEW FROM THE SOUTHWEST - James Frederic Clarke House, 500 South Main Street, Fairfield, Jefferson County, IA

  2. Susquehanna River Bridge swing span. Havre de Grace, Hareford Co., ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Susquehanna River Bridge swing span. Havre de Grace, Hareford Co., MD. Sec. 1201, MP 60.07. - Northeast Railroad Corridor, Amtrak route between District of Columbia/Maryland state line & Maryland/Delaware state line, Baltimore, Independent City, MD

  3. Susquehanna River Bridge. Havre de Grace, Hareford Co., MD. Sec. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Susquehanna River Bridge. Havre de Grace, Hareford Co., MD. Sec. 1201, MP 60.07. - Northeast Railroad Corridor, Amtrak route between District of Columbia/Maryland state line & Maryland/Delaware state line, Baltimore, Independent City, MD

  4. Juniata Street Culvert. Havre de Grace, Hareford Co., MD. Sec. ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Juniata Street Culvert. Havre de Grace, Hareford Co., MD. Sec. 1201, MP 60.77. - Northeast Railroad Corridor, Amtrak route between District of Columbia/Maryland state line & Maryland/Delaware state line, Baltimore, Independent City, MD

  5. 42 CFR 408.8 - Grace period and termination date.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... MEDICARE PROGRAM PREMIUMS FOR SUPPLEMENTARY MEDICAL INSURANCE General Provisions § 408.8 Grace period and... the billing month. (2) For payments required because the monthly benefit is less than the...

  6. 42 CFR 408.8 - Grace period and termination date.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... MEDICARE PROGRAM PREMIUMS FOR SUPPLEMENTARY MEDICAL INSURANCE General Provisions § 408.8 Grace period and... the billing month. (2) For payments required because the monthly benefit is less than the...

  7. 42 CFR 408.8 - Grace period and termination date.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... MEDICARE PROGRAM PREMIUMS FOR SUPPLEMENTARY MEDICAL INSURANCE General Provisions § 408.8 Grace period and... the billing month. (2) For payments required because the monthly benefit is less than the...

  8. 42 CFR 408.8 - Grace period and termination date.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... MEDICARE PROGRAM PREMIUMS FOR SUPPLEMENTARY MEDICAL INSURANCE General Provisions § 408.8 Grace period and... the billing month. (2) For payments required because the monthly benefit is less than the...

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

    EPA Science Inventory

    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...

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

    NASA Astrophysics Data System (ADS)

    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.

  11. Atmospheric Pressure Error of GRACE in Antarctic Ice Mass Change

    NASA Astrophysics Data System (ADS)

    Kim, B.; Eom, J.; Seo, K. W.

    2014-12-01

    As GRACE has observed time-varying gravity longer than a decade, long-term mass changes have been emerged. In particular, linear trends and accelerated patterns in Antarctica were reported and paid attention for the projection of sea level rise. The cause of accelerated ice mass loss in Antarctica is not known since its amplitude is not significantly larger than ice mass change associated with natural climate variations. In this study, we consider another uncertainty in Antarctic ice mass loss acceleration due to unmodeled atmospheric pressure field. We first compare GRACE AOD product with in-situ atmospheric pressure data from SCAR READER project. GRACE AOD (ECMWF) shows spurious jump near Transantarctic Mountains, which is due to the regular model update of ECMWF. In addition, GRACE AOD shows smaller variations than in-situ observation in coastal area. This is possibly due to the lower resolution of GRACE AOD, and thus relatively stable ocean bottom pressure associated with inverted barometric effect suppresses the variations of atmospheric pressure near coast. On the other hand, GRACE AOD closely depicts in-situ observations far from oceans. This is probably because GRACE AOD model (ECMWF) is assimilated with in-situ observations. However, the in-situ observational sites in interior of Antarctica are sparse, and thus it is still uncertain the reliability of GRACE AOD for most region of Antarctica. To examine this, we cross-validate three different reanalysis; ERA Interim, NCEP DOE and MERRA. Residual atmospheric pressure fields as a measure of atmospheric pressure errors, NCEP DOE - ERA Interim or MERRA - ERA Interim, show long-term changes, and the estimated uncertainty in acceleration of Antarctic ice mass change is about 9 Gton/yr^2 from 2003 to 2012. This result implies that the atmospheric surface pressure error likely hinders the accurate estimate of the ice mass loss acceleration in Antarctica.

  12. Application of Assimilated GRACE Data for Drought Monitoring

    NASA Astrophysics Data System (ADS)

    Rodell, M.; Li, B.; Beaudoing, H. K.; Zaitchik, B. F.; Famiglietti, J. S.

    2014-12-01

    A unique aspect of the Gravity Recovery and Climate Experiment (GRACE) satellites is their ability to detect changes in water stored in all levels of the soil column, including groundwater. Thus GRACE is well suited for identifying hydrological droughts, when total water storage is low. The potential for GRACE to contribute to global drought monitoring is clear, but first it is necessary to overcome GRACE's low spatial and temporal resolutions (relative to other hydrological observations) and data latency. To do so we synthesize GRACE data with other ground and space based meteorological observations within a sophisticated numerical model of land surface water and energy processes. The resulting high resolution, near real-time fields of soil moisture and groundwater storage variations are then used to generate drought indicator maps. Since 2011, such maps have been produced on a weekly basis for the continental U.S., disseminated through the University of Nebraska's National Drought Mitigation Center website, and incorporated into the U.S. and North American Drought Monitors. Expansion of these GRACE-based drought indicators to the global scale is ongoing and is expect to be completed over the next 12-18 months.

  13. Chandler wobble parameters from SLR and GRACE

    NASA Astrophysics Data System (ADS)

    Nastula, J.; Gross, R.

    2015-06-01

    The period and quality factor Q of the Chandler wobble are functions of the internal structure and dissipation processes of the Earth. Better estimates of the period and Q of the Chandler wobble can therefore be used to better understand these properties of the Earth. Here the period and Q of the Chandler wobble are estimated by finding those values that minimize the power in the Chandler frequency band of the difference between observed and modeled polar motion excitation functions. The observations of the polar motion excitation functions that we used are derived from both space-geodetic polar motion observations and from satellite laser ranging (SLR) and Gravity Recovery and Climate Experiment (GRACE) observations of the degree-2 coefficients of the Earth's time-varying gravitational field. The models of the polar motion excitation functions that we used are derived from general circulation models of the atmosphere and oceans and from hydrologic models. Our preferred values for the period and Q of the Chandler wobble that we estimated using this approach are 430.9 ± 0.7 solar days and 127 (56, 255), respectively.

  14. Quantifying renewable groundwater stress with GRACE

    PubMed Central

    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

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

    NASA Astrophysics Data System (ADS)

    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.

  16. GRACE follow-on sensor noise with realistic background models

    NASA Astrophysics Data System (ADS)

    Ellmer, Matthias; Mayer-Gürr, Torsten

    2015-04-01

    We performed multiple simulation studies of a GRACE-like satellite mission based on the current K-Band ranging instrument (KBR). We also simulated a laser-ranging instrument (LRI) configuration as a drop-in replacement for GRACE low-low satellite to satellite tracking, the remaining parameters of the simulation are shared between the two scenarios. Our simulated data are based on real GRACE observations for April 2006, which allows us to compare our results to published gravity field models for this particular month. The variational equation approach was employed to generate independent reduced-dynamic orbits for both GRACE satellites. These orbits were then fitted to the actual GRACE kinematic orbits. The resulting orbit was then used to synthesize artificial satellite ranging, star camera, accelerometer and kinematic orbit data. We synchronized all simulated instruments with real instrument data for the simulated month, which guarantees realistic data gaps. Appropriate noise was added to all observables. In the recovery step, the AOD1B de-aliasing product -- previously used in the generation of the fundamental reduced-dynamic orbit data -- was degraded with partial constituents of the updated ESA earth system model dataset. Specifically, the atmosphere, ocean, and hydrology components were used. This has the effect that the computed gravity field possesses the characteristic structure associated with a residual time-variable gravity field signal. An overview of the achieved results is given in the presentation.

  17. The Status and Future Directions for the GRACE Mission

    NASA Astrophysics Data System (ADS)

    Tapley, Byron; Bettadpur, Srinivas; Flechtner, Frank; Watkins, Michael

    2015-04-01

    The twin satellites of the Gravity Recovery and Climate Experiment (GRACE) were launched on March 17, 2002 and have operated for over 13 years. The mission objectives are to sense the spatial and temporal variations of the Earth's mass through its effects on the gravity field at the GRACE satellite altitude. The primary mission objectives of GRACE are to measure: 1) the Earth's time-averaged gravity field over the mission life and 2) the monthly variations in the mean gravity field at wave lengths between 300 and 4000 km. The major cause of the time varying mass is water motion and the GRACE mission has provided a continuous decade long measurement sequences which characterizes the seasonal cycle of mass transport between the oceans, land, cryosphere and atmosphere; its inter-annual variability; and the climate driven secular, or long period, mass transport signals. Measurements of continental aquifer mass change, polar ice mass change and ocean bottom currents are examples of paradigm shifting remote sensing observations enabled by the GRACE satellite measurements. In 2012, a complete reanalysis of the mission data, referred to as the RL05 data release, was initiated. The monthly solutions from this effort were released in mid-2013 with the mean fields following in 2014. Corrections to the original release along with alternate solution sets have been reported in 2014. This presentation will review some of the improvements achieved in the reanalysis and the impact of results from this reanalysis on the science investigations. The current mission status and the operations strategy, which are focused on extending the mission lifetime, will be discussed along with the impact of the operations on the future science data products. Finally, the challenges involved in achieving mission overlap with the GRACE Follow On Mission will be summarized.

  18. Requirements Analysis for Future Satellite Gravity Mission Improved-GRACE

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Hsu, Houtse; Zhong, Min; Yun, Meijuan

    2014-09-01

    The Earth's gravitational field from the Next-Generation Gravimetry Mission (NGGM) and the Improved-Gravity Recovery and Climate Experiment (Improved-GRACE) complete up to degree and order 120 is recovered by a closed-loop numerical simulation using different orbital altitudes of 325 and 300 km, different orbital inclinations of 96.78° and 89° and different inter-satellite ranges of 10 and 50 km. The preferred orbit parameters of the future twin Improved-GRACE satellites are proposed based on the results of the simulations in this study. The research results show: (1) In order to achieve the scientific objectives, which require that the accuracy of the next-generation Earth gravity field models is at least one order of magnitude better than that of the current gravity models, the orbit design at an altitude of 300 ± 50 km is recommended for the future Improved-GRACE mission. This altitude is determined by a trade-off analysis between the recovery accuracy of the gravity field and the operational lifetime of the satellite system. (2) Because the accuracy of the Earth's gravitational field from NGGM with an orbital inclination of 96.78° will be decreased due to a lack of the observation data in the polar areas, we propose that a near-polar orbit (inclination of 89° ± 2°) is a preferable selection for the future twin Improved-GRACE satellites. (3) The future Improved-GRACE mission has to adopt an inter-satellite range of 50 ± 10 km, because the common signals of the Earth's gravitational field between the twin NGGM satellites will be substantially eliminated with a shorter inter-satellite range of 10 km. With these orbit design parameters, the Earth's gravitational field from the Improved-GRACE mission is precisely recovered complete up to degree and order 120 with a cumulative geoid height error of about 0.7 mm.

  19. Requirements Analysis for Future Satellite Gravity Mission Improved-GRACE

    NASA Astrophysics Data System (ADS)

    Zheng, Wei; Hsu, Houtse; Zhong, Min; Yun, Meijuan

    2015-01-01

    The Earth's gravitational field from the Next-Generation Gravimetry Mission (NGGM) and the Improved-Gravity Recovery and Climate Experiment (Improved-GRACE) complete up to degree and order 120 is recovered by a closed-loop numerical simulation using different orbital altitudes of 325 and 300 km, different orbital inclinations of 96.78° and 89° and different inter-satellite ranges of 10 and 50 km. The preferred orbit parameters of the future twin Improved-GRACE satellites are proposed based on the results of the simulations in this study. The research results show: (1) In order to achieve the scientific objectives, which require that the accuracy of the next-generation Earth gravity field models is at least one order of magnitude better than that of the current gravity models, the orbit design at an altitude of 300 ± 50 km is recommended for the future Improved-GRACE mission. This altitude is determined by a trade-off analysis between the recovery accuracy of the gravity field and the operational lifetime of the satellite system. (2) Because the accuracy of the Earth's gravitational field from NGGM with an orbital inclination of 96.78° will be decreased due to a lack of the observation data in the polar areas, we propose that a near-polar orbit (inclination of 89° ± 2°) is a preferable selection for the future twin Improved-GRACE satellites. (3) The future Improved-GRACE mission has to adopt an inter-satellite range of 50 ± 10 km, because the common signals of the Earth's gravitational field between the twin NGGM satellites will be substantially eliminated with a shorter inter-satellite range of 10 km. With these orbit design parameters, the Earth's gravitational field from the Improved-GRACE mission is precisely recovered complete up to degree and order 120 with a cumulative geoid height error of about 0.7 mm.

  20. Combining GRACE and GOCE for a new combined EIGEN model

    NASA Astrophysics Data System (ADS)

    Marty, J.; Bruinsma, S. L.; Balmino, G.; Biancale, R.; Foerste, C.; Flechtner, F.; Abrikosov, O.; Dahle, C.; Neumayer, H.; Koenig, R.; Raimondo, J.

    2010-12-01

    GOCE is equipped with a 3-axes gradiometer (approximately radial, along-track, normal to the orbit plane), which provides gravity gradients that are measured with high precision within the measurement bandwidth of approximately 200 to 10 seconds (0.005 to 0.1 Hz; this translates to a distance along the satellite track of about 80-1600 km), whereas outside this interval the noise increases rapidly (i.e., colored noise). Due to this instrumental behavior, the gravity gradient observation equations must be filtered in order to retain only the precise information that is contained in the measurement bandwidth, i.e. the medium and short wavelengths of the gravity field. The GRACE satellites are equipped with a very precise microwave ranging system, and the mission was designed to accurately measure the long wavelengths of the gravity field every 30 days. Hence, GRACE and GOCE are complementary in the spectral domain. When combining GRACE and GOCE data however, particular care must be taken not to degrade the lower degrees of the resulting solution due to a filter pass band that is too wide. The high accuracy of GRACE-only models such as ITG-GRACE2010S up to degree 120-140 (spatial resolution of 167-143 km) implies that the high-pass cut-off period of the optimum filter actually should not be 200 seconds, but much less. The GOCE GPS-SST data are used to geo-locate the gradients, and satellite-to-satellite tracking normal equations are generated equally and their impact on the combined solution is evaluated. The construction of an accurate satellite-only model to degree and order 200 is therefore only possible after a rigorous filter selection procedure, which entails computing as many complete gravity field solutions as there are filters to assess. The solutions are evaluated through comparison with EIGEN-51C and ITG-GRACE2010S, as well as orbit computation tests.

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

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Map 1Map 2

    Gravity 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

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

    NASA Astrophysics Data System (ADS)

    Mulder, G.; Olsthoorn, T. N.; Al-Manmi, D. A. M. A.; Schrama, E. J. O.; Smidt, E. H.

    2014-10-01

    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.

  3. Gracing Our Work: Generating Theory from Writing across the Curriculum.

    ERIC Educational Resources Information Center

    Fletcher, Susan Laemmle

    Theoretical thinking is needed to help establish writing across the curriculum as a real field and not just a passing fad. The metaphor of the Three Graces--Giving, Receiving, and Returning--suggests a procedure that could generate and sustain both theories and programs. English teachers usually give the initial impetus to cross-curricular…

  4. Saving Grace - A Climate Change Documentary Education Program

    NASA Astrophysics Data System (ADS)

    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.

  5. Laser beam steering for GRACE Follow-On intersatellite interferometry.

    PubMed

    Schütze, Daniel; Stede, Gunnar; Müller, Vitali; Gerberding, Oliver; Bandikova, Tamara; Sheard, Benjamin S; Heinzel, Gerhard; Danzmann, Karsten

    2014-10-01

    The GRACE Follow-On satellites will use, for the first time, a Laser Ranging Interferometer to measure intersatellite distance changes from which fluctuations in Earth's geoid can be inferred. We have investigated the beam steering method that is required to maintain the laser link between the satellites. Although developed for the specific needs of the GRACE Follow-On mission, the beam steering method could also be applied to other intersatellite laser ranging applications where major difficulties are common: large spacecraft separation and large spacecraft attitude jitter. The beam steering method simultaneously coaligns local oscillator beam and transmitted beam with the laser beam received from the distant spacecraft using Differential Wavefront Sensing. We demonstrate the operation of the beam steering method on breadboard level using GRACE satellite attitude jitter data to command a hexapod, a six-degree-of-freedom rotation and translation stage. We verify coalignment of local oscillator beam/ transmitted beam and received beam of better than 10 μrad with a stability of 10 μrad/ √Hz in the GRACE Follow-On measurement band of 0.002...0.1 Hz. Additionally, important characteristics of the beam steering setup such as Differential Wavefront Sensing signals, heterodyne efficiency, and suppression of rotation-to-pathlength coupling are investigated and compared with analysis results. PMID:25321987

  6. Grace and compassion at "ground zero," New York City.

    PubMed

    Rogers, James R; Soyka, Karen M

    2004-01-01

    Responding to the request to write about our work at "ground zero" the site of the former World Trade Center in New York City following the September 11, 2001, terrorist attack has proved to be a challenging task. Challenging in that we have found it difficult to discuss and honor our experiences with mere words alone. Thus, this work has been "in progress" for a long period of time. Part of the challenge is reflected for us in the title of the article by the choice of the word "grace." That is, writing about grace at ground zero does not fit comfortably with our scientist-practitioner training. In searching for words to describe our experiences, however, we tried out a number of alternatives to "grace" including luck, chance, coincidence, and serendipity. None of these alternatives quite captured our experiences and our sense that certain events may best be conceptualized as unsolicited "gifts" that facilitated our work at the WTC site. So while the term "grace" may seem out of place in the scientific and professional literature, it fits well as a descriptor of some of our experiences as we continue our struggle to understand PMID:15384654

  7. The Grace Commission's View of Federal Research and Development.

    ERIC Educational Resources Information Center

    Aines, Andrew A.

    1984-01-01

    Focuses on the information aspects of the Grace Commission's (President's Private Sector Survey on Cost Control) findings and recommendations contained in the report on federal research and development. Research project reporting and redundancy, database provided by National Technical Information Service, cost controls, and measuring research and…

  8. The Current Status and Future Prospects for the GRACE Mission

    NASA Astrophysics Data System (ADS)

    Tapley, Byron; Flechtner, Frank; Watkins, Michael; Bettadpur, Srinivas; Boening, Carmen

    2016-04-01

    The twin satellites of the Gravity Recovery and Climate Experiment (GRACE) were launched on March 17, 2002 and have operated for over 13 years. The mission objectives are to sense the spatial and temporal variations of the Earth's mass through its effects on the gravity field at the GRACE satellite altitude. The major cause of the time varying mass is water motion and the GRACE mission has provided a continuous decade long measurement sequences which characterizes the seasonal cycle of mass transport between the oceans, land, cryosphere and atmosphere; its inter-annual variability; and the climate driven secular, or long period, mass transport signals. In 2012, the RLO5 solution, based on a complete reanalysis of the mission data, data release, was initiated. The monthly solutions from this effort were released in mid-2013 with the mean fields following in 2014 and 2015. The mission is entering the final phases of operations. The current mission operations strategy emphasizes extending the mission lifetime to achieve mission overlap with the GRACE Follow On Mission. This presentation will review the mission status and the projections for mission lifetime, summarize plans for the RL 06 data re-analysis, describe the issues that influence the operations philosophy and discuss the impact the operations may have on the scientific data products.

  9. Grace: Mission profile and its relation to science goals

    NASA Astrophysics Data System (ADS)

    Bettadpur, S.

    2003-04-01

    On Mar. 17, 2002, the twin GRACE satellites were successfully launched, with the purpose of collecting data leading to dramatic improvements in the estimates of the long-term mean and temporal variability of the Earth gravity field. The gravity information from GRACE is contained within the inter-satellite (microwave) range-change data. Ensuring sufficient quality of these measurements to meet the science goals had led to unique requirements on the GRACE system - including its attitude control, dimensional stability, precision of instrument accomodation and alignments, as well as other aspects of mission design. In this paper, certain aspects of the ongoing work of a multi-national GRACE project team is encapsulated into a description of the mission profile and its relationship to the science goals. Areas of focus include the orbit &station-keeping activities; the attitude pointing performance; the thermal stability performance; instrument configuration; and the status of key in-flight verification of the instrument alignments, the center-of-mass calibration and the K-Band boresight calibration. The impact of each of these on the science data quality, and current performance relative to pre-flight expectations will be presented. Arising from these considerations, the talk will conclude with an outline of the science mission plan for the near future.

  10. Attention, Asceticism, and Grace: Simone Weil and Higher Education

    ERIC Educational Resources Information Center

    Roberts, Peter

    2011-01-01

    The work of the French thinker Simone Weil has exerted an important influence on scholars in a wide range of fields. To date, however, her writings have attracted comparatively little interest from educationists. This article discusses some of the key concepts in Weil's philosophy--gravity, grace, decreation, and attention--and assesses their…

  11. Reducing errors in the GRACE gravity solutions using regularization

    NASA Astrophysics Data System (ADS)

    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

  12. Does GRACE see the terrestrial water cycle "intensifying"?

    NASA Astrophysics Data System (ADS)

    Eicker, Annette; Forootan, Ehsan; Springer, Anne; Longuevergne, Laurent; Kusche, Jürgen

    2016-01-01

    Several researchers have postulated that, under a changing climate due to anthropogenic forcing, an intensification of the water cycle is already under way. This is usually related to increases in hydrological fluxes as precipitation (P), evapotranspiration (E), and river discharge (R). It is under debate, however, whether such observed or reconstructed flux changes are real and on what scales. Large-scale increase or decrease of the flux deficit (P-E-R), i.e., flux changes that do not compensate, would lead to acceleration or deceleration of water storage anomalies potentially visible in Gravity Recovery and Climate Experiment (GRACE) data. In agreement with earlier studies, we do find such accelerations in global maps of gridded GRACE water storage anomalies over 2003-2012. However, these have been generally associated with interannual and decadal climate variability. Yet we show that even after carefully isolating and removing the contribution of El Niño that partially masks long-term changes, using a new method, accelerations of up to 12 mm/yr2 remain in regions such as Australia, Turkey, and Northern India. We repeat our analysis with flux fields from two global atmospheric reanalyses that include land surface models (ERA-Interim and MERRA-Land). While agreeing well with GRACE on shorter time scales, they fall short in displaying long-term trends corresponding to GRACE accelerations. We hypothesize that this may be due to time-varying biases in the reanalysis fluxes as noticed in other studies. We conclude that even though its data record is short, GRACE provides new information that should be used to constrain future reanalyses toward a better representation of long-term water cycle evolution.

  13. Improved Uncertainty Quantification in Groundwater Flux Estimation Using GRACE

    NASA Astrophysics Data System (ADS)

    Reager, J. T., II; Rao, P.; Famiglietti, J. S.; Turmon, M.

    2015-12-01

    Groundwater change is difficult to monitor over large scales. One of the most successful approaches is in the remote sensing of time-variable gravity using NASA Gravity Recovery and Climate Experiment (GRACE) mission data, and successful case studies have created the opportunity to move towards a global groundwater monitoring framework for the world's largest aquifers. To achieve these estimates, several approximations are applied, including those in GRACE processing corrections, the formulation of the formal GRACE errors, destriping and signal recovery, and the numerical model estimation of snow water, surface water and soil moisture storage states used to isolate a groundwater component. A major weakness in these approaches is inconsistency: different studies have used different sources of primary and ancillary data, and may achieve different results based on alternative choices in these approximations. In this study, we present two cases of groundwater change estimation in California and the Colorado River basin, selected for their good data availability and varied climates. We achieve a robust numerical estimate of post-processing uncertainties resulting from land-surface model structural shortcomings and model resolution errors. Groundwater variations should demonstrate less variability than the overlying soil moisture state does, as groundwater has a longer memory of past events due to buffering by infiltration and drainage rate limits. We apply a model ensemble approach in a Bayesian framework constrained by the assumption of decreasing signal variability with depth in the soil column. We also discuss time variable errors vs. time constant errors, across-scale errors v. across-model errors, and error spectral content (across scales and across model). More robust uncertainty quantification for GRACE-based groundwater estimates would take all of these issues into account, allowing for more fair use in management applications and for better integration of GRACE

  14. Characteristic mega-basin water storage behavior using GRACE

    PubMed Central

    Reager, J T; Famiglietti, James S

    2013-01-01

    [1] A long-standing challenge for hydrologists has been a lack of observational data on global-scale basin hydrological behavior. With observations from NASA’s Gravity Recovery and Climate Experiment (GRACE) mission, hydrologists are now able to study terrestrial water storage for large river basins (>200,000 km2), with monthly time resolution. Here we provide results of a time series model of basin-averaged GRACE terrestrial water storage anomaly and Global Precipitation Climatology Project precipitation for the world’s largest basins. We address the short (10 year) length of the GRACE record by adopting a parametric spectral method to calculate frequency-domain transfer functions of storage response to precipitation forcing and then generalize these transfer functions based on large-scale basin characteristics, such as percent forest cover and basin temperature. Among the parameters tested, results show that temperature, soil water-holding capacity, and percent forest cover are important controls on relative storage variability, while basin area and mean terrain slope are less important. The derived empirical relationships were accurate (0.54 ≤ Ef ≤ 0.84) in modeling global-scale water storage anomaly time series for the study basins using only precipitation, average basin temperature, and two land-surface variables, offering the potential for synthesis of basin storage time series beyond the GRACE observational period. Such an approach could be applied toward gap filling between current and future GRACE missions and for predicting basin storage given predictions of future precipitation. PMID:24563556

  15. Acceleration of terrestrial water storage changes from GRACE data

    NASA Astrophysics Data System (ADS)

    Ogawa, R.; Chao, B. F.; Heki, K.

    2008-12-01

    Gravity Recovery and Climate Experiment (GRACE) satellite has been producing scientific results on mass variations since its launch in 2002, particularly land water storage on seasonal and inter-annual timescales as the soil moisture reflects the time integration of fluxes of precipitation, evapo-transpiration and runoff. For example, in Amazon Basin (e.g. Tapley et al., 2004), Alaska glacial melting (e.g. Tamisiea et al., 2005), ENSO precipitation anomalies (Morishita and Heki, 2008), and seasonal land water storage with global hydrological model (Syed et al., 2008). If climate changes have trends of time scale longer than inter-annual, we can expect to see quadratic trends in land water time series now that over six years have passed since GRACE"fs launch and the time span is becoming long enough to study such trends, which signify the temporal acceleration in gravity, and hence climatic, changes. To look for such accelerations, we compute time series of equivalent water thicknesses in global land regions from monthly GRACE data of gravity anomaly, and model the changes with quadratic functions in addition to seasonal components. We repeat similar calculations for the GLDAS global hydrological model data as well. We found that the geographic distribution of the quadratic trends shows good agreement between GRACE and GLDAS, prominent in East Africa, East Europe, Ural Mountains, eastern North America and southern South America. Amplitudes of the signals are generally larger in GRACE than the corresponding GLDAS model. We also compare and verify such acceleration terms with trends in meteorological data of precipitation and evapo-transpiration.

  16. Synergies Between Grace and Regional Atmospheric Modeling Efforts

    NASA Astrophysics Data System (ADS)

    Kusche, J.; Springer, A.; Ohlwein, C.; Hartung, K.; Longuevergne, L.; Kollet, S. J.; Keune, J.; Dobslaw, H.; Forootan, E.; Eicker, A.

    2014-12-01

    In the meteorological community, efforts converge towards implementation of high-resolution (< 12km) data-assimilating regional climate modelling/monitoring systems based on numerical weather prediction (NWP) cores. This is driven by requirements of improving process understanding, better representation of land surface interactions, atmospheric convection, orographic effects, and better forecasting on shorter timescales. This is relevant for the GRACE community since (1) these models may provide improved atmospheric mass separation / de-aliasing and smaller topography-induced errors, compared to global (ECMWF-Op, ERA-Interim) data, (2) they inherit high temporal resolution from NWP models, (3) parallel efforts towards improving the land surface component and coupling groundwater models; this may provide realistic hydrological mass estimates with sub-diurnal resolution, (4) parallel efforts towards re-analyses, with the aim of providing consistent time series. (5) On the other hand, GRACE can help validating models and aids in the identification of processes needing improvement. A coupled atmosphere - land surface - groundwater modelling system is currently being implemented for the European CORDEX region at 12.5 km resolution, based on the TerrSysMP platform (COSMO-EU NWP, CLM land surface and ParFlow groundwater models). We report results from Springer et al. (J. Hydromet., accept.) on validating the water cycle in COSMO-EU using GRACE and precipitation, evapotranspiration and runoff data; confirming that the model does favorably at representing observations. We show that after GRACE-derived bias correction, basin-average hydrological conditions prior to 2002 can be reconstructed better than before. Next, comparing GRACE with CLM forced by EURO-CORDEX simulations allows identifying processes needing improvement in the model. Finally, we compare COSMO-EU atmospheric pressure, a proxy for mass corrections in satellite gravimetry, with ERA-Interim over Europe at

  17. Status of the GRACE Follow-On Mission

    NASA Astrophysics Data System (ADS)

    Watkins, Michael; Flechtner, Frank; Morton, Phil; Massmann, Franz-Heinrich; Gaston, Rob; Grunwaldt, Ludwig

    2015-04-01

    GRACE Follow-On, a joint US/German satellite mission to extend the critical global mass flux data records from the GRACE mission, continues to mature and advance on both sides of the Atlantic. In January 2014 the Preliminary Design Review (PDR) was conducted, and transition into phase C was accomplished in March 2014. The project Critical Design Review (CDR) is scheduled for February 2015. The current launch date remains August 2017. The presentation will focus on the project status after the CDR of major spacecraft systems, science payloads (microwave ranging system, GNSS receiver, and accelerometer), a demonstration payload (laser ranging interferometer), mission operations, launch services and the science data system. In addition, since we now have more mature predictions of the spacecraft and instrument expected performance, we have continued to update the expected science performance via detailed colored noise simulations.

  18. The GRACE Follow-On Laser Ranging Interferometer

    NASA Astrophysics Data System (ADS)

    Müller, Vitali

    2016-07-01

    The GRACE Follow-On mission consists of a pair of satellites to be launched in 2017 into a low-Earth polar orbit. As the precursor mission GRACE, it will provide monthly global maps of Earth's gravity field to study mass changes within the System Earth, like glacier melting or ground-water depletion. The new mission will be equipped with two ranging instruments: a conventional Microwave Ranging Instrument, as already present in the precursor mission, and with a Laser Ranging Interferometer (LRI). Latter acts as a technical demonstrator, which will show the capability for enhanced sensitivity and additional precise attitude information of this new technology. The satellite and in particular the LRI working principle will be introduced together with observables and major noise and error contributors. Furthermore potential modifications and extensions for future gravimetric missions are addressed as well as applications in space-based gravitational wave detectors (i.e. eLISA).

  19. Using GRACE as an Orbiting Fiducial Laboratory for GPS

    NASA Astrophysics Data System (ADS)

    Haines, B. J.; Bar-Sever, Y. E.; Bertiger, W.; Byun, S.; Desai, S. D.; Hajj, G.

    2006-12-01

    Uncertainties in the phase-center variations (PCV) of the GPS transmitter antennas are among the limiting sources of error in GPS-based global geodesy. We have used data from the BlackJack GPS receivers onboard the twin GRACE satellites to develop new estimates of GPS satellite antenna PCV. The estimates are expressed as tracking observable (distance) corrections mapped in two dimensions (nadir angle and azimuth). We have developed maps for both ionosphere-free carrier phase (LC) and pseudorange (PC). The GRACE tandem mission offers a number of substantial advantages for developing GPS PCV maps. The scale (mean height) of our GRACE orbit solutions is well determined at the cm level from dynamical constraints, and there is no troposphere signal to confound interpretation of the measurements. The multipath environment is also very favorable. We discuss our strategy for determining the GPS satellite PCV estimates from these data, and describe evaluations of the estimates using independent GPS data from both the TOPEX/POSEIDON (T/P; 1992--2005) and Jason-1 (2001 - ) missions. A heretofore unexplained 5--6 cm offset in the solved-for position of the T/P receiver antenna is reduced to less than 1 cm by applying the GRACE-based GPS PCV maps. The corresponding offset for Jason-1 is similarly decreased. Equally important, a spurious long-term (4-yr) drift in the daily estimated Jason-1 offsets is significantly reduced. These results hint at the potential benefits of these new GPS antenna PCV maps for wide-ranging geodetic applications wherein scale and long-term stability are important.

  20. Determining dislocation love numbers using GRACE satellite mission gravity data

    NASA Astrophysics Data System (ADS)

    Junyan, Yang; Zhou, Xin; Yi, Shuang; Sun, Wenke

    2015-10-01

    In this study, we propose a method to determine dislocation Love numbers using co-seismic gravity changes from GRACE measurements. First, we present an observation equation to model GRACE observations taking into account the effect of ocean water mass redistribution. The L-curve method was used to determine the regulation parameter in the inversion of the geopotential dislocation Love numbers constrained by an a priori preliminary reference Earth (PREM) model. Then, the GRACE data error was estimated in the study area to evaluate the uncertainty of our inversion, and our inverted Love numbers are significantly deviated from the PREM ones even the uncertainty is considered. Finally, GRACE data observed for the 2011 Tohoku-Oki earthquake (Mw = 9.0) were used to estimate the gravity dislocation Love numbers, considering three different fault-slip models. The results show that the inverted dislocation Love numbers deviate from PREM model, especially for k_{l1}^{32} and k_{l0}^{33} - k_{l0}^{22}, which indicates that the inverted dislocation Love numbers can reflect the local structure that is different from the global average. This inconsistency is possibly because that the cold denser oceanic slab dives from the Japanese Trench into the softer asthenosphere, and then changes the local density here higher than the global average. And with these sets of Love numbers, we can invert for more accurate fault model and analyse focal rupture mechanism when some other earthquake in this area occurs in the future. This study provides a new approach to invert for dislocation Love numbers linked with local geological information.

  1. Graceful exit via polymerization of pre-big-bang cosmology

    SciTech Connect

    De Risi, Giuseppe; Maartens, Roy; Singh, Parampreet

    2007-11-15

    We consider a phenomenological modification of the pre-big-bang scenario using ideas from the resolution of curvature singularities in loop quantum cosmology. We show that nonperturbative loop modifications to the dynamics, arising from the underlying polymer representation, can resolve the graceful exit problem. The curvature and the dilaton energy stay finite at all times, in both the string and Einstein frames. In the string frame, the dilaton tends to a constant value at late times after the bounce.

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

    NASA Technical Reports Server (NTRS)

    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. Validation of the EGSIEM combined monthly GRACE gravity fields

    NASA Astrophysics Data System (ADS)

    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.

  4. Mass Loss and Surface Displacement Estimates in Greenland from GRACE

    NASA Astrophysics Data System (ADS)

    Jensen, Tim; Forsberg, Rene

    2015-04-01

    The estimation of ice sheet mass changes from GRACE is basically an inverse problem, the solution is non-unique and several procedures for determining the mass distribution exists. We present Greenland mass loss results from two such procedures, namely a direct spherical harmonic inversion procedure possible through a thin layer assumption, and a generalized inverse masscon procedure. These results are updated to the end of 2014, including the unusual 2013 mass gain anomaly, and show a good agreement when taking into account leakage from the Canadian Icecaps. The GRACE mass changes are further compared to GPS uplift data on the bedrock along the edge of the ice sheet. The solid Earth deformation is assumed to consist of an elastic deformation of the crust and an anelastic deformation of the underlying mantle (GIA). The crustal deformation is due to current surface loading effects and therefore contains a strong seasonal component of variation, superimposed on a secular trend. The majority of the anelastic GIA deformation of the mantle is believed to be approximately constant. An accelerating secular trend and seasonal changes, as seen in Greenland, is therefore assumed to be due to elastic deformation from changes in surface mass loading from the ice sheet. The GRACE and GPS comparison is only valid by assuring that the signal content of the two observables are consistent. The GPS receivers are measuring movement at a single point on the bedrock surface, and therefore sensitive to a limited loading footprint, while the GRACE satellites on the other hand measures a filtered, attenuated gravitational field, at an altitude of approximately 500 km, making it sensitive to a much larger area. Despite this, the seasonal loading signal in the two observables show a reasonably good agreement.

  5. Grace's story: prolonged incestuous abuse from childhood into adulthood.

    PubMed

    Salter, Michael

    2013-02-01

    Some sexually abused women in mental health settings are reporting prolonged incest and yet little is known about the circumstances that enable fathers to sexually abuse their daughters over a period of decades. This article draws from the life history of Grace, a woman who survived prolonged incest, in order to document and analyze the interplay of familial, social, and political factors that entrap girls and women within prolonged incestuous abuse. PMID:23420835

  6. GOCE before launch: a complementary mission to GRACE

    NASA Astrophysics Data System (ADS)

    Flury, J.; Rummel, R.; Ilk, K.

    2006-12-01

    GOCE is an ESA mission to be launched in summer 2007 and dedicated to the precise mapping of the Earth's gravity field. Measuring the quasi-static gravity field with an increased spatial detail resolution, it is complementary to the GRACE mission. The integration of the GOCE platform and instrumentation, and the preparations of the ground segment are nearing completion. The core instrument is a three axis gravity gradiometer, based on the principle of differential accelerometry. In addition, GOCE carries a GPS receiver and is furnished with active drag compensation and angular control. The drag compensation will maintain the spacecraft at an extremely low orbit altitude (250 km). The GOCE gravity model is intended to serve solid Earth geophysics, oceanography, geodesy, and sea level research. In Germany, the use of GOCE data will represent an important contribution to the new priority research program `Mass Transport and Mass Distribution in the Earth System' starting in October 2006. This program aims at the synergetic use of GRACE, GOCE and satellite altimetry observations for the study of mass related processes, mass balance and mass exchange between oceans, ice caps, continental hydrology, atmosphere, and within solid Earth. The program integrates research projects on each of these Earth system components. From GRACE data, the large scale time variable mass changes in all parts of the hydrological cycle are derived. GOCE observations are particularly important for a detailed modelling of the quasi-static components of ocean circulation.

  7. California Drought Recovery Assessment Using GRACE Satellite Gravimetry Information

    NASA Astrophysics Data System (ADS)

    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.

  8. Identifying water mass depletion in northern Iraq observed by GRACE

    NASA Astrophysics Data System (ADS)

    Mulder, G.; Olsthoorn, T. N.; Al-Manmi, D. A. M. A.; Schrama, E. J. O.; Smidt, E. H.

    2015-03-01

    Observations acquired by Gravity Recovery And Climate Experiment (GRACE) mission indicate a mass loss of 146 ± 6 mm equivalent water height (EWH) in northern Iraq between 2007 and 2009. These data are used as an independent validation of lake mass variations and a rainfall-runoff model, which is based on local geology and climate conditions. Model inputs are precipitation from Tropical Rainfall Measurement Mission (TRMM) observations, and climatic parameters from Global Land Data Assimilation Systems (GLDAS) model parameters. The model is calibrated with observed river discharge and includes a representation of the karstified aquifers in the region to improve model realism. Lake mass variations were 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 captures the annual cycle and longer trend of the observed GRACE data. The total mass depletion seen by GRACE between 2007 and 2009 is mainly explained by a lake mass depletion of 75 ± 3 mm EWH and a natural groundwater depletion of 39 ± 8 mm EWH. Our findings indicate that anthropogenic groundwater extraction has a minor influence in this region, while a decline in lake mass and natural depletion of groundwater play a key role.

  9. Time Variable Gravity from Local Mascon Analysis of GRACE Data

    NASA Technical Reports Server (NTRS)

    Lemoine, Frank G.; Luthcke, Scott B.; Klosko, Steven M.; Rowlands, David; Chinn, Douglas S.; McCarthy, John J.; Cox, Christopher M.; Williams, Terry A.; Pavlis, Despina E.

    2004-01-01

    We have analyzed GRACE Level 1-B data in 2003 and assessed a new approach for extracting time variable gravity that isolates the gravity signal in both time and space. The Level-1B satellite-to-satellite range rate (KBRR) data and accelerometry are processed in daily arcs using the precise orbit products produced by the GRACE team from GPS to calibrate both the accelerometer and KBRR data. We then adjusted select components of the intersatellite baseline vector for each data segment isolated to the region of interest. Herein, we solved for mass anomalies in 45 deg x 45 deg blocks over the Amazon and the nearby Atlantic Ocean and estimate mass flux in units of cm of water over each block. We show with this approach that we can recover mass anomalies on a submonthly basis with 10 to 15 day temporal resolution. We discuss the important issues related to this solution, including the size of the mascon blocks, the weight given to the temporal and spatial constraint used to stabalize the solutions, as well as the optimal correlation in time and distance. We compare the the mascon results with solutions obtained from the more standard approach using spherical harmonics and with independent hydrology models and lake data. This technique demonstrates that sub-monthly medium wavelength mass flux phenomena are well sensed by the hyper-precise line of sight velocity data produced from GRACE.

  10. Application of GRACE for Monitoring Groundwater in Data Scarce Regions

    NASA Technical Reports Server (NTRS)

    Rodell, Matt; Li, Bailing; Famiglietti, Jay; Zaitchik, Ben

    2012-01-01

    In the United States, groundwater storage is somewhat well monitored (spatial and temporal data gaps notwithstanding) and abundant data are freely and easily accessible. Outside of the U.S., groundwater often is not monitored systematically and where it is the data are rarely centralized and made available. Since 2002 the Gravity Recovery and Climate Experiment (GRACE) satellite mission has delivered gravity field observations which have been used to infer variations in total terrestrial water storage, including groundwater, at regional to continental scales. Challenges to using GRACE for groundwater monitoring include its relatively coarse spatial and temporal resolutions, its inability to differentiate groundwater from other types of water on and under the land surface, and typical 2-3 month data latency. Data assimilation can be used to overcome these challenges, but uncertainty in the results remains and is difficult to quantify without independent observations. Nevertheless, the results are preferable to the alternative - no data at all- and GRACE has already revealed groundwater variability and trends in regions where only anecdotal evidence existed previously.

  11. An evaluation of GRACE groundwater estimates over East Africa

    NASA Astrophysics Data System (ADS)

    Nanteza, J.; Thomas, B. F.; de Linage, C.; Famiglietti, J. S.

    2013-12-01

    The East African (EA) region, comprised of five countries (Uganda, Kenya, Tanzania, Rwanda and Burundi), is among those regions characterized as vulnerable to water stress. The region's freshwater resources, both surface and groundwater, are impacted due to increased pressure from changes in climate and human activities. Better management approaches are required to ensure that these pressures do not significantly impact water availability and accessibility. However, the lack of adequate ground-based observation networks to monitor freshwater resources - especially groundwater (the major source of freshwater in EA), limits effective management of the available water resources. In this study, we explore the potential of using remotely sensed data to monitor freshwater resources over EA. The study uses data from the Gravity Recovery and Climate Experiment (GRACE) satellite to estimate groundwater storage variations over EA during the last decade. The satellite's performance in accurately observing changes in groundwater storage is examined by evaluating the GRACE groundwater estimates against spatially interpolated in-situ groundwater observations using goodness of fit criteria including linear regression coefficient, coefficient of determination and root mean square errors. The results demonstrate that GRACE performs well in observing the behavior of groundwater storage. These results can be useful in improving land surface model simulations - a basis for better decision making in water resources management in the region.

  12. The GRACE satellites detect recent extreme climate events in China

    NASA Astrophysics Data System (ADS)

    Tang, Jingshi; Liu, Lin

    2012-07-01

    As the climate changes, the extreme climates are occurring more frequenly over the globe. In China, drought or flood recently strikes almost every year and there have been several disastrous events in these years. We show that some of the disastrous events are so strong that corresponding gravity change can be observed by geodetic satellies. We use the Gravity Recovery and Climate Experiment (GRACE), which is a joint mission between NASA and DLR. One primary job of GRACE is to map Earth temporal gravity field with high resolution. Over the years the twin satellites have observed the loss of mass in Antarctic and Greenland, strong earthquakes, severe climate change in South America and so on, which provides a unique way to study the geophysical or climatological process. In this report, the Level-2 product in recent few years from Center for Space Research is used and specific areas in China are focused on. It is shown that after decorrelation, filter and other processes, the gravity anomalies observed by GRACE match the extreme climate events and the hydrological data from the Global Land Data Assimilation System (GLDAS).

  13. Constraints of Melting, Sea-Level and the Paleoclimate from GRACE

    NASA Technical Reports Server (NTRS)

    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].

  14. Innovative analysis constraints in the ANU GRACE mascon solutions

    NASA Astrophysics Data System (ADS)

    Tregoning, P.; McClusky, S.; Purcell, A.; Lescarmontier, L.

    2013-12-01

    The GRACE products used by many scientists to study mass changes on and within the surface of the Earth are typically in the form of spherical harmonics. We have developed new software that processes the Level-1B data of the GRACE mission to derive estimates of mass changes using the 'mascons' (mass concentration) approach. We have taken a fresh look at the Level-1B observations and the way in which the observations contribute to the estimation of the temporal gravity field and will present several new ideas of ways in which the processing of the observations can be improved. We include in our analysis a multi-tiered definition of the shape of each mascon which enables a more accurate computation of the effect of mass changes on the satellite orbits as well as irregular-shaped mascons to be used. We use a topography model of the Earth's surface to define more accurately the spatial relation between the location of mass change and the GRACE satellites, which can affect the mass change estimates by 5-10%. From an understanding of what forces are acting upon the GRACE satellites while in the shadow of the Earth, it is possible to place constraints on the values of the calibrated accelerometer observations during this time in the cross-track and radial directions. We have derived corresponding constraint equations that we apply during eclipse periods to aid in the estimation of accelerometer bias estimates. It is well known that the regular thrust events designed to maintain the orientation of the GRACE satellites do generate some linear component of acceleration that is detected by the onboard accelerometers. Once filtered in the process of generating the Level-1B accelerometer observations, these short-period square-pulse thrusts are smeared over tens of seconds. We derived a model to remove the filtered linear accelerations from thruster firings found in the accelerometer observations then insert square thrust pulses that better reflects the actual forces that acted

  15. 29 CFR 779.418 - Grace period for computing portion of compensation representing commissions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Grace period for computing portion of compensation... § 779.418 Grace period for computing portion of compensation representing commissions. Where it is not practicably possible for the employer to compute the commission earnings of the employee for all...

  16. 29 CFR 779.418 - Grace period for computing portion of compensation representing commissions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 29 Labor 3 2011-07-01 2011-07-01 false Grace period for computing portion of compensation... § 779.418 Grace period for computing portion of compensation representing commissions. Where it is not practicably possible for the employer to compute the commission earnings of the employee for all...

  17. 29 CFR 779.418 - Grace period for computing portion of compensation representing commissions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 3 2012-07-01 2012-07-01 false Grace period for computing portion of compensation... § 779.418 Grace period for computing portion of compensation representing commissions. Where it is not practicably possible for the employer to compute the commission earnings of the employee for all...

  18. 29 CFR 779.418 - Grace period for computing portion of compensation representing commissions.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 3 2014-07-01 2014-07-01 false Grace period for computing portion of compensation... § 779.418 Grace period for computing portion of compensation representing commissions. Where it is not practicably possible for the employer to compute the commission earnings of the employee for all...

  19. 29 CFR 779.418 - Grace period for computing portion of compensation representing commissions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 3 2013-07-01 2013-07-01 false Grace period for computing portion of compensation... § 779.418 Grace period for computing portion of compensation representing commissions. Where it is not practicably possible for the employer to compute the commission earnings of the employee for all...

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

    NASA Technical Reports Server (NTRS)

    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.

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

    NASA Astrophysics Data System (ADS)

    Rodell, M.; Watkins, M. M.; Famiglietti, J. S.

    2011-12-01

    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. Estimating continental water storage variations in Central Asia area using GRACE data

    NASA Astrophysics Data System (ADS)

    Dapeng, Mu; Zhongchang, Sun; Jinyun, Guo

    2014-03-01

    The goal of GRACE satellite is to determine time-variations of the Earth's gravity, and particularly the effects of fluid mass redistributions at the surface of the Earth. This paper uses GRACE Level-2 RL05 data provided by CSR to estimate water storage variations of four river basins in Asia area for the period from 2003 to 2011. We apply a two-step filtering method to reduce the errors in GRACE data, which combines Gaussian averaging function and empirical de-correlation method. We use GLDAS hydrology to validate the result from GRACE. Special averaging approach is preformed to reduce the errors in GLDAS. The results of former three basins from GRACE are consistent with GLDAS hydrology model. In the Tarim River basin, there is more discrepancy between GRACE and GLDAS. Precipitation data from weather station proves that the results of GRACE are more plausible. We use spectral analysis to obtain the main periods of GRACE and GLDAS time series and then use least squares adjustment to determine the amplitude and phase. The results show that water storage in Central Asia is decreasing.

  3. SLR-determined Low-Degree Geopotential Harmonics and their use With GRACE Data Products

    NASA Astrophysics Data System (ADS)

    Ries, J. C.; Cheng, M.; Bettadpur, S.; Chambers, D. P.

    2008-12-01

    GRACE provides estimates of the temporal variations in the Earth's gravity field with extraordinary precision, but as with any non-synoptic measurement system, the problem of aliasing of high- frequency signals errors is an important concern. In the case of GRACE, errors in the models for the diurnal and semi-diurnal (solid earth and ocean) tides will alias into long-period variations in the low-degree geopotential harmonics. This issue is particularly apparent for the degree-2 zonal harmonic, C20. In addition, after removing the tidal aliases, the GRACE C20 series is still noisier than SLR by about a factor of 3. As a consequence, GRACE data product users typically replace the C20 estimates from GRACE with estimates derived independently (but using consistent modeling) from SLR tracking of several geodetic satellites. For the other low degree harmonics, the GRACE estimates do not appear to suffer from significant tidal aliasing or excessive noise. In this paper, we will discuss the characteristics of the GRACE and SLR time series for the low-degree harmonics. In particular, we discuss the SLR and GRACE estimates for the harmonic terms describing the orientation of the Earth's principal figure axis, C21 and S21, and compare them to the conventional model for the long-term evolution of these terms.

  4. Impact of GRACE signal leakage over the Congo River Basin

    NASA Astrophysics Data System (ADS)

    Lee, H.; Beighley, R. E.; Duan, J.; Shum, C.; Alsdorf, D. E.; Andreadis, K.

    2013-05-01

    The Congo Basin is the world's third largest in size, and second only to the Amazon River in discharge. The impact and connections of this hydrologic flux with the region's climate, biogeochemical cycling, and terrestrial water storage (TWS), especially in wetlands, is clearly of great importance. Yet, there is a great lack of published research documenting the Congo Basin terrestrial water balance. This lack of research is related in part to the limited amount of in-situ data; however, the abundance of spaceborne data suggests an opportunity for discovery. The Congo River is the only major river to cross the equator twice. In doing so, the basin lies in both the Northern and Southern Hemisphere such that it receives year-round rainfall from the migration of Inter-Tropical Convergence Zone (ITCZ). After the north has its wet season in the spring and summer, the ITCZ moves south and the remainder of the basin receives large amounts of rain. Consequently, the movement of ITCZ can also be observed from the Gravity Recovery and Climate Experiment (GRACE) TWS changes over the northern and southern boundaries over the Congo. This spatial pattern of the TWS variations are different from that over the Amazon Basin, where the strongest positive or negative annual water storage anomalies are observed to be centered inside the basin. In this study, we examine individual monthly geographical distribution of GRACE TWS changes from various RL05 products, and determine the leakage-contaminated monthly solutions by comparison with reproduced TWS variations from Hillslope River Routing (HRR) model in sub-basin scale. We also present a methodology to empirically remove the signal leakage, and consequently improve the GRACE TWS estimates over the entire Congo Basin.

  5. Flood potential index over China based on GRACE

    NASA Astrophysics Data System (ADS)

    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

  6. Magnetic torquer induced disturbing signals within GRACE accelerometer data

    NASA Astrophysics Data System (ADS)

    Peterseim, Nadja; Flury, Jakob; Schlicht, Anja

    2012-05-01

    The GRACE (Gravity Recovery And Climate Experiment) gravity field satellite mission was launched in 2002. Although many investigations have been carried out, not all disturbances and perturbations upon satellite instruments and sensors are resolved yet. In this work the issue of acceleration disturbances onboard of GRACE due to magnetic torquers is investigated and discussed. Each of the GRACE satellites is equipped with a three-axes capacitive accelerometer to measure non-gravitational forces acting on the spacecraft. We used 10 Hz Level 1a raw accelerometer data in order to determine the impact of electric current changes on the accelerometer. After reducing signals which are induced by highly dominating processes in the low frequency range, such as thermospheric drag and solar radiation pressure, which can easily be done by applying a high-pass filter, disturbing signals from onboard instruments such as thruster firing events or heater switch events need to be removed from the previously filtered data. Afterwards the spikes which are induced by the torquers can be very well observed. Spikes vary in amplitude with respect to an increasing or decreasing current used for magnetic torquers, and can be as large as 20 nm/s2. Furthermore, we were able to set up a model for the spikes of each scenario with which we were able to compute model spike time series. With these time series the spikes can successfully be removed from the 10 Hz raw accelerometer data. Spectral analysis of the time series reveal that an influence onto gravity field determination due to these effects is very unlikely, but can theoretically not be excluded.

  7. Drought prediction using GRACE observation and NOAH model simulation

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Wu, J.; Castle, E.

    2012-12-01

    Drought causes severe impacts on agricultural production, economics and society, with annual loss about $6-8 billion in US alone. It is critical to develop drought predicting capability because drought develops more slowly than other disasters like floods and hurricanes and it is hard to recognize drought until it becomes severe. Gravity Recovery and Climate Experiment (GRACE) measures changes in the Earth's gravity. One product derived from GRACE data is the monthly terrestrial water storage over large scale, which has been used for drought monitoring. NOAH model, as a part of GLDAS land surface modeling system, integrates satellite and ground base observations to simulate a variety of geophysical variables. NOAH derived soil moisture estimates have also been used in drought monitoring. A new drought prediction method was developed with to forecast drought occurrence one month in advance. The prediction method combines two water indices, Total Storage Deficit Index (TSDI) from GRACE terrestrial water storage estimates and Soil Moisture Deficit Index (SMDI) from NOAH modeled soil moisture content. Because the two indices react differently to the same climatic forcing, with a delay in TSDI typically observed, confirmation between each other could indicate a high probability of occurring. Drought condition is predicted by comparing the combined index with the historical monthly water surplus/deficit. Evaluation over the Red River Valley of the North showed that the method was able to predict a severe drought occurring during 2006-2008 and the current drought that we are experiencing now. Currently, we are evaluating the method over a much larger scale.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. Checkpointing for graceful degradation in distributed embedded systems

    NASA Astrophysics Data System (ADS)

    Sababha, Belal Hussein

    Graceful degradation is an approach to developing dependable safety-critical embedded applications, where redundant active or standby resources are used to cope with faults through a system reconfiguration at run-time. Compared to traditional hardware and software redundancy, it is a promising technique that may achieve dependability with a significant reduction in cost, size, weight, and power requirements. Reconfiguration at run-time necessitates using proper checkpointing protocols to support state reservation to ensure correct task restarts after a system reconfiguration. One of the most common checkpointing protocols are communication induced checkpointing (CIC) protocols, which are well developed and understood for large parallel and information systems, but not much has been done for resource limited embedded systems. This work implements and evaluates some of the most common CIC protocols in a periodic resource constrained distributed embedded system for graceful degradation purposes. A test-bed has been developed and used for the evaluation of the various protocols. The implemented protocols are thoroughly studied and performances are contrasted. Specifically the periodicity property and how it benefits checkpointing in embedded systems is investigated. This work introduces a unique effort of CIC protocol implementation and evaluation in the field of distributed embedded systems. Other than providing a test-bed for graceful degradation support, this work shows that some checkpointing protocols that are not efficient in large information systems and supercomputers perform well in embedded systems. We show that a simple index-based CIC protocol, such as the BCS protocol, is more appropriate in embedded system applications compared to other protocols that piggyback a significant amount of information to reduce the number of forced checkpoints. Finally, this work proposes a whole graceful degradation approach to achieve fault tolerance in resource constrained

  10. Complete mitogenome of the Graceful Shark Carcharhinus amblyrhynchoides (Carcharhiniformes: Carcharhinidae).

    PubMed

    Feutry, Pierre; Pillans, Richard D; Kyne, Peter M; Chen, Xiao

    2016-01-01

    In this manuscript we describe the first complete mitochondrial sequence for the Near Threatened Graceful Shark Carcharhinus amblyrhynchoides. It is 16,705 bp in length, consists of two rRNA genes, 22 tRNA genes, 13 protein-coding genes and one control region with the typical gene arrangement pattern and translate orientation in vertebrates. The overall base composition is 31.4% A, 25.1% C, 13.2% G and 30.3% T. The shortest tRNA-Ser2 cannot fold into a clover-leaf secondary structure due to the lack of the dihydrouridine arm. PMID:24617479

  11. Evaluating flood potential with GRACE in the United States

    NASA Astrophysics Data System (ADS)

    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.

  12. GRACE KBR and Accelerometer Data Reduction and Calibration

    NASA Technical Reports Server (NTRS)

    Rowlands, David D.; Lutheke, Scott B.; Klosko, Steven M.; Lemoine, Frank G.; Williams, Terry A.

    2004-01-01

    The Gravity Recovery and Climate Experiment (GRACE), launched on March 17, 2002, represents the state-of-the-art in geodetic observations of the static and time varying components of the Earth's geopotential field. The fundamental measurement used to observe gravity is the inter-satellite range and range rate between two coplanar, low altitude satellites obtained from a K-band ranging (KBR) system. In addition to the K-band ranging system, each satellite possess a Super-STAR Accelerometer, a GPS receiver/antenna package, Star Cameras and a Laser Retro Reflector (LRR) to complete the compliment of science instruments. The GRACE project has now released two years of Level 1B data derived from the science instruments and sensors. An integral component of our time variable gravity research is the reduction, calibration and analyses of these Level 1B data. In particular we have analyzed several months of K-band ranging (KBR1B), accelerometry (ACC1B) and GPS navigation (GNAV1B) data. Accelerometer calibration and KBR data reduction methodology and results will be presented. We discuss the impact of these analyses on the recovery of time variable gravity.

  13. Analyses of altimetry errors using Argo and GRACE data

    NASA Astrophysics Data System (ADS)

    Prandi, Pierre; Legeais, Jean-François; Ablain, Michael; Picot, Nicolas

    2015-04-01

    Since the first altimeter missions and the improvements performed in the accuracy of sea surface height measurements from 1992 onwards, the importance of global quality assessment of altimeter data has been increasing. Global Cal/Val studies are usually performed by the analysis of internal consistency and cross-comparison between all missions. In this study, the steric and mass contributions to the sea level provided by Argo profiling floats and the Gravity Recovery And Climate Experiment (GRACE) mission respectively are used as independent sources of comparison to analyze the altimetry errors. Argo profiling floats are spread out over almost the global open ocean since 2004. However, they measure temperature and salinity vertical profiles, providing only the steric contribution to the total sea level content measured by altimeters. The missing mass contribution is derived from the GRACE data set from 2003 onwards. The comparison is performed with the first objective of detecting global and regional altimeter mean sea level drifts. A second goal is to assess the impact of new altimeter standards (orbit, geophysical corrections, ground processing) and new versions of altimeter merged products such as the 2014 AVISO reprocessing or the Sea Level CCI data set. We also focus our work on sensitivity analyses of the method of comparison to various parameters. In particular, we determine to which extent the altimeter quality assessment is affected by a different pre-processing of altimeter data, a sub sampling of the Argo network and a change of the reference depth used to compute Argo dynamic heights.

  14. Dual GRACE-type Mission Architectures for Temporal Gravity Recovery

    NASA Astrophysics Data System (ADS)

    Wiese, D. N.; Nerem, R.

    2009-12-01

    While the expected end-of-lifetime date for the GRACE mission draws nearer, more attention is being given to the design of a follow-on mission for GRACE. The primary purpose of the follow-on mission should be to continue the time series of global mass flux measurements, with a secondary focus on improving the spatial and/or temporal resolution of the GRACE gravity measurements. Previous studies have explored a variety of ways to increase the spatial and/or temporal resolution of the derived gravity fields, including flying an upgraded instrumentation suite (i.e. replacing the microwave ranging instrument with a laser interferometer, and flying drag-free rather than having an accelerometer onboard to measure non-conservative forces), flying an alternate satellite formation (i.e. cartwheel and pendulum formations), and flying multiple pairs of satellites in collinear formations similar to the current GRACE mission. Simulation studies have shown that when flying the upgraded instrumentation suite, the limiting error source in recovering the gravity field is high frequency variations in the atmosphere and ocean; i.e. temporal aliasing errors. This result suggests that a reduction of temporal aliasing errors should be a top priority in mission design considerations. One way in which temporal aliasing errors can be reduced is by making more frequent measurements of the gravity field, which can be accomplished through using multiple satellite pairs. An in-depth study of finding an optimum configuration of two pairs of satellites in a collinear formation has been performed. All satellites are assumed to carry a laser interferometer and fly drag-free. One pair of satellites is in a repeating polar orbit while the other pair is in a repeating lower inclined orbit (~65 deg inclination). The repeat period of the polar pair is varied between approximately three and eight sidereal days, while the repeat period of the lower inclined pair is varied between approximately ten and

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

    NASA Astrophysics Data System (ADS)

    Liesch, Tanja; Ohmer, Marc

    2016-04-01

    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.

  16. Estimation of the Earth's gravity field by combining normal equation matrices from GRACE and SLR

    NASA Astrophysics Data System (ADS)

    Haberkorn, Christoph; Bloßfeld, Mathis; Bouman, Johannes

    2014-05-01

    Since 2002, GRACE observes the Earth's gravity field with a spatial resolution up to 150 km. The main goal of this mission is the determination of temporal variations in the Earth's gravity field to detect mass displacements. The GRACE mission consists of two identical satellites, which observe the range along the line of sight of both satellites. GRACE observations can be linked with the Earth's gravitational potential, which is expressed in terms of spherical harmonics for global solutions. However, the estimation of low degree coefficients is difficult with GRACE. In contrast to gravity field missions, which observe the gravity field with high spectral resolution, SLR data allow to estimate the lower degree coefficients. Therefore, the coefficient C20 is often replaced by a value derived from Satellite Laser Ranging (SLR). Instead of replacing C20, it can be determined consistently by a combined estimation using GRACE and SLR data. We compute monthly normal equation (NEQ) matrices for GRACE and SLR. Coefficients from monthly GRACE gravity field models of different institutions (Center for Space Research (CSR), USA, Geoforschungszentrum Potsdam (GFZ), Germany and Jet Propulsion Laboratory (JPL), USA) and coefficients from monthly gravity field models of our SLR processing are then combined using the NEQ matrices from both techniques. We will evaluate several test scenarios with gravity field models from different institutions and with different set ups for the SLR NEQ matrices. The effect of the combination on the estimated gravity field will be analysed and presented.

  17. Arctic terrestrial water storage changes from GRACE satellite estimates and a land surface hydrology model

    NASA Astrophysics Data System (ADS)

    Su, F.; Alsdorf, D.; Shumb, C.; Lettenmaier, D.

    2008-12-01

    Continental water storage plays a key role in the global hydrological cycle. Since 2002, the Gravity Recovery and Climate Experiment (GRACE) satellite mission has provided a basis for estimating spatial and temporal variations of terrestrial water storage over areas order of 105 km2. These estimates show strong interseasonal and interannual variations in terrestrial water storage at high latitudes, which are attributable at least in part to the important role of snow water storage on the seasonal water cycle. Evaluation of the accuracy of the GRACE terrestrial water storage is complicated by the absence of direct observations of terrestrial water storage. Land surface hydrology models, forced with observations, provide an opportunity for evaluating GRACE estimates regionally and globally. In this study, the Variable Infiltration Capacity (VIC) land surface hydrology model, which calculates the land surface water and energy balance, is used to evaluate the GRACE over the pan-Arctic region. The VIC model is driven by ECMWF analysis fields, which have been shown to give comparable hydrologic results to gridded observations at high latitudes, and are available in near-real time. The VIC runs cover the GRACE period 2002-2007. The VIC calculated total terrestrial water storage changes over major Arctic river basins are compared with GRACE estimates. Storage components simulated by VIC including snow, soil moisture, lake/wetland storage, and stream storage changes are segregated from the VIC simulations, and the contributions of each of these components to seasonal and interannual variations in GRACE terrestrial water storage are analyzed.

  18. Assimilation of GRACE Terrestrial Water Storage Data into a Land Surface Model

    NASA Technical Reports Server (NTRS)

    Reichle, Rolf H.; Zaitchik, Benjamin F.; Rodell, Matt

    2008-01-01

    The NASA Gravity Recovery and Climate Experiment (GRACE) system of satellites provides observations of large-scale, monthly terrestrial water storage (TWS) changes. In. this presentation we describe a land data assimilation system that ingests GRACE observations and show that the assimilation improves estimates of water storage and fluxes, as evaluated against independent measurements. The ensemble-based land data assimilation system uses a Kalman smoother approach along with the NASA Catchment Land Surface Model (CLSM). We assimilated GRACE-derived TWS anomalies for each of the four major sub-basins of the Mississippi into the Catchment Land Surface Model (CLSM). Compared with the open-loop (no assimilation) CLSM simulation, assimilation estimates of groundwater variability exhibited enhanced skill with respect to measured groundwater. Assimilation also significantly increased the correlation between simulated TWS and gauged river flow for all four sub-basins and for the Mississippi River basin itself. In addition, model performance was evaluated for watersheds smaller than the scale of GRACE observations, in the majority of cases, GRACE assimilation led to increased correlation between TWS estimates and gauged river flow, indicating that data assimilation has considerable potential to downscale GRACE data for hydrological applications. We will also describe how the output from the GRACE land data assimilation system is now being prepared for use in the North American Drought Monitor.

  19. Ninety-day oral toxicity studies on two genetically modified maize MON810 varieties in Wistar Han RCC rats (EU 7th Framework Programme project GRACE).

    PubMed

    Zeljenková, Dagmar; Ambrušová, Katarína; Bartušová, Mária; Kebis, Anton; Kovrižnych, Jevgenij; Krivošíková, Zora; Kuricová, Miroslava; Líšková, Aurélia; Rollerová, Eva; Spustová, Viera; Szabová, Elena; Tulinská, Jana; Wimmerová, Soňa; Levkut, Mikuláš; Révajová, Viera; Ševčíková, Zuzana; Schmidt, Kerstin; Schmidtke, Jörg; La Paz, Jose Luis; Corujo, Maria; Pla, Maria; Kleter, Gijs A; Kok, Esther J; Sharbati, Jutta; Hanisch, Carlos; Einspanier, Ralf; Adel-Patient, Karine; Wal, Jean-Michel; Spök, Armin; Pöting, Annette; Kohl, Christian; Wilhelm, Ralf; Schiemann, Joachim; Steinberg, Pablo

    2014-12-01

    The GMO Risk Assessment and Communication of Evidence (GRACE; www.grace-fp7.eu ) project is funded by the European Commission within the 7th Framework Programme. A key objective of GRACE is to conduct 90-day animal feeding trials, animal studies with an extended time frame as well as analytical, in vitro and in silico studies on genetically modified (GM) maize in order to comparatively evaluate their use in GM plant risk assessment. In the present study, the results of two 90-day feeding trials with two different GM maize MON810 varieties, their near-isogenic non-GM varieties and four additional conventional maize varieties are presented. The feeding trials were performed by taking into account the guidance for such studies published by the EFSA Scientific Committee in 2011 and the OECD Test Guideline 408. The results obtained show that the MON810 maize at a level of up to 33 % in the diet did not induce adverse effects in male and female Wistar Han RCC rats after subchronic exposure, independently of the two different genetic backgrounds of the event. PMID:25270621

  20. Tone-assisted time delay interferometry on GRACE Follow-On

    NASA Astrophysics Data System (ADS)

    Francis, Samuel P.; Shaddock, Daniel A.; Sutton, Andrew J.; de Vine, Glenn; Ware, Brent; Spero, Robert E.; Klipstein, William M.; McKenzie, Kirk

    2015-07-01

    We have demonstrated the viability of using the Laser Ranging Interferometer on the Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) space mission to test key aspects of the interspacecraft interferometry proposed for detecting gravitational waves. The Laser Ranging Interferometer on GRACE-FO will be the first demonstration of interspacecraft interferometry. GRACE-FO shares many similarities with proposed space-based gravitational wave detectors based on the Laser Interferometer Space Antenna (LISA) concept. Given these similarities, GRACE-FO provides a unique opportunity to test novel interspacecraft interferometry techniques that a LISA-like mission will use. The LISA Experience from GRACE-FO Optical Payload (LEGOP) is a project developing tests of arm locking and time delay interferometry (TDI), two frequency stabilization techniques, that could be performed on GRACE-FO. In the proposed LEGOP TDI demonstration one GRACE-FO spacecraft will have a free-running laser while the laser on the other spacecraft will be locked to a cavity. It is proposed that two one-way interspacecraft phase measurements will be combined with an appropriate delay in order to produce a round-trip, dual one-way ranging (DOWR) measurement independent of the frequency noise of the free-running laser. This paper describes simulated and experimental tests of a tone-assisted TDI ranging (TDIR) technique that uses a least-squares fitting algorithm and fractional-delay interpolation to find and implement the delays needed to form the DOWR TDI combination. The simulation verifies tone-assisted TDIR works under GRACE-FO conditions. Using simulated GRACE-FO signals the tone-assisted TDIR algorithm estimates the time-varying interspacecraft range with a rms error of ±0.2 m , suppressing the free-running laser frequency noise by 8 orders of magnitude. The experimental results demonstrate the practicability of the technique, measuring the delay at the 6 ns level in the presence of a

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

    NASA Astrophysics Data System (ADS)

    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.

  2. Evolution and characterization of drought events from GRACE and other satellite and observation.

    NASA Astrophysics Data System (ADS)

    Zhao, M.; A, G.; Velicogna, I.; Kimball, J. S.

    2015-12-01

    We use GRACE Terrestrial Water Storage (TWS) changes to calculate a newly developed global drought severity index (GRACE-DSI) for monthly monitoring of water supply changes during 2002-2015. We compare GRACE-DSI with Palmer Drought Severity Index (PDSI) and other ancillary data to characterize drought timing, evolution and magnitude in the continental US since 2002. Overall GRACE-DSI and PDSI show an excellent correspondence in the US. However PDSI is very sensitive to atmospheric moisture stress, while GRACE-DSI only responds to changes in terrestrial water storage. We use the complementary nature of these two indices together with temperature and precipitation observations to characterize drought evolution and its nature. For instance, during the 2012 flash drought in the Great Plains, the PDSI decreases several months earlier than the GRACE-DSI in response to the enhanced atmosphere moisture demand caused by unusual early season warming. When the drought peaks later in the summer, the PDSI indicates exceptional drought, while the GRACE-DSI observes moderate drought conditions in the underlying total water supply, implying a meteorological drought in nature. GRACE-DSI is based solely on satellite observations; hence it has the advantage of not being affected by uncertainty associated with variable that are not well known at the global scale (e.g. precipitation estimates) and by biases associated to global climate model outputs. We find that GRACE-DSI captures major drought events in the globe occurring during 2002-2015, including those in sub-Sahara Africa, Australia, Amazon, Asia, North America and the Arctic.

  3. Crustal dilatation observed by GRACE after the 2004 Sumatra-Andaman earthquake.

    PubMed

    Han, Shin-Chan; Shum, C K; Bevis, Michael; Ji, Chen; Kuo, Chung-Yen

    2006-08-01

    We report the detection of an earthquake by a space-based measurement. The Gravity Recovery and Climate Experiment (GRACE) satellites observed a +/-15-microgalileo gravity change induced by the great December 2004 Sumatra-Andaman earthquake. Coseismic deformation produces sudden changes in the gravity field by vertical displacement of Earth's layered density structure and by changing the densities of the crust and mantle. GRACE's sensitivity to the long spatial wavelength of gravity changes resulted in roughly equal contributions of vertical displacement and dilatation effects in the gravity measurements. The GRACE observations provide evidence of crustal dilatation resulting from an undersea earthquake. PMID:16888136

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

    NASA Astrophysics Data System (ADS)

    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

  5. Current Status of the GRACE Follow-On Mission

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  7. GRACE measurements of mass variability in the Earth system.

    PubMed

    Tapley, Byron D; Bettadpur, Srinivas; Ries, John C; Thompson, Paul F; Watkins, Michael M

    2004-07-23

    Monthly gravity field estimates made by the twin Gravity Recovery and Climate Experiment (GRACE) satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers. The annual cycle in the geoid variations, up to 10 millimeters in some regions, peaked predominantly in the spring and fall seasons. Geoid variations observed over South America that can be largely attributed to surface water and groundwater changes show a clear separation between the large Amazon watershed and the smaller watersheds to the north. Such observations will help hydrologists to connect processes at traditional length scales (tens of kilometers or less) to those at regional and global scales. PMID:15273390

  8. Calibrating SWAT with River flows, Groundwater table, and GRACE

    NASA Astrophysics Data System (ADS)

    Qiao, L.

    2010-12-01

    Various combinations of model parameters can provide equal simulations for certain water component (like river discharge) due to compensating interactions among parameters in most hydrologic models. SWAT (Soil and Water Assessment Tool) physically simulates the movements and distributions for water, sediments and nutrients with widely varied parameters usually encountering this kind of problem. Previous SWAT applications mostly limited model calibrations on surface runoff (sometime including nutrients and sediments) and lose overall control to the whole hydrologic process consisting of ET, Surface runoff, soil water, and ground water variations. This study constrains the SWAT model in lower Missouri River Basin with surface water recharge and discharge (river flows), basin-wide water storage (Gravity Recovery and Climate Experiment (GRACE)), Groundwater table fluctuations(well logs) under a SUFI (sequential uncertainty fitting) framework. This would reduce the parameter uncertainty and provide reliable model for hydrologic studies within the basin.

  9. Pearl Kendrick, Grace Eldering, and the Pertussis Vaccine

    PubMed Central

    2010-01-01

    In light of the reemergence of pertussis (whooping cough), the pioneering research of Pearl Kendrick and Grace Eldering is worth revisiting. In the 1930s, working in the Michigan Department of Health laboratory in Grand Rapids, Michigan, USA, they began researching a pertussis vaccine. Their research offers an instructive case study of the creative public health research performed in state health department laboratories during the interwar years. State department of health laboratory directors actively promoted research by supporting advanced education; making facilities and funding available for individual projects; and, when possible, procuring new facilities. Using Michigan Department of Health resources and local and federal funding, Kendrick and Eldering developed standardized diagnostic tools; modified and improved extant vaccines; conducted the first successful, large-scale, controlled clinical trial of pertussis vaccine; and participated in international efforts to standardize and disseminate the vaccine. Their model may again offer a promising avenue for groundbreaking research. PMID:20678322

  10. Towards Improved Snow Water Equivalent Estimation via GRACE Assimilation

    NASA Technical Reports Server (NTRS)

    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.

  11. Analyses of altimetry errors using Argo and GRACE data

    NASA Astrophysics Data System (ADS)

    Legeais, Jean-François; Prandi, Pierre; Guinehut, Stéphanie

    2016-05-01

    This study presents the evaluation of the performances of satellite altimeter missions by comparing the altimeter sea surface heights with in situ dynamic heights derived from vertical temperature and salinity profiles measured by Argo floats. The two objectives of this approach are the detection of altimeter drift and the estimation of the impact of new altimeter standards that requires an independent reference. This external assessment method contributes to altimeter calibration-validation analyses that cover a wide range of activities. Among them, several examples are given to illustrate the usefulness of this approach, separating the analyses of the long-term evolution of the mean sea level and its variability, at global and regional scales and results obtained via relative and absolute comparisons. The latter requires the use of the ocean mass contribution to the sea level derived from Gravity Recovery and Climate Experiment (GRACE) measurements. Our analyses cover the estimation of the global mean sea level trend, the validation of multi-missions altimeter products as well as the assessment of orbit solutions.Even if this approach contributes to the altimeter quality assessment, the differences between two versions of altimeter standards are getting smaller and smaller and it is thus more difficult to detect their impact. It is therefore essential to characterize the errors of the method, which is illustrated with the results of sensitivity analyses to different parameters. This includes the format of the altimeter data, the method of collocation, the temporal reference period and the processing of the ocean mass solutions from GRACE. We also assess the impact of the temporal and spatial sampling of Argo floats, the choice of the reference depth of the in situ profiles and the importance of the deep steric contribution. These analyses provide an estimation of the robustness of the method and the characterization of associated errors. The results also allow us

  12. Relative time and frequency alignment between two low Earth orbiters, GRACE

    NASA Technical Reports Server (NTRS)

    Bertiger, W.; Dunn, C.; Harris, I.; Kruizinga, G.; Romans, L.; Watkins, M.; Wu, S.

    2003-01-01

    The two GRACE (Gravity Recovery and Climate Experiment) spacecraft were launched into a near polar circular orbit around the earth in March of 2002. The two spacecraft serve as test masses to measure the Earth's gravitational field.

  13. RCRA Facility Investigation/Remedial Investigation Report for the Grace Road Site (631-22G)

    SciTech Connect

    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.

  14. Measuring Earth: Current status of the GRACE Follow-On Laser Ranging Interferometer

    NASA Astrophysics Data System (ADS)

    Schütze, Daniel; LRI team

    2016-05-01

    The GRACE mission that was launched in 2002 has impressively proven the feasibility of low-orbit satellite-to-satellite tracking for Earth gravity observations. Especially mass transport related to Earth's hydrological system could be well resolved both spatially and temporally. This allows to study processes such as polar ice sheet decline and ground water depletion in great detail. Owing to GRACE's success, NASA and GFZ will launch the successor mission GRACE Follow-On in 2017. In addition to the microwave ranging system, GRACE Follow-On will be the first mission to use a Laser Ranging Interferometer as technology demonstrator to track intersatellite distance changes with unprecedented precision. This new ranging device inherits some of the technologies which have been developed for the future spaceborne gravitational wave detector LISA. I will present the architecture of the Laser Ranging Interferometer, point out similarities and differences to LISA, and conclude with the current status of the flight hardware production.

  15. Integrating Data from GRACE and Other Observing Systems for Hydrological Research and Applications

    NASA Technical Reports Server (NTRS)

    Rodell, M.; Famiglietti, J. S.; McWilliams, E.; Beaudoing, H. K.; Li, B.; Zaitchik, B.; Reichle, R.; Bolten, J.

    2011-01-01

    The Gravity Recovery and Climate Experiment (GRACE) mission provides a unique view of water cycle dynamics, enabling the only space based observations of water on and beneath the land surface that are not limited by depth. GRACE data are immediately useful for large scale applications such as ice sheet ablation monitoring, but they are even more valuable when combined with other types of observations, either directly or within a data assimilation system. Here we describe recent results of hydrological research and applications projects enabled by GRACE. These include the following: 1) global monitoring of interannual variability of terrestrial water storage and groundwater; 2) water balance estimates of evapotranspiration over several large river basins; 3) NASA's Energy and Water Cycle Study (NEWS) state of the global water budget project; 4) drought indicator products now being incorporated into the U.S. Drought Monitor; 5) GRACE data assimilation over several regions.

  16. Hydrological Variations in Australia Recovered by GRACE High-Resolution Mascons Solutions

    NASA Technical Reports Server (NTRS)

    Carabajal, Claudia C.; Boy, Jean-Paul; Sabaka, Terence J.; Lemoine, Frank G.; Rowlands. David; Luthcke, Scott B.; Brown, M. Y.

    2011-01-01

    Australia represents a challenging region in which to study hydrological variations as recovered by the GRACE (Gravity Recovery And Climate Experiment) mission data. Much of Australia is characterized by relatively small hydrological signals, with large precipitation gradients between the North and the South. These signals are better recovered using innovative GRACE processing techniques such as high-resolution mascon solutions, which may help overcome the deficiencies in the standard GRACE data processing and filtering methods. We will show the power of using regional and global mas con solutions to recover hydrological variations from 2003 to 2011, as well as the oceanic mass variations in the surrounding regions. We will compare the GRACE signals with state of the art hydrology and ocean general circulation models, precipitation, soil moisture and groundwater data sets. We especially emphasize the gravity signatures observed during the decadal drought in the Murray-Darling river basin and the early 2011 floods in North-Western Australia.

  17. SITE TECHNOLOGY CAPSULE: GRACE DEARBORN INC.'S DARAMEND BIOREMEDIATION TECHNOLOGY

    EPA Science Inventory

    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...

  18. Prognostic Value of TIMI Score versus GRACE Score in ST-segment Elevation Myocardial Infarction

    PubMed Central

    Correia, Luis C. L.; Garcia, Guilherme; Kalil, Felipe; Ferreira, Felipe; Carvalhal, Manuela; Oliveira, Ruan; Silva, André; Vasconcelos, Isis; Henri, Caio; Noya-Rabelo, Márcia

    2014-01-01

    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. PMID:25029471

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

    NASA Astrophysics Data System (ADS)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. Bridging a possible gap of GRACE observations in the Arctic Ocean using existing GRACE data and in situ bottom pressure sensors

    NASA Astrophysics Data System (ADS)

    Peralta Ferriz, C.; Morison, J.

    2014-12-01

    Since 2003, the Gravity Recovery and Climate Experiment (GRACE) satellite system has provided the means of investigating month-to-month to inter-annual variability of, among many other things, Arctic Ocean circulation over the entire Arctic Basin. Such a comprehensive picture could not have been achieved with the limited in situ pressure observations available. Results from the first 10 years of ocean bottom pressure measurements from GRACE in the Arctic Ocean reveal distinct patterns of ocean variability that are strongly associated with changes in large-scale atmospheric circulation (Peralta-Ferriz et al., 2014): the leading mode of variability being a wintertime basin-coherent mass change driven by winds in the Nordic Seas; the second mode of variability corresponding to a mass signal coherent along the Siberian shelves, and driven by the Arctic Oscillation; and the third mode being a see-saw between western and eastern Arctic shelves, also driven by the large-scale wind patterns. In order to understand Arctic Ocean changes, it is fundamental to continue to track ocean bottom pressure. Our concern is what to do if the present GRACE system, which is already well beyond its design lifetime, should fail before its follow-on is launched, currently estimated to be in 2017. In this work, we regress time series of pressure from the existing and potential Arctic Ocean bottom pressure recorder locations against the fundamental modes of bottom pressure variation. Our aim is to determine the optimum combination of in situ measurements to represent the broader scale variability now observed by GRACE. With this understanding, we can be better prepared to use in situ observations to at least partially cover a possible gap in GRACE coverage. Reference:Peralta-Ferriz, Cecilia, James H. Morison, John M. Wallace, Jennifer A. Bonin, Jinlun Zhang, 2014: Arctic Ocean Circulation Patterns Revealed by GRACE. J. Climate, 27, 1445-1468. doi: http://dx.doi.org/10.1175/JCLI-D-13-00013.1

  2. Analysis of a GRACE global mascon solution for Gulf of Alaska glaciers

    USGS Publications Warehouse

    Arendt, Anthony; Luthcke, Scott; Gardner, Alex; O'Neel, Shad; Hill, David; Moholdt, Geir; Abdalati, Waleed

    2013-01-01

    We present a high-resolution Gravity Recovery and Climate Experiment (GRACE) mascon solution for Gulf of Alaska (GOA) glaciers and compare this with in situ glaciological, climate and other remote-sensing observations. Our GRACE solution yields a GOA glacier mass balance of –65 ± 11 Gt a–1 for the period December 2003 to December 2010, with summer balances driving the interannual variability. Between October/November 2003 and October 2009 we obtain a mass balance of –61 ± 11 Gt a–1 from GRACE, which compares well with –65 ± 12 Gt a–1 from ICESat based on hypsometric extrapolation of glacier elevation changes. We find that mean summer (June–August) air temperatures derived from both ground and lower-troposphere temperature records were good predictors of GRACE-derived summer mass balances, capturing 59% and 72% of the summer balance variability respectively. Large mass losses during 2009 were likely due to low early melt season surface albedos, measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) and likely associated with the 31 March 2009 eruption of Mount Redoubt, southwestern Alaska. GRACE data compared well with in situ measurements at Wolverine Glacier (maritime Alaska), but poorly with those at Gulkana Glacier (interior Alaska). We conclude that, although GOA mass estimates from GRACE are robust over the entire domain, further constraints on subregional and seasonal estimates are necessary to improve fidelity to ground observations.

  3. Analysis of a GRACE Global Mascon Solution for Gulf of Alaska Glaciers

    NASA Technical Reports Server (NTRS)

    Arendt, Anthony; Luthcke, Scott B.; Gardner, Alex; O'Neel, Shad; Hill, David; Moholdt, Geir; Abdalati, Waleed

    2013-01-01

    We present a high-resolution Gravity Recovery and Climate Experiment (GRACE) mascon solution for Gulf of Alaska (GOA) glaciers and compare this with in situ glaciological, climate and other remote-sensing observations. Our GRACE solution yields a GOA glacier mass balance of -6511 Gt a(exp.-1) for the period December 2003 to December 2010, with summer balances driving the interannual variability. Between October/November 2003 and October 2009 we obtain a mass balance of -6111 Gt a(exp. -1) from GRACE, which compares well with -6512 Gt a(exp. -1) from ICESat based on hypsometric extrapolation of glacier elevation changes. We find that mean summer (June-August) air temperatures derived from both ground and lower-troposphere temperature records were good predictors of GRACE-derived summer mass balances, capturing 59% and 72% of the summer balance variability respectively. Large mass losses during 2009 were likely due to low early melt season surface albedos, measured by the Moderate Resolution Imaging Spectroradiometer (MODIS) and likely associated with the 31 March 2009 eruption of Mount Redoubt, southwestern Alaska. GRACE data compared well with in situ measurements atWolverine Glacier (maritime Alaska), but poorly with those at Gulkana Glacier (interior Alaska). We conclude that, although GOA mass estimates from GRACE are robust over the entire domain, further constraints on subregional and seasonal estimates are necessary to improve fidelity to ground observations.

  4. The Value of Information from a GRACE-Enhanced Drought Severity Index

    NASA Astrophysics Data System (ADS)

    Kuwayama, Y.; Bernknopf, R.; Brookshire, D.; Macauley, M.; Zaitchik, B. F.; Rodell, M.; Vail, P.; Thompson, A.

    2015-12-01

    In this project, we develop a framework to estimate the economic value of information from the Gravity and Climate Experiment (GRACE) for drought monitoring and to understand how the GRACE Data Assimilation (GRACE-DA) system can inform decision making to improve regional economic outcomes. Specifically, we consider the potential societal value of further incorporating GRACE-DA information into the U.S. Drought Monitor mapmaking process. Research activities include (a) a literature review, (b) a series of listening sessions with experts and stakeholders, (c) the development of a conceptual economic framework based on a Bayesian updating procedure, and (d) an econometric analysis and retrospective case study to understand the GRACE-DA contribution to agricultural policy and production decisions. Taken together, the results from these research activities support our conclusion that GRACE-DA has the potential to lower the variance associated with our understanding of drought and that this improved understanding has the potential to change policy decisions that lead to tangible societal benefits.

  5. Regional GRACE-based estimates of water mass variations over Australia: validation and interpretation

    NASA Astrophysics Data System (ADS)

    Seoane, L.; Ramillien, G.; Frappart, F.; Leblanc, M.

    2013-04-01

    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).

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Apparent acceleration in 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 (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/yr2, which is large relative to prior GRACE estimates of Antarctic ice mass acceleration in the range of -12 to -14 Gt/yr2. 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/yr2). 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.

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

    NASA Astrophysics Data System (ADS)

    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

  8. Time Periods of Unusual Density Behavior Observed by GRACE and CHAMP

    NASA Astrophysics Data System (ADS)

    McLaughlin, C. A.; Fattig, E.; Mysore Krishna, D.; Locke, T.; Mehta, P. M.

    2011-12-01

    Time periods of low cross correlation between precision orbit ephemeris (POE) derived density and accelerometer density for CHAMP and GRACE are examined. In particular, the cross correlation for GRACE dropped from typical values near 0.9 to much lower values and then returned to typical over the time period of late October to late December of 2005. This time period includes a maneuver where GRACE-A and GRACE-B swapped positions. However, the drop in cross correlation begins and reaches its low point before the maneuvers begin. In addition, the densities were found using GRACE-A, but GRACE-B did most of the maneuvering. The time period is characterized by high frequency variations in accelerometer density of the same magnitude as the daylight to eclipse variations over the course of an orbit. However, the daylight to eclipse variations are particularly small during this time period because the orbit plane is near the terminator. Additionally, the difference between the accelerometer and POE derived densities are not unusually large during this time period. This implies the variations are not unusual, just more significant when the orbit plane is near terminator. Cyclical variations in correlation of the POE derived densities with accelerometer derived densities are seen for both GRACE and CHAMP, but the magnitude of the variations are much larger for GRACE, possibly because of the higher altitude of GRACE. The cycles seem to be phased so that low correlations occur with low beta angle when the orbit plane is near the terminator. The low correlation is possibly caused by the lower amplitude of the daylight to eclipse signal making higher frequency variations relatively more important. However, another possible explanation is terminator waves in density that propagate to the thermosphere from lower in the atmosphere. These waves have been observed in CHAMP accelerometer data and global circulation model simulations. Further investigation is needed to see if the

  9. Anthropogenic Impact on the Non-closure of GRACE-based Water Budget in Hai River Basin, China

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Zhang, C.; Yeh, P. J. F.; Gong, H.; Wang, X.

    2015-12-01

    The budget non-closure is commonly found in GRACE-based water budget (GRACE-WB) and usually explained as measurement errors. Since GRACE has a unique ability to detect the change of water storage both due to natural and anthropogenic factors, the non-closure needs to be investigated from not only measurement errors but also anthropogenic effects. The Hai River Basin (HRB) is selected as the study area to explore the relationship between the GRACE-WB non-closure and human modifications to water, including groundwater consumption and water diversion, with a considering of the outstanding feature of GRACE. The in situ measured precipitaion (P) and net runoff (R), together with evapotranspiration (E) from GLDAS land surface models (LSMs), are used to calculate the budget error between terrestrial water storage change (ΔTWS) derived from GRACE and P-E-R. It is found that the budget errors are comparable to bulletin reported water consumption and human modifications to water (groundwater use + water diversion), at annual and inter-annual scale, respectively. It is concluded that the GRACE-WB non-closure in HRB is dominated by the difference between LSM-simulated and GRACE-monitored water storage change resulted from anthropogenic use of water, which is usually not included in most LSMs but still seen by GRACE.

  10. Inter-annual precipitation changes as quadratic signals in the GRACE time-variable gravity

    NASA Astrophysics Data System (ADS)

    Ogawa, R.; Chao, B. F.; Heki, K.

    2009-04-01

    The Gravity Recovery and Climate Experiment (GRACE) satellite mission has been producing scientific results on mass variations on inter-annual timescales, e.g. melting of ice sheet in Greenland and mountain glaciers in Alaska, Eastern Africa drought, water level increase in Caspian Sea, etc. In these discussions only linear trends and the seasonal components have been analyzed in the monthly GRACE time series, whereas little attention has been paid so far to the existence of the quadratic changes which signify the temporal accelerations. With over 6 years of GRACE data and revisiting the time-variable gravity field of various regions, we find that such acceleration/deceleration terms are quite often significantly different from zero. They include East Africa, near Obi River, Caspian Sea, Black Sea, Central Asia, and southern South America, whereof discussions of linear trends without specifying the epochs are inadequate. Here we investigate geophysical implication of these quadratic terms; in particular gravity changes in land areas reflect, to a large extent, soil moisture variations. Soil moisture is the time integration of water fluxes, i.e. precipitation, evapotranspiration and runoff. Here we consider that the linear trend in precipitation is responsible for the quadratic change in gravity, and examine trends of observed precipitation in various regions from CMAP (Climate Prediction Center Merged Analysis of Precipitation). Thus, in order to compare linear trend in CMAP and acceleration in GRACE, we calculate month-to-month difference of equivalent water depth at GRACE grid points, and modeled them with seasonal variations and linear trends. We found good agreement between their geographical distributions although amplitudes are smaller in GRACE, meaning the quadratic gravity changes in the GRACE data do reflect inter-annual changes of precipitation fairly faithfully.

  11. A systematic impact assessment of GRACE error correlation on data assimilation in hydrological models

    NASA Astrophysics Data System (ADS)

    Schumacher, Maike; Kusche, Jürgen; Döll, Petra

    2016-02-01

    Recently, ensemble Kalman filters (EnKF) have found increasing application for merging hydrological models with total water storage anomaly (TWSA) fields from the Gravity Recovery And Climate Experiment (GRACE) satellite mission. Previous studies have disregarded the effect of spatially correlated errors of GRACE TWSA products in their investigations. Here, for the first time, we systematically assess the impact of the GRACE error correlation structure on EnKF data assimilation into a hydrological model, i.e. on estimated compartmental and total water storages and model parameter values. Our investigations include (1) assimilating gridded GRACE-derived TWSA into the WaterGAP Global Hydrology Model and, simultaneously, calibrating its parameters; (2) introducing GRACE observations on different spatial scales; (3) modelling observation errors as either spatially white or correlated in the assimilation procedure, and (4) replacing the standard EnKF algorithm by the square root analysis scheme or, alternatively, the singular evolutive interpolated Kalman filter. Results of a synthetic experiment designed for the Mississippi River Basin indicate that the hydrological parameters are sensitive to TWSA assimilation if spatial resolution of the observation data is sufficiently high. We find a significant influence of spatial error correlation on the adjusted water states and model parameters for all implemented filter variants, in particular for subbasins with a large discrepancy between observed and initially simulated TWSA and for north-south elongated sub-basins. Considering these correlated errors, however, does not generally improve results: while some metrics indicate that it is helpful to consider the full GRACE error covariance matrix, it appears to have an adverse effect on others. We conclude that considering the characteristics of GRACE error correlation is at least as important as the selection of the spatial discretisation of TWSA observations, while the choice

  12. Application of GRACE Data for Quantifying Mesoscale Groundwater Stress - Urucuia Aquifer System, Northeastern Brazil

    NASA Astrophysics Data System (ADS)

    Stollberg, R.; Gonçalves, R. D.; Weiss, H.; Chang, H. K.

    2015-12-01

    The Gravity Recovery and Climate Experiment (GRACE) mission provides a couple of applications in hydrology research such as total water storage (TWS) changes monitoring, quantitative water cycle components estimation, drought monitoring and hydrological modelling. Limited spatial resolutions of gravity measurements and noise contamination can cause errors and uncertainty of the study objective. Therefore, several GRACE studies recommend application of GRACE data retrievals to areas of interests only larger 200,000 km². The Urucuia Aquifer System (UAS) represents a major strategic water resource for Brazil. UAS is located in the drought-stricken northeast of Brazil and its discharge covers about 30% of the São Francisco River water (4th largest river in South America). Hydrological monitoring of the UAS is of increased importance to guarantee future river water supply and related ecosystem services for the territories crossed. A pre-processed GRACE three-model-ensemble was used to account for TWS changes and a negative balance was revealed for the UAS territory indicating potential water stress. Individual water cycle components needed to be excluded from the total GRACE signal using supplemental data sets to characterize the remaining storage term equivalent to 'water stress'. Comprehensive hydrological ground measurements of precipitation, river discharge, hydraulic heads plus further climate remote-sensing data sources were taken into account trying to distinguish natural from anthropogenic groundwater stress. Consideration of climate data from global hydrological models showed an insufficient accuracy which is related to spatial scaling issues whereas the inclusion of available ground data could increase the overall significance of the GRACE signal for this study. GRACE-based TWS retrievals were applied successfully in combination with comprehensive hydrological monitoring data to quantify potential groundwater storage changes of the 120,000 km² large UAS.

  13. Stochastic filtering for determining gravity variations for decade-long time series of GRACE gravity

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Davis, James L.; Hill, Emma M.; Tamisiea, Mark E.

    2016-04-01

    We present a new stochastic filter technique for statistically rigorous separation of gravity signals and correlated "stripe" noises in a series of monthly gravitational spherical harmonic coefficients (SHCs) produced by the Gravity Recovery and Climate Experiment (GRACE) satellite mission. Unlike the standard destriping process that removes the stripe contamination empirically, the stochastic approach simultaneously estimates gravity signals and correlated noises relying on covariance information that reflects both the spatial spectral features and temporal correlations among them. A major benefit of the technique is that by estimating the stripe noise in a Bayesian framework, we are able to propagate statistically rigorous covariances for the destriped GRACE SHCs, i.e. incorporating the impact of the destriping on the SHC uncertainties. The Bayesian approach yields a natural resolution for the gravity signal that reflects the correlated stripe noise, and thus achieve a kind of spatial smoothing in and of itself. No spatial Gaussian smoothing is formally required although it might be useful for some circumstances. Using the stochastic filter, we process a decade-length series of GRACE monthly gravity solutions, and compare the results with GRACE Tellus data products that are processed using the "standard" destriping procedure. The results show that the stochastic filter is able to remove the correlated stripe noise to a remarkable degree even without an explicit smoothing step. The estimates from the stochastic filter for each destriped GRACE field are suitable for Bayesian integration of GRACE with other geodetic measurements and models, and the statistically rigorous estimation of the time-varying rates and seasonal cycles in GRACE time series.

  14. A systematic impact assessment of GRACE error correlation on data assimilation in hydrological models

    NASA Astrophysics Data System (ADS)

    Schumacher, Maike; Kusche, Jürgen; Döll, Petra

    2016-06-01

    Recently, ensemble Kalman filters (EnKF) have found increasing application for merging hydrological models with total water storage anomaly (TWSA) fields from the Gravity Recovery And Climate Experiment (GRACE) satellite mission. Previous studies have disregarded the effect of spatially correlated errors of GRACE TWSA products in their investigations. Here, for the first time, we systematically assess the impact of the GRACE error correlation structure on EnKF data assimilation into a hydrological model, i.e. on estimated compartmental and total water storages and model parameter values. Our investigations include (1) assimilating gridded GRACE-derived TWSA into the WaterGAP Global Hydrology Model and, simultaneously, calibrating its parameters; (2) introducing GRACE observations on different spatial scales; (3) modelling observation errors as either spatially white or correlated in the assimilation procedure, and (4) replacing the standard EnKF algorithm by the square root analysis scheme or, alternatively, the singular evolutive interpolated Kalman filter. Results of a synthetic experiment designed for the Mississippi River Basin indicate that the hydrological parameters are sensitive to TWSA assimilation if spatial resolution of the observation data is sufficiently high. We find a significant influence of spatial error correlation on the adjusted water states and model parameters for all implemented filter variants, in particular for subbasins with a large discrepancy between observed and initially simulated TWSA and for north-south elongated sub-basins. Considering these correlated errors, however, does not generally improve results: while some metrics indicate that it is helpful to consider the full GRACE error covariance matrix, it appears to have an adverse effect on others. We conclude that considering the characteristics of GRACE error correlation is at least as important as the selection of the spatial discretisation of TWSA observations, while the choice

  15. Mapping groundwater storage variations with GRACE: a case study in Alberta, Canada

    NASA Astrophysics Data System (ADS)

    Huang, Jianliang; Pavlic, Goran; Rivera, Alfonso; Palombi, Dan; Smerdon, Brian

    2016-05-01

    The applicability of the Gravity Recovery and Climate Experiment (GRACE) to adequately represent broad-scale patterns of groundwater storage (GWS) variations and observed trends in groundwater-monitoring well levels (GWWL) is examined in the Canadian province of Alberta. GWS variations are derived over Alberta for the period 2002-2014 using the Release 05 (RL05) monthly GRACE gravity models and the Global Land Data Assimilation System (GLDAS) land-surface models. Twelve mean monthly GWS variation maps are generated from the 139 monthly GWS variation grids to characterize the annual GWS variation pattern. These maps show that, overall, GWS increases from February to June, and decreases from July to October, and slightly increases from November to December. For 2002-2014, the GWS showed a positive trend which increases from west to east with a mean value of 12 mm/year over the province. The resulting GWS variations are validated using GWWLs in the province. For the purpose of validation, a GRACE total water storage (TWS)-based correlation criterion is introduced to identify groundwater wells which adequately represent the regional GWS variations. GWWLs at 36 wells were found to correlate with both the GRACE TWS and GWS variations. A factor f is defined to up-scale the GWWL variations at the identified wells to the GRACE-scale GWS variations. It is concluded that the GWS variations can be mapped by GRACE and the GLDAS models in some situations, thus demonstrating the conditions where GWS variations can be detected by GRACE in Alberta.

  16. Ice loading model for Glacial Isostatic Adjustment in the Barents Sea constrained by GRACE gravity observations

    NASA Astrophysics Data System (ADS)

    Root, Bart; Tarasov, Lev; van der Wal, Wouter

    2014-05-01

    The global ice budget is still under discussion because the observed 120-130 m eustatic sea level equivalent since the Last Glacial Maximum (LGM) can not be explained by the current knowledge of land-ice melt after the LGM. One possible location for the missing ice is the Barents Sea Region, which was completely covered with ice during the LGM. This is deduced from relative sea level observations on Svalbard, Novaya Zemlya and the North coast of Scandinavia. However, there are no observations in the middle of the Barents Sea that capture the post-glacial uplift. With increased precision and longer time series of monthly gravity observations of the GRACE satellite mission it is possible to constrain Glacial Isostatic Adjustment in the center of the Barents Sea. This study investigates the extra constraint provided by GRACE data for modeling the past ice geometry in the Barents Sea. We use CSR release 5 data from February 2003 to July 2013. The GRACE data is corrected for the past 10 years of secular decline of glacier ice on Svalbard, Novaya Zemlya and Frans Joseph Land. With numerical GIA models for a radially symmetric Earth, we model the expected gravity changes and compare these with the GRACE observations after smoothing with a 250 km Gaussian filter. The comparisons show that for the viscosity profile VM5a, ICE-5G has too strong a gravity signal compared to GRACE. The regional calibrated ice sheet model (GLAC) of Tarasov appears to fit the amplitude of the GRACE signal. However, the GRACE data are very sensitive to the ice-melt correction, especially for Novaya Zemlya. Furthermore, the ice mass should be more concentrated to the middle of the Barents Sea. Alternative viscosity models confirm these conclusions.

  17. GRACE data assimilation into WGHM: Validation of updated water states and fluxes in the Mississippi Basin

    NASA Astrophysics Data System (ADS)

    Schumacher, Maike; Müller Schmied, Hannes; Kusche, Jürgen; Döll, Petra; Rodell, Matthew; van Dijk, Albert

    2015-04-01

    The Gravity Recovery And Climate Experiment (GRACE) satellite mission provides the unique opportunity of observing the water storage changes including soil, surface and groundwater with global coverage. However, the relatively coarse spatial (few 100 km) and temporal resolution (monthly) and the necessary disaggregation of total water storage anomalies (TWSA) into individual water storage compartments provide challenges for hydrological studies. The GRACE-derived TWSA fields are increasingly used for data assimilation into hydrological models for model improvement and downscaling of GRACE data. Recently, Eicker et al. (2014) proposed a new ensemble Kalman filter (EnKF) method that integrates gridded TWSA fields into the WaterGAP Global Hydrology Model (WGHM) and simultaneously calibrates its parameters. Application to the Mississippi River Basin showed promising results when comparing post-assimilation model-predicted TWSA to GRACE observations. Here, we carry out an extensive validation of the reported assimilation results with independent data sets. The focus is on individual water compartments, such as snow, soil, surface water and groundwater, and fluxes, like river discharge. The validation data includes in-situ data (e.g. groundwater well observations, river discharge) and remote sensing data (altimetry). In addition, we compare to GRACE and to snow, lake, river and sub-surface estimates from the Global Water Cycle Re-analysis product, independently derived through GRACE assimilation into a multi-model ensemble. The results demonstrate that the established calibration and data assimilation framework enables an improved fit of modeled TWSA with observations. Moreover, we show to what extent estimates of individual water compartments and fluxes improve. Eicker, A., Schumacher, M., Kusche, J., Döll, P., Müller Schmied, H. (2014): Calibration/Data Assimilation Approach for Integrating GRACE Data into the WaterGAP Global Hydrology Model (WGHM) Using an Ensemble

  18. 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.

    NASA Astrophysics Data System (ADS)

    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.

  19. Loop corrections and graceful exit in string cosmology

    NASA Astrophysics Data System (ADS)

    Foffa, Stefano; Maggiore, Michele; Sturani, Riccardo

    1999-07-01

    We examine the effect of perturbative string loops on the cosmological pre-big-bang evolution. We study loop corrections derived from heterotic string theory compactified on a ZN orbifold and we consider the effect of the all-order loop corrections to the Kähler potential and of the corrections to gravitational couplings, including both threshold corrections and corrections due to the mixed Kähler-gravitational anomaly. We find that string loops can drive the evolution into the region of the parameter space where a graceful exit is in principle possible, and we find solutions that, in the string frame, connect smoothly the superinflationary pre-big-bang evolution to a phase where the curvature and the derivative of the dilaton are decreasing. We also find that at a critical coupling the loop corrections to the Kähler potential induce a ghost-like instability, i.e. the kinetic term of the dilaton vanishes. This is similar to what happens in Seiberg-Witten theory and signals the transition to a new regime where the light modes in the effective action are different and are related to the original ones by S-duality. In a string context, this means that we enter a D-brane dominated phase.

  20. Mass Loss in Greenland and Antarctica from 1993 to 2013 Determined from a Combination of GRACE and SLR Data

    NASA Astrophysics Data System (ADS)

    Talpe, Matthieu; Nerem, Steven; Lemoine, Frank; Chinn, Doug; Riva, Riccardo; Pilinski, Emily

    2014-05-01

    The objective of this work is to extend the record of ice melt derived from space-borne gravity prior to the GRACE mission. We merge GRACE fields with conventional tracking data spanning 1993 to the present. The conventional tracking data consist of satellite laser ranging (SLR) and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) data and are provided as weekly global fields of degree and order five. Their multi-decade timespan complements the monthly fields of GRACE of degree and order 60 that start in 2003 and will end when the GRACE mission terminates. The two datasets are combined via an empirical orthogonal function (EOF) analysis, whereby the GRACE fields are first decomposed into spatial and temporal modes that are reflective of interannual gravity variability. Conventional tracking data temporal modes are then obtained by fitting GRACE spatial modes via normal equations; combining those temporal modes with GRACE spatial modes yields the reconstructed global gravity fields. We will show that the reconstructed Greenland and Antarctica mass changes capture the recent behavior of the ice melt over 1993 - 2013. The accelerating term, linear trend, and mass changes match with existing literature values, specifically, with similar GRACE analyses over 2002 - 2013 and with glaciological and altimetric evidence prior to the GRACE mission. We will also show current efforts to mitigate the limits of the reconstructions (e.g., in the EOF fitting process, the accuracy of the SLR/DORIS solutions, etc.) and their impact on the evolution and spatial accuracy of mass change in Greenland and Antarctica. The technique also has important implications for bridging the potential gap in global gravity coverage between the GRACE and GRACE Follow On missions, slated to launch in 2017.

  1. Postseismic GRACE and GPS observations indicate a rheology contrast above and below the Sumatra slab

    NASA Astrophysics Data System (ADS)

    Broerse, Taco; Riva, Riccardo; Simons, Wim; Govers, Rob; Vermeersen, Bert

    2015-07-01

    More than 7 years of observations of postseismic relaxation after the 2004 Sumatra-Andaman earthquake provide an improving view on the deformation in the wide vicinity of the 2004 rupture. We include both Gravity Recovery and Climate Experiment (GRACE) gravity field data that show a large postseismic signal over the rupture area and GPS observations in the back arc region. With increasing time GPS and GRACE show contrasting relaxation styles that were not easily discernible on shorter time series. We investigate whether mantle creep can simultaneously explain the far-field surface displacements and the long-wavelength gravity changes. We interpret contrasts in the temporal behavior of the GPS-GRACE observations in terms of lateral variations in rheological properties of the asthenosphere below and above the slab. Based on 1-D viscoelastic models, our results support an (almost) order of magnitude contrast between oceanic lithosphere viscosity and continental viscosity, which likely means that the low viscosities frequently found from postseismic deformation after subduction earthquakes are valid only for the mantle wedge. Next to mantle creep, we also consider afterslip as an alternative mechanism for postseismic deformation. We investigate how the combination of GRACE and GPS data can better discriminate between different mechanisms of postseismic relaxation: distributed deformation (mantle creep) versus localized deformation (afterslip). We conclude that the GRACE-observed gravity changes rule out afterslip as the dominant mechanism explaining long-wavelength deformation even over the first year after the event.

  2. Assimilating GRACE terrestrial water storage data into a conceptual hydrology model for the River Rhine

    NASA Astrophysics Data System (ADS)

    Widiastuti, E.; Steele-Dunne, S. C.; Gunter, B.; Weerts, A.; van de Giesen, N.

    2009-12-01

    Terrestrial water storage (TWS) is a key component of the terrestrial and global hydrological cycles, and plays a major role in the Earth’s climate. The Gravity Recovery and Climate Experiment (GRACE) twin satellite mission provided the first space-based dataset of TWS variations, albeit with coarse resolution and limited accuracy. Here, we examine the value of assimilating GRACE observations into a well-calibrated conceptual hydrology model of the Rhine river basin. In this study, the ensemble Kalman filter (EnKF) and smoother (EnKS) were applied to assimilate the GRACE TWS variation data into the HBV-96 rainfall run-off model, from February 2003 to December 2006. Two GRACE datasets were used, the DMT-1 models produced at TU Delft, and the CSR-RL04 models produced by UT-Austin . Each center uses its own data processing and filtering methods, yielding two different estimates of TWS variations and therefore two sets of assimilated TWS estimates. To validate the results, the model estimated discharge after the data assimilation was compared with measured discharge at several stations. As expected, the updated TWS was generally somewhere between the modeled and observed TWS in both experiments and the variance was also lower than both the prior error covariance and the assumed GRACE observation error. However, the impact on the discharge was found to depend heavily on the assimilation strategy used, in particular on how the TWS increments were applied to the individual storage terms of the hydrology model.

  3. GRACE storage-streamflow hystereses reveal the dynamics of regional watersheds

    NASA Astrophysics Data System (ADS)

    Sproles, E. A.; Leibowitz, S. G.; Reager, J. T.; Wigington, P. J., Jr.; Famiglietti, J. S.; Patil, S. D.

    2014-10-01

    We characterize how regional watersheds function as simple, dynamic systems through a series of hysteresis loops. These loops illustrate the temporal relationship between runoff and terrestrial water storage using measurements from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites in three regional-scale watersheds (>150 000 km2) of the Columbia River Basin, USA and Canada. The direction of the hystereses for the GRACE signal move in opposite directions from the isolated groundwater hystereses, suggesting that regional scale watersheds require soil water storage to reach a certain threshold before groundwater recharge and peak runoff occur. While the physical processes underlying these hystereses are inherently complex, the vertical integration of terrestrial water in the GRACE signal encapsulates the processes that govern the non-linear function of regional-scale watersheds. We use this process-based understanding to test how GRACE data can be applied prognostically to predict seasonal runoff (mean R2 of 0.91) and monthly runoff (mean R2 of 0.77) in all three watersheds. The global nature of GRACE data allows this same methodology to be applied in other regional-scale studies, and could be particularly useful in regions with minimal data and in trans-boundary watersheds.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. Assessing Global Water Storage Variability from GRACE: Trends, Seasonal Cycle, Subseasonal Anomalies and Extremes

    NASA Astrophysics Data System (ADS)

    Humphrey, Vincent; Gudmundsson, Lukas; Seneviratne, Sonia I.

    2016-03-01

    Throughout the past decade, the Gravity Recovery and Climate Experiment (GRACE) has given an unprecedented view on global variations in terrestrial water storage. While an increasing number of case studies have provided a rich overview on regional analyses, a global assessment on the dominant features of GRACE variability is still lacking. To address this, we survey key features of temporal variability in the GRACE record by decomposing gridded time series of monthly equivalent water height into linear trends, inter-annual, seasonal, and subseasonal (intra-annual) components. We provide an overview of the relative importance and spatial distribution of these components globally. A correlation analysis with precipitation and temperature reveals that both the inter-annual and subseasonal anomalies are tightly related to fluctuations in the atmospheric forcing. As a novelty, we show that for large regions of the world high-frequency anomalies in the monthly GRACE signal, which have been partly interpreted as noise, can be statistically reconstructed from daily precipitation once an adequate averaging filter is applied. This filter integrates the temporally decaying contribution of precipitation to the storage changes in any given month, including earlier precipitation. Finally, we also survey extreme dry anomalies in the GRACE record and relate them to documented drought events. This global assessment sets regional studies in a broader context and reveals phenomena that had not been documented so far.

  6. Low-degree gravity change from GPS data of COSMIC and GRACE satellite missions

    NASA Astrophysics Data System (ADS)

    Lin, Tingjung; Hwang, Cheinway; Tseng, Tzu-Pang; Chao, B. F.

    2012-01-01

    This paper demonstrates estimation of time-varying gravity harmonic coefficients from GPS data of COSMIC and GRACE satellite missions. The kinematic orbits of COSMIC and GRACE are determined to the cm-level accuracy. The NASA Goddard's GEODYN II software is used to model the orbit dynamics of COSMIC and GRACE, including the effect of a static gravity field. The surface forces are estimated per one orbital period. Residual orbits generated from kinematic and reference orbits serve as observables to determine the harmonic coefficients in the weighted-constraint least-squares. The monthly COSMIC and GRACE GPS data from September 2006 to December 2007 (16 months) are processed to estimate harmonic coefficients to degree 5. The geoid variations from the GPS and CSR RL04 (GRACE) solutions show consistent patterns over space and time, especially in regions of active hydrological changes. The monthly GPS-derived second zonal coefficient closely resembles the SLR-derived and CSR RL04 values, and third and fourth zonal coefficients resemble the CSR RL04 values.

  7. Crustal vertical deformation response to different spatial scales of GRACE and GCMs surface loading

    NASA Astrophysics Data System (ADS)

    Yan, Haoming; Chen, Wu; Yuan, Linguo

    2016-01-01

    Crustal vertical deformation (CVD) observed by continuous GPS height time-series can be explained largely by surface loading effects recovered from both Gravity Recover and Climate Experiment (GRACE) and General Circulation Models (GCMs) data. We first show that lower degree CVD spatial spectrum due to the Earth's elastic response to a uniform surface loading plays more important roles than that of high-degree case. We then demonstrate that GRACE data with 300-400 km spatial resolution have the ability to detect 99 per cent power of global and regional CVD in spatial spectrum domain using a global frequency-wavenumber spectrum method. We can just use either GRACE or GCMs 36 degree/order (d/o) spherical harmonic coefficients (SHCs) which correspond to 500 km spatial resolution to acquire more than 90 per cent variance of total CVD modeled by up to 180 d/o SHCs at 98 per cent global gridpoints. Globally, CVD modeled by GRACE loading can explain 72 per cent annual amplitude and 69 per cent variance of GPS observed height time-series, which is better than the GCMs results of 64 per cent for annual amplitude and 41 per cent for variance. Using a three cornered hat method, we also show that the noise level of monthly averaged CVD is about 3 mm for both GPS height time-series and GRACE loading result, while that of GCMs result is only 1.3 mm.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. GRACE storage-runoff hystereses reveal the dynamics of regional watersheds

    NASA Astrophysics Data System (ADS)

    Sproles, E. A.; Leibowitz, S. G.; Reager, J. T.; Wigington, P. J., Jr.; Famiglietti, J. S.; Patil, S. D.

    2015-07-01

    We characterize how regional watersheds function as simple, dynamic systems through a series of hysteresis loops using measurements from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites. These loops illustrate the temporal relationship between runoff and terrestrial water storage in three regional-scale watersheds (> 150 000 km2) of the Columbia River Basin, USA and Canada. The shape and size of the hysteresis loops are controlled by the climate, topography, and geology of the watershed. The direction of the hystereses for the GRACE signals moves in opposite directions from the isolated groundwater hystereses. The subsurface water (soil moisture and groundwater) hystereses more closely resemble the storage-runoff relationship of a soil matrix. While the physical processes underlying these hystereses are inherently complex, the vertical integration of terrestrial water in the GRACE signal encapsulates the processes that govern the non-linear function of regional-scale watersheds. We use this process-based understanding to test how GRACE data can be applied prognostically to predict seasonal runoff (mean Nash-Sutcliffe Efficiency of 0.91) and monthly runoff during the low flow/high demand month of August (mean Nash-Sutcliffe Efficiency of 0.77) in all three watersheds. The global nature of GRACE data allows this same methodology to be applied in other regional-scale studies, and could be particularly useful in regions with minimal data and in trans-boundary watersheds.

  10. "A Prairie Childhood" by Edith Abbott: An Excerpt from "The Children's Champion," a Biography of Grace Abbott

    ERIC Educational Resources Information Center

    Sorensen, John

    2003-01-01

    Grace Abbott's courageous struggles--to protect the rights of immigrants, to increase the role of women in government, and to improve the lives of all children--are filled with adventurous tales of the remarkable human ability to seek out suffering and to do something about it. "A Prairie Childhood" is an excerpt from the Grace Abbott biography…

  11. Grace and Courtesy: A Human Responsibility. AMI/USA Conference (Oak Brook, Illinois, July 23-26, 1998).

    ERIC Educational Resources Information Center

    American Montessori International of the United States, Inc., Rochester, NY.

    This conference proceedings compile presentations from a 1998 meeting of the American Montessori International of the United States, focusing on the importance of grace and courtesy in children's lives and in Montessori education. The papers presented are: (1) "Grace--The Felicity of Being" (Renilde Montessori); (2) "A Montessori Community for…

  12. Optimal Scaling of Filtered GRACE dS/dt Anomalies over Sacramento and San Joaquin River Basins, California

    NASA Astrophysics Data System (ADS)

    Ukasha, M.; Ramirez, J. A.

    2014-12-01

    Signals from Gravity Recovery and Climate Experiments (GRACE) twin satellites mission mapping the time invariant earth's gravity field are degraded due to measurement and leakage errors. Dampening of these errors using different filters results in a modification of the true geophysical signals. Therefore, use of a scale factor is suggested to recover the modified signals. For basin averaged dS/dt anomalies computed from data available at University of Colorado GRACE data analysis website - http://geoid.colorado.edu/grace/, optimal time invariant and time variant scale factors for Sacramento and San Joaquin river basins, California, are derived using observed precipitation (P), runoff (Q) and evapotranspiration (ET). Using the derived optimal scaling factor for GRACE data filtered using a 300 km- wide gaussian filter resulted in scaled GRACE dS/dt anomalies that match better with observed dS/dt anomalies (P-ET-Q) as compared to the GRACE dS/dt anomalies computed from scaled GRACE product at University of Colorado GRACE data analysis website. This paper will present the procedure, the optimal values, and the statistical analysis of the results.

  13. 76 FR 10899 - Decision To Evaluate a Petition To Designate a Class of Employees From the W.R. Grace and Company...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-28

    ... HUMAN SERVICES Decision To Evaluate a Petition To Designate a Class of Employees From the W.R. Grace and... class of employees from the W.R. Grace and Company in Curtis, Maryland, to be included in the Special... evaluation, is as follows: Facility: W.R. Grace and Company. Location: Curtis, Maryland. Job Titles...

  14. GRace: a MATLAB-based application for fitting the discrimination-association model.

    PubMed

    Stefanutti, Luca; Vianello, Michelangelo; Anselmi, Pasquale; Robusto, Egidio

    2014-01-01

    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. PMID:26054728

  15. Simulation study of a follow-on gravity mission to GRACE

    NASA Astrophysics Data System (ADS)

    Loomis, Bryant D.; Nerem, R. S.; Luthcke, S. B.

    2012-05-01

    The gravity recovery and climate experiment (GRACE) has been providing monthly estimates of the Earth's time-variable gravity field since its launch in March 2002. The GRACE gravity estimates are used to study temporal mass variations on global and regional scales, which are largely caused by a redistribution of water mass in the Earth system. The accuracy of the GRACE gravity fields are primarily limited by the satellite-to-satellite range-rate measurement noise, accelerometer errors, attitude errors, orbit errors, and temporal aliasing caused by un-modeled high-frequency variations in the gravity signal. Recent work by Ball Aerospace & Technologies Corp., Boulder, CO has resulted in the successful development of an interferometric laser ranging system to specifically address the limitations of the K-band microwave ranging system that provides the satellite-to-satellite measurements for the GRACE mission. Full numerical simulations are performed for several possible configurations of a GRACE Follow-On (GFO) mission to determine if a future satellite gravity recovery mission equipped with a laser ranging system will provide better estimates of time-variable gravity, thus benefiting many areas of Earth systems research. The laser ranging system improves the range-rate measurement precision to ~0.6 nm/s as compared to ~0.2 μm/s for the GRACE K-band microwave ranging instrument. Four different mission scenarios are simulated to investigate the effect of the better instrument at two different altitudes. The first pair of simulated missions is flown at GRACE altitude (~480 km) assuming on-board accelerometers with the same noise characteristics as those currently used for GRACE. The second pair of missions is flown at an altitude of ~250 km which requires a drag-free system to prevent satellite re-entry. In addition to allowing a lower satellite altitude, the drag-free system also reduces the errors associated with the accelerometer. All simulated mission scenarios

  16. A modified acceleration-based monthly gravity field solution from GRACE data

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    This paper describes an alternative acceleration approach for determining GRACE monthly gravity field models. The main differences compared to the traditional acceleration approach can be summarized as: (1) The position errors of GRACE orbits in the functional model are taken into account; (2) The range ambiguity is eliminated via the difference of the range measurements and (3) The mean acceleration equation is formed based on Cowell integration. Using this developed approach, a new time-series of GRACE monthly solution spanning the period January 2003 to December 2010, called Tongji_Acc RL01, has been derived. The annual signals from the Tongji_Acc RL01 time-series agree well with those from the GLDAS model. The performance of Tongji_Acc RL01 shows that this new model is comparable with the RL05 models released by CSR and JPL as well as with the RL05a model released by GFZ.

  17. Simulation Study of a Follow-on Gravity Mission to GRACE

    NASA Technical Reports Server (NTRS)

    Loomis, Bryant D.; Nerem, R. S.; Luthcke, Scott B.

    2012-01-01

    The gravity recovery and climate experiment (GRACE) has been providing monthly estimates of the Earth's time-variable gravity field since its launch in March 2002. The GRACE gravity estimates are used to study temporal mass variations on global and regional scales, which are largely caused by a redistribution of water mass in the Earth system. The accuracy of the GRACE gravity fields are primarily limited by the satellite-to-satellite range-rate measurement noise, accelerometer errors, attitude errors, orbit errors, and temporal aliasing caused by unmodeled high-frequency variations in the gravity signal. Recent work by Ball Aerospace and Technologies Corp., Boulder, CO has resulted in the successful development of an interferometric laser ranging system to specifically address the limitations of the K-band microwave ranging system that provides the satellite-to-satellite measurements for the GRACE mission. Full numerical simulations are performed for several possible configurations of a GRACE Follow-On (GFO) mission to determine if a future satellite gravity recovery mission equipped with a laser ranging system will provide better estimates of time-variable gravity, thus benefiting many areas of Earth systems research. The laser ranging system improves the range-rate measurement precision to approximately 0.6 nm/s as compared to approx. 0.2 micro-seconds for the GRACE K-band microwave ranging instrument. Four different mission scenarios are simulated to investigate the effect of the better instrument at two different altitudes. The first pair of simulated missions is flown at GRACE altitude (approx. 480 km) assuming on-board accelerometers with the same noise characteristics as those currently used for GRACE. The second pair of missions is flown at an altitude of approx. 250 km which requires a drag-free system to prevent satellite re-entry. In addition to allowing a lower satellite altitude, the drag-free system also reduces the errors associated with the

  18. Estimation and Validation of Oceanic Mass Circulation from the GRACE Mission

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

    Since the launch of the Gravity Recovery And Climate Experiment (GRACE) in March 2002, the Earth's surface mass variations have been monitored with unprecedented accuracy and resolution. Compared to the classical spherical harmonic solutions, global high-resolution mascon solutions allows the retrieval of mass variations with higher spatial and temporal sampling (2 degrees and 10 days). We present here the validation of the GRACE global mascon solutions by comparing mass estimates to a set of about 100 ocean bottom pressure (OSP) records, and show that the forward modelling of continental hydrology prior to the inversion of the K-band range rate data allows better estimates of ocean mass variations. We also validate our GRACE results to OSP variations modelled by different state-of-the-art ocean general circulation models, including ECCO (Estimating the Circulation and Climate of the Ocean) and operational and reanalysis from the MERCATOR project.

  19. Regional ice mass balance for Greenland from GRACE and ICESat modelled by radial basis functions

    NASA Astrophysics Data System (ADS)

    Eicker, A.; Springer, A.; Jensen, L.; Kusche, J.

    2012-04-01

    This contribution presents a tailored regional mass balance for the Greenland ice sheet from GRACE and ICESat observations. A regional gravity field trend model is calculated directly from the GRACE level 1B observations using the short arc method. The gravity field model is parameterized by harmonic space localizing radial basis functions that can be tailored to the specific signal characteristics in Greenland. The ICESat along-track ice elevation changes are co-estimated together with the local topography in order to be independent from external elevation models. The along-track observations are then evaluated without any necessary gridding consistently with the GRACE processing in the same basis of radial basis functions. This allows further joint analysis of the two data sets in this same basis.

  20. A Record-High Ocean Bottom Pressure in the South Pacific Observed by GRACE

    NASA Technical Reports Server (NTRS)

    Boening, Carmen; Lee, Tong; Zlotnicki, Victor

    2011-01-01

    In late 2009 to early 2010, the Gravity Recovery and Climate Experiment (GRACE) satellite pair observed a record increase in ocean bottom pressure (OBP) over a large mid-latitude region of the South East Pacific. Its magnitude is substantially larger than other oceanic events in the Southern Hemisphere found in the entire GRACE data records (2003-2010) on multi-month time scales. The OBP data help to understand the nature of a similar signal in sea surface height (SSH) anomaly observed by altimetry: the SSH increase is mainly due to mass convergence. Analysis of the barotropic vorticity equation using scatterometer data, atmospheric reanalysis product, and GRACE and altimeter an atmospheric reanalysis product observations suggests that the observed OBP/SSH signal was primarily caused by wind stress curl associated with a strong and persistent anticyclone in late 2009 in combination with effects of planetary vorticity gradient, bottom topography, and friction

  1. Vertical crustal movement around the southeastern Tibetan Plateau constrained by GPS and GRACE data

    NASA Astrophysics Data System (ADS)

    Hao, Ming; Freymueller, Jeffrey T.; Wang, Qingliang; Cui, Duxin; Qin, Shanlan

    2016-03-01

    Using measurements of continuous GPS stations and GRACE across the southeastern Tibetan Plateau, we found that the GRACE-derived vertical displacements are highly correlated with GPS-modeled vertical annual and semiannual displacements, which demonstrates that the vertical seasonal variations on ground surface are mainly caused by hydrological mass loading. After removing GRACE-modeled seasonal variations from the GPS time series, we used a stacking technique to filter out the common mode errors. Then we estimated the best noise model for the filtered time series, which can be best characterized by power law noise model. Finally, we determined the rates of vertical crustal movement of southeastern Tibetan Plateau. Our results suggest that the southeastern Tibetan Plateau is undergoing uplift, whereas the southern Sichuan-Yunnan fragment is subsiding with respect to the region to the north. The assumption of uniform extension throughout the crust does not explain the subsidence of southern Sichuan-Yunnan fragment.

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

    NASA Astrophysics Data System (ADS)

    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; p<0.001) and autumn (τ=0.45; p<0.001) cholera 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%; p<0.05] in the spring season, while an increase in regional water by one unit, through floods, increased odds of above average cholera in the autumn by 29% [CI:22-33%; p<0.05]. Epidemic cholera 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.

  3. GRACES observations of young [α/Fe]-rich stars

    NASA Astrophysics Data System (ADS)

    Yong, David; Casagrande, Luca; Venn, Kim A.; Chené, André-Nicolas; Keown, Jared; Malo, Lison; Martioli, Eder; Alves-Brito, Alan; Asplund, Martin; Dotter, Aaron; Martell, Sarah L.; Meléndez, Jorge; Schlesinger, Katharine J.

    2016-06-01

    We measure chemical abundance ratios and radial velocities in four massive (i.e. young) [α/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 disc red giants. We confirm that the program stars have enhanced [α/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 binaries. In addition, we find that two (possibly three) stars show evidence for an infrared excess, indicative of a debris disc. This is consistent with these young [α/Fe]-rich stars being evolved blue stragglers, suggesting their apparent young age is a consequence of a merger or mass transfer. We would expect a binary fraction of ˜50 per cent or greater for the entire sample of these stars, but the signs of the circumbinary disc may have been lost since these features can have short time-scales. Radial velocity monitoring is needed to confirm the blue straggler origin.

  4. Hydrological Response to the 2011 Drought in Texas Using Land Surface Modeling, Remote Sensing, and GRACE

    NASA Astrophysics Data System (ADS)

    Long, D.; Scanlon, B. R.; Longuevergne, L.

    2013-12-01

    Texas was subjected to the most extreme one-year drought on record in 2011, which had a tremendous impact on water resources statewide. This study aims to quantify evapotranspiration (ET) from land surface models (LSMs), remote sensing, and GRACE during the drought. Uncertainties in ET output from four LSMs, i.e., Noah, Mosaic, VIC, and SAC in NLDAS-2, two remote sensing-based products, i.e., MODIS and AVHRR, and GRACE-derived ET as a residual in the water budget (ET = P - R - ΔTWS) based on precipitation (P) from PRISM, monitored runoff (R), and total water storage (TWS) change from GRACE satellites were quantified using the three corner hat method that does not require a priori knowledge of the true value of ET. Water budgets were calculated using the traditional flux approach and a new storage approach in combination with the different ET products and GRACE TWS. The analyses were conducted using data from three river basins (humid - arid) primarily in Texas as case studies. Remote sensing-based ET shows markedly higher magnitudes during drought but significantly lower magnitudes at other times, particularly during wet periods than land surface model-based ET. Overestimation of ET during drought would result in overestimation of soil moisture depletion and much longer projected times for drought recovery. Uncertainties in ET are lowest in LSM ET (~5 mm/month), moderate in remote sensing MODIS- or AVHRR-based ET (10 - 15 mm/month), and highest in GRACE-based ET (20 - 30 mm/month). Uncertainties in total water storage changes from the water budget approach (ΔTWS = P-R-ET) are about half of uncertainties in GRACE-derived TWS changes for each of the basins. Future ET estimation should consider a hybrid approach that integrates LSM and satellite-based products to constrain uncertainties.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Annual and seasonal water storage changes detected from GRACE data in the La Plata Basin

    NASA Astrophysics Data System (ADS)

    Pereira, Ayelen; Pacino, María Cristina

    2012-12-01

    The gravity does not remain constant, but changes over time depending on the redistribution of the masses. Aquatic environments, like a river basin, perform important functions in nature such as control of climate, floods and nutrients; and they also provide goods and services for humanity. To monitor these environments at large spatial scales, the satellite gravity mission GRACE provides time-variable gravity field models that reflect the Earth's gravity field variations due to mass transport processes, like continental water storage variations. The La Plata Basin is the second largest in South America and is a sample of the abundance, variety and quality of natural resources and possibilities offered in connection with the production of goods and services. The objective of this work is to analyze GRACE capability to monitor the water storage variations in the La Plata Basin. Firstly, GRACE solutions from four different processing centers are used to estimate the gravity trend and gravity amplitude over this basin. Afterwards, the calculated hydrological signal is used to obtain mass change models over this hydrographic system's area, using two different methods and for the period from 2002 to 2009. Next, the annual and seasonal water storage changes from GRACE solutions are validated in Argentina by rainfall data over the time periods where extreme weather conditions took place. The results indicate that GRACE detected the variations of the continental water storage in the La Plata Basin, and particularly, it detected the important decrease in the South of the basin. Moreover, a coherency between the estimates of water mass changes and rainfall data was found, which shows that GRACE also detected extreme weather events (such as drought and intense rain episodes) that occurred in the 2004-2009 period in Argentina.

  7. Acceleration of the Greenland ice sheet mass loss as observed by GRACE: Confidence and sensitivity

    NASA Astrophysics Data System (ADS)

    Svendsen, P. L.; Andersen, O. B.; Nielsen, A. A.

    2013-02-01

    We examine the scale and spatial distribution of the mass change acceleration in Greenland and its statistical significance, using processed gravimetric data from the GRACE mission for the period 2002-2011. Three different data products - the CNES/GRGS, DMT-1b and GGFC GRACE solutions - have been used, all revealing an accelerating mass loss in Greenland, though with significant local differences between the three datasets. Compensating for leakage effects, we obtain acceleration values of -18.6 Gt/yr2 for CNES/GRGS, -8.8 Gt/yr2 for DMT-1b, and -14.8 Gt/yr2 for GGFC. We find considerable mass loss acceleration in the Canadian Arctic Archipelago, some of which will leak into the values for Greenland, depending on the approach used, and for our computations the leakage has been estimated at up to -4.7 Gt/yr2. The length of the time series of the GRACE data makes a huge difference in establishing an acceleration of the data. For both 10-day and monthly GRACE solutions, an observed acceleration on the order of 10-20 Gt/yr2 is shown to require more than 5 yrs of data to establish with statistical significance. In order to provide an independent evaluation, ICESat laser altimetry data have been smoothed to match the resolution of the GRACE solutions. This gives us an estimated upper bound for the acceleration of about -29.7 Gt/yr2 for the period 2003-2009, consistent with the acceleration values and corresponding confidence intervals found with GRACE data.

  8. Estimating sub-monthly TWS using MODIS and GRACE satellite observations, a case study over Tonlé Sap floodplain

    NASA Astrophysics Data System (ADS)

    Steele-Dunne, S. C.; Tangdamrongsub, N.; Ditmar, P.; Gunter, B. C.; Sutanudjaja, E.

    2015-12-01

    Knowledge of Terrestrial Water Storage (TWS) can provide valuable information that can be used to improve our understanding of the hydrological cycle and the impact of extreme climate events. Global TWS observations are currently only available from the Gravity Recovery And Climate Experiment satellite mission (GRACE) at monthly time scales. In this study, we present a new approach to derive the sub-monthly TWS variation over a regularly inundated area by using MODIS reflectance data in addition to GRACE solutions. In the "training" phase, monthly TWS are computed from filtered GRACE solutions. A signal restoration method is applied to correct for signal leakage caused by filtering. In parallel, a time-series of mean monthly inundated area estimates is computed based on the Normalized Difference Water Index (NDWI), derived from MODIS data. The training phase completes by finding an empirical relationship between the inundated area and the GRACE-based TWS variations, using a regression analysis. Then, the estimated parameters can be used to convert inundated area estimates into TWS variations without a further need in GRACE data. This approach has 3 major advantages over the usage of GRACE data alone. First, it can be used to cross-validate GRACE and MODIS reflectance data in order to identify and eliminate unreliable estimates. Second, it can provide sub-monthly (e.g., 8-day) TWS variations without loss of spatial resolution. Lastly, it can be used to fill gaps in TWS estimates based on GRACE data and to extend the time-series of TWS estimates beyond the time interval when GRACE data are available. The methodology is demonstrated using the Tonlé Sap floodplain located in Central Cambodia as a test case. The analysis shows an excellent agreement between the 8-day NDWI-based TWS estimates averaged over monthly intervals and the GRACE-based monthly TWS variations. The approach developed would have similar application in other areas that experience regular large

  9. Quantifying Modern Recharge to the Nubian Sandstone Aquifer System: Inferences from GRACE and Land Surface Models

    NASA Astrophysics Data System (ADS)

    Mohamed, A.; Sultan, M.; Ahmed, M.; Yan, E.

    2014-12-01

    The Nubian Sandstone Aquifer System (NSAS) is shared by Egypt, Libya, Chad and Sudanand is one of the largest (area: ~ 2 × 106 km2) groundwater systems in the world. Despite its importance to the population of these countries, major hydrological parameters such as modern recharge and extraction rates remain poorly investigated given: (1) the large extent of the NSAS, (2) the absence of comprehensive monitoring networks, (3) the general inaccessibility of many of the NSAS regions, (4) difficulties in collecting background information, largely included in unpublished governmental reports, and (5) limited local funding to support the construction of monitoring networks and/or collection of field and background datasets. Data from monthly Gravity Recovery and Climate Experiment (GRACE) gravity solutions were processed (Gaussian smoothed: 100 km; rescaled) and used to quantify the modern recharge to the NSAS during the period from January 2003 to December 2012. To isolate the groundwater component in GRACE data, the soil moisture and river channel storages were removed using the outputs from the most recent Community Land Model version 4.5 (CLM4.5). GRACE-derived recharge calculations were performed over the southern NSAS outcrops (area: 835 × 103 km2) in Sudan and Chad that receive average annual precipitation of 65 km3 (77.5 mm). GRACE-derived recharge rates were estimated at 2.79 ± 0.98 km3/yr (3.34 ± 1.17 mm/yr). If we take into account the total annual extraction rates (~ 0.4 km3; CEDARE, 2002) from Chad and Sudan the average annual recharge rate for the NSAS could reach up to ~ 3.20 ± 1.18 km3/yr (3.84 ± 1.42 mm/yr). Our recharge rates estimates are similar to those calculated using (1) groundwater flow modelling in the Central Sudan Rift Basins (4-8 mm/yr; Abdalla, 2008), (2) WaterGAP global scale groundwater recharge model (< 5 mm/yr, Döll and Fiedler, 2008), and (3) chloride tracer in Sudan (3.05 mm/yr; Edmunds et al. 1988). Given the available global

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

    NASA Astrophysics Data System (ADS)

    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

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

    NASA Astrophysics Data System (ADS)

    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

  12. Source Parameters Inversion for Recent Large Undersea Earthquakes from GRACE Data

    NASA Astrophysics Data System (ADS)

    Dai, Chunli

    The north component of gravity and gravity gradient changes from the Gravity Recovery And Climate Experiment (GRACE) are used to study the coseismic gravity change for five earthquakes over the last decade: the 2004 Sumatra-Andaman earthquake, the 2007 Bengkulu earthquake, the 2010 Maule, Chile earthquake, the 2011 Tohoku earthquake, and the 2012 Indian Ocean earthquakes. We demonstrate the advantage of these north components to reduce north-south stripes and preserve higher spatial resolution signal in GRACE Level 2 (L2) monthly Stokes Coefficients data products. By using the high spherical harmonic degree (up to degree 96) data products and the innovative GRACE data processing approach developed in this study, the retrieved gravity change is up to --34+/-1.4 muGal for the 2004 Sumatra and 2005 Nias earthquakes, which is by far the highest coseismic signal retrieved among published studies. Our study reveals the detectability of earthquakes as small as Mw 8.5 (i.e., the 2007 Bengkulu earthquake) from GRACE data. The localized spectral analysis is applied as an efficient method to determine the practical spherical harmonic truncation degree leading to acceptable signal-to-noise ratio, and to evaluate the noise level for each component of gravity and gravity gradient change of the seismic deformations. By establishing the linear algorithm of gravity and gravity gradient change with respect to the double-couple moment tensor, the point source parameters are estimated through the least squares adjustment combined with the simulated annealing algorithm. The GRACE-inverted source parameters generally agree well with the slip models estimated using other data sets, including seismic, GPS, or combined data. For the 2004 Sumatra-Andaman and 2005 Nias earthquakes, GRACE data produce a shallower centroid depth (9.1 km) compared to the depth (28.3 km) from GPS data, which may be explained by the closer-to-trench centroid location and by the aseismic slip over the shallow

  13. Groundwater Storage Depletion in the Northwest India Aquifer using Forward Modeling and GRACE Satellites

    NASA Astrophysics Data System (ADS)

    Long, D.; Scanlon, B. R.; Chen, J.

    2014-12-01

    Signal restoration of GRACE total water storage (TWS) and groundwater storage (GWS) changes for aquifers is challenging because human-induced water storage changes are often not simulated and have large uncertainties in land surface models (LSMs). This study demonstrates the effectiveness of forward modeling for restoring GRACE signal loss due to low-pass filtering applied to GRACE data. A new approach integrating the strengths of LSMs and forwarding modeling is developed to recover TWS and GWS changes using the North India Aquifer as a case study. GWS for a broad region of North India (~1,000,000 km2) during the past decade (Jan 2003-Jan 2013) showed a generally consistent decreasing trend at a rate of -2.1 cm/a (-22. 3 km3/a), and GWS changes for the three-state region (Punjab, Haryana & Delhi, and Rajasthan, 436,390 km2) for the period Jul 2003-Jul 2008 was estimated to be -2.9 cm/a (-12.7 km3/a). This study provides new insights into GRACE signal restoration for TWS and GWS estimation over aquifers.

  14. Recovering the filtered GRACE TVG signal by iterative method with application to mass change in Antarctic

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Chen, J.; Chao, B. F.; Lu, Y.

    2013-12-01

    The dual-satellite mission of GRACE (Gravity Recovery And Climate Experiment) launched in 2002 has been making precise measurement of the Earth's (tiny) time-variable gravity (TVG), providing new and important information about mass transport on or in the Earth. Given the nature of the measurement technique, the GRACE TVG solutions, in the standard form of monthly spherical harmonic (SH) Stokes coefficients, are plagued with short-wavelength noises on regional to local scales, preventing proper interpretation of the TVG signals. Spatial low-pass filtering, or 'smoothing', is necessary. However, all kinds of filters remove noises and useful signal synchronously. In case of processing GRACE TVG solutions, when we use the Gaussian filter to remove short-wavelength noises, it also causes a reduction on spatial resolution. Here we devise an approach to recover the filtered GRACE TVG signal by iterative method. We deduce a formula to do iteration as a function of filter weight in spherical harmonic domain, so its implementation is straightforward and its iteration error is convergence. The simulation tests based on land hydrological monthly model solutions show that this method is able to recover the reduced amplitude caused by low-pass filter and improve spatial resolution. Without removing the glacial isostatic adjustment (GIA) effect, the slopes of mass change rates are -4.46Gt/yr and -28.73Gt/yr before and after recovering by iteration.

  15. Flight-Like Optical Reference Cavity for GRACE Follow-On Laser Frequency Stabilization

    NASA Technical Reports Server (NTRS)

    Folkner, W. M.; deVine, G.; Klipstein, W. M.; McKenzie, K.; Spero, R.; Thompson, R.; Yu, N.; Stephens, M.; Leitch, J.; Pierce, R.; Shaddock, D.; Lam, T.

    2011-01-01

    We describe a prototype optical cavity and associated optics that has been developed to provide a stable frequency reference for a future space-based laser ranging system. This instrument is being considered for inclusion as a technology demonstration on the recently announced GRACE follow-on mission, which will monitor variations in the Earth's gravity field.

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

    NASA Astrophysics Data System (ADS)

    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.

  17. Ocean calibration approach for data from the GRACE Follow-On mission

    NASA Astrophysics Data System (ADS)

    Bender, Peter L.; Betts, Casey R.

    2016-02-01

    The Gravity Recovery and Climate Experiment (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 the Pacific and of other oceans are the extended regions where the a priori uncertainties in the time variations of the geopotential heights due to mass distribution changes are known best. In addition, advantage can be taken of the repeated crossings of the South Pole and the North Pole, since the uncertainties in changes in the geopotential heights at the poles during the time required for four orbit revolutions are likely to be small.

  18. Estimation of Greenland's Ice Sheet Mass Balance Using ICESat and GRACE Data

    NASA Astrophysics Data System (ADS)

    Slobbe, D.; Ditmar, P.; Lindenbergh, R.

    2007-12-01

    Data of the GRACE gravity mission and the ICESat laser altimetry mission are used to create two independent estimates of Greenland's ice sheet mass balance over the full measurement period. For ICESat data, a processing strategy is developed using the elevation differences of geometrically overlapping footprints of both crossing and repeated tracks. The dataset is cleaned using quality flags defined by the GLAS science team. The cleaned dataset reveals some strong, spatially correlated signals that are shown to be related to physical phenomena. Different processing strategies are used to convert the observed temporal height differences to mass changes for 6 different drainage systems, further divided into a region above and below 2000 meter elevation. The results are compared with other altimetry based mass balance estimates. In general, the obtained results confirm trends discovered by others, but we also show that the choice of processing strategy strongly influences our results, especially for the areas below 2000 meter. Furthermore, GRACE based monthly variations of the Earth's gravity field as processed by CNES, CSR, GFZ and DEOS are used to estimate the mass balance change for North and South Greenland. It is shown that our results are comparable with recently published GRACE estimates (mascon solutions). On the other hand, the estimates based on GRACE data are only partly confirmed by the ICESat estimates. Possible explanations for the obvious differences will be discussed.

  19. GRACE Hydrological estimates for small basins: Evaluating processing approaches on the High Plains Aquifer, USA

    NASA Astrophysics Data System (ADS)

    Longuevergne, Laurent; Scanlon, Bridget R.; Wilson, Clark R.

    2010-11-01

    The Gravity Recovery and Climate Experiment (GRACE) satellites provide observations of water storage variation at regional scales. However, when focusing on a region of interest, limited spatial resolution and noise contamination can cause estimation bias and spatial leakage, problems that are exacerbated as the region of interest approaches the GRACE resolution limit of a few hundred km. Reliable estimates of water storage variations in small basins require compromises between competing needs for noise suppression and spatial resolution. The objective of this study was to quantitatively investigate processing methods and their impacts on bias, leakage, GRACE noise reduction, and estimated total error, allowing solution of the trade-offs. Among the methods tested is a recently developed concentration algorithm called spatiospectral localization, which optimizes the basin shape description, taking into account limited spatial resolution. This method is particularly suited to retrieval of basin-scale water storage variations and is effective for small basins. To increase confidence in derived methods, water storage variations were calculated for both CSR (Center for Space Research) and GRGS (Groupe de Recherche de Géodésie Spatiale) GRACE products, which employ different processing strategies. The processing techniques were tested on the intensively monitored High Plains Aquifer (450,000 km2 area), where application of the appropriate optimal processing method allowed retrieval of water storage variations over a portion of the aquifer as small as ˜200,000 km2.

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

    NASA Astrophysics Data System (ADS)

    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.

  1. GRACE-assisted Budyko Hypothesis for Improved Estimates of Long-term Water Partitioning

    NASA Astrophysics Data System (ADS)

    Fang, K.; Shen, C.; Fisher, J. B.; Niu, J.

    2015-12-01

    The Budyko hypothesis provides a reference condition of water balance and describes an empirical relationship between precipitation (P), evapotranspiration (E) and potential evapotranspiration (Ep). However, real-world catchments often deviate significantly from the theoretical Budyko curve. Recent advances of understanding in the impacts of seasonal water balances on long-term averaged water balance showed that phase difference between P and Ep is a major cause of downward departure from the Budyko curve. The phase difference and its processing by the catchments are in fact recorded over the globe in the form of Gravity Recovery and Climate Experiment satellite (GRACE) terrestrial water storage anomalies (TWSA). Here we present a GRACE-assisted Budyko-type formula that has improved predictive accuracy for long term E/P using the aridity index and storage patterns. We established an error model for the residual between Turk-Pike form of the Budyko curve and the observed E, based on a seamless United States basin water balance dataset. We found that the error model could improve the prediction efficiency by more than 60% comparing to Budyko model. The form of the error model was supported by Monte Carlo analysis. We compared the results with NLDAS predict E and found that the GRACE-corrected formula are in closer agreement with NLDAS than that without GRACE correction. In addition, we apply this error model to the whole world and global E was predicted. By comparing with other E products we found this error model can correct Budyko curve effectively.

  2. Wavelet and Gaussian Approaches for Estimation of Groundwater Variations Using GRACE Data.

    PubMed

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

    2016-01-01

    In this study, a scheme is presented to estimate groundwater storage variations in Iran. The variations are estimated using 11 years of Gravity Recovery and Climate Experiments (GRACE) observations from period of 2003 to April 2014 in combination with the outputs of Global Land Data Assimilation Systems (GLDAS) model including soil moisture, snow water equivalent, and total canopy water storage. To do so, the sums of GLDAS outputs are subtracted from terrestrial water storage variations determined by GRACE observations. Because of stripping errors in the GRACE data, two methodologies based on wavelet analysis and Gaussian filtering are applied to refine the GRACE data. It is shown that the wavelet approach could better localize the desired signal and increase the signal-to-noise ratio and thus results in more accurate estimation of groundwater storage variations. To validate the results of our procedure in estimation of ground water storage variations, they are compared with the measurements of pisometric wells data near the Urmia Lake which shows favorable agreements with our results. PMID:25962402

  3. Using an SLR inversion to measure the mass balance of Greenland before and during GRACE

    NASA Astrophysics Data System (ADS)

    Bonin, Jennifer

    2016-04-01

    The GRACE mission has done an admirable job of measuring large-scale mass changes over Greenland since its launch in 2002. However before that time, measurements of large-scale ice mass balance were few and far between, leading to a lack of baseline knowledge. High-quality Satellite Laser Ranging (SLR) data existed a decade earlier, but normally has too low a spatial resolution to be used for this purpose. I demonstrate that a least squares inversion technique can reconstitute the SLR data and use it to measure ice loss over Greenland. To do so, I first simulate the problem by degrading today's GRACE data to a level comparable with SLR, then demonstrating that the inversion can re-localize Greenland's contribution to the low-resolution signal, giving an accurate time series of mass change over all of Greenland which compares well with the full-resolution GRACE estimates. I then utilize that method on the actual SLR data, resulting in an independent 1994-2014 time series of mass change over Greenland. I find favorable agreement between the pure-SLR inverted results and the 2012 Ice-sheet Mass Balance Inter-comparison Exercise (IMBIE) results, which are largely based on the "input-output" modeling method before GRACE's launch.

  4. Between Dissonance and Grace: The Experience of Post-Secondary Leaders

    ERIC Educational Resources Information Center

    Davison, Philip; Burge, Elizabeth J.

    2010-01-01

    This study explores what it means for academic leaders to work in post-secondary institutional contexts. Four themes emerge: balancing daily dissonance; learning experientially to lead; creating learning spaces; and needing moments of grace. The research reveals that leaders seek deeper understandings of their work and their characterization.

  5. Observations of Atlantic overturning variability and latitudinal coherence with GRACE time-variable gravity

    NASA Astrophysics Data System (ADS)

    Landerer, Felix; Wiese, David; Bentel, Katrin; Watkins, Michael; Boening, Carmen

    2016-04-01

    The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism of pole-ward planetary heat transport. Concerns about AMOC changes imply the need for a continuous, large-scale observation capability to detect and monitor changes on interannual to decadal time scales. Here we present measurements of AMOC component transport changes directly obtained from time-variable gravity observations of the Gravity Recovery and Climate Experiment (GRACE) satellites from 2003 until now. Recent improvements at JPL of monthly gravity field retrievals allow the detection of AMOC-related interannual bottom pressure anomalies and in turn LNADW transport estimates. In the Atlantic at 26N, these GRACE AMOC estimates are in good agreement with those from the Rapid Climate Change-Meridional Overturning Circulation and Heatflux Array (RAPID/MOCHA) . We extend the GRACE-based estimates of AMOC variability from the Southern Ocean to the Northern sinking branch to assess meridional coherence and discuss challenges of the GRACE observing system. Our results highlight the efficacy and utility of space-gravimetry for observing AMOC variations to evaluate latitudinal coherency and long-term variability.

  6. Generating a Reduced-energy Antiproton beam using Channeling Electrostatic elements (GRACE)

    NASA Astrophysics Data System (ADS)

    Lawler, Gerard; Pacifico, Nicola; Aegis Collaboration

    2016-03-01

    A device was designed for Generating a Reduced-energy Antiproton-beam using Channeling Electrostatic elements (GRACE). A series of einzel lenses and electrodes are used to create a slow beam of antiprotons with tunable mean energy (0 to 16 keV with root mean squared value below 20%) using antiprotons (mean energy of 5 MeV) from the Antiproton Decelerator (AD) at CERN. Degrader foil is in place, so GRACE further deflects the beam bunches away from the annihilation products, focusing them on a 14 mm x 14 mm detector. Manufacturing parameters were found using simulations written in C++. The device is currently in use by the Antihydrogen Experiment: Gravity, Interferometry, Spectroscopy (AEgIS) collaboration at CERN, which seeks to measure the sign of the gravitational constant for antimatter by performing interferometry studies on an antihydrogen beam. GRACE delivers on the order of 10 events per beam bunch from the AD. Antiprotons will eventually be used together with a pulse of positronium atoms to make antihydrogen atoms with horizontal velocity. GRACE is being used to perform intermediary experiments concerning interferometry of antiprotons, an important stepping stone on the way to measuring the sign of gravity. Special thanks to Boston University Undergraduate Research Opportunities Program, Lawrence Sulak, and Michael Doser.

  7. Glacial isostatic adjustment on the Northern Hemisphere - new results from GRACE

    NASA Astrophysics Data System (ADS)

    Mueller, J.; Steffen, H.; Gitlein, O.; Denker, H.; Timmen, L.

    2007-12-01

    The Earth's gravity field mapped by the Gravity Recovery and Climate Experiment (GRACE) satellite mission shows variations due to the integral effect of mass variations in the atmosphere, hydrosphere and geosphere. The Earth's gravity field is provided in form of monthly solutions by several institutions, e.~g. GFZ Potsdam, CSR and JPL. During the GRACE standard processing of these analysis centers, oceanic and atmospheric contributions as well as tidal effects are reduced. The solutions of the analysis centers differ slightly, which is due the application of different reduction models and center-specific processing schemes. We present our investigation of mass variations in the areas of glacial isostatic adjustment (GIA) in North America and Northern Europe from GRACE data. One key issue is the separation of GIA parts and the reduction of the observed quantities by applying dedicated filters (e.~g. isotropic, non-isotropic, and destriping filters) and global models of hydrological variations (e.~g. WGHM, LaDWorld, GLDAS). In a further step, we analyze the results of both regions regarding their reliability, and finally present a comparison to results of a geodynamical modeling and absolute gravity measurements. Our results clearly show that the quality of the GRACE-derived gravity- change signal benefits from improved reduction models and chosen analysis techniques. Nevertheless, the comparison to results of geodynamic models still reveals differences, and thus further studies are in progress.

  8. GRACE and ICESat Data for Estimation of Ice Sheet Surface Changes in LAS, East Antarctica

    NASA Astrophysics Data System (ADS)

    Xie, H.; Ju, X.; Liu, J.; Gu, Z.; Liu, S.; Tian, Y.; Chen, L.; Shen, Y.; Tong, X.; Sun, B.; Li, R.

    2014-12-01

    Knowledge of mass changes of the Antarctic ice sheet is essential for understanding global climate change, specifically, for sea-level change. This presentation reports the the results of a comparative study on changes of regional ice sheet mass and surface elevation based on observations of GRACE and ICESat satellites over the period of 2004 - 2008 in the Lambert Glacier-Amery Ice Shelf System (LAS), East Antarctica. LAS is an important drainage system in East Antarctica and one of the significant contributors to the mass budget of the Antarctic. We fitted the GRACE monthly solutions to a model that contains a linear trend, an acceleration, annual and semiannual terms, and a 161 days tide aliasing term (S2). We employed the IJ05 R2 GIA model. For ICESat observations, we employed a modified spatial-temporal polynomial model to describe the ice surface topography and an annual elevation change rate (trend), which is solved by using repeat-track points within a moving box along the repeating tracks. Uncertainties of the source data and the estimated trends from both GRACE and ICESat data are given. The mass changes from GRACE and ICESat are compared and the differences are analyzed. A number of key issues in the comparison and mass - volume conversion are discussed. Afterwards, spatial and temporal correlations between the results at the annual change level derived from the two data sets are analyzed. Impact of firn models, GIA models, and comparison with other research results in LAS demonstrated.

  9. Child Center of Our Lady of Grace. Statement of Policies and Guidelines.

    ERIC Educational Resources Information Center

    Child Center of Our Lady of Grace, St. Louis, MO.

    The document contains policies and guidelines for the Child Center of Our Lady of Grace, a facility offering psychiatric evaluation and treatment for children (ages 4 to 17) in the St. Louis (Missouri and Illinois) region. After a brief statement of program rationale and an introduction to the program, services and policies are described.…

  10. 76 FR 75797 - Transportation Conformity Rule: MOVES Regional Grace Period Extension

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... analyses''). DATES: Effective December 5, 2011, EPA withdraws the direct final rule published at 76 FR... extending the MOVES regional conformity grace period, published on October 13, 2011 (76 FR 63554). We stated... be based on the parallel proposed rule also published on October 13, 2011 (76 FR 63575). As stated...

  11. Precise orbit determination for GRACE using undifferenced or doubly differenced GPS data

    NASA Astrophysics Data System (ADS)

    Jäggi, A.; Hugentobler, U.; Bock, H.; Beutler, G.

    The two GRACE satellites provide the ideal platform to study the performance of different strategies for precise orbit determination using undifferenced or doubly differenced GPS data. We use pseudo-stochastic orbit modeling techniques in a batch least-squares environment for the two GRACE satellites to outline the mutual benefits of processing doubly differenced instead of undifferenced GPS data. We either process the space baseline only, the space-ground baselines only, or both types of baselines together, and show that the fixing of the GPS double difference carrier phase ambiguities has a significant impact on the space baseline, but also on the space-ground baselines. The validation of the relative orbit positions by inter-satellite K-band observations shows precisions of better than 1 mm in the case of fixed space baseline ambiguities, precisions of a few millimeter in the case of fixed space-ground baseline ambiguities, and precisions of about 1 cm in the case of float ambiguities. We discuss the differences between the various GRACE orbit solutions in order to formulate well suited orbit determination strategies tailored to the GRACE configuration. Satellite laser ranging observations indicate that accuracies between 2 cm and 2.5 cm are achieved.

  12. Women in History--Grace Abbott: A Leader in Social Reform

    ERIC Educational Resources Information Center

    Hoffman, Shari Cole

    2006-01-01

    This article profiles Grace Abbott, one of the earlier 20th century American women leaders in Progressivism. Abbott's heritage influenced her lifetime commitment to social improvement. She was born on November 17, 1878 in Grand Island, Nebraska into a family of activists. Her Quaker mother, Elizabeth Griffin Abbott, came from an abolitionist…

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

    NASA Technical Reports Server (NTRS)

    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.

  14. Assimilation of GRACE-derived oceanic mass distributions with a global ocean circulation model

    NASA Astrophysics Data System (ADS)

    Saynisch, J.; Bergmann-Wolf, I.; Thomas, M.

    2015-02-01

    To study the sub-seasonal distribution and generation of ocean mass anomalies, Gravity Recovery and Climate Experiment (GRACE) observations of daily and monthly resolution are assimilated into a global ocean circulation model with an ensemble-based Kalman-Filter technique. The satellite gravimetry observations are processed to become time-variable fields of ocean mass distribution. Error budgets for the observations and the ocean model's initial state are estimated which contain the full covariance information. The consistency of the presented approach is demonstrated by increased agreement between GRACE observations and the ocean model. Furthermore, the simulations are compared with independent observations from 54 bottom pressure recorders. The assimilation improves the agreement to high-latitude recorders by up to 2 hPa. The improvements are caused by assimilation-induced changes in the atmospheric wind forcing, i.e., quantities not directly observed by GRACE. Finally, the use of the developed Kalman-Filter approach as a destriping filter to remove artificial noise contaminating the GRACE observations is presented.

  15. Variability in land water storage from GRACE and ENVISAT, and rainfall in South American river basins

    NASA Astrophysics Data System (ADS)

    Xavier, L.; Cazenave, A.; Bonnet, M.; Rotunno, O.

    2008-12-01

    Previous work has demonstrated the capability of GRACE to capture important aspects of the hydrological cycle, in particular seasonal and interannual fluctuations in land water storage of large river basins. Part of this behaviour can be immediately assigned to seasonal/interannual fluctuations of precipitation. In this study, we investigate existing correlations between GRACE water storage (two GRACE products are used and compared, the GRGS and GSFC/Mascons solutions), ENVISAT-based surface water levels and precipitation data over four large river basins of South America (Orinoco, Amazon, Tocantins and Parana). At the seasonal time scale, precipitation and total water storage correlate well in the Parana basin, with a few weeks lag of storage with respect to forcing. Over the Amazon, Tocantins and Orinoco, the two variables also correlate well. But in some years, storage response to forcing is enhanced, suggesting that other terms of the water balance (e.g., runoff) play a significant role. To investigate this, discharge data at the most downstream stations in these river basins are analysed, while the water balance is studied using outputs of global hydrological models available over the same time span as GRACE data. We also analyse water level data from ENVISAT altimetry over the main rivers. Finally, we study the interannual connection between rainfall and water storage, using among others, Empirical Orthogonal Functions (EOF). Compared to the seasonal cycle, the interannual signal displays larger regional variability both in precipitation and water storage.

  16. Assimilation of GRACE Derived Terrestrial Water Storage Data into a Hydrological Model

    NASA Astrophysics Data System (ADS)

    Rodell, M.; Zaitchik, B. F.; Reichle, R. H.

    2007-12-01

    GRACE has great potential to benefit hydrology, because no other observation system, ground- or space-based, has ever mapped variations in terrestrial water storage (TWS; the sum of groundwater, soil moisture, surface water, and snow). However, because its spatial and temporal resolutions are low relative to other hydrological observing systems and because total terrestrial water storage is a variable unfamiliar to hydrologists, GRACE has yet to become a standard tool for hydrology. Land surface models (LSMs) simulate the redistribution of water and energy incident on the land surface, but their accuracy is limited by the quality of the input data used to parameterize and force the models, the model developers' understanding of the physics involved, and the simplifications necessary to depict the Earth system economically. The advantages of GRACE and LSMs can be harnessed by data assimilation, which synthesizes discontinuous and imperfect observations with our knowledge of physical processes, as represented in a LSM. The model fills observational gaps, provides quality control, and enables data from disparate measurement systems to be merged, while the observations anchor the results in reality. We have assimilated TWS anomalies derived from GRACE into the Catchment LSM. The experimental domain was the Mississippi River Basin. Monthly GRACE estimates were derived for each of the four major sub-basins. Assimilation was performed using an Ensemble Kalman smoother. In addition to simulating soil and snow water storages, the Catchment LSM accounts for variations in the elevation of the water table, making it appropriate for total terrestrial water storage applications. The assimilated results produced groundwater storage time series which more closely resembled piezometer based estimates, relative to the open loop (non-assimilating) simulations. These results emphasize the potential for GRACE to improve the accuracy of hydrologic model output, which will benefit water

  17. GRACE L1b inversion through a self-consistent modified radial basis function approach

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Kusche, Juergen; Rietbroek, Roelof; Eicker, Annette

    2016-04-01

    Implementing a regional geopotential representation such as mascons or, more general, RBFs (radial basis functions) has been widely accepted as an efficient and flexible approach to recover the gravity field from GRACE (Gravity Recovery and Climate Experiment), especially at higher latitude region like Greenland. This is since RBFs allow for regionally specific regularizations over areas which have sufficient and dense GRACE observations. Although existing RBF solutions show a better resolution than classical spherical harmonic solutions, the applied regularizations cause spatial leakage which should be carefully dealt with. It has been shown that leakage is a main error source which leads to an evident underestimation of yearly trend of ice-melting over Greenland. Unlike some popular post-processing techniques to mitigate leakage signals, this study, for the first time, attempts to reduce the leakage directly in the GRACE L1b inversion by constructing an innovative modified (MRBF) basis in place of the standard RBFs to retrieve a more realistic temporal gravity signal along the coastline. Our point of departure is that the surface mass loading associated with standard RBF is smooth but disregards physical consistency between continental mass and passive ocean response. In this contribution, based on earlier work by Clarke et al.(2007), a physically self-consistent MRBF representation is constructed from standard RBFs, with the help of the sea level equation: for a given standard RBF basis, the corresponding MRBF basis is first obtained by keeping the surface load over the continent unchanged, but imposing global mass conservation and equilibrium response of the oceans. Then, the updated set of MRBFs as well as standard RBFs are individually employed as the basis function to determine the temporal gravity field from GRACE L1b data. In this way, in the MRBF GRACE solution, the passive (e.g. ice melting and land hydrology response) sea level is automatically

  18. Glacial isostatic adjustment in Fennoscandia from GRACE data and comparison with geodynamical models

    NASA Astrophysics Data System (ADS)

    Steffen, Holger; Denker, Heiner; Müller, Jürgen

    2008-10-01

    The Earth's gravity field observed by the Gravity Recovery and Climate Experiment (GRACE) satellite mission shows variations due to the integral effect of mass variations in the atmosphere, hydrosphere and geosphere. Several institutions, such as the GeoForschungsZentrum (GFZ) Potsdam, the University of Texas at Austin, Center for Space Research (CSR) and the Jet Propulsion Laboratory (JPL), Pasadena, provide GRACE monthly solutions, which differ slightly due to the application of different reduction models and centre-specific processing schemes. The GRACE data are used to investigate the mass variations in Fennoscandia, an area which is strongly influenced by glacial isostatic adjustment (GIA). Hence the focus is set on the computation of secular trends. Different filters (e.g. isotropic and non-isotropic filters) are discussed for the removal of high frequency noise to permit the extraction of the GIA signal. The resulting GRACE based mass variations are compared to global hydrology models (WGHM, LaDWorld) in order to (a) separate possible hydrological signals and (b) validate the hydrology models with regard to long period and secular components. In addition, a pattern matching algorithm is applied to localise the uplift centre, and finally the GRACE signal is compared with the results from a geodynamical modelling. The GRACE data clearly show temporal gravity variations in Fennoscandia. The secular variations are in good agreement with former studies and other independent data. The uplift centre is located over the Bothnian Bay, and the whole uplift area comprises the Scandinavian Peninsula and Finland. The secular variations derived from the GFZ, CSR and JPL monthly solutions differ up to 20%, which is not statistically significant, and the largest signal of about 1.2 μGal/year is obtained from the GFZ solution. Besides the GIA signal, two peaks with positive trend values of about 0.8 μGal/year exist in central eastern Europe, which are not GIA-induced, and

  19. Insights about data assimilation frameworks for integrating GRACE with hydrological models

    NASA Astrophysics Data System (ADS)

    Schumacher, Maike; Kusche, Jürgen; Van Dijk, Albert I. J. M.; Döll, Petra; Schuh, Wolf-Dieter

    2016-04-01

    Improving the understanding of changes in the water cycle represents a challenging objective that requires merging information from various disciplines. Debates exist on selecting an appropriate assimilation technique to integrate GRACE-derived terrestrial water storage changes (TWSC) into hydrological models in order to downscale and disaggregate GRACE TWSC, overcome model limitations, and improve monitoring and forecast skills. Yet, the effect of the specific data assimilation technique in conjunction with ill-conditioning, colored noise, resolution mismatch between GRACE and model, and other complications is still unclear. Due to its simplicity, ensemble Kalman filters or smoothers (EnKF/S) are often applied. In this study, we show that modification of the filter approach might open new avenues to improve the integration process. Particularly, we discuss an improved calibration and data assimilation (C/DA) framework (Schumacher et al., 2016), which is based on the EnKF and was extended by the square root analysis scheme (SQRA) and the singular evolutive interpolated Kalman (SEIK) filter. In addition, we discuss an off-line data blending approach (Van Dijk et al., 2014) that offers the chance to merge multi-model ensembles with GRACE observations. The investigations include: (i) a theoretical comparison, focusing on similarities and differences of the conceptual formulation of the filter algorithms, (ii) a practical comparison, for which the approaches were applied to an ensemble of runs of the WaterGAP Global Hydrology Model (WGHM), as well as (iii) an impact assessment of the GRACE error structure on C/DA results. First, a synthetic experiment over the Mississippi River Basin (USA) was used to gain insights about the C/DA set-up before applying it to real data. The results indicated promising performances when considering alternative methods, e.g. applying the SEIK algorithm improved the correlation coefficient and root mean square error (RMSE) of TWSC by 0

  20. Mass variations of the Baltic Sea compared to superconducting gravimeter and GRACE

    NASA Astrophysics Data System (ADS)

    Virtanen, H.; Virtanen, J.; Nordman, M.; Bilker-Koivula, M.; Mäkinen, J.

    2009-04-01

    We study the gravity effect of Baltic Sea mass variations observed using different methods and time resolutions. We compare data from tide gauges, from superconductive gravimeter (SG) at Metsähovi, Finland and from the GRACE gravity satellite. The mass variation in the semi-enclosed Baltic Sea is due to both internal redistribution of the water mass and due to changes in the so-called fill level caused by water exchange with the North Sea. The monthly variation in the water mass is about 60 Gt over an area of 390000 km-2. Due to a dense network of tide gauges, the Baltic Sea is one of best monitored mass variations in this size in the world. For modeling the observed water mass, we have used both monthly PSMSL tide gauge records and hourly values from several sources. In addition, we have hydrodynamic models for comparisons. To calculate gravity effect, we have used Green's function formalism for modeled sea surface. We have previously used temporal gravity field data from GRACE satellite to show that GRACE can recover the total mass variation in the Baltic Sea on monthly scales. In addition to monthly GRACE solutions with different filters, we now also use 10-day mascon block solutions from Goddard Space Flight Center. As the GRACE solutions are already corrected for gravity changes due to oceans, we have restored the contribution due to the Baltic Sea. We have also corrected for an effect due to leakage of continental water storage using the GLDAS hydrology model. The fundamental station Metsähovi is located 10 km from the nearest bay of the Baltic Sea and 15 km from the open sea. Using a single tide gauge at the distance of 30 km from SG at Metsähovi, very clear correlation is found between gravity and sea level. Superconducting gravity data has been corrected by tides and polar motion, atmospheric mass redistribution, local groundwater and drift. Hourly mass variations of sea are clearly separable. Theoretically one-meter even-layer water cause 30 nms-2

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  3. Synthesis of GRACE Based Hydrology With Other Data Products and Land Surface Models

    NASA Astrophysics Data System (ADS)

    Rodell, M.

    2005-12-01

    Time series of terrestrial water storage variations are now being derived from GRACE satellite gravity observations. These could be extremely valuable for water cycle research, water resources and natural hazards, and other applications, because GRACE provides information on water stored at depths not resolvable using space-borne radar or radiometers. However, interpreting and utilizing GRACE data is challenging to hydrologists due to three issues: 1) their spatial and temporal resolutions are low relative to other observations, 2) there is a tradeoff between resolution and accuracy for which optimization varies based on the application and region of interest, and 3) auxiliary information is required in order to disaggregate the terrestrial water storage variations into changes in ground water, soil moisture, snow, surface water, and vegetation mass. Addressing those issues through the synthesis of GRACE data with other hydrological products and tools will be crucial for maximizing the value of these data for terrestrial hydrological research and applications. Land surface models (LSMs) simulate the redistribution of water and energy incident on the land surface, but their accuracy is limited by the quality of the input data used to parameterize and force the models, the model developers' understanding of the physics involved, and the simplifications necessary to depict the Earth system economically. Remote sensing observations are generally preferable, but they have their own problems, including data gaps, errors from multiple sources, and low resolutions. The advantages of each can be harnessed by data assimilation, which integrates discontinuous and imperfect observations with our knowledge of physical processes, as represented in LSMs. Models fill observational gaps, provide quality control, and enable data from disparate measurement systems to be merged, while the observations anchor the results in reality. Hence data assimilation may be the best hope for

  4. Constraining Earth's Rheology of the Barents Sea Using Grace Gravity Change Observations

    NASA Astrophysics Data System (ADS)

    van der Wal, W.; Root, B. C.; Tarasov, L.

    2014-12-01

    The Barents Sea region was ice covered during last glacial maximum and experiences Glacial Isostatic Adjustment (GIA). Because of the limited amount of relevant geological and geodetic observations, it is difficult to constrain GIA models for this region. With improved ice sheet models and gravity observations from GRACE, it is possible to better constrain Earth rheology. This study aims to constrain the upper mantle viscosity and elastic lithosphere thickness from GRACE data in the Barents Sea region. The GRACE observations are corrected for current ice melting on Svalbard, Novaya Zemlya and Frans Joseph Land. A secular trend in gravity rate trend is estimated from the CSR release 5 GRACE data for the period of February 2003 to July 2013. Furthermore, long wavelength effects from distant large mass balance signals such as Greenland ice melting are filtered out. A new high-variance set of ice loading histories from calibrated glaciological modeling are used in the GIA modeling as it is found that ICE-5G over-estimates the observed GIA gravity change in the region. It is found that the rheology structure represented by VM5a results in over-estimation of the observed gravity change in the region for all ice sheet chronologies investigated. Therefore, other rheological Earth models were investigated. The best fitting upper mantle viscosity and elastic lithosphere thickness in the Barents Sea region are 4 (±0.5)*10^20 Pas and 110 (±20) km, respectively. The GRACE satellite mission proves to be a useful constraint in the Barents Sea Region for improving our knowledge on the upper mantle rheology.

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

    NASA Astrophysics Data System (ADS)

    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.

  6. Detectability of groundwater storage change within the Great Lakes Water Basin using GRACE

    NASA Astrophysics Data System (ADS)

    Huang, J.; Halpenny, J.; van der Wal, W.; Klatt, C.; James, T. S.; Rivera, A.

    2012-08-01

    Groundwater is a primary hydrological reservoir of the Great Lakes Water Basin (GLB), which is an important region to both Canada and US in terms of culture, society and economy. Due to insufficient observations, there is a knowledge gap about groundwater storage variation and its interaction with the Great Lakes. The objective of this study is to examine the detectability of the groundwater storage change within the GLB using the monthly models from the Gravity Recovery And Climate Experiment (GRACE) satellite mission, auxiliary soil moisture, snow and lake (SMSL) data, and predictions from glacial isostatic adjustment (GIA) models. A two-step filtering method is developed to optimize the extraction of GRACE signal. A two dimensional basin window weight function is also introduced to reduce ringing artifacts caused by the band-limited GRACE models in estimating the water storage change within the GLB. The groundwater storage (GWS) as deviation from a reference mean storage is estimated for the period of 2002 to 2009. The average GWS of the GLB clearly show an annual cycle with an amplitude range from 27 to 91 mm in water thickness equivalent (WTE), and a phase range of about two months. The estimated phases of GWS variations have a half year shift with respect to the phase of SMSL water storage variations which show peaks in March and April. The least squares estimation gives a GWS loss trend of from 2.3 to 9.3 km3/yr within the GLB for the period of study. This wide range of the GRACE GWS results is caused largely by the differences of soil moisture and snow storage from different land surface models (LSMs), and to a lesser extent by the GRACE commission and omission errors, and the GIA model error.

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

    NASA Astrophysics Data System (ADS)

    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

  8. A Smallsat Multi-pair GRACE-like Mission: Concept and Simulated Performance

    NASA Astrophysics Data System (ADS)

    Stephens, M.; Weimer, C. S.; Leitch, J. W.; Bennett, S. C.; Weinberg, J. D.; Rohrschneider, R.; Walther, R.; Landin, B.; Pierce, R.; Nerem, R. S.; Choe, J.

    2014-12-01

    The GRACE mission uses two spacecraft in near identical Earth orbits with a phase sensitive microwave ranging instrument that measures changes in spacecraft separation. High precision measurements of the spacecraft separation yield monthly Earth gravity field measurements. The GRACE FO mission adds the Laser Ranging Instrument (LRI) to demonstrate high resolution spacecraft separation measurements with phase-sensitive detection of a frequency-stabilized laser transponder. Previous studies show the improvements in mass change detection afforded by the higher sensitivity range change measurements. The sparse spatial/temporal sampling and single gravity field component detection of a polar orbiting satellite pair leads to aliasing and artifacts in the gravity field data. These effects limit the mass change detection capability of a GRACE-like mission. Adding a second pair of satellites improves overall system performance by filling in data gaps and sampling the gravity field in different directions. The added expense of a second satellite pair has made this option for improved performance untenable. A SmallSat GRACE-like mission addresses the cost concern for a multi-pair mission by reducing spacecraft expense and making common launch possible. Through use of a laser ranging sensor and other low-power subsystems and use of existing smallsat architectures, a complete spacecraft-instrument system is shown to meet measurement requirements and make the overall system expense comparable to existing single-pair missions. The resulting multi-pair space segment approach offers a viable option for a GRACE-like mission while improving the science through its better sampling of the gravity field. We show the system concept and simulated gravity field retrievals based on estimates of instrument and spacecraft performance.

  9. Hydrologic implications of GRACE satellite data in the Colorado River Basin

    NASA Astrophysics Data System (ADS)

    Scanlon, Bridget R.; Zhang, Zizhan; Reedy, Robert C.; Pool, Donald R.; Save, Himanshu; Long, Di; Chen, Jianli; Wolock, David M.; Conway, Brian D.; Winester, Daniel

    2015-12-01

    Use of GRACE (Gravity Recovery and Climate Experiment) satellites for assessing global water resources is rapidly expanding. Here we advance application of GRACE satellites by reconstructing long-term total water storage (TWS) changes from ground-based monitoring and modeling data. We applied the approach to the Colorado River Basin which has experienced multiyear intense droughts at decadal intervals. Estimated TWS declined by 94 km3 during 1986-1990 and by 102 km3 during 1998-2004, similar to the TWS depletion recorded by GRACE (47 km3) during 2010-2013. Our analysis indicates that TWS depletion is dominated by reductions in surface reservoir and soil moisture storage in the upper Colorado basin with additional reductions in groundwater storage in the lower basin. Groundwater storage changes are controlled mostly by natural responses to wet and dry cycles and irrigation pumping outside of Colorado River delivery zones based on ground-based water level and gravity data. Water storage changes are controlled primarily by variable water inputs in response to wet and dry cycles rather than increasing water use. Surface reservoir storage buffers supply variability with current reservoir storage representing ˜2.5 years of available water use. This study can be used as a template showing how to extend short-term GRACE TWS records and using all available data on storage components of TWS to interpret GRACE data, especially within the context of droughts. This article was corrected on 12 JAN 2016. See the end of the full text for details.

  10. Inferring regional surface mass anomalies from GRACE KBRR data by energy integral approach

    NASA Astrophysics Data System (ADS)

    Zhong, Bo; Luo, Zhicai; Li, Qiong; Zhou, Hao

    2016-04-01

    GRACE mission provides an effective technique to detect the mass redistribution through its effects on Earth gravity. Although the mass anomalies on the earth's surface inferred from the monthly average of the spherical harmonic coefficients has been largely successful, this approach has not revealed the submonthly time scale information and fundamental resolution of the GRACE observations. As the GRACE K-band range rate (KBRR) can reveal the local signature more sensitively, the regional recovered approach based on regional basic function is offered to recovery the local mass redistribution with submonthly and high spatial resolution. We established an approach to estimate regional surface mass anomalies by inverting GRACE-based potential difference anomalies at satellite altitude. Spatial constraints versus spherical distance between the mass concentrations are introduced to stabilize the linear system to eliminate the effects of the north-south striping. The efficiency of our approach has been validated using a closed-loop simulation study over South America. It is demonstrated that spatial constraints assist the solutions on reducing striping error inherent in the measurement configuration and temporal aliasing. Finally, time series of 10-day and 30-day regional surface mass anomalies over Tibet plateau also prove to be consistent with independent hydrological models. The time series of mass anomalies reveal the seasonal changes in the source area of three rivers and the accumulation in the north-east Gan-Qing block and Tibet block. Keywords: regional surface mass anomalies, GRACE KBRR, spatial constraints Acknowledgements: This research was jointly supported by the National 973 Program of China (No.2013CB733302), the National Natural Science Foundation of China (No.41474019, No.41131067,No. 41504014).