Science.gov

Sample records for plant grace c-m-g

  1. Site confirmation report. 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

    1982-03-01

    In January 1982, it was agreed to modify the Cooperative Agreement between W.R. Grace and Co. (Grace) and the US Department of Energy calling for the design and assessment of a coal-to-methanol-to-gasoline plant (Gasoline Plant) which would produce 50,000 barrels per day (BPD) of gasoline from high-sulfur agglomerating coal to include the preparation of a capital and operating cost estimate for a 12,500 BPD Gasoline Plant. The smaller 12,500 BPD Gasoline Plant uses the same basic equipment and processes as the larger plant. The major changes occur in process units after methanol synthesis, where two smaller sulfur recovery and removal units, one methanol-to-gasoline unit, a smaller fractionation unit, and smaller heavy gasoline treating and alkylation units are required. Thus, all processes used in the larger plant are used in the smaller plant. Products produced are identical but less in quantity. The coal pile is reduced considerably in size, and the concept of operation changed. The capacity of the steam generating facilities is reduced, but not by a factor of four, because sufficient steam is still required to start up the air separation plants. There are fewer air separation plants, but each still has a capacity of 2500 TPD. However, instead of three steam generating units each capable of generating 600,000 lb/hr of steam, fewer units of somewhat smaller capacity are used in the 12,500 BPD Gasoline Plant. Consequently, the reduction in scale does not influence the processes used to remove particulates and SO/sub x/ from flue gas. Fewer cooling towers, or towers of reduced capacity, are required instead of the four necessary for the 50,000 BPD Gasoline Plant.

  2. 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.

  3. 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)

  4. Amazing Grace

    NASA Astrophysics Data System (ADS)

    Talbot, G.; Chopping, A.; Dee, K.; Gray, D.; Jolley, P.

    2003-12-01

    T he profile of the William Herschel Telescope (WHT) has changed since the beginning of this year, with the addition of a new facility at one of the telescope's Nasmyth platforms. For many years the WHT has had the GHRIL building on the Nasmyth1 platform - now the ING has added GRACE to the opposite side of the telescope. GRACE (GRound based Adaptive optics Controlled Environment) is a dedicated structure designed to facilitate the routine use of adaptive optics (AO) at the WHT, using ING's AO instrument suite. The design of GRACE allows for the future use of laser guide stars.

  5. 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.

  6. Grace Nash: Nine Decades of Graceful Teaching.

    ERIC Educational Resources Information Center

    Cole, Judith

    2000-01-01

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

  7. 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…

  8. 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.…

  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 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.…

  11. 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…

  12. GRACE Hydrology: Applications of Current and Future GRACE Missions

    NASA Astrophysics Data System (ADS)

    Bolten, J. D.; Srinivasan, M. M.; Ivins, E. R.; Rodell, M.; Landerer, F. W.; Zaitchik, B.; Bergaoui, K.; McDonnell, R.; Hung, C. J.; Lakshmi, V.; Famiglietti, J. S.

    2013-12-01

    The Gravity Recovery And Climate Experiment (GRACE) mission has delivered over a decade of continuous data on global mass variations, providing unprecedented observations of global change. In addition to solid Earth, cryosphere, and oceanography applications of the data, the relevance of GRACE for hydrology studies is abundant and expanding. GRACE is being used to estimate large-scale aquifer dynamics, improve drought and flood monitoring, and constrain regional hydrological estimates by assimilating GRACE terrestrial water storage observations into hydrological models. Recently, GRACE data have been successfully applied to enhance hydrological estimates in North America, Middle East Northern Africa, and the Lower Mekong River Basin regions. The extended time series from GRACE into the GRACE-II future is expected to support global water management plans and strategies, enhance understanding of climate variations such as drought, and allow for continued monitoring of large-scale basins into the coming decade. Thus, a significant objective of future GRACE applications efforts is to leverage off of these activities and develop useful tools for water resources management, and to provide more effective and timely data input for large-scale operational hydrological applications such as drought monitoring and flood risk assessments. A summary of several GRACE activities and a strategy for incorporating future GRACE FO into these projects will be presented.

  13. 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.

  14. Remote Sensing of Groundwater with GRACE and GRACE Follow On

    NASA Astrophysics Data System (ADS)

    Rodell, M.; Famiglietti, J. S.; Reager, J. T., II; Wiese, D. N.; Beaudoing, H. K.; Li, B.

    2016-12-01

    Aquifers provide an alternative, reliable source of fresh water when precipitation and surface waters are insufficient, and as a result people worldwide depend on groundwater for domestic water and crop irrigation. However, groundwater is difficult to monitor because it is hidden deep below the surface. Outside of a few industrialized nations groundwater is not monitored systematically, and where it is the data are rarely centralized and publicly available. Since 2002 the NASA/German 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 distinguish groundwater from other types of water on and under the land surface, and its typical 2-3 month data latency. Nevertheless, GRACE provides the only global, consistent measurements that are directly applicable for groundwater monitoring. This presentation will describe what we have learned to date from GRACE about regional to global scale groundwater variability and trends. While GRACE will stop delivering data near the end of 2017, the GRACE Follow On mission is scheduled to launch by February 2018, enabling this essential climate data record to continue.

  15. 42 CFR 136a.33 - Grace period.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

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

  16. The Vigorous Pursuit of Grace and Style.

    ERIC Educational Resources Information Center

    Walpole, Jane R.

    Grace and style are elements of composition rarely demanded by teachers or developed by students. Since both terms are elusive to define and because asking students to make attempts at grace and style can have unappealing results, perhaps vigor is a better element to encourage students to pursue. Vigor does not outlaw graceful flourishes and…

  17. 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…

  18. Say Good-Bye Gracefully.

    ERIC Educational Resources Information Center

    Armstrong, Coleen

    1994-01-01

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

  19. Graceful entrance to braneworld inflation

    SciTech Connect

    Lidsey, James E.; Mulryne, David J.

    2006-04-15

    Positively-curved, oscillatory universes have recently been shown to have important consequences for the preinflationary dynamics of the early universe. In particular, they may allow a self-interacting scalar field to climb up its potential during a very large number of these cycles. The cycles are naturally broken when the potential reaches a critical value and the universe begins to inflate, thereby providing a 'graceful entrance' to early universe inflation. We study the dynamics of this behavior within the context of braneworld scenarios which exhibit a bounce from a collapsing phase to an expanding one. The dynamics can be understood by studying a general class of braneworld models that are sourced by a scalar field with a constant potential. Within this context, we determine the conditions a given model must satisfy for a graceful entrance to be possible in principle. We consider the bouncing braneworld model proposed by Shtanov and Sahni and show that it exhibits the features needed to realise a graceful entrance to inflation for a wide region of parameter space.

  20. 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.

  1. 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,…

  2. 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…

  3. Grace and Courtesy for the Whole School

    ERIC Educational Resources Information Center

    Cobb, Mary Lou

    2015-01-01

    Mary Lou Cobb gives a framework from a very practical point of view, leaning on the aspects of grace and courtesy that are fundamental and arise out of a Montessori administrative point of view. Her examples are pragmatic, such as the grace and courtesy of a greeting, of movement, as a whole-school culture, and the right use of language. She calls…

  4. 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.

  5. 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.

  6. 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.

  7. 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. .

  8. Groundwater Depletion in India Revealed by GRACE

    NASA Image and Video Library

    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...

  9. 15 Years of GRACE Earth Observations

    NASA Image and Video Library

    2017-03-15

    For 15 years, the GRACE mission has unlocked mysteries of how water moves around our planet. It gave us the first view of underground aquifers from space, and shows how fast polar ice sheets and mountain glaciers are melting.

  10. GRACE Sees Groundwater Losses Around the World

    NASA Image and Video Library

    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....

  11. 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.

  12. The GRACE Mission Status and Future Directions

    NASA Astrophysics Data System (ADS)

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

    The twin satellites of the Gravity Recovery and Climate Experiment (GRACE) were launched on March 17, 2002 and have operated continuously for over 12 years. During this time, the results from this mission have been used in a wide range of contemporary studies of Earth System Dynamics. 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 and have been applied in numerous science and application related investigations. The RL05 mean and combined models, involving the GRACE/GOCE data combinations, are still in development. This presentation will review some of the science improvements from the RL05 data and the remaining tasks to be conducted in completing the solution, describe the current mission status and the current operations, which are focused on extending enhance the mission lifetime. Finally, plans for the GRACE Follow On Mission, whose objectives extend the GRACE measurement set, will be discussed.

  13. Uncertainty in ocean mass trends from GRACE

    NASA Astrophysics Data System (ADS)

    Quinn, Katherine J.; Ponte, Rui M.

    2010-05-01

    Ocean mass, together with steric sea level, are the key components of total observed sea level change. Monthly observations from the Gravity Recovery and Climate Experiment (GRACE) can provide estimates of the ocean mass component of the sea level budget, but full use of the data requires a detailed understanding of its errors and biases. We have examined trends in ocean mass calculated from 6 yr of GRACE data and found differences of up to 1 mmyr-1 between estimates derived from different GRACE processing centre solutions. In addition, variations in post-processing masking and filtering procedures required to convert the GRACE data into ocean mass lead to trend differences of up to 0.5 mmyr-1. Necessary external model adjustments add to these uncertainties, with reported postglacial rebound corrections differing by as much as 1 mmyr-1. Disagreement in the regional trends between the GRACE processing centres is most noticeably in areas south of Greenland, and in the southeast and northwest Pacific Ocean. Non-ocean signals, such as in the Indian Ocean due to the 2004 Sumatran-Andean earthquake, and near Greenland and West Antarctica due to land signal leakage, can also corrupt the ocean trend estimates. Based on our analyses, formal errors may not capture the true uncertainty in either regional or global ocean mass trends derived from GRACE.

  14. Uncertainty in ocean mass trends from GRACE

    NASA Astrophysics Data System (ADS)

    Quinn, K. J.; Ponte, R. M.

    2009-12-01

    Ocean mass, together with steric sea level, are the key components of total observed sea level rise. Monthly observations from the Gravity Recovery and Climate Experiment (GRACE) can provide estimates of the ocean mass component of the sea level budget, but full use of the data requires a detailed understanding of its errors and biases. We have examined trends in ocean mass calculated from six years of GRACE data and found differences of up to 1 mm/yr between estimates derived from different GRACE processing center solutions. In addition, variations in post-processing masking and filtering procedures required to convert the GRACE data into ocean mass lead to trend differences of up to 0.5 mm/yr. Necessary external model adjustments add to these uncertainties, with reported post-glacial rebound corrections differing by as much as 1 mm/yr. Disagreement in the regional trends between the GRACE processing centers is most noticeable in areas south of Greenland, and in the southeast and northwest Pacific Ocean. Non-ocean signals, such as in the Indian Ocean due to the 2004 Sumatran-Andean earthquake, and near Greenland and West Antarctica due to land signal leakage, can also corrupt the ocean trend estimates. Based on our analyses, formal errors may not capture the true uncertainty in either regional or global ocean mass trends derived from GRACE.

  15. 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/).

  16. 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.

  17. 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.

  18. Analysis of the GRACE Gravity Sensor System

    NASA Astrophysics Data System (ADS)

    Frommknecht, B.; Meyer, U.; Schmidt, R.; Flechtner, F.

    2007-12-01

    The quality, strength and homogeneity of global gravity field models from the US-German gravity mission GRACE (Gravity Recovery and Climate Experiment, launched in 2002) is unprecedented and the derived models are superior to any previous satellite-only gravity field model. However, the predicted accuracy of these GRACE-only models (so-called GRACE baseline) has not yet been completely reached, thus still limiting a full geophysical exploitation of the GRACE mission data. Among others, the cause could lie in a degraded performance or interaction of elements of the gravity field sensor system. Another possible reason is that suboptimal signal processing methods have been applied. The gravity field sensor system consists of the K-Band distance measurements, the star sensor data for the orientation in inertial space, the accelerometer data and the GPS phase and code data. This investigation focuses on the analysis of the raw star sensor data and the related signal processing applied to generate higher level (so-called L1B) star sensor data which are used in the gravity recovery process. First, the performance of the raw star sensor data is discussed. Then the related signal processing is analyzed: In particular we investigate 1) the combination of star sensor data from the two available sensor heads aboard each GRACE satellite and 2) the combination of the star sensor and the angular acceleration data to derive improved(?) L1B star sensor data. The results are discussed and the expected impact on the gravity field recovery is evaluated.

  19. 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.; hide

    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.

  20. 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.

  1. 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... calendar days following the maturity of a time deposit, the bank may continue to pay interest on...

  2. 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…

  3. 42 CFR 408.8 - Grace period and termination date.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... subsequent monthly or quarterly payments, the grace period ends with the last day of the third month after... employees, the grace period is extended to the next succeeding work day. (c) Termination date. The end of... premium, the grace period ends on April 30 of the year following the calendar year which the premiums are...

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. Does GRACE see the water cycle 'intensifying'?

    NASA Astrophysics Data System (ADS)

    Eicker, Annette; Kusche, Jürgen; Forootan, Ehsan; Springer, Anne; Schumacher, Maike; Ohlwein, Christian

    2014-05-01

    Several researchers have postulated that, under a changing climate due to anthropogenic forcing, an intensification of the water cycle is already under way (Huntington, 2006). This is usually related to increases in hydrological fluxes such 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) would lead to acceleration or deceleration of water storage anomalies possibly visible in GRACE time series, when discharge variability is small or properly accounted for. We investigate to what extent such accelerations, which are indeed found in maps of global gridded GRACE water storage anomalies, can be explained using output fields derived from global and regional atmospheric (re-)analyses and from hydrological models. We find this analysis challenging, since the GRACE time series is short and dominated by ENSO-type natural variability. Observed accelerations strongly depend on the analysis time frame, and may be explained to a large percentage by natural variability, thus masking a possible anthropogenically driven intensification of the terrestrial water cycle. This motivates us to apply statistical decomposition techniques in order to identify modes of natural variabilities and to remove them from the GRACE time series prior to the estimation of accelerations. Huntington T.G. (2006): Evidence for intensification of the global water cycle: Review and synthesis. J. Hydrology, 319:83-95

  10. 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…

  11. The GRACE Mission in the Final Stage

    NASA Astrophysics Data System (ADS)

    Tapley, B. D.; Flechtner, F.; Watkins, M. M.; Boening, C.; Bettadpur, S. V.

    2016-12-01

    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. The mission is entering the final phase of operations. The current mission operations strategy emphasizes extending the mission lifetime to achieve mission overlap with the GRACE Follow On Mission, whose launch is scheduled for late 2017. The mission operations decisions necessary to extend the mission lifetime impact both the science data yield and the data quality. This presentation will review the mission status, 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 on the science data products during the remaining mission lifetime.

  12. Antarctic mass balance changes from GRACE

    NASA Astrophysics Data System (ADS)

    Kallenberg, B.; Tregoning, P.

    2012-04-01

    The Antarctic ice sheet contains ~30 million km3 of ice and constitutes a significant component of the global water balance with enough freshwater to raise global sea level by ~60 m. Altimetry measurements and climate models suggest variable behaviour across the Antarctic ice sheet, with thickening occurring in a vast area of East Antarctica and substantial thinning in West Antarctica caused by increased temperature gradients in the surrounding ocean. However, the rate at which the polar ice cap is melting is still poorly constrained. To calculate the mass loss of an ice sheet it is necessary to separate present day mass balance changes from glacial isostatic adjustment (GIA), the response of the Earth's crust to mass loss, wherefore it is essential to undertake sufficient geological and geomorphological sampling. As there is only a limited possibility for this in Antarctica, all models (i.e. geological, hydrological as well as atmospheric) are very poorly constrained. Therefore, space-geodetic observations play an important role in detecting changes in mass and spatial variations in the Earth's gravity field. The Gravity Recovery And Climate Experiment (GRACE) observed spatial variations in the Earth's gravity field over the past ten years. The satellite detects mass variations in the Earth system including geophysical, hydrological and atmospheric shifts. GRACE itself is not able to separate the GIA from mass balance changes and, due to the insufficient geological and geomorphological database, it is not possible to model the GIA effect accurately for Antarctica. However, the results from GRACE can be compared with other scientific results, coming from other geodetic observations such as satellite altimetry and GPS or by the use of geological observations. In our contribution we compare the GRACE data with recorded precipitation patterns and mass anomalies over East Antarctica to separate the observed GRACE signal into its two components: GIA as a result of mass

  13. 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

  14. 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.

  15. 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.

  16. 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).

  17. 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).

  18. Tracking Flooding, Drought, Fire and other Natural Hazards with GRACE

    NASA Astrophysics Data System (ADS)

    Famiglietti, J. S.

    2015-12-01

    While the NASA GRACE mission has proven adept at tracking rates of ice sheet melting, ocean mass rise, and groundwater depletion, its contributions to understanding regional flooding, drought and fire have received less attention. In this presentation we review the status of GRACE efforts to characterize regional flood potential, quantification of drought parameters, and the occurrence of fire. Examples are used to demonstrate how the use of GRACE data can improve early warning times, or can enhance existing operational methodologies.

  19. 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...

  20. Monitoring Continental Water Mass Variations by GRACE

    NASA Astrophysics Data System (ADS)

    Mercan, H.; Akyılmaz, O.

    2015-12-01

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

  1. 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.

  2. Groundwater Storage Changes: Present Status from GRACE Observations

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  3. 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.

  4. Groundwater Storage Changes: Present Status from GRACE Observations

    NASA Technical Reports Server (NTRS)

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

    2015-01-01

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

  5. High-resolution CSR GRACE RL05 mascons

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  6. 33 CFR 147.1102 - Platform GRACE safety zone.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 33 Navigation and Navigable Waters 2 2014-07-01 2014-07-01 false Platform GRACE safety zone. 147.1102 Section 147.1102 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.1102 Platform GRACE safety zone. (a...

  7. 33 CFR 147.1102 - Platform GRACE safety zone.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 33 Navigation and Navigable Waters 2 2012-07-01 2012-07-01 false Platform GRACE safety zone. 147.1102 Section 147.1102 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.1102 Platform GRACE safety zone. (a...

  8. 33 CFR 147.1102 - Platform GRACE safety zone.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 33 Navigation and Navigable Waters 2 2011-07-01 2011-07-01 false Platform GRACE safety zone. 147.1102 Section 147.1102 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.1102 Platform GRACE safety zone. (a...

  9. 33 CFR 147.1102 - Platform GRACE safety zone.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Platform GRACE safety zone. 147.1102 Section 147.1102 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.1102 Platform GRACE safety zone. (a...

  10. 33 CFR 147.1102 - Platform GRACE safety zone.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 33 Navigation and Navigable Waters 2 2013-07-01 2013-07-01 false Platform GRACE safety zone. 147.1102 Section 147.1102 Navigation and Navigable Waters COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) OUTER CONTINENTAL SHELF ACTIVITIES SAFETY ZONES § 147.1102 Platform GRACE safety zone. (a...

  11. 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.

  12. Antarctic tides from GRACE satellite accelerations

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  14. 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

  15. 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.

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

    NASA Astrophysics Data System (ADS)

    Cheng, Minkang; Ries, John

    2017-08-01

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

  17. 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.

  18. Estimation of GRACE water storage components by temporal decomposition

    NASA Astrophysics Data System (ADS)

    Andrew, Robert; Guan, Huade; Batelaan, Okke

    2017-09-01

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

  19. Towards a global GRACE basin-scale database

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Managing water resources is a critical issue because of water scarcity, increased anthropic pressure and reduced reliability related to climate change. The GRACE mission has emerged as the first satellite able to measure total water storage variations and solve water budgets with sufficient accuracy and spatial sensitivity to monitor hydrological systems larger than ~200 000 km2. The objective of this study was to increase access to GRACE water storage variations by providing processed GRACE data for river basins globally. Particular attention was paid to provide unbiased water storage with associated uncertainty estimates, with processing methods validated on the highly instrumented High Plains Aquifer. The global GRACE product includes time series of GRACE total water storage changes (TWSC) from 2002 - 2012 and GLDAS land surface model soil moisture outputs (NOAH, CLM, VIC, and MOSAIC) to estimate GRACE groundwater storage changes. We show how this GRACE product can be used to solve water budgets by applying it to depleted aquifers for irrigation in the Ganges and California Central Valley.

  20. Development of a Daily GRACE Water Storage Estimate for Hydrology

    NASA Astrophysics Data System (ADS)

    Croteau, M. J.; Loomis, B.; Luthcke, S. B.; Nerem, R. S.

    2016-12-01

    As a global data source, GRACE water storage estimates have enabled studies of large-scale hydrological signals, and efforts have been made to use these estimates in hydrological forecasting and modeling. Unfortunately, these efforts are hindered by GRACE's temporal resolution. To date, the majority of GRACE products are released on monthly timescales to ensure maximum global spatial resolution. While some products have been developed on shorter timescales, there is a desire to further improve the temporal resolution of GRACE data in order to better and more completely integrate GRACE data into hydrological modeling. This study discusses the development of a daily-updated GRACE mascon solution that aims to address this goal. Leveraging the GSFC monthly mascon solution process and GEODYN estimation program, monthly converged GRACE mascons are used as a background model in our estimation technique. Data is processed daily to estimate variations on the monthly solution using a least squares approach, driven by the tracks of the twin GRACE satellites. The work done in this study largely centers on the development and tuning of the least squares constraints and regularization of the mascon solution. We describe the methodology to ensure a valid solution. As a result, the developed daily solutions are an iteration of the monthly solutions distributed by GSFC. We summarize the solution process and report the initial results of our new daily solutions. Drainage basins are investigated to study the impacts of these daily results on basin water storage estimates. Comparisons are made with monthly GRACE solutions, focusing on new information provided by the recovered sub-monthly signal.

  1. GRACE Harmonic and Mascon Solutions at JPL

    NASA Astrophysics Data System (ADS)

    Watkins, M. M.; Yuan, D.; Kuang, D.; Bertiger, W.; Kim, M.; Kruizinga, G. L.

    2005-12-01

    Gravity field solutions at JPL over the past few years have explored use of range, range-rate, and range-acceleration K/Ka-band satellite-satellite data types (with and without GPS), and with both spherical harmonic and mascon-type local mass representations. Until recently, resource and computing limitations have limited the scope of our mascon and other local solutions to a few months and/or small spatial regions and the standard GRACE products have remained spherical harmonic fields. The use of a new very large (~500 node) beowulf machine at JPL is now enabling a wider range of solutions over longer time spans and deeper understanding of their characteristics. These include much higher spherical harmonic degrees, mascons, and hybrids of the two. We will present the current status for several solution types, strengths and weaknesses of each, and our assessments of limiting errors including data noise and aliasing sensitivity.

  2. 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...

  3. 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...

  4. LISA-like Laser Ranging for GRACE Follow-on

    NASA Astrophysics Data System (ADS)

    Schütze, D.; Stede, G.; Müller, V.; Gerberding, O.; Mahrdt, C.; Sheard, B.; Heinzel, G.; Danzmann, K.

    2013-01-01

    The Gravity Recovery and Climate Experiment (GRACE) mission successfully demonstrated that low-orbit satellite-to-satellite tracking is a powerful tool to analyze spatial and temporal changes in Earth's gravity field. Especially hydrological mass transports are well-resolved. To continue longterm observations, a GRACE follow-on mission is planned for 2017 which will almost be an identical copy of the GRACE mission. Additionally, for technological demonstration, a Laser Ranging Interferometer is planned supplementary to the conventional microwave ranging device to potentially improve the intersatellite range measurements. The frequency band of interest for Earth gravity observations coincides with the LISA frequency band, thus LISA technology can be inherited. We describe the basic concept of the Laser Ranging Interferometer for GRACE follow-on and present a testbed to investigate its functionality and key components.

  5. Thermospheric density and winds from GRACE accelerometer data

    NASA Astrophysics Data System (ADS)

    Cheng, Minkang; Tapley, Byron D.; Bettadpur, Srinivas; Ries, John C.

    The high-accuracy accelerometer data carried by the GRACE satellites represents the best measurements of the total surface forces acting on the spacecraft, including atmospheric drag, solar and earth radiation pressure. The GRACE accelerometer data are particularly well suited for exploring the variation in the thermospheric density and winds in response to changes in the solar and magnetic activity. In this study, the total atmospheric neutral density and winds are derived from analysis of the accelerometer data over a six-year period starting August 2002, which spans the complete range of solar activity. This paper will present the comparison of the six-year GRACE density with several density models, including DTM-78, NRLMSIS-00, JB2006 and HASDM. The GRACE-derived thermospheric winds will be compared with the HWM-93 model.

  6. Status of the GRACE Follow-On Mission

    NASA Astrophysics Data System (ADS)

    Watkins, M.; Flechtner, F.

    2012-04-01

    GRACE Follow-On, a joint US/German 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 early January 2012, GRACE FO was advanced by NASA to Phase A following the successful MIssion Concept Review in late October, 2011. The key teams are now onboard for major spacecraft and payload system (microwave system, GPS, Accelerometer, and Laser interferometer system) development in both the US and in Germany, heading for System Requirements Review in May 2012, allowing transition to Phase B in summer 2012. In this talk, we will present the latest programmatic and technical status of the mission, with special attention to important improvements to observed systematic errors in GRACE, and potential impact to gravity field accuracy.

  7. 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.

  8. 1. Historic American Buildings Survey Courtesy Mrs. Grace S. Caldron ...

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

    1. Historic American Buildings Survey Courtesy Mrs. Grace S. Caldron (Granddaughter of Geronimo Lopez Photo: ca. 1900 SOUTHEAST CORNER - Casa de Geronimo Lopez, 1102 Pico Street, San Fernando, Los Angeles County, CA

  9. 2. Historic American Buildings Survey Courtesy Mrs. Grace S. Caldron ...

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

    2. Historic American Buildings Survey Courtesy Mrs. Grace S. Caldron (Granddaughter of Geronimo Lopez Photo: ca. 1912 NORTHEAST ELEVATION - Casa de Geronimo Lopez, 1102 Pico Street, San Fernando, Los Angeles County, CA

  10. Evaluation of GRACE data using terrestrial gravity observations

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  11. GRACE and GEORGE: Autonomous Robots for the AAAI Robot Challenge

    DTIC Science & Technology

    2004-01-01

    GRACE and GEORGE: Autonomous Robots for the AAAI Robot Challenge Reid Simmons, Allison Bruce, Dani Goldberg, Adam Goode, Michael Montemerlo, Nicholas...2004 2. REPORT TYPE 3. DATES COVERED - 4. TITLE AND SUBTITLE GRACE and GEORGE: Autonomous Robots for the AAAI Robot Challenge 5a. CONTRACT...Simmons. “A Social Robot that Stands in Line.” Autonomous Robots , 12:3 pp.313-324, May 2002. [Ortony, 1988] A. Ortony, G. L. Clore, and A. Collins

  12. Recent GRACE-Enabled Hydrologic Research and Applications

    NASA Technical Reports Server (NTRS)

    Rodell, Matt; Farmiglietti, Jay

    2011-01-01

    This presentation will describe recent hydrology research and applications which make use of GRACE data. These include the following: 1) water balance estimates of evapotranspiration over several large river basins; 2) a summary of NASA's Energy and Water Cycle Study (NEWS) state of the global water budget project; 3) drought indicator products now being incorporated into the U.S. Drought Monitor; 4) new GRACE data assimilation results over several regions

  13. Grace buys aquatic quimica to boost water treatment stake

    SciTech Connect

    Hunter, D.

    1993-02-17

    How W.R. Grace (Boca Raton, FL) president and newly appointed CEO J.P. Bolduc plans to expand Grace's core businesses following his drastic portfolio pruning during the past 18 months is a key question for Grace watchers. Grace's acquisition of $70-million/year water treatment firm Aquatec Quimica (Sao Paulo) is one indicator. Grace's $300-million/year Dearborn water treatment business is currently a weak number three [in the world market], and we want to be number one or number two, nothing less, Bolduc insists. The Aquatc buy meets his criterion of a synergistic and strategic acquisition with which he plans to expand the business, backed by more focused R D. Disposal last month of Homco oil field services operation, for $98.5 million, takes Bolduc toward his $500-million target for the year for asset sales. These totaled $1.1 billion at the end of 1992. The final tally will be more than the $1.5-billion target previously stated, Bolduc says, due to higher realizations on certain sales and additions to the list, including Grace Culinary and Colowyo Coal.

  14. Using GRACE to constrain precipitation amount over cold mountainous basins

    NASA Astrophysics Data System (ADS)

    Behrangi, Ali; Gardner, Alex S.; Reager, John T.; Fisher, Joshua B.

    2017-01-01

    Despite the importance for hydrology and climate-change studies, current quantitative knowledge on the amount and distribution of precipitation in mountainous and high-elevation regions is limited due to instrumental and retrieval shortcomings. Here by focusing on two large endorheic basins in High Mountain Asia, we show that satellite gravimetry (Gravity Recovery and Climate Experiment (GRACE)) can be used to provide an independent estimate of monthly accumulated precipitation using mass balance equation. Results showed that the GRACE-based precipitation estimate has the highest agreement with most of the commonly used precipitation products in summer, but it deviates from them in cold months, when the other products are expected to have larger errors. It was found that most of the products capture about or less than 50% of the total precipitation estimated using GRACE in winter. Overall, Global Precipitation Climatology Project (GPCP) showed better agreement with GRACE estimate than other products. Yet on average GRACE showed 30% more annual precipitation than GPCP in the study basins. In basins of appropriate size with an absence of dense ground measurements, as is a typical case in cold mountainous regions, we find GRACE can be a viable alternative to constrain monthly and seasonal precipitation estimates from other remotely sensed precipitation products that show large bias.

  15. Global Assessment of New GRACE Mascons Solutions for Hydrologic Applications

    NASA Astrophysics Data System (ADS)

    Save, H.; Zhang, Z.; Scanlon, B. R.; Wiese, D. N.; Landerer, F. W.; Long, D.; Longuevergne, L.; Chen, J.

    2016-12-01

    Advances in GRACE (Gravity Recovery and Climate Experiment) satellite data processing using new mass concentration (mascon) solutions have greatly increased the spatial localization and amplitude of recovered total Terrestrial Water Storage (TWS) signals; however, limited testing has been conduct on land hydrologic applications. In this study we compared TWS anomalies from (1) Center for Space Research mascons (CSR-M) solution with (2) NASA JPL mascon (JPL-M) solution, and with (3) a CSR gridded spherical harmonic rescaled (sf) solution from Tellus (CSRT-GSH.sf) in 176 river basins covering 80% of the global land area. There is good correspondence in TWS anomalies from mascons (CSR-M and JPL-M) and SH solutions based on high correlations between time series (rank correlation coefficients mostly >0.9). The long-term trends in basin TWS anomalies represent a relatively small signal (up to ±20 mm/yr) with differences among GRACE solutions and inter-basin variability increasing with decreasing basin size. Long-term TWS declines are greatest in (semi)arid and irrigated basins. Annual and semiannual signals have much larger amplitudes (up to ±250 mm). There is generally good agreement among GRACE solutions, increasing confidence in seasonal fluctuations from GRACE data. Rescaling spherical harmonics to restore lost signal increases agreement with mascons solutions for long-term trends and seasonal fluctuations. There are many advantages to using GRACE mascons solutions relative to SH solutions, such as reduced leakage from land to ocean increasing signal amplitude, and constraining results by applying geophysical data during processing with little or no post-processing requirements, making mascons more user friendly for non-geodetic users. This inter-comparison of various GRACE solutions should allow hydrologists to better select suitable GRACE products for hydrologic applications.

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

    NASA Astrophysics Data System (ADS)

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

    2017-08-01

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

  17. Studies of GRACE Gravity Field Inversion Techniques

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  18. 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

  19. 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.

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

    NASA Astrophysics Data System (ADS)

    McKenzie, Kirk

    We propose to develop in-flight tests of high-risk elements of laser interferometry for gravitational wave astronomy missions, such as the Laser Interferometer Space Antenna (LISA) mission, for deployment on the GRACE-FO mission. The proposed set of experiments, LISA Experience from GRACE-FO Optical Payload (LEGOP), exploits the similarities between the LISA and GRACE-FO optical links to use GRACE-FO as a "mission of opportunity" for demonstration of high-risk and innovative technologies for the LISA mission. We will develop FPGA algorithms for the tests and perform laboratory experiments and hardware-in-the-loop simulations to verify them. Specifically, we will target the following aspects of LISA inter-spacecraft interferometry: 1. Absolute optical-ranging and Time Delay Interferometry (TDI). TDI is the process used on LISA to combine one-way inter-spacecraft measurements to form synthesized interferometers, such as the Michelson interferometer, that are free of laser frequency noise, but retain the gravitational wave signal. The one-way measurements must be combined with precise delays, proportional to the light travel time between spacecraft (the range) and difference of on board clocks. The proposed in-flight experiment would see a LISA like optical ranging system deployed to provide the required delays for a TDI experiment on GRACE-FO. We will develop the FPGA code required for this experiment and perform validation of this optical-ranging system for GRACE-FO through a TDI experiment on the JPL LISA interferometer testbed. 2. Arm-locking: A technique for transferring the stability of the spacecraft separation to the laser frequency. Because arm-locking uses the LISA arms, the best frequency reference available, it offers unparalleled stability and requires no additional flight hardware. It cannot be demonstrated experimentally in a LISA-like environment on Earth. An in-flight demonstration of arm-locking would validate the operation of arm- locking, enabling

  1. 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.

  2. GRACE storage-runoff hystereses reveal the dynamics of ...

    EPA Pesticide Factsheets

    Watersheds function as integrated systems where climate and geology govern the movement of water. In situ instrumentation can provide local-scale insights into the non-linear relationship between streamflow and water stored in a watershed as snow, soil moisture, and groundwater. However, there is a poor understanding of these processes at the regional scale—primarily because of our inability to measure water stores and fluxes in the subsurface. Now NASA’s Gravity Recovery and Climate Experiment (GRACE) satellites quantify changes in the amount of water stored across and through the Earth, providing measurements of regional hydrologic behavior. Here we apply GRACE data to characterize for the first time how regional watersheds function as simple, dynamic systems through a series of hysteresis loops. While the physical processes underlying the loops are inherently complex, the vertical integration of terrestrial water in the GRACE signal provides process-based insights into the dynamic and non-linear function of regional-scale watersheds. We use this process-based understanding with GRACE data to effectively forecast seasonal runoff (mean R2 of 0.91) and monthly runoff (mean R2 of 0.77) in three regional-scale watersheds (>150,000 km2) of the Columbia River Basin, USA. Data from the Gravity Recovery and Climate Experiment (GRACE) satellites provide a novel dataset for understanding changes in the amount of water stored across and through the surface of the Ear

  3. An Adiabatic Quantum Algorithm for Determining Gracefulness of a Graph

    NASA Astrophysics Data System (ADS)

    Hosseini, Sayed Mohammad; Davoudi Darareh, Mahdi; Janbaz, Shahrooz; Zaghian, Ali

    2017-07-01

    Graph labelling is one of the noticed contexts in combinatorics and graph theory. Graceful labelling for a graph G with e edges, is to label the vertices of G with 0, 1, ℒ, e such that, if we specify to each edge the difference value between its two ends, then any of 1, 2, ℒ, e appears exactly once as an edge label. For a given graph, there are still few efficient classical algorithms that determine either it is graceful or not, even for trees - as a well-known class of graphs. In this paper, we introduce an adiabatic quantum algorithm, which for a graceful graph G finds a graceful labelling. Also, this algorithm can determine if G is not graceful. Numerical simulations of the algorithm reveal that its time complexity has a polynomial behaviour with the problem size up to the range of 15 qubits. A general sufficient condition for a combinatorial optimization problem to have a satisfying adiabatic solution is also derived.

  4. Determination of the Earth's structure in Fennoscandia from GRACE and implications for the optimal post-processing of GRACE data

    NASA Astrophysics Data System (ADS)

    Steffen, Holger; Wu, Patrick; Wang, Hansheng

    2010-09-01

    Analysis of data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission allows us to identify regions of long-term mass changes such as the areas of Glacial Isostatic Adjustment (GIA) in North America and Fennoscandia. As there are now more than 7 yr of data available, the determined trends are robust enough for the inference of viscosity structure of the Earth's mantle. In this study, we focus on the Fennoscandian rebound area as there are abundant high-quality terrestrial data to use as ground-truth. In the first step, GRACE data are taken to fix the optimal radial (1-D) viscosity profile and the lithospheric thickness combination, which are needed as background parameters in 3-D earth modelling. The results are in basic agreement with results based upon relative sea level and GPS data, showing a lithospheric thickness in Fennoscandia between 90 and 160 km and an upper mantle viscosity of about [2-4] × 1020 Pa s. The lower mantle viscosity is poorly resolved, however. In the second step, GRACE data are used to constrain the 3-D viscosity using spherical finite element modelling. In this case, the results also agree with past investigations, but GRACE data alone cannot discriminate between lateral heterogeneities in the mantle that are thermal in origin from those due to changes in chemical composition. More notably, we treat in detail GRACE-related questions such as implementation of an adequate Level-2 filter technique and identification of the best reduction method for hydrological mass change signals. It turns out that the Gaussian filter technique is the best for this type of investigation. Even the best global hydrology models used in GRACE investigations still fail to improve the mismatches-thus one should be careful not to blindly use them for `improving' GIA models in North America or other centres of rebound. In conclusion, our study clearly shows that GRACE data greatly complement the study of GIA. As there are new GRACE releases in

  5. Water Level Temporal Variation Analysis at Prata Basin Using GRACE

    NASA Astrophysics Data System (ADS)

    Guimaraes, G.; Blitzkow, D.; Matos, A.; Vaz, F.; Campos, I.; Barbosa, A.

    2008-12-01

    A comparison between daily in-situ water level time series measured at ground-based hydrometric stations of Agência Nacional de Águas (ANA) with vertically-integrated water height deduced from GRACE geoid (height anomaly) is carried out. The 10-day intervals of GRACE models were computed by Groupe de Recherches de Géodésie Spatiale (CNES/GRGS). The height anomaly was converted into equivalent water height, over the Prata basin for a ~6-year period (July-2002 to May-2008). A correlation around 74 per cent has been detected. This correlation allows defining a local transfer function by adjusting a linear relationship between GRACE-based and in situ observation time-series. The study of the Continuous Wavelet Transform was applied in the hydrometric stations and a time-scale correlation was figured out.

  6. 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

  7. Response to Grace's Reflections on Allen and West's Paper

    ERIC Educational Resources Information Center

    Allen, Rebecca; West, Anne

    2009-01-01

    This article presents the authors' response to the Comment by Gerald Grace on their paper "Religious schools in London: school admissions, religious composition and selectivity". The Comment is a useful contribution to the academic and policy debates about religious schools and the role that empirical research can play. The authors are…

  8. GRACE and the development of an education and training curriculum.

    PubMed

    Finch, R G; Blasi, F B; Verheij, T J M; Goossens, H; Coenen, S; Loens, K; Rohde, G; Saenz, H; Akova, M

    2012-09-01

    Antimicrobial resistance is a serious threat and compromises the management of infectious disease. This has particular significance in relation to infections of the respiratory tract, which are the lead cause of antibiotic prescribing. Education is fundamental to the correct use of antibiotics. A novel open access curriculum has been developed in the context of a European Union funded research project Genomics to combat Resistance against Antibiotics in Community-acquired lower respiratory tract infections in Europe (GRACE http://www.grace-lrti.org). The curriculum was developed in modular format and populated with clinical and scientific topics relevant to community-acquired lower respiratory tract infections. This curriculum informed the content of a series of postgraduate courses and workshops and permitted the creation of an open access e-Learning portal. A total of 153 presentations matching the topics within the curriculum together with slide material and handouts and 104 webcasts are available through the GRACE e-Learning portal, which is fully searchable using a 'mindmap' to navigate the contents. Metrics of access provided a means for assessing usage. The GRACE project has permitted the development of a unique on-line open access curriculum that comprehensively addresses the issues relevant to community-acquired lower respiratory tract infections and has provided a resource not only for personal learning, but also to support independent teaching activities such as lectures, workshops, seminars and course work. © 2012 The Authors. Clinical Microbiology and Infection © 2012 European Society of Clinical Microbiology and Infectious Diseases.

  9. DRAGraces: An open source pipeline to extract your GRACES data!

    NASA Astrophysics Data System (ADS)

    Chené, André-Nicolas

    2017-01-01

    Written in IDL, the DRAGraces pipeline is designed to reduce and extract data from the Gemini high-resolution spectrograph GRACES*. It is barely more than a thousand lines long, and everyone is invited to download, use and modify it as needed (https://github.com/AndreNicolasChene/DRAGRACES/releases/tag/1.0.1).This poster details how to retrieve observed GRACES data from the Gemini Observatory Archive, and explains how to run DRAGraces. It also describes the pipeline's steps, capability and performances. It is recommended to use this code and/or the other open soure pipeline, OPERA, to obtain an optimized extraction of GRACES data, before publication. It is the best way to keep control on all the reduction steps, most importantly calibration.*Gemini Remote Access to CFHT ESPaDOnS Spectrograph (GRACES) is the result of a cooperation between the Canada-France-Hawaii Telescope (CFHT), Gemini, and NRC-Herzberg (Canada). It combines the large collecting area of the Gemini North telescope with the high resolving power and high efficiency of the ESPaDOnS spectrograph at CFHT, to deliver high resolution spectroscopy across the optical region. This is achieved through a 270 m fiber optics feed from the Gemini North telescope to ESPaDOnS.

  10. Advances in precision orbit determination of GRACE satellites

    NASA Astrophysics Data System (ADS)

    Bettadpur, Srinivas; Save, Himanshu; Kang, Zhigui

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

  11. 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.

  12. 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…

  13. Analysis of water level variations in Brazilian basins using GRACE

    NASA Astrophysics Data System (ADS)

    Matos, A.; Blitzkow, D.; Almeida, F.; Costa, S.; Campos, I.; Barbosa, A.

    2012-01-01

    A comparison between daily in-situ water level time series measured at ground-based hydrometric stations (HS - 1,899 stations located in twelve Brazilian basins) of the Agência Nacional de Águas (ANA) with vertically-integrated water height anomaly deduced from the Gravity Recovery and Climate Experiment (GRACE) geoid is carried out in Brazil. The equivalent water height (EWH) of 10-day intervals of GRACE models were computed by GRGS/CNES. It is a 6-year analysis (July-2002 to May-2008). The coefficient of determination is computed between the ANA water level and GRACE EWH. Values higher than 0.6 were detected in the following basins: Amazon, north of Paraguay, Tocantins-Araguaia, Western North-East Atlantic and north of the Parnaíba. In the Uruguay (Pampas region) and the west of São Francisco basins, the coefficient of determination is around 0.5 and 0.6. These results were adjusted with a linear transfer function and two second degree polynomials (flood and ebb period) between GRACE EWH and ANA water level. The behavior of these two polynomials is related to the phase difference of the two time series and yielded four different types of responses. This paper shows seven ANA stations that represent these responses and relates them with their hydro-geological domain.

  14. 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

    2014-10-06

    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.

  15. "Amazing Grace": Literature as a Window on Colonial Slavery.

    ERIC Educational Resources Information Center

    Basker, James G.

    2003-01-01

    Describes the book, "Amazing Grace: An Anthology of Poems about Slavery 1660-1810." Presents poems, written by 250 writers, that focus on slavery during the 150 year period. Provides examples of materials included in this book and how it can enable students to increase their understanding of slavery. (CMK)

  16. GRACE: Providing A New View of the Earth

    NASA Astrophysics Data System (ADS)

    Watkins, M. M.

    2015-12-01

    With the launch of GRACE in 2002, we were for the first time able to view the Earth's time-variable mass distribution - providing a truly unique window into a a large number of key processes within the Earth system, many of which are difficult to fully observe in any other way. These processes range from polar ice sheet dynamics and mass balance, hydrological processes including deep aquifers, ocean mass transport, glacial isostatic adjustment, and even large earthquakes. GRACE has provided data that is not only critically valuable on its own, but also as an excellent complement to ocean altimetry, radar, and soil moisture measuements to more fully characterize these complex processes. The value of this data led to the development of the GRACE Follow-On mission, set to launch in 2017. In this talk, we will review the history of gravity mapping from space, the realization of the value of measuring time variable gravity vs the static mean field, the future technologies in this field, and the inextricable linkage between GRACE and other geodetic techniques. We will also highlight the key science findings of the mission.

  17. The Three Graces: canons of beauty or disease repulsion.

    PubMed

    Bonafini, Beatrice; Pozzilli, Paolo

    2013-06-20

    The theme of the Three Graces has been approached by several artists and writers but very few physicians. Here distinct versions of the Three Graces are considered through the lens of medical analysis and contemporary conceptions of ideal beauty. Graces have been traced back to the same origins as the Nymphs, old goddesses of nature and representation, and being also a paradigm of beauty. This is in stark contrast to Rubens's Three Graces, who present womanly traits such as voluptuousness and full, round forms. It is paradoxical that when analysed medically, these painted women show signs of disease that inevitably affect our reading of the image. Medical conditions include presence of overweight close to obesity with a calculated BMI between 26 and 29 associated with an increased risk of cardiovascular disease. Today canons of beauty comprise women with BMI of 20 or less, a figure associated with increased risks of anorexia and suicide. It seems we approach the paradox that beauty and repulsion will always go hand in hand, shifting together with our changing perception over time. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  18. 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…

  19. 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…

  20. 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.

  1. 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

  2. Characteristic mega-basin water storage behavior using GRACE.

    PubMed

    Reager, J T; Famiglietti, James S

    2013-06-01

    [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 km(2)), 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  4. 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.

  5. 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

  6. Greenland ice mass balance estimation from GRACE: a reexamination

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    In recent years there have been several studies using GRACE satellite data to investigate the melting of the Greenland ice sheet. The results of the different investigations vary considerably. In this study, monthly GRACE solutions calculated by the Institute of Geodesy and Geoinformation of the University Bonn (ITG-GRACE2010 solutions) are evaluated to obtain a new estimate for the mass balance of the Greenland ice sheet including the corresponding error estimate. One of the major issues when dealing with the mass variations in Greenland is the leakage problem. In the contribution at hand, leakage-in effects caused by external mass variations are adressed by estimating a regional adjustment of the applied ocean model. The approach assumes time-invariant spatial patterns of ocean mass variations to be correctly reproduced in the circulation model but their time-variable amplitudes to be improvable. New amplitudes are determined by comparison to the GRACE observations in a least-squares estimation process. Leakage-out can be compensated for by rescaling the ice mass changes with a constant factor. In addition to a simple technique, a more complex approach developed by Baur et al. (2009) is applied in this investigation to obtain the rescaling factor. Besides mass variations in the area of Greenland also mass variations in an extended area around Greenland are taken into account in this procedure. A further important aspect is the problem of signal separation, especially separating the ice mass variations from mass trends caused by glacial isostatic adjustment (GIA). A comparison of different GIA models shows why this is one of the major sources of uncertainty when trying to determine the Greenland ice mass balance. The possibility to improve GIA modelling using geodetic data is therefore another aspect which will be discussed on the poster. The results of the new ice mass balance estimate from GRACE will be compared to the results obtained from alternative

  7. 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

  8. Characterizing Seasonal Drought, Water Supply Pattern and Their Impact on Vegetation Growth Using Satellite Soil Moisture Data, GRACE Water Storage and Precipitation Observations

    NASA Astrophysics Data System (ADS)

    A, G.; Velicogna, I.; Kimball, J. S.; Du, J.; Kim, Y.; Njoku, E. G.; Colliander, A.

    2016-12-01

    We combine soil moisture (SM) data from AMSR-E, AMSR-2 and SMAP, terrestrial water storage (TWS) changes from GRACE and precipitation measurements from GPCP to delineate and characterize drought and water supply pattern and its impact on vegetation growth. GRACE TWS provides spatially continuous observations of total terrestrial water storage changes and regional drought extent, persistence and severity, while satellite derived soil moisture estimates provide enhanced delineation of plant-available soil moisture. Together these data provide complementary metrics quantifying available plant water supply and have important implications for water resource management. We use these data to investigate the supply changes from different water components in relation to satellite based vegetation productivity metrics from MODIS, before, during and following the major drought events observed in the continental US during the past 13 years. We observe consistent trends and significant correlations between monthly time series of TWS, SM, and vegetation productivity. In Texas and surrounding semi-arid areas, we find that the spatial pattern of the vegetation-moisture relation follows the gradient in mean annual precipitation. In Texas, GRACE TWS and surface SM show strong coupling and similar characteristic time scale in relatively normal years, while during the 2011 onward hydrological drought, GRACE TWS manifests a longer time scale than that of surface SM, implying stronger drought persistence in deeper water storage. In the Missouri watershed, we find a spatially varying vegetation-moisture relationship where in the drier northwestern portion of the basin, the inter-annual variability in summer vegetation productivity is closely associated with changes in carry-on GRACE TWS from spring, whereas in the moist southeastern portion of the basin, summer precipitation is the dominant controlling factor on vegetation growth.

  9. Optimization of Spherical Cap Mascon Processing on the Ice Sheets for the GRACE and GRACE-FO Missions

    NASA Astrophysics Data System (ADS)

    Mohajerani, Y.; Velicogna, I.

    2016-12-01

    The GRACE mission has been providing time-variable gravity data crucial to studying the earth system since 2002, and the record will continue with the launch of the GRACE Follow-On (FO) mission in 2017. One way to obtain regional surface mass change estimates is fitting the GRACE data to regionally defined areas - "mascons" - in the harmonic domain. While previous studies using spherical cap mascons have considered uniform distributions, here we design a dynamic mascon design that can be optimized in both size and position based on the spatial pattern of signal to noise ratio for different regions. We use centroidal Voronoi tessellations to optimize the packing of the mascons to avoid leakage, and we develop regionally-tailored density functions to take advantage of the signal-to-noise ratio. We focus on the Greenland and Antarctic ice sheets and develop refined mascons for areas of high mass change. Regional time-series are also compared with independent datasets such as altimetry and regional climate models. We also evaluate the improvements by performing synthetic tests assuming GRACE-FO errors. These dynamic mascons allow for improved regional time-series, which can result in better quantification and understanding of changes in the cryosphere.

  10. Implications of GRACE Satellite Gravity Measurements for Diverse Hydrological Applications

    NASA Astrophysics Data System (ADS)

    Yirdaw-Zeleke, Sitotaw

    Soil moisture plays a major role in the hydrologic water balance and is the basis for most hydrological models. It influences the partitioning of energy and moisture inputs at the land surface. Because of its importance, it has been used as a key variable for many hydrological studies such as flood forecasting, drought studies and the determination of groundwater recharge. Therefore, spatially distributed soil moisture with reasonable temporal resolution is considered a valuable source of information for hydrological model parameterization and validation. Unfortunately, soil moisture is difficult to measure and remains essentially unmeasured over spatial and temporal scales needed for a number of hydrological model applications. In 2002, the Gravity Recovery And Climate Experiment (GRACE) satellite platform was launched to measure, among other things, the gravitational field of the earth. Over its life span, these orbiting satellites have produced time series of mass changes of the earth-atmosphere system. The subsequent outcome of this, after integration over a number of years, is a time series of highly refined images of the earth's mass distribution. In addition to quantifying the static distribution of mass, the month-to-month variation in the earth's gravitational field are indicative of the integrated value of the subsurface total water storage for specific catchments. Utilization of these natural changes in the earth's gravitational field entails the transformation of the derived GRACE geopotential spherical harmonic coefficients into spatially varying time series estimates of total water storage. These remotely sensed basin total water storage estimates can be routinely validated against independent estimates of total water storage from an atmospheric-based water balance approach or from well calibrated macroscale hydrologic models. The hydrological relevance and implications of remotely estimated GRACE total water storage over poorly gauged, wetland

  11. Reconstruction of Greenland and Antarctica Mass Changes Prior to the GRACE Mission

    NASA Astrophysics Data System (ADS)

    Nerem, R. Steven; Talpe, Matthieu; Pilinski, Emily; Lemoine, Frank G.; Chinn, Douglas S.

    2013-04-01

    Low order coefficients of the gravity field can be determined using conventional satellite tracking data such satellite laser ranging (SLR) and DORIS, a method that extends the gravitational data record across multiple decades. More recently, the Gravity Recovery and Climate Experiment (GRACE) mission has contributed monthly solutions of the gravity field to degree and order 60, which have led to fundamental advances in our knowledge of changes in the distribution of water across the planet. In particular, GRACE has provided new insight into mass changes in Greenland and Antarctica. The objective of this work is to extend mass change data beyond the ten years of the GRACE mission using SLR data that both predates the GRACE mission and is expected to continue beyond it. This work uses a technique to fuse the two data sets by applying empirical orthogonal function (EOF) analysis to the GRACE data to isolate the temporal variability and spatial maps associated with the critical modes of mass change. The EOF modes are then reconstructed using the conventional tracking data allowing for a comparison of reconstructed EOF modes and GRACE data products. We will show results from reconstructing Greenland and Antarctica mass changes during the GRACE mission (to validate the technique) as well as prior to the launch of the GRACE mission in 2002. The technique also has important implications for bridging potential gaps between the GRACE and GRACE Follow On missions.

  12. Examination of Numerical Integration Accuracy and Modeling for GRACE-FO and GRACE-II

    NASA Astrophysics Data System (ADS)

    McCullough, C.; Bettadpur, S.

    2012-12-01

    As technological advances throughout the field of satellite geodesy improve the accuracy of satellite measurements, numerical methods and algorithms must be able to keep pace. Currently, the Gravity Recovery and Climate Experiment's (GRACE) dual one-way microwave ranging system can determine changes in inter-satellite range to a precision of a few microns; however, with the advent of laser measurement systems nanometer precision ranging is a realistic possibility. With this increase in measurement accuracy, a reevaluation of the accuracy inherent in the linear multi-step numerical integration methods is necessary. Two areas where this can be a primary concern are the ability of the numerical integration methods to accurately predict the satellite's state in the presence of numerous small accelerations due to operation of the spacecraft attitude control thrusters, and due to small, point-mass anomalies on the surface of the Earth. This study attempts to quantify and minimize these numerical errors in an effort to improve the accuracy of modeling and propagation of these perturbations; helping to provide further insight into the behavior and evolution of the Earth's gravity field from the more capable gravity missions in the future.

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

    NASA Astrophysics Data System (ADS)

    Miller, K. A.; Clancy, K.

    2016-12-01

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

  14. Assessment of Gravity Recovery and Climate Experiment (GRACE) temporal signature over the upper Zambezi

    NASA Astrophysics Data System (ADS)

    Winsemius, H. C.; Savenije, H. H. G.; van de Giesen, N. C.; van den Hurk, B. J. J. M.; Zapreeva, E. A.; Klees, R.

    2006-12-01

    The temporal signature of terrestrial storage changes inferred from the Gravity Recovery and Climate Experiment (GRACE) has been assessed by comparison with outputs from a calibrated hydrological model (lumped elementary watershed (LEW)) of the upper Zambezi and surroundings and an inspection of the within-month ground track coverage of GRACE together with spatial-temporal rainfall patterns. The comparison of the hydrological model with GRACE reveals temporal inconsistencies between both data sets. Because the LEW model has been calibrated and validated with independent data sources, we believe that this is a GRACE artifact. The within-month ground track coverage shows an irregular orbit behavior which may well cause aliasing in the GRACE monthly deconvolutions. This aliasing is the most probable cause of observed temporal inconsistencies between GRACE and other data sets.

  15. The role of accelerometer data calibration within GRACE gravity field recovery: Results from ITSG-Grace2016

    NASA Astrophysics Data System (ADS)

    Klinger, Beate; Mayer-Gürr, Torsten

    2016-11-01

    For more than 14 years, the Gravity Recovery and Climate Experiment (GRACE) mission has provided information about Earth's gravity field with unprecedented accuracy. The twin satellites GRACE-A and GRACE-B are both equipped with a three-axis electrostatic accelerometer, measuring the non-gravitational forces acting on the spacecraft. In order to make use of the uncalibrated Level-1B accelerometer (ACC1B) data during gravity field recovery, bias and scale parameters have to be estimated. The proposed calibration method is a two-step approach and makes use of modeled non-conservative accelerations. The simulated non-conservative accelerations serve as reference for the a priori accelerometer calibration, i.e. for the ACC1B data. During gravity field recovery the calibration parameters are re-estimated. Several calibration parameters for the GRACE accelerometers using different methods have already been published. The aim of our study was primarily to analyze the temperature-dependent behavior of the accelerometer scale factors and biases, and the impact of the parametrization of scale factors and biases on the recovered gravity field solutions; but not to obtain calibrated accelerometer data. Within the ITSG-Grace2016 release, the accelerometer biases are estimated daily using uniform cubic basis splines (UCBS), the scale factors are also estimated daily using a fully-populated scale factor matrix. Therefore, not only the scale factors in along-track, cross-track, and radial direction are estimated, but also the non-orthogonality of the accelerometer axes (cross-talk) and the misalignment between the Accelerometer Frame (AF) and Science Reference Frame (SRF) are taken into account. The time evolution of the estimated calibration parameters over the whole GRACE period (2002-04 to 2016-01) shows a clear temperature-dependency for both scale factors and biases. Using this new approach, the estimates of the C20 coefficient significantly improve, with results now

  16. Large scale ocean circulation from the GRACE GGM01 Geoid

    NASA Astrophysics Data System (ADS)

    Tapley, B. D.; Chambers, D. P.; Bettadpur, S.; Ries, J. C.

    2003-11-01

    The GRACE Gravity Model 01 (GGM01), computed from 111 days of GRACE K-band ranging (KBR) data, is differenced from a global mean sea surface (MSS) computed from a decade of satellite altimetry to determine a mean dynamic ocean topography (DOT). As a test of the GGM01 gravity model, large-scale zonal and meridional surface geostrophic currents are computed from the topography and are compared with those derived from a mean hydrographic surface. Reduction in residual RMS between the two by 30-60% (and increased correlation) indicates that the GGM01 geoid represents a dramatic improvement over older geoid models, which were developed from multiple satellite tracking data, altimetry, and surface gravity measurements. For the first time, all major current systems are clearly observed in the DOT from space-based measurements.

  17. Drag coefficient modeling for grace using Direct Simulation Monte Carlo

    NASA Astrophysics Data System (ADS)

    Mehta, Piyush M.; McLaughlin, Craig A.; Sutton, Eric K.

    2013-12-01

    Drag coefficient is a major source of uncertainty in predicting the orbit of a satellite in low Earth orbit (LEO). Computational methods like the Test Particle Monte Carlo (TPMC) and Direct Simulation Monte Carlo (DSMC) are important tools in accurately computing physical drag coefficients. However, the methods are computationally expensive and cannot be employed real time. Therefore, modeling of the physical drag coefficient is required. This work presents a technique of developing parameterized drag coefficients models using the DSMC method. The technique is validated by developing a model for the Gravity Recovery and Climate Experiment (GRACE) satellite. Results show that drag coefficients computed using the developed model for GRACE agree to within 1% with those computed using DSMC.

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

    NASA Astrophysics Data System (ADS)

    Reager, J. T.; Famiglietti, J. S.

    2009-12-01

    Terrestrial water storage anomaly from the Gravity Recovery and Climate Experiment (GRACE) and precipitation observations from the Global Precipitation Climatology Project (GPCP) are applied at the regional scale to show the usefulness of a remotely sensed, storage-based flood potential method. Over the GRACE record length, instances of repeated maxima in water storage anomaly that fall short of variable maxima in cumulative precipitation suggest an effective storage capacity for a given region, beyond which additional precipitation must be met by marked increases in runoff or evaporation. These saturation periods indicate the possible transition to a flood-prone situation. To investigate spatially and temporally variable storage overflow, a monthly storage deficit variable is created and a global map of effective storage capacity is presented for possible use in land surface models. To highlight a flood-potential application, we design a monthly global flood index and compare with Dartmouth Flood Observatory flood maps.

  19. GRACE Mission And Data Re-Processing Status

    NASA Astrophysics Data System (ADS)

    Bettadpur, S. V.; Tapley, B. D.

    2006-05-01

    The Gravity Recovery And Climate Experiment was launched on Mar 17, 2002 in order to measure mass flux within the Earth system through its effects on Earth's gravity field. Since that time, using the inter-satellite tracking data between the twin GRACE satellites, monthly gravity field estimates for nearly 4 years have been delivered to the user community. These fields have shown clear evidence of hydrological, oceanographic & glaciological phenomena. The GRACE Science Data System is in the midst of a re-processing activity, focusing on improvements to the background models and processing methodology. In addition to an overview of the mission status and future plans, this paper describes the status of the new results from the re- processing. These include changes to the background models, improvement in the processing, and the resulting error characteristics.

  20. Status of Next Generation GRACE Gravity Field Data Products

    NASA Astrophysics Data System (ADS)

    Bettadpur, S.; Team, L.

    2006-12-01

    The Gravity Recovery And Climate Experiment was launched on Mar 17, 2002 in order to measure mass flux within the Earth system through its effects on Earth's gravity field. Since that time, using the inter-satellite tracking data between the twin GRACE satellites, monthly gravity field estimates for more than 4 years have been delivered to the user community, and these fields have shown clear evidence of hydrological, oceanographic & glaciological phenomena. The GRACE Science Data System is in the midst of a re-processing activity, focusing on improvements to the background models and processing methodology. This paper describes the status of the new results from the re-processing, including changes to the background models, improvement in the processing, and the resulting error characteristics.

  1. Detection of sea level fingerprints derived from GRACE gravity data

    NASA Astrophysics Data System (ADS)

    Hsu, Chia-Wei; Velicogna, Isabella

    2017-09-01

    Mass changes of ice sheets, glaciers and ice caps, land water hydrology, atmosphere, and ocean cause a nonuniform sea level rise due to the self-attraction and loading effects called sea level fingerprints (SLF). SLF have been previously derived from a combination of modeled and observed mass fluxes from the continents into the ocean. Here we derive improved SLF from time series of time variable gravity data from the Gravity Recovery and Climate Experiment (GRACE) mission for April 2002 to October 2014. We evaluate the GRACE-derived SLF using ocean bottom pressure (OBP) data from stations in the tropics, where OBP errors are the lowest. We detect the annual phase of the SLF in the OBP signal and separate it unambiguously from the barystatic sea level (BSL) at two stations. At the basin scale, the SLF explain a larger fraction of the variance in steric-corrected altimetry than the BSL, which has implications for evaluating mass transport between ocean basins.

  2. 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).

  3. Mass Transport Separation via Grace: Anthropogenic and Natural Change

    NASA Astrophysics Data System (ADS)

    Dickey, J. O.; de Viron, O.

    2011-12-01

    The GRACE satellite has been monitoring the change in the mass distribution at the Earth surface for nearly 10 years. This becomes enough to study long-term mass change, and to separate interannual variations from trends. Up to now, many studies have shown a fast (and non-linear) loss of mass in many glaciers and ice sheets. They all have been attributed to global warming, though part of the mass variation is also associated with the classical long-term climate variation. Using climatic data as well as the GRACE mascon solution, we can separate the part associated to the anthropogenic part from the non-anthropogenic part, in order to better estimate those contributions. Results and implications from our analyses will be presented.

  4. Testing the GRACE follow-on triple mirror assembly

    NASA Astrophysics Data System (ADS)

    Fleddermann, R.; Ward, R. L.; Elliot, M.; Wuchenich, D. M.; Gilles, F.; Herding, M.; Nicklaus, K.; Brown, J.; Burke, J.; Dligatch, S.; Farrant, D. I.; Green, K. L.; Seckold, J. A.; Blundell, M.; Brister, R.; Smith, C.; Sheard, B. S.; Heinzel, G.; Danzmann, K.; Klipstein, B.; McClelland, D. E.; Shaddock, D. A.

    2014-10-01

    We report on the successful testing of the GRACE follow-on triple mirror assembly (TMA) prototype. This component serves to route the laser beam in a proposed follow-on mission to the Gravity Recovery and Climate Explorer (GRACE) mission, containing an optical instrument for space-based distance measurement between satellites. As part of this, the TMA has to meet a set of stringent requirements on both the optical and mechanical properties. The purpose of the TMA prototype testing is to establish the feasibility of the design, materials choice and fabrication techniques. Here we report on co-alignment testing of this device to the arc second (5 μrad) level and thermal alignment stability testing to 1 μ rad {{K}-1}.

  5. 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.

  6. 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.

  7. 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.

  8. Greenland's mass balance observed by GRACE between 2003-2008

    NASA Astrophysics Data System (ADS)

    Wouters, B.; Schrama, E.

    2009-04-01

    The Gravity Recovery and Climate Experiment (GRACE) satellites have been providing the scientific community with a quasi-continuous record of the Earth's gravity field over the last 6 years. Due to its global coverage, it offers an excellent tool to study mass changes over large regions. Among others, GRACE has lead to a leap in our understanding of the mass balance of Greenland ice sheet, which was indirectly known until a few years ago. In this presentation, we demonstrate how the GRACE observations can be used to monitor changes in Greenland's mass distribution on a regional scale. Over the period of 2003-2008, the ice sheet lost annually approximately 210 cubic kilometers of ice on average, contributing 0.5 mm per year to global mean sea level. According to (Rignot,2008) this value is unprecedented in the last 50 years suggesting a significant impact of global warming on the Greenland's ice volume. A forward modeling technique significantly helps to identify the hydrologic basins where the melt occurs. As a result we now know from the GRACE data that the main melting signal occurs during summer along the southeastern coast, although spreading to the northwest, with most pronounced changes so far occurring in 2007. Although 2008 was not a record year in terms of total mass lost, it may be called exceptional in terms of the spatial pattern of the summer losses, which mainly took place in the high North, consistent with surface melt observations and regional climate model results. Largest mass losses are observed in the regions surroundig the Humboldt Glacier and Zachariae Isstrom, two glaciers that have been reported to have retreated significantly in 2008.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. Ice Mass Trend Observations from GRACE and ICESat

    NASA Astrophysics Data System (ADS)

    Luthcke, S. B.; Rowlands, D. D.; Klosko, S. M.; Lemoine, F. G.; Williams, T. A.

    2005-12-01

    On multi-decadal time scales or longer, the most important process affecting sea level are those associated with the mass balance over the Earth's ice sheets. The vulnerability of the cryosphere to climate change along with the difficulty in acquiring uniform in situ observations in these inhospitable regions, makes the problem of understanding ice sheet mass trends a focus within NASA's earth observing program. Towards this objective NASA has on orbit both the Ice Cloud and land Elevation Satellite (ICESat) and the Gravity Recovery and Climate Experiment (GRACE) mission. In combination, these missions provide unique observations to monitor ice sheet topographic change and relate these changes to their underlying mass flux. In order to improve upon the ice trend obtained from these two missions, we have employed unique data analysis approaches to further refine both the ice sheet elevation and mass change observations. Greenland and Antarctica ice sheet mass trend observations derived from our refined ICESat solutions are presented and compared to GRACE mass flux solutions derived from both regional mass anomalies as well as global spherical harmonic solutions estimated from KBRR data alone. ICESat and GRACE data processing refinement techniques, their contribution to more accurate signal recovery, and a preliminary comparison of dh/dt and dm/dt trends are presented.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  18. Inter-comparison of GRACE data over India

    NASA Astrophysics Data System (ADS)

    Banerjee, Chandan; Kumar, D. Nagesh

    2016-05-01

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

  19. 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.

  20. 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.

  1. 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].

  2. GRACE gravity field recovery using refined acceleration approach

    NASA Astrophysics Data System (ADS)

    Li, Zhao; van Dam, Tonie; Weigelt, Matthias

    2017-04-01

    Since 2002, the GRACE mission has yielded monthly gravity field solutions with such a high level of quality that we have been able to observe so many changes to the Earth mass system. Based on GRACE L1B observations, a number of official monthly gravity field models have been developed and published using different methods, e.g. the CSR RL05, JPL RL05, and GFZ RL05 are being computed by a dynamic approach, the ITSG and Tongji GRACE are generated using what is known as the short-arc approach, the AIUB models are computed using celestial mechanics approach, and the DMT-1 model is calculated by means of an acceleration approach. Different from the DMT-1 model, which links the gravity field parameters directly to the bias-corrected range measurements at three adjacent epochs, in this work we present an alternative acceleration approach which connects range accelerations and velocity differences to the gradient of the gravitational potential. Due to the fact that GPS derived velocity difference is provided at a lower precision, we must reduce this approach to residual quantities using an a priori gravity field which allows us to subsequently neglect the residual velocity difference term. We find that this assumption would cause a problem in the low-degree gravity field coefficient, particularly for degree 2 and also from degree 16 to 26. To solve this problem, we present a new way of handling the residual velocity difference term, that is to treat this residual velocity difference term as unknown but estimable quantity, as it depends on the unknown residual gravity field parameters and initial conditions. In other word, we regard the kinematic orbit position vectors as pseudo observations, and the corrections of orbits are estimated together with both the geopotential coefficients and the accelerometer scale/bias by using a weighted least square adjustment. The new approach is therefore a refinement of the existing approach but offers a better approximation to reality

  3. Assimilation of Gridded GRACE Terrestrial Water Storage Estimates in the North American Land Data Assimilation System

    NASA Technical Reports Server (NTRS)

    Kumar, Sujay V.; Zaitchik, Benjamin F.; Peters-Lidard, Christa D.; Rodell, Matthew; Reichle, Rolf; Li, Bailing; Jasinski, Michael; Mocko, David; Getirana, Augusto; De Lannoy, Gabrielle; hide

    2016-01-01

    The objective of the North American Land Data Assimilation System (NLDAS) is to provide best available estimates of near-surface meteorological conditions and soil hydrological status for the continental United States. To support the ongoing efforts to develop data assimilation (DA) capabilities for NLDAS, the results of Gravity Recovery and Climate Experiment (GRACE) DA implemented in a manner consistent with NLDAS development are presented. Following previous work, GRACE terrestrial water storage (TWS) anomaly estimates are assimilated into the NASA Catchment land surface model using an ensemble smoother. In contrast to many earlier GRACE DA studies, a gridded GRACE TWS product is assimilated, spatially distributed GRACE error estimates are accounted for, and the impact that GRACE scaling factors have on assimilation is evaluated. Comparisons with quality-controlled in situ observations indicate that GRACE DA has a positive impact on the simulation of unconfined groundwater variability across the majority of the eastern United States and on the simulation of surface and root zone soil moisture across the country. Smaller improvements are seen in the simulation of snow depth, and the impact of GRACE DA on simulated river discharge and evapotranspiration is regionally variable. The use of GRACE scaling factors during assimilation improved DA results in the western United States but led to small degradations in the eastern United States. The study also found comparable performance between the use of gridded and basin averaged GRACE observations in assimilation. Finally, the evaluations presented in the paper indicate that GRACE DA can be helpful in improving the representation of droughts.

  4. Assimilation of Gridded GRACE Terrestrial Water Storage Estimates in the North American Land Data Assimilation System

    NASA Technical Reports Server (NTRS)

    Kumar, Sujay V.; Zaitchik, Benjamin F.; Peters-Lidard, Christa D.; Rodell, Matthew; Reichle, Rolf; Li, Bailing; Jasinski, Michael; Mocko, David; Getirana, Augusto; De Lannoy, Gabrielle; Cosh, Michael H.; Hain, Christopher R.; Anderson, Martha; Arsenault, Kristi R.; Xia, Youlong; Ek, Michael

    2016-01-01

    The objective of the North American Land Data Assimilation System (NLDAS) is to provide best available estimates of near-surface meteorological conditions and soil hydrological status for the continental United States. To support the ongoing efforts to develop data assimilation (DA) capabilities for NLDAS, the results of Gravity Recovery and Climate Experiment (GRACE) DA implemented in a manner consistent with NLDAS development are presented. Following previous work, GRACE terrestrial water storage (TWS) anomaly estimates are assimilated into the NASA Catchment land surface model using an ensemble smoother. In contrast to many earlier GRACE DA studies, a gridded GRACE TWS product is assimilated, spatially distributed GRACE error estimates are accounted for, and the impact that GRACE scaling factors have on assimilation is evaluated. Comparisons with quality-controlled in situ observations indicate that GRACE DA has a positive impact on the simulation of unconfined groundwater variability across the majority of the eastern United States and on the simulation of surface and root zone soil moisture across the country. Smaller improvements are seen in the simulation of snow depth, and the impact of GRACE DA on simulated river discharge and evapotranspiration is regionally variable. The use of GRACE scaling factors during assimilation improved DA results in the western United States but led to small degradations in the eastern United States. The study also found comparable performance between the use of gridded and basin averaged GRACE observations in assimilation. Finally, the evaluations presented in the paper indicate that GRACE DA can be helpful in improving the representation of droughts.

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

    NASA Astrophysics Data System (ADS)

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

    2017-05-01

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

  6. 76 FR 75797 - Transportation Conformity Rule: MOVES Regional Grace Period Extension

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-05

    ... AGENCY 40 CFR Part 93 RIN 2060-AR03 Transportation Conformity Rule: MOVES Regional Grace Period Extension... for regional emissions analyses for transportation conformity determinations (``regional conformity... extending the MOVES regional conformity grace period, published on October 13, 2011 (76 FR 63554). We...

  7. 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.

  8. 76 FR 67254 - Requested Administrative Waiver of the Coastwise Trade Laws: Vessel LINDA GRACE; Invitation for...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-31

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF TRANSPORTATION Maritime Administration Requested Administrative Waiver of the Coastwise Trade Laws: Vessel LINDA GRACE... the vessel LINDA GRACE is: INTENDED COMMERCIAL USE OF VESSEL: ``2 to 8 hour day sails,...

  9. Use of GRACE Data to Detect the Present Land Uplift Rate in Fennoscandia

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  10. Improving GRACE Mass Estimates for the Baltic Sea and Validation Using in Situ Measurements

    NASA Astrophysics Data System (ADS)

    Virtanen, J.; Mäkinen, J.; Bilker-Koivula, M.; Nordman, M.; Virtanen, H.; Shum, C.; Guo, J.; Wang, L.; Kangas, A.; Johansson, M.; Thomas, M.

    2008-12-01

    The variation in the sea level of the semi-closed Baltic Sea has been monitored in several complimentary ways. Now GRACE provides a method to directly measure the total mass variability in the Baltic. Using in situ and modelled Baltic data, we show that GRACE is able to recover the variation in the total water mass. We derive sea level surfaces from tide gauge data and estimate steric effects using hydrodynamic models as well as in situ salinity and temperature measurements for their verification. With its areal extent (~400 km x 1000 km) as well as fast temporal variations (hourly to monthly), the Baltic Sea provides a challenging test field for the temporal and spatial resolution of GRACE. We use both the standard monthly GRACE gravity field solutions and regional solutions and compare their capability to recover Baltic water mass variations. Due to spatial averaging, the GRACE mass estimates over the elongated area are contaminated by signals outside the region. The contribution of continental hydrology can be removed using water storage models to estimate mass variations on surrounding land areas. We discuss the processing steps required for the different GRACE solutions to improve the GRACE mass estimates for the Baltic, including mitigation of signal leakage as a result of spatial filtering. The capability of GRACE to recover internal mass redistributions in the Baltic is also investigated. Finally, we discuss the reduction of the Baltic contribution for studying land-uplift signal due to post-glacial rebound.

  11. The instrument on NASA's GRACE Mission: Augmentation of GPS to achieve unprecedented gravity field measurements

    NASA Technical Reports Server (NTRS)

    Dunn, C.; Bertiger, W.; Franklin, G.; Harris, I.; Kruizinga, G.; Meehan, T.; Nandi, S.; Nguyen, D.; Rogstad, T.; Thomas, J. B.; hide

    2002-01-01

    This paper will describe the design and on-orbit performance of the GRACE Instrument Processing Unit (IPU) that integrates most of the critical science functions required by the GRACE mission to perform its gravity science and atmospheric radio occultation tasks.

  12. 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...

  13. Validation of GRACE based groundwater storage anomaly using in-situ groundwater level measurements in India

    NASA Astrophysics Data System (ADS)

    Bhanja, Soumendra N.; Mukherjee, Abhijit; Saha, Dipankar; Velicogna, Isabella; Famiglietti, James S.

    2016-12-01

    In this study, we tried to validate groundwater storage (GWS) anomaly obtained from a combination of GRACE and land-surface model based estimates, for the first time, with GWS anomaly obtained from a dense network of in-situ groundwater observation wells within 12 major river basins in India. We used seasonal data from >15,000 groundwater observation wells between 2005 and 2013, distributed all over the country. Two recently released GRACE products, RL05 spherical harmonics (SH) and RL05 mascon (MS) products are used for comparison with in-situ data. To our knowledge, this is the first study of comparing the performance of two independent GRACE products at a sub-continental scale. Also for the first time, we have created a high resolution (0.10 × 0.10) map of specific yield for the entire country that was used for calculating GWS. Observed GWS anomalies have been computed using water level anomalies and specific yield information for the locale of individual observation wells that are up-scaled to basin-scale in order to compare with GRACE-based estimates. In general GRACE-based estimates match well (on the basis of the statistical analyses performed in the study) with observed estimates in most of the river basins. On comparing with observed GWS anomaly, GRACE-SH estimates match well in terms of RMSE, while GRACE-MS estimates show better association in terms of correlation, while the output of skewness, kurtosis, coefficient of variation (CV) and scatter analyses remain inconclusive for inter-comparison between two GRACE estimates. We used a non-parametric trend estimation approach, the Hodrick-Prescott (HP) filter, to further assess the performance of the two GRACE estimates. GRACE-MS estimates clearly outperform GRACE-SH estimates for reproducing observed GWS anomaly trends with significantly (>95% confidence level) strong association in 10 out of 12 basins for GRACE-MS estimates, on the other hand, GRACE-SH estimates show significantly (>95% confidence level

  14. 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.

  15. Evaluating Renewable Groundwater Stress with GRACE data in Greece

    NASA Astrophysics Data System (ADS)

    Lakshmi, V.; Gemitzi, A.

    2016-12-01

    Groundwater is a resilient water source and its importance as a fundamental resource is even greater in times of drought where groundwater stress conditions are greatest for areas like Mediterranean and adverse climate change effects are expected. The present study evaluates Renewable Groundwater Stress (RGS) as the ratio of groundwater use to groundwater availability, quantifying use as the trend in GRACE-derived subsurface anomalies (ΔGWtrend) and renewable groundwater availability as mean annual recharge. Estimates for mean annual recharge were used from groundwater studies conducted for the various regions in Greece, mainly in the form of numerical models. Our results highlighted two RGS regimes in Greece out of the four characteristic stress regimes, i.e. Overstressed, Variable Stress, Human-Dominated Stress and Unstressed, defined as a function of the sign of use and the sign of groundwater availability (positive or negative). Variable Stress areas are found in central Greece (Thessaly region), where intense agricultural activities take place, with negative ΔGWtrend values combined with positive mean annual recharge rates. RGS values range from -0.05 - 0, indicating however a low impact area. Within this region, adverse effects of groundwater overexploitation are already evident, based on the negative GRACE anomalies, recharge however still remains positive, amending the adverse over pumping impacts. The rest of Greek aquifers fall within the unstressed category, with RGS values from 0.02 - 0.05, indicating that the rate of use is less than the natural recharge rate. The highest Unstressed RGS values are observed in Crete Island and in Northeastern Greece. However, the case of Crete is highly uncertain, as precipitation and recharge in this area demonstrate exceptionally high variability and the coarse resolution of GRACE results does not allow for reliable estimates.

  16. Recent ice sheet mass change observations from GRACE mascon solutions

    NASA Astrophysics Data System (ADS)

    Luthcke, S. B.; Zwally, H. J.; Rowlands, D. D.; Abdalati, W.; Nerem, R. S.; Ray, R. D.; Lemoine, F.; Chinn, D.

    2006-12-01

    On multi-decadal time scales or longer, the most important processes affecting sea level are those associated with the mass balance over the Earth's ice sheets. The vulnerability of the cryosphere to climate change along with the difficulty in acquiring uniform in situ observations in these inhospitable regions, makes the problem of understanding ice sheet mass trends a high Earth science research priority at NASA. The Gravity Recovery and Climate Experiment (GRACE) mission has acquired ultra-precise inter-satellite ranging data since 2002. These data provide new opportunities to observe and understand ice mass changes at unprecedented temporal and spatial resolution. In order to improve upon the ice mass trend observations obtained from GRACE, we have employed unique data analysis approaches to obtain high resolution local mass change (mascon solutions) from GRACE inter-satellite observations alone. We have applied our mascon solution technique to the Greenland and Antarctic ice sheets estimating surface mass change for irregularly shaped regions defined by the ice sheet drainage basins and further sub-divided by elevation. We estimate the surface mass change of each ice sheet drainage basin sub-divided by elevation at 10-day resolution. We have computed multi-year time series of surface mass change for each ice sheet drainage basin. These mascon solutions provide unprecedented observations of the seasonal and inter-annual evolution of ice-sheet mass flux. In this presentation we discuss our analysis techniques and the details of our ice sheet mascon solutions, as well as compare these results with mass change observations derived from NASA's ICESat mission.

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

    NASA Astrophysics Data System (ADS)

    Ellmer, Matthias; Mayer-Gürr, Torsten

    2014-05-01

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

  18. 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

  19. 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.

  20. Evaluating flood potential with GRACE in the United States

    NASA Astrophysics Data System (ADS)

    Molodtsova, T.; Molodtsov, S.; Kirilenko, A.; Zhang, X.; VanLooy, J.

    2015-11-01

    One of the Gravity Recovery and Climate Experiment (GRACE) products, the Terrestrial Water Storage Anomaly (TWSA), was used for assessing large-scale flood risk through Reager's Flood Potential Index (RFPI) by Reager and Famiglietti (2009). The efficacy of the proposed RFPI for flood risk assessment was evaluated over the continental US using multi-year flood observation data from 2003 to 2012 by the US Geological Survey and Dartmouth Flood Observatory. In general, the flood risk based on the RFPI agreed well with the observed floods on regional and even local scales. The method exhibits higher skill in predicting the large-area, long-duration floods, especially during the summer season.

  1. 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.

  2. GRACE-FO: seeking an optimal mission scenario

    NASA Astrophysics Data System (ADS)

    Biancale, R.; Lemoine, J.-M.; Bruinsma, S.; Perosanz, F.; da Costa, E. D.

    2009-04-01

    The GRACE mission has brought enormous improvement in the knowledge of the Earth's gravity field and particularly in its temporal evolution, which has led to a large amount of applied research in geosciences. It has demonstrated the capability of measuring the effect of gravitation in space to monitor surface water changes globally (through a satellite-to-satellite tracking technique of very high accuracy) and the question of a follow-on mission has been raised. Of course, spatial and temporal resolution remain coarse, at the level of some 500 km / 10 days to a month, respectively. However, this limitation is not only due to the mission's characteristics, but also to some limitation of aliased effects of higher frequency, such as from ocean tides and from atmosphere perturbations, which are today not modelled precisely enough. Nevertheless, it is essential to persevere in continuing the monitoring from space of global water changes. That is why CNES/GRGS performed a series of simulations for a proposed GRACE-FO mission under different scenario assumptions, considering a range or range-rate link between two or more satellites. Characteristics and results of these simulations will be presented.

  3. Current Status Of The GRACE Follow-On Mission

    NASA Astrophysics Data System (ADS)

    Flechtner, Frank; Webb, Frank; Watkins, Michael; Landerer, Felix; Dahle, Christoph; Bettadpur, Srinivas

    2017-04-01

    As of the time of this abstract submission, the GRACE Follow-On satellites have been constructed and transferred to Ottobrunn near Munich for several months of operational testing in the IABG test centre. The Russian/Ukraine Dnepr launcher had to be exchanged and a corresponding new contract has been signed by GFZ and Iridium Satellite LLC. This includes a "Rideshare" between GRACE-FO and 5 Iridium-Next satellites on a Space-X Falcon-9 from Vandenberg Air Force Base in California within the launch period December 2017 till February 2018. The project team is conducting tests of satellite and instrument operation and performance and evaluating updated simulations of expected performance on-orbit, including the assessment of inter-satellite ranging (for both microwave and laser instruments), accelerometer, thermal variability and deformation, and other instrument and measurement errors. In addition, all required ground analysis software of the Science Data System is in development and being tested at JPL, UTCSR, and GFZ, in preparation for fully integrated end-to-end (international) testing from Level-1 through Level-3 data within 2017. In this presentation, we will provide the detailed status of project integration and test, the latest simulations of science performance, and a revised schedule for remaining project milestones.

  4. Mass Concentration Technique for GRACE and GRAIL Gravity Recovery (Invited)

    NASA Astrophysics Data System (ADS)

    Yuan, D.; Konopliv, A. S.; Wiese, D. N.; Watkins, M. M.

    2013-12-01

    The spherical harmonic basis functions have been widely used to analyze the inter-spacecraft measurement collected from the Gravity Recovery and Climate Experiment (GRACE) mission for time varying gravity field of the Earth and the Gravity Recovery and Interior Laboratory (GRAIL) mission for static gravity field of the Moon. For GRACE, advanced solutions making of the mass concentration (mascon) element as a basis function to model the gravity variation due to surface mass redistribution allows for convenient application of geophysically derived a priori information in the local spatial domain to eliminate, among other artifacts, the longitudinal striping which plague the unconstrained spherical harmonic solutions. Comparisons of hydrology and ocean results demonstrate that the mascon solutions have greater correlation with in-situ data than do post-processed unconstrained spherical harmonic solutions. The GRAIL-derived static lunar gravity field to spherical harmonic degree and order 900, corresponding to one fifth degree of surface resolution, shows over 98% of the lunar gravitational signature is correlated with topography derived gravity field from harmonics degrees 80 through 640. Its exact surface resolution depends on the spacecraft altitude and ground track coverage. In this talk we present results for selected lunar areas, including Mare Orientale, in which the gravity field resolution is extended beyond that of equivalent harmonic degree 900 by augmenting the harmonic field with mascons to efficiently extract additional gravitational information in these regions. The Bouguer anomaly map and topography correlation are compared for both the harmonic field and regional mass anomaly solution.

  5. Quantifying Water Stress Using Total Water Volumes and GRACE

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  6. One-year oral toxicity study on a genetically modified maize MON810 variety in Wistar Han RCC rats (EU 7th Framework Programme project GRACE).

    PubMed

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

    2016-10-01

    The GRACE (GMO Risk Assessment and Communication of Evidence; www.grace-fp7.eu ) project was funded by the European Commission within the 7th Framework Programme. A key objective of GRACE was to conduct 90-day animal feeding trials, animal studies with an extended time frame as well as analytical, in 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 a 1-year feeding trial with a GM maize MON810 variety, its near-isogenic non-GM comparator and an additional conventional maize variety 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 452. 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 a chronic exposure.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

    Klinger, Beate; Mayer-Gürr, Torsten

    2017-04-01

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

  9. Effect of the improved accelerometer calibration method on AIUB's GRACE monthly gravity field solution

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The monthly global gravity field solutions derived using the measurements from the GRACE (Gravity Recovery and Climate Experiment) satellites have been continuously improved by the processing centers. One of the improvements in the processing method is a more detailed calibration of the on-board accelerometers in the GRACE satellites. The accelerometer data calibration is usually restricted to the scale factors and biases. It has been assumed that the three different axes are perfectly orthogonal in the GRACE science reference frame. Recently, it was shown by Klinger and Mayer-Gürr (2016) that a fully-populated scale matrix considering the non-orthogonality of the axes and the misalignment of the GRACE science reference frame and the GRACE accelerometer frame improves the quality of the C20 coefficient in the GRACE monthly gravity field solutions. We investigate the effect of the more detailed calibration of the GRACE accelerometer data on the C20 coefficient in the case of the AIUB (Astronomical Institute of the University of Bern) processing method using the Celestial Mechanics Approach. We also investigate the effect of the new calibration parameters on the stochastic parameters in the Celestial Mechanics Approach.

  10. 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.

  11. Full scale simulation of MWI and LRI based GRACE-FO gravity models

    NASA Astrophysics Data System (ADS)

    Flechtner, Frank; Raimondo, Jean-Claude; Dobslaw, Henryk; Fagiolini, Elisa

    2014-05-01

    During 12 years of very successful operation in orbit, the US-German GRACE mission has demonstrated its outstanding capability to monitor mass motions in the Earth system with unprecedented accuracy and temporal resolution. These results have stimulated many novel research activities in hydrology, oceanography, glaciology, geophysics, and geodesy which also indicate that long term monitoring of such mass variations, possibly with improved spatial and temporal resolution, is a must for further understanding of phenomena such as ice mass los in Polar Regions and large glacier systems or the continental hydrological cycle. Due to the onboard battery situation, GRACE can likely not be operated further than 2015. Fortunately, a GRACE follow-on mission is currently being implemented jointly by JPL/NASA and GFZ and due for launch in August 2017. GRACE-FO will be based on GRACE heritage and lessons learnt during operation. Therefore, the prime SST (satellite-to-satellite tracking) instrument will be again the Microwave Ranging Instrument (MWI). Additionally, GRACE-FO will carry a Laser Ranging Interferometer (LRI) demonstrator which will have a factor of 10-50 improved SST measurement accuracy. We will present a multi-years full scale simulation based on realistic error assumptions for instrument noise and background models such as tidal and non-tidal mass variations. The results shall indicate what the users can expect in terms of precision and spatial and temporal resolution when using future GRACE-FO MWI and LRI based gravity models.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Liesch, Tanja; Ohmer, Marc

    2016-09-01

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

  15. 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.

  16. 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.

  17. Using Tikhonov Regularization for Spatial Projections from CSR Regularized Spherical Harmonic GRACE Solutions

    NASA Astrophysics Data System (ADS)

    Save, H.; Bettadpur, S. V.

    2013-12-01

    It has been demonstrated before that using Tikhonov regularization produces spherical harmonic solutions from GRACE that have very little residual stripes while capturing all the signal observed by GRACE within the noise level. This paper demonstrates a two-step process and uses Tikhonov regularization to remove the residual stripes in the CSR regularized spherical harmonic coefficients when computing the spatial projections. We discuss methods to produce mass anomaly grids that have no stripe features while satisfying the necessary condition of capturing all observed signal within the GRACE noise level.

  18. 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

  19. Hydrologic Applications of GRACE Terrestrial Water Storage Data

    NASA Technical Reports Server (NTRS)

    Rodell, Matthew; Zaitchik, Benjamin F.; Li, Bailing; Bolten, John; Hourborg, Rasmus; Velicogna, Isabella; Famiglietti, Jay

    2009-01-01

    Gravimetry-based terrestrial water storage time series have great potential value for hydrological research and applications, because no other observing system can provide global maps of the integrated quantity of water stored on and below the land surface. However, these data are challenging to use because their spatial and temporal resolutions are low relative to other hydrological observations and because total terrestrial water storage is a measurement unfamiliar to hydrologists. In this presentation we will review techniques for temporal, horizontal, and vertical disaggregation of GRACE terrestrial water storage anomalies, including data assimilation and integration within a land surface model. We will then discuss initial results from three efforts to use the methods for water resources applications. These include drought monitoring across North America, water cycle assessment over the Middle East North African region, and groundwater depletion estimates for northern India.

  20. 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.

  1. Current Status of the GRACE Follow-On Mission

    NASA Astrophysics Data System (ADS)

    Webb, F.; Watkins, M. M.; Flechtner, F.; Landerer, F. W.; Grunwaldt, L.

    2016-12-01

    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 late 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.

  2. Hydrologic Applications of GRACE Terrestrial Water Storage Data

    NASA Technical Reports Server (NTRS)

    Rodell, Matthew; Zaitchik, Benjamin F.; Li, Bailing; Bolten, John; Hourborg, Rasmus; Velicogna, Isabella; Famiglietti, Jay

    2009-01-01

    Gravimetry-based terrestrial water storage time series have great potential value for hydrological research and applications, because no other observing system can provide global maps of the integrated quantity of water stored on and below the land surface. However, these data are challenging to use because their spatial and temporal resolutions are low relative to other hydrological observations and because total terrestrial water storage is a measurement unfamiliar to hydrologists. In this presentation we will review techniques for temporal, horizontal, and vertical disaggregation of GRACE terrestrial water storage anomalies, including data assimilation and integration within a land surface model. We will then discuss initial results from three efforts to use the methods for water resources applications. These include drought monitoring across North America, water cycle assessment over the Middle East North African region, and groundwater depletion estimates for northern India.

  3. 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

  4. 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.

  5. A Simulated Comparison of Level-1b GRACE Analysis Techniques

    NASA Astrophysics Data System (ADS)

    Andrews, Stuart; Moore, Philip; King, Matt

    2014-05-01

    GRACE estimates of temporal mass anomalies have been obtained using a number of different approaches including; conventional spherical harmonic using a standard Gaussian smoothing filter and the mascon approach which applies a constraint matrix between mascon parameters that share geophysical similarities. Temporal gravity fields are frequently produced by different groups and obtained using different codes and algorithms making it hard to directly compare any subsequent mass flux analysis. It is therefore important that an assessment of the different methodologies is undertaken to provide users with an understanding of the errors and to assess the ability of each technique to resolve basin-level mass changes at a variety of spatial scales. In this study we undertake a comparison of solutions generated through the estimation of mascon and spherical harmonic coefficients. Simulations provide an accurate assessment and quantify the capability of each technique to resolve basin-level mass changes at a variety of spatial scales while understanding how the methodologies handle the noise inherent at higher degree and order. We will present results of our simulations and show how masses leak into their surrounding region through the GRACE KBRR residuals. Through a simulated recovery of a GLDAS anomaly with added noise in the form of 'stripes' we will show the advantage of the mascon solution over a spherical harmonic recovery. The study is subsequently extended to simulate the recovery of an Antarctic mass signal validating the use of the mascon methodology in Polar Regions. We will show how the addition of a constraint between mascon parameters that share geophysical similarities result in a reduction of the signal lost at all degrees and an improvement in the recovered signal.

  6. GRACE Measurements of the Mackenzie River Basin Water Balance

    NASA Astrophysics Data System (ADS)

    Snelgrove, K. R.; Yirdaw-Zeleke, S.; Soulis, E. D.

    2004-12-01

    Direct measurement of an integrated watershed storage amount may be considered a panacea for the ills of watershed modeling. Watershed models typically transfer moisture and energy between model "stores" using physically based transfer laws and conservation equations to produce streamflow hydrographs. Because of the problem of non-uniqueness in the generation of model hydrographs, it has become increasingly important to ensure the representativeness of model results. This is being accomplished by: a) performing model integrations over long, multi-year periods, b) applying models to watersheds with diverse hydroclimatic conditions, c) comparing model "stores" with measured components of watershed storage such as snow depth, soil moisture, groundwater levels, and lake storage. Many of these components, however, either are not regularly measured or have large uncertainties associated with their values. Lack of a true integrated storage measurement represents an unwanted degree of freedom in watershed modeling. In 2002, the GRACE (Gravity Recovery And Climate Experiment Mission) satellite platform was launched to measure, among other things, the gravitational field of the earth. Over its five year life a pair of orbiting satellites will produce a time series of "mass" changes of the earth-atmosphere system. When integrated over a number of years, this will yield a highly refined picture of the earth's gravity. However, month to month changes in mass is an indicator of the integrated value of watershed moisture storage. It has been reported by Wahr et al. (2004) that when smoothed over 1000 km that centimeter accuracy can be achieved in monthly storage change. The goal of this research to compare changes in moisture storage over the Mackenzie River basin using GRACE data with those developed by atmospheric and hydrologic water balances developed under the Mackenzie GEWEX Project (MAGS). Monthly estimates of watershed storage have been developed for the basin through the

  7. Evaluating Renewable Groundwater Stress with GRACE Data in Greece.

    PubMed

    Gemitzi, Alexandra; Lakshmi, Venkat

    2017-09-22

    Groundwater is a resilient water source and its importance is even greater in periods of drought. Areas such as the Mediterranean where adverse climate change effects are expected are bell-weather locations for groundwater depletion and are of considerable interest. The present study evaluates renewable groundwater stress (RGS) as the ratio of groundwater use to groundwater availability, quantifying use as the trend in gravity recovery and climate experiment-derived (GRACE) subsurface anomalies (ΔGWtrend ) and renewable groundwater availability as mean annual recharge. Estimates for mean annual recharge for the various regions in Greece have been derived using numerical models. Our results highlight two RGS regimes in Greece (variable stress and unstressed) of the four characteristic stress regimes, that is, overstressed, variable stress, human-dominated stress, and unstressed, defined as a function of the sign of use and the sign of groundwater availability (positive or negative). Variable stress areas are found in Central Greece (Thessaly region), where intensive agriculture results in negative ΔGWtrend values combined with positive mean annual recharge rates. RGS values range from -0.05 to 0, indicating a low impact area. Within this region, adverse effects of groundwater overexploitation are already evident based on the negative GRACE anomalies; however, recharge is still positive, mitigating the effects of over-pumping. The rest of Greek aquifers fall within the unstressed category, with RGS values from 0.02 to 0.05, indicating that the rate of use is less than the natural recharge rate. © 2017, National Ground Water Association.

  8. 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.

  9. 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...

  10. 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...

  11. Crustal subsidence observed by GRACE after the 2013 Okhotsk deep-focus earthquake

    NASA Astrophysics Data System (ADS)

    Tanaka, Yusaku; Heki, Kosuke; Matsuo, Koji; Shestakov, Nikolay V.

    2015-05-01

    Coseismic gravity changes stem from (1) vertical deformation of layer boundaries with density contrast (i.e., surface and Moho) and (2) density changes of rocks at depth. They have been observed in earthquakes with Mw exceeding ~8.5 by Gravity Recovery and Climate Experiment (GRACE) satellites, but those of M8 class earthquakes have never been detected clearly. Here we report coseismic gravity change of the 24 May 2013 Okhotsk deep earthquake (Mw8.3), smaller than the detection threshold. In shallow thrust faulting, factor (2) is dominant, while factor (1) remains secondary due to poor spatial resolution of GRACE. In the 2013 Okhotsk earthquake, however, factor (2) is insignificant because they occur at depth exceeding 600 km. On the other hand, factor (1) becomes dominant because the centers of uplift and subsidence are well separated and GRACE can resolve them. This enables GRACE to map vertical ground movements of deep earthquakes over both land and ocean.

  12. Gravitational gradient changes following the 2004 December 26 Sumatra-Andaman Earthquake inferred from GRACE

    NASA Astrophysics Data System (ADS)

    Wang, Lei; Shum, C. K.; Jekeli, Christopher

    2012-12-01

    It has been demonstrated that the Gravity Recovery And Climate Experiment (GRACE) spaceborne gravimetry data are capable of observing coseismic gravity changes resulting from great earthquakes, such as the 2004 December 26 Sumatra-Andaman event (Mw 9.1-9.3). Here, we show for the first time that refined deformation signals from the 2004 December 26 Sumatra-Andaman Earthquake (Mw 9.1-9.3) together with the 2005 March 28 Nias earthquake (Mw 8.6) can be revealed by deriving the full gravitational gradient tensor from GRACE monthly gravitational field. The GRACE-inferred coseismic gravitational gradient changes agree well with coseismic slip model predictions. Since the high-frequency contents in gravitational field variation can be amplified by deriving the gravitational gradients, the GRACE-derived coseismic gravitational gradient changes clearly delineate the fault lines, locate significant slips, and better define the extent of the coseismic deformation.

  13. The Generic Resolution Advisor and Conflict Evaluator (GRACE) for Detect-And-Avoid (DAA) Systems

    NASA Technical Reports Server (NTRS)

    Abramson, Michael; Refai, Mohamad; Santiago, Confesor

    2017-01-01

    The paper describes the Generic Resolution Advisor and Conflict Evaluator (GRACE), a novel alerting and guidance algorithm that combines flexibility, robustness, and computational efficiency. GRACE is "generic" in that it makes no assumptions regarding temporal or spatial scales, aircraft performance, or its sensor and communication systems. Accordingly, GRACE is well suited to research applications where alerting and guidance is a central feature and requirements are fluid involving a wide range of aviation technologies. GRACE has been used at NASA in a number of real-time and fast-time experiments supporting evolving requirements of DAA research, including parametric studies, NAS-wide simulations, human-in-the-loop experiments, and live flight tests.

  14. 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.

  15. Proxy representation of Arctic ocean bottom pressure variability: Bridging gaps in GRACE observations

    NASA Astrophysics Data System (ADS)

    Peralta-Ferriz, Cecilia; Morison, James H.; Wallace, John M.

    2016-09-01

    Using time-varying ocean bottom pressure (OBP) from the Gravity Recovery and Climate Experiment (GRACE), a 9 year in situ OBP record at the North Pole, and wind reanalysis products, we perform a linear regression analysis to identify primary predictor time series that enable us to create a proxy representation of the Arctic time-varying OBP that explains the largest fraction of the observed Arctic OBP variability. After cross validation, two predictors—North Pole OBP record and wind-OBP coupling from maximum covariance analysis—explain 50% of the total variance of the Arctic OBP. This work provides a means for bridging existing short gaps in GRACE measurements and potentially longer future gaps that may result if GRACE and its follow-on mission do not overlap. The technique may be applicable to bridge gaps in GRACE measurements in other oceanic regions.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. Aquifer-scale Application of GRACE across the South Platte Basin, Colorado, for Assessing Groundwater Resources

    NASA Astrophysics Data System (ADS)

    Ruybal, C. J.; Hogue, T. S.; McCray, J. E.

    2016-12-01

    Few studies have evaluated the validity of using GRACE over smaller basins which are less than the recommended footprint of 200,000 km2, despite the interest in using remote sensing as another tool to asses groundwater depletion and storage trends in areas lacking monitoring data. Given the lack of adequate temporal and spatial groundwater data in many water-limited systems and the growing need for water among urban users, agriculture, industry, ecosystems, and energy development, it is important to determine whether GRACE can provide useful information at smaller scales to better understand system dynamics and help in regional resource management. The purpose of this study is to investigate whether GRACE can be applied across the South Platte Basin (area of 61,000 km2) to understand groundwater storage changes and provide another tool for water practitioners. Auxiliary datasets from NLDAS, SNODAS, and State/Federal reservoir gages were used to remove components of soil moisture, snow water equivalent, and surface water signals from GRACE and infer groundwater anomalies. We compare GRACE derived groundwater storage changes with available ground-based data from 277 water-wells within the Denver Basin Aquifer System (four vertically sequenced aquifers) and the South Platte Alluvial Aquifer. Preliminary results for GRACE derived depletion rates for the Denver Basin Aquifer System from 2002 - 2008 are approximately 0.07 km3/year which shows good agreement to current literature estimates. GRACE variability within the South Platte Basin also matches regional drought patterns, where the severity of the 2012 drought is reflected by higher rates of groundwater storage depletion. Well data indicate significant long-term decreasing trends for two of the sequenced aquifers, which are likely due to a combination of natural and anthropogenic influences. Ongoing work includes comparing well data for both confined and unconfined aquifers against GRACE and assessing the

  2. Repairing signal damage in GRACE due to filtering: A comprehensive data-driven approach

    NASA Astrophysics Data System (ADS)

    Dutt Vishwakarma, Bramha; Horwath, Martin; Devaraju, Balaji; Groh, Andreas; Sneeuw, Nico

    2017-04-01

    The monthly GRACE products are contaminated with short wavelength noise. Therefore, filtering is essential for minimizing noise and extracting meaningful signal. However, filtering also affects the signal by introducing leakage that changes its phase and amplitude, which is a source of uncertainty in GRACE products. The approach that is widely applied to minimize this uncertainty is to use model-derived leakage, bias or scale factors to improve GRACE products. This raises a number of concerns, such as which model to use, how the uncertainty in the model affects corrected GRACE. Moreover, GRACE was expected to help us improve models, but we are improving GRACE with the help of models. In a recent contribution, we developed a data-driven method for estimating leakage and correcting GRACE derived time series of total water storage change that is superior to model dependent approaches. The data-driven method demonstrated better performance for a majority of hydrological catchments, but it failed for catchments below the filter resolution, which is a major limitation of the method. In this contribution, we analyse the source for this limitation and tackle it to improve the data-driven method for small catchments also. The performance of the updated data-driven method is not limited by the size of catchment. We validate our findings in two different simulation environments emulating GRACE monthly products. In order to demonstrate that the updated data-driven approach is comprehensive, we compare its performance with the previous data-driven method and three model dependent methods over 32 catchments, covering different scenarios. We find that the updated data-driven method outperforms other methods significantly.

  3. Mitigation of along-track artifacts in unconstrained mass transport models based on GRACE satellite data

    NASA Astrophysics Data System (ADS)

    Ditmar, Pavel; Hashemi Farahani, Hassan; Encarnação, João.

    2010-05-01

    The satellite gravity mission GRACE (Gravity Recovery And Climate Experiment), which was launched in 2002, offers a unique opportunity to monitor tiny variations of the Earth's gravity and associated mass transport from space. In particular, the redistribution of water in the Earth's system can be traced in this way, which is critical for monitoring key climate indicators such as ice-sheet mass balance, terrestrial water-storage change, sea-level rise, and ocean circulation. Unfortunately, mass transport models based on GRACE data suffer from along-track artifacts. In order to suppress these artifacts, various filtering algorithms are applied to unconstrained GRACE-based models at the post-processing stage. However, any filtering not only suppresses noise but also distorts signals. Therefore, it is important to study the precise origin of the along-track artifacts in an attempt to mitigate them already at the level of unconstrained solutions. We identify two major causes of along-track artifacts: (1) the presence of low-frequency noise in GRACE data and (2) the observation principle of the GRACE satellite mission, which results in a poor sensitivity of the collected inter-satellite ranging data to the East-West gradient of the gravity field. According to our studies, an increased level of noise at low frequencies can be mostly explained by inaccuracies in the estimated orbits of GRACE satellites. To suppress this type of noise, we propose: (i) to use more advanced orbit determination procedures that allow deficiencies of available force models to be mitigated; (ii) to apply proper data weighting in the frequency domain, so that that the influence of frequencies with a large noise level is downweighted. As far as East-West gradients are concerned, we find it important to use the statistically optimal combination of GRACE inter-satellite ranging data with other observations (particularly, absolute positions of GRACE and CHAMP satellites). The added value of each of

  4. 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.

  5. Towards Designing Graceful Degradation into Trajectory Based Operations: A Human-systems Integration Approach

    NASA Technical Reports Server (NTRS)

    Edwards, Tamsyn; Lee, Paul

    2017-01-01

    One of the most fundamental changes to the air traffic management system in NextGen is the concept of trajectory based operations (TBO). With the introduction of such change, system safety and resilience is a critical concern, in particular, the ability of systems to gracefully degrade. In order to design graceful degradation into a TBO envrionment, knowledge of the potential causes of degradation, and appropriate solutions, is required. In addition, previous research has predominantly explored the technological contribution to graceful degradation, frequently neglecting to consider the role of the human operator, specifically, air traffic controllers (ATCOs). This is out of step with real-world operations, and potentially limits an ecologically valid understanding of achieving graceful degradation in an air traffic control (ATC) environment. The following literature review aims to identify and summarize the literature to date on the potential causes of degradation in ATC and the solutions that may be applied within a TBO context, with a specific focus on the contribution of the air traffic controller. A framework of graceful degradation, developed from the literature, is presented. It is argued that in order to achieve graceful degradation within TBO, a human-system integration approach must be applied.

  6. Estimation of water storage change of Lake Nasser using GRACE gravity data

    NASA Astrophysics Data System (ADS)

    Zahran, Khaled

    2010-05-01

    Lake Nasser, which impounds by the High Dam, is the main water reservoir for the whole Egyptian territory. Water storage at the lake plays an essential role in water demands and affects almost the whole country. Thus, observation based information about water income, the spatial distribution and temporal variation of water storage is of great importance. We used data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission to determine the spatiotemporal variation of water stored on the Lake or beneath the crust surrounding it. Integrated gravity signals from Grace have been separated into its individual components related to mass redistribution in and around the Lake. Temporal gravity variation from GRACE correlated quiet well with the hydrological cycle of the Lake. Spectral analysis has been used to differentiate between water storage in the Lake and the spatial distribution of underground water variation. On the other hand, GRACE data enable the complete scope of the whole Nile basin and its relation to the water storage of the Lake. In this manner, filtering of the spherical harmonics from GRACE plays an important role and has been tested in the current research. Finally, global data from GRACE to the whole Nile basin together with global hydrological models give important information of the seasonal water income to the Lake and puts an important step toward for the construction of a hydrological model to predict water income to the Lake.

  7. 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.

  8. A Comparison of Approaches to Merge GRACE Observations with Hydrological Models

    NASA Astrophysics Data System (ADS)

    Schumacher, M.; Kusche, J.; Rodell, M.

    2016-12-01

    Global hydrological models contribute to the understanding and quantification of the global water cycle. However, large model uncertainties persist due to the simplified representation of hydrological processes and due to uncertainties of forcing data. The Gravity Recovery And Climate Experiment (GRACE) satellite mission is the first geodetic tool that since 2002 provides an independent observation of total water storage (TWS) changes, i.e. the sum of vegetation, surface and sub-surface water changes, with global coverage and a spatial resolution of a few hundred kilometers. Merging GRACE TWS changes and hydrological model simulations has a twofold advantage: (i) the limited representation of the real world, simulated by hydrological models, can be constrained by GRACE observations, and (ii) GRACE TWS can be disaggregated into individual water storage compartments, as well as in the lateral and temporal dimensions. In this presentation, we will discuss three successful data-model fusion frameworks: (1) the data-model blending approach developed at the Australian National University, (2) the NASA's data assimilation strategy, and (3) the calibration and data assimilation framework developed at the University of Bonn. Similarities and differences of these three frameworks and their benefits and limitations will be demonstrated. Possible strategies to address the temporal and spatial resolution mismatch (between model simulations and GRACE observations), as well as to realistically describe the sources of uncertainties in hydrological model simulations and GRACE observations will be explained. Finally, we will show data-model fusion results for the Mississippi (USA) and the Murray-Darling River Basin (Australia).

  9. 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.

  10. Additive value of the CRUSADE score to the GRACE score for mortality risk prediction in patients with acute coronary syndromes.

    PubMed

    Cordero, Alberto; Rodriguez-Manero, Moisés; García-Acuña, Jose M; López-Palop, Ramón; Cid, Belen; Carrillo, Pilar; Agra-Bermejo, Rosa; González-Salvado, Violeta; Iglesias-Alvarez, Diego; Bertomeu-Martínez, Vicente; González-Juanatey, Jose R

    2017-10-15

    Acute coronary syndrome (ACS) treatments increase bleeding complications that also impair prognosis. Bleeding risk scores reclassification of actual mortality risk estimated by the GRACE score might improve overall estimation. Observational and prospective study of all ACS patients admitted in two hospitals. Mortality risk was assessed by the GRACE score and bleeding risk by the CRUSADE score. We analyzed the net reclassification improvement (NRI) of adding the CRUSADE score to the GRACE score. We included 6997 patients, mean age 67.4 (12.9), 38.0% ST-elevation ACS, mean GRACE score 145.2 (39.9). The percentage of patients with CRUSADE score >20 or >50 increased as the GRACE score was higher. Hospital mortality was 5.3% and the addition of the CRUSADE score reclassified a relevant percentage of patients with GRACE score >109; NRI was 3.80% (1.10-6.10). During follow-up, (median 53.0months) mortality rate was 22.6% and patients with CRUSADE score >50 had significantly higher mortality rates in all GRACE score categories; NRI was high (46.6%, 95% CI 41.0-53.1). The multivariate analysis outlined the independent predictive value of CRUSADE score >20 or >50 as well as GRACE scores 109-139 and >140. The addition of the CRUSADE score to the GRACE score improved mortality risk estimation. A CRUSADE score >50 identified patients with higher post-discharge mortality and higher hospital mortality if GRACE score was >109. The CRUSADE score improved hospital and long-term mortality prediction in patients with GRACE score >140. Individual mortality risk estimation should integrate the CRUSADE and GRACE scores. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. 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

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

  15. Extending the record of time-variable gravity from GRACE and conventional tracking data

    NASA Astrophysics Data System (ADS)

    Talpe, M.; Nerem, R.; Lemoine, F. G.; Pilinski, E. B.; Chinn, D. S.; Riva, R.

    2013-12-01

    Time-variable gravity offers an invaluable perspective of mass redistribution processes. The monthly, high-resolution fields collected by GRACE have enabled the study of the time-variable component of Earth's gravity field since 2002. In this work, we seek to extend the time-dependent record of gravity beyond the time frame of the GRACE mission. Conventional tracking data from SLR and DORIS provide an extensive and continuous record of Earth's lower degree gravity coefficients. As such, they are used to complement the high-resolution fields from GRACE via Empirical Orthogonal Functions (EOF). The spatial modes of the GRACE Release 5 fields, obtained from an EOF decomposition, are combined with the temporal modes of the conventional tracking data, determined from normal equations, to generate reconstructed fields. These fields are global fields of GRACE resolution (up to degree and order 60) covering the timespan of the conventional tracking data (1993 - present). The errors of the reconstructed fields are defined from the measurement error covariances of the conventional tracking data. To validate the reconstructions, we first apply spatially averaging kernels of Greenland and Antarctica to the reconstructed global fields. Over the GRACE data timespan (2003 - 2013), the resulting mass change curves from the reconstructed fields match with mass change values found in recent literature. We plan to further test the validation of the reconstructed mass change curves that predate GRACE by comparing them against in situ glaciological data. Finally, we seek to further improve the reconstruction by isolating the signals of Greenland, Antarctica, and glaciers via individual fingerprints in the EOF analysis. We will show how the use of fingerprints influences the reconstructed fields and mass change curves.

  16. 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.

  17. 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

    2016-11-01

    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.

  18. 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

  19. Analysis of RL05 GRACE-Based and GOCE/GRACE-Based GGMs Using Gravity Measurements at Borowa Gora Geodetic-Geophysical Observatory

    NASA Astrophysics Data System (ADS)

    Godah, Walyeldeen; Szelachowska, Malgorzata; Krynski, Jan; Dykowski, Przemyslaw

    2016-08-01

    The dedicated gravity satellite missions have contributed to many geodynamics and geophysics related studies. They also revolutionized the understanding of the climate system. The GRACE- based monthly Global Geopotential Models (GGMs) are available for more than 13.5 years. Recently, GGMs containing spherical harmonic coefficients as a function of time have been developed using GRACE and GOCE data.Absolute gravity measurements were conducted on a gravity test network at the Borowa Gora Geodetic- Geophysical Observatory (north of Warsaw) on a monthly basis since September 2008 using the A10-020 absolute gravimeter. In this contribution temporal gravity variations obtained from RL05 GRACE-based GGMs and from GOCE/GRACE-based GGMs were compared with the corresponding ones obtained from the abovementioned time-series of absolute gravity measurements. The results of the comparison were analysed. The possibility of using monthly based time series of absolute gravity data for calibration/validation of temporal mass variations derived from satellite observations was discussed.

  20. Revisiting GRACE Antarctic ice mass trends and accelerations considering autocorrelation

    NASA Astrophysics Data System (ADS)

    Williams, Simon D. P.; Moore, Philip; King, Matt A.; Whitehouse, Pippa L.

    2014-01-01

    Previous GRACE-derived ice mass trends and accelerations have almost entirely been based on an assumption that the residuals to a regression model (including also semi-annual, annual and tidal aliasing terms) are not serially correlated. We consider ice mass change time series for Antarctica and show that significant autocorrelation is, in fact, present. We examine power-law and autoregressive models and compare them to those that assume white (uncorrelated) noise. The data do not let us separate autoregressive and power-law models but both indicate that white noise uncertainties need to be scaled up by a factor of up to 4 for accelerations and 6 for linear rates, depending on length of observations and location. For the whole of Antarctica, East Antarctica and West Antarctica the scale factors are 1.5, 1.5 and 2.2 respectively for the trends and, for the accelerations, 1.5, 1.5 and 2.1. Substantially lower scale-factors are required for offshore time series, suggesting much of the time-correlation is related to continental mass changes. Despite the higher uncertainties, we find significant (2-sigma) accelerations over much of West Antarctica (overall increasing mass loss) and Dronning Maud Land (increasing mass gain) as well as a marginally significant acceleration for the ice sheet as a whole (increasing mass loss).

  1. Continental-scale hydrological consistency of evapotranspiration products using GRACE

    NASA Astrophysics Data System (ADS)

    Lopez, O.; McCabe, M. F.

    2014-12-01

    Multiple remote sensing products based on satellite observations are available at regional and global scales, allowing to obtain an estimation of the individual components of the hydrological cycle. However, using these products to provide closure of the water budget at the basin scale with accuracy remains a challenge. In this work, 12 large continental-scale basins covering a range of various climate types were chosen as regions of interest. Terrestrial water storage changes from GRACE, streamflow data from the Global Runoff Database and precipitation from the Tropical Rainfall Measuring Mission (TRMM) Multi Satellite Precipitation Analysis (TMPA) and Global Precipitation Climatology Project (GPCP), were used as a surrogate evaluation of observed spatio-temporal patterns of multi-model evapotranspiration estimates, derived from a long-term flux product as part of the LandFLUX project. The 10 year period of analysis also allows for the estimation of temporal trends in water storage changes and provides an opportunity to examine the capacity for water budget closure.

  2. 3-D GRACE gravity model for the 2011 Japan earthquake

    NASA Astrophysics Data System (ADS)

    Sastry, Rambhatla G.; Sonker, Mahendra K.

    2017-02-01

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

  3. Inflation with a graceful exit in a random landscape

    NASA Astrophysics Data System (ADS)

    Pedro, F. G.; Westphal, A.

    2017-03-01

    We develop a stochastic description of small-field inflationary histories with a graceful exit in a random potential whose Hessian is a Gaussian random matrix as a model of the unstructured part of the string landscape. The dynamical evolution in such a random potential from a small-field inflation region towards a viable late-time de Sitter (dS) minimum maps to the dynamics of Dyson Brownian motion describing the relaxation of non-equilibrium eigenvalue spectra in random matrix theory. We analytically compute the relaxation probability in a saddle point approximation of the partition function of the eigenvalue distribution of the Wigner ensemble describing the mass matrices of the critical points. When applied to small-field inflation in the landscape, this leads to an exponentially strong bias against small-field ranges and an upper bound N ≪ 10 on the number of light fields N participating during inflation from the non-observation of negative spatial curvature.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    By operating for more than one decade now, the GRACE satellite provides valuable information on the total water storage (TWS) for hydrological and hydro-meteorological applications. The increasing interest in use of the GRACE-based TWS requires an in-depth assessment of the reliability of the outputs and also its uncertainties. Through years of development, different post-processing methods have been suggested for TWS estimation. However, since GRACE offers an unique way to provide high spatial and temporal scale TWS, there is no global ground truth data available to fully validate the results. In this contribution, we re-assess a number of commonly used post-processing methods using a simulated GRACE-type 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. Three non-isotropic filter methods from Kusche (2007) and a combined filter from DDK1 and DDK3 based on the ground tracks are tested. Rescaling factors estimated from five different hydrological models and the ensemble median are applied to the post-processed simulated GRACE-type TWS estimates to correct the bias and leakage. Time variant rescaling factors as monthly scaling factors and scaling factors for seasonal and long-term variations separately are investigated as well. 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 (Zhang et al., 2016) and will subsequently recommend a processing strategy that shall also be applied for planned GRACE and GRACE-FO Level-3 products for terrestrial 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

  6. Approaching 8 Years On Orbit: Status and Outlook for GRACE (Invited)

    NASA Astrophysics Data System (ADS)

    Watkins, M. M.; Tapley, B. D.; Flechtner, F.; Bettadpur, S. V.

    2009-12-01

    GRACE was launched in March 2002 and since then has produced an essentially continuous set of gravity data now approaching 8 years in length. This ever-lengthening data span has been key in allowing users of the data to begin to understand the important relationships between annual, interannual, and longer term variability in mass flux in the Earth system, and the GRACE Project and sponsoring agencies are dedicated to maximizing the usable life of the mission. Although the spacecraft each show some signs of "old age" in their extended mission phase, they continue to produce data equal in quality to that of the prime mission, while our analysis techniques continue to very significantly improve. Most of the improvements in analysis have come from superior treatment of aliasing effects due to ocean tides, non-tidal ocean mass variations, and atmospheric mass, and high frequency hydrological variability. In this talk, we will provide a summary of the latest science results from the cutting edge of GRACE, review the engineering health and status of the spacecraft, including outlook for the next several years, and finally we will review the plans by the project analysis centers (CSR and JPL in the US, and GFZ in Germany) for the next major reprocessing of the entire GRACE dataset, referred to in the project as Release 5. All centers expect significant improvements to the quality of the entire multi-year GRACE dataset with this reprocessing, expected to be released in mid-2010.

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

    PubMed

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

    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.

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

    USGS Publications Warehouse

    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

    2015-01-01

    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.

  9. The Generic Resolution Advisor and Conflict Evaluator (GRACE) for Detect-And-Avoid Systems

    NASA Technical Reports Server (NTRS)

    Abramson, Michael; Refai, Mohamad; Santiago, Confesor

    2017-01-01

    Java Architecture for Detect-And-Avoid (DAA) Extensibility and Modeling (JADEM) was developed at NASA Ames Research Center as a research and modeling tool for Unmanned Aircraft Systems (UAS) Integration in the National Airspace System (NAS). UAS will be required to have DAA systems in order to fulfill the regulatory requirement to remain well clear'' of other traffic. JADEM supports research on technological requirements and Minimum Operational Performance Standards (MOPS) for UAS DAA systems by providing a flexible and extensible software platform that includes models and algorithms for all major DAA functions. This paper describes one of these algorithms, the Generic Resolution Advisor and Conflict Evaluator (GRACE). GRACE supports two core DAA functions: threat evaluation and guidance. GRACE is generic in the sense that it is designed to work with any aircraft or sensor type (both cooperative and non-cooperative), and to be used in various applications and DAA guidance concepts, thus supporting evolving MOPS requirements and research. GRACE combines flexibility, robustness, and computational efficiency. It has modest memory requirements and can handle multiple cooperative and noncooperative intruders. GRACE has been used as a core JADEM component in several real-time and fast-time experiments, including human-in-the-loop simulations and live flight tests.

  10. 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.

  11. Status of GRACE-FO accelerometers and of the future accelerometer development for next gravity missions

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    The GRACE FO mission, led by the JPL (Jet Propulsion Laboratory) and GFZ (GeoForschungsZentrum), is an Earth-orbiting gravity mission, continuation of the GRACE mission, which will produce an accurate model of the Earth's gravity field variation providing global climatic data during five years at least. Europe and US propose new gravity missions beyond GRACE-FO, with improving performance thanks to laser interferometry and better accelerometers. The poster will firstly present the status of GRACE-FO accelerometers which was delivered beginning of 2016, with the expected performance and the main test results. Then, the improvement of the accelerometer design for future gravity mission will be detailed. This new design is based on MicroSTAR configuration, a 3-axes ultra-sensitive accelerometer, with a cubic proof-mass which give, beyond the linear acceleration, the 3 angular accelerations for a better satellite attitude control. For linear acceleration, the performance will be improved by at least an order of magnitude with respect to GRACE-FO.

  12. Global runoff estimates derived from GRACE dataset and in situ observations

    NASA Astrophysics Data System (ADS)

    Chandanpurkar, H. A.; Famiglietti, J. S.; Reager, J. T.; David, C. H.; Syed, T. H.

    2012-12-01

    Global in situ measurements of river discharge from streamflow gauge-stations are available with some consistency for the past several decades. However, the gauge-stations suffer from three major limitations: 1. Lack of regular maintenance and consequent data gaps; 2. Inadequate density of the gauge-stations in the delta regions at the continental margins; and 3. No representation of the sub-surface runoff. Since 2002, Gravity Recovery and Climate Experiment (GRACE) mission has been providing monthly datasets of terrestrial water storage anomaly that can be used to derive runoff values when combined with an atmospheric water balance reanalysis dataset during the last decade. In this research, we compare the GRACE dataset with the corresponding streamflow observations for the world's major river basins. Based on this comparison, we calculate a correction factor to the streamflow observations and estimate adjustment from various limitations on accuracy, from both the GRACE derived runoff estimates as well as those associated with the gauge-station observations, using Bayesian Model Averaging technique. The correction factor is assigned separately for major river basins. Then we apply these correction factors to the streamflow observations outside of the GRACE dataset to produce a gapless, extended time series of global river runoff providing the longevity of the streamflow observations and the improved accuracy due to the GRACE dataset.

  13. 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.

  14. GRACE satellite gravimetry to monitor AMOC variability and coherence in the Atlantic Ocean

    NASA Astrophysics Data System (ADS)

    Bentel, K.; Landerer, F. W.; Boening, C.; Wiese, D. N.; Watkins, M. M.

    2015-12-01

    The Atlantic Meridional Overturning Circulation (AMOC) is a key mechanism in basin-scale heat transport to high latitudes. It has significant impact in particular in the Northern Hemisphere and on Northwestern Europe's climate. The dynamics of the AMOC especially in the North Atlantic have been observed and described in recent model and observational studies. However, in-situ observations are limited to a few latitudes where observational arrays are deployed. Also, the physical relationship between ocean bottom pressure (OBP) and the AMOC has been characterized in recent literature. Here, we employ GRACE-derived OBP (from the JPL-RL05M mascons solution) to derive AMOC anomalies through physical relations. Viability of the approach to infer AMOC variability from GRACE-OBP observations has been demonstrated by comparing the GRACE-derived AMOC signal to in-situ observations by the RAPID array at 26.5N. In contrast to in-situ observations, GRACE observations provide the unique opportunity to derive AMOC anomalies continuously (for the GRACE time period from 2003 until present) across all latitudes of the basin, and evaluate spatial and temporal coherence.

  15. Correlating total dissolved solid concentration changes with GRACE-based changes in water table depth

    NASA Astrophysics Data System (ADS)

    Gibbons, A.; Famiglietti, J. S.; Reager, J. T.

    2012-12-01

    NASA's Gravity Recovery and Climate Experiment (GRACE) mission has been used to monitor monthly groundwater storage variations in some of the world's largest basins. However, only large-scale changes in groundwater storage (> 150,000 km2) can be inferred because of the coarse resolution of the monthly GRACE solution. Such studies have also failed to address groundwater quality, which is nearly matched by the importance of its quantity. This study correlated in-situ total dissolved solid (TDS) concentrations to GRACE-derived changes in groundwater table depth for the High Plains groundwater basin of the central United States. The change in groundwater storage was calculated from the change in total water storage by subtracting the other hydrologic components (surface water, snow water equivalent, and soil moisture) using observed and modeled records. The GRACE-derived change in monthly groundwater storage was converted to water table depth changes using specific yield data for the High Plains aquifer. The GRACE groundwater storage variation was down-scaled by spatially interpolating in situ water-level data using kriging. Observed TDS concentrations were also spatially interpolated with kriging. A correlation coefficient was calculated to evaluate the validity of the relationship between changes in quantity and changes in quality. This work has implications for improving groundwater management practices by estimating groundwater quality on a global scale using remote sensing.

  16. 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.

  17. 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…

  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. 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

  20. Optimized smoothing of Gravity Recovery and Climate Experiment (GRACE) time-variable gravity observations

    NASA Astrophysics Data System (ADS)

    Chen, J. L.; Wilson, C. R.; Seo, K.-W.

    2006-06-01

    High-degree and high-order spherical harmonics of time-variable gravity fields observed by the Gravity Recovery and Climate Experiment (GRACE) gravity mission are dominated by noise. We develop two smoothing methods that suppress these high-degree and high-order errors with results superior to more commonly used Gaussian smoothing. These optimized smoothing methods considerably improve signal-to-noise levels of GRACE terrestrial water storage estimates relative to residual signal and noise over the oceans and show significantly better spatial resolution and lower leakage error. On the basis of analysis using an advanced land surface model, the equivalent spatial resolution from these optimized smoothing estimates is about 500 km, compared to the roughly 800-1000 km Gaussian smoothing that is required to suppress high-degree noise in the GRACE fields.

  1. 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.

  2. 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.

  3. The quest for a consistent signal in ground and GRACE gravity time-series

    NASA Astrophysics Data System (ADS)

    Camp, Michel Van; Viron, Olivier de; Métivier, Laurent; Meurers, Bruno; Francis, Olivier

    2014-04-01

    Recent studies show that terrestrial and space-based observations of gravity agree over Europe. In this paper, we compare time-series of terrestrial gravity (including the contribution due to surface displacement) as measured by superconducting gravimeters (SGs), space-based observations from Gravity Recovery and Climate Experiment (GRACE) and predicted changes in gravity derived from two global hydrological models at 10 SG stations in central Europe. Despite the fact that all observations and models observe a maximum in the same season due to water storage changes, there is little agreement between the SG time-series even when they are separated by distances smaller than the spatial resolution of GRACE. We also demonstrate that GRACE and the SG observations and the water storage models do not display significant correlation at seasonal periods nor at interannual periods. These findings are consistent with the fact that the SGs are sensitive primarily to mass changes in the few hundred metres surrounding the station.

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

    PubMed

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

    2014-10-28

    The Implicit Association Test (IAT) is a computerized two-choice discrimination task in which stimuli have to be categorized as belonging to target categories or attribute categories by pressing, as quickly and accurately as possible, one of two response keys. The discrimination association model has been recently proposed for the analysis of reaction time and accuracy of an individual respondent to the IAT. The model disentangles the influences of three qualitatively different components on the responses to the IAT: stimuli discrimination, automatic association, and termination criterion. The article presents General Race (GRace), a MATLAB-based application for fitting the discrimination association model to IAT data. GRace has been developed for Windows as a standalone application. It is user-friendly and does not require any programming experience. The use of GRace is illustrated on the data of a Coca Cola-Pepsi Cola IAT, and the results of the analysis are interpreted and discussed.

  5. 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

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

    PubMed

    Sun, Y; Ditmar, P; Riva, R

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

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

    NASA Astrophysics Data System (ADS)

    Kostelecky, Jan; Klokocnik, Jaroslav; Bezdek, Ales

    2017-04-01

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

  8. 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

  9. 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.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Gu, Yanchao; Fan, Dongming; You, Wei

    2017-07-01

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

  13. Performance of GOCE and GRACE-derived mean dynamic topographies in resolving Antarctic Circumpolar Current fronts

    NASA Astrophysics Data System (ADS)

    Volkov, Denis L.; Zlotnicki, Victor

    2012-06-01

    Presently, two satellite missions, Gravity Recovery and Climate Experiment (GRACE) and Gravity field and steady-state Ocean Circulation Explorer (GOCE), are making detailed measurements of the Earth's gravity field, from which the geoid can be obtained. The mean dynamic topography (MDT) is the difference between the time-averaged sea surface height and the geoid. The GOCE mission is aimed at determining the geoid with superior accuracy and spatial resolution, so that a more accurate MDT can be estimated. In this study, we determine the mean positions of the Antarctic Circumpolar Current fronts using the purely geodetic estimates of the MDT constructed from an altimetric mean sea surface and GOCE and GRACE geoids. Overall, the frontal positions obtained from the GOCE and GRACE MDTs are close to each other. This means that these independent estimates are robust and can potentially be used to validate frontal positions obtained from sparse and irregular in situ measurements. The geodetic frontal positions are compared to earlier estimates as well as to those derived from MDTs based on satellite and in situ measurements and those obtained from an ocean data synthesis product. The position of the Sub-Antarctic Front identified in the GOCE MDT is found to be in better agreement with the previous estimates than that identified in the GRACE MDT. The geostrophic velocities derived from the GOCE MDT are also closer to observations than those derived from the GRACE MDT. Our results thus show that the GOCE mission represents an improvement upon GRACE in terms of the time-averaged geoid.

  14. GRACE Score Validation in Predicting Hospital Mortality: Analysis of the Role of Sex.

    PubMed

    de-Miguel-Balsa, Eva; Latour-Pérez, Jaime; Baeza-Román, Anna; Amorós-Verdú, Cristina; Fernández-Lozano, Juan Antonio

    2017-01-20

    The GRACE (Global Registry of Acute Coronary Events) risk score is recommended for risk stratification in acute coronary syndrome (ACS). It does not include sex, a variable strongly associated with ACS prognosis. The aim of this study was to examine if sex adds prognostic information to the GRACE score in a contemporary population. Analysis of discrimination and calibration of GRACE score in the validation population, derived from the ARIAM-SEMICYUC registry (2012-2015). Outcome was hospital mortality. The uniformity of fit of the score was tested in predefined subpopulations: with and without ST-segment elevation myocardial infarction (STEMI and NSTEMI). A total of 9781 patients were included: 4598 with NSTEMI (28% women) and 5183 with STEMI (23% women). Discriminative capacity of the GRACE score was significantly lower in women with STEMI compared to men (area under the receiver operating characteristic curve [AUC] 0.82, 95% CI 0.78-0.86 vs. AUC 0.90, 95% CI 0.88-0.92, p = 0.0006). In multivariate analysis, female sex predicted hospital mortality independently of GRACE in STEMI (p = 0.019) but not in NSTEMI (p = 0.356) (interaction p = 0.0308). However, neither the AUC nor the net reclassification index (NRI) improved by including female sex in the STEMI subpopulation (NRI 0.0011, 95% CI -0.023 to 0.025; p = 0.928). Although female sex was an independent predictor of hospital mortality in the STEMI subpopulation, it does not substantially improve the discriminative ability of GRACE score.

  15. 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.

  16. 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.

  17. Evolution of high-latitude snow mass derived from GRACE regional solutions

    NASA Astrophysics Data System (ADS)

    Frappart, Frédéric; Ramillien, Guillaume; Seoane, Lucia; Güntner, Andreas

    2015-04-01

    Since the launch of the GRACE gravimetry from space mission in March 2002, GRACE data allow the determination of tiny time variations of the Earth's gravity and particularly the effects of fluid mass redistributions at the surface of the Earth. Since GRACE provides vertically-integrated gravity measurements that represent the sum of all mass redistributions in the Earth's system, we propose to apply a method to unravel these different contributions to the satellite gravity measurements, that are related to the variations of water mass of the main reservoirs (i.e., atmosphere, oceans, continental water storage and solid Earth). The approach was previously developed to separate these contributions by inverting Stokes coefficients (i.e., spherical harmonics) up to degree 60 of the Level-2 GRACE solutions with the input of the a priori information of space and time correlations derived from hydrology models such as WGHM and ISBA-TRIP. GRACE Level-2 solutions suffer from the presence of important north-south striping when determining Stokes coefficients which are geophysically unrealistic, and aliasing of short-time phenomena. To overcome this problem, we use GRACE regional solutions obtained adjusting the surface mass density distribution at the surface of the Earth from the accurate satellite to satellite velocity variations or K-Band Range Rate (KBRR) measurements. We propose here to adapt the separation technique to regional grid points. For this purpose, we use a generalized least-square adjustment to extract in particular the time series of the gridded snow mass variations in high latitude regions, and assuming a simple linear mixing of the source signals.

  18. Signal and noise in Gravity Recovery and Climate Experiment (GRACE) observed surface mass variations

    NASA Astrophysics Data System (ADS)

    Schrama, Ernst J. O.; Wouters, Bert; LavalléE, David A.

    2007-08-01

    The Gravity Recovery and Climate Experiment (GRACE) product used for this study consists of 43 monthly potential coefficient sets released by the GRACE science team which are used to generate surface mass thickness grids expressed as equivalent water heights (EQWHs). We optimized both the smoothing radius and the level of approximation by empirical orthogonal functions (EOFs) and found that 6.25° and three modes are able to describe more than 73.5% of the variance. The EQWHs obtained by the EOF method describe all known variations in the continental hydrology, present-day ice sheet melting, and global isostatic adjustment. To assess the quality of the estimated grids, we constructed degree error spectra of EQWHs. We conclude that a significant part of the errors in GRACE can be explained by a scaling factor of 0.85 relative to degree error estimates provided by the GGM02C gravity model but that the present-day errors in the GRACE data are a factor 2 to 5 larger than forecasted by tide model differences and atmospheric pressure differences. Comparison to a network of 59 International GNSS Service (IGS) stations confined the filter parameter settings to three EOF modes and 5° or 6.25° smoothing radius. Residuals that remain after the EOF method do exhibit S2 aliasing errors and a semiannual continental hydrology signal contained in the Global Land Data Assimilation Systems (GLDAS) model. Further analysis of the residual EOF signal revealed alternating track correlation patterns that are partially explained by the GRACE covariance matrix and the handling of nuisance parameters in the GRACE data processing.

  19. Comparing the data-driven and the model-dependent strategies for improving filtered GRACE signal

    NASA Astrophysics Data System (ADS)

    Dutt Vishwakarma, Bramha; Sneeuw, Nico

    2017-04-01

    The noisy level 02 GRACE products from various groups need to be filtered in order to obtain meaningful information about water mass transport within the Earth system. Filtering affects signal, which increases the uncertainty in the filtered GRACE observed total water storage time series. The signal loss is counter acted using a correction strategy that typically makes use of models. The accuracy of model-dependent methods is dependent on the accuracy of the model, which raises doubts on accuracy of corrected GRACE products over poorly modeled regions. This led to the development of data-driven methods. Although research contributions using a model-dependent method or a data-driven method claim that the corrected GRACE products are superior to filtered products, a comparison of model dependent methods and the data-driven methods is essential to choose the best one. In this contribution, we compare the three most popular model-dependent approaches: additive approach, multiplicative approach, scaling approach, and two data-driven methods proposed recently. In order to be comprehensive, we analyze the performance of these correction strategies over 32 catchments of different sizes located in different climate zones. In a realistic closed-loop simulation, we find that the data-driven methods are consistently superior to the model-dependent approaches. At last we analyze the desiccation of Aral Sea and lake Urmia with the GRACE products, and compare the corrected total water storage change with reports and contributions from different groups. We find that the model-dependent approaches have a tendency to overestimate the rate of water mass loss recorded by GRACE satellites.

  20. Human-induced Terrestrial Water Storage Change: A Global Analysis using Hydrological Models and GRACE

    NASA Astrophysics Data System (ADS)

    Felfelani, F.; Pokhrel, Y. N.

    2016-12-01

    Hydrological models and data derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are used to study terrestrial water storage (TWS) change; however, both have disadvantages that necessitate the integrated use of them. While GRACE doesn't disintegrate the vertical storage into its components, most models do not account for human activities. Here we use two Land Surface Models (LSMs), i.e., HiGW-MAT and PCRGLOBWB that fully couple natural and human drivers of changes in water cycle, explicitly simulating the changes in various TWS compartments. We first evaluate the models performance with GRACE observations. Then, we quantify the human footprint over global river basins located in different geographic and climate regions. To quantify human impacts, a new framework is proposed based on the GRACE observations (representing both climate variability and human activities) together with the natural simulation of LSMs using water budget equation (P-ET-R; P for precipitation, ET for evapotranspiration, and R for runoff). Finally, we examine the uncertainty in TWS simulations arising from the uncertainties in forcing data. Results indicate that, in snow-dominated regions, PCRGLOBWB generally fails to reproduce neither the interannual variability of observed TWS nor the seasonal cycle, while HiGW-MAT model shows significantly better results. In basins with human signatures, PCRGLOBWB generally shows better agreement with GRACE compared to HiGW-MAT. It is found that HiGW-MAT tends to overestimate groundwater depletion in basins with human impacts (e.g., Amudarya, Colorado, Euphrates and Indus), which results in larger negative interannual TWS trend compared to GRACE. Euphrates and Ganges river basins experience the highest human-induced TWS deficit rates (2.08 cm/yr and 1.94 cm/yr, respectively) during the simulation period of 2002-2010. Uncertainty analysis of results from the same model but with different forcing data suggests a high standard

  1. 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.

  2. Downscaling GRACE satellite data for sub-region groundwater storage estimates in California's Central Valley

    NASA Astrophysics Data System (ADS)

    Kuss, A. M.; Newcomer, M. E.; Hsu, W.; Bourai, A.; Puranam, A.; Landerer, F. W.; Schmidt, C.

    2012-12-01

    The Central Valley aquifer (CVA) is a vital economic and environmental resource for California and the United States, and supplies water for one of the most agriculturally productive regions in the world. Recent estimates of groundwater (GW) availability in California have indicated declines in GW levels that may pose a threat to sustainable groundwater use in this region. The Gravity Recovery and Climate Experiment (GRACE) can be used to estimate variations in total water storage (TWS) and are therefore used to estimate GW storage changes within the CVA. However, using GRACE data in the CVA is challenging due to the coarse spatial resolution and increased error. To compensate for this, we used a statistical downscaling approach applied to GRACE data at the sub-region level using GW storage estimates from the California Department of Water Resources' (DWR) C2VSim hydrological model. This method produced a spatially and temporally variable GW anomaly dataset for sub-region GW management and for analysis of GW changes influenced by spatial and temporal variability. An additional challenge for this region is the influence of natural climate variability, altering GW recharge and influencing pumping practices. Understanding the effects of climate variability on GW storage changes, may improve GRACE TWS and GW estimates during periods of increased rain or droughts. Thus, the GRACE TWS and GW storage estimates were compared to the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO) using singular spectral analysis (SSA). Results from SSA indicate that variations in GRACE TWS are moderately correlated to PDO (10-25 year cycle), although low correlations were observed when compared to ENSO (2-7 year cycle). The incorporation of these new methods for estimating variations in groundwater storage in highly productive aquifers may improve water management techniques in California.

  3. 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

  4. 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

  5. Odd-graceful labeling algorithm and its implementation of generalized ring core network

    NASA Astrophysics Data System (ADS)

    Xie, Jianmin; Hong, Wenmei; Zhao, Tinggang; Yao, Bing

    2017-08-01

    The computer implementation of some labeling algorithms of special networks has practical guiding significance to computer communication network system design of functional, reliability, low communication cost. Generalized ring core network is a very important hybrid network topology structure and it is the basis of generalized ring network. In this paper, based on the requirements of research of generalized ring network addressing, the author has designed the odd-graceful labeling algorithm of generalized ring core network when n1, n2,…nm ≡ 0(mod 4), proved odd-graceful of the structure, worked out the corresponding software, and shown the practical effectiveness of this algorithm with our experimental data.

  6. 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

  7. Determination of dominant periodic components of water storage changes from GRACE and global hydrology models

    NASA Astrophysics Data System (ADS)

    Schmidt, R.; Petrovic, S.; Guntner, A.; Wunsch, J.; Barthelmes, F.; Hengst, R.; Kusche, J.

    2007-12-01

    Variations of mass anomalies at the Earth's surface derived from monthly time series of global models of the Earth's gravity field of the US-German twin satellite mission GRACE (Gravity Recovery and Climate Experiment) clearly trace mass redistributions induced by continental hydrology. Previous studies indicate that such mass redistributions are dominated by annual and - in some regions - semiannual variations. In this contribution, we explicitly estimate for the first time the spectra of such dominant periodic patterns (in terms of periods, phases and amplitudes) that are not restricted to the fundamental annual frequency and its overtones. To this end we use a novel method that combines conventional empirical orthogonal functions (EOF) analysis with a determination of sine waves of arbitrary periods from the principal components based on time series of spatial maps of surface mass anomalies from GRACE and global hydrology models. The significance of the GRACE-derived spectra in view of the correlated GRACE data errors is assessed by means of a Monte-Carlo technique using available GRACE error covariance information. Considering only the significant, but dominating terms we can construct filtered GRACE data series which will serve for an improved validation and calibration of global hydrology models. This is demonstrated using the results from about 5 years of GRACE gravity fields of the GFZ-RL04 series and from independent state-of-the-art hydrology models. As one result our study reveals a systematic advance of the phases of the dominating annual terms of the hydrological models as compared to GRACE in the range of 1 to 6 weeks. This indicates deficiencies of the hydrological models w.r.t. runoff routing in the river network and/or water retention in lakes and wetlands. As a further result the analysis shows that besides annual and semiannual variations (specific only to some basins) also long-periodic signals with periods in the range of 2.1 to 2.5 years

  8. 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

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  10. 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

  11. Monitoring groundwater storage changes in complex basement aquifers: An evaluation of the GRACE satellites over East Africa

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Although the use of the Gravity Recovery and Climate Experiment (GRACE) satellites to monitor groundwater storage changes has become commonplace, our evaluation suggests that careful processing of the GRACE data is necessary to extract a representative signal especially in regions with significant surface water storage (i.e., lakes/reservoirs). In our study, we use cautiously processed data sets, including GRACE, lake altimetry, and model soil moisture, to reduce scaling factor bias and compare GRACE-derived groundwater storage changes to in situ groundwater observations over parts of East Africa. Over the period 2007-2010, a strong correlation between in situ groundwater storage changes and GRACE groundwater estimates (Spearman's ρ = 0.6) is found. Piecewise trend analyses for the GRACE groundwater estimates reveal significant negative storage changes that are attributed to groundwater use and climate variability. Further analysis comparing groundwater and satellite precipitation data sets permits identification of regional groundwater characterization. For example, our results identify potentially permeable and/or shallow groundwater systems underlying Tanzania and deep and/or less permeable groundwater systems underlying the Upper Nile basin. Regional groundwater behaviors in the semiarid regions of Northern Kenya are attributed to hydraulic connections to recharge zones outside the subbasin boundary. Our results prove the utility of applying GRACE in monitoring groundwater resources in hydrologically complex regions that are undersampled and where policies limit data accessibility.

  12. 14 CFR 135.301 - Crewmember: Tests and checks, grace provisions, training to accepted standards.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... provisions, training to accepted standards. 135.301 Section 135.301 Aeronautics and Space FEDERAL AVIATION...: CERTIFICATION AND OPERATIONS OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING..., grace provisions, training to accepted standards. (a) If a crewmember who is required to take a test...

  13. 14 CFR 135.301 - Crewmember: Tests and checks, grace provisions, training to accepted standards.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... provisions, training to accepted standards. 135.301 Section 135.301 Aeronautics and Space FEDERAL AVIATION...: CERTIFICATION AND OPERATIONS OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING..., grace provisions, training to accepted standards. (a) If a crewmember who is required to take a test...

  14. 14 CFR 135.301 - Crewmember: Tests and checks, grace provisions, training to accepted standards.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... provisions, training to accepted standards. 135.301 Section 135.301 Aeronautics and Space FEDERAL AVIATION...: CERTIFICATION AND OPERATIONS OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING..., grace provisions, training to accepted standards. (a) If a crewmember who is required to take a test...

  15. 14 CFR 135.301 - Crewmember: Tests and checks, grace provisions, training to accepted standards.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... provisions, training to accepted standards. 135.301 Section 135.301 Aeronautics and Space FEDERAL AVIATION...: CERTIFICATION AND OPERATIONS OPERATING REQUIREMENTS: COMMUTER AND ON DEMAND OPERATIONS AND RULES GOVERNING..., grace provisions, training to accepted standards. (a) If a crewmember who is required to take a test...

  16. GRACE: a controlled environment for adaptive optics at the William Herschel Telescope

    NASA Astrophysics Data System (ADS)

    Talbot, Gordon; Abrams, Don C.; Benn, Chris R.; Chopping, Alan; Dee, Kevin; Els, Sebastian; Fisher, Martin; Goodsell, Stephen; Gray, Doug; Jolley, Paul D.

    2004-10-01

    The William Herschel Telescope (WHT) has an adaptive optics (AO) suite consisting of the AO system NAOMI, near IR imager INGRID, optical field spectrograph OASIS and coronagraph OSCA. GRACE (GRound based Adaptive optics Controlled Environment) is a dedicated structure at a Nasmyth focus designed to facilitate routine AO use by providing a controlled environment for the instrument system. However, GRACE is not just a building; it is all of the systems associated with providing the controlled environment, especially the control of air quality, temperature and flow. A key concern was that adding the GRACE building to the Nasmyth platform would not adversely change the telescope performance. This paper gives the background to GRACE, its specification and design, the building construction and installation, the environmental controls installed and their performance, the services provided, the effect of the new structure on telescope performance, the results of the project, including the effect having a controlled environment on AO performance and its planned use for a Rayleigh laser guide star system.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Grace-Derived Groundwater Depletion from Both Shallow and Deep Aquifers within North China Plain

    NASA Astrophysics Data System (ADS)

    Pan, Y.; Huang, Z.; Yeh, P. J. F.; Gong, H.

    2014-12-01

    This study explores the capability of GRACE to detect groundwater storage variations in the two sub-regions in the North China Plain (NCP): the Piedmont Plain (PP, mainly shallow unconfined-aquifers) and East-Central Plain (ECP, mainly deep confined-aquifers), both of which have the areas smaller than the typical GRACE footprint (~200,000 km2). Our assessments were based on the forward modeling method using GRACE release-05 (RL-05) solutions, hydrological models (2003-2013), and in situ groundwater level measurements (2005~2010) from both shallow and deep aquifers. Results show that the GRACE-derived GWS variation in the PP experienced a severe depletion of GWS (-46.5±6.4 mm yr-1) over the past decade, nearly 3 times that of the ECP (-16.9±2.1 mm yr-1). There were apparent renewal episodes of GWS (e.g. since 2010) in PP, which may reveal the high replenishing capability of unconfined aquifers. Despite the lower depletion rate, the deep GWS with poor recoverability may have been overexploited. The depletion rate (-16.9±2.1 mm yr-1) exceeded the maximum allowable depletion rate (~12.4 mm yr-1) based on a 50-year groundwater budget.

  4. 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.

  5. Comparison of Antarctic Basin Scale Mass Change from GRACE/GOCE and CryoSat-2

    NASA Astrophysics Data System (ADS)

    Bouman, J.; McMillan, M.; Ivins, E. R.; Blossfeld, M.; Fuchs, M.; Horwath, M.

    2014-12-01

    When data of the GRACE satellite gravity mission are combined with those of the satellite gravity gradiometer mission GOCE, it can be shown that trends in ice mass balance can be resolved at basin scale for the Amundsen Sea Sector in West Antarctica. We will extend our analysis to the complete Antarctic continent, paying special attention to unavoidable leakage effects between basins, and glacial isotactic adjustment and its uncertainty. In addition, it is known that the gravitational flattening coefficient is better determined from satellite laser ranging (SLR) than from GRACE. The GRACE C20 coefficients are therefore routinely replaced by those from SLR. We will show that an alternative SLR time series, using tracking data to more satellites, may give ice mass trend differences of 10 - 15 Gt/yr (in the order of 13% of the total signal) compared with the commonly applied SLR time series. With data of the CryoSat-2 radar altimeter mission Antarctic ice sheet elevation changes can be determined, which can be converted to mass changes. GRACE/GOCE and CryoSat-2 ice mass trends will be compared and the possible cause of differences will be discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2007-04-01

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

  7. A new unified approach to determine geocentre motion using space geodetic and GRACE gravity data

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoping; Kusche, Jürgen; Landerer, Felix W.

    2017-06-01

    Geocentre motion between the centre-of-mass of the Earth system and the centre-of-figure of the solid Earth surface is a critical signature of degree-1 components of global surface mass transport process that includes sea level rise, ice mass imbalance and continental-scale hydrological change. To complement GRACE data for complete-spectrum mass transport monitoring, geocentre motion needs to be measured accurately. However, current methods of geodetic translational approach and global inversions of various combinations of geodetic deformation, simulated ocean bottom pressure and GRACE data contain substantial biases and systematic errors. Here, we demonstrate a new and more reliable unified approach to geocentre motion determination using a recently formed satellite laser ranging based geocentric displacement time-series of an expanded geodetic network of all four space geodetic techniques and GRACE gravity data. The unified approach exploits both translational and deformational signatures of the displacement data, while the addition of GRACE's near global coverage significantly reduces biases found in the translational approach and spectral aliasing errors in the inversion.

  8. 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.

  9. 14 CFR 125.293 - Crewmember: Tests and checks, grace provisions, accepted standards.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... AIRCRAFT Flight Crewmember Requirements § 125.293 Crewmember: Tests and checks, grace provisions, accepted standards. (a) If a crewmember who is required to take a test or a flight check under this part completes the test or flight check in the calendar month before or after the calendar month in which it...

  10. 14 CFR 125.293 - Crewmember: Tests and checks, grace provisions, accepted standards.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... AIRCRAFT Flight Crewmember Requirements § 125.293 Crewmember: Tests and checks, grace provisions, accepted standards. (a) If a crewmember who is required to take a test or a flight check under this part completes the test or flight check in the calendar month before or after the calendar month in which it...

  11. 14 CFR 125.293 - Crewmember: Tests and checks, grace provisions, accepted standards.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... AIRCRAFT Flight Crewmember Requirements § 125.293 Crewmember: Tests and checks, grace provisions, accepted standards. (a) If a crewmember who is required to take a test or a flight check under this part completes the test or flight check in the calendar month before or after the calendar month in which it...

  12. 14 CFR 125.293 - Crewmember: Tests and checks, grace provisions, accepted standards.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... AIRCRAFT Flight Crewmember Requirements § 125.293 Crewmember: Tests and checks, grace provisions, accepted standards. (a) If a crewmember who is required to take a test or a flight check under this part completes the test or flight check in the calendar month before or after the calendar month in which it...

  13. 14 CFR 125.293 - Crewmember: Tests and checks, grace provisions, accepted standards.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... AIRCRAFT Flight Crewmember Requirements § 125.293 Crewmember: Tests and checks, grace provisions, accepted standards. (a) If a crewmember who is required to take a test or a flight check under this part completes the test or flight check in the calendar month before or after the calendar month in which it...

  14. 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…

  15. 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.

  16. 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.

  17. A New Unified Approach to Determine Geocenter Motion Using Space Geodetic and GRACE Gravity Data

    NASA Astrophysics Data System (ADS)

    Wu, Xiaoping; Kusche, Jürgen; Landerer, Felix W.

    2017-03-01

    Geocenter motion between the center-of-mass of the Earth system (CM) and the center-of-figure of the solid Earth surface is a critical signature of degree-1 components of global surface mass transport process that includes sea level rise, ice mass imbalance, and continental-scale hydrological change. To complement GRACE data for complete-spectrum mass transport monitoring, geocenter motion needs to be measured accurately. However, current methods of geodetic translational approach and global inversions of various combinations of geodetic deformation, simulated ocean bottom pressure, and GRACE data contain substantial biases and systematic errors. Here, we demonstrate a new and more reliable unified approach to geocenter motion determination using a recently formed satellite laser ranging based geocentric displacement time series of an expanded geodetic network of all four space geodetic techniques and GRACE gravity data. The unified approach exploits both translational and deformational signatures of the displacement data, while the addition of GRACE's near global coverage significantly reduces biases found in the translational approach and spectral aliasing errors in the inversion.

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

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

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

  19. 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…

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

    NASA Astrophysics Data System (ADS)

    Sharifi, Mohammad Ali; Shahamat, Abolfazl

    2017-05-01

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

  1. High precision dynamic orbit integration for spaceborne gravimetry in view of GRACE Follow-on

    NASA Astrophysics Data System (ADS)

    Ellmer, Matthias; Mayer-Gürr, Torsten

    2017-07-01

    Future gravity missions like GRACE Follow-on and beyond will deliver low-low satellite-to-satellite ranging measurements of a much increased precision on the order of nanometers. This necessitates a re-evaluation of the processes used in gravity field determination with an eye to numerical stability and computational precision. This study investigates the computation of dynamic orbits, which are used for multiple purposes in gravity recovery. They are, for example, used in computing linearized observations for the low-low satellite-to-satellite tracking instruments. The precision at which the dynamic orbits are determined thus must surpass the precision of the ranging observations. Dynamic orbits for GRACE were computed both in a simple simulation, where the force model was reduced to a static potential of degree and order 60, and for real observational data. Encke's method was employed while using a novel reference trajectory determined through rigorous optimization. This reference trajectory was parametrized with equinoctial elements to minimize errors resulting from imprecision in the reference motion. The differences in coordinates between successive iterations of orbit determination were used as a benchmark for the quality of the orbit solution. Using Encke's method with equinoctial elements, the coordinate difference between iterations was reduced from on the order of tens of micrometers to some nanometers in the spectral range relevant to GRACE satellite-to-satellite tracking observations. The resulting dynamic orbits are self-consistent to below the expected precision of the GRACE Follow-on ranging instruments.

  2. Modeling of the Assiniboine Delta Aquifer (ADA) of Manitoba using the Groundwater Storage from GRACE

    NASA Astrophysics Data System (ADS)

    Yirdaw-Zeleke, S.; Snelgrove, K.

    2007-12-01

    This paper investigates the use of GRACE (Gravity Recovery and Climate Experiment) moisture storages for modeling of the Assiniboine Delta Aquifer (ADA) of Manitoba, Canada. There are great promises from GRACE in capturing regional groundwater storages that are potentially used for modeling application. However, it is well known that these storages are difficult to measure over the scales needed for hydrological model applications. Therefore, prior to modeling the aquifer using GRACE moisture storages, the storages need to be downscaled in to regional groundwater storages using the measured groundwater head data available in the area. Previous studies in the ADA have shown that the downscaled moisture storage estimates compared favorably with the measured groundwater storage over the area. This study focuses on the modeling of the ADA aquifer using the downscaled GRACE moisture storages. These storages will be used to initialize, calibration and potentially steer the hydrologic simulation. The calibrated model then will be validated independently using the measured data. These validations will hopefully provide better explanations for the underlying reasons for the differences in model predictions and measurements. This will identify some of the key assumptions and uncertainties in predicting moisture storage, and so highlight topics for further discussion and research.

  3. 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.

  4. 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.

  5. Unique Approaches to Analysis of Time-Variable Gravity from GRACE

    NASA Technical Reports Server (NTRS)

    Lemoine, Frank G.; Luthcke, S. B.; Rowlands, D. D.; Cox, C. M.; Kloska, S. M.; Chinn, D. S.

    2004-01-01

    We have developed an innovative analysis strategy for analysis of GRACE data. We have developed a capability to recover local/regional gravity changes using non-global functional representations (Le. surface anomalies vs. global spherical harmonics) h m the GRACE data. Our approach can take regularly or irregularly shaped regions, populate them with surface anomaly blocks of suitable area and solve for the resulting mass flux with respect to a mean field. The surface mass or gravity anomalies benefit from the application of spatial and temporal constraints to add stability to the solution. In this paper we discuss the analysis of four months of GRACE Level 1B data (accelerometry, intersatellite data, attitude information and precise orbits) from July to October 2003, recently released to the GRACE Science Team. We compare and contrast this local approach to gravity recovery, with the more conventional approach using global spherical harmonics. We review simulations of this technique which allow us to pinpoint optimum strategies for applications of this local gravity recovery approach.

  6. Analysis of Seasonal Variability in Gulf of Alaska Glacier Mass Balance using GRACE

    NASA Astrophysics Data System (ADS)

    Arendt, A. A.; Luthcke, S. B.; Oneel, S.; Gardner, A. S.; Hill, D. F.

    2011-12-01

    Mass variations of glaciers in Alaska/northwestern Canada must be quantified in order to assess impacts on ecosystems, human infrastructure, and global sea level. Here we combine Gravity Recovery and Climate Experiment (GRACE) observations with a wide range of satellite and field data to investigate drivers of these recent changes, with a focus on seasonal variations. Our central focus will be the exceptionally high mass losses of 2009, which do not correlate with weather station temperature and precipitation data, but may be linked to ash fall from the March 31, 2009 eruption of Mt. Redoubt. The eruption resulted in a significant decrease in MODIS-derived surface albedo over many Alaska glacier regions, and likely contributed to some of the 2009 anomalous mass loss observed by GRACE. We also focus on the Juneau and Stikine Icefield regions that are far from the volcanic eruption but experienced the largest mass losses of any region in 2009. Although rapid drawdown of tidewater glaciers was occurring in southeast Alaska during 2009, we show these changes were probably not sufficiently widespread to explain all of the GRACE signal in those regions. We examine additional field and satellite datasets to quantify potential errors in the climate and GRACE fields that could result in the observed discrepancy.

  7. Regional hydrological recovery using one year of simulated observations of the GRACE and Bender constellations

    NASA Astrophysics Data System (ADS)

    Elsaka, Basem; Forootan, Ehsan; Kusche, Jürgen; Alothman, Abdulaziz

    2014-05-01

    Increasing the spatial sampling isotropy has become a major issue in designing future missions dedicated to pursue the task of GRACE, from which the Bender-type multi-orbit satellite configuration seems to be a suitable choice since it reduces the temporal aliasing and has the potential to provide better spatial resolution. Via simulations, this contribution examines the performance of a Bender-type solution, consisting 2 GRACE-like orbits with inclinations of 89.5o and 63o, for hydrological applications. To this end, we created one full year of simulated observations of the GRACE and Bender configurations. Our investigations include: 1) evaluating the feasible spatial resolution for recovery of hydrological signals in the presence of realistic instrumental noise and errors in the background models; 2) assessing the behavior of the aliasing errors in the hydrological recovery and its separation from instrumental noise and the introduced hydrological signals; 3) examining the regional behavior of the hydrological products by computing water storage changes over the 33 world largest river basins. From our results, the Bender-derived error curves at different spatial resolutions indicated that, away from the instrumental noises, the aliasing errors still contaminate the gravity solution as a dominant error source. Moreover, our analyses show that the Bender constellation determines the annual mass variations in small basins which are undetected by the simulated GRACE solution. The results are given in different spectral domains up to spherical harmonic degrees and orders 40, 80 and 100.

  8. 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.…

  9. GRACE principles: recognizing high-quality observational studies of comparative effectiveness.

    PubMed

    Dreyer, Nancy A; Schneeweiss, Sebastian; McNeil, Barbara J; Berger, Marc L; Walker, Alec M; Ollendorf, Daniel A; Gliklich, Richard E

    2010-06-01

    Nonrandomized comparative effectiveness studies contribute to clinical and biologic understanding of treatments by themselves, via subsequent confirmation in a more targeted randomized clinical trial, or through advances in basic science. Although methodological challenges and a lack of accepted principles to assess the quality of nonrandomized studies of comparative effectiveness have limited the practical use of these investigations, even imperfect studies can contribute useful information if they are thoughtfully designed, well conducted, carefully analyzed, and reported in a manner that addresses concerns from skeptical readers and reviewers. The GRACE (Good Research for Comparative Effectiveness) principles have been developed to help healthcare providers, researchers, journal readers, and editors evaluate the quality inherent in observational research studies of comparative effectiveness. The GRACE principles were developed by experienced academic and private sector researchers and were vetted over several years through presentation, critique, and consensus building among outcomes researchers, pharmacoepidemiologists, and other medical scientists and via formal review by the International Society of Pharmacoepidemiology. In contrast to other documents that guide systematic review and reporting, the GRACE principles are high-level concepts about good practice for nonrandomized comparative effectiveness research. The GRACE principles comprise a series of questions to guide evaluation. No scoring system is provided or encouraged, as interpretation of these observational studies requires weighing of all available evidence, tempered by judgment regarding the applicability of the studies to routine care.

  10. Global Scale Determination of "Drainable" Water Resources by GRACE and/or Runoff

    NASA Astrophysics Data System (ADS)

    Riegger, Johannes

    2017-04-01

    In the context of water resources management and climate change there is an ongoing discussion on how to assess available water resources. A rate based definition for a sustainable use of water resources (given by long term recharge) (Sophocleous 1997, Bredehoeft 2002, Zhou 2009) does not help to determine the absolute volume of available resources. Thus the attempt was made to estimate the volume of the respective groundwater resources based on homogeneous assumptions for aquifers with respect to thickness, porosity and accessibility (Nace [1969] and Korzun [1978]). As ground based measurements of storage compartments like groundwater, surface water, snow water equivalent and soil moisture are point measurements the determination of total water storage is still quite inaccurate and unreliable on large spatial scales. Recent GRACE measurements allow to determine mass variations of global scale catchments. These mass variations do not directly represent the absolute storage volumes, which could be considerably larger than the mass variations themselves, yet cannot be recognized by GRACE, as they correspond to a static mass offset. In addition the mass variations comprise all storage compartments and thus do not allow to distinguish different storage compartments such as hydraulically coupled components contributing to river runoff and those which are not coupled like isolated surface water, soil moisture and snow / ice. Investigations of the Runoff - Storage relationship by GRACE and remote sensing however allow to discriminate between coupled / uncoupled storage components of a catchment (Riegger & Tourian. 2014). The linear relationship found between runoff and the coupled storage components allows to determine the respective hydraulic time constant and - based on the reasonable assumption of proportionality - to quantify the respective mass offset, which corresponds to the mean drainable water storage. Thus the total "Drainable Storage" i.e. the absolute water

  11. 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

  12. Interannual variations of the mass balance of the Antarctica and Greenland ice sheets from GRACE

    NASA Astrophysics Data System (ADS)

    Ramillien, G.; Lombard, A.; Cazenave, A.; Ivins, E. R.; Llubes, M.; Remy, F.; Biancale, R.

    2006-09-01

    We propose a new estimate of the mass balance of the West/East Antarctica and Greenland ice sheets from GRACE for the recent period (July 2002-March 2005) and compute the corresponding contribution to the global mean sea level. We use new GRACE geoid solutions provided by the Groupe de Recherche en Géodésie Spatiale (GRGS/CNES), at the resolution of ˜ 400 km and sampled at 10-day interval. In the three regions, significant interannual variations are observed, which we approximate as linear trends over the short time span of analysis. Over Greenland, an apparent total volume loss of 119 +/- 10 cu km/yr water is observed. For the Antarctica ice sheet, a bimodal behaviour is apparent, with volume loss amounting to 88 +/- 10 cu km/yr water in the West, and increase in the East amounting to 72 +/- 20 cu km/yr water. These GRACE results are affected by land hydrology contamination and glacial isostatic adjustment (GIA) of the solid Earth since last deglaciation. We correct for both land hydrology contamination (using a global hydrological model) and GIA using the ICE-4G model for Greenland and the IJ05 model for Antarctica. Corrected for both land hydrology contamination and GIA, GRACE volume rates are - 129 +/- 15 cu km/yr, - 107 +/- 23 cu km/yr and + 67 +/- 28 cu km/yr for Greenland, West Antarctica and East Antarctica respectively. In terms of sea level rise, the GRACE-based ice sheets contributions are + 0.36 +/- 0.04 mm/yr for Greenland, + 0.30 +/- 0.06 mm/yr for West Antarctica and - 0.19 +/- 0.07 for East Antarctica for the time interval of study. The total Antarctica contribution to sea level over this short time span is thus slightly positive (+ 0.11 +/- 0.09 mm/yr). The ice sheets together contribute to a sea level rise of 0.47 +/- 0.1 mm/yr. The results reported here are in qualitative agreement with recent estimates of the mass balance of the ice sheets based on GRACE and with those based upon other remote sensing observations. Due to the very short

  13. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    There is Increasing interest in global hydrology based on modeling and remote sensing, highlighting the need to compare output from modeling and remote sensing approaches. Here we evaluate simulated terrestrial Total Water Storage anomalies (TWSA) from global hydrologic models (GHMs: WGHM and PRC-GLOBWB) and global land surface models (LSMs, such as GLDAS NOAH, MOSAIC, VIC, and CLM) using newly released GRACE mascons solutions from the Univ. of Texas Center for Space Research. The comparisons are based on monthly TWS anomalies over 13 years (April 2002 - April 2015) for 176 basins globally. Performance metrics include scatter plots of simulated and GRACE observed TWSA by basin with median slopes for different models indicating bias, correlations (shape and timing of TWS time series), and variability ratio (standard deviation of model TWSA/std. dev. GRACE observed TWSA), with optimal values of 1 indicating perfect agreement. The GRACE data were also disaggregated into long-term trends and seasonal amplitudes. Modeled TWS anomalies are biased low by 20 - 30% relative to GRACE TWSA with similar bias levels for basins in different size classes but greater bias with increasing basin aridity. Discrepancies between models and GRACE TWSA are greatest for long-term trends in TWSA with 60 - 95% underestimation of GRACE TWSA by models. There is good agreement in seasonal amplitudes from models and GRACE (< 10-30% bias in models). Comparing times series of modeled and GRACE TWSA time series shows good agreement, with median correlation coefficients ranging from 0.7 - 0.8 but much lower correlation coefficients in arid settings (range: 0.4 - 0.7). The variability ratios are > 0.9 for models with little impact of basin size or climate for most models. These comparisons highlight reliable model performance in terms of seasonal amplitudes in TWSA and underestimation of long-term trends in TWSA and in arid basins.

  15. Sensitivity of Groundwater Depletion Rates Estimated from Different GRACE Products and Water Balance Models of Different Spatial Scale

    NASA Astrophysics Data System (ADS)

    Ukasha, M.; Ramirez, J. A.

    2015-12-01

    Observations of water storage anomalies monitored by the Gravity Recovery and Climate Experiments (GRACE) satellite mission have recently been used to estimate regional-scale groundwater depletion. Different GRACE products are available such as the JPL 1°x1° GRACE Tellus dataset and the University of Colorado (CU) dataset of regional-averages. In addition, in order to estimate groundwater depletion rates, GRACE data must be used in conjunction with auxiliary hydrologic and land-use information such as soil moisture, vegetation types, snow storage, etc. These auxiliary datasets are usually estimated using coarse scale (usually 1°x1°) hydrological/land surface observations and models. Therefore, it is important to quantify the sensitivity of estimates of groundwater depletion to different GRACE products, types of auxiliary datasets, and different spatial scales. In this study we show results of a sensitivity analysis of groundwater depletion trends for the Central Valley aquifer of California using three different GRACE products: i) GRACE Tellus, ii) CU GRACE data and, iii) Scaled CU data (filtered CU data optimally scaled to capture peaks in observed water balance). Using soil moisture and snow water storage estimated from 1/8th degree Variable Infiltration Capacity (VIC) model and observed surface water storages (e.g., reservoirs etc.), groundwater depletion from April 2006-March 2010 for three GRACE products is estimated as 15.8, 13.9 and 36.3 km3 respectively. For the time period April 2006-September 2009 these estimates are 7.95, 5.5 and 29.2 km3, respectively. In addition, a sensitivity analysis with respect to spatial scale of VIC model will be presented, which involves using estimates of soil moisture and snow storage at the following three different spatial scales: i) 1 degree, ii) 1/8th degree and, iii) 1/16th degree.

  16. 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.

  17. 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).

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  19. 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

  20. Glacial Isostatic Adjustment as a Source of Noise for the Interpretation of GRACE Data

    NASA Astrophysics Data System (ADS)

    Wahr, J.; Velicogna, I.; Paulson, A.

    2009-05-01

    Viscoelastic relaxation in the Earth's mantle caused by wide-spread deglaciation following the last glacial maximum (LGM), can appear as a secular trend in measurements of the Earth's time-variable gravity field. The presence of this trend can provide an opportunity to use gravity observations to constrain models of the glacial isostatic adjustment (GIA) process. But it can also be a nuisance for people who are using the gravity observations to learn about other things. Gravity observations, whether from satellites or from ground-based gravimeters, can not distinguish between the gravitational effects of water/snow/ice variations on or near the surface, and those caused by density variations deep within the mantle. Unmodeled or mismodeled GIA signals can sometimes make it difficult to use gravity observations to learn about secular changes in water/snow/ice from such places as northern Canada, Scandinavia, Antarctica, and Greenland: places where there was considerable long-term deglaciation following the LGM. These issues have become particularly important since the 2002 launch of the GRACE gravity satellite mission. GIA signals in northern Canada and Scandinavia are clearly evident in the GRACE data. But the presence of GIA signals in these and other regions has sometimes caused problems for long-term hydrological and, especially, cryospheric studies with GRACE. GIA model errors, for example, are by far the largest source of uncertainty when using GRACE to estimate present-day thinning rates of the Antarctic ice sheet. This talk will discuss the contributions of the GIA signal to GRACE time-variable gravity measurements; partly as an opportunity to study the GIA process, but mostly as a source of uncertainty for other applications.

  1. Inferring Aquifer Storage Parameters Using GRACE and In-Situ Measurement: Estimation Under Data Uncertainty (Invited)

    NASA Astrophysics Data System (ADS)

    Sun, A. Y.; Green, R. T.; Rodell, M.; Swenson, S. C.

    2010-12-01

    Terrestrial water storage (TWS) data derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have been widely used to assess water storage changes at the regional and continental scales. Although promising, the accuracy of GRACE data is inherently limited by instrumentation error, inaccuracies in atmospheric and ocean fields, and leakage error arising from using a limited range of spherical harmonics to represent the gravity field variations. Similarly, the ancillary data used for disaggregating GRACE data to track changes in individual hydrologic cycle components are also subject to uncertainty. This reflects a familiar dilemma in water resources management, where the remotely sensed and in-situ data provide increasingly more information content and call for more application uses, but the uncertainty inherent in these Earth observation products poses a barrier to the timely fusion of these data. In the worst case scenario, the data uncertainty can render the estimated solution completely meaningless. We present a robust optimization method for inferring aquifer storage parameters (i.e., specific yield or storativity) under uncertainty. The data involved are GRACE TWS, in-situ well level observations, and model-generated soil moisture distributions, all of which are uncertain. The robust optimization paradigm only requires knowing the uncertainty bounds of parameters, but not their actual probability distributions. Error bounds are either specified by data processing centers when distributing the processed satellite data or can be estimated from time series analysis. We demonstrate our method for the interconnected Edwards-Trinity Plateau and Pecos Valley aquifers in central Texas. The study area is divided into multiple zones based on the geology and monitor well coverage. Our estimated aquifer storage parameters are consistent with previous results obtained from pumping tests and model calibration, demonstrating the potential of using

  2. 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.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  5. Can we observe the fronts of the Antarctic Circumpolar Current using GRACE OBP?

    NASA Astrophysics Data System (ADS)

    Makowski, J.; Chambers, D. P.; Bonin, J. A.

    2014-12-01

    The Antarctic Circumpolar Current (ACC) and the Southern Ocean remains one of the most undersampled regions of the world's oceans. The ACC is comprised of four major fronts: the Sub-Tropical Front (STF), the Polar Front (PF), the Sub-Antarctic Front (SAF), and the Southern ACC Front (SACCF). These were initially observed individually from repeat hydrographic sections and their approximate locations globally have been quantified using all available temperature data from the World Ocean and Climate Experiment (WOCE). More recent studies based on satellite altimetry have found that the front positions are more dynamic and have shifted south by up to 1° on average since 1993. Using ocean bottom pressure (OBP) data from the current Gravity Recovery and Climate Experiment (GRACE) we have measured integrated transport variability of the ACC south of Australia. However, differentiation of variability of specific fronts has been impossible due to the necessary smoothing required to reduce noise and correlated errors in the measurements. The future GRACE Follow-on (GFO) mission and the post 2020 GRACE-II mission are expected to produce higher resolution gravity fields with a monthly temporal resolution. Here, we study the resolution and error characteristics of GRACE gravity data that would be required to resolve variations in the front locations and transport. To do this, we utilize output from a high-resolution model of the Southern Ocean, hydrology models, and ice sheet surface mass balance models; add various amounts of random and correlated errors that may be expected from GFO and GRACE-II; and quantify requirements needed for future satellite gravity missions to resolve variations along the ACC fronts.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  7. Mass Evolution of Mediterranean, Black, Red, and Caspian Seas from GRACE and Altimetry: Accuracy Assessment and Solution Calibration

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    We present new measurements of mass evolution for the Mediterranean, Black, Red, and Caspian Seas as determined by the NASA Goddard Space Flight Center (GSFC) GRACE time-variable global gravity mascon solutions. These new solutions are compared to sea surface altimetry measurements of sea level anomalies with steric corrections applied. To assess their accuracy, the GRACE and altimetry-derived solutions are applied to the set of forward models used by GSFC for processing the GRACE Level-1B datasets, with the resulting inter-satellite range acceleration residuals providing a useful metric for analyzing solution quality.

  8. Mass Evolution of Mediterranean, Black, Red, and Caspian Seas from GRACE and Altimetry: Accuracy Assessment and Solution Calibration

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    We present new measurements of mass evolution for the Mediterranean, Black, Red, and Caspian Seas as determined by the NASA Goddard Space Flight Center (GSFC) GRACE time-variable global gravity mascon solutions. These new solutions are compared to sea surface altimetry measurements of sea level anomalies with steric corrections applied. To assess their accuracy, the GRACE and altimetry-derived solutions are applied to the set of forward models used by GSFC for processing the GRACE Level-1B datasets, with the resulting inter-satellite range acceleration residuals providing a useful metric for analyzing solution quality.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  10. Assimilation of Gridded Terrestrial Water Storage Observations from GRACE into a Land Surface Model

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    Observations of terrestrial water storage (TWS) from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have a coarse resolution in time (monthly) and space (roughly 150,000 km(sup 2) at midlatitudes) and vertically integrate all water storage components over land, including soil moisture and groundwater. Data assimilation can be used to horizontally downscale and vertically partition GRACE-TWS observations. This work proposes a variant of existing ensemble-based GRACE-TWS data assimilation schemes. The new algorithm differs in how the analysis increments are computed and applied. Existing schemes correlate the uncertainty in the modeled monthly TWS estimates with errors in the soil moisture profile state variables at a single instant in the month and then apply the increment either at the end of the month or gradually throughout the month. The proposed new scheme first computes increments for each day of the month and then applies the average of those increments at the beginning of the month. The new scheme therefore better reflects submonthly variations in TWS errors. The new and existing schemes are investigated here using gridded GRACE-TWS observations. The assimilation results are validated at the monthly time scale, using in situ measurements of groundwater depth and soil moisture across the U.S. The new assimilation scheme yields improved (although not in a statistically significant sense) skill metrics for groundwater compared to the open-loop (no assimilation) simulations and compared to the existing assimilation schemes. A smaller impact is seen for surface and root-zone soil moisture, which have a shorter memory and receive smaller increments from TWS assimilation than groundwater. These results motivate future efforts to combine GRACE-TWS observations with observations that are more sensitive to surface soil moisture, such as L-band brightness temperature observations from Soil Moisture Ocean Salinity (SMOS) or Soil Moisture Active

  11. Assimilation of Gridded Terrestrial Water Storage Observations from GRACE into a Land Surface Model

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    Observations of terrestrial water storage (TWS) from the Gravity Recovery and Climate Experiment (GRACE) satellite mission have a coarse resolution in time (monthly) and space (roughly 150,000 km(sup 2) at midlatitudes) and vertically integrate all water storage components over land, including soil moisture and groundwater. Data assimilation can be used to horizontally downscale and vertically partition GRACE-TWS observations. This work proposes a variant of existing ensemble-based GRACE-TWS data assimilation schemes. The new algorithm differs in how the analysis increments are computed and applied. Existing schemes correlate the uncertainty in the modeled monthly TWS estimates with errors in the soil moisture profile state variables at a single instant in the month and then apply the increment either at the end of the month or gradually throughout the month. The proposed new scheme first computes increments for each day of the month and then applies the average of those increments at the beginning of the month. The new scheme therefore better reflects submonthly variations in TWS errors. The new and existing schemes are investigated here using gridded GRACE-TWS observations. The assimilation results are validated at the monthly time scale, using in situ measurements of groundwater depth and soil moisture across the U.S. The new assimilation scheme yields improved (although not in a statistically significant sense) skill metrics for groundwater compared to the open-loop (no assimilation) simulations and compared to the existing assimilation schemes. A smaller impact is seen for surface and root-zone soil moisture, which have a shorter memory and receive smaller increments from TWS assimilation than groundwater. These results motivate future efforts to combine GRACE-TWS observations with observations that are more sensitive to surface soil moisture, such as L-band brightness temperature observations from Soil Moisture Ocean Salinity (SMOS) or Soil Moisture Active

  12. Determination of groundwater abstractions by means of GRACE data and Artificial Neural Networks

    NASA Astrophysics Data System (ADS)

    Gemitzi, Alexandra; Tsagkarakis, Konstantinos; Lakshmi, Venkat

    2017-04-01

    The EU Water Framework Directive requires for each groundwater body the determination of annual average rates of abstraction from all points providing more than 10m3 per day as well as groundwater level monitoring, so as to ensure that the available groundwater resource is not exceeded by the long-term annual average rate of abstraction. In order to acquire such information in situ observation networks are necessary. However, there are cases, e.g. Greece where WFD monitoring programme has not yet become operational due to bureaucratic, socioeconomic and often political constraints. The present study aims at determining groundwater use at the aquifer scale by using Gravity Recovery and Climate Experiment (GRACE) satellite data coupled with readily available meteorological data. Traditionally, GRACE data have been used at the global and regional scale due to their coarse resolution and the difficulties in disaggregating the various Total Water Storage (TWS) components. Previous works have evaluated the subsurface anomalies (ΔGW), using supplementary data sets and hydrologic modeling results in order to disaggregate GRACE TWS anomalies into their various components. Recent works however, have shown that changes in groundwater storage are dominating the GRACE Total Water Storage (TWS) changes, therefore it was though reasonable to use changes in Grace derived TWS in order to quantify abstractions from a groundwater body. Statistical downscaling was performed using an Artificial Neural Network in the form a Multilayer Perceptron model, in conjunction with local meteorological data. An ensemble of 100 ANNs provided a means of quantifying uncertainty and improving generalization. The methodology was applied in Rhodope area (NE Greece) and proved to be an efficient way of downscaling GRACE data in order to estimate the monthly quantity of water extracted from a certain aquifer. Although our methodology does not aim at estimating abstractions at single points, it manages

  13. Stress Variation Caused by the Terrestrial Water Storage Inferred from GRACE Data

    NASA Astrophysics Data System (ADS)

    Yi, H.; Wen, L.

    2014-12-01

    We estimate stress variation caused by the terrestrial water storage (TWS) change from 2003 to 2013. We first infer the TWS change from the monthly gravity field change in the Gravity Recovery and Climate Experiment (GRACE). We then estimate the stress change at the Earth's surface caused by elastic loading of mass change associated with the inferred TWS change.The monthly spherical harmonics of the GRACE gravity solutions are processed using a decorrelation filter and Gaussian smoothing, to suppress the noise in high degree and order, following the approach of Swenson and Wahr [2006] and Chen et al. [2007]. The gravity variation associated with the glacial isostatic adjustment (GIA) is further removed from the GRACE solutions based on a geodynamical model by Paulson et al. [2007]. The inferred TWS changes exhibit a trend of increase from 2003 to 2013 in Amazon basin, southern Africa, the northern United State America (USA) and Queen Maud Land of Antarctica, and a trend of decrease in the same period in central Argentina, southern Chile, northern India, northern Iran, Alaska of the USA, Greenland and Marie Byrd Land of Antarctica.Surface stress variation due to the TWS loading is calculated, assuming an incompressible and self-gravitating Earth, with an elastic crust and a viscoelastic mantle overlying an inviscid core based on PREM model. We will present the geographical distribution of the stress variation caused by the TWS loading and discuss its possible implications. Chen, J. L., C. R. Wilson, B. D. Tapley, and S. Grand (2007), GRACE detects coseismic and postseismic deformation from the Sumatra-Andaman earthquake, Geophys Res Lett, 34(13), doi:10.1029/2007GL030356. Paulson, A., S. J. Zhong, and J. Wahr (2007), Inference of mantle viscosity from GRACE and relative sea level data, Geophys J Int, 171(2), 497-508, doi:10.1111/j.1365-246X.2007.03556.x. Swenson, S., and J. Wahr (2006), Post-processing removal of correlated errors in GRACE data, Geophys Res Lett, 33

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  15. GRACE Time-Variable Gravity Field Recovery Using an Improved Energy Balance Formalism

    NASA Astrophysics Data System (ADS)

    Shang, Kun

    Earth's gravity is continuously varying with respect to time due primarily to mass transports within the Earth system and external gravitational forcing. A new formalism based on energy conservation principle for time-variable gravity field recovery using satellite gravimetry has been developed and yields more accurate estimation of in-situ geopotential difference observables using K-Band Ranging (KBR) measurements from the Gravity Recovery and Climate Experiment (GRACE) twin-satellite mission. The new approach can preserve more time-variable gravity information sensed by KBR range-rate measurements and reduce orbit error as compared to previous energy balance studies. Results based on analysis of more than 10 years of GRACE data indicate that the estimated geopotential differences agree well with the predicted values from official Level 2 solutions: with much higher correlation of 0.9, as compared to 0.5-0.8 reported by previous energy balance studies. This study demonstrates that the new approach is more flexible for both global and regional temporal gravity recovery, leading to the first independent GRACE monthly solution series based on energy conservation principle, which is comparable to the results from different approach. The developed formalism is applicable to the general case of low-low satellite-to-satellite radiometric or laser interferometric tracking measurements, such as GRACE Follow-on or other Next Generation Gravity Field missions, for efficient retrieval and studies of Earth's mass transport evolutions. The regional gravity analysis over Greenland reveals that a substantially higher temporal resolution is achievable at 10 or 11-day interval from GRACE data, as compared to the official monthly solutions, but without the compromise of spatial resolution, nor the need to use regularization or post-processing. Studies of the terrestrial and ground water storage change over North China Plain show high correlation in sub-monthly scale, among the 11

  16. Consistent patterns of Antarctic ice sheet interannual variations from ENVISAT radar altimetry and GRACE

    NASA Astrophysics Data System (ADS)

    Horwath, Martin; Legrésy, Benoît.; Blarel, Fabien; Rémy, Frédérique; Lemoine, Jean-Michel

    2010-05-01

    By observing temporal volume and mass changes, respectively, satellite radar altimetry (RA) and satellite gravimetry are complementary tools for ice sheet mass balance studies. We compare and jointly interpret results from ENVISAT RA and GRACE. The underlying RA products were generated with the Along-Track Satellite Radar Altimetry approach which exploits all observations along the repeat track and accounts for time-variable volume echo effects through analyzing the temporal variations of the radar echo shape. The used GRACE products are the CNES/GRGS 10-daily global gravity solutions obtained with a regularisation during processing and requiring no additional filtering. In order to render the spatial resolution of both datasets comparable we rigorously describe the spatial filtering of geophysical signals that is inherent to the GRACE processing. We then apply the same filtering to the maps of altimetric height changes. After correction for glacial isostatic adjustment, the spatial patterns of linear trends shown by RA and GRACE over a common period agree well, not only for the extreme ice losses in the Amundsen Sea Sector of West Antarctica but also for an alternating sequence of gains and losses along the East Antarctic coast. Differences between ENVISAT ice sheet thickness changes and GRACE equivalent ice thickness changes are primarily due to the lack of RA coverage and secondarily due to changes in the firn density structure associated with surface mass balance fluctuations as well as due to errors in either observational data sets. Moreover, the general patterns of year-to-year nonlinear variations on top of the trends agree between the two data sets. This agreement gives confidence in the interannual variations of both data sets. As a consequence, the high-resolution patterns provided by RA can be used to relate the interannual mass variations observed by GRACE to either flow variations or surface mass balance (SMB) variations and to validate atmospheric

  17. Antarctic Circumpolar Current Transport Variability during 2003-05 from GRACE

    NASA Technical Reports Server (NTRS)

    Zlotnicki, Victor; Wahr, John; Fukumori, Ichiro; Song, Yuhe T.

    2006-01-01

    Gravity Recovery and Climate Experiment (GRACE) gravity data spanning January 2003 - November 2005 are used as proxies for ocean bottom pressure (BP) averaged over 1 month, spherical Gaussian caps 500 km in radius, and along paths bracketing the Antarctic Circumpolar Current's various fronts. The GRACE BP signals are compared with those derived from the Estimating the Circulation and Climate of the Ocean (ECCO) ocean modeling-assimilation system, and to a non-Boussinesq version of the Regional Ocean Model System (ROMS). The discrepancy found between GRACE and the models is 1.7 cm(sub H2O) (1 cm(sub H2O) similar to 1 hPa), slightly lower than the 1.9 cm(sub H2O) estimated by the authors independently from propagation of GRACE errors. The northern signals are weak and uncorrelated among basins. The southern signals are strong, with a common seasonality. The seasonal cycle GRACE data observed in the Pacific and Indian Ocean sectors of the ACC are consistent, with annual and semiannual amplitudes of 3.6 and 0.6 cm(sub H2O) (1.1 and 0.6 cm(sub H2O) with ECCO), the average over the full southern path peaks (stronger ACC) in the southern winter, on days of year 197 and 97 for the annual and semiannual components, respectively; the Atlantic Ocean annual peak is 20 days earlier. An approximate conversion factor of 3.1 Sv ( Sv equivalent to 10(exp 6) m(exp 3) s(exp -1)) of barotropic transport variability per cm(sub H2O) of BP change is estimated. Wind stress data time series from the Quick Scatterometer (QuikSCAT), averaged monthly, zonally, and over the latitude band 40 de - 65 deg S, are also constructed and subsampled at the same months as with the GRACE data. The annual and semiannual harmonics of the wind stress peak on days 198 and 82, respectively. A decreasing trend over the 3 yr is observed in the three data types.

  18. Antarctic Circumpolar Current Transport Variability during 2003-05 from GRACE

    NASA Technical Reports Server (NTRS)

    Zlotnicki, Victor; Wahr, John; Fukumori, Ichiro; Song, Yuhe T.

    2007-01-01

    Gravity Recovery and Climate Experiment (GRACE) gravity data spanning January 2003-November 2005 are used as proxies for ocean bottom pressure (BP) averaged over 1 month, spherical Gaussian caps 500 km in radius, and along paths bracketing the Antarctic Circumpolar Current's various fronts. The GRACE BP signals are compared with those derived from the Estimating the Circulation and Climate of the Ocean (ECCO) ocean modeling-assimilation system, and to a non-Boussinesq version of the Regional Ocean Model System (ROMS). The discrepancy found between GRACE and the models is 1.7 cmH2O (1 cmH2O approx. 1 hPa), slightly lower than the 1.9 cmH2O estimated by the authors independently from propagation of GRACE errors. The northern signals are weak and uncorrelated among basins. The southern signals are strong, with a common seasonality. The seasonal cycle GRACE data observed in the Pacific and Indian Ocean sectors of the ACC are consistent, with annual and semiannual amplitudes of 3.6 and 0.6 cmH2O (1.1 and 0.6 cmH2O with ECCO), the average over the full southern path peaks (stronger ACC) in the southern winter, on days of year 197 and 97 for the annual and semiannual components, respectively; the Atlantic Ocean annual peak is 20 days earlier. An approximate conversion factor of 3.1 Sv (Sv equiv 10(exp 6)cu m/s) of barotropic transport variability per cmH2O of BP change is estimated. Wind stress data time series from the Quick Scatterometer (QuikSCAT), averaged monthly, zonally, and over the latitude band 40(deg)- 65(deg)S, are also constructed and subsampled at the same months as with the GRACE data. The annual and semiannual harmonics of the wind stress peak on days 198 and 82, respectively. A decreasing trend over the 3 yr is observed in the three data types.

  19. A Multi-Satellite GRACE-like Mission Using Small Satellites

    NASA Astrophysics Data System (ADS)

    Stephens, M.; Bender, P. L.; Nerem, R.; Pierce, R.; Wiese, D. N.

    2010-12-01

    Measurement of global water variation provides information critical to climate change and water resource monitoring. The Gravity Recovery and Climate Experiment II (GRACE II) was chosen as a Tier III mission by National Research Council's decadal survey because of its unique ability to measure the global mass distributions and variations in the mass distribution caused primarily by water variation. We discuss a multi-satellite approach to a GRACE-like mission. Enhanced spatial resolution of mass variations over those provided by the current GRACE mission can be achieved by improving the ranging accuracy; an interferometric ranging concept that improves the ranging accuracy has been demonstrated[1]. However, recent calculations show that to obtain the full science improvement using interferometric ranging, temporal aliasing errors due to modeling and to undersampling of geophysical signals must be mitigated[2]. One approach is to improve the data analysis techniques and validation processes. Another approach is to fly two or more pairs of satellites, thereby sampling the Earth's gravitational field at shorter time intervals[3]. A multiple-pair mission is often dismissed as too expensive, but the mission costs of a multiple-pair GRACE-like mission could be greatly reduced by developing compact ranging systems so that the mass, power, and volume usage is consistent with small spacecraft buses. Such size reduction drastically reduces the launch costs by allowing the spacecraft to be launched as auxiliary payloads. We will discuss the technological challenges that are associated with a GRACE-like mission that uses smallsats to reduce costs of more than one pair of satellites, as well as the scientific benefits of the two or more satellite pairs. The technological challenges include reducing the size of the payload and developing a low-drag, low-pointing jitter spacecraft. [1]Pierce, R., J. Leitch, M. Stephens, P. Bender, and R. Nerem, “Intersatellite range monitoring

  20. Comparison of Seasonal Terrestrial Water Storage Variations from GRACE with Groundwater-level Measurements from the High Plains Aquifer (USA)

    NASA Technical Reports Server (NTRS)

    Strassberg, Gil; Scanlon, Bridget R.; Rodell, Matthew

    2007-01-01

    This study presents the first direct comparison of variations in seasonal GWS derived from GRACE TWS and simulated SM with GW-level measurements in a semiarid region. Results showed that variations in GWS and SM are the main sources controlling TWS changes over the High Plains, with negligible storage changes from surface water, snow, and biomass. Seasonal variations in GRACE TWS compare favorably with combined GWS from GW-level measurements (total 2,700 wells, average 1,050 GW-level measurements per season) and simulated SM from the Noah land surface model (R = 0.82, RMSD = 33 mm). Estimated uncertainty in seasonal GRACE-derived TWS is 8 mm, and estimated uncertainty in TWS changes is 11 mm. Estimated uncertainty in SM changes is 11 mm and combined uncertainty for TWS-SM changes is 15 mm. Seasonal TWS changes are detectable in 7 out of 9 monitored periods and maximum changes within a year (e.g. between winter and summer) are detectable in all 5 monitored periods. Grace-derived GWS calculated from TWS-SM generally agrees with estimates based on GW-level measurements (R = 0.58, RMSD = 33 mm). Seasonal TWS-SM changes are detectable in 5 out of the 9 monitored periods and maximum changes are detectable in all 5 monitored periods. Good correspondence between GRACE data and GW-level measurements from the intensively monitored High Plains aquifer validates the potential for using GRACE TWS and simulated SM to monitor GWS changes and aquifer depletion in semiarid regions subjected to intensive irrigation pumpage. This method can be used to monitor regions where large-scale aquifer depletion is ongoing, and in situ measurements are limited, such as the North China Plain or western India. This potential should be enhanced by future advances in GRACE processing, which will improve the spatial and temporal resolution of TWS changes, and will further increase applicability of GRACE data for monitoring GWS.

  1. GRACE gravity model: assssment in terms of deep ocean currents from hydrography and from the ECCO ocean model

    NASA Technical Reports Server (NTRS)

    Zlotnicki, V.; Stammer, D.; Fukumori, I.

    2003-01-01

    Here we assess the new generation of gravity models, derived from GRACE data. The differences between a global geoid model (one from GRACE data and one the well-known EGM-96), minus a Mean Sea Surface derived from over a decade of altimetric data are compared to hydrographic data from the Levitus compilation and to the ECCO numerical ocean model, which assimilates altimetry and other data.

  2. Monthly and sub-monthly hydrological variability: in-orbit validation by GRACE level 1B observations

    NASA Astrophysics Data System (ADS)

    Eicker, Annette; Springer, Anne

    2016-06-01

    In this study, we present an approach to validate hydrological model output directly on the level of GRACE level 1B observations by analyzing K-band range-rate residuals. Modeled water mass variations are converted to simulated satellite observations and subtracted from the original measurements. This procedure bypasses the downward continuation and filtering steps generally required for water cycle analysis on the basis of gravity field maps. The goal of the study is twofold: (1) we demonstrate the feasibility of using residuals analysis for hydrological model validation in general and (2) we focus on the potential of the approach to investigate the signal content of temporally high-frequent (daily) modeled hydrological mass variations. In addition to the output of three different hydrological process models, we study mass changes computed from two different daily GRACE products. GRACE here serves as a reference, but its spatial resolution is limited and the daily models are not computed independently. Regarding aspect (1), our results show that the agreement of each of the models with GRACE varies strongly depending on geographical location. Aspect (2) is not only interesting for model validation, but it is also important in the context of improving the GRACE de-aliasing concept. We demonstrate that not only the daily GRACE models, but also the daily hydrological model output contains information on time scales smaller than 1 month. Realistically modeled or observed short-term hydrological mass changes may serve as additional de-aliasing product for GRACE and thus contribute to increasing the accuracy and resolution of future GRACE products.

  3. Comparison of Seasonal Terrestrial Water Storage Variations from GRACE with Groundwater-level Measurements from the High Plains Aquifer (USA)

    NASA Technical Reports Server (NTRS)

    Strassberg, Gil; Scanlon, Bridget R.; Rodell, Matthew

    2007-01-01

    This study presents the first direct comparison of variations in seasonal GWS derived from GRACE TWS and simulated SM with GW-level measurements in a semiarid region. Results showed that variations in GWS and SM are the main sources controlling TWS changes over the High Plains, with negligible storage changes from surface water, snow, and biomass. Seasonal variations in GRACE TWS compare favorably with combined GWS from GW-level measurements (total 2,700 wells, average 1,050 GW-level measurements per season) and simulated SM from the Noah land surface model (R = 0.82, RMSD = 33 mm). Estimated uncertainty in seasonal GRACE-derived TWS is 8 mm, and estimated uncertainty in TWS changes is 11 mm. Estimated uncertainty in SM changes is 11 mm and combined uncertainty for TWS-SM changes is 15 mm. Seasonal TWS changes are detectable in 7 out of 9 monitored periods and maximum changes within a year (e.g. between winter and summer) are detectable in all 5 monitored periods. Grace-derived GWS calculated from TWS-SM generally agrees with estimates based on GW-level measurements (R = 0.58, RMSD = 33 mm). Seasonal TWS-SM changes are detectable in 5 out of the 9 monitored periods and maximum changes are detectable in all 5 monitored periods. Good correspondence between GRACE data and GW-level measurements from the intensively monitored High Plains aquifer validates the potential for using GRACE TWS and simulated SM to monitor GWS changes and aquifer depletion in semiarid regions subjected to intensive irrigation pumpage. This method can be used to monitor regions where large-scale aquifer depletion is ongoing, and in situ measurements are limited, such as the North China Plain or western India. This potential should be enhanced by future advances in GRACE processing, which will improve the spatial and temporal resolution of TWS changes, and will further increase applicability of GRACE data for monitoring GWS.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  5. Identifying GRACE+GOCE Combination Gravity Field Error Introduced in Geodetic MDT Using Local Fourier 2D Spatial Spectra

    NASA Astrophysics Data System (ADS)

    Pie, N.; Bettadpur, S. V.; Giuliani, S.

    2016-12-01

    The gravity missions GRACE (Gravity Recovery And Climate Experiment) and GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) have brought great improvements in the study of Earth Dynamic processes. Though they are very different in nature, the two missions provide very complementary gravity products, expressed in the form of spherical harmonic expansions. GOCE, a single satellite mission, relies on a very sensitive Electrostatic Gravity Gradiometer (EGG) composed of 6 accelerometers out of which 6 gravity gradients are computed. On the other hand, GRACE observations of the gravity field are based on a microwave ranging system between its two satellites. The complementarity of the two missions comes from the fact that GRACE gravity products have superior accuracy in the estimation of the low to medium degree terms, while GOCE prevails in the higher degrees. Several combination gravity fields already make use of this complementarity. However, detailed quality analysis of this products reveals characteristic errors in gravity fields resulting in North-South striations, or even small-scale bumpy patterns over the ocean. It is believed that the striations are likely to be attributed to the GRACE data at degree superior to 100 of the spherical harmonic expansion, while the bumpy pattern could be the results of non-optimal weighting at degrees where GRACE and GOCE's accuracy are commensurate. The focus of this study is to characterize the geoid error in GRACE+GOCE combination gravity models in the spatial domain and in the context of the determination of the Mean Dynamic Topography (MDT).

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  7. Crustal deformation modulation due to regional mass redistribution in China and its adjacent region constrained by GPS and GRACE measurements

    NASA Astrophysics Data System (ADS)

    Zhang, K.; Gan, W.; Liang, S.

    2016-12-01

    The elastic Earth deforms in response to seasonal and secular loads imposed on the crust by large-scale mass redistribution from both the hydrosphere and atmosphere. In this study, we calculate 3D surface displacements in China and its adjacent region due to mass redistribution from the GRACE measurements, and obtain the strain rates from their secular horizontal change rates estimated through least-square method. The GRACE 3D displacements are comparable with continuous GPS data of the most sites in Mainland China and Nepal. The secular horizontal rates show consistent deforming pattern as mass variations, that is, the crust moves to (away from) the region where mass increases (decreases). In contrast to the strain rates obtained from GPS velocity field, the GRACE strain rates show different patterns. In most regions, the GRACE strain rates are at the level of 2 to several nanostrain, about 1/50 1/100 times of the maximal GPS strain rate; while in the Central Tibetan Plateau (CTP) and the North China (NC), the ratio of GRACE to GPS strain rates is up to 1/10 and their principal directions are nearly parallel to each other, thus promote the process of strain energy accumulation. Though the sources of GRACE strain rates of CTP and NC are likely to relate to climatic changes and anthropogenic activities such as groundwater over withdrawal, respectively, the mass loading induced deformation plays an important role in modulating the crustal deformation and thus has significant implications to the future seismicity.

  8. Validation of static gravity field models using GRACE K-band ranging and GOCE gradiometry data

    NASA Astrophysics Data System (ADS)

    Hashemi Farahani, H.; Ditmar, P.; Klees, R.; Teixeira da Encarnação, J.; Liu, X.; Zhao, Q.; Guo, J.

    2013-08-01

    The ability of satellite gravimetry data to validate global static models of the Earth's gravity field is studied. Two types of data are considered: K-band ranging (KBR) data from the Gravity Recovery and Climate Experiment (GRACE) mission and Satellite Gravity Gradiometry (SGG) data from the GOCE (Gravity field and steady-state Ocean Circulation Explorer) mission. The validation is based on analysis of misfits obtained as the differences between the data observed and those computed with a force model that includes, in particular, a static gravity field model to be assessed. To facilitate the model assessment on a region-by-region basis, we convert KBR data into so-called range combinations, which are approximately equivalent to the intersatellite accelerations. We only use the accurately measured components of SGG data, that is, xx, yy, zz and xz components with x, y and z being along-track, cross-track and radial axes. We perform the validation in spectral and spatial domain. The latter requires elimination of low-frequency noise in the misfit data with a subsequent averaging over pre-defined blocks. Only `independent' data are used, that is, those that have not been used in the production of the models under consideration. The proposed methodology is applied to eight models: EGM2008 (truncated at degree 250), EIGEN-6C (truncated at degree 250), two GRACE-only models (ITG-Grace03 and ITG-Grace2010s) and four (satellite-only) combined GRACE/GOCE models (GOCO01S, EIGEN-6S, GOCO02S and DGM-1S). The latter is a novel model developed at Delft University of Technology in collaboration with GNSS Research Centre of Wuhan University. The GRACE KBR and GOCE SGG data demonstrate a pronounced sensitivity to inaccuracies of EGM2008 in 5-22 mHz (27-120 cycles-per-revolution, cpr) and 10-28 mHz (54-150 cpr) frequency ranges, respectively. The latter data also show a high sensitivity to inaccuracies of ITG-Grace2010s in 25-37 mHz (135-200 cpr) frequency range. From the

  9. Comparison of precision orbit derived density estimates for CHAMP and GRACE satellites

    NASA Astrophysics Data System (ADS)

    Fattig, Eric Dale

    Current atmospheric density models cannot adequately represent the density variations observed by satellites in Low Earth Orbit (LEO). Using an optimal orbit determination process, precision orbit ephemerides (POE) are used as measurement data to generate corrections to density values obtained from existing atmospheric models. Densities obtained using these corrections are then compared to density data derived from the onboard accelerometers of satellites, specifically the CHAMP and GRACE satellites. This comparison takes two forms, cross correlation analysis and root mean square analysis. The densities obtained from the POE method are nearly always superior to the empirical models, both in matching the trends observed by the accelerometer (cross correlation), and the magnitudes of the accelerometer derived density (root mean square). In addition, this method consistently produces better results than those achieved by the High Accuracy Satellite Drag Model (HASDM). For satellites orbiting Earth that pass through Earth's upper atmosphere, drag is the primary source of uncertainty in orbit determination and prediction. Variations in density, which are often not modeled or are inaccurately modeled, cause difficulty in properly calculating the drag acting on a satellite. These density variations are the result of many factors; however, the Sun is the main driver in upper atmospheric density changes. The Sun influences the densities in Earth's atmosphere through solar heating of the atmosphere, as well as through geomagnetic heating resulting from the solar wind. Data are examined for fourteen hour time spans between November 2004 and July 2009 for both the CHAMP and GRACE satellites. This data spans all available levels of solar and geomagnetic activity, which does not include data in the elevated and high solar activity bins due to the nature of the solar cycle. Density solutions are generated from corrections to five different baseline atmospheric models, as well as

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

    NASA Astrophysics Data System (ADS)

    Thomas, Alys C.; Reager, John T.; Famiglietti, James S.; Rodell, Matthew

    2014-03-01

    We present a quantitative approach for measuring hydrological drought occurrence and severity based on terrestrial water storage observations from NASA's Gravity Recovery and Climate Experiment (GRACE) satellite mission. GRACE measurements are applied by calculating the magnitude of the deviation of regional, monthly terrestrial water storage anomalies from the time series' monthly climatology, where negative deviations represent storage deficits. Monthly deficits explicitly quantify the volume of water required to return to normal water storage conditions. We combine storage deficits with event duration to calculate drought severity. Drought databases are referenced to identify meteorological drought events in the Amazon and Zambezi River basins and the southeastern United States and Texas regions. This storage deficit method clearly identifies hydrological drought onset, end, and duration; quantifies instantaneous severity and peak drought magnitude; and compares well with the meteorological drought databases. It also reveals information about the hydrological effects of meteorological drought on regional water storage.

  11. A demonstration of arm-locking for LISA using the GRACE-FO Laser Ranging Instrument

    NASA Astrophysics Data System (ADS)

    Thorpe, Ira; McKenzie, Kirk; Sutton, Andrew

    2015-04-01

    The mitigation of laser frequency noise is a key challenge for the design of space-based interferometric gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA) and its derivatives. Arm locking is novel technique of stabilizing the laser frequency using the LISA arms that has been studied through simulations and in the laboratory. The Laser Ranging Instrument (LRI) on the upcoming GRACE-FO geodesy mission provides an opportunity to perform an on-orbit demonstration of arm-locking in a configuration that is representative of LISA in many aspects. In this talk, I will describe a potential arm-locking experiment for GRACE-FO and present preliminary results from time-domain simulations being used to refine the proposed experiment design.

  12. Large-scale hydrological changes in North America and Scandinavia from GRACE

    NASA Astrophysics Data System (ADS)

    Steffen, Holger; Wang, Hansheng; Jia, Lulu; Wu, Patrick; Jiang, Liming; Hsu, Houtse; Xiang, Longwei; Wang, Zhiyong; Hu, Bo

    2013-04-01

    The Gravity Recovery and Climate Experiment (GRACE) satellite mission has proven to be an invaluable tool in monitoring hydrological changes. Due to the fact that GRACE detects combined mass changes from different sources, dedicated hydrological studies, however, have been mainly limited to areas where the GRACE signal is assumed to be solely related to hydrology or where other overlapping processes can be removed as accurately as possible. In North America and northern Europe, the dominating glacial isostatic adjustment (GIA) signal is shadowing water storage changes. Here, modeled GIA data are used for removal, but model imperfections contaminate the hydrology signal. With a new separation approach we are able to self-determine the hydrological contribution in North America and northern Europe from GRACE and GPS data (Wang et al., 2012). The separation of the hydrological signal is not GIA model dependent and thus provides a clear picture of water storage changes in those areas free of the usually large remnant GIA contributions. From August 2002 to March 2011, the derived mass increase in central North America is about 43.0±5.0 Gt/yr. This is about three quarter of all water falling down Niagara Falls every year. Average groundwater variations from wells in Alberta and central Saskatchewan are in very good agreement to our result and show a significant increase from the year 2002 on. Before that year, there is a significant drop in water levels beginning in 1999/2000, which is related to a drought in the Canadian Prairies during these years. The increase from about 2003 on can be interpreted as the recovery of the water storage after the drought. As the GRACE observation period begins during that time, GRACE exactly observes this recovery in form of a significant mass increase. Changes in water levels from tide gauges for the Great Lakes and groundwater wells in the Lower Peninsula of Michigan also agree to our findings. At the southern tip of the Scandinavian

  13. Comparison of Polar Motion Excitation Series Derived from GRACE and from Analyses of Geophysical Fluids

    NASA Technical Reports Server (NTRS)

    Nastula, J.; Ponte, R. M.; Salstein, D. A.

    2007-01-01

    Three sets of degree-2, order-1 harmonics of the gravity field, derived from the Gravity Recovery and Climate Experiment (GRACE) data processed at the Center for Space Research (CSR), Jet Propulsion Laboratory (JPL) and GeoforschungsZentrum (GFZ), are used to compute polar motion excitation functions X1 and X2. The GFZ and JPL excitations and the CSR X2, excitation compare generally well with geodetically observed excitation after removal of effects of oceanic currents and atmospheric winds. The agreement considerably exceeds that from previous GRACE data releases. For the JPL series, levels of correlation with the geodetic observations and the variance explained are comparable to, but still lower than, those obtained independently from available models and analyses of the atmosphere, ocean, and land hydrology. Improvements in data quality of gravity missions are still needed to deliver even tighter constraints on mass-related excitation of polar motion.

  14. Product shipping information using graceful labeling on undirected tree graph approach

    NASA Astrophysics Data System (ADS)

    Kuan, Yoong Kooi; Ghani, Ahmad Termimi Ab

    2017-08-01

    Product shipping information is the related information of an ordered product that ready to be shipped to the foreign customer's company, where the information represents as an irrefutable proof in black and white to the local manufacturer by E-mails. This messy and unordered list of information is stored in E-mail folders by the people incharge, which do not function in collating the information properly. So, in this paper, an algorithm is proposed on how to rearrange the messy information from the sequence of a path graph structure into a concise version of a caterpillar graph with achieving the concept of graceful labeling. The final graceful caterpillar graph consists of the full listed information together with the numbering, which able to assist people get the information fleetly for shipping arrangement procedure.

  15. The influence of ENSO on global terrestrial water storage using GRACE

    NASA Astrophysics Data System (ADS)

    Phillips, T.; Nerem, R. S.; Fox-Kemper, Baylor; Famiglietti, J. S.; Rajagopalan, B.

    2012-08-01

    The influence of the El Nino/Southern Oscillation (ENSO) on terrestrial water storage is analyzed for the time period 2003-2010 using monthly estimates of continental water storage from the Gravity Recovery and Climate Experiment (GRACE). Peak correlation between NOAA's Multivariate ENSO Index (MEI) and the measured mass anomaly timeseries shows an R2 of 0.65 for the Amazon Basin and Borneo in Southeast Asia. By including a Hilbert transformation of the MEI to account for time lag, the R2 is improved to 0.76. Tropical regions show strong negative correlation with the MEI and arid regions are positively correlated. GRACE is able to detect all the significant known ENSO teleconnection patterns around the globe, including Alaska and Antarctica. In addition, a significant correlation suggests some of Greenland's recent mass loss could be ENSO-related.

  16. Mass-induced [|#8#|]Sea Level Variations in the Red Sea from Satellite Altimetry and GRACE

    NASA Astrophysics Data System (ADS)

    Feng, W.; Lemoine, J.; Zhong, M.; Hsu, H.

    2011-12-01

    We have analyzed mass-induced sea level variations (SLVs) in the Red Sea from steric-corrected altimetry and GRACE between January 2003 and December 2010. The steric component of SLVs in the Red Sea calculated from climatological temperature and salinity data is relatively small and anti-phase with the mass-induced SLV. The total SLV in the Red Sea is mainly driven by the mass-induced SLV, which increases in winter when the Red Sea gains the water mass from the Gulf of Aden and vice versa in summer. Spatial and temporal patterns of mass-induced SLVs in the Red Sea from steric-corrected altimetry agree very well with GRACE observations. Both of two independent observations show high annual amplitude in the central Red Sea (>20cm). Total mass-induced SLVs in the Red Sea from two independent observations have similar annual amplitude and phase. One main purpose of our work is to see whether GRGS's ten-day GRACE results can observe intra-seasonal mass change in the Red Sea. The wavelet coherence analysis indicates that GRGS's results show the high correlation with the steric-corrected SLVs on intra-seasonal time scale. The agreement is excellent for all the time-span until 1/3 year period and is patchy between 1/3 and 1/16 year period. Furthermore, water flux estimates from current-meter arrays and moorings show mass gain in winter and mass loss in summer, which is also consistent with altimetry and GRACE.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    PubMed Central

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

    2015-01-01

    In southern Tibet, ongoing vertical and horizontal motions due to the collision between India and Eurasia are monitored by large numbers of global positioning system (GPS) continuous and campaign sites installed in the past decade. Displacements measured by GPS usually include tectonic deformation as well as non-tectonic, time-dependent signals. To estimate the regional long-term tectonic deformation using GPS more precisely, seasonal elastic deformation signals associated with surface loading must be removed from the observations. In this study, we focus on seasonal variation in vertical and horizontal motions of southern Tibet by performing a joint analysis of GRACE (Gravity Recovery and Climate Experiment) and GPS data, not only using continuous sites but also GPS campaign-mode sites. We found that the GPS-observed and GRACE-modeled seasonal oscillations are in good agreements, and a seasonal displacement model demonstrates that the main reason for seasonal variations in southern Tibet is from the summer monsoon and its precipitation. The biggest loading appears from July to August in the summer season. Vertical deformations observed by GPS and modeled by GRACE are two to three times larger than horizontal oscillations, and the north components demonstrate larger amplitudes than the east components. We corrected the GPS position time series using the GRACE-modeled seasonal variations, which gives significant reductions in the misfit and weighted root-mean-squares (WRMS). Misfit (χ2 divided by degree of freedom) reductions for campaign sites range between 20% and 56% for the vertical component, and are much smaller for the horizontal components. Moreover, time series of continuous GPS (cGPS) sites near the 2015 Nepal earthquakes must be corrected using appropriate models of seasonal loading for analyzing postseismic deformation to avoid biasing estimates of the postseismic relaxation. PMID:26690157

  19. Non-ST-elevation acute coronary syndromes in octogenarians: applicability of the GRACE and CRUSADE scores.

    PubMed

    Faustino, Ana; Mota, Paula; Silva, Joana

    2014-10-01

    Assessment of ischemic and bleeding risk is critical for the management of elderly patients with acute coronary syndromes, but it has been little studied. This study aims to assess the applicability of the GRACE and CRUSADE scores in patients aged ≥80 years with non-ST-elevation acute coronary syndrome (NSTE-ACS), and to identify the main predictors of in-hospital mortality and major bleeding in this population. We analyzed 544 patients aged ≥80 years with NSTE-ACS included in the Portuguese Registry on Acute Coronary Syndromes and identified the predictors of in-hospital mortality and major bleeding during hospitalization. Prediction models were created for these endpoints, then compared with the GRACE and CRUSADE scores, and their applicability to the study population was assessed. Use of coronary angiography was associated with reduced risk of in-hospital mortality, without increasing risk of major bleeding (OR 0.2, 95% CI 0.006-0.49, p=0.001). Major bleeding was an independent predictor of in-hospital mortality (OR 10.9, 95% CI 2.36-50.74, p=0.002), and was associated with comorbidities and pharmacological therapy during hospitalization. The GRACE score showed good diagnostic accuracy for in-hospital mortality (AUC 0.75, 95% CI 0.63-0.87, p<0.001), but the CRUSADE score had weak discriminatory capacity for major bleeding (AUC 0.51, 95% CI 0.30-0.63, p=0.942), unlike our prediction model (AUC 0.68, 95% CI 0.52-0.84, p=0032). The GRACE score is suitable for risk assessment in octogenarians with NSTE-ACS, but the CRUSADE score is inadequate, and new scores are required to assess bleeding risk in this age-group. Copyright © 2013 Sociedade Portuguesa de Cardiologia. Published by Elsevier España. All rights reserved.

  20. Graceful exit from inflation for minimally coupled Bianchi A scalar field models

    NASA Astrophysics Data System (ADS)

    Beyer, F.; Escobar, L.

    2013-10-01

    We consider the dynamics of Bianchi A scalar field models which undergo inflation. The main question is under which conditions does inflation come to an end and is succeeded by a decelerated epoch. This so-called ‘graceful exit’ from inflation is an important ingredient in the standard model of cosmology, but is, at this stage, only understood for restricted classes of solutions. We present new results obtained by a combination of analytical and numerical techniques.

  1. A GRACE-based assessment of interannual groundwater dynamics in the Community Land Model

    NASA Astrophysics Data System (ADS)

    Swenson, S. C.; Lawrence, D. M.

    2015-11-01

    The estimation of groundwater storage variations is important for quantifying available water resources and managing storage surpluses to alleviate storage deficiencies during droughts. This is particularly true in semi-arid regions, where multiyear droughts can be common. To complement the local information provided by soil moisture and well level measurements, land models such as the Community Land Model (CLM) can be used to simulate regional scale water storage variations. CLM includes a bulk aquifer model to simulate saturated water storage dynamics below the model soil column. Aquifer storage increases when it receives recharge from the overlying soil column, and decreases due to lateral flow (i.e., base flow) and capillary rise. In this study, we examine the response of the CLM aquifer model to transitions between low and high recharge inputs, and show that the model simulates unrealistic long-period behavior relative to total water storage (TWS) observations from the Gravity Recovery and Climate Experiment (GRACE). We attribute the model's poor response to large wetting events to the lack of a finite lower boundary in the bulk aquifer model. We show that by removing the bulk aquifer model and adding a zero-flux boundary condition at the base of the soil column, good agreement with GRACE observations can be achieved. In addition, we examine the sensitivity of simulated total water storage to the depth at which the zero-flux boundary is applied, i.e., the thickness of the soil column. Based on comparisons to GRACE, an optimal soil thickness map is constructed. Simulations using the modified CLM with the derived soil thickness map are shown to perform as well or better than standard CLM simulations. The improvements in simulated, climatically induced, long-period water storage variability will reduce the uncertainty in GRACE-based estimates of anthropogenic groundwater depletion.

  2. A Statistical Filtering Approach for Gravity Recovery and Climate Experiment (GRACE) Gravity Data

    NASA Technical Reports Server (NTRS)

    Davis. J. L.; Tamisiea, M. E.; Elosegui, P.; Mitrovica, J. X.; Hill, E. M.

    2008-01-01

    We describe and analyze a statistical filtering approach for GRACE data that uses a parametrized model for the temporal evolution of the GRACE coefficients. After least-squares adjustment, a statistical test is performed to assess the significance of the estimated parameters. If the test is passed, the parameters are used by the filter in the reconstruction of the field; otherwise they are rejected. The test is performed, and the filter is formed, separately for annual components of the model and the trend. This new approach is distinct from Gaussian smoothing since it uses the data themselves to test for specific components of the time-varying gravity field. The statistical filter appears inherently to remove most of the "stripes" present in the GRACE fields, although destriping the fields prior to filtering seems to help the trend recovery. We demonstrate that the statistical filter produces reasonable maps for the annual components and trend. We furthermore assess the statistical filter for the annual components using ground-based GPS data in South America by assuming that the annual component of the gravity signal is associated only with groundwater storage. The un-destriped, statistically filtered field has a X2 value relative to the GPS data consistent with the best result from smoothing. In the space domain, the statistical filters are qualitatively similar to Gaussian smoothing. Unlike Gaussian smoothing, however, the statistical filter has significant sidelobes, including large negative sidelobes on the north-south axis, potentially revealing information on the errors, and the correlations among the errors, for the GRACE coefficients.

  3. Spatiotemporal evolution of water storage changes in India from the updated GRACE-derived gravity records

    NASA Astrophysics Data System (ADS)

    Panda, Dileep K.; Wahr, John

    2016-01-01

    Investigating changes in terrestrial water storage (TWS) is important for understanding response of the hydrological cycle to recent climate variability worldwide. This is particularly critical in India where the current economic development and food security greatly depend on its water resources. We use 129 monthly gravity solutions from NASA's Gravity Recovery and Climate Experiment (GRACE) satellites for the period of January 2003 to May 2014 to characterize spatiotemporal variations of TWS and groundwater storage (GWS). The spatiotemporal evolution of GRACE data reflects consistent patterns with that of several hydroclimatic variables and also shows that most of the water loss has occurred in the northern parts of India. Substantial GWS depletion at the rate of 1.25 and 2.1 cm yr-1 has taken place, respectively in the Ganges Basin and Punjab state, which are known as the India's grain bowl. Of particular concern is the Ganges Basin's storage loss in drought years, primarily due to anthropogenic groundwater withdrawals that sustain rice and wheat cultivation. We estimate these losses to be approximately 41, 44, and 42 km3 in 2004, 2009, and 2012, respectively. The GWS depletions that constitute about 90% of the observed TWS loss are also influenced by a marked rise in temperatures since 2008. A high degree of correspondence between GRACE-derived GWS and in situ groundwater levels from observation well validates the results. This validation increases confidence level in the application of GRACE observations in monitoring large-scale storage changes in intensely irrigated areas in India and other regions around the world.

  4. Utilizing Grace TWS, NDVI, and Precipitation for Drought Identification and Classification in Texas

    NASA Astrophysics Data System (ADS)

    McCandless, S. E.; Bettadpur, S. V.; Howard, T.; Wells, G. L.

    2014-12-01

    Drought is one of the most widespread natural phenomena in the world and many indices exist today to monitor drought progression. The "Merged-dataset Drought Index" (MDI) is a new quantitative index calculated using the US/German Gravity Recovery and Climate Experiment total water storage (GRACE TWS), NASA MODIS-derived normalized difference vegetation index (NDVI), and NOAA/NWS precipitation data. These particular datasets constitute MDI because each correlates with a different drought type. Dataset deviations from established climatology are used, where negative deviations indicate deficits. MDI is objectively and transparently calculated based on dataset z-scores. GRACE TWS is the least mature dataset used in these calculations, but TWS solution variance does not negatively impact MDI. A new classification scheme to categorize drought severity is also proposed. MDI is studied in Texas and its smaller sub-regions. Within these sub-regions, MDI identifies multiple droughts during 2002 - 2014, with the most severe beginning in 2011. Drought analysis using MDI shows for the first time that GRACE data provides information on a sub-regional scale in Texas, an area with low overall signal amplitudes. Past studies have shown TWS capable of identifying drought, but MDI is the first index to quantitatively use GRACE TWS in a manner consistent with current practices of identifying drought. MDI also establishes a framework for a future, completely remote-sensing based index that can enable temporally and spatially consistent drought identification across the globe. This study is useful as well for establishing a baseline for the necessary spatial resolution required from future geodetic space missions for use in drought identification at smaller scales.

  5. Correction of Correlation Errors in Greenland Ice Mass Variations from GRACE using Empirical Orthogonal Function

    NASA Astrophysics Data System (ADS)

    Eom, J.; Seo, K. W.

    2015-12-01

    Since its launch in March 2002, the Gravity Recovery And Climate Experiment (GRACE) has provided monthly geopotential fields represented by Stokes coefficients of spherical harmonics (SH). Nominally, GRACE gravity solutions exclude effects from tides, ocean dynamics and barometric pressure by incorporating geophysical models for them. However, those models are imperfect, and thus GRACE solutions include the residual gravity effects. Particularly, unmodeled gravity variations of sub-monthly or shorter time scale cause aliasing error, which produces peculiar longitudinal stripes. Those north-south patterns are removed by spatial filtering, but caution is necessary for the aliasing correction because signals with longitudinal patterns are possibly removed during the procedure. This would be particularly problematic for studies associated with Greenland ice mass balance since large ice mass variations are expected in the West and South-West coast of Greenland that are elongated along the longitudinal direction. In this study, we develop a novel method to remove the correlation error using extended Empirical Orthogonal Function (extended EOF). The extended EOF is useful to separate spatially and temporally coherent signal from high frequency variations. Since temporal variability of the correlation error is high, the error is possibly removed via the extended EOF. Ice mass variations reduced by the extended EOF show more detail patterns of ice mass loss/gain than those from the conventional spatial filtering. Large amount of ice loss has occurred along the West, South-West and East coastal area during summer. The extended EOF is potentially useful to enhance signal to noise ratio and increase spatial resolution of GRACE data.

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

    PubMed

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

    2015-12-04

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

  7. GRACE Hydrologic Mass Balance Secular Trends and Variations on Arctic Permafrost Watersheds

    NASA Astrophysics Data System (ADS)

    Muskett, R. R.

    2008-12-01

    Permafrost is largest component of the Arctic cryosphere by area extent. Over the last century, substantial changes in storage and cycling of fresh water have been observed. Observations of the globally distributed hydrologic mass balance (water equivalent thickness change relative to the geoid) from the Gravity Recovery and Climate Experiment mission offer to provide a greater understanding of the processes controlling redistribution of water mass (groundwater storage, discharge, snow water equivalent storage, vegetation water storage, and ice sheet mass balance) under ongoing effects of climate warming. Using newly processed monthly GRACE grids, Level-3 Release 4, de-striped, adjusted for post-glacial rebound I investigate the hydrologic mass balance of the Arctic watershed regions. Regionally-averaged monthly time series show strong seasonal periodicity, with maxima occurring in April/May and minima in September/October. Eurasian watersheds have significant positive secular trends. The Ob-Irtysh watershed shows a water equivalent gain of 22.7 ± 13.5 km3/yr, and the Lena watershed shows a water equivalent gain of 44.7 ± 0.8 km3/yr from August 2002 through March 2008. The Mackenzie watershed shows a water equivalent volume change of -5.6 ± 7.2 km3/yr in the same time period. The permafrost area extent in the watersheds investigated shows the Ob-Irtysh draining the least continuous permafrost extent and the Lena draining the most. The Mackenzie watershed drains a mixture of continuous and discontinuous permafrost area extents. Regionally-average snow water equivalent time series show seasonal periodicity whose maxima and minima occur one month ahead of the GRACE time series. Secular trends of snow water equivalent show neither significant gain nor loss over the time period. This removes snow water equivalent (a component of surface water storage) as being the source of the GRACE secular trends. A subsurface source of water mass exchange of the GRACE secular

  8. A Statistical Filtering Approach for Gravity Recovery and Climate Experiment (GRACE) Gravity Data

    NASA Technical Reports Server (NTRS)

    Davis. J. L.; Tamisiea, M. E.; Elosegui, P.; Mitrovica, J. X.; Hill, E. M.

    2008-01-01

    We describe and analyze a statistical filtering approach for GRACE data that uses a parametrized model for the temporal evolution of the GRACE coefficients. After least-squares adjustment, a statistical test is performed to assess the significance of the estimated parameters. If the test is passed, the parameters are used by the filter in the reconstruction of the field; otherwise they are rejected. The test is performed, and the filter is formed, separately for annual components of the model and the trend. This new approach is distinct from Gaussian smoothing since it uses the data themselves to test for specific components of the time-varying gravity field. The statistical filter appears inherently to remove most of the "stripes" present in the GRACE fields, although destriping the fields prior to filtering seems to help the trend recovery. We demonstrate that the statistical filter produces reasonable maps for the annual components and trend. We furthermore assess the statistical filter for the annual components using ground-based GPS data in South America by assuming that the annual component of the gravity signal is associated only with groundwater storage. The un-destriped, statistically filtered field has a X2 value relative to the GPS data consistent with the best result from smoothing. In the space domain, the statistical filters are qualitatively similar to Gaussian smoothing. Unlike Gaussian smoothing, however, the statistical filter has significant sidelobes, including large negative sidelobes on the north-south axis, potentially revealing information on the errors, and the correlations among the errors, for the GRACE coefficients.

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

    NASA Technical Reports Server (NTRS)

    Shum, C. K.

    2002-01-01

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

  10. Late Consequences of Acute Coronary Syndromes: Global Registry of Acute Coronary Events (GRACE) Follow-up.

    PubMed

    Alnasser, Sami M A; Huang, Wei; Gore, Joel M; Steg, Ph Gabriel; Eagle, Kim A; Anderson, Frederick A; Fox, Keith A A; Gurfinkel, Enrique; Brieger, David; Klein, Werner; van de Werf, Frans; Avezum, Álvaro; Montalescot, Gilles; Gulba, Dietrich C; Budaj, Andrzej; Lopez-Sendon, Jose; Granger, Christopher B; Kennelly, Brian M; Goldberg, Robert J; Fleming, Emily; Goodman, Shaun G

    2015-07-01

    Short-term outcomes have been well characterized in acute coronary syndromes; however, longer-term follow-up for the entire spectrum of these patients, including ST-segment-elevation myocardial infarction, non-ST-segment-elevation myocardial infarction, and unstable angina, is more limited. Therefore, we describe the longer-term outcomes, procedures, and medication use in Global Registry of Acute Coronary Events (GRACE) hospital survivors undergoing 6-month and 2-year follow-up, and the performance of the discharge GRACE risk score in predicting 2-year mortality. Between 1999 and 2007, 70,395 patients with a suspected acute coronary syndrome were enrolled. In 2004, 2-year prospective follow-up was undertaken in those with a discharge acute coronary syndrome diagnosis in 57 sites. From 2004 to 2007, 19,122 (87.2%) patients underwent follow-up; by 2 years postdischarge, 14.3% underwent angiography, 8.7% percutaneous coronary intervention, 2.0% coronary bypass surgery, and 24.2% were re-hospitalized. In patients with 2-year follow-up, acetylsalicylic acid (88.7%), beta-blocker (80.4%), renin-angiotensin system inhibitor (69.8%), and statin (80.2%) therapy was used. Heart failure occurred in 6.3%, (re)infarction in 4.4%, and death in 7.1%. Discharge-to-6-month GRACE risk score was highly predictive of all-cause mortality at 2 years (c-statistic 0.80). In this large multinational cohort of acute coronary syndrome patients, there were important later adverse consequences, including frequent morbidity and mortality. These findings were seen in the context of additional coronary procedures and despite continued use of evidence-based therapies in a high proportion of patients. The discriminative accuracy of the GRACE risk score in hospital survivors for predicting longer-term mortality was maintained. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. The new GRACE AOD1B Product Release 06: Product Details and Initial Validation

    NASA Astrophysics Data System (ADS)

    Poropat, Lea; Bergmann-Wolf, Inga; Dobslaw, Henryk; Thomas, Maik

    2016-04-01

    The GRACE satellites, orbiting the Earth at very low altitudes, are affected by rapid changes in the Earth's gravity field caused by mass redistribution in atmosphere and oceans. To avoid temporal aliasing of such high-frequency variability into the final monthly-mean gravity fields, those effects are typically modeled during the numerical orbit integration by applying the 6-hourly GRACE Atmosphere and Ocean De-Aliasing Level-1B (AOD1B) a priori model. In preparation of the next GRACE gravity field re-processing planned by the GRACE Science Data System for the second half of the year 2016, a new version of AOD1B is currently calculated. The data-set is based on 3-hourly surface pressure anomalies from ECMWF that have been mapped to a common reference orography by means of ECMWF's mean sea level pressure diagnostic. Atmospheric tides as well as the corresponding oceanic response at the S1, S2, and M2 frequencies and its annual modulations have been removed in order to retain the non-tidal variability only. The data-set is expanded into spherical harmonics complete up to degree and order 180. AOD1B RL06 will be available since 1976 in order to allow for the consistent reprocessing of all SLR observations to LAGEOS, and of all relevant satellite altimetry missions. The processing of the whole 40-years-long time-series is expected to be complete in May 2016, and we will present in this talk the current status of our efforts including some preliminary validation of the oceanic component against in situ ocean bottom pressure observations.

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Agustin Brena Naranjo, Jose; Pedrozo Acuña, Adrian

    2016-04-01

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

  14. Are GRACE-era terrestrial water trends driven by anthropogenic climate change?

    DOE PAGES

    Fasullo, J. T.; Lawrence, D. M.; Swenson, S. C.

    2016-01-01

    To provide context for observed trends in terrestrial water storage (TWS) during GRACE (2003–2014), trends and variability in the CESM1-CAM5 Large Ensemble (LE) are examined. Motivated in part by the anomalous nature of climate variability during GRACE, the characteristics of both forced change and internal modes are quantified and their influences on observations are estimated. Trends during the GRACE era in the LE are dominated by internal variability rather than by the forced response, with TWS anomalies in much of the Americas, eastern Australia, Africa, and southwestern Eurasia largely attributable to the negative phases of the Pacific Decadal Oscillation (PDO)more » and Atlantic Multidecadal Oscillation (AMO). While similarities between observed trends and the model-inferred forced response also exist, it is inappropriate to attribute such trends mainly to anthropogenic forcing. For several key river basins, trends in the mean state and interannual variability and the time at which the forced response exceeds background variability are also estimated while aspects of global mean TWS, including changes in its annual amplitude and decadal trends, are quantified. Lastly, the findings highlight the challenge of detecting anthropogenic climate change in temporally finite satellite datasets and underscore the benefit of utilizing models in the interpretation of the observed record.« less

  15. Change in land water storage in the East Africa region inferred from GRACE and altimetry data.

    NASA Astrophysics Data System (ADS)

    Becker, M.; Cazenave, A.

    2008-12-01

    Drought can be regarded as one of the most damaging of natural disasters in human, environmental, and economic terms. It occurs as a result of extremes in climate that are driven by natural variability but may be exacerbated or dampened by anthropogenic influences. In East Africa rainfall exhibits a great spatial and temporal variability. Such events have impact on the water budget of this region. But water use and more generally anthropogenic forcing also affect regional hydrology. In this study, we investigate water storage change (surface and ground) using in synergy satellite radar altimetry, GRACE satellite gravity and other data to quantify recent change in surface waters and total land storage in East Africa over the recent years. Water levels of most East African lakes display significant decrease since the strong ENSO event of 1997- 1998. GRACE data available since 2002 also show decrease in total water storage over this region. The volume of water stored within lakes and reservoirs is a sensitive proxy for precipitation and may be used to study the combined impact of climate change and water-resource management. We also combine GRACE, altimetry and precipitation data sets to explore the relative contributions of the source term to the seasonal and interannual hydrological balance of this area and its link with the western Indian Ocean thermal change

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

    PubMed Central

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

    2016-01-01

    The Northwest India Aquifer (NWIA) has been shown to have the highest groundwater depletion (GWD) rate globally, threatening crop production and sustainability of groundwater resources. Gravity Recovery and Climate Experiment (GRACE) satellites have been emerging as a powerful tool to evaluate GWD with ancillary data. Accurate GWD estimation is, however, challenging because of uncertainties in GRACE data processing. We evaluated GWD rates over the NWIA using a variety of approaches, including newly developed constrained forward modeling resulting in a GWD rate of 3.1 ± 0.1 cm/a (or 14 ± 0.4 km3/a) for Jan 2005–Dec 2010, consistent with the GWD rate (2.8 cm/a or 12.3 km3/a) from groundwater-level monitoring data. Published studies (e.g., 4 ± 1 cm/a or 18 ± 4.4 km3/a) may overestimate GWD over this region. This study highlights uncertainties in GWD estimates and the importance of incorporating a priori information to refine spatial patterns of GRACE signals that could be more useful in groundwater resource management and need to be paid more attention in future studies. PMID:27075595

  17. Have GRACE Satellites Overestimated Groundwater Depletion in the Northwest India Aquifer?

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  19. Gravimetric excitation function of polar motion from the GRACE RL05 solution

    NASA Astrophysics Data System (ADS)

    Nastula, Y.

    2014-12-01

    Impact of land hydrosphere on polar motion excitation is still not as well known as the impact of the angular momentum of the atmosphere and ocean. Satellite mission Gravity Recovery and Climate Experiment (GRACE) from 2002 provides additional information about mass distribution of the land hydrosphere. However, despite the use of similar computational procedures, the differences between GRACE data series made available by the various centers of computations are still considerable. In the paper we compare three series of gravimetric excitation functions of polar motion determined from Rl05 GRACE solution from the Center for Space Research (CSR), the Jet Propulsion Laboratory (JPL) and the GeoForschungsZentrum (GFZ). These data are used to determine the gravimetric polar motion excitation function. Gravimetric signal is compared also with the geodetic residuals computed by subtracting atmospheric and oceanic signals from geodetic excitation functions of polar motion. Gravimetric excitation functions obtained on the basis of JPL data differ significantly from the geodetic residuals while and the series obtained from CSR and GFZ are more compatible.

  20. Greenland mass variation from time-variable gravity in the absence of GRACE

    NASA Astrophysics Data System (ADS)

    Baur, O.

    2013-08-01

    In a recent paper, the authors succeeded in the inference of time-variable gravity from orbit analysis of the CHAMP satellite. The authors demonstrated the potential of the adopted methods by validation against GRACE data and surface height changes from GPS ground stations. This paper presents the capability of orbit analysis for the spatiotemporal quantification of Greenland mass change trends. Based on CHAMP time-variable gravity fields from January 2003 to December 2009, we estimated the ice mass loss over the entire of Greenland to 246±10 Gt/yr. This result is in line with the findings from GRACE data analysis (223±10 Gt/yr) over the same period; the trend estimates differ by only 10%. Moreover, for some areas, the spatial mass variation patterns are in good agreement, pinpointing dominant deglaciation along the Greenland coastline. We conclude that orbit analysis of low-Earth orbiting spacecraft is suitable to assess Greenland mass balance in the absence of the GRACE satellites.

  1. On the decorrelation filtering of RL05 GRACE data for global applications

    NASA Astrophysics Data System (ADS)

    Belda, Santiago; García-García, David; Ferrándiz, José M.

    2015-01-01

    In autumn 2012, the new release 05 (RL05) of monthly geopotencial spherical harmonics Stokes coefficients (SC) from Gravity Recovery and Climate Experiment (GRACE) mission was published. This release reduces the noise in high degree and order SC, but they still need to be filtered. One of the most common filtering processing is the combination of decorrelation and Gaussian filters. Both of them are parameters dependent and must be tuned by the users. Previous studies have analyzed the parameters choice for the RL05 GRACE data for oceanic applications, and for RL04 data for global application. This study updates the latter for RL05 data extending the statistics analysis. The choice of the parameters of the decorrelation filter has been optimized to: (1) balance the noise reduction and the geophysical signal attenuation produced by the filtering process; (2) minimize the differences between GRACE and model-based data and (3) maximize the ratio of variability between continents and oceans. The Gaussian filter has been optimized following the latter criteria. Besides, an anisotropic filter, the fan filter, has been analyzed as an alternative to the Gauss filter, producing better statistics.

  2. Solar flare effects on the thermosphere and E-layer as observed by GRACE and DEMETER

    NASA Astrophysics Data System (ADS)

    Boudjada, Mohammed Y.; Krauss, Sandro; Sawas, Sami; Hausleitner, Walter; Parrot, Michel; Voller, Wolfgang

    2013-04-01

    We investigate the effect of solar flares on the lower thermosphere and ionosphere of the Earth. For this study we select solar flares which occurred in the period from Nov. 2004 to Sept. 2005. We combine the measurements of the GRACE and DEMETER satellites which lead us to estimate, respectively, the atmospheric density and the electric field variation at an altitude of about 100 km. The accelerometer measurements from GRACE orbiting at an altitude of about 450 km comprise all non gravitational forces acting on the satellite and may be used to determine the atmospheric neutral density. The intensity variation of the transmitter ground signals is detected by DEMETER at an altitude in the order of 700 km. In this study we insist on an atmosphere-ionosphere coupling effect which may appear at an altitude of about 100 km. This crucial altitude corresponds to critical regions where important changes are observed in the atmosphere (Mesosphere/Thermosphere) and in the ionosphere (D/E layers). We discuss the possible correlation between the measurements of GRACE and DEMETER observations, where both the local and global effects are taken into consideration.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    Continuous observations of temporal variations in the Earth's gravity field have recently become available at an unprecedented resolution of a few hundreds of kilometers. The gravity field is a product of the Earth's mass distribution, and these data—provided by the satellites of the Gravity Recovery And Climate Experiment (GRACE)—can be used to study the exchange of mass both within the Earth and at its surface. Since the launch of the mission in 2002, GRACE data has evolved from being an experimental measurement needing validation from ground truth, to a respected tool for Earth scientists representing a fixed bound on the total change and is now an important tool to help unravel the complex dynamics of the Earth system and climate change. In this review, we present the mission concept and its theoretical background, discuss the data and give an overview of the major advances GRACE has provided in Earth science, with a focus on hydrology, solid Earth sciences, glaciology and oceanography.

  4. The European Gravity Field 2002-2005 from GRACE and GGP Data

    NASA Astrophysics Data System (ADS)

    Crossley, D.; Hinderer, J.; Boy, J.; Wilmes, H.; Kroner, C.; Meurers, B.

    2005-12-01

    This paper continues the study of the European gravity field as determined simultaneously from the GGP network of superconducting gravimeters and from the GRACE satellites. The period of study is from August 2002 to 2005 (as data is available) and covers the region between Membach (eastern Belgium), Vienna, and Medicina (northern Italy); during the last year, station Bad Homburg in western Germany has been added to make a total of 7 stations. As in previous similar studies, we combine the gravity residuals from the ground stations to make a smoothed map of the gravity field every 15 days and compare it to the GRACE field snapshots over the same area. Comparisons are done using both EOF principal component analysis and MSSA for both data sets. We confirm the predominance of annual signals and also examine the trends in GRACE and ground absolute gravity measurements to find the limiting secular change detectable in the data. Our primary goal is to correlate both data sets with hydrological models using meteorologically driven snow and soil moisture estimates for Europe, as well as hydrological observations and GPS results at the gravity sites, where available. We show the relationship between the sign of the hydrology signal, separated into attraction and loading, and the local topography surrounding each station.

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

    PubMed

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

    2016-04-14

    The Northwest India Aquifer (NWIA) has been shown to have the highest groundwater depletion (GWD) rate globally, threatening crop production and sustainability of groundwater resources. Gravity Recovery and Climate Experiment (GRACE) satellites have been emerging as a powerful tool to evaluate GWD with ancillary data. Accurate GWD estimation is, however, challenging because of uncertainties in GRACE data processing. We evaluated GWD rates over the NWIA using a variety of approaches, including newly developed constrained forward modeling resulting in a GWD rate of 3.1 ± 0.1 cm/a (or 14 ± 0.4 km(3)/a) for Jan 2005-Dec 2010, consistent with the GWD rate (2.8 cm/a or 12.3 km(3)/a) from groundwater-level monitoring data. Published studies (e.g., 4 ± 1 cm/a or 18 ± 4.4 km(3)/a) may overestimate GWD over this region. This study highlights uncertainties in GWD estimates and the importance of incorporating a priori information to refine spatial patterns of GRACE signals that could be more useful in groundwater resource management and need to be paid more attention in future studies.

  6. Evaluating the Amazon water cycle components using ED model against GRACE

    NASA Astrophysics Data System (ADS)

    Lee, E.; Han, S. C.; Yeo, I. Y.; Longo, M.; Swann, A. L. S.; Knox, R. G.; Briscoe, J.; Moorcroft, P. R.

    2014-12-01

    Changes in the water cycle components of the Amazon and its surrounding regions are a key to assessing regional impacts of climate and land-cover changes, as they may affect rain-fed agriculture and hydroelectric power generation in Brazil. A comprehensive validation of the modeled water budget, therefore, is a necessary part of understanding the region's hydroclimatology. We evaluate the water cycle components from Ecosystem Demography (ED) model both as a stand-alone model and a coupled model to the Brazilian Regional Atmospheric Modeling System (BRAMS). Model results are compared with satellite-driven observations and a flux tower measurement in central Amazon. Our results indicate that the modeled EDBRAMS precipitation over Amazonia replicates the observed patterns of the Tropical Rainfall Measuring Mission (TRMM) from 2001 to 2009. Total Water Storage Change (TWSC) anomalies from the ED model at the Paraná River basin shows a better agreement with the Gravity Recovery And Climate Experiment (GRACE) satellite observation from 2002 to 2008, as compared to the Global Land Data Assimilation System (GLDAS)/NOAH model. The Nash-Sutcliff model efficiency coefficient improved from 0.50 (GLDAS/NOAH vs. GRACE) to 0.65 (ED vs. GRACE). We also evaluate the modeled evapotranspiration (ET) against the flux tower measurement. Our study affirms the capabilities of the ED model in simulating the Amazon hydrological cycle, which helps investigate its sustainable thresholds with various land-cover and climate change scenarios.

  7. Flight phasemeter on the Laser Ranging Interferometer on the GRACE Follow-On mission

    NASA Astrophysics Data System (ADS)

    Bachman, B.; de Vine, G.; Dickson, J.; Dubovitsky, S.; Liu, J.; Klipstein, W.; McKenzie, K.; Spero, R.; Sutton, A.; Ware, B.; Woodruff, C.

    2017-05-01

    As the first inter-spacecraft laser interferometer, the Laser Ranging Interferometer (LRI) on the GRACE Follow-On Mission will demonstrate interferometry technology relevant to the LISA mission. This paper focuses on the completed LRI Laser Ranging Processor (LRP), which includes heterodyne signal phase tracking at μ {{cycle/}}\\sqrt{{{Hz}}} precision, differential wavefront sensing, offset frequency phase locking and Pound-Drever-Hall laser stabilization. The LRI design has characteristics that are similar to those for LISA: 1064 nm NPRO laser source, science bandwidth in the mHz range, MHz-range intermediate frequency and Doppler shift, detected optical power of tens of picoWatts. Laser frequency stabilization has been demonstrated at a level below 30{{Hz/}}\\sqrt{{{Hz}}}, better than the LISA requirement of 300{{Hz/}}\\sqrt{{{Hz}}}. The LRP has completed all performance testing and environmental qualification and has been delivered to the GRACE Follow-On spacecraft. The LRI is poised to test the LISA techniques of tone-assisted time delay interferometry and arm-locking. GRACE Follow-On launches in 2017.

  8. The GRACE Follow-On Laser Ranging Instrument - On track for launch in 2017

    NASA Astrophysics Data System (ADS)

    Görth, Alexander; LRI Team

    2016-04-01

    The Gravity Recovery and Climate Experiment (GRACE) is a highly successful satellite mission whose main purpose is to record the temporal and spatial variations of the gravitational field of the Earth. Its successor mission, GRACE Follow-On, is scheduled for launch in the summer of 2017. It will be the first space mission to host a laser-based intersatellite ranging system as a technology demonstrator: the laser ranging interferometer (LRI). The ranging sensitivity of the LRI is expected to be ≤80 nm/sqrt(Hz) which would exceed the original GRACE ranging noise by at least one order of magnitude. Additionally, the LRI will provide new precise data streams for the line-of-sight alignment of the two spacecraft. 
In January 2015 the LRI's critical design review, a major project milestone, was passed successfully. By the end of last year the production of flight hardware was completed. Currently, the LRI is being integrated into the spacecraft and important calibration measurements are performed.
 In my talk I will give an overview of the unique design of the LRI and give an update on the current status of the instrument.

  9. GRACE gravity solutions using a combination of spherical harmonics and surface density grids

    NASA Astrophysics Data System (ADS)

    Lemoine, Jean-Michel; Bourgogne, Stéphane; Biancale, Richard; Bruinsma, Sean

    2017-04-01

    CNES/GRGS has been committed for the last twelve years to computing spherical harmonics models of the Earth gravity field from the GRACE dataset. Due to the tradeoff that has to be found between spatial resolution and stability of the solutions, it is difficult with spherical harmonics to accurately model the strong but narrow signals like, for instance, the ocean-continent gravity contrast along the coastlines. In order to overcome this limitation, CNES/GRGS is exploring, after some other groups ( JPL, GSFC, GET…) but with a slightly different method, the possibility to use surface gravity grids in combination with spherical harmonics for the GRACE solutions. In our case the spherical harmonics model is used for the static part of the gravity field and the direct gravitational attraction of a surface regular grid for the time-varying part. Not ignoring the caveats on the interpretation of EWH or surface mascons raised by Chao (2016), we will present the results obtained from simulation studies and from the use of actual GRACE measurements. In particular a comparison between the "direct attraction" approach and the "energy integral" approach will be made and, in the first case, between a purely spherical harmonics solution and a "spherical harmonics + surface grid" solution.

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

    NASA Astrophysics Data System (ADS)

    Michel, V.

    2005-12-01

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

  11. States of grace: Eureka moments and the recognition of the unthought known.

    PubMed

    Crowther, Catherine; Schmidt, Martin

    2015-02-01

    In this paper we consider states of grace in analysis. These encompass a range of phenomena which share an experience of something being received or revealed rather than produced by the ego. It feels that they are events that happen rather than events that are made to occur. They are marked by a profound sense of transformation of feeling tone. The quality of relatedness in the analytic dyad is also heightened. Some of these phenomena have been referred to as experiences of the self, synchronicities, moments of meeting, the unthought known and Eureka moments. The latter are experiences of sudden realization where a meaningful thought or image emerges which results in a dramatic shift in direction of the analysis and a transcendence of impasse. Although many authors describe these phenomena, we find that a Jungian approach provides a loom on which these threads can be woven together. Jung's concept of the transcendent function and his understanding of the gift of grace are particularly illuminating here. We also consider the conditions which allow grace to be experienced and how these inform our analytic practice.

  12. New density estimates derived using accelerometers on board the CHAMP and GRACE satellites

    NASA Astrophysics Data System (ADS)

    Mehta, Piyush M.; Walker, Andrew C.; Sutton, Eric K.; Godinez, Humberto C.

    2017-04-01

    Atmospheric mass density estimates derived from accelerometers onboard satellites such as CHAllenging Minisatellite Payload (CHAMP) and Gravity Recovery and Climate Experiment (GRACE) are crucial in gaining insight into open science questions about the dynamic coupling between space weather events and the upper atmosphere. Recent advances in physics-based satellite drag coefficient modeling allow derivation of new density data sets. This paper uses physics-based satellite drag coefficient models for CHAMP and GRACE to derive new estimates for the neutral atmospheric density. Results show an average difference of 14-18% for CHAMP and 10-24% for GRACE between the new and existing data sets depending on the space weather conditions (i.e., solar and geomagnetic activity levels). The newly derived densities are also compared with existing models, and results are presented. These densities are expected to be useful to the wider scientific community for validating the development of physics-based models and helping to answer open scientific questions regarding our understanding of upper atmosphere dynamics such as the sensitivity of temporal and global density variations to solar and geomagnetic forcing.

  13. Validation of GRACE-based regional solutions of water mass over Australia

    NASA Astrophysics Data System (ADS)

    Seoane, Lucia; Ramillien, Guillaume; Frappart, Frédéric; Leblanc, Marc

    2013-04-01

    Time series of 10-day regional solutions of water mass over Australia [112°E-156°E; 44°S-10°S] have been computed from 2003 to 2011 by using an energy integral method. This approach uses the dynamical orbit analysis of GRACE Level-1 measurements, and specially the accurate along-track K-Band Range Rate (KBRR) residuals for estimating the continental hydrology changes over 2-by-2 degree surface tiles. The advantages of regional solutions are: (1) a significant reduction of GRACE aliasing errors (North-South striping seen in the classical GRACE Level-2 solutions), and (2) a better localization of the hydrological patterns. Once the dominant seasonal cycle is removed, Principal Component Analysis (PCA) of regional and global data sets reveal consistent main modes of variability that are highly related to SOI and PDO indexes, and thus the long term 2006 drought in the Southeastern region of Australia. The validation of our regional solutions, in the case short term and localized water mass-related events, consists of comparing them to independent datasets such as exceptional rainfall rate due to cyclone Charlotte, as well as in situ water level and discharge stream records of the Fitzroy river floodings.

  14. A methodology for evaluating evapotranspiration estimates at the watershed-scale using GRACE

    NASA Astrophysics Data System (ADS)

    Billah, Mirza M.; Goodall, Jonathan L.; Narayan, Ujjwal; Reager, J. T.; Lakshmi, Venkat; Famiglietti, James S.

    2015-04-01

    Accurate quantification of evapotranspiration (ET) at the watershed-scale remains an important research challenge. ET products from model simulations and remote sensing, even after incorporating in situ ET observations from flux towers in calibration or assimilation procedures, often produce different watershed areal-averaged ET estimates. These differences in ET estimates are magnified when they are integrated over time as part of water balance calculations. To address this challenge, we present a methodology for comparing watershed-average ET within a water balance framework that makes use of Gravity Recovery and Climate Experiment (GRACE)-observed terrestrial water storage change (TWSC). The methodology is demonstrated for South Carolina for a five-year period (2003-2007) using four different ET products: ET generated using a locally calibrated VIC model, a MODIS-derived ET product, and ET generated from two models (NOAH and VIC) as part of the North American Land Data Assimilation Systems 2 (NLDAS-2) project. The results of the example application suggest that the NLDAS-NOAH ET product is most consistent with GRACE-observed TWSC for the overall study region and time period. However, for periods of decreasing TWS, when ET becomes a more significant term in the water balance, the locally calibrated VIC model showed the most agreement with GRACE-observed TWSC. Application of the methodology for other regions and time periods can provide insight into different ET products when used for watershed-scale water resources management.

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

    PubMed

    Pan, Yuanjin; Shen, Wen-Bin; Hwang, Cheinway; Liao, Chaoming; Zhang, Tengxu; Zhang, Guoqing

    2016-08-02

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

  16. Intensified water storage loss by biomass burning in Kalimantan: Detection by GRACE

    NASA Astrophysics Data System (ADS)

    Han, Jiancheng; Tangdamrongsub, Natthachet; Hwang, Cheinway; Abidin, Hasanuddin Z.

    2017-03-01

    Biomass burning is the principal tool for land clearing and a primary driver of land use change in Kalimantan (the Indonesian part of Borneo island). Biomass burning here has consumed millions of hectares of peatland and swamp forests. It also degrades air quality in Southeast Asia, perturbs the global carbon cycle, threatens ecosystem health and biodiversity, and potentially affects the global water cycle. Here we present the optimal estimate of water storage changes over Kalimantan from NASA's Gravity Recovery and Climate Experiment (GRACE). Over August 2002 to December 2014, our result shows a north-south dipole pattern in the long-term changes in terrestrial water storage (TWS) and groundwater storage (GWS). Both TWS and GWS increase in the northern part of Kalimantan, while they decrease in the southern part where fire events are the most severe. The loss rates in TWS and GWS in the southern part are 0.56 ± 0.11 cm yr-1 and 0.55 ± 0.10 cm yr-1, respectively. We use GRACE estimates, burned area, carbon emissions, and hydroclimatic data to study the relationship between biomass burning and water storage losses. The analysis shows that extensive biomass burning results in excessive evapotranspiration, which then increases long-term water storage losses in the fire-prone region of Kalimantan. Our results show the potentials of GRACE and its follow-on missions in assisting water storage and fire managements in a region with extensive biomass burning such as Kalimantan.

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

    PubMed

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

    2014-11-01

    Continuous observations of temporal variations in the Earth's gravity field have recently become available at an unprecedented resolution of a few hundreds of kilometers. The gravity field is a product of the Earth's mass distribution, and these data-provided by the satellites of the Gravity Recovery And Climate Experiment (GRACE)-can be used to study the exchange of mass both within the Earth and at its surface. Since the launch of the mission in 2002, GRACE data has evolved from being an experimental measurement needing validation from ground truth, to a respected tool for Earth scientists representing a fixed bound on the total change and is now an important tool to help unravel the complex dynamics of the Earth system and climate change. In this review, we present the mission concept and its theoretical background, discuss the data and give an overview of the major advances GRACE has provided in Earth science, with a focus on hydrology, solid Earth sciences, glaciology and oceanography.

  18. The celestial mechanics approach: application to data of the GRACE mission

    NASA Astrophysics Data System (ADS)

    Beutler, Gerhard; Jäggi, Adrian; Mervart, Leoš; Meyer, Ulrich

    2010-11-01

    The celestial mechanics approach (CMA) has its roots in the Bernese GPS software and was extensively used for determining the orbits of high-orbiting satellites. The CMA was extended to determine the orbits of Low Earth Orbiting satellites (LEOs) equipped with GPS receivers and of constellations of LEOs equipped in addition with inter-satellite links. In recent years the CMA was further developed and used for gravity field determination. The CMA was developed by the Astronomical Institute of the University of Bern (AIUB). The CMA is presented from the theoretical perspective in (Beutler et al. 2010). The key elements of the CMA are illustrated here using data from 50 days of GPS, K-Band, and accelerometer observations gathered by the Gravity Recovery And Climate Experiment (GRACE) mission in 2007. We study in particular the impact of (1) analyzing different observables [Global Positioning System (GPS) observations only, inter-satellite measurements only], (2) analyzing a combination of observations of different types on the level of the normal equation systems (NEQs), (3) using accelerometer data, (4) different orbit parametrizations (short-arc, reduced-dynamic) by imposing different constraints on the stochastic orbit parameters, and (5) using either the inter-satellite ranges or their time derivatives. The so-called GRACE baseline, i.e., the achievable accuracy of the GRACE gravity field for a particular solution strategy, is established for the CMA.

  19. A GRACE-based Index of Global Freshwater Availability and Stress

    NASA Astrophysics Data System (ADS)

    Richey, A. S.; Famiglietti, J. S.

    2010-12-01

    In order to reach sustainable solutions to ensure freshwater access globally, there must be a better understanding of how much freshwater is available for human use from both surface water and groundwater supplies, and how it is distributed in both time and space. This study uses remote sensing observations to develop a global freshwater scarcity index, accounting for available surface water, available groundwater, and human water use. Traditional techniques to monitor surface water and groundwater, mainly stream gauges and monitoring wells, respectively, rely on devices that are often sporadic in time and space. This study utilizes the Gravity Recovery and Climate Experiment (GRACE) and satellite altimetry to create a freshwater stress index based on the ratio of freshwater withdrawals to combined surface water and groundwater availability for the period 2002 to the present. GRACE is unique in that it detects changes in total terrestrial water storage as a result of both natural and anthropogenic changes. By contrasting GRACE data with land-surface model results that do not capture water management practices, this study isolates the anthropogenic perturbations to available water supplies in order to quantify human water use as compared to available resources.

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

    PubMed Central

    Pan, Yuanjin; Shen, Wen-Bin; Hwang, Cheinway; Liao, Chaoming; Zhang, Tengxu; Zhang, Guoqing

    2016-01-01

    Surface vertical deformation includes the Earth’s elastic response to mass loading on or near the surface. Continuous Global Positioning System (CGPS) stations record such deformations to estimate seasonal and secular mass changes. We used 41 CGPS stations to construct a time series of coordinate changes, which are decomposed by empirical orthogonal functions (EOFs), in northeastern Tibet. The first common mode shows clear seasonal changes, indicating seasonal surface mass re-distribution around northeastern Tibet. The GPS-derived result is then assessed in terms of the mass changes observed in northeastern Tibet. The GPS-derived common mode vertical change and the stacked Gravity Recovery and Climate Experiment (GRACE) mass change are consistent, suggesting that the seasonal surface mass variation is caused by changes in the hydrological, atmospheric and non-tidal ocean loads. The annual peak-to-peak surface mass changes derived from GPS and GRACE results show seasonal oscillations in mass loads, and the corresponding amplitudes are between 3 and 35 mm/year. There is an apparent gradually increasing gravity between 0.1 and 0.9 μGal/year in northeast Tibet. Crustal vertical deformation is determined after eliminating the surface load effects from GRACE, without considering Glacial Isostatic Adjustment (GIA) contribution. It reveals crustal uplift around northeastern Tibet from the corrected GPS vertical velocity. The unusual uplift of the Longmen Shan fault indicates tectonically sophisticated processes in northeastern Tibet. PMID:27490550

  1. Aerothermal Analysis and Design of the Gravity Recovery and Climate Experiment (GRACE) Spacecraft

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  3. Development of an Interferometric Laser Ranging System for a Follow-On Gravity Mission to GRACE

    NASA Astrophysics Data System (ADS)

    Nerem, R. S.; Bender, P.; Loomis, B.; Watkins, M. M.; Folkner, W. M.; Stephens, M.; Craig, R.; Leitch, J.; Pierce, R.

    2006-12-01

    The Gravity Recovery and Climate Experiment (GRACE) has ushered in a new era for satellite measurements of the Earth system. The tremendous advances made by GRACE have led to an interest in launching a follow- on mission with even better spatial resolution. The spatial resolution can be improved by improving the ranging performance, implementing a drag-free control system, and flying at a lower altitude. This presentation will focus on an effort, funded by NASA's Instrument Incubator Program, to develop an interferometric laser ranging system that we expect to perform near the 1 nm/sec level or better over 5 second intervals, which when coupled with other mission improvements, would improve the spatial resolution to ~100 km for 1 cm water equivalent accuracy. We have built an engineering model of the instrument, and will report results from testing this instrument in the laboratory. The laser system will range directly to the proof mass of the drag-free system, eliminating many of the difficulties associated with post-processing the accelerometer data on GRACE. Using the expected instrument performance, we will also summarize the gravity recovery accuracies expected if the instrument were flown.

  4. Mass balance of Greenland from combined GRACE and satellite altimetry inversion

    NASA Astrophysics Data System (ADS)

    Forsberg, R.; Sandberg Sørensen, L.; Nilsson, J.; Simonsen, S. B.

    2014-12-01

    With 12 years of GRACE satellite data now available, the ice mass loss trend of Greenland are clearly demonstrating ice mass loss in marginal zones of the ice sheets, and increasing mass loss trends in some regions such as the north west marginal zones. Although the GRACE release-5 products have provided a significant increase in resolution, the detailed space-based detection of where the ice sheet is loosing mass needs to come from other sources, notably satellite altimetry from EnviSat, IceSat and CryoSat, which point out the detailed location of areas of change, and - when combined with firn compaction and density models - also can be used to infer mass changes. In the paper we outline results of a novel direct inversion method, where all satellite data can be utilized in a general inverse estimation scheme, and the leakage from neighbouring ice caps minimized. We demonstrate overall mass change results from Greenland and Eastern Canadian Ice Caps 2003-14, highlighting the increasing melt in the marginal zones both in NW and NE Greenland. Most of the used data used are provided by the ESA Ice Sheets CCI project 2012-14, which makes available long term Essential Climate Variables such as Surface Elevation Changes, Ice Velocity and Calving Front Locations for the Greenland ice sheet. In the upcoming 2nd phase of the CCI project, Gravimetric Mass Balance from GRACE will be included as a ECV time series, and a similar CCI project started for Antarctica.

  5. Arm-Locking with the GRACE Follow-On Laser Ranging Instrument

    NASA Technical Reports Server (NTRS)

    Thorpe, James Ira; Mckenzie, Kirk

    2016-01-01

    Arm-locking is a technique for stabilizing the frequency of a laser in an inter-spacecraft interferometer by using the spacecraft separation as the frequency reference. A candidate technique for future space-based gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA), arm-locking has been extensive studied in this context through analytic models, time-domain simulations, and hardware-in-the-loop laboratory demonstrations. In this paper we show the Laser Ranging Instrument flying aboard the upcoming Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) mission provides an appropriate platform for an on-orbit demonstration of the arm-locking technique. We describe an arm-locking controller design for the GRACE-FO system and a series of time-domain simulations that demonstrate its feasibility. We conclude that it is possible to achieve laser frequency noise suppression of roughly two orders of magnitude around a Fourier frequency of 1Hz with conservative margins on the system's stability. We further demonstrate that `pulling' of the master laser frequency due to fluctuating Doppler shifts and lock acquisition transients is less than 100MHz over several GRACE-FO orbits. These findings motivate further study of the implementation of such a demonstration.

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  8. Determination of the Canadian Gravimetric Geoid 2005 (CGG05) Using GRACE and Terrestrial Gravity Data

    NASA Astrophysics Data System (ADS)

    Huang, J.; Véronneau, M.

    2005-12-01

    The remove-restore technique and the Stokes kernel modification allow the combination of satellite gravity models and terrestrial gravity data for the determination of regional/continental high-resolution gravimetric geoid models. A number of kernel modifications have been suggested over the years to minimize errors in the satellite models and terrestrial data. However, the selection of the proper modification to the Stokes kernel depends largely on data quality. The Vanicek and Kleusberg (VK) kernel provides an efficient way to reduce the far-zone contribution (or truncation) error in the case of poor satellite models and poor remote (far zone) terrestrial gravity data. On the other hand, the degree-banded kernel acts as a filter weight function to remove systematic errors in the long wavelength components of the terrestrial gravity anomalies. It places significant emphasis on the satellite model. Back in 2000, the VK kernel and EGM96 were used in determining the Canadian Gravimetric Geoid 2000 (CGG2000). The kernel was modified to degree 30 to prevent error accumulation from EGM96. The validation of CGG2000 at 430 precise GPS-leveling stations indicates a standard deviation of 21.7 cm. Today, the GRACE mission is advancing the determination of the Earth gravity field to a new level. It poses a compelling question: What is the proper approach to combine GRACE models and the terrestrial gravity data? This presentation investigates methods of combining the high-accuracy of the GRACE gravity models with the high precision of the terrestrial gravity data for optimal estimation of the long- and short-wavelength components of the geoid model. First, a series of numerical simulations are conducted to study the effect of systematic and random errors in the satellite and terrestrial data on geoid modeling. Second, geoid models for North America are estimated from the GRACE gravity model (GGM02C) and terrestrial gravity data using different combination approaches. The

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

  10. Sub-monthly hydrological variability: In-orbit validation by GRACE level 1B observations

    NASA Astrophysics Data System (ADS)

    Springer, Anne; Eicker, Annette; Kusche, Jürgen

    2015-04-01

    Here, K-band range rate (KBRR) residuals are computed from GRACE level 1B observations and hydrological model output. The validation of hydrological models is usually performed by employing monthly gravity field solutions which have a very limited spatial and temporal resolution. The presented approach avoids the downward continuation and filtering process required for computing monthly solutions and, thus, enables to assess model-derived water storage variations with a high temporal resolution and at small spatial scales. In a first step, modeled water mass variations are converted into simulated KBRR observations. Secondly, those simulated observations and a number of geophysical corrections are reduced from the original GRACE K-band observations to obtain the residuals. Smaller residuals imply that the model is able to better explain the observations. Time series of daily and monthly RMS of KBRR residuals are computed globally and for selected regions. Additionally, the residuals are investigated in space domain by computing spatial RMS values for one year on a regular grid. In this study, three global hydrological models, the Land Surface Discharge Model (LSDM), the WaterGAP Global Hydrology Model (WGHM), and the GLDAS-Noah land surface model are evaluated exemplarily. Residuals from monthly model outputs are contrasted against daily model fields in order to quantify the information content on time scales shorter than one month. Furthermore, the high-frequent signal content is studied by comparing monthly solutions and the daily Kalman filter solutions from ITG-Grace2010 and ITSG-Grace2014. Globally, the residuals are reduced by 2.54% if the daily instead of the monthly ITSG solutions are used. As a reference: the application of AOD-RL05 leads to a reduction of 1.12% with respect to AOD-RL04. Daily information from LSDM reduce the residuals from the monthly model output further by 0.67% considering only the continents. WGHM is found to produce smaller residuals

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  12. Assessment of noise in non-tectonic displacement derived from GRACE time-variable gravity filed

    NASA Astrophysics Data System (ADS)

    Li, Weiwei; Shen, Yunzhong

    2017-04-01

    Many studies have been focusing on estimating the noises in GNSS monitoring time series. While the noises of GNSS time series after the correction with non-tectonic displacement should be re-estimated. Knowing the noises in the non-tectonic can help to better identify the sources of re-estimated noises. However, there is a lack of knowledge of noises in the non-tectonic displacement. The objective of this work is to assess the noise in the non-tectonic displacement. GRACE time-variable gravity is used to reflect the global mass variation. The GRACE stokes coefficients of the gravity field are used to calculate the non-tectonic surface displacement at any point on the surface. The Atmosphere and Ocean AOD1B de-aliasing model to the GRACE solutions is added because the complete mass variation is requested. The monthly GRACE solutions from CSR, JPL, GFZ and Tongji span from January 2003 to September 2015 are compared. The degree-1 coefficients derived by Swenson et al (2008) are added and also the C20 terms are replaced with those obtained from Satellite Laser Ranging. The P4M6 decorrelation and Fan filter with a radius of 300 km are adopted to reduce the stripe errors. Optimal noise models for the 1054 stations in ITRF2014 are presented. It is found that white noise only take up a small proportion: less than 18% in horizontal and less than 13% in vertical. The dominant models in up and north components are ARMA and flicker, while in east the power law noise shows significance. The local distribution comparison of the optimal noise models among different products is quite similar, which shows that there is little dependence on the different strategies adopted. In addition, the reasons that caused to different distributions of the optimal noise models are also investigated. Meanwhile different filtering methods such as Gaussian filters, Han filters are applied to see whether the noise is related with filters. Keyword: optimal noise model; non-tectonic displacement;GRACE

  13. A New Unified Approach to Determine Geocenter Motion Using Space Geodesy and GRACE Gravity Data

    NASA Astrophysics Data System (ADS)

    Wu, X.; Kusche, J.; Landerer, F. W.

    2016-12-01

    Spherical harmonic expansions of Earth's surface mass variations start from three degree-1 terms. These longest-wavelength terms induce geocenter motion between the center-of-mass of the total Earth system (CM) and the center-of-figure of the solid Earth surface (CF), and a degree-1 surface deformation field. For complete spectral coverage and robust assessment of geographic mass budget using GRACE data, very accurate knowledge of geocenter motion between CM and CF is required with precision goals of 0.2 mm in annual amplitude and 0.2 mm/yr leading to equivalent degree-1 coefficients. However, GRACE's K-band ranging data system is not sensitive to these variation modes. Although satellite laser ranging (SLR) system is thought to have the most reliable sensitivity to CM, its surface network is very sparse and can only deliver motion between CM and the center of a changing network (CN) of roughly 20 unevenly distributed stations. Recently, the network has been extended to include 82 stations with their geocentric displacements derived by transferring SLR's CM sensitivity to other technique networks through local tie and co-motion constraints. The CM-CN motion of this network has a better agreement with the geocenter motion result from a global inversion of relative GPS, GRACE, and the ECCO ocean bottom pressure (OBP) model. Still, there is no guarantee that such a CM-CN motion is the same as the CM-CF motion. Also, the global inversion result is subject to the impact of unknown errors in the OBP model. To improve reliability of geocenter motion determination, we use a new unified approach to geocenter motion determination by combining geocentric displacements of ground stations with GRACE gravity data. Both translational and deformational signatures will be exploited for retrieval of the degree-1 surface mass variation coefficients. Higher degree terms are estimated simultaneously using GRACE gravity data, which further improves CF knowledge and reduces aliasing

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

  15. Recent changes in terrestrial water storage in the Upper Nile Basin: an evaluation of commonly used gridded GRACE products

    NASA Astrophysics Data System (ADS)

    Shamsudduha, Mohammad; Taylor, Richard G.; Jones, Darren; Longuevergne, Laurent; Owor, Michael; Tindimugaya, Callist

    2017-09-01

    GRACE (Gravity Recovery and Climate Experiment) satellite data monitor large-scale changes in total terrestrial water storage (ΔTWS), providing an invaluable tool where in situ observations are limited. Substantial uncertainty remains, however, in the amplitude of GRACE gravity signals and the disaggregation of TWS into individual terrestrial water stores (e.g. groundwater storage). Here, we test the phase and amplitude of three GRACE ΔTWS signals from five commonly used gridded products (i.e. NASA's GRCTellus: CSR, JPL, GFZ; JPL-Mascons; GRGS GRACE) using in situ data and modelled soil moisture from the Global Land Data Assimilation System (GLDAS) in two sub-basins (LVB: Lake Victoria Basin; LKB: Lake Kyoga Basin) of the Upper Nile Basin. The analysis extends from January 2003 to December 2012, but focuses on a large and accurately observed reduction in ΔTWS of 83 km3 from 2003 to 2006 in the Lake Victoria Basin. We reveal substantial variability in current GRACE products to quantify the reduction of ΔTWS in Lake Victoria that ranges from 80 km3 (JPL-Mascons) to 69 and 31 km3 for GRGS and GRCTellus respectively. Representation of the phase in TWS in the Upper Nile Basin by GRACE products varies but is generally robust with GRGS, JPL-Mascons, and GRCTellus (ensemble mean of CSR, JPL, and GFZ time-series data), explaining 90, 84, and 75 % of the variance respectively in "in situ" or "bottom-up" ΔTWS in the LVB. Resolution of changes in groundwater storage (ΔGWS) from GRACE ΔTWS is greatly constrained by both uncertainty in changes in soil-moisture storage (ΔSMS) modelled by GLDAS LSMs (CLM, NOAH, VIC) and the low annual amplitudes in ΔGWS (e.g. 1.8-4.9 cm) observed in deeply weathered crystalline rocks underlying the Upper Nile Basin. Our study highlights the substantial uncertainty in the amplitude of ΔTWS that can result from different data-processing strategies in commonly used, gridded GRACE products; this uncertainty is disregarded in analyses of

  16. Earth Surface Deformation in the North China Plain Detected by Joint Analysis of GRACE and GPS Data

    PubMed Central

    Liu, Renli; Li, Jiancheng; Fok, Hok Sum; Shum, C.K.; Li, Zhao

    2014-01-01

    Mass redistribution of the Earth causes variable loading that deforms the solid Earth. While most recent studies using geodetic techniques focus on regions (such as the Amazon basin and the Nepal Himalayas) with large seasonal deformation amplitudes on the order of 1–4 cm due to hydrologic loading, few such studies have been conducted on the regions where the seasonal deformation amplitude is half as large. Here, we use joint GPS and GRACE data to investigate the vertical deformation due to hydrologic loading in the North China Plain, where significant groundwater depletion has been reported. We found that the GPS- and GRACE-derived secular trends and seasonal signals are in good agreement, with an uplift magnitude of 1–2 mm/year and a correlation of 85.0%–98.5%, respectively. This uplift rate is consistent with groundwater depletion rate estimated from GRACE data and in-situ groundwater measurements from earlier report studies; whereas the seasonal hydrologic variation reflects human behavior of groundwater pumping for agriculture irrigation in spring, leading to less water storage in summer than that in the winter season. However, less than 20% of weighted root-mean-squared (WRMS) reductions were detected for all the selected GPS stations when GRACE-derived seasonal deformations were removed from detrended GPS height time series. This discrepancy is probably because the GRACE-derived seasonal signals are large-scale, while the GPS-derived signals are local point measurements. PMID:25340454

  17. Improved constraints on seismic source parameters of the 2011 Tohoku earthquake from GRACE gravity and gravity gradient changes

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    A new approach of using only the north component of gravity change from Gravity Recovery and Climate Experiment (GRACE) data reveals that a substantially higher spatial resolution of the observed seismic deformation following the 2011 Tohoku earthquake is achievable at 333 km or longer. Here we show that GRACE-observed north component of gravity change, -17.6 ± 1.1 μGal, and the corresponding gravity gradient change, e.g., Txz at 1.25 ± 0.09 mEötvös, agree well with seismic/GPS model predictions. Localized Slepian spectrum analysis further confirms that the GRACE gravity and gravity gradient changes agree well with seismic model spectra and have powers up to the limit of the GRACE solution complete to spherical harmonic degree 60. Using the gravity observations for the fault parameter inversion via simulated annealing algorithm, we show that the estimated slip orientation and centroid location are different from GPS/seismic solutions and potentially due to the additional offshore constraint from GRACE data.

  18. GRACE satellite monitoring of large depletion in water storage in response to the 2011 drought in Texas

    NASA Astrophysics Data System (ADS)

    Long, Di; Scanlon, Bridget R.; Longuevergne, Laurent; Sun, Alexander Y.; Fernando, D. Nelun; Save, Himanshu

    2013-07-01

    Texas experienced the most extreme one-year drought on record in 2011 with precipitation at 40% of long-term mean and agricultural losses of $7.6 billion. We assess the value of Gravity Recovery and Climate Experiment (GRACE) satellite-derived total water storage (TWS) change as an alternative remote sensing-based drought indicator, independent of traditional drought indicators based on in situ monitoring. GRACE shows depletion in TWS of 62.3 ± 17.7 km3 during the 2011 drought. Large uncertainties in simulated soil moisture storage depletion (14-83 km3) from six land surface models indicate that GRACE TWS is a more reliable drought indicator than disaggregated soil moisture or groundwater storage. Groundwater use and groundwater level data indicate that depletion is dominated by changes in soil moisture storage, consistent with high correlation between GRACE TWS and the Palmer Drought Severity Index. GRACE provides a valuable tool for monitoring statewide water storage depletion, linking meteorological and hydrological droughts.

  19. The GRACE Follow-On Laser Ranging Interferometer; A inter-spacecraft laser interferometry technology demonstrator with similarities to LISA

    NASA Astrophysics Data System (ADS)

    Klipstein, William; McKenzie, Kirk; Grace Follow-On LASER Ranging Interferometer Team

    2016-03-01

    GRACE Follow-On will replace the Gravity Recovery and Climate Experiment (GRACE) mission, which has been measuring Earth's gravity field since 2002. Like GRACE, GRACE Follow-On will use a microwave link as its primary instrument to measure micron-level changes in the 200km separation of a pair of satellites in a following polar orbit. GRACE Follow-On will also include a 2-way laser-link, the Laser Ranging Interferometer (LRI), as a technology demonstrator package. The LRI is an NASA/German partnership and will demonstrate inter-spacecraft laser interferometry with a goal of 10 times better precision than the microwave instrument, or about 90 nm/ √(Hz) between 10 and 100 mHz. The similarities between the LRI and a single arm of Laser Interferometer Space Antenna (LISA) mean many of the required technologies will be the same. This talk will give an overview of the LRI and the status of the LRI instruments, and implications for LISA.

  20. Validation of GRACE electron densities by incoherent scatter radar data and estimation of plasma scale height in the topside ionosphere

    NASA Astrophysics Data System (ADS)

    Xiong, Chao; Lühr, Hermann; Ma, ShuYing; Schlegel, Kristian

    2015-04-01

    This paper presents an effort of using incoherent scatter radar data for validating electron density (Ne) measurements performed by the GRACE satellites from year 2002 to 2012. For adjusting the bias of GRACE Ne data, the observations at high latitudes from EISCAT at Tromsø and Svalbard, as well as two incoherent scatter radars (ISR) at mid- and low latitudes, Millstone Hill and Arecibo, are used. The adjusted GRACE Ne data are further compared with the observations from the four ISRs. For EISCAT observations at Tromsø and Svalbard the comparison results are quite consistent, yielding correlation coefficients as high as 0.92, and an average bias value of about 3 · 1010 m-3 is obtained. For the radars at Millstone Hill and Arecibo the results show excellent agreement, yielding correlation coefficients as high as 0.97 and an average bias of 1 · 1010 m-3. The scale factor of adjusted GRACE Ne data is lower by 1% and 5% compared to Millstone Hill and Arecibo readings, respectively. We consider these differences as within the uncertainty of radar measurements. Using the adjusted GRACE Ne as well as CHAMP observations during four periods of coplanar orbits between 2003 and 2008, the plasma scale heights of the topside ionosphere are determined and further compared with IRI model predictions. We find significantly larger scale heights in particular at middle and high latitudes than expected from IRI. Outstanding are the regions of the mid-latitude electron density trough.

  1. Subregional-scale groundwater depletion detected by GRACE for both shallow and deep aquifers in North China Plain

    NASA Astrophysics Data System (ADS)

    Huang, Zhiyong; Pan, Yun; Gong, Huili; Yeh, Pat J.-F.; Li, Xiaojuan; Zhou, Demin; Zhao, Wenji

    2015-03-01

    This study explores the capability of Gravity Recovery and Climate Experiment (GRACE) to detect heterogeneous groundwater storage (GWS) variations in two subregions of the North China Plain: the Piedmont Plain (PP, ~54,000 km2, mainly exploiting shallow groundwater) and East Central Plain (ECP, ~86,000 km2, mainly exploiting deep groundwater). Results show that the GWS anomalies estimated from GRACE data (2003-2013) agree well with those estimated from in situ observations (2005-2010) for both PP (R2 = 0.91) and ECP (R2 = 0.75). The shallow GWS (2003-2013) in PP declines faster (-46.5 ± 6.8 mm/yr) than the deep GWS in ECP (-16.9 ± 1.9 mm/yr). However, the shallow GWS in PP recovered more quickly especially during the 2008-2011 drought period. Despite its lower magnitude, the GRACE-derived GWS depletion in ECP reveals the overexploitation of deep GWS. This study demonstrated that the heterogeneous GWS variations can potentially be detected by GRACE at the subregional scale smaller than the typical GRACE footprint (200,000 km2).

  2. Earth surface deformation in the North China Plain detected by joint analysis of GRACE and GPS data.

    PubMed

    Liu, Renli; Li, Jiancheng; Fok, Hok Sum; Shum, C K; Li, Zhao

    2014-10-22

    Mass redistribution of the Earth causes variable loading that deforms the solid Earth. While most recent studies using geodetic techniques focus on regions (such as the Amazon basin and the Nepal Himalayas) with large seasonal deformation amplitudes on the order of 1-4 cm due to hydrologic loading, few such studies have been conducted on the regions where the seasonal deformation amplitude is half as large. Here, we use joint GPS and GRACE data to investigate the vertical deformation due to hydrologic loading in the North China Plain, where significant groundwater depletion has been reported. We found that the GPS- and GRACE-derived secular trends and seasonal signals are in good agreement, with an uplift magnitude of 1-2 mm/year and a correlation of 85.0%-98.5%, respectively. This uplift rate is consistent with groundwater depletion rate estimated from GRACE data and in-situ groundwater measurements from earlier report studies; whereas the seasonal hydrologic variation reflects human behavior of groundwater pumping for agriculture irrigation in spring, leading to less water storage in summer than that in the winter season. However, less than 20% of weighted root-mean-squared (WRMS) reductions were detected for all the selected GPS stations when GRACE-derived seasonal deformations were removed from detrended GPS height time series. This discrepancy is probably because the GRACE-derived seasonal signals are large-scale, while the GPS-derived signals are local point measurements.

  3. Assessment of the capabilities of the temporal and spatiotemporal ICA method for geophysical signal separation in GRACE data

    NASA Astrophysics Data System (ADS)

    Boergens, Eva; Rangelova, Elena; Sideris, Michael G.; Kusche, Juergen

    2014-05-01

    We investigate the potential of two independent component analysis (ICA) methods, i.e., the temporal and spatiotemporal ICA, for separating geophysical signals in Gravity Recovery and Climate Experiment (GRACE) data. These methods are based on the assumption of the statistical independence of the signals and thus separate the GRACE-observed mass changes into maximal independent signals. These two ICA methods are compared to the conventional principal component analysis (PCA) method. We test the three methods with respect to their ability to separate a periodic hydrological signal from a trend signal originating in the solid Earth or the cryosphere with simulated and Center for Space Research GRACE mass changes for the time period of January 2003 to December 2010. In addition, we investigate whether the methods are capable of separating hydrological annual and semiannual mass variations. It is shown that both ICA methods are superior to PCA when non-Gaussian mass variations are analyzed. Furthermore, the spatiotemporal ICA resolves successfully the lack of full temporal and spatial independence of the geophysical signals observed by GRACE both in global and regional simulation scenarios. Although the temporal and spatiotemporal ICA are nearly equivalent, both superior to PCA in the global GRACE analysis, the spatiotemporal ICA proves to be more efficient in regional applications by recover more reliably the postglacial rebound trend in North America and the bimodal total water storage variability in Africa.

  4. High Resolution Recovery of Amazon Basin Water Storage Change Using Line-Of-Sight (LOS) Gravity Difference Data from GRACE

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Alsdorf, D.; Beighley, R.; Shum, C.; Schaffrin, B.

    2007-12-01

    GRACE Level 1B data have been analyzed and processed to recover continental water storage in a regional solution, by first estimating in situ Line-Of-Sight (LOS) gravity differences simultaneously with the relative position and velocity vectors of the twin GRACE satellites. This new approach has been validated using a simulation study over the Amazon basin (with three different regularization methods to stabilize the downward continuation solutions) and it is demonstrated that the method achieves an improved spatial resolution as compared to some of the other GRACE processing techniques, including global spherical harmonic solutions, and regional solution using in situ geopotential differences. When compared with a fine-scale (20 km full-wavelength) hydrologic model of the Amazon basin, which accounts for the modeling of surface, subsurface, channel and floodplain stores and fluxes, the GRACE solutions show no discernible time lags with respect to the hydrologic model, resolving the controversy of the allegedly observed 1-2 month lags between GRACE and a number of global hydrologic models. The comparison also enables quantification of the respective contributors of the Amazon Basin water flow dynamics.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Houborg, Rasmus; Rodell, Matthew; Lawrimore, Jay; Li, Bailing; Reichle, Rolf; Heim, Richard; Rosencrans, Matthew; Tinker, Rich; Famiglietti, James S.; Svoboda, Mark; hide

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  9. The Grace Mission: The Challenges of Using Micron-Level Satellite-to-Satellite Ranging to Measure the Earth's Gravity Field

    NASA Technical Reports Server (NTRS)

    Watkins, M.; Bettadpur, S.

    2000-01-01

    The GRACE Mission, to be launched in mid-2001, will provide an unprecedented map of the Earth's gravity field every month. In this paper, we outline the challenges associated with this micron-level satellite-to-satellite ranging, the solutions used by the GRACE project, and the expected science applications of the data.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    We study fluctuations in the degree-2 zonal spherical harmonic coefficient of the Earth's gravity potential, C20, over the period 2003-2015. This coefficient is related to the Earth's oblateness and studying its temporal variations, ΔC20, can be used to monitor large-scale mass movements between high and low latitude regions. We examine ΔC20 inferred from six different sources, including satellite laser ranging (SLR), GRACE and global geophysical fluids models. We further include estimates that we derive from measured variations in the length-of-day (LOD), from the inversion of global crustal displacements as measured by GPS, as well as from the combination of GRACE and the output of an ocean model as described by Sun et al. (2016). We apply a sequence of trend- and seasonal moving average filters to the different time series in order to decompose them into an interannual, a seasonal and an intraseasonal component. We then perform a comparison analysis for each component, and we further estimate the noise level contained in the different series using an extended version of the three-cornered-hat method. For the seasonal component, we generally obtain a very good agreement between the different sources, and except for the LOD-derived series, we find that over 90% of the variance in the seasonal components can be explained by the sum of an annual and semiannual oscillation of constant amplitudes and phases, indicating that the seasonal pattern is stable over the considered time period. High consistency between the different estimates is also observed for the intraseasonal component, except for the solution from GRACE, which is known to be affected by a strong tide-like alias with a period of about 161 days. Estimated interannual components from the different sources are generally in agreement with each other, although estimates from GRACE and LOD present some discrepancies. Slight deviations are further observed for the estimate from the geophysical models, likely

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  13. Benefits and pitfalls of GRACE data assimilation: A case study of terrestrial water storage depletion in India

    NASA Astrophysics Data System (ADS)

    Girotto, Manuela; De Lannoy, Gabriëlle J. M.; Reichle, Rolf H.; Rodell, Matthew; Draper, Clara; Bhanja, Soumendra N.; Mukherjee, Abhijit

    2017-05-01

    This study investigates some of the benefits and drawbacks of assimilating terrestrial water storage (TWS) observations from the Gravity Recovery and Climate Experiment (GRACE) into a land surface model over India. GRACE observes TWS depletion associated with anthropogenic groundwater extraction in northwest India. The model, however, does not represent anthropogenic groundwater withdrawals and is not skillful in reproducing the interannual variability of groundwater. Assimilation of GRACE TWS introduces long-term trends and improves the interannual variability in groundwater. But the assimilation also introduces a negative trend in simulated evapotranspiration, whereas in reality evapotranspiration is likely enhanced by irrigation, which is also unmodeled. Moreover, in situ measurements of shallow groundwater show no trend, suggesting that the trends are erroneously introduced by the assimilation into the modeled shallow groundwater, when in reality the groundwater is depleted in deeper aquifers. The results emphasize the importance of representing anthropogenic processes in land surface modeling and data assimilation systems.

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

    NASA Astrophysics Data System (ADS)

    Godah, Walyeldeen; Szelachowska, Malgorzata; Krynski, Jan

    2017-07-01

    Temporal mass variations in the Earth system, which can be detected from the Gravity Recovery and Climate Experiment (GRACE) mission data, cause temporal variations of geoid heights. The main objective of this contribution is to analyze temporal variations of geoid heights over the area of Poland using global geopotential models (GGMs) developed on the basis of GRACE mission data. Time series of geoid height variations were calculated for the chosen subareas of the aforementioned area using those GGMs. Thereafter, these variations were analyzed using two different methods. On the basis of the analysis results, models of temporal geoid height variations were developed and discussed. The possibility of prediction of geoid height variations using GRACE mission data over the area of Poland was also investigated. The main findings reveal that the geoid height over the area of Poland vary within 1.1 cm which should be considered when defining the geoid model of 1 cm accuracy for this area.

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

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

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

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

    NASA Astrophysics Data System (ADS)

    van der Wal, Wouter; Xu, Zheng

    2016-04-01

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

  17. Assessing Aridity, Hydrological Drought, and Recovery Using GRACE and GLDAS: a Case Study in Iraq

    NASA Astrophysics Data System (ADS)

    Moradkhani, H.; Almamalachy, Y. S.; Yan, H.; Ahmadalipour, A.; Irannezhad, M.

    2016-12-01

    Iraq has suffered from several drought events during the period of 2003-2012, which imposed substantial impacts on natural environment and socioeconomic sectors, e.g. lower discharge of Tigris and Euphrates, groundwater depletion and increase in its salinity, population migration, and agricultural degradation. To investigate the aridity and climatology of Iraq, Global Land Data Assimilation System (GLDAS) monthly datasets of precipitation, temperature, and evapotranspiration at 0.25 degree spatial resolution are used. The Gravity Recovery and Climate Experiment (GRACE) satellite-derived monthly Terrestrial Water Storage (TWS) deficit is used as the hydrological drought indicator. The data is available globally at 1 degree spatial resolution. This study aims to monitor hydrological drought and assess drought recovery time for the period of August 2002 until December 2015. Two approaches are implemented to derive the GRACE-based TWS deficit. The first approach estimates the TWS deficit based on the difference from its own climatology, while the second approach directly calculates the deficit from TWS anomaly. Severity of drought events are calculated by integrating monthly water deficit over the drought period. The results indicate that both methods are capable of capturing the severe drought events in Iraq, while the second approach quantifies higher deficit and severity. In addition, two methods are employed to assess drought recovery time based on the estimated deficit. Both methods indicate similar drought recovery times, varying from less than a month to 9 months. The results demonstrate that the GRACE TWS is a reliable indicator for drought assessment over Iraq, and provides useful information to decision makers for developing drought adaptation and mitigation strategies over data-sparse regions.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  19. Variations of the Earth's figure axis from satellite laser ranging and GRACE

    NASA Astrophysics Data System (ADS)

    Cheng, Minkang; Ries, John C.; Tapley, Byron D.

    2011-01-01

    Satellite laser ranging (SLR) data were used to determine the variations in the Earth's principal figure axis represented by the degree 2 and order 1 geopotential coefficients: C21 and S21. Significant variations at the annual and Chandler wobble frequencies appear in the SLR time series when the rotational deformation or "pole tides" (i.e., the solid Earth and ocean pole tides) were not modeled. The contribution of the ocean pole tide is estimated to be only ˜8% of the total annual variations in the normalized coefficients: ?/? based on the analysis of SLR data. The amplitude of the nontidal annual variation of ? is only ˜ 30% of ? from the SLR time series. The estimates of the annual variation in ? from SLR, the Gravity Recovery and Climate Experiment (GRACE) and polar motion excitation function, are in a good agreement. The nature of the linear trend for the Earth's figure axis determined by these techniques during the last several years is in general agreement but does not agree as well with results predicted from current glacial isostatic adjustment (GIA) models. The "fluid Love number" for the Earth is estimated to be ˜0.9 based on the position of the mean figure axis from the GRACE gravity model GGM03S and the mean pole defined by the IERS 2003 conventions. The estimate of ?/? from GRACE and SLR provides an improved constraint on the relative rotation of the core. The results presented here indicate a possible tilt of the inner core figure axis of ˜2° and ˜3 arc sec displacement for the figure axis of the entire core.

  20. Hydrogeology and water quality in the Graces Quarters area of Aberdeen Proving Ground, Maryland

    USGS Publications Warehouse

    Tenbus, Frederick J.; Blomquist, Joel D.

    1995-01-01

    Graces Quarters was used for open-air testing of chemical-warfare agents from the late 1940's until 1971. Testing and disposal activities have resulted in the contamination of ground water and surface water. The hydrogeology and water quality were examined at three test areas, four disposal sites, a bunker, and a service area on Graces Quarters. Methods of investigation included surface and borehole geophysics, water-quality sampling, water- level measurement, and hydrologic testing. The hydrogeologic framework is complex and consists of a discontinuous surficial aquifer, one or more upper confining units, and a confined aquifer system. Directions of ground-water flow vary spatially and temporally, and results of site investigations show that ground-water flow is controlled by the geology of the area. The ground water and surface water at Graces Quarters generally are unmineralized; the ground water is mildly acidic (median pH is 5.38) and poorly buffered. Inorganic constituents in excess of certain Federal drinking-water regulations and ambient water-quality criteria were detected at some sites, but they probably were present naturally. Volatile and semivolatile organic com- pounds were detected in the ground water and surface water at seven of the nine sites that were investi- gated. Concentrations of organic compounds at two of the nine sites exceeded Federal drinking-water regulations. Volatile compounds in concentrations as high as 6,000 m/L (micrograms per liter) were detected in the ground water at the site known as the primary test area. Concentrations of volatile compounds detected in the other areas ranged from 0.57 to 17 m/L.

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

    NASA Astrophysics Data System (ADS)

    Yi, Shuang; Wang, Qiuyu; Sun, Wenke

    2016-05-01

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

  2. Passive-ocean radial basis function approach to improve temporal gravity recovery from GRACE observations

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Kusche, Jürgen; Forootan, Ehsan; Rietbroek, Roelof

    2017-08-01

    We present a state-of-the-art approach of passive-ocean modified radial basis functions (MRBFs) that improves the recovery of time-variable gravity fields from Gravity Recovery and Climate Experiment (GRACE). As is well known, spherical harmonics (SHs), which are commonly used to recover gravity fields, are orthogonal basis functions with global coverage. However, the chosen SH truncation involves a global compromise between data coverage and obtainable resolution, and strong localized signals may not be fully captured. Radial basis functions (RBFs) provide another representation, which has been proposed in earlier works to be better suited to retrieve regional gravity signals. In this paper, we propose a MRBF approach by embedding the known coastal geometries in the RBF parameterization and imposing global mass conservation and equilibrium behavior of the oceans. Our hypothesis is that with this physically justified constraint, the GRACE-derived gravity signals can be more realistically partitioned into the land and ocean contributions along the coastlines. We test this new technique to invert monthly gravity fields from GRACE level-1b observations covering 2005-2010, for which the numerical results indicate that (1) MRBF-based solutions reduce the number of parameters by approximately 10% and allow for more flexible regularization when compared to ordinary RBF solutions and (2) the MRBF-derived mass flux is better confined along coastal areas. The latter is particularly tested in the southern Greenland, and our results indicate that the trend of mass loss from the MRBF solutions is approximately 11% larger than that from the SH solutions and approximately 4%-6% larger than that of RBF solutions.

  3. Water resource monitoring in Iran using satellite altimetry and satellite gravimetry (GRACE)

    NASA Astrophysics Data System (ADS)

    Khaki, Mehdi; Sneeuw, Nico

    2015-04-01

    Human civilization has always been in evolution by having direct access to water resources throughout history. Water, with its qualitative and quantitative effects, plays an important role in economic and social developments. Iran with an arid and semi-arid geographic specification is located in Southwest Asia. Water crisis has appeared in Iran as a serious problem. In this study we're going to use various data sources including satellite radar altimetry and satellite gravimetry to monitor and investigate water resources in Iran. Radar altimeters are an invaluable tool to retrieve from space vital hydrological information such as water level, volume and discharge, in particular from regions where the in situ data collection is difficult. Besides, Gravity Recovery and Climate Experiment (GRACE) provide global high resolution observations of the time variable gravity field of the Earth. This information is used to derive spatio-temporal changes of the terrestrial water storage body. This study isolates the anthropogenic perturbations to available water supplies in order to quantify human water use as compared to available resources. Long-term monitor of water resources in Iran is contain of observing freshwaters, lakes and rivers as well as exploring ground water bodies. For these purposes, several algorithms are developed to quantitatively monitor the water resources in Iran. The algorithms contain preprocessing on datasets, eliminating biases and atmospheric corrections, establishing water level time series and estimating terrestrial water storage considering impacts of biases and leakage on GRACE data. Our primary goal in this effort is to use the combination of satellite radar altimetry and GRACE data to study on water resources as well as methods to dealing with error sources include cross over errors and atmospheric impacts.

  4. Using GRACE Gravity Data to Constrain Continental Dynamics and Structure over Laurentia (Invited)

    NASA Astrophysics Data System (ADS)

    Mitrovica, J. X.; Tamisiea, M. E.; Forte, A. M.; Davis, J. L.

    2009-12-01

    The free-air gravity anomaly over Canada has contributions from a variety of geophysical signals, including remnant isostatic disequilibrium following the ice age and the signature of mantle convective flow. Tamisiea et al. (Science, v.316, 2007) isolated the signal due to glacial isostatic adjustment (GIA) in this region by using data collected from the Gravity Recovery and Climate Experiment (GRACE) to estimate a regional map of the time rate of change of free-air gravity. Discussions generated by this paper have primarily centred on the inference of a multidomal morphology for the ancient Laurentide ice sheet (an inference that confirms the arguments of J.T. Andrews and A.S. Dyke). However, the article also provided and applied a framework for using the GRACE data to constrain the partitioning of the static gravity anomaly into components due to GIA and mantle convection. Specifically, GIA models that were found to reconcile the peak free-air gravity rates yielded 25-45% of the observed static gravity field. (The upper bound contribution is consistent with the localized analysis of the static gravity spectrum by Simons and Hager, 1997). Our result indicated that mantle convective flow contributes at least half of the static field, which in turn suggests that Laurentia is dynamically depressed by some combination of (potentially non-zero) tectosphere buoyancy and deeper-seated mantle flow (Forte et al., Tectonophysics, 2009). In this talk we will return to this application, and revisit our conclusions, using the longer time series of available GRACE data. We will also compare our revised inferences to independent predictions of the static gravity field generated using mantle flow simulations based on high-resolution seismic tomography.

  5. A new monthly gravity field model based on GRACE observations computed by the modified dynamic approach

    NASA Astrophysics Data System (ADS)

    Zhou, H.; Luo, Z.; Li, Q.; Zhong, B.

    2016-12-01

    The monthly gravity field model can be used to compute the information about the mass variation within the system Earth, i.e., the relationship between mass variation in the oceans, land hydrology, and ice sheets. For more than ten years, GRACE has provided valuable information for recovering monthly gravity field model. In this study, a new time series of GRACE monthly solution, which is truncated to degree and order 60, is computed by the modified dynamic approach. Compared with the traditional dynamic approach, the major difference of our modified approach is the way to process the nuisance parameters. This type of parameters is mainly used to absorb low-frequency errors in KBRR data. One way is to remove the nuisance parameters before estimating the geo-potential coefficients, called Pure Predetermined Strategy (PPS). The other way is to determine the nuisance parameters and geo-potential coefficients simultaneously, called Pure Simultaneous Strategy (PSS). It is convenient to detect the gross error by PPS, while there is also obvious signal loss compared with the solutions derived from PSS. After comparing the difference of practical calculation formulas between PPS and PSS, we create the Filter Predetermine Strategy (FPS), which can combine the advantages of PPS and PSS efficiently. With FPS, a new monthly gravity field model entitled HUST-Grace2016s is developed. The comparisons of geoid degree powers and mass change signals in the Amazon basin, the Greenland and the Antarctic demonstrate that our model is comparable with the other published models, e.g., the CSR RL05, JPL RL05 and GFZ RL05 models. Acknowledgements: This work is supported by China Postdoctoral Science Foundation (Grant No.2016M592337), the National Natural Science Foundation of China (Grant Nos. 41131067, 41504014), the Open Research Fund Program of the State Key Laboratory of Geodesy and Earth's Dynamics (Grant No. SKLGED2015-1-3-E).

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  7. Water Mass Loss of the Himalayas from GRACE, ICESat and SRTM

    NASA Astrophysics Data System (ADS)

    Muskett, Reginald

    2010-05-01

    The Himalayas and the Tibet Plateau form a region of about 3.4 million square kilometers. Home to numerous large lakes and tarns (glacier lakes), and to more than 50,000 glaciers and high-elevation snowfields, this region is the source of the Indus, Ganga, Brahmaputra, and Yamuna Rivers, the Indo-Gangetic River system. The Himalayan Mountains and associated ranges form a boundary separating continental air masses associated with the westerlies, and marine air masses associated with the summer South Asian monsoon. Adverse changes in water storage / river discharge driven by effects of climate change will impact agriculture, hydroelectric power facilities, commerce, and the lives of more than 1.3 billion people. We are investigating water mass loss derived by the Gravity Recovery and Climate Experiment (GRACE), the ICE, Cloud and land Elevation (ICESat) and the Shuttle Radar Topograghy Mission (SRTM). In our current analysis we remove the effects of isostatic glacial adjustment and both retain and remove the annual cycle of water equivalent mass change for evaluation. Least-squares regression of GRACE monthly time-series shows the Himalaya region lost 17.9 ± 11.0 km3/yr water equivalent mass from August 2002 through December 2006 (annual cycle removed basis). Retaining the annual cycle of water equivalent mass change and extending the time series for one additional year, the least-squares trend is 9.9 ± 4.7 km3/yr of water equivalent mass loss from August 2002 through December 2007. Comparison of same-datum ICESat and SRTM elevations above 5000 meters shows snow surface elevations are decreasing at 1.1 ± 0.7 m/yr from June 2005 through April 2007. We will present updated analyses of the trends of regional water equivalent mass and elevation changes from GRACE and ICESat - SRTM measurements.

  8. Application of GRACE to the Evaluation of an Ice Flow Model of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Schlegel, N.; Wiese, D. N.; Watkins, M. M.; Larour, E. Y.; Box, J. E.; Fettweis, X.; van den Broeke, M. R.; Morlighem, M.; Boening, C.; Seroussi, H. L.

    2014-12-01

    Quantifying Greenland's future contribution to sea level rise is a challenging task and requires accurate estimates of ice flow sensitivity to climate change. Transient ice flow models are promising tools for estimating future ice sheet behavior. However, confidence in these types of future projections is low, especially because evaluation of model historical runs is so challenging due to the scarcity of continental-wide data for validation. For more than a decade, NASA's GRACE has continuously acquired time-variable measurements of the Earth's gravity field and has provided unprecedented surveillance of mass balance of the ice sheets, offering an opportunity for ice sheet model evaluation. Here, we take advantage of a new high-resolution (~300 km) monthly mascon solution for the purpose of mass balance comparison with an independent, historical ice flow model simulation using the Ice Sheet System Model (ISSM). The comparison highlights which regions of the ice sheet differ most from GRACE. Investigation of regional differences in trends and seasonal amplitudes between simulations forced with three different Regional Climate Model (RCM)-based estimates of surface mass balance (SMB) allows us to make conclusions about the relative contributions of various error sources in the model hindcast. This study constitutes the first regional comparison of GRACE data and an ice sheet model. Conclusions will aid in the improvement of RCM SMB estimates as well as ice sheet simulation estimates of present and future rates of sea level rise. This work was performed at the California Institute of Technology's Jet Propulsion Laboratory under a contract with the National Aeronautics and Space Administration's Cryosphere Program and President's and Director's Fund Program.

  9. GRACE Mass Flux Measurements of Inland and Marginal Seas from Mascons: Analysis and Validation

    NASA Astrophysics Data System (ADS)

    Loomis, B.; Luthcke, S. B.; Sabaka, T. J.

    2015-12-01

    The latest GRACE time-variable gravity mascon solution from the NASA Goddard Space Flight Center (GSFC) applies an optimized set of models and constraints towards the direct measurement of 1-arc-degree global mass flux parameters each month. Separate mascon spatial constraint regions have been defined for the largest inland and marginal seas: Mediterranean Sea, Black Sea, Caspian Sea, Red Sea, and Hudson Bay. The mascon estimation approach, when applied with well-designed constraints, minimizes signal leakage across regional boundaries and eliminates the need for post-processing strategies. These post-processing techniques (e.g. smoothed averaging kernels) are necessary for computing regional mass change from the unconstrained spherical harmonics provided by the GRACE project to reduce the effect of noisy high degree and order terms, but introduce signal leakage into and out of the considered region. These mass signals are also difficult to obtain from altimetry measurements due to the comparatively sparse temperature and salinity data in these regions, which is needed to compute and remove the steric component of sea level variations. We provide new GSFC mascon measurements of these inland and marginal seas and compare to results obtained from kernel-averaged spherical harmonic solutions and steric-corrected altimetry measurements. The relative accuracy of the various solutions is determined by incorporating their output into the set of forward models applied in our processing of the GRACE Level-1B data and analyzing the effect on the inter-satellite range-rate residuals, where a reduction in residuals is a direct validation of improved solution quality.

  10. Cumulative Total South America Freshwater Losses as Seen by NASA GRACE, 2002-15

    NASA Image and Video Library

    2015-12-08

    Cumulative total freshwater losses in South America from 2002 to 2015 (in inches) observed by NASA's Gravity Recovery and Climate Experiment (GRACE) mission. Total water refers to all of the snow, surface water, soil water and groundwater combined. Much of the Amazon River basin experienced increasing total water storage during this time period, though the persistent Brazilian drought is apparent to the east. Groundwater depletion strongly impacted total water losses in the Guarani aquifer of Argentina and neighboring countries. Significant water losses due to the melting ice fields of Patagonia are also observed. http://photojournal.jpl.nasa.gov/catalog/PIA20205

  11. Precision Laser Development for Interferometric Space Missions NGO, SGO, and GRACE Follow-On

    NASA Technical Reports Server (NTRS)

    Numata, Kenji; Camp, Jordan

    2011-01-01

    Optical fiber and semiconductor laser technologies have evolved dramatically over the last decade due to the increased demands from optical communications. We are developing a laser (master oscillator) and optical amplifier based on those technologies for interferometric space missions, including the gravitational-wave missions NGO/SGO (formerly LISA) and the climate monitoring mission GRACE Follow-On, by fully utilizing the matured wave-guided optics technologies. In space, where simpler and more reliable system is preferred, the wave-guided components are advantageous over bulk, crystal-based, free-space laser, such as NPRO (Nonplanar Ring Oscillator) and bulk-crystal amplifier.

  12. Improvement of the GRACE star camera data based on the revision of the combination method

    NASA Astrophysics Data System (ADS)

    Bandikova, Tamara; Flury, Jakob

    2014-11-01

    The new release of the sensor and instrument data (Level-1B release 02) of the Gravity Recovery and Climate Experiment (GRACE) had a substantial impact on the improvement of the overall accuracy of the gravity field models. This has implied that improvements on the sensor data level can still significantly contribute to arriving closer to the GRACE baseline accuracy. The recent analysis of the GRACE star camera data (SCA1B RL02) revealed their unexpectedly higher noise. As the star camera (SCA) data are essential for the processing of the K-band ranging data and the accelerometer data, thorough investigation of the data set was needed. We fully reexamined the SCA data processing from Level-1A to Level-1B with focus on the combination method of the data delivered by the two SCA heads. In the first step, we produced and compared our own combined attitude solution by applying two different combination methods on the SCA Level-1A data. The first method introduces the information about the anisotropic accuracy of the star camera measurement in terms of a weighing matrix. This method was applied in the official processing as well. The alternative method merges only the well dete