论文信息 - GRACE-Based Estimates of Terrestrial Freshwater Discharge from Basin to Continental Scales

2014

Characterization of polymer synthesized from the nonequilibrium plasma conversion of CFC-12 and methane in a dielectric barrier discharge reactor

A dielectric barrier discharge (DBD) nonequilibrium plasma reactor was employed to polymerize CFC-12 (CCl2F2, dichlorodifluoromethane) at atmospheric pressure. The plasma polymerization of this saturated halogenated hydrocarbon was conducted in the presence of methane as reactant, in an argon bath gas and where the reaction environment was free from oxygen and nitrogen. The reaction resulted in the formation of non-cross-linked polymer product and whereby the non-cross-linked nature of the polymer enabled its characterization by solution state 13C and 19F nuclear magnetic resonance (NMR) spectroscopic analysis. The generated polymer was also analyzed by Fourier transform infrared (FTIR) spectrometry, and the spectra thus obtained were consistent with the analysis by NMR. The analyses of NMR and FTIR spectroscopy reveal the formation of fluoropolymers from the conversion of CFC-12.

2012

On-site Partial Discharges Measurement of XLPE Cables

The contribution deals with the methodol ogy of on-line measurement of partial discharges in XLPE cab les. After the specification of measuring methodology an d used apparatus the evaluation of the measured data follo ws. Contribution gives an example of a real on-site measurement on 110kV XLPE cable power line in operation.

2019 - Remote. Sens.

Gravity Field Recovery Using High-Precision, High-Low Inter-Satellite Links

Past temporal gravity field solutions from the Gravity Recovery and Climate Experiment (GRACE), as well as current solutions from GRACE Follow-On, suffer from temporal aliasing errors due to undersampling of the signal to be recovered (e.g., hydrology), which arise in terms of stripes caused by the north–south observation direction. In this paper, we investigate the potential of the proposed mass variation observing system by high–low inter-satellite links (MOBILE) mission. We quantify the impact of instrument errors of the main sensors (inter-satellite link and accelerometer) and high-frequency tidal and non-tidal gravity signals on achievable performance of the temporal gravity field retrieval. The multi-directional observation geometry of the MOBILE concept with a strong dominance of the radial component result in a close-to-isotropic error behavior, and the retrieved gravity field solutions show reduced temporal aliasing errors of at least 30% for non-tidal, as well as tidal, mass variation signals compared to a low–low satellite pair configuration. The quality of the MOBILE range observations enables the application of extended alternative processing methods leading to further reduction of temporal aliasing errors. The results demonstrate that such a mission can help to get an improved understanding of different components of the Earth system.

2014 - Quality Management in Health Care

Implementation of the Re-Engineered Discharge (RED) Toolkit to Decrease All-Cause Readmission Rates at a Rural Community Hospital

Overview: National hospital readmission rates average 19%. One in 5 Medicare patients are readmitted within 30 days of discharge each year, resulting in $17.5 billion in additional costs. Objective/Purpose: The aim of this quality improvement project was to use the methodology outlined by Joint Commission Resources-Hospital Engagement Network and Project Re-Engineered Discharge (Project RED) to redesign the discharge process, reduce hospital 30-day all-cause readmission rates, and improve patient/family involvement in the discharge process. Method: The methodology of the Joint Commission Resources-Hospital Engagement Network and the Agency for Healthcare Research and Quality Project RED toolkit, the After Hospital Care Plan, and a patient discharge questionnaire were used to incorporate best discharge practices into patient care and evaluate the outcomes of the project. Monthly readmission rates and patient/family involvement in the discharge process were examined for 336 patients discharged from a dedicated 30-bed medical-surgical unit in a rural community hospital over a 4-month period. Results: During the 4-month project, readmissions were reduced by 32% (rate 7.12); the overall monthly reduction from baseline was 27%, with a 44% reduction from baseline during the previous 6 months. The patient and family perception of their discharge process was positive.

2020

Tilt-to-Length Coupling in the GRACE Follow-On Laser Ranging Interferometer

The Laser Ranging Interferometer onboard the Gravity Recovery and Climate Experiment Follow-On satellites is the first laser interferometer in space measuring satellite-to-satellite distance variat...

2017 - Remote. Sens.

Assessing Terrestrial Water Storage and Flood Potential Using GRACE Data in the Yangtze River Basin, China

Floods have caused tremendous economic, societal and ecological losses in the Yangtze River Basin (YRB) of China. To reduce the impact of these disasters, it is important to understand the variables affecting the hydrological state of the basin. In this study, we used Gravity Recovery and Climate Experiment (GRACE) satellite data, flood potential index (FPI), precipitation data (Tropical Rainfall Measuring Mission, TRMM 3B43), and other meteorological data to generate monthly terrestrial water storage anomalies (TWSA) and to evaluate flood potential in the YRB. The results indicate that the basin contained increasing amounts of water from 2003 to 2014, with a slight increase of 3.04 mm/year in the TWSA. The TWSA and TRMM data exhibit marked seasonal characteristics with summer peaks and winter dips. Estimates of terrestrial water storage based on GRACE, measured as FPI, are critical for understanding and predicting flooding. The 2010 flood (FPI ~ 0.36) was identified as the most serious disaster during the study period, with discharge and precipitation values 37.95% and 19.44% higher, respectively, than multi-year average values for the same period. FPI can assess reliably hydrological extremes with high spatial and temporal resolution, but currently, it is not suitable for smaller and/or short-term flood events. Thus, we conclude that GRACE data can be effectively used for monitoring and examining large floods in the YRB and elsewhere, thus improving the current knowledge and presenting potentially important political and economic implications.

2007 - Chemical Geology

Upper crustal abundances of trace elements: A revision and update

Abstract We report new estimates of abundances of rarely analyzed elements (As, B, Be, Bi, Cd, Ge, In, Mo, Sb, Sn, Te, Tl, W) in the upper continental crust based on precise ICP-MS analyses of well-characterized upper crustal samples (shales, pelites, loess, graywackes, granitoids and their composites) from Australia, China, Europe, New Zealand and North American. Obtaining a better understanding of the upper crustal abundance and associated uncertainties of these elements is important in placing better constraints on bulk crust composition and, from that, whole Earth models of element cycling and crust generation. We also present revised abundance estimates of some more commonly analyzed trace elements (Li, Cr, Ni, and Tm) that vary by > 20% compared to previous estimates. The new estimates are mainly based on significant ( r 2 > 0.6) inter-element correlations observed in clastic sediments and sedimentary rocks, which yield upper continental crust elemental ratios that are used in conjunction with well-determined abundances for certain key elements to place constraints on the concentrations of the rarely analyzed elements. Using the well-established upper crustal abundances of La (31 ppm), Th (10.5 ppm), Al 2 O 3 (15.40%), K 2 O (2.80%) and Fe 2 O 3 (5.92%), these ratios lead to revised upper crustal abundances of B = 47 ppm, Bi = 0.23 ppm, Cr = 73 ppm, Li = 41 ppm, Ni = 34 ppm, Sb = 0.075, Te = 0.027 ppm, Tl = 0.53 ppm and W = 1.4 ppm. No significant correlations exist between Mo and Cd and other elements in the clastic sediments and sedimentary rocks, probably due to their enrichment in organic carbon. We thus calculate abundances of these elements by assuming the upper continental crust consists of 65% granitoid rocks plus 35% clastic sedimentary rocks. The validity of this approach is supported by the similarity of SiO 2 , Al 2 O 3 , La and Th abundances calculated in this way with their upper crustal abundances given in Rudnick and Gao [Rudnick, R., Gao, S., 2003. Composition of the continental crust. In: Rudnick, R.L. (Ed.), The Crust. In: Holland, H.D., Turekian, K.K. (Eds.), Treatise on Geochemistry, vol. 3. Elsevier–Pergamon, Oxford, pp. 1–64.]. The upper crustal abundances thus obtained are Mo = 0.6 ppm and Cd = 0.06 ppm. Our data also suggest a ∼ 20% increase of the Tm, Yb and Lu abundances reported in Rudnick and Gao [Rudnick, R., Gao, S., 2003. Composition of the continental crust. In: Rudnick, R.L. (Ed.), The Crust. In: Holland, H.D., Turekian, K.K. (Eds.), Treatise on Geochemistry, vol. 3. Elsevier–Pergamon, Oxford, pp. 1–64.].

1999

The GRACE Mission: Meeting the Technical Challenges

The Gravity Recovery and Climate Experiment (GRACE) Mission is scheduled for launch in June 2001. Within the first year of the GRACE Mission, the project has a minimum science requirement to deliver a new model of the Earth's static geoid with an error of less than 1 cm to spherical harmonic degree seventy (70). However, the performance of the GRACE Mission is designed to exceed this minimum requirement by a factor of 25 or more. For spherical harmonic degrees of up to 40, we expect to improve the current knowledge of the gravity field by one thousand (1000x). The GRACE Mission uses the satellite-to-satellite tracking (SST) technique. The twin GRACE satellites are the instruments that measure the nonuniformities in the Earth's gravity field. Nonuniformities in the gravity field cause the relative distance between the centers-of-mass of the two satellites to vary as they fly over the Earth. Atmospheric drag is the largest non-gravitational disturbing force. Drag is measured and will be used to correct changes in the satellite-to-satellite range measured by an SST microwave link. The microwave link will measure changes in the range between the two GRACE satellites with an error approaching 1 micron. We will discuss how these instrumentation requirements affect the configuration, the mass balance, the thermal control and the aerodynamic design of the satellites, and the design of the microwave SST link and the accelerometer. Finally, the question of how noise in these components limits the overall accuracy of the gravity models will be addressed.

2019 - Sensors (Basel, Switzerland)

Bridging Terrestrial Water Storage Anomaly During GRACE/GRACE-FO Gap Using SSA Method: A Case Study in China

The terrestrial water storage anomaly (TWSA) gap between the Gravity Recovery and Climate Experiment (GRACE) and its follow-on mission (GRACE-FO) is now a significant issue for scientific research in high-resolution time-variable gravity fields. This paper proposes the use of singular spectrum analysis (SSA) to predict the TWSA derived from GRACE. We designed a case study in six regions in China (North China Plain (NCP), Southwest China (SWC), Three-River Headwaters Region (TRHR), Tianshan Mountains Region (TSMR), Heihe River Basin (HRB), and Lishui and Wenzhou area (LSWZ)) using GRACE RL06 data from January 2003 to August 2016 for inversion, which were compared with Center for Space Research (CSR), Helmholtz-Centre Potsdam-German Research Centre for Geosciences (GFZ), Jet Propulsion Laboratory (JPL)’s Mascon (Mass Concentration) RL05, and JPL’s Mascon RL06. We evaluated the accuracy of SSA prediction on different temporal scales based on the correlation coefficient (R), Nash–Sutcliffe efficiency (NSE), and root mean square error (RMSE), which were compared with that of an auto-regressive and moving average (ARMA) model. The TWSA from September 2016 to May 2019 were predicted using SSA, which was verified using Mascon RL06, the Global Land Data Assimilation System model, and GRACE-FO results. The results show that: (1) TWSA derived from GRACE agreed well with Mascon in most regions, with the highest consistency with Mascon RL06 and (2) prediction accuracy of GRACE in TRHR and SWC was higher. SSA reconstruction improved R, NSE, and RMSE compared with those of ARMA. The R values for predicting TWS in the six regions using the SSA method were 0.34–0.98, which was better than those for ARMA (0.26–0.97), and the RMSE values were 0.03–5.55 cm, which were better than the 2.29–5.11 cm RMSE for ARMA as a whole. (3) The SSA method produced better predictions for obvious periodic and trending characteristics in the TWSA in most regions, whereas the detailed signal could not be effectively predicted. (4) The predicted TWSA from September 2016 to May 2019 were basically consistent with Global Land Data Assimilation System (GLDAS) results, and the predicted TWSA during June 2018 to May 2019 agreed well with GRACE-FO results. The research method in this paper provides a reference for bridging the gap in the TWSA between GRACE and GRACE-FO.

2014 - Geophysical Research Letters

Improved methods for satellite‐based groundwater storage estimates: A decade of monitoring the high plains aquifer from space and ground observations

The impacts of climate extremes and water use on groundwater storage across large aquifers can be quantified using Gravity Recovery and Climate Experiment (GRACE) satellite monitoring. We present new methods to improve estimates of changes in groundwater storage by incorporating irrigation soil moisture corrections to common data assimilation products. These methods are demonstrated using data from the High Plains Aquifer (HPA) for 2003 to 2013. Accounting for the impacts of observed and inferred irrigation on soil moisture significantly improves estimates of groundwater storage changes as verified by interpolated measurements from ~10,000 HPA wells. The resulting estimates show persistent declines in groundwater storage across the HPA, more severe in the southern and central HPA than in the north. Groundwater levels declined by an average of approximately 276 ± 23 mm from 2003 to 2013, resulting in a storage loss of 125 ± 4.3 km3, based on the most accurate of the three methods developed here.

2017 - Sensors (Basel, Switzerland)

Terrestrial Water Storage in African Hydrological Regimes Derived from GRACE Mission Data: Intercomparison of Spherical Harmonics, Mass Concentration, and Scalar Slepian Methods

Spherical harmonics (SH) and mascon solutions are the two most common types of solutions for Gravity Recovery and Climate Experiment (GRACE) mass flux observations. However, SH signals are degraded by measurement and leakage errors. Mascon solutions (the Jet Propulsion Laboratory (JPL) release, herein) exhibit weakened signals at submascon resolutions. Both solutions require a scale factor examined by the CLM4.0 model to obtain the actual water storage signal. The Slepian localization method can avoid the SH leakage errors when applied to the basin scale. In this study, we estimate SH errors and scale factors for African hydrological regimes. Then, terrestrial water storage (TWS) in Africa is determined based on Slepian localization and compared with JPL-mascon and SH solutions. The three TWS estimates show good agreement for the TWS of large-sized and humid regimes but present discrepancies for the TWS of medium and small-sized regimes. Slepian localization is an effective method for deriving the TWS of arid zones. The TWS behavior in African regimes and its spatiotemporal variations are then examined. The negative TWS trends in the lower Nile and Sahara at −1.08 and −6.92 Gt/year, respectively, are higher than those previously reported.

2007 - Diversity and Distributions

Comparing the rate of invasion by Heracleum mantegazzianum at continental, regional, and local scales

This paper compares the rate of invasion of Heracleum mantegazzianum (Apiaceae), a Caucasian species invading Europe, at three spatial scales (continental, regional, and local). The rate of invasion was evaluated using inclusion curves, by plotting the cumulative number of invaded countries against time on the continental scale of Europe, number of occupied grid cells at the regional scale of the Czech Republic, and invaded area inferred from a series of aerial photographs taken at the local scale over a period of 49 years in the Slavkovký les region, Czech Republic. Time of 50% inclusion (with 95% confidence intervals, CI) of invaded countries, occupied grid cells, and invaded area was assessed. The invasion was slowest at the continental scale (62 years, CI = 53–70) and did not differ significantly between regional (16 years, CI = 10–20) and local (22 years, CI = 19–24) scales. Our results indicate that there are two different mechanisms of spread acting together in this system, namely human influences and natural spread, and the relative influence of these mechanisms appears to change in an inverse proportion from the largest to the smallest scale. At the local scale, under suitable habitat conditions, the process is driven by biological traits of the species related to dispersal. At the continental and regional scales, humans played a crucial role in the invasion of H. mantegazzianum by planting it as a garden ornamental. At these scales, human‐mediated dispersal seems to have been the major driver of spread, responsible for creating dispersal foci in the initial phases of invasion. Species traits played an important role in local spread, resulting in the colonization of new sites.

2018 - Remote. Sens.

Downscaling GRACE Remote Sensing Datasets to High-Resolution Groundwater Storage Change Maps of California's Central Valley

NASA’s Gravity Recovery and Climate Experiment (GRACE) has already proven to be a powerful data source for regional groundwater assessments in many areas around the world. However, the applicability of GRACE data products to more localized studies and their utility to water management authorities have been constrained by their limited spatial resolution (~200,000 km2). Researchers have begun to address these shortcomings with data assimilation approaches that integrate GRACE-derived total water storage estimates into complex regional models, producing higher-resolution estimates of hydrologic variables (~2500 km2). Here we take those approaches one step further by developing an empirically based model capable of downscaling GRACE data to a high-resolution (~16 km2) dataset of groundwater storage changes over a portion of California’s Central Valley. The model utilizes an artificial neural network to generate a series of high-resolution maps of groundwater storage change from 2002 to 2010 using GRACE estimates of variations in total water storage and a series of widely available hydrologic variables (PRISM precipitation and temperature data, digital elevation model (DEM)-derived slope, and Natural Resources Conservation Service (NRCS) soil type). The neural network downscaling model is able to accurately reproduce local groundwater behavior, with acceptable Nash-Sutcliffe efficiency (NSE) values for calibration and validation (ranging from 0.2445 to 0.9577 and 0.0391 to 0.7511, respectively). Ultimately, the model generates maps of local groundwater storage change at a 100-fold higher resolution than GRACE gridded data products without the use of computationally intensive physical models. The model’s simulated maps have the potential for application to local groundwater management initiatives in the region.

2015 - Geodesy and Geodynamics

Variations in China’s terrestrial water storage over the past decade using GRACE data

Abstract Variations in China's terrestrial water storage from March 2003 to February 2013 were determined using data from the Gravity Recovery and Climate Experiment (GRACE) monthly gravity field model provided by the Center for Space Research. The results were compared with the variations in surface water estimated using the Global Land Data Assimilation System (GLDAS) hydrological model. The results indicated a decline in terrestrial water storage in the Shanxi and Xinjiang Tianshan regions over the past decade with a downward trend that reached −7.76 ± 0.71 mm/a and −5.8 ± 0.67 mm/a, respectively. Anthropogenic activities were considered to be the major cause of this terrestrial water loss (especially groundwater) in these regions. In contrast, the intersection of the Xinjiang and Tibet Autonomous Regions and the Qinghai Province showed an upward trend in the terrestrial water storage at a rate of 9.06 ± 0.37 mm/a, which is closely related to the high-quality local ecological environment and lack of human activities. At the intersections between the Chongqing, Guizhou, and Hunan Provinces and between the Jiangxi, Zhejiang, and Fujian Provinces, the terrestrial water storage increased at rates of 7.86 ± 0.9 and 8.68 ± 0.8 mm/a, respectively. These two regions received abundant annual precipitation; moreover, there was no considerable variation in the amount of groundwater storage over the past decade. In addition, the empirical orthogonal function (EOF) method used in this study could eliminate correlated errors in the GRACE monthly gravity field model more effectively than the traditional polynomial fitting method, and it did not generate false signals.

2009

Closing the terrestrial water budget from satellite remote sensing

The increasing availability of remote sensing products for all components of the terrestrial water cycle makes it now possible to evaluate the potential of water balance closure purely from remote sensing sources. We take precipitation (P) from the TMPA and CMORPH products, a Penman‐Monteith based evapotranspiration (E) estimate derived from NASA Aqua satellite data and terrestrial water storage change (ΔS) from the GRACE satellite. Their combined ability to close the water budget is evaluated over the Mississippi River basin for 2003–5 by estimating streamflow (Q) as a residual of the water budget and comparing to streamflow measurements. We find that Q is greatly overestimated due mainly to the high bias in P, especially in the summer. Removal of systematic biases in P reduces the error significantly. However, uncertainties in the individual budget components due to simplifications in process algorithms and input data error are generally larger than the measured streamflow.

2000

Simulation study of a low-low satellite-to-satellite tracking mission

The Gravity Recovery and Climate Experiment (GRACE) is a dedicated spaceborne mission to map the Earth's gravity field with unprecedented accuracy. The GRACE mission is planned to launch in 2001, for a lifetime of approximately 5 years. It consists of two satellites, co-orbiting in nearly polar orbit, at approximately 300–500 km altitude, separated by 100–500 km along track. Primary measurements are the range change between the two satellites, which represents the gravity perturbation differences between the two locations. These range changes are measured by a high accuracy microwave raging system. To detect the non-gravitational perturbations, which also affect the range change, three axis accelerometers are used. In this study, full numerical simulations were performed to evaluate the gravity recovery accuracy, and to determine sensitivity of gravity estimation to mission and design parameters. The measurement and dynamic model equations were derived and presented along with the description of the simulation procedure. The error models on two major instruments, the inter-satellite ranging system and accelerometer, were described and their effect on the estimation accuracy were discussed. Series of extensive simulations were performed to analyze the impact of the various simulation parameters, which included the orbit parameters, measurement types, and so on. Comprehensive error models made it possible to perform realistic analyses. To the extent that the error sources assumed in the simulations represent those actually encountered during the mission, the simulation results will predict the performance of the GRACE mission. The GRACE mission is expected to improve the current knowledge of the Earth gravity field by order of magnitude. The geoid error level is expected to be less than 1 cm to spherical harmonic degree 70.

2014 - Geophysical Research Letters

Regional acceleration in ice mass loss from Greenland and Antarctica using GRACE time‐variable gravity data

We use Gravity Recovery and Climate Experiment (GRACE) monthly gravity fields to determine the regional acceleration in ice mass loss in Greenland and Antarctica for 2003-2013. We find that the total mass loss is controlled by only a few regions. In Greenland, the southeast and northwest generate 70% of the loss (280 ± 58 Gt/yr) mostly from ice dynamics, the southwest accounts for 54% of the total acceleration in loss (25.4 ± 1.2 Gt/yr 2 ) from a decrease in surface mass balance (SMB), followed by the northwest (34%), and we find no significant acceleration in the northeast. In Antarctica, the Amundsen Sea (AS) sector and the Antarctic Peninsula account for 64% and 17%, respectively, of the total loss (180 ± 10 Gt/yr) mainly from ice dynamics. The AS sector contributes most of the acceleration in loss (11 ± 4 Gt/yr 2 ), and Queen Maud Land, East Antarctica, is the only sector with a significant mass gain due to a local increase in SMB (63 ± 5 Gt/yr).

2007

Estimating groundwater storage changes in the Mississippi River basin (USA) using GRACE

Based on satellite observations of Earth’s time variable gravity field from the Gravity Recovery and Climate Experiment (GRACE), it is possible to derive variations in terrestrial water storage, which includes groundwater, soil moisture, and snow. Given auxiliary information on the latter two, one can estimate groundwater storage variations. GRACE may be the only hope for groundwater depletion assessments in data-poor regions of the world. In this study, soil moisture and snow were simulated by the Global Land Data Assimilation System (GLDAS) and used to isolate groundwater storage anomalies from GRACE water storage data for the Mississippi River basin and its four major sub-basins. Results were evaluated using water level records from 58 wells set in the unconfined aquifers of the basin. Uncertainty in the technique was also assessed. The GRACE-GLDAS estimates compared favorably with the well based time series for the Mississippi River basin and the two sub-basins that are larger than 900,000 km2. The technique performed poorly for the two sub-basins that have areas of approximately 500,000 km2. Continuing enhancement of the GRACE processing methods is likely to improve the skill of the technique in the future, while also increasing the temporal resolution.RésuméA partir d’observations satellitaires du programme Gravity Recovery and Climate Experiment (GRACE), l’étude de la variation dans le temps du champ de gravité terrestre permet de déduire les variations du stock d’eau terrestre, ce qui comprend l’eau souterraine, l’humidité du sol et la neige. Les variations de stock d’eau souterraine peuvent être estimées à partir d’informations auxiliaires sur les deux autres composantes. GRACE pourrait être le seul espoir pour l’établissement des bilans d’eau souterraine dans les régions du monde où les données sont peu nombreuses. Dans cette étude concernant le bassin du fleuve Mississippi et ses quatre sous bassins principaux, l’humidité du sol et la neige ont été simulées par le modèle Global Land Data Assimilation System (GLDAS) et utilisées pour isoler les anomalies de stock d’eau souterraine à partir des données de stock d’eau du GRACE. Les résultats ont été évalués à partir d’enregistrements de niveaux piézomètriques réalisés dans 58 puits localisés dans les aquifères libres du bassin. L’incertitude liée à la technique a également été évaluée. Les estimations GRACE-GLDAS concordaient avec les chroniques de puits pour le bassin du Mississippi ainsi que pour les deux sous bassins présentant une superficie supérieure à 900,000 km2. La technique s’est avérée peu performante pour les deux sous bassins d’environ 500,000 km2. L’amélioration continue des méthodes de traitement des données du GRACE devrait à l’avenir augmenter la performance de la technique ainsi que la résolution temporelle.ResumenEs posible derivar variaciones en el almacenamiento de agua terrestre en base a observaciones de satélite del campo gravitacional temporal variable de la Tierra a partir del Experimento Clima y Recuperación de Gravedad (GRACE), el cual incluye agua subterránea, humedad del suelo, y nieve. Dada la información auxiliar de los dos últimos, uno puede estimar variaciones en almacenamiento de agua subterránea. GRACE puede ser la única esperanza para las evaluaciones de agotamiento de agua subterránea en regiones del mundo con datos pobres. En este estudio se simularon la nieve y humedad del suelo mediante el Sistema de Asimilación de Datos Globales del Terreno (GLDAS) y se usaron para aislar anomalías de almacenamiento de agua subterránea de los datos de almacenamiento de agua GRACE para la cuenca del Río Mississippi y sus cuatros sub-cuencas principales. Los resultados se evaluaron utilizando registros de niveles de agua para 58 pozos emplazados en acuíferos no confinados de la cuenca. También se evaluó la incertidumbre de la técnica. Los estimados provenientes de GLDAS-GRACE se comparan favorablemente con las series de tiempo de los pozos para la cuenca del Río Mississippi y las dos sub-cuencas cuyas áreas son mayores de 900,000 km2. La técnica se desempeñó pobremente para las dos sub-cuencas que tienen áreas de aproximadamente 500,000 km2. El mejoramiento continuo de los métodos de procesamiento GRACE es posible que mejore la habilidad de la técnica en el futuro mejorando al mismo tiempo la resolución temporal.

2006 - Science

Measurements of Time-Variable Gravity Show Mass Loss in Antarctica

Using measurements of time-variable gravity from the Gravity Recovery and Climate Experiment satellites, we determined mass variations of the Antarctic ice sheet during 2002–2005. We found that the mass of the ice sheet decreased significantly, at a rate of 152 ± 80 cubic kilometers of ice per year, which is equivalent to 0.4 ± 0.2 millimeters of global sea-level rise per year. Most of this mass loss came from the West Antarctic Ice Sheet.

2002 - Journal of Hydrometeorology

Estimates of Freshwater Discharge from Continents: Latitudinal and Seasonal Variations

Annual and monthly mean values of continental freshwater discharge into the oceans are estimated at 18 resolution using several methods. The most accurate estimate is based on streamflow data from the world’s largest 921 rivers, supplemented with estimates of discharge from unmonitored areas based on the ratios of runoff and drainage area between the unmonitored and monitored regions. Simulations using a river transport model (RTM) forced by a runoff field were used to derive the river mouth outflow from the farthest downstream gauge records. Separate estimates are also made using RTM simulations forced by three different runoff fields: 1) based on observed streamflow and a water balance model, and from estimates of precipitation P minus evaporation E computed as residuals from the atmospheric moisture budget using atmospheric reanalyses from 2) the National Centers for Environmental Prediction‐National Center for Atmospheric Research (NCEP‐NCAR) and 3) the European Centre for Medium-Range Weather Forecasts (ECMWF). Compared with previous estimates, improvements are made in extending observed discharge downstream to the river mouth, in accounting for the unmonitored streamflow, in discharging runoff at correct locations, and in providing an annual cycle of continental discharge. The use of river mouth outflow increases the global continental discharge by ;19% compared with unadjusted streamflow from the farthest downstream stations. The river-based estimate of global continental discharge presented here is 37 288 6 662 km3 yr21, which is ;7.6% of global P or 35% of terrestrial P. While this number is comparable to earlier estimates, its partitioning into individual oceans and its latitudinal distribution differ from earlier studies. The peak discharges into the Arctic, the Pacific, and global oceans occur in June, versus May for the Atlantic and August for the Indian Oceans. Snow accumulation and melt are shown to have large effects on the annual cycle of discharge into all ocean basins except for the Indian Ocean and the Mediterranean and Black Seas. The discharge and its latitudinal distribution implied by the observation-based runoff and the ECMWF reanalysis-based P‐E agree well with the river-based estimates, whereas the discharge implied by the NCEP‐NCAR reanalysis-based P‐E has a negative bias.

GRACE-Based Estimates of Terrestrial Freshwater Discharge from Basin to Continental Scales

Snow water equivalent in the Sierra Nevada: Blending snow sensor observations with snowmelt model simulations

Interannual variations in degree‐2 Earth's gravity coefficients C2,0, C2,2, and S2,2 reveal large‐scale mass transfers of climatic origin

River basin flood potential inferred using GRACE gravity observations at several months lead time

Observations, Monitoring and Data Management

An integrated representation of the services provided by global water resources.

Improved Remotely Sensed Total Basin Discharge and Its Seasonal Error Characterization in the Yangtze River Basin

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

Water Level Reconstruction Based on Satellite Gravimetry in the Yangtze River Basin

Estimating Total Discharge in the Yangtze River Basin Using Satellite-Based Observations

Short-term trends in Africa's freshwater resources: Rates and drivers.

Regional Energy and Water Cycles: Transports from Ocean to Land

Inroads of remote sensing into hydrologic science during the WRR era

Assessment of Physical Water Scarcity in Africa Using GRACE and TRMM Satellite Data

Remote detection of water management impacts on evapotranspiration in the Colorado River Basin

Estimating Runoff in the Nile River Basin from Multi-Satellite Measurements

How Does the Unique Space‐Time Sampling of the SWOT Mission Influence River Discharge Series Characteristics?

Estimating River Depth From Remote Sensing Swath Interferometry Measurements of River Height, Slope, and Width

Monitoring Groundwater Storage Changes Using the Gravity Recovery and Climate Experiment (GRACE) Satellite Mission: A Review

Sensitivity Analysis of Leakage Correction of GRACE Data in Southwest China Using A-Priori Model Simulations: Inter-Comparison of Spherical Harmonics, Mass Concentration and In Situ Observations

Representation of Spatial Variability of the Water Fluxes over the Congo Basin Region