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Sample records for recharge artificielle dune

  1. Groundwater recharge from Long Lake, Indiana Dunes National Lakeshore

    SciTech Connect

    Isiorho, S.A.; Beeching, F.M. . Geosciences Dept.); Whitman, R.L.; Stewart, P.M. . Indiana Dunes National Lakeshore); Gentleman, M.A.

    1992-01-01

    Long Lake, located between Lake Michigan and the Dune-complexes of Indiana Dunes, was formed during Pleistocene and Holocene epochs. The lake is currently being studied to understand the detailed hydrology. One of the objective of the study is to understand the hydrologic relationship between the lake and a water treatment holding pond to the northeast. Understanding the water movement between the two bodies of water, if any, would be very important in the management and protection of nature preserves in the area. Seepage measurement and minipiezometric tests indicate groundwater recharge from Long Lake. The groundwater recharge rate is approximately 1.40 to 22.28 x 10[sup [minus]4] m/day. An estimate of the amount of recharge of 7.0 x 10[sup 6] m[sup 3]/y may be significant in terms of groundwater recharge of the upper aquifer system of the Dunes area. The water chemistry of the two bodies of water appears to be similar, however, the pH of the holding pond is slightly alkaline (8.5) while that of Long Lake is less alkaline (7.7). There appears to be no direct contact between the two bodies of water (separated by approximately six meters of clay rich sediment). The geology of the area indicates a surficial aquifer underlying Long Lake. The lake should be regarded as a recharge area and should be protected from pollutants as the degradation of the lake would contaminate the underlying aquifer.

  2. Ground-water recharge through active sand dunes in northwestern Nevada

    USGS Publications Warehouse

    Berger, D.L.

    1992-01-01

    Most water-resource investigations in semiarid basins of the Great Basin in western North America conclude that ground-water recharge from direct precipitation on the valley floor is negligible. However, many of these basins contain large areas covered by unvegetated, active sand dunes that may act as conduits for ground-water recharge. The potential for this previously undocumented recharge was investigated in an area covered by sand dunes in Desert Valley, northwestern Nevada, using a deep percolation model. The model uses daily measurements of precipitation and temperature to determine energy and moisture balance, from which estimates of long-term mean annual recharge are made. For the study area, the model calculated a mean annual recharge rate of as much as 1.3 inches per year, or 17 percent of the long-term mean precipitation. Model simulations also indicate that recharge would be virtually zero if the study area were covered by vegetation rather than dunes.

  3. Spatial and Temporal Variability of Groundwater Recharge in Changing Semiarid Dune Environments

    NASA Astrophysics Data System (ADS)

    Zlotnik, Vitaly; Rossman, Nathan; Rowe, Clinton; Szilagyi, Jozsef

    2014-05-01

    Groundwater recharge (GWR) is one of the major factors controlling water resources in semiarid and arid regions. This time-space-dependent flux is needed for groundwater modeling, analysis of climate change impacts, and water resources management. Typically, climate changes are studied on multi-decadal to centennial time scales, but travel times of soil moisture across the vadose zone vary broadly and may exceed multi-centennial periods in semiarid and arid environments. For given climatic conditions on the land surface, we evaluate travel times in the vadose zone and compare with times scales of climate change studies. This comparison defines the land surface areas contributing to GWR changes where travel times are shorter than times scales of climate change studies. In areas with travel times longer than climate change time scales, GWR remains unchanged over the considered period of water resources management. Such analysis allows for separation of the effect of land surface topography and vadose zone thickness from that of spatial and temporal variations in climate. Our simple travel time estimates are based on the velocity of a pressure pulse from the land surface, equivalent to a kinematic wave approximation of Richards' equation. The underlying assumptions of a unit hydraulic head gradient and relatively small magnitude of changes to upper boundary flux, caused by slow climate changes, are supported by observations in the High Plains aquifer region, USA. The input data include DEMs of land surface and groundwater table elevations, future projections of hydroclimatic variables, precipitation and evapotranspiration (WCRP-CMIP3 with hydrology VIC model outputs), and estimates of hydraulic conductivity from pedotransfer functions. Future GWR rates are estimated in four steps: GIS analysis of vadose zone thickness using difference in DEMs; evaluation of deep drainage rates based on difference between precipitation and evapotranspiration rates (PRISM and MODIS

  4. Recharge

    SciTech Connect

    Fayer, Michael J.

    2008-01-17

    This chapter describes briefly the nature and measurement of recharge in support of the CH2M HILL Tank Farm Vadose Zone Project. Appendix C (Recharge) and the Recharge Data Package (Fayer and Keller 2007) provide a more thorough and extensive review of the recharge process and the estimation of recharge rates for the forthcoming RCRA Facility Investigation report for Hanford single-shell tank (SST) Waste Management Areas (WMAs).

  5. Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    This image shows relatively dark coarse grained material forming individual dunes coalescing into a relatively uniform sand sheet. The origin of the dark sand that formed these dunes have been suggested to be the northern polar layered deposits.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude 77.7, Longitude 309.4 East (50.6 West). 19 meter/pixel resolution.

  6. Recharge to the inter-dune lakes and Holocene climatic changes in the Badain Jaran Desert, western China

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoping; Ma, Nina; Dong, Jufeng; Zhu, Bingqi; Xu, Bing; Ma, Zhibang; Liu, Jiaqi

    2010-01-01

    We present new estimates on evaporation and groundwater recharge in the Badain Jaran Desert, western Inner Mongolia of northwestern China, based on a modified Penman Equation suitable for lakes in China. Geochemical data and water balance calculations suggest that local rainfall makes a significant contribution to groundwater recharge and that past lake-level variations in this desert environment should reflect palaeoclimatic changes. The chronology of lake-level change, established by radiocarbon and U-series disequilibrium dating methods, indicates high lake levels and a wetter climate beginning at ca. 10 ka and lasting until the late mid-Holocene in the Badain Jaran Desert. The greatest extension of lakes in the inter-dune depressions indicates that the water availability was greatest during the mid-Holocene. Relicts of Neolithic tools and pottery of Qijia Culture (2400-1900 BC) suggest relatively intensive human activity in the Badain Jaran Desert during the early and middle Holocene, supporting our interpretation of a less harsh environment. Wetter climates during the Holocene were likely triggered by an intensified East Asian summer monsoon associated with strong insolation.

  7. A post audit and inverse modeling in reactive transport: 50 years of artificial recharge in the Amsterdam Water Supply Dunes

    NASA Astrophysics Data System (ADS)

    Karlsen, R. H.; Smits, F. J. C.; Stuyfzand, P. J.; Olsthoorn, T. N.; van Breukelen, B. M.

    2012-08-01

    SummaryThis article describes the post audit and inverse modeling of a 1-D forward reactive transport model. The model simulates the changes in water quality following artificial recharge of pre-treated water from the river Rhine in the Amsterdam Water Supply Dunes using the PHREEQC-2 numerical code. One observation dataset is used for model calibration, and another dataset for validation of model predictions. The total simulation time of the model is 50 years, from 1957 to 2007, with recharge composition varying on a monthly basis and the post audit is performed 26 years after the former model simulation period. The post audit revealed that the original model could reasonably predict conservative transport and kinetic redox reactions (oxygen and nitrate reduction coupled to the oxidation of soil organic carbon), but showed discrepancies in the simulation of cation exchange. Conceptualizations of the former model were inadequate to accurately simulate water quality changes controlled by cation exchange, especially concerning the breakthrough of potassium and magnesium fronts. Changes in conceptualization and model design, including the addition of five flow paths, to a total of six, and the use of parameter estimation software (PEST), resulted in a better model to measurement fit and system representation. No unique parameter set could be found for the model, primarily due to high parameter correlations, and an assessment of the predictive error was made using a calibration constrained Monte-Carlo method, and evaluated against field observations. The predictive error was found to be low for Na+ and Ca2+, except for greater travel times, while the K+ and Mg2+ error was restricted to the exchange fronts at some of the flow paths. Optimized cation exchange coefficients were relatively high, especially for potassium, but still within the observed range in literature. The exchange coefficient for potassium agrees with strong fixation on illite, a main clay mineral in

  8. Ground-Water Flow Direction, Water Quality, Recharge Sources, and Age, Great Sand Dunes National Monument, South-Central Colorado, 2000-2001

    USGS Publications Warehouse

    Rupert, Michael G.; Plummer, L. Niel

    2004-01-01

    Great Sand Dunes National Monument is located in south-central Colorado along the eastern edge of the San Luis Valley. The Great Sand Dunes National Monument contains the tallest sand dunes in North America; some rise up to750 feet. Important ecological features of the Great Sand Dunes National Monument are palustrine wetlands associated with interdunal ponds and depressions along the western edge of the dune field. The existence and natural maintenance of the dune field and the interdunal ponds are dependent on maintaining ground-water levels at historic elevations. To address these concerns, the U.S. Geological Survey conducted a study, in collaboration with the National Park Service, of ground-water flow direction, water quality, recharge sources, and age at the Great Sand Dunes National Monument. A shallow unconfined aquifer and a deeper confined aquifer are the two principal aquifers at the Great Sand Dunes National Monument. Ground water in the unconfined aquifer is recharged from Medano and Sand Creeks near the Sangre de Cristo Mountain front, flows underneath the main dune field, and discharges to Big and Little Spring Creeks. The percentage of calcium in ground water in the unconfined aquifer decreases and the percentage of sodium increases because of ionic exchange with clay minerals as the ground water flows underneath the dune field. It takes more than 60 years for the ground water to flow from Medano and Sand Creeks to Big and Little Spring Creeks. During this time, ground water in the upper part of the unconfined aquifer is recharged by numerous precipitation events. Evaporation of precipitation during recharge prior to reaching the water table causes enrichment in deuterium (2H) and oxygen-18 (18O) relative to waters that are not evaporated. This recharge from precipitation events causes the apparent ages determined using chlorofluorocarbons and tritium to become younger, because relatively young precipitation water is mixing with older waters

  9. Effect of ground-water recharge on configuration of the water table beneath sand dunes and on seepage in lakes in the sandhills of Nebraska, U.S.A.

    NASA Astrophysics Data System (ADS)

    Winter, Thomas C.

    1986-10-01

    Analysis of water-level fluctuations in about 30 observation wells and 5 lakes in the Crescent Lake National Wildlife Refuge in the sandhills of Nebraska indicates water-table configuration beneath sand dunes in this area varies considerably, depending on the configuration of the topography of the dunes. If the topography of an interlake dunal area is hummocky, ground-water recharge is focused at topographic lows causing formation of water-table mounds. These mounds prevent ground-water movement from topographically high lakes to adjacent lower lakes. If a dune ridge is sharp, the opportunity for focused recharge does not exist, resulting in water-table troughs between lakes. Lakes aligned in descending altitudes, parallel to the principal direction of regional ground-water movement, generally have seepage from higher lakes toward lower lakes.

  10. Effect of ground-water recharge on configuration of the water table beneath sand dunes and on seepage in lakes in the sandhills of Nebraska, U.S.A.

    USGS Publications Warehouse

    Winter, T.C.

    1986-01-01

    Analysis of water-level fluctuations in about 30 observation wells and 5 lakes in the Crescent Lake National Wildlife Refuge in the sandhills of Nebraska indicates water-table configuration beneath sand dunes in this area varies considerably, depending on the configuration of the topography of the dunes. If the topography of an interlake dunal area is hummocky, ground-water recharge is focused at topographic lows causing formation of water-table mounds. These mounds prevent ground-water movement from topographically high lakes to adjacent lower lakes. If a dune ridge is sharp, the opportunity for focused recharge does not exist, resulting in water-table troughs between lakes. Lakes aligned in descending altitudes, parallel to the principal direction of regional ground-water movement, generally have seepage from higher lakes toward lower lakes. ?? 1986.

  11. Effects of Heterogeneous Vadose Zone Thickness on Spatial and Temporal Groundwater Recharge Characteristics in Dune Environments: An Example from the Nebraska Sand Hills

    NASA Astrophysics Data System (ADS)

    Zlotnik, V. A.; Rossman, N. R.; Rowe, C. M.; Szilagyi, J.

    2013-12-01

    We investigate effects of land surface topography on the spatial and temporal distribution of groundwater recharge (GWR). Such effects are important for groundwater modeling, analysis of climate change impacts, and water resources management. Typically, climate changes are investigated on multi-decadal to centennial time scales. However, travel times of soil moisture across the vadose zone vary broadly, extending to multi-centennial periods in arid and semi-arid environments. For given climatic conditions on the land surface, we evaluate travel times in thick vadose zones and compare with climate change time scales. This comparison allows determination of the land surface areas contributing to GWR changes where travel times are shorter than climate change time scales. In areas with travel times longer than climate change time scales, GWR remains unchanged over the considered period of water resources management. Such analysis allows separating the effect of land surface topography from that of spatial and temporal climate variations. Our travel time calculations, based on vertical velocity of the pressure pulse from the land surface, are equivalent to a kinematic wave approximation of Richards' equation. The underlying assumptions (unit head gradients over the entire soil profile and relatively small magnitude of climate changes on the surface) are supported by observations in the High Plains Aquifer region. The computations require a DEM of land surface topography, mapped water table elevations, mapped climate variables on the land surface (IPCC 2007, CMIP3, hydrologic VIC model outputs), and estimates of vadose zone hydraulic conductivity as a function of soil moisture content from pedotransfer functions. The method to generate future GWR estimates includes 4 steps: (1) GIS analysis of vadose zone thickness using DEM and water table map; (2) evaluation of deep drainage based on difference between precipitation and evapotranspiration rates (PRISM and MODIS

  12. Kaiser Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    16 March 2004 Kaiser Crater, located in Noachis Terra near 46.5oS, 340.7oW, has some rather large, dark, sand dunes on its floor. Some of the dunes are seen in this February 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view. Dark streaks on the dunes were formed by passing springtime and summer dust devils that disrupted a very thin, fine coating of dust on the dunes. The light-toned patch at the upper (north) end of this image is an exposure of the rock that underlies the dune field in Kaiser Crater. This picture covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left.

  13. Dune morphodynamics

    NASA Astrophysics Data System (ADS)

    Courrech du Pont, Sylvain

    2015-01-01

    The physics of dunes relies on the interaction between a wind flow and an erodible topography. Thus, if strong enough to transport grains, the wind shapes sandy areas into dune fields. These dunes are reminiscent of a wavy sea so that sandy deserts are called sand seas. However, the comparison stops there. Contrary to water waves, dunes propagate only under wind action and when the wind stops, they do not vanish but stand. Consequently, dunes are not only the result of the present winds, but can integrate the wind regimes over long periods. Thus, they exhibit a range of shapes and sizes with superimposed patterns. They are witnesses of past wind regimes and their shape and orientation are used to constraint climatic models on other planetary bodies where they are observed as well (e.g., Mars, Titan and Venus). Here, we discuss the morphodynamics of dunes and endeavor to identify and to explain the physical mechanisms at play in the selection of their shape, size and orientation, whilst focusing on Earth desert sand dunes.

  14. Tyrrhena Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    8 April 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a portion of a field of dark sand dunes superposed on the light-toned floor of a crater in eastern Tyrrhena Terra. The orientation of the dunes -- with the steep faces toward the south (bottom) -- suggests that winds generally blew from north to south at the time the dunes were formed.

    Location near: 14.6oS, 262.3oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Southern Summer

  15. Barchan Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    28 April 2004 One of the simplest forms a sand dune can take is the barchan. The term, apparently, comes from the Arabic word for crescent-shaped dunes. They form in areas with a single dominant wind direction that are also not overly-abundant in sand. The barchan dunes shown here were imaged in March 2004 by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) as it passed over a crater in western Arabia Terra near 21.1oN, 17.6oW. The horns and steep slope on each dune, known as the slip face, point toward the south, indicating prevailing winds from the north (top). The picture covers an area about 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

  16. Spring Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    22 July 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dunes in the north polar region of Mars. In this scene, the dunes, and the plain on which the dunes reside, are at least in part covered by a bright carbon dioxide frost. Dark spots indicate areas where the frost has begun to change, either by subliming away to expose dark sand, changing to a coarser particle size, or both. The winds responsible for the formation of these dunes blew from the lower left (southwest) toward the upper right (northeast).

    Location near: 76.3oN, 261.2oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

  17. Groovy Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    23 April 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a favorite among the MGS MOC operations team at Malin Space Science Systems, another example of the grooved dunes in Herschel Crater. The fine-scale grooves on the sand dune surfaces were formed by wind erosion. The sand dune surfaces have, over time, become crusted and the dunes immobilized. Wind now has to scour sand from the surfaces of these bedforms, creating small wind erosion features known as yardangs in the sand.

    Location near: 15.7oS, 228.9oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter

  18. Arkhangelsky Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    29 April 2004 These dark-toned barchan sand dunes in Arkhangelsky Crater were viewed by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) in late southern summer on 17 February 2004. Hundreds of narrow, dark streaks crisscross the dunes and the interdune terrain; these were most likely formed by the disruption of fine sediment by passing dust devils. The dune field is located near 41.2oS, 25.0oW, and is illuminated by sunlight from the upper left. Dune horns and slip faces indicate that the dominant winds blow from the southwest (lower left). The picture covers an area about 3 km (1.9 mi) across.

  19. Russell Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    26 March 2004 Dark streaks made by dozens of spring and summer dust devils created a form of martian graffiti on the sand dunes of Russell Crater near 54.5oS, 347.4oW. Gullies have developed on some of the dune slopes, as well. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left.

  20. Dune Variety

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    Our final look at the north polar erg was taken at 80 degrees North latitude during Northern summer. This image is of lower resolution than the previous images, but covers a much larger area. The dunes have very little remaining frost cover. Note the large extent of coverage, and the different dune forms.

    Image information: VIS instrument. Latitude 80.8, Longitude 184.6 East (175.4 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  1. Arabian Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    11 June 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of low-albedo (dark) barchan sand dunes in a crater located in western Arabia Terra. Small dunes like these are common in the craters of western Arabia Terra and they are often the source of finer, dark sediment that forms windstreaks further downwind. The steepest slopes on the dunes, their slipfaces, are pointed toward the southeast (lower right), indicating that the dominant winds in this location come from the opposite direction.

    Location near: 6.4oN, 346.2oW Image width: 3 km (1.9 mi Illumination from: lower left Season: Northern Autumn

  2. Martian Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    22 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes in a south mid-latitude crater near 49.5oS, 352.9oW. The elongated portions of these dunes indicate that, for some period of time during their development, there were two dominant wind directions involved. The most dominant of these winds blew from the south-southeast (lower right), as indicated by the presence of the steepest dune slopes on their northwest (facing upper left) sides. This image covers an area approximately 3 km (1.9 mi) across and is illuminated by sunlight from the upper left.

  3. Windblown Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    18 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows barchan and linear dunes that seem to have grown from the coalescence of barchans in a crater in the Noachis Terra region. The winds responsible for these dunes blow from the lower left (southwest). The image occurs near 46.0oS, 323.6oW, and covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the upper left.

  4. Copernicus Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    22 December 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark teardrop-shaped sand dunes in eastern Copernicus Crater. The winds responsible for these dunes generally blow from the south-southwest (lower left).

    Location near: 48.7oS, 167.4oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  5. Frosty Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    29 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows frost-covered sand dunes in the martian north polar region. The winds responsible for these dunes generally blew from the southwest (lower left).

    Location near: 80.0oN, 114.6oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Spring

  6. Nilosyrtis Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    31 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a rare patch of dark sand dunes in the Nilosyrtis Mensae region of Mars. The steepest slopes on these dunes, their slipfaces, point toward the south-southwest, indicating that the dominant winds that formed them came from the north-northeast (top/upper right).

    Location near: 34.5oN, 295.1oW Image width: width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Autumn

  7. Caterpillar Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    28 June 2004 Looking somewhat like caterpillars, this April 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows some of the rounded, wind-eroded sand dune features in a crater in the southern hemisphere near 61.7oS, 160.3oW. For such rounding to occur, the dune sand might need to be somewhat cemented. The picture covers an area about 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.

  8. Dune Variety

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA02173 Dune Variety

    This image of the east end of Coprates Chasma contains several dune fields. The dunes in the center of the image are larger and darker than the dunes at the bottom.

    Image information: VIS instrument. Latitude -14.8N, Longitude 304.3E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  9. Jenkins Dune

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This image is of a landform informally called Jenkins Dune and is thought to be a small barchan dune. This feature is less than 1 foot (0.3 m) tall and perhaps 2-3 meters wide. Inferred wind direction is from the left to the right. Near the crest of the feature is a demarcation that may represent the exposure of a crust on the sediments; similar features were seen on sediments on the rock Big Joe at the Viking landing site.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  10. Rippled Dune

    NASA Technical Reports Server (NTRS)

    2004-01-01

    10 October 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows ripples on the surface of a dune in a crater west of Sinus Meridiani near 2.5oN, 9.3oW. Most martian dune surfaces do not show ripples at the scale of MOC images---a higher resolution (better than 15 cm/pixel) view would be needed. These ripples are probably not typical sand ripples; they may be coarser-grained granule ripples (usually made up, in part, of grains 1-4 millimeters in size). The light-toned features in the image are wind-eroded outcrops of sedimentary rock. The image covers an area about 1.5 km (0.9 mi) wide. Sunlight illuminates the scene from the upper left.

  11. Frosty Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    12 April 2006 Today, the MOC Team celebrates the 45th anniversary of the first human flight into space, that of Yuri Gagarin on 12 April 1961, and the 25th anniversary of the first NASA Space Shuttle flight on 12 April 1981, by briefly pondering the wonders of our Solar System and the opportunities of the age in which we live. Although humans have not ventured to the Moon in more than 30 years, and have not yet gone to Mars, we can all go there through the eyes of our robotic explorers.

    Mars, perhaps the most Earth-like (yet so very different!) planet in our star's system, is tilted on its axis by about 25o-not all that different than Earth's 23.5o. Thus, Mars, like Earth, experiences a changing of seasons as the planet revolves around the Sun. At high latitudes in each hemisphere during autumn and winter, carbon dioxide frost accumulates on the surface.

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dunes covered and delineated by seasonal frost in the north polar region of Mars. The winds responsible for the formation of these dunes blew primarily from the northwest (upper left), with additional influences from the north and northeast. During the late spring and summer seasons, these dunes would look much darker than their surroundings, but in this late winter image, the dunes and the plains on which they occur are all covered with carbon dioxide frost.

    Location near: 78.4oN, 76.7oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Winter

  12. Richardson Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    25 December 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a summertime view of sand dunes in Richardson Crater in the Mare Chromium region of the martian southern hemisphere.

    Location near: 72.4oS, 179.7oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  13. ASTER Dunes

    NASA Technical Reports Server (NTRS)

    2000-01-01

    This image of Saudi Arabia shows a great sea of linear dunes in part of the Rub' al Khali, or the Empty Quarter. Acquired on June 25, 2000, the image covers an area 37 kilometers (23 miles) wide and 28 kilometers (17 miles) long in three bands of the reflected visible and infrared wavelength region. The dunes are yellow due to the presence of iron oxide minerals. The inter-dune area is made up of clays and silt and appears blue due to its high reflectance in band 1. The Rub' al Khali is the world's largest continuous sand desert. It covers about 650,000 square kilometers (250,966 square miles) and lies mainly in southern Saudi Arabia, though it does extend into the United Arab Emirates, Oman, and Yemen. One of the world's driest areas, it is uninhabited except for the Bedouin nomads who cross it. The first European to travel through the desert was Bertram Thomas in 1930.

    Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is one of five Earth-observing instruments launched December 18, 1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of International Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. science team leader; Moshe Pniel of JPL is the project manager. ASTER is the only high-resolution imaging sensor on Terra. The primary goal of the ASTER mission is to obtain high-resolution image data in 14 channels over the entire land surface, as well as black and white stereo images. With revisit time of between 4 and 16 days, ASTER will provide the capability for repeat coverage of changing areas on Earth's surface.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping and monitoring dynamic conditions and temporal change. Examples

  14. Marching Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 15 September 2003

    The Ruza impact crater observed in this THEMIS image taken north of Argyre Planitia shows very interesting gullies and migrating sand dunes. The gullies appear to be more mature and subdued than some previously described gullies and are possibly being covered by a mantle of material. The barchan sand dunes observed in the northern edge of the impact crater are likely migrating up the crater wall as indicated by the crescent shape that points in the wind direction.

    Image information: VIS instrument. Latitude -34.2, Longitude 307.2 East (52.8 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  15. Dark Dunes Over-riding Bright Dunes

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Some martian sand dunes may be more active than others. In this picture, wind has caused the dark and somewhat crescent-shaped dunes to advance toward the lower left. While their movement cannot actually be seen in this April 1998snapshot, the location of their steepest slopes--their slip faces--on their southwestern sides indicates the direction of movement. Oddly, these dark dunes have moved across and partly cover sets of smaller, bright ridges that also formed by wind action.

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image illustrates an intriguing martian 'find.' Strangely, the two dune types have different shapes and a different relative brightness. There are two explanations for the relationship seen here, and neither can be distinguished as 'the answer'--(1) it is possible that the brighter dunes are old and cemented, and represent some ancient wind activity, whereas the dark dunes are modern and are marching across the older, 'fossilized' dune forms, or (2) the bright dunes are composed of grains that are much larger or more dense than those that compose the dark dunes. In the latter scenario, the bright dunes move more slowly and are over-taken by the dark dunes because their grains are harder to transport. An interpretation involving larger or denser grains is consistent with the small size and even-spacing of the bright dunes, as well, but usually on Earth such features occur on the surfaces of larger, finer-grained dunes, not under them. The actual composition of either the bright or dark materials are unknown. This example is located on the floor of an impact crater in western Arabia Terra at 10.7oN, 351.0oW. The picture is illuminated from the right.

  16. Hydrogeology and hydrochemistry of dunes and wetlands along the southern shore of Lake Michigan, Indiana

    USGS Publications Warehouse

    Shedlock, Robert J.; Cohen, D.A.; Imbrigiotta, T.E.; Thompson, T.A.

    1994-01-01

    The dunes and the wetlands along the southern shore of Lake Michigan are underlain by a complex aquifer system composed of unconsolidated glacial, lacustrine, and eolian deposits. Surficial dune, beach, and glacial lacustrine sands compose an extensive surficial aquifer. The underlying drift contains three major confined sand aquifers. Potentiometric and hydrochemical data are consistent with a conceptual model in which regional and intermediate flow systems, recharged in end moraines south of the dune-beach complexes, discharge into Lake Michigan and the Great Marsh by upward leakage through unconsolidated sediments. Local flow systems in the surficial aquifer, recharged in the major dune-beach complexes, discharge into streams, ditches, and ponded areas in the adjacent interdunal wetlands. Shallow ground water discharges directly into Lake Michigan only north of a water-table divide that underlies the dune-beach complex along the shoreline. The position of ground-water seepage faces is affected by transient water-table mounds observed in the dune-beach complexes at the margins of wetlands. Substantial recharge to the dune complexes probably occurs near these dune-wetland margins. In the dune-beach complexes and intradunal wetlands, the shallow ground and wetland waters are dilute calcium bicarbonate and calcium bicarbonate sulfate types. More mineralized bicarbonate water types having variable proportions of calcium, magnesium, and sodium are found in interior parts of the Great Marsh because this area is probably a discharge zone for the regional and intermediate flow systems.

  17. Transverse instability of dunes.

    PubMed

    Parteli, Eric J R; Andrade, José S; Herrmann, Hans J

    2011-10-28

    The simplest type of dune is the transverse one, which propagates with invariant profile orthogonally to a fixed wind direction. Here we show, by means of numerical simulations, that transverse dunes are unstable with respect to along-axis perturbations in their profile and decay on the bedrock into barchan dunes. Any forcing modulation amplifies exponentially with growth rate determined by the dune turnover time. We estimate the distance covered by a transverse dune before fully decaying into barchans and identify the patterns produced by different types of perturbation. PMID:22107675

  18. Transverse Instability of Dunes

    NASA Astrophysics Data System (ADS)

    Parteli, Eric J. R.; Andrade, José S., Jr.; Herrmann, Hans J.

    2011-10-01

    The simplest type of dune is the transverse one, which propagates with invariant profile orthogonally to a fixed wind direction. Here we show, by means of numerical simulations, that transverse dunes are unstable with respect to along-axis perturbations in their profile and decay on the bedrock into barchan dunes. Any forcing modulation amplifies exponentially with growth rate determined by the dune turnover time. We estimate the distance covered by a transverse dune before fully decaying into barchans and identify the patterns produced by different types of perturbation.

  19. Unchanging Desert Sand Dunes

    NASA Astrophysics Data System (ADS)

    Gadhiraju, S.; Banerjee, B.; Buddhiraju, K.; Shah, V.

    2013-12-01

    Deserts are one of the major landforms on earth. They occupy nearly 20% of the total land area but are relatively less studied. With the rise in human population, desert regions are being gradually occupied for settlement posing a management challenge to the concerned authorities. Unrestrained erosion is generally a feature of bare dunes. Stabilized dunes, on the other hand, do not undergo major changes in textures, and can thus facilitate the growth of vegetation. Keeping in view of the above factors, better mapping and monitoring of deserts and particularly of sand dunes is needed. Mapping dunes using field instruments is very arduous and they generate relatively sparse data. In this communication, we present a method of clustering and monitoring sand dunes through imagery captured by remote sensing sensors. Initially Radon spectrum of an area is obtained by decomposition of the image into various projections sampled at finer angular directions. Statistical features such as mode, entropy and standard deviation of Radon spectrum are used in delineation and clustering of regions with different dune orientations. These clustered boundaries are used to detect if there are any changes occurring in the dune regions. In the experiment's, remote sensing data covering various dune regions of the world are observed for possible changes in dune orientations. In all the cases, it is seen that there are no major changes in desert dune orientations. While these findings have implications for understanding of dune geomorphology and changes occurring in dune directions, they also highlight the importance of a wider study of dunes and their evolution both at regional and global scales. Results for Dataset 1 & Dataset 2 Results for Dataset 3

  20. Experimental studies in natural groundwater-recharge dynamics: The analysis of observed recharge events

    USGS Publications Warehouse

    Sophocleous, M.; Perry, C.A.

    1985-01-01

    The amounts and time distribution of groundwater recharge from precipitation over an approximately 19-month period were investigated at two instrumented sites in south-central Kansas. Precipitation and evapotranspiration sequences, soil-moisture profiles and storage changes, water fluxes in the unsaturated zone and hydraulic gradients in the saturated zone at various depths, soil temperatures, water-table hydrographs, and water-level changes in nearby wells clearly depict the recharge process. Antecedent moisture conditions and the thickness and nature of the unsaturated zone were found to be the major factors affecting recharge. Although the two instrumented sites are located in sand-dune environments in areas characterized by shallow water table and subhumid continental climate, a significant difference was observed in the estimated effective recharge. The estimates ranged from less than 2.5 to approximately 154 mm at the two sites from February to June 1983. The main reasons for this large difference in recharge estimates were the greater thickness of the unsaturated zone and the lower moisture content in that zone resulting from lower precipitation and higher potential evapotranspiration for one of the sites. Effective recharge took place only during late winter and spring. No summer or fall recharge was observed at either site during the observation period of this study. ?? 1985.

  1. Dune Avalanche Scars

    NASA Technical Reports Server (NTRS)

    2004-01-01

    05 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows large, low albedo (dark) sand dunes in Kaiser Crater near 47.2oS, 340.4oW. The dunes are--ever so slowly--moving east to west (right to left) as sand avalanches down the steeper, slip face slopes of each. Avalanching sand in the Kaiser dune field has left deep scars on these slopes, suggesting that the sand is not loose but is instead weakly cemented. The image covers an area approximately 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.

  2. North Polar Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    23 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes in the north polar region of Mars. Surrounding much of the north polar ice cap are fields of sand dunes. In this case, the strongest winds responsible for the dunes blew off the polar cap (not seen here), from the north-northwest (upper left).

    Location near: 76.5oN, 63.7oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

  3. Dark Martian Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    30 June 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes in a crater in the Hesperia region of Mars. The steepest slopes on the dunes -- their slipfaces -- point toward the south-southwest, indicating that the winds responsible for the dunes blew from the north-northeast (top/upper right).

    Location near: 12.4oS, 236.5oW Image width: 3 km (1.9 mi) Illumination from: upper left Season Southern Spring

  4. Dunes in Brashear

    NASA Technical Reports Server (NTRS)

    2005-01-01

    10 October 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes on the floor of Brashear Crater in the southern hemisphere. The dominant winds responsible for these dunes blew from the southeast (lower right). Grooves on some of the dune surfaces suggest that the sand may be somewhat cemented; the grooves form by wind erosion.

    Location near: 53.9oS, 119.6oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  5. Fortune Cookie Sand Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-432, 25 July 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of small barchan sand dunes in the north polar region near 71.7oN, 51.3oW. Some of them are shaped like fortune cookies. The message these dunes provide: winds blow through this region from the lower right toward the upper left. The steep slip face slopes of these dunes, which point toward the upper left, indicate the wind direction. The scene is illuminated by sunlight from the upper right. The image is 3 km (1.9 mi) wide.

  6. Chasma Boreale Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-354, 8 May 2003

    In this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, wind has streaked a field of defrosting sand dunes in Chasma Boreale in the martian north polar region. Dune slip faces--the steep slope formed by avalanching sand on each dune--and the dark streaks indicate that wind transports sediment from the lower left toward the upper right. The picture covers an area about 3 km (1.9 mi) wide near 84.6oN, 358.5oW. Sunlight illuminates the scene from the lower left.

  7. Mid-latitude Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    7 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes on the floor of a southern mid-latitude impact crater. Craters are commonly the site of sand dunes, as sand may become trapped in these topographic depressions. In this case, the winds responsible for the dunes generally blew from the south/southeast (bottom/lower right),

    Location near: 51.8oS, 105.5oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  8. Vegetation against dune mobility.

    PubMed

    Durán, Orencio; Herrmann, Hans J

    2006-11-01

    Vegetation is the most common and most reliable stabilizer of loose soil or sand. This ancient technique is for the first time cast into a set of equations of motion describing the competition between aeolian sand transport and vegetation growth. Our set of equations is then applied to study quantitatively the transition between barchans and parabolic dunes driven by the dimensionless fixation index theta which is the ratio between the dune characteristic erosion rate and vegetation growth velocity. We find a fixation index theta(c) below which the dunes are stabilized, characterized by scaling laws. PMID:17155579

  9. Defrosting Sand Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-434, 27 July 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows retreating patches of frost on a field of large, dark sand dunes in the Noachis region of Mars. Large, windblown ripples of coarse sediment are also seen on some of the dunes. This dune field is located in a crater at 47.5oS, 326.3oW. The scene is illuminated by sunlight from the upper left.

  10. Syrtis Major Dune Field

    NASA Technical Reports Server (NTRS)

    2004-01-01

    20 December 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows barchan sand dunes west of the Meroe Patera volcanic caldera in central Syrtis Major. The winds that shape these dunes blow from the right/upper right (northeast). The surface across which the dunes have traveled is probably composed of volcanic rocks; the dunes, too, may have volcanic materials, such as sand-sized grains of tephra-volcanic ash-in them. This October 2003 view is located near 7.4oN, 292.3oW, and covers an area 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  11. Windblown Sand Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-557, 27 November 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows sand dunes and large ripples in a crater in the Hellespontus region of Mars. The winds that formed these dunes generally blew from the left/lower-left (west/southwest). Unlike the majority of dunes on Earth, sand dunes on Mars are mostly made up of dark, rather than light, grains. This scene is located near 50.3oS, 327.5oW. The image covers an area 3 km (1.9 mi) wide, and is illuminated by sunlight from the upper left.

  12. Booming Sand Dunes

    NASA Astrophysics Data System (ADS)

    Vriend, Nathalie

    "Booming" sand dunes are able to produce low-frequency sound that resembles a pure note from a music instrument. The sound has a dominant audible frequency (70-105 Hz) and several higher harmonics and may be heard from far distances away. A natural or induced avalanche from a slip face of the booming dune triggers the emission that may last for several minutes. There are various references in travel literature to the phenomenon, but to date no scientific explanation covered all field observations. This thesis introduces a new physical model that describes the phenomenon of booming dunes. The waveguide model explains the selection of the booming frequency and the amplification of the sound in terms of constructive interference in a confined geometry. The frequency of the booming is a direct function of the dimensions and velocities in the waveguide. The higher harmonics are related to the higher modes of propagation in the waveguide. The experimental validation includes quantitative field research at the booming dunes of the Mojave Desert and Death Valley National Park. Microphone and geophone recordings of the acoustic and seismic emission show a variation of booming frequency in space and time. The analysis of the sensor data quantifies wave propagation characteristics such as speed, dispersion, and nonlinear effects and allows the distinction between the source mechanism of the booming and the booming itself. The migration of sand dunes results from a complicated interplay between dune building, wind regime, and precipitation. The morphological and morphodynamical characteristics of two field locations are analyzed with various geophysical techniques. Ground-penetrating radar images the subsurface structure of the dunes and reveal a natural, internal layering that is directly related to the history of dune migration. The seismic velocity increases abruptly with depth and gradually increases with downhill position due to compaction. Sand sampling shows local

  13. Lohse Crater Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    8 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows windblown sand dunes in Lohse Crater in Noachis Terra near 43.8oS, 16.8oW. The winds responsible for these dunes blew largely from the lower left (southwest) toward the upper right (northeast). The picture covers an area about 3 km (1.9 mi) across, and is illuminated by sunlight from the upper left.

  14. Dark Sand Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    13 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes in the north polar region of Mars. The dominant winds responsible for these dunes blew from the lower left (southwest). They are located near 76.6oN, 257.2oW. The picture covers an area 3 km (1.9 mi) across; sunlight illuminates the scene from the upper right.

  15. Isolated Northern Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    This VIS image was taken at 81 degrees North latitude during Northern spring. In this region, the dunes are isolated from each other. The dunes are just starting to emerge from the winter frost covering appearing dark with bright crests. These dunes are located on top of ice.

    Image information: VIS instrument. Latitude 82.1, Longitude 191.3 East (168.7 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  16. Frost on Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    18 March 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark dunes on a crater floor during the southern spring. Some of the dunes have frost on their south-facing slopes.

    Location near: 52.3oS, 326.7oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  17. Dark Barchan Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    13 May 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows north polar sand dunes in the summertime. During winter and early spring, north polar dunes are covered with bright frost. When the frost sublimes away, the dunes appear darker than their surroundings. To a geologist, sand has a very specific meaning. A sand grain is defined independently of its composition; it is a particle with a size between 62.5 and 2000 microns. Two thousand microns equals 2 millimeters. The dunes are dark because they are composed of sand grains made of dark minerals and/or rock fragments. Usually, dark grains indicate the presence of unoxidized iron, for example, the dark volcanic rocks of Hawaii, Iceland, and elsewhere. This dune field is located near 71.7oN, 51.3oW. Dune slip faces indicate winds that blow from the upper left toward lower right. This picture covers an area approximately 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

  18. Sand dunes as migrating strings.

    PubMed

    Guignier, L; Niiya, H; Nishimori, H; Lague, D; Valance, A

    2013-05-01

    We develop a reduced complexity model for three-dimensional sand dunes, based on a simplified description of the longitudinal and lateral sand transport. The spatiotemporal evolution of a dune migrating over a nonerodible bed under unidirectional wind is reduced to the dynamics of its crest line, providing a simple framework for the investigation of three-dimensional dunes, such as barchan and transverse dunes. Within this model, we derive analytical solutions for barchan dunes and investigate the stability of a rectilinear transverse dune against lateral fluctuations. We show, in particular, that the latter is unstable only if the lateral transport on the dune slip face prevails over that on the upwind face. We also predict the wavelength and the characteristic time that control the subsequent evolution of an unstable transverse dune into a wavy ridge and the ultimate fragmentation into barchan dunes. PMID:23767529

  19. Sand dunes as migrating strings

    NASA Astrophysics Data System (ADS)

    Guignier, L.; Niiya, H.; Nishimori, H.; Lague, D.; Valance, A.

    2013-05-01

    We develop a reduced complexity model for three-dimensional sand dunes, based on a simplified description of the longitudinal and lateral sand transport. The spatiotemporal evolution of a dune migrating over a nonerodible bed under unidirectional wind is reduced to the dynamics of its crest line, providing a simple framework for the investigation of three-dimensional dunes, such as barchan and transverse dunes. Within this model, we derive analytical solutions for barchan dunes and investigate the stability of a rectilinear transverse dune against lateral fluctuations. We show, in particular, that the latter is unstable only if the lateral transport on the dune slip face prevails over that on the upwind face. We also predict the wavelength and the characteristic time that control the subsequent evolution of an unstable transverse dune into a wavy ridge and the ultimate fragmentation into barchan dunes.

  20. Holden Crater Dune Field

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    A common location for dune fields on Mars is in the basin of large craters. This dune field is located in Holden Crater at 25 degrees South atitude.

    Image information: VIS instrument. Latitude -25.5, Longitude 326.8 East (33.2 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  1. Crater Floor Dune Field

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    Our final dune image shows a small dune field inside an unnamed crater south of Nili Fossae.

    Image information: VIS instrument. Latitude 20.6, Longitude 79 East (281 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  2. Aligned Defrosting Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    17 August 2004 This July 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a group of aligned barchan sand dunes in the martian north polar region. At the time, the dunes were covered with seasonal frost, but the frost had begun to sublime away, leaving dark spots and dark outlines around the dunes. The surrounding plains exhibit small, diffuse spots that are also the result of subliming seasonal frost. This northern spring image, acquired on a descending ground track (as MGS was moving north to south on the 'night' side of Mars) is located near 78.8oN, 34.8oW. The image covers an area about 3 km (1.9 mi) across and sunlight illuminates the scene from the upper left.

  3. Dunes of the North

    NASA Technical Reports Server (NTRS)

    2005-01-01

    30 March 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows linear and barchan sand dunes in Chasma Boreale, a broad erosional trough in the martian north polar region. Winds responsible for these dunes generally blow from upper right toward the lower left. Martian dunes tend to be darker than their counterparts on Earth because they are composed of darker, iron-bearing minerals and rock fragments.

    Location near: 84.2oN, 37.9oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

  4. Bright dunes on mars

    USGS Publications Warehouse

    Thomas, P.C.; Malin, M.C.; Carr, M.H.; Danielson, G.E.; Davies, M.E.; Hartmann, W.K.; Ingersoll, A.P.; James, P.B.; McEwen, A.S.; Soderblom, L.A.; Veverka, J.

    1999-01-01

    Seasonal changes observed on the surface of Mars can in part be attributed to the transport of geological materials by wind. Images obtained by orbiting spacecraft in the 1970s showed large wind-formed features such as dunes, and revealed regional time-varying albedos that could be attributed to the effects of dust erosion and deposition. But the resolution of these images was insufficient to identify different types and sources of aeolian materials, nor could they reveal aeolian deposits other than large dunes or extensive surface coverings that were redistributed by dust storms. Here we present images of Mars with up to 50 times better resolution. These images show that martian dunes include at least two distinct components, the brighter of which we interpret to be composed of relatively soft minerals, possibly sulphates. We also find large areas of the martian surface that have several metres or more of aeolian mantle lacking obvious bedforms.

  5. Dunes with Frost

    NASA Technical Reports Server (NTRS)

    2004-01-01

    31 May 2004 Springtime for the martian northern hemisphere brings defrosting spots and patterns to the north polar dune fields. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows an example located near 76.7oN, 250.4oW. In summer, these dunes would be darker than their surroundings. However, while they are still covered by frost, they are not any darker than the substrate across which the sand is slowly traveling. Dune movement in this case is dominated by winds that blow from the southwest (lower left) toward the northeast (upper right). The picure covers an area about 3 km (1.9 mi) across and is illuminated by sunlight from the lower left.

  6. Dynamic sand dunes.

    PubMed

    Amarouchene, Y; Boudet, J F; Kellay, H

    2001-05-01

    When sand falling in the spacing between two plates goes past an obstacle, a dynamic dune with a parabolic shape and an inner triangular region of nonflowing or slowly creeping sand forms. The angle of the triangular zone increases with the height of the dune and saturates at a value determined by the geometry of the cell. The width of the dune, related to the radius of curvature at the tip, shows universal features versus its height rescaled by geometrical parameters. The velocity profile in the flowing part is determined and found to be nonlinear. The parabolic shape can be accounted for using a simple driven convection-diffusion equation for the interface. PMID:11328156

  7. Ripples and Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    27 May 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes on the floor of an impact crater west of Hellas Planitia. Portions of the crater floor are exposed near the center and lower right corner of the image but, in general, the floor is covered by large, windblown ripples. The dark dune sand typically covers ripples, indicating that the dunes are younger and made of a more mobile material.

    Location near: 43.7oS, 320.4oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  8. Nili Patera Dune Field

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form.

    This VIS image shows a dune field within Nili Patera, the northern caldera of a large volcanic complex in Syrtis Major.

    Image information: VIS instrument. Latitude 9, Longitude 67 East (293 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  9. Sand Dunes, Afghanistan

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This ASTER image covers an area of 10.5 x 15 km in southern Afghanistan and was acquired on August 20, 2000. The band 3-2-1 composite shows part of an extensive field of barchan sand dunes south of Kandahar. The shape of the dunes indicates that the prevailing wind direction is from the west. The image is located at 30.7 degrees north latitude and 65.7 degrees east longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  10. North Polar Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    10 April 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows low-albedo sand dunes in the north polar region. The slip faces on the dunes face toward the lower left, indicating that the dominant winds in this region blow or blew from the upper right.

    Location near: 82.4oN, 46.5oW Image width: 3 km (1.9 mi) Illumination from: lower left Season: Northern Summer

  11. Dunes of Herschel

    NASA Technical Reports Server (NTRS)

    2005-01-01

    4 August 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-toned sand dunes on the floor of the large martian impact crater, Herschel, located in the Terra Cimmeria region of Mars. The winds responsible for these dunes blew from the northeast (upper right).

    Location near: 15.7oS, 228.6oW Image width: width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Spring

  12. Dunes in Brashear

    NASA Technical Reports Server (NTRS)

    2006-01-01

    8 January 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of dark sand dunes on the northwestern floor of Brashear Crater. The dunes formed largely from winds that blew from the southeast (lower right).

    Location near: 253.7oS, 119.4oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  13. Nili Patera Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    6 July 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark, windblown sand dunes in the caldera of Nili Patera, a volcanic crater in Syrtis Major. The dunes were formed by winds blowing from the northeast (upper right).

    Location near: 9.0oN, 292.9oW Image width: 3 km (1.9 mi) Illumination from: lower left Season Northern Autumn

  14. Frosted Chasma Boreale Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-390, 13 June 2003

    This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of frost-covered sand dunes in Chasma Boreale in the early northern spring season. Dark spots, some of them with bright halos of re-precipitated frost, have formed as the dunes begin to defrost. Most of the frost is carbon dioxide which freezes out of the atmosphere during the cold martian polar winters. This picture is located near 84.7oN, 358.8oW, and is illuminated from the lower left.

  15. Sand Dunes with Frost

    NASA Technical Reports Server (NTRS)

    2004-01-01

    9 May 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of frost-covered sand dunes in the north polar region of Mars in early spring, 2004. The dunes indicate wind transport of sand from left to right (west to east). These landforms are located near 78.1oN, 220.8oW. This picture is illuminated by sunlight from the lower left and covers an area about 3 km (1.9 mi) across.

  16. Sand Dunes in Hellas

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-537, 7 November 2003

    The smooth, rounded mounds in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture are sand dunes. The scene is located in southern Hellas Planitia and was acquired in mid-southern autumn, the ideal time of year for Hellas imaging. Sunlight illuminates the scene from the upper left. These dunes are located near 49.1oS, 292.6oW. The picture covers an area 3 km (1.9 mi) wide.

  17. Springtime Dunes, 2004

    NASA Technical Reports Server (NTRS)

    2004-01-01

    12 April 2004 Today is April 12, 2004, the 43rd anniversary of the first human flight into space (Yuri Gagarin, 1961) and the 23rd anniversary of the first NASA Space Shuttle flight (Columbia, 1981). Meanwhile, on Mars, spring is in full swing in the martian northern hemisphere. With spring comes the annual defrosting of the north polar dunes. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, acquired on April 7, 2004, shows a field of small barchan (crescent-shaped) dunes covered with the remains of wintertime frost. The dark spots around the base of each dune mark the first signs of the spring thaw. The sand in these dunes is dark, like the black sand beaches of Hawaii or the dark, sandy soil of the rover, Opportunity, landing site, but in winter and spring their dark tone is obscured by bright carbon dioxide frost. This picture is located near 75.9oN, 45.3oW, and covers an area about 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.

  18. Frost-covered dunes

    NASA Technical Reports Server (NTRS)

    1999-01-01

    MOC image of dunes in Chasma Boreale, a giant trough in the north polar cap. This September 1998 view shows dark sand emergent from beneath a veneer of bright frost left over from the northern winter that ended in July 1998.

  19. Proctor Crater Dunes

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    This image, located near 30E and 47.5S, displays sand dunes within Proctor Crater. These dunes are composed of basaltic sand that has collected in the bottom of the crater. The topographic depression of the crater forms a sand trap that prevents the sand from escaping. Dune fields are common in the bottoms of craters on Mars and appear as dark splotches that lean up against the downwind walls of the craters. Dunes are useful for studying both the geology and meteorology of Mars. The sand forms by erosion of larger rocks, but it is unclear when and where this erosion took place on Mars or how such large volumes of sand could be formed. The dunes also indicate the local wind directions by their morphology. In this case, there are few clear slipfaces that would indicate the downwind direction. The crests of the dunes also typically run north-south in the image. This dune form indicates that there are probably two prevailing wind directions that run east and west (left to right and right to left).

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project

  20. Two modes for dune orientation

    NASA Astrophysics Data System (ADS)

    Courrech Du Pont, Sylvain; Narteau, Clément; Gao, Xin

    2015-11-01

    Earth sand seas experience winds that blow with different strengths and from different directions in line with the seasons. In response, dune fields show a rich variety of shapes from small crescentic barchans to big star and linear dunes. Linear dunes often exhibit complex and compound patterns with different length scales and orientations, which seem difficult to relate to a single wind cycle. We present results of underwater experiments and numerical simulations where a single wind regime can lead to two different dunes orientation depending on sediment availability. Sediment availability selects the overriding mechanism for the formation of dunes: increasing in height from the destabilization of a sand bed or elongating in a finger on a non-erodible ground from a localized sand source. These mechanisms drive the dunes orientation. Therefore, dunes alignment maximizes dunes orthogonality to sand fluxes in the bed instability mode, while dunes are aligned with the sand transport direction in the fingering mode. Then, we derive a model for dunes orientation, which explains the coexistence of bedforms with different alignments and quantitatively predicts the orientation of dunes in Earth deserts. Finally, we explore the phase diagram and the stability of the fingering mode.

  1. Dunes reveal Titan's recent history

    NASA Astrophysics Data System (ADS)

    Savage, Christopher J.; Radebaugh, Jani

    2010-04-01

    Large fields of linear dunes are abundant on Titan, covering nearly 20% of the surface. They are among the youngest features and represent interactions between near-surface winds and sediment. This interaction may vary from area to area creating unique populations of eolian features identified by dune field parameters such as crest-to-crest spacing, dune width and orientation. These parameters respond to changes in near-surface conditions over periods of time ranging from minutes to many thousands of years depending on dune size and the duration of the changes. While pattern analysis of dune field parameters on Earth and, in this study, Titan reveals much about current climatic conditions, such as wind regimes and wetter vs. drier areas, many inferences about past conditions can also be made. Initial pattern analysis of linear dunes on Titan reveals a single population of linear dunes representing a large percentage of all observed dunes. This single population is the result of two leading possibilities: Either there has been only one long period of dune building, leading to very old cores that have been built upon over long periods of time, perhaps punctuated with few or many intervals of non-deposition; or the current conditions of dune building have persisted long enough to completely erase any evidence of previous conditions. We have not yet worked through all the input parameters to adjust Earth's time scales to Titan's, and thus it is not yet possible to give a precise age for Titan's dunes. However, if these large linear dunes are similar to Earth's large linear dunes, they may represent at least several thousand years of dune building.

  2. Underground physics with DUNE

    SciTech Connect

    Kudryavtsev, Vitaly A.

    2016-01-01

    The Deep Underground Neutrino Experiment (DUNE) is a project to design, construct and operate a next-generation long-baseline neutrino detector with a liquid argon (LAr) target capable also of searching for proton decay and supernova neutrinos. It is a merger of previous efforts of the LBNE and LBNO collaborations, as well as other interested parties to pursue a broad programme with a staged 40-kt LAr detector at the Sanford Underground Research Facility (SURF) 1300 km from Fermilab. This programme includes studies of neutrino oscillations with a powerful neutrino beam from Fermilab, as well as proton decay and supernova neutrino burst searches. In this study, we will focus on the underground physics with DUNE.

  3. Underground physics with DUNE

    DOE PAGESBeta

    Kudryavtsev, Vitaly A.

    2016-01-01

    The Deep Underground Neutrino Experiment (DUNE) is a project to design, construct and operate a next-generation long-baseline neutrino detector with a liquid argon (LAr) target capable also of searching for proton decay and supernova neutrinos. It is a merger of previous efforts of the LBNE and LBNO collaborations, as well as other interested parties to pursue a broad programme with a staged 40-kt LAr detector at the Sanford Underground Research Facility (SURF) 1300 km from Fermilab. This programme includes studies of neutrino oscillations with a powerful neutrino beam from Fermilab, as well as proton decay and supernova neutrino burst searches.more » In this study, we will focus on the underground physics with DUNE.« less

  4. Underground physics with DUNE

    NASA Astrophysics Data System (ADS)

    Kudryavtsev, Vitaly A.; DUNE Collaboration

    2016-05-01

    The Deep Underground Neutrino Experiment (DUNE) is a project to design, construct and operate a next-generation long-baseline neutrino detector with a liquid argon (LAr) target capable also of searching for proton decay and supernova neutrinos. It is a merger of previous efforts of the LBNE and LBNO collaborations, as well as other interested parties to pursue a broad programme with a staged 40-kt LAr detector at the Sanford Underground Research Facility (SURF) 1300 km from Fermilab. This programme includes studies of neutrino oscillations with a powerful neutrino beam from Fermilab, as well as proton decay and supernova neutrino burst searches. In this paper we will focus on the underground physics with DUNE.

  5. Layer Outcrops and Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-561, 1 December 2003

    This October 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture shows dark, windblown sand dunes amid outcrops of light-toned, sedimentary rock in a crater in western Arabia Terra. The darkest material in the scene is windblown sand; the steep slopes--the slip faces--of the dunes face toward the southwest (lower left), indicating that wind transport of sand has been from the northeast (upper right). The layered mounds are the remains of sedimentary rock that were once more extensive across this crater floor. The image is located near 8.9oN, 1.2oW, and covers an area 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  6. Martian Dune Field

    NASA Technical Reports Server (NTRS)

    1976-01-01

    This spectacular picture of the Martian landscape by the Viking 1 Lander shows a dune field with features remarkably similar to many seen in the deserts of Earth. The dramatic early morning lighting - 7:30 a.m. local Mars time--reveals subtle details and shading. Taken yesterday (August 3) by the Lander s camera #1, the picture covers 100 , looking northeast at left and southeast at right. Viking scientists have studied areas very much like the one in this view in Mexico and in California (Kelso, Death Valley, Yuma). The sharp dune crests indicate the most recent wind storms capable of moving sand over the dunes in the general direction from upper left to lower right. Small deposits downwind of rocks also indicate this wind direction. Large boulder at left is about eight meters (25 feet) from the spacecraft and measures about one by three meters (3 by 10 feet). The meteorology boom, which supports Viking s miniature weather station, cuts through the picture s center. The sun rose two hours earlier and is about 30 above the horizon near the center of the picture.

  7. Russell Dune Gullies

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-343, 27 April 2003

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows the mysterious dune gullies of Russell Crater. The terrain shown here is one very large sand dune; the surface slopes from upper right toward lower left. Gullies start on the slope at the upper right and indicate flow toward the lower left. These might have formed by the presence of a fluid-either liquid or gas-mixed with sand that avalanched down the dune slope. Or not. Their origin is unknown, although it is known that they tend to occur only on slopes facing southward. The MOC team has re-imaged these gullies several times in the past three Mars years, but no new gullies have formed. The picture covers an area about 3 km (1.9 mi) wide near 54.5oS, 347.3oW. Sunlight illuminates the scene from the upper left.

  8. Frost-free Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03291 Frost-free Dunes

    These dark dunes are frost covered for most of the year. As southern summer draws to a close, the dunes have been completely defrosted.

    Image information: VIS instrument. Latitude -66.6N, Longitude 37.0E. 34 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  9. Windblown Dunes and Ripples

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-411, 4 July 2003

    July 4, 2003, is the 6th anniversary of the Mars Pathfinder landing. One of the elements carried to the red planet by Pathfinder was the Wind Sock Experiment. This project was designed to measure wind activity by taking pictures of three aluminum 'wind socks.' While the winds at the Mars Pathfinder site did not blow particularly strong during the course of that mission, dust storms seen from orbit and Earth-based telescopes attest to the fact that wind is a major force of change on the dry, desert surface of Mars today. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) narrow angle image shows dark sand dunes and lighter-toned ripples trapped among the mountainous central peak of an old impact crater in Terra Tyrrhena near 13.9oS, 246.7oW. The dune slip faces--the steepest slope on the larger dunes--indicate sand transport is from the top/upper left toward the bottom/lower right. North is toward the top/upper right; the picture is 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left. This picture was obtained in April 2003.

  10. Defrosting Richardson Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-492, 23 September 2003

    This is a mid-southern spring view, taken in August 2003, of defrosting patterns on sand dunes in Richardson Crater. The picture was acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC). The frost on these dunes might be a combination of frozen carbon dioxide left over from the previous winter, and water ice. As the ices sublime away, they create dark spots. Winds create dark streaks, either by moving the dark sand that underlies the frost, or by removing frost to expose the sand. Alternatively, the frost itself is roughened by the wind or has been made coarse by wind and sublimation processes. The Richardson dune field undergoes a long series of changes as it defrosts from late winter through spring and into early summer. Summer will arrive at the end of September 2003. This picture is located near 72oS, 181oW, and covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the upper left.

  11. Dune formation under bimodal winds

    PubMed Central

    Parteli, Eric J. R.; Durán, Orencio; Tsoar, Haim; Schwämmle, Veit; Herrmann, Hans J.

    2009-01-01

    The study of dune morphology represents a valuable tool in the investigation of planetary wind systems—the primary factor controlling the dune shape is the wind directionality. However, our understanding of dune formation is still limited to the simplest situation of unidirectional winds: There is no model that solves the equations of sand transport under the most common situation of seasonally varying wind directions. Here we present the calculation of sand transport under bimodal winds using a dune model that is extended to account for more than one wind direction. Our calculations show that dunes align longitudinally to the resultant wind trend if the angle θw between the wind directions is larger than 90°. Under high sand availability, linear seif dunes are obtained, the intriguing meandering shape of which is found to be controlled by the dune height and by the time the wind lasts at each one of the two wind directions. Unusual dune shapes including the “wedge dunes” observed on Mars appear within a wide spectrum of bimodal dune morphologies under low sand availability. PMID:20018703

  12. Appendix C: Recharge

    SciTech Connect

    Fayer, Michael J.; Keller, Jason M.

    2008-01-17

    This appendix provides estimates of recharge rates for the soil and vegetation conditions in and around the single-shell tank (SST) waste management areas (WMAs). The purpose is to combine published data with recent information to provide the most current recharge estimates. Recharge rates were estimated for areas that remain natural and undisturbed, areas where the vegetation has been disturbed, areas where both the vegetation and the soil have been disturbed, and areas that are engineered (e.g., surface barrier). Methods used include lysimetry, tracers, and simuations. This appendix summarizes the information in the recharge data package for the SST Waste Management Areas), which builds upon previous reports on the Hanford vadose zone data and Integrated Disposal Facility recharge with information available after those reports were published, including field measurements and simulations using weather data through 2006.

  13. The Exxon rechargeable cells. [solar rechargeable clocks

    NASA Technical Reports Server (NTRS)

    Malachesky, P. A.

    1980-01-01

    The design and performance of ambient temperature secondary cells based on the titanium disulfide cathode are discussed. These limited performance products were developed for microelectronic applications such as solar rechargeable watches and clocks which require low drain rate and do not require many deep cycles.

  14. Dunes on Ice

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 14 October 2003

    Dark dunes caught in a crater in the southern mid-latitudes slowly climb out. Winds push the sand to the NW (upper left), burying features on the crater wall that may be gullies. Gullies tend to be the youngest features in their environments, but this image may show an exception to the rule: the dark dunes override the gully-like features, so these features must have formed before the dark dunes encroached on them.

    Image information: VIS instrument. Latitude -52.8, Longitude 215.6 East (144.4 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  15. Martian Dunes in Infrared

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This collage of six images taken by the camera system on NASA's Mars Odyssey, shows examples of the daytime temperature patterns of martian dunes seen by the infrared camera. The dunes can be seen in this daytime image because of the temperature differences between the sunlit (warm and bright) and shadowed (cold and dark) slopes of the dunes. The temperatures in each image vary, but typically range from approximately -35 degrees Celsius (-31 degrees Fahrenheit) to -15degrees Celsius (5 degrees Fahrenheit). Each image covers an area approximately 32 by 32 kilometers (20 by 20 miles) and was acquired using the infrared Band 9, centered at 12.6 micrometers. Clockwise from the upper left, these images are: (a) Russel crater, 54 degrees south latitude, 13 degrees east longitude; (b) Kaiser crater. 45degrees south latitude, 19 degrees east longitude; (c) Rabe crater, 43south latitude, 35 east longitude; (d) 22 north latitude, 66 degrees east longitude; (e) Proctor crater. 47 degrees south latitude, 30 degrees east longitude; (f) 61 degrees south latitude, 201 degrees east longitude.

    The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the 2001 Mars Odyssey mission for NASA's Office of Space Science in Washington, D.C. Investigators at Arizona State University in Tempe, the University of Arizona in Tucson and NASA's Johnson Space Center, Houston, operate the science instruments. Additional science partners are located at the Russian Aviation and Space Agency and at Los Alamos National Laboratories, New Mexico. Lockheed Martin Astronautics, Denver, is the prime contractor for the project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL.

  16. Geophysical Monitoring of Active Infiltration Experiments for Recharge Estimation: Gains and Pains

    NASA Astrophysics Data System (ADS)

    Noell, U.; Lamparter, A.; Houben, G.; Koeniger, P.; Stoeckl, L.; Guenther, T.

    2014-12-01

    Drinking water supply on the island of Langeoog, North Sea, solely depends on groundwater from a freshwater lens. The correct estimation of the recharge rate is critical for a sustainable use of the resource. Extensive hydrogeological and geophysical studies have revealed differences in groundwater recharge by a factor of two and more between the top of the dunes and the dune valleys. The most convincing proof of these differences in recharge is based on isotope analysis (age dating) but boreholes are scarce and a direct proof of recharge is desired. For this purpose active infiltration experiments are performed and geophysically monitored. Former applications of this method in sand and loess soil gave evidence for the applicability of the geophysical observation when combined with tensiometers installed in situ at depth. These results showed firstly that in sandy soil the water reaches the groundwater table quicker than anticipated due to the water repellent characteristic of the dry sand, inhibiting the lateral spreading of the water. The studies also revealed that in loess preferential flow is initiated by ponding and that sprinkling caused very slow movement of water within the unsaturated zone and the water remained near the surface. On the island of Langeoog field experiments underlined the importance of water repellency on the dune surface, indicating that the rain water runs off superficially into the dune valleys where higher recharge is found. The active infiltration zone of the experiment covers an area of some 7m² and includes steeper parts of the dune. The infiltration will vary depending on rainfall intensity and duration, original water content and vegetation cover. What results can we reliably expect from the active experiment and what additional measurements are required to back up the findings? Results are ambiguous with regard to the quantitative assessment but the processes can be visualized by geophysical monitoring in situ.

  17. Sojourner at Mermaid Dune

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This color image of the Sojourner rover was taken at the end of day on Sol 30. The rover is perched atop Mermaid Dune, a dark material distinct from the surrounding bright surface. Dark red rover tracks extend from the foreground to the base of the rover's wheels.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and managed the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  18. Sedimentary Rocks and Dunes

    NASA Technical Reports Server (NTRS)

    2004-01-01

    25 November 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows buttes composed of light-toned, sedimentary rock exposed by erosion within a crater occurring immediately west of Schiaparelli Basin near 4.0oS, 347.9oW. Surrounding these buttes is a field of dark sand dunes and lighter-toned, very large windblown ripples. The sedimentary rocks might indicate that the crater interior was once the site of a lake. The image covers an area about 3 km (1.9 mi) wide. Sunlight illuminates the scene from the lower left.

  19. Predicting vegetation-stabilized dune field morphology

    NASA Astrophysics Data System (ADS)

    Barchyn, Thomas E.; Hugenholtz, Chris H.

    2012-09-01

    The morphology of vegetation-stabilized dune fields on the North American Great Plains (NAGP) mostly comprises parabolic dunes; stabilized barchan and transverse dunes are rare, with the exception of transverse and barchan mega-dunes in the Nebraska Sand Hills. We present a hypothesis from a numerical dune field model explaining the vegetation-stabilized morphology of dunes under unidirectional wind. Simulations with a range of initial dune morphologies (closely-spaced transverse to disperse barchans) indicate that stabilized morphology is determined by the ratio of slipface deposition rate to deposition tolerance of vegetation. Slipface deposition rate is related to dune height, flux, and celerity. With a fixed depositional tolerance, large, slow-moving dunes have low slipface deposition rates and ‘freeze’ in place once vegetation is introduced. Relatively small, fast dunes have high slipface deposition rates and evolve into parabolic dunes, often colliding during stabilization. Our hypothesis could explain differences in stabilized morphology across the NAGP and elsewhere.

  20. Seepage measurements from Long Lake, Indiana Dunes National Lakeshore

    USGS Publications Warehouse

    Isiorho, S.A.; Beeching, F.M.; Stewart, P.M.; Whitman, R.L.

    1996-01-01

    Long Lake, located near Lake Michigan within the dune-complexes of Indiana Dunes National Lakeshore, USA, was formed some time during the Pleistocene and Holocene epochs. A surficial aquifer underlies Long Lake, which is either a source or sink for the later. The hydrologic processes in the lakeshore and surrounding environs have been significantly altered during the agricultural, municipal, and industrial development of the region. Limited data suggest that the organisms of Long Lake have elevated levels of several contaminants. This study attempts to quantify seepage within the lake to assess the potential threat to groundwater quality. Seepage measurements and minipiezometric tests were used to determine seepage within the lake. Seepage measurements and minipiezometric tests suggest that water seeps out of Long Lake, thus recharging the groundwater that flows southwest away from the lake. There is a great deal of variability in the seepage rate, with a mean of 11.5×10-4±11.2×10-4 m d-1. The mean seepage rate of 0.3 m yr-1 for Long Lake is greater than the 0.2 m yr-1 recharge rate estimated for the drainage basin area. The Long Lake recharge volume of 2.5 × 105 m3 yr-1 is approximately 22% of the volume of the lake and is significant when compared to the total surface recharge volume of 4.8 × 105 m3 yr-1 to the upper aquifer of the drainage area. There is a potential for contamination of the groundwater system through seepage from the lake from contaminants derived from aerial depositions.

  1. Ripples or Dunes?

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This approximate true-color image taken by the Mars Exploration Rover Spirit's panoramic camera shows the windblown waves of soil that characterize the rocky surface of Gusev Crater, Mars. Scientists were puzzled about whether these geologic features were 'ripples' or 'dunes.' Ripples are shaped by gentle winds that deposit coarse grains on the tops or crests of the waves. Dunes are carved by faster winds and contain a more uniform distribution of material. Images taken of these features by the rover's microscopic imager on the 41st martian sol, or day, of the rover's mission revealed their identity to be ripples. This information helps scientists better understand the winds that shape the landscape of Mars. This image was taken early in Spirit's mission.

    [figure removed for brevity, see original site] Click on image for larger view [Image credit: NASA/JPL/ASU]

    This diagram illustrates how windblown sediments travel. There are three basic types of particles that undergo different motions depending on their size. These particles are dust, sand and coarse sand, and their sizes approximate flour, sugar, and ball bearings, respectively. Sand particles move along the 'saltation' path, hitting the surface downwind. When the sand hits the surface, it sends dust into the atmosphere and gives coarse sand a little shove. Mars Exploration Rover scientists are studying the distribution of material on the surface of Mars to better understand how winds shaped the landscape.

  2. Closeup of Mermaid Dune

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This pair of images shows a broad view (upper image) and detailed close-up view (lower image) of the disturbed surface near and on Mermaid Dune. Seen slightly right of center in the upper image are two diggings by the rover's wheel. The uppermost rut is in the surface away from Mermaid and is considered to be typical of the surface at the landing site. The closer rut represents the surface at the base of Mermaid on the upwind side. The lower image is an enlargement of the disturbed Mermaid sediments plus those of the underlying substrate; that is, the ground upon which the dune lies. Seen in the close-up are at least two types of sediment, one that seems to be approximately 1.4 cm thick and forms piles with sides sloping at approximately 35 degrees, and another at least 3 cm deep composed of sediment that has a characteristic slope of 41 degrees when piled. It is apparent in the images that there is a size range of sediment present in the rut, sediment that ranges from a few millimeters in size down to below the resolution of the camera.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  3. Proctor Cr. Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03293 Proctor Cr. Dunes

    This large dune field is located on the floor of Proctor Crater.

    Image information: VIS instrument. Latitude -47.4N, Longitude 30.7E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  4. Dunes on Plains

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03047 Dunes on Plains

    These dunes are located on the plains around Doanus Vallis.

    Image information: VIS instrument. Latitude 62.3S, Longitude 335.3E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  5. Estimating groundwater recharge

    USGS Publications Warehouse

    Stonestrom, David A.

    2011-01-01

    Groundwater recharge is the entry of fresh water into the saturated portion of the subsurface part of the hydrologic cycle, the modifier "saturated" indicating that the pressure of the pore water is greater than atmospheric.

  6. Sand Dunes in Kaiser Crater

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Full size (780 KBytes) This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) high resolution image shows a field of dark sand dunes on the floor of Kaiser Crater in southeastern Noachis Terra. The steepest slopes on each dune, the slip faces, point toward the east, indicating that the strongest winds that blow across the floor of Kaiser move sand in this direction. Wind features of three different scales are visible in this image: the largest (the dunes) are moving across a hard surface (light tone) that is itself partially covered by large ripples. These large ripples appear not to be moving--the dunes are burying some and revealing others. Another type of ripple pattern is seen on the margins of the dunes and where dunes coalesce. They are smaller (both in their height and in their separation) than the large ripples. These are probably coarse sediments that are moving with the dunes. This picture covers an area approximately 3 km (1.9 mi) across and is illuminated from the upper left.

  7. Lethal Sandslides from Eolian Dunes.

    PubMed

    Loope; Mason; Dingus

    1999-11-01

    Fossil vertebrates entombed within the Upper Cretaceous Djadokhta Formation of southern Mongolia bear testimony to a heretofore unknown geologic phenomenon: mass wasting of eolian dunes during heavy rainstorms. Evaporation of shallow-penetrating rainwater led to progressive calcite accumulation in a thin layer of sand about 0.5 m below the surface of dune lee slopes. During rare heavy rainstorms, a perched water table developed at the top of calcitic zones. Positive pore water pressure led to translational slides and fast-moving sediment gravity flows that overwhelmed animals on the lee slopes of large dunes and in interdune areas. PMID:10517885

  8. Ripples and Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    21 July 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small portion of the floor of Kaiser Crater in the Noachis Terra region, Mars. The terrain in the upper (northern) half of the image is covered by large windblown ripples and a few smoother-surfaced sand dunes. The dominant winds responsible for these features blew from the west/southwest (left/lower left).

    Location near: 47.2oS, 341.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter

  9. Gullies and Dunes

    NASA Technical Reports Server (NTRS)

    2006-01-01

    7 July 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows gullies overlain by seasonal frost in the north wall of an unnamed crater west of Hellas Planitia. The gullies likely formed by a combination of mass movement (i.e., landsliding) and fluid flow (i.e., water-rich debris flows). Below (south of) the gullies is a field of sand dunes; they, too, are covered by seasonal frost.

    Location near: 47.4oS, 322.8oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter

  10. Transport Conditions and Stages of Dune Development in the Olympia Undae Dune Field

    NASA Astrophysics Data System (ADS)

    Ewing, R. C.; Bourke, M.; Kocurek, G.

    2009-03-01

    Dune patterns analyzed in Olympia Undae indicate two generations of dune construction and a change in wind regime. Flow fields inferred from wind ripple orientations indicate transport from the ENE, which aligns with the youngest dunes.

  11. Sand Dunes of Schaeberle Crater

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-391, 14 June 2003

    This March 2003 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes near the center of Schaeberle Crater, located at 24.6oS, 310.3oW. The steepest slopes on the dunes point toward the left/upper left (northwest), indicating that, when the dunes were active, the dominant regional winds blew from the right/lower right (southeast). The dunes today, however, have a somewhat stunted and sculpted appearance, which suggests that in the most recent part of their history, they have been somewhat eroded. This image covers an area 3 km (1.9 mi) wide and is illuminated from the upper left.

  12. Sand Dunes in Noachis Terra

    NASA Technical Reports Server (NTRS)

    2004-01-01

    11 February 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-toned sand dunes in a crater in eastern Noachis Terra. Most big martian dunes tend to be dark, as opposed to the more familiar light-toned dunes of Earth. This difference is a product of the composition of the dunes; on Earth, most dunes contain abundant quartz. Quartz is usually clear (transparent), though quartz sand grains that have been kicked around by wind usually develop a white, frosty surface. On Mars, the sand is mostly made up of the darker minerals that comprise iron- and magnesium-rich volcanic rocks--i.e., like the black sand beaches found on volcanic islands like Hawaii. Examples of dark sand dunes on Earth are found in central Washington state and Iceland, among other places. This picture is located near 49.0oS, 326.3oW. Sunlight illuminates this scene from the upper left; the image covers an area 3 km (1.9 mi) wide.

  13. Exploring the topography and structure of Saharan linear dunes: Implications for characterizing dunes on Titan

    NASA Astrophysics Data System (ADS)

    Farr, T. G.; Heggy, E.; Radebaugh, J.

    2011-12-01

    Tens of thousands of sand dunes encircle the equatorial latitudes of Saturn's moon Titan, as seen by the Cassini Radar and visible-NIR instruments. These are linear in form, comparable in size and morphology to large linear dunes in the Egyptian Sahara. Studies of linear dunes in the Sahara can therefore assist in understanding the characteristics and formation of Titan's dunes. High-resolution topographic profiles of the Egyptian dunes indicate winds draw dune sands into broad stable plinths with steep summits that shift with recent winds. The summits of the Qattaniya Dunes west of Cairo are drawn out into crescents along the dune long axis from dominant, northerly winds on a NNW-trending crestline. Ground penetrating radar surveys show equally spaced layers within the dune, suggesting continuous, regular wind regimes formed the dunes. Larger dunes of the Great Sand Sea south of Siwa Oasis exhibit generally similar topographic profiles and fine layering although numerous flanking features complicate the overall morphology. These analyses can be related to studies of wind pattern effects on Titan's dune forms, residence time of sands within dunes on Titan, and the creation and maintenance of evolved dune forms across Titan. Studies of the effects of morphology and internal structure of these dunes on terrestrial radar remote sensing observations will yield additional information concerning Titan's dunes. Scattering models, for example, seek to explain the radar returns from Titan's dunes based on geometry and sand composition so it is valuable to understand the effects of these parameters on terrestrial dunes.

  14. Rechargeable hybrid aqueous batteries

    NASA Astrophysics Data System (ADS)

    Yan, Jing; Wang, Jing; Liu, Hao; Bakenov, Zhumabay; Gosselink, Denise; Chen, P.

    2012-10-01

    A new aqueous rechargeable battery combining an intercalation cathode with a metal (first order electrode) anode has been developed. The concept is demonstrated using LiMn2O4 and zinc metal electrodes in an aqueous electrolyte containing two electrochemically active ions (Li+ and Zn2+). The battery operates at about 2 V and preliminarily tests show excellent cycling performance, with about 90% initial capacity retention over 1000 charge-discharge cycles. Use of cation-doped LiMn2O4 cathode further improves the cyclability of the system, which reaches 95% capacity retention after 4000 cycles. The energy density for a prototype battery, estimated at 50-80 Wh kg-1, is comparable or superior to commercial 2 V rechargeable batteries. The combined performance attributes of this new rechargeable aqueous battery indicate that it constitutes a viable alternative to commercial lead-acid system and for large scale energy storage application.

  15. Recent Aeolian Dune Change on Mars

    NASA Technical Reports Server (NTRS)

    Bourke, M. C.; Edgett, K. S.; Cantor, B. A.

    2007-01-01

    Previous comparisons of Martian aeolian dunes in satellite images have not detected any change in dune form or position. Here, we show dome dunes in the north polar region that shrank and then disappeared over a period of 3.04 Mars years (5.7 Earth years), while larger, neighboring dunes showed no erosion or movement. The removal of sand from these dunes indicates that not only is the threshold wind speed for saltation exceeded under present conditions on Mars, but that any sand that is available for transport is likely to be moved. Dunes that show no evidence of change could be crusted, indurated. or subject to infrequent episodes of movement.

  16. Stratigraphic Architecture of Aeolian Dune Interactions

    NASA Astrophysics Data System (ADS)

    Brothers, S. C.; Kocurek, G.

    2015-12-01

    Dune interactions, which consist of collisions and detachments, are a known driver of changing dune morphology and provide the dynamics for field-scale patterning. Although interactions are ubiquitous in modern dune fields, the stratigraphic record of interactions has not been explored. This raises the possibility that an entire class of signature architectures of bounding surfaces and cross-strata has gone misidentified or unrecognized. A unique data set for the crescentic dunes of the White Sands Dune Field, New Mexico, allows for the coupling of dune interactions with their resultant stratigraphic architecture. Dune interactions are documented by a decadal time-series of aerial photos and LiDAR-derived digital elevation models. Plan-view cross-strata in interdune areas provide a record tying past dune positions and morphologies to the current dunes. Three-dimensional stratigraphic architecture is revealed by imaging of dune interiors with ground-penetrating radar. The architecture of a dune defect merging with a target dune downwind consists of lateral truncation of the target dune set by an interaction bounding surface. Defect cross-strata tangentially approach and downlap onto the surface. Downwind, the interaction surface curves, and defect and adjacent target dune sets merge into a continuous set. Predictable angular relationships reflect field-scale patterns of dune migration direction and approach angle of migrating defects. The discovery of interaction architectures emphasizes that although dunes appear as continuous forms on the surface, they consist of discrete segments, each with a distinct morphodynamic history. Bedform interactions result in the morphologic recombination of dune bodies, which is manifested stratigraphically within the sets of cross-strata.

  17. Predicting vegetation-stabilized dune morphology

    NASA Astrophysics Data System (ADS)

    Barchyn, T.; Hugenholtz, C.

    2012-04-01

    The morphology of vegetation-stabilized dune fields on the North American Great Plains mostly comprises parabolic dunes; stabilized barchan and transverse dunes are rare. One notable exception is the Nebraska Sand Hills (NSH), where massive grass-covered barchan and transverse dunes bear proof of former desert-like conditions. We present a hypothesis from a numerical dune field model to explain the vegetation-stabilized morphology of dunes. The model incorporates a growth curve that preferentially grows vegetation in regions of sediment deposition with a sharp drop in growth at the peak depositional tolerance of vegetation, qualitatively matching biological response to erosion and deposition. Simulations on a range of pre-stabilization dune morphologies, from large closely-spaced transverse dunes to small dispersed barchans, indicate that the stabilized morphology is largely determined by the ratio of slipface deposition rate to peak depositional tolerance of vegetation. Conceptually, slipface deposition rate is related to dune height and celerity. By keeping depositional tolerance constant (representing a constant vegetation type and climate) the model shows that large slow-moving dunes have low slipface deposition rates and essentially 'freeze' in place once vegetation is introduced, retaining their pre-vegetation morphology. Small fast-moving dunes have higher slipface deposition rates and evolve into parabolic dunes. We hypothesize that, when barchan and transverse dunes are subjected to a stabilizing climate shift that increases vegetation growth rate, they retain their pre-stabilization morphology if deposition rates are below the depositional tolerance of stabilizing vegetation, otherwise they become parabolic dunes. This could explain why NSH dunes are stabilized in barchan and transverse morphologies while elsewhere on the Great Plains dune fields are dominated by smaller parabolic dunes.

  18. Breeding and solitary wave behavior of dunes.

    PubMed

    Durán, O; Schwämmle, V; Herrmann, H

    2005-08-01

    Beautiful dune patterns can be found in deserts and along coasts due to the instability of a plain sheet of sand under the action of the wind. Barchan dunes are highly mobile aeolian dunes found in areas of low sand availability and unidirectional wind fields. Up to now modelization mainly focused on single dunes or dune patterns without regarding the mechanisms of dune interactions. We study the case when a small dune bumps into a bigger one. Recently Schwämmle and Herrmann [Nature (London) 426, 610 (2003)] and Katsuki [(e-print cond-mat 0403312)] have shown that under certain circumstances dunes can behave like solitary waves. This means that they can "cross" each other which has been questioned by many researchers before. In other cases we observe coalescence--i.e., both dunes merge into one--breeding--i.e., the creation of three baby dunes at the center and horns of a Barchan dune--or budding--i.e., the small dune, after "crossing" the big one, is unstable and splits into two new dunes. PMID:16196557

  19. Recharging Batteries Chemically

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Rowlette, J.; Graf, J.

    1985-01-01

    Iron/air batteries recharged chemically by solution of strong base in alcohol or by basic alcohol solution of reducing agent. Although method still experimental, it has potential for batteries in electric automobiles or as energy system in remote applications. Also used in quiet operations where noise or infrared signature of diesel engine is not desired.

  20. Depth-specific groundwater age determination on the island of Langeoog reveals climate archive and spatially variable recharge

    NASA Astrophysics Data System (ADS)

    Houben, Georg; Koeniger, Paul; Sültenfuß, Jürgen

    2015-04-01

    Depth-specific sampling of groundwater, followed by geochemical and stable isotope analysis, as well as groundwater age determination using the tritium-helium method, was performed on the freshwater lens of the island of Langeoog, Germany. The obtained age stratification shows marked spatial differences in recharge rates, which can be related to the type of land use. Recharge at the dune tops is significantly lower than in the dune valleys, due to the high water repellency of the dry sand. Dune valleys can contribute up to four times more recharge per unit of area than other areas. The development of housing in such areas can thus significantly decrease the recharge of fresh groundwater. The fresh groundwater samples show markedly heavier stable water isotope values with decreasing depths. This is obviously a refelection of a change of the climatic conditions during the time of recharge. The freshwater column thus preserves a climate archive. Using age data obtained from tritium-helium dating, this pattern was successfully matched to actually measured climate records for the last century which indicate an increase of the temperature during the last 100 and especíally the last 30 years.

  1. Development and steady states of transverse dunes: A numerical analysis of dune pattern coarsening and giant dunes

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Narteau, Clément; Rozier, Olivier

    2015-10-01

    We investigate the development and steady states of transverse dunes for ranges of flow depths and velocities using a cellular automaton dune model. Subsequent to the initial bed instability, dune pattern coarsening is driven by bed form interactions. Collisions lead to two types of coalescence associated with upstream or downstream dominant dunes. In addition, a single collision-ejection mechanism enhances the exchange of mass between two adjacent bed forms (throughpassing dunes). The power law increases in wavelength and amplitude exhibit the same exponents, which are independent of flow properties. Contrary to the wavelength, dune height is limited not only by flow depth but also by the strength of the flow. Superimposed bed forms may propagate and continuously destabilize the largest dunes. We identify three classes of steady state transverse dune fields according to the periodicity in crest-to-crest spacing and the mechanism of size limitation. In all cases, the steady state is reached and maintained through the dynamic equilibrium between flow strength and dune aspect ratio. In the limit of low flow strength, where it becomes the primary factor of size limitation, the bed shear stress in the dune trough regions is close to its critical value for motion inception. Comparisons with natural dune fields suggest that many of them may have reached a steady state. Finally, we infer that the sedimentary patterns in the model may be used to bring new constraints on the development of modern and ancient dune fields.

  2. Stars and linear dunes on Mars

    NASA Technical Reports Server (NTRS)

    Edgett, Kenneth S.; Blumberg, Dan G.

    1994-01-01

    A field containing 11 star and incipient star dunes occurs on Mars at 8.8 deg S, 270.9 deg W. Examples of linear dunes are found in a crater at 59.4 deg S, 343 deg W. While rare, dune varieties that form in bi- and multidirectional wind regimes are not absent from the surface of Mars. The occurence of both of these dune fields offers new insight into the nature of martian wind conditions and sand supply. The linear dunes appears to have formed through modification of a formerly transverse aeolian deposit, suggesting a relatively recent change in local wind direction. The 11 dunes in the star dune locality show a progressive change from barchan to star form as each successive dune has traveled up into a valley, into a more complex wind regime. The star dunes corroborate the model of N. Lancaster (1989), for the formation of star dunes by projection of transverse dunes into a complex, topographically influenced wind regime. The star dunes have dark streaks emanating from them, providing evidence that the dunes were active at or near the time the relevant image was obtained by the Viking 1 orbiter in 1978. The star and linear dunes described here are located in different regions on the martian surface. Unlike most star and linear dunes on Earth, both martian examples are isolated occurrences; neither is part of a major sand sea. Previously published Mars general circulation model results suggest that the region in which the linear dune field occurs should be a bimodal wind regime, while the region in which the star dunes occur should be unimodal. The star dunes are probably the result of localized complication of the wind regime owing to topographic confinement of the dunes. Local topographic influence on wind regime is also evident in the linear dune field, as there are transverse dunes in close proximity to the linear dunes, and their occurrence is best explained by funneling of wind through a topographic gap in the upwind crater wall.

  3. Dunes and Dust Devil Tracks

    NASA Technical Reports Server (NTRS)

    2004-01-01

    22 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of dark sand dunes that formed in winds blowing from east (right) to west (left), along with smaller, lighter-toned ripples and many dark dust devil tracks. The dust devil tracks indicate movement from a variety of directions, while the dunes only indicate winds from the east. In the lower left quarter of the image, dune sand has flowed around a layered rock obstacle. This scene is located near 19.9oN, 280.5oW. The image covers an area about 3 km (1.9 mi) across and sunlight illuminates the scene from the lower left.

  4. Dunes and Dust Devil Tracks

    NASA Technical Reports Server (NTRS)

    2003-01-01

    MGS MOC Release No. MOC2-352, 6 May 2003

    March 6, 2003, is the first day of spring in the martian southern hemisphere. As spring progresses in the south, dust devils will begin to form and sweep up some of the veneer of bright dust that accumulated during the recent autumn and winter seasons.

    This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows sand dunes in Wirtz Crater. The dark streaks that criss-cross each dune were probably formed by passing dust devils that disrupted or removed some of the thin layer of dust that coats the dunes. The picture covers an area about 3 km (1.9 mi) wide near 48.3oS, 25.4oW. Sunlight illuminates the scene from the upper left.

  5. Eolian reservoir characteristics predicted from dune type

    SciTech Connect

    Kocurek, G.; Nielson, J.

    1985-02-01

    The nature of eolian-dune reservoirs is strongly influenced by stratification types (in decreasing order of quality: grain-flow, grain-fall, wind-ripple deposits) and their packaging by internal bounding surfaces. These are, in turn, a function of dune surface processes and migration behavior, allowing for predictive models of reservoir behavior. Migrating, simple crescentic dunes produce tabular bodies consisting mainly of grain-flow cross-strata, and form the best, most predictable reservoirs. Reservoir character improves as both original dune height and preserved set thickness increase, because fewer grain-fall deposits and a lower percentage of dune-apron deposits occur in the cross-strata, respectively. It is probable that many linear and star dunes migrate laterally, leaving a blanket of packages of wind ripple laminae reflecting deposition of broad, shifting aprons. This is distinct from models generated by freezing large portions of these dunes in place. Trailing margins of linear and star dunes are prone to reworking by sand-sheet processes that decrease potential reservoir quality. The occurrence of parabolic dunes isolated on vegetated sand sheets results in a core of grain-flow and grain-fall deposits surrounded by less permeable and porous deposits. Compound crescentic dunes, perhaps the most preservable dune type, may yield laterally (1) single sets of cross-strate, (2) compound sets derived from superimposed simple dunes, or (3) a complex of diverse sets derived from superimposed transverse and linear elements.

  6. DUNE - a granular flow code

    SciTech Connect

    Slone, D M; Cottom, T L; Bateson, W B

    2004-11-23

    DUNE was designed to accurately model the spectrum of granular. Granular flow encompasses the motions of discrete particles. The particles are macroscopic in that there is no Brownian motion. The flow can be thought of as a dispersed phase (the particles) interacting with a fluid phase (air or water). Validation of the physical models proceeds in tandem with simple experimental confirmation. The current development team is working toward the goal of building a flexible architecture where existing technologies can easily be integrated to further the capability of the simulation. We describe the DUNE architecture in some detail using physics models appropriate for an imploding liner experiment.

  7. Crest line minimal model for sand dune

    NASA Astrophysics Data System (ADS)

    Guignier, Lucie; Valance, Alexandre; Lague, Dimitri

    2013-04-01

    In desert, complex patterns of dunes form. Under unidirectional wind, transverse rectilinear dunes or crescent shaped dunes called barchan dunes can appear, depending on the amount of sediment available. Most rectilinear transverse sand dunes are observed to fragment, for example at White Sands (New Mexico, United States of America) or Walvis Bay (Namibia). We develop a reduced complexity model to investigate the morphodynamics of sand dunes migrating over a non-erodible bed under unidirectional wind. The model is simply based on two physical ingredients, namely, the sand capture process at the slip face and the cross-wind sand transport. The efficiency of the sand capture process is taken to be dependent of the dune height and lateral diffusion is considered on both the windward and lee sides of the dune. In addition, the dune cross section is assumed to be scale invariant and is approximated by a triangular shape. In this framework, the dune dynamics is reduced to the motion of a string representing the dune crest line and is expressed as a set of two coupled nonlinear differential equations. This simple model reveals its ability to reproduce basic features of barchan and transverse dunes. Analytical predictions are drawn concerning dune equilibrium shape, stability and long-term dynamics. We derive, in particular, analytical solutions for barchan dunes, yielding explicit relationships between their shape and the lateral sand diffusion; and analytical predictions for the migration speed and equilibrium sand flux. A stability analysis of a rectilinear transverse dune allows us to predict analytically the wavelength emerging from fluctuations of the dune crest. We also determine the characteristic time needed for the rectilinear dune to fragment into a multitude of barchan dunes. These outcomes show that extremely simple ingredients can generate complex patterns for migrating dunes. From several dune field data, we are able to determine values of the model

  8. Moreux Crater Dunes

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site]

    The THEMIS VIS camera is capable of capturing color images of the Martian surface using five different color filters. In this mode of operation, the spatial resolution and coverage of the image must be reduced to accommodate the additional data volume produced from using multiple filters. To make a color image, three of the five filter images (each in grayscale) are selected. Each is contrast enhanced and then converted to a red, green, or blue intensity image. These three images are then combined to produce a full color, single image. Because the THEMIS color filters don't span the full range of colors seen by the human eye, a color THEMIS image does not represent true color. Also, because each single-filter image is contrast enhanced before inclusion in the three-color image, the apparent color variation of the scene is exaggerated. Nevertheless, the color variation that does appear is representative of some change in color, however subtle, in the actual scene. Note that the long edges of THEMIS color images typically contain color artifacts that do not represent surface variation.

    This false color image shows part of the interior of Moreux Crater. The crater peak is at the right edge of the image. Many dunes and a dunefield are also visible in the iamge. This image was collected during the Northern Spring season.

    Image information: VIS instrument. Latitude 41.9, Longitude 44.1 East (315.9 West). 35 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

  9. Dune Field in Nili Pateria

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) took this image of the southeastern edge of a large dune field within Nili Patera, an irregularly shaped volcanic caldera that is about 65 kilometers (40 miles) in diameter. The image was acquired at 1333 UTC (8:33 a.m. EST) on Feb. 1, 2007, near 8.8 degrees north latitude, 67.3 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. The region covered by the image is just over 10 kilometers (6 miles) wide at its narrowest point.

    The top image was constructed from three visible wavelengths that correspond to what our eyes would see; the colors are stretched to bring out subtle color contrast. The bottom image is a spectral map constructed using three infrared wavelengths that usually highlight compositional variations. Areas with high concentrations of iron- and magnesium-rich igneous minerals appear red.

    The entire dune field, covering about 500 square kilometers, resides mainly in the southwest quadrant of the caldera, occupying approximately 15% of its floor. Some of the dune forms seen here are 'barchans' -- individual, crescent shaped dunes that form when winds come primarily from one direction, resulting in one slipface. The orientation of the slipfaces indicates that primary winds were coming from the east-northeast. Using images from Mars Global Surveyor's narrow-angle camera, researchers measured approximately 400 slipfaces throughout the dune field and calculated an average azimuth of 245 degrees. Some of the barchans have elongated horns, suggesting that they experienced a slight secondary wind, or that the primary wind direction varied a little. When sufficient sand is available, barchans will coalesce, losing their individual crescentic shape. The resulting dune form, referred to as barchanoid, describes the vast majority of dunes in this image.

    In the lower left portion of

  10. Rechargeable Magnesium Power Cells

    NASA Technical Reports Server (NTRS)

    Koch, Victor R.; Nanjundiah, Chenniah; Orsini, Michael

    1995-01-01

    Rechargeable power cells based on magnesium anodes developed as safer alternatives to high-energy-density cells like those based on lithium and sodium anodes. At cost of some reduction in energy density, magnesium-based cells safer because less susceptible to catastrophic meltdown followed by flames and venting of toxic fumes. Other advantages include ease of handling, machining, and disposal, and relatively low cost.

  11. REMOTELY RECHARGEABLE EPD

    SciTech Connect

    Vrettos, N; Athneal Marzolf, A; Scott Bowser, S

    2007-11-13

    Radiation measurements inside the Contact Decon Maintenance Cell (CDMC) in the Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS) are required to determine stay times for personnel. A system to remotely recharge the transmitter of an Electronic Personnel Dosimeter (EPD) and bail assembly to transport the EPD within the CDMC was developed by the Savannah River National Laboratory (SRNL) to address this need.

  12. Advanced Small Rechargeable Batteries

    NASA Technical Reports Server (NTRS)

    Halpert, Gerald

    1989-01-01

    Lithium-based units offer highest performance. Paper reviews status of advanced, small rechargeable batteries. Covers aqueous systems including lead/lead dioxide, cadmium/nickel oxide, hydrogen/nickel oxide, and zinc/nickel oxide, as well as nonaqueous systems. All based on lithium anodes, nonaqueous systems include solid-cathode cells (lithium/molybdenum disulfide, lithium/titanium disulfide, and lithium/vanadium oxide); liquid-cathode cells (lithium/sulfur dioxide cells); and new category, lithium/polymer cells.

  13. Mean residence time in barchan dunes

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Yang, X.; Rozier, O.; Narteau, C.

    2013-12-01

    A barchan dune migrates when the sediment trapped on its lee side is remobilized by the flow. Then, sand grains may undergo many dune turnover cycles before their ejection along the horns, but the amount of time a sand grain contributes to the dune morphodynamics remains unknown. To estimate such a residence time, we analyze sediment particle motions in steady-state barchan dunes by tracking individual cells of a 3D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan dune shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchan dunes. Then, for different flow strengths and dune sizes, we find that the mean residence time of sediment particles in barchan dunes is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan dune morphodynamics. Finally, we initiate a discussion about sediment transport and memory in presence of bed forms using the advantages of the particle tracking technique.

  14. 'Endurance Crater's' Dazzling Dunes (false-color)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    As NASA's Mars Exploration Rover Opportunity creeps farther into 'Endurance Crater,' the dune field on the crater floor appears even more dramatic. This false-color image taken by the rover's panoramic camera shows that the dune crests have accumulated more dust than the flanks of the dunes and the flat surfaces between them. Also evident is a 'blue' tint on the flat surfaces as compared to the dune flanks. This results from the presence of the hematite-containing spherules ('blueberries') that accumulate on the flat surfaces.

    Sinuous tendrils of sand less than 1 meter (3.3 feet) high extend from the main dune field toward the rover. Scientists hope to send the rover down to one of these tendrils in an effort to learn more about the characteristics of the dunes. Dunes are a common feature across the surface of Mars, and knowledge gleaned from investigating the Endurance dunes close-up may apply to similar dunes elsewhere.

    Before the rover heads down to the dunes, rover drivers must first establish whether the slippery slope that leads to them is firm enough to ensure a successful drive back out of the crater. Otherwise, such hazards might make the dune field a true sand trap.

  15. Recharge into a shingle beach

    NASA Astrophysics Data System (ADS)

    Keating, T.

    1984-04-01

    Traditionally, groundwater recharge in the U.K. has been calculated by the Penman method on a monthly basis, using values of potential evaporation derived from averaged meteorological data and monthly totals of rainfall. Recent work by K.W.F. Howard and J.W. Lloyd has shown that these monthly totals considerably underestimate recharge calculated over shorter time periods and they suggested that 1-day, or at worst, 10-day intervals should be used. In this paper field experiments to measure recharge into a shingle beach are reported. These experiments were made with a lysimeter over a 6-yr. period and have shown that recharge into the shingle occurs whenever significant precipitation occurs, even during the summer months. The Penman model is shown to be unrealistic for estimating recharge into such a beach and an alternative model for calculating recharge is proposed. This model is shown to yield good results.

  16. Defrosting of Russell Crater Dunes

    NASA Technical Reports Server (NTRS)

    2007-01-01

    These two images (at right) were acquired by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) 39 days apart at 19:10 UTC (2:10 PM EST) on December 28, 2006 (upper right) and at 20:06 UTC (3:06 PM EST) on February 5, 2007 (lower right). These CRISM data were acquired in 544 colors covering the wavelength range from 0.36-3.92 micrometers, and show features as small as 20 meters (about 65 feet) across. Both images are false color composites of bands at 2.5, 1.5, and 1.25 micrometers, and are nearly centered at the same location, 54.875oS, 12.919oE (upper right) and 54.895oS, 12.943oE (lower right). Each image is approximately 11 kilometers (7 miles) across at its narrowest. These are part of a series of images capturing the evolution of carbon dioxide frost on the surface of the dunes in Russell Crater.

    Russell Crater is one of many craters in the southern highland region of Mars that contain large areas of sand dunes. The sand in these dunes has accumulated over a very long time period -- perhaps millions of years -- as wind blows over the highland terrain, picking up sand in some places and depositing in others. The topography of the craters forces the wind to blow up and over the crater rims, and the wind often isn't strong enough to keep the tiny grains suspended. This makes the sand fall to the ground and gradually pile up, and over time the surface breezes shape the sand into ripples and dunes. A similar process is at work at the Great Sand Dunes National Park and Preserve in Colorado, USA.

    The above left image shows a THEMIS daytime infrared mosaic of Russell Crater and the location of its (approximately) 30-kilometer wide dune field in the northeastern quadrant of the crater floor. Superposed on this view and shown enlarged at the upper right is CRISM image FRT000039DF. This CRISM image was acquired during the late Martian southern winter (solar longitude = 157.7o), and the bright blue in this false color composite indicates the

  17. Timing of frost deposition on Martian dunes: A clue to properties of dune particles?

    NASA Technical Reports Server (NTRS)

    Thomas, P.

    1987-01-01

    Scans were made across the Martian dunes found in images taken at several different times to determine the time history of the dune albedo. Atmospheric contributions were estimated using optical depth data and the brightness of shadows in some images. The data show that the dunes brighten very substantially between L(s) = 10 and 40 deg, depending on the latitude. Bright coverings on dunes form outliers 1 to 5 deg north of the cap edge. Formation of the general cap then sometimes reverses the contrast of the dune field with the surrounding area. Causes for the early deposition of frost on dunes relative to surroundings are discussed.

  18. Experimental and numerical investigations of soil water balance at the hinterland of the Badain Jaran Desert for groundwater recharge estimation

    NASA Astrophysics Data System (ADS)

    Hou, Lizhu; Wang, Xu-Sheng; Hu, Bill X.; Shang, Jie; Wan, Li

    2016-09-01

    Quantification of groundwater recharge from precipitation in the huge sand dunes is an issue in accounting for regional water balance in the Badain Jaran Desert (BJD) where about 100 lakes exist between dunes. In this study, field observations were conducted on a sand dune near a large saline lake in the BJD to investigate soil water movement through a thick vadose zone for groundwater estimation. The hydraulic properties of the soils at the site were determined using in situ experiments and laboratory measurements. A HYDRUS-1D model was built up for simulating the coupling processes of vertical water-vapor movement and heat transport in the desert soil. The model was well calibrated and validated using the site measurements of the soil water and temperature at various depths. Then, the model was applied to simulate the vertical flow across a 3-m-depth soil during a 53-year period under variable climate conditions. The simulated flow rate at the depth is an approximate estimation of groundwater recharge from the precipitation in the desert. It was found that the annual groundwater recharge would be 11-30 mm during 1983-2012, while the annual precipitation varied from 68 to 172 mm in the same period. The recharge rates are significantly higher than those estimated from the previous studies using chemical information. The modeling results highlight the role of the local precipitation as an essential source of groundwater in the BJD.

  19. Size distribution and structure of Barchan dune fields

    NASA Astrophysics Data System (ADS)

    Durán, O.; Schwämmle, V.; Lind, P. G.; Herrmann, H. J.

    2011-07-01

    Barchans are isolated mobile dunes often organized in large dune fields. Dune fields seem to present a characteristic dune size and spacing, which suggests a cooperative behavior based on dune interaction. In Duran et al. (2009), we propose that the redistribution of sand by collisions between dunes is a key element for the stability and size selection of barchan dune fields. This approach was based on a mean-field model ignoring the spatial distribution of dune fields. Here, we present a simplified dune field model that includes the spatial evolution of individual dunes as well as their interaction through sand exchange and binary collisions. As a result, the dune field evolves towards a steady state that depends on the boundary conditions. Comparing our results with measurements of Moroccan dune fields, we find that the simulated fields have the same dune size distribution as in real fields but fail to reproduce their homogeneity along the wind direction.

  20. Numerical modeling of subaqueous sand dune morphodynamics

    NASA Astrophysics Data System (ADS)

    Doré, Arnaud; Bonneton, Philippe; Marieu, Vincent; Garlan, Thierry

    2016-03-01

    The morphodynamic evolution of subaqueous sand dunes is investigated, using a 2-D Reynolds-averaged Navier-Stokes numerical model. A laboratory experiment where dunes are generated under stationary unidirectional flow conditions is used as a reference case. The model reproduces the evolution of the erodible bed until a state of equilibrium is reached. In particular, the simulation exhibits the different stages of the bed evolution, e.g., the incipient ripple generation, the nonlinear bed form growing phase, and the dune field equilibrium phase. The results show good agreement in terms of dune geometrical dimensions and time to equilibrium. After the emergence of the first ripple field, the bed growth is driven by cascading merging sequences between bed forms of different heights. A sequence extracted from the simulation shows how the downstream bed form is first eroded before merging with the upstream bed form. Superimposed bed forms emerge on the dune stoss sides during the simulation. An analysis of the results shows that they emerge downstream of a slight deflection on the dune profile. The deflection arises due to a modification of the sediment flux gradient consecutive to a reduction in the turbulence relaxation length while the upstream bed form height decreases. As they migrate, superimposed bed forms grow on the dune stoss side and eventually provoke the degeneration of the dune crest. Cascading merging sequences and superimposed bed forms dynamics both influence the dune field evolution and size and therefore play a fundamental role in the dune field self-organization process.

  1. Vegetated dune morphodynamics during recent stabilization of the Mu Us dune field, north-central China

    NASA Astrophysics Data System (ADS)

    Xu, Zhiwei; Mason, Joseph A.; Lu, Huayu

    2015-01-01

    The response of dune fields to changing environmental conditions can be better understood by investigating how changing vegetation cover affects dune morphodynamics. Significant increases in vegetation and widespread dune stabilization over the years 2000-2012 are evident in high-resolution satellite imagery of the Mu Us dune field in north-central China, possibly a lagged response to changing wind strength and temperature since the 1970s. These trends provide an opportunity to study how dune morphology changes with increasing vegetation stabilization. Vegetation expansion occurs mainly by expansion of pre-existing patches in interdunes. As vegetation spreads from interdunes onto surrounding dunes, it modifies their shapes in competition with wind-driven sand movement, primarily in three ways: 1) vegetation anchoring horns of barchans transforms them to parabolic dunes; 2) vegetation colonizes stoss faces of barchan and transverse dunes, resulting in lower dune height and an elongated stoss face, with shortening of barchan horns; and 3) on transverse dunes, the lee face is fixed by plants that survive sand burial. Along each of these pathways of stabilization, dune morphology tends to change from more barchanoid to more parabolic forms, but that transformation is not always completed before full stabilization. Artificial stabilization leads to an extreme case of "frozen" barchans or transverse dunes with original shapes preserved by rapid establishment of vegetation. Observations in the Mu Us dune field emphasize the point that vegetation growth and aeolian sand transport not only respond to external factors such as climate but also interact with each other. For example, some barchans lose sand mass during vegetation fixation, and actually migrate faster as they become smaller, and vegetation growth on a barchan's lower stoss face may alter sand transport over the dune in a way that favors more rapid stabilization. Conceptual models were generalized for the

  2. Heat transport in the vicinity of an artificial recharge site

    NASA Astrophysics Data System (ADS)

    Vandenbohede, Alexander; van Houtte, Emmanuel; Lebbe, Luc

    2010-05-01

    Since July 2002, the Intermunicipal Water Company of the Veurne region (IWVA) artificially recharges fresh water in the dunes of the western Belgian coastal plain by means of two recharge ponds. This recharge water is produced from secondary treated waste water effluent by the combination of ultra filtration and reverse osmosis. Extraction wells (112) are located north and south of the ponds. The artificial recharge project loops the water cycle: extracted water goes to the users and their waste water is purified and re-used. Therefore, it is an example of sustainable water management in coastal aquifers. Groundwater flow of this recharge site has been examined in the past by the use of a tracer test, hydrochemistry (environmental isotopes, conservative tracers) and groundwater flow modelling. Temperature, however, forms a relatively easy measurement which can add to or confirm the knowledge of the groundwater flow. Temperature time series (temperature as function of time) were measured at different levels in a number of wells located between the recharge ponds and the extraction wells, and in one well south of the recharge and extraction area. Secondly, temperature logs (temperature as function of depth) were measured in these wells at different times over the course of 2 years. Finally, the temperature of the recharged and extracted water is constantly monitored by the water company. The temperature of the recharge water shows a yearly fluctuation, ranging from 25 °C during summer to slightly above 0 °C during the winter. The temperature of the extracted water (combination of water extracted in all the wells) ranges between 17 °C during summer and 10 °C during winter. Minima and maxima in the extracted water are observed between 76 and 110 days (mean of 90 days and standard deviation of 13.5 days) later in the extracted water with respect to the recharged water. Measurements show that the difference in time when maxima and minima are observed in an

  3. Stability of transverse dunes against perturbations: A theoretical study using dune skeleton model

    NASA Astrophysics Data System (ADS)

    Niiya, Hirofumi; Awazu, Akinori; Nishimori, Hiraku

    2013-06-01

    The dune skeleton model is a reduced model to describe the formation process and dynamics of characteristic types of dunes emerging under unidirectional steady wind. Using this model, we study the dependency of the morphodynamics of transverse dunes on the initial random perturbations and the lateral field size. It was found that (i) an increase of the lateral field size destabilizes the transverse dune to cause deformation of a barchan, (ii) the initial random perturbations decay with time by the power function until a certain time; thereafter, the dune shapes change into three phases according to the amount of sand and sand diffusion coefficient, and (iii) the duration time, until the transverse dune is broken, increases exponentially with increasing the amount of sand and sand diffusion coefficient. Moreover, under the condition without the sand supply from windward ground, the destabilization of transverse dune in this model qualitatively corresponds to the subaqueous dunes in water tank experiments.

  4. Daily cycles in coastal dunes

    USGS Publications Warehouse

    Hunter, R.E.; Richmond, B.M.

    1988-01-01

    Daily cycles of summer sea breezes produce distinctive cyclic foreset deposits in dune sands of the Texas and Oregon coasts. In both areas the winds are strong enough to transport sand only during part of the day, reach a peak during the afternoon, and vary little in direction during the period of sand transport. Cyclicity in the foreset deposits is made evident by variations in the type of sedimentary structure, the texture, and the heavy-mineral content of the sand. Some of the cyclic deposits are made up entirely of one basic type of structure, in which the character of the structure varies cyclically; for example, the angle of climb in a climbing-wind-ripple structure may vary cyclically. Other cyclic deposits are characterized by alternations of two or more structural types. Variations in the concentration of fine-grained heavy minerals, which account for the most striking cyclicity, arise mainly because of segregation on wind-rippled depositional surfaces: where the ripples climb at low angles, the coarsegrained light minerals, which accumulate preferentially on ripple crests, tend to be excluded from the local deposit. Daily cyclic deposits are thickest and best developed on small dunes and are least recognizable near the bases of large dunes. ?? 1988.

  5. Dune formation on the present Mars.

    PubMed

    Parteli, Eric J R; Herrmann, Hans J

    2007-10-01

    We apply a model for sand dunes to calculate formation of dunes on Mars under the present Martian atmospheric conditions. We find that different dune shapes as those imaged by Mars Global Surveyor could have been formed by the action of sand-moving winds occurring on today's Mars. Our calculations show, however, that Martian dunes could be only formed due to the higher efficiency of Martian winds in carrying grains into saltation. The model equations are solved to study saltation transport under different atmospheric conditions valid for Mars. We obtain an estimate for the wind speed and migration velocity of barchan dunes at different places on Mars. From comparison with the shape of bimodal sand dunes, we find an estimate for the time scale of the changes in Martian wind regimes. PMID:17994981

  6. Relevant length scale of barchan dunes.

    PubMed

    Hersen, Pascal; Douady, Stéphane; Andreotti, Bruno

    2002-12-23

    A new experiment can create small scale barchan dunes under water: some sand is put on a tray moving periodically and asymmetrically in a water tank, and barchans rapidly form. We measure basic morphological and dynamical properties of these dunes and compare them to field data. These favorable results demonstrate experimentally the relevance of the so-called "saturation length" for the control of the dunes physics. PMID:12484824

  7. Development and stability of bed forms: a numerical analysis of dune pattern coarsening and giant dunes

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Narteau, Clement; Rozier, Olivier

    2015-04-01

    We investigate the development and stability of transverse dunes for ranges of flow depths and velocities using a cellular automaton dune model. Subsequent to the initial bed instability, dune pattern coarsening is driven by bed form interactions. Collisions lead to two types of coalescence associated with upstream or downstream dominant dunes. In addition, a single collision-ejection mechanism enhances the exchange of mass between two consecutive bed forms (through-passing dunes). The power-law increases in wavelength and amplitude exhibit the same exponents, which are independent of flow properties. Contrary to the wavelength, dune height is not only limited by flow depth but also by the strength of the flow. Superimposed bedforms may propagate and continuously destabilize the largest dunes. Then, we identify three classes of steady-state transverse dune fields according to the periodicity in crest-to-crest spacing and the mechanism of size limitation. In all cases, the steady state is reached when the bed shear stress in the dune trough regions is close to its critical value for motion inception. Such a critical shear stress value is reached and maintained through the dynamic equilibrium between flow strength and dune aspect ratio. Comparisons with natural dune fields show that many of them may have reached such a steady state. Finally, we infer that the sedimentary patterns in the model may be used to bring new constraints on the stability of modern and ancient dune fields.

  8. Predicting the migration rates of subaqueous dunes

    NASA Astrophysics Data System (ADS)

    Mohrig, David; Smith, J. Dungan

    1996-10-01

    In this paper we develop a simple, physically based method for predicting what fraction of sediment moving over the crests of dunes will bypass their lee faces. The bypass fraction is found by calculating a characteristic excursion length for every grain size making up a particular train of dunes. All particles with excursion lengths greater than the downstream span of the lee face of the average dune are assumed not to contribute to dune propagation. Bypass fractions based on distributions of excursion lengths account for the discrepancies between total sediment discharge and dune migration rate measured by Stein [1965] and Guy et al. [1966] in laboratory flumes, as well as by us in the North Loup River of Nebraska. Calculations and these data agree over sediment-transporting conditions associated with the entire stability field for dunes composed of medium sand. The two laboratory studies show that commonly 30-60% of all sand moving over fully developed dunes is not deposited on slip faces. Measurements from the North Loup River reveal that of all sediment moving over the dune crests there, roughly 45% is not being captured on lee faces even though 99% of sediment is transported within 2 cm of the bed. The method developed herein successfully estimates measured values for the bypass fraction from 0 to 80%. Our analysis indicates that the division between grains that are deposited versus those that are bypassing falls within the range of sand sizes making up the suspended load at dune crests.

  9. FLUIDIC: Metal Air Recharged

    SciTech Connect

    Friesen, Cody

    2014-03-07

    Fluidic, with the help of ARPA-E funding, has developed and deployed the world's first proven high cycle life metal air battery. Metal air technology, often used in smaller scale devices like hearing aids, has the lowest cost per electron of any rechargeable battery storage in existence. Deploying these batteries for grid reliability is competitive with pumped hydro installations while having the advantages of a small footprint. Fluidic's battery technology allows utilities and other end users to store intermittent energy generated from solar and wind, as well as maintain reliable electrical delivery during power outages. The batteries are manufactured in the US and currently deployed to customers in emerging markets for cell tower reliability. As they continue to add customers, they've gained experience and real world data that will soon be leveraged for US grid reliability.

  10. FLUIDIC: Metal Air Recharged

    ScienceCinema

    Friesen, Cody

    2014-04-02

    Fluidic, with the help of ARPA-E funding, has developed and deployed the world's first proven high cycle life metal air battery. Metal air technology, often used in smaller scale devices like hearing aids, has the lowest cost per electron of any rechargeable battery storage in existence. Deploying these batteries for grid reliability is competitive with pumped hydro installations while having the advantages of a small footprint. Fluidic's battery technology allows utilities and other end users to store intermittent energy generated from solar and wind, as well as maintain reliable electrical delivery during power outages. The batteries are manufactured in the US and currently deployed to customers in emerging markets for cell tower reliability. As they continue to add customers, they've gained experience and real world data that will soon be leveraged for US grid reliability.

  11. Hematite Outlier and Sand Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 4 December 2003

    This image shows a crater just south of the edge of the famous hematite-bearing surface, which is visible in the context image as a smooth area to the north. The crater has two features of immediate note. The first is a layered mound in the north part of the crater floor. This mound contains hematite, and it is an outlying remnant of the greater deposits to the north that have otherwise completely disappeared in this crater. The second feature is a dune field in the center of the crater floor, with dark dunes indicating winds from the northwest. The dunes grade into a dark sand sheet with no coherent structure, indicating that the sand layer thins out to the south and east.

    Image information: VIS instrument. Latitude -4.4, Longitude 357.3 East (2.7 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  12. Pathfinder Rover Atop Mermaid Dune

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Mars Pathfinder Lander camera image of Sojourner Rover atop the Mermaid 'dune' on Sol 30. Note the dark material excavated by the rover wheels. These, and other excavations brought materials to the surface for examination and allowed estimates of mechanical properties of the deposits.

    NOTE: original caption as published in Science Magazine

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages the Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is a division of the California Institute of Technology (Caltech).

  13. Size of Suspended Sediment Over Dunes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Samples of suspended sediment were collected at four elevations simultaneously over two-dimensional mobile dunes in 0.5 mm sand in a laboratory flume channel. A constant sampling position relative to the dunes was maintained by adjusting the translation rate of the sampling carriage to be the same ...

  14. Size of Suspended Sediment over Dunes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Samples of suspended sediment were collected at four elevations simultaneously over two-dimensional mobile dunes in two mixtures of 0.5 mm sand in a laboratory flume channel. A constant sampling position relative to the dunes was maintained by adjusting the translation rate of the sampling carriage...

  15. Ecogeomorphology of Sand Dunes Shaped by Vegetation

    NASA Astrophysics Data System (ADS)

    Tsoar, H.

    2014-12-01

    Two dune types associated with vegetation are known: Parabolic and Vegetated Linear Dunes (VLDs), the latters are the dominant dune type in the world deserts. Parabolic dunes are formed in humid, sub-humid and semi-arid environments (rather than arid) where vegetation is nearby. VLDs are known today in semiarid and arid lands where the average yearly rainfall is ≥100 mm, enough to support sparse cover of vegetation. These two dune types are formed by unidirectional winds although they demonstrate a different form and have a distinct dynamics. Conceptual and mathematical models of dunes mobility and stability, based on three control parameters: wind power (DP), average annual precipitation (p), and the human impact parameter (μ) show that where human impact is negligible the effect of wind power (DP) on vegetative cover is substantial. The average yearly rainfall of 60-80 mm is the threshold of annual average rainfall for vegetation growth on dune sand. The model is shown to follow a hysteresis path, which explains the bistability of active and stabilized dunes under the same climatic conditions with respect to wind power. We have discerned formation of parabolic dunes from barchans and transverse dunes in the coastal plain of Israel where a decrease in human activity during the second half of the 20th century caused establishment of vegetation on the crest of the dunes, a process that changed the dynamics of these barchans and transverse dunes and led to a change in the shape of the windward slope from convex to concave. These dunes gradually became parabolic. It seems that VLDs in Australia or the Kalahari have always been vegetated to some degree, though the shrubs were sparser in colder periods when the aeolian erosion was sizeable. Those ancient conditions are characterized by higher wind power and lower rainfall that can reduce, but not completely destroy, the vegetation cover, leading to the formation of lee (shadow) dunes behind each shrub. Formation of

  16. Thermally-Rechargeable Electrochemical Cell

    NASA Technical Reports Server (NTRS)

    Richter, R.

    1985-01-01

    Proposed liquid-sodium/sulfur electrochemical cell recharged by heat, rather than electric generator. Concept suitable for energy storage for utilites, mobile electronic equipment, and solar thermoelectric power systems. Sodium ions driven across membrane with aid of temperature differential.

  17. Vegetated linear dunes - chronologically discontinuous archives of several short-term and major dune growth episodes

    NASA Astrophysics Data System (ADS)

    Roskin, Joel

    2013-04-01

    Quartz sand dunes cover massive areas defined as arid, making them a potentially important archive of past climates and environments. But, dunes, being highly dynamic and relatively uniform in sedimentological composition, often compromise this potential. Most inland dunes are of the linear type that has a sinuous planar shape. Linear dunes, also associated with active seif dunes, are elongated by oblique cross-(dune) crest deflection of sand grains due to acutely bimodal sand-transporting winds. This prevents formation of long-term and stratigraphically continuous internal dune structure (though fully exposed internal linear dune structures to support this conclusion are rarely found). Therefore, dating of the dune sand by luminescence methods is mainly restricted to the last (re)mobilization phase and cannot track earlier dune growth history. Vegetated linear dunes (VLDs), mainly found in low-latitudes, are characterized by a straight planar shape and a partial shrub cover, and have been proposed to comprise an independent dune type. The stratigraphic cross-section of the VLD includes a sequence of chronologically discontinuous sand units forming the dune core. The accumulation of the units is generally interpreted to pertain to major episodes of strong wind power when sand was available. Possible minor events of sand accumulation are presumed to have been erased by major episodes. The units, often structureless and of similar sedimentological properties can only be discerned by luminescence dating as contacts between units do not necessarily imply chronological boundaries. The VLD core is overlaid by a mantle of sand that while being intermittently morphologically and structurally configured by seasonal winds to depths of several meters, preserves the dune core stratigraphy. Therefore, in a sense, the VLD is a prominent sedimentary body archiving influential short-time and possibly extreme events. Based upon exposed dune stratigraphy, ground-penetrating radar

  18. Insights from a Geophysical and Geomorphological Mars Analog Field Study at the Great Kobuk Sand Dunes, Northwestern Alaska

    NASA Astrophysics Data System (ADS)

    McGinnis, R. N.; Dinwiddie, C. L.; Stillman, D.; Bjella, K.; Hooper, D. M.; Grimm, R. E.

    2010-12-01

    system-wide geophysical surveys and ten boreholes revealed the presence of a shallow water table throughout the active portion of the GKSD. The distinctive water table radar signature was that of a reflector that closely parallels topography and cuts across steeply dipping bedforms. The water table is slightly nearer the surface within interdunes than it is below dune crests. The presence of water did not inhibit signal penetration; features were recognizable at two-way travel times of 560 to 1100 ns using 25, 50, and 100 MHz antennas. Our results suggest the dune field may serve as a localized recharge zone, with volatiles emplaced through both snowfall and rainfall, although a supra-permafrost talik cannot yet be ruled out. We interpret the available evidence to suggest that longlived snowcover combined with a shallow aqueous reservoir is primarily responsible for the low migration rate of this dune system (1.3 m per year).

  19. Hybrid eolian dunes of William River Dune field, northern Saskatchewan, Canada

    SciTech Connect

    Carson, M.A.; MacLean, P.A.

    1985-02-01

    A series of northwest-southeast aligned, large-scale (up to 30 m high) eolian dunes, occurring in a confined (600 km/sup 2/) desert area in northern Saskatchewan, Canada, was examined in the field. Observations were made of dune morphology and internal structure, and patterns of sand movement on the dunes were analyzed in relation to wind events during the summer of 1981. Present cross-sectional profiles exhibit steeper northeast slopes, the lower segment of which are intermittently covered by psammophilous grasses. Dune structure is dominated by northeast-dipping accretion laminae. Three /sup 14/C dates from organic material cropping out on the lower southwest slopes reveal that the dunes have migrated as transverse bed forms at rates of roughly 0.5 m/yr during the last few hundred years. However, a progressive increase in height, bulk, and symmetry along the dune axis from northwest to southeast, suggests an along-dune component of sand transport. This view is supported by (1) field measurements of airflow and along-dune sand transport patterns on 2 dunes, and (2) the present-day wind regime (1963-78). Dominated by north-northeast to northeast winds from January to June and by west-southwest winds from July to December, the resultant potential sand transport vector is toward the southeast, virtually identical to the dune axis.

  20. Conceptual models of the evolution of transgressive dune field systems

    NASA Astrophysics Data System (ADS)

    Hesp, Patrick A.

    2013-10-01

    This paper examines the evolutionary paths of some transgressive dune fields that have formed on different coasts of the world, and presents some initial conceptual models of system dynamics for transgressive dune sheets and dune fields. Various evolutionary pathways are conceptualized based on a visual examination of dune fields from around the world. On coasts with high sediment supply, dune sheets and dune fields tend to accumulate as large scale barrier systems with little colonization of vegetation in arid-hyper to arid climate regimes, and as multiple, active discrete phases of dune field and deflation plain couplets in temperate to tropical environments. Active dune fields tend to be singular entities on coasts with low to moderate sediment supply. Landscape complexity and vegetation richness and diversity increases as dune fields evolve from simple active sheets and dunes to single and multiple deflation plains and basins, precipitation ridges, nebkha fields and a host of other dune types associated with vegetation (e.g. trailing ridges, slacks, remnant knobs, gegenwalle ridges and dune track ridges, 'tree islands' and 'bush pockets'). Three principal scenarios of transgressive dune sheet and dune field development are discussed, including dune sheets or dune fields evolving directly from the backshore, development following foredune and/or dune field erosion, and development from the breakdown or merging of parabolic dunes. Various stages of evolution are outlined for each scenario. Knowledge of evolutionary patterns and stages in coastal dune fields is very limited and caution is urged in attempts to reverse, change and/or modify dune fields to 'restore' some perceived loss of ecosystem or dune functioning.

  1. Conceptual models of the evolution of transgressive dune field systems

    NASA Astrophysics Data System (ADS)

    A. Hesp, Patrick

    2013-10-01

    This paper examines the evolutionary paths of some transgressive dune fields that have formed on different coasts of the world, and presents some initial conceptual models of system dynamics for transgressive dune sheets and dune fields. Various evolutionary pathways are conceptualized based on a visual examination of dune fields from around the world. On coasts with high sediment supply, dune sheets and dune fields tend to accumulate as large scale barrier systems with little colonization of vegetation in arid-hyper to arid climate regimes, and as multiple, active discrete phases of dune field and deflation plain couplets in temperate to tropical environments. Active dune fields tend to be singular entities on coasts with low to moderate sediment supply. Landscape complexity and vegetation richness and diversity increases as dune fields evolve from simple active sheets and dunes to single and multiple deflation plains and basins, precipitation ridges, nebkha fields and a host of other dune types associated with vegetation (e.g. trailing ridges, slacks, remnant knobs, gegenwalle ridges and dune track ridges, ‘tree islands' and ‘bush pockets'). Three principal scenarios of transgressive dune sheet and dune field development are discussed, including dune sheets or dune fields evolving directly from the backshore, development following foredune and/or dune field erosion, and development from the breakdown or merging of parabolic dunes. Various stages of evolution are outlined for each scenario. Knowledge of evolutionary patterns and stages in coastal dune fields is very limited and caution is urged in attempts to reverse, change and/or modify dune fields to ‘restore' some perceived loss of ecosystem or dune functioning.

  2. Minimal size of a barchan dune.

    PubMed

    Parteli, E J R; Durán, O; Herrmann, H J

    2007-01-01

    Barchans are dunes of high mobility which have a crescent shape and propagate under conditions of unidirectional wind. However, sand dunes only appear above a critical size, which scales with the saturation distance of the sand flux [P. Hersen, S. Douady, and B. Andreotti, Phys. Rev. Lett. 89, 264301 (2002); B. Andreotti, P. Claudin, and S. Douady, Eur. Phys. J. B 28, 321 (2002); G. Sauermann, K. Kroy, and H. J. Herrmann, Phys. Rev. E 64, 31305 (2001)]. It has been suggested by P. Hersen, S. Douady, and B. Andreotti, Phys. Rev. Lett. 89, 264301 (2002)] that this flux fetch distance is itself constant. Indeed, this could not explain the protosize of barchan dunes, which often occur in coastal areas of high litoral drift, and the scale of dunes on Mars. In the present work, we show from three-dimensional calculations of sand transport that the size and the shape of the minimal barchan dune depend on the wind friction speed and the sand flux on the area between dunes in a field. Our results explain the common appearance of barchans a few tens of centimeter high which are observed along coasts. Furthermore, we find that the rate at which grains enter saltation on Mars is one order of magnitude higher than on Earth, and is relevant to correctly obtain the minimal dune size on Mars. PMID:17358139

  3. Non-standard neutrino interactions at DUNE

    NASA Astrophysics Data System (ADS)

    de Gouvêa, André; Kelly, Kevin J.

    2016-07-01

    We explore the effects of non-standard neutrino interactions (NSI) and how they modify neutrino propagation in the Deep Underground Neutrino Experiment (DUNE). We find that NSI can significantly modify the data to be collected by the DUNE experiment as long as the new physics parameters are large enough. For example, if the DUNE data are consistent with the standard three-massive-neutrinos paradigm, order 0.1 (in units of the Fermi constant) NSI effects will be ruled out. On the other hand, if large NSI effects are present, DUNE will be able to not only rule out the standard paradigm but also measure the new physics parameters, sometimes with good precision. We find that, in some cases, DUNE is sensitive to new sources of CP-invariance violation. We also explored whether DUNE data can be used to distinguish different types of new physics beyond nonzero neutrino masses. In more detail, we asked whether NSI can be mimicked, as far as the DUNE setup is concerned, by the hypothesis that there is a new light neutrino state.

  4. Reestablishing Naturally Functioning Dunes on Developed Coasts.

    PubMed

    Nordstrom; Lampe; Vandemark

    2000-01-01

    / The potential for reestablishing dune habitat is investigated in municipalities in New Jersey, USA, where natural coastal landforms and biota have been eliminated or reduced in extent. Dunes are classified using width, relationship to natural and cultural features, and changes through time, and they are assessed for their value as naturally functioning landforms in developed municipalities. The relationship between size and longevity that exists under natural conditions is altered by human activity. Small dunes on privately owned lots can survive as long as larger dunes in natural areas that are located farther inland, and foredunes repaired using sand fences and earth-moving equipment can survive where they could not under natural conditions.Common beach management practices reduce the ecological values of coastal dunes. Mechanical beach cleaning eliminates incipient dunes, habitat for nesting birds, seed sources for pioneer dune colonizers and food for fauna, and artificially small, stabilized foredunes reduce the variability in microenvironments necessary for biodiversity. Recent initiatives for reducing coastal hazards, protecting nesting birds, and encouraging nature-based tourism provide incentive for the development of a restoration program for beaches and dunes that is compatible with human use. Suggested changes in management practice include restricting or rerouting pedestrian traffic, altering beach-cleaning procedures, using symbolic fences to allow for aeolian transport while preventing trampling of dunes, and eliminating or severely restricting exotic species. Landforms will be more natural in function and appearance but will be more dynamic, smaller and in a different position from those in natural areas. Research needs are specified for ecological, geomorphological, and attitudinal studies to support and inform restoration planning. PMID:10552101

  5. Mapping the Stratigraphy of Booming Sand Dunes

    NASA Astrophysics Data System (ADS)

    Vriend, N. M.; Hunt, M. L.; Clayton, R. W.

    2008-12-01

    Booming dunes emit a loud rumbling sound after a man-made or natural sand avalanche is generated on the slip face of a large desert dune. The sound consist of one dominant frequency (70 - 105 Hz) with several higher harmonics. A recent publication (Vriend et al., 2007) presented a model of an internal, natural waveguide that propagates the booming emission, amplifies the sound, and sets the booming frequency. The mapping of the subsurface layering, which is necessary for the existence of a waveguide, prompted additional work on the dune structure and stratigraphy. The current work highlights geophysical measurements at Eureka Dunes in Death Valley National Park, CA and Dumont Dunes in the Mojave Desert, CA. Seismic refraction studies indicate strong layering with large velocity jumps across the interfaces. Ground Penetrating Radar (GPR) profiles, at frequencies of 100 MHz and 200 MHz, map out the stratigraphic structure of the dunes. Variations in the near surface layering are able to predict the seasonal variability in booming frequency both quantitatively and qualitatively. The Kirchhoff migrated GPR profiles are superimposed on the local topography obtained with a laser rangefinder. The complex dune structure is resolved to a depth of over 30 meters for the 100 MHz antenna. The GPR profiles of the longitudinal Eureka dune display complex internal structures from old dune crests. Both slopes have slip faces at 30 degrees with parallel layering (< 2m) at the near surface. At the transverse Dumont dune the GPR profile exhibits strong parallel layering on the booming leeward slipface only. The shallower windward face features a remarkable tilted repetitive layering that cuts through the surface. At Dumont Dunes the layering on the leeward face explains the change in booming frequency between 70 - 95 Hertz in the period 2005 - 2008. The tilted layering structure of the shallow windward face prevents the formation of a waveguide and is never able to sustain the

  6. Longitudinal dunes on Mars: Relation to current wind regimes

    NASA Technical Reports Server (NTRS)

    Lee, Pascal; Thomas, Peter C.

    1995-01-01

    Longitudinal dunes are extremely rare on Mars, but constitute a substantial fraction of terrestrial desert dunes. We report finding isolated examples of longitudinal dunes on Mars and relate their occurence to expected sand transport regimes. Terrestrial longitudinal dunes form in bimodal and multimodal transport regimes. General circulation models and streak data indicate that bimodal and multimodal transport of sand should be very rare on Mars. Thus the dearth of longitudinal dunes on Mars is consistant with their apparent formation conditions on Earth.

  7. Longitudinal dunes on Mars: Relation to current wind regimes

    NASA Technical Reports Server (NTRS)

    Lee, Pascal; Thomas, Peter C.

    1995-01-01

    Longitudinal dunes are extremely rare on Mars, but constitute a substantial fraction of terrestrial desert dunes. We report finding isolated examples of longitudinal dunes on Mars and relate their occurrence to expected sand transport regimes. Terrestrial longitudinal dunes form in bimodal and multimodal transport regimes. General circulation models and streak data indicate that bimodal and multimodal transport of sand should be very rare on Mars. Thus the dearth of longitudinal dunes on Mars is consistent with their apparent formation conditions on Earth.

  8. Freshwater lenses as archive of climate, groundwater recharge, and hydrochemical evolution: Insights from depth-specific water isotope analysis and age determination on the island of Langeoog, Germany

    NASA Astrophysics Data System (ADS)

    Houben, Georg J.; Koeniger, Paul; Sültenfuß, Jürgen

    2014-10-01

    The age stratification of a freshwater lens on the island of Langeoog, Germany, was reconstructed through depth-specific sampling and groundwater dating using the tritium-helium method. The stratification is strongly affected by the land use and resulting differences in recharge rates. Infiltration at the dune tops is significantly lower than in the valleys, due to repellency of the dry sand. Dune valleys contribute up to four times more groundwater recharge per area than other areas. Housing development in dune areas might therefore significantly decrease the available fresh groundwater. The freshwater column shows a distinct increase of stable isotope values with decreasing depths. Hence, the freshwater lens contains a climate archive which reflects changing environmental conditions at the time of recharge. Combined with tritium-helium dating, this pattern could be matched to climate records which show an increase of the temperature at the time of recharge and rainfall rates during the last 50 years. The spatial and temporal developments of water chemistry during the passage through the lens follow a marked pattern from a sodium and chloride-dominated rainwater of low conductivity to a more mineralized sodium bicarbonate water type, caused by dissolution of carbonate shells close to the surface and subsequent ion exchange of calcium for sodium in the deeper parts.

  9. Functional materials for rechargeable batteries.

    PubMed

    Cheng, Fangyi; Liang, Jing; Tao, Zhanliang; Chen, Jun

    2011-04-19

    There is an ever-growing demand for rechargeable batteries with reversible and efficient electrochemical energy storage and conversion. Rechargeable batteries cover applications in many fields, which include portable electronic consumer devices, electric vehicles, and large-scale electricity storage in smart or intelligent grids. The performance of rechargeable batteries depends essentially on the thermodynamics and kinetics of the electrochemical reactions involved in the components (i.e., the anode, cathode, electrolyte, and separator) of the cells. During the past decade, extensive efforts have been dedicated to developing advanced batteries with large capacity, high energy and power density, high safety, long cycle life, fast response, and low cost. Here, recent progress in functional materials applied in the currently prevailing rechargeable lithium-ion, nickel-metal hydride, lead acid, vanadium redox flow, and sodium-sulfur batteries is reviewed. The focus is on research activities toward the ionic, atomic, or molecular diffusion and transport; electron transfer; surface/interface structure optimization; the regulation of the electrochemical reactions; and the key materials and devices for rechargeable batteries. PMID:21394791

  10. Real barchan dune collisions and ejections

    NASA Astrophysics Data System (ADS)

    Hugenholtz, Chris H.; Barchyn, Thomas E.

    2012-01-01

    From high-resolution satellite imagery of barchan sand dunes, we provide geomorphological evidence of collisions that result in the ejection of a barchan from the wake of another barchan dune. Previous interpretations suggest this outcome is evidence of soliton or solitary wave behaviour; however, the physical mechanisms for mass exchange are not fully understood, resulting in debate. Our evidence and interpretation indicates that mass is transferred to the upwind barchan by shadowing a portion of downwind barchan's stoss slope. Turbulent, unsaturated airflow erodes the surface between the dunes, creating a smaller dune that ejects from the wake region. Previous observations lacked the spatial resolution required to document this process; therefore, our observations clarify the collision dynamics of barchans. A broader implication of our observations is the role of collisions in maintaining an “equilibrium” size distribution in barchan swarms.

  11. Observation of density segregation inside migrating dunes.

    PubMed

    Groh, Christopher; Rehberg, Ingo; Kruelle, Christof A

    2011-11-01

    Spatiotemporal patterns in nature, such as ripples or dunes, formed by a fluid streaming over a sandy surface show complex behavior despite their simple forms. Below the surface, the granular structure of the sand particles is subject to self-organization processes, exhibiting such phenomena as reverse grading when larger particles are found on top of smaller ones. Here we report results of an experimental investigation with downscaled model dunes revealing that, if the particles differ not in size but in density, the heavier particles, surprisingly, accumulate in the central core close to the top of the dune. This finding contributes to the understanding of sedimentary structures found in nature and might be helpful to improve existing dating methods for desert dunes. PMID:22181357

  12. 'Sharks Teeth' -- Sand Dunes in Proctor Crater

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Sometimes, pictures received from Mars Global Surveyor's Mars Orbiter Camera (MOC) are 'just plain pretty.' This image, taken in early September 2000, shows a group of sand dunes at the edge of a much larger field of dark-toned dunes in Proctor Crater. Located at 47.9oS, 330.4oW, in the 170 km (106 mile) diameter crater named for 19th Century British astronomer Richard A. Proctor (1837-1888), the dunes shown here are created by winds blowing largely from the east/northeast. A plethora of smaller, brighter ripples covers the substrate between the dunes. Sunlight illuminates them from the upper left.

  13. Early diagenesis of eolian dune and interdune sands at White Sands, New Mexico

    USGS Publications Warehouse

    Schenk, C.J.; Fryberger, S.G.

    1988-01-01

    The degree of early diagenesis in eolian dune and interdune sands at White Sands, New Mexico, is largely a function of the relationship between sand location and the water table. Most active and vegetation-stabilized dune sands are in the vadose zone, whereas interdune sands are in the capillary fringe and phreatic zones. Crystallographically controlled dissolution of the framework gypsum grains results in elongate, prismatic etch pits on sand grains from the capillary fringe and phreatic zones, whereas dissolution of sand grains in the vadose zone is slight, causing minute irregularities on grain surfaces. Vadose water percolating through the sand is manifest as meniscus layers. Consequently, dune sands in the vadose zone are cemented mainly by meniscus-shaped gypsum at grain contacts. Pendant cements formed on the lower margins of some sand grains. Cementation in the capillary fringe and the phreatic zone is more extensive than the vadose regardless of strata type. Typically, well-developed gypsum overgrowths form along the entire edge of a grain, or may encompass the entire grain. Complex diagenetic histories are suggested by multiple overgrowths and several episodes of dissolution on single grains, attesting to changing saturation levels with respect to gypsum in the shallow ground water. These changes in saturation are possibly due to periods of dilution by meteoric recharge, alternating with periods of concentration of ions and the formation of cement due to evaporation through the capillary fringe. ?? 1988.

  14. Hydrogeochemical transport modeling of the infiltration of tertiary treated wastewater in a dune area, Belgium

    NASA Astrophysics Data System (ADS)

    Vandenbohede, Alexander; Wallis, Ilka; Van Houtte, Emmanuel; Van Ranst, Eric

    2013-09-01

    Managed artificial recharge (MAR) is a well-established practice for augmentation of depleted groundwater resources or for environmental benefit. At the St-André MAR site in the Belgian dune area, groundwater resources are optimised through re-use of highly treated wastewater by means of infiltration ponds. The very high quality of the infiltration water sets this system apart from other MAR systems. The low total dissolved solid (TDS) content in the infiltration water (less than 50 mg/L) compared to the dune aquifer (500 mg/L) triggers a number of reactions, increasing the TDS through soil-aquifer passage. Multi-component reactive transport modelling was applied to analyse the geochemical processes that occur. Carbonate dissolution is the main process increasing the TDS of the infiltration water. Oxic aquifer conditions prevail between the infiltration ponds and the extraction wells. This is driven by the high flow velocities, leaving no time to consume O2 between the ponds and extraction wells. Cation exchange is important when infiltration water is replaced by native dune water or when significant changes in infiltration-water quality occur. The seasonal variation of O2 and temperature in the infiltration water are the main drivers for seasonal changes in the concentration of all major ions.

  15. New Ways to Continuous Measurements of Soil Moisture in a Hyper-arid Dune Sand Environment

    NASA Astrophysics Data System (ADS)

    Rödiger, T.; Königer, F.; Bonitz, F.; Siebert, C.

    2014-12-01

    Particularly in arid regions, a profound knowledge about infiltration rates eventually leading to groundwater recharge is the major parameter for any resources management. Unfortunately, in arid areas, the rate of infiltration is one of the most difficult values to derive with sufficient accuracy. In 2010 a 3D monitoring site was developed within a sand-dune belt SW of Riyadh (KSA). At the site, one 45°-sloped and 6 vertical drillings were deepened down to max. 13 m below ground and each is equipped with (i) continuous TDR sensors: Taupe- (sloped drilling) and tube- (vertical drilling) sensors as well as (ii) discrete temperature sensors to allow continuous moisture and temperature monitoring within the upper 13 m. The combination of the chosen sensors and the application of direct push by using a Geoprobe 7730DT guaranteed two major advantages: minimal invasiveness and continuous measurements of the relative dielectric permittivity along the borehole walls. Topp equation (Topp et al. 1980) was used to convert the raw signals from sensor into volumetric water content. To calibrate TDR data, the actual soil-moisture contents in the upper 8 m of the dune were derived from drilling core samples. Within the dune, the moisture fluctuates between 0-10.3 vol.-% and quickly reacts on seasonal climatic impacts in the uppermost 2 m, while moisture below persists at around 1.5 vol.-%. Only precipitation events with exceeding 6 mm/d induce increasing moisture in the uppermost 1.5 m of minimum 1.5 vol.-%. That indicates a threshold for effective precipitation of 6 mm/d below of which no remarkable infiltration occurs. During the observation, we derived from the observed precipitation events and the depth of the resulting infiltration fronts, that the infiltration process is driven by the amount of a singular precipitation event. As a consequence, recharge estimations for the so-called sand seas based on annual or monthly precipitation data are not applicable for the region.

  16. Mean sediment residence time in barchan dunes

    NASA Astrophysics Data System (ADS)

    Zhang, D.; Yang, X.; Rozier, O.; Narteau, C.

    2014-03-01

    When a barchan dune migrates, the sediment trapped on its lee side is later mobilized when exposed on the stoss side. Then sand grains may undergo many dune turnover cycles before their ejection along the horns, but the amount of time a sand grain contributes to the dune morphodynamics remains unknown. To estimate such a residence time, we analyze sediment particle motions in steady state barchans by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than the convergent sediment fluxes associated with avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchans. Then, for different flow strengths and dune sizes, we find that the mean residence time of sediment particles in barchans is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan morphodynamics. Finally, we initiate a discussion about sediment transport and memory in the presence of bed forms using the advantages of the particle tracking technique.

  17. Autumn Frost, North Polar Sand Dunes

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Autumn in the martian northern hemisphere began around August 1, 1999. Almost as soon as northern fall began, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) started documenting the arrival of autumn frost--a precursor to the cold winter that will arrive in late December 1999. The first features to become covered by frost were the sand dunes that surround the north polar ice cap. The dunes seen here would normally appear very dark--almost black--except when covered by frost. Why the dunes begin to frost sooner than the surrounding surfaces is a mystery: perhaps the dunes contain water vapor that emerges from the sand during the day and condenses again at night. This picture shows dunes near 74.7oN, 61.4oW at a resolution of about 7.3 meters (24 feet) per pixel. The area covered is about 3 km (1.9 mi) across and is illuminated from the upper right. The picture appears to be somewhat fuzzy and grainy because the dunes here are seen through the thin haze of the gathering north polar winter hood (i.e., clouds).

  18. Mars Global Digital Dune Database (MGD3): Global dune distribution and wind pattern observations

    USGS Publications Warehouse

    Hayward, Rosalyn K.; Fenton, Lori; Titus, Timothy N.

    2013-01-01

    The Mars Global Digital Dune Database (MGD3) is complete and now extends from 90°N to 90°S latitude. The recently released south pole (SP) portion (MC-30) of MGD3 adds ∼60,000 km2 of medium to large-size dark dune fields and ∼15,000 km2 of sand deposits and smaller dune fields to the previously released equatorial (EQ, ∼70,000 km2), and north pole (NP, ∼845,000 km2) portions of the database, bringing the global total to ∼975,000 km2. Nearly all NP dunes are part of large sand seas, while the majority of EQ and SP dune fields are individual dune fields located in craters. Despite the differences between Mars and Earth, their dune and dune field morphologies are strikingly similar. Bullseye dune fields, named for their concentric ring pattern, are the exception, possibly owing their distinctive appearance to winds that are unique to the crater environment. Ground-based wind directions are derived from slipface (SF) orientation and dune centroid azimuth (DCA), a measure of the relative location of a dune field inside a crater. SF and DCA often preserve evidence of different wind directions, suggesting the importance of local, topographically influenced winds. In general however, ground-based wind directions are broadly consistent with expected global patterns, such as polar easterlies. Intriguingly, between 40°S and 80°S latitude both SF and DCA preserve their strongest, though different, dominant wind direction, with transport toward the west and east for SF-derived winds and toward the north and west for DCA-derived winds.

  19. Mars Global Digital Dune Database (MGD3): Global dune distribution and wind pattern observations

    NASA Astrophysics Data System (ADS)

    Hayward, R. K.; Fenton, L. K.; Titus, T. N.

    2014-02-01

    The Mars Global Digital Dune Database (MGD3) is complete and now extends from 90°N to 90°S latitude. The recently released south pole (SP) portion (MC-30) of MGD3 adds ˜60,000 km2 of medium to large-size dark dune fields and ˜15,000 km2 of sand deposits and smaller dune fields to the previously released equatorial (EQ, ˜70,000 km2), and north pole (NP, ˜845,000 km2) portions of the database, bringing the global total to ˜975,000 km2. Nearly all NP dunes are part of large sand seas, while the majority of EQ and SP dune fields are individual dune fields located in craters. Despite the differences between Mars and Earth, their dune and dune field morphologies are strikingly similar. Bullseye dune fields, named for their concentric ring pattern, are the exception, possibly owing their distinctive appearance to winds that are unique to the crater environment. Ground-based wind directions are derived from slipface (SF) orientation and dune centroid azimuth (DCA), a measure of the relative location of a dune field inside a crater. SF and DCA often preserve evidence of different wind directions, suggesting the importance of local, topographically influenced winds. In general however, ground-based wind directions are broadly consistent with expected global patterns, such as polar easterlies. Intriguingly, between 40°S and 80°S latitude both SF and DCA preserve their strongest, though different, dominant wind direction, with transport toward the west and east for SF-derived winds and toward the north and west for DCA-derived winds.

  20. A bibliography of dunes: Earth, Mars, and Venus

    NASA Technical Reports Server (NTRS)

    Lancaster, N.

    1988-01-01

    Dunes are important depositional landforms and sedimentary environments on Earth and Mars, and may be important on Venus. The similarity of dune forms on Earth and Mars, together with the dynamic similarity of aeolian processes on the terrestrial planets indicates that it is appropriate to interpret dune forms and processes on Mars and Venus by using analog studies. However, the literature on dune studies is large and scattered. The aim of this bibliography is to assist investigators by providing a literature resource on techniques which have proved successful in elucidating dune characteristics and processes on Earth, Mars, and Venus. This bibliography documents the many investigations of dunes undertaken in the last century. It concentrates on studies of inland dunes in both hot and cold desert regions on Earth and includes investigations of coastal dunes only if they discuss matters of general significance for dune sediments, processes, or morphology.

  1. A method for building 3D models of barchan dunes

    NASA Astrophysics Data System (ADS)

    Nai, Yang; Li-lan, Su; Lin, Wan; Jie, Yang; Shi-yi, Chen; Wei-lu, Hu

    2016-01-01

    The distributions of barchan dunes are usually represented by digital terrain models (DTMs) overlaid with digital orthophoto maps. Given that most regions with barchan dues have low relief, a 3D map obtained from a DTM may ineffectively show the stereoscopic shape of each dune. The method of building 3D models of barchan dunes using existing modeling software seldom considers the geographical environment. As a result, barchan dune models are often inconsistent with actual DTMs and incompletely express the morphological characteristics of dunes. Manual construction of barchan dune models is also costly and time consuming. Considering these problems, the morphological characteristics of barchan dunes and the mathematical relationships between the morphological parameters of the dunes, such as length, height, and width, are analyzed in this study. The methods of extracting the morphological feature points of barchan dunes, calculating their morphological parameters and building dune outlines and skeleton lines based on the medial axes, are also presented. The dune outlines, skeleton lines, and part of the medial axes of dunes are used to construct a constrained triangulated irregular network. C# and ArcEngine are employed to build 3D models of barchan dunes automatically. Experimental results of a study conducted in Tengger Desert show that the method can be used to approximate the morphological characteristics of barchan dunes and is less time consuming than manual methods.

  2. Modeling emergent large-scale structures of barchan dune fields

    NASA Astrophysics Data System (ADS)

    Worman, S. L.; Murray, A. B.; Littlewood, R.; Andreotti, B.; Claudin, P.

    2013-10-01

    In nature, barchan dunes typically exist as members of larger fields that display striking, enigmatic structures that cannot be readily explained by examining the dynamics at the scale of single dunes, or by appealing to patterns in external forcing. To explore the possibility that observed structures emerge spontaneously as a collective result of many dunes interacting with each other, we built a numerical model that treats barchans as discrete entities that interact with one another according to simplified rules derived from theoretical and numerical work and from field observations: (1) Dunes exchange sand through the fluxes that leak from the downwind side of each dune and are captured on their upstream sides; (2) when dunes become sufficiently large, small dunes are born on their downwind sides (`calving'); and (3) when dunes collide directly enough, they merge. Results show that these relatively simple interactions provide potential explanations for a range of field-scale phenomena including isolated patches of dunes and heterogeneous arrangements of similarly sized dunes in denser fields. The results also suggest that (1) dune field characteristics depend on the sand flux fed into the upwind boundary, although (2) moving downwind, the system approaches a common attracting state in which the memory of the upwind conditions vanishes. This work supports the hypothesis that calving exerts a first-order control on field-scale phenomena; it prevents individual dunes from growing without bound, as single-dune analyses suggest, and allows the formation of roughly realistic, persistent dune field patterns.

  3. Modeling emergent large-scale structures of barchan dune fields

    NASA Astrophysics Data System (ADS)

    Worman, S. L.; Murray, A.; Littlewood, R. C.; Andreotti, B.; Claudin, P.

    2013-12-01

    In nature, barchan dunes typically exist as members of larger fields that display striking, enigmatic structures that cannot be readily explained by examining the dynamics at the scale of single dunes, or by appealing to patterns in external forcing. To explore the possibility that observed structures emerge spontaneously as a collective result of many dunes interacting with each other, we built a numerical model that treats barchans as discrete entities that interact with one another according to simplified rules derived from theoretical and numerical work, and from field observations: Dunes exchange sand through the fluxes that leak from the downwind side of each dune and are captured on their upstream sides; when dunes become sufficiently large, small dunes are born on their downwind sides ('calving'); and when dunes collide directly enough, they merge. Results show that these relatively simple interactions provide potential explanations for a range of field-scale phenomena including isolated patches of dunes and heterogeneous arrangements of similarly sized dunes in denser fields. The results also suggest that (1) dune field characteristics depend on the sand flux fed into the upwind boundary, although (2) moving downwind, the system approaches a common attracting state in which the memory of the upwind conditions vanishes. This work supports the hypothesis that calving exerts a first order control on field-scale phenomena; it prevents individual dunes from growing without bound, as single-dune analyses suggest, and allows the formation of roughly realistic, persistent dune field patterns.

  4. Global map of Titan's dune fields

    NASA Astrophysics Data System (ADS)

    Le Corre, L.; Le Mouélic, S.; Sotin, C.; Barnes, J. W.; Brown, R. H.; Baines, K.; Buratti, B.; Clark, R.; Nicholson, P.

    2008-09-01

    Introduction Methane is the second major constituent of Titan's atmosphere; but it should be totally removed at least in ten million years by photochemistry in the stratosphere and condensation in the troposphere [1]. The first process produces hydrocarbons which form the haze and can condensate onto the surface. The second process causes methane rains on the surface, which carve channels networks. The loss of methane is possibly balanced by outgassing during cryovolcanic event [2]. But hydrocarbons grains deposited onto the surface cannot be recycled. They may be stored in the dunes [3], which were first seen by SAR (Synthetic Aperture Radar) [4]. We focus our study on the mapping of the dune fields in order to determine their global distribution. The aim is to constrain the amount of hydrocarbon material existing in the dunes, and to relate it to the duration of the methane cycle. Data from the Visual and Infrared Mapping Spectrometer (VIMS) and RADAR instruments onboard Cassini spacecraft can be used to map Titan's surface. Infrared images, which are mainly sensitive to composition and grain size, are very complementary to the microwave measurements which depend mainly on roughness and topography. We used spectral criteria after empirical correction of aerosols to map the distribution of heterogeneous units on Titan [5]. These units are compared with SAR images in overlapping regions. Titan's surface mosaics with VIMS VIMS probes the first ten of microns of the ground in seven narrow atmospheric windows in the 0.88 to 5.11 μm wavelength range. We built infrared mosaics with cubes sorted by spatial resolution, by keeping cubes corresponding to favorable observing conditions (incidence, emergence, phase and time exposure). Band ratios were computed and combined in false color composite images (red as 1.59/1.27-μm, green as 2.03/1.27-μm and blue as 1.27/1.08-μm). Band ratios are useful to minimize the effect of illuminating conditions and albedo variations [6

  5. Reusable Energy and Power Sources: Rechargeable Batteries

    ERIC Educational Resources Information Center

    Hsiung, Steve C.; Ritz, John M.

    2007-01-01

    Rechargeable batteries are very popular within consumer electronics. If one uses a cell phone or portable electric tool, she/he understands the need to have a reliable product and the need to remember to use the recharging systems that follow a cycle of charge/discharge. Rechargeable batteries are being called "green" energy sources. They are a…

  6. Choosing appropriate techniques for quantifying groundwater recharge

    USGS Publications Warehouse

    Scanlon, B.R.; Healy, R.W.; Cook, P.G.

    2002-01-01

    Various techniques are available to quantify recharge; however, choosing appropriate techniques is often difficult. Important considerations in choosing a technique include space/time scales, range, and reliability of recharge estimates based on different techniques; other factors may limit the application of particular techniques. The goal of the recharge study is important because it may dictate the required space/time scales of the recharge estimates. Typical study goals include water-resource evaluation, which requires information on recharge over large spatial scales and on decadal time scales; and evaluation of aquifer vulnerability to contamination, which requires detailed information on spatial variability and preferential flow. The range of recharge rates that can be estimated using different approaches should be matched to expected recharge rates at a site. The reliability of recharge estimates using different techniques is variable. Techniques based on surface-water and unsaturated-zone data provide estimates of potential recharge, whereas those based on groundwater data generally provide estimates of actual recharge. Uncertainties in each approach to estimating recharge underscore the need for application of multiple techniques to increase reliability of recharge estimates.

  7. Rechargeable nickel-zinc batteries

    NASA Technical Reports Server (NTRS)

    Soltis, D. G.

    1977-01-01

    Device proves superiority in having two and one half to three times the energy content of popular lead-zinc or nickel-cadmium batteries. Application to electric utility vehicles improved acceleration rate and nearly doubled driving range between rechargings. Unit contributes substantially toward realization of practical urban electrical automobiles.

  8. The role of dune interactions and wind fluctuations in the selection of dune sizes within barchan fields

    NASA Astrophysics Data System (ADS)

    Duran Vinent, O.; Parteli, E. J.; Herrmann, H. J.

    2012-12-01

    Sand dunes dominate desert morphology. They naturally emerge under strong winds and sufficient sand supply from the interaction between sand transport, topography and hydrodynamics. The fact that dunes are mobile landforms gives a dynamical character to desert geomorphology with potential implications for the surrounding ecosystems. As dune mobility is closely related to dune morphology, in particular its size, the study of the long-term evolution of desert areas requires a better understanding of (1) the factors behind dune size selection and (2) the multi-scale nature of dune morphology. Recently it has been shown that dune size is bounded both at small and large scales by sand transport and hydrodynamics, respectively. The smallest dune size is limited to several meters in length by the existence of the so called "saturation length", i.e. the characteristic length of transport transients. The maximum dune size, in the order of hundreds of meters, is in turn limited by the stabilizing effect of the upper limit of the atmospheric boundary layer. Dune dynamics at both scales is also qualitatively different as elementary dunes emerge from a linear instability, and are thus ubiquitous, while giant dunes seem to result from the coalescence of smaller ones. In consequence, a typical dune field should consist in a roughly continuous hierarchy of dune sizes, with many elementary dunes and very few giant dunes. However, in several cases this is not the correct picture as dune sizes are quite uniform and seems to cluster around an intermediate value that is well above the minimum but much smaller than the maximum one. This points to an alternative selection mechanism different from the simple dune merging. Here, we argue that the combination of dune collisions and wind fluctuations, at least within barchan fields, is able to stop the continuous merging process and select a characteristic dune size in function of local conditions. To that end we use a morphodynamic dune

  9. Relation of hydrologic processes to groundwater and surface-water levels and flow directions in a dune-beach complex at Indiana Dunes National Lakeshore and Beverly Shores, Indiana

    USGS Publications Warehouse

    Buszka, Paul M.; Cohen, David A.; Lampe, David C.; Pavlovic, Noel B.

    2011-01-01

    The potential for high groundwater levels to cause wet basements (groundwater flooding) is of concern to residents of communities in northwestern Indiana. Changes in recharge from precipitation increases during 2006-9, water-level changes from restoration of nearby wetlands in the Great Marsh in 1998-2002, and changes in recharge due to the end of groundwater withdrawals for water supply since 2005 in a community at Beverly Shores, Ind., were suspected as factors in increased groundwater levels in an unconfined surficial aquifer beneath nearby parts of a dune-beach complex. Results of this study indicate that increased recharge from precipitation and snowmelt was the principal cause of raised water levels in the dune-beach complex from 2006 to 2009. Annual precipitation totals in 2006-9 ranged from 43.88 to 55.75 inches per year (in/yr) and were substantially greater than the median 1952-2009 precipitation of 36.35 in/yr. Recharge to groundwater from precipitation in 2006-9 ranged from 13.5 to 22 in/yr; it was higher than the typical 11 in/yr because of large precipitation events and precipitation amounts received during non-growing-season months. An estimated increase in net recharge from reduced groundwater use in Beverly Shores since 2005 ranged from 1.6 in/yr in 2006 to 1.9 in/yr in 2009. Surface-water levels in the wetland were as much as about 1.1 feet higher in 2007-9 (after the 1998-2002 wetland restoration) than during seasonally wet periods in 1979-89. Similar surface-water levels and ponded water were likely during winter and spring wet periods before and after wetland restoration. High water levels similar to those in 2009 were measured elsewhere in the dune-beach complex near a natural wetland during the spring months in 1991 and 1993 after receipt of near record precipitation. Recharge from similarly high precipitation amounts in 2008-9 was also a likely cause of high groundwater levels in other parts of the dune-beach complex, such as at Beverly

  10. Hierarchical organization of a Sardinian sand dune plant community.

    PubMed

    Cusseddu, Valentina; Ceccherelli, Giulia; Bertness, Mark

    2016-01-01

    Coastal sand dunes have attracted the attention of plant ecologists for over a century, but they have largely relied on correlations to explain dune plant community organization. We examined long-standing hypotheses experimentally that sand binding, inter-specific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removing foundation species from the fore-, middle- and back-dune habitats over three years led to erosion and habitat loss on the fore-dune and limited plant recovery that increased with dune elevation. Reciprocal species removals in all zones suggested that inter-specific competition is common, but that dominance is transient, particularly due to sand burial disturbance in the middle-dune. A fully factorial 2-year manipulation of water, nutrient availability and substrate stability revealed no significant proximate response to these physical factors in any dune zone. In the fore- and middle-dune, plant seeds are trapped under adult plants during seed germination, and seedling survivorship and growth generally increase with dune height in spite of increased herbivory in the back-dune. Sand and seed erosion leads to limited seed recruitment on the fore-dune while high summer temperatures and preemption of space lead to competitive dominance of woody plants in the back-dune. Our results suggest that Sardinian sand dune plant communities are organized hierarchically, structured by sand binding foundation species on the fore-dune, sand burial in the middle-dune and increasingly successful seedling recruitment, growth and competitive dominance in the back-dune. PMID:27478701

  11. Hierarchical organization of a Sardinian sand dune plant community

    PubMed Central

    Ceccherelli, Giulia; Bertness, Mark

    2016-01-01

    Coastal sand dunes have attracted the attention of plant ecologists for over a century, but they have largely relied on correlations to explain dune plant community organization. We examined long-standing hypotheses experimentally that sand binding, inter-specific interactions, abiotic factors and seedling recruitment are drivers of sand dune plant community structure in Sardinia, Italy. Removing foundation species from the fore-, middle- and back-dune habitats over three years led to erosion and habitat loss on the fore-dune and limited plant recovery that increased with dune elevation. Reciprocal species removals in all zones suggested that inter-specific competition is common, but that dominance is transient, particularly due to sand burial disturbance in the middle-dune. A fully factorial 2-year manipulation of water, nutrient availability and substrate stability revealed no significant proximate response to these physical factors in any dune zone. In the fore- and middle-dune, plant seeds are trapped under adult plants during seed germination, and seedling survivorship and growth generally increase with dune height in spite of increased herbivory in the back-dune. Sand and seed erosion leads to limited seed recruitment on the fore-dune while high summer temperatures and preemption of space lead to competitive dominance of woody plants in the back-dune. Our results suggest that Sardinian sand dune plant communities are organized hierarchically, structured by sand binding foundation species on the fore-dune, sand burial in the middle-dune and increasingly successful seedling recruitment, growth and competitive dominance in the back-dune. PMID:27478701

  12. Ecology of Pacific Northwest coastal sand dunes: a community profile

    SciTech Connect

    Wiedemann, A.M.

    1984-03-01

    Sand dunes occur in 33 localities along the 950 km of North American Pacific coast between the Straits of Juan de Fuca (49/sup 0/N) and Cape Mendocino (40/sup 0/). The dune landscape is a mosaic of dune forms: transverse ridge, oblique dune, retention ridge, foredune, parabola dune, sand hummock, blowout, sand plain, deflation plain, dune ridge, swale, remnant forest, and ponds and lakes. These forms are the basic morphological units making up the four dune systems: parallel ridge, parabola dune, transverse ridge, and bay dune. Vegetation is well-developed on stabilized dunes. Of the 21 plant communities identified, nine are herbaceous, five are shrub, and seven are forest. A wide variety of vertebrate animals occur in seven distinct habitats: open dunes, grassland and meadow, shrub thicket, forest, marsh, riparian, and lakes and ponds. Urban development, increased rate of stabilization due to the introduction of European beachgrass (Ammophila arenaria (L.) Link), and massive disturbance resulting from heavy off-road vehicle traffic are the greatest threats to the long-term survival and stability of a number of sand dune habitats. Two animals and three plants dependent on dune habitats are listed as rare, threatened, or endangered. 93 references, 52 figures, 13 tables.

  13. Big, Dark Dunes Northeast of Syrtis Major

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Big sand dunes! Mars is home to some very large, windblown dunes. The dunes shown here rise to almost 100 meters (275 feet) at their crests. Unlike dunes on Earth, the larger dunes of Mars are composed of dark, rather than light grains. This is probably related to the composition of the sand, since different materials will have different brightnesses. For example, beaches on the island of Oahu in Hawaii are light colored because they consist of ground-up particles of seashells, while beaches in the southern shores of the island of Hawaii (the 'Big Island' in the Hawaiian island chain) are dark because they consist of sand derived from dark lava rock.

    The dunes in this picture taken by the Mars Orbiter Camera (MOC) are located on the floor of an old, 72 km-(45 mi)-diameter crater located northeast of Syrtis Major. The sand is being blown from the upper right toward the lower left. The surface that the dunes have been travelling across is pitted and cratered. The substrate is also hard and bright--i.e., it is composed of a material of different composition than the sand in the dunes. The dark streaks on the dune surfaces area puzzle...at first glance one might conclude they are the result of holiday visitors with off-road vehicles. However, the streaks more likely result from passing dust devils or wind gusts that disturb the sand surface just enough to leave a streak. The image shown here covers an area approximately 2.6 km (1.6 mi) wide, and is illuminated from the lower right.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  14. A Mystery Unraveled: Booming Sand Dunes

    NASA Astrophysics Data System (ADS)

    Vriend, N. M.; Hunt, M. L.; Clayton, R. W.

    2007-12-01

    "Booming" sand dunes have intrigued travelers and scientist for centuries. These dunes emit a persistent, low-frequency sound during a slumping event or a natural avalanche on the leeward face of the dune. The sound can last for several minutes and be audible from miles away. The resulting acoustic emission is characterized by a dominant audible frequency (70 - 105 Hz) and several higher harmonics. In the work of Vriend et al. (2007), seismic refraction experiments proved the existence of a multi-layer internal structure in the dune that acts as a waveguide for the acoustic energy. Constructive interference between the reflecting waves enables the amplification and sets the frequency of each boom. A relationship was established that correctly predicts the measured frequency in terms of the thickness (~ 2.0 m) and the seismic body wave velocity of the loose, dry surficial layer (~ 240 m/s) and the substrate half-space (~ 350 m/s). The current work highlights additional measurements and simulations supporting the waveguide model for booming sand dunes. Experiments with ground penetrating radar continuously display the subsurface features which confirm the layered subsurface structure within the dune. Cross-correlation analysis shows that the booming sound propagates at speeds close to the measured body wave velocity. Squeaking sounds, which are generated during the onset of the slide and precede the sustained booming emission, have been found to have distinctly different characteristics. These short bursts of sound are emitted at a lower frequency (50 - 65 Hz) and propagate at a lower propagation speed (125 m/s) than the booming emission. The acoustic and elastic wave propagation in the dune has been simulated with a finite difference code. The interaction between the air and the ground produces a coupling wave along the surface. The reflections in the surficial layer propagate in a dispersive band at a group velocity that is slower than the phase velocity of the

  15. Dark Streaks Over-riding Inactive Dunes

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Not all sand dunes on Mars are active in the modern martian environment. This example from the Lycus Sulci (Olympus Mons'aureole') region shows a case where small windblown dunes at the base of a slope have been over-ridden by more recent dark streaks (arrows). The dark streaks are most likely caused by what geologists call mass wasting or mass movement (landslides and avalanches are mass movements). Dark slope streaks such as these are common in dustier regions of Mars, and they appear to result from movement of extremely dry dust or sand in an almost fluidlike manner down a slope. This movement disrupts the bright dust coating on the surface and thus appears darker than the surrounding terrain.

    In this case, the dark slope streaks have moved up and over the dunes at the bottom of the slope, indicating that the process that moves sediment down the slope is more active (that is, it has occurred more recently and hence is more likely to occur) in the modern environment than is the movement of dunes and ripples at this location on Mars. The dunes, in fact, are probably mantled by dust. This October 1997 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) picture is illuminated from the left and located near 31.6oN, 134.0oW.

  16. Dunes on Titan observed by Cassini Radar

    USGS Publications Warehouse

    Radebaugh, J.; Lorenz, R.D.; Lunine, J.I.; Wall, S.D.; Boubin, G.; Reffet, E.; Kirk, R.L.; Lopes, R.M.; Stofan, E.R.; Soderblom, L.; Allison, M.; Janssen, M.; Paillou, P.; Callahan, P.; Spencer, C.; The Cassini Radar Team

    2008-01-01

    Thousands of longitudinal dunes have recently been discovered by the Titan Radar Mapper on the surface of Titan. These are found mainly within ??30?? of the equator in optically-, near-infrared-, and radar-dark regions, indicating a strong proportion of organics, and cover well over 5% of Titan's surface. Their longitudinal duneform, interactions with topography, and correlation with other aeolian forms indicate a single, dominant wind direction aligned with the dune axis plus lesser, off-axis or seasonally alternating winds. Global compilations of dune orientations reveal the mean wind direction is dominantly eastwards, with regional and local variations where winds are diverted around topographically high features, such as mountain blocks or broad landforms. Global winds may carry sediments from high latitude regions to equatorial regions, where relatively drier conditions prevail, and the particles are reworked into dunes, perhaps on timescales of thousands to tens of thousands of years. On Titan, adequate sediment supply, sufficient wind, and the absence of sediment carriage and trapping by fluids are the dominant factors in the presence of dunes. ?? 2007 Elsevier Inc. All rights reserved.

  17. Identifying Groundwater Recharge in Arid Regions

    NASA Astrophysics Data System (ADS)

    Thomas, B. F.; Famiglietti, J. S.

    2015-12-01

    Recharge epodicity in arid regions provides a method to estimate annual groundwater recharge given a relationship expressed as the recharge to precipitation ratio. Traditionally, in-situ observations are required to identify aquifer recharge events, while more advanced approaches such as the water-table fluctuation method or the episodic master recession method are necessary to delineate the recharge event. Our study uses the Gravity Recovery and Climate Experiment (GRACE) observations to estimate monthly changes in groundwater storage which are attributed to the combination of groundwater abstraction and episodic recharge in the arid southwestern United States. Our results illustrate the ability of remote sensing technologies to identify episodic groundwater recharge in arid regions which can be used within sustainable groundwater management frameworks to effectively manage groundwater resources.

  18. Layers, Landslides, and Sand Dunes

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 27 October 2003

    This image shows the northern rim of one of the Valles Marineris canyons. Careful inspection shows many interesting features here. Note that the spurs and gullies in the canyon wall disappear some distance below the top of the canyon wall, indicating the presence of some smooth material here that weathers differently from the underlying rocks. On the floor of the canyon, there are remains from a landslide that came hurtling down the canyon wall between two spurs. Riding over the topography of the canyon floor are many large sand dunes, migrating generally from the lower right to upper left.

    Image information: VIS instrument. Latitude -14.1, Longitude 306.7 East (53.3 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  19. Inconsistencies in coastal dune genesis and development in the western Mediterranean Cabopino Dune system, southern Spain

    NASA Astrophysics Data System (ADS)

    Guisado-Pintado, Emilia; Malvárez, Gonzalo; Jackson, Derek; Navas, Fatima

    2016-04-01

    It is generally agreed that a falling sea level regime is required in the long term to establish dunes as distinctive landform features along a coast. Sedimentary (supply) bodies from fluvial, glacial sources or marine platform processes also need to be in place. In most Atlantic-facing coastal dune systems the current morpho-sedimentary structures are usually associated with the period between 18K BP and present when both glacial and riverine sediments emplaced sediments within the active zone of present sea level to help form beaches and dunes. Mediterranean coastal dunes fronted by steep continental shelves, such as in the western Mediterranean coast of southern Spain are, however, not associated with glacial deposits and thus are only present in association with river mouths and/or coastal lagoons. Their development is attributed to very recent sediment supply, which, combined with other forcing factors such as wind and waves, several orders of magnitude below those of north Atlantic systems, explains their limited extent. Some coastal dune fields however, do not seem to respond to this general pattern because of their scale and, more importantly, their origin linked possibly to marine platform processes rather than riverine or lagoonal development. Here, we examine the Cabopino dune system in southern Spain offering a conceptual model of their genesis and development as an "Atlantic" dune system within a Mediterranean setting. This is demonstrated by their scale (the largest in the Spanish Mediterranean) and their morphodynamic link to nearshore and platform processes in the last 18,000 years.

  20. Indirect Interaction of Barchan Dunes by Inter-dune Sand Flow

    NASA Astrophysics Data System (ADS)

    Katsuki, A.

    2008-12-01

    The most impressive sand structure seen in desert is crescent sand dunes called barchan. Barchan dune has two horns and sand flow release from the tips of them. Seeing aerial photos of deserts, we recognize that barchan dunes tend to align in a characteristic pattern, that is, the horn of one barchan pointing to the center of leeward barchan. As a result, barchans form a convoy with a geese-flying like triangular pattern or align in an slanted line. The pattern has been observed also for barchans found on Mars, and thus there should be some universal mechanism underlying it. Also barchan dunes are highly mobile; human-made structures such as roads or pipelines in their way are sometimes buried in sand. It has been a long-standing problem how we can control this unstoppable march of barchan dunes. There are some interaction such as collision and inter-dune sand flow in marching barchan dunes. Here we investigated interaction dynamics of barchan dunes focusing on the effect of indirect interactions mediated by an inter-dune sand flow using computer simulations. We showed that a barchan is driven laterally by a sand stream to right below the point source of sand.Principal mechanism of this motion is a fast mixing of sand in a barchan that keeps the symmetric shape unchanged.We thereby propose a possibility of controlling the motion of a barchan using a sand stream. In addition,the very same mechanism produces an indirect interaction between barchans mediated by sand stream and can induce the self-organization of the geese-flying like pattern.

  1. Dynamics of a cliff top dune

    NASA Astrophysics Data System (ADS)

    Rasmussen, K. R.

    2012-12-01

    Morphological changes during more than 100 years have been investigated for a cliff-top dune complex at Rubjerg at the Danish North Sea coast. Here the lower 50 m of the cliff front is composed of Pleistocene steeply inclined floes of silt and clay with coarse sand in between which gives it a saw-tooth appearance. On top of this the dunes are found for several kilometres along the coastline. Due to erosion by the North Sea the cliff has retreated about 120 m between approximately 1880 and 1970 as indicated from two national surveys, and recent GPS-surveys indicate that erosion is continuing at a similar rate. Nevertheless the cliff top dune complex has survived, but its morphology has undergone some changed. The old maps indicate that around 1880 the dune complex was composed of several up to about 20 m high dunes streamlined in the East-West direction which is parallel to the prevailing wind direction. When protective planting started during the first half of the 20th Century the cliff top dunes gradually merged together forming a narrow, tall ridge parallel to the shore line with the highest part reaching about 90 m near 1970. In 1993 the highest points along the ridge was almost 95 m high, but then the protective planting was considerably reduced and recent annual GPS-surveys indicate that the dunes respond quickly to this by changing their morphology towards the original appearance. It is remarkable that despite the mass wasting caused by the constant erosion of the cliff front the dunes have remained more or less intact. Theoretical studies of hill flow indicate given the proper geometry of the cliff then suspension of even coarse grains can be a very effective agent for carrying sand from the exposed parts of the cliff front to and beyond the cliff-top. Mostly the sand grains are deposited within some hundred meters downwind of the cliff dune while silt is often carried more than 10 km inland. Field observations indicate that where the dislodged floes and

  2. The Signature of Life in Stabilized Dune Topography

    NASA Astrophysics Data System (ADS)

    Barchyn, T. E.; Hugenholtz, C.

    2012-12-01

    Life dramatically affects aeolian dunes on Earth by modifying dune morphology and immobilizing sediment. Complete immobilization (stabilization) occurs when vegetation growth shelters the surface and eliminates sediment transport (and the capacity of the dune to clear vegetation). In unidirectional dune forms stabilization is usually preceded by a period of transition dominated by pronounced morphological change (e.g., parabolic dunes). Here, we hypothesize that stabilized topography holds previously unidentified clues detailing the kinematics and behavior of vegetation during stabilization (a 'signature'). During stabilization dune ridges advance downwind and 'bulldoze' vegetation in their path. We split dune ridges into a series of wind-parallel 'dune slices' and outline how slipface vegetation could prove to be a 'tipping point' in stabilization for each dune slice. Slipface vegetation sets off a self-reinforcing stabilization feedback, simplifying our treatment and yielding two predictable behaviors: slipfaces either clear vegetation (deposition rate > vegetation deposition tolerance), or succumb to vegetation and become immobilized (deposition rate < vegetation deposition tolerance). We model slipface deposition rates through slipface geometry and show how predictable variations in classical dune forms (i) could be responsible for incipient transformation of barchan to parabolic dunes, (ii) result in a progressive stabilization feedback fundamentally inconsistent with widely used dune activity indices, and (iii) record a quantitative signature of the relative kinematics of sediment flux and vegetation growth in stabilized slipface geometries. To explore the idea in real dune fields, we extract slipface deposition rates through slipface geometry recorded in digital terrain data for three dune fields: (i) Bigstick Sand Hills, SK, Canada, (ii) White Sands, NM, USA, and (iii) Cape Cod, MA, USA. With independent estimates of sediment flux and vegetation deposition

  3. Lateral migration of linear dunes in the Strzelecki Desert, Australia

    USGS Publications Warehouse

    Rubin, D.M.

    1990-01-01

    Preferential accumulation of sand on east-facing flanks indicates that the dunes migrated eastward several metres during the Holocene. Moreover, the west-facing flanks of some dunes have experienced a minimum of tens of metres of erosion. This asymmetric erosion and deposition were caused by dune obliquity and lateral migration that may have begun as early as the Pleistocene. Dunes in the Strzelecki Desert and in the adjacent Simpson Desert display a variety of grossly different internal structures. -from Author

  4. Mars Global Digital Dune Database and initial science results

    NASA Astrophysics Data System (ADS)

    Hayward, Rosalyn K.; Mullins, Kevin F.; Fenton, Lori K.; Hare, Trent M.; Titus, Timothy N.; Bourke, Mary C.; Colaprete, Anthony; Christensen, Philip R.

    2007-11-01

    A new Mars Global Digital Dune Database (MGD3) constructed using Thermal Emission Imaging System (THEMIS) infrared (IR) images provides a comprehensive and quantitative view of the geographic distribution of moderate- to large-size dune fields (area >1 km2) that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of Mars. MGD3 extends from 65°N to 65°S latitude and includes ~550 dune fields, covering ~70,000 km2, with an estimated total volume of ~3,600 km3. This area, when combined with polar dune estimates, suggests moderate- to large-size dune field coverage on Mars may total ~800,000 km2, ~6 times less than the total areal estimate of ~5,000,000 km2 for terrestrial dunes. Where availability and quality of THEMIS visible (VIS) or Mars Orbiter Camera narrow-angle (MOC NA) images allow, we classify dunes and include dune slipface measurements, which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. For dunes located within craters, the azimuth from crater centroid to dune field centroid (referred to as dune centroid azimuth) is calculated and can provide an accurate method for tracking dune migration within smooth-floored craters. These indicators of wind direction are compared to output from a general circulation model (GCM). Dune centroid azimuth values generally correlate to regional wind patterns. Slipface orientations are less well correlated, suggesting that local topographic effects may play a larger role in dune orientation than regional winds.

  5. Mars global digital dune database and initial science results

    USGS Publications Warehouse

    Hayward, R.K.; Mullins, K.F.; Fenton, L.K.; Hare, T.M.; Titus, T.N.; Bourke, M.C.; Colaprete, A.; Christensen, P.R.

    2007-01-01

    A new Mars Global Digital Dune Database (MGD3) constructed using Thermal Emission Imaging System (THEMIS) infrared (IR) images provides a comprehensive and quantitative view of the geographic distribution of moderate- to large-size dune fields (area >1 kM2) that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of Mars. MGD3 extends from 65??N to 65??S latitude and includes ???550 dune fields, covering ???70,000 km2, with an estimated total volume of ???3,600 km3. This area, when combined with polar dune estimates, suggests moderate- to large-size dune field coverage on Mars may total ???800,000 km2, ???6 times less than the total areal estimate of ???5,000,000 km2 for terrestrial dunes. Where availability and quality of THEMIS visible (VIS) or Mars Orbiter Camera. narrow-angle (MOC NA) images allow, we classify dunes and include dune slipface measurements, which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. For dunes located within craters, the azimuth from crater centroid to dune field centroid (referred to as dune centroid azimuth) is calculated and can provide an accurate method for tracking dune migration within smooth-floored craters. These indicators of wind direction are compared to output from a general circulation model (GCM). Dune centroid azimuth values generally correlate to regional wind patterns. Slipface orientations are less well correlated, suggesting that local topographic effects may play a larger role in dune orientation than regional winds. Copyright 2007 by the American Geophysical Union.

  6. Recharge Data for Hawaii Island

    DOE Data Explorer

    Nicole Lautze

    2015-01-01

    Recharge data for Hawaii Island in shapefile format. The data are from the following sources: Whittier, R.B and A.I. El-Kadi. 2014. Human Health and Environmental Risk Ranking of On-Site Sewage Disposal systems for the Hawaiian Islands of Kauai, Molokai, Maui, and Hawaii – Final, Prepared for Hawaii Dept. of Health, Safe Drinking Water Branch by the University of Hawaii, Dept. of Geology and Geophysics. Oki, D. S. 1999. Geohydrology and Numerical Simulation of the Ground-Water Flow System of Kona, Island of Hawaii. U.S. Water-Resources Investigation Report: 99-4073. Oki, D. S. 2002. Reassessment of Ground-water Recharge and Simulated Ground-Water Availability for the Hawi Area of North Kohala, Hawaii. U.S. Geological Survey Water-Resources Investigation report 02-4006.

  7. Research on rechargeable oxygen electrodes

    NASA Technical Reports Server (NTRS)

    Giner, J.; Malachesky, P. A.; Holleck, G.

    1971-01-01

    Studies were carried out on a number of factors which may influence the behavior of the platinum electrocatalyst of oxygen electrodes for use in rechargeable metal-oxygen batteries or hydrogen-oxygen fuel cells. The effects of pretreatments for various potentials and added ionic species, which could be present in such systems, were studied with reguard to: (1) the state of surface oxidation, (2) platinum dissolution, (3) the kinetics of oxygen evolution and reduction (including the role of hydrogen peroxide), and (4) changes in porous electrode structure. These studies were carried out on smooth platinum, platinized platinum, and Teflon-bonded platinum black electrodes in carefully purified electrolyte solutions. The main factors which appear to affect rechargeable oxygen electrode performance and life are: (1) the buildup of a refractory anodic layer on extended cycling, and (2) the dissolution of platinum.

  8. Electrically rechargeable REDOX flow cell

    NASA Technical Reports Server (NTRS)

    Thaller, L. H. (Inventor)

    1976-01-01

    A bulk energy storage system is designed with an electrically rechargeable reduction-oxidation (REDOX) cell divided into two compartments by a membrane, each compartment containing an electrode. An anode fluid is directed through the first compartment at the same time that a cathode fluid is directed through the second compartment. Means are provided for circulating the anode and cathode fluids, and the electrodes are connected to an intermittent or non-continuous electrical source, which when operating, supplies current to a load as well as to the cell to recharge it. Ancillary circuitry is provided for disconnecting the intermittent source from the cell at prescribed times and for circulating the anode and cathode fluids according to desired parameters and conditions.

  9. Rechargeable Aluminum-Ion Batteries

    SciTech Connect

    Paranthaman, Mariappan Parans; Liu, Hansan; Sun, Xiao-Guang; Dai, Sheng; Brown, Gilbert M

    2015-01-01

    This chapter reports on the development of rechargeable aluminum-ion batteries. A possible concept of rechargeable aluminum/aluminum-ion battery based on low-cost, earth-abundant Al anode, ionic liquid EMImCl:AlCl3 (1-ethyl-3-methyl imidazolium chloroaluminate) electrolytes and MnO2 cathode has been proposed. Al anode has been reported to show good reversibility in acid melts. However, due to the problems in demonstrating the reversibility in cathodes, alternate battery cathodes and battery concepts have also been presented. New ionic liquid electrolytes for reversible Al dissolution and deposition are needed in the future for replacing corrosive EMImCl:AlCl3 electrolytes.

  10. Nanomaterials for rechargeable lithium batteries.

    PubMed

    Bruce, Peter G; Scrosati, Bruno; Tarascon, Jean-Marie

    2008-01-01

    Energy storage is more important today than at any time in human history. Future generations of rechargeable lithium batteries are required to power portable electronic devices (cellphones, laptop computers etc.), store electricity from renewable sources, and as a vital component in new hybrid electric vehicles. To achieve the increase in energy and power density essential to meet the future challenges of energy storage, new materials chemistry, and especially new nanomaterials chemistry, is essential. We must find ways of synthesizing new nanomaterials with new properties or combinations of properties, for use as electrodes and electrolytes in lithium batteries. Herein we review some of the recent scientific advances in nanomaterials, and especially in nanostructured materials, for rechargeable lithium-ion batteries. PMID:18338357

  11. Linking restoration ecology with coastal dune restoration

    NASA Astrophysics Data System (ADS)

    Lithgow, D.; Martínez, M. L.; Gallego-Fernández, J. B.; Hesp, P. A.; Flores, P.; Gachuz, S.; Rodríguez-Revelo, N.; Jiménez-Orocio, O.; Mendoza-González, G.; Álvarez-Molina, L. L.

    2013-10-01

    Restoration and preservation of coastal dunes is urgently needed because of the increasingly rapid loss and degradation of these ecosystems because of many human activities. These activities alter natural processes and coastal dynamics, eliminate topographic variability, fragment, degrade or eliminate habitats, reduce diversity and threaten endemic species. The actions of coastal dune restoration that are already taking place span contrasting activities that range from revegetating and stabilizing the mobile substrate, to removing plant cover and increasing substrate mobility. Our goal was to review how the relative progress of the actions of coastal dune restoration has been assessed, according to the ecosystem attributes outlined by the Society of Ecological Restoration: namely, integrity, health and sustainability and that are derived from the ecological theory of succession. We reviewed the peer reviewed literature published since 1988 that is listed in the ISI Web of Science journals as well as additional references, such as key books. We exclusively focused on large coastal dune systems (such as transgressive and parabolic dunefields) located on natural or seminatural coasts. We found 150 articles that included "coastal dune", "restoration" and "revegetation" in areas such as title, keywords and abstract. From these, 67 dealt specifically with coastal dune restoration. Most of the studies were performed in the USA, The Netherlands and South Africa, during the last two decades. Restoration success has been assessed directly and indirectly by measuring one or a few ecosystem variables. Some ecosystem attributes have been monitored more frequently (ecosystem integrity) than others (ecosystem health and sustainability). Finally, it is important to consider that ecological succession is a desirable approach in restoration actions. Natural dynamics and disturbances should be considered as part of the restored system, to improve ecosystem integrity, health and

  12. Survey of rechargeable battery technology

    SciTech Connect

    Not Available

    1993-07-01

    We have reviewed rechargeable battery technology options for a specialized application in unmanned high altitude aircraft. Consideration was given to all rechargeable battery technologies that are available commercially or might be available in the foreseeable future. The LLNL application was found to impose very demanding performance requirements which cannot be met by existing commercially available battery technologies. The most demanding requirement is for high energy density. The technology that comes closest to providing the LLNL requirements is silver-zinc, although the technology exhibits significant shortfalls in energy density, charge rate capability and cyclability. There is no battery technology available ``off-the-shelf` today that can satisfy the LLNL performance requirements. All rechargeable battery technologies with the possibility of approaching/meeting the energy density requirements were reviewed. Vendor interviews were carried out for all relevant technologies. A large number of rechargeable battery systems have been developed over the years, though a much smaller number have achieved commercial success and general availability. The theoretical energy densities for these systems are summarized. It should be noted that a generally useful ``rule-of-thumb`` is that the ratio of packaged to theoretical energy density has proven to be less than 30%, and generally less than 25%. Data developed for this project confirm the usefulness of the general rule. However, data shown for the silver-zinc (AgZn) system show a greater conversion of theoretical to practical energy density than would be expected due to the very large cell sizes considered and the unusually high density of the active materials.

  13. Iron-Air Rechargeable Battery

    NASA Technical Reports Server (NTRS)

    Narayan, Sri R. (Inventor); Prakash, G.K. Surya (Inventor); Kindler, Andrew (Inventor)

    2014-01-01

    Embodiments include an iron-air rechargeable battery having a composite electrode including an iron electrode and a hydrogen electrode integrated therewith. An air electrode is spaced from the iron electrode and an electrolyte is provided in contact with the air electrode and the iron electrodes. Various additives and catalysts are disclosed with respect to the iron electrode, air electrode, and electrolyte for increasing battery efficiency and cycle life.

  14. Charge Characteristics of Rechargeable Batteries

    NASA Astrophysics Data System (ADS)

    Maheswaranathan, Ponn; Kelly, Cormac

    2014-03-01

    Rechargeable batteries play important role in technologies today and they are critical for the future. They are used in many electronic devices and their capabilities need to keep up with the accelerated pace of technology. Efficient energy capture and storage is necessary for the future rechargeable batteries. Charging and discharging characteristics of three popular commercially available re-chargeable batteries (NiCd, NiMH, and Li Ion) are investigated and compared with regular alkaline batteries. Pasco's 850 interface and their voltage & current sensors are used to monitor the current through and the potential difference across the battery. The discharge current and voltage stayed fairly constant until the end, with a slightly larger drop in voltage than current, which is more pronounced in the alkaline batteries. After 25 charge/discharge cycling there is no appreciable loss of charge capacities in the Li Ion battery. Energy densities, cycle characteristics, and memory effects will also be presented. Sponsored by the South Carolina Governor's school for Science and Mathematics under the Summer Program for Research Interns program.

  15. Groundwater recharge and agricultural contamination

    USGS Publications Warehouse

    Böhlke, J.K.

    2002-01-01

    Agriculture has had direct and indirect effects on the rates and compositions of groundwater recharge and aquifer biogeochemistry. Direct effects include dissolution and transport of excess quantities of fertilizers and associated materials and hydrologic alterations related to irrigation and drainage. Some indirect effects include changes in water-rock reactions in soils and aquifers caused by increased concentrations of dissolved oxidants, protons, and major ions. Agrilcultural activities have directly or indirectly affected the concentrations of a large number of inorganic chemicals in groundwater, for example NO3-, N2, Cl, SO42-, H+, P, C, K, Mg, Ca, Sr, Ba, Ra, and As, as well a wide variety of pesticides and other organic compounds. For reactive contaminants like NO3-, a combination of chemical, isotopic, and environmental-tracer analytical approaches might be required to resolve changing inputs from subsequent alterations as causes of concentration gradients in groundwater. Groundwater records derived from multi-component hydrostratigraphic data can be used to quantify recharge rates and residence times of water and dissolved contaminants, document past variations in recharging contaminant loads, and identify natural contaminant-remediation processes. These data indicate that many of the world's surficial aquifers contain transient records of changing agricultural contamination from the last half of the 20th century. The transient agricultural groundwater signal has important implications for long-term trends and spatial heterogeneity in discharge.

  16. Sand availability control on dune shape and orientation

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Narteau, Clement; Rozier, Olivier; Courrech Du Pont, Sylvain

    2015-04-01

    An increasing body of evidence indicates that sand availability does not only control dune type but also the underlying dune growth mechanism. Consequently, the same wind regime can produce different bedform orientations. Here, we use numerical simulations with different conditions of sand availability to predict dune shape and alignment in asymmetric bimodal wind regimes. In zones of abundant sand supply, linear dunes grow in height and propagate selecting the orientation for which the normal to crest components of transport reaches a maximum. In zones of limited sand supply, linear dunes grow by extension in the direction of the resultant sand flux. Considering these two independent dune growth mechanisms, we find good agreement between numerical and analytical models, and estimate the magnitude of wind velocity acceleration up the dune stoss slopes. In the extensional mode of linear dune formation, there is no abrupt change in dune trend when the divergence angle between the two winds crosses 90°. Instead, there are systematic transitions in dune type from linear to barchan for critical values of the divergence angle that depend on the transport ratio. We show how the growth rates of the two dune growth mechanisms may be used to infer the dune field morphology in zones of low sediment availability.

  17. Barchan dunes morphology dynamics under different environmental conditions

    NASA Astrophysics Data System (ADS)

    Dluzewski, M.

    2012-04-01

    The aim of this study was to emphasize significance of diversified dynamics of barchans dune morphology. We analyzed and compared barchans found in two dune fields: Kharga (S Egypt) and Tarfaya-Laâyoune (S-Morocco). These dune fields are characterized by significantly different factors responsible for dunes development e.g. textural and mineralogical composition of dune sand, dune sand moisture, air humidity, inter dune vegetation cover. For each investigated dune filed and study period (2008, 2010, 2012 for Kharga and 2007, 2011, 2012 for Tarfaya-Laâyoune dune fields) detailed shape measurement of 20 simple isolated barchans of different dune sizes was made. The ± 10-2 m horizontal and ± 1,5 10-2m vertical accuracy was obtained (1 measuring point per 1m2 on average).In order to compare barchan dunes morphology and to determine depositional and erosional patterns, the 3D models were created. For better understanding of this processes, sand bulk density of barchan surface was measured (1 measuring point per 2m2 on average). The velocity of dunes in relation to dune shape was also analyzed. The results show that the relationship between typically correlated parameters change during movement of the barchans. Most values change by a few percent per year (slip face height, dune base area and dune volume) or by a dozen or so percent per year (windward side length, horns length and width). We obtain good linear relationship (with 0,05 significant level) between slip face height and the dune base area (0,77 < R2 < 0,83), dune volume (0,66 < R2 < 0,72), windward side length (0,58 < R2 < 0,87), horns length (0,71 < R2 < 0,90) or horns width (0,79 < R2 < 0,93). The linear relationship between displacement rate and the morphological parameters is not strong (0,54< R2 < 0,81) for Kharga dune field and (0,41< R2 < 0,66) for Tarfaya-Laâyoune dune field. We noted also good linear relationship between displacement rate and the angle of span of the horns (R2=0,73 on Tarfaya

  18. Exploring inner structure of Titan's dunes from Cassini Radar observations

    NASA Astrophysics Data System (ADS)

    Sharma, P.; Heggy, E.; Farr, T. G.

    2013-12-01

    Linear dunes discovered in the equatorial regions of Titan by the Cassini-Huygens mission are morphologically very similar to many terrestrial linear dune fields. These features have been compared with terrestrial longitudinal dune fields like the ones in Namib desert in western Africa. This comparison is based on the overall parallel orientation of Titan's dunes to the predominant wind direction on Titan, their superposition on other geomorphological features and the way they wrap around topographic obstacles. Studying the internal layering of dunes has strong implications in understanding the hypothesis for their origin and evolution. In Titan's case, although the morphology of the dunes has been studied from Cassini Synthetic Aperture Radar (SAR) images, it has not been possible to investigate their internal structure in detail as of yet. Since no radar sounding data is available for studying Titan's subsurface yet, we have developed another technique to examine the inner layering of the dunes. In this study, we utilize multiple complementary radar datasets, including radar imaging data for Titan's and Earth's dunes and Ground Penetrating Radar (GPR)/radar sounding data for terrestrial dunes. Based on dielectric mixing models, we suggest that the Cassini Ku-band microwaves should be able to penetrate up to ~ 3 m through Titan's dunes, indicating that the returned radar backscatter signal would include contributions from both surface and shallow subsurface echoes. This implies that the shallow subsurface properties can be retrieved from the observed radar backscatter (σ0). In our analysis, the variation of the radar backscatter as a function of dune height is used to provide an insight into the layering in Titan's dunes. We compare the variation of radar backscatter with elevation over individual dunes on Titan and analogous terrestrial dunes in three sites (Great Sand Sea, Siwa dunes and Qattaniya dunes) in the Egyptian Sahara. We observe a strong, positive

  19. Experimental measurement of diffusive extinction depth and soil moisture gradients in dune sand of Western Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Mughal, I.; Jadoon, K. Z.; Mai, P. M.; Al-Mashharawi, S.; Missimer, T. M.

    2012-12-01

    In arid lands, a major contribution to water loss is by soil water evaporation. Desert sand dunes in arid regions are devoid of runoff and have high rates of infiltration and water is commonly stored within them because of the low hydraulic conductivity soils within the underlying desert pavement. In such cases, moisture is confined in the sand dune below a depth, termed as the "extinction depth", where it is protected from evaporation during the long dry periods. The stored moisture below the extinction depth can be utilized to support desert agriculture and the subsurface areas below this depth can serve as potential sites for storage of surface runoff or treated waste water by artificial recharge. In this study, field experiments were conducted in Western Saudi Arabia to monitor the soil moisture gradients and determine the diffusive extinction depth of dune sand. A barrel with a diameter 150 cm and a height of 150 cm was installed underground in the field and was filled with dune sand. The sand was saturated with water and was exposed to natural conditions (evaporation and precipitation) for thirty days. The decline of the water level in the sand column was continuously recorded by using transducers and sensors installed at different depths to monitor the temporal variation of temperature and moisture content within the sand. The moisture content gradient showed a gradual decline during measurement. The effect of the diurnal variation of temperature was observed by the sensors installed in the upper 75 cm and was negligible at greater depths. The water level decline stabilized after twenty days and the extinction depth was established at 85 cm. In the field, a similar extinction depth was observed in the region where sand dunes overlay an impervious basement.

  20. Variation of bee communities on a sand dune complex in the Great Basin: Implications for sand dune conservation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sand dunes across the Mojave and Great Basin Deserts house rich bee communities. The pollination services these bees provide can be vital in maintaining the diverse, and often endemic, dune flora. These dune environments, however, are threatened by intense off-highway vehicle (OHV) use. Conservati...

  1. Infiltration in layered loessial deposits: Revised numerical simulations and recharge assessment

    NASA Astrophysics Data System (ADS)

    Dafny, Elad; Šimůnek, Jirka

    2016-07-01

    The objective of this study is to assess recharge rates and their timing under layered loessial deposits at the edge of arid zones. Particularly, this study is focused on the case of the coastal plain of Israel and Gaza. First, results of a large-scale field infiltration test were used to calibrate the van Genuchten parameters of hydraulic properties of the loessial sediments using HYDRUS (2D/3D). Second, optimized soil hydraulic parameters were used by HYDRUS-1D to simulate the water balance of the sandy-loess sediments during a 25-year period (1990-2015) for three environmental conditions: bare soil, and soil with both sparse and dense natural vegetation. The best inverse parameter optimization run fitted the infiltration test data with the RMSE of 0.27 d (with respect to a moisture front arrival) and R2 of 96%. The calibrated model indicates that hydraulic conductivities of the two soil horizons, namely sandy loam and sandy clay loam, are 81 cm/d and 17.5 cm/d, respectively. These values are significantly lower than those previously reported, based on numerical simulations, for the same site. HYDRUS-1D simulation of natural recharge under bare soil resulted in recharge estimates (to the aquifer) in the range of 21-93 mm/yr, with an average recharge of 63 mm/yr. Annual precipitation in the same period varied between 100 and 300 mm/yr, with an average of 185 mm/yr. For semi-stabilized dunes, with 26% of the soil surface covered by local shrub (Artemisia monosperma), the mean annual recharge was 28 mm. For the stabilized landscape, with as much as 50% vegetation coverage, it was only 2-3 mm/yr. In other words, loessial sediments can either be a source of significant recharge, or of no recharge at all, depending on the degree of vegetative cover. Additionally, the time lag between specific rainy seasons and corresponding recharge events at a depth of 22 m, increased from 2.5 to 5 years, and to about 20 years, respectively, with an increasing vegetative cover. For

  2. Development of spatially diverse and complex dune-field patterns: Gran Desierto Dune Field, Sonora, Mexico

    USGS Publications Warehouse

    Beveridge, C.; Kocurek, G.; Ewing, R.C.; Lancaster, N.; Morthekai, P.; Singhvi, A.K.; Mahan, S.A.

    2006-01-01

    The pattern of dunes within the Gran Desierto of Sonora, Mexico, is both spatially diverse and complex. Identification of the pattern components from remote-sensing images, combined with statistical analysis of their measured parameters demonstrate that the composite pattern consists of separate populations of simple dune patterns. Age-bracketing by optically stimulated luminescence (OSL) indicates that the simple patterns represent relatively short-lived aeolian constructional events since ???25 ka. The simple dune patterns consist of: (i) late Pleistocene relict linear dunes; (ii) degraded crescentic dunes formed at ???12 ka; (iii) early Holocene western crescentic dunes; (iv) eastern crescentic dunes emplaced at ???7 ka; and (v) star dunes formed during the last 3 ka. Recognition of the simple patterns and their ages allows for the geomorphic backstripping of the composite pattern. Palaeowind reconstructions, based upon the rule of gross bedform-normal transport, are largely in agreement with regional proxy data. The sediment state over time for the Gran Desierto is one in which the sediment supply for aeolian constructional events is derived from previously stored sediment (Ancestral Colorado River sediment), and contemporaneous influx from the lower Colorado River valley and coastal influx from the Bahia del Adair inlet. Aeolian constructional events are triggered by climatic shifts to greater aridity, changes in the wind regime, and the development of a sediment supply. The rate of geomorphic change within the Gran Desierto is significantly greater than the rate of subsidence and burial of the accumulation surface upon which it rests. ?? 2006 The Authors. Journal compilation 2006 International Association of Sedimentologists.

  3. Solitary wave behavior in sand dunes observed from space

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.

    2011-11-01

    Although the dynamics of individual barchan dunes are well understood, their interactions are the subject of ongoing scientific interest and debate. Numerical and analog model predictions of shape-preserving binary dune collisions have been hard to test due to the long timescales over which such processes typically occur. This paper documents ten binary dune collisions in a 45-year time sequence of satellite images from the Bodélé Depression in Chad. The observations confirm that when two barchan dunes collide, a transfer of mass occurs so that one dune appears to travel through the other unscathed, like a solitary wave.

  4. How Altitude and Latitude Control Dune Morphometry on Titan

    NASA Technical Reports Server (NTRS)

    Le Gall, A.; Hayes, A.; Ewing, R.; Janssen, M. A.; Radebaugh, J.; Savage, C.; Encrenaz, P.

    2011-01-01

    Dune fields are one of the dominant landforms and represent the largest known organic reservoir on Titan. SAR-derived topography show that Titan's dune terrains tend to occupy the lowest altitude areas in equatorial regions occurring at mean elevations between approx.-400 and 0 m. In elevated dune terrains, there is a definite trend towards a smaller dune to interdune ratio, interpreted as due to limited sediment availability. A similar linear correlation is observed with latitude, suggesting that the quantity of windblown sand in the dune fields tends to decrease as one moves farther north. These findings place important constraints on Titan's geology and climate.

  5. Observations on dune dynamics in covered flow

    NASA Astrophysics Data System (ADS)

    radice, alessio; Ballio, Francesco

    2016-04-01

    An experiment is presented for bed-form migration in a pressurized duct. The hydrodynamic discharge corresponded to 1.4 times the threshold value for incipient motion of light-weight particles with a size of 3 mm. Under these conditions, dunes (i.e., bed-forms with steep front and mild tail) with a height of around 2 cm developed and migrated along the duct. Dune length, period and celerity were also considered. Long-duration movies were taken from above the duct, to depict the different features of the sediment transport over the crests and in the troughs of the dunes. Eulerian measurements of concentration and velocity of bed-load particles were conducted by image analysis, the quantitative analysis showing the temporal and spatial coherence of the sediment motion. Despite the relatively simple (one-dimensional) nature of the process, transverse motion and impulsive gusts of grains were present because the dunes generated sediment motion patterns similar to those measured in local sediment transport processes. The present observations, though limited to a single experimental configuration, yield insight into the details of bed-form dynamics.

  6. Probabilistic assessment of beach and dune changes

    USGS Publications Warehouse

    Sallenger, A.H., Jr.; Stockdon, H.; Haines, J.; Krabill, W.; Swift, R.; Brock, J.

    2004-01-01

    The recent availability of spatially-dense airborne lidar data makes assessment of the vulnerability of beaches and dunes to storm impacts practical over long reaches of coast. As an initial test, elevations of the tops (D high) and bases (Dlow) of foredune ridges along a 55-km reach on the northern Outer Banks, NC were found to have considerable spatial variability suggesting that different parts of the barrier island would respond differently to storms. Comparing statistics of storm wave runup to D high and Dlow, we found that net erosion due to overwash and dune retreat should be greatest at the northern and southern ends of the study area and least in the central section. This predicted spatial pattern of storm-induced erosion is similar to the spatial pattern of long-term erosion of the shoreline which may be controlled by additional processes (such as gradients in longshore transport) as well as the cross-shore processes considered here. However, consider feedback where at erosional hot spots there is a deficit of sand (caused by gradients in longshore transport) which lead to lower dunes and enhanced erosional cross-shore processes, such as overwash. Hence, the erosional hot spots would be exacerbated, further increasing the vulnerability of the beach and dunes to net erosion.

  7. Beaches, Dunes, and Barrier Islands. Habitat Pac.

    ERIC Educational Resources Information Center

    Fish and Wildlife Service (Dept. of Interior), Washington, DC.

    The materials in this educational packet are designed for use with students in grades 4 through 7. They consist of a leader overview, teaching guides and student data sheets for three activities, and a poster. The leader overview describes the nature of beaches, dunes, and barrier islands, tracing their development, settlement, and management and…

  8. Variability in simulated recharge using different GCMs

    NASA Astrophysics Data System (ADS)

    Allen, D. M.; Cannon, A. J.; Toews, M. W.; Scibek, J.

    2010-10-01

    Variations in the prediction of recharge is addressed by comparing recharge simulated using climate data generated using a state-of-the-art downscaling method, TreeGen, with a range of global climate models (GCMs). The study site is the transnational Abbotsford-Sumas aquifer in coastal British Columbia, Canada and Washington State, USA, and is representative of a wet coastal climate. Sixty-four recharge zones were defined based on combinations of classed soil permeability, vadose zone permeability, and unsaturated zone depth (or depth to water table) mapped in the study area. One-dimensional recharge simulations were conducted for each recharge zone using the HELP hydrologic model, which simulates percolation through a vertical column. The HELP model is driven by mean daily temperature, daily precipitation, and daily solar radiation. For the historical recharge simulations, the climate data series was generated using the LARS-WG stochastic weather generator. Historical recharge was compared to recharge simulated using climate data series derived from the TreeGen downscaling model for three future time periods: 2020s (2010-2039), 2050s (2040-2069), and 2080s (2070-2099) for each of four GCMs (CGCM3.1, ECHAM5, PCM1, and CM2.1). Recharge results are compared on an annual basis for the entire aquifer area. Both increases and decreases relative to historical recharge are simulated depending on time period and model. By the 2080s, the range of model predictions spans -10.5% to +23.2% relative to historical recharge. This variability in recharge predictions suggests that the seasonal performance of the downscaling tool is important and that a range of GCMs should be considered for water management planning.

  9. Rechargeable lithium battery technology - A survey

    NASA Technical Reports Server (NTRS)

    Halpert, Gerald; Surampudi, Subbarao

    1990-01-01

    The technology of the rechargeable lithium battery is discussed with special attention given to the types of rechargeable lithium cells and to their expected performance and advantages. Consideration is also given to the organic-electrolyte and polymeric-electrolyte cells and to molten salt lithium cells, as well as to technical issues, such as the cycle life, charge control, rate capability, cell size, and safety. The role of the rechargeable lithium cell in future NASA applications is discussed.

  10. Origins of barchan dune asymmetry: Insights from numerical simulations

    NASA Astrophysics Data System (ADS)

    Parteli, Eric J. R.; Durán, Orencio; Bourke, Mary C.; Tsoar, Haim; Pöschel, Thorsten; Herrmann, Hans

    2014-03-01

    Barchan dunes — crescent-shaped dunes that form in areas of unidirectional winds and low sand availability — commonly display an asymmetric shape, with one limb extended downwind. Several factors have been identified as potential causes for barchan dune asymmetry on Earth and Mars: asymmetric bimodal wind regime, topography, influx asymmetry and dune collision. However, the dynamics and potential range of barchan morphologies emerging under each specific scenario that leads to dune asymmetry are far from being understood. In the present work, we use dune modeling in order to investigate the formation and evolution of asymmetric barchans. We find that a bimodal wind regime causes limb extension when the divergence angle between primary and secondary winds is larger than 90°, whereas the extended limb evolves into a seif dune if the ratio between secondary and primary transport rates is larger than 25%. Calculations of dune formation on an inclined surface under constant wind direction also lead to barchan asymmetry, however no seif dune is obtained from surface tilting alone. Asymmetric barchans migrating along a tilted surface move laterally, with transverse migration velocity proportional to the slope of the terrain. Limb elongation induced by topography can occur when a barchan crosses a topographic rise. Furthermore, transient asymmetric barchan shapes with extended limb also emerge during collisions between dunes or due to an asymmetric influx. Our findings can be useful for making quantitative inference on local wind regimes or spatial heterogeneities in transport conditions of planetary dune fields hosting asymmetric barchans.

  11. Seasonal erosion and restoration of Mars' northern polar dunes

    USGS Publications Warehouse

    Hansen, C.J.; Bourke, M.; Bridges, N.T.; Byrne, S.; Colon, C.; Diniega, S.; Dundas, C.; Herkenhoff, K.; McEwen, A.; Mellon, M.; Portyankina, G.; Thomas, N.

    2011-01-01

    Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars' CO 2 seasonal polar caps. Numerous dunes in Mars' north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter. Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars' current climate.

  12. Changes of Bulgarian Coastal Dune Landscape under Anthropogenic Impact

    NASA Astrophysics Data System (ADS)

    Palazov, A.; Young, R.; Stancheva, M.; Stanchev, H.

    2012-04-01

    At one time large sand dune formations were widely distributed along the Bulgarian coast. However, due to increased urbanization in the coastal zone, the areas of total dune landscape has been constantly reduced. Dunes presently comprise only 10% of the entire 412 km long coastline of Bulgaria: they embrace a total length of 38.57 km and a total area of 8.78 km2 Important tasks in dune protection are identification of landscape changes for a certain period of time and accurate delineation of sand dune areas. The present research traces sand dune changes along the Bulgarian Black Sea coast over a 27 year period (1983-2010). This period includes also the time of expanded tourist boom and overbuilding of the coastal zone, and respectively presents the largest dune changes and reductions. Based on the landscape change analyst in GIS environment the study also aims to explore the importance of different natural and human factors in driving the observed dune alterations and destruction. To detect and assess dune changes during the last 3 decades, we used data for sand dunes derived from several sources at different time periods in order to compare changes in shoreline positions, dune contours and areas: i) Topographic maps in 1:5,000 scale from 1983; ii) Modern Very High Resolution orthophotographs from 2006 and 2010; iii) QuickBird Very High Resolution satellite images from 2009; iv) Statistical information for population and tourist infrastructure is also used to consider the influence of human pressure and hotel developments on the dune dynamics. In addition, for more detailed description and visualization of main dune types, digital photos have been taken at many parts of the Bulgarian coast. The study was performed in GIS environment. Based on the results obtained the dunes along the Bulgarian coast were divided into three main groups with relation to the general factors responsible for their alterations: i) Dunes that have decreased in result of shoreline retreat

  13. Geomorphology of coastal sand dunes, Baldwin County, Alabama

    USGS Publications Warehouse

    Bearden, Bennett L.; Hummell, Richard L.; Mink, Robert M.

    1989-01-01

    Alabama's coastal eolian deposits are primarily vegetated dunes that are exemplified by sand ridges with flat to undulating upper surfaces and continuous irregular crests. Dune fields occur along Morgan peninsula between the foredune line and Little Lagoon and the Mobile Bay area. These dune fields consist primarily of one or more continuous ridges that parallel the coast and are generally vegetaed to grassy. Washover of the beach and backshore during Hurricane Frederic (1979) and subsequent smaller scale storms resulted in significant erosion of many of Alabama's dune fields. The primary dunes or foredunes are beginning to recover from the effects of these storms; however, numerous breaks in the primary dune line are present. Sand dunes in coastal Alabama provide protection against storm-generated waves and washover. The foredunes are protected by adherence to a Coastal Construction Control Line (CCCL) or construction setback line identified by markers along coastal Baldwin County.

  14. Seasonal erosion and restoration of Mars' northern polar dunes.

    PubMed

    Hansen, C J; Bourke, M; Bridges, N T; Byrne, S; Colon, C; Diniega, S; Dundas, C; Herkenhoff, K; McEwen, A; Mellon, M; Portyankina, G; Thomas, N

    2011-02-01

    Despite radically different environmental conditions, terrestrial and martian dunes bear a strong resemblance, indicating that the basic processes of saltation and grainfall (sand avalanching down the dune slipface) operate on both worlds. Here, we show that martian dunes are subject to an additional modification process not found on Earth: springtime sublimation of Mars' CO(2) seasonal polar caps. Numerous dunes in Mars' north polar region have experienced morphological changes within a Mars year, detected in images acquired by the High-Resolution Imaging Science Experiment on the Mars Reconnaissance Orbiter. Dunes show new alcoves, gullies, and dune apron extension. This is followed by remobilization of the fresh deposits by the wind, forming ripples and erasing gullies. The widespread nature of these rapid changes, and the pristine appearance of most dunes in the area, implicates active sand transport in the vast polar erg in Mars' current climate. PMID:21292976

  15. Defrosting Polar Dunes--'The Snow Leopard'

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The patterns created by dark spots on defrosting south polar dunes are often strange and beautiful. This picture, which the Mars Orbiter Camera team has dubbed, 'the snow leopard,' shows a dune field located at 61.5oS, 18.9oW, as it appeared on July 1, 1999. The spots are areas where dark sand has been exposed from beneath bright frost as the south polar winter cap begins to retreat. Many of the spots have a diffuse, bright ring around them this is thought to be fresh frost that was re-precipitated after being removed from the dark spot. The spots seen on defrosting polar dunes are a new phenomenon that was not observed by previous spacecraft missions to Mars. Thus, there is much about these features that remains unknown. For example, no one yet knows why the dunes become defrosted by forming small spots that grow and grow over time. No one knows for sure if the bright rings around the dark spots are actually composed of re-precipitated frost. And no one knows for sure why some dune show spots that appear to be 'lined-up' (as they do in the picture shown here).

    This Mars Global Surveyor Mars Orbiter Camera image is illuminated from the upper left. North is toward the upper right. The scale bar indicates a distance of 200 meters (656 feet).

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  16. Quantifying energy and water fluxes in dry dune ecosystems of the Netherlands

    NASA Astrophysics Data System (ADS)

    Voortman, B. R.; Bartholomeus, R. P.; van der Zee, S. E. A. T. M.; Bierkens, M. F. P.; Witte, J. P. M.

    2015-09-01

    water resources, especially during a changing climate with an increasing number of drought days. Therefore, such feedbacks need to be integrated into a coupled plant physiological and hydrometeorological model to accurately simulate ETa. In addition, our study showed that groundwater recharge in dunes can be increased considerably by promoting moss vegetation, especially of open-structured moss species.

  17. Quantifying energy and water fluxes in dry dune ecosystems of the Netherlands

    NASA Astrophysics Data System (ADS)

    Voortman, B. R.; Bartholomeus, R. P.; van der Zee, S. E. A. T. M.; Bierkens, M. F. P.; Witte, J. P. M.

    2015-04-01

    of importance to water resources, especially during a changing climate with increasing number of drought days. Therefore, such feedbacks need to be integrated into a coupled plant physiological and hydro-meteorological model to accurately simulate ETa. In addition, our study showed that groundwater recharge in dunes can be increased considerably by promoting moss vegetation, especially of open structured moss species.

  18. Dune Morphometry in the Age of Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Lancaster, N.

    2014-12-01

    Dune patterns can be characterized in many different ways. Relationships between dune height, width and spacing, and the spatial variation in these parameters have been widely employed to provide quantitative information that can be used to describe dune patterns and make comparisons between dunes in widely separated areas, as well as to identify different generations of dunes. Digital elevation models (e.g. ASTER GDEM) provide a rich resource of data for analyses of dune patterns at landscape scales in several ways, including: (1) more extensive analyses using traditional measures, such as relationships between dune height and spacing, and the spatial variation in these parameters; and (2) estimation of sediment thickness on a regional scale. Analyses of data for Arabian and Namibian sand seas and dune fields show that dune height and spacing relationships are much more variable than previously reported and call into question existing models. Regional patterns of sediment thickness reveal areas of erosion, bypass, and accumulation that can be related to transport pathways and wind regimes. The widespread occurrence of complex dune patterns as well as the magnitude of the newly available data sets however requires more sophisticated analyses than simple extraction of dune morphometric parameters using GIS approaches. Geostatistical analyses using spatial autocorrelation, Fourier, and Wavelet methods have been employed in analyses of sub-aqueous bedforms and show promise for dune systems. Automated or semi-automated identification of dune length, width, spacing, and trends using advanced image analysis techniques such as linear segment detection is a potentially transformative approach. The strengths and weaknesses of these methods to provide pertinent geomorphic information are currently being evaluated, but they have the potential to provide new insights into the nature of dune patterns.

  19. Corridors of barchan dunes: Stability and size selection.

    PubMed

    Hersen, P; Andersen, K H; Elbelrhiti, H; Andreotti, B; Claudin, P; Douady, S

    2004-01-01

    Barchans are crescentic dunes propagating on a solid ground. They form dune fields in the shape of elongated corridors in which the size and spacing between dunes are rather well selected. We show that even very realistic models for solitary dunes do not reproduce these corridors. Instead, two instabilities take place. First, barchans receive a sand flux at their back proportional to their width while the sand escapes only from their horns. Large dunes proportionally capture more sand than they lose, while the situation is reversed for small ones: therefore, solitary dunes cannot remain in a steady state. Second, the propagation speed of dunes decreases with the size of the dune: this leads, through the collision process, to a coarsening of barchan fields. We show that these phenomena are not specific to the model, but result from general and robust mechanisms. The length scales needed for these instabilities to develop are derived and discussed. They turn out to be much smaller than the dune field length. As a conclusion, there should exist further, yet unknown, mechanisms regulating and selecting the size of dunes. PMID:14995611

  20. Multiple origins of linear dunes on Earth and Titan

    USGS Publications Warehouse

    Rubin, David M.; Hesp, Patrick A.

    2009-01-01

    Dunes with relatively long and parallel crests are classified as linear dunes. On Earth, they form in at least two environmental settings: where winds of bimodal direction blow across loose sand, and also where single-direction winds blow over sediment that is locally stabilized, be it through vegetation, sediment cohesion or topographic shelter from the winds. Linear dunes have also been identified on Titan, where they are thought to form in loose sand. Here we present evidence that in the Qaidam Basin, China, linear dunes are found downwind of transverse dunes owing to higher cohesiveness in the downwind sediments, which contain larger amounts of salt and mud. We also present a compilation of other settings where sediment stabilization has been reported to produce linear dunes. We suggest that in this dune-forming process, loose sediment accumulates on the dunes and is stabilized; the stable dune then functions as a topographic shelter, which induces the deposition of sediments downwind. We conclude that a model in which Titan's dunes formed similarly in cohesive sediments cannot be ruled out by the existing data.

  1. NORTH CAROLINA GROUNDWATER RECHARGE RATES 1994

    EPA Science Inventory

    North Carolina Groundwater Recharge Rates, from Heath, R.C., 1994, Ground-water recharge in North Carolina: North Carolina State University, as prepared for the NC Department of Environment, Health and Natural Resources (NC DEHNR) Division of Enviromental Management Groundwater S...

  2. INTRODUCTION TO ARTIFICIAL GROUND-WATER RECHARGE

    EPA Science Inventory

    Artificial ground-water recharge has been practiced for scores of years throughout the world. The purpose of artificial recharge is to increase the rate at which water infiltrates the land surface in order to supplement the quantity of ground water in storage. A variety of rechar...

  3. Identifying and quantifying urban recharge: a review

    NASA Astrophysics Data System (ADS)

    Lerner, David N.

    2002-02-01

    The sources of and pathways for groundwater recharge in urban areas are more numerous and complex than in rural environments. Buildings, roads, and other surface infrastructure combine with man-made drainage networks to change the pathways for precipitation. Some direct recharge is lost, but additional recharge can occur from storm drainage systems. Large amounts of water are imported into most cities for supply, distributed through underground pipes, and collected again in sewers or septic tanks. The leaks from these pipe networks often provide substantial recharge. Sources of recharge in urban areas are identified through piezometry, chemical signatures, and water balances. All three approaches have problems. Recharge is quantified either by individual components (direct recharge, water-mains leakage, septic tanks, etc.) or holistically. Working with individual components requires large amounts of data, much of which is uncertain and is likely to lead to large uncertainties in the final result. Recommended holistic approaches include the use of groundwater modelling and solute balances, where various types of data are integrated. Urban recharge remains an under-researched topic, with few high-quality case studies reported in the literature.

  4. Improved Carbon Anodes For Rechargeable Lithium Cells

    NASA Technical Reports Server (NTRS)

    Huang, Chen-Kuo; Surampudi, Subbarao; Attia, Alan; Halpert, Gerald

    1994-01-01

    Carbon anodes for rechargeable lithium cells improved by choosing binder contents and fabrication conditions to achieve maximum porosity, uniform loading, and maximum reversible lithium capacity. Stacking electrodes under pressure during assembly of cells increases cyclability of lithium. Rechargeable, high-energy-density lithium cells containing improved carbon anodes find use in spacecraft, military, communications, automotive, and other demanding applications.

  5. Transformer Recharging with Alpha Channeling in Tokamaks

    SciTech Connect

    N.J. Fisch

    2009-12-21

    Transformer recharging with lower hybrid waves in tokamaks can give low average auxiliary power if the resistivity is kept high enough during the radio frequency (rf) recharging stage. At the same time, operation in the hot ion mode via alpha channeling increases the effective fusion reactivity. This paper will address the extent to which these two large cost saving steps are compatible. __________________________________________________

  6. Reflections on Dry-Zone Recharge

    NASA Astrophysics Data System (ADS)

    Gee, G. W.

    2005-05-01

    Quantifying recharge in regions of low precipitation remains a challenging task. The design of permanent nuclear-waste isolation at Yucca Mountain, Nevada, the design of arid-site landfill covers and the pumping of groundwater in desert cities, like Las Vegas, are examples where accurate recharge estimates are needed because they affect billion-dollar decisions. Recharge cannot be measured directly and must rely on estimation methods of various kinds including chemical tracers, thermal profiling, lysimetry, and water-balance modeling. Chemical methods, like chloride-mass-balance can significantly underestimate actual recharge rates and water-balance models are generally limited by large uncertainties. Studies at the U. S. Department of Energy's Hanford Site in Washington State, USA illustrate how estimates of recharge rates have changed over time and how these estimates can affect waste management decisions. Lysimetry has provided reliable estimates of recharge for a wide range of surface condittions. Lysimetric observations of reduced recharge, resulting from advective drying of coarse rock piles, suggest a way to avoid costly recharge protection using titanium shields at Yucca Mountain. The Pacific Northwest National Laboratory is funded by the U. S. Department of Energy under contract DE-AC05-76-RL01830.

  7. Recharge at the Hanford Site: Status report

    SciTech Connect

    Gee, G.W.

    1987-11-01

    A variety of field programs designed to evaluate recharge and other water balance components including precipitation, infiltration, evaporation, and water storage changes, have been carried out at the Hanford Site since 1970. Data from these programs have indicated that a wide range of recharge rates can occur depending upon specific site conditions. Present evidence suggests that minimum recharge occurs where soils are fine-textured and surfaces are vegetated with deep-rooted plants. Maximum recharge occurs where coarse soils or gravels exist at the surface and soils are kept bare. Recharge can occur in areas where shallow-rooted plants dominate the surface, particularly where soils are coarse-textured. Recharge estimates have been made for the site using simulation models. A US Geological Survey model that attempts to account for climate variability, soil storage parameters, and plant factors has calculated recharge values ranging from near zero to an average of about 1 cm/yr for the Hanford Site. UNSAT-H, a deterministic model developed for the site, appears to be the best code available for estimating recharge on a site-specific basis. Appendix I contains precipitation data from January 1979 to June 1987. 42 refs., 11 figs., 11 tabs.

  8. Understanding and Predicting Time-Dependent Dune Erosion

    NASA Astrophysics Data System (ADS)

    Long, J.; Stockdon, H. F.; Smith, J. R.

    2014-12-01

    The vulnerability of coastal ecosystems, habitats, and infrastructure is largely dictated by how protective sand dunes respond to extreme waves and water levels during storms. Predicting the type of dune response (e.g., scarping, overwashing, breaching) is often done with conditional storm-impact scale models (e.g. Sallenger 2000) however, these models do not describe the magnitude of expected changes or account for the continuum of dune responses throughout the duration of a storm event. Alternatively, process-based dune erosion models like XBeach explicitly compute interactions between waves, water levels, and sediment transport but are limited in regional applications due to computational requirements and inadequate knowledge of required boundary conditions. Using historical observations of storm-induced coastal change, we are developing and testing a variety of new static, probabilistic, and time-dependent models for dune erosion. Model development is informed by the observed dune response from four events that impacted geomorphically diverse regions along the U.S. Atlantic and Gulf of Mexico coastlines. Results from the static models indicate that alongshore differences in the magnitude of dune elevation change can be related to the depth of water over of the dune crest (e.g. freeboard) but that increasing freeboard does not always correspond to an increased lowering of the dune crest. Applying the concept of dune freeboard in a time-dependent approach that incorporates rising water levels that cause a dune to sequentially experience collision, overwash and then inundation shows that reasonable estimates of dune erosion are obtained. The accuracy of each of the models is now being evaluated along the large and diverse regions of coast that were impacted by Hurricane Sandy in 2012 where dune response was highly variable.

  9. Measuring and computing natural ground-water recharge at sites in south-central Kansas

    USGS Publications Warehouse

    Sophocleous, M.A.; Perry, C.A.

    1987-01-01

    To measure the natural groundwater recharge process, two sites in south-central Kansas were instrumented with sensors and data microloggers. The atmospheric-boundary layer and the unsaturated and saturated soil zones were monitored as a single regime. Direct observations also were used to evaluate the measurements. Atmospheric sensors included an anemometer, a tipping-bucket rain gage, an air-temperature thermistor, a relative-humidity probe, a net radiometer, and a barometric-pressure transducer. Sensors in the unsaturated zone consisted of soil-temperature thermocouples, tensiometers coupled with pressure transducers and dial gages, gypsum blocks, and a neutron-moisture probe. The saturated-zone sensors consisted of a water-level pressure transducer, a conventional float gage connected to a variable potentiometer, soil thermocouples, and a number of multiple-depth piezometers. Evaluation of the operation of these sensors and recorders indicates that certain types of equipment, such as pressure transducers, are very sensitive to environmental conditions. A number of suggestions aimed at improving instrumentation of recharge investigations are outlined. Precipitation and evapotranspiration data, taken together with soil moisture profiles and storage changes, water fluxes in the unsaturated zone and hydraulic gradients in the saturated zone at various depths, soil temperature, water table hydrographs, and water level changes in nearby wells, describe the recharge process. Although the two instrumented sites are located in sand-dune environments in area characterized by a shallow water table and a sub-humid continental climate, a significant difference was observed in the estimated total recharge. The estimates ranged from less than 2.5 mm at the Zenith site to approximately 154 mm at the Burrton site from February to June 1983. The principal reasons that the Burrton site had more recharge than the Zenith site were more precipitation, less evapotranspiration, and a

  10. Great Kobuk Sand Dunes, Alaska: A Terrestrial Analog Site for Polar, Topographically Confined Martian Dune Fields

    NASA Astrophysics Data System (ADS)

    Dinwiddie, C. L.; Hooper, D. M.; Michaels, T. I.; McGinnis, R. N.; Stillman, D.; Bjella, K.; Stothoff, S.; Walter, G. R.; Necsoiu, M.; Grimm, R. E.

    2010-12-01

    Martian dune systems belong to two broad categories: (i) the sprawling north polar erg, rich in and immobilized by seasonal and perennial volatiles; and (ii) isolated low- to high-latitude dune fields confined by topography. While modern dune migration on Mars is nearly imperceptibly slow, recent studies are producing robust evidence for aeolian activity, including bedform modification. Cold-climate terrestrial dunes containing volatile reservoirs provide an important analog to Martian polar dunes because permafrost and seasonal cycles of CO2 and H2O frost mantling are thought to partially decouple Martian polar dunes from atmospheric forcing. The 67°N latitude, 62 km2 Great Kobuk Sand Dunes (GKSD) are a terrestrial analog for polar, intercrater dune fields on Mars. Formative winds affected by complex topography and the presence of volatiles and intercalated snow within the GKSD have direct analogy to factors that impede migration of Martian polar dunes. This system offers the opportunity to study cold-climate, noncoastal, topographically constrained, climbing and reversing barchanoid, transverse, longitudinal, and star dunes. The Kobuk Valley climate is subarctic and semiarid with long, cold winters and brief, warm summers. Niveoaeolian sedimentation occurs within west-facing lee slope catchments. In March 2010, we found the seasonally frozen layer to range in thickness from 1.5 to 4.0 m, and no evidence for shallow permafrost. Instead, using GPR and boreholes, we found a system-wide groundwater aquifer that nearly parallels topography and cuts across steeply dipping bedforms. GPR cannot uniquely detect ice and water; however, a similar analysis of rover-based GPR might be used to detect volatiles in Martian dunes. The perennial volatile reservoir is liquid because of mean annual air temperature, intense solar heating before, during, and after 38 days of continuous summer daylight, high dry sand thermal conductivity, higher wet sand thermal conductivity

  11. Equilibrium versus disequilibrium of barchan dunes

    NASA Astrophysics Data System (ADS)

    El belrhiti, Hicham; Douady, Stéphane

    2011-02-01

    Barchans are crescentic dunes which occur in mainly mono-directional winds. Shape, aspect ratios and velocities of these dunes have been studied as if they were in equilibrium. However, following a study of the shape and migration of 11 barchans of different sizes for 18 months in the field on Moroccan Atlantic Sahara, we show that they only appear to be in a stationary state if studied over a long timeframe (at the scale of the year or several years), but are never in equilibrium at the scale of weeks or months. Rather, they are always 'trying' to reach a possible equilibrium state but never have enough time to accomplish this. This may be the main reason for the large variation observed in previous measurements, and justifies some caution in what can be deduced from them.

  12. Beaches and Dunes of Developed Coasts

    NASA Astrophysics Data System (ADS)

    Nordstrom, Karl F.

    2004-06-01

    This volume discusses the role of humans in transforming the coastal landscape. The book details the many ways beaches and dunes are eliminated, altered and replaced and the differences between natural landforms and the human artefacts that replace them. Emphasis is placed on the importance of retaining naturally functioning beaches and dunes in ways that achieve natural values while accommodating development and use. The issues dealt with in this book will be of interest to practising coastal engineers and research scientists, as well as to planners and managers of coastal resources at all levels of government. It will be of particular value to investigators planning for the future of coastal development under accelerated sea level rise. The book will also be useful as a reference text for graduate and advanced undergraduate courses in geography, geology, ecology and other disciplines dealing with the interaction between science, technology and society.

  13. Pooh Bear rock and Mermaid Dune

    NASA Technical Reports Server (NTRS)

    1997-01-01

    One of the two forward cameras aboard Sojourner imaged this area of Martian terrain on Sol 26. The large rock dubbed 'Pooh Bear' is at far left, and stands between four and five inches high. Mermaid Dune is the smooth area stretching horizontally across the top quarter of the image. The Alpha Proton X-Ray Spectrometer (APXS) instrument aboard Sojourner will be deployed on Mermaid Dune, and the rover will later use its cleated wheels to dig into it.

    Mars Pathfinder is the second in NASA's Discovery program of low-cost spacecraft with highly focused science goals. The Jet Propulsion Laboratory, Pasadena, CA, developed and manages and Mars Pathfinder mission for NASA's Office of Space Science, Washington, D.C. JPL is an operating division of the California Institute of Technology (Caltech). The Imager for Mars Pathfinder (IMP) was developed by the University of Arizona Lunar and Planetary Laboratory under contract to JPL. Peter Smith is the Principal Investigator.

  14. Object-based Dune Analysis: Automated dune mapping and pattern characterization for Ganges Chasma and Gale crater, Mars

    NASA Astrophysics Data System (ADS)

    Vaz, David A.; Sarmento, Pedro T. K.; Barata, Maria T.; Fenton, Lori K.; Michaels, Timothy I.

    2015-12-01

    A method that enables the automated mapping and characterization of dune fields on Mars is described. Using CTX image mosaics, the introduced Object-based Dune Analysis (OBDA) technique produces an objective and reproducible mapping of dune morphologies over extensive areas. The data set thus obtained integrates a large variety of data, allowing a simple cross-analysis of dune patterns, spectral and morphometric information, and mesoscale wind models. Two dune fields, located in Gale crater and Ganges Chasma, were used to test and validate the methodology. The segmentation of dune-related morphologies is highly efficient, reaching overall accuracies of 95%. In addition, we show that the automated segmentation of slipface traces is also possible with expected accuracies of 85-90%. A qualitative and quantitative comparison of the final outputs with photointerpretations is performed, and the precision of the directional characterization of the dune patterns is evaluated. We demonstrate a good agreement between the OBDA outputs and the photointerpreted dune morphologies, with local trend deviations below 45° for 80-95% of the mapped areas. Because the developed algorithm is tuned for the recognition of linear features from the imagery, the slipfaces of small barchans can be preferentially overlooked owing to their small extent at the spatial resolution of the CTX mosaics. Dune types composed of longer linear morphologies are much better represented, including correct mapping of secondary structures. Having proved the effectiveness and accuracy of the mapping procedure, we discuss its future applications for the improvement of dune catalogs on Mars.

  15. Mulitple Origins of Sand Dune-Topography Interactions on Titan

    NASA Astrophysics Data System (ADS)

    Goggin, H.; Ewing, R. C.; Hayes, A.; Cisneros, J.; Epps, J. C.

    2015-12-01

    The interaction between sand dune patterns and topographic obstacles is a primary signal of sand transport direction in the equatorial region of Saturn's moon, Titan. The streamlined, tear drop appearance of the sand-dune patterns as they wrap around obstacles and a dune-free zone on the east side of many obstacles gives the impression that sand transport is from the west to east at equatorial latitudes. However, the physical mechanism behind the dune-obstacle interaction is not well explained, leaving a gap in our understanding of the equatorial sand transport and implied wind directions and magnitudes on Titan. In order to better understand this interaction and evaluate wind and sand transport direction, we use morphometric analysis of optical images on Earth and Cassini SAR images on Titan combined with analog wind tunnel experiments to study dune-topography interactions. Image analysis is performed in a GIS environment to map spatial variations in dune crestline orientations proximal to obstacles. We also use digital elevation models to and analyze the three-dimensional geometry - height, length, width and slope of the dune-topography relationships on Earth. Preliminary results show that dune patterns are deflected similarly around positive, neutral, or negative topography, where positive topography is greater than the surrounding dune height, neutral topography is at dune height and negative topography is lower than dune heights. In the latter case these are typically intra-dune field playas. The obstacle height, width, slope and wind variability appear to play a primary role in determining if a lee-dune, rather than a dune-free lee-zone, develops. In many cases a dune-free playa with evaporite and mud desiccation polygons forms lee-ward of the obstacle. To support and elaborate on the mapping and spatial characterization of dune-topography interactions, a series of experiments using a wind tunnel were conducted. Wind tunnel experiments examine the formation

  16. Dune Field in a Southern Highlands Crater

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 5 September 2003

    Dark dunes sit on a rough, eroding sedimentary surface in the floor of an 83 km diameter crater. This crater is one of dozens in Noachis Terra, in the southern highlands of Mars, to have both dark dunes and an eroding surface. Note how the dunes seem to ignore the underlying rough surface in some cases, while in other places the dunes seem to have wrapped themselves around sharp knobs.

    Image information: VIS instrument. Latitude -40.5, Longitude 34.6 East (325.4 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  17. D and D (Dunes and Devils)

    NASA Technical Reports Server (NTRS)

    2006-01-01

    3 February 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows streaks created by late spring and early summer dust devils on a field of dark sand dunes on the floor of Hooke Crater.

    Location near: 45.0oS, 44.8oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Summer

  18. Annual monsoon rains recorded by Jurassic dunes.

    PubMed

    Loope, D B; Rowe, C M; Joeckel, R M

    2001-07-01

    Pangaea, the largest landmass in the Earth's history, was nearly bisected by the Equator during the late Palaeozoic and early Mesozoic eras. Modelling experiments and stratigraphic studies have suggested that the supercontinent generated a monsoonal atmospheric circulation that led to extreme seasonality, but direct evidence for annual rainfall periodicity has been lacking. In the Mesozoic era, about 190 million years ago, thick deposits of wind-blown sand accumulated in dunes of a vast, low-latitude desert at Pangaea's western margin. These deposits are now situated in the southwestern USA. Here we analyse slump masses in the annual depositional cycles within these deposits, which have been described for some outcrops of the Navajo Sandstone. Twenty-four slumps, which were generated by heavy rainfall, appear within one interval representing 36 years of dune migration. We interpret the positions of 20 of these masses to indicate slumping during summer monsoon rains, with the other four having been the result of winter storms. The slumped lee faces of these Jurassic dunes therefore represent a prehistoric record of yearly rain events. PMID:11452305

  19. Global map of Titan's dune fields

    NASA Astrophysics Data System (ADS)

    Le Corre, L.; Le Mouélic, S.; Sotin, C.; Barnes, J. W.; Brown, R. H.; Baines, K.; Buratti, B.; Clark, R.; Nicholson, P.

    2008-09-01

    Introduction Methane is the second major constituent of Titan's atmosphere; but it should be totally removed at least in ten million years by photochemistry in the stratosphere and condensation in the troposphere [1]. The first process produces hydrocarbons which form the haze and can condensate onto the surface. The second process causes methane rains on the surface, which carve channels networks. The loss of methane is possibly balanced by outgassing during cryovolcanic event [2]. But hydrocarbons grains deposited onto the surface cannot be recycled. They may be stored in the dunes [3], which were first seen by SAR (Synthetic Aperture Radar) [4]. We focus our study on the mapping of the dune fields in order to determine their global distribution. The aim is to constrain the amount of hydrocarbon material existing in the dunes, and to relate it to the duration of the methane cycle. Data from the Visual and Infrared Mapping Spectrometer (VIMS) and RADAR instruments onboard Cassini spacecraft can be used to map Titan's surface. Infrared images, which are mainly sensitive to composition and grain size, are very complementary to the microwave measurements which depend mainly on roughness and topography. We used spectral criteria after empirical correction of aerosols to map the distribution of heterogeneous units on Titan [5]. These units are compared with SAR images in overlapping regions. Titan's surface mosaics with VIMS VIMS probes the first ten of microns of the ground in seven narrow atmospheric windows in the 0.88 to 5.11 μm wavelength range. We built infrared mosaics with cubes sorted by spatial resolution, by keeping cubes corresponding to favorable observing conditions (incidence, emergence, phase and time exposure). Band ratios were computed and combined in false color composite images (red as 1.59/1.27-μm, green as 2.03/1.27-μm and blue as 1.27/1.08-μm). Band ratios are useful to minimize the effect of illuminating conditions and albedo variations [6

  20. Winter Frosted Dunes in Kaiser Crater

    NASA Technical Reports Server (NTRS)

    2001-01-01

    As the Mars Global Surveyor Primary Mission draws to an end, the southern hemisphere of Mars is in the depths of winter. At high latitudes, it is dark most, if not all, of the day. Even at middle latitudes, the sun shines only thinly through a veil of water and carbon dioxide ice clouds, and the ground is so cold that carbon dioxide frosts have formed. Kaiser Crater (47oS, 340oW) is one such place. At a latitude comparable to Seattle, Washington, Duluth, Minnesota, or Helena, Montana, Kaiser Crater is studied primarily because of the sand dune field found within the confines of its walls (lower center of the Mars Orbiter Camera image, above). The normally dark-gray or blue-black sand can be seen in this image to be shaded with light-toned frost. Other parts of the crater are also frosted. Kaiser Crater and its dunes were the subject of an earlier presentation of results. Close-up pictures of these and other dunes in the region show details of their snow-cover, including small avalanches. The two Mars Global Surveyor Mars Orbiter Camera images that comprise this color view (M23-01751 and M23-01752) were acquired on January 26, 2001.

  1. Avalanche grainflow on a simulated aeolian dune

    NASA Astrophysics Data System (ADS)

    Sutton, S. L. F.; McKenna Neuman, C.; Nickling, W.

    2013-09-01

    Avalanches maintain the slipface of aeolian dunes, which alters their airflow characteristics and sediment dynamics, and results in the development of grainflow cross-bedding. We report on a series of experiments in which avalanches were observed on a 1:1 replica of a small (1.2 m brink height) transverse dune in the Dune Simulation Wind Tunnel under wind velocities of 8-11 m s-1. Changes in slipface topography were observed photographically and measured utilizing a 3-D laser scanner with 1 mm2 spatial resolution. Avalanches in noncohesive sands were observed to progress through scarp recession from the point of initiation and continue until the slope angle is reduced. Changes in local slope confirm that the steep, pre-avalanche mean slope relaxes to a uniform value equal to the angle of repose of the test sand (32°) over all involved portions of the slipface. Avalanche volumes are measured, and demonstrate that avalanche magnitude is independent of wind speed over the range of velocities observed. This independence provides the potential to significantly simplify the modeling of grainflow as a function of only the total cross brink sediment transport.

  2. Detection of Barchan Dunes in High Resolution Satellite Images

    NASA Astrophysics Data System (ADS)

    Azzaoui, M. A.; Adnani, M.; El Belrhiti, H.; Chaouki, I. E.; Masmoudi, C.

    2016-06-01

    Barchan dunes are the fastest moving sand dunes in the desert. We developed a process to detect barchans dunes on High resolution satellite images. It consisted of three steps, we first enhanced the image using histogram equalization and noise reduction filters. Then, the second step proceeds to eliminate the parts of the image having a texture different from that of the barchans dunes. Using supervised learning, we tested a coarse to fine textural analysis based on Kolomogorov Smirnov test and Youden's J-statistic on co-occurrence matrix. As an output we obtained a mask that we used in the next step to reduce the search area. In the third step we used a gliding window on the mask and check SURF features with SVM to get barchans dunes candidates. Detected barchans dunes were considered as the fusion of overlapping candidates. The results of this approach were very satisfying in processing time and precision.

  3. DUNE: A Large International Collaboration From the Start

    NASA Astrophysics Data System (ADS)

    Thomson, Mark

    2016-03-01

    LBNF/DUNE will be the first large-scale scientific endeavor hosted by the United States that is set up as a truly international project from the start. The Long Baseline Neutrino Facility (LBNF) will consist of a 1.2 MW proton beam neutrino source at Fermilab in Illinois, sending high-energy neutrinos to large liquid argon detectors located 1300 kilometers away and a mile underground at the Sanford Underground Research Facility in South Dakota. The detectors will be constructed and operated by the Deep Underground Neutrino Experiment (DUNE) collaboration. DUNE is a global collaboration of over 800 scientists and engineers from 145 institutes from 27 nations. The international governance of LBNF and DUNE is adapted from the successful model of the LHC at CERN. The status of LBNF/DUNE and the model adopted for the international partnerships for LBNF and DUNE will be discussed.

  4. Lithium ion rechargeable systems studies

    SciTech Connect

    Levy, S.C.; Lasasse, R.R.; Cygan, R.T.; Voigt, J.A.

    1995-02-01

    Lithium ion systems, although relatively new, have attracted much interest worldwide. Their high energy density, long cycle life and relative safety, compared with metallic lithium rechargeable systems, make them prime candidates for powering portable electronic equipment. Although lithium ion cells are presently used in a few consumer devices, e.g., portable phones, camcorders, and laptop computers, there is room for considerable improvement in their performance. Specific areas that need to be addressed include: (1) carbon anode--increase reversible capacity, and minimize passivation; (2) cathode--extend cycle life, improve rate capability, and increase capacity. There are several programs ongoing at Sandia National Laboratories which are investigating means of achieving the stated objectives in these specific areas. This paper will review these programs.

  5. Lithium ion rechargeable systems studies

    NASA Astrophysics Data System (ADS)

    Levy, Samuel C.; Lasasse, Robert R.; Cygan, Randall T.; Voigt, James A.

    Lithium ion systems, although relatively new, have attracted much interest worldwide. Their high energy density, long cycle life and relative safety, compared with metallic lithium rechargeable systems, make them prime candidates for powering portable electronic equipment. Although lithium ion cells are presently used in a few consumer devices, e.g., portable phones, camcorders, and laptop computers, there is room for considerable improvement in their performance. Specific areas that need to be addressed include: (1) carbon anode-increase reversible capacity, and minimize passivation; (2) cathode-extend cycle life, improve rate capability, and increase capacity. There are several programs ongoing at Sandia National Laboratories which are investigating means of achieving the stated objectives in these specific areas. This paper will review these programs.

  6. Rechargeable lithium-ion cell

    DOEpatents

    Bechtold, Dieter; Bartke, Dietrich; Kramer, Peter; Kretzschmar, Reiner; Vollbert, Jurgen

    1999-01-01

    The invention relates to a rechargeable lithium-ion cell, a method for its manufacture, and its application. The cell is distinguished by the fact that it has a metallic housing (21) which is electrically insulated internally by two half shells (15), which cover electrode plates (8) and main output tabs (7) and are composed of a non-conductive material, where the metallic housing is electrically insulated externally by means of an insulation coating. The cell also has a bursting membrane (4) which, in its normal position, is located above the electrolyte level of the cell (1). In addition, the cell has a twisting protection (6) which extends over the entire surface of the cover (2) and provides centering and assembly functions for the electrode package, which comprises the electrode plates (8).

  7. Groundwater Recharge Estimates under Agricultural Lands based on Deep Vadose Zone Sampling, Monitoring and Modeling, Mediterranean Climate, Israel

    NASA Astrophysics Data System (ADS)

    Kurtzman, D.; Turkeltub, T.; Shapira, R.; Dahan, O.

    2011-12-01

    Models of unsaturated flow and chloride transport under different agricultural settings were calibrated to deep vadose-zone samples or monitoring systems' data. The land settings include irrigated citrus orchards in light and heavy soils, a rain-fed winter crop field, an irrigated summer crop field and a bare sand dune. Vadose zone monitoring system (VMS), which enables continuous measurements of the vadose zone water content and frequent sampling of pore water at selected points across the entire vadose zone were used in three sites. In other sites direct push rigs were used for obtaining continuous core to depths ~ 10 m, and all physical and chemical characterization were derived in the lab. Hydrus 1D code was used for calibrating the models, validation runs (only in monitored sites) and simulations. In orchards, large variability of rechrge rates within the same orchard was observed. On average, relatively low recharge rates were calculated (~10% of precipitation+ irrigation), and high masses of chloride accumulations are found in many profiles obtained under orchards. Recharge variability within the same crop-field was usually smaller than the variability found in orchards while average relative recharge rates are usually higher than in orchards. Calibrated models were used for simulation of long periods and some simple precipitation-recharge statistics for the different land uses were obtained. Scenarios of land-use and climate change where used to produce estimates of the effects of these changes on recharge (e.g. 25% drop in rainfall will lead to ~50% drop in recharge under rain-fed crop).

  8. Rechargeable lead-acid batteries.

    PubMed

    1990-09-01

    Batteries used in medical equipment, like their counterparts in consumer products, attract little attention until they fail to function effectively. In some applications, such as in emergency medical devices, battery failure can have fatal consequences. While modern batteries are usually quite reliable, ECRI has received 53 written problem reports and countless verbal reports or questions related to battery problems in hospitals during the past five years. This large number of reports is due, at least in part, to the enormous quality of batteries used to operate or provide backup power in contemporary hospital equipment. As part of an ongoing evaluation of rehabilitation assistive equipment, ECRI has been studying the performance of 12 V rechargeable deep-cycle lead-acid batteries used in powered wheelchairs. During the course of this evaluation, it has become apparent that many professionals, both clinical and industrial, regard batteries as "black box" devices and know little about proper care and maintenance--and even less about battery selection and purchase. Because equipment performance and reliability can be strongly influenced by different battery models, an understanding of battery characteristics and how they affect performance is essential when selecting and purchasing batteries. The types of rechargeable batteries used most commonly in hospitals are lead-acid and nickel-cadmium (nicad), which we compare below; however, the guidance we provide in this article focuses on lead-acid batteries. While the examples given are for high-capacity 12 V deep-cycle batteries, similar analyses can be applied to smaller lead-acid batteries of different voltages. PMID:2211174

  9. Crescentic dunes on the inner continental shelf off northern California

    USGS Publications Warehouse

    Cacchione, D.A.; Field, M.E.; Drake, D.E.; Tate, G.B.

    1987-01-01

    These dunes appear to be migrating obliquely to the regional shelf gradient; a preferred offshore direction of tranpsort is indicated by the extended southern wings of many dunes. Over longer time periods (decades), the seaward transport of fine to medium sand in the crescentic dunes is probably an important way by which sand escapes the shallow part of the continental shelf in this region and mixes with the muddy deposits of the central shelf. -from Authors

  10. Dune migration in a steep, coarse-bedded stream

    USGS Publications Warehouse

    Dinehart, R.L.

    1989-01-01

    In the North Fork Toutle River at Kid Valley, Washington, weak correlation between flow depth and the standard deviation of bed elevation was noted. Dunes were often superposed on larger bed forms with wave periods between 10 and 30 min. Gradual changes in waveform height and periodicity occurred over several hours during storm runoff. Rates of migration for typical dunes were estimated to be 3 cm s-1, and dune wavelengths were estimated to be 6 to 7 m. -from Author

  11. Submarine sand dunes and sedimentary environments in Oceanographer Canyon.

    USGS Publications Warehouse

    Valentine, P.C.; Cooper, R.A.; Uzmann, J.R.

    1984-01-01

    Reveals an extensive field of large sand dunes on the canyon floor. The dunes are medium to coarse sand, are oriented across the axis, and the largest of them are as high as 3m and have wavelengths up to 15m. Their asymmetry, grain size, and height suggest that they are formed by axial currents flowing up- and downcanyon and that the largest dunes require flows of at least 70 cm/sec.-from Authors

  12. Recharge and groundwater models: An overview

    USGS Publications Warehouse

    Sanford, W.

    2002-01-01

    Recharge is a fundamental component of groundwater systems, and in groundwater-modeling exercises recharge is either measured and specified or estimated during model calibration. The most appropriate way to represent recharge in a groundwater model depends upon both physical factors and study objectives. Where the water table is close to the land surface, as in humid climates or regions with low topographic relief, a constant-head boundary condition is used. Conversely, where the water table is relatively deep, as in drier climates or regions with high relief, a specified-flux boundary condition is used. In most modeling applications, mixed-type conditions are more effective, or a combination of the different types can be used. The relative distribution of recharge can be estimated from water-level data only, but flux observations must be incorporated in order to estimate rates of recharge. Flux measurements are based on either Darcian velocities (e.g., stream base-flow) or seepage velocities (e.g., groundwater age). In order to estimate the effective porosity independently, both types of flux measurements must be available. Recharge is often estimated more efficiently when automated inverse techniques are used. Other important applications are the delineation of areas contributing recharge to wells and the estimation of paleorecharge rates using carbon-14.

  13. Barchan dunes in two dimensions: experimental tests for minimal models.

    PubMed

    Groh, Christopher; Wierschem, Andreas; Aksel, Nuri; Rehberg, Ingo; Kruelle, Christof A

    2008-08-01

    A well-defined two-dimensional single barchan dune under the force of a shearing water flow is investigated experimentally. From an initially prepared triangular heap a rapid relaxation to a steady-state solution is observed with constant mass, shape, and velocity. This attractor exhibits all characteristic features of barchan dunes found in nature, namely a gently inclined windward side, crest, brink, and steep lee face. The relaxation time towards the steady state increases with mass. For small dunes we find significant deviations from a fixed height-length aspect ratio. As predicted by recent theoretical models, the migration velocity scales reciprocal to the length of the dune. PMID:18850828

  14. Preliminary study of Kelso Dunes using AVIRIS, TM, and AIRSAR

    NASA Technical Reports Server (NTRS)

    Xu, Pung; Blumberg, Dan G.; Greeley, Ronald

    1995-01-01

    Remote sensing of sand dunes helps in the understanding of aeolian process and provides important information about the regional geologic history, environmental change, and desertification. Remotely sensed data combined with field studies are valuable in studying dune morphology, regional aeolian dynamics, and aeolian depositional history. In particular, active and inactive sands of the Kelso Dunes have been studied using landsat TM and AIRSAR. In this report, we describe the use of AVIRIS data to study the Kelso dunes and to compare the AVIRIS information with that from TM and AIRSAR.

  15. Multi-spatial analysis of aeolian dune-field patterns

    NASA Astrophysics Data System (ADS)

    Ewing, Ryan C.; McDonald, George D.; Hayes, Alex G.

    2015-07-01

    Aeolian dune-fields are composed of different spatial scales of bedform patterns that respond to changes in environmental boundary conditions over a wide range of time scales. This study examines how variations in spatial scales of dune and ripple patterns found within dune fields are used in environmental reconstructions on Earth, Mars and Titan. Within a single bedform type, different spatial scales of bedforms emerge as a pattern evolves from an initial state into a well-organized pattern, such as with the transition from protodunes to dunes. Additionally, different types of bedforms, such as ripples, coarse-grained ripples and dunes, coexist at different spatial scales within a dune-field. Analysis of dune-field patterns at the intersection of different scales and types of bedforms at different stages of development provides a more comprehensive record of sediment supply and wind regime than analysis of a single scale and type of bedform. Interpretations of environmental conditions from any scale of bedform, however, are limited to environmental signals associated with the response time of that bedform. Large-scale dune-field patterns integrate signals over long-term climate cycles and reveal little about short-term variations in wind or sediment supply. Wind ripples respond instantly to changing conditions, but reveal little about longer-term variations in wind or sediment supply. Recognizing the response time scales across different spatial scales of bedforms maximizes environmental interpretations from dune-field patterns.

  16. Digital mapping of the extent of global dune systems

    NASA Astrophysics Data System (ADS)

    Hesse, Paul; Lancaster, Nicholas; Telfer, Matt

    2015-04-01

    Inland dune systems occur on all continents and at all latitudes, yet until now there is no digital map of their location and extent. We have compiled a new digital map of the extent of inland dune systems worldwide from published and unpublished sources, supplemented by manual digitizing of additional sand seas and dune fields. The digital database is compiled in ArcGIS, allowing mapping at scales from global to regional. The database contains spatial information on approximately 200 dune fields and sand seas ranging in size from less than 2 square km to as much as 630,000 sq km, covering a total global area of 29.4 million sq km. It includes both currently active unvegetated sand seas and dune fields, as well as partially vegetated and vegetated areas of dunes and sand sheets. Where available, the database contains information on dune type and status (active or stabilized). Manual digitizing of dune and sand sheet areas, as well as correction of existing digital coverages was accomplished mainly using ESRI imagery resources, with constant reference to ancillary information from publications and previous mapping. Compilation of the database required extensive research on the geographic names for different dune areas, as well as dunefield status and extent. The database and maps derived from it will be available online at http://inquadunesatlas.dri.edu/. We envisage it will be a dynamic and ongoing project and solicit corrections and additional information, including new and revised digital coverages, from the scientific community.

  17. Sand dune materials and polar layered deposits on Mars

    NASA Astrophysics Data System (ADS)

    Thomas, P.; Weitz, C.

    1989-09-01

    The possible place of sand in the Martian polar layered deposits is examined. The erosional features in layered deposits and the morphologic relationship of dunes and the layered deposits are discussed. The colors of the polar dunes are shown to be similar to the colors of dunes at other latitudes, suggesting that the polar dunes can be explained without any special or exotic mechanism. Consideration is given to mixing and segregation of materials by eolian processes observed on Mars, showing that sand was probably carried to the polar regions during part of the formation of the layered deposits.

  18. Column experiments to study nonlinear removal of bacteriophages by passage through saturated dune sand.

    PubMed

    Schijven, J F; Hassanizadeh, S M; de Bruin, H A M

    2002-10-01

    In a recent field study on dune recharge, bacteriophages MS2 and PRD1 were found to be removed 3 log10 over the first 2.4 m and only 5 log10 over the next 27 m. To understand the causes of this nonlinear removal, column experiments were carried out under conditions similar to the field: same recharge water, temperature (5 +/- 3 degrees C) and pore water velocity (1.5 m day(-1)). Soil samples were taken along a streamline between the recharge canal and the first monitoring well. Bacteriophage phiX174 was included for comparison. The high initial removal in the field was found not to be due to heterogeneity of phage suspensions but to soil heterogeneity. Phage removal rates correlated strongly positively with soil organic carbon content, and relatively strongly positively with silt content and the presence of ferric oxyhydroxides. Soil organic carbon content, silt content and the presence of ferric oxyhydroxides were found to decrease exponentially with travel distance. Removal rates of phiX174 were found to be 3-10 times higher than those of MS2 and PRD1 due to the lower electrostatic repulsion that the less negatively charged phiX174 experiences. It is suggested that the high initial removal in the field is due to the presence of favorable sites for attachment formed by ferric oxyhydroxides that decrease exponentially with travel distance. Similar removal rates may be found at both laboratory and field scale. However, due to local variations at field scale detailed knowledge on soil heterogeneity may be needed to enable a reliable prediction of removal. PMID:12400835

  19. High albedo dune features suggest past dune migration and possible geochemical cementation of aeolian sediments on Mars

    NASA Astrophysics Data System (ADS)

    Gardin, Emilie; Bourke, Mary C.; Allemand, Pascal; Quantin, Cathy

    2011-04-01

    High albedo features are identified in association with barchan dunes in an equatorial inter-crater dune field on Mars using images from the MRO mission. This paper describes the morphometric properties of these features and their association with the present barchan dune field. We propose that these features are cemented aeolian deposits that form at the foot of the dune avalanche face. A possible terrestrial analog exists at White Sands National Monument, in south-central New Mexico, USA. The presence of these features suggests past episodes of dune migration in inter-crater dunefields and liquid water in the near sub-surface in sufficient quantity to cause the cementation of aeolian dune sediment.

  20. A Comparative Analysis of Barchan Dunes in the Intra-Crater Dune Fields and the North Polar Sand Sea

    NASA Technical Reports Server (NTRS)

    Bourke, M. C.; Balme, M.; Zimbelman, J.

    2004-01-01

    Martian sand dunes have the potential to contribute data on geological history through a study of their form. Recognition of the characteristics of both recent and ancient dunes is the first step towards understanding the present as well as past aeolian systems, and by proxy, climatic conditions on Mars. Dunes studied in detail in Viking 1 and 2 Orbiter images have been classified as barchan, barchanoid, transverse, and complex. Regionally, they are concentrated in four locations: The North and South Polar regions, in intra crater dune fields and in troughs and valleys. Here we present the results of a morphometric analysis of barchan dunes in two of these locations: the North Polar Sand Sea (NPSS) and intra-crater dunes.

  1. 44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... storm-induced dune erosion potential in its determination of coastal flood hazards and risk mapping efforts. The criterion to be used in the evaluation of dune erosion will apply to primary frontal dunes...

  2. 44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... storm-induced dune erosion potential in its determination of coastal flood hazards and risk mapping efforts. The criterion to be used in the evaluation of dune erosion will apply to primary frontal dunes...

  3. 44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... storm-induced dune erosion potential in its determination of coastal flood hazards and risk mapping efforts. The criterion to be used in the evaluation of dune erosion will apply to primary frontal dunes...

  4. 44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... storm-induced dune erosion potential in its determination of coastal flood hazards and risk mapping efforts. The criterion to be used in the evaluation of dune erosion will apply to primary frontal dunes...

  5. Dune field pattern formation and recent transporting winds in the Olympia Undae Dune Field, north polar region of Mars

    NASA Astrophysics Data System (ADS)

    Ewing, Ryan C.; Peyret, Aymeric-Pierre B.; Kocurek, Gary; Bourke, Mary

    2010-08-01

    High-Resolution Imaging Science Experiment (HiRISE) imagery of the central Olympia Undae Dune Field in the north polar region of Mars shows a reticulate dune pattern consisting of two sets of nearly orthogonal dune crestlines, with apparent slipfaces on the primary crests, ubiquitous wind ripples, areas of coarse-grained wind ripples, and deflated interdune areas. Geomorphic evidence and dune field pattern analysis of dune crest length, spacing, defect density, and orientation indicates that the pattern is complex, representing two constructional generations of dunes. The oldest and best-organized generation forms the primary crestlines and is transverse to circumpolar easterly winds. Gross bed form-normal analysis of the younger pattern of crestlines indicates that it emerged with both circumpolar easterly winds and NE winds and is reworking the older pattern. Mapping of secondary flow fields over the dunes indicates that the most recent transporting winds were from the NE. The younger pattern appears to represent an influx of sediment to the dune field associated with the development of the Olympia Cavi reentrant, with NE katabatic winds channeling through the reentrant. A model of the pattern reformation based upon the reconstructed primary winds and resulting secondary flow fields shows that the development of the secondary pattern is controlled by the boundary condition of the older dune topography.

  6. Mars Global Digital Dune Database: MC2-MC29

    USGS Publications Warehouse

    Hayward, Rosalyn K.; Mullins, Kevin F.; Fenton, L.K.; Hare, T.M.; Titus, T.N.; Bourke, M.C.; Colaprete, Anthony; Christensen, P.R.

    2007-01-01

    Introduction The Mars Global Digital Dune Database presents data and describes the methodology used in creating the database. The database provides a comprehensive and quantitative view of the geographic distribution of moderate- to large-size dune fields from 65? N to 65? S latitude and encompasses ~ 550 dune fields. The database will be expanded to cover the entire planet in later versions. Although we have attempted to include all dune fields between 65? N and 65? S, some have likely been excluded for two reasons: 1) incomplete THEMIS IR (daytime) coverage may have caused us to exclude some moderate- to large-size dune fields or 2) resolution of THEMIS IR coverage (100m/pixel) certainly caused us to exclude smaller dune fields. The smallest dune fields in the database are ~ 1 km2 in area. While the moderate to large dune fields are likely to constitute the largest compilation of sediment on the planet, smaller stores of sediment of dunes are likely to be found elsewhere via higher resolution data. Thus, it should be noted that our database excludes all small dune fields and some moderate to large dune fields as well. Therefore the absence of mapped dune fields does not mean that such dune fields do not exist and is not intended to imply a lack of saltating sand in other areas. Where availability and quality of THEMIS visible (VIS) or Mars Orbiter Camera narrow angle (MOC NA) images allowed, we classifed dunes and included dune slipface measurements, which were derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. For dunes located within craters, the azimuth from crater centroid to dune field centroid was calculated. Output from a general circulation model (GCM) is also included. In addition to polygons locating dune fields, the database includes over 1800 selected Thermal Emission Imaging System (THEMIS) infrared (IR), THEMIS visible (VIS) and Mars Orbiter Camera Narrow Angle (MOC NA

  7. Groundwater recharge estimation and regionalization: the Great Bend Prairie of central Kansas and its recharge statistics

    USGS Publications Warehouse

    Sophocleous, M.

    1992-01-01

    The results of a 6 year recharge study in the Great Bend Prairie of central Kansas are statistically analyzed to regionalize the limited number of site-specific but year-round measurements. Emphasis is placed on easily measured parameters and field-measured data. The results of the statistical analysis reveal that a typical recharge event in central Kansas lasts 5-7 days, out of which 3 or 4 days are precipitation days with total precipitation of ??? 83 mm. The maximum soil-profile water storage and the maximum groundwater level resulting from the recharge event exhibit the lowest coefficients of variation, whereas the amount of recharge exhibits the highest coefficient of variation. The yearly recharge in the Great Bend Prairie ranged from 0 to 177 mm with a mean of 56 mm. Most of the recharge events occur during the months of April, May, and June, which coincide with the months of highest precipitation in the region. A multiple regression analysis revealed that the most influential variables affecting recharge are, in order of decreasing importance, total annual precipitation average maximum soil-profile water storage during the spring months, average shallowest depth to water table during the same period, and spring rainfall rate. Classification methods, whereby relatively homogeneous hydrologic-unit areas based on the four recharge-affecting variables are identified, were combined with a Geographic Information Systems (ARC/INFO) overlay analysis to derive an area-wide map of differing recharge regions. This recharge zonation is in excellent agreement with the field-site recharge values. The resulting area-weighted average annual recharge for the region is 36 mm. ?? 1992.

  8. Aeolian Processes of the Pismo-Oceano Dune Complex, California

    NASA Astrophysics Data System (ADS)

    Barrineau, C. P.; Tchakerian, V.; Houser, C.

    2012-12-01

    The Pismo Dunes are located approximately 250 km northwest of Los Angeles and consist of 90 km2 of transverse, parabolic and paleodunes. The Pismo Dunes are one of the largest dune complexes on the west coast and are the largest remaining south of San Francisco Bay, but despite their size, relatively few process morphology studies have focused on their form and history. Specifically, the dune field includes 12 km2 of actively migrating transverse dune ridges advancing onshore in three distinct phases separated by small depressions easily indentified using a LiDAR-generated elevation model. An early field investigation by Tchakerian (1983) revealed a uniform increase in slip face heights and crestline wavelengths inland with no apparent change in grain size. Measurement of recent aerial imagery shows variable migration rates throughout the dunes and wavelengths between 30 and 100 m closest to the beach, in the second ridge between 50 and 140 m, and from 70 to 250 m furthest inland. During El Niño and La Niña periods, westerly winds advance onshore nearly perpendicular to the crestlines, fueling episodic migration of the dune field. It is hypothesized that particularly strong ENSO periods may have led to the development of distinct dune phases with separating depressions and the development of defects along the dune crest. Defects associated with the wakes of incipient vegetation and inter-dune depressions are conspicuous and widespread, though localized and variable through time and space. Aerial imagery taken in September 1994 shows a wider, more even distribution of defects across the dune field than currently visible. The signal is, however, complicated by the closure of the dune field to oversand vehicles in 1982. The closure of much of the complex to vehicular traffic in 1982 may play a role, as Tchakerian's crestline wavelength measurements were far smaller than those obtained for this study while maintaining a likewise increase between phases. At a decadal

  9. Morphodynamic implications of flow around interacting barchan dunes

    NASA Astrophysics Data System (ADS)

    Tang, Z.; Blois, G.; Best, J.; Jiang, N.; Christensen, K. T.

    2013-12-01

    Barchan dunes are three-dimensional topographic features characterized by a crescentic shape. These bedforms are ubiquitous on Earth's surface and are also observed on Mars. Barchan dunes are predominantly found in regions of sediment starvation and unidirectional flow. The barchans-dune migration rates for a given wind speed are a function of their respective volume. A barchan dune field is composed of a widely distributed dune size, which provides the potential for barchan dunes to approach and amalgamate. The mechanisms governing dune-dune interaction, collision and merging remain poorly understood for such complex three-dimensional bedforms due to the complexity of their shape and the high number of geometrical configurations that can occur. In order to quantify the flow structure produced by interacting barchan dunes, particle-image Velocimetry (PIV) is coupled with a refractive-index-matching (RIM) approach, facilitating full optical access to the obstructed regions of flow and eliminates reflections from the liquid-solid boundaries, allowing near-wall data to be collected. Transparent barchan dune models with different volumes are arranged in tandem, immersed in a turbulent flow and rendered invisible through accurate matching of the index of refraction of the solid and fluid phases. The approach applied herein facilitates flow-field measurements in both streamwise-wall-normal planes at varying spanwise positions and streamwise-spanwise planes at varying elevations. Ensemble-averaged flow fields and Reynolds stresses were obtained for different barchan dune spacings and compared to the reference case of an isolated barchan. Additionally, proper orthogonal decomposition (POD) analysis was employed to shed light as to the energetic attributes of the shear-layer interactions. The morphodynamic implications of these results are discussed. Shear-layer interactions between adjacent bedforms, stoss-side erosion and downstream separation of new bedforms from the

  10. Relating climate and sand transport to incipient dune development.

    NASA Astrophysics Data System (ADS)

    van Puijenbroek, Marinka; Limpens, Juul; Gleichman, Maurits; Berendse, Frank

    2014-05-01

    Sea levels are continuously rising, increasing the risk of flooding and coastal erosion in low-elevation countries, such as the Netherlands. Coastal dunes are seen as a flexible and natural type of coastal defence, that is able to keep pace with rising water levels. Until now most research has focussed on dynamics and maintenance of established dunes, largely ignoring two critical transitions in early dune development: the transition from bare beach to vegetated incipient dune and that from incipient dune to established foredune. This knowledge is essential to enable more accurate prediction and even stimulation of new dune formation through sand nourishment. We explored the relative contributions of climate and sand transport to incipient dune development combining a 30 year time-series of aerial photographs (1979 - 2010) of the natural Wadden Island coast with high-resolution monitoring data of sand volume changes and climatic parameters. We selected 20 strips of 2.5 km in length along the coast of the Wadden Islands, with a 2 km buffer between them to avoid autocorrelation. For each of these strips of coast we assessed the changes in presence and area of incipient dunes over periods of 5-6 years. Change in fore dune volume and beach width were derived from high resolution beach elevation data. Seawater level and climate data were derived from a nearby meteorological station Preliminary analysis of the first half of the dataset showed that incipient dune area was positively related to beach width, but negatively to storm intensity. In our poster we will present the whole dataset and discuss the implications of our results for future dune development and anthropogenic sand nourishment schemes.

  11. Titan dune heights retrieval by using Cassini Radar Altimeter

    NASA Astrophysics Data System (ADS)

    Mastrogiuseppe, M.; Poggiali, V.; Seu, R.; Martufi, R.; Notarnicola, C.

    2014-02-01

    The Cassini Radar is a Ku band multimode instrument capable of providing topographic and mapping information. During several of the 93 Titan fly-bys performed by Cassini, the radar collected a large amount of data observing many dune fields in multiple modes such as SAR, Altimeter, Scatterometer and Radiometer. Understanding dune characteristics, such as shape and height, will reveal important clues on Titan's climatic and geological history providing a better understanding of aeolian processes on Earth. Dunes are believed to be sculpted by the action of the wind, weak at the surface but still able to activate the process of sand-sized particle transport. This work aims to estimate dunes height by modeling the shape of the real Cassini Radar Altimeter echoes. Joint processing of SAR/Altimeter data has been adopted to localize the altimeter footprints overlapping dune fields excluding non-dune features. The height of the dunes was estimated by applying Maximum Likelihood Estimation along with a non-coherent electromagnetic (EM) echo model, thus comparing the real averaged waveform with the theoretical curves. Such analysis has been performed over the Fensal dune field observed during the T30 flyby (May 2007). As a result we found that the estimated dunes' peak to trough heights difference was in the order of 60-120 m. Estimation accuracy and robustness of the MLE for different complex scenarios was assessed via radar simulations and Monte-Carlo approach. We simulated dunes-interdunes different composition and roughness for a large set of values verifying that, in the range of possible Titan environment conditions, these two surface parameters have weak effects on our estimates of standard dune heights deviation. Results presented here are the first part of a study that will cover all Titan's sand seas.

  12. Boundary Conditions for Aeolian Activity in North American Dune Fields

    NASA Astrophysics Data System (ADS)

    Halfen, A. F.; Lancaster, N.; Wolfe, S.

    2014-12-01

    Geomorphic and chronological data for dune fields are evaluated for three contrasting areas of North America: 1) the Prairie-Parkland-Boreal ecozones of the northern Great Plains in Canada; 2) the Central Great Plains of the USA; and 3) the deserts of southwestern USA and northern Mexico. Luminescence and radiocarbon ages for periods of dune accumulation and stability are compared with palaeoenvironment proxies to provide an assessment of the boundary conditions of dune system response to changes in sediment supply, availability, and mobility. Dune fields in the northern Great Plains were formed from sediment originating from glaciofluvial or glaciolacustrine sediments deposited during deglaciation 16-11 ka. Subsequent aeolian deposition occurred in Parkland and Prairie dune fields as a result of mid-Holocene (8-5 ka) and late-Holocene (< 3.5 ka) activity related to drought conditions that reworked pre-existing aeolian sands. In the Central Great Plains, dune fields are closely linked to fluvial sediment sources. Sediment supply was high during deglaciation of the Rocky Mountains and resulted in widespread dune construction 16-10 ka. Multiple periods of Holocene reactivation are recorded and reflect increased sediment availability during drought episodes. Dune fields in the southwestern deserts experienced periods of construction as a result of enhanced supply of sediment from fluvial and lacustrine sources during the period 11.8-8 ka and at multiple intervals during the late Holocene. Despite spatial and temporal gaps in chronometric data as a result of sampling biases, the record from North American dune fields indicates the strong influence of sediment supply on dune construction, with changes in sediment availability as a result of drought episodes resulting in dune field reactivation and reworking of pre-existing sediment.

  13. Riverine Eolian Dunes in Uruguay: OSL Ages and Paleoenvironmental Significance

    NASA Astrophysics Data System (ADS)

    Leigh, D. S.; Suarez, R.; Brook, G. A.

    2012-12-01

    Relict parabolic dunes occur along Rio Negro and Rio Tacuarembó in Uruguay under the current humid temperate climate. These dunes offer important terrestrial evidence of drier conditions in the past and may provide foresight about landscape consequences of future climate change. The ages of these dunes previously had not been measured by any absolute dating technique. Two dune fields were selected for optically stimulated luminescence (OSL) dating using the single aliquot regeneration method, including four samples along Rio Negro near Pueblo de la Arena and three samples along Rio Tacuarembó near Ansina. Results indicate that the dunes were active during the late Pleistocene, with five of the OSL ages in the 22 ka to 12 ka range. One OSL age at the Ansina dune field returned an age of 6 ka, indicating the possibility of limited dune reactivation during the Holocene. There is clear evidence of historical dune activation (e.g. buried fences) at both the Rio Negro and Rio Tacuarembó sites; one OSL sample from Rio Negro dunes confirms an historical age of 107 years BP. However, human land disturbance rather than climatic factors may explain the historical reactivation. Late Pleistocene dune activity in central Uruguay indicates much drier and windier paleoclimate (at least seasonally) than present, and correlates well with eolian activity in more arid parts of South America in western Argentina. Age and paleoenvironment of the riverine dunes in Uruguay are remarkably similar to those of the southeastern United States (USA), indicating similar patterns of paleoclimate in both hemispheres. Such similarities help to resolve the spatial patterns of global scale climate change.

  14. REVISED NORTH CAROLINA GROUNDWATER RECHARGE RATES 1998

    EPA Science Inventory

    Revised North Carolina Groundwater Recharge Rates, from Heath, R.C., 1994, unpublished map: North Carolina State University, as modified by the NC Department of Environment and Natural Resources (DENR) Division of Water Quality (DWQ) Groundwater Section, (polygons)

  15. Issues and challenges facing rechargeable lithium batteries.

    PubMed

    Tarascon, J M; Armand, M

    2001-11-15

    Technological improvements in rechargeable solid-state batteries are being driven by an ever-increasing demand for portable electronic devices. Lithium-ion batteries are the systems of choice, offering high energy density, flexible and lightweight design, and longer lifespan than comparable battery technologies. We present a brief historical review of the development of lithium-based rechargeable batteries, highlight ongoing research strategies, and discuss the challenges that remain regarding the synthesis, characterization, electrochemical performance and safety of these systems. PMID:11713543

  16. Proposed artificial recharge studies in northern Qatar

    USGS Publications Warehouse

    Kimrey, J.O.

    1985-01-01

    The aquifer system in northern Qatar comprises a water-table aquifer in the Rus Formation which is separated by an aquitard from a partially confined aquifer in the top of the overlying Umm er Radhuma Formation. These two aquifers are composed of limestone and dolomite of Eocene and Paleocene age and contain a fragile lens of freshwater which is heavily exploited as a source of water for agricultural irrigation. Net withdrawals are greatly in excess of total recharge, and quality of ground water is declining. Use of desalinated seawater for artificial recharge has been proposed for the area. Artificial recharge, on a large scale, could stabilize the decline in ground-water quality while allowing increased withdrawals for irrigation. The proposal appears technically feasible. Recharge should be by injection to the Umm er Radhuma aquifer whose average transmissivity is about 2,000 meters squared per day (as compared to an average of about 200 meters squared per day for the Rus aquifer). Implementation of artificial recharge should be preceded by a hydrogeologic appraisal. These studies should include test drilling, conventional aquifer tests, and recharge-recovery tests at four sites in northern Qatar. (USGS)

  17. Artificial recharge of groundwater: hydrogeology and engineering

    NASA Astrophysics Data System (ADS)

    Bouwer, Herman

    2002-02-01

    Artificial recharge of groundwater is achieved by putting surface water in basins, furrows, ditches, or other facilities where it infiltrates into the soil and moves downward to recharge aquifers. Artificial recharge is increasingly used for short- or long-term underground storage, where it has several advantages over surface storage, and in water reuse. Artificial recharge requires permeable surface soils. Where these are not available, trenches or shafts in the unsaturated zone can be used, or water can be directly injected into aquifers through wells. To design a system for artificial recharge of groundwater, infiltration rates of the soil must be determined and the unsaturated zone between land surface and the aquifer must be checked for adequate permeability and absence of polluted areas. The aquifer should be sufficiently transmissive to avoid excessive buildup of groundwater mounds. Knowledge of these conditions requires field investigations and, if no fatal flaws are detected, test basins to predict system performance. Water-quality issues must be evaluated, especially with respect to formation of clogging layers on basin bottoms or other infiltration surfaces, and to geochemical reactions in the aquifer. Clogging layers are managed by desilting or other pretreatment of the water, and by remedial techniques in the infiltration system, such as drying, scraping, disking, ripping, or other tillage. Recharge wells should be pumped periodically to backwash clogging layers. Electronic supplementary material to this paper can be obtained by using the Springer LINK server located at http://dx.doi.org/10.1007/s10040-001-0182-4.

  18. Evidence for community structure and habitat partitioning in coastal dune stiletto flies at the Guadalupe-Nipomo dunes system, California

    PubMed Central

    Holston, Kevin C.

    2005-01-01

    This study provides empirical evidence for habitat selection by North American species of stiletto flies (Diptera: Therevidae), based on local distributions of adults and immatures, and the first hypothesis of community assemblages proposed for a stiletto fly community. Sites at three localities within the Guadalupe-Nipomo dune system were sampled for stiletto flies in 1997 and 2001 by sifting sand, malaise trapping, and hand netting. Nine species were collected from four ecological zones and three intermediate ecological zones: Acrosathe novella (Coquillett), Brachylinga baccata (Loew), Nebritus powelli (Webb and Irwin), Ozodiceromyia sp., Pherocera sp., Tabudamima melanophleba (Loew), Thereva comata Loew, Thereva elizabethae Holston and Irwin, and Thereva fucata Loew. Species associations of adults and larvae with habitats and ecological zones were consistent among sites, suggesting that local distributions of coastal dune stiletto fly species are influenced by differences in habitat selection. In habitats dominated by the arroyo willow,Salix lasiolepsis, stiletto fly larvae of three species were collected in local sympatry, demonstrating that S. lasiolepsis stands along stabilized dune ridges can provide an intermediate ecological zone linking active dune and riparian habitat in the Guadalupe-Nipomo dune system. Sites dominated by European beach grass, Ammophilia arenaria, blue gum, Eucalyptus globulus, and Monterey cypress, Cupressus macrocarpa, are considered unsuitable for stiletto flies, which emphasizes the importance of terrestrial habitats with native vegetation for stiletto fly species. The local distributions of stiletto fly species at the Guadalupe-Nipomo dune system allow the community to be divided into three assemblages; active dune, pioneer scrub, and scrub-riparian. These assemblages may be applicable to other coastal dune stiletto fly communities, and may have particular relevance to stiletto fly species collected in European coastal dunes. The

  19. Evidence for community structure and habitat partitioning in coastal dune stiletto flies at the Guadalupe-Nipomo dunes system, California.

    PubMed

    Holston, Kevin C

    2005-01-01

    This study provides empirical evidence for habitat selection by North American species of stiletto flies (Diptera: Therevidae), based on local distributions of adults and immatures, and the first hypothesis of community assemblages proposed for a stiletto fly community. Sites at three localities within the Guadalupe-Nipomo dune system were sampled for stiletto flies in 1997 and 2001 by sifting sand, malaise trapping, and hand netting. Nine species were collected from four ecological zones and three intermediate ecological zones: Acrosathe novella (Coquillett), Brachylinga baccata (Loew), Nebritus powelli (Webb and Irwin), Ozodiceromyia sp., Pherocera sp., Tabudamima melanophleba (Loew), Thereva comata Loew, Thereva elizabethae Holston and Irwin, and Thereva fucata Loew. Species associations of adults and larvae with habitats and ecological zones were consistent among sites, suggesting that local distributions of coastal dune stiletto fly species are influenced by differences in habitat selection. In habitats dominated by the arroyo willow,Salix lasiolepsis, stiletto fly larvae of three species were collected in local sympatry, demonstrating that S. lasiolepsis stands along stabilized dune ridges can provide an intermediate ecological zone linking active dune and riparian habitat in the Guadalupe-Nipomo dune system. Sites dominated by European beach grass, Ammophilia arenaria, blue gum, Eucalyptus globulus, and Monterey cypress, Cupressus macrocarpa, are considered unsuitable for stiletto flies, which emphasizes the importance of terrestrial habitats with native vegetation for stiletto fly species. The local distributions of stiletto fly species at the Guadalupe-Nipomo dune system allow the community to be divided into three assemblages; active dune, pioneer scrub, and scrub-riparian. These assemblages may be applicable to other coastal dune stiletto fly communities, and may have particular relevance to stiletto fly species collected in European coastal dunes. The

  20. Particle tracking and mean residence time in barchan dunes

    NASA Astrophysics Data System (ADS)

    Zhang, Deguo; Narteau, Clement; Rozier, Olivier

    2013-04-01

    We analyze sediment particles motions in steady-state barchan dunes by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan dune shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchan dunes. Then, for different flow strength and dune size, we find that the mean residence time of sediment particles in barchan dunes is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan dune morphodynamics. Finally, we initiate a discussion about sediment transport and memory in presence of bedforms using the advantages of the particle tracking technique.

  1. Narrowing the gap between real and simulated barchan dune dynamics

    NASA Astrophysics Data System (ADS)

    Hugenholtz, C.; Barchyn, T. E.

    2011-12-01

    There are a growing number of computer simulation models capable of reproducing many of the morphological characteristics and dynamics of real barchan sand dunes. While these models offer tremendous insight and opportunities to develop hypotheses, there is a relative paucity of empirical observations to use as a basis for validation. To address this issue we present empirical observations of barchan dune dynamics using high-resolution, multi-temporal satellite imagery from locations in Peru, Namibia, and Mauritania. We highlight the response of barchan dunes to collisions, wind direction variability, interactions with bedrock topography, and depletion of sediment supply. First, we document the process of dunes emerging from the slipfaces of barchan dunes. In the past, this process was only observed in numerical models or interpreted from single-date imagery. We also show that collisions can result in calving or shedding of dunes from the horns. Second, we present the first empirical evidence of barchans changing into dome and "wedge" dunes under the influence of bimodal winds. Third, we show that barchans break down when they encounter uphill topography. However, they can re-form in the lee of a bedrock obstacle if sediment supply is sufficient. Finally, we show that, in the absence of collisions, small barchans can disappear quickly when they lose upwind sediment supply. Altogether, our observations add to the empirical record of barchan dune dynamics and are useful for evaluating the behaviour of numerical models.

  2. Luminescence chronology of the inland sand dunes from SE India

    NASA Astrophysics Data System (ADS)

    Reddy, Dontireddy Venkat; Singaraju, Vuddaraju; Mishra, Rakesh; Kumar, Devender; Thomas, Puthusserry Joseph; Rao, Karra Kameshwa; Singhvi, Ashok Kumar

    2013-09-01

    Records of past climate changes have been preserved variously on the earth's surface. Sand dunes are one such prominent imprint, and it is suggested that their presence is an indicator of periods of transition from arid to less arid phases. We report inland sand dunes from Andhra Pradesh (SE India) spread over an area of ~ 500 km2, ~ 75 km inland from the east coast. The dune sands are examined to understand their provenance, transportation, timing of sand aggradation and their relationship to past climates. The dune distribution, grain morphology and the grain-size studies on sands suggest an aeolian origin. Physiography of the study area, heavy mineral assemblage, and abundance of quartz in the parent rocks indicate that the dune sands are largely derived from first-order streams emanating from hills in the region and from weathering of the Nellore schist belt. It appears that the geomorphology and wind direction pattern both facilitated and restricted the dune aggradation and preservation to a limited area. OSL dating of 47 dune samples ranged from the present to ~ 50 ka, thereby suggesting a long duration of sand-dune aggradation and/or reworking history.

  3. Methane storms as a driver of Titan's dune orientation

    NASA Astrophysics Data System (ADS)

    Charnay, Benjamin; Barth, Erika; Rafkin, Scot; Narteau, Clément; Lebonnois, Sébastien; Rodriguez, Sébastien; Courrech Du Pont, Sylvain; Lucas, Antoine

    2015-05-01

    The equatorial regions of Saturn's moon Titan are covered by linear dunes that propagate eastwards. Global climate models (GCMs), however, predict westward mean surface winds at low latitudes on Titan, similar to the trade winds on Earth. This apparent contradiction has been attributed to Saturn's gravitational tides, large-scale topography and wind statistics, but none of these hypotheses fully explains the global eastward propagation of dunes in Titan's equatorial band. However, above altitudes of about 5 km, Titan's atmosphere is in eastward super-rotation, suggesting that this momentum may be delivered to the surface. Here we assess the influence of equatorial tropical methane storms--which develop at high altitudes during the equinox--on Titan's dune orientation, using mesoscale simulations of convective methane clouds with a GCM wind profile that includes super-rotation. We find that these storms produce fast eastward gust fronts above the surface that exceed the normal westward surface winds. These episodic gusts generated by tropical storms are expected to dominate aeolian transport, leading to eastward propagation of dunes. We therefore suggest a coupling between super-rotation, tropical methane storms and dune formation on Titan. This framework, applied to GCM predictions and analogies to some terrestrial dune fields, explains the linear shape, eastward propagation and poleward divergence of Titan's dunes, and implies an equatorial origin of dune sand.

  4. 36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Sleeping Bear Dunes National... INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National... applicable State law is allowed. (c) Bicycling. (1) The Sleeping Bear Heritage Trail, approximately 27...

  5. 36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless flight. The use...

  6. 36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 1 2011-07-01 2011-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes...

  7. 36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes...

  8. 36 CFR 7.88 - Indiana Dunes National Lakeshore.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore....

  9. 36 CFR 7.88 - Indiana Dunes National Lakeshore.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 36 Parks, Forests, and Public Property 1 2014-07-01 2014-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore....

  10. 36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 36 Parks, Forests, and Public Property 1 2010-07-01 2010-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes...

  11. 36 CFR 7.88 - Indiana Dunes National Lakeshore.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 36 Parks, Forests, and Public Property 1 2012-07-01 2012-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore....

  12. Coastal Sand Dune Plant Ecology: Field Phenomena and Interpretation

    ERIC Educational Resources Information Center

    McDonald, K.

    1973-01-01

    Discusses the advantages and disadvantages of selecting coastal sand dunes as the location for field ecology studies. Presents a descriptive zonal model for seaboard sand dune plant communities, suggestions concerning possible observations and activities relevant to interpreting phenomena associated with these forms of vegetation, and additional…

  13. 36 CFR 7.88 - Indiana Dunes National Lakeshore.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 36 Parks, Forests, and Public Property 1 2011-07-01 2011-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore....

  14. Holocene eolian activity in the Minot dune field, North Dakota

    USGS Publications Warehouse

    Muhs, D.R.; Stafford, Thomas W., Jr.; Been, J.; Mahan, S.A.; Burdett, J.; Skipp, G.; Rowland, Z.M.

    1997-01-01

    Stabilized eolian sand is common over much of the Great Plains region of the United States and Canada, including a subhumid area of ??? 1500 km2 near Minot, North Dakota. Eolian landforms consist of sand sheets and northwest-trending parabolic dunes. Dunes and sand sheets in the Minot field are presently stabilized by a cover of prairie grasses or oak woodland. Stratigraphic studies and accelerator mass spectrometry radiocarbon dating of paleosols indicate at least two periods of eolian sand movement in the late Holocene. Pedologic data suggest that all of the dune field has experienced late Holocene dune activity, though not all parts of the dune field may have been active simultaneously. Similar immobile element (Ti, Zr, La, Ce) concentrations support the interpretation that eolian sands are derived from local glaciofluvial and glaciolacustrine sediments. However, glaciolacustrine and glaciofluvial source sediments have high Ca concentrations from carbonate minerals, whereas dune sands are depleted in Ca. Because noneolian-derived soils in the area are calcareous, these data indicate that the Minot dune field may have had extended periods of activity in the Holocene, such that eolian abrasion removed soft carbonate minerals. The southwest-facing parts of some presently stabilized dunes were active during the 1930s drought, but were revegetated during the wetter years of the 1940s. These observations indicate that severe droughts accompanied by high temperatures are the most likely cause of Holocene eolian activity.

  15. 36 CFR 7.88 - Indiana Dunes National Lakeshore.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 36 Parks, Forests, and Public Property 1 2013-07-01 2013-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks, Forests, and Public Property NATIONAL PARK SERVICE, DEPARTMENT OF THE INTERIOR SPECIAL REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore....

  16. Movement of Whole Martian Dunes Difficult to Detect or Confirm

    NASA Technical Reports Server (NTRS)

    2000-01-01

    Dunes on Earth move downwind at different speeds depending upon the local wind conditions, the amount of loose sand available to be transported by wind, the shape and volume of the dunes, and overgrowths of vegetation. Typically, smaller dunes move faster than larger dunes. On Earth, some of the fastest-moving dunes that have been measured (e.g., in the deserts of Peru) move 10 to 30 meters (33 to 100 feet) per year. Small dunes usually have an almost crescent-shape to them, and are known to geologists as barchan dunes.

    To look for evidence of dune movement on Mars, the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) has been used to re-visit some areas of known barchan dunes--because these types move the fastest--that were observed by the Mariner 9 orbiter in 1972 and the Viking 1 and 2 orbiters between 1976 and 1980. The picture above, left, shows a MOC high-resolution image taken December 25, 1999. The classic, crescentic shape of the dark barchan dunes can be seen in this picture. The steep slopes, also known as the dune slip faces, on these dunes are facing toward the southwest (north is up in both pictures). Thus, the shape of the dunes indicates that they are moving toward the southwest.

    The picture above right shows the MOC image from December 1999 superimposed on a Viking 1 image taken May 27, 1978. During the 11 1/2 Mars years that passed between these two dates, it turns out that no difference can be detected in the position of the dunes seen in the MOC image and the Viking image. The earlier Viking image had a resolution of about 17 meters (56 ft) per pixel, while the MOC image had a resolution of about 3.8 meters (12 ft) per pixel. Although it looks like the dunes didn't move between the Viking and MOC images, this observation is limited by the resolution of the Viking image. It is entirely possible that the dunes have moved as much as 17-20 meters (16-66 ft) and one would not be able to tell by comparing the images. As it is, movement

  17. The dune effect on sand-transporting winds on Mars

    PubMed Central

    Jackson, Derek W. T.; Bourke, Mary C; Smyth, Thomas A. G.

    2015-01-01

    Wind on Mars is a significant agent of contemporary surface change, yet the absence of in situ meteorological data hampers the understanding of surface–atmospheric interactions. Airflow models at length scales relevant to landform size now enable examination of conditions that might activate even small-scale bedforms (ripples) under certain contemporary wind regimes. Ripples have the potential to be used as modern ‘wind vanes' on Mars. Here we use 3D airflow modelling to demonstrate that local dune topography exerts a strong influence on wind speed and direction and that ripple movement likely reflects steered wind direction for certain dune ridge shapes. The poor correlation of dune orientation with effective sand-transporting winds suggests that large dunes may not be mobile under modelled wind scenarios. This work highlights the need to first model winds at high resolution before inferring regional wind patterns from ripple movement or dune orientations on the surface of Mars today. PMID:26537669

  18. The dune effect on sand-transporting winds on Mars.

    PubMed

    Jackson, Derek W T; Bourke, Mary C; Smyth, Thomas A G

    2015-01-01

    Wind on Mars is a significant agent of contemporary surface change, yet the absence of in situ meteorological data hampers the understanding of surface-atmospheric interactions. Airflow models at length scales relevant to landform size now enable examination of conditions that might activate even small-scale bedforms (ripples) under certain contemporary wind regimes. Ripples have the potential to be used as modern 'wind vanes' on Mars. Here we use 3D airflow modelling to demonstrate that local dune topography exerts a strong influence on wind speed and direction and that ripple movement likely reflects steered wind direction for certain dune ridge shapes. The poor correlation of dune orientation with effective sand-transporting winds suggests that large dunes may not be mobile under modelled wind scenarios. This work highlights the need to first model winds at high resolution before inferring regional wind patterns from ripple movement or dune orientations on the surface of Mars today. PMID:26537669

  19. Climate change impacts on dunes erosion in the Netherlands

    NASA Astrophysics Data System (ADS)

    de Winter, Renske; Ruessink, Gerben

    2016-04-01

    The dunes in the Netherlands are occasionally eroded as a result of storms and corresponding storm surge levels and extreme waves. We discuss the effect of climate change and the corresponding sea level rise on dune erosion. With the XBeach dune erosion model we studied two representative profiles and analysed the effect of sea-level rise ranging from 0.20 to 2.50 m on dune erosion, as well as changes in the angle of wave incidence. The eroded volume in our XBeach model under storm conditions is in the order of magnitude of previous studies. In contrast with the Bruun-rule, which suggests a relation between sea-level rise and retreat distance, we found a linear relation between SLR and the amount of eroded volume of the dunes. Changes in the wave angle from shore normal to ~40 degrees, increase the erosion volume to the same extend as 40 cm sea-level rise.

  20. The dune effect on sand-transporting winds on Mars

    NASA Astrophysics Data System (ADS)

    Jackson, Derek W. T.; Bourke, Mary C.; Smyth, Thomas A. G.

    2015-11-01

    Wind on Mars is a significant agent of contemporary surface change, yet the absence of in situ meteorological data hampers the understanding of surface-atmospheric interactions. Airflow models at length scales relevant to landform size now enable examination of conditions that might activate even small-scale bedforms (ripples) under certain contemporary wind regimes. Ripples have the potential to be used as modern `wind vanes' on Mars. Here we use 3D airflow modelling to demonstrate that local dune topography exerts a strong influence on wind speed and direction and that ripple movement likely reflects steered wind direction for certain dune ridge shapes. The poor correlation of dune orientation with effective sand-transporting winds suggests that large dunes may not be mobile under modelled wind scenarios. This work highlights the need to first model winds at high resolution before inferring regional wind patterns from ripple movement or dune orientations on the surface of Mars today.

  1. Where to dig for gold? - Density segregation inside migrating dunes

    NASA Astrophysics Data System (ADS)

    Groh, Christopher; Rehberg, Ingo; Kruelle, Christof A.

    2013-06-01

    If a fluid streams over an extended area of sand, the grains will self-organize by forming complex structures like ripples or dunes. Below the surface, the inner structure of a dune is determined by the individual fate of the particles. In general, agitated granular matter is known to show de-mixing whenever particles differ in size or density, and indeed size segregation is a well-known feature for dunes, called reverse grading. Here we report results of a recent experimental investigation with two particle species differing not in size but in density. Our experimental setup consists of a stadium-shaped flow channel which is filled with water. Measurements are made with a CCD-camera, placed in front of the straight part, recording side views of the dunes migrating downstream. From an initially prepared triangular heap a rapid relaxation to a steady-state solution is observed with constant mass, shape, and velocity. This attractor exhibits all characteristic features of barchan dunes found in nature, namely a gently inclined windward side, crest, brink, and steep lee face. In addition, if the dune consists of a bi-dense mixture of particles, the heavier particles accumulate at the top of migrating dunes whereas light particles are buried at its bottom. This insight into the sedimentology of dunes composed of different types of sand has, loosely speaking, the implication, that in a dune mixed of gold and sand, gold nuggets are likely to be found at the top of the dune, close to the surface at its crest.

  2. Argon-39 Background in DUNE Photon Detectors

    NASA Astrophysics Data System (ADS)

    Sinev, Gleb; DUNE Collaboration

    2016-03-01

    The Deep Underground Neutrino Experiment (DUNE) is a 40-kt liquid argon detector that will be constructed 5000 ft underground in the Sanford Underground Research Facility in order to study neutrino and proton decay physics. Instrumenting liquid argon with photon detectors to record scintillation in addition to the ionization signal can significantly improve time and energy resolution of the experiment. Argon produces light with wavelength of 128 nm. The reference design for the photon detectors includes acrylic bars covered in wavelength shifter, where the scintillation light can be captured and reemitted with longer wavelengths, then detected using silicon photomultipliers. Radiological backgrounds may noticeably deteriorate the photon detection system performance, especially for low-energy interactions. A particularly important background comes from argon-39 decays, because argon-39 is present in natural argon that will be used in DUNE and the background rate increases with the size of the experiment. The effect of the argon-39 background has been studied and is presented in this talk.

  3. Channels on Dunes in Russell Crater

    NASA Technical Reports Server (NTRS)

    2006-01-01

    Hundreds of enigmatic small channels are seen to carve into the slopes of these dark sand dunes lying within Russell Crater on Mars. These features were previously identified as gullies in images from the Mars Orbiter Camera (MOC) on Mars Global Surveyor, but the higher resolution HiRISE image brings out many new details and mysteries. The channels extend from near the top of the dunes to their bases, indicating that some fluid material carved into the sand. The channels commonly begin as smaller tributaries joined together, suggesting several sources of fluid. Distinct dark spots are located near where the channels seem to originate. Several channels appear to originate at alcoves. Several of these channels have sinuous middle reaches while others are straighter. Further down slope, some channel edges appear elevated above the surrounding terrain, particularly in the lower reaches. The channels seem to terminate abruptly, with no deposition of material, unlike at the bases of some other gullies on Mars that are not on dunes.

    One hypothesis for the origin of the channels, which has previously been proposed by the MOC team, is that CO2 (or maybe H2O) frost is deposited on the dunes in shadows or at night. Some frost may also be incorporated into the internal parts of the dunes due to natural avalanching. When the frost is eventually heated by sunlight, rapid sublimation triggers an avalanche of fluidized sand, forming a gully. HiRISE will continue to target small channel features such as these and may return to search for any changes over time.

    Image PSP_001440_1255 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 16, 2006. The complete image is centered at -54.2 degrees latitude, 12.9 degrees East longitude. The range to the target site was 251.4 km (157.1 miles). At this distance the image scale is 50.3 cm/pixel (with 2 x 2 binning) so

  4. Large-eddy simulation of unidirectional turbulent flow over dunes

    NASA Astrophysics Data System (ADS)

    Omidyeganeh, Mohammad

    We performed large eddy simulation of the flow over a series of two- and three-dimensional dune geometries at laboratory scale using the Lagrangian dynamic eddy-viscosity subgrid-scale model. First, we studied the flow over a standard 2D transverse dune geometry, then bedform three-dimensionality was imposed. Finally, we investigated the turbulent flow over barchan dunes. The results are validated by comparison with simulations and experiments for the 2D dune case, while the results of the 3D dunes are validated qualitatively against experiments. The flow over transverse dunes separates at the dune crest, generating a shear layer that plays a crucial role in the transport of momentum and energy, as well as the generation of coherent structures. Spanwise vortices are generated in the separated shear; as they are advected, they undergo lateral instabilities and develop into horseshoe-like structures and finally reach the surface. The ejection that occurs between the legs of the vortex creates the upwelling and downdrafting events on the free surface known as "boils". The three-dimensional separation of flow at the crestline alters the distribution of wall pressure, which may cause secondary flow across the stream. The mean flow is characterized by a pair of counter-rotating streamwise vortices, with core radii of the order of the flow depth. Staggering the crestlines alters the secondary motion; two pairs of streamwise vortices appear (a strong one, centred about the lobe, and a weaker one, coming from the previous dune, centred around the saddle). The flow over barchan dunes presents significant differences to that over transverse dunes. The flow near the bed, upstream of the dune, diverges from the centerline plane; the flow close to the centerline plane separates at the crest and reattaches on the bed. Away from the centerline plane and along the horns, flow separation occurs intermittently. The flow in the separation bubble is routed towards the horns and leaves

  5. Feasibility of using sand dunes as archives of old air

    NASA Astrophysics Data System (ADS)

    Severinghaus, Jeffrey P.; Keeling, Ralph F.; Miller, Benjamin R.; Weiss, Ray F.; Deck, Bruce; Broecker, Wallace S.

    1997-07-01

    Large unaltered samples of the atmosphere covering the past century would complement the history of atmospheric gases obtained from bubbles in ice cores, enabling measurement of geochemically important species such as O2, 14CH4, and 14CO. Sand dunes are a porous media with interstitial air in diffusive contact with the atmosphere, somewhat analogous to the unconsolidated layer of firn atop glaciers. Recent studies have demonstrated the value of firn as an archive of old air [Battle et al., 1996; Bender et al., 1994a]. Unlike firn, sand dunes are incompressible and so remain permeable to greater depths and may extend the firn record into the past century. To evaluate the feasibility of using sand dunes as archives of old air, we drilled 60 m deep test holes in the Algodones Dunes, Imperial Valley, California. The main objective was to see if the air in a sand dune is as old as predicted by a diffusion model, or if the dune is rapidly flushed by advective pumping during windstorms and barometric pressure changes. We dated the air with chlorofluorocarbons and krypton-85, anthropogenic tracers whose atmospheric concentrations are known and have been increasing rapidly in the past half century. These tracer data match the pure diffusion model well, showing that advection in this dune is negligible compared to diffusion as a transport mechanism and that the mean age of the air at 61 m depth is ˜10 years. Dunes therefore do contain old air. However, dunes appear to suffer from two serious drawbacks as archives. Microbial metabolism is evident in elevated CO2 and N2O and depressed CH4 and O2 concentrations in this dune, corrupting the signals of interest in this and probably most dunes. Second, isotopic analyses of N2 and O2 from the dune show that fractionation of the gases occurs due to diffusion of water vapor, complicating the interpretation of the O2 signal beyond the point of viability for an air archive. Sand dunes may be useful for relatively inert gases with

  6. Late Pleistocene dune activity in the central Great Plains, USA

    USGS Publications Warehouse

    Mason, J.A.; Swinehart, J.B.; Hanson, P.R.; Loope, D.B.; Goble, R.J.; Miao, X.; Schmeisser, R.L.

    2011-01-01

    Stabilized dunes of the central Great Plains, especially the megabarchans and large barchanoid ridges of the Nebraska Sand Hills, provide dramatic evidence of late Quaternary environmental change. Episodic Holocene dune activity in this region is now well-documented, but Late Pleistocene dune mobility has remained poorly documented, despite early interpretations of the Sand Hills dunes as Pleistocene relicts. New optically stimulated luminescence (OSL) ages from drill cores and outcrops provide evidence of Late Pleistocene dune activity at sites distributed across the central Great Plains. In addition, Late Pleistocene eolian sands deposited at 20-25 ka are interbedded with loess south of the Sand Hills. Several of the large dunes sampled in the Sand Hills clearly contain a substantial core of Late Pleistocene sand; thus, they had developed by the Late Pleistocene and were fully mobile at that time, although substantial sand deposition and extensive longitudinal dune construction occurred during the Holocene. Many of the Late Pleistocene OSL ages fall between 17 and 14 ka, but it is likely that these ages represent only the later part of a longer period of dune construction and migration. At several sites, significant Late Pleistocene or Holocene large-dune migration also probably occurred after the time represented by the Pleistocene OSL ages. Sedimentary structures in Late Pleistocene eolian sand and the forms of large dunes potentially constructed in the Late Pleistocene both indicate sand transport dominated by northerly to westerly winds, consistent with Late Pleistocene loess transport directions. Numerical modeling of the climate of the Last Glacial Maximum has often yielded mean monthly surface winds southwest of the Laurentide Ice Sheet that are consistent with this geologic evidence, despite strengthened anticyclonic circulation over the ice sheet. Mobility of large dunes during the Late Pleistocene on the central Great Plains may have been the result of

  7. Estimated recharge rates at the Hanford Site

    SciTech Connect

    Fayer, M.J.; Walters, T.B.

    1995-02-01

    The Ground-Water Surveillance Project monitors the distribution of contaminants in ground water at the Hanford Site for the U.S. Department of Energy. A subtask called {open_quotes}Water Budget at Hanford{close_quotes} was initiated in FY 1994. The objective of this subtask was to produce a defensible map of estimated recharge rates across the Hanford Site. Methods that have been used to estimate recharge rates at the Hanford Site include measurements (of drainage, water contents, and tracers) and computer modeling. For the simulations of 12 soil-vegetation combinations, the annual rates varied from 0.05 mm/yr for the Ephrata sandy loam with bunchgrass to 85.2 mm/yr for the same soil without vegetation. Water content data from the Grass Site in the 300 Area indicated that annual rates varied from 3.0 to 143.5 mm/yr during an 8-year period. The annual volume of estimated recharge was calculated to be 8.47 {times} 10{sup 9} L for the potential future Hanford Site (i.e., the portion of the current Site bounded by Highway 240 and the Columbia River). This total volume is similar to earlier estimates of natural recharge and is 2 to 10x higher than estimates of runoff and ground-water flow from higher elevations. Not only is the volume of natural recharge significant in comparison to other ground-water inputs, the distribution of estimated recharge is highly skewed to the disturbed sandy soils (i.e., the 200 Areas, where most contaminants originate). The lack of good estimates of the means and variances of the supporting data (i.e., the soil map, the vegetation/land use map, the model parameters) translates into large uncertainties in the recharge estimates. When combined, the significant quantity of estimated recharge, its high sensitivity to disturbance, and the unquantified uncertainty of the data and model parameters suggest that the defensibility of the recharge estimates should be improved.

  8. Transient, spatially varied groundwater recharge modeling

    NASA Astrophysics Data System (ADS)

    Assefa, Kibreab Amare; Woodbury, Allan D.

    2013-08-01

    The objective of this work is to integrate field data and modeling tools in producing temporally and spatially varying groundwater recharge in a pilot watershed in North Okanagan, Canada. The recharge modeling is undertaken by using the Richards equation based finite element code (HYDRUS-1D), ArcGIS™, ROSETTA, in situ observations of soil temperature and soil moisture, and a long-term gridded climate data. The public version of HYDUS-1D and another version with detailed freezing and thawing module are first used to simulate soil temperature, snow pack, and soil moisture over a one year experimental period. Statistical analysis of the results show both versions of HYDRUS-1D reproduce observed variables to the same degree. After evaluating model performance using field data and ROSETTA derived soil hydraulic parameters, the HYDRUS-1D code is coupled with ArcGIS™ to produce spatially and temporally varying recharge maps throughout the Deep Creek watershed. Temporal and spatial analysis of 25 years daily recharge results at various representative points across the study watershed reveal significant temporal and spatial variations; average recharge estimated at 77.8 ± 50.8 mm/year. Previous studies in the Okanagan Basin used Hydrologic Evaluation of Landfill Performance without any attempt of model performance evaluation, notwithstanding its inherent limitations. Thus, climate change impact results from this previous study and similar others, such as Jyrkama and Sykes (2007), need to be interpreted with caution.

  9. Numerical simulation of the flow over Barchan dunes

    NASA Astrophysics Data System (ADS)

    Omidyeganeh, Mohammad; Piomelli, Ugo; Christensen, Kenneth T.; Best, Jim

    2012-11-01

    We performed large-eddy simulation of the turbulent flow over a typical barchan dune model. The configuration is similar to that of experiments carried out at the University of Illinois, but the Reynolds number based on the free-surface velocity and the dune height is one fifth of the experiment. The simulation adopts the volume-of-fluid technique to model the dune. The use of periodic boundary conditions in the streamwise and spanwise directions implies that we are considering a fully developed flow over one dune in an infinite array. The height of the domain is close to the thickness of the approaching boundary layer, upstream of the dunes in the experiment. The resolution used is close to a typical DNS; Δx+ < 20 . 7 , Δy+ < 0 . 8 , and Δz+ < 10 . 3 . The approaching flow to the dune accelerates over the stoss (upstream) side and rises up to the crest, while at the same time diverging slowly in the spanwise direction toward the closest horn. The separated flow either reattaches on the plane or moves helically inside the recirculation zone toward the closest horn. The separated shear-layer extends downstream and toward the free-surface and contribute to downstream dunes. The agreement of the turbulence statistics with the experiment is good.

  10. Vegetation controls on the maximum size of coastal dunes

    NASA Astrophysics Data System (ADS)

    Durán, Orencio; Moore, Laura J.

    2013-10-01

    Coastal dunes, in particular foredunes, support a resilient ecosystem and reduce coastal vulnerability to storms. In contrast to dry desert dunes, coastal dunes arise from interactions between biological and physical processes. Ecologists have traditionally addressed coastal ecosystems by assuming that they adapt to preexisting dune topography, whereas geomorphologists have studied the properties of foredunes primarily in connection to physical, not biological, factors. Here, we study foredune development using an ecomorphodynamic model that resolves the coevolution of topography and vegetation in response to both physical and ecological factors. We find that foredune growth is eventually limited by a negative feedback between wind flow and topography. As a consequence, steady-state foredunes are scale invariant, which allows us to derive scaling relations for maximum foredune height and formation time. These relations suggest that plant zonation (in particular for strand "dune-building" species) is the primary factor controlling the maximum size of foredunes and therefore the amount of sand stored in a coastal dune system. We also find that aeolian sand supply to the dunes determines the timescale of foredune formation. These results offer a potential explanation for the empirical relation between beach type and foredune size, in which large (small) foredunes are found on dissipative (reflective) beaches. Higher waves associated with dissipative beaches increase the disturbance of strand species, which shifts foredune formation landward and thus leads to larger foredunes. In this scenario, plants play a much more active role in modifying their habitat and altering coastal vulnerability than previously thought.

  11. Understanding early-stage dune development: morphodynamics of aeolian protodunes

    NASA Astrophysics Data System (ADS)

    Baddock, Matthew; Wiggs, Giles; Nield, Joanna

    2016-04-01

    For such a fundamental aspect of bedform development, the initiation and early-stage growth of sand dunes remain poorly understood. Protodunes are bedforms within the continuum of early-stage depositional aeolian features that exist between flat sand patches and small dunes. As transitory bedforms with the potential to develop into dunes, the detailed study of protodune morphodynamics can provide significant insights into nascent dune development. As part of a multi-annual study investigating bedform change through repeat morphological surveys of bedforms with differing maturity, measurements of near-surface airflow and sand transport were conducted over a protodune in a small Namibian barchan dune field. The protodune was approximately 85 m in length and 1 m high, and was without a slipface. Data show that over the course of a week, patterns of airflow and transport flux variation were linked with accretion at the crest, and erosion of the leeside edge showing an increase in protodune height, and providing evidence of the dune's vertical development. Surveys reveal the longer term evolution of the protodune, in the context of changes exhibited by nearby, fully developed barchan dunes, and long term monitoring of wind regime at the site.

  12. Vegetation controls on the maximum size of coastal dunes

    PubMed Central

    Durán, Orencio; Moore, Laura J.

    2013-01-01

    Coastal dunes, in particular foredunes, support a resilient ecosystem and reduce coastal vulnerability to storms. In contrast to dry desert dunes, coastal dunes arise from interactions between biological and physical processes. Ecologists have traditionally addressed coastal ecosystems by assuming that they adapt to preexisting dune topography, whereas geomorphologists have studied the properties of foredunes primarily in connection to physical, not biological, factors. Here, we study foredune development using an ecomorphodynamic model that resolves the coevolution of topography and vegetation in response to both physical and ecological factors. We find that foredune growth is eventually limited by a negative feedback between wind flow and topography. As a consequence, steady-state foredunes are scale invariant, which allows us to derive scaling relations for maximum foredune height and formation time. These relations suggest that plant zonation (in particular for strand “dune-building” species) is the primary factor controlling the maximum size of foredunes and therefore the amount of sand stored in a coastal dune system. We also find that aeolian sand supply to the dunes determines the timescale of foredune formation. These results offer a potential explanation for the empirical relation between beach type and foredune size, in which large (small) foredunes are found on dissipative (reflective) beaches. Higher waves associated with dissipative beaches increase the disturbance of strand species, which shifts foredune formation landward and thus leads to larger foredunes. In this scenario, plants play a much more active role in modifying their habitat and altering coastal vulnerability than previously thought. PMID:24101481

  13. Effects of sand fences on coastal dune vegetation distribution

    NASA Astrophysics Data System (ADS)

    Grafals-Soto, Rosana

    2012-04-01

    Sand fences are important human adjustments modifying the morphology of developed shores. The effects of sand fences on sediment transport and deposition in their initial stages have been well studied, but little is known about the effect of deteriorated sand fences that have become partially buried low scale barriers within the dune, potentially benefiting vegetation growth by protecting it from onshore stress. Data on vegetation, topography and fence characteristics were gathered at three dune sites in Ocean City, New Jersey on September 2007 and March 2008 to evaluate the effect of fences within the dune on vegetation distribution. Variables include: distance landward of dune toe, degree of sheltering from onshore stressors, net change in surface elevation (deposition or erosion), vegetation diversity and density, presence of remnant fence, and distance landward of fence. Results for the studied environment reveal that 1) vegetation diversity or density does not increase near remnant fences because most remnants are lower than average vegetation height and can not provide shelter; but 2) vegetation distribution is related to topographic variables, such as degree of sheltering, that are most likely the result of sand accretion caused by fence deployment. Fence deployment that prioritizes the creation of topographically diverse dunes within a restricted space may increase the diversity and density of the vegetation, and the resilience and value of developed dunes. Managers should consider the benefits of using sand fences on appropriately wide beaches to create a protective dune that is also diverse, functional and better able to adapt to change.

  14. Sand dunes on the central Delmarva Peninsula, Maryland and Delaware

    USGS Publications Warehouse

    Denny, Charles Storrow; Owens, James Patrick

    1979-01-01

    Inconspicuous ancient sand dunes are present in parts of the central Delmarva Peninsula, Maryland and Delaware. Many dunes are roughly V-shaped, built by northwest winds, especially on the east sides of some of the large rivers. On the uplands, the form and spacing of the dunes are variable. A surficial blanket composed mainly of medium and fine-grained sand-the Parsonsburg Sand-forms both the ancient dunes and the broad plains between the dunes. The sand that forms the dunes is massive and intensely burrowed in the upper part; traces of horizontal or slightly inclined bedding appear near the base. Quartz is the dominant mineral constituent of the sand. Microline is abundant in the very fine to fine sand fraction. The heavy-mineral assemblages (high zircon, tourmaline, rutile) are more mature than in most of the possible source rocks. The most abundant minerals in the clay-sized fraction are dioctahedral vermiculite, kaolinite, illite, montmorillonite, and gibbsite. The first four minerals are common in deposits of late Wisconsin and Holocene age. The gibbsite may be detrital, coming from weathered rocks of Tertiary age. The soil profile in the dune sand is weakly to moderately developed. At or near the base of the Parsonsburg Sand are peaty beds that range in age from about 30,000 to about 13,000 radiocarbon years B.P. Microfloral assemblages in the peaty beds suggest that the dunes on the uplands formed in a spruce parkland during the late Wisconsin glacial maximum. The river dunes may also be of late Wisconsin age, but could be Holocene.

  15. Is Titan's Dune Orientation Controlled by Tropical Methane Storms?

    NASA Astrophysics Data System (ADS)

    Charnay, Benjamin; Barth, Erika; Rafkin, Scot; Narteau, Clément; Lebonnois, Sébastien; Rodriguez, Sébastien; Courrech du Pont, Sylvain; Lucas, Antoine

    2014-11-01

    Titan’s equatorial regions are covered by eastward oriented linear dunes. This direction is opposite to mean surface winds simulated by Global Climate Models (GCMs) at these latitudes, oriented westward as trade winds on Earth [1, 2].Here, we propose that Titan’s dune orientation is actually determined by equinoctial tropical methane storms producing a coupling with superrotation and dune formation. Using meso-scale simulations of convective methane clouds [3, 4] with a GCM wind profile featuring the superrotation [5, 6], we show that Titan’s storms should produce fast eastward gust fronts above the surface. Such gusts dominate the aeolian transport. Using GCM wind roses and analogies with terrestrial dune fields [7], we show that Titan's dune growth occurs eastward under these conditions. Finally, this scenario combining global circulation winds and methane storms can explain other major features of Titan's dunes (i.e. divergence from the equator, size and spacing).References:[1] Lorenz et al.: The Sand Seas of Titan: Cassini RADAR Observations of Longitudinal Dunes, Science (2006)[2] Lorenz & Radebaugh: Global pattern of Titan’s dunes: Radar survey from the Cassini prime mission, Geophysical Research Letter (2009)[3] Barth & Rafkin.: TRAMS: A new dynamic cloud model for Titan’s methane clouds, Geophysical Research Letter (2007)[4] Barth & Rafkin.: Convective cloud heights as a diagnostic for methane environment on Titan, Icarus (2010)[5] Charnay & Lebonnois: Two boundary layers in Titan's lower troposphere inferred from a climate model, Nature Geoscience (2012)[6] Lebonnois et al.: Titan global climate model: A new 3-dimensional version of the IPSL Titan GCM, Icarus (2012)[7] Courrech du Pont, Narteau & Gao: Two modes for dune orientation, Geology (2014)

  16. An introduction to the INQUA Dunes Atlas Chronologic Database

    NASA Astrophysics Data System (ADS)

    Lancaster, Nicholas; Bristow, Charlie; Bubenzer, Olaf; Burrough, Sallie; Duller, Geoff; Halfen, Alan; Hesse, Paul; Roskin, Joel; Singhvi, Ashok; Thomas, David; Tripaldi, Alfonsina; Yang, Xiaoping; Wolfe, Stephen; Zarate, Marcelo

    2015-04-01

    The INQUA Dunes Atlas project has developed a global digital database of chronologic information for periods of desert sand dune accumulation and stabilization. The database currently contains 3278 luminescence and 535 radiocarbon records of directly dated periods of aeolian sand deposition from 1200 inland dune locations throughout the world, mostly in low- and mid-latitudes. Co-authors of this abstract have compiled data for their geographic region of expertise. Additional data are being added from publications, reports, and theses and dissertations as they become available. In addition to age data, the database includes information on the site location (including coordinates), dune type, and stratigraphic context, pertinent analytical information (e.g. luminescence procedures), and literature citations to the original data source (with doi). The database has so far enabled: (1) analysis of patterns of dated dune deposits at multiple temporal and spatial scales; (2) correlation of these patterns with other paleoclimatic proxies; and (3) assessment of the paleoclimatic and paleohydrologic implications of periods of aeolian deposition. The database has highlighted several issues with the available luminescence data set, especially the uneven spatial coverage of dated dune deposits and the heterogenous nature of the dune sedimentary record in many areas. It is clear that resolution of these issues to provide a better understanding of dune and dunefield responses to Quaternary climate change is not just a matter of additional dates. A systematic dating program that reflects fundamental patterns of dunefield sensitivity to climatic and hydrologic changes and relates dated deposits to patterns of dune morphology and sedimentology is needed as a research priority.

  17. Summary of the Third International Planetary Dunes Workshop: remote sensing and image analysis of planetary dunes

    USGS Publications Warehouse

    Fenton, Lori K.; Hayward, Rosalyn K.; Horgan, Briony H.N.; Rubin, David M.; Titus, Timothy N.; Bishop, Mark A.; Burr, Devon M.; Chojnacki, Matthew; Dinwiddie, Cynthia L.; Kerber, Laura; Gall, Alice Le; Michaels, Timothy I.; Neakrase, Lynn D.V.; Newman, Claire E.; Tirsch, Daniela; Yizhaq, Hezi; Zimbelman, James R.

    2013-01-01

    The Third International Planetary Dunes Workshop took place in Flagstaff, AZ, USA during June 12–15, 2012. This meeting brought together a diverse group of researchers to discuss recent advances in terrestrial and planetary research on aeolian bedforms. The workshop included two and a half days of oral and poster presentations, as well as one formal (and one informal) full-day field trip. Similar to its predecessors, the presented work provided new insight on the morphology, dynamics, composition, and origin of aeolian bedforms on Venus, Earth, Mars, and Titan, with some intriguing speculation about potential aeolian processes on Triton (a satellite of Neptune) and Pluto. Major advancements since the previous International Planetary Dunes Workshop include the introduction of several new data analysis and numerical tools and utilization of low-cost field instruments (most notably the time-lapse camera). Most presentations represented advancement towards research priorities identified in both of the prior two workshops, although some previously recommended research approaches were not discussed. In addition, this workshop provided a forum for participants to discuss the uncertain future of the Planetary Aeolian Laboratory; subsequent actions taken as a result of the decisions made during the workshop may lead to an expansion of funding opportunities to use the facilities, as well as other improvements. The interactions during this workshop contributed to the success of the Third International Planetary Dunes Workshop, further developing our understanding of aeolian processes on the aeolian worlds of the Solar System.

  18. Interdisciplinary research produces results in understanding planetary dunes

    USGS Publications Warehouse

    Titus, Timothy N.; Hayward, Rosalyn K.; Dinwiddie, Cynthia L.

    2012-01-01

    Third International Planetary Dunes Workshop: Remote Sensing and Image Analysis of Planetary Dunes; Flagstaff, Arizona, 12–16 June 2012. This workshop, the third in a biennial series, was convened as a means of bringing together terrestrial and planetary researchers from diverse backgrounds with the goal of fostering collaborative interdisciplinary research. The small-group setting facilitated intensive discussions of many problems associated with aeolian processes on Earth, Mars, Venus, Titan, Triton, and Pluto. The workshop produced a list of key scientifc questions about planetary dune felds.

  19. Towards a calcium-based rechargeable battery

    NASA Astrophysics Data System (ADS)

    Ponrouch, A.; Frontera, C.; Bardé, F.; Palacín, M. R.

    2016-02-01

    The development of a rechargeable battery technology using light electropositive metal anodes would result in a breakthrough in energy density. For multivalent charge carriers (Mn+), the number of ions that must react to achieve a certain electrochemical capacity is diminished by two (n = 2) or three (n = 3) when compared with Li+ (ref. ). Whereas proof of concept has been achieved for magnesium, the electrodeposition of calcium has so far been thought to be impossible and research has been restricted to non-rechargeable systems. Here we demonstrate the feasibility of calcium plating at moderate temperatures using conventional organic electrolytes, such as those used for the Li-ion technology. The reversibility of the process on cycling has been ascertained and thus the results presented here constitute the first step towards the development of a new rechargeable battery technology using calcium anodes.

  20. Towards a calcium-based rechargeable battery.

    PubMed

    Ponrouch, A; Frontera, C; Bardé, F; Palacín, M R

    2016-02-01

    The development of a rechargeable battery technology using light electropositive metal anodes would result in a breakthrough in energy density. For multivalent charge carriers (M(n+)), the number of ions that must react to achieve a certain electrochemical capacity is diminished by two (n = 2) or three (n = 3) when compared with Li(+) (ref. ). Whereas proof of concept has been achieved for magnesium, the electrodeposition of calcium has so far been thought to be impossible and research has been restricted to non-rechargeable systems. Here we demonstrate the feasibility of calcium plating at moderate temperatures using conventional organic electrolytes, such as those used for the Li-ion technology. The reversibility of the process on cycling has been ascertained and thus the results presented here constitute the first step towards the development of a new rechargeable battery technology using calcium anodes. PMID:26501412

  1. Using groundwater levels to estimate recharge

    USGS Publications Warehouse

    Healy, R.W.; Cook, P.G.

    2002-01-01

    Accurate estimation of groundwater recharge is extremely important for proper management of groundwater systems. Many different approaches exist for estimating recharge. This paper presents a review of methods that are based on groundwater-level data. The water-table fluctuation method may be the most widely used technique for estimating recharge; it requires knowledge of specific yield and changes in water levels over time. Advantages of this approach include its simplicity and an insensitivity to the mechanism by which water moves through the unsaturated zone. Uncertainty in estimates generated by this method relate to the limited accuracy with which specific yield can be determined and to the extent to which assumptions inherent in the method are valid. Other methods that use water levels (mostly based on the Darcy equation) are also described. The theory underlying the methods is explained. Examples from the literature are used to illustrate applications of the different methods.

  2. Groundwater recharge from point to catchment scale

    NASA Astrophysics Data System (ADS)

    Leterme, Bertrand; Di Ciacca, Antoine; Laloy, Eric; Jacques, Diederik

    2016-04-01

    Accurate estimation of groundwater recharge is a challenging task as only a few devices (if any) can measure it directly. In this study, we discuss how groundwater recharge can be calculated at different temporal and spatial scales in the Kleine Nete catchment (Belgium). A small monitoring network is being installed, that is aimed to monitor the changes in dominant processes and to address data availability as one goes from the point to the catchment scale. At the point scale, groundwater recharge is estimated using inversion of soil moisture and/or water potential data and stable isotope concentrations (Koeniger et al. 2015). At the plot scale, it is proposed to monitor the discharge of a small drainage ditch in order to calculate the field groundwater recharge. Electrical conductivity measurements are necessary to separate shallow from deeper groundwater contribution to the ditch discharge (see Di Ciacca et al. poster in session HS8.3.4). At this scale, two or three-dimensional process-based vadose zone models will be used to model subsurface flow. At the catchment scale though, using a mechanistic, process-based model to estimate groundwater recharge is debatable (because of, e.g., the presence of numerous drainage ditches, mixed land use pixels, etc.). We therefore investigate to which extent various types of surrogate models can be used to make the necessary upscaling from the plot scale to the scale of the whole Kleine Nete catchment. Ref. Koeniger P, Gaj M, Beyer M, Himmelsbach T (2015) Review on soil water isotope based groundwater recharge estimations. Hydrological Processes, DOI: 10.1002/hyp.10775

  3. Improved Separators For Rechargeable Lithium Cells

    NASA Technical Reports Server (NTRS)

    Shen, David; Surampudi, Subbarao; Huang, Chen-Kuo; Halpert, Gerald

    1994-01-01

    Improved pairs of separators proposed for use in rechargeable lithium cells operating at ambient temperature. Block growth of lithium dendrites and help prevent short circuits. Each cell contains one separator made of microporous polypropylene placed next to anode, and one separator made of microporous polytetrafluoroethylene (PTFE) next to cathode. Separators increase cycle lives of secondary lithium cells. Cells to which concept applicable those of Li/TiS(2), Li/NbSe(3), Li/CoO(2), Li/MoS(2), Li/VO(x), and Li/MnO(2) chemical systems. Advantageous in spacecraft, military, communications, automotive, and other applications in which high energy density and rechargeability needed.

  4. Global-scale modeling of groundwater recharge

    NASA Astrophysics Data System (ADS)

    Döll, P.; Fiedler, K.

    2007-11-01

    Long-term average groundwater recharge, which is equivalent to renewable groundwater resources, is the major limiting factor for the sustainable use of groundwater. Compared to surface water resources, groundwater resources are more protected from pollution, and their use is less restricted by seasonal and inter-annual flow variations. To support water management in a globalized world, it is necessary to estimate groundwater recharge at the global scale. Here, we present a best estimate of global-scale long-term average diffuse groundwater recharge (i.e. renewable groundwater resources) that has been calculated by the most recent version of the WaterGAP Global Hydrology Model WGHM (spatial resolution of 0.5° by 0.5°, daily time steps). The estimate was obtained using two state-of-the art global data sets of gridded observed precipitation that we corrected for measurement errors, which also allowed to quantify the uncertainty due to these equally uncertain data sets. The standard WGHM groundwater recharge algorithm was modified for semi-arid and arid regions, based on independent estimates of diffuse groundwater recharge, which lead to an unbiased estimation of groundwater recharge in these regions. WGHM was tuned against observed long-term average river discharge at 1235 gauging stations by adjusting, individually for each basin, the partitioning of precipitation into evapotranspiration and total runoff. We estimate that global groundwater recharge was 12 666 km3/yr for the climate normal 1961-1990, i.e. 32% of total renewable water resources. In semi-arid and arid regions, mountainous regions, permafrost regions and in the Asian Monsoon region, groundwater recharge accounts for a lower fraction of total runoff, which makes these regions particularly vulnerable to seasonal and inter-annual precipitation variability and water pollution. Average per-capita renewable groundwater resources of countries vary between 8 m3/(capita yr) for Egypt to more than 1 million m3

  5. Global-scale modeling of groundwater recharge

    NASA Astrophysics Data System (ADS)

    Döll, P.; Fiedler, K.

    2008-05-01

    Long-term average groundwater recharge, which is equivalent to renewable groundwater resources, is the major limiting factor for the sustainable use of groundwater. Compared to surface water resources, groundwater resources are more protected from pollution, and their use is less restricted by seasonal and inter-annual flow variations. To support water management in a globalized world, it is necessary to estimate groundwater recharge at the global scale. Here, we present a best estimate of global-scale long-term average diffuse groundwater recharge (i.e. renewable groundwater resources) that has been calculated by the most recent version of the WaterGAP Global Hydrology Model WGHM (spatial resolution of 0.5° by 0.5°, daily time steps). The estimate was obtained using two state-of-the-art global data sets of gridded observed precipitation that we corrected for measurement errors, which also allowed to quantify the uncertainty due to these equally uncertain data sets. The standard WGHM groundwater recharge algorithm was modified for semi-arid and arid regions, based on independent estimates of diffuse groundwater recharge, which lead to an unbiased estimation of groundwater recharge in these regions. WGHM was tuned against observed long-term average river discharge at 1235 gauging stations by adjusting, individually for each basin, the partitioning of precipitation into evapotranspiration and total runoff. We estimate that global groundwater recharge was 12 666 km3/yr for the climate normal 1961-1990, i.e. 32% of total renewable water resources. In semi-arid and arid regions, mountainous regions, permafrost regions and in the Asian Monsoon region, groundwater recharge accounts for a lower fraction of total runoff, which makes these regions particularly vulnerable to seasonal and inter-annual precipitation variability and water pollution. Average per-capita renewable groundwater resources of countries vary between 8 m3/(capita yr) for Egypt to more than 1 million m3

  6. Karst and artificial recharge: Theoretical and practical problems. A preliminary approach to artificial recharge assessment

    NASA Astrophysics Data System (ADS)

    Daher, Walid; Pistre, Séverin; Kneppers, Angeline; Bakalowicz, Michel; Najem, Wajdi

    2011-10-01

    SummaryManaged Aquifer Recharge (MAR) is an emerging sustainable technique that has already generated successful results and is expected to solve many water resource problems, especially in semi-arid and arid zones. It is of great interest for karst aquifers that currently supply 20-25% of the world's potable water, particularly in Mediterranean countries. However, the high heterogeneity in karst aquifers is too complex to be able to locate and describe them simply via field observations. Hence, as compared to projects in porous media, MAR is still marginal in karst aquifers. Accordingly, the present work presents a conceptual methodology for Aquifer Rechargeability Assessment in Karst - referred to as ARAK. The methodology was developed noting that artificial recharge in karst aquifers is considered an improbable challenge to solve since karst conduits may drain off recharge water without any significant storage, or recharge water may not be able to infiltrate. The aim of the ARAK method is to determine the ability of a given karst aquifer to be artificially recharged and managed, and the best sites for implementing artificial recharge from the surface. ARAK is based on multi-criteria indexation analysis modeled on karst vulnerability assessment methods. ARAK depends on four independent criteria, i.e. Epikarst, Rock, Infiltration and Karst. After dividing the karst domain into grids, these criteria are indexed using geological and topographic maps refined by field observations. ARAK applies a linear formula that computes the intrinsic rechargeability index based on the indexed map for every criterion, coupled with its attributed weighting rate. This index indicates the aptitude for recharging a given karst aquifer, as determined by studying its probability first on a regional scale for the whole karst aquifer, and then by characterizing the most favorable sites. Subsequently, for the selected sites, a technical and economic feasibility factor is applied, weighted

  7. Investigation of groundwater recharge in arid environments through continuous monitoring of water fluxes within the unsaturated zone

    NASA Astrophysics Data System (ADS)

    Kallioras, A.; Reshid, M.; Dietrich, P.; Rausch, R.; Al-Saud, M.; Schuth, C.

    2012-04-01

    For groundwater resources management in arid environments the rate of aquifer replenishment due to groundwater recharge is one of the most important factors and unfortunately also one of the most difficult to derive with sufficient accuracy. In general, the potential evaporation by far exceeds the precipitation limiting groundwater recharge. Unsaturated zone processes play a key role in groundwater recharge as the thickness of the unsaturated zone in arid areas may reach several thenth of meters, compared to millimeters or centimeters of assumed groundwater recharge per year. This indicates the complexity of the problem. Overcoming the field capacity along the infiltration path to initiate downward movement on such a long distance to the groundwater table would require the recharge of tenths or even hundreds of years. Also, precipitation is highly variable in space, time, and intensity and may be followed by hot and dry conditions leading to an alternation of downward and upward movement of water. For this study, field sites in the Kingdom of Saudi Arabia (located app. 200km SW of Riyadh) were selected that represent typical settings for potential groundwater recharge in arid regions, i.e. sand dune areas and wadi beds. In the field campaign vibro-coring techniques applying direct-push technologies (Geoprobe 7720DT) were used to retrieve undisturbed soil sampling down to depths of about 15 m in the unsaturated zone. The drilled boreholes were consequently used for the installation of specially designed flat cable TDR sensors that provide continuous monitoring of the soil moisture content in high vertical resolution. In addition, temperature sensors were installed to monitor temperature fluctuations in the unsaturated zone. We present data on the analyses of soil samples as well as on the measured water content evolution over time as determined by the TDR flat band cables. Results show, that significant changes in water content occurred within the observation time

  8. Groundwater dynamics converted to a groundwater classification as a tool for nature development programs in the dunes

    NASA Astrophysics Data System (ADS)

    Martens, Kristine; Van Camp, Marc; Van Damme, Dirk; Walraevens, Kristine

    2013-08-01

    Within the European Union, Habitat Directives are developed with the aim of restoration and preservation of endangered species. The level of biodiversity in coastal dune systems is generally very high compared to other natural ecosystems, but suffers from deterioration. Groundwater extraction and urbanisation are the main reasons for the decrease in biodiversity. Many restoration actions are being carried out and are focusing on the restoration of groundwater level with the aim of re-establishing rare species. These actions have different degrees of success. The evaluation of the actions is mainly based on the appearance of red list species. The groundwater classes, developed in the Netherlands, are used for the evaluation of opportunities for vegetation, while the natural variability of the groundwater level and quality are under-estimated. Vegetation is used as a seepage indicator. The existing classification is not valid in the Belgian dunes, as the vegetation observed in the study area is not in correspondence with this classification. Therefore, a new classification is needed. The new classification is based on the variability of the groundwater level on a long term with integration of ecological factors. Based on the new classification, the importance of seasonal and inter-yearly fluctuations of the water table can be deduced. Inter-yearly fluctuations are more important in recharge areas while seasonal fluctuations are dominant in discharge areas. The new classification opens opportunities for relating vegetation and groundwater dynamics.

  9. Characteristics of groundwater recharge on the North China Plain.

    PubMed

    Tan, Xiu-Cui; Wu, Jing-Wei; Cai, Shu-Ying; Yang, Jin-Zhong

    2014-01-01

    Groundwater recharge is an important component of the groundwater system. On the North China Plain (NCP), groundwater is the main water supply. Because of large-scale overexploitation, the water table has declined, which has produced severe adverse effects on the environment and ecosystem. In this article, tracer experiment and watershed model were used to calculate and analyze NCP groundwater recharge. In the tracer experiment, average recharge was 108 mm/year and recharge coefficient 0.16. With its improved irrigation, vegetation coverage and evapotranspiration modules, the INFIL3.0 model was used for calculation of groundwater recharge. Regional modeling results showed an average recharge of 102 mm/year and recharge coefficient 0.14, for 2001-2009. These values are very similar to those from the field tracer experiment. Influences in the two methods were analyzed. The results can provide an important reference for NCP groundwater recharge. PMID:24032445

  10. REFLEAK: NIST Leak/Recharge Simulation Program for Refrigerant Mixtures

    National Institute of Standards and Technology Data Gateway

    SRD 73 NIST REFLEAK: NIST Leak/Recharge Simulation Program for Refrigerant Mixtures (PC database for purchase)   REFLEAK estimates composition changes of zeotropic mixtures in leak and recharge processes.

  11. Song of the Dunes as a Self-Synchronized Instrument

    NASA Astrophysics Data System (ADS)

    Douady, S.; Manning, A.; Hersen, P.; Elbelrhiti, H.; Protière, S.; Daerr, A.; Kabbachi, B.

    2006-07-01

    Since Marco Polo it has been known that some sand dunes have the peculiar ability to emit a loud sound with a well-defined frequency, sometimes for several minutes. The origin of this sustained sound has remained mysterious, partly because of its rarity in nature. It has been recognized that the sound is not due to the air flow around the dunes but to the motion of an avalanche, and not to an acoustic excitation of the grains but to their relative motion. By comparing singing dunes around the world and two controlled experiments, in the laboratory and the field, we prove that the frequency of the sound is the frequency of the relative motion of the sand grains. Sound is produced because moving grains synchronize their motions. The laboratory experiment shows that the dune is not needed for sound emission. A velocity threshold for sound emission is found in both experiments, and an interpretation is proposed.

  12. 25. Wide view from the dune to the southeast, showing ...

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

    25. Wide view from the dune to the southeast, showing from right to left, surf, beach, bluff, stilwell Hall. - Fort Ord, Soldiers' Club, California State Highway 1 near Eighth Street, Seaside, Monterey County, CA

  13. Aerial view of old station and sand dunes looking east ...

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

    Aerial view of old station and sand dunes looking east from tower of newer station. - Vermilion Life Saving Station, Shore of Lake Superior, 10 miles west of Whitefish Point, Paradise, Chippewa County, MI

  14. Documentation of Recent Surface Winds on Martian Sand Dunes

    NASA Astrophysics Data System (ADS)

    Zimbelman, J. R.; Johnson, M. B.

    2013-12-01

    Images from the High Resolution Imaging Science Experiment (HiRISE) are of sufficient resolution to record wind ripple patterns on the surfaces of sand dunes present across the surface of Mars. We are in the early stages of an investigation to map the ripple orientations preserved on Martian sand dunes, in order to evaluate the recent wind flow over the dunes, and compare that wind flow pattern to the winds documented over terrestrial sand dunes. HiRISE image ESP_025645_1455 covers a sand dune field on the floor of a 20-km-diameter unnamed impact crater in the Terra Cimmeria region of the southern highlands, east of the Hellas impact basin. This image is centered at 34.23 S latitude, 138.437 E longitude with 25 cm/pixel resolution, and was taken on Jan 25 of 2012 during northern spring (Ls = 57.4). Using ArcGIS, lines were drawn across three ripples perpendicular to the ripple crests, avoiding places where complex ripple patterns suggest more than one recent wind direction. The length of the lines provides a measure of ripple wavelength, and the line orientation gives azimuth (with a 180 degree absolute ambiguity). The barchan-like shape of some dunes, including occasional slip faces, suggest sand driving winds were from the southwest, although dune asymmetries indicate the wind regime likely was much more complex than a unimodal wind. Measurements of ripple orientations are being collected from dune locations across the planet, which should provide new constraints for the modeling of recent Martian winds. This work was supported by NASA MDAP grant NNX12AJ38G.

  15. Habitat change in a perched dune system along Lake Superior

    USGS Publications Warehouse

    Loope, Walter L.; McEachern, A. Kathryn

    1998-01-01

    Episodes of habitat change, driven by changes in levels of the Great Lakes, must be considered when assessing human effects upon coastal vegetation and rare species. Paleoecological studies, baseline inventories, and long-term monitoring programs within the Grand Sable Dunes, a perched-dune system along Lake Superior, provide a window on vegetation change at different spatial and temporal scales and also provide an illustrative case study.

  16. Natural vs. artificial groundwater recharge, quantification through inverse modeling

    NASA Astrophysics Data System (ADS)

    Hashemi, H.; Berndtsson, R.; Kompani-Zare, M.; Persson, M.

    2012-08-01

    Estimating the change in groundwater recharge from an introduced artificial recharge system is important in order to evaluate future water availability. This paper presents an inverse modeling approach to quantify the recharge contribution from both an ephemeral river channel and an introduced artificial recharge system based on floodwater spreading in arid Iran. The study used the MODFLOW-2000 to estimate recharge for both steady and unsteady-state conditions. The model was calibrated and verified based on the observed hydraulic head in observation wells and model precision, uncertainty, and model sensitivity were analyzed in all modeling steps. The results showed that in a normal year without extreme events the floodwater spreading system is the main contributor to recharge with 80% and the ephemeral river channel with 20% of total recharge in the studied area. Uncertainty analysis revealed that the river channel recharge estimation represents relatively more uncertainty in comparison to the artificial recharge zones. The model is also less sensitive to the river channel. The results show that by expanding the artificial recharge system the recharge volume can be increased even for small flood events while the recharge through the river channel increases only for major flood events.

  17. Natural vs. artificial groundwater recharge, quantification through inverse modeling

    NASA Astrophysics Data System (ADS)

    Hashemi, H.; Berndtsson, R.; Kompani-Zare, M.; Persson, M.

    2013-02-01

    Estimating the change in groundwater recharge from an introduced artificial recharge system is important in order to evaluate future water availability. This paper presents an inverse modeling approach to quantify the recharge contribution from both an ephemeral river channel and an introduced artificial recharge system based on floodwater spreading in arid Iran. The study used the MODFLOW-2000 to estimate recharge for both steady- and unsteady-state conditions. The model was calibrated and verified based on the observed hydraulic head in observation wells and model precision, uncertainty, and model sensitivity were analyzed in all modeling steps. The results showed that in a normal year without extreme events, the floodwater spreading system is the main contributor to recharge with 80% and the ephemeral river channel with 20% of total recharge in the studied area. Uncertainty analysis revealed that the river channel recharge estimation represents relatively more uncertainty in comparison to the artificial recharge zones. The model is also less sensitive to the river channel. The results show that by expanding the artificial recharge system, the recharge volume can be increased even for small flood events, while the recharge through the river channel increases only for major flood events.

  18. Design considerations for rechargeable lithium batteries

    NASA Technical Reports Server (NTRS)

    Shen, D. H.; Huang, C.-K.; Davies, E.; Perrone, D.; Surampudi, S.; Halpert, Gerald

    1993-01-01

    Viewgraphs of a discussion of design considerations for rechargable lithium batteries. The objective is to determine the influence of cell design parameters on the performance of Li-TiS2 cells. Topics covered include cell baseline design and testing, cell design and testing, cell design parameters studies, and cell cycling performance.

  19. Alloys of clathrate allotropes for rechargeable batteries

    SciTech Connect

    Chan, Candace K; Miller, Michael A; Chan, Kwai S

    2014-12-09

    The present disclosure is directed at an electrode for a battery wherein the electrode comprises clathrate alloys of silicon, germanium or tin. In method form, the present disclosure is directed at methods of forming clathrate alloys of silicon, germanium or tin which methods lead to the formation of empty cage structures suitable for use as electrodes in rechargeable type batteries.

  20. Anodes for Rechargeable Lithium-Sulfur Batteries

    SciTech Connect

    Cao, Ruiguo; Xu, Wu; Lu, Dongping; Xiao, Jie; Zhang, Jiguang

    2015-04-10

    In this work, we will review the recent developments on the protection of Li metal anode in Li-S batteries. Various strategies used to minimize the corrosion of Li anode and reducing its impedance increase will be analyzed. Other potential anodes used in sulfur based rechargeable batteries will also be discussed.

  1. Anode for rechargeable ambient temperature lithium cells

    NASA Technical Reports Server (NTRS)

    Huang, Chen-Kuo (Inventor); Surampudi, Subbarao (Inventor); Attia, Alan I. (Inventor); Halpert, Gerald (Inventor)

    1994-01-01

    An ambient room temperature, high density, rechargeable lithium battery includes a Li(x)Mg2Si negative anode which intercalates lithium to form a single crystalline phase when x is up to 1.0 and an amorphous phase when x is from 1 to 2.0. The electrode has good reversibility and mechanical strength after cycling.

  2. Rechargeable solid polymer electrolyte battery cell

    DOEpatents

    Skotheim, Terji

    1985-01-01

    A rechargeable battery cell comprising first and second electrodes sandwiching a solid polymer electrolyte comprising a layer of a polymer blend of a highly conductive polymer and a solid polymer electrolyte adjacent said polymer blend and a layer of dry solid polymer electrolyte adjacent said layer of polymer blend and said second electrode.

  3. Application potential of rechargeable lithium batteries

    SciTech Connect

    Hunger, H.F.; Bramhall, P.J.

    1983-10-01

    Rechargeable lithium cells with Cr /SUB 0.5/ V/sub 0/ /sub 5/S/sub 2/ and MoO/sub 3/ cathodes were investigated in the temperature range of -30/sup 0/C to +25/sup 0/C. The electrolyte was 1.5M LiAsF/sub 6/ in 2-methyl tetrahydrofuran with tetrahydrofuran (50:50 V percent). Current densities and capacities as a function of temperature, cathode utilization efficiencies versus cycle life, and shelf lives were determined. The state of charge could be related to open circuit voltages after partial discharge. The potential of the system for communication applications is discussed. Recent advances in rechargeable lithium batteries were mainly due to the discovery of stable, cyclic ether electrolyte solvents (1) and to the use of rechargeable cathode materials (2). The practical usefulness of rechargeable lithium cells with Cr /SUB 0.5/ V /SUB 0.5/ S/sub 2/ and MoO/sub 3/ cathodes was investigated in the temperature range of -30/sup 0/C to +25/sup 0/C. The electrolyte was mainly 1.5M LiAsF/sub 6/ in 2-methyl tetrahydrofuran with tetrahydrofuran (50:50 V percent). The two cathode materials were chosen because Cr /SUB 0.5/ V /SUB 0.5/ S/sub 2/ resembles TiS/sub 2/ in capacity and cycling behavior and MoO/sub 3/ is a low cost cathode material of interest.

  4. Recharging Our Sense of Idealism: Concluding Thoughts

    ERIC Educational Resources Information Center

    D'Andrea, Michael; Dollarhide, Colette T.

    2011-01-01

    In this article, the authors aim to recharge one's sense of idealism. They argue that idealism is the Vitamin C that sustains one's commitment to implementing humanistic principles and social justice practices in the work of counselors and educators. The idealism that characterizes counselors and educators who are humanistic and social justice…

  5. Temporal observations of a linear sand dune in the Simpson Desert, central Australia: Testing models for dune formation on planetary surfaces

    NASA Astrophysics Data System (ADS)

    Craddock, Robert A.; Tooth, Stephen; Zimbelman, James R.; Wilson, Sharon A.; Maxwell, Ted A.; Kling, Corbin

    2015-10-01

    Linear dunes are the most common dune form found on planetary surfaces, yet questions remain about their formation. Temporal observations of a linear dune located in the Simpson Desert of central Australia were made to monitor dune movement and to test competing hypotheses regarding linear dune formation. Our observations were collected on three separate occasions from 2006 to 2014. Rebar stakes were placed in a gridded pattern so that multiple measurements of sand thickness, GPS surveys, and photographs could be taken at the same locations over time. We observed widespread reworking of sand on and around the dune crest, with sand accumulation locally exceeding a meter between surveys. Overall, the height of the dune crest increased by several centimeters. We also observed fluctuations in the sand cover in the adjacent swales that often exceeded 2-3 cm between surveys, yet we did not observe any appreciable changes in the position of the dune's downwind terminus. Weather data indicate that the effective sand-transporting winds in the Simpson are widely unimodal. Net sediment flux (resultant drift direction) is toward the north-northwest, locally at an oblique angle to dune orientation. Collectively, our results suggest that the linear dune is actively maintained by vertical accretion. The implications from our observations are that linear dunes on other planetary surfaces could form in wind regimes that are widely unimodal, even where the resultant drift direction is locally oblique to dune orientation. In particular, such findings may provide support for global circulation models of Titan.

  6. Maximizing the DUNE early physics output with current experiments

    NASA Astrophysics Data System (ADS)

    Ghosh, Monojit; Goswami, Srubabati; Raut, Sushant K.

    2016-03-01

    The deep underground neutrino experiment (DUNE) is a proposed next generation superbeam experiment at Fermilab. Its aims include measuring the unknown neutrino oscillation parameters—the neutrino mass hierarchy, the octant of the mixing angle θ _{23}, and the CP-violating phase δ _{CP}. The current and upcoming experiments T2K, NOν A, and ICAL@INO will also be collecting data for the same measurements. In this paper, we explore the sensitivity reach of DUNE in combination with these other experiments. We evaluate the least exposure required by DUNE to determine the above three unknown parameters with reasonable confidence. We find that for each case, the inclusion of data from T2K, NOν A, and ICAL@INO help to achieve the same sensitivity with a reduced exposure from DUNE thereby helping to economize the configuration. Further, we quantify the effect of the proposed near detector on systematic errors and study the consequent improvement in sensitivity. We also examine the role played by the second oscillation cycle in furthering the physics reach of DUNE. Finally, we present an optimization study of the neutrino-antineutrino running of DUNE.

  7. Simulation model of erosion and deposition on a barchan dune

    NASA Technical Reports Server (NTRS)

    Howard, A. D.; Morton, J. B.; Gal-El-hak, M.; Pierce, D. B.

    1977-01-01

    Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity.

  8. Material transport map of Titan: The fate of dunes

    NASA Astrophysics Data System (ADS)

    Malaska, Michael J.; Lopes, Rosaly M.; Hayes, Alex G.; Radebaugh, Jani; Lorenz, Ralph D.; Turtle, Elizabeth P.

    2016-05-01

    Using SAR data from Cassini's RADAR instrument, we examined the orientations of three terrain units on Titan, bright lineated plains, streak-like plains, and linear dunes. From the overall integrated pattern of their orientation, we were able to determine Titan's global material transport vectors. The analysis indicates that, in both the northern and southern hemispheres, materials from 0 to 35 deg latitude are transported poleward to a belt centred at roughly 35 deg. Materials from 60 to 35 deg latitude are transported equatorward to the belt at roughly 35 deg. Comparison with the global topographical gradient (Lorenz, R.D. et al. [2013]. Icarus 225, 367-377) suggests that fluvial transport is not the dominant process for material transport on Titan, or that it is at least overprinted with another transport mechanism. Our results are consistent with aeolian transport being the dominant mechanism in the equatorial and mid-latitude zones. The zone at 35 deg is thus the ultimate sink for materials from the equator to low polar latitudes; materials making up the equatorial dunes will be transported to the latitude 35-deg belts. Only plains units are observed at latitudes of ∼35 deg; dunes and materials with the spectral characteristics of dunes are not observed at these latitudes. This observation suggests that either dune materials are converted or modified into plains units or that the margins of dunes are transport limited.

  9. Large-eddy simulations of unidirectional water flow over dunes

    NASA Astrophysics Data System (ADS)

    Grigoriadis, D. G. E.; Balaras, E.; Dimas, A. A.

    2009-06-01

    The unidirectional, subcritical flow over fixed dunes is studied numerically using large-eddy simulation, while the immersed boundary method is implemented to incorporate the bed geometry. Results are presented for a typical dune shape and two Reynolds numbers, Re = 17,500 and Re = 93,500, on the basis of bulk velocity and water depth. The numerical predictions of velocity statistics at the low Reynolds number are in very good agreement with available experimental data. A primary recirculation region develops downstream of the dune crest at both Reynolds numbers, while a secondary region develops at the toe of the dune crest only for the low Reynolds number. Downstream of the reattachment point, on the dune stoss, the turbulence intensity in the developing boundary layer is weaker than in comparable equilibrium boundary layers. Coherent vortical structures are identified using the fluctuating pressure field and the second invariant of the velocity gradient tensor. Vorticity is primarily generated at the dune crest in the form of spanwise "roller" structures. Roller structures dominate the flow dynamics near the crest, and are responsible for perturbing the boundary layer downstream of the reattachment point, which leads to the formation of "horseshoe" structures. Horseshoe structures dominate the near-wall dynamics after the reattachment point, do not rise to the free surface, and are distorted by the shear layer of the next crest. The occasional interaction between roller and horseshoe structures generates tube-like "kolk" structures, which rise to the free surface and persist for a long time before attenuating.

  10. Regional Analysis of Ground-Water Recharge

    USGS Publications Warehouse

    Flint, Lorraine E.; Flint, Alan L.

    2007-01-01

    A modeling analysis of runoff and ground-water recharge for the arid and semiarid southwestern United States was performed to investigate the interactions of climate and other controlling factors and to place the eight study-site investigations into a regional context. A distributed-parameter water-balance model (the Basin Characterization Model, or BCM) was used in the analysis. Data requirements of the BCM included digital representations of topography, soils, geology, and vegetation, together with monthly time-series of precipitation and air-temperature data. Time-series of potential evapotranspiration were generated by using a submodel for solar radiation, taking into account topographic shading, cloudiness, and vegetation density. Snowpack accumulation and melting were modeled using precipitation and air-temperature data. Amounts of water available for runoff and ground-water recharge were calculated on the basis of water-budget considerations by using measured- and generated-meteorologic time series together with estimates of soil-water storage and saturated hydraulic conductivity of subsoil geologic units. Calculations were made on a computational grid with a horizontal resolution of about 270 meters for the entire 1,033,840 square-kilometer study area. The modeling analysis was composed of 194 basins, including the eight basins containing ground-water recharge-site investigations. For each grid cell, the BCM computed monthly values of potential evapotranspiration, soil-water storage, in-place ground-water recharge, and runoff (potential stream flow). A fixed percentage of runoff was assumed to become recharge beneath channels operating at a finer resolution than the computational grid of the BCM. Monthly precipitation and temperature data from 1941 to 2004 were used to explore climatic variability in runoff and ground-water recharge. The selected approach provided a framework for classifying study-site basins with respect to climate and dominant recharge

  11. Large Eddy Simulation of Flow and Sediment Transport over Dunes

    NASA Astrophysics Data System (ADS)

    Agegnehu, G.; Smith, H. D.

    2012-12-01

    Understanding the nature of flow over bedforms has a great importance in fluvial and coastal environments. For example, a bedform is one source of energy dissipation in water waves outside the surf zone in coastal environments. In rivers, the migration of dunes often affects the stability of the river bed and banks. In general, when a fluid flows over a sediment bed, the sediment transport generated by the interaction of the flow field with the bed results in the periodic deformation of the bed in the form of dunes. Dunes generally reach an equilibrium shape, and slowly propagate in the direction of the flow, as sand is lifted in the high shear regions, and redeposited in the separated flow areas. Different numerical approaches have been used in the past to study the flow and sediment transport over bedforms. In most research works, Reynolds Averaged Navier Stokes (RANS) equations are employed to study fluid motions over ripples and dunes. However, evidences suggests that these models can not represent key turbulent quantities in unsteady boundary layers. The use of Large Eddy Simulation (LES) can resolve a much larger range of smaller scales than RANS. Moreover, unsteady simulations using LES give vital turbulent quantities which can help to study fluid motion and sediment transport over dunes. For this steady, we use a three-dimensional, non-hydrostatic model, OpenFOAM. It is a freely available tool which has different solvers to simulate specific problems in engineering and fluid mechanics. Our objective is to examine the flow and sediment transport from numerical stand point for bed geometries that are typical of fixed dunes. At the first step, we performed Large Eddy Simulation of the flow over dune geometries based on the experimental data of Nelson et al. (1993). The instantaneous flow field is investigated with special emphasis on the occurrence of coherent structures. To assess the effect of bed geometries on near bed turbulence, we considered different

  12. Dark Dune Spots: possible biomarkers on Mars?

    PubMed

    Gánti, Tibor; Horváth, András; Bérczi, Szaniszló; Gesztesi, Albert; Szathmáry, Eörs

    2003-10-01

    Dark Dune Spots (DDSs) are transitional geomorphologic formations in the frost-covered polar regions of Mars. Our analysis of the transformations and arrangements of subsequent stages of DDSs into time sequence revealed their: (i) hole-like characteristics, (ii) development and formation from the bottom of the frosted layer till the disapperance of the latter, (iii) repeated (seasonal and annual) appearance in a pattern of multiple DDSs on the surface, and (iv) probable origin. We focused our studies on a model in which DDSs were interpreted as objects triggered by biological activity involved in the frosting and melting processes. We discuss two competing interpretations of DDSs: development by defrosting alone, and by defrosting and melting enhanced by the activity of Martian Surface Organisms (MSOs). MSOs are hypothetical Martian photosynthetic surface organisms thought to absorb sunlight. As a result they warm up by late winter and melt the ice around them, whereby their growth and reproduction become possible. The ice cover above the liquid water lens harbouring the MSOs provides excellent heat and UV insulation, prevents fast evaporation, and sustains basic living conditions until the ice cover exists. When the frost cover disappears MSOs go to a dormant, desiccated state. We propose further studies to be carried out by orbiters and landers travelling to Mars and by analysis of partial analogues on earth. PMID:14604189

  13. Manganese oxide cathodes for rechargeable batteries

    NASA Astrophysics Data System (ADS)

    Im, Dongmin

    Manganese oxides are considered as promising cathodes for rechargeable batteries due to their low cost and low toxicity as well as the abundant natural resources. In this dissertation, manganese oxides have been investigated as cathodes for both rechargeable lithium and alkaline batteries. Nanostructured lithium manganese oxides designed for rechargeable lithium cells have been synthesized by reducing lithium permanganate with methanol or hydrogen in various solvents followed by firing at moderate temperatures. The samples have been characterized by wet-chemical analyses, thermal methods, spectroscopic methods, and electron microscopy. It has been found that chemical residues in the oxides such as carboxylates and hydroxyl groups, which could be controlled by varying the reaction medium, reducing agents, and additives, make a significant influence on the electrochemical properties. The Li/Mn ratio in the material has also been found to be a critical factor in determining the rechargeability of the cathodes. The optimized samples exhibit a high capacity of close to 300 mAh/g with good cyclability and charge efficiency. The high capacity with a lower discharge voltage may make these nanostructured oxides particularly attractive for lithium polymer batteries. The research on the manganese oxide cathodes for alkaline batteries is focused on an analysis of the reaction products generated during the charge/discharge processes or by some designed chemical reactions mimicking the electrochemical processes. The factors influencing the formation of Mn3O4 in the two-electron redox process of delta-MnO2 have been studied with linear sweep voltammetry combined with X-ray diffraction. The presence of bismuth, the discharge rate, and the microstructure of the electrodes are found to affect the formation of Mn3O4, which is known to be electrochemically inactive. A faster voltage sweep and a more intimate mixing of the manganese oxide and carbon in the cathode are found to suppress

  14. Reply to ``Comment on `Minimal size of a barchan dune' ''

    NASA Astrophysics Data System (ADS)

    Parteli, E. J. R.; Durán, O.; Herrmann, H. J.

    2007-12-01

    We reply to the preceding comment by Andreotti and Claudin [Phys. Rev. E 76, 063301 (2007)] on our paper [Phys. Rev. E 75, 011301 (2007)]. We show that the equations of the dune model used in our calculations are self-consistent and effectively lead to a dependence of the minimal dune size on the wind speed through the saturation length. Furthermore, we show that Meridiani Planum ripples are probably not a good reference to estimate the grain size of Martian dune sands: the soil in the ripple troughs at the landing site is covered with nonerodible elements (“blueberries”), which increase the minimal threshold for saltation by a factor of 2.0. We conclude that, in the absence of large fragments as the ones found at the landing site, basaltic grains of diameter d=500±100μm that compose the large, typical dark Martian dunes [K. S. Edgett and P. R. Christensen, J. Geophys. Res. 96, 22765 (1991)] probably saltate during the strongest storms on Mars. We also show that the wind friction speed u∗≈3.0m/s that we found from the calculations of Martian dunes is within the values of maximum wind speeds that occur during Martian storms a few times a decade [R. E. Arvidson , Science 222, 463 (1983); H. J. Moore, J. Geophys. Res. 90, 163 (1985); R. Sullivan , Nature (London) 436, 58 (2005); D. J. Jerolmack , J. Geophys. Res. 111, E12S02 (2006)]. In this manner, the dune model predicts that Martian dunes can be formed under present Martian conditions, with no need to assume other conditions of wind and atmosphere that could have prevailed in the past.

  15. Martian Dune Ripples as Indicators of Recent Surface Wind Patterns

    NASA Astrophysics Data System (ADS)

    Johnson, M.; Zimbelman, J. R.

    2015-12-01

    Sand dunes have been shown to preserve the most recent wind patterns in their ripple formations. This investigation continues the manual documentation of ripples on Martian dunes in order to assess surface wind flow. Study sites investigated must have clear HiRISE frames and be able to represent diverse locations across the surface, decided primarily by their spread of latitude and longitude values. Additionally, frames with stereo pairs are preferred because of their ability to create digital terrain models. This will assist in efforts to relate dune slopes and obstacles to ripple patterns. The search and analysis period resulted in 40 study sites with mapped ripples. Lines were drawn perpendicular to ripple crests across three adjacent ripples in order to document both ripple wavelength from line length and inferred wind direction from azimuth. It is not possible to infer a unique wind direction from ripple orientation alone and therefore these inferred directions have a 180 degree ambiguity. Initial results from all study sites support previous observations that the Martian surface has many dune types in areas with adequate sand supply. The complexity of ripple patterns varies greatly across sites as well as within individual sites. Some areas of uniform directionality for hundreds of kilometers suggest a unimodal wind regime while overlapping patterns suggest multiple dominant winds or seasonally varying winds. In most areas, form flow related to dune shape seems to have a large effect on orientation and must be considered along with the dune type. As long as the few steep slip faces on these small dunes are avoided, form flow can be considered the dominant cause of deviation from the regional wind direction. Regional results, wind roses, and comparisons to previous work will be presented for individual sites.

  16. Differing Abundances of Gypsum in the Primary and Secondary Dunes of the Martian Dune Field Olympia Undae

    NASA Astrophysics Data System (ADS)

    Szumila, I. T.; Bishop, J. L.; Fenton, L. K.; Brown, A. J.

    2012-12-01

    We report on a compositional study in Olympia Undae, located around the polar cap of Mars. Gypsum has been detected throughout the sand sea but with a decline in abundance westward (Langevin et al., 2005). Dune crests are the regions of highest apparent gypsum concentration in CRISM images. Olympia Undae consists of primary dunes formed transverse to circumpolar easterly winds and secondary dunes which lie almost orthogonal to the primary dunes (Ewing et al. 2010). METHODS: We examined a number of CRISM and HiRISE images across the dune field. We focused our preliminary study on FRT0000C31A and FRT0000C2FC, which exhibited the best spectral signatures. Gypsum was identified in CRISM images by its unique 1.45/1.49/1.54 μm triplet, ~1.94-1.95 μm band, 2.22/2.27 μm doublet and 2.49 μm band with a 2.42 μm shoulder. Spectra were acquired from regions of interest (ROIs) created along the crests of primary dunes and the low-relief crests of the secondary dunes (Fig. 1). FINDINGS: CRISM spectra of primary and secondary dune crest ROIs from FRT0000C2FC are compared with a gypsum-rich unit in FRT0000CA5C (Fig. 2). The I/F of gypsum-bearing regions is much darker than pure gypsum indicating a mixture composition containing darker components. The depth of the ~1.95 μm hydration band is ~20-30% stronger for primary dune crests relative to the secondaries, which suggests a similar relationship among the gypsum abundance of these features, assuming similar components and grain sizes. Semi-quantitative analyses are underway to measure this in more detail. Continuing studies are planned with additional images as well. Figure 1 A map-projected view of CRISM image FRT0000C2FC with ROI locations for the primary (P) and secondary (S) dune crests marked. Figure 2 CRISM I/F spectra of gypsum-bearing units in Olympia Undae compared with laboratory reflectance spectra of minerals.

  17. Assessing controls on diffuse groundwater recharge using unsaturated flow modeling

    NASA Astrophysics Data System (ADS)

    Keese, K. E.; Scanlon, B. R.; Reedy, R. C.

    2005-06-01

    Understanding climate, vegetation, and soil controls on recharge is essential for estimating potential impacts of climate variability and land use/land cover change on recharge. Recharge controls were evaluated by simulating drainage in 5-m-thick profiles using a one-dimensional (1-D) unsaturated flow code (UNSAT-H), climate data, and vegetation and soil coverages from online sources. Soil hydraulic properties were estimated from STATSGO/SSURGO soils data using pedotransfer functions. Vegetation parameters were obtained from the literature. Long-term (1961-1990) simulations were conducted for 13 county-scale regions representing arid to humid climates and different vegetation and soil types, using data for Texas. Areally averaged recharge rates are most appropriate for water resources; therefore Geographic Information Systems were used to determine spatial weighting of recharge results from 1-D models for the combination of vegetation and soils in each region. Simulated 30-year mean annual recharge in bare sand is high (51-709 mm/yr) and represents 23-60% (arid-humid) of mean annual precipitation (MAP). Adding vegetation reduced recharge by factors of 2-30 (humid-arid), and soil textural variability reduced recharge by factors of 2-11 relative to recharge in bare sand. Vegetation and soil textural variability both resulted in a large range of recharge rates within each region; however, spatially weighted, long-term recharge rates were much less variable and were positively correlated with MAP (r2 = 0.85 for vegetated sand; r2 = 0.62 for variably textured soils). The most realistic simulations included vegetation and variably textured soils, which resulted in recharge rates from 0.2 to 118 mm/yr (0.1-10% of MAP). Mean annual precipitation explains 80% of the variation in recharge and can be used to map recharge.

  18. Cellular automata to understand the behaviour of beach-dune systems: Application to El Fangar Spit active dune system (Ebro delta, Spain)

    NASA Astrophysics Data System (ADS)

    Barrio-Parra, Fernando; Rodríguez-Santalla, Inmaculada

    2016-08-01

    Coastal dunes are sedimentary environments characterized by their high dynamism. Their evolution is determined by sedimentary exchanges between the beach-dune subsystems and the dune dynamics itself. Knowledge about these exchanges is important to prioritize management and conservation strategies of these environments. The aim of this work is the inclusion of the aeolian transport rates obtained using a calibrated cellular automaton to estimate the beach-dune sediment exchange rates in a real active dune field at El Fangar Spit (Ebro Delta, Spain). The dune dynamics model is able to estimate average aeolian sediment fluxes. These are used in combination with the observed net sediment budget to obtain a quantitative characterization of the sediment exchange interactions. The methods produce a substantial improvement in the understanding of coastal sedimentary systems that could have major implications in areas where the management and conservation of dune fields are of concern.

  19. Morphology and dynamics of large subtidal dunes in Bahia Blanca estuary, Argentina

    NASA Astrophysics Data System (ADS)

    Minor Salvatierra, Marta; Aliotta, Salvador; Ginsberg, Silvia Susana

    2015-10-01

    The purpose of this paper is to carry out a detailed analysis of subtidal dune morphology and temporal variability and to estimate dune migration rate to improve knowledge of this topic, and so enhance the existing data on different marine environments in the world and especially in South America where this information is limited. Two swath bathymetry surveys were conducted across a dune field in the Bahia Blanca Estuary (Argentina). Morphometric parameters and migration rate according to the dune type, were analyzed. The field is composed of large dunes exhibiting two morphological configurations, which are differentiated into sinuous and barchan dunes. The dunes studied are the largest of the estuary, with heights and wavelengths greater than 5 m and 130 m, respectively. The crests of the large dunes are arranged with an orientation perpendicular to the axis of the channel. From geometrical analysis of the parameters, the dunes show a weakly positive correlation between dune height and wavelength as too between dune height and water depth. No clear relationship was observed between maximum height and wavelength parameters with water depth. Across the estuary, the bedforms migrate in the ebb direction, with mean rate of 43 m year- 1. Comparison of our results with previous data shows that during three decades the western boundary of dune field has been displaced 900 m towards the outer estuary, however the dune field configuration and distribution of diverse types of bedform appear to be relatively stable.

  20. Origin and lateral migration of linear dunes in the Qaidam Basin of NW China revealed by dune sediments, internal structures, and optically stimulated luminescence ages, with implications for linear dunes on Titan: discussion

    USGS Publications Warehouse

    Rubin, David M.; Rubin, Alan M.

    2013-01-01

    Zhou et al. (2012) proposed that longitudinal dunes in the Qaidam Basin, China, formed like yardangs: by erosion into sediment that was not deposited by those dunes. Because erosion occurs on the upwind flanks of most migrating dunes (Rubin and Hunter, 1982, 1985), the key to demonstrating a yardang-like origin is to show that the dunes did not deposit the strata that they contain. Zhou et al. made this argument by proposing that: (1) The dunes have not deposited cross-strata in the past 810 yr. (2) Cross-bedding within the dunes was not deposited by the dunes on the present-day land surface, but rather by older dunes that had a different morphology. (3) The present dunes are a later generation, “most likely of erosional origin similar to yardangs with orientations controlled by strikes of joints,” (p. 1147). (4) Rates of deflation in the dune field have been extremely high for the past 810–2440 yr. This commentary reviews these conclusions, reviews contradictory observations, and considers alternative interpretations.

  1. Morphological characteristics and sand volumes of different coastal dune types in Essaouira Province, Atlantic Morocco

    NASA Astrophysics Data System (ADS)

    Flor-Blanco, Germán; Flor, Germán; Lharti, Saadia; Pando, Luis

    2013-04-01

    Altogether three coastal dune fields, one located north and two south of the city of Essaouira, Atlantic Morocco, have been investigated to establish the distribution and overall sand volumes of various dune types. The purpose of the study was to characterize and classify the aeolian landforms of the coastal dune belt, to estimate their sand volumes and to assess the effectiveness of coastal dune stabilization measures. The northern dune field is 9 km long and lined by a wide artificial foredune complex fixed by vegetation, fences and branches forming a rectangular grid. Active and ephemeral aklé dunes border the inner backshore, while some intrusive dunes have crossed the foredune belt and are migrating farther inland. The total sand volume of the northern dune belt amounts 13,910,255 m3. The central coastal sector comprises a much smaller dune field located just south of the city. It is only 1.2 km long and, with the exception of intrusive dunes, shows all other dune types. The overall sand volume of the central dune field amounts to about 172,463 m3. The southern dune field is characterized by a narrower foredune belt and overall lower dunes that, in addition, become progressively smaller towards the south. In this sector, embryonic dunes (coppice, shadow dunes), tongue-like and tabular dunes, and sand sheets intrude from the beach, the profile of which has a stepped appearance controlled by irregular outcrops of old aeolianite and beach rock. The total volume of the southern dune field amounts 1,446,389 m3. For the whole study area, i.e. for all three dune fields combined, a sand volume of about 15,529,389 m3 has been estimated. The sand of the dune fields is derived from coastal erosion and especially the Tensift River, which enters the sea at Souira Qedima some 70 km north of Essaouira. After entering the sea, the sand is transported southwards by littoral drift driven by the mainly north-westerly swell climate and the Trade Winds blowing from the NNE. This

  2. Nanocomposite polymer electrolyte for rechargeable magnesium batteries

    SciTech Connect

    Shao, Yuyan; Rajput, Nav Nidhi; Hu, Jian Z.; Hu, Mary Y.; Liu, Tianbiao L.; Wei, Zhehao; Gu, Meng; Deng, Xuchu; Xu, Suochang; Han, Kee Sung; Wang, Jiulin; Nie, Zimin; Li, Guosheng; Zavadil, K.; Xiao, Jie; Wang, Chong M.; Henderson, Wesley A.; Zhang, Jiguang; Wang, Yong; Mueller, Karl T.; Persson, Kristin A.; Liu, Jun

    2014-12-28

    Nanocomposite polymer electrolytes present new opportunities for rechargeable magnesium batteries. However, few polymer electrolytes have demonstrated reversible Mg deposition/dissolution and those that have still contain volatile liquids such as tetrahydrofuran (THF). In this work, we report a nanocomposite polymer electrolyte based on poly(ethylene oxide) (PEO), Mg(BH4)2 and MgO nanoparticles for rechargeable Mg batteries. Cells with this electrolyte have a high coulombic efficiency of 98% for Mg plating/stripping and a high cycling stability. Through combined experiment-modeling investigations, a correlation between improved solvation of the salt and solvent chain length, chelation and oxygen denticity is established. Following the same trend, the nanocomposite polymer electrolyte is inferred to enhance the dissociation of the salt Mg(BH4)2 and thus improve the electrochemical performance. The insights and design metrics thus obtained may be used in nanocomposite electrolytes for other multivalent systems.

  3. Recharge and Evapotranspiration Assessment In Kalahari

    NASA Astrophysics Data System (ADS)

    Lubczynski, M.; Obakeng, O.

    2006-12-01

    Sustainability of groundwater resources in Kalahri is constrained not only by recharge to the aquifers but also by discharge from them. Natural groundwater discharge takes place in 3 different ways, as aquifer groundwater outflow, direct tree root water uptake called groundwater transpiration (Tg) and as upward vapor-liquid water movement called groundwater evaporation (Eg), the latter two called groundwater evapotranspiration (ETg). The evaluation of ETg and recharge was the main goal of this study. Due to generally large depth of groundwater table in Kalahari, >60 m, Eg was assumed as negligible component of groundwater balances while in contrast Tg has been considered significant already since 90-ties. This was because of fragments of tree roots of Boscia albitrunca and Acacia erioloba found in borehole cores at depth of >60 m. Some of those roots reach groundwater, which allow them to remain green throughout dry seasons. This study was carried out using hydrological monitoring consisting of 10 multi-sensor towers and 17 groundwater monitoring points. Soil moisture movement was investigated by profile monitoring. The deepest profile was down to 76 m depth. The soil moisture results revealed complicated pattern characterized by a combination of diffuse and preferential flow. The actual evapotranspiration was estimated by the Bowen-ratio and temperature-profile methods which provided overestimated results as compared with rainfall so the recharge could not be deduced directly. Therefore recharge was derived indirectly, through 1D lumped parameter model that used rainfall and PET as input and heads as calibration reference. That model indicated recharge 0-50 mm/yr. For understanding tree impact upon groundwater recharge, tree sap velocity was monitored for 2 years using the Granier method on 41 trees of 9 species in 8 plots of 30x30m. The estimated plot transpirations showed large spatio-temporal variability, 3-71 mm/yr and occasionally exceeded recharge. In order

  4. The Mediterranean Coastal Dunes in Egypt: An Endangered Landscape

    NASA Astrophysics Data System (ADS)

    Batanouny, K. H.

    1999-08-01

    The Mediterranean coast in Egypt extends almost 900 km, the major part of which is bordered by sand dunes of different natures and types. Along the coastline between Alexandria and El-Alamein, a distance of some 100 km, the sand dunes represent a particular landscape with special characteristics and features, and consequently plants with particular attributes. In this area, the belt of sand dunes has developed immediately south of the shore and these dunes may rise up to 10 m in height and extend about 0·5-1·5 km inland from the shore. These dunes are famous as a habitat for the fig (Ficus carica L.) cultivation depending on the irregular rainfall. They also represent a landing station and a cross-road for birds such as quail migrating from Europe in the north. In the past, summer resort areas were confined to limited areas with few people, these same areas support the growth of some important plant species, for example, sand binders, medicinal and range plants. For more than two decades, there has been considerable socio-economic change and an open-door policy in the economy of the country has been adopted. One of the consequences of this change is that a great part of the coastal dune belt west of Alexandria till El-Alamein, has been subjected to destruction, due to the continuous construction of summer resort villages. These were built at a distance of about 100 m of the shoreline, extending 400-600 m inland and a breadth of 400 m or more along the shoreline. The area already covered by the dunes is now almost occupied by new buildings, gardens and other infrastructure. The consequences of these human activities are numerous and include impacts on the soil, water resources, the flora and the fauna, migrating birds, trends of the indigenous people, and the cultural environment. The present paper gives a concise environmental setting of the dune belt before the advent of the new activities, and the socio-economic and political attitudes which threaten the dunes

  5. Solid-state rechargeable magnesium battery

    DOEpatents

    Shao, Yuyan; Liu, Jun; Liu, Tianbiao; Li, Guosheng

    2016-09-06

    Embodiments of a solid-state electrolyte comprising magnesium borohydride, polyethylene oxide, and optionally a Group IIA or transition metal oxide are disclosed. The solid-state electrolyte may be a thin film comprising a dispersion of magnesium borohydride and magnesium oxide nanoparticles in polyethylene oxide. Rechargeable magnesium batteries including the disclosed solid-state electrolyte may have a coulombic efficiency .gtoreq.95% and exhibit cycling stability for at least 50 cycles.

  6. Inorganic rechargeable non-aqueous cell

    SciTech Connect

    Bowden, William L.; Dey, Arabinda N.

    1985-05-07

    A totally inorganic non-aqueous rechargeable cell having an alkali or alkaline earth metal anode such as of lithium, a sulfur dioxide containing electrolyte and a discharging metal halide cathode, such as of CuCl.sub.2, CuBr.sub.2 and the like with said metal halide being substantially totally insoluble in SO.sub.2 and admixed with a conductive carbon material.

  7. The rechargeable aluminum-ion battery.

    PubMed

    Jayaprakash, N; Das, S K; Archer, L A

    2011-12-21

    We report a novel aluminium-ion rechargeable battery comprised of an electrolyte containing AlCl(3) in the ionic liquid, 1-ethyl-3-methylimidazolium chloride, and a V(2)O(5) nano-wire cathode against an aluminium metal anode. The battery delivered a discharge capacity of 305 mAh g(-1) in the first cycle and 273 mAh g(-1) after 20 cycles, with very stable electrochemical behaviour. PMID:22051794

  8. Charge Control Investigation of Rechargeable Lithium Cells

    NASA Technical Reports Server (NTRS)

    Otzinger, B.; Somoano, R.

    1984-01-01

    An ambient temperature rechargeable Li-TiS2 cell was cycled under conditions which simulate aerospace applications. A novel charge/discharge state-of-charge control scheme was used, together with tapered current charging, to overcome deleterious effects associated with end-of-charge and end-of-discharge voltages. The study indicates that Li-TiS2 cells hold promise for eventual synchronous satellite-type applications. Problem areas associated with performance degradation and reconditioning effects are identified.

  9. The rechargeable aluminum-ion battery

    SciTech Connect

    Navaneedhakrishnan, Jayaprakash; Das, Shyamal K; Archer, Lynden A.

    2011-01-01

    We report a novel aluminium-ion rechargeable battery comprised of an electrolyte containing AlCl₃ in the ionic liquid, 1-ethyl-3-methylimidazolium chloride, and a V₂O₅ nano-wire cathode against an aluminium metal anode. The battery delivered a discharge capacity of 305 mAh g⁻¹ in the first cycle and 273 mAh g⁻¹ after 20 cycles, with very stable electrochemical behaviour.

  10. Ampere-Hour Meter For Rechargeable Battery

    NASA Technical Reports Server (NTRS)

    Tripp, John S.; Schott, Timothy D.; Tcheng, Ping

    1993-01-01

    Low-power analog/digital electronic circuit meters discharge of storage battery in ampere-hours. By metering discharge, one obtains indication of state of charge of battery and avoids unnecessary recharging, maintaining capacity of battery and prolonging life. Because of its small size and low power consumption, useful in such applications as portable video cameras, communication equipment on boats, portable audio equipment, and portable medical equipment.

  11. Large-eddy simulation of sand dune morphodynamics

    NASA Astrophysics Data System (ADS)

    Khosronejad, Ali; Sotiropoulos, Fotis; St. Anthony Falls Laboratory, University of Minnesota Team

    2015-11-01

    Sand dunes are natural features that form under complex interaction between turbulent flow and bed morphodynamics. We employ a fully-coupled 3D numerical model (Khosronejad and Sotiropoulos, 2014, Journal of Fluid Mechanics, 753:150-216) to perform high-resolution large-eddy simulations of turbulence and bed morphodynamics in a laboratory scale mobile-bed channel to investigate initiation, evolution and quasi-equilibrium of sand dunes (Venditti and Church, 2005, J. Geophysical Research, 110:F01009). We employ a curvilinear immersed boundary method along with convection-diffusion and bed-morphodynamics modules to simulate the suspended sediment and the bed-load transports respectively. The coupled simulation were carried out on a grid with more than 100 million grid nodes and simulated about 3 hours of physical time of dune evolution. The simulations provide the first complete description of sand dune formation and long-term evolution. The geometric characteristics of the simulated dunes are shown to be in excellent agreement with observed data obtained across a broad range of scales. This work was supported by NSF Grants EAR-0120914 (as part of the National Center for Earth-Surface Dynamics). Computational resources were provided by the University of Minnesota Supercomputing Institute.

  12. Sand transport on an estuarine submarine dune field

    NASA Astrophysics Data System (ADS)

    Gómez, Eduardo A.; Cuadrado, Diana G.; Pierini, Jorge O.

    2010-09-01

    By means of surveys carried out with a Phase Measuring Bathymetric System and current profiles obtained through an ADCP of the internal area of the Bahía Blanca estuary, a field of large dunes was analysed. There are two different and well-defined zones characterized by particular dune morphology and differing hydrodynamics. The reduction in the channel cross-section by a geological control leads to the increase in tidal current velocity, which together with the available sediment leads to the formation of Very Large Dunes ( H > 4 m and L > 100 m) with the typical morphology of a limited amount of sediment overlying a rigid substrate. The migration rate of these dunes, between 65 and 130 m year - 1 , decreases as the bedform height increases. Differing sediment transport rates across the channel result in a non-uniform migration rate, which is responsible for the formation of dunes with linear crests oblique to the tidal current direction. This fact indicates that determination of the sediment transport direction by using only large bedform orientation may be subject to a significant error.

  13. Numerical modeling of the wind flow over a transverse dune

    PubMed Central

    Araújo, Ascânio D.; Parteli, Eric J. R.; Pöschel, Thorsten; Andrade, José S.; Herrmann, Hans J.

    2013-01-01

    Transverse dunes, which form under unidirectional winds and have fixed profile in the direction perpendicular to the wind, occur on all celestial objects of our solar system where dunes have been detected. Here we perform a numerical study of the average turbulent wind flow over a transverse dune by means of computational fluid dynamics simulations. We find that the length of the zone of recirculating flow at the dune lee — the separation bubble — displays a surprisingly strong dependence on the wind shear velocity, u*: it is nearly independent of u* for shear velocities within the range between 0.2 m/s and 0.8 m/s but increases linearly with u* for larger shear velocities. Our calculations show that transport in the direction opposite to dune migration within the separation bubble can be sustained if u* is larger than approximately 0.39 m/s, whereas a larger value of u* (about 0.49 m/s) is required to initiate this reverse transport. PMID:24091456

  14. Dune field reactivation from blowouts: Sevier Desert, UT, USA

    NASA Astrophysics Data System (ADS)

    Barchyn, Thomas E.; Hugenholtz, Chris H.

    2013-12-01

    Dune field reactivation (a shift from vegetated to unvegetated state) has important economic, social, and environmental implications. In some settings reactivation is desired to preserve environmental values, but in arid regions reactivation is typically a form of land degradation. Little is known about reactivation due to a lack of published records, making modeling and prediction difficult. Here we detail dune reactivations from blowout expansion in the Sevier Desert, Utah, USA. We use historical aerial photographs and satellite imagery to track the transition from stable, vegetated dunes to actively migrating sediment in 3 locations. We outline a reactivation sequence: (i) disturbance breaches vegetation and exposes sediment, then (ii) creates a blowout with a deposition apron that (iii) advances downwind with a slipface or as a sand sheet. Most deposition aprons are not colonized by vegetation and are actively migrating. To explore causes we examine local sand flux, climate data, and stream flow. Based on available data the best explanation we can provide is that some combination of anthropogenic disturbance and climate may be responsible for the reactivations. Together, these examples provide a rare glimpse of dune field reactivation from blowouts, revealing the timescales, behaviour, and morphodynamics of devegetating dune fields.

  15. Ground water recharge from Lake Chad

    SciTech Connect

    Isiorho, S.; Matisoff, G.; McCall, P.L.

    1985-01-01

    Lake Chad is a shallow, closed basin lake located in Sub-Sharan Africa. It has the largest drainage basin of any lake in the world, and is also very old, being formed by tectonic processes during the Cretaceous. These features should combine to form a saline lake, but the open waters of Lake Chad are reasonably fresh, having a total dissolved solids concentration of about 320 mg/1. This apparent discrepancy can be explained by noting that recharge of the unconfined aquifer to the SW in Nigeria by ground water infiltration through the lakebed can remove significant quantities of water and dissolved solutes from the lake. The authors have measured and calculated ground water infiltration and velocities by several techniques. Direct, volumetric measurements of ground water recharge seepage give velocities on the order of .28-8.8 x 10/sup -3/ m/day. Tracer monitoring in a borehole dilution test yielded ground water velocities of 3.6 m/day to the SW (away from the lake). Hydraulic conductivities approx. .004-.6 m/day were determined by falling head measurements. Finally, using static water levels, the potentiometric surface within approx. 80 km of the southwest portion of Lake Chad yields water table gradients of 1.0-1.7 x 10/sup -4/ away from the lake. These results confirm that surface water and solute inflow to Lake Chad is removed by recharge to the unconfined aquifer in Nigeria.

  16. Dendrites Inhibition in Rechargeable Lithium Metal Batteries

    NASA Astrophysics Data System (ADS)

    Aryanfar, Asghar

    The specific high energy and power capacities of rechargeable lithium metal (Li0) batteries are ideally suited to portable devices and are valuable as storage units for intermittent renewable energy sources. Lithium, the lightest and most electropositive metal, would be the optimal anode material for rechargeable batteries if it were not for the fact that such devices fail unexpectedly by short-circuiting via the dendrites that grow across electrodes upon recharging. This phenomenon poses a major safety issue because it triggers a series of adverse events that start with overheating, potentially followed by the thermal decomposition and ultimately the ignition of the organic solvents used in such devices. In this thesis, we developed experimental platform for monitoring and quantifying the dendrite populations grown in a Li battery prototype upon charging under various conditions. We explored the effects of pulse charging in the kHz range and temperature on dendrite growth, and also on loss capacity into detached "dead" lithium particles. Simultaneously, we developed a computational framework for understanding the dynamics of dendrite propagation. The coarse-grained Monte Carlo model assisted us in the interpretation of pulsing experiments, whereas MD calculations provided insights into the mechanism of dendrites thermal relaxation. We also developed a computational framework for measuring the dead lithium crystals from the experimental images.

  17. Quantifying Potential Groundwater Recharge In South Texas

    NASA Astrophysics Data System (ADS)

    Basant, S.; Zhou, Y.; Leite, P. A.; Wilcox, B. P.

    2015-12-01

    Groundwater in South Texas is heavily relied on for human consumption and irrigation for food crops. Like most of the south west US, woody encroachment has altered the grassland ecosystems here too. While brush removal has been widely implemented in Texas with the objective of increasing groundwater recharge, the linkage between vegetation and groundwater recharge in South Texas is still unclear. Studies have been conducted to understand plant-root-water dynamics at the scale of plants. However, little work has been done to quantify the changes in soil water and deep percolation at the landscape scale. Modeling water flow through soil profiles can provide an estimate of the total water flowing into deep percolation. These models are especially powerful with parameterized and calibrated with long term soil water data. In this study we parameterize the HYDRUS soil water model using long term soil water data collected in Jim Wells County in South Texas. Soil water was measured at every 20 cm intervals up to a depth of 200 cm. The parameterized model will be used to simulate soil water dynamics under a variety of precipitation regimes ranging from well above normal to severe drought conditions. The results from the model will be compared with the changes in soil moisture profile observed in response to vegetation cover and treatments from a study in a similar. Comparative studies like this can be used to build new and strengthen existing hypotheses regarding deep percolation and the role of soil texture and vegetation in groundwater recharge.

  18. An ultrafast rechargeable aluminium-ion battery

    NASA Astrophysics Data System (ADS)

    Lin, Meng-Chang; Gong, Ming; Lu, Bingan; Wu, Yingpeng; Wang, Di-Yan; Guan, Mingyun; Angell, Michael; Chen, Changxin; Yang, Jiang; Hwang, Bing-Joe; Dai, Hongjie

    2015-04-01

    The development of new rechargeable battery systems could fuel various energy applications, from personal electronics to grid storage. Rechargeable aluminium-based batteries offer the possibilities of low cost and low flammability, together with three-electron-redox properties leading to high capacity. However, research efforts over the past 30 years have encountered numerous problems, such as cathode material disintegration, low cell discharge voltage (about 0.55 volts ref. 5), capacitive behaviour without discharge voltage plateaus (1.1-0.2 volts or 1.8-0.8 volts) and insufficient cycle life (less than 100 cycles) with rapid capacity decay (by 26-85 per cent over 100 cycles). Here we present a rechargeable aluminium battery with high-rate capability that uses an aluminium metal anode and a three-dimensional graphitic-foam cathode. The battery operates through the electrochemical deposition and dissolution of aluminium at the anode, and intercalation/de-intercalation of chloroaluminate anions in the graphite, using a non-flammable ionic liquid electrolyte. The cell exhibits well-defined discharge voltage plateaus near 2 volts, a specific capacity of about 70 mA h g-1 and a Coulombic efficiency of approximately 98 per cent. The cathode was found to enable fast anion diffusion and intercalation, affording charging times of around one minute with a current density of ~4,000 mA g-1 (equivalent to ~3,000 W kg-1), and to withstand more than 7,500 cycles without capacity decay.

  19. Solar Storms, Devils, Dunes, and Gullies

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 12 December 2003

    Man, there sure is a lot going on here! This image was acquired during the peak of the late October record breaking solar storm outbursts. The white dots in this image were in fact caused when the charged particles from the sun hit our camera. One can also see the enigmatic gullies, dark barchan sand dunes and numerous dust devil tracks. This image is in the Noachis region of the heavily cratered southern hemisphere.

    Image information: VIS instrument. Latitude -42.1, Longitude 328.2 East (31.8 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  20. A regression model to estimate regional ground water recharge.

    PubMed

    Lorenz, David L; Delin, Geoffrey N

    2007-01-01

    A regional regression model was developed to estimate the spatial distribution of ground water recharge in subhumid regions. The regional regression recharge (RRR) model was based on a regression of basin-wide estimates of recharge from surface water drainage basins, precipitation, growing degree days (GDD), and average basin specific yield (SY). Decadal average recharge, precipitation, and GDD were used in the RRR model. The RRR estimates were derived from analysis of stream base flow using a computer program that was based on the Rorabaugh method. As expected, there was a strong correlation between recharge and precipitation. The model was applied to statewide data in Minnesota. Where precipitation was least in the western and northwestern parts of the state (50 to 65 cm/year), recharge computed by the RRR model also was lowest (0 to 5 cm/year). A strong correlation also exists between recharge and SY. SY was least in areas where glacial lake clay occurs, primarily in the northwest part of the state; recharge estimates in these areas were in the 0- to 5-cm/year range. In sand-plain areas where SY is greatest, recharge estimates were in the 15- to 29-cm/year range on the basis of the RRR model. Recharge estimates that were based on the RRR model compared favorably with estimates made on the basis of other methods. The RRR model can be applied in other subhumid regions where region wide data sets of precipitation, streamflow, GDD, and soils data are available. PMID:17335484

  1. A regression model to estimate regional ground water recharge

    USGS Publications Warehouse

    Lorenz, D.L.; Delin, G.N.

    2007-01-01

    A regional regression model was developed to estimate the spatial distribution of ground water recharge in subhumid regions. The regional regression recharge (RRR) model was based on a regression of basin-wide estimates of recharge from surface water drainage basins, precipitation, growing degree days (GDD), and average basin specific yield (SY). Decadal average recharge, precipitation, and GDD were used in the RRR model. The RRR estimates were derived from analysis of stream base flow using a computer program that was based on the Rorabaugh method. As expected, there was a strong correlation between recharge and precipitation. The model was applied to statewide data in Minnesota. Where precipitation was least in the western and northwestern parts of the state (50 to 65 cm/year), recharge computed by the RRR model also was lowest (0 to 5 cm/year). A strong correlation also exists between recharge and SY. SY was least in areas where glacial lake clay occurs, primarily in the northwest part of the state; recharge estimates in these areas were in the 0- to 5-cm/year range. In sand-plain areas where SY is greatest, recharge estimates were in the 15- to 29-cm/year range on the basis of the RRR model. Recharge estimates that were based on the RRR model compared favorably with estimates made on the basis of other methods. The RRR model can be applied in other subhumid regions where region wide data sets of precipitation, streamflow, GDD, and soils data are available.

  2. Basin-scale recharge in the Southwestern United States

    NASA Astrophysics Data System (ADS)

    Hogan, J. F.; Duffy, C.; Eastoe, C.; Ferre, T. P. A.; Goodrich, D.; Hendrickx, J.; Hibbs, B.; Phillips, F.; Small, E.; Wilson, J.

    2003-04-01

    The major domestic water source in the arid southwestern United States is groundwater from alluvial basin aquifers. Accurate estimates of basin-scale groundwater recharge rates are a critical need for developing sustainable or "safe yield" groundwater pumping. Basin-scale recharge rates are typically estimated using inverse hydrologic modeling or geochemical tracers (e.g. chloride mass balance). These methods, while useful, have a high level of uncertainty and provide no information about the mechanisms of groundwater recharge. SAHRA - an NSF Science and Technology Center focused on the Sustainability of semi-Arid Hydrology and Riparian Areas - has developed an integrated research plan to address this problem. Our approach is two-fold. First we are investigating the "input" components that comprise basin-scale recharge: basin floor recharge, alluvial channel recharge, mountain front recharge, and mountain block recharge. Each component has unique spatial and temporal scales and thus requires distinct methods. Our research is aimed at understanding the factors (e.g. vegetation type, bedrock lithology, soil structure) that control recharge rates in each of these locations. With such an understanding one could then scale from point measurements to the basin-scale using remote sensing data. Our second approach is to employ isotopic tracers to determine water sources, groundwater ages and residence times of the groundwater and surface water "outputs"; these values can then be used to better calibrate recharge rates in groundwater models. By focusing our studies on two basins, the San Pedro River Basin in Arizona and the Rio Grande in New Mexico, we hope to develop a better understanding of the importance of different recharge pathways for basin-scale recharge and which methods are best suited for estimating basin-scale recharge.

  3. Une angiocholite secondaire à un thrombus tumoral d'une tumeur neuroendocrine primitive du foie

    PubMed Central

    Baba, Hicham; Allaoui, Mohamed; Elfahssi, Mohammed; Bounaim, Ahmed; Ali, Abdelmounaim Ait; Oukabli, Mohamed; Sair, Khalid; Zentar, Aziz

    2015-01-01

    Nous rapportons le cas exceptionnel d'une patiente de 54 ans prise en charge pour une angiocholite due à un thrombus tumoral, d'une tumeur neuroendocrine primitive (TNE Ive) du foie, dans la voie biliaire principale. PMID:26966504

  4. Genesis of Dune Fields Under Unidirectional Wind with Sand Input Flux Control: An Experimental Approach

    NASA Astrophysics Data System (ADS)

    Garcia, A.; Courrech du Pont, S.; Rodriguez, S.; Valance, A.; Narteau, C.; Gao, X.; Lucas, A.

    2015-05-01

    Our experimental studies with control of wind and sediment source will characterize more precisely the different modes of dune formation and long-term evolution, and constrain the physics behind the morphogenesis and dynamics of dunes fields.

  5. Temperature and humidity measurements within desert barchan sand dunes, relation to dune aeolian mobility and microbial growth

    NASA Astrophysics Data System (ADS)

    Louge, Michel; Hay, Anthony; Richer, Renee; Valance, Alexandre; Ould el Moctar, Ahmed; Xu, Jin; Abdul-Majid, Sara

    2013-04-01

    We present diurnal variations of temperature and humidity profiles below the surface of hyper-arid aeolian crescent-shaped "barchan" dunes in Qatar and Mauritania, measured using a thermal probe and a new ultra-sensitive capacitance instrument that we developed for this purpose. We also report long-term measurements from a probe sunk on the downwind avalanche face of a mobile Qatar barchan, recording temperature and humidity until it emerged on the upwind slope 15 months later. We interpret the data by modeling heat and moisture transfer at the surface in terms of measured net surface radiation, wind, and atmospheric conditions. We demonstrate the presence of microbes on sand grains within these mobile dunes using microscopic observations, fluorescence counts, metagenomic sequencing, and C12/C13 isotope analysis of carbon dioxide sampled below the surface. By determining how water activity grows with moisture adsorbed on these sands, we delimit regions within the dune where our instruments recorded humidity conducive to microbial growth. Finally, we compare the mobility of two adjacent Mauritania barchans having distinct surface grain size, shape, and depth humidity profiles. Armored by large grains on its surface, the smaller dune was more oblong. As a result, it lacked flow recirculation in its wake, trapped less aeolian sand downwind, and was much less mobile than its smaller size would suggest. This slower mobility led to greater humidity and cohesion at depth than the larger dune exposed to the same atmospheric and wind conditions.

  6. Spring Time View of North Polar Sand Dunes

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Spring has come to the martian northern hemisphere. The northern spring season began in mid-July 1998. With the arrival of spring comes the annual shrinkage of the north polar frost cap. Sunlight is now falling on the north polar cap, and all of the carbon dioxide frost and snow that accumulated during winter has been sublimating--going directly from solid to gas--and the surface beneath the frost is being revealed.

    The MOC image shown above, 45205, was obtained during the 452nd orbit of Mars Global Surveyor at 3:10 p.m. PDT on July 26, 1998. The image is located near latitude 76.87oN, longitude 253.81oW, and it shows a close-up view of martian sand dunes. These dunes were not visible to MOC until the last week of July. Just a few months earlier, the dunes were likely covered with frost, obscured by thick clouds, and cloaked by the darkness of the martian polar winter. Indeed, small patches of bright frost were still present when the picture was taken (e.g., the bright patches on the west (left) side of each crescentic dune in (left image).

    As the above picture illustrates, the camera on board Mars Global Surveyor (MOC) continued to take exciting new views of the martian surface throughout July 1998. As the month progressed, the ground track-- the area visible to the camera--migrated farther north. Simultaneously, sunlight began falling on the north polar regions, making it possible to take some pictures at far northern latitudes. However, these regions have been tricky to photograph because of thick clouds and hazes. The image shown here, for example, is relatively bland gray (has relatively low contrast) because of clouds.

    As first seen by the Viking 2 Orbiter in 1976, a vast 'sea' of sand dunes surrounds the north polar cap. The dunes imaged by MOC (above) are classic forms known as barchan dunes--the small, crescent-shaped hills (see left image above)-- and transverse dunes--ridges that resemble coalesced barchans (shown in right image above). These

  7. A model of Barchan dunes including lateral shear stress.

    PubMed

    Schwämmle, V; Herrmann, H J

    2005-01-01

    Barchan dunes are found where sand availability is low and wind direction quite constant. The two dimensional shear stress of the wind field and the sand movement by saltation and avalanches over a barchan dune are simulated. The model with one dimensional shear stress is extended including surface diffusion and lateral shear stress. The resulting final shape is compared to the results of the model with a one dimensional shear stress and confirmed by comparison to measurements. We found agreement and improvements with respect to the model with one dimensional shear stress. Additionally, a characteristic edge at the center of the windward side is discovered which is also observed for big barchans. Diffusion effects reduce this effect for small dunes. PMID:15688141

  8. Defrosting Polar Dunes--'They Look Like Bushes!'

    NASA Technical Reports Server (NTRS)

    1999-01-01

    'They look like bushes!' That's what almost everyone says when they see the dark features found in pictures taken of sand dunes in the polar regions as they are beginning to defrost after a long, cold winter. It is hard to escape the fact that, at first glance, these images acquired by the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) over both polar regions during the spring and summer seasons, do indeed resemble aerial photographs of sand dune fields on Earth--complete with vegetation growing on and around them! Of course, this is not what the features are, as we describe below and in related picture captions. Still, don't they look like vegetation to you? Shown here are two views of the same MGS MOC image. On the left is the full scene, on the right is an expanded view of a portion of the scene on the left. The bright, smooth surfaces that are dotted with occasional, nearly triangular dark spots are sand dunes covered by winter frost.

    The MGS MOC has been used over the past several months (April-August 1999) to monitor dark spots as they form and evolve on polar dune surfaces. The dark spots typically appear first along the lower margins of a dune--similar to the position of bushes and tufts of grass that occur in and among some sand dunes on Earth.

    Because the martian air pressure is very low--100 times lower than at Sea Level on Earth--ice on Mars does not melt and become liquid when it warms up. Instead, ice sublimes--that is, it changes directly from solid to gas, just as 'dry ice' does on Earth. As polar dunes emerge from the months-long winter night, and first become exposed to sunlight, the bright winter frost and snow begins to sublime. This process is not uniform everywhere on a dune, but begins in small spots and then over several months it spreads until the entire dune is spotted like a leopard.

    The early stages of the defrosting process--as in the picture shown here--give the impression that something is 'growing' on the dunes

  9. Advanced InSAR imaging for dune mapping

    NASA Astrophysics Data System (ADS)

    Havivi, Shiran; August, Yitzhak; Blumberg, Dan G.; Rotman, Stanley R.

    2015-04-01

    Aeolian morphologies are formed in the presence of sufficient wind energy and available particles. These processes occur naturally or are further enhanced or reduced by human intervention. The dimensions of change are dependent primarily on the wind energy and surface properties. Since the 1970's, remote sensing imagery both optical and radar, are used for documentation and interpretation of the geomorphologic changes of sand dunes. Remote sensing studies of Aeolian morphologies is mostly useful to document major changes, yet, subtle changes, occurring in a period of days or months in scales of centimeters, are very difficult to detect in imagery. Interferometric Synthetic Aperture Radar (InSAR) is an imaging technique for measuring Earth's surface topography and deformation. InSAR images are produced by measuring the radar phase difference between two separated antennas that view the same surface area. Classical InSAR is based on high coherence between two images or more. The output (interferogram) can show subtle changes with an accuracy of several millimeters to centimeters. Very little work has been done on measuring or identifying the changes in dunes using InSAR. The reason is that dunes tend to be less coherent than firm, stable, surfaces. This research aims to demonstrate how interferometric decorrelation, or, coherence change detection, can be used for identifying dune instability. We hypothesize and demonstrate that the loss of radar coherence over time on dunes can be used as an indication of the dune's instability. When SAR images are acquired at sufficiently close intervals one can measure the time it takes to lose coherence and associate this time with geomorphic stability. To achieve our goals, the Nitzanim coastal dunes along the Mediterranean, 40 km south of Tel-Aviv, Israel, were chosen as a case study. The dunes in this area are of varying levels of stability and vegetation cover and have been monitored meteorologically, geomorphologically and

  10. First Results from the DUNE 35-ton Prototype using Cosmics

    NASA Astrophysics Data System (ADS)

    Insler, Jonathan; DUNE Collaboration

    2016-03-01

    The 35-ton prototype for the Deep Underground Neutrino Experiment (DUNE) Far Detector is a single-phase liquid argon time projection chamber (LAr-TPC) integrated detector that will take cosmics data for a two month run beginning in February 2016. The 35-ton prototype will characterize DUNE's Far Detector technology performance and provide a sample of real data for DUNE reconstruction algorithms. The 35-ton prototype has two drift volumes of lengths 2.23 m and 0.23 m on either side of its anode plane assembly (APA) and makes use of wire planes with wrapped wires and a photon detection system (PDS) utilizing photon detection panels read out by silicon photomultipliers (SiPMs). Data from the 35-ton LAr detector are expected to provide rich information on scintillation light and charged particle tracks. We present a preliminary analysis of cosmics data taken with the 35-ton detector with a focus on stopping muons.

  11. Effects of trampling limitation on coastal dune plant communities.

    PubMed

    Santoro, Riccardo; Jucker, Tommaso; Prisco, Irene; Carboni, Marta; Battisti, Corrado; Acosta, Alicia T R

    2012-03-01

    Sandy coastlines are sensitive ecosystems where human activities can have considerable negative impacts. In particular, trampling by beach visitors is a disturbance that affects dune vegetation both at the species and community level. In this study we assess the effects of the limitation of human trampling on dune vegetation in a coastal protected area of Central Italy. We compare plant species diversity in two recently fenced sectors with that of an unfenced area (and therefore subject to human trampling) using rarefaction curves and a diversity/dominance approach during a two year study period. Our results indicate that limiting human trampling seems to be a key factor in driving changes in the plant diversity of dune systems. In 2007 the regression lines of species abundance as a function of rank showed steep slopes and high Y-intercept values in all sectors, indicating a comparable level of stress and dominance across the entire study site. On the contrary, in 2009 the regression lines of the two fenced sectors clearly diverge from that of the open sector, showing less steep slopes. This change in the slopes of the tendency lines, evidenced by the diversity/dominance diagrams and related to an increase in species diversity, suggests the recovery of plant communities in the two fences between 2007 and 2009. In general, plant communities subject to trampling tended to be poorer in species and less structured, since only dominant and tolerant plant species persisted. Furthermore, limiting trampling appears to have produced positive changes in the dune vegetation assemblage after a period of only two years. These results are encouraging for the management of coastal dune systems. They highlight how a simple and cost-effective management strategy, based on passive recovery conservation measures (i.e., fence building), can be a quick (1–2 years) and effective method for improving and safeguarding the diversity of dune plant communities. PMID:22302225

  12. Orographic forcing of dune forming winds on Titan

    NASA Astrophysics Data System (ADS)

    Larson, E. J.; Toon, O. B.; Friedson, A. J.

    2013-12-01

    Cassini has observed hundreds of dune fields on Titan, nearly all of which lie in the tropics and suggest westerly (from west to east) winds dominate at the surface [1,2]. Most GCMs however have obtained easterly surface winds in the tropics, seemingly contradicting the wind direction suggested by the dunes. This has led to an active debate in the community about the origin of the dune forming winds on Titan and their direction and modality. This discussion is mostly driven by a study of Earth dunes seen as analogous to Titan [1,2,3]. One can find examples of dunes on Earth that fit several wind regimes. To date only one GCM, that of Tokano [4,5], has presented detailed analysis of its near surface winds and their dune forming capabilities. Despite the bulk of the wind being easterly, this GCM produces faster westerlies at equinox, thus transporting sand to the east. Our model, the Titan CAM [6], is unable to reproduce the fast westerlies, although it is possible we are not outputting frequently enough to catch them. Our GCM has been updated to include realistic topography released by the Cassini radar team. Preliminary results suggest our tropical wind regime now has net westerly winds in the tropics, albeit weak. References: [1], Lorenz, R. et al. 2006. Science, 312, 724-727. [2], Radebaugh, J. et al. 2008. Icarus, 194, 690-703. [3] Rubin, D. and Hesp, P. 2009. Nature Geoscience 2, 653-658. [4] Tokano, T. 2008. Icarus 194, 243-262. [5] Tokano, T. 2010. Aeolian Research 2, 113-127. [6] Friedson, J. et al. 2009. Planetary Space Science, 57, 1931-1949.

  13. Effects of Trampling Limitation on Coastal Dune Plant Communities

    NASA Astrophysics Data System (ADS)

    Santoro, Riccardo; Jucker, Tommaso; Prisco, Irene; Carboni, Marta; Battisti, Corrado; Acosta, Alicia T. R.

    2012-03-01

    Sandy coastlines are sensitive ecosystems where human activities can have considerable negative impacts. In particular, trampling by beach visitors is a disturbance that affects dune vegetation both at the species and community level. In this study we assess the effects of the limitation of human trampling on dune vegetation in a coastal protected area of Central Italy. We compare plant species diversity in two recently fenced sectors with that of an unfenced area (and therefore subject to human trampling) using rarefaction curves and a diversity/dominance approach during a two year study period. Our results indicate that limiting human trampling seems to be a key factor in driving changes in the plant diversity of dune systems. In 2007 the regression lines of species abundance as a function of rank showed steep slopes and high Y-intercept values in all sectors, indicating a comparable level of stress and dominance across the entire study site. On the contrary, in 2009 the regression lines of the two fenced sectors clearly diverge from that of the open sector, showing less steep slopes. This change in the slopes of the tendency lines, evidenced by the diversity/dominance diagrams and related to an increase in species diversity, suggests the recovery of plant communities in the two fences between 2007 and 2009. In general, plant communities subject to trampling tended to be poorer in species and less structured, since only dominant and tolerant plant species persisted. Furthermore, limiting trampling appears to have produced positive changes in the dune vegetation assemblage after a period of only two years. These results are encouraging for the management of coastal dune systems. They highlight how a simple and cost-effective management strategy, based on passive recovery conservation measures (i.e., fence building), can be a quick (1-2 years) and effective method for improving and safeguarding the diversity of dune plant communities.

  14. Aeolian dunes as ground truth for atmospheric modeling on Mars

    USGS Publications Warehouse

    Hayward, R.K.; Titus, T.N.; Michaels, T.I.; Fenton, L.K.; Colaprete, A.; Christensen, P.R.

    2009-01-01

    Martian aeolian dunes preserve a record of atmosphere/surface interaction on a variety of scales, serving as ground truth for both Global Climate Models (GCMs) and mesoscale climate models, such as the Mars Regional Atmospheric Modeling System (MRAMS). We hypothesize that the location of dune fields, expressed globally by geographic distribution and locally by dune centroid azimuth (DCA), may record the long-term integration of atmospheric activity across a broad area, preserving GCM-scale atmospheric trends. In contrast, individual dune morphology, as expressed in slipface orientation (SF), may be more sensitive to localized variations in circulation, preserving topographically controlled mesoscale trends. We test this hypothesis by comparing the geographic distribution, DCA, and SF of dunes with output from the Ames Mars GCM and, at a local study site, with output from MRAMS. When compared to the GCM: 1) dunes generally lie adjacent to areas with strongest winds, 2) DCA agrees fairly well with GCM modeled wind directions in smooth-floored craters, and 3) SF does not agree well with GCM modeled wind directions. When compared to MRAMS modeled winds at our study site: 1) DCA generally coincides with the part of the crater where modeled mean winds are weak, and 2) SFs are consistent with some weak, topographically influenced modeled winds. We conclude that: 1) geographic distribution may be valuable as ground truth for GCMs, 2) DCA may be useful as ground truth for both GCM and mesoscale models, and 3) SF may be useful as ground truth for mesoscale models. Copyright 2009 by the American Geophysical Union.

  15. Aeolian sedimentary processes at the Bagnold Dunes, Mars: Implications for modern dune dynamics and sedimentary structures in the aeolian stratigraphic record of Mars

    NASA Astrophysics Data System (ADS)

    Ewing, Ryan C.; Bridges, Nathan T.; Sullivan, Rob; Lapotre, Mathieu G. A.; Fischer, Woodward W.; Lamb, Mike P.; Rubin, David M.; Lewis, Kevin W.; Gupta, Sanjeev

    2016-04-01

    Wind-blown sand dunes are ubiquitous on the surface of Mars and are a recognized component of the martian stratigraphic record. Our current knowledge of the aeolian sedimentary processes that determine dune morphology, drive dune dynamics, and create aeolian cross-stratification are based upon orbital studies of ripple and dune morphodynamics, rover observations of stratification on Mars, Earth analogs, and experimental and theoretical studies of sand movement under Martian conditions. In-situ observations of sand dunes (informally called the Bagnold Dunes) by Curiosity Rover in Gale Crater, Mars provide the first opportunity to make observations of dunes from the grain-to-dune scale thereby filling the gap in knowledge between theory and orbital observations and refining our understanding of the martian aeolian stratigraphic record. We use the suite of cameras on Curiosity, including Navigation Camera (Navcam), Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI), to make observations of the Bagnold Dunes. Measurements of sedimentary structures are made where stereo images are available. Observations indicate that structures generated by gravity-driven processes on the dune lee slopes, such as grainflow and grainfall, are similar to the suite of aeolian sedimentary structures observed on Earth and should be present and recognizable in Mars' aeolian stratigraphic record. Structures formed by traction-driven processes deviate significantly from those found on Earth. The dune hosts centimeter-scale wind ripples and large, meter-scale ripples, which are not found on Earth. The large ripples migrate across the depositional, lee slopes of the dune, which implies that these structures should be present in Mars' stratigraphic record and may appear similar to compound-dune stratification.The Mars Science Laboratory Curiosity Rover Team is acknowledged for their support of this work.

  16. 76 FR 57074 - Transfer of Administrative Jurisdiction at or Near Great Sand Dunes National Park

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-15

    ... National Park Service Transfer of Administrative Jurisdiction at or Near Great Sand Dunes National Park... benefit of Great Sand Dunes National Park, Baca National Wildlife Refuge, and the Rio Grande National... (Secretary) acquired certain lands and interests in land for the benefit of Great Sand Dunes National...

  17. 76 FR 68503 - Ungulate Management Plan/Environmental Impact Statement, Great Sand Dunes National Park and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-04

    ... National Park Service Ungulate Management Plan/Environmental Impact Statement, Great Sand Dunes National... Intent to prepare an Environmental Impact Statement for the Ungulate Management Plan, Great Sand Dunes... Ungulate Management Plan, Great Sand Dunes National Park and Preserve, Colorado. The purpose of this...

  18. Phase diagrams of dune shape and orientation depending on sand availability.

    PubMed

    Gao, Xin; Narteau, Clément; Rozier, Olivier; Courrech du Pont, Sylvain

    2015-01-01

    New evidence indicates that sand availability does not only control dune type but also the underlying dune growth mechanism and the subsequent dune orientation. Here we numerically investigate the development of bedforms in bidirectional wind regimes for two different conditions of sand availability: an erodible sand bed or a localized sand source on a non-erodible ground. These two conditions of sand availability are associated with two independent dune growth mechanisms and, for both of them, we present the complete phase diagrams of dune shape and orientation. On an erodible sand bed, linear dunes are observed over the entire parameter space. Then, the divergence angle and the transport ratio between the two winds control dune orientation and dynamics. For a localized sand source, different dune morphologies are observed depending on the wind regime. There are systematic transitions in dune shape from barchans to linear dunes extending away from the localized sand source, and vice-versa. These transitions are captured fairly by a new dimensionless parameter, which compares the ability of winds to build the dune topography in the two modes of dune orientation. PMID:26419614

  19. 36 CFR 28.3 - Boundaries: The Community Development District; The Dune District; The Seashore District.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Development District; The Dune District; The Seashore District. 28.3 Section 28.3 Parks, Forests, and Public... General Provisions § 28.3 Boundaries: The Community Development District; The Dune District; The Seashore... Community Development District, the Seashore District, and the Dune District. (b) The Community...

  20. 36 CFR 28.3 - Boundaries: The Community Development District; The Dune District; The Seashore District.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... Development District; The Dune District; The Seashore District. 28.3 Section 28.3 Parks, Forests, and Public... General Provisions § 28.3 Boundaries: The Community Development District; The Dune District; The Seashore... Community Development District, the Seashore District, and the Dune District. (b) The Community...

  1. 76 FR 10915 - Minor Boundary Revision at Indiana Dunes National Lakeshore

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-02-28

    ... National Park Service Minor Boundary Revision at Indiana Dunes National Lakeshore AGENCY: National Park..., pursuant to 16 U.S.C. 460l- 9(c)(1), the boundary of Indiana Dunes National Lakeshore in the State of... Dunes National Lakeshore, Proposed Boundary Adjustment,'' dated October 2009, and numbered...

  2. 36 CFR 28.3 - Boundaries: The Community Development District; The Dune District; The Seashore District.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Development District; The Dune District; The Seashore District. 28.3 Section 28.3 Parks, Forests, and Public... General Provisions § 28.3 Boundaries: The Community Development District; The Dune District; The Seashore... Community Development District, the Seashore District, and the Dune District. (b) The Community...

  3. 36 CFR 28.3 - Boundaries: The Community Development District; The Dune District; The Seashore District.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Development District; The Dune District; The Seashore District. 28.3 Section 28.3 Parks, Forests, and Public... General Provisions § 28.3 Boundaries: The Community Development District; The Dune District; The Seashore... Community Development District, the Seashore District, and the Dune District. (b) The Community...

  4. 36 CFR 28.3 - Boundaries: The Community Development District; The Dune District; The Seashore District.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Development District; The Dune District; The Seashore District. 28.3 Section 28.3 Parks, Forests, and Public... General Provisions § 28.3 Boundaries: The Community Development District; The Dune District; The Seashore... Community Development District, the Seashore District, and the Dune District. (b) The Community...

  5. Phase diagrams of dune shape and orientation depending on sand availability

    PubMed Central

    Gao, Xin; Narteau, Clément; Rozier, Olivier; du Pont, Sylvain Courrech

    2015-01-01

    New evidence indicates that sand availability does not only control dune type but also the underlying dune growth mechanism and the subsequent dune orientation. Here we numerically investigate the development of bedforms in bidirectional wind regimes for two different conditions of sand availability: an erodible sand bed or a localized sand source on a non-erodible ground. These two conditions of sand availability are associated with two independent dune growth mechanisms and, for both of them, we present the complete phase diagrams of dune shape and orientation. On an erodible sand bed, linear dunes are observed over the entire parameter space. Then, the divergence angle and the transport ratio between the two winds control dune orientation and dynamics. For a localized sand source, different dune morphologies are observed depending on the wind regime. There are systematic transitions in dune shape from barchans to linear dunes extending away from the localized sand source, and vice-versa. These transitions are captured fairly by a new dimensionless parameter, which compares the ability of winds to build the dune topography in the two modes of dune orientation. PMID:26419614

  6. Windblown Dunes on the Floor of Herschel Impact Basin

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Herschel Basin, one of many meteor impact craters on Mars, has some dark material on its floor that appeared from earlier spacecraft missions to have been blown and/or deposited by wind. Herschel Basin was imaged at low resolution by the Mariner 9 and Viking orbiters ((A) above) in the 1970s, and again by the Phobos 2 orbiter in 1989.

    On June 14, 1998, Mars Global Surveyor's Mars Orbiter Camera revealed that part of the dark surface on the floor of Herschel Basin consists of a field of sand dunes ((B) above). These dunes have a distinct crescent-like shape characteristic of dunes on Earth called barchan dunes. They result from winds that blow from a single dominant direction.

    In the case of Herschel Basin, the dunes indicate that the strongest winds blow approximately north-to-south. The crescent horns on the ends of some of the dunes in this image are elongated. This condition indicates that the dominant winds do not always blow in exactly the same direction-- sometimes the winds blow from the northeast, sometimes from the northwest, and sometimes from the north. The local topography probably influences the wind direction--and hence dune shape--because this dune field is located on a narrow, low plain between a high crater rim to the east, and a narrow mountain range-- the inner ring of the Herschel impact basin--to the west (see image (A)).

    MOC image 36507 was obtained on Mars Global Surveyor's 365th orbit around 10:51 a.m. PDT on June 14, 1998. This subframe is centered around 14.27oS, 231.68oW.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.

  7. Defrosting Polar Dunes--Changes Over a 26-Day Period

    NASA Technical Reports Server (NTRS)

    1999-01-01

    As the retreat of the south polar winter frost cap became visible in June 1999, high resolution images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) began to show dark spots forming on the surfaces of frost-covered sand dunes. Immediately, the MOC science team began to plan to observe several dune fields more than once, should that opportunity arise, so that the evolution of these dark spots could be documented and studied. Such work will eventually lead to abetter understanding of how the martian polar caps retreat as winter ends and spring unfolds in each hemisphere.

    MGS is in a polar orbit, which means that, unlike many other places on Mars, the spacecraft has more opportunities to take pictures of the same place. Dune fields near 87o latitude can be repeatedly viewed; dunes near the equator are not likely to be photographed more than once during the entire MGS mission.

    The pictures presented here show changes on a set of nearly pear-shaped sand dunes located on the floor of an unnamed crater at 59oS, 353oW. The picture on the left shows the dunes as they appeared on June 19, 1999, the picture on the right shows the same dunes on July 15, 1999. The dark spots in the June 19picture--indicating areas where frost has sublimed away--became larger by July 15th. In addition, new spots had appeared as of mid-July. If possible, these dunes will be photographed by MOC again in mid-August and each month until the frost is gone.

    The pictures shown in (B) (above) are expanded views of portions of the pictures in (A). The 200 meter scale bar equals 656 feet; the 100 meter bar is 328 feet (109 yards) long. All images are illuminated from the upper left; north is toward the upper right.

    Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations

  8. Observations Regarding Small Eolian Dunes and Large Ripples on Mars

    NASA Technical Reports Server (NTRS)

    Edgett, Kenneth S.

    2001-01-01

    Eolian bedforms occur at the interface between a planetary surface and its atmosphere; they present a proxy record of the influence of climate, expressed in sediment transport, over that surface. High resolution images (1.5 - 12 m/pixel) from the Mars Global Surveyor (MGS) Mars Orbiter Camera provide glimpses of the most recent events shaping the martian landscape. Thousands of images exhibit small transverse dunes or large eolian ripples that have crest-to-crest spacings of 10 to 60 m, heights of a few to 10 m. Bedforms of the size and patterns seen in the Mars photographs are rarely described among Earth's eolian landforms; in terms of size and morphology, most of these fall between traditional definitions of "ripples" and "dunes". Dunes are composed chiefly of materials transported by saltation, ripples are smaller forms moved along by the impact of saltating grains (traction). The largest reported eolian ripples on Earth (granule ripples, megaripples) are typically smaller than the bedforms observed on Mars; likewise, most dunes are typically larger. The small dunes and large ripples on Mars come in a variety of relative albedos, despite an early MGS impression that they are all of high albedo. Some ripples occur on the surfaces of sand dunes; these are most likely true granule ripples. However, most of these bedforms occur in troughs, pits, craters, and on deflated plains. Despite impressions early in the MGS mission, they do not occur everywhere (e.g., they are rare on the northern plains) but they do occur at a range of elevations from the highest volcanoes to the deepest basins. Where they occur on a hard substrate among larger sand dunes, the big dunes have over-ridden the smaller bedforms, indicating that the smaller features are older and perhaps indurated or very coarse-grained. At other locales, the small bedforms have been mantled by material settled from suspension, in other cases they are being exhumed and may be lithified. Still other examples are

  9. Southern high latitude dune fields on Mars: Morphology, aeolian inactivity, and climate change

    USGS Publications Warehouse

    Fenton, L.K.; Hayward, R.K.

    2010-01-01

    In a study area spanning the martian surface poleward of 50?? S., 1190 dune fields have been identified, mapped, and categorized based on dune field morphology. Dune fields in the study area span ??? 116400km2, leading to a global dune field coverage estimate of ???904000km2, far less than that found on Earth. Based on distinct morphological features, the dune fields were grouped into six different classes that vary in interpreted aeolian activity level from potentially active to relatively inactive and eroding. The six dune field classes occur in specific latitude zones, with a sequence of reduced activity and degradation progressing poleward. In particular, the first signs of stabilization appear at ???60?? S., which broadly corresponds to the edge of high concentrations of water-equivalent hydrogen content (observed by the Neutron Spectrometer) that have been interpreted as ground ice. This near-surface ground ice likely acts to reduce sand availability in the present climate state on Mars, stabilizing high latitude dunes and allowing erosional processes to change their morphology. As a result, climatic changes in the content of near-surface ground ice are likely to influence the level of dune activity. Spatial variation of dune field classes with longitude is significant, suggesting that local conditions play a major role in determining dune field activity level. Dune fields on the south polar layered terrain, for example, appear either potentially active or inactive, indicating that at least two generations of dune building have occurred on this surface. Many dune fields show signs of degradation mixed with crisp-brinked dunes, also suggesting that more than one generation of dune building has occurred since they originally formed. Dune fields superposed on early and late Amazonian surfaces provide potential upper age limits of ???100My on the south polar layered deposits and ???3Ga elsewhere at high latitudes. No craters are present on any identifiable dune

  10. Modelling overbank flood recharge at a continental scale

    NASA Astrophysics Data System (ADS)

    Doble, R.; Crosbie, R.; Peeters, L.; Joehnk, K.; Ticehurst, C.

    2013-10-01

    Accounting for groundwater recharge from overbank flooding is required to reduce uncertainty and error in river loss terms and groundwater sustainable yield calculations. However, continental and global scale models of surface water-groundwater interactions rarely include an explicit process to account for overbank flood recharge (OFR). This paper upscales previously derived analytical equations to a continental scale using national soil atlas data and satellite imagery of flood inundation, resulting in recharge maps for seven hydrologically distinct Australian catchments. Recharge for three of the catchments was validated against independent recharge estimates from bore hydrograph responses and one catchment was additionally validated against point scale recharge modelling and catchment scale change in groundwater storage. Flood recharge was predicted for four of the seven catchments modelled, but there was also unexplained recharge present from the satellite flood inundation mapping data. At a catchment scale, recharge from overbank flooding was somewhat under predicted using the analytical equations, but there was good confidence in the spatial patterns of flood recharge produced. Due to the scale of the input data, there were no significant relationships found when compared at a point scale. Satellite derived flood inundation data and uncertainty in soil maps were the key limitations to the accuracy of the modelled recharge. Use of this method to model OFR was found to be appropriate at a catchment to continental scale, given appropriate data sources. The proportion of OFR was found to be at least 4% of total change in groundwater storage in one of the catchments for the period modelled, and at least 15% of the riparian recharge. Accounting for OFR is an important, and often overlooked, requirement for closing water balances in both the surface water and groundwater domains.

  11. Modelling overbank flood recharge at a continental scale

    NASA Astrophysics Data System (ADS)

    Doble, R.; Crosbie, R.; Peeters, L.; Joehnk, K.; Ticehurst, C.

    2014-04-01

    Accounting for groundwater recharge from overbank flooding is required to reduce uncertainty and error in river-loss terms and groundwater sustainable-yield calculations. However, continental- and global-scale models of surface water-groundwater interactions rarely include an explicit process to account for overbank flood recharge (OFR). This paper upscales previously derived analytical equations to a continental scale using national soil atlas data and satellite imagery of flood inundation, resulting in recharge maps for seven hydrologically distinct Australian catchments. Recharge for three of the catchments was validated against independent recharge estimates from bore hydrograph responses and one catchment was additionally validated against point-scale recharge modelling and catchment-scale change in groundwater storage. Flood recharge was predicted for four of the seven catchments modelled, but there was also unexplained recharge present from the satellite's flood inundation mapping data. At a catchment scale, recharge from overbank flooding was somewhat under-predicted using the analytical equations, but there was good confidence in the spatial patterns of flood recharge produced. Due to the scale of the input data, there were no significant relationships found when compared at a point scale. Satellite-derived flood inundation data and uncertainty in soil maps were the key limitations to the accuracy of the modelled recharge. Use of this method to model OFR was found to be appropriate at a catchment to continental scale, given appropriate data sources. The proportion of OFR was found to be at least 4% of total change in groundwater storage in one of the catchments for the period modelled, and at least 15% of the riparian recharge. Accounting for OFR is an important, but often overlooked, requirement for closing water balances in both the surface water and groundwater domains.

  12. Generator and rechargeable battery system for pedal powered vehicles

    SciTech Connect

    Ryan, D.

    1985-11-26

    A generator and rechargeable battery system for use with pedal powered vehicles, such as bicycles, and where either the generator or battery can intermittently power a load such as a lighting system of the vehicle in one mode of operation, and in which the generator can recharge the battery in another mode of operation. A simple selection switch which is manually operable by the operator of the vehicle enables selection between powering of the load or recharging of the battery.

  13. [Study on the guideline for groundwater recharge with reclaimed water].

    PubMed

    He, Xing-hai; Ma, Shi-hao

    2004-09-01

    Groundwater recharge with reclaimed water is the most beneficial way to extend reuse applications, and has the vast development foreground. In this paper, the domestic and international applications and guidelines for groundwater recharge with reclaimed water were summarized. Based on the quality of reclaimed water and the conditions of hydrological geology, the reclaimed water quality criteria for groundwater recharge was suggested including 22 basic controlling items and 52 selective controlling items, and the control technology was presented. PMID:15623024

  14. Environmental Controls and Eco-geomorphic Interactions of the Barchan-to-parabolic Dune Stabilisation and the Parabolic-to-barchan Dune Reactivation

    NASA Astrophysics Data System (ADS)

    Yan, Na; Baas, Andreas

    2015-04-01

    Parabolic dunes are one of a few common aeolian landforms which are highly controlled by eco-geomorphic interactions. Parabolic dunes, on the one hand, can be developed from highly mobile dune landforms, barchans for instance, in an ameliorated vegetation condition; or on the other hand, they can be reactivated and transformed back into mobile dunes due to vegetation deterioration. The fundamental mechanisms and eco-geomorphic interactions controlling both dune transformations remain poorly understood. To bridge the gap between complex processes involved in dune transformations on a relatively long temporal scale and real world monitoring records on a very limited temporal scale, this research has extended the DECAL model to incorporate 'dynamic' growth functions and the different 'growth' of perennial shrubs between growing and non-growing seasons, informed by field measurements and remote sensing analysis, to explore environmental controls and eco-geomorphic interactions of both types of dune transformation. A non-dimensional 'dune stabilising index' is proposed to capture the interactions between environmental controls (i.e. the capabilities of vegetation to withstand wind erosion and sand burial, the sandy substratum thickness, the height of the initial dune, and the sand transport potential), and establish the linkage between these controls and the geometry of a stabilising dune. An example demonstrates how to use the power-law relationship between the dune stabilising index and the normalised migration distance to assist in extrapolating the historical trajectories of transforming dunes. The modelling results also show that a slight increase in vegetation cover of an initial parabolic dune can significantly increase the reactivation threshold of climatic impact (both drought stress and wind strength) required to reactivate a stabilising parabolic dune into a barchan. Four eco-geomorphic interaction zones that govern a barchan-to-parabolic dune transformation

  15. A review of groundwater recharge under irrigated agriculture in Australia

    NASA Astrophysics Data System (ADS)

    Riasat, Ali; Mallants, Dirk; Walker, Glen; Silberstein, Richard

    2014-05-01

    Quantification of recharge under irrigated agriculture is one of the most important but difficult tasks. It is the least understood component in groundwater studies because of its large variability in space and time and the difficulty of direct measurement. Better management of groundwater resources is only possible if we can accurately determine all fluxes going into and out of a groundwater system. One of the major challenges facing irrigated agriculture in Australia, and the world, is to reduce uncertainty in estimating or measuring the recharge flux. Reducing uncertainty in groundwater recharge under irrigated agriculture is a pre-requisite for effective, efficient and sustainable groundwater resource management especially in dry areas where groundwater usage is often the key to economic development. An accurate quantification of groundwater recharge under irrigated systems is also crucial because of its potential impacts on soil profile salinity, groundwater levels and groundwater quality. This paper aims to identify the main recharge control parameters thorough a review of past field and modelling recharge studies in Australia. We find that the main recharge control parameters under irrigated agriculture are soil type, irrigation management, watertable depth, land cover or plant water uptake, soil surface conditions, and soil, irrigation water and groundwater chemistry. The most commonly used recharge estimation approaches include chloride mass balance, water budget equation, lysimeters, Darcy's law and numerical models. Main sources and magnitude of uncertainty in recharge estimates associated with these approaches are discussed.

  16. Making Li-air batteries rechargeable: material challenges

    SciTech Connect

    Shao, Yuyan; Ding, Fei; Xiao, Jie; Zhang, Jian; Xu, Wu; Park, Seh Kyu; Zhang, Jiguang; Wang, Yong; Liu, Jun

    2013-02-25

    A Li-air battery could potentially provide three to five times higher energy density/specific energy than conventional batteries, thus enable the driving range of an electric vehicle comparable to a gasoline vehicle. However, making Li-air batteries rechargeable presents significant challenges, mostly related with materials. Herein, we discuss the key factors that influence the rechargeability of Li-air batteries with a focus on nonaqueous system. The status and materials challenges for nonaqueous rechargeable Li-air batteries are reviewed. These include electrolytes, cathode (electocatalysts), lithium metal anodes, and oxygen-selective membranes (oxygen supply from air). The perspective of rechargeable Li-air batteries is provided.

  17. Geophysical Methods for Investigating Ground-Water Recharge

    USGS Publications Warehouse

    Ferre, Ty P.A.; Binley, Andrew M.; Blasch, Kyle W.; Callegary, James B.; Crawford, Steven M.; Fink, James B.; Flint, Alan L.; Flint, Lorraine E.; Hoffmann, John P.; Izbicki, John A.; Levitt, Marc T.; Pool, Donald R.; Scanlon, Bridget R.

    2007-01-01

    While numerical modeling has revolutionized our understanding of basin-scale hydrologic processes, such models rely almost exclusively on traditional measurements?rainfall, streamflow, and water-table elevations?for calibration and testing. Model calibration provides initial estimates of ground-water recharge. Calibrated models are important yet crude tools for addressing questions about the spatial and temporal distribution of recharge. An inverse approach to recharge estimation is taken of necessity, due to inherent difficulties in making direct measurements of flow across the water table. Difficulties arise because recharging fluxes are typically small, even in humid regions, and because the location of the water table changes with time. Deep water tables in arid and semiarid regions make recharge monitoring especially difficult. Nevertheless, recharge monitoring must advance in order to improve assessments of ground-water recharge. Improved characterization of basin-scale recharge is critical for informed water-resources management. Difficulties in directly measuring recharge have prompted many efforts to develop indirect methods. The mass-balance approach of estimating recharge as the residual of generally much larger terms has persisted despite the use of increasing complex and finely gridded large-scale hydrologic models. Geophysical data pertaining to recharge rates, timing, and patterns have the potential to substantially improve modeling efforts by providing information on boundary conditions, by constraining model inputs, by testing simplifying assumptions, and by identifying the spatial and temporal resolutions needed to predict recharge to a specified tolerance in space and in time. Moreover, under certain conditions, geophysical measurements can yield direct estimates of recharge rates or changes in water storage, largely eliminating the need for indirect measures of recharge. This appendix presents an overview of physically based, geophysical methods

  18. Definition and origin of the dune-field pattern at White Sands, New Mexico

    NASA Astrophysics Data System (ADS)

    Baitis, Elke; Kocurek, Gary; Smith, Virginia; Mohrig, David; Ewing, Ryan C.; Peyret, A.-P. B.

    2014-12-01

    A LiDAR-derived digital elevation model (DEM) of a representative portion of the White Sands Dune Field, New Mexico, allows for characterization of an unprecedented range of dune-field parameters and serves as a basis for pattern analysis. Dune-field parameters were measured and statistically analyzed for populations of dunes selected at random and occurring along transects. Populations sampled by these two different methods are comparable, but highlight the sensitivity of transect placement in a dune field that has pattern heterogeneity. Based upon coefficients of variation, pattern emerges at White Sands primarily because of a strong fabric of crestline orientation, and secondarily because of the regularity of spacing between dunes of similar shape as defined by sinuosity, height and length. Linear regression of dune parameters shows that dune geometric relationships vary primarily with crestline length, but there is little correlation between other parameters, including dune spacing and height. This result highlights the sensitivity of identifying topographic heterogeneity in a LiDAR-derived DEM, given that mean ratios conform to global averages. Stripping off the dunes in Matlab shows a terraced surface, which is interpreted to represent paleo-shorelines formed during relative still stands in the overall retreat of Lake Otero. Elevated bands of higher, more closely spaced dunes occur just leeward of the paleo-shorelines. A revised model for the White Sands Dune Field consists of the basinward progradation of successive dune-field segments. Each segment is associated with a paleo-shoreline, and consists of an upwind dune ridge, represented by the elevated bands, and a leeward dune field.

  19. An ultrafast rechargeable aluminium-ion battery.

    PubMed

    Lin, Meng-Chang; Gong, Ming; Lu, Bingan; Wu, Yingpeng; Wang, Di-Yan; Guan, Mingyun; Angell, Michael; Chen, Changxin; Yang, Jiang; Hwang, Bing-Joe; Dai, Hongjie

    2015-04-16

    The development of new rechargeable battery systems could fuel various energy applications, from personal electronics to grid storage. Rechargeable aluminium-based batteries offer the possibilities of low cost and low flammability, together with three-electron-redox properties leading to high capacity. However, research efforts over the past 30 years have encountered numerous problems, such as cathode material disintegration, low cell discharge voltage (about 0.55 volts; ref. 5), capacitive behaviour without discharge voltage plateaus (1.1-0.2 volts or 1.8-0.8 volts) and insufficient cycle life (less than 100 cycles) with rapid capacity decay (by 26-85 per cent over 100 cycles). Here we present a rechargeable aluminium battery with high-rate capability that uses an aluminium metal anode and a three-dimensional graphitic-foam cathode. The battery operates through the electrochemical deposition and dissolution of aluminium at the anode, and intercalation/de-intercalation of chloroaluminate anions in the graphite, using a non-flammable ionic liquid electrolyte. The cell exhibits well-defined discharge voltage plateaus near 2 volts, a specific capacity of about 70 mA h g(-1) and a Coulombic efficiency of approximately 98 per cent. The cathode was found to enable fast anion diffusion and intercalation, affording charging times of around one minute with a current density of ~4,000 mA g(-1) (equivalent to ~3,000 W kg(-1)), and to withstand more than 7,500 cycles without capacity decay. PMID:25849777

  20. Electrical Resistivity Imaging and Depression Focused Recharge

    NASA Astrophysics Data System (ADS)

    Bentley, L. R.; Hayashi, M.; Berthold, S.

    2003-12-01

    Seasonal wetlands and small depressions play a fundamental role in recharging regional aquifers in the northern glaciated planes. Water from snowmelt collects in the depressions in the spring and infiltrates into the ground after the soil unfreezes. Infiltrating water leaches salts from the soil beneath depressions. The majority of the infiltrating water moves to the local uplands where it leaves the ground through ET leaving behind zones of evaporitically concentrated salts. A small percentage infiltrates down to the regional aquifer. Leaching and concentrating salts effect the electrical resistivity distribution of the subsurface. Three-dimensional electrical resistivity imaging (ERI) was combined with groundwater and soil measurements to generate a conceptual model of three dimensional fluid flow at San Denis, Saskatchewan. Water chemistry was used to generate a conceptual model of different geochemical zones which could be distinguished by the electrical conductivity of pore water. The Waxman-Smits equation was used to link groundwater electrical conductivity to in situ bulk resistivity. Electrical resisistivity from ERI was then used to map geochemical zones in the subsurface. ERI and chemistry show that infiltrating water reaches a regional aquifer at 20 meters depth. Seasonal wetlands have large zones of high resistivity that reach to the regional water table indicating that salts have been leached out of the tills to the depth of the regional aquifer. Small local depressions also have zones of leached soil beneath them indicating that they contribute to regional groundwater recharge. Since there are millions of small depressions, they may play a fundamental role in groundwater recharge and must be considered in land management. The images show a complex distribution of salts. Most of the salt is located in the upper weathered zone in the glacial tills and the horizontal distribution is controled by the locations of wetlands, steepness of slopes and the

  1. Thin-film Rechargeable Lithium Batteries

    DOE R&D Accomplishments Database

    Dudney, N. J.; Bates, J. B.; Lubben, D.

    1995-06-01

    Thin film rechargeable lithium batteries using ceramic electrolyte and cathode materials have been fabricated by physical deposition techniques. The lithium phosphorous oxynitride electrolyte has exceptional electrochemical stability and a good lithium conductivity. The lithium insertion reaction of several different intercalation materials, amorphous V{sub 2}O{sub 5}, amorphous LiMn{sub 2}O{sub 4}, and crystalline LiMn{sub 2}O{sub 4} films, have been investigated using the completed cathode/electrolyte/lithium thin film battery.

  2. Evolution of strategies for modern rechargeable batteries.

    PubMed

    Goodenough, John B

    2013-05-21

    This Account provides perspective on the evolution of the rechargeable battery and summarizes innovations in the development of these devices. Initially, I describe the components of a conventional rechargeable battery along with the engineering parameters that define the figures of merit for a single cell. In 1967, researchers discovered fast Na(+) conduction at 300 K in Na β,β''-alumina. Since then battery technology has evolved from a strongly acidic or alkaline aqueous electrolyte with protons as the working ion to an organic liquid-carbonate electrolyte with Li(+) as the working ion in a Li-ion battery. The invention of the sodium-sulfur and Zebra batteries stimulated consideration of framework structures as crystalline hosts for mobile guest alkali ions, and the jump in oil prices in the early 1970s prompted researchers to consider alternative room-temperature batteries with aprotic liquid electrolytes. With the existence of Li primary cells and ongoing research on the chemistry of reversible Li intercalation into layered chalcogenides, industry invested in the production of a Li/TiS2 rechargeable cell. However, on repeated recharge, dendrites grew across the electrolyte from the anode to the cathode, leading to dangerous short-circuits in the cell in the presence of the flammable organic liquid electrolyte. Because lowering the voltage of the anode would prevent cells with layered-chalcogenide cathodes from competing with cells that had an aqueous electrolyte, researchers quickly abandoned this effort. However, once it was realized that an oxide cathode could offer a larger voltage versus lithium, researchers considered the extraction of Li from the layered LiMO2 oxides with M = Co or Ni. These oxide cathodes were fabricated in a discharged state, and battery manufacturers could not conceive of assembling a cell with a discharged cathode. Meanwhile, exploration of Li intercalation into graphite showed that reversible Li insertion into carbon occurred

  3. Recharge from rectangular areas to finite aquifers

    NASA Astrophysics Data System (ADS)

    Rao, N. H.; Sarma, P. B. S.

    1981-10-01

    A generalized analytical solution is derived for the growth of groundwater mound in finite aquifers bounded by open water bodies, in response to recharge from rectangular areas. Finite Fourier transforms are used to solve the linearized differential equation of groundwater flow. Unlike earlier solutions, the method presented here does not require the use of tables for evaluation of complicated functions. The solution is evaluated by comparison with existing numerical and analytical results. In stream-aquifer systems similar to those described above, application of the proposed solution is more realistic than using solutions available for infinite aquifers.

  4. Glossary of testing terminology for rechargeable batteries

    SciTech Connect

    Butler, P.C.

    1988-10-01

    The Battery Test Working Task Force was formed in 1983 for the purpose of coordinating the evaluation of development rechargeable batteries by DOE-funded labs. The Task Force developed this glossary of testing terminology to improve the accuracy of communication and to permit meaningful comparisons of test results. It consists of a section of technical terms and a separate section of programmatic phrases and acronyms. The glossary emphasizes terms related to electric vehicle batteries due to the significant development and testing activities in this area. 8 refs.

  5. Thin-film rechargeable lithium batteries

    SciTech Connect

    Dudney, N.J.; Bates, J.B.; Lubben, D.

    1995-06-01

    Thin-film rechargeable lithium batteries using ceramic electrolyte and cathode materials have been fabricated by physical deposition techniques. The lithium phosphorous oxynitride electrolyte has exceptional electrochemical stability and a good lithium conductivity. The lithium insertion reaction of several different intercalation materials, amorphous V{sub 2}O{sub 5}, amorphous LiMn{sub 2}O{sub 4}, and crystalline LiMn{sub 2}O{sub 4} films, have been investigated using the completed cathode/electrolyte/lithium thin-film battery.

  6. Organic Cathode Materials for Rechargeable Batteries

    SciTech Connect

    Cao, Ruiguo; Qian, Jiangfeng; Zhang, Jiguang; Xu, Wu

    2015-06-28

    This chapter will primarily focus on the advances made in recent years and specify the development of organic electrode materials for their applications in rechargeable lithium batteries, sodium batteries and redox flow batteries. Four various organic cathode materials, including conjugated carbonyl compounds, conducting polymers, organosulfides and free radical polymers, are introduced in terms of their electrochemical performances in these three battery systems. Fundamental issues related to the synthesis-structure-activity correlations, involved work principles in energy storage systems, and capacity fading mechanisms are also discussed.

  7. Climate-driven changes to dune activity during the Last Glacial Maximum and deglaciation in the Mu Us dune field, north-central China

    NASA Astrophysics Data System (ADS)

    Xu, Zhiwei; Lu, Huayu; Yi, Shuangwen; Vandenberghe, Jef; Mason, Joseph A.; Zhou, Yali; Wang, Xianyan

    2015-10-01

    One significant change of terrestrial landscapes in response to past climate change has been the transformation between activity and stability of extensively distributed wind-blown sand dunes. The relations between the dynamics of the aeolian landscape and its drivers are not yet completely understood, however. Evidence of aeolian sand deposition during the Last Glacial Maximum (LGM) is scarce in many mid-latitude dune fields, whereas abundant evidence exists for aeolian sand accumulation during the deglaciation, i.e. after about 15 ka. Whether this contrast actually reflects changes in dune activity is still unclear, making paleoclimatic interpretation uncertain. Comprehensive field investigation and luminescence dating in the Mu Us dune field, north-central China, demonstrates that aeolian sands deposited during the LGM are preserved as fills in periglacial sand wedges and beneath loess deposits near the downwind dune field margin. The scarcity of LGM dune sand elsewhere in the dune field is interpreted as the result of intensive aeolian activity without substantial net sand accumulation. Increasing sand accumulation after 15 ka, reflected by much more extensive preservation, signals a change in sand supply relative to sand transportation through the dune field. Reduced wind strength and other environmental changes including regional permafrost degradation after 15 ka transformed the dune field state from net erosion to net accumulation; the dunes, however, remained largely mobile as they were in the LGM. Similar diverging patterns of dune sand accumulation and preservation before and after 15 ka in many mid-latitude dune fields imply broad climatic controls linked to the changes in high-northern-latitude forcing.

  8. Two-dimensional airflow modeling underpredicts the wind velocity over dunes.

    PubMed

    Michelsen, Britt; Strobl, Severin; Parteli, Eric J R; Pöschel, Thorsten

    2015-01-01

    We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune's symmetry axis - that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected. PMID:26572966

  9. Analysis of links between groundwater recharge and discharge areas and wetland plant communities distribution in Middle Biebrza Basin, Poland

    NASA Astrophysics Data System (ADS)

    Grygoruk, Mateusz; Batelaan, Okke; Okruszko, Tomasz; Kotowski, Wiktor; Rycharski, Marek; Chormanski, Jaroslaw; Miroslaw-Swiatek, Dorota

    2010-05-01

    Natural evolution of wetlands is strongly dependent on groundwater dynamics, soil aeration and climate. These environmental factors determine the constant development of wetland plant communities and peat forming processes. Depending on spatial distribution of groundwater flow systems and recharge and discharge conditions, shallow groundwater can also be influenced by phreatophytic plants. Such feedback plays an important role in wetland development, especially when landuse or climate changes occur. Thus, understanding the links between dynamics of biotopic and biocenotic relations is crucial for wetland management aimed at the comprehensive set of conservation strategies. Main aim of this study was to review links between valuable wetland plant communities and the groundwater recharge/discharge conditions of particular habitats of Middle Biebrza Basin, Poland. The study area consists of various types of wetland landscapes, of which the dominant are fens. Organogenic top layer is intersected locally by sandy dunes and glaci-fluvial residual plateaus. The northern boundary of the study area is covered with an outwash plateau. A three-dimensional regional groundwater flow model was set up to quantify groundwater system and flow paths. Model calibration involved measured heads of the unconfined organogenic top layer and the underlaying, confined sandy aquifer. Measured thickness of unsaturated zone as well as physical parameters of organogenic layer were taken into account in interpretation of shallow groundwater dynamics. Recharge to groundwater was spatially distributed in accordance to analysis of measured precipitation-groundwater level relationships. Cell-by-cell flow analysis and groundwater exfiltration analysis were applied to map groundwater recharge and discharge areas within the modelled area. Results of groundwater modelling were validated with phytosociologic research combined with remote-sensing based spatial analysis of wetland habitats distribution

  10. Simulation of barchan dynamics with inter-dune sand streams

    NASA Astrophysics Data System (ADS)

    Katsuki, Atsunari; Kikuchi, Macoto

    2011-06-01

    A group of barchans, crescent sand dunes, exhibit a characteristic flying-geese pattern in deserts on Earth and Mars. This pattern implies that an indirect interaction between barchans, mediated by an inter-dune sand stream, which is released from one barchan's horns and caught by another barchan, plays an important role in the dynamics of barchan fields. We used numerical simulations of a recently proposed cell model to investigate the effects of inter-dune sand streams on barchan fields. We found that a sand stream from a point source moves a downstream barchan laterally until the head of the barchan is finally situated behind the stream. This final configuration was shown to be stable by a linear stability analysis. These results indicate that flying-geese patterns are formed by the lateral motion of barchans mediated by inter-dune sand streams. By using simulations we also found a barchan mono-corridor generation effect, which is another effect of sand streams from point sources.

  11. Fire scars and ancient sand dunes in southern Australia

    NASA Technical Reports Server (NTRS)

    1994-01-01

    The rectangular green areas in this view of southern Australia are protected areas of natural forest (national parks and biospheric reserves), and the lighter surrounding colors (tan-brown) are agricultural croplands occupying land which once must have looked as green as the nature reserves but are now cleared of forest. The major green patch has been recently burned, as shown by the irregular pattern of a large, multiple burn scar. The pattern of the fire scar indicates that the fires were driven by winds blowing from left to right. Close examination of the view shows that the forests are rooted in a soil made up of a widespread sheet of ancient dune sand. The dunes can be seen best within the area of the large fire scar where the characteristic wavy, scalloped pattern of crescent dunes can be detected. The crescents indicate that the sand was heaped up by winds blowing from right to left in this view, in the opposite direction to the winds which fanned the fires. A few straight dunes

  12. Analysis of Coastal Dunes: A Remote Sensing and Statistical Approach.

    ERIC Educational Resources Information Center

    Jones, J. Richard

    1985-01-01

    Remote sensing analysis and statistical methods were used to analyze the coastal dunes of Plum Island, Massachusetts. The research methodology used provides an example of a student project for remote sensing, geomorphology, or spatial analysis courses at the university level. (RM)

  13. Discussion. Cemented horizon in subarctic Alaskan sand dunes.

    USGS Publications Warehouse

    Galloway, J.P.; Koster, E.A.; Hamilton, T.D.

    1985-01-01

    Exception is taken to the conclusions (M.A. 84M/4465) concerning the distribution, age and origin of the cementing materials of carbonate crusts in the eaeolian sand deposits of the dune field in the central Kobuk Valley. (Following abstract)-M.S.

  14. The Influence of Physical & Biological Cohesion on Dune Development

    NASA Astrophysics Data System (ADS)

    Schindler, Robert; Parsons, Daniel; Ye, Leiping; Baas, Jaco; Hope, Julie; Manning, Andy; Malarkey, Jonathan; Aspden, Rebecca; Lichtman, Dougal; Thorne, Peter; Peakall, Jeff; Patterson, David; Davies, Alan; Bass, Sarah; O'Boyle, Louise

    2014-05-01

    Existing predictions for dune bedforms are based on simplified physical parameters, with assumptions that sediment consists only of cohesionless sand. They do not include the complexities of mud: physical cohesion is imparted by cohesive clays and biological cohesion is created by the presence of organisms which, among other things, generate extra-cellular polymers (EPS). Using controlled experiments we show the profound influence on the size, development and equilibrium morphology of dune bedforms of both physical and biological cohesion. Experiments were completed at the Total Environment Simulator facility at Hull University, UK in a 10 x 2 m channel. A flat sediment bed was laid to 0.15 m depth. A unidirectional flow of 0.25 m depth was passed over the sediment for 10 h. In Phase 1 eight different sand:clay mixes were examined, where clay content was 18.0 - 2.1%. In Phase 2, the same mixtures were used with additions of EPS. A velocity of 0.8 m s-1 was used throughout, corresponding to the dune regime for the selected sand. Bedform development was monitored via ultrasonic ranging transducers, sediment cores and water samples. Phase 1 showed substantial differences in bedform type with clay content, with size inversely related to clay content, e.g. Run 1 (18.0% clay) generated 2D ripples; Run 7 (2.1% clay) generated 3D dunes. Transitional forms, included dunes with superimposed ripples, were present between these extremes. In Phase 2, EPS contents equivalent to only 1/30th of 1% by mass prevented the development of bedforms. Bedforms were generated in sediments with 1/20th and 1/10th of 1%, with an inverse relationship between bedform size and EPS content. Comparison of Phase 1 and Phase 2 runs with equal sand:mud ratios reveals that EPS acts to severely inhibit bedform development compared with the mud-only case. We can conclude that (1) the ripple-dune transition can occur under constant flow conditions, i.e. clay content may dictate bedform type, that (2) EPS

  15. Artificial recharge of groundwater and its role in water management

    USGS Publications Warehouse

    Kimrey, J.O.

    1989-01-01

    This paper summarizes and discusses the various aspects and methods of artificial recharge with particular emphasis on its uses and potential role in water management in the Arabian Gulf region. Artificial recharge occurs when man's activities cause more water to enter an aquifer, either under pumping or non-pumping conditions, than otherwise would enter the aquifer. Use of artificial recharge can be a practical means of dealing with problems of overdraft of groundwater. Methods of artificial recharge may be grouped under two broad types: (a) water spreading techniques, and (b) well-injection techniques. Successful use of artificial recharge requires a thorough knowledge of the physical and chemical characteristics of the aquifier system, and extensive onsite experimentation and tailoring of the artificial-recharge technique to fit the local or areal conditions. In general, water spreading techniques are less expensive than well injection and large quantities of water can be handled. Water spreading can also result in significant improvement in quality of recharge waters during infiltration and movement through the unsaturated zone and the receiving aquifer. In comparison, well-injection techniques are often used for emplacement of fresh recharge water into saline aquifer zones to form a manageable lens of fresher water, which may later be partially withdrawn for use or continue to be maintained as a barrier against salt-water encroachment. A major advantage in use of groundwater is its availability, on demand to wells, from a natural storage reservoir that is relatively safe from pollution and from damage by sabotage or other hostile action. However, fresh groundwater occurs only in limited quantities in most of the Arabian Gulf region; also, it is heavily overdrafted in many areas, and receives very little natural recharge. Good use could be made of artificial recharge by well injection in replenishing and managing aquifers in strategic locations if sources of

  16. Using noble gases to investigate mountain-front recharge

    USGS Publications Warehouse

    Manning, A.H.; Solomon, D.K.

    2003-01-01

    Mountain-front recharge is a major component of recharge to inter-mountain basin-fill aquifers. The two components of mountain-front recharge are (1) subsurface inflow from the mountain block (subsurface inflow), and (2) infiltration from perennial and ephemeral streams near the mountain front (stream seepage). The magnitude of subsurface inflow is of central importance in source protection planning for basin-fill aquifers and in some water rights disputes, yet existing estimates carry large uncertainties. Stable isotope ratios can indicate the magnitude of mountain-front recharge relative to other components, but are generally incapable of distinguishing subsurface inflow from stream seepage. Noble gases provide an effective tool for determining the relative significance of subsurface inflow, specifically. Dissolved noble gas concentrations allow for the determination of recharge temperature, which is correlated with recharge elevation. The nature of this correlation cannot be assumed, however, and must be derived for the study area. The method is applied to the Salt Lake Valley Principal Aquifer in northern Utah to demonstrate its utility. Samples from 16 springs and mine tunnels in the adjacent Wasatch Mountains indicate that recharge temperature decreases with elevation at about the same rate as the mean annual air temperature, but is on average about 2??C cooler. Samples from 27 valley production wells yield recharge elevations ranging from the valley elevation (about 1500 m) to mid-mountain elevation (about 2500 m). Only six of the wells have recharge elevations less than 1800 m. Recharge elevations consistently greater than 2000 m in the southeastern part of the basin indicate that subsurface inflow constitutes most of the total recharge in this area. ?? 2003 Published by Elsevier Science B.V.

  17. Modeling the biogeomorphic evolution of coastal dunes in response to climate change

    NASA Astrophysics Data System (ADS)

    Keijsers, J. G. S.; De Groot, A. V.; Riksen, M. J. P. M.

    2016-06-01

    Coastal dunes form in many parts of the world the first flood defense line against the sea. To study effects of climate change on coastal dune evolution, we used a cellular model of dune, beach, and vegetation development. The model was calibrated and validated against field measurements of the Dutch coast, showing good performance for 10 year simulations. A sensitivity analysis showed that dune size and morphology are most sensitive to the rate of aeolian input and wave dissipation. Finally, 100 year climate change scenarios were run to establish the impacts of sea level rise and changes in vegetation growth rate on dune evolution. The results are in good agreement with conceptual models of dune evolution. Sea level rise largely determines the direction of dune evolution: the rate of rising controls whether dunes are able to preserve their height or sand volume while migrating landward. The effect of changing vegetation growth rates, resulting from climate change, is most manifest in dune response to large disturbances. If vegetation is removed halfway into the simulation, vegetation growth rate determines whether a foredune will revegetate and recover its height. Low vegetation growth rates result in mobile dunes that lose sand. The good agreement between observations and predictions indicates that the model successfully incorporates the suite of biogeomorphic and marine processes involved in dune building.

  18. The origin and fate of the sediments composing a migrating dune field, Amagansett, NY

    SciTech Connect

    Maher, T. . Environmental Science Dept.); Kandelin, J. . Dept. of Earth and Space Science); Black, J.A. )

    1993-03-01

    The migrating dune system, located in Amagansett, NY, consists of a series of three parabolic dunes ranging in heights from 10 to 30 meters. The dunes are migrating under the influence of the prevailing winds, in a southeasterly direction. The migration continues until the dunes encounter the countervailing prevailing winds, off the Atlantic Ocean. A series of flow charts have been prepared to indicate the possible sources of sediment for this system. These charts, in conjunction with geomorphic analysis, stratigraphic data and various sediment characteristics indicate that the sediments are transported by coastal currents. Once deposited they form a linear dune system. Eolian transport from this dune then supplies the sediment to the migrating dune system.

  19. Marine litter in Mediterranean sandy littorals: Spatial distribution patterns along central Italy coastal dunes.

    PubMed

    Poeta, Gianluca; Battisti, Corrado; Acosta, Alicia T R

    2014-12-15

    Sandy shores are generally considered important sinks for marine litter and the presence of this litter may represent a serious threat to biotic communities and dune integrity mostly due to cleaning activities carried out through mechanical equipment. In spring (April-May) 2012 we sampled 153 2×2m random plots to assess the spatial distribution patterns of litter on Central Italy sandy shores. We analysed the relationship between the presence of litter and coastal dune habitats along the sea-inland gradient. Our results showed that the most frequent litter items were plastic and polystyrene. Differences of marine litter spatial distribution were found between upper beach and fore dune habitats and fixed dune habitats: embryo dune and mobile dune habitats show the highest frequency of litter, but, surprisingly, marine litter did not impact fixed dune habitats, these possibly acting as a natural barrier protecting the inner part of the coast from marine litter dispersion. PMID:25455823

  20. Hydrogeochemical transport modeling of 24 years of Rhine water infiltration in the dunes of the Amsterdam Water Supply

    NASA Astrophysics Data System (ADS)

    van Breukelen, B. M.; Appelo, C. A. J.; Olsthoorn, T. N.

    1998-08-01

    Water quality changes were modelled along a flowpath in a plume of artificially recharged, pretreated Rhine water in the dunes of the Amsterdam Water Supply, after 24 years of infiltration. The hydrogeochemical transport model PHREEQC was extended with dispersion/diffusion and kinetics for selected chemical reactions. In the model the following reactions were included: cation-exchange, calcite dissolution and precipitation, and kinetic oxygen consumption and denitrification by oxidation of organic matter. Monthly-averaged values were used for the infiltration water quality. Traveltimes from infiltration area to sampling points were determined with chloride and tritium, and used to place the 3D field-observations in the 1D column-model. Values for CEC were variable for seven layers in the model. Infiltration of pretreated Rhine water in the dune aquifer can be considered an intrusion of more saline water. It caused desorption of Ca 2+, in exchange for Na +, K + and Mg 2+ from Rhine water. Because of variations in total solute concentrations in infiltration water, local small scale freshening fronts (Ca 2+ sorption, Na + desorption) were created by seasonally decreasing salt concentrations. The undersaturation with respect to calcite in the infiltration water, and the CO 2 produced during consumption of oxygen, resulted in dissolution of calcite. Precipitation of calcite occurred in response to desorption of calcium from the exchanger in the downstream parts. Overall, a net dissolution of calcite was simulated. Good results were generally achieved for all components: sulfate, nitrate, chloride, alkalinity, calcium, magnesium, potassium, sodium, 3H and O 2. The contributions of the different geochemical reactions to the water quality are illustrated with computer simulations for the individual processes.

  1. Lithium Metal Anodes for Rechargeable Batteries

    SciTech Connect

    Xu, Wu; Wang, Jiulin; Ding, Fei; Chen, Xilin; Nasybulin, Eduard N.; Zhang, Yaohui; Zhang, Jiguang

    2013-10-29

    Rechargeable lithium metal batteries have much higher energy density than those of lithium ion batteries using graphite anode. Unfortunately, uncontrollable dendritic lithium growth inherent in these batteries (upon repeated charge/discharge cycling) and limited Coulombic efficiency during lithium deposition/striping has prevented their practical application over the past 40 years. With the emerging of post Li-ion batteries, safe and efficient operation of lithium metal anode has become an enabling technology which may determine the fate of several promising candidates for the next generation of energy storage systems, including rechargeable Li-air battery, Li-S battery, and Li metal battery which utilize lithium intercalation compounds as cathode. In this work, various factors which affect the morphology and Coulombic efficiency of lithium anode will be analyzed. Technologies used to characterize the morphology of lithium deposition and the results obtained by modeling of lithium dendrite growth will also be reviewed. At last, recent development in this filed and urgent need in this field will also be discussed.

  2. Prototype systems for rechargeable magnesium batteries.

    PubMed

    Aurbach, D; Lu, Z; Schechter, A; Gofer, Y; Gizbar, H; Turgeman, R; Cohen, Y; Moshkovich, M; Levi, E

    2000-10-12

    The thermodynamic properties of magnesium make it a natural choice for use as an anode material in rechargeable batteries, because it may provide a considerably higher energy density than the commonly used lead-acid and nickel-cadmium systems. Moreover, in contrast to lead and cadmium, magnesium is inexpensive, environmentally friendly and safe to handle. But the development of Mg batteries has been hindered by two problems. First, owing to the chemical activity of Mg, only solutions that neither donate nor accept protons are suitable as electrolytes; but most of these solutions allow the growth of passivating surface films, which inhibit any electrochemical reaction. Second, the choice of cathode materials has been limited by the difficulty of intercalating Mg ions in many hosts. Following previous studies of the electrochemistry of Mg electrodes in various non-aqueous solutions, and of a variety of intercalation electrodes, we have now developed rechargeable Mg battery systems that show promise for applications. The systems comprise electrolyte solutions based on Mg organohaloaluminate salts, and Mg(x)Mo3S4 cathodes, into which Mg ions can be intercalated reversibly, and with relatively fast kinetics. We expect that further improvements in the energy density will make these batteries a viable alternative to existing systems. PMID:11048714

  3. Electrochemically active polymers for rechargeable batteries

    SciTech Connect

    Novak, P.; Haas, O.; Santhanam, K.S.V.; Mueller, K.

    1997-01-01

    Electrochemical energy storage systems (batteries) have a tremendous role in technical applications. In this review the authors examine the prospects of electroactive polymers in view of the properties required for such batteries. Conducting organic polymers are considered here in the light of their rugged chemical environment: organic solvents, acids, and alkalis. The goal of the present article is to provide, first of all in tabular form, a survey of electroactive polymers in view of potential applications in rechargeable batteries. It reviews the preparative methods and the electrochemical performance of polymers as rechargeable battery electrodes. The theoretical values of specific charge of the polymers are comparable to those of metal oxide electrodes, but are not as high as those of most of the metal electrodes normally used in batteries. Therefore, it is an advantage in conventional battery designs to use the conducting polymer as a positive electrode material in combination with a negative electrode such as Li, Na, Mg, Zn, MeH{sub x}, etc. 504 refs.

  4. Urban Network Implications On Groundwater Recharge

    NASA Astrophysics Data System (ADS)

    Duque, J.; Chambel, A.

    Urbanisation has had a major impact on groundwater beneath Évora city (South Portu- gal). Évora is an ancient city and the growth of impermeable areas due to urbanisation has lead to a reduction in groundwater recharge. The specific type of residential land use has a major influence on the permeability of the recharge area. The use of ground- water inside the city of Évora is largely for particular gardening and small farming supplies. In the oldest part of the city (inside of the city walls) there is little use of groundwater, while in the part of the city outside the city walls usage is more effec- tive. This study provides evidence that the municipality or particular people can use groundwater to irrigate the majority gardens, instead of using cleaned water from the Monte Novo Dam. This will also provide a solution to the control of pollution that occurs due to losses from the sewerage system of the city.

  5. Rechargeable Thin-film Lithium Batteries

    DOE R&D Accomplishments Database

    Bates, J. B.; Gruzalski, G. R.; Dudney, N. J.; Luck, C. F.; Yu, Xiaohua

    1993-08-01

    Rechargeable thin film batteries consisting of lithium metal anodes, an amorphous inorganic electrolyte, and cathodes of lithium intercalation compounds have recently been developed. The batteries, which are typically less than 6 {mu}m thick, can be fabricated to any specified size, large or small, onto a variety of substrates including ceramics, semiconductors, and plastics. The cells that have been investigated include Li TiS{sub 2}, Li V{sub 2}O{sub 5}, and Li Li{sub x}Mn{sub 2}O{sub 4}, with open circuit voltages at full charge of about 2.5, 3.6, and 4.2, respectively. The development of these batteries would not have been possible without the discovery of a new thin film lithium electrolyte, lithium phosphorus oxynitride, that is stable in contact with metallic lithium at these potentials. Deposited by rf magnetron sputtering of Li{sub 3}PO{sub 4} in N{sub 2}, this material has a typical composition of Li{sub 2.9}PO{sub 3.3}N{sub 0.46} and a conductivity at 25{degrees}C of 2 {mu}S/cm. The maximum practical current density obtained from the thin film cells is limited to about 100 {mu}A/cm{sup 2} due to a low diffusivity of Li{sup +} ions in the cathodes. In this work, the authors present a short review of their work on rechargeable thin film lithium batteries.

  6. Morphology and origin of the Fair Oaks Dunes in NW Indiana, USA

    NASA Astrophysics Data System (ADS)

    Kilibarda, Z.; Blockland, J.

    2011-01-01

    The Fair Oaks Dunes (FOD) of NW Indiana, USA is a large (~ 4500 km 2) inland dune field associated with the late Wisconsin deglaciation of the Laurentide Ice Sheet. Meltwaters released by the Michigan, Saginaw, and Huron-Erie lobes transported fluvioglacial sediment through the Kankakee and Tippecanoe Valleys and their tributaries. The texture and composition of the sand in the FOD suggest a Saginaw Lobe origin of sediment with some Huron-Erie Lobe sediment. Sub-mature sand with sub-angular grains and a large feldspar content suggests relatively short distance of transport during two or possibly three dune-building and dune reworking events. We propose a model which explains the development of the dunes in three stages. Dune development began during the Bølling-Allerød (stage 1, ~ 15-13 ka) interval. During this stage anticyclonic easterly and north-easterly winds deflated the sand from outwash deposits and built transverse and barchanoid dunes on the western sides of the Tippecanoe Valley and paleo-channels. Further downwind, on the western and southwestern windward margins of the FOD, loess was deposited. During the early Younger Dryas (stage 2, ~ 12.5 ka) atmospheric circulation changed, and westerly winds reworked the original dunes to create a great variety of parabolic dunes. Simple, hemicyclic and lobate parabolic dunes developed in the western FOD, while further downwind, in the eastern and the southern FOD, more elongated hairpin and windrift dunes developed. On the upwind side of the dune field, loess deposits remained stable and were not remobilized during the second stage dune development. By the early Holocene the FOD dunes were stabilized until their minor remobilization during the Middle Holocene (stage 3). Minor disturbances caused by anthropogenic activities have occurred in last two centuries.

  7. A comparison of seed banks across a sand dune successional gradient at Lake Michigan dunes (Indiana, USA)

    USGS Publications Warehouse

    Leicht-Young, S. A.; Pavlovic, N.B.; Grundel, R.; Frohnapple, K.J.

    2009-01-01

    In habitats where disturbance is frequent, seed banks are important for the regeneration of vegetation. Sand dune systems are dynamic habitats in which sand movement provides intermittent disturbance. As succession proceeds from bare sand to forest, the disturbance decreases. At Indiana Dunes National Lakeshore, we examined the seed banks of three habitat types across a successional gradient: foredunes, secondary dunes, and oak savanna. There were differences among the types of species that germinated from each of the habitats. The mean seed bank density increased across the successional gradient by habitat, from 376 to 433 to 968 seeds m-2, but with foredune and secondary dune seed bank densities being significantly lower than the savanna seed bank density. The number of seeds germinated was significantly correlated with soil organic carbon, demonstrating for this primary successional sequence that seed density increases with stage and age. The seed bank had much lower species richness than that of the aboveground vegetation across all habitats. Among sites within a habitat type, the similarity of species germinated from the seed banks was very low, illustrating the variability of the seed bank even in similar habitat types. These results suggest that restoration of these habitats cannot rely on seed banks alone. ?? 2008 Springer Science+Business Media B.V.

  8. Experimental Observation of Flow Structure and Resistance over High- and Low-angle Dunes

    NASA Astrophysics Data System (ADS)

    Kwoll, E.; Venditti, J. G.; Bradley, R. W.; Winter, C.

    2015-12-01

    A prominent control on the flow over dunes in sedimentary environments is the slope of the downstream lee-side. While previous work has focused on steep (~30°), asymmetric dunes with permanent flow separation ('high-angle dunes'), little is known about dunes with lower lee-slope angles for which flow separation is absent or intermittent ('low-angle dunes'). Here, we use laboratory experiments to systematically vary and isolate the effect of the dune lee-slope on the turbulent flow field over dunes. Three sets of fixed dunes with lee-slope angles of 10°, 20° and 30° were separately installed in a 15 m long and 1 m wide flume and subjected to flow 0.20 m deep. At present, no clear hydraulic scaling has been demonstrated for low- and high-angle dunes as both dune configurations occur at the same Froude and Reynolds numbers. However, observations indicate that low-angle dunes are more frequent in environments dominated by suspension of bed material. Therefore, we focus on matching the transport stage between field conditions and our experiments using field observations of bedform morphology and flow stage. Measurements consisted of high-frequency, vertical profiles collected with a Laser Doppler Velocimeter (LDV) along one dune-length and Particle Image Velocimetry (PIV) of the flow field. We show that the temporal and spatial occurrence of flow separation decreases with dune lee-slope and may be fully absent for lee-slopes <<10°, only. Velocity gradients in the dune leeside depict a free shear layer downstream of the 30° dunes and a weaker shear layer closer to the bed for the 20° and 10° dunes. The decrease in velocity gradients leads to lower turbulence production for gentle lee-slopes. Consequently, flow resistance of dunes decreases with lee-slope; the transition being non-linear. Over the 10°, 20° and 30° dunes, shear stress is 8%, 33% and 90 % greater than a flat bed, respectively. Our results demonstrate that dune shape plays an important, but often

  9. Current collectors for rechargeable Li-Air batteries

    SciTech Connect

    Veith, Gabriel M; Dudney, Nancy J

    2011-01-01

    Here we report the negative influence of porous nickel foam for use as current collectors in rechargeable Li-air batteries. Uncoated nickel foam promotes the decomposition of LiPF6-organic carbonate electrolytes under normal charging conditions reported for rechargeable Li-air cells. We have identified Ni free porous carbon supports as more appropriate cathode current collectors.

  10. Advances of aqueous rechargeable lithium-ion battery: A review

    NASA Astrophysics Data System (ADS)

    Alias, Nurhaswani; Mohamad, Ahmad Azmin

    2015-01-01

    The electrochemical characteristic of the aqueous rechargeable lithium-ion battery has been widely investigated in efforts to design a green and safe technology that can provide a highly specific capacity, high efficiency and long life for high power applications such as the smart grid and electric vehicle. It is believed that the advantages of this battery will overcome the limitations of the rechargeable lithium-ion battery with organic electrolytes that comprise safety and create high fabrication cost issues. This review focuses on the opportunities of the aqueous rechargeable lithium-ion battery compared to the conventional rechargeable lithium-ion battery with organic-based electrolytes. Previously reported studies are briefly summarised, together with the presentation of new findings based on the conductivity, morphology, electrochemical performance and cycling stability results. The factors that influence the electrochemical performance, the challenges and potential of the aqueous rechargeable lithium-ion battery are highlighted in order to understand and maintained the excellent battery performance.

  11. Global synthesis of groundwater recharge in semiarid and arid regions

    USGS Publications Warehouse

    Scanlon, B.R.; Keese, K.E.; Flint, A.L.; Flint, L.E.; Gaye, C.B.; Edmunds, W.M.; Simmers, I.

    2006-01-01

    Global synthesis of the findings from ???140 recharge study areas in semiarid and arid regions provides important information on recharge rates, controls, and processes, which are critical for sustainable water development. Water resource evaluation, dryland salinity assessment (Australia), and radioactive waste disposal (US) are among the primary goals of many of these recharge studies. The chloride mass balance (CMB) technique is widely used to estimate recharge. Average recharge rates estimated over large areas (40-374000 km2) range from 0.2 to 35 mm year-1, representing 0.1-5% of long-term average annual precipitation. Extreme local variability in recharge, with rates up to ???720 m year-1, results from focussed recharge beneath ephemeral streams and lakes and preferential flow mostly in fractured systems. System response to climate variability and land use/land cover (LU/LC) changes is archived in unsaturated zone tracer profiles and in groundwater level fluctuations. Inter-annual climate variability related to El Nin??o Southern Oscillation (ENSO) results in up to three times higher recharge in regions within the SW US during periods of frequent El Nin??os (1977-1998) relative to periods dominated by La Nin??as (1941-1957). Enhanced recharge related to ENSO is also documented in Argentina. Climate variability at decadal to century scales recorded in chloride profiles in Africa results in recharge rates of 30 mm year-1 during the Sahel drought (1970-1986) to 150 mm year-1 during non-drought periods. Variations in climate at millennial scales in the SW US changed systems from recharge during the Pleistocene glacial period (??? 10 000 years ago) to discharge during the Holocene semiarid period. LU/LC changes such as deforestation in Australia increased recharge up to about 2 orders of magnitude. Changes from natural grassland and shrublands to dryland (rain-fed) agriculture altered systems from discharge (evapotranspiration, ET) to recharge in the SW US. The

  12. Laboratory Analyses Of Basaltic Dunes In The Ka'u Desert Of Hawaii And Implications For Understanding Dark Dunes On Mars

    NASA Astrophysics Data System (ADS)

    Tirsch, D.; Craddock, R. A.; Nanson, G.; Tooth, S.; Langhans, M.

    2010-12-01

    Dark dunes are the dominant aeolian bedforms on Mars and consist of ancient volcanic ashes and reworked basaltic lavas. Basaltic dunes are rare on Earth and only occur in limited areas, such Hawaii. Because the Hawaiian dunes are composed of reworked basaltic sediments transported by eolian processes, they are a promising subject matter of analogy studies. Samples of dark dune sands, ash, and tephra collected in Hawaii's Ka'u Desert were collected during field trips in summer 2009 and 2010. They were analyzed by a variety of laboratory methods, including spectral, microscope, and microprobe investigations, in order examine their detailed mineralogical composition and constitution. We then compared the results to the eolian dunes on Mars. Sand samples were collected from three different dark dunes in Ka'u Desert: a large, vegetated, parabolic dune, a falling dune, and a large climbing dune. Tephra from the phreatic eruption that began in March 2008 was collected over a two year period using sample collectors placed at different locations downwind of Kilauea caldera. Analyses of these samples allow us to determining the initial composition, grain shape, and grain size of probable source materials. The visible and near-infrared reflectance spectra of the samples were acquired for the 0.5 to 2.5µm range. The overall spectral shape of the dune sand samples indicates a mineralogical correlation between Martian and terrestrial dune sands indicating a similar volcanic origin of the sediments. The spectra of the Hawaiian samples reveal some aqueous alteration, which is probably related to hydrated amorphous silica. Initial microscope and microprobe analyses reveal a high amount of volcanic glass and rock fragments in the samples, followed by olivine, feldspars, and pyroxene. Vitric particles that dominate the majority of the dune samples indicate in situ material accumulation following larger phreatic eruptions. The top coarse-grained layer of the climbing dune comprises a

  13. Testing the limits of the dune phase-stability diagram: the influence of velocity profile shape on dune morphology

    NASA Astrophysics Data System (ADS)

    Unsworth, C. A.; Parsons, D. R.; Reesink, A. J. H.; McLelland, S.

    2014-12-01

    The past 100 years of research on fluvial dunes and their deposits has produced bedform scaling laws based on flow depth, grain size and flow velocity. Such flow-form-deposit scaling is used ubiquitously for a wide range of paleo-environmental interpretations and in predictions of river bed roughness in floods. Recent research from marine environments, density currents, and fluvial flows with strong secondary circulation shows that these laws are often extrapolated beyond the limits of the original research. In submarine density currents, for example, paleo-hydraulic reconstructions commonly predict dune forming flow conditions, but preserved dune cross strata are rarely found. One particular difference between these geophysical flows is the velocity profile shape and bed shear stress that results. In a series of novel laboratory experiments the shape of the mean downstream velocity profile was systematically altered so the velocity maximum was lowered toward the bed through the addition of roughness elements at the water surface; whilst maintaining flow depth and depth-averaged velocities. This produced velocity profile shapes closer to those in density currents, and open-channel flows with strong secondary circulation. The initial lowering of the velocity maximum position increased dune height and length by 250%. The lowest velocity maximum position produced a stable upper-stage plane bed, whilst predictions based on flow depth and mean velocity remained within the dune regime phase-space. The results therefore demonstrate that the vertical position of the downstream velocity maximum can be a better predictor of equilibrium bedform geometries than flow depth or depth averaged velocity and also highlight that paleo-hydraulic reconstructions need to account for the possible variation in profile shape between geophysical flows. This research improves fundamental understanding of fluvial bedform stability and flow-form-deposit scaling laws for extrapolation into in a

  14. The effects of dune slopes and material heterogeneity on the thermal behavior of dune fields in Mars' Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    O'Shea, P. M.; Putzig, N. E.; Van Kooten, S.; Fenton, L. K.

    2015-12-01

    We analyzed the effects of slopes on the thermal properties of three dune fields in Mars' southern hemisphere. Although slope has important thermal effects, it is not the main driver of observed apparent thermal inertia (ATI) for these dunes. Comparing the ATI seasonal behavior as derived from Thermal Emission Spectrometer (TES) data with that modeled for compositional heterogeneities, we found that TES results correlate best with models of duricrust overlying and/or horizontally mixing with fines. We measured slopes and aspects in digital terrain models created from High Resolution Imaging Science Experiment (HiRISE) images of dunes within Proctor, Kaiser, and Wirtz craters. Using the MARSTHERM web toolset, we incorporated the slopes and aspects together with TES albedo, TES thermal inertia, surface pressure, and TES dust opacity, into models of seasonal ATI. Models that incorporate sub-pixel slopes show seasonal day and night ATI values that differ from the TES results by 0-300 J m-2 K-1 s-½. In addition, the models' day-night differences are opposite in sign from those of the TES results, indicating that factors other than slope are involved. We therefore compared the TES data to model results for a broad range of horizontally mixed and two-layered surfaces to seek other possible controls on the observed data, finding that a surface layer of higher thermal inertia is a likely contributor. However, it is clear from this study that the overall composition and morphology of the dune fields are more complex than currently available models allow. Future work will combine slopes with other model parameters such as multi-layered surfaces and lateral changes in layer thickness. Coupling these improvements with broader seasonal coverage from the Thermal Emission Imaging System (THEMIS) at more thermally favorable times of day would allow more accurate characterization of dune thermal behavior.

  15. Chloride-Mass-Balance: Cautions in Predicting Increased Recharge Rates

    SciTech Connect

    Gee, Glendon W.; Zhang, Z. F.; Tyler , S. W.; Albright , W. H.; Singleton , M. J.

    2005-02-01

    The chloride-mass-balance (CMB) method has been used extensively to estimate recharge in arid and semi-arid environments. Required data include estimates of annual precipitation, total chloride input (from dry fallout and precipitation), and pore-water chloride concentrations. Typically, CMB has been used to estimate ancient recharge but recharge from recent land-use change has also been documented. Recharge rates below a few mm/yr are reliably detected with CMB; however, estimates above a few mm/yr appear to be less reliable. We tested the CMB method against 26 years of drainage from a 7.6 m deep lysimeter at a simulated waste-burial ground, located on the Department of Energy’s Hanford Site in southeastern Washington State, USA where land-use change has increased recharge rates. Measured drainage from the lysimeter for the past 26 years averaged 62 mm/yr. Precipitation averaged 190 mm/yr with an estimated chloride input of 0.225 mg/L. Initial pore-water chloride concentration was 88 mg/L and decreased to about 6 mg/L after 26 years, while the drainage water decreased to less than 1 mg/L. A recharge estimate made using chloride concentrations in drain water was within 20% of the measured drainage rate. In contrast, recharge estimates using 1:1 (water: soil) extracts were lower than actual by factors ranging from 2 to 8 or more. The results suggest that when recharge is above a few mm/yr, soil water extracts can lead to unreliable estimates of recharge. For conditions of elevated recharge, direct sampling of pore water is the preferred method, because chloride concentrations are often 20 to 50 times higher in directly-sampled pore water than in pore-water extracts.

  16. Groundwater recharge rate and zone structure estimation using PSOLVER algorithm.

    PubMed

    Ayvaz, M Tamer; Elçi, Alper

    2014-01-01

    The quantification of groundwater recharge is an important but challenging task in groundwater flow modeling because recharge varies spatially and temporally. The goal of this study is to present an innovative methodology to estimate groundwater recharge rates and zone structures for regional groundwater flow models. Here, the unknown recharge field is partitioned into a number of zones using Voronoi Tessellation (VT). The identified zone structure with the recharge rates is associated through a simulation-optimization model that couples MODFLOW-2000 and the hybrid PSOLVER optimization algorithm. Applicability of this procedure is tested on a previously developed groundwater flow model of the Tahtalı Watershed. Successive zone structure solutions are obtained in an additive manner and penalty functions are used in the procedure to obtain realistic and plausible solutions. One of these functions constrains the optimization by forcing the sum of recharge rates for the grid cells that coincide with the Tahtalı Watershed area to be equal to the areal recharge rate determined in the previous modeling by a separate precipitation-runoff model. As a result, a six-zone structure is selected as the best zone structure that represents the areal recharge distribution. Comparison to results of a previous model for the same study area reveals that the proposed procedure significantly improves model performance with respect to calibration statistics. The proposed identification procedure can be thought of as an effective way to determine the recharge zone structure for groundwater flow models, in particular for situations where tangible information about groundwater recharge distribution does not exist. PMID:23746002

  17. Improved Recharge Estimation from Portable, Low-Cost Weather Stations.

    PubMed

    Holländer, Hartmut M; Wang, Zijian; Assefa, Kibreab A; Woodbury, Allan D

    2016-03-01

    Groundwater recharge estimation is a critical quantity for sustainable groundwater management. The feasibility and robustness of recharge estimation was evaluated using physical-based modeling procedures, and data from a low-cost weather station with remote sensor techniques in Southern Abbotsford, British Columbia, Canada. Recharge was determined using the Richards-based vadose zone hydrological model, HYDRUS-1D. The required meteorological data were recorded with a HOBO(TM) weather station for a short observation period (about 1 year) and an existing weather station (Abbotsford A) for long-term study purpose (27 years). Undisturbed soil cores were taken at two locations in the vicinity of the HOBO(TM) weather station. The derived soil hydraulic parameters were used to characterize the soil in the numerical model. Model performance was evaluated using observed soil moisture and soil temperature data obtained from subsurface remote sensors. A rigorous sensitivity analysis was used to test the robustness of the model. Recharge during the short observation period was estimated at 863 and 816 mm. The mean annual recharge was estimated at 848 and 859 mm/year based on a time series of 27 years. The relative ratio of annual recharge-precipitation varied from 43% to 69%. From a monthly recharge perspective, the majority (80%) of recharge due to precipitation occurred during the hydrologic winter period. The comparison of the recharge estimates with other studies indicates a good agreement. Furthermore, this method is able to predict transient recharge estimates, and can provide a reasonable tool for estimates on nutrient leaching that is often controlled by strong precipitation events and rapid infiltration of water and nitrate into the soil. PMID:26011672

  18. Nanocarbon networks for advanced rechargeable lithium batteries.

    PubMed

    Xin, Sen; Guo, Yu-Guo; Wan, Li-Jun

    2012-10-16

    Carbon is one of the essential elements in energy storage. In rechargeable lithium batteries, researchers have considered many types of nanostructured carbons, such as carbon nanoparticles, carbon nanotubes, graphene, and nanoporous carbon, as anode materials and, especially, as key components for building advanced composite electrode materials. Nanocarbons can form efficient three-dimensional conducting networks that improve the performance of electrode materials suffering from the limited kinetics of lithium storage. Although the porous structure guarantees a fast migration of Li ions, the nanocarbon network can serve as an effective matrix for dispersing the active materials to prevent them from agglomerating. The nanocarbon network also affords an efficient electron pathway to provide better electrical contacts. Because of their structural stability and flexibility, nanocarbon networks can alleviate the stress and volume changes that occur in active materials during the Li insertion/extraction process. Through the elegant design of hierarchical electrode materials with nanocarbon networks, researchers can improve both the kinetic performance and the structural stability of the electrode material, which leads to optimal battery capacity, cycling stability, and rate capability. This Account summarizes recent progress in the structural design, chemical synthesis, and characterization of the electrochemical properties of nanocarbon networks for Li-ion batteries. In such systems, storage occurs primarily in the non-carbon components, while carbon acts as the conductor and as the structural buffer. We emphasize representative nanocarbon networks including those that use carbon nanotubes and graphene. We discuss the role of carbon in enhancing the performance of various electrode materials in areas such as Li storage, Li ion and electron transport, and structural stability during cycling. We especially highlight the use of graphene to construct the carbon conducting

  19. Lithium electronic environments in rechargeable battery electrodes

    NASA Astrophysics Data System (ADS)

    Hightower, Adrian

    This work investigates the electronic environments of lithium in the electrodes of rechargeable batteries. The use of electron energy-loss spectroscopy (EELS) in conjunction with transmission electron microscopy (TEM) is a novel approach, which when coupled with conventional electrochemical experiments, yield a thorough picture of the electrode interior. Relatively few EELS experiments have been preformed on lithium compounds owing to their reactivity. Experimental techniques were established to minimize sample contamination and control electron beam damage to studied compounds. Lithium hydroxide was found to be the most common product of beam damaged lithium alloys. Under an intense electron beam, halogen atoms desorbed by radiolysis in lithium halides. EELS spectra from a number of standard lithium compounds were obtained in order to identify the variety of spectra encountered in lithium rechargeable battery electrodes. Lithium alloys all displayed characteristically broad Li K-edge spectra, consistent with transitions to continuum states. Transitions to bound states were observed in the Li K and oxygen K-edge spectra of lithium oxides. Lithium halides were distinguished by their systematic chemical shift proportional to the anion electronegativity. Good agreement was found with measured lithium halide spectra and electron structure calculations using a self-consistant multiscattering code. The specific electrode environments of LiC6, LiCoO2, and Li-SnO were investigated. Contrary to published XPS predictions, lithium in intercalated graphite was determined to be in more metallic than ionic. We present the first experimental evidence of charge compensation by oxygen ions in deintercalated LiCoO2. Mossbauer studies on cycled Li-SnO reveal severely defective structures on an atomic scale. Metal hydride systems are presented in the appendices of this thesis. The mechanical alloying of immiscible Fe and Mg powders resulted in single-phase bcc alloys of less than 20

  20. Temporal and spatial variation of groundwater in quantity and quality in sand dune at coastal region, Kamisu city, central Japan.

    NASA Astrophysics Data System (ADS)

    Umei, Yohei; Tsujimura, Maki; Sakakibara, Koichi; Watanabe, Yasuto; Minema, Motomitsu

    2016-04-01

    The role of groundwater in integrated water management has become important in recent 10 years, though the surface water is the major source of drinking water in Japan. Especially, it is remarked that groundwater recharge changed due to land cover change under the anthropogenic and climatic condition factors. Therefore, we need to investigate temporal and spatial variation of groundwater in quantity and quality focusing on the change during recent 10-20 years in specific region. We performed research on groundwater level and quality in sand dune at coastal region facing Pacific Ocean, Kamisu city, Ibaraki Prefecture, which have been facing environmental issues, such as land cover change due to soil mining for construction and urbanization. We compared the present situation of groundwater with that in 2000 using existed data to clarify the change of groundwater from 2000 to 2015. The quality of water is dominantly characterized by Ca2+-HCO3‑ in both 2000 and 2015, and nitrate was not observed in 2015, though it was detected in some locations in 2000. This may be caused by improvement of the domestic wastewater treatment. The topography of groundwater table was in parallel with that of ground surface in 2015, same as that in 2000. However, a depletion of groundwater table was observed in higher elevation area in 2015 as compared with that in 2000, and this area corresponds to the locations where the land cover has changed due to soil mining and urbanization between 2015 and 2000. In the region of soil mining, the original soil is generally replaced by impermeable soil after mining, and this may cause a decrease of percolation and net groundwater recharge, thus the depletion of groundwater table occurred after the soil mining.

  1. Sensitivity of the Automatic Determination of Sand Transport Direction and Rate to Dune Morphology (Invited)

    NASA Astrophysics Data System (ADS)

    Scheidt, S. P.; Lancaster, N.

    2010-12-01

    Measurements of rates of dune migration and sand flux are important to understanding the dynamics of aeolian systems, including sand encroachment, desertification, and response to changes in climate. The recent development of the Coregistration of Optically Sensed Images and Correlation (COSI-Corr) algorithm allows a unique remote-sensing approach for measuring dune migration rates. Fast- and slow-moving dunes have been analyzed by previous researchers using the algorithm, but the technique has mostly been tested on simple dune forms, which lack second-order geomorphic features that might cause errors. Our work tested the algorithm’s sensitivity to different dune types and evaluated the performance of the algorithm by making comparisons to previous studies and manual traces of the dunes in a GIS. Different parameters were chosen when applying the COSI-Corr algorithm, which were set according to the expected magnitude of dune displacement and the dune size with respect to image resolution. The dunes under study were chosen from the Namib Desert in locations where dune migration rates had previously been measured. These areas included (1) barchan dunes in Walvis Bay, (2) linear dunes just south of the Kuiseb River and (3) convoys of barchan dunes in the southern Namib. Orthorectified ASTER data from different dates were used to study the incremental and maximal changes between 1967 and 2009. These and other dune areas were studied to understand how varied geographic conditions (e.g.., the presence of coastlines, topography and background surface reflectance) affect the algorithm results. Walvis Bay dune migration vectors indicate rates between 3 and 30 m/yr to the north-northeast, which compares well to the range of previously reported values (2-27 m/yr). Individual dune migration rates between 1961 and 2005 also compared well to distances measured from dune crests in a GIS. Some vectors are overestimated because of interdune albedo effects, resulting from variable

  2. Dune ages in the sand deserts of the southern Sahara and Sahel

    NASA Astrophysics Data System (ADS)

    Bristow, Charlie; Armitage, Simon

    2015-04-01

    In this paper we aim to document the history of aeolian processes within the southern Sahara as part of the INQUA Dune Atlas. We review available luminescence ages for sand dunes across the southern Sahara and attempt to correlate periods of sand accumulation and to develop an improved understanding of the dune chronology on a regional basis. This was achieved by analysing dune age by country, as well as by latitude and longitude. The results show a very patchy spatial distribution of dune ages with large gaps that encompass some of the largest sand seas. Despite these gaps, some related patterns in dune morphology and stratigraphy appear to be consistent between northern Nigeria and southern Mali where older linear dunes are distinct from younger Late Holocene transverse and barchanoid dunes. Elsewhere in Mauretania linear dunes with different orientations appear to have accumulated at different times, most likely in response to changes in atmospheric circulation. Regional climatic changes are identified where dunes are transgressed by lake deposits within endorehic basins. We identify four locations where dune accumulation is terminated by lacustrine transgressions, two of which, in Lake Chad and the Bodélé Depression, occur shortly after the last glacial maximum (LGM). The third example at Gobiero in Niger occurred later, in the early Holocene, around 8.4 ka and a fourth marks a later transgression of Palaeolake MegaChad after 4.7 ka. Larger-scale latitudinal and longitudinal distributions in dune ages across the southern Sahara do not show any consistent patterns, though this may due to the small sample size relative to the study area. In addition, local variations in external controls such as wind regime, rainfall, vegetation and sand supply need to be considered, sometimes on a site by site basis. Limiting the analysis to dune ages determined using the single-aliquot regenerative-dose (SAR) protocol indicates a lack of dune preservation during the LGM and

  3. Sedimentological, Mineralogical and Geochemical Characterization of Sand Dunes in Saudi Arabia

    NASA Astrophysics Data System (ADS)

    Benaafi, Mohammed; Abdullatif, Osman

    2014-05-01

    Sedimentological, mineralogical, morphological and geochemical studies of sand dunes from ten locations in Saudi Arabia were conducted in order to determine the differences between them and to find out the provenance and tectonic setting of these sand dunes. Sixty seven samples were collected from different sand dunes types ranging in morphology from linear, barchans, parabolic to stars dunes. In overall, the sand dunes are fine to coarse grained mean grain size, moderately sorted, near symmetrical skewness with mesokurtic distribution characterized sand dunes in most locations. The sand dunes grains are subrounded in all locations except in the Red sea, Qassim, central Arabia and the eastern province which showed sub-angular grains. The main mineral compositions of studied aeolian sand dunes are quartz, feldspar, calcite, and mica. Quartz is the dominant mineral in locations with significant amount of feldspars and mica in Najran, Red sea and Central Arabia locations. Moreover, calcite is present in Sakaka and NW Empty Quarter (Jafurah). Basement related sand dunes in Najran, Central Arabia and Red sea locations are sub-mature in terms of their mineralogical maturity. Whereas, sand dunes in other locations are texturally mature except those from the Red sea which showed sub-mature sand. The sands are classified as quartz arenite, except in the basement related sand dunes in Najran, central Arabia and the Red sea are ranging from sub-arkose, sub-litharenite and lithraenite. Morphologically, parallel to sub-parallel sand ridges with NE-SW orientation occurred in east and north parts of Empty Quarter (Najran and Jafurah) and NW-SE orientation in Dahna and Nafud deserts in central and north regions of Saudi Arabia. Parabolic sand dunes characterized the Nafud desert (Hail, Sakaka, Tayma locations). Barchans and star sand dunes characterize the Empty Quarter (Jafurah). Major, trace, and rare earth elements studies were carried out to determine the composition

  4. Modeling the Large-Scale Structure and Long-Term Evolution of a Barchan Dune Field

    NASA Astrophysics Data System (ADS)

    Worman, S.; Littlewood, R. C.; Murray, A.; Andreotti, B.; Claudin, P.

    2011-12-01

    Barchans are mobile, crescent-shaped dunes that form atop hard, flat surfaces in regions where sediment supply is limited and fluid flow is approximately unidirectional. At the dune-scale, coupled models of sand transport and fluid dynamics have successfully reproduced their characteristic behavior and morphology. However, in nature, dunes rarely exist as isolated individuals but are instead found in highly-structured fields: Within a dune field with a cross-wind dimension on the order of 10 kilometers, patches of dunes can alternate spatially with sparse or dune-free regions, and the patches may have different characteristic dune size and spacing. The origin of such enigmatic structures cannot seem to be explained by differences in external forcing and remains an open research question. We use a partly rule-based numerical model that treats single dunes as discrete entities, based on the results of a dune-scale fluid-dynamics/sediment transport model. Our model integrates all currently known processes through which dunes interact with one another (i.e. sand flux exchange, collision, and calving). A rich array of patterns similar to those observed in nature emerge from these relatively simple interactions, offering a potential explanation of field-scale phenomena. We also develop simple statistics to characterize these structures and furnish testable predictions for future empirical work.

  5. Dunes and Microdunes on Venus: Why Were So Few Found in the Magellan Data?

    NASA Technical Reports Server (NTRS)

    Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven

    1994-01-01

    A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle I images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel reflections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be the most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.

  6. Dunes and microdunes on Venus: Why were so few found in the Magellan data?

    NASA Technical Reports Server (NTRS)

    Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven

    1994-01-01

    A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle 1 images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel relfections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.

  7. Plant distribution at the mobile dune scale and its relevance to soil properties and topographic features

    NASA Astrophysics Data System (ADS)

    Zuo, Xiaoan; Zhao, Halin; Zhao, Xueyong; Guo, Yirui; Li, Yulin; Luo, Yayong

    2008-05-01

    A survey was conducted in an 11-year recovery mobile dune (RMD11) and a 20-year recovery mobile dune (RMD20), in Horqin Sandy Land, Northern China, to determine plant distribution at the mobile dune scale and its relevance to soil properties and topographic features. The results showed that (1) vegetation cover and species number increased from dune top to bottom in the restoration process of mobile dune; (2) the average value of soil organic C, total N, pH, relative height of sampling site, very fine sand content and soil water contents (40-60 and 60-80 cm) of RMD11 were less than that of RMD20, respectively, and there were significant differences ( P < 0.05) between the two dunes; (3) soil resources were redistributed by shrub restoration and relative height of sampling site on dune. The distribution of sand pioneer plant, Agriophyllum squarrosum, was positively related to the relative height of sampling site and soil water content, while that of other herbaceous plants was positively related to soil nutrients in the restoration process of mobile dune. These results suggest that at mobile dune scale, plant distributions are determined by a combination of soil properties and topographic feature. Much effort should be made to preserve the interdune lowland and to improve the level of soil nutrients on mobile dune.

  8. Late Holocene dune activity in the Eastern Platte River Valley, Nebraska

    NASA Astrophysics Data System (ADS)

    Hanson, P. R.; Joeckel, R. M.; Young, A. R.; Horn, J.

    2009-02-01

    Large-scale dune activity in the Nebraska Sand Hills and elsewhere on the western Great Plains has been linked to prehistoric "megadroughts" that triggered the activation of regional dune fields. The effect of megadroughts on the smaller dune fields east of the Nebraska Sand Hills has never been assessed, however. This study focuses on the Duncan dune field near the confluence of the Loup and Platte rivers in eastern Nebraska. Seventeen optically stimulated luminescence age estimates were obtained and reveal two periods of dune activation that occurred between 4.4 to 3.4 ka and 0.8 to 0.5 ka. Significantly, both periods chronologically overlap large-scale dune activity identified in the Nebraska Sand Hills. Geochemical evidence indicates that the Duncan dunes received sand not only from the terrace underlying them, but also from the Loup River. These data link dune activity in the Duncan area, at least indirectly, to increased sediment supply from streams that drain the Sand Hills during megadroughts, implying the activation of the dunes occurred as an indirect response to regional megadroughts. Calculations of dune migration rates, however, argue in favor of local, drought-driven hydrologic changes as a causative factor in dune activation, in other words, a direct effect of megadroughts. Whether the impact was direct or indirect, it is highly likely that the repeated reactivation of the Duncan dunes resulted in some way from regional, large-magnitude droughts. Other paleoclimate proxies from the Great Plains tend to support this conclusion. We conclude that the megadroughts that have been identified in the Sand Hills and other Great Plains dune fields were indeed regional events with far-reaching effects.

  9. 3D airflow dynamics over transverse ridges Mpekweni, South Africa: implications for dune field migration behaviour

    NASA Astrophysics Data System (ADS)

    Jackson, Derek; Cooper, Andrew; Green, Andrew; Beyers, Meiring; Wiles, Errol; Benallack, Keegan

    2016-04-01

    Un-vegetated dune fields provide excellent opportunities to examine airflow dynamics over various types and scales of dune landforms. The three dimensional surface over which lower boundary layers travel, help adjust surface airflow and consequently the aeolian response of the dunes themselves. The use of computational fluid dynamic (CFD) modelling in recent studies now enables investigation of the 3D behaviour of airflow over complex terrain, providing new insights into heterogeneous surface flow and aeolian response of dune surfaces on a large (dunefield) scale. Using a largely un-vegetated coastal dune field site at Mpekweni, Eastern Cape, South Africa, a detailed (0.1m gridded) terrestrial laser scanning survey was conducted to create a high resolution topographical surface. Using local wind flow measurements and local met station records as input, CFD modelling was performed for a number of scenarios involving variable direction and magnitude to examine surface flow patterns across multiple dune forms. Near surface acceleration, expansion and separation of airflow inducing convergence and divergence (steering) of flow velocity streamlines are investigated. Flow acceleration over dune crests/brink lines is a key parameter in driving dune migration and slip face dynamics. Dune aspect ratio (height to length) is also important in determining the degree of crestal flow acceleration, with an increase in flow associated with increasing aspect ratios. Variations in dune height appear to be the most important parameter in driving general flow acceleration. The results from the study provide new insights into dune migration behaviour at this site as well as surface flow behaviour across multiple dune configurations and length scales within un-vegetated dune fields.

  10. Flow structure and resistance over subaquaeous high- and low-angle dunes

    NASA Astrophysics Data System (ADS)

    Kwoll, E.; Venditti, J. G.; Bradley, R. W.; Winter, C.

    2016-03-01

    A prominent control on the flow over subaqueous dunes is the slope of the downstream leeside. While previous work has focused on steep (~30°), asymmetric dunes with permanent flow separation, little is known about dunes with lower lee slope angles for which flow separation is absent or intermittent. Here we present a laboratory investigation where we systematically varied the dune lee slope, holding other geometric parameters and flow hydraulics constant, to explore effects on the turbulent flow field and flow resistance. Three sets of fixed dunes (lee slopes of 10°, 20°, and 30°) were separately installed in a 15 m long and 1 m wide flume and subjected to 0.20 m deep flow. Measurements consisted of high-frequency, vertical profiles collected with a Laser Doppler Velocimeter. We show that the temporal and spatial occurrence of flow separation decreases with dune lee slope. Velocity gradients in the dune leeside depict a free shear layer downstream of the 30° dunes and a weaker shear layer closer to the bed for the 20° and 10° dunes. The decrease in velocity gradients leads to lower magnitude of turbulence production for gentle lee slopes. Aperiodic, strong ejection events dominate the shear layer but decrease in strength and frequency for low-angle dunes. Flow resistance of dunes decreases with lee slope; the transition being nonlinear. Over the 10°, 20°, and 30° dunes, shear stress is 8%, 33%, and 90% greater than a flat bed, respectively. Our results demonstrate that dune lee slope plays an important but often ignored role in flow resistance.

  11. Artificial Recharge Coupled with Flood Mitigation in Jeju, Korea

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Koo, M.; Lee, K.; Moon, D.; Barry, J. M.; Park, W.

    2010-12-01

    The primary goal of this study is to develop and apply the artificial recharge system at Han Stream in Jeju Island, Korea, for not only securing sustainable groundwater resources, but also mitigating severe floods occurred due to the global climate changes. Jeju-friendly Aquifer Recharge Technology (J-ART) in this study has been developed by capturing ephemeral stream water with no interference in the environments such as natural recharge or eco-system, storing the flood water in the reservoirs, recharging it through designed borehole after appropriate water treatment, and then making it to be used at down-gradient production wells. For optimal design of J-ART, we conducted injection tests at the monitoring well (MW5) as well as at the planned recharge site during drilling the recharge wells and performed a modeling with the data obtained. Based on the modeling results, the artificial recharge wells were developed with a design of 10-meter spacing between the wells and 35-40 meter depths, which has a capacity of more than 2,500,000 m3 of groundwater resources in a year. Characterizing groundwater flow from recharge area to discharge area should be achieved to assess the efficiency of J-ART. The resistivity logging employed to predict water flow in unsaturated zone during artificial recharge based on the inverse modeling and resistivity change patterns. Stable isotope studies of deuterium and oxygen-18 of surface waters and groundwaters were carried out to interpret mixing and flow in groundwaters impacted by artificial recharge. Transient models were developed to predict the effects of artificial recharge using the hydraulic properties of aquifers, groundwater levels, and meteorological data. Time series changes of water balance after artificial recharge were analyzed, and residence time of the recharged water was also predicted with a certain degree of uncertainty. Keywords: J-ART, Hydrogeological methods, Geophysical survey, Stable isotopes, Groundwater modeling

  12. Rechargeable metal hydrides for spacecraft application

    NASA Technical Reports Server (NTRS)

    Perry, J. L.

    1988-01-01

    Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.

  13. Nanostructured cathode materials for rechargeable lithium batteries

    NASA Astrophysics Data System (ADS)

    Myung, Seung-Taek; Amine, Khalil; Sun, Yang-Kook

    2015-06-01

    The prospect of drastic climate change and the ceaseless fluctuation of fossil fuel prices provide motivation to reduce the use of fossil fuels and to find new energy conversion and storage systems that are able to limit carbon dioxide generation. Among known systems, lithium-ion batteries are recognized as the most appropriate energy storage system because of their high energy density and thus space saving in applications. Introduction of nanotechnology to electrode material is beneficial to improve the resulting electrode performances such as capacity, its retention, and rate capability. The nanostructure is highly available not only when used alone but also is more highlighted when harmonized in forms of core-shell structure and composites with carbon nanotubes, graphene or reduced graphene oxides. This review covers syntheses and electrochemical properties of nanoscale, nanosized, and nanostructured cathode materials for rechargeable lithium batteries.

  14. Rechargeable high-temperature batteries [Book Chapter

    SciTech Connect

    Cairns, Elton J.

    1981-01-01

    There has been growing research and development effort in the area of high-specific-energy, high-specific-power rechargeable batteries since the mid 1960s and it has been used in electric vehicles, electric utility networks, and solar- and wind-powered electric generator systems. Nonaqueous systems have been found to be the most attractive candidates for the above relatively large-scale applications. Only the high-temperature cells offer the attractive combination of features sought for the cited applications: a specific energy above 100 Wh/kg, a specific power above 100 W/kg, a cycle life in excess of 500 cycles (at 100% depth of discharge), and a projected cost of less than $50† per kWh of energy storage capability.

  15. Polymer Energy Rechargeable System Battery Being Developed

    NASA Technical Reports Server (NTRS)

    Manzo, Michelle A.

    2003-01-01

    Long description. Illustrations of discotic liquid crystals, rod-coil polymers, lithium-ion conducting channel dilithium phthalocyanine (Li2Pc) from top and side, novel star polyethylene oxide structures, composite polyethylene oxide materials (showing polyethylene oxide + lithium salt, carbon atoms and oxygen atoms), homopolyrotaxanes, and diblock copolymers In fiscal year 2000, NASA established a program to develop the next generation, lithium-based, polymer electrolyte batteries for aerospace applications. The goal of this program, known as Polymer Energy Rechargeable Systems (PERS), is to develop a space-qualified, advanced battery system embodying polymer electrolyte and lithium-based electrode technologies and to establish world-class domestic manufacturing capabilities for advanced batteries with improved performance characteristics that address NASA s future aerospace battery requirements.

  16. Spinel electrodes for rechargeable lithium batteries.

    SciTech Connect

    Thackeray, M. M.

    1999-11-10

    This paper gives a historical account of the development of spinel electrodes for rechargeable lithium batteries. Research in the late 1970's and early 1980's on high-temperature . Li/Fe{sub 3}O{sub 4} cells led to the evaluation of lithium spinels Li[B{sub 2}]X{sub 4} at room temperature (B = metal cation). This work highlighted the importance of the [B{sub 2}]X{sub 4}spinel framework as a host electrode structure and the ability to tailor the cell voltage by selection of different B cations. Examples of lithium-ion cells that operate with spinel anode/spinel cathode couples are provided. Particular attention is paid to spinels within the solid solution system Li{sub 1+x}Mn{sub 2-x}O{sub 4} (0 {le} x {le} 0.33).

  17. Unlinkable Priced Oblivious Transfer with Rechargeable Wallets

    NASA Astrophysics Data System (ADS)

    Camenisch, Jan; Dubovitskaya, Maria; Neven, Gregory

    We present the first truly unlinkable priced oblivious transfer protocol. Our protocol allows customers to buy database records while remaining fully anonymous, i.e., (1) the database does not learn who purchases a record, and cannot link purchases by the same customer; (2) the database does not learn which record is being purchased, nor the price of the record that is being purchased; (3) the customer can only obtain a single record per purchase, and cannot spend more than his account balance; (4) the database does not learn the customer's remaining balance. In our protocol customers keep track of their own balances, rather than leaving this to the database as done in previous protocols. Our priced oblivious transfer protocol is also the first to allow customers to (anonymously) recharge their balances. Finally, we prove our protocol secure in the standard model (i.e., without random oracles).

  18. Polymer Energy Rechargeable System (PERS) Development Program

    NASA Technical Reports Server (NTRS)

    Baldwin, Richard S.; Manzo, Michelle A.; Dalton, Penni J.; Marsh, Richard A.; Surampudi, Rao

    2001-01-01

    The National Aeronautics and Space Administration (NASA) and the Air Force Research Laboratory (AFRL) have recently established a collaborative effort to support the development of polymer-based, lithium-based cell chemistries and battery technologies to address the next generation of aerospace applications and mission needs. The overall objective of this development program, which is referred to as PERS, Polymer Energy Rechargeable System, is to establish a world-class technology capability and U.S. leadership in polymer-based battery technology for aerospace applications. Programmatically, the PERS initiative will exploit both interagency collaborations to address common technology and engineering issues and the active participation of academia and private industry. The initial program phases will focus on R&D activities to address the critical technical issues and challenges at the cell level.

  19. Advances in rechargeable lithium molybdenum disulfide batteries

    NASA Technical Reports Server (NTRS)

    Brandt, K.; Stiles, J. A. R.

    1985-01-01

    The lithium molybdenum disulfide system as demonstrated in a C size cell, offers performance characteristics for applications where light weight and low volume are important. A gravimetric energy density of 90 watt hours per kilogram can be achieved in a C size cell package. The combination of charge retention capabilities, high energy density and a state of charge indicator in a rechargeable cell provides power package for a wide range of devices. The system overcomes the memory effect in Nicads where the full capacity of the battery cannot be utilized unless it was utilized on previous cycles. The development of cells with an advanced electrolyte formulation led to an improved rate capability especially at low temperatures and to a significantly improved life cycle.

  20. Oxygen electrodes for rechargeable alkaline fuel cells

    NASA Technical Reports Server (NTRS)

    Swette, Larry; Giner, Jose

    1987-01-01

    Electrocatalysts and supports for the positive electrode of moderate temperature single unit rechargeable alkaline fuel cells were investigated and developed. The electrocatalysts are defined as the material with a higher activity for the oxygen electrode reaction than the support. Advanced development will require that the materials be prepared in high surface area forms, and may also entail integration of various candidate materials. Eight candidate support materials and seven electrocatalysts were investigated. Of the 8 support, 3 materials meet the preliminary requirements in terms of electrical conductivity and stability. Emphasis is now on preparing in high surface area form and testing under more severe corrosion stress conditions. Of the 7 electrocatalysts prepared and evaluated, at least 5 materials remain as potential candidates. The major emphasis remains on preparation, physical characterization and electrochemical performance testing.