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Sample records for elevation models lahar

  1. Using Digital Elevation Models and LAHARZ to Forecast Inundation by Lahars

    NASA Astrophysics Data System (ADS)

    Schilling, S. P.; Iverson, R. M.

    2005-12-01

    LAHARZ is a statistically based method for evaluating the effects of three-dimensional topography on lahar inundation patterns. The method applies the average behavior of past lahars to forecast inundation areas and portray them on maps. LAHARZ software runs on a Geographic Information System (GIS) and requires inputs consisting of prospective lahar volumes appropriate for the size and geologic history of a given volcano, identification of lahar source areas, and a digital elevation model (DEM) of topography. When using LAHARZ, the attributes of the input DEM have a significant impact on delineation of hazard zones. During a volcano crisis, there may be no option other than to select any available DEM to construct hazard zones. Ideally, users should obtain and evaluate existing or construct new DEMs before a crisis situation. Considerations before using a DEM are its extent, resolution, projection, datum, construction method, and quality. DEMs should include the volcano edifice and its drainages, which may reach hundreds of kilometers away from the volcano. The DEM should have sufficient resolution to depict drainage shapes accurately. For example, a DEM with 1-km resolution will not portray a 500-m wide drainage accurately. Projection, datum, and algoritm used for DEM generation ensure the constructed hazard zones can be displayed accurately with other data used in hazard map preparation. Methods for checking horizontal and vertical accuracy can range from inspecting the DEM visually and comparing it with published topographic maps to visiting locations in the field visible in the DEM (e.g., road intersections or mountain peaks) and comparing coordinates with a global positioning system (GPS) at an accuracy equal to or higher than the DEM for comparison. The DEM should be hydrologically correct. It should route a hypothetical flow of water along drainage thalwegs downstream effectively. Hydrologic functions called by LAHARZ can be used to ensure continuity of flow

  2. Modeling Lahar Hazard Zones for Eruption-Generated Lahars from Lassen Peak, California

    NASA Astrophysics Data System (ADS)

    Robinson, J. E.; Clynne, M. A.

    2010-12-01

    Lassen Peak, a high-elevation, seasonally snow-covered peak located within Lassen Volcanic National Park, has lahar deposits in several drainages that head on or near the lava dome. This suggests that these drainages are susceptible to future lahars. The majority of the recognized lahar deposits are related to the May 19 and 22, 1915 eruptions of Lassen Peak. These small-volume eruptions generated lahars and floods when an avalanche of snow and hot rock, and a pyroclastic flow moved across the snow-covered upper flanks of the lava dome. Lahars flowed to the north down Lost Creek and Hat Creek. In Lost Creek, the lahars flowed up to 16 km downstream and deposited approximately 8.3 x 106 m3 of sediment. This study uses geologic mapping of the 1915 lahar deposits as a guide for LAHARZ modeling to assist in the assessment of present-day susceptibility for lahars in drainages heading on Lassen Peak. The LAHARZ model requires a Height over Length (H/L) energy cone controlling the initiation point of a lahar. We chose a H/L cone with a slope of 0.3 that intersects the earth’s surface at the break in slope at the base of the volcanic dome. Typically, the snow pack reaches its annual maximum by May. Average and maximum May snow-water content, a depth of water equal to 2.1 m and 3.5 m respectively, were calculated from a local snow gauge. A potential volume for individual 1915 lahars was calculated using the deposit volume, the snow-water contents, and the areas stripped of snow by the avalanche and pyroclastic flow. The calculated individual lahars in Lost Creek ranged in size from 9 x 106 m3 to 18.4 x 106 m3. These volumes modeled in LAHARZ matched the 1915 lahars remarkably well, with the modeled flows ending within 4 km of the mapped deposits. We delineated six drainage basins that head on or near Lassen Peak with the highest potential for lahar hazards: Lost Creek, Hat Creek, Manzanita Creek, Mill Creek, Warner Creek, and Bailey Creek. We calculated the area of each

  3. Modeling lahar behavior and hazards

    USGS Publications Warehouse

    Manville, Vernon; Major, Jon J.; Fagents, Sarah A.

    2013-01-01

    Lahars are highly mobile mixtures of water and sediment of volcanic origin that are capable of traveling tens to > 100 km at speeds exceeding tens of km hr-1. Such flows are among the most serious ground-based hazards at many volcanoes because of their sudden onset, rapid advance rates, long runout distances, high energy, ability to transport large volumes of material, and tendency to flow along existing river channels where populations and infrastructure are commonly concentrated. They can grow in volume and peak discharge through erosion and incorporation of external sediment and/or water, inundate broad areas, and leave deposits many meters thick. Furthermore, lahars can recur for many years to decades after an initial volcanic eruption, as fresh pyroclastic material is eroded and redeposited during rainfall events, resulting in a spatially and temporally evolving hazard. Improving understanding of the behavior of these complex, gravitationally driven, multi-phase flows is key to mitigating the threat to communities at lahar-prone volcanoes. However, their complexity and evolving nature pose significant challenges to developing the models of flow behavior required for delineating their hazards and hazard zones.

  4. Lahar Hazard Modeling at Tungurahua Volcano, Ecuador

    NASA Astrophysics Data System (ADS)

    Sorensen, O. E.; Rose, W. I.; Jaya, D.

    2003-04-01

    lahar-hazard-zones using a digital elevation model (DEM), was used to construct a hazard map for the volcano. The 10 meter resolution DEM was constructed for Tungurahua Volcano using scanned topographic lines obtained from the GIS Department at the Escuela Politécnica Nacional, Quito, Ecuador. The steep topographic gradients and rapid downcutting of most rivers draining the edifice prevents the deposition of lahars on the lower flanks of Tungurahua. Modeling confirms the high degree of flow channelization in the deep Tungurahua canyons. Inundation zones observed and shown by LAHARZ at Baños yield identification of safe zones within the city which would provide safety from even the largest magnitude lahar expected.

  5. Evaluation of ASTER and SRTM DEM data for lahar modeling: A case study on lahars from Popocatépetl Volcano, Mexico

    NASA Astrophysics Data System (ADS)

    Huggel, C.; Schneider, D.; Miranda, P. Julio; Delgado Granados, H.; Kääb, A.

    2008-02-01

    Lahars are among the most serious and far-reaching volcanic hazards. In regions with potential interactions of lahars with populated areas and human structures the assessment of the related hazards is crucial for undertaking appropriate mitigating actions and reduce the associated risks. Modeling of lahars has become an important tool in such assessments, in particular where the geologic record of past events is insufficient. Mass-flow modeling strongly relies on digital terrain data. Availability of digital elevation models (DEMs), however, is often limited and thus an obstacle to lahar modeling. Remote-sensing technology has now opened new perspectives in generating DEMs. In this study, we evaluate the feasibility of DEMs derived from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and the Shuttle Radar Topography Mission (SRTM) for lahar modeling on Popocatépetl Volcano, Mexico. Two GIS-based models are used for lahar modeling, LAHARZ and a flow-routing-based debris-flow model (modified single-flow direction model, MSF), both predicting areas potentially affected by lahars. Results of the lahar modeling show that both the ASTER and SRTM DEMs are basically suitable for use with LAHARZ and MSF. Flow-path prediction is found to be more reliable with SRTM data, though with a coarser spatial resolution. Errors of the ASTER DEM affecting the prediction of flow paths due to the sensor geometry are associated with deeply incised gorges with north-facing slopes. LAHARZ is more sensitive to errors of the ASTER DEM than the MSF model. Lahar modeling with the ASTER DEM results in a more finely spaced predicted inundation area but does not add any significant information in comparison with the SRTM DEM. Lahars at Popocatépetl are modeled with volumes of 1 × 10 5 to 8 × 10 6 m 3 based on ice-melt scenarios of the glaciers on top of the volcano and data on recent and historical lahar events. As regards recently observed lahars, the travel

  6. Hydraulic modeling for lahar hazards at cascades volcanoes

    USGS Publications Warehouse

    Costa, J.E.

    1997-01-01

    The National Weather Service flood routing model DAMBRK is able to closely replicate field-documented stages of historic and prehistoric lahars from Mt. Rainier, Washington, and Mt. Hood, Oregon. Modeled time-of-travel of flow waves are generally consistent with documented lahar travel-times from other volcanoes around the world. The model adequately replicates a range of lahars and debris flows, including the 230 million km3 Electron lahar from Mt. Rainier, as well as a 10 m3 debris flow generated in a large outdoor experimental flume. The model is used to simulate a hypothetical lahar with a volume of 50 million m3 down the East Fork Hood River from Mt. Hood, Oregon. Although a flow such as this is thought to be possible in the Hood River valley, no field evidence exists on which to base a hazards assessment. DAMBRK seems likely to be usable in many volcanic settings to estimate discharge, velocity, and inundation areas of lahars when input hydrographs and energy-loss coefficients can be reasonably estimated.

  7. A SPH Depth Integrated Model for Popocatepetl 2001 Lahar.

    NASA Astrophysics Data System (ADS)

    Haddad, B.; Pastor, M.; Palacios, D.; Muñoz, E.

    2009-04-01

    Lahars at volcanoes inundate surrounding areas and damage or destroy nearby communities. Unlike any other volcanic hazard, lahars do not require an eruption to occur. They can be triggered by bad weather or by edifice failure long after an eruption a timing that can worsen the hazard. Modeling of lahars has become an important tool in the assessment of the related hazards in order to undertake appropriate mitigation actions and reduce the associated risks. In January 22, 2001, a violent explosion occurred in the Popocatépetl volcano (México) and a pumice- rich pyroclastic flows were spread out over a distance of 7 Km. The remobilization of this deposit formed a lahar that flowed through Huiloac Gorge for as far 12 Km to the town of Santiago Xalizintla. In this paper, we used a depth integrated coupled mathematical model derived from the velocity-pressure of the Biot-Zienkiewicz model which was discretised using SPH method to simulate Popocatepetl 2001 lahar. In order to investigate the convergence of the model we use a range of different SPH mesh resolutions. Once the optimum mesh resolution is bounded we analyse the model sensitivity to initial lahar volume, the density of the geomaterial, and the rheological parameter of the Bingham fluid. The obtained results highlight the capability of the proposed model to replicate the propagation stage of such complex phenomena. Moreover, the paper shows the effects of SPH mesh resolution and the relevant role played by the rheological parameters. Keywords: Numerical modelling, SPH, fluidised geomaterial, lahar, Popocatépetl volcano.

  8. Rain-triggered lahar susceptibility using a shallow landslide and surface erosion model

    NASA Astrophysics Data System (ADS)

    Mead, Stuart; Magill, Christina; Hilton, James

    2016-11-01

    Lahars are mass flows containing variable concentrations of water and volcanic debris that can cause catastrophic impacts to life, livelihoods and infrastructure downstream from their volcanic origin. Accurate and quantitative information on lahar hazards are essential for reducing the impact of these events. Lahar hazard assessments often focus on the use of numeric or empirical models to describe flow behaviour and inundation areas, which rely on historic lahar events and expert elicitation to define model inputs. This results in qualitative or semi-quantitative estimates of hazard that do not account for the mechanics of lahar initiation or, in the case of rain-triggered lahars, the dependence of rainfall intensity and duration on initiation. Here we develop a method for calculating rain-triggered lahar susceptibility, defined as the occurrence probability of a particular lahar initial volume at a specific location. The model relies on terrain and deposit characteristics and a probabilistic measure of rainfall in the form of rainfall intensity-frequency-duration relationships. Results for a case study of the October 28, 1995 lahar at Mangatoetoenui stream, Ruapehu Volcano, New Zealand, indicate lahar volume is controlled by a characteristic timescale, relating the deposit depth H to the hydraulic diffusivity D0 in the ratio H2/D0. The timescale describes the transmission of positive pore pressures within the deposit, leading to shallow failure. As a consequence of this timescale, rainfall duration is the most important factor determining initial lahar sediment volume. Rainfall intensity plays a minor role, controlling the volume of water in the lahar mixture. This observation is consistent with power-law relationships used to determine lahar triggering rainfall thresholds. The rain-triggered lahar susceptibility approach developed here is anticipated to improve probabilistic lahar hazard assessments by providing quantitative, reproducible estimates of initial

  9. Modeling of the Guagua Pichincha volcano (Ecuador) lahars

    NASA Astrophysics Data System (ADS)

    Canuti, Paolo; Casagli, Nicola; Catani, Filippo; Falorni, Giacomo

    Lahars, here defined as debris flows of volcanic origin, are rapid mass movements that pose a serious threat to cities located in the vicinity of many volcanoes. Quito, capital city of Ecuador and placed at the foot of the Pichincha volcano complex, is exposed to serious inundation hazard as part of the city is built on numerous deposits of large lahars that have occurred in the last 10,000 years. The objective of this paper is to model the potential lahars of the Pichincha volcano to predict inundation areas within the city of Quito. For this purpose two models that apply different approaches were utilized and their results were compared. The programs used were LAHARZ, a semi-empirical model conceived by the United States Geological Survey (USGS), and FLO-2D, a hydraulic model distributed by FLO Software Inc. LAHARZ is designed as a rapid, objective and reproducible automated method for mapping areas of potential lahar inundation (Proc. First Int. Conf. on Debris Flow Hazards Mitigation, San Francisco, USA, ASCE, 1998, p. 176). FLO-2D is a two-dimensional flood routing model for simulating overland flow on complex surfaces such as floodplains, alluvial fans or urbanized areas (FLO-2D Users manual, version 99.2). Both models run within geographical information systems (GIS). Fieldwork was focused on collecting all available information involved in lahar modeling. A total of 49 channel cross-sections were measured along the two main streams and stratigraphic investigations were carried out on the fans to estimate the volume of previous events. A global positioning system was utilized to determine the coordinates of each cross-section. Further data collection concerned topography, rainfall characteristics and ashfall thicknesses. All fieldwork was carried out in cooperation with the Instituto Geofisico of the Escuela Politecnica Nacional. Modeling in a GIS environment greatly aided the exportation of results for the creation of thematic maps and facilitated model

  10. Challenges of modeling current very large lahars at Nevado del Huila Volcano, Colombia

    NASA Astrophysics Data System (ADS)

    Worni, Raphael; Huggel, Christian; Stoffel, M.; Pulgarín, B.

    2012-03-01

    Nevado del Huila, a glacier-covered volcano in the South of Colombia's Cordillera Central, had not experienced any historical eruptions before 2007. In 2007 and 2008, the volcano erupted with phreatic and phreatomagmatic events which produced lahars with flow volumes of up to about 300 million m3 causing severe damage to infrastructure and loss of lives. The magnitude of these lahars and the prevailing potential for similar or even larger events, poses significant hazards to local people and makes appropriate modeling a real challenge. In this study, we analyze the recent lahars to better understand the main processes and then model possible scenarios for future events. We used lahar inundation depths, travel duration, and flow deposits to constrain the dimensions of the 2007 event and applied LAHARZ and FLO-2D for lahar modeling. Measured hydrographs, geophone seismic sensor data and calculated peak discharges served as input data for the reconstruction of flow hydrographs and for calibration of the models. For model validation, results were compared with field data collected along the Páez and Simbola Rivers. Based on the results of the 2007 lahar simulation, we modeled lahar scenarios with volumes between 300 million and 1 billion m3. The approach presented here represents a feasible solution for modeling high-magnitude flows like lahars and allows an assessment of potential future events and related consequences for population centers downstream of Nevado del Huila.

  11. Loss Estimation Modeling Of Scenario Lahars From Mount Rainier, Washington State, Using HAZUS-MH

    NASA Astrophysics Data System (ADS)

    Walsh, T. J.; Cakir, R.

    2011-12-01

    We have adapted lahar hazard zones developed by Hoblitt and others (1998) and converted to digital data by Schilling and others (2008) into the appropriate format for HAZUS-MH, which is FEMA's loss estimation model. We assume that structures engulfed by cohesive lahars will suffer complete loss, and structures affected by post-lahar flooding will be appropriately modeled by the HAZUS-MH flood model. Another approach investigated is to estimate the momentum of lahars, calculate a lateral force, and apply the earthquake model, substituting the lahar lateral force for PGA. Our initial model used the HAZUS default data, which include estimates of building type and value from census data. This model estimated a loss of about 12 billion for a repeat lahar similar to the Electron Mudflow down the Puyallup River. Because HAZUS data are based on census tracts, this estimated damage includes everything in the census tract, even buildings outside of the lahar hazard zone. To correct this, we acquired assessors data from all of the affected counties and converted them into HAZUS format. We then clipped it to the boundaries of the lahar hazard zone to more precisely delineate those properties actually at risk in each scenario. This refined our initial loss estimate to about 6 billion with exclusion of building content values. We are also investigating rebuilding the lahar hazard zones applying Lahar-Z to a more accurate topographic grid derived from recent Lidar data acquired from the Puget Sound Lidar Consortium and Mount Rainier National Park. Final results of these models for the major drainages of Mount Rainier will be posted to the Washington Interactive Geologic Map (http://www.dnr.wa.gov/ResearchScience/Topics/GeosciencesData/Pages/geology_portal.aspx).

  12. Modelling 2001 lahars at Popocatépetl volcano using FLO2D numerical code

    NASA Astrophysics Data System (ADS)

    Caballero, L.; Capra, L.

    2013-12-01

    Popocatépetl volcano is located on the central part of the Transmexican Volcanic Belt. It is one of the most active volcanoes in Mexico and endanger more than 25 million people that lives in its surroundings. In the last months, the renewal of its volcanic activity put into alert scientific community. One of the possible scenarios is the 2001 explosive activity, which was characterized by a 8 km eruptive column and the subsequent formation of pumice flows up to 4 km from the crater. Lahars were generated few hours after, remobilizing the new deposits towards NE flank of the volcano, along Huiloac Gorge, almost reaching Santiago Xalitzintla town (Capra et al., 2004). The occurrence of a similar scenario makes very important to reproduce this event to delimitate accurately lahar hazard zones. In this work, 2001 lahar deposit is modeled using FLO2D numerical code. Geophone data is used to reconstruct initial hydrograph and sediment concentration. Sensitivity study of most important parameters used by this code like Manning, and α and β coefficients was conducted in order to achieve a good simulation. Results obtained were compared with field data and demonstrated a good agreement in thickness and flow distribution. A comparison with previously published data with laharZ program (Muñoz-Salinas, 2009) is also made. Additionally, lahars with fluctuating sediment concentrations but with similar volume are simulated to observe the influence of the rheological behavior on lahar distribution.

  13. Elysium-Utopia flows as mega-lahars: A model of dike intrusion, cryosphere cracking, and water-sediment release

    NASA Astrophysics Data System (ADS)

    Russell, Patrick S.; Head, James W.

    2003-06-01

    High-resolution altimetry from the Mars Orbiter Laser Altimeter (MOLA) provides new data to test the interpretation that unusual flow-like deposits in Elysium-Utopia were emplaced as lahars (mass flows fluidized by water that are induced by volcanism). Using several data products derived from MOLA altimetry, we confirm that two major types of terrain dominate the region: (1) lava flows and (2) deposits consistent with emplacement by debris flows along medial channels, supporting the lahar hypothesis of previous workers. Associated terrain types are interpreted to be the result of modification of lavas by water and/or ice associated with the debris outflows and by later climatically controlled deposition and removal of a volatile-rich dust layer at high latitudes. Both lava flows and debris flows originate from northwest-trending, radial fossae on the flanks of the Elysium rise. The fossae are interpreted here to have been formed by laterally propagating dikes from Elysium Mons that have intersected or approached the surface. Fossae that are sources for only lava flows lie at higher elevations (-3400 m and above) than those that are the sources of lahars and channels (-3100 m to -4300 m). This discrepancy in source location suggests that the availability of groundwater responsible for lahar formation is elevation-dependent and reflects a hydrostatic-equilibrium distribution of water in the subsurface. These observations at Elysium allow a geologic test of the prevailing hypothesis on the configuration of the subsurface Martian hydrosphere: that an interconnected groundwater system at hydrostatic equilibrium may exist below a confining cryosphere. If water at a certain elevation is under hydrostatic pressure and this cryosphere is disrupted, the potential arises for groundwater to flow to the surface. We propose the following flow-emplacement model in which geologic activity in northwest Elysium is consistent with the preceding hydrological model. Laterally

  14. Using Bayesian Belief Networks to model volcanic hazards interaction: an application for rain-triggered lahars

    NASA Astrophysics Data System (ADS)

    Tierz, Pablo; Odbert, Henry; Phillips, Jeremy; Woodhouse, Mark; Sandri, Laura; Selva, Jacopo; Marzocchi, Warner

    2016-04-01

    Quantification of volcanic hazards is a challenging task for modern volcanology. Assessing the large uncertainties involved in the hazard analysis requires the combination of volcanological data, physical and statistical models. This is a complex procedure even when taking into account only one type of volcanic hazard. However, volcanic systems are known to be multi-hazard environments where several hazardous phenomena (tephra fallout, Pyroclastic Density Currents -PDCs-, lahars, etc.) may occur whether simultaneous or sequentially. Bayesian Belief Networks (BBNs) are a flexible and powerful way of modelling uncertainty. They are statistical models that can merge information coming from data, physical models, other statistical models or expert knowledge into a unified probabilistic assessment. Therefore, they can be applied to model the interaction between different volcanic hazards in an efficient manner. In this work, we design and preliminarily parametrize a BBN with the aim of forecasting the occurrence and volume of rain-triggered lahars when considering: (1) input of pyroclastic material, in the form of tephra fallout and PDCs, over the catchments around the volcano; (2) remobilization of this material by antecedent lahar events. Input of fresh pyroclastic material can be modelled through a combination of physical models (e.g. advection-diffusion models for tephra fallout such as HAZMAP and shallow-layer continuum models for PDCs such as Titan2D) and uncertainty quantification techniques, while the remobilization efficiency can be constrained from datasets of lahar observations at different volcanoes. The applications of this kind of probabilistic multi-hazard approach can range from real-time forecasting of lahar activity to calibration of physical or statistical models (e.g. emulators) for long-term volcanic hazard assessment.

  15. Smoothed particle hydrodynamic modeling of volcanic debris flows: Application to Huiloac Gorge lahars (Popocatépetl volcano, Mexico)

    NASA Astrophysics Data System (ADS)

    Haddad, Bouchra; Palacios, David; Pastor, Manuel; Zamorano, José Juan

    2016-09-01

    Lahars are among the most catastrophic volcanic processes, and the ability to model them is central to mitigating their effects. Several lahars recently generated by the Popocatépetl volcano (Mexico) moved downstream through the Huiloac Gorge towards the village of Santiago Xalitzintla. The most dangerous was the 2001 lahar, in which the destructive power of the debris flow was maintained throughout the extent of the flow. Identifying the zone of hazard can be based either on numerical or empirical models, but a calibration and validation process is required to ensure hazard map quality. The Geoflow-SPH depth integrated numerical model used in this study to reproduce the 2001 lahar was derived from the velocity-pressure version of the Biot-Zienkiewicz model, and was discretized using the smoothed particle hydrodynamics (SPH) method. The results of the calibrated SPH model were validated by comparing the simulated deposit depth with the field depth measured at 16 cross sections distributed strategically along the gorge channel. Moreover, the dependency of the results on topographic mesh resolution, initial lahar mass shape and dimensions is also investigated. The results indicate that to accurately reproduce the 2001 lahar flow dynamics the channel topography needed to be discretized using a mesh having a minimum 5 m resolution, and an initial lahar mass shape that adopted the source area morphology. Field validation of the calibrated model showed that there was a satisfactory relationship between the simulated and field depths, the error being less than 20% for 11 of the 16 cross sections. This study demonstrates that the Geoflow-SPH model was able to accurately reproduce the lahar path and the extent of the flow, but also reproduced other parameters including flow velocity and deposit depth.

  16. Secondary lahar hazard assessment for Villa la Angostura, Argentina, using Two-Phase-Titan modelling code during 2011 Cordón Caulle eruption

    NASA Astrophysics Data System (ADS)

    Córdoba, G.; Villarosa, G.; Sheridan, M. F.; Viramonte, J. G.; Beigt, D.; Salmuni, G.

    2015-04-01

    This paper presents the results of lahar modelling in the town of Villa La Angostura (Neuquén-Argentina) based on the Two-Phase-Titan modelling computer code. The purpose of this exercise is to provide decision makers with a useful tool to assess lahar hazard during the 2011 Puyehue-Cordón Caulle Volcanic Complex eruption. The possible occurrence of lahars mobilized from recent ash falls that could reach the city was analysed. The performance of the Two-Phase-Titan model using 15 m resolution digital elevation models (DEMs) developed from optical satellite images and from radar satellite images was evaluated. The output of these modellings showed inconsistencies that, based on field observations, were attributed to bad adjustment of the DEMs to real topography. Further testing of results using more accurate radar-based 10 m DEM, provided more realistic predictions. This procedure allowed us to simulate the path of flows from Florencia, Las Piedritas and Colorado creeks, which are the most hazardous streams for debris flows in Villa La Angostura. The output of the modelling is a valuable tool for city planning and risk management especially considering the glacial geomorphic features of the region, the strong urban development growth and the land occupation that has occurred in the last decade in Villa La Angostura and its surroundings.

  17. Simulation of three lahars in the Mount St Helens area, Washington using a one-dimensional, unsteady-state streamflow model

    USGS Publications Warehouse

    Laenen, Antonius; Hansen, R.P.

    1988-01-01

    A one-dimensional, unsteady-state, open-channel model was used to analytically reproduce three lahar events. Factors contributing to the success of the modeling were: (1) the lahars were confined to a channel, (2) channel roughness was defined by field information, and (3) the volume of the flow remained relatively unchanged for the duration of the peak. Manning 's 'n ' values used in computing conveyance in the model were subject to the changing rheology of the debris flow and were calculated from field cross-section information (velocities used in these calculations were derived from super-elevation or run-up formulas). For the events modeled in this exercise, Manning 's 'n ' calculations ranged from 0.020 to 0.099. In all lahar simulations, the rheology of the flow changed in a downstream direction during the course of the event. Chen 's 'U ', the mudflow consistency index, changed approximately an order of magnitude for each event. The ' u ' values ranged from 5-2,260 kg/m for three events modeled. The empirical approach adopted in this paper is useful as a tool to help predict debris-flow behavior, but does not lead to understanding the physical processes of debris flows. (Author 's abstract)

  18. Simulating the Osceola Mudflow Lahar Event in the Pacific Northwest using a GPU Based 2-Dimensional Hydraulic Model

    NASA Astrophysics Data System (ADS)

    Katz, B. G.; Eppert, S.; Lohmann, D.; Li, S.; Goteti, G.; Kaheil, Y. H.

    2011-12-01

    At 4,400 meters, Mount Rainer has been the point of origin for several major lahar events. The largest event, termed the "Osceola Mudflow," occurred 5,500 years ago and covered an area of approximately 550km2 with a total volume of deposited material from 2 to 4km3. Particularly deadly, large lahars are estimated to have maximum flow velocities in of 100km/h with a density often described as "Flowing Concrete." While rare, these events typically cause total destruction within a lahar inundation zone. It is estimated that approximately 150,000 people live on top of previous deposits left by lahars which can be triggered by anything from earthquakes to glacial and chemical erosion of volcanic bedrock over time to liquefaction caused by extreme rainfall events. A novel methodology utilizing a 2 dimensional hydraulic model has been implemented allowing for high resolution (30m) lahar inundation maps to be generated. The utility of this model above or in addition to other methodologies such as that of Iverson (1998), lies in its portability to other lahar zones as well as its ability to model any total volume specified by the user. The process for generating lahar flood plains requires few inputs including: a Digital Terrain Map of any resolution (DTM), a mask defining the locations for lahar genesis, a raster of friction coefficients, and a time series depicting uniform material accumulation over the genesis mask which is allowed to flow down-slope. Finally, a significant improvement in speed has been made for solving the two dimensional model by utilizing the latest in graphics processing unit (GPU) technology which has resulted in a greater than 200 times speed up in model run time over previous CPU-based methods. The model runs for the Osceola Mudflow compare favorably with USGS derived inundation regions as derived using field measurements and GIS based approaches such as the LAHARZ program suit. Overall gradation of low to high risk match well, however the new

  19. The 2005 Vazcun Valley Lahar: Evaluation of the TITAN2D Two-Phase Flow Model Using an Actual Event.

    NASA Astrophysics Data System (ADS)

    Williams, R.; Stinton, A. J.; Sheridan, M. F.

    2005-12-01

    TITAN2D is a depth-averaged, thin-layer computational fluid dynamics (CFD) code, suitable for simulating a variety of geophysical mass flows. TITAN2D output data include pile thickness and flow momentum at each time step for all cells traversed by the flow during the simulation. From this the flow limit, run-out path, pile velocity, deposit thickness, and travel time can be calculated. Results can be visualized in the open source GRASS GIS software or with the built-in TITAN2D viewer. A new two-phase TITAN2D version allows simulation of flows containing various mixtures of water and solids. The purpose of this study is to compare simulations by the two-phase flow version of TITAN2D with an actual event. The chosen natural flow is a small ash-rich lahar (volume approximately 60,000 m3) that occurred on 12 February 2005 in the Vazcún Valley, located on the north-east flank of Volcán Tungurahua, Ecuador. Lahars and pyroclastic flows along this valley could potentially threaten the 20,000 inhabitants living in and near the city of Baños. A variety of data sources exist for this lahar, including: pre- and post-event meter-scale topography, and photographic, video, seismic and acoustic flow monitoring (AFM) records from during the event. These data permit detailed comparisons between the dynamics of the actual lahar and those of the TITAN2D simulated flow. In particular, detailed comparisons are made between run-up heights, flow velocity, inundation area, and deposit area and thickness. Simulations utilize a variety of data derived from field observations such as lahar volume, solid to pore-fluid ratio and pre-event topography. TITAN2D is important in modeling lahars because it allows assessment of the impact of the flows on buildings and infrastructure lifelines located near drainages that descend from volcanoes.

  20. Geographical information system approaches for hazard mapping of dilute lahars on Montserrat, West Indies

    NASA Astrophysics Data System (ADS)

    Darnell, A. R.; Barclay, J.; Herd, R. A.; Phillips, J. C.; Lovett, A. A.; Cole, P.

    2012-08-01

    Many research tools for lahar hazard assessment have proved wholly unsuitable for practical application to an active volcanic system where field measurements are challenging to obtain. Two simple routing models, with minimal data demands and implemented in a geographical information system (GIS), were applied to dilute lahars originating from Soufrière Hills Volcano, Montserrat. Single-direction flow routing by path of steepest descent, commonly used for simulating normal stream-flow, was tested against LAHARZ, an established lahar model calibrated for debris flows, for ability to replicate the main flow routes. Comparing the ways in which these models capture observed changes, and how the different modelled paths deviate can also provide an indication of where dilute lahars, do not follow behaviour expected from single-phase flow models. Data were collected over two field seasons and provide (1) an overview of gross morphological change after one rainy season, (2) details of dominant channels at the time of measurement, and (3) order of magnitude estimates of individual flow volumes. Modelling results suggested both GIS-based predictive tools had associated benefits. Dominant flow routes observed in the field were generally well-predicted using the hydrological approach with a consideration of elevation error, while LAHARZ was comparatively more successful at mapping lahar dispersion and was better suited to long-term hazard assessment. This research suggests that end-member models can have utility for first-order dilute lahar hazard mapping.

  1. Water, ice and mud: Lahars and lahar hazards at ice- and snow-clad volcanoes

    USGS Publications Warehouse

    Waythomas, Christopher F.

    2014-01-01

    Large-volume lahars are significant hazards at ice and snow covered volcanoes. Hot eruptive products produced during explosive eruptions can generate a substantial volume of melt water that quickly evolves into highly mobile flows of ice, sediment and water. At present it is difficult to predict the size of lahars that can form at ice and snow covered volcanoes due to their complex flow character and behaviour. However, advances in experiments and numerical approaches are producing new conceptual models and new methods for hazard assessment. Eruption triggered lahars that are ice-dominated leave behind thin, almost unrecognizable sedimentary deposits, making them likely to be under-represented in the geological record.

  2. The use of FLO2D numerical code in lahar hazard evaluation at Popocatépetl volcano: a 2001-lahar scenario

    NASA Astrophysics Data System (ADS)

    Caballero, L.; Capra, L.

    2014-07-01

    Lahar modelling represents an excellent tool to design hazard maps. It allows the definition of potential inundation zones for different lahar magnitude scenarios and sediment concentrations. Here we present the results obtained for the 2001 syneruptive lahar at Popocatépetl volcano, based on simulations performed with FLO2D software. An accurate delineation of this event is needed since it is one of the possible scenarios considered during a volcanic crisis. One of the main issues for lahar simulation using FLO2D is the calibration of the input hydrograph and rheologic flow properties. Here we verified that geophone data can be properly calibrated by means of peak discharge calculations obtained by superelevation method. Simulation results clearly show the influence of concentration and rheologic properties on lahar depth and distribution. Modifying rheologic properties during lahar simulation strongly affect lahar distribution. More viscous lahars have a more restricted aerial distribution, thicker depths, and resulting velocities are noticeable smaller. FLO2D proved to be a very successful tool to delimitate lahar inundation zones as well as to generate different lahar scenarios not only related to lahar volume or magnitude but also to take into account different sediment concentrations and rheologies widely documented to influence lahar prone areas.

  3. Secondary lahar hazard assessment for Villa la Angostura, Argentina, using Two-Phase-Titan modelling code during 2011 Cordón Caulle eruption

    NASA Astrophysics Data System (ADS)

    Córdoba, G.; Villarosa, G.; Sheridan, M. F.; Viramonte, J. G.; Beigt, D.; Salmuni, G.

    2014-10-01

    This paper shows the results of secondary lahar modelling in Villa La Angostura town (Neuquén-Argentina) based on the Two-Phase-Titan modelling computer code, which aimed to provide decision makers a useful tool to assess lahar hazard during the 2011 Puyehue-Cordón Caulle Volcanic Complex eruption. Possible occurrence of secondary lahars that could reach the city was analized. The performance of the Two-Phase-Titan model using 15 m resolution DEMs developed from optical satellite images and from radar satellite images was evaluated. The output of these modellings showed inconsistencies that, based on field observations, were attributed to bad adjustment of DEMs to real topography. Further testing of results using more accurate radar based 10 m DEM, proved more realistic predictions. The procedure allowed to simulate the path of flows from Florencia, Las Piedritas and Colorado creeks, which are the most influencing streams in Villa La Angostura. The output of the modelling is a valuable tool for city planning and risk management especially considering the glacial geomorphology features of the region, the strong urban development growth and the land occupation tendencies observed in last decade in Villa La Angostura and its surroundings.

  4. Assessing lahars from ice-capped volcanoes using ASTER satellite data, the SRTM DTM and two different flow models: case study on Iztaccíhuatl (Central Mexico)

    NASA Astrophysics Data System (ADS)

    Schneider, D.; Delgado Granados, H.; Huggel, C.; Kääb, A.

    2008-06-01

    Lahars frequently affect the slopes of ice-capped volcanoes. They can be triggered by volcano-ice interactions during eruptions but also by processes such as intense precipitation or by outbursts of glacial water bodies not directly related to eruptive activity. We use remote sensing, GIS and lahar models in combination with ground observations for an initial lahar hazard assessment on Iztaccíhuatl volcano (5230 m a.s.l.), considering also possible future developments of the glaciers on the volcano. Observations of the glacial extent are important for estimations of future hazard scenarios, especially in a rapidly changing tropical glacial environment. In this study, analysis of the glaciers on Iztaccíhuatl shows a dramatic retreat during the last 150 years: the glaciated area in 2007 corresponds to only 4% of the one in 1850 AD and the glaciers are expected to survive no later than the year 2020. Most of the glacial retreat is considered to be related to climate change but in-situ observations suggest also that geo- and hydrothermal heat flow at the summit-crater area can not be ruled out, as emphasized by fumarolic activity documented in a former study. However, development of crater lakes and englacial water reservoirs are supposed to be a more realistic scenario for lahar generation than sudden ice melting by rigorous volcano-ice interaction. Model calculations show that possible outburst floods have to be larger than ~5×105 m3 or to achieve an H/L ratio (Height/runout Length) of 0.2 and lower in order to reach the populated lower flanks. This threshold volume equals 2.4% melted ice of Iztaccíhuatl's total ice volume in 2007, assuming 40% water and 60% volumetric debris content of a potential lahar. The model sensitivity analysis reveals important effects of the generic type of the Digital Terrain Model (DTM) used on the results. As a consequence, the predicted affected areas can vary significantly. For such hazard zonation, we therefore suggest the use of

  5. Digital Elevation Models

    USGS Publications Warehouse

    ,

    1993-01-01

    The Earth Science Information Center (ESIC) distributes digital cartographic/geographic data files produced by the U.S. Geological Survey (USGS) as part of the National Mapping Program. Digital cartographic data files may be grouped into four basic types. The first of these, called a Digital Line Graph (DLG), is the line map information in digital form. These data files include information on base data categories, such as transportation, hypsography, hydrography, and boundaries. The second type, called a Digital Elevation Model (DEM), consists of a sampled array of elevations for a number of ground positions at regularly spaced intervals. The third type is Land Use and Land Cover digital data which provides information on nine major classes of land use such as urban, agricultural, or forest as well as associated map data such as political units and Federal land ownership. The fourth type, the Geographic Names Information System, provides primary information for all known places, features, and areas in the United States identified by a proper name.

  6. Community Exposure to Lahar Hazards from Mount Rainier, Washington

    USGS Publications Warehouse

    Wood, Nathan J.; Soulard, Christopher E.

    2009-01-01

    Geologic evidence of past events and inundation modeling of potential events suggest that lahars associated with Mount Rainier, Washington, are significant threats to downstream development. To mitigate potential impacts of future lahars and educate at-risk populations, officials need to understand how communities are vulnerable to these fast-moving debris flows and which individuals and communities may need assistance in preparing for and responding to an event. To support local risk-reduction planning for future Mount Rainier lahars, this study documents the variations among communities in King, Lewis, Pierce, and Thurston Counties in the amount and types of developed land, human populations, economic assets, and critical facilities in a lahar-hazard zone. The lahar-hazard zone in this study is based on the behavior of the Electron Mudflow, a lahar that traveled along the Puyallup River approximately 500 years ago and was due to a slope failure on the west flank of Mount Rainier. This lahar-hazard zone contains 78,049 residents, of which 11 percent are more than 65 years in age, 21 percent do not live in cities or unincorporated towns, and 39 percent of the households are renter occupied. The lahar-hazard zone contains 59,678 employees (4 percent of the four-county labor force) at 3,890 businesses that generate $16 billion in annual sales (4 and 7 percent, respectively, of totals in the four-county area) and tax parcels with a combined total value of $8.8 billion (2 percent of the study-area total). Employees in the lahar-hazard zone are primarily in businesses related to manufacturing, retail trade, transportation and warehousing, wholesale trade, and construction. Key road and rail corridors for the region are in the lahar-hazard zone, which could result in significant indirect economic losses for businesses that rely on these networks, such as the Port of Tacoma. Although occupancy values are not known for each site, the lahar-hazard zone contains numerous

  7. Lahars of Mount Pinatubo, Philippines

    USGS Publications Warehouse

    Newhall, Christopher G.; Stauffer, Peter H.; Hendley, James W.

    1997-01-01

    On June 15, 1991, Mount Pinatubo in the Philippines exploded in the second largest volcanic eruption on Earth this century. This eruption deposited more than 1 cubic mile (5 cubic kilometers) of volcanic ash and rock fragments on the volcano's slopes. Within hours, heavy rains began to wash this material down into the surrounding lowlands in giant, fast-moving mudflows called lahars. In the next four rainy seasons, lahars carried about half of the deposits off the volcano, causing even more destruction in the lowlands than the eruption itself.

  8. Rheological behaviour of lahar flow

    NASA Astrophysics Data System (ADS)

    Lafarge, N.; Chambon, G.; Thouret, J. C.; Laigle, D.

    2012-04-01

    Lahars are mixtures of water and debris flowing down the flanks of volcanoes. These flows generally occur after heavy rainfalls and carry sediments deposited by volcanic eruptions. They are among the most destructive volcanic phenomena, and were responsible, in the 20th century, for 40% of the fatalities associated with volcanic eruptions worldwide. However, the mechanical behaviour and the propagation of these particular debris flows still remain poorly understood. In the frame of the research project Laharisk, Mount Semeru in Java (Indonesia) was chosen as a test site to monitor lahar activity and flows properties owing to the frequent occurrence of lahars on its flanks during the monsoon rainy period. Two observation stations, situated 510 m apart, were installed in the Curah Lengkong Valley on the southeast flank of Semeru volcano. The relatively straight and box-shaped channel between the two stations represents a natural flume well suited to study the hydraulics of the flows. Both stations are equipped with video cameras, pore-pressure and load sensors, AFM geophones, and one broad-band seismometer to measure the evolution over time of lahar flow height, speed, and discharge. Bucket samples are also directly taken in the flows at regular time-intervals in order to provide sediment concentration and grain-size distribution. The rheological behaviour of the material is studied through laboratory vane tests at constant imposed shear rate conducted on the fine-sized fraction (< 400 µm) of the samples. The flows generally comprise several distinct pulses or 'packets' that can be traced between the two instrumented stations. Each pulse lasts between 5 and 30 minutes. Typical flow heights, peak velocities, and maximum discharges range between 0.5-2 m, 3-6 m.s-1, and 25-250 m3.s-1, respectively. The rheometrical tests indicate a mechanical behaviour of the frictional type, the shear stress being almost independent of the shear rate. In addition, the friction

  9. Lahar Hazard Mapping of Mount Shasta, California: A GIS-based Delineation of Potential Inundation Zones in Mud and Whitney Creek Basins

    NASA Astrophysics Data System (ADS)

    McClung, S. C.; Roberts, M.

    2005-12-01

    Mount Shasta, the southernmost stratovolcano in the Cascade Range (41.4°N) has frequently produced lahars of various magnitudes during the last 10,000 years. These include large flows of eruptive origin, reaching more than 40 km from the summit, and studies have shown that at least 70 debris flows of noneruptive origin have occurred during the last 1,000 years in various stream channels. The Mud and Whitney Creek drainages have historically produced more debris flows than any other glacier-headed channel on the volcano. Periods of accelerated glacial melt have produced lahars in Whitney Creek with a volume of 4 x 106 m3 and a runout distance of about 27 km from the summit. Mud Creek flows from 1924 to 1931 covered an area of more than 6 km2 near the community of McCloud with an estimated 23 x 106 m3 of mud. A much older lahar in Big Canyon Creek may have deposited a volume of 70 x 106 m3 over present day Mount Shasta City and beyond. The LAHARZ inundation modeling tool was used to objectively delineate lahar inundation zones in Whitney and Mud Creek basins based on a 30 m digital elevation model and a range of potential volumes extrapolated from local events. The predicted inundation areas for the largest volume modeled are between 31 and 34 km2, reaching distances of about 32 km from the summit, well within reach of populated areas and significant bodies of water on the NW and SE flanks of the volcano. The resulting lahar inundation hazard zones are discussed with a focus on model limitations, cartographic implications, and the advantages of using 3D hazard maps.

  10. Implications for Hazards Maps of Identification, Routing, and Initiation of ca. 2 ka Lahars at Misti Volcano, Southern Peru

    NASA Astrophysics Data System (ADS)

    Harpel, C. J.; de Silva, S.; Scott, W. E.; Salas, G.

    2005-12-01

    About 2 ka a subplinian eruption at Misti volcano produced extensive volcaniclastic deposits. Our work to make a volcanic-hazard map based on these deposits illustrates some of the complications that arise from genetic interpretations, flow routing, and initiation processes. Earlier workers identified the deposits as pyroclastic flow deposits and evaluated the hazards accordingly (e.g. Thouret et al., 1999; 2001). However, abundant evidence indicates that they are lahar deposits. Needless to say, hazards implications of these different modes of emplacement are such that correct interpretation of the genesis of deposits is a critical first step in hazard assessment. Detailed field mapping shows that the most voluminous lahars were shed onto the southern portion of the ring plain of the volcano. Many of these lahars were channelized into narrow canyons (quebradas) in the ring plain, but, in several instances, lahars filled quebradas, overtopped interfluves and spilled into adjacent quebradas. As a result several quebradas not containing large lahars at their heads had voluminous lahars at their lower reaches. Accurate modeling and portrayal of potential lahar hazards must include an assessment of such diversions and be able to accommodate this behavior. Field mapping of deposits of past lahars can help to identify potential diversion points. Initiation processes of the lahars are not yet definitively understood, but the volume of deposits requires a voluminous source of water. Several lines of evidence point to interaction of hot pyroclasts with snow or ice as the initiation mechanism, but rain may also be involved. Currently, the volcano is in an arid climate, rarely has voluminous snow, and does not have permanent ice. Therefore, the 2 ka lahar deposits may not be a relevant analogue for the assessment of modern lahar hazards. When using mapping and modeling to make a lahar hazards assessment and map, it is critical to correctly identify the origin of deposits

  11. A New Two-phase Flow Model Applied to the 2007 Crater Lake Break-out Lahar, Mt. Ruapehu, New Zealand

    NASA Astrophysics Data System (ADS)

    Sheridan, M. F.; Cordoba, G.; Pitman, E.; Cronin, S. J.; Procter, J.

    2010-12-01

    The 2007 Crater Lake break-out lahar, Mt. Ruapehu, New Zealand, is a complex but well-characterized natural debris flow that follows an intricate course over an array of topographic features (see Manville et al., this conference). Detailed digital terrain data (DEM) and accurate flow characterization allow us to test our computational model with an unusually high level of control for such a large natural flood wave. The new two-phase flow code is imbedded within the TITAN2D framework (Patra et al. 2005) that is widely used in hazard assessment for both dry (granular) and wet (debris flow) flows (Murcia et al., 2010). Because TITAN2D is actually valid for dry flows (avalanches) we developed a new two-phase model based on balance laws for mass and momentum for each phase. The granular material is assumed to obey a Coulomb constitutive relation and the fluid is assumed to be inviscid. The Darcy-Weisbach formulation is used to account for bed friction, and a phenomenological drag coefficient mediates the momentum exchange between phases. The resulting system of 6 partial differential equations are depth averaged and correspond to the Savage and Hutter model in the limit of no fluid, and to the typical shallow water solutions (Ortiz, et al., 2005) for pure water. This model is capable of simulating particle volumetric fractions as dilute as 0.001 and as concentrated as 0.55. To confirm the usefulness of the new code for complex flows we used data from four observation stations at Ruapehu located at runout distances of 2 km, 5 km, 7 km and 9 km. The specific flow data that we compare with the model outcomes include: 1) arrival time of the flood front, 2) maximum flood depth, and 3) flow velocity. The computed values for these flow characteristics are all within about ± 10% of the observed figures. References: Manville, V., et al., 2010, Anatomy of a basin break-out flood: The 2007 Crater Lake break-out lahar, Mt. Ruapehu, New Zealand, this conference. Murcia, H

  12. Lahar hazard zones for eruption-generated lahars in the Lassen Volcanic Center, California

    USGS Publications Warehouse

    Robinson, Joel E.; Clynne, Michael A.

    2012-01-01

    Lahar deposits are found in drainages that head on or near Lassen Peak in northern California, demonstrating that these valleys are susceptible to future lahars. In general, lahars are uncommon in the Lassen region. Lassen Peak's lack of large perennial snowfields and glaciers limits its potential for lahar development, with the winter snowpack being the largest source of water for lahar generation. The most extensive lahar deposits are related to the May 1915 eruption of Lassen Peak, and evidence for pre-1915 lahars is sparse and spatially limited. The May 1915 eruption of Lassen Peak was a small-volume eruption that generated a snow and hot-rock avalanche, a pyroclastic flow, and two large and four smaller lahars. The two large lahars were generated on May 19 and 22 and inundated sections of Lost and Hat Creeks. We use 80 years of snow depth measurements from Lassen Peak to calculate average and maximum liquid water depths, 2.02 meters (m) and 3.90 m respectively, for the month of May as estimates of the 1915 lahars. These depths are multiplied by the areal extents of the eruptive deposits to calculate a water volume range, 7.05-13.6x106 cubic meters (m3). We assume the lahars were a 50/50 mix of water and sediment and double the water volumes to provide an estimate of the 1915 lahars, 13.2-19.8x106 m3. We use a representative volume of 15x106 m3 in the software program LAHARZ to calculate cross-sectional and planimetric areas for the 1915 lahars. The resultant lahar inundation zone reasonably portrays both of the May 1915 lahars. We use this same technique to calculate the potential for future lahars in basins that head on or near Lassen Peak. LAHARZ assumes that the total lahar volume does not change after leaving the potential energy, H/L, cone (the height of the edifice, H, down to the approximate break in slope at its base, L); therefore, all water available to initiate a lahar is contained inside this cone. Because snow is the primary source of water for

  13. 1-Meter Digital Elevation Model specification

    USGS Publications Warehouse

    Arundel, Samantha T.; Archuleta, Christy-Ann M.; Phillips, Lori A.; Roche, Brittany L.; Constance, Eric W.

    2015-10-21

    In January 2015, the U.S. Geological Survey National Geospatial Technical Operations Center began producing the 1-Meter Digital Elevation Model data product. This new product was developed to provide high resolution bare-earth digital elevation models from light detection and ranging (lidar) elevation data and other elevation data collected over the conterminous United States (lower 48 States), Hawaii, and potentially Alaska and the U.S. territories. The 1-Meter Digital Elevation Model consists of hydroflattened, topographic bare-earth raster digital elevation models, with a 1-meter x 1-meter cell size, and is available in 10,000-meter x 10,000-meter square blocks with a 6-meter overlap. This report details the specifications required for the production of the 1-Meter Digital Elevation Model.

  14. The Mount Rainier Lahar Detection System

    NASA Astrophysics Data System (ADS)

    Lockhart, A. B.; Murray, T. L.

    2003-12-01

    To mitigate the risk of unheralded lahars from Mount Rainier, the U.S. Geological Survey, in cooperation with Pierce County, Washington, installed a lahar-detection system on the Puyallup and Carbon rivers that originate on Mount Rainier's western slopes. The system, installed in 1998, is designed to automatically detect the passage of lahars large enough to potentially affect populated areas downstream (approximate volume threshold 40 million cubic meters), while ignoring small lahars, earthquakes, extreme weather and floods. Along each river valley upstream, arrays of independent lahar-monitoring stations equipped with geophones and short tripwires telemeter data to a pair of redundant computer base stations located in and near Tacoma at existing public safety facilities that are staffed around the clock. Monitored data consist of ground-vibration levels, tripwire status, and transmissions at regular intervals. The base stations automatically evaluate these data to determine if a dangerous lahar is passing through the station array. The detection algorithm requires significant ground vibration to occur at those stations in the array that are above the anticipated level of inundation, while lower level `deadman' stations, inundated by the flow, experience tripwire breakage or are destroyed. Once a base station detects a lahar, it alerts staff who execute a call-down of public-safety officials and schools, initiating evacuation of areas potentially at risk. Because the system's risk-mitigation task imposes high standards of reliability on all components, it has been under test for several years. To date, the system has operated reliably and without false alarms, including during the nearby M6.8 Nisqually Earthquake on February 28, 2001. The system is being turned over to Pierce County, and activated as part of their lahar warning system.

  15. Causes, Dynamics and Impacts of Lahar Mass Flows due to the April 2015 Eruption of Calbuco Volcano, Chile

    NASA Astrophysics Data System (ADS)

    Dussaillant, Alejandro; Russell, Andy; Meier, Claudio; Rivera, Andres; Mella, Mauricio; Garrido, Natalia; Hernandez, Jorge; Napoleoni, Felipe; Gonzalez, Cristian

    2016-04-01

    provides large volumes of sediment to distal portions of fluvial systems radiating from Calbuco, continuing impact on infrastructure and settlements, including secondary lahars due to rain and melt events. The database generated by this study hopes to contribute to further studies into lahars, including its use to test lahar numerical models.

  16. Lahars of Ruapehu Volcano, New Zealand: risk mitigation

    NASA Astrophysics Data System (ADS)

    Keys, Harry J. R.

    A dam-break lahar resulting from the last eruption of Ruapehu is expected when Crater Lake reaches a critical high level, probably within the next 1-5 summers. A high level of public consultation, political decision-making and ongoing scientific input has occurred to address the risks. Decisions about managing lahar risk have taken into account the fact that lahars are common on the active Ruapehu Volcano (2797 m) and in valleys draining the mountain and that most lahars are generated by eruptions, about half of which have no useful precursors. Lahars threaten New Zealand's largest ski area and nationally important infrastructure. Public safety has been the main consideration but the need for long-term risk mitigation and reducing impacts on Tongariro National Park World Heritage Area have also been important. Lahar mitigation on Ruapehu now includes six lahar warning systems, each with active response plans, and some infrastructure isolated from or hardened against lahars.

  17. Lahar simulation with SPH and field calibration at the Colima Volcano (Mexico)

    NASA Astrophysics Data System (ADS)

    Calvo, Leticia; Haddad, Bouchra; Capra, Lucia; Palacios, David

    2015-04-01

    As a result of the frequent effusive activity of Volcán de Colima (10° 30'44''N, 103° 37'02'' W), the most active volcano in Mexico, plenty of rain triggered lahars are produced, especially during the rainy season. Along the recent period of activity, particularly from 2010, many of these lahars channelled through the main ravines of the volcano and reach large distances, representing high risk for more than 10,000 people at the surroundings. Modeling of lahars has become an important tool in the assessment of the related hazards, in order to undertake appropriate mitigation actions and reduce the associated risks. Recent lahars at the Colima Volcano are well documented, so they can be used to prove the accuracy of modelling. In this work, we used the SPH (Smoothed Particle Hydrodynamics) method, a depth integrated coupled model created by Pastor in 2005, to replicate the propagation stage of 3 recent Colima lahars occurred on Montegrande ravine in 1992, 2011 and 2012. The studied events include hyperconcentrated, debris and a mixture of the previous flow natures. The inputs used for the SPH simulations were the initial point, volume of each lahar and an adapted morphology of its mass. Field data used to verify the SPH results include the stopping point of the lahar, its path, velocity and height values, as the floodplain area. All this information was a result of fieldwork recognition (cross section profiles of the inner part of the ravine) and free satellite imagery analysis. The best results were obtained using Bingham rheology. The proposed parameters to simulate Colima lahars were 20 Pa of yield strength and 30 Pa.s of viscosity for the 1992 lahar (hyperconcentrated flow), 200 Pa and 50 Pa.s in case of the 2011 debris flow, and finally 20 Pa and 24 Pa.s for the 2012 event, whose nature evolved from debris to an hyperconcentrated flow. In all cases a 1900 kg/m3 density was used. Highly accurate results showed the relevant role played by rheological

  18. US GeoData digital elevation models

    USGS Publications Warehouse

    ,

    1997-01-01

    Digital elevation model (DEM) data consist of a sampled array of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. the U.S> Geological Survey (USGS) produces five primary types of elevation data: 7.5-minute DEM, 30-minute DEM, 1-degree DEM, 7.5-minute Alaska DEM, and 15-minute Alaska DEM.

  19. US GeoData Digital Elevation Models

    USGS Publications Warehouse

    ,

    2000-01-01

    Digital elevation model (DEM) data are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection or to a geographic coordinate system. The grid cells are spaced at regular intervals along south to north profiles that are ordered from west to east. The U.S. Geological Survey (USGS) produces five primary types of elevation data: 7.5-minute DEM, 30-minute DEM, 1-degree DEM, 7.5-minute Alaska DEM, and 15-minute Alaska DEM.

  20. Multidisciplinary determination of Lahar Erosion Dynamics at the Colima Volcano (Mexico)

    NASA Astrophysics Data System (ADS)

    Calvo, Leticia; Renschler, Crish; Haddad, Bouchra; Palacios, David

    2015-04-01

    Volcán de Colima (10° 30'44''N, 103° 37'02'' W) is currently the most active volcano in Mexico and the North American plate. Associated to its frequent volcanic activity, renovated in 1998 and later in 2010, secondary processes like lahars, triggered by rain mixing with the loose pyroclastic debris produced, are common. Colima lahars channelled through the main water drainages (ravines), and reach large distances along their path (from 7 to 15 km long) burying farmland and all kind of human infrastructures at the surrounding area. The inner part of the ravines is greatly affected by lahars, especially by the bulking processes, so establish an appropriate method to determine its affection rate seems to be needed. In order to analyze 1-year lahar erosion dynamics inside one of the most active ravine (Montegrande 2011-2012 period), our team proposed a multidisciplinary perspective that combines numerical modeling (ArcGeoWEPP), fieldwork recognition and free satellite imagery, in the assessment of the related hazards. On the one hand, ArcGeoWEPP model allowed simulation of watersheds and hillslope profiles within ravines, taking into account climate parameters, land and vegetation covers. This tool was especially useful in areas where the terrain complexity prevented access. The results of this model were combined with 16 real cross-section topographies observed inside the Montegrande ravine and the floodplain delineation of lahars created from satellite imagery. The total 1-year volume of debris at Montegrande was finally reached, but also the erosive, sedimentary and balanced areas were identified, so as the lahar and its deposit dimensions. 750,000 tons per year were eroded inside the Montegrande ravine during 2011-2012 lahars, 805,000 tons if the hillslopes of the surrounding area were considered, and 580,000 tons were deposited along the path. The flood plain area was 1,100,000 m2. Numerical models combined with field data obtained from different sources seems

  1. Early succession on lahars spawned by Mount St. Helens.

    PubMed

    Del Moral, R

    1998-06-01

    The effects of isolation on primary succession are poorly documented. I monitored vegetation recovery on two Mount St. Helens lahars (mud flows) with different degrees of isolation using contiguous plots. Seventeen years after the eruption, species richness was stable, but cover continued to increase. That isolation affects community structure was confirmed in several ways. The dominance hierarchies of the lahars differed sharply. Detrended correspondence analysis on Lahar I showed a trend related to distance from an adjacent woodland, whereas vegetation on Lahar II was relatively homogeneous. Spectra of growth forms and dispersal types also differed. Lahar I was dominated by species with modest dispersal ability, while Lahar II was dominated by species with better dispersal. Variation between plots should decline through time, a prediction confirmed on Lahar II. Lahar I remained heterogeneous despite having developed significantly higher cover. Here, the increasing distance from the forest has prevented plots from becoming more homogeneous. At this stage of early primary succession, neither lahar is converging towards the species composition of adjacent vegetation. This study shows that isolation and differential dispersal ability combine to determine initial vegetation structure. Stochastic effects resulting from dispersal limitations may resist the more deterministic effects of competition that could lead to floristic convergence.

  2. Digital Elevation Model Mosaic of Mercury

    NASA Technical Reports Server (NTRS)

    Cook, A. C.; Watters, T. R.; Robinson, M. S.

    2001-01-01

    At CEPS (Center for Earth and Planetary Studies) work has been underway since 2000 to semi-automatically stereo match all Mariner 10 stereo pairs. The resulting matched image coordinates are converted into longitude, latitude, and height points and then combined to form a map projected Digital Elevation Model (DEM) mosaic of the planet's surface. Stereo images from Mariner 10 cover one quarter of the planet's surface, mostly in the southern hemisphere. Additional information is contained in the original extended abstract.

  3. Stochastic Downscaling of Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Rasera, Luiz Gustavo; Mariethoz, Gregoire; Lane, Stuart N.

    2016-04-01

    High-resolution digital elevation models (HR-DEMs) are extremely important for the understanding of small-scale geomorphic processes in Alpine environments. In the last decade, remote sensing techniques have experienced a major technological evolution, enabling fast and precise acquisition of HR-DEMs. However, sensors designed to measure elevation data still feature different spatial resolution and coverage capabilities. Terrestrial altimetry allows the acquisition of HR-DEMs with centimeter to millimeter-level precision, but only within small spatial extents and often with dead ground problems. Conversely, satellite radiometric sensors are able to gather elevation measurements over large areas but with limited spatial resolution. In the present study, we propose an algorithm to downscale low-resolution satellite-based DEMs using topographic patterns extracted from HR-DEMs derived for example from ground-based and airborne altimetry. The method consists of a multiple-point geostatistical simulation technique able to generate high-resolution elevation data from low-resolution digital elevation models (LR-DEMs). Initially, two collocated DEMs with different spatial resolutions serve as an input to construct a database of topographic patterns, which is also used to infer the statistical relationships between the two scales. High-resolution elevation patterns are then retrieved from the database to downscale a LR-DEM through a stochastic simulation process. The output of the simulations are multiple equally probable DEMs with higher spatial resolution that also depict the large-scale geomorphic structures present in the original LR-DEM. As these multiple models reflect the uncertainty related to the downscaling, they can be employed to quantify the uncertainty of phenomena that are dependent on fine topography, such as catchment hydrological processes. The proposed methodology is illustrated for a case study in the Swiss Alps. A swissALTI3D HR-DEM (with 5 m resolution

  4. Magnitude and frequency of lahars and lahar-runout flows in the Toutle-Cowlitz River system

    SciTech Connect

    Scott, K.M.

    1989-01-01

    The recurrence interval of a lahar or lahar-runout flow at least large enough to inundate flood plains 50 kilometers from Mount St. Helens is less than 100 years. Lahars are volcanic debris flows and their deposits; lahar-runout flows are the hyperconcentrated streamflow evolved from distal lahars. The recurrence interval is conditional on eruptive state and is based on the most recent 4,500 years of the volcano's approximately 40,000- to 50,000-year history. The 100-year recurrence interval is within a normal time frame for long-term planning. Therefore engineering works in the Toutle River system should be designed for lahars, as well as floods, of a particular frequency. Unlike a water flood, a lahar that has a flow depth at least 1 meter on flood plains can cause a significant part of the maximum possible damage. Trees are killed, many structures are inundated and made unusable even if they are not crushed by timber floating in the lahar, and agriculture is not feasible for periods of as much as several years. The largest lahar in this history of the watershed was formed by the bulking of the sediment in a flood surge that originated from breaching of a natural dam of ancestral Spirit Lake. The flow had a peak discharge of 300,000 to 300,000 m{sup 3}/s at a distance of 30 to 50 km from the volcano, and was the first of four lake-breakout lahars that occurred during a span of several years near the end of Pine Creek time. This series of lahars is interpreted as an analog of the events that would have happened, without engineering intervention, after the 1980 eruption. In 1980, a debris avalanche catastrophically raised Spirit Lake more than 60 m and created new lakes in blocked tributaries.

  5. The coalescence and organization of lahars at Semeru volcano, Indonesia

    NASA Astrophysics Data System (ADS)

    Doyle, E. E.; Cronin, S. J.; Cole, S. E.; Thouret, J.-C.

    2010-10-01

    We present multi-parameter geophysical measurements of rainfall-induced lahars at Semeru Volcano, East Java, using two observation sites 510 m apart, 11.5 km from the summit. Our study site in the Curah Lengkong channel is composed of a 30-m wide box-valley, with a base of gravel and lava bedrock, representing an ideal geometry for high density measurements of active lahars. Instrumentation included pore-pressure sensors (stage), a broad-band seismograph (arrival times, vibrational energy, and turbulence), video footage, and direct bucket sampling. A total of 8 rainfall-induced lahars were recorded, with durations of 1-3 h, heights 0.5-2 m, and peak velocities 3-6 m/s. Flow types ranged from dilute to dense hyperconcentrated flows. These recorded flows were commonly composed of partly coalesced, discrete and unsteady gravity current packets, represented by multiple peaks within each lahar. These packets most likely originate from multiple lahar sources, and can be traced between instrument sites. Those with the highest concentrations and greatest wetted areas were often located mid-lahar at our measured reach, accelerating towards the flow front. As these lahars travel downstream, the individual packets thus coalesce and the flow develops a more organised structure. Observations of different degrees of coalescence between these discrete flow packets illustrate that a single mature debris flow may have formed from multiple dynamically independent lahars, each with different origins.

  6. Digital elevation modelling using ASTER stereo imagery.

    PubMed

    Forkuo, Eric Kwabena

    2010-04-01

    Digital elevation model (DEM) in recent times has become an integral part of national spatial data infrastructure of many countries world-wide due to its invaluable importance. Although DEMs are mostly generated from contours maps, stereo aerial photographs and air-borne and terrestrial laser scanning, the stereo interpretation and auto-correlation from satellite image stereo-pairs such as with SPOT, IRS, and relatively new ASTER imagery is also an effective means of producing DEM data. In this study, terrain elevation data were derived by applying photogrammetric process to ASTER stereo imagery. Also, the quality ofDEMs produced from ASTER stereo imagery was analysed by comparing it with DEM produced from topographic map at a scale of 1:50,000. While analyzing the vertical accuracy of the generated ASTER DEM, fifty ground control points were extracted from the map and overlaid on the DEM. Results indicate that a root-mean-square error in elevation of +/- 14 m was achieved with ASTER stereo image data of good quality. The horizontal accuracy obtained from the ground control points was 14.77, which is within the acceptable range of +/- 7m to +/- 25 m. The generated (15 m) DEM was compared with a 20m, 25m, and a 30 m pixel DEM to the original map. In all, the results proved that, the 15 m DEM conform to the original map DEM than the others. Overall, this analysis proves that, the generated digital terrain model, DEM is acceptable.

  7. ASTER Stereoscopic Data and Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Toutin, Thierry

    Digital elevation models (DEMs) provide a digital representation of the Earth's relief, and are used in a variety of applications in geo-spatial analysis. Elevation data as DEMs are required to produce geocoded, orthorectified raster images, which often are incorporated in a geographic information system. The atmospheric, geometric, and radiometric correction of satellite data from optical and microwave instruments also require topographic information. Satellite data-derived DEMs form a vibrant research and development (R&D) topic for the last 30 years since the launch of the first civilian remote sensing satellite (Toutin 2000). Various methods exist to extract DEMs from both active and passive sensor-based satellite data-derived images ­(clinometry, stereoscopy, interferometry, polarimetry, and altimetry).

  8. Erosional and Depositional Processes of the 18 March 2007 Lahar at Mt. Ruapehu, New Zealand

    NASA Astrophysics Data System (ADS)

    Kastl, B. C.; Fagents, S. A.; Houghton, B. F.

    2010-12-01

    Spatiotemporal variability in the deposits of lahars offers clues into the characteristics and fluid dynamics of sediment-laden flows. The 18 March 2007 Crater Lake break-out lahar at Mount Ruapehu, New Zealand, emplaced 1.4 million m3 of boulder-bearing, matrix-rich, massively and weakly bedded deposits over the first 47.4 km of its flow-path. Traditionally these would be classified as debris flow and hyperconcentrated flow deposits, respectively. Grain size and componentry analyses were performed on samples collected over the first 11 km of flow path, for both the 2007 lahar and existing deposits that contributed sediment to the lahar. Heavily altered landslide material contributed a major proportion of sediment to the flow 0.6 km from source, and was used as a marker to establish downstream evolution of flow characteristics. Variations in the proportions of altered material with grain size suggest that abrasion and cataclasis occurred during transport. Furthermore, oxidized components are more rounded than all other sediment contributions, demonstrating greater vulnerability of the former to mechanical breakdown. Ten of sixteen samples of the 2007 lahar have distinctive sand-sized (1-2 Φ) secondary modes that become more pronounced with depth in the deposit, while primary modes coarsen. Similar but primary modes of 1-2 Φ exist 7 km from source, in deposits near the head of a side channel that captured the upper portion of the lahar after it overtopped a drainage divide. The grain size data suggest that sand may percolate downwards from a dilute upper region of the flow into a lower depositional region. We put forth a model for deposition in the first 11 km reach by the waning hyperconcentrated phase of a lahar with a concentrated basal flow but a strong vertical concentration gradient. During peak sediment concentration, the laminar basal region underwent en masse deposition, containing an abundance of sand. As the sediment concentration decreased over time

  9. A comparison of the Landsat image and LAHARZ-simulated lahar inundation hazard zone by the 2010 Merapi eruption

    NASA Astrophysics Data System (ADS)

    Lee, Seul-Ki; Lee, Chang-Wook; Lee, Saro

    2015-06-01

    Located above the Java subduction zone, Merapi Volcano is an active stratovolcano with a volcanic activity cycle of 1-5 years. Most Merapi eruptions are relatively small with volcanic explosivity index (VEI) of 1-3. However, the most recent eruption, which occurred in 2010, was quite violent with a VEI of 4 and 386 people were killed. In this study, lahars and pyroclastic flow zones were detected using optical Landsat images and the lahar and pyroclastic flow zone simulated using the LAHARZ program. To detect areal extents of lahar and pyroclastic flows using Landsat images, supervised classification was performed after atmospheric correction by using a cosine of the solar zenith correction (COST) model. As a result, the extracted dimensions of pyroclastic flows are nearly identical to the Calatrava Volcanic Province (CVP) monthly reports. Then, areas of potential lahar and pyroclastic flow inundation based on flow volume using the LAHARZ program were simulated and mapped. Finally, the detected lahars and pyroclastic flow zones were compared with the simulated potential zones using LAHARZ program and verified. Results showed satisfactory similarity (55.63 %) between the detected and simulated zone. The simulated zones using the LAHARZ program can be used as an essential volcanic hazard map for preventing life and property damages for Merapi Volcano and other hazardous volcanic areas. Also, the LAHARZ program can be used to map volcano hazards in other hazardous volcanic areas.

  10. Laharz_py: GIS tools for automated mapping of lahar inundation hazard zones

    USGS Publications Warehouse

    Schilling, Steve P.

    2014-01-01

    Laharz_py is written in the Python programming language as a suite of tools for use in ArcMap Geographic Information System (GIS). Primarily, Laharz_py is a computational model that uses statistical descriptions of areas inundated by past mass-flow events to forecast areas likely to be inundated by hypothetical future events. The forecasts use physically motivated and statistically calibrated power-law equations that each has a form A = cV2/3, relating mass-flow volume (V) to planimetric or cross-sectional areas (A) inundated by an average flow as it descends a given drainage. Calibration of the equations utilizes logarithmic transformation and linear regression to determine the best-fit values of c. The software uses values of V, an algorithm for idenitifying mass-flow source locations, and digital elevation models of topography to portray forecast hazard zones for lahars, debris flows, or rock avalanches on maps. Laharz_py offers two methods to construct areas of potential inundation for lahars: (1) Selection of a range of plausible V values results in a set of nested hazard zones showing areas likely to be inundated by a range of hypothetical flows; and (2) The user selects a single volume and a confidence interval for the prediction. In either case, Laharz_py calculates the mean expected A and B value from each user-selected value of V. However, for the second case, a single value of V yields two additional results representing the upper and lower values of the confidence interval of prediction. Calculation of these two bounding predictions require the statistically calibrated prediction equations, a user-specified level of confidence, and t-distribution statistics to calculate the standard error of regression, standard error of the mean, and standard error of prediction. The portrayal of results from these two methods on maps compares the range of inundation areas due to prediction uncertainties with uncertainties in selection of V values. The Open-File Report

  11. A global digital elevation model - GTOP030

    USGS Publications Warehouse

    1999-01-01

    GTOP030, the U.S. Geological Survey's (USGS) digital elevation model (DEM) of the Earth, provides the flrst global coverage of moderate resolution elevation data.  The original GTOP30 data set, which was developed over a 3-year period through a collaborative effort led by the USGS, was completed in 1996 at the USGS EROS Data Center in Sioux Falls, South Dakota.  The collaboration involved contributions of staffing, funding, or source data from cooperators including the National Aeronautics and Space Administration (NASA), the United Nations Environment Programme Global Resource Information Database (UNEP/GRID), the U.S. Agency for International Development (USAID), the Instituto Nacional de Estadistica Geografia e Informatica (INEGI) of Mexico, the Geographical Survey Institute (GSI) of Japan, Manaaki Whenua Landcare Research of New Zealand, and the Scientific Committee on Antarctic Research (SCAR). In 1999, work was begun on an update to the GTOP030 data set. Additional data sources are being incorporated into GTOP030 with an enhanced and improved data set planned for release in 2000.

  12. Digital Elevation Models Aid the Analysis of Flows at Hrad Vallis, Mars

    NASA Astrophysics Data System (ADS)

    Mouginis-Mark, P. J.; Hamilton, C.; Garbeil, H.

    2015-12-01

    We have identified several landforms in the Hrad Vallis region of Mars (33.0o - 35.5oN, 216o - 218oW), which suggest that this area was covered by an ice sheet concurrent with volcanic eruptions. Using digital elevation models derived from High Resolution Imaging Science (HiRISE) and Context Camera (CTX) data, a reexamination of the area reveals a complex history including flow inflation and topographic control by transient topographic barriers. Among Amazonian-age outflow channels, Hrad Vallis is exceptional as it exhibits good evidence of magma/water interactions. It is inferred to have formed in association with a shallow igneous sill that melted part of the martian cryosphere and/or released water from an extensive aquifer to produce enormous lahar-like mud flows. Exposed ~30 m high dikes, 20 m high eroded mounds, and flow paths that are inconsistent with present-day topographic gradients, lead us to speculate that this area was covered by at least ~40 m of material (eolian deposits or ice) at the time of volcanic dike intrusion and flow emplacement. This material was subsequently removed leaving no clear morphologic signs (e.g., wind streaks, if eolian material; moraines, if ice). We favor the ice model because if this area was once ice-covered, it offers a plausible mode of formation (as pingoes) for some enigmatic 30 m high domes in the vicinity. At least one 120 km long flow from Hrad Vallis was emplaced as a pahoehoe-like flow that was confined by topographic obstacles and subsequently inflated to thickness of ~45 m. Although the direct relationship between this flow and Hrad Vallis remains to be determined, the inflated flow suggests a longer period of eruption/emplacement at a slower effusion rate than was previously believed.

  13. Lahar hazards at Agua volcano, Guatemala

    USGS Publications Warehouse

    Schilling, S.P.; Vallance, J.W.; Matías, O.; Howell, M.M.

    2001-01-01

    At 3760 m, Agua volcano towers more than 3500 m above the Pacific coastal plain to the south and 2000 m above the Guatemalan highlands to the north. The volcano is within 5 to 10 kilometers (km) of Antigua, Guatemala and several other large towns situated on its northern apron. These towns have a combined population of nearly 100,000. It is within about 20 km of Escuintla (population, ca. 100,000) to the south. Though the volcano has not been active in historical time, or about the last 500 years, it has the potential to produce debris flows (watery flows of mud, rock, and debris—also known as lahars when they occur on a volcano) that could inundate these nearby populated areas.

  14. Instrumental lahar monitoring at Merapi Volcano, Central Java, Indonesia

    USGS Publications Warehouse

    Lavigne, F.; Thouret, J.-C.; Voight, B.; Young, K.; LaHusen, R.; Marso, J.; Suwa, H.; Sumaryono, A.; Sayudi, D.S.; Dejean, M.

    2000-01-01

    More than 50 volcanic debris flows or lahars were generated around Mt Merapi during the first rainy season following the nuees ardentes of 22 November 1994. The rainfalls that triggered the lahars were analyzed, using such instruments as weather radar and telemetered rain gauges. Lahar dynamics were also monitored, using new non-contact detection instrumentation installed on the slopes of the volcano. These devices include real-time seismic amplitude measurement (RSAM), seismic spectral amplitude measurement (SSAM) and acoustic flow monitoring (AFM) systems. Calibration of the various systems was accomplished by field measurements of flow velocities and discharge, contemporaneously with instrumental monitoring. The 1994–1995 lahars were relatively short events, their duration in the Boyong river commonly ranging between 30 min and 1 h 30 min. The great majority (90%) of the lahars was recognized at Kaliurang village between 13:00 and 17:30 h, due to the predominance of afternoon rainfalls. The observed mean velocity of lahar fronts ranged between 1.1 and 3.4 m/s, whereas the peak velocity of the flows varied from 11 to 15 m/s, under the Gardu Pandang viewpoint location at Kaliurang, to 8–10 m/s at a section 500 m downstream from this site. River slopes vary from 28 to 22 m/km at the two sites. Peak discharges recorded in various events ranged from 33 to 360 m3/s, with the maximum value of peak discharge 360 m3/s, on 20 May 1995. To improve the lahar warning system along Boyong river, some instrumental thresholds were proposed: large and potentially hazardous lahars may be detected by RSAM units exceeding 400, SSAM units exceeding 80 on the highest frequency band, or AFM values greater than 1500 mV on the low-gain, broad-band setting.

  15. Comparative lahar hazard mapping at Volcan Citlaltépetl, Mexico using SRTM, ASTER and DTED-1 digital topographic data

    NASA Astrophysics Data System (ADS)

    Hubbard, Bernard E.; Sheridan, Michael F.; Carrasco-Núñez, Gerardo; Díaz-Castellón, Rodolfo; Rodríguez, Sergio Raúl

    2007-02-01

    In this study, we evaluated and compared the utility of spaceborne SRTM and ASTER DEMs with baseline DTED-1 "bald-earth" topography for mapping lahar inundation hazards from volcan Citlaltépetl, Mexico, a volcano which has had a history of producing debris flows of various extents. In particular, we tested the utility of these topographic datasets for resolving ancient valley-filling deposits exposed around the flanks of the volcano, for determining their magnitude using paleohydrologic methods and for forecasting their inundation limits in the future. We also use the three datasets as inputs to a GIS stream inundation flow model, LAHARZ, and compare the results. In general all three datasets, with spatial resolution of 90 m or better, were capable of resolving debris flow and lahar deposits at least 3 × 10 6 m 3 in volume or larger. Canopy- and slope-related height errors in the ASTER and SRTM DEMs limit their utility for measuring valley-filling cross-sectional area and deriving flow magnitude for the smallest deposits using a cross-sectional area to volume scaling equation. Height errors in the ASTER and SRTM DEMs also causes problems in resolving stream valley hydrography which controls lahar flow paths and stream valley morphology which controls lahar filling capacity. However, both of the two spaceborne DEM datasets are better than DTED-1 at resolving fine details in stream hydrography and erosional morphologies of volcaniclastics preserved in the valleys around the more humid, eastern flanks of the volcanic range. The results of LAHARZ flow inundation modeling using all three DEMs as inputs are remarkably similar and co-validate one another. For example, at Citlaltépetl all lahar simulations show that the city of Orizaba is the most vulnerable to flows similar in magnitude to, or larger than, one that occurred in 1920. Many of the other cities and towns illustrated are built higher up on terrace deposits of older debris flows, and are safe from all but

  16. Digital elevation modeling via curvature interpolation for lidar data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Digital elevation model (DEM) is a three-dimensional (3D) representation of a terrain's surface - for a planet (including Earth), moon, or asteroid - created from point cloud data which measure terrain elevation. Its modeling requires surface reconstruction for the scattered data, which is an ill-p...

  17. Factors controlling erosion/deposition phenomena related to lahars at Volcán de Colima, Mexico

    NASA Astrophysics Data System (ADS)

    Vázquez, Rosario; Capra, Lucia; Coviello, Velio

    2016-08-01

    comparing rainfalls associated with lahars that originated after the last main eruptive episode that occurred in 2004-2005, we observed that higher accumulated rainfall was needed to trigger lahars in the 2013 and 2014 seasons, which points to a progressive stabilization of the volcano slope during a post-eruptive period. These results can be used as a tool to foresee the channel response to future volcanic activity, to improve the input parameters for lahar modeling and to better constrain the hazard zonation at Volcán de Colima.

  18. Quantifying the geomorphic impacts and sediment transport of a lake break-out lahar, Mt. Ruapehu, New Zealand.

    NASA Astrophysics Data System (ADS)

    Procter, J. N.; Zernack, A. V.; Fuller, I.; Philips, E.; Cronin, S. J.

    2012-04-01

    Pre- and post- LiDAR surveys analysed from the 2007 Mt. Ruapehu Crater Lake breakout lahar display the net impact a lahar has on the landscape and provides a proxy for the net sediment entrained and transported. Between 22-40 km from source, the lahar was carrying its maximum sediment load of 3x106 m3, a quantity that remained stable for this stretch of river indicating a volumetric bulking of ~2.5 times its initial starting volume. Despite maintaining a stable total quantity of sediment along this river stretch, a complex interplay of erosion and deposition continued, effectively exchanging and recycling sediment between the flow and its substrate. Controls on this exchange appear to relate to channel sinuosity, depth, width, roughness and local slope. The resulting lahar deposits comprise several discrete units that differ in grainsize, texture, thickness and distribution depending on local channel conditions and time-variant flow rheology. The dynamic flow data show a rapidly rising watery bow-wave ahead of the lahar, which emplaced bedded, moderately-sorted medium sands on middle- to high-level banks. High flow velocity and turbulence promoted erosion in near-channel sites. Overlying massive, reversely graded, very poorly-sorted sandy gravels were deposited by the highly sediment-charged main lahar body. Decrease in stage height and retreat of the concentrated flow back into the channel ceased deposition on the upper banks and initiated near-channel accumulation of thick, normally graded gravelly units at channel bends and a thin coarse sandy layer along straight sections. The final depositional stage was marked by bedded, moderately- to poorly-sorted sandy deposits in near-channel sites and initially on middle slopes, with pulses in the waning flow producing alternating layers of coarse and medium sands. The step-wise drop in flow stage resulted in simultaneous erosion of the previously deposited sediments and successive cutting of terraces. The model of

  19. Simulating Lahars Using A Rotating Drum

    NASA Astrophysics Data System (ADS)

    Neather, Adam; Lube, Gert; Jones, Jim; Cronin, Shane

    2014-05-01

    A large (0.5 m in diameter, 0.15 m wide) rotating drum is used to investigate the erosion and deposition mechanics of lahars. To systematically simulate the conditions occurring in natural mass flows our experimental setup differs from the common rotating drum employed in industrial/engineering studies. Natural materials with their typical friction properties are used, as opposed to the frequently employed spherical glass beads; the drum is completely water-proof, so solid/air and solid/liquid mixtures can be investigated; the drum velocity and acceleration can be precisely controlled using a software interface to a micro-controller, allowing for the study of steady, unsteady and intermediate flow regimes. The drum has a toughened glass door, allowing high-resolution, high-speed video recording of the material inside. Vector maps of the velocities involved in the flows are obtained using particle image velocimetry (PIV). The changes in velocity direction and/or magnitude are used to locate the primary internal boundaries between layers of opposite flow direction, as well as secondary interfaces between shear layers. A range of variables can be measured: thickness and number of layers; the curvature of the free surface; frequency of avalanching; position of the centre of mass of the material; and the velocity profiles of the flowing material. Experiments to date have focussed on dry materials, and have had a fill factor of approximately 0.3. Combining these measured variables allows us to derive additional data of interest, such as mass and momentum flux. It is these fluxes that we propose will allow insight into the erosion/deposition mechanics of a lahar. A number of conclusions can be drawn to date. A primary interface separates flowing and passive region (this interface has been identified in previous studies). As well as the primary interface, the flowing layer separates into individual shear layers, with individual erosion/deposition and flow histories. This

  20. Integrated research in constitutive modelling at elevated temperatures, part 1

    NASA Technical Reports Server (NTRS)

    Haisler, W. E.; Allen, D. H.

    1986-01-01

    Topics covered include: numerical integration techniques; thermodynamics and internal state variables; experimental lab development; comparison of models at room temperature; comparison of models at elevated temperature; and integrated software development.

  1. Digital Elevation Models of the Lunar Surface

    NASA Astrophysics Data System (ADS)

    Cook, A. C.; Robinson, M. S.

    1999-01-01

    Several digital elevation models (DEMs) have been produced at a scale of 1km/pixel and covering approximately one-fifth of the lunar surface. These were produced mostly by semiautomatically matching the stereo available between Clementine UV/VIS images, although some localized DEMs have been produced by applying this technique to Apollo Metric stereo pairs, or by digitizing an existing Apollo Metric contour map. The DEMS that result from Clementine UV/VIS images, although Of Poorer height accuracy (1300-600 in for a single matched point) than the Clementine laser altimeter point measurements (<+/-100 m), do provide considerably higher spatial resolution (e.g., every kilometer vs. every tens of kilometers) and allow topography in the polar regions to be determined. Nadir-pointing Clementine UV-VIS stereo pairs are automatically stereo matched using a patch-based matcher and fed through A stereo intersection camera model to yield a digital terrain model (DTM) of longitude, latitude, and height points. The DTM for each stereo pair is then replotted and interpolated to form map-projected DEM tiles. The DEM files can then be fitted to absolute height laser altimeter points, or iteratively to each other, to form a DEM mosaic. Uncertainties in UV-VIS camera pointing and the need to accumulate a sufficiently good topographic S/N ratio necessitates the use of 1 km pixels for the UV-VIS derived DEMs. For Apollo Metric stereo, an internal camera geometry correction and a full photogrammetric block adjustment must be performed using ground- control points to derive a DEM. The image scale of Apollo Metric, as well as the stereo angle, allow for a DEM with 100 m pixels and a height accuracy of +/- 25m. Apollo Metric imagery had previously been used to derive contour maps for much of the lunar equatorial regions; however, to recover this information in digital form these maps must be digitized. Most of the mare areas mapped contain noticeable topographic noise. This results from

  2. Model-based approach for elevator performance estimation

    NASA Astrophysics Data System (ADS)

    Esteban, E.; Salgado, O.; Iturrospe, A.; Isasa, I.

    2016-02-01

    In this paper, a dynamic model for an elevator installation is presented in the state space domain. The model comprises both the mechanical and the electrical subsystems, including the electrical machine and a closed-loop field oriented control. The proposed model is employed for monitoring the condition of the elevator installation. The adopted model-based approach for monitoring employs the Kalman filter as an observer. A Kalman observer estimates the elevator car acceleration, which determines the elevator ride quality, based solely on the machine control signature and the encoder signal. Finally, five elevator key performance indicators are calculated based on the estimated car acceleration. The proposed procedure is experimentally evaluated, by comparing the key performance indicators calculated based on the estimated car acceleration and the values obtained from actual acceleration measurements in a test bench. Finally, the proposed procedure is compared with the sliding mode observer.

  3. Alteration, slope-classified alteration, and potential lahar inundation maps of volcanoes for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Volcano Archive

    USGS Publications Warehouse

    Mars, John C.; Hubbard, Bernard E.; Pieri, David; Linick, Justin

    2015-01-01

    This study was undertaken during 2012–2013 in cooperation with the National Aeronautics and Space Administration (NASA). Since completion of this study, a new lahar modeling program (LAHAR_pz) has been released, which may produce slightly different modeling results from the LAHARZ model used in this study. The maps and data from this study should not be used in place of existing volcano hazard maps published by local authorities. For volcanoes without hazard maps and (or) published lahar-related hazard studies, this work will provide a starting point from which more accurate hazard maps can be produced. This is the first dataset to provide digital maps of altered volcanoes and adjacent watersheds that can be used for assessing volcanic hazards, hydrothermal alteration, and other volcanic processes in future studies.

  4. Topobathymetric elevation model development using a new methodology: Coastal National Elevation Database

    USGS Publications Warehouse

    Danielson, Jeffrey J.; Poppenga, Sandra; Brock, John C.; Evans, Gayla A.; Tyler, Dean; Gesch, Dean B.; Thatcher, Cindy; Barras, John

    2016-01-01

    During the coming decades, coastlines will respond to widely predicted sea-level rise, storm surge, and coastalinundation flooding from disastrous events. Because physical processes in coastal environments are controlled by the geomorphology of over-the-land topography and underwater bathymetry, many applications of geospatial data in coastal environments require detailed knowledge of the near-shore topography and bathymetry. In this paper, an updated methodology used by the U.S. Geological Survey Coastal National Elevation Database (CoNED) Applications Project is presented for developing coastal topobathymetric elevation models (TBDEMs) from multiple topographic data sources with adjacent intertidal topobathymetric and offshore bathymetric sources to generate seamlessly integrated TBDEMs. This repeatable, updatable, and logically consistent methodology assimilates topographic data (land elevation) and bathymetry (water depth) into a seamless coastal elevation model. Within the overarching framework, vertical datum transformations are standardized in a workflow that interweaves spatially consistent interpolation (gridding) techniques with a land/water boundary mask delineation approach. Output gridded raster TBDEMs are stacked into a file storage system of mosaic datasets within an Esri ArcGIS geodatabase for efficient updating while maintaining current and updated spatially referenced metadata. Topobathymetric data provide a required seamless elevation product for several science application studies, such as shoreline delineation, coastal inundation mapping, sediment-transport, sea-level rise, storm surge models, and tsunami impact assessment. These detailed coastal elevation data are critical to depict regions prone to climate change impacts and are essential to planners and managers responsible for mitigating the associated risks and costs to both human communities and ecosystems. The CoNED methodology approach has been used to construct integrated TBDEM models

  5. Influence of Elevation Data Source on 2D Hydraulic Modelling

    NASA Astrophysics Data System (ADS)

    Bakuła, Krzysztof; StĘpnik, Mateusz; Kurczyński, Zdzisław

    2016-08-01

    The aim of this paper is to analyse the influence of the source of various elevation data on hydraulic modelling in open channels. In the research, digital terrain models from different datasets were evaluated and used in two-dimensional hydraulic models. The following aerial and satellite elevation data were used to create the representation of terrain-digital terrain model: airborne laser scanning, image matching, elevation data collected in the LPIS, EuroDEM, and ASTER GDEM. From the results of five 2D hydrodynamic models with different input elevation data, the maximum depth and flow velocity of water were derived and compared with the results of the most accurate ALS data. For such an analysis a statistical evaluation and differences between hydraulic modelling results were prepared. The presented research proved the importance of the quality of elevation data in hydraulic modelling and showed that only ALS and photogrammetric data can be the most reliable elevation data source in accurate 2D hydraulic modelling.

  6. Rain-triggered lahars following the 2010 eruption of Merapi volcano, Indonesia: A major risk

    NASA Astrophysics Data System (ADS)

    de Bélizal, Edouard; Lavigne, Franck; Hadmoko, Danang Sri; Degeai, Jean-Philippe; Dipayana, Gilang Aria; Mutaqin, Bachtiar Wahyu; Marfai, Muh Aris; Coquet, Marie; Mauff, Baptiste Le; Robin, Anne-Kyria; Vidal, Céline; Cholik, Noer; Aisyah, Nurnaning

    2013-07-01

    The 2010 VEI 4 eruption of Merapi volcano deposited roughly ten times the volume of pyroclastic materials of the 1994 and 2006 eruptions, and is recognized as one of the most intense eruption since 1872. However, as the eruptive phase is now over, another threat endangers local communities: rain-triggered lahars. Previous papers on lahars at Merapi presented lahar-related risk following small-scale dome-collapse PDCs. Thus the aim of this study is to provide new insights on lahar-related risk following a large scale VEI 4 eruption. The paper highlights the high number of events (240) during the 2010-2011 rainy season (October 2010-May 2011). The frequency of the 2010-2011 lahars is also the most important ever recorded at Merapi. Lahars occurred in almost all drainages located under the active cone, with runout distances exceeding 15 km. The geomorphic impacts of lahars on the distal slope of the volcano are then explained as they directly threaten houses and infrastructures: creation of large corridors, avulsions, riverbank erosion and riverbed downcutting are detailed through local scale examples. Related damage is also studied: 860 houses damaged, 14 sabo-dams and 21 bridges destroyed. Sedimentological characteristics of volcaniclastic sediments in lahar corridors are presented, with emphasis on the resource in building material that they represent for local communities. Risk studies should not forget that thousands of people are exposing themselves to lahar hazard when they quarry volcaniclastic sediment on lahar corridors. Finally, the efficient community-based crisis management is explained, and shows how local people organize themselves to manage the risk: 3 fatalities were reported, although lahars reached densely populated areas. To summarize, this study provides an update of lahar risk issues at Merapi, with emphasis on the distal slope of the volcano where lahars had not occurred for 40 years, and where lahar corridors were rapidly formed.

  7. Elevation control system model for the DSS 13 antenna

    NASA Technical Reports Server (NTRS)

    Gawronski, W.; Mellstrom, J. A.

    1991-01-01

    In order to meet the requirements for precision pointing of 34-m antennas, adequate control design and simulation software have to be developed along with a detailed description of the supporting analytical tools. This article describes a control system model for the elevation drive of the DSS 13 antenna. The model allows one to simulate elevation dynamics, cross-coupled dynamics in azimuth and elevation, and RF pointing error. A modal state-space model of the antenna structure was obtained from its finite-element model with a free rotating tipping structure. Model reduction techniques were applied separately for the antenna model and rate-loop model, thereby reducing the system order to one-third of the original one while preserving its dynamic properties. Extensive simulation results illustrate properties of the model.

  8. Farmland terrace slope detection from Pleiades digital elevation models

    NASA Astrophysics Data System (ADS)

    Bailly, Jean-Stephane; Sofia, Giulia; Chehata, Nesrine; Tarolli, Paolo; Levavasseur, Florent

    2015-04-01

    The automatic mapping of terrace slopes in terraced landscape from remote sensing is still an open question. Among remote sensing data, high resolution digital elevation models appear obviously as the required data to perform such automatic mapping. Pleiades satellite constellation, with its agility, provide new highly resoluted digital elevation models with metric resolution. The objective of this work is to quantify the performances of Pleiades DEMs in Farmland terrace slope mapping. Detection of terrace slopes are performed comparing two existing methods : one using the Fast Line Segment Detector algorithm and the other using curvature thresholding. The obtained detection performances on a South of France farmland landscape are compared using a surface model or a terrain model, and in comparison with LiDAR models. Results show that, despite having lower performances than LiDAR models, Pleiades metric elevation models, even surface models allow the automatic detection of terraces slopes higher than 2 meters.

  9. Evaluation Digital Elevation Model Generated by Synthetic Aperture Radar Data

    NASA Astrophysics Data System (ADS)

    Makineci, H. B.; Karabörk, H.

    2016-06-01

    Digital elevation model, showing the physical and topographical situation of the earth, is defined a tree-dimensional digital model obtained from the elevation of the surface by using of selected an appropriate interpolation method. DEMs are used in many areas such as management of natural resources, engineering and infrastructure projects, disaster and risk analysis, archaeology, security, aviation, forestry, energy, topographic mapping, landslide and flood analysis, Geographic Information Systems (GIS). Digital elevation models, which are the fundamental components of cartography, is calculated by many methods. Digital elevation models can be obtained terrestrial methods or data obtained by digitization of maps by processing the digital platform in general. Today, Digital elevation model data is generated by the processing of stereo optical satellite images, radar images (radargrammetry, interferometry) and lidar data using remote sensing and photogrammetric techniques with the help of improving technology. One of the fundamental components of remote sensing radar technology is very advanced nowadays. In response to this progress it began to be used more frequently in various fields. Determining the shape of topography and creating digital elevation model comes the beginning topics of these areas. It is aimed in this work , the differences of evaluation of quality between Sentinel-1A SAR image ,which is sent by European Space Agency ESA and Interferometry Wide Swath imaging mode and C band type , and DTED-2 (Digital Terrain Elevation Data) and application between them. The application includes RMS static method for detecting precision of data. Results show us to variance of points make a high decrease from mountain area to plane area.

  10. The anatomy of a lahar: Deciphering the 15th September 2012 lahar at Volcán de Colima, Mexico

    NASA Astrophysics Data System (ADS)

    Vázquez, R.; Capra, L.; Caballero, L.; Arámbula-Mendoza, R.; Reyes-Dávila, G.

    2014-02-01

    Volcán de Colima is one of the most active volcanoes in Mexico where lahars are a common phenomenon. Since the reactivation of the volcanic activity in 1991, lahars have become more frequent during the June-October rainy season, in this region. Therefore, Volcán de Colima represents a natural laboratory, ideal for the constant monitoring of lahars and to study factors controlling their origin, flow transport and deposition. Since 2007 the systematic detection of lahars in Volcán de Colima has been carried out using seismic data from the broadband stations of the RESCO network, the seismological network of Colima University, along with three rain gauge stations located on the southern ravines of the volcano. In 2011 a new monitoring station was built at 2000 m.a.s.l. along the Montegrande ravine, which consists of a geophone, a video camera and a rain gauge station coupled with a moisture sensor, transmitting in real time to the RESCO facilities at Colima University. With all the instrumentation currently installed on the volcano flanks, we could monitor and describe the lahar that occurred on 15th September 2012 along the Montegrande ravine, and correlate the monitoring data with information gathered by the field campaign conducted two days after the event. The high quality of collected data enabled us to describe the “anatomy” of this lahar. The event consisted of a lahar that lasted 40 min, triggered by 20 mm of accumulated rainfall with a maximum intensity of 95 mm/h. The lahar was characterized by three main surges at 4-5 minute intervals that formed an 80 cm-thick terrace. The first surge was a debris flow with a block-rich front followed by the main body that progressively diluted to a hyperconcentrated flow, from which a 40 cm-thick massive unit was emplaced (33 wt.% gravel and > 60 wt.% of sand); it was followed by a more dilute hyperconcentrated flow that left a massive 10 cm-thick sandy layer (80 wt.% of sand); the third surge deposited a 30-cm

  11. The effects of wavelet compression on Digital Elevation Models (DEMs)

    USGS Publications Warehouse

    Oimoen, M.J.

    2004-01-01

    This paper investigates the effects of lossy compression on floating-point digital elevation models using the discrete wavelet transform. The compression of elevation data poses a different set of problems and concerns than does the compression of images. Most notably, the usefulness of DEMs depends largely in the quality of their derivatives, such as slope and aspect. Three areas extracted from the U.S. Geological Survey's National Elevation Dataset were transformed to the wavelet domain using the third order filters of the Daubechies family (DAUB6), and were made sparse by setting 95 percent of the smallest wavelet coefficients to zero. The resulting raster is compressible to a corresponding degree. The effects of the nulled coefficients on the reconstructed DEM are noted as residuals in elevation, derived slope and aspect, and delineation of drainage basins and streamlines. A simple masking technique also is presented, that maintains the integrity and flatness of water bodies in the reconstructed DEM.

  12. A Unified Low-Elevation-Angle Scintillation Model

    NASA Astrophysics Data System (ADS)

    Lee, C. H.; Cheung, K.-M.; Ho, C.

    2011-05-01

    Enabling communications at very low elevation angles can lengthen the duration of a tracking pass between a satellite and a ground station, which in turn can increase the amount of data return and possibly reduce the number of required supporting ground station tracking passes. Link performance, especially at very low angles and high frequencies, depends heavily on terrain, atmosphere, and weather conditions. Among the different contributions to attenuation, scintillation fading plays a very significant role and can impair the performance of the link. It is therefore necessary to accurately model the overall impact to the link due to scintillation fading. The current International Telecommunication Union ITU-R P.618-10 Recommendation describes three scintillation loss models as a function of elevation angle and percentage of time for which the loss exceeds a certain threshold. Implementation of the recommendation resulted in the uncovering of several issues. Particularly, it was identified that (i) iterative solutions to an implicit nonlinear exponential model, in some cases, are not guaranteed to exist, (ii) there is a discontinuity in fading values between models at the cross-over elevation angle, (iii) at certain low elevation angles scintillation from the shallow fade model generates unrealistically small losses, and (iv) for elevation angles lying between 4 and 5 deg, there are two applicable scintillation models that yield conflicting values. In this article, we develop a new approach to unify the different fading models within the current ITU recommendation and fully remove the discrepancies. We further validated our models with ITU-adopted scintillation data measured at Goonhilly, Great Britain, and data from several recent NASA Space Shuttle launches. This improved model was provisionally approved at the ITU International Meeting in Italy, November 2010, and is being evaluated by the ITU members for adoption into the next-version ITU Recommendation.

  13. Modeling low elevation GPS signal propagation in maritime atmospheric ducts

    NASA Astrophysics Data System (ADS)

    Zhang, Jinpeng; Wu, Zhensen; Wang, Bo; Wang, Hongguang; Zhu, Qinglin

    2012-05-01

    Using the parabolic wave equation (PWE) method, we model low elevation GPS L1 signal propagation in maritime atmospheric ducts. To consider sea surface impedance, roughness, and the effects of earth's curvature, we propose a new initial field model for the GPS PWE split-step solution. On the basis of the comparison between the proposed model and the conventional initial field model for a smooth, perfectly conducting sea surface on a planar earth, we conclude that both the amplitude and phase of the initial field are influenced by surface impedance and roughness, and that the interference behavior between direct and reflected GPS rays is affected by earth's curvature. The performance of the proposed model is illustrated with examples of low elevation GPS L1 signal propagation in three types of ducts: an evaporation duct, a surface-based duct, and an elevated duct. The GPS PWE is numerically implemented using the split-step discrete mixed Fourier transform algorithm to enforce impedance-type boundary conditions at the rough sea surface. Because the GPS signal is right hand circularly polarized, we calculate its power strength by combining the propagation predictions of the horizontally and the vertically polarized components. The effects of the maritime atmospheric ducts on low elevation GPS signal propagation are demonstrated according to the presented examples, and the potential applications of the GPS signals affected by ducts are discussed.

  14. Mechanism of sand slide - cold lahar induced by extreme rainfall

    NASA Astrophysics Data System (ADS)

    Fukuoka, Hiroshi; Yamada, Masumi; Dok, Atitkagna

    2014-05-01

    Along with the increasing frequencies of extreme rainfall events in almost every where on the earth, shallow slide - debris flow, i.e. cold lahars running long distance often occurs and claims downslope residents lives. In the midnight of 15 October 2013, Typhoon Wilpha attacked the Izu-Oshima, a active volcanic Island and the extreme rainfall of more than 800 mm / 24 hours was recorded. This downpour of more than 80 mm/hr lasted 4 hours at its peak and caused a number of cold lahars. The initial stage of those lahars was shallow slides of surface black volcanic ash deposits, containing mostly fine sands. The thickness was only 50 cm - 1 m. In the reconnaissance investigation, author found that the sliding surface was the boundary of two separate volcanic ash layers between the black and yellow colored and apparently showing contrast of permeability and hardness. Permeability contrast may have contributed to generation of excess pore pressure on the border and trigger the slide. Then, the unconsolidated, unpacked mass was easily fluidized and transformed into mud flows, that which volcanologists call cold lahars. Seismometers installed for monitoring the active volcano's activities, succeeded to detect many tremors events. Many are spikes but 5 larger and longer events were extracted. They lasted 2 -3 minutes and if we assume that this tremors reflects the runout movement, then we can calculate the mean velocity of the lahars. Estimated velocity was 45 - 60 km/h, which is much higher than the average speed 30 - 40 km/h of debris flows observed in Japan. Flume tests of volcanic ash flows by the Forestry and Forest Products Research Institute showed the wet volcanic ash can run at higher speed than other materials. The two tremor records were compare d with the local residents witnessed and confirmed by newspaper reported that the reach of the lahar was observed at the exact time when tremor ends. We took the black volcanic ash and conducted ring shear tests to

  15. How processing digital elevation models can affect simulated water budgets.

    PubMed

    Kuniansky, Eve L; Lowery, Mark A; Campbell, Bruce G

    2009-01-01

    For regional models, the shallow water table surface is often used as a source/sink boundary condition, as model grid scale precludes simulation of the water table aquifer. This approach is appropriate when the water table surface is relatively stationary. Since water table surface maps are not readily available, the elevation of the water table used in model cells is estimated via a two-step process. First, a regression equation is developed using existing land and water table elevations from wells in the area. This equation is then used to predict the water table surface for each model cell using land surface elevation available from digital elevation models (DEM). Two methods of processing DEM for estimating the land surface for each cell are commonly used (value nearest the cell centroid or mean value in the cell). This article demonstrates how these two methods of DEM processing can affect the simulated water budget. For the example presented, approximately 20% more total flow through the aquifer system is simulated if the centroid value rather than the mean value is used. This is due to the one-third greater average ground water gradients associated with the centroid value than the mean value. The results will vary depending on the particular model area topography and cell size. The use of the mean DEM value in each model cell will result in a more conservative water budget and is more appropriate because the model cell water table value should be representative of the entire cell area, not the centroid of the model cell.

  16. Dendrogeomorphic reconstruction of lahar activity and triggers: Shiveluch volcano, Kamchatka Peninsula, Russia

    NASA Astrophysics Data System (ADS)

    Salaorni, E.; Stoffel, M.; Tutubalina, O.; Chernomorets, S.; Seynova, I.; Sorg, A.

    2017-01-01

    Lahars are highly concentrated, water-saturated volcanic hyperconcentrated flows or debris flows containing pyroclastic material and are a characteristic mass movement process on volcanic slopes. On Kamchatka Peninsula (Russian Federation), lahars are widespread and may affect remote settlements. Historical records of past lahar occurrences are generally sparse and mostly limited to events which damaged infrastructure on the slopes or at the foot of volcanoes. In this study, we present a tree-ring-based reconstruction of spatiotemporal patterns of past lahar activity at Shiveluch volcano. Using increment cores and cross sections from 126 Larix cajanderi trees, we document 34 events covering the period AD 1729-2012. Analyses of the seasonality of damage in trees reveal that 95% of all lahars occurred between October and May and thus point to the predominant role of the sudden melt of the snow cover by volcanic material. These observations suggest that most lahars were likely syn-eruptive and that lahar activity is largely restricted to periods of volcanic activity. By contrast, rainfall events do not seem to play a significant role in lahar triggering.

  17. Elevator model based on a tiny PLC for teaching automation

    NASA Astrophysics Data System (ADS)

    Kim, Kee Hwan; Lee, Young Dae

    2005-12-01

    The development of control related applications requires knowledge of different subject matters like mechanical components, control equipment and physics. To understand the behavior of these heterogeneous applications is not easy especially the students who begin to study the electronic engineering. In order to introduce to them the most common components and skills necessary to put together a functioning automated system, we have designed a simple elevator model controlled by a PLC which was designed based on a microcontroller.

  18. Lahar infrasound associated with Volcán Villarrica's 3 March 2015 eruption

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey B.; Palma, Jose L.

    2015-08-01

    The paroxysmal 2015 eruption of Volcán Villarrica (Chile) produced a 2.5 h long lahar, which descended more than 20 km within the Rio Correntoso/Turbio drainage and destroyed two small bridges. A three-element infrasound array 10 km from the summit, and 4 km from the lahar's closest approach, was used to study the flow's progression. Array processing using cross-correlation lag times and semblance places constraints on the lahar's dynamics, including detection of an initial flow pulse that traveled from 2 to 12 km at an average speed of 38 m/s. Subsequently, the lahar signal evolved to a relatively stationary infrasonic tremor located 10 to 12 km from the vent and adjacent to a topographic notch, through which sound may have preferentially diffracted toward the recording site. This study demonstrates the powerful capabilities of infrasound arrays for lahar study and suggests their potential application for future hazard monitoring.

  19. Causes, Dynamics and Impacts of Lahars Generated by the April, 2015 Calbuco Eruption, Chile.

    NASA Astrophysics Data System (ADS)

    Russell, A. J.; Dussaillant, A. R.; Meier, C. I.; Rivera, A.; Barra, M. M.; Urzua, N. G.; Hernandez, J. F.; Napoleoni, F.; Gonzalez, C.

    2015-12-01

    Calbuco is a 2015m high, glacier capped, stratovolcano in the heavily populated Los Lagos district of southern Chile with a history of large volcanic eruptions in 1893-95, 1906-7, 1911-12, 1917, 1932, 1945, 1961 and 1972. Calbuco experienced a powerful 90 minute eruption at 18:04h on 22 April, 2015 followed by additional major eruptions at 01:00h and 13:10h on 23 & 30 April, respectively, resulting in the evacuation of 6500 people and the imposition of a 20 km radius exclusion zone. Pyroclastic flows descended into several river catchments radiating from the volcano with lahars travelling distances of up to 14 km, reaching populated areas. We present preliminary findings regarding the causes, dynamics and impacts of lahars generated by the April 2015 eruption. Pyroclastic flows melted glacier ice and snow generating the largest lahars in the Rio Este and Rio Blanco Sur on the southern flanks of the volcano. Lahar deposits in the Rio Blanco Norte were buried by pyroclastic flow deposits with measured temperatures of up to 282°C three months after emplacement. Lahar erosional impacts included bedrock erosion, alluvial channel incision, erosion of surficial deposits and the felling of large areas of forest. Depositional landforms included boulder run-ups on the outsides of channel bends, boulder clusters and large woody debris jams. Lahars deposited up to 8m of sediment within distal reaches. Deposits on the southern flanks of Calbuco indicate the passage of multiple pulses of contrasting rheology. Lahar occurrence and magnitude was controlled by the pre-eruption distribution of snow and ice on the volcano. Pre-existing lahar channels controlled flows to lower piedmont zones where routing was determined by palaeo lahar geomorphology. Ongoing erosion of proximal pyroclastic flow and lahar deposits provides large volumes of sediment to distal portions of fluvial systems radiating from Calbuco.

  20. A wind model for an elevated STOL-port configuration

    NASA Technical Reports Server (NTRS)

    Peterka, J. A.; Cermak, J. E.

    1974-01-01

    Measurements of mean velocity magnitude and direction as well as three-dimensional turbulence intensity were made in the flow over a model of an elevated STOL-port. A 1:300 scale model was placed in a wind tunnel flow simulating the mean velocity profile and turbulence characteristics of atmospheric winds over a typical city environment excluding detailed wake structures of possible nearby buildings. Hot-wire anemometer measurements of velocity and turbulence were made along approach and departure paths of aircraft operating on the runway centerline and at specified lateral distances from the centerline. Approach flow directions simulated were 0 and 30 degrees to the runway centerline.

  1. Elevated temperature alters carbon cycling in a model microbial community

    NASA Astrophysics Data System (ADS)

    Mosier, A.; Li, Z.; Thomas, B. C.; Hettich, R. L.; Pan, C.; Banfield, J. F.

    2013-12-01

    Earth's climate is regulated by biogeochemical carbon exchanges between the land, oceans and atmosphere that are chiefly driven by microorganisms. Microbial communities are therefore indispensible to the study of carbon cycling and its impacts on the global climate system. In spite of the critical role of microbial communities in carbon cycling processes, microbial activity is currently minimally represented or altogether absent from most Earth System Models. Method development and hypothesis-driven experimentation on tractable model ecosystems of reduced complexity, as presented here, are essential for building molecularly resolved, benchmarked carbon-climate models. Here, we use chemoautotropic acid mine drainage biofilms as a model community to determine how elevated temperature, a key parameter of global climate change, regulates the flow of carbon through microbial-based ecosystems. This study represents the first community proteomics analysis using tandem mass tags (TMT), which enable accurate, precise, and reproducible quantification of proteins. We compare protein expression levels of biofilms growing over a narrow temperature range expected to occur with predicted climate changes. We show that elevated temperature leads to up-regulation of proteins involved in amino acid metabolism and protein modification, and down-regulation of proteins involved in growth and reproduction. Closely related bacterial genotypes differ in their response to temperature: Elevated temperature represses carbon fixation by two Leptospirillum genotypes, whereas carbon fixation is significantly up-regulated at higher temperature by a third closely related genotypic group. Leptospirillum group III bacteria are more susceptible to viral stress at elevated temperature, which may lead to greater carbon turnover in the microbial food web through the release of viral lysate. Overall, this proteogenomics approach revealed the effects of climate change on carbon cycling pathways and other

  2. Validation of Orthorectified Interferometric Radar Imagery and Digital Elevation Models

    NASA Technical Reports Server (NTRS)

    Smith Charles M.

    2004-01-01

    This work was performed under NASA's Verification and Validation (V&V) Program as an independent check of data supplied by EarthWatch, Incorporated, through the Earth Science Enterprise Scientific Data Purchase (SDP) Program. This document serves as the basis of reporting results associated with validation of orthorectified interferometric interferometric radar imagery and digital elevation models (DEM). This validation covers all datasets provided under the first campaign (Central America & Virginia Beach) plus three earlier missions (Indonesia, Red River: and Denver) for a total of 13 missions.

  3. Registering Thematic Mapper imagery to digital elevation models

    NASA Technical Reports Server (NTRS)

    Frew, J.

    1984-01-01

    The problems encountered when attempting to register Landsat Thematic Mapper (TM) data to U.S. geological survey digital elevation models (DEMs) are examined. It is shown that TM and DEM data are not available in the same map projection, necessitating geometric transformation of one of the data type, that the TM data are not accurately located in their nominal projection, and that TM data have higher resolution than most DEM data, but oversampling the DEM data to TM resolution introduces systematic noise. Further work needed in this area is discussed.

  4. Characteristics of the syneruptive-spouted type lahar generated by the September 2014 eruption of Mount Ontake, Japan

    NASA Astrophysics Data System (ADS)

    Sasaki, Hisashi; Chiba, Tatsuro; Kishimoto, Hiroshi; Naruke, Shino

    2016-08-01

    Mount Ontake erupted at 11:52 am on September 27, 2014, which generated pyroclastic density currents, ballistic projectiles, ash falls, and a small-scale lahar that spouted directly from craters formed by the eruption. Because this lahar may have been generated by water released from within these craters, we refer to this lahar as a "syneruptive-spouted type lahar" in this study. The lahar of the 2014 eruption was small relative to the other syneruptive type lahars reported in the past that were snowmelt type or crater lake breakout type lahars. Nevertheless, in the 2014 event, the syneruptive-spouted type lahar extended approximately 5 km downstream from the Jigokudani crater via the Akagawa River, with an estimated total volume of ~1.2 × 105 m3. We have reviewed other representative syneruptive-spouted type lahars that have been reported in Japan. The syneruptive-spouted type lahar attributed to the September 2014 eruption had the longest runout distance and largest volume of all cases studied. The mineral assemblage identified from samples of the lahar deposits is similar to that of ash-fall deposits from the same eruption. Previous workers deduced that the ash was derived mainly from shallow depths (within 2 km of the surface). The syneruptive-spouted type lahar deposits are therefore also considered to have originated from shallow depths. A syneruptive-spouted type lahar is a small-scale phenomenon that causes little direct damage to infrastructure, but has long-term influence on water quality. Increases in turbidity and decreases in pH are expected to occur in the Mount Ontake area downstream of Nigorisawa after heavy rainfall events in the future. Therefore, the potential indirect (but long term) damage of syneruptive-spouted type lahars should be considered for hazard mapping and planning volcanic disaster prevention measures.

  5. Variations in population exposure and sensitivity to lahar hazards from Mount Rainier, Washington

    USGS Publications Warehouse

    Wood, N.; Soulard, C.

    2009-01-01

    Although much has been done to understand, quantify, and delineate volcanic hazards, there are fewer efforts to assess societal vulnerability to these hazards, particularly demographic differences in exposed populations or spatial variations in exposure to regional hazards. To better understand population diversity in volcanic hazard zones, we assess the number and types of people in a single type of hazard zone (lahars) for 27 communities downstream of Mount Rainier, Washington (USA). Using various socioeconomic and hazard datasets, we estimate that there are more than 78 000 residents, 59 000 employees, several dependent-population facilities (e.g., child-day-care centers, nursing homes) and numerous public venues (e.g., churches, hotels, museums) in a Mount Rainier lahar-hazard zone. We find that communities vary in the primary category of individuals in lahar-prone areas-exposed populations are dominated by residents in some communities (e.g., Auburn), employees in others (e.g., Tacoma), and tourists likely outnumber both of these groups in yet other areas (e.g., unincorporated Lewis County). Population exposure to potential lahar inundation varies considerably-some communities (e.g., Auburn) have large numbers of people but low percentages of them in hazard zones, whereas others (e.g., Orting) have fewer people but they comprise the majority of a community. A composite lahar-exposure index is developed to help emergency managers understand spatial variations in community exposure to lahars and results suggest that Puyallup has the highest combination of high numbers and percentages of people and assets in lahar-prone areas. Risk education and preparedness needs will vary based on who is threatened by future lahars, such as residents, employees, tourists at a public venue, or special-needs populations at a dependent-care facility. Emergency managers must first understand the people whom they are trying to prepare before they can expect these people to take

  6. Variations in population exposure and sensitivity to lahar hazards from Mount Rainier, Washington

    NASA Astrophysics Data System (ADS)

    Wood, Nathan; Soulard, Christopher

    2009-12-01

    Although much has been done to understand, quantify, and delineate volcanic hazards, there are fewer efforts to assess societal vulnerability to these hazards, particularly demographic differences in exposed populations or spatial variations in exposure to regional hazards. To better understand population diversity in volcanic hazard zones, we assess the number and types of people in a single type of hazard zone (lahars) for 27 communities downstream of Mount Rainier, Washington (USA). Using various socioeconomic and hazard datasets, we estimate that there are more than 78 000 residents, 59 000 employees, several dependent-population facilities (e.g., child-day-care centers, nursing homes) and numerous public venues (e.g., churches, hotels, museums) in a Mount Rainier lahar-hazard zone. We find that communities vary in the primary category of individuals in lahar-prone areas—exposed populations are dominated by residents in some communities (e.g., Auburn), employees in others (e.g., Tacoma), and tourists likely outnumber both of these groups in yet other areas (e.g., unincorporated Lewis County). Population exposure to potential lahar inundation varies considerably—some communities (e.g., Auburn) have large numbers of people but low percentages of them in hazard zones, whereas others (e.g., Orting) have fewer people but they comprise the majority of a community. A composite lahar-exposure index is developed to help emergency managers understand spatial variations in community exposure to lahars and results suggest that Puyallup has the highest combination of high numbers and percentages of people and assets in lahar-prone areas. Risk education and preparedness needs will vary based on who is threatened by future lahars, such as residents, employees, tourists at a public venue, or special-needs populations at a dependent-care facility. Emergency managers must first understand the people whom they are trying to prepare before they can expect these people to take

  7. Variations in community exposure to lahar hazards from multiple volcanoes in Washington State (USA)

    USGS Publications Warehouse

    Diefenbach, Angela K.; Wood, Nathan J.; Ewert, John W.

    2015-01-01

    Understanding how communities are vulnerable to lahar hazards provides critical input for effective design and implementation of volcano hazard preparedness and mitigation strategies. Past vulnerability assessments have focused largely on hazards posed by a single volcano, even though communities and officials in many parts of the world must plan for and contend with hazards associated with multiple volcanoes. To better understand community vulnerability in regions with multiple volcanic threats, we characterize and compare variations in community exposure to lahar hazards associated with five active volcanoes in Washington State, USA—Mount Baker, Glacier Peak, Mount Rainier, Mount Adams and Mount St. Helens—each having the potential to generate catastrophic lahars that could strike communities tens of kilometers downstream. We use geospatial datasets that represent various population indicators (e.g., land cover, residents, employees, tourists) along with mapped lahar-hazard boundaries at each volcano to determine the distributions of populations within communities that occupy lahar-prone areas. We estimate that Washington lahar-hazard zones collectively contain 191,555 residents, 108,719 employees, 433 public venues that attract visitors, and 354 dependent-care facilities that house individuals that will need assistance to evacuate. We find that population exposure varies considerably across the State both in type (e.g., residential, tourist, employee) and distribution of people (e.g., urban to rural). We develop composite lahar-exposure indices to identify communities most at-risk and communities throughout the State who share common issues of vulnerability to lahar-hazards. We find that although lahars are a regional hazard that will impact communities in different ways there are commonalities in community exposure across multiple volcanoes. Results will aid emergency managers, local officials, and the public in educating at-risk populations and developing

  8. Void-Filled SRTM Digital Elevation Model of Afghanistan

    USGS Publications Warehouse

    Chirico, Peter G.; Barrios, Boris

    2005-01-01

    EXPLANATION The purpose of this data set is to provide a single consistent elevation model to be used for national scale mapping, GIS, remote sensing applications, and natural resource assessments for Afghanistan's reconstruction. For 11 days in February of 2000, the National Aeronautics and Space Administration (NASA), the National Geospatial-Intelligence Agency ian Space Agency (ASI) flew X-band and C-band radar interferometry onboard the Space Shuttle Endeavor. The mission covered the Earth between 60?N and 57?S and will provide interferometric digital elevation models (DEMs) of approximately 80% of the Earth's land mass when processing is complete. The radar-pointing angle was approximately 55? at scene center. Ascending and descending orbital passes generated multiple interferometric data scenes for nearly all areas. Up to eight passes of data were merged to form the final processed Shuttle Radar Topography Mission (SRTM) DEMs. The effect of merging scenes averages elevation values recorded in coincident scenes and reduces, but does not completely eliminate, the amount of area with layover and terrain shadow effects. The most significant form of data processing for the Afghanistan DEM was gap-filling areas where the SRTM data contained a data void. These void areas are as a result of radar shadow, layover, standing water, and other effects of terrain as well as technical radar interferometry phase unwrapping issues. To fill these gaps, topographic contours were digitized from 1:200,000 - scale Soviet General Staff Topographic Maps which date from the middle to late 1980's. Digital contours were gridded to form elevation models for void areas and subsequently were merged with the SRTM data through GIS and image processing techniques. The data contained in this publication includes SRTM DEM quadrangles projected and clipped in geographic coordinates for the entire country. An index of all available SRTM DEM quadrangles is displayed here: Index_Geo_DD.pdf. Also

  9. Integrated firn elevation change model for glaciers and ice caps

    NASA Astrophysics Data System (ADS)

    Saß, Björn; Sauter, Tobias; Braun, Matthias

    2016-04-01

    We present the development of a firn compaction model in order to improve the volume to mass conversion of geodetic glacier mass balance measurements. The model is applied on the Arctic ice cap Vestfonna. Vestfonna is located on the island Nordaustlandet in the north east of Svalbard. Vestfonna covers about 2400 km² and has a dome like shape with well-defined outlet glaciers. Elevation and volume changes measured by e.g. satellite techniques are becoming more and more popular. They are carried out over observation periods of variable length and often covering different meteorological and snow hydrological regimes. The elevation change measurements compose of various components including dynamic adjustments, firn compaction and mass loss by downwasting. Currently, geodetic glacier mass balances are frequently converted from elevation change measurements using a constant conversion factor of 850 kg m-³ or the density of ice (917 kg m-³) for entire glacier basins. However, the natural conditions are rarely that static. Other studies used constant densities for the ablation (900 kg m-³) and accumulation (600 kg m-³) areas, whereby density variations with varying meteorological and climate conditions are not considered. Hence, each approach bears additional uncertainties from the volume to mass conversion that are strongly affected by the type and timing of the repeat measurements. We link and adapt existing models of surface energy balance, accumulation and snow and firn processes in order to improve the volume to mass conversion by considering the firn compaction component. Energy exchange at the surface is computed by a surface energy balance approach and driven by meteorological variables like incoming short-wave radiation, air temperature, relative humidity, air pressure, wind speed, all-phase precipitation, and cloud cover fraction. Snow and firn processes are addressed by a coupled subsurface model, implemented with a non-equidistant layer discretisation. On

  10. From digital elevation model data to terrain depiction data

    NASA Astrophysics Data System (ADS)

    Helmetag, Arnd; Smietanski, Guillaume; Baumgart, Michael; Kubbat, Wolfgang

    1999-07-01

    The analysis of accidents focused our work on the avoidance of 'Controlled Flight Into Terrain' caused by insufficient situation awareness. Analysis of safety concepts led us to the design of the proposed synthetic vision system that will be described. Since most information on these 3D-Displays is shown in a graphical way, it can intuitively be seized by the pilot. One key element of SVS is terrain depiction, that is the topic of this paper. Real time terrain depiction has to face two requirements. On the one hand spatial awareness requires recognition of synthetic environment demanding characteristics. On the other hand the number of rendered polygons has to be minimized due to limitations of real time image generation performance. Visual quality can significantly be enhanced if equidistant data like Digital Elevation Model data (DEM) are vectorized. One method of data vectorization will be explained in detail and advantages will be mentioned. In Virtual Reality (VR) applications, conventional decimation software degrades the visual quality of geometry that is compensated by complex textures and lighting. Since terrain decimated with those tools looses its characteristics, and textures are not acceptable for several reasons, a terrain specific decimation has to be performed. How can a Digital Elevation Model (DEM) be decimated without decreasing the visualization value? In this paper, extraction of terrain characteristics and adapted decimation will be proposed. Steps from DEM to Terrain Depiction Data (TDD) are discussed in detail.

  11. Preparation of the Digital Elevation Model for Orthophoto CR Production

    NASA Astrophysics Data System (ADS)

    Švec, Z.; Pavelka, K.

    2016-06-01

    The Orthophoto CR is produced in co-operation with the Land Survey Office and the Military Geographical and Hydrometeorological Office. The product serves to ensure a defence of the state, integrated crisis management, civilian tasks in support of the state administration and the local self-government of the Czech Republic as well. It covers the whole area of the Republic and for ensuring its up-to-datedness is reproduced in the biennial period. As the project is countrywide, it keeps the project within the same parameters in urban and rural areas as well. Due to economic reasons it cańt be produced as a true ortophoto because it requires large side and forward overlaps of the aerial photographs and a preparation of the digital surface model instead of the digital terrain model. Use of DTM without some objects of DSM for orthogonalization purposes cause undesirable image deformations in the Orthophoto. There are a few data sets available for forming a suitable elevation model. The principal source should represent DTMs made from data acquired by the airborne laser scanning of the entire area of the Czech Republic that was carried out in the years 2009-2013, the DMR4G in the grid form and the DMR5G in TIN form respectively. It can be replenished by some vector objects (bridges, dams, etc.) taken from the geographic base data of the Czech Republic or obtained by new stereo plotting. It has to be taken into account that the option of applying DSM made from image correlation is also available. The article focuses on the possibilities of DTM supplement for ortogonalization. It looks back to the recent transition from grid to hybrid elevation models, problems that occurred, its solution and getting some practical remarks. Afterwards it assesses the current state and deals with the options for updating the model. Some accuracy analysis are included.

  12. Object-oriented classification of drumlins from digital elevation models

    NASA Astrophysics Data System (ADS)

    Saha, Kakoli

    Drumlins are common elements of glaciated landscapes which are easily identified by their distinct morphometric characteristics including shape, length/width ratio, elongation ratio, and uniform direction. To date, most researchers have mapped drumlins by tracing contours on maps, or through on-screen digitization directly on top of hillshaded digital elevation models (DEMs). This paper seeks to utilize the unique morphometric characteristics of drumlins and investigates automated extraction of the landforms as objects from DEMs by Definiens Developer software (V.7), using the 30 m United States Geological Survey National Elevation Dataset DEM as input. The Chautauqua drumlin field in Pennsylvania and upstate New York, USA was chosen as a study area. As the study area is huge (approximately covers 2500 sq.km. of area), small test areas were selected for initial testing of the method. Individual polygons representing the drumlins were extracted from the elevation data set by automated recognition, using Definiens' Multiresolution Segmentation tool, followed by rule-based classification. Subsequently parameters such as length, width and length-width ratio, perimeter and area were measured automatically. To test the accuracy of the method, a second base map was produced by manual on-screen digitization of drumlins from topographic maps and the same morphometric parameters were extracted from the mapped landforms using Definiens Developer. Statistical comparison showed a high agreement between the two methods confirming that object-oriented classification for extraction of drumlins can be used for mapping these landforms. The proposed method represents an attempt to solve the problem by providing a generalized rule-set for mass extraction of drumlins. To check that the automated extraction process was next applied to a larger area. Results showed that the proposed method is as successful for the bigger area as it was for the smaller test areas.

  13. Lahar Hazards at Concepción volcano, Nicaragua

    USGS Publications Warehouse

    Vallance, J.W.; Schilling, S.P.; Devoli, G.; Howell, M.M.

    2001-01-01

    Concepción is one of Nicaragua’s highest and most active volcanoes. The symmetrical cone occupies the northeastern half of a dumbbell shaped island called Isla Ometepa. The dormant volcano, Maderas, occupies the southwest half of the island. A narrow isthmus connects Concepción and Maderas volcanoes. Concepción volcano towers more than 1600 m above Lake Nicaragua and is within 5 to 10 km of several small towns situated on its aprons at or near the shoreline. These towns have a combined population of nearly 5,000. The volcano has frequently produced debris flows (watery flows of mud, rock, and debris—also known as lahars when they occur on a volcano) that could inundate these nearby populated areas. Concepción volcano has erupted more than 25 times in the last 120 years. Its first recorded activity was in AD 1883. Eruptions in the past century, most of which have originated from a small summit crater, comprise moderate explosions, ash that falls out of eruption plumes (called tephra), and occasional lava flows. Near the summit area, there are accumulations of rock that were emplaced hot (pyroclastic deposits), most of which were hot enough to stick together during deposition (a process called welding). These pyroclastic rocks are rather weak, and tend to break apart easily. The loose volcanic rock remobilizes during heavy rain to form lahars. Volcanic explosions have produced blankets of tephra that are distributed downwind, which on Isla Ometepe is mostly to the west. Older deposits at the west end of the island that are up to 1 m thick indicate larger explosive events have happened at Concepción volcano in prehistoric time. Like pyroclastic-flow deposits, loose tephra on the steep slopes of the volcano provides source material that heavy rainstorms and earthquakes can mobilize to trigger debris flow.

  14. Registratiom of TM data to digital elevation models

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Several problems arise when attempting to register LANDSAT thematic mapper data to U.S. B Geological Survey digital elevation models (DEMs). The TM data are currently available only in a rotated variant of the Space Oblique Mercator (SOM) map projection. Geometric transforms are thus; required to access TM data in the geodetic coordinates used by the DEMs. Due to positional errors in the TM data, these transforms require some sort of external control. The spatial resolution of TM data exceeds that of the most commonly DEM data. Oversampling DEM data to TM resolution introduces systematic noise. Common terrain processing algorithms (e.g., close computation) compound this problem by acting as high-pass filters.

  15. Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials

    NASA Technical Reports Server (NTRS)

    Keith, Theo G.

    2005-01-01

    The purpose of this report is to provide a final report for the period of 12/1/03 through 11/30/04 for NASA Cooperative Agreement NCC3-776, entitled "Elevated Temperature Testing and Modeling of Advanced Toughened Ceramic Materials." During this final period, major efforts were focused on both the determination of mechanical properties of advanced ceramic materials and the development of mechanical test methodologies under several different programs of the NASA-Glenn. The important research activities made during this period are: 1. Mechanical properties evaluation of two gas-turbine grade silicon nitrides. 2) Mechanical testing for fuel-cell seal materials. 3) Mechanical properties evaluation of thermal barrier coatings and CFCCs and 4) Foreign object damage (FOD) testing.

  16. Reducing risk from lahar hazards: concepts, case studies, and roles for scientists

    USGS Publications Warehouse

    Pierson, Thomas C.; Wood, Nathan J.; Driedger, Carolyn L.

    2014-01-01

    Lahars are rapid flows of mud-rock slurries that can occur without warning and catastrophically impact areas more than 100 km downstream of source volcanoes. Strategies to mitigate the potential for damage or loss from lahars fall into four basic categories: (1) avoidance of lahar hazards through land-use planning; (2) modification of lahar hazards through engineered protection structures; (3) lahar warning systems to enable evacuations; and (4) effective response to and recovery from lahars when they do occur. Successful application of any of these strategies requires an accurate understanding and assessment of the hazard, an understanding of the applicability and limitations of the strategy, and thorough planning. The human and institutional components leading to successful application can be even more important: engagement of all stakeholders in hazard education and risk-reduction planning; good communication of hazard and risk information among scientists, emergency managers, elected officials, and the at-risk public during crisis and non-crisis periods; sustained response training; and adequate funding for risk-reduction efforts. This paper reviews a number of methods for lahar-hazard risk reduction, examines the limitations and tradeoffs, and provides real-world examples of their application in the U.S. Pacific Northwest and in other volcanic regions of the world. An overriding theme is that lahar-hazard risk reduction cannot be effectively accomplished without the active, impartial involvement of volcano scientists, who are willing to assume educational, interpretive, and advisory roles to work in partnership with elected officials, emergency managers, and vulnerable communities.

  17. A study of the Taisho lahar generated by the 1926 eruption of Tokachidake Volcano, central Hokkaido, Japan, and implications for the generation of cohesive lahars

    NASA Astrophysics Data System (ADS)

    Uesawa, Shimpei

    2014-01-01

    Understanding the generation mechanisms of lahars is important for improving volcanic hazard assessments. The Taisho lahar (TL) was generated during the 1926 eruption of Tokachidake Volcano, Japan, and was considered a typical snowmelt lahar caused by the runout of hot debris onto a snow-covered slope. A similar mechanism produced a huge mud flow during the 1985 eruption of Nevado del Ruiz, Colombia. However, the origin of water in such lahars remains a controversial topic because the calculated water mass is based on the assumption that all of the snow on the runout area of the TL was melted, although this is much less than the estimated water volume in the TL estimated by previous studies. I have re-examined proximal deposits of the TL and their paleomagnetic characteristics in order to better understand the eruption sequence and formation of the TL. The TL produced two debris avalanche deposits and a surge-like deposit that had relatively high emplacement temperature (~ 350 °C). The deposits are composed of hydrothermally altered andesitic gravel, sand and mud. The high clay content (3-5 wt.% clay in the < 2 mm fraction) and sedimentary characteristics indicate that the flow was a cohesive lahar, most likely induced by collapse of a hydrothermally altered pyroclastic cone (hypocenter). The presence of the surge deposit indicates that the TL was not caused by simple collapse of a cinder cone but by a phreatic explosion that resulted in sector collapse. This suggests that the hydrothermal system was related to the 1926 eruption. The present-day volcano has a large hydrothermal system (1 × 106 m3 water) beneath the active crater. This study indicates that hydrothermal system explosions can trigger cohesive lahars that contain both snow melt and hydrothermal pore water, and this indicates the need to monitor hydrothermal systems.

  18. Fast Ray Tracing of Lunar Digital Elevation Models

    NASA Technical Reports Server (NTRS)

    McClanahan, Timothy P.; Evans, L. G.; Starr, R. D.; Mitrofanov, I.

    2009-01-01

    Ray-tracing (RT) of Lunar Digital Elevation Models (DEM)'s is performed to virtually derive the degree of radiation incident to terrain as a function of time, orbital and ephemeris constraints [I- 4]. This process is an integral modeling process in lunar polar research and exploration due to the present paucity of terrain information at the poles and mission planning activities for the anticipated spring 2009 launch of the Lunar Reconnaissance Orbiter (LRO). As part of the Lunar Exploration Neutron Detector (LEND) and Lunar Crater Observation and Sensing Satellite (LCROSS) preparations RI methods are used to estimate the critical conditions presented by the combined effects of high latitude, terrain and the moons low obliquity [5-7]. These factors yield low incident solar illumination and subsequently extreme thermal, and radiation conditions. The presented research uses RT methods both for radiation transport modeling in space and regolith related research as well as to derive permanently shadowed regions (PSR)'s in high latitude topographic minima, e.g craters. These regions are of scientific and human exploration interest due to the near constant low temperatures in PSRs, inferred to be < 100 K. Hydrogen is thought to have accumulated in PSR's through the combined effects of periodic cometary bombardment and/or solar wind processes, and the extreme cold which minimizes hydrogen sublimation [8-9]. RT methods are also of use in surface position optimization for future illumination dependent on surface resources e.g. power and communications equipment.

  19. Lahars at Cotopaxi and Tungurahua Volcanoes, Ecuador: Highlights from stratigraphy and observational records and related downstream hazards: Chapter 6

    USGS Publications Warehouse

    Mothes, Patricia A; Vallance, James W.

    2015-01-01

    Lahars are volcanic debris flows that are dubbed primary when triggered by eruptive activity or secondary when triggered by other factors such as heavy rainfall after eruptive activity has waned. Variation in time and space of the proportion of sediment to water within a lahar dictates lahar flow phase and the resultant sedimentary character of deposits. Characteristics of source material and of debris eroded and incorporated during flow downstream may strongly affect the grain-size composition of flowing lahars and their deposits. Lahars borne on the flanks of two steep-sided stratocones in Ecuador exemplify two important lahar types. Glacier-clad Cotopaxi volcano has been a producer of primary lahars that flow great distances downstream. Such primary lahars include those of both clast-rich and matrix-rich composition—some of which have flowed as far as 325 km to the Pacific Ocean. Cotopaxi's last important eruption in 1877 generated formidable syneruptive lahars comparable in size to those that buried Armero, Colombia, following the 1985 eruption of Nevado del Ruiz volcano. In contrast, ash-producing eruptive activity during the past 15 years at Tungurahua volcano has generated a continual supply of fresh volcaniclastic debris that is regularly remobilized by precipitation. Between 2000 and 2011, 886 rain-generated lahars were registered at Tungurahua. These two volcanoes pose dramatically different hazards to nearby populations. At Tungurahua, the frequency and small sizes of lahars have resulted in effective mitigation measures. At Cotopaxi 137 years have passed since the last important lahar-producing eruption, and there is now a high-risk situation for more than 100,000 people living in downstream valleys.

  20. Modeling Ka-band low elevation angle propagation statistics

    NASA Technical Reports Server (NTRS)

    Russell, Thomas A.; Weinfield, John; Pearson, Chris; Ippolito, Louis J.

    1995-01-01

    The statistical variability of the secondary atmospheric propagation effects on satellite communications cannot be ignored at frequencies of 20 GHz or higher, particularly if the propagation margin allocation is such that link availability falls below 99 percent. The secondary effects considered in this paper are gaseous absorption, cloud absorption, and tropospheric scintillation; rain attenuation is the primary effect. Techniques and example results are presented for estimation of the overall combined impact of the atmosphere on satellite communications reliability. Statistical methods are employed throughout and the most widely accepted models for the individual effects are used wherever possible. The degree of correlation between the effects is addressed and some bounds on the expected variability in the combined effects statistics are derived from the expected variability in correlation. Example estimates are presented of combined effects statistics in the Washington D.C. area of 20 GHz and 5 deg elevation angle. The statistics of water vapor are shown to be sufficient for estimation of the statistics of gaseous absorption at 20 GHz. A computer model based on monthly surface weather is described and tested. Significant improvement in prediction of absorption extremes is demonstrated with the use of path weather data instead of surface data.

  1. Spatio-temporal reconstruction of lahars on the southern slopes of Colima volcano, Mexico - A dendrogeomorphic approach

    NASA Astrophysics Data System (ADS)

    Franco-Ramos, Osvaldo; Stoffel, Markus; Vázquez-Selem, Lorenzo; Capra, Lucia

    2013-11-01

    Historical records of lahar occurrence and distribution are typically scarce in volcanic environments, even more so if they occur outside of human settlements. In the context of hazard assessment and process understanding, documenting their temporal frequency and drivers of activity might be crucial. On forested volcanoes, lahars may significantly damage trees along their flow paths, and sometimes even eliminate entire forest stands. This study is based on growth disturbances in trees affected by lahars (i) to assess the potential of dendrogeomorphic techniques in lahar research and (ii) to analyze the temporal frequency and spatial patterns of lahars at Montegrande and Arena, two of the most active of the ephemeral streams on the southern sector of Colima volcano. A total of 78 Pinus leiophylla live trees were sampled along the ravines, yielding evidence for 20 lahar events after the AD 1913 eruption, adding seven events to the historic records. Although the number of lahars reconstructed with tree-ring records can only be considered as a minimum frequency, the method clearly improves the local lahar chronology. Despite the scarcity of meteorological records at the study sites, the timing of reconstructed lahars points to heavy rainfalls after explosive activity as the main driver of events.

  2. Levee crest elevation profiles derived from airborne lidar-based high resolution digital elevation models in south Louisiana

    USGS Publications Warehouse

    Palaseanu-Lovejoy, Monica; Thatcher, Cindy A.; Barras, John A.

    2014-01-01

    This study explores the feasibility of using airborne lidar surveys to construct high-resolution digital elevation models (DEMs) and develop an automated procedure to extract levee longitudinal elevation profiles for both federal levees in Atchafalaya Basin and local levees in Lafourche Parish, south Lousiana. This approach can successfully accommodate a high degree of levee sinuosity and abrupt changes in levee orientation (direction) in planar coordinates, variations in levee geometries, and differing DEM resolutions. The federal levees investigated in Atchafalaya Basin have crest elevations between 5.3 and 12 m while the local counterparts in Lafourche Parish are between 0.76 and 2.3 m. The vertical uncertainty in the elevation data is considered when assessing federal crest elevation against the U.S. Army Corps of Engineers minimum height requirements to withstand the 100-year flood. Only approximately 5% of the crest points of the two federal levees investigated in the Atchafalaya Basin region met this requirement.

  3. Budapest, Hungary, Perspective View, SRTM Elevation Model with Landsat Overlay

    NASA Technical Reports Server (NTRS)

    2004-01-01

    After draining the northern flank of the Alps Mountains in Germany and Austria, the Danube River flows east as it enters this west-looking scene (upper right) and forms the border between Slovakia and Hungary. The river then leaves the border as it enters Hungary and transects the Transdanubian Mountains, which trend southwest to northeast. Upon exiting the mountains, the river turns southward, flowing past Budapest (purplish blue area) and along the western margin of the Great Hungarian Plain.

    South and west of the Danube, the Transdanubian Mountains have at most only about 400 meters (about 1300 feet) of relief but they exhibit varied landforms, which include volcanic, tectonic, fluvial (river), and eolian (wind) features. A thick deposit of loess (dust deposits likely blown from ancient glacial outwash) covers much of this area, and winds from the northwest, funneled between the Alps and the Carpathian Mountains, are apparently responsible for a radial pattern of erosional streaks across the entire region.

    This image was generated from a Landsat satellite image draped over an elevation model produced by the Shuttle Radar Topography Mission (SRTM). The view uses a 3-times vertical exaggeration to enhance topographic expression. The false colors of the scene result from displaying Landsat bands 1, 4, and 7 in blue, green, and red, respectively. Band 1 is visible blue light, but bands 4 and 7 are reflected infrared light. This band combination maximizes color contrasts between the major land cover types, namely vegetation (green), bare ground (red), and water (blue). Shading of the elevation model was used to further highlight the topographic features.

    Elevation data used in this image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on

  4. Object representations at multiple scales from digital elevation models

    PubMed Central

    Drăguţ, Lucian; Eisank, Clemens

    2011-01-01

    In the last decade landform classification and mapping has developed as one of the most active areas of geomorphometry. However, translation from continuous models of elevation and its derivatives (slope, aspect, and curvatures) to landform divisions (landforms and landform elements) is filtered by two important concepts: scale and object ontology. Although acknowledged as being important, these two issues have received surprisingly little attention. This contribution provides an overview and prospects of object representation from DEMs as a function of scale. Relationships between object delineation and classification or regionalization are explored, in the context of differences between general and specific geomorphometry. A review of scales issues in geomorphometry—ranging from scale effects to scale optimization techniques—is followed by an analysis of pros and cons of using cells and objects in DEM analysis. Prospects for coupling multi-scale analysis and object delineation are then discussed. Within this context, we propose discrete geomorphometry as a possible approach between general and specific geomorphometry. Discrete geomorphometry would apply to and describe land-surface divisions defined solely by the criteria of homogeneity in respect to a given land-surface parameter or a combination of several parameters. Homogeneity, in its turn, should always be relative to scale. PMID:21760655

  5. Quantitative characterization of lahars at Volcán de Colima, México

    NASA Astrophysics Data System (ADS)

    Vázquez, Rosario; Suriñach, Emma; Capra, Lucia; Arámbula, Raúl; Reyes, Gabriel

    2015-04-01

    Since 1991 Volcán de Colima has presented intermittent magmatic, that resulted in the accumulation of loose material on the volcano slopes, which is gradually removed as lahars during the rainy season, from June to October for this region. Lahar formation is more frequent just after a main magmatic phase (dome growth and collapse) and decreases gradually during the following years This process became evident during 2012 because the size and magnitude of the lahars developed during that season was diminishing according to the data gathered by the instrumentation installed in Montegrande ravine, one of the most active gullies forming lahars, located in the southern slope of Volcán de Colima. The laharic activity in Montegrande ravine has been monitored since 2011 from a main station installed at 2000 m.a.s.l., and other instruments located along the ravine. The actual monitoring process also counts with the seismic data of RESCO broadband station situated 500 m away from the main monitoring site. During the 2012-2013 rainy season, Montegrande ravine developed 7 lahars, 3 during the 2012 and the other 4 in 2013, when the explosive activity of the volcano was renewed. Regarding this aspect, the lahars formed in 2012 were similar in magnitude, duration and velocity, and presented a depositional regime on the medial reach of the ravine, while the flows developed during the 2013, were bigger, larger and more erosive. This feature was also due because of the meteorological events presented in the rainy season of 2013. By coupling visual and seismic data with field observations, a quantitative characterization of the studied events was performed, mainly focused to correlate changes in flow behavior, as well as the estimation of downflow volume variations.

  6. Catastrophic precipitation-triggered lahar at Casita volcano, Nicaragua: Occurrence, bulking and transformation

    USGS Publications Warehouse

    Scott, K.M.; Vallance, J.W.; Kerle, N.; Macias, J.L.; Strauch, W.; Devoli, G.

    2005-01-01

    A catastrophic lahar began on 30 October 1998, as hurricane precipitation triggered a small flank collapse of Casita volcano, a complex and probably dormant stratovolcano. The initial rockslide-debris avalanche evolved on the flank to yield a watery debris flood with a sediment concentration less than 60 per cent by volume at the base of the volcano. Within 2-5 km, however, the watery flow entrained (bulked) enough sediment to transform entirely to a debris flow. The debris flow, 6 km downstream and 1??2 km wide and 3 to 6 m deep, killed 2500 people, nearly the entire populations of the communities of El Porvenir and Rolando Rodriguez. These 'new towns' were developed in a prehistoric lahar pathway: at least three flows of similar size since 8330 14C years BP are documented by stratigraphy in the same 30-degree sector. Travel time between perception of the flow and destruction of the towns was only 2??5-3??0 minutes. The evolution of the flow wave occurred with hydraulic continuity and without pause or any extraordinary addition of water. The precipitation trigger of the Casita lahar emphasizes the nee d, in volcano hazard assessments, for including the potential for non-eruption-related collapse lahars with the more predictable potential of their syneruption analogues. The flow behaviour emphasizes that volcano collapses can yield not only volcanic debris avalanches with restricted runouts, but also mobile lahars that enlarge by bulking as they flow. Volumes and hence inundation areas of collapse-runout lahars can increase greatly beyond their sources: the volume of the Casita lahar bulked to at least 2??6 times the contributing volume of the flank collapse and 4??2 times that of the debris flood. At least 78 per cent of the debris flow matrix (sediment < -1??0??; 2 mm) was entrained during flow. Copyright c 2004 John Wiley & Sons, Ltd.

  7. Interpolation of phenological phases on a digital elevation model (DEM)

    NASA Astrophysics Data System (ADS)

    Schöngaßner, Thomas C.; Scheifinger, Helfried

    2010-05-01

    The main objective of the VegDyn project (a cooperation between Joanneum Research, Institute of Digital Image Processing, LFZ Raumberg-Gumpenstein and ZAMG) consists in quantifying and modelling the relationship between individual growth stages of grassland on the one hand and atmospheric parameters, remotely sensed data and phenological observations on the other. The model simulates the beginning and the end of the vegetation period and the growth stages of grassland with temperature as input variable. Thus it will be possible to explore changes of the timing of the vegetation period and the growth stages of grassland in possible future climate scenarios, which are calculated by climate models. In the context of the VegDyn project we developed methods for the spatial interpolation of phenological phases on a digital elevation model with a 250 m grid resolution in the complex terrain of the Alps. The final result is a series of maps of long term mean entry dates and maps of entry dates of individual years, which can for instance be related with the Net Difference Vegetation Index (NDVI) parameter maps from satellite observations. Apart from the yearly input via the conventional observational network based on voluntary observers and the input via the web interface, the Austrian phenological data base is still being supplemented by data from the paper archive. The elevation of the station network ranges from 100 to 1700 m. The station density can reach up to 100 or more stations per phase and season during 1951 - 2009. From more than 280 observed phases including phases from wild (woody and herbaceous) and agricultural plants those have been selected, which are related to cultivated grassland and which can be detected by remote sensing. In order to be selected for spatial interpolation the phase must satisfy a number of criteria: a minimum number of stations and, in order to have a meaningful long term mean entry date, a minimum number of observations per station

  8. Mount Baker lahars and debris flows, ancient, modern, and future

    USGS Publications Warehouse

    Tucker, David S; Scott, Kevin M.; Grossman, Eric E.; Linneman, Scott

    2014-01-01

    Holocene lahars and large debris flows (>106 m3) have left recognizable deposits in the Middle Fork Nooksack valley. A debris flow in 2013 resulting from a landslide in a Little Ice Age moraine had an estimated volume of 100,000 m3, yet affected turbidity for the entire length of the river, and produced a slug of sediment that is currently being reworked and remobilized in the river system. Deposits of smaller-volume debris flows, deposited as terraces in the upper valley, may be entirely eroded within a few years. Consequently, the geologic record of small debris flows such as those that occurred in 2013 is probably very fragmentary. Small debris flows may still have significant impacts on hydrology, biology, and human uses of rivers downstream. Impacts include the addition of waves of fine sediment to stream loads, scouring or burying salmon-spawning gravels, forcing unplanned and sudden closure of municipal water intakes, damaging or destroying trail crossings, extending river deltas into estuaries, and adding to silting of harbors near river mouths.

  9. The ASTER Global Digital Elevation Model (GDEM) -for societal benefit -

    NASA Astrophysics Data System (ADS)

    Hato, M.; Tsu, H.; Tachikawa, T.; Abrams, M.; Bailey, B.

    2009-12-01

    The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) was developed jointly by the Ministry of Economy, Trade and Industry (METI) of Japan and the United States National Aeronautics and Space Administration (NASA) under the agreement of contribution to GEOSS and a public release was started on June 29th. ASTER GDEM can be downloaded to users from the Earth Remote Sensing Data Analysis Center (ERSDAC) of Japan and NASA’s Land Processes Distributed Active Archive Center (LP DAAC) free of charge. The ASTER instrument was built by METI and launched onboard NASA’s Terra spacecraft in December 1999. It has an along-track stereoscopic capability using its near infrared spectral band (NIR) and its nadir-viewing and backward-viewing telescopes to acquire stereo image data with a base-to-height ratio of 0.6. The ASTER GDEM was produced by applying newly-developed automated algorithm to more than 1.2 million NIR data Produced DEMs of all scene data was stacked after cloud masking and finally partitioned into 1° x 1°unit (called ‘tile’) data for convenience of distribution and handling by users. Before start of public distribution, ERSDAC and USGS/NASA together with many volunteers did validation and characterization by using a preliminary product of the ASTER GDEM. As a result of validation, METI and NASA evaluated that Version 1 of the ASTER GDEM has enough quality to be used as “experimental” or “research grade” data and consequently decided to release it. The ASTER GDEM covering almost all land area of from 83N to 83S on the earth represents as an important contribution to the global earth observation community. We will show our effort of development of ASTER GDEM and its accuracy and character.

  10. Recent lahars at Volcán de Colima (Mexico): Drainage variation and spectral classification

    NASA Astrophysics Data System (ADS)

    Davila, N.; Capra, L.; Gavilanes-Ruiz, J. C.; Varley, N.; Norini, G.; Vazquez, Angel Gómez

    2007-09-01

    Volcán de Colima is the most active volcano in Mexico, and represents a high risk for more than 500,000 people. In 1998 the volcano renewed its activity, with the extrusion of a lava dome and subsequent lava and block and ash flows. During the recent period of activity pyroclastic products did not directly affect villages around the volcano, however, several lahars did. We used LIDAR topographic coverage, ASTER and LANDSAT images for the recognition of morphological changes in the drainage system and lahar detection. For lahar delineation we applied principal components analysis and canonical classification (Tasseled Cap) in order to perform a supervised image classification using the maximum likelihood rule algorithm. LAHARZ (objective delineation of distal debris flow hazard zones) has been used and tested using two topographic datasets with different resolutions, which provided evidence of the importance of high-resolution topographic coverage in hazard assessment. Finally a hazard map for lahars is presented, showing that several villages and ranchos can be affected. In contrast, due to morphological changes produced by products of the intense explosive activity, other populated areas such as La Yerbabuena, are outside of the high risk zone. They could be affected by lahars only in case of cataclysmic eruptions such as the 1913 Plinian event.

  11. An evaluation of onshore digital elevation models for modelling tsunami inundation zones

    NASA Astrophysics Data System (ADS)

    Griffin, Jonathan; Latief, Hamzah; Kongko, Widjo; Harig, Sven; Horspool, Nick; Hanung, Raditya; Rojali, Aditia; Maher, Nicola; Fuchs, Annika; Hossen, Jakir; Upi, Supriyati; Edi, Dewanto; Rakowsky, Natalja; Cummins, Phil

    2015-06-01

    A sensitivity study is undertaken to assess the utility of different onshore digital elevation models (DEM) for simulating the extent of tsunami inundation using case studies from two locations in Indonesia. We compare airborne IFSAR, ASTER and SRTM against high resolution LiDAR and stereo-camera data in locations with different coastal morphologies. Tsunami inundation extents modelled with airborne IFSAR DEMs are comparable with those modelled with the higher resolution datasets and are also consistent with historical run-up data, where available. Large vertical errors and poor resolution of the coastline in the ASTER and SRTM elevation datasets cause the modelled inundation extent to be much less compared with the other datasets and observations. Therefore ASTER and SRTM should not be used to underpin tsunami inundation models. a model mesh resolution of 25 m was sufficient for estimating the inundated area when using elevation data with high vertical accuracy in the case studies presented here. Differences in modelled inundation between digital terrain models (DTM) and digital surface models (DSM) for LiDAR and IFSAR are greater than differences between the two data types. Models using DTM may overestimate inundation while those using DSM may underestimate inundation when a constant Manning’s roughness value is used. We recommend using DTM for modelling tsunami inundation extent with further work needed to resolve the scale at which surface roughness should be parameterised.

  12. High-resolution digital elevation model of lower Cowlitz and Toutle Rivers, adjacent to Mount St. Helens, Washington, based on an airborne lidar survey of October 2007

    USGS Publications Warehouse

    Mosbrucker, Adam

    2015-01-01

    The lateral blast, debris avalanche, and lahars of the May 18th, 1980, eruption of Mount St. Helens, Washington, dramatically altered the surrounding landscape. Lava domes were extruded during the subsequent eruptive periods of 1980–1986 and 2004–2008. More than three decades after the emplacement of the 1980 debris avalanche, high sediment production persists in the Toutle River basin, which drains the northern and western flanks of the volcano. Because this sediment increases the risk of flooding to downstream communities on the Toutle and lower Cowlitz Rivers, the U.S. Army Corps of Engineers (USACE), under the direction of Congress to maintain an authorized level of flood protection, continues to monitor and mitigate excess sediment in North and South Fork Toutle River basins to help reduce this risk and to prevent sediment from clogging the shipping channel of the Columbia River. From October 22–27, 2007, Watershed Sciences, Inc., under contract to USACE, collected high-precision airborne lidar (light detection and ranging) data that cover 273 square kilometers (105 square miles) of lower Cowlitz and Toutle River tributaries from the Columbia River at Kelso, Washington, to upper North Fork Toutle River (below the volcano's edifice), including lower South Fork Toutle River. These data provide a digital dataset of the ground surface, including beneath forest cover. Such remotely sensed data can be used to develop sediment budgets and models of sediment erosion, transport, and deposition. The U.S. Geological Survey (USGS) used these lidar data to develop digital elevation models (DEMs) of the study area. DEMs are fundamental to monitoring natural hazards and studying volcanic landforms, fluvial and glacial geomorphology, and surface geology. Watershed Sciences, Inc., provided files in the LASer (LAS) format containing laser returns that had been filtered, classified, and georeferenced. The USGS produced a hydro-flattened DEM from ground-classified points at

  13. High-resolution digital elevation model of Mount St. Helens crater and upper North Fork Toutle River basin, Washington, based on an airborne lidar survey of September 2009

    USGS Publications Warehouse

    Mosbrucker, Adam

    2014-01-01

    The lateral blast, debris avalanche, and lahars of the May 18th, 1980, eruption of Mount St. Helens, Washington, dramatically altered the surrounding landscape. Lava domes were extruded during the subsequent eruptive periods of 1980–1986 and 2004–2008. More than three decades after the emplacement of the 1980 debris avalanche, high sediment production persists in the North Fork Toutle River basin, which drains the northern flank of the volcano. Because this sediment increases the risk of flooding to downstream communities on the Toutle and Cowlitz Rivers, the U.S. Army Corps of Engineers (USACE), under the direction of Congress to maintain an authorized level of flood protection, built a sediment retention structure on the North Fork Toutle River in 1989 to help reduce this risk and to prevent sediment from clogging the shipping channel of the Columbia River. From September 16–20, 2009, Watershed Sciences, Inc., under contract to USACE, collected high-precision airborne lidar (light detection and ranging) data that cover 214 square kilometers (83 square miles) of Mount St. Helens and the upper North Fork Toutle River basin from the sediment retention structure to the volcano's crater. These data provide a digital dataset of the ground surface, including beneath forest cover. Such remotely sensed data can be used to develop sediment budgets and models of sediment erosion, transport, and deposition. The U.S. Geological Survey (USGS) used these lidar data to develop digital elevation models (DEMs) of the study area. DEMs are fundamental to monitoring natural hazards and studying volcanic landforms, fluvial and glacial geomorphology, and surface geology. Watershed Sciences, Inc., provided files in the LASer (LAS) format containing laser returns that had been filtered, classified, and georeferenced. The USGS produced a hydro-flattened DEM from ground-classified points at Castle, Coldwater, and Spirit Lakes. Final results averaged about five laser last

  14. Quality assessment of Digital Elevation Model (DEM) in view of the Altiplano hydrological modeling

    NASA Astrophysics Data System (ADS)

    Satgé, F.; Arsen, A.; Bonnet, M.; Timouk, F.; Calmant, S.; Pilco, R.; Molina, J.; Lavado, W.; Crétaux, J.; HASM

    2013-05-01

    Topography is crucial data input for hydrological modeling but in many regions of the world, the only way to characterize topography is the use of satellite-based Digital Elevation Models (DEM). In some regions, the quality of these DEMs remains poor and induces modeling errors that may or not be compensated by model parameters tuning. In such regions, the evaluation of these data uncertainties is an important step in the modeling procedure. In this study, which focuses on the Altiplano region, we present the evaluation of the two freely available DEM. The shuttle radar topographic mission (SRTM), a product of the National Aeronautics and Space Administration (NASA) and the Advanced Space Born Thermal Emission and Reflection Global Digital Elevation Map (ASTER GDEM), data provided by the Ministry of Economy, Trade and Industry of Japan (MESI) in collaboration with the NASA, are widely used. While the first represents a resolution of 3 arc seconds (90m) the latter is 1 arc second (30m). In order to select the most reliable DEM, we compared the DEM elevation with high qualities control points elevation. Because of its large spatial coverture (track spaced of 30 km with a measure of each 172 m) and its high vertical accuracy which is less than 15 cm in good weather conditions, the Geoscience Laser Altimeter System (GLAS) on board on the Ice, Cloud and Land elevation Satellite of NASA (ICESat) represent the better solution to establish a high quality elevation database. After a quality check, more than 150 000 ICESat/GLAS measurements are suitable in terms of accuracy for the Altiplano watershed. This data base has been used to evaluate the vertical accuracy for each DEM. Regarding to the full spatial coverture; the comparison has been done for both, all kind of land coverture, range altitude and mean slope.

  15. High Resolution Digital Elevation Models of Pristine Explosion Craters

    NASA Technical Reports Server (NTRS)

    Farr, T. G.; Krabill, W.; Garvin, J. B.

    2004-01-01

    In order to effectively capture a realistic terrain applicable to studies of cratering processes and landing hazards on Mars, we have obtained high resolution digital elevation models of several pristine explosion craters at the Nevada Test Site. We used the Airborne Terrain Mapper (ATM), operated by NASA's Wallops Flight Facility to obtain DEMs with 1 m spacing and 10 cm vertical errors of 4 main craters and many other craters and collapse pits. The main craters that were mapped are Sedan, Scooter, Schooner, and Danny Boy. The 370 m diameter Sedan crater, located on Yucca Flat, is the largest and freshest explosion crater on Earth that was formed under conditions similar to hypervelocity impact cratering. As such, it is effectively pristine, having been formed in 1962 as a result of a controlled detonation of a 100 kiloton thermonuclear device, buried at the appropriate equivalent depth of burst required to make a simple crater. Sedan was formed in alluvium of mixed lithology and subsequently studied using a variety of field-based methods. Nearby secondary craters were also formed at the time and were also mapped by ATM. Adjacent to Sedan and also in alluvium is Scooter, about 90 m in diameter and formed by a high-explosive event. Schooner (240 m) and Danny Boy (80 m) craters were also important targets for ATM as they were excavated in hard basalt and therefore have much rougher ejecta. This will allow study of ejecta patterns in hard rock as well as engineering tests of crater and rock avoidance and rover trafficability. In addition to the high resolution DEMs, crater geometric characteristics, RMS roughness maps, and other higher-order derived data products will be generated using these data. These will provide constraints for models of landing hazards on Mars and for rover trafficability. Other planned studies will include ejecta size-frequency distribution at the resolution of the DEM and at finer resolution through air photography and field measurements

  16. Orthographic terrain views using data derived from digital elevation models

    NASA Technical Reports Server (NTRS)

    Dubayah, R. O.; Dozier, J.

    1986-01-01

    A fast algorithm for producing three-dimensional orthographic terrain views uses digital elevation data and co-registered imagery. These views are created using projective geometry and are designed for display on high-resolution raster graphics devices. The algorithm's effectiveness is achieved by (1) the implementation of two efficient gray-level interpolation routines that offer the user a choice between speed and smoothness, and (2) a unique visible surface determination procedure based on horizon angles derived from the elevation data set.

  17. The anatomy of a lahar: deciphering the 15th September 2012 lahar at Volcán de Colima, México

    NASA Astrophysics Data System (ADS)

    Vázquez, Rosario; Capra, Lucia; Caballero, Lizeth; Arámbula, Raúl; Reyes, Gabriel

    2014-05-01

    Volcán de Colima is one of the most active volcanoes in Mexico where lahars area common phenomenon. Since the reactivation of the volcanic activity in 1991, lahars have become more frequent during the June-October rainy season, in this region. Therefore, Volcán de Colima represents a natural laboratory, ideal for the constant monitoring of lahars and to study factors controlling their origin, flow transport and deposition. Since 2007 the systematic detection of lahars in Volcán de Colima has been carried out using seismic data from the broadband stations of the RESCO network, the seismological network of Colima University, along with three rain gauge stations located on the southern ravines of the volcano. In 2011 a new monitoring station was built at 2000 m.a.s.l. along the Montegrande ravine, which consists of a geophone, a video camera and a rain gauge station coupled with a moisture sensor, transmitting in real time to the RESCO facilities at Colima University. With all the instrumentation currently installed on the volcano flanks, we could monitor and describe the lahar that occurred on 15th September 2012 along the Montegrande ravine, and correlate the monitoring data with information gathered by the field campaign conducted two days after the event. The high quality of collected data enabled us to describe the "anatomy" of this lahar. The event consisted of a lahar that lasted 40 minutes, triggered by 20 mm of accumulated rainfall with a maximum intensity of 95 mm/h. The lahar was characterized by three main surges at 4-5 minutes intervals that formed a 80 cm-thick terrace. The first surge was a debris flow with a block-rich front followed by the main body that progressively diluted to an hyperconcentrated flow, from which a 40 cm-thick massive unit was emplaced (33 wt% gravel and >60 wt% of sand); it was followed by a more dilute hyperconcentrated flow that left a massive 10 cm-thick sandy layer (80 wt% of sand); the third surge deposited a 30-cm thick

  18. Lahar Inundation of the Drift River Valley During the 2009 Eruption of Redoubt Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Waythomas, C. F.; Scott, W. E.; Pierson, T. C.; Major, J. J.

    2009-12-01

    Redoubt Volcano in south-central Alaska began its most recent eruption on March 15 and erupted explosively at least 20 times between then and April 4, 2009. The 3110 m high, snow-and-ice-clad stratovolcano includes a circular, ice-filled summit crater that is breached to the north. The volcano supports about 4 km3 of ice and snow and about 1 km3 of this makes up Drift glacier on the north side of the volcano. Explosive eruptions between March 22 and April 4, which included the destruction of at least two lava domes, triggered two large lahars in the Drift River valley on March 23 and April 4, and several smaller lahars between March 24 and March 31. The heights of mud lines, character of deposits examined in the field, areas of deposition, and estimates of flow width, depth, and velocity revealed that the lahars on March 23 and April 4 were the largest mass flows of the eruption. In the ~1.5-km-wide upper Drift River valley, flow depths averaged about 10 m, flow velocities, although not measured directly, were at least 10-14 m/s, and peak discharges were on the order of 105 m3/s. Depositional areas (about 12.5 km2) and volumes (0.063-0.088 km3) were similar. Despite these similarities, the two lahars had very different compositions and origins. The March 23 lahar was a flowing slurry of snow and ice that entrained tablular blocks of river ice, seasonal snow in the valley, and glacier ice eroded from Drift glacier. Its deposit was up to 5 m thick, and contained roughly 30% sediment, rock debris and water, and 70% or more river and glacier ice. It was frozen soon after it was emplaced and later buried by the April 4 lahar. Juvenile material has not yet been found in the deposit. The lahar of April 4, in contrast, was a hyperconcentrated flow, as interpreted from massive to faintly and horizontally stratified sand to fine gravel deposits up to 4 m thick. Gravel clasts were predominantly juvenile andesite. We infer the March 23 lahar to have been initiated by a rapid

  19. Glacier Destruction and Lahar Generation during the 2009 Eruption of Redoubt Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Waythomas, C. F.

    2010-12-01

    Two large lahars with volumes of 0.4-0.6 km3 and several smaller lahars with volumes of 0.05-0.1 km3 inundated the Drift River valley on the north flank of Redoubt Volcano during its 2009 eruption. Significant lahars were produced on March 22-23 during the initial explosive phase of the eruption following about 8 months of precursory unrest that included increased fumarolic melting of glacier ice and snow in the summit crater and upper Drift glacier. From the beginning of unrest in late July 2008 through March 20, 2009 about 3-7 x 106 m3 of glacier ice and snow were lost from upper Drift glacier as a result of fumarolic emissions and associated melting. Water and debris outflow during this period was minor and posed no downstream flow hazard beyond the base of the volcano. On March 22-23, explosive eruptions from a summit crater vent destroyed a significant amount of ice in upper Drift glacier and produced a funnel-shaped explosion crater within the larger summit crater. Glacier ice, 50-100 m thick, in the gorge below the vent was stripped to bedrock by pyroclastic flows and melt water. By the next available clear views of the volcano on March 26, about 0.5-1.0 x 108 m3 of ice had been removed from upper Drift glacier including part of the ice field in the summit crater. Melt water liberated by eruptive activity on March 22-23 also eroded or removed most of the river ice and snowpack present in the Drift River valley which may have added an additional 0.1-0.2 km3 of water to the lahars produced during that time. Additional explosions from March 26-April 4 caused further melting of Drift glacier and produced small lahars, but the extent of ice loss and lahar inundation during this period could not be determined because clouds obscured the volcano and much of the Drift River valley. The final explosive event and lahar of the eruption occurred on April 4 when pyroclastic flows produced by lava dome collapse swept over upper Drift glacier and a portion of its piedmont

  20. Record of late holocene debris avalanches and lahars at Iliamna Volcano, Alaska

    USGS Publications Warehouse

    Waythomas, C.F.; Miller, T.P.; Beget, J.E.

    2000-01-01

    Iliamna Volcano is a 3053-meter high, glaciated stratovolcano in the southern Cook Inlet region of Alaska and is one of seven volcanoes in this region that have erupted multiple times during the past 10,000 yr. Prior to our studies of Iliamna Volcano, little was known about the frequency, magnitude, and character of Holocene volcanic activity. Here we present geologic evidence of the most recent eruptive activity of the volcano and provide the first outline of Late Holocene debris-avalanche and lahar formation. Iliamna has had no documented historical eruptions but our recent field investigations indicate that the volcano has erupted at least twice in the last 300 yr. Clay-rich lahar deposits dated by radiocarbon to ???1300 and ???90 yr BP are present in two major valleys that head on the volcano. These deposits indicate that at least two large, possibly deep-seated, flank failures of the volcanic edifice have occurred in the last 1300 yr. Noncohesive lahar deposits likely associated with explosive pyroclastic eruptions date to 2400-1300,>1500,???300, and <305 yr BP. Debris-avalanche deposits from recent and historical small-volume slope failures of the hydrothermally altered volcanic edifice cover most of the major glaciers on the volcano. Although these deposits consist almost entirely of hydrothermally altered rock debris and snow and ice, none of the recently generated debris avalanches evolved to lahars. A clay-rich lahar deposit that formed <90??60 radiocarbon yr BP and entered the Johnson River Valley southeast of the volcano cannot be confidently related to an eruption of Iliamna Volcano, which has had no known historical eruptions. This deposit may record an unheralded debris avalanche and lahar. ?? 2000 Elsevier Science B.V. All rights reserved.

  1. The October 16, 2013 rainfall-induced landslides and associated lahars at Izu Oshima Volcano, Japan

    NASA Astrophysics Data System (ADS)

    Miyabuchi, Yasuo; Maeno, Fukashi; Nakada, Setsuya

    2015-09-01

    Intense rainfall related to the typhoon T1326 on October 15-16, 2013 (total 824 mm; maximum hourly rainfall 118.5 mm) triggered numerous landslides and associated lahars at Izu Oshima Volcano, the northernmost part of Izu Mariana volcanic arc, Japan. The landslides were concentrated mainly in a 2-km2 area located on the western slope of Izu Oshima Volcano. Most of the landslides were shallow soil slips (< 2 m thick) in unconsolidated fallout tephra layers overlying lava flows and pyroclastic rocks. The rupture surfaces of them were located near the base of Y1 tephra (AD 1777-1778) and/or the base of Y4 tephra (AD 1421). The Y1 and Y4 tephras differ from the underlying paleosols in permeability, grain size and degree of compaction. The saturated hydraulic conductivities of the paleosols were one to two orders of magnitude smaller than those of the overlying Y1 and Y4 tephras. Most landslides mobilized completely into lahars, traveling along stream channels or flat slopes and flooding at the foot of the volcano. The associated lahars severely damaged inhabited areas and caused thirty five fatalities. Although the lahars eroded slopes and transported boulders up to 1 m in diameter and a large amount of woody debris, they contained more than 90% of sand-to-silt-size particles, similar in composition to the original sliding materials. Sediment discharge volumes from three basins were estimated at 1.8-4.1 × 104 m3/km2, based on debris volumes trapped by sediment retention dams. The characteristics of rainfall-induced landslides and associated lahars at Izu Oshima Volcano in 2013 provide an important lesson about future non-eruption-related landslide and lahar hazards at tephra-rich volcanoes.

  2. Uncertainty Analysis of LROC NAC Derived Elevation Models

    NASA Astrophysics Data System (ADS)

    Burns, K.; Yates, D. G.; Speyerer, E.; Robinson, M. S.

    2012-12-01

    One of the primary objectives of the Lunar Reconnaissance Orbiter Camera (LROC) [1] is to gather stereo observations with the Narrow Angle Camera (NAC) to generate digital elevation models (DEMs). From an altitude of 50 km, the NAC acquires images with a pixel scale of 0.5 meters, and a dual NAC observation covers approximately 5 km cross-track by 25 km down-track. This low altitude was common from September 2009 to December 2011. Images acquired during the commissioning phase and those acquired from the fixed orbit (after 11 December 2011) have pixel scales that range from 0.35 meters at the south pole to 2 meters at the north pole. Alimetric observations obtained by the Lunar Orbiter Laser Altimeter (LOLA) provide measurements of ±0.1 m between the spacecraft and the surface [2]. However, uncertainties in the spacecraft positioning can result in offsets (±20m) between altimeter tracks over many orbits. The LROC team is currently developing a tool to automatically register alimetric observations to NAC DEMs [3]. Using a generalized pattern search (GPS) algorithm, the new automatic registration adjusts the spacecraft position and pointing information during times when NAC images, as well as LOLA measurements, of the same region are acquired to provide an absolute reference frame for the DEM. This information is then imported into SOCET SET to aide in creating controlled NAC DEMs. For every DEM, a figure of merit (FOM) map is generated using SOCET SET software. This is a valuable tool for determining the relative accuracy of a specific pixel in a DEM. Each pixel in a FOM map is given a value to determine its "quality" by determining if the specific pixel was shadowed, saturated, suspicious, interpolated/extrapolated, or successfully correlated. The overall quality of a NAC DEM is a function of both the absolute and relative accuracies. LOLA altimetry provides the most accurate absolute geodetic reference frame with which the NAC DEMs can be compared. Offsets

  3. Integrated research in constitutive modelling at elevated temperatures, part 2

    NASA Technical Reports Server (NTRS)

    Haisler, W. E.; Allen, D. H.

    1986-01-01

    Four current viscoplastic models are compared experimentally with Inconel 718 at 1100 F. A series of tests were performed to create a sufficient data base from which to evaluate material constants. The models used include Bodner's anisotropic model; Krieg, Swearengen, and Rhode's model; Schmidt and Miller's model; and Walker's exponential model.

  4. An evaluation of onshore digital elevation models for tsunami inundation modelling

    NASA Astrophysics Data System (ADS)

    Griffin, J.; Latief, H.; Kongko, W.; Harig, S.; Horspool, N.; Hanung, R.; Rojali, A.; Maher, N.; Fountain, L.; Fuchs, A.; Hossen, J.; Upi, S.; Dewanto, S. E.; Cummins, P. R.

    2012-12-01

    Tsunami inundation models provide fundamental information about coastal areas that may be inundated in the event of a tsunami along with additional parameters such as flow depth and velocity. This can inform disaster management activities including evacuation planning, impact and risk assessment and coastal engineering. A fundamental input to tsunami inundation models is adigital elevation model (DEM). Onshore DEMs vary widely in resolution, accuracy, availability and cost. A proper assessment of how the accuracy and resolution of DEMs translates into uncertainties in modelled inundation is needed to ensure results are appropriately interpreted and used. This assessment can in turn informdata acquisition strategies depending on the purpose of the inundation model. For example, lower accuracy elevation data may give inundation results that are sufficiently accurate to plan a community's evacuation route but not sufficient to inform engineering of a vertical evacuation shelters. A sensitivity study is undertaken to assess the utility of different available onshore digital elevation models for tsunami inundation modelling. We compare airborne interferometric synthetic aperture radar (IFSAR), ASTER and SRTM against high resolution (<1 m horizontal resolution, < 0.15 m vertical accuracy) LiDAR or stereo-camera data in three Indonesian locations with different coastal morphologies (Padang, West Sumatra; Palu, Central Sulawesi; and Maumere, Flores), using three different computational codes (ANUGA, TUNAMI-N3 and TsunAWI). Tsunami inundation extents modelled with IFSAR are comparable with those modelled with the high resolution datasets and with historical tsunami run-up data. Large vertical errors (> 10 m) and poor resolution of the coastline in the ASTER and SRTM elevation models cause modelled inundation to be much less compared with models using better data and with observations. Therefore we recommend that ASTER and SRTM should not be used for modelling tsunami

  5. Preliminary observations of voluminous ice-rich and water-rich lahars generated during the 2009 eruption of Redoubt, Alaska

    USGS Publications Warehouse

    Waythomas, Christopher F.; Pierson, Thomas C.; Major, Jon J.; Scott, William E.

    2012-01-01

    Redoubt Volcano in south-central Alaska began erupting on March 15, 2009, and by April 4, 2009, had produced at least 20 explosive events that generated plumes of ash and lahars. The 3,108-m high, snow- and -ice-clad stratovolcano has an ice-filled summit crater that is breached to the north. The volcano supports about 4 km3 of ice and snow and about 1 km3 of this makes up the Drift glacier on the northern side of the volcano. Explosive eruptions between March 22 and April 4, which included the destruction of at least two lava domes, triggered significant lahars in the Drift River valley on March 23 and April 4 and several smaller lahars between March 24 and March 31. High-flow marks, character of deposits, areas of inundation, and estimates of flow velocity revealed that the lahars on March 23 and April 4 were the largest of the eruption. In the 2-km-wide upper Drift River valley, average flow depths were about 3–5 m. Average peak-flow velocities were likely between 10 and 15 ms-1, and peak discharges were on the order of 104–105 m3s-1. The area inundated by lahars on March 23 was at least 100 km2 and on April 4 about 125 km2. The lahars emplaced on March 23 and April 4 had volumes on the order of 107–108 m3 and were similar in size to the largest lahar of the 1989–90 eruption. The March 23 lahars were primarily flowing slurries of snow and ice entrained from the Drift glacier and seasonal snow and tabular blocks of river ice from the Drift River valley. Only a single, undifferentiated deposit up to 5 m thick was found and contained about 80–95 percent of poorly sorted, massive to imbricate assemblages of snow and ice. The deposit was frozen soon after it was emplaced and later eroded and buried by the April 4 lahar. The lahar of April 4, in contrast, was primarily a hyperconcentrated flow, as interpreted from 1- to 6-m thick deposits of massive to horizontally stratified sand-to-fine-gravel. Rock material in the April 4 lahar deposit is predominantly

  6. Comparison of 7.5-minute and 1-degree digital elevation models

    NASA Technical Reports Server (NTRS)

    Isaacson, Dennis L.; Ripple, William J.

    1990-01-01

    Two digital elevation models are compared for the Echo Mountain SE quadrangle in the Cascade Mountains of Oregon. Comparisons were made between 7.5-minute (1:24,000-scale) and 1-degree (1:250,000-scale) images using the variables of elevation, slope aspect, and slope gradient. Both visual and statistical differences are presented.

  7. Comparison of 7.5-minute and 1-degree digital elevation models

    NASA Technical Reports Server (NTRS)

    Isaacson, Dennis L.; Ripple, William J.

    1995-01-01

    We compared two digital elevation models (DEM's) for the Echo Mountain SE quadrangle in the Cascade Mountains of Oregon. Comparisons were made between 7.5-minute (1:24,000-scale) and 1-degree (1:250,000-scale) images using the variables of elevation, slope aspect, and slope gradient. Both visual and statistical differences are presented.

  8. Elevation dependency of the surface climate change signal: A model study

    SciTech Connect

    Giorgi, F.; Hurrell, J.W.; Marinucci, M.R.

    1997-02-01

    Results are presented from a present-day and a doubled CO{sub 2} experiment over the Alpine region with a nested regional climate model. The simulated temperature change signal shows a substantial elevation dependency, mostly during the winter and spring seasons, resulting in more pronounced warming at high elevations than low elevations. This is caused by a depletion of snowpack in doubled CO{sub 2} conditions and further enhanced by the snow-albedo feedback. This result is consistent with some observed temperature trends for anomalously warm years over the Alpine region and suggests that high elevation temperature changes could be used as an early detection tool for global warming. Changes in precipitation, as well as other components of the surface energy and water budgets, also show an elevation signal, which may have important implications for impact assessments in high elevation regions. 22 refs., 10 figs., 2 tabs.

  9. Developing building-damage scales for lahars: application to Merapi volcano, Indonesia

    NASA Astrophysics Data System (ADS)

    Jenkins, Susanna F.; Phillips, Jeremy C.; Price, Rebecca; Feloy, Kate; Baxter, Peter J.; Hadmoko, Danang Sri; de Bélizal, Edouard

    2015-09-01

    Lahar damage to buildings can include burial by sediment and/or failure of walls, infiltration into the building and subsequent damage to contents. The extent to which a building is damaged will be dictated by the dynamic characteristics of the lahar, i.e. the velocity, depth, sediment concentration and grain size, as well as the structural characteristics and setting of the building in question. The focus of this paper is on quantifying how buildings may respond to impact by lahar. We consider the potential for lahar damage to buildings on Merapi volcano, Indonesia, as a result of the voluminous deposits produced during the large (VEI 4) eruption in 2010. A building-damage scale has been developed that categorises likely lahar damage levels and, through theoretical calculations of expected building resistance to impact, approximate ranges of impact pressures. We found that most weak masonry buildings on Merapi would be destroyed by dilute lahars with relatively low velocities (ca. 3 m/s) and pressures (ca. 5 kPa); however, the majority of stronger rubble stone buildings may be expected to withstand higher velocities (to 6 m/s) and pressures (to 20 kPa). We applied this preliminary damage scale to a large lahar in the Putih River on 9 January 2011, which inundated and caused extensive building damage in the village of Gempol, 16 km southwest of Merapi. The scale was applied remotely through the use of public satellite images and through field studies to categorise damage and estimate impact pressures and velocities within the village. Results were compared with those calculated independently from Manning's calculations for flow velocity and depth within Gempol village using an estimate of flow velocity at one upstream site as input. The results of this calculation showed reasonable agreement with an average channel velocity derived from travel time observations. The calculated distribution of flow velocities across the area of damaged buildings was consistent with

  10. Hydrologic connectivity: Quantitative assessments of hydrologic-enforced drainage structures in an elevation model

    USGS Publications Warehouse

    Poppenga, Sandra; Worstell, Bruce B.

    2016-01-01

    Elevation data derived from light detection and ranging present challenges for hydrologic modeling as the elevation surface includes bridge decks and elevated road features overlaying culvert drainage structures. In reality, water is carried through these structures; however, in the elevation surface these features impede modeled overland surface flow. Thus, a hydrologically-enforced elevation surface is needed for hydrodynamic modeling. In the Delaware River Basin, hydrologic-enforcement techniques were used to modify elevations to simulate how constructed drainage structures allow overland surface flow. By calculating residuals between unfilled and filled elevation surfaces, artificially pooled depressions that formed upstream of constructed drainage structure features were defined, and elevation values were adjusted by generating transects at the location of the drainage structures. An assessment of each hydrologically-enforced drainage structure was conducted using field-surveyed culvert and bridge coordinates obtained from numerous public agencies, but it was discovered the disparate drainage structure datasets were not comprehensive enough to assess all remotely located depressions in need of hydrologic-enforcement. Alternatively, orthoimagery was interpreted to define drainage structures near each depression, and these locations were used as reference points for a quantitative hydrologic-enforcement assessment. The orthoimagery-interpreted reference points resulted in a larger corresponding sample size than the assessment between hydrologic-enforced transects and field-surveyed data. This assessment demonstrates the viability of rules-based hydrologic-enforcement that is needed to achieve hydrologic connectivity, which is valuable for hydrodynamic models in sensitive coastal regions. Hydrologic-enforced elevation data are also essential for merging with topographic/bathymetric elevation data that extend over vulnerable urbanized areas and dynamic coastal

  11. An algorithm for treating flat areas and depressions in digital elevation models using linear interpolation

    EPA Science Inventory

    Digital elevation model (DEM) data are essential to hydrological applications and have been widely used to calculate a variety of useful topographic characteristics, e.g., slope, flow direction, flow accumulation area, stream channel network, topographic index, and others. Excep...

  12. Quantifying Slopes with Digital Elevation Models of the Verdugo Hills, California: Effects of Resolution

    NASA Technical Reports Server (NTRS)

    Fielding, E. J.; Burbank, D. W.; Duncan, C. C.

    1996-01-01

    Quantification of surface slope angles is valuable in a wide variety of earth sciences. Slopes measured from digital elevation models (DEMs) or other topographic data sets depend strongly on the length scale or window size used in the slope calculations.

  13. The Costa Rican Central Valley Lavina Formation: Lahar or Debris Avalanche?

    NASA Astrophysics Data System (ADS)

    Hidalgo, P. J.; Alvarado Induni, G. E.; Linkimer, L.

    2005-12-01

    The Lavina Formation of the Central Valley of Costa Rica consists of lava blocks floating in a volcanic mud matrix. Different authors have interpreted this deposit genetically as a lahar or debris flow deposit. Based on geomorphologic, textural, and morphometric evidence, we conclude that the origin of this deposit is a debris avalanche event that transformed into a debris flow on its path down the valley. Using aerial photographs, many debris avalanche amphitheaters are found in the western sector of the Irazu volcanic complex. However, textural and morphometric characteristics of the deposit are consistent with the source of the sector collapse being located on the west flank of the Cabeza de Vaca volcano. Three-dimensional modeling of the Lavina Formation was done using data from 213 drill cores distributed along the Central Valley area. Maps of isopaches and isohipses of the roof and floor of this stratum were created. These allowed for qualification of morphometry of the stratigraphic surfaces, characterization of the paleoslopes, and quantification of the compacted deposit volume. The data derived form the isopach and isohipse contour maps indicate that abrupt changes in the thickness of the stratum are common. Also, it illustrates the morphological differences between the roof, elongated hills in the direction of the flux, and the floor of the stratum, smooth and uniform. The morphometric, geomorphologic, and textural evidence, were used to conclude that the Lavina deposit originated as a debris avalanche event in the Cabeza de Vaca Volcano. The debris avalanche was eventually fluidized into a debris flow that spread extensively (130 km2) along the Central Valley of Costa Rica.

  14. Temperature elevation of biological tissue model exposed by focused ultrasound with acoustic radiation force

    NASA Astrophysics Data System (ADS)

    Nitta, Naotaka; Kudo, Nobuki; Akiyama, Iwaki

    2012-09-01

    Focused ultrasound with acoustic radiation force (ARF) is beginning to be used for imaging and measuring tissue elasticity. On the other hand, it was suggested that the temperature elevation near bone at focus may be significant within the limits of acoustic output regulation in diagnostic ultrasound devices (Herman; 2002). In this study, with the aim of obtaining the relationships between temperature elevations and parameters of ultrasound exposure with ARF, temperature elevations in two kinds of tissue models with or without bone were numerically evaluated. The results showed that the temperature elevation at focus on the surface of bone may exceed an allowable temperature elevation which WFUMB guideline recommends, even though the acoustic intensity is within the limits of acoustic output regulation in diagnostic ultrasound devices.

  15. Comparative study of lahars generated by the 1961 and 1971 eruptions of Calbuco and Villarrica volcanoes, Southern Andes of Chile

    NASA Astrophysics Data System (ADS)

    Castruccio, Angelo; Clavero, Jorge; Rivera, Andrés

    2010-02-01

    The Villarrica and Calbuco volcanoes, of the Andean Southern Volcanic Zone, are two of the most active volcanoes in Chile and have erupted several times in the XX century. The 1961 eruption at Calbuco volcano generated lahars on the North, East and Southern flanks, while the 1971 eruption at Villarrica volcano generated lahars in almost all the drainages towards the north, west and south of the volcano. The deposits from these eruptions in the Voipir and Chaillupén River (Villarrica) and the Tepú River (Calbuco) are studied. The 1971 lahar deposits on Villarrica volcano show a great number of internal structures such as lamination, lenses, grading of larger clasts and a great abundance of large floating blocks on top of the deposits. The granulometry can be unimodal or bimodal with less than 5% by weight of silt + clay material. SEM images reveal a great variety of forms and compositions of clasts. The 1961 lahar deposits on Calbuco volcano have a scarce number of internal structures, steeper margins and features of hot emplacement such as semi-carbonized vegetal rests, segregation pipes and a more consolidated matrix. The granulometry usually is bimodal with great quantities of silt + clay material (> 10% by weight). SEM images show a uniformity of composition and forms of clasts. Differences on deposits reveal different dynamics on both lahars. The Villarrica lahar was generated by sudden melt of ice and snow during the paroxysmal phase of the 1971 eruption, when a high fountain of lava was formed. The melted water flowed down on the flanks of the volcano and incorporated sediments to become transition flows, highly energetic and were emplaced incrementally. Dilution of the flows occurs when the lahars reached unconfined and flatter areas. In cases where the lahar flow found large water streams, dilution is enhanced. The Calbuco lahars were generated by the dilution of block and ash pyroclastic flows by flowing over the ice or snow or by entering active rivers

  16. Stratigraphic and sedimetological study of relevant lahar deposits of La Lumbre ravine, Colima volcano (Mexico): preliminary results.

    NASA Astrophysics Data System (ADS)

    Sarocchi, D.; Rodriguez-Sedano, L. A.; Saucedo, R.; Capra, L.

    2009-04-01

    Volcán de Colima is the most active volcano of Mexico with more than fifty eruptions documented in the last four centuries. The great amount of pyroclastic material deposited in the volcano slopes represents a perfect source for an intense lahar activity. Despite the intense volcanic activity with production of explosive eruptions and pyroclastic flows, lahars are greatly the most dangerous phenomena at Volcán de Colima. Pyroclastic flows did not reach long distances, generally less than 5 km from the crater. In contrast, lahars travel long distances, up to 10 km, causing damage to infrastructure and being able to affect populated areas. For this reason in the last 100 years more than 350 people died for lahars in the Colima Volcanic Complex and only 8 lost their lives for pyroclastic flows in 1913 plinian eruption. "La Lumbre" ravine is a very important morphological feature in the western-southwestern sector of the volcano, there, it gathers the main drainage system and collects water from "El Playon", a wide intra-caldera basin delimited by the Volcán de Colima to the south and the "Paleofuego" caldera rim to the north. This ravine produced huge lahars such as the 1906 lahar which killed almost 325 people, or the lahars associated with the great 1913 eruption, other associated with de 1990-91 volcanic crisis, and is still very active, continuously remobilizing the 1998-99 pyroclastic flow deposits. In 2002 near the confluence between "La Lumbre" and "El Zarco" Ravine, a house was destroyed fortunately with no danger for people. In order to perform future accurate lahar numerical simulation and obtain reliable hazard study along this ravine, is very important to reconstruct the complex stratigraphy and understand which of such important deposits is related with the 1906, 1913 or 1991 eruptive crisis. For this reason we are performing a detailed stratigraphic study of the lahars sequence. We selected the best outcrops at different distances from the crater. In

  17. Dynamic modeling and experiments on the coupled vibrations of building and elevator ropes

    NASA Astrophysics Data System (ADS)

    Yang, Dong-Ho; Kim, Ki-Young; Kwak, Moon K.; Lee, Seungjun

    2017-03-01

    This study is concerned with the theoretical modelling and experimental verification of the coupled vibrations of building and elevator ropes. The elevator ropes consist of a main rope which supports the cage and the compensation rope which is connected to the compensation sheave. The elevator rope is a flexible wire with a low damping, so it is prone to vibrations. In the case of a high-rise building, the rope length also increases significantly, so that the fundamental frequency of the elevator rope approaches the fundamental frequency of the building thus increasing the possibility of resonance. In this study, the dynamic model for the analysis of coupled vibrations of building and elevator ropes was derived by using Hamilton's principle, where the cage motion was also considered. An experimental testbed was built to validate the proposed dynamic model. It was found that the experimental results are in good agreement with the theoretical predictions thus validating the proposed dynamic model. The proposed model was then used to predict the vibrations of real building and elevator ropes.

  18. Seismic characterisation of lahars at Volcán de Colima, Mexico

    NASA Astrophysics Data System (ADS)

    Vázquez, R.; Suriñach, E.; Capra, L.; Arámbula-Mendoza, R.; Reyes-Dávila, G.

    2016-02-01

    Volcán de Colima is one of the most active volcanoes in Mexico, not only for its eruptive history, but also for its annual occurrence of lahars. This makes the volcano a natural laboratory for monitoring and studying lahar processes. Since 2011, monitoring instruments have been deployed along the highly active Montegrande ravine, with at least three lahar events per year. Here, we report the datasets of three events collected during the 2012 and 2013 seasons, then interpret the acquired data. An event classification scheme based on lahar magnitude, duration and seismic characteristics is presented to distinguish "single-pulse" events (SPEs) from "multi-pulse" events (MPE). SPEs lasted approximately 60 min, had average velocities of ~2 m/s and mean peak discharges of ~24 m3/s. MPEs endured for more than 3 h, reached mean velocities of ~4.5 m/s and peak discharges of ~60 m3/s (for block-rich surges). The seismic signal-analysis also allowed us to discriminate physical flow fluctuations within single lahars, i.e. between the arrival of block-rich fronts and subsequent variations in flow discharge. The exponential regression analysis showed a best fit, with correlation coefficients around 0.92 and exponential coefficients of ~0.01 s, for the block-rich fronts, with seismic amplitudes increasing from 4.8 × 10-4 to 2.3 × 10-3 m/s and frequency ranges from 10 to 20 Hz. The variations in flow discharge were distinguished by lower amplitudes of ~5.7 × 10-4 m/s than those of the block-rich fronts and with frequency ranges of 10-40 Hz. The results presented in this paper demonstrate that the seismic data of events allowed us to describe and discriminate among different flow types; these records are thus a useful investigation tool for lahar events that have a seismic record but are not observed directly. We propose that a seismic early warning system can be developed to help civil protection authorities in designing risk mitigation strategies.

  19. Comparative lahar hazard mapping at Volcan Citlaltépetl, Mexico using SRTM, ASTER and DTED-1 digital topographic data

    USGS Publications Warehouse

    Hubbard, Bernard E.; Sheridan, Michael F.; Carrasco-Nunez, Gerardo; Diaz-Castellon, Rodolfo; Rodriguez, Sergio R.

    2007-01-01

    Finally, ASTERs 60 km swath width and 8% duty cycle presents a challenge for mapping lahar inundation hazards at E–W oriented stream valleys in low-latitude areas with persistent cloud cover. However, its continued operations enhances its utility as a means for updating the continuous but one-time coverage of SRTM, and for filling voids in the SRTM dataset such as those that occur along steep-sided valleys prone to hazards from future lahars.

  20. Mitigation of hazards from future lahars from Mount Merapi in the Krasak River channel near Yogyakarta, central Java

    USGS Publications Warehouse

    Ege, John R.; ,

    1983-01-01

    Procedures for reducing hazards from future lahars and debris flows in the Krasak River channel near Yogyakarta, Central Java, Indonesia, include (1) determining the history of the location, size, and effects of previous lahars and debris flows, and (2) decreasing flow velocities. The first may be accomplished by geologic field mapping along with acquiring information by interviewing local residents, and the second by increasing the cross sectional area of the river channel and constructing barriers in the flow path.

  1. Rainfall-triggered lahars at Volcán de Colima, Mexico: Surface hydro-repellency as initiation process

    NASA Astrophysics Data System (ADS)

    Capra, L.; Borselli, L.; Varley, N.; Gavilanes-Ruiz, J. C.; Norini, G.; Sarocchi, D.; Caballero, L.; Cortes, A.

    2010-01-01

    Volcán de Colima is currently the most active volcano in Mexico. Since 1998 intermittent activity has been observed with vulcanian eruptions, lava flows and growing domes that have collapsed producing several block-and-ash flow deposits. During the period of heightened activity since 1998 at Volcán de Colima, pyroclastic flows from dome or column collapse have not reached long distances, most of the time less than 6 km from the crater. In contrast, rain-induced lahars were more frequent and have reached relatively long distances, up to 15 km, causing damage to infrastructure and affecting small villages. In 2007 two rain gauge stations were installed on the southern flank of the volcano registering events from June through to October, the period when rains are intense and lahars frequent. By comparing lahar frequency with rainfall intensity and the rainfall accumulated during the previous 3 days, lahars more frequently occur at the beginning of the rainfall season, with low rain accumulation (< 10 mm) and triggered by low rain intensities (< 20 mm/h). During the months with more rainfall (July and August) lahars are less frequent and higher peak intensities (up to 70 mm/h) are needed to trigger an event. In both cases, lahars were initiated as dilute, sediment-laden streamflows, which transformed with entrainment of additional sediment into hyperconcentrated and debris flows, with alternations between these two flow types. A hydro-repellency mechanism in highly vegetated areas (i.e. evergreen tree types with considerable amount of resins and waxes such as pines) with sandy soils can probably explain the high frequency of lahars at the beginning of the rain season during low rainfall events. Under hydrophobic conditions, infiltration is inhibited and runoff is facilitated at more highly peaked discharges that are more likely to initiate lahars.

  2. Process-scale modeling of elevated wintertime ozone in Wyoming.

    SciTech Connect

    Kotamarthi, V. R.; Holdridge, D. J.; Environmental Science Division

    2007-12-31

    Measurements of meteorological variables and trace gas concentrations, provided by the Wyoming Department of Environmental Quality for Daniel, Jonah, and Boulder Counties in the state of Wyoming, were analyzed for this project. The data indicate that highest ozone concentrations were observed at temperatures of -10 C to 0 C, at low wind speeds of about 5 mph. The median values for nitrogen oxides (NOx) during these episodes ranged between 10 ppbv and 20 ppbv (parts per billion by volume). Measurements of volatile organic compounds (VOCs) during these periods were insufficient for quantitative analysis. The few available VOCs measurements indicated unusually high levels of alkanes and aromatics and low levels of alkenes. In addition, the column ozone concentration during one of the high-ozone episodes was low, on the order of 250 DU (Dobson unit) as compared to a normal column ozone concentration of approximately 300-325 DU during spring for this region. Analysis of this observation was outside the scope of this project. The data analysis reported here was used to establish criteria for making a large number of sensitivity calculations through use of a box photochemical model. Two different VOCs lumping schemes, RACM and SAPRC-98, were used for the calculations. Calculations based on this data analysis indicated that the ozone mixing ratios are sensitive to (a) surface albedo, (b) column ozone, (c) NOx mixing ratios, and (d) available terminal olefins. The RACM model showed a large response to an increase in lumped species containing propane that was not reproduced by the SAPRC scheme, which models propane as a nearly independent species. The rest of the VOCs produced similar changes in ozone in both schemes. In general, if one assumes that measured VOCs are fairly representative of the conditions at these locations, sufficient precursors might be available to produce ozone in the range of 60-80 ppbv under the conditions modeled.

  3. A voluminous avalanche-induced lahar from Citlaltépetl volcano, Mexico: Implications for hazard assessment

    NASA Astrophysics Data System (ADS)

    Carrasco-Núñez, Gerardo; Vallance, James W.; Rose, William I.

    1993-12-01

    During the late Pleistocene the ancestral edifice of Citlaltépetl volcano (also known as Pico de Orizaba) collapsed to form a clay-rich deposit that extends 85 km from its source, has a volume of 1.8 km 3, and covers an area of 143 km 2 east of the volcano. The deposit has clay content ranging from 10 to 16% and contains secondary alteration minerals such as smectite and kaolinite. The deposit's features suggest that it had an origin as a sector collapse of hydrothermally altered rock that transformed from a debris avalanche to a cohesive lahar very close to its source. The presence of glacier ice and a hydrothermal system during late Pleistocene times apparently provided a source of pore water which enhanced the hydrothermal alteration of the summit of Citlaltépetl and was the origin of most of the water for the lahar. This deposit and several others suggest that glaciated volcanoes are sites where hydrothermal alteration and resulting cohesive lahars are most likely. Although cohesive lahars and debris avalanches both have origins as sector collapses, cohesive lahars are more mobile than similar-sized debris avalanches. Thus potential hazard of edifice collapse at glaciated volcanoes, especially those with large volumes of hydrothermally altered rock, includes the possibility of large-volume cohesive lahars.

  4. Monitoring the Dynamic of a Fluvial Channel after Lahar Disturbance: Huiloac Gorge (Popocatepetl Volcano, Mexico)

    NASA Astrophysics Data System (ADS)

    Andres, N.; Palacios, D.; Zamorano, J. J.; Tanarro, L. M.; Renschler, C.; Sanjosé, J. J.; Atkinson, A.

    2009-04-01

    Volcanic eruptions generate disturbances that affect hydrological systems (Major, 2003) by depositing large volumes of sediments in watersheds that exceed amounts common to non-volcanic river systems (Montgomery, 2005). If the eruption releases abundant melt water, the river system may respond immediately by forming hazardous flows called lahars. River system recovery following eruptive and laharic impact is an important process, but it has received little attention (Gran and Montgomery, 2005) despite the fact that Major et al. (2000) and Hayes et al. (2002) have shown that these disruptions cause long term instability and their effects persist for decades. Lahar deposits resulting from interaction between volcanic activity and the glacier located above the Huiloac Gorge on the northern slope of Popocatepetl volcano (19°02´ N, 98°62´ W, 5,424 m), have infilled the gorge (Palacios, 1995; Palacios et al., 1998 and 2001; Capra et al., 2004; Muñoz, 2007). All of the major lahars that occurred on the volcano in 1995 (4 km), 1997 (21 km), and 2001 (14 km) have channelled through Huiloac Gorge, and have dramatically altered its morphology and dynamics through erosion and deposition. The present study traces these changes in the aftermath of the laharic events that occurred from 1997-2001. A sector of the channel, located at 3200m-3240m altitude, of 500 m long and 15 to 20 m wide, in the mid-section of the gorge, was chosen as the control site. Precipitation is heaviest there and is most apt to trigger secondary post-eruptive lahars. ArcGis software was used to draw 6 geomorphic maps of the site showing spatial variations in the landforms for the period February 2002 - February 2008. In addition, 29 cross-profiles were made of the gorge for the same time interval, excluding February 2004. The volume of sediment eroded and deposited was calculated for each date by comparing variations in the height of the floor and banks of the gorge depicted in the cross-profile, and

  5. Mouse model of sustained elevation in intraocular pressure produced by episcleral vein occlusion.

    PubMed

    Ruiz-Ederra, Javier; Verkman, A S

    2006-05-01

    We have developed an inducible mouse model of glaucoma based on episcleral vein cauterization (EVC). Intraocular pressure (IOP) elevation in adult mice was produced by cauterizing three episcleral veins. Serial IOP measurements were done by induction-impact tonometry. IOP was significantly elevated by 104+/-20% in 20 out of 23 mice (87%) within the first day after EVC, and remained elevated for 4 weeks, with mean IOP 94% higher in EVC-treated vs. contralateral control eyes. Aqueous outflow blockade was verified from the IOP response to pulsed fluid infusions into the anterior chamber. Retinal ganglion cell (RGC) loss, determined by retrograde labelling using Fluoro-Gold applied to the superior colliculous, was approximately 20% at 2 weeks after EVC. We conclude that episcleral vein occlusion in mice produces significant and sustained elevation in IOP associated with increased outflow resistance and RGC loss, and thus may be useful to model glaucoma in genetically modified and drug-treated mice.

  6. Eruption-triggered avalanche, flood, and lahar at mount st. Helens--effects of winter snowpack.

    PubMed

    Waitt, R B; Pierson, T C; Macleod, N S; Janda, R J; Voight, B; Holcomb, R T

    1983-09-30

    An explosive eruption of Mount St. Helens on 19 March 1982 had substantial impact beyond the vent because hot eruption products interacted with a thick snowpack. A blast of hot pumice, dome rocks, and gas dislodged crater-wall snow that avalanched through the crater and down the north flank. Snow in the crater swiftly melted to form a transient lake, from which a destructive flood and lahar swept down the north flank and the North Fork Toutle River.

  7. Eruption-triggered avalanche, flood, and lahar at Mount St. Helens - Effects of winter snowpack

    USGS Publications Warehouse

    Waitt, R.B.; Pierson, T.C.; MacLeod, N.S.; Janda, R.J.; Voight, B.; Holcomb, R.T.

    1983-01-01

    An explosive eruption of Mount St. Helens on 19 March 1982 had substantial impact beyond the vent because hot eruption products interacted with a thick snowpack. A blast of hot pumice, dome rocks, and gas dislodged crater-wall snow that avalanched through the crater and down the north flank. Snow in the crater swiftly melted to form a transient lake, from which a destructive flood and lahar swept down the north flank and the North Fork Toutle River.

  8. Assessment of Required Accuracy of Digital Elevation Data for Hydrologic Modeling

    NASA Technical Reports Server (NTRS)

    Kenward, T.; Lettenmaier, D. P.

    1997-01-01

    The effect of vertical accuracy of Digital Elevation Models (DEMs) on hydrologic models is evaluated by comparing three DEMs and resulting hydrologic model predictions applied to a 7.2 sq km USDA - ARS watershed at Mahantango Creek, PA. The high resolution (5 m) DEM was resempled to a 30 m resolution using method that constrained the spatial structure of the elevations to be comparable with the USGS and SIR-C DEMs. This resulting 30 m DEM was used as the reference product for subsequent comparisons. Spatial fields of directly derived quantities, such as elevation differences, slope, and contributing area, were compared to the reference product, as were hydrologic model output fields derived using each of the three DEMs at the common 30 m spatial resolution.

  9. Calculation and Error Analysis of a Digital Elevation Model of Hofsjokull, Iceland from SAR Interferometry

    NASA Technical Reports Server (NTRS)

    Barton, Jonathan S.; Hall, Dorothy K.; Sigurosson, Oddur; Williams, Richard S., Jr.; Smith, Laurence C.; Garvin, James B.

    1999-01-01

    Two ascending European Space Agency (ESA) Earth Resources Satellites (ERS)-1/-2 tandem-mode, synthetic aperture radar (SAR) pairs are used to calculate the surface elevation of Hofsjokull, an ice cap in central Iceland. The motion component of the interferometric phase is calculated using the 30 arc-second resolution USGS GTOPO30 global digital elevation product and one of the ERS tandem pairs. The topography is then derived by subtracting the motion component from the other tandem pair. In order to assess the accuracy of the resultant digital elevation model (DEM), a geodetic airborne laser-altimetry swath is compared with the elevations derived from the interferometry. The DEM is also compared with elevations derived from a digitized topographic map of the ice cap from the University of Iceland Science Institute. Results show that low temporal correlation is a significant problem for the application of interferometry to small, low-elevation ice caps, even over a one-day repeat interval, and especially at the higher elevations. Results also show that an uncompensated error in the phase, ramping from northwest to southeast, present after tying the DEM to ground-control points, has resulted in a systematic error across the DEM.

  10. The Importance of Precise Digital Elevation Models (DEM) in Modelling Floods

    NASA Astrophysics Data System (ADS)

    Demir, Gokben; Akyurek, Zuhal

    2016-04-01

    Digital elevation Models (DEM) are important inputs for topography for the accurate modelling of floodplain hydrodynamics. Floodplains have a key role as natural retarding pools which attenuate flood waves and suppress flood peaks. GPS, LIDAR and bathymetric surveys are well known surveying methods to acquire topographic data. It is not only time consuming and expensive to obtain topographic data through surveying but also sometimes impossible for remote areas. In this study it is aimed to present the importance of accurate modelling of topography for flood modelling. The flood modelling for Samsun-Terme in Blacksea region of Turkey is done. One of the DEM is obtained from the point observations retrieved from 1/5000 scaled orthophotos and 1/1000 scaled point elevation data from field surveys at x-sections. The river banks are corrected by using the orthophotos and elevation values. This DEM is named as scaled DEM. The other DEM is obtained from bathymetric surveys. 296 538 number of points and the left/right bank slopes were used to construct the DEM having 1 m spatial resolution and this DEM is named as base DEM. Two DEMs were compared by using 27 x-sections. The maximum difference at thalweg of the river bed is 2m and the minimum difference is 20 cm between two DEMs. The channel conveyance capacity in base DEM is larger than the one in scaled DEM and floodplain is modelled in detail in base DEM. MIKE21 with flexible grid is used in 2- dimensional shallow water flow modelling. The model by using two DEMs were calibrated for a flood event (July 9, 2012). The roughness is considered as the calibration parameter. From comparison of input hydrograph at the upstream of the river and output hydrograph at the downstream of the river, the attenuation is obtained as 91% and 84% for the base DEM and scaled DEM, respectively. The time lag in hydrographs does not show any difference for two DEMs and it is obtained as 3 hours. Maximum flood extents differ for the two DEMs

  11. Tectonic development of the Northwest Bonaparte Basin, Australia by using Digital Elevation Model (DEM)

    NASA Astrophysics Data System (ADS)

    Wahid, Ali; Salim, Ahmed Mohamed Ahmed; Ragab Gaafar, Gamal; Yusoff, AP Wan Ismail Wan

    2016-02-01

    The Bonaparte Basin consist of majorly offshore part is situated at Australia's NW continental margin, covers an area of approx. 270,000km2. Bonaparte Basin having a number of sub-basins and platform areas of Paleozoic and Mesozoic is structurally complex. This research established the geologic and geomorphologic studies using Digital Elevation Model (DEM) as a substitute approach in morphostructural analysis to unravel the geological complexities. Although DEMs have been in practice since 1990s, they still have not become common tool for mapping studies. The research work comprised of regional structural analysis with the help of integrated elevation data, satellite imageries, available open topograhic images and internal geological maps with interpreted seismic. The structural maps of the study area have been geo-referenced which further overlaid onto SRTM data and satellite images for combined interpretation which facilitate to attain Digital Elevation Model of the study area. The methodology adopts is to evaluate and redefine development of geodynamic processes involved in formation of Bonaparte Basin. The main objectives is to establish the geological histories by using digital elevation model. The research work will be useful to incorporate different tectonic events occurred at different Geological times in a digital elevation model. The integrated tectonic analysis of different digital data sets benefitted substantially from combining them into a common digital database. Whereas, the visualization software facilitates the overlay and combined interpretation of different data sets which is helpful to reveal hidden information not obvious or accessible otherwise for regional analysis.

  12. An approach to source characterization of tremor signals associated with eruptions and lahars

    NASA Astrophysics Data System (ADS)

    Kumagai, Hiroyuki; Mothes, Patricia; Ruiz, Mario; Maeda, Yuta

    2015-11-01

    Tremor signals are observed in association with eruption activity and lahar descents. Reduced displacement ( D R) derived from tremor signals has been used to quantify tremor sources. However, tremor duration is not considered in D R, which makes it difficult to compare D R values estimated for different tremor episodes. We propose application of the amplitude source location (ASL) method to characterize the sources of tremor signals. We used this method to estimate the tremor source location and source amplitude from high-frequency (5-10 Hz) seismic amplitudes under the assumption of isotropic S-wave radiation. We considered the source amplitude to be the maximum value during tremor. We estimated the cumulative source amplitude ( I s) as the offset value of the time-integrated envelope of the vertical seismogram of tremor corrected for geometrical spreading and medium attenuation in the 5-10-Hz band. For eruption tremor signals, we also estimated the cumulative source pressure ( I p) from an infrasonic envelope waveform corrected for geometrical spreading. We studied these parameters of tremor signals associated with eruptions and lahars and explosion events at Tungurahua volcano, Ecuador. We identified two types of eruption tremor at Tungurahua: noise-like inharmonic waveforms and harmonic oscillatory signals. We found that I s increased linearly with increasing source amplitude for lahar tremor signals and explosion events, but I s increased exponentially with increasing source amplitude for inharmonic eruption tremor signals. The source characteristics of harmonic eruption tremor signals differed from those of inharmonic tremor signals. We found a linear relation between I s and I p for both explosion events and eruption tremor. Because I p may be proportional to the total mass involved during an eruption episode, this linear relation suggests that I s may be useful to quantify eruption size. The I s values we estimated for inharmonic eruption tremor were

  13. Syn and post- emplacement transformations of the Misti (Peru) volcanic debris avalanches into lahars

    NASA Astrophysics Data System (ADS)

    Bernard, K.; Van Wyk de Vries, B.; Thouret, J.

    2012-12-01

    We identify stratigraphic, sedimentological and structural variations in lithofacies of debris-avalanche deposits from El Misti volcano in the Quebrada San Lazaro and Río Chili Valley, near the city of Arequipa (south Peru), to determine lithofacies transformations. We describe the internal process associated to the external conditions acting on debris-avalanche deposits in order to assess stages of transformations from the proximal to distal debris-avalanche deposits and the associated epiclastic deposits. Syn-emplacement transformations inside the volcanic debris-avalanche deposits in the upper course of the Rio Chili Valley: within a few meters, the proximal block facies of the sheared debris-avalanche deposit is transformed at the contact of the ash-rich alluvial deposits in thick units comprising a strongly sheared base of the deposit, then stratified matrix dominated beds with normally sorted boulders aligned with the beds. This is interpreted as the effect of strong shearing inside the confined and proximal debris avalanche during motion, which generated a localised stretching near the base of the deposit and the bulking of the thin water saturated basal layers: the bearing capacity of the matrix debris- avalanche is modified, the block facies has been transformed in a stratified matrix facies. The transformations by bulking along a strong sheared contact contribute to reduce the run-out distance of the debris avalanches in the Río Chili valley. Post-deposition evolutions of the debris-avalanche deposits in the Quebrada San Lazaro: in the upper course of the valley, the landslides in the debris- avalanche deposits related to water circulation destabilise the covering scree and volcanic colluvium dipping at 70°. The fragmentation and sorting due to gravity and water are the external processes which separate matrix and block elements; This is the first stage of transformation. The remobilisation of these separated fractions into lahars transforms this

  14. The influence of digital elevation model resolution on overland flow networks for modelling urban pluvial flooding.

    PubMed

    Leitão, J P; Boonya-Aroonnet, S; Prodanović, D; Maksimović, C

    2009-01-01

    This paper presents the developments towards the next generation of overland flow modelling of urban pluvial flooding. Using a detailed analysis of the Digital Elevation Model (DEM) the developed GIS tools can automatically generate surface drainage networks which consist of temporary ponds (floodable areas) and flow paths and link them with the underground network through inlets. For different commercially-available Rainfall-Runoff simulation models, the tool will generate the overland flow network needed to model the surface runoff and pluvial flooding accurately. In this paper the emphasis is placed on a sensitivity analysis of ponds and preferential overland flow paths creation. Different DEMs for three areas were considered in order to compare the results obtained. The DEMs considered were generated using different acquisition techniques and hence represent terrain with varying levels of resolution and accuracy. The results show that DEMs can be used to generate surface flow networks reliably. As expected, the quality of the surface network generated is highly dependent on the quality and resolution of the DEMs and successful representation of buildings and streets.

  15. Voluminous ice-rich and water-rich lahars generated during the 2009 eruption of Redoubt Volcano, Alaska

    NASA Astrophysics Data System (ADS)

    Waythomas, Christopher F.; Pierson, Thomas C.; Major, Jon J.; Scott, William E.

    2013-06-01

    Redoubt Volcano in south-central Alaska began erupting on March 15, 2009, and by April 4, 2009, had produced at least 20 explosive events that generated multiple plumes of ash and numerous lahars. The 3108-m-high, snow- and ice-clad stratovolcano has an ice-filled summit crater that is breached to the north. The volcano supports about 4 km3 of ice and snow and about 1 km3 of this makes up the Drift glacier on the north side of the volcano. Explosive eruptions between March 23 and April 4, which included the destruction of at least two lava domes, triggered significant lahars in the Drift River valley on March 23 and April 4, and several smaller lahars between March 24 and March 31. Mud-line high-water marks, character of deposits, areas of inundation, and estimates of flow velocity revealed that the lahars on March 23 and April 4 were the largest of the eruption. In the 2-km-wide upper Drift River valley, average flow depths were at least 2-5 m. Average peak-flow velocities were likely between 10 and 15 ms- 1, and peak discharges were on the order of 104-105 m3 s- 1. The area inundated by lahars on March 23 was at least 100 km2 and on April 4 about 125 km2. Two substantial lahars emplaced on March 23 and one on April 4 had volumes on the order of 107-108 m3 and were similar in size to the largest lahar of the 1989-90 eruption. The two principal March 23 lahars were primarily flowing slurries of snow and ice derived from Drift glacier and the Drift River valley where seasonal snow and tabular blocks of river ice were entrained and incorporated into the lahars. Despite morphologic evidence of two lahars, only a single deposit up to 5 m thick was found in most places and it contained about 80-95% of poorly sorted, massive to imbricate assemblages of snow and ice clasts. The deposit was frozen soon after it was emplaced and later eroded and buried by the April 4 lahar. The lahar of April 4, in contrast, was primarily a hyperconcentrated flow, as interpreted from 1- to

  16. Test of the depression distress amplification model in young adults with elevated risk of current suicidality.

    PubMed

    Capron, Daniel W; Lamis, Dorian A; Schmidt, Norman B

    2014-11-30

    Suicide is a leading cause of death among young adults and the rate of suicide has been increasing for decades. A depression distress amplification model posits that young adults with comorbid depression and anxiety have elevated suicide rates due to the intensification of their depressive symptoms by anxiety sensitivity cognitive concerns. The current study tested the effects of anxiety sensitivity subfactors as well as the depression distress amplification model in a very large sample of college students with elevated suicide risk. Participants were 721 college students who were at elevated risk of suicidality (scored>0 on the Beck Scale for Suicide Ideation). Consistent with prior work, anxiety sensitivity cognitive concerns, but not physical or social concerns, were associated with suicidal ideation. Consistent with the depression distress amplification model, in individuals high in depression, anxiety sensitivity cognitive concerns predicted elevated suicidal ideation but not among those with low depression. The results of this study corroborate the role of anxiety sensitivity cognitive concerns and the depression distress amplification model in suicidal ideation among a large potentially high-risk group of college students. The depression distress amplification model suggests a specific mechanism, anxiety sensitivity cognitive concerns, that may be responsible for increased suicide rates among those with comorbid anxiety and depression.

  17. Modeling forest ecosystem responses to elevated carbon dioxide and ozone using artificial neural networks.

    PubMed

    Larsen, Peter E; Cseke, Leland J; Miller, R Michael; Collart, Frank R

    2014-10-21

    Rising atmospheric levels of carbon dioxide and ozone will impact productivity and carbon sequestration in forest ecosystems. The scale of this process and the potential economic consequences provide an incentive for the development of models to predict the types and rates of ecosystem responses and feedbacks that result from and influence of climate change. In this paper, we use phenotypic and molecular data derived from the Aspen Free Air CO2 Enrichment site (Aspen-FACE) to evaluate modeling approaches for ecosystem responses to changing conditions. At FACE, it was observed that different aspen clones exhibit clone-specific responses to elevated atmospheric levels of carbon dioxide and ozone. To identify the molecular basis for these observations, we used artificial neural networks (ANN) to examine above and below-ground community phenotype responses to elevated carbon dioxide, elevated ozone and gene expression profiles. The aspen community models generated using this approach identified specific genes and subnetworks of genes associated with variable sensitivities for aspen clones. The ANN model also predicts specific co-regulated gene clusters associated with differential sensitivity to elevated carbon dioxide and ozone in aspen species. The results suggest ANN is an effective approach to predict relevant gene expression changes resulting from environmental perturbation and provides useful information for the rational design of future biological experiments.

  18. Acute Electrocardiographic ST Segment Elevation May Predict Hypotension in a Swine Model of Severe Cyanide Toxicity

    DTIC Science & Technology

    2012-04-21

    induced shock, 30 swine were anesthetized and monitored and then intoxicated with a continuous cyanide infusion until severe hypotension (50 % of...TOXICOLOGY INVESTIGATION Acute Electrocardiographic ST Segment ElevationMay Predict Hypotension in a Swine Model of Severe Cyanide Toxicity Tylan A...Toxicology 2012 Abstract Cyanide causes severe cardiac toxicity resulting in tachycardia, hypotension, and cardiac arrest; however, the clinical diagnosis can

  19. Lunar Topography and Basins Mapped Using a Clementine Stereo Digital Elevation Model

    NASA Technical Reports Server (NTRS)

    Cook, A. C.; Spudis, P. D.; Robinson, M. S.; Watters, T. R.

    2002-01-01

    Planet-wide (1 km/pixel and 5 km/pixel) Digital Elevation Models (DEM) of the Moon have been produced using Clementine UVVIS (Ultraviolet-Visible) stereo. Six new basins have been discovered, two suspected basins have been confirmed, and the dimensions of existing basins better defined. Additional information is contained in the original extended abstract.

  20. Modeling the population dynamics of Culex quinquefasciatus (Diptera: Culicidae), along an elevational gradient in Hawaii.

    PubMed

    Ahumada, Jorge A; Lapointe, Dennis; Samuel, Michael D

    2004-11-01

    We present a population model to understand the effects of temperature and rainfall on the population dynamics of the southern house mosquito, Culex quinquefasciatus Say, along an elevational gradient in Hawaii. We use a novel approach to model the effects of temperature on population growth by dynamically incorporating developmental rate into the transition matrix, by using physiological ages of immatures instead of chronological age or stages. We also model the effects of rainfall on survival of immatures as the cumulative number of days below a certain rain threshold. Finally, we incorporate density dependence into the model as competition between immatures within breeding sites. Our model predicts the upper altitudinal distributions of Cx. quinquefasciatus on the Big Island of Hawaii for self-sustaining mosquito and migrating summer sink populations at 1,475 and 1,715 m above sea level, respectively. Our model predicts that mosquitoes at lower elevations can grow under a broader range of rainfall parameters than middle and high elevation populations. Density dependence in conjunction with the seasonal forcing imposed by temperature and rain creates cycles in the dynamics of the population that peak in the summer and early fall. The model provides a reasonable fit to the available data on mosquito abundance for the east side of Mauna Loa, Hawaii. The predictions of our model indicate the importance of abiotic conditions on mosquito dynamics and have important implications for the management of diseases transmitted by Cx. quinquefasciatus in Hawaii and elsewhere.

  1. The effects of elevation data representation on mesoscale atmospheric model simulations

    SciTech Connect

    Walker, H.; Leone, J.M. Jr.; Kim, Jinwon

    1996-01-01

    Mesoscale atmospheric model simulations rely on descriptions of the land surface characteristics, which must be developed from geographic databases. Certain features of the geographic data, such as its resolution and accuracy, as well as the method of processing for use in the model, can be very important in producing accurate model simulations. The work described here is part of research effort into the relationship between these aspects of geographic data and the performance of mesoscale atmospheric models and is particularly focused on elevation data and how it is prepared for use in such models. A source for digital elevation data will typically not be at the resolution required for a given model simulation and so a resampling step is required. In addition, predictive non-linear model often cannot accept forcing at high spatial frequencies due to the terrain, thus smoothing is also required. The effect of different means of resampling and smoothing elevation data on two types of model simulations is investigated. At smaller spatial scales, nocturnal drainage winds in mountain valleys in Colorado are examined for effects on the general characteristics as well as the details of the flows. At the larger end of the mesoscale, extended simulations of California weather are examined for effects on orographic lifting, low-level convergence and divergence and ultimately rain and snow distribution.

  2. Incorporating Community Knowledge to Lahar Hazard Maps: Canton Buenos Aires Case Study, at Santa Ana (Ilamatepec) Volcano

    NASA Astrophysics Data System (ADS)

    Bajo, J. V.; Martinez-Hackert, B.; Polio, C.; Gutierrez, E.

    2015-12-01

    Santa Ana (Ilamatepec) Volcano is an active composite volcano located in the Apaneca Volcanic Field located in western part of El Salvador, Central America. The volcano is surrounded by rural communities in its proximal areas and the second (Santa Ana, 13 km) and fourth (Sonsosante, 15 km) largest cities of the country. On October 1st, 2005, the volcano erupted after months of increased activity. Following the eruption, volcanic mitigation projects were conducted in the region, but the communities had little or no input on them. This project consisted in the creation of lahar volcanic hazard map for the Canton Buanos Aires on the northern part of the volcano by incorporating the community's knowledge from prior events to model parameters and results. The work with the community consisted in several meetings where the community members recounted past events. They were asked to map the outcomes of those events using either a topographic map of the area, a Google Earth image, or a blank paper poster size. These maps have been used to identify hazard and vulnerable areas, and for model validation. These maps were presented to the communities and they accepted their results and the maps.

  3. Controls on interior West Antarctic Ice Sheet Elevations: inferences from geologic constraints and ice sheet modeling

    NASA Astrophysics Data System (ADS)

    Ackert, Robert P.; Putnam, Aaron E.; Mukhopadhyay, Sujoy; Pollard, David; DeConto, Robert M.; Kurz, Mark D.; Borns, Harold W.

    2013-04-01

    Knowledge of the West Antarctic Ice Sheet (WAIS) response to past sea level and climate forcing is necessary to predict its response to warmer temperatures in the future. The timing and extent of past interior WAIS elevation changes provides insight to WAIS behavior and constraints for ice sheet models. Constraints prior to the Last Glacial Maximum (LGM) however, are rare. Surface exposure ages of glacial erratics near the WAIS divide at Mt. Waesche in Marie Byrd Land, and at the Ohio Range in the Transantarctic Mountains, range from ∼10 ka to >500 ka without a dependence on elevation. The probability distribution functions (PDF) of the exposure ages at both locations, are remarkably similar. During the last glaciation, maximum interior ice elevations as recorded by moraines and erratics were reached between 10 ka and 12 ka. However, most exposure ages are older than the LGM and cluster around ∼40 ka and ∼80 ka. The peak in the exposure age distributions at ∼40 ka includes ages of alpine moraine boulders at Mercer Ridge in the Ohio Range. Comparison of the PDF of exposures ages from the Ohio Range and Mt. Waesche with the temperature record from the Fuji Dome ice core indicates that the youngest peak in the exposure age distributions corresponds to the abrupt warming during the Last Glacial termination. A prominent peak in the Ohio Range PDF corresponds to the penultimate termination (stage 5e). During the intervening glacial period, there is not a consistent relationship between the peaks in the PDF at each location and temperature. A combined ice sheet/ice shelf model with forcing scaled to marine δ18O predicts that interior WAIS elevations near the ice divide have varied ∼300 m over the Last Glacial cycle. Peaks in the PDF correspond to model highstands over the last 200 ka. In the simulated elevation history, maximum ice elevations at Ohio Range (+100 m) and Mt. Waesche (+60 m) occur at ∼10 ka, in agreement with observations from these sites

  4. A seamless, high-resolution digital elevation model (DEM) of the north-central California coast

    USGS Publications Warehouse

    Foxgrover, Amy C.; Barnard, Patrick L.

    2012-01-01

    A seamless, 2-meter resolution digital elevation model (DEM) of the north-central California coast has been created from the most recent high-resolution bathymetric and topographic datasets available. The DEM extends approximately 150 kilometers along the California coastline, from Half Moon Bay north to Bodega Head. Coverage extends inland to an elevation of +20 meters and offshore to at least the 3 nautical mile limit of state waters. This report describes the procedures of DEM construction, details the input data sources, and provides the DEM for download in both ESRI Arc ASCII and GeoTIFF file formats with accompanying metadata.

  5. ICESat Lidar and Global Digital Elevation Models: Application to DESDynI

    NASA Technical Reports Server (NTRS)

    Carabajal, Claudia C.; Harding, David J.; Suchdeo, Vijay P.

    2010-01-01

    Geodetic control is extremely important in the production and quality control of topographic data sets, enabling elevation results to be referenced to an absolute vertical datum. Global topographic data with improved geodetic accuracy achieved using global Ground Control Point (GCP) databases enable more accurate characterization of land topography and its change related to solid Earth processes, natural hazards and climate change. The multiple-beam lidar instrument that will be part of the NASA Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) mission will provide a comprehensive, global data set that can be used for geodetic control purposes. Here we illustrate that potential using data acquired by NASA's Ice, Cloud and land Elevation Satellite (ICEsat) that has acquired single-beam, globally distributed laser altimeter profiles (+/-86deg) since February of 2003 [1, 2]. The profiles provide a consistently referenced elevation data set with unprecedented accuracy and quantified measurement errors that can be used to generate GCPs with sub-decimeter vertical accuracy and better than 10 m horizontal accuracy. Like the planned capability for DESDynI, ICESat records a waveform that is the elevation distribution of energy reflected within the laser footprint from vegetation, where present, and the ground where illuminated through gaps in any vegetation cover [3]. The waveform enables assessment of Digital Elevation Models (DEMs) with respect to the highest, centroid, and lowest elevations observed by ICESat and in some cases with respect to the ground identified beneath vegetation cover. Using the ICESat altimetry data we are developing a comprehensive database of consistent, global, geodetic ground control that will enhance the quality of a variety of regional to global DEMs. Here we illustrate the accuracy assessment of the Shuttle Radar Topography Mission (SRTM) DEM produced for Australia, documenting spatially varying elevation biases of several meters

  6. Gravity modeling reveals that the "Miocene Pyrenean peneplain" developed at high elevation

    NASA Astrophysics Data System (ADS)

    Bosch, Gemma V.; Van Den Driessche, Jean; Robert, Alexandra; Babault, Julien; Le Carlier, Christian

    2016-04-01

    Geodynamics that shaped the present morphology of the western Mediterranean are mostly linked to the African-Eurasia collision and the extension related to the Mediterranean opening. The Pyrenean chain formed by the collision between the Iberian microplate and the Eurasian plate from the Eocene to the late Oligocene. This resulted in lithosphere thickening especially below the Central Pyrenees that becomes thinner eastwards. Whether the later thinning of the lithosphere in the easternmost Pyrenees involves the removal of the lithospheric mantle or not is debated. This issue joins the problematics about the origin of the high-elevation of the "Miocene Pyrenean peneplain" remnants. Indeed the most striking feature of the Pyrenean morphology is the occurrence of high-elevation, low relief erosional surfaces that are interpreted as the remnants of a Miocene single planation surface, dissected and reworked by Quaternary fluvial and glacial erosion. Two end-member interpretations have proposed to explain the high elevation of this original surface. The first considers that the Miocene Pyrenean peneplain develops near sea-level and was later uplifted, the second claims that the planation surface developed at high elevation in response to the inhibition of erosion consecutively to the progressive rise of the base-level of the Pyrenean drainage network. The first interpretation implies the return to normal crustal thickness by erosion and later uplift by removal of the lithospheric mantle. The second interpretation considers that the mean elevation of the original planation surface matches the thickness of the lithosphere below the chain, taking into account some hundred meters of isostatic rebound due to Quaternary erosion. To test these interpretations, we first restore the Miocene original planation surface by mapping and interpolating the high-elevation, low relief surfaces across the Pyrenees. We then performed 1D and 2D gravity models that we compare with recent

  7. Extraction of Subsurface Features from InSAR-Derived Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Xiong, Siting; Muller, Jan-Peter

    2015-05-01

    Microwave remote sensing has the potential to be a beneficial tool to detect and analyse subsurface features in desert areas due to its penetration ability over hyperarid regions with extremely low loss and low bulk humidity. Global Digital Elevation Models (DEMs) of resolution up to 30 m are now publicly available, some of which show subsurface features over these hyperarid areas. This study compares different elevations detected by different EO microwave and lidar profilers and demonstrates their effectiveness in terms of extraction of subsurface features compared with that delineated in ALOS/PALSAR polarisation map. Results show that SRTM-C DEM agrees closely with ICESat elevations and that SRTM-C DEM clearly show paleoriver features, some of which can’t be observed in ALOS/PALSAR images affected by background backscatter. However, craterlike features are more recognisable in ALOS/PALSAR images compared with SRTM-C DEM.

  8. A computational-grid based system for continental drainage network extraction using SRTM digital elevation models

    NASA Technical Reports Server (NTRS)

    Curkendall, David W.; Fielding, Eric J.; Pohl, Josef M.; Cheng, Tsan-Huei

    2003-01-01

    We describe a new effort for the computation of elevation derivatives using the Shuttle Radar Topography Mission (SRTM) results. Jet Propulsion Laboratory's (JPL) SRTM has produced a near global database of highly accurate elevation data. The scope of this database enables computing precise stream drainage maps and other derivatives on Continental scales. We describe a computing architecture for this computationally very complex task based on NASA's Information Power Grid (IPG), a distributed high performance computing network based on the GLOBUS infrastructure. The SRTM data characteristics and unique problems they present are discussed. A new algorithm for organizing the conventional extraction algorithms [1] into a cooperating parallel grid is presented as an essential component to adapt to the IPG computing structure. Preliminary results are presented for a Southern California test area, established for comparing SRTM and its results against those produced using the USGS National Elevation Data (NED) model.

  9. Initial Everglades Depth Estimation Network (EDEN) Digital Elevation Model Research and Development

    USGS Publications Warehouse

    Jones, John W.; Price, Susan D.

    2007-01-01

    Introduction The Everglades Depth Estimation Network (EDEN) offers a consistent and documented dataset that can be used to guide large-scale field operations, to integrate hydrologic and ecological responses, and to support biological and ecological assessments that measure ecosystem responses to the Comprehensive Everglades Restoration Plan (Telis, 2006). To produce historic and near-real time maps of water depths, the EDEN requires a system-wide digital elevation model (DEM) of the ground surface. Accurate Everglades wetland ground surface elevation data were non-existent before the U.S. Geological Survey (USGS) undertook the collection of highly accurate surface elevations at the regional scale. These form the foundation for EDEN DEM development. This development process is iterative as additional high accuracy elevation data (HAED) are collected, water surfacing algorithms improve, and additional ground-based ancillary data become available. Models are tested using withheld HAED and independently measured water depth data, and by using DEM data in EDEN adaptive management applications. Here the collection of HAED is briefly described before the approach to DEM development and the current EDEN DEM are detailed. Finally future research directions for continued model development, testing, and refinement are provided.

  10. Appending High-Resolution Elevation Data to GPS Speed Traces for Vehicle Energy Modeling and Simulation

    SciTech Connect

    Wood, E.; Burton, E.; Duran, A.; Gonder, J.

    2014-06-01

    Accurate and reliable global positioning system (GPS)-based vehicle use data are highly valuable for many transportation, analysis, and automotive considerations. Model-based design, real-world fuel economy analysis, and the growing field of autonomous and connected technologies (including predictive powertrain control and self-driving cars) all have a vested interest in high-fidelity estimation of powertrain loads and vehicle usage profiles. Unfortunately, road grade can be a difficult property to extract from GPS data with consistency. In this report, we present a methodology for appending high-resolution elevation data to GPS speed traces via a static digital elevation model. Anomalous data points in the digital elevation model are addressed during a filtration/smoothing routine, resulting in an elevation profile that can be used to calculate road grade. This process is evaluated against a large, commercially available height/slope dataset from the Navteq/Nokia/HERE Advanced Driver Assistance Systems product. Results will show good agreement with the Advanced Driver Assistance Systems data in the ability to estimate road grade between any two consecutive points in the contiguous United States.

  11. Subreflector model depending on elevation for the Tianma 65m Radio Telescope

    NASA Astrophysics Data System (ADS)

    Sun, Zheng-Xiong; Wang, Jin-Qing; Chen, Lan

    2016-08-01

    A subreflector adjustment system for the Tianma 65 m radio telescope, administered by Shanghai Astronomical Observatory, has been installed to compensate for gravitational deformation of the main reflector and the structure supporting the subreflector. The position and attitude of the subreflector are variable in order to improve the efficiency at different elevations. The subreflector model has the goal of improving the antenna's performance. A new fitting formulation which is different from the traditional formulation is proposed to reduce the fitting error in the Y direction. The only difference in the subreflector models of the 65m radio telescope is the bias of a constant term in the Z direction. We have investigated the effect of movements of the subreflector on the pointing of the antenna. The results of these performance measurements made by moving the antenna in elevation show that the subreflector model can effectively improve the efficiency of the 65 m radio telescope at each elevation. An antenna efficiency of about 60% at the Ku band is reached in the whole angular range of elevation.

  12. Lahar Hazards at Casita and San Cristóbal Volcanoes, Nicaragua

    USGS Publications Warehouse

    Vallance, J.W.; Schilling, S.P.; Devoli, G.; Reid, M.E.; Howell, M.M.; Brien, D.L.

    2004-01-01

    to form ash-fall deposits (tephra), debris avalanches, lava flows, and hot flowing mixtures of ash and rock (called pyroclastic flows). The chronology of activity at Casita is rather poorly known. Its last documented eruption occurred 8300 years ago, and included a pyroclastic flow. Tephra deposits exposed in the east crater suggest the possibility of subsequent eruptions. Work prior to Hurricane Mitch suggested that a part of the volcano’s apron that included the area inundated during the 1998 event south of Casita was a lahar pathway. Erosion during Hurricane Mitch revealed that at least three large lahars descended this pathway to distances of up to 10 km. This report describes the hazards of landslides and lahars in general, and discusses potential hazards from future landslides and lahars at San Cristóbal and Casita volcanoes in particular. The report also shows, in the accompanying lahar hazard-zonation maps, which areas are likely to be at risk from future landslides and lahars at Casita and San Cristóbal.

  13. A prehistoric lahar-dammed lake and eruption of Mount Pinatubo described in a Philippine aborigine legend

    NASA Astrophysics Data System (ADS)

    Rodolfo, Kelvin S.; Umbal, Jesse V.

    2008-10-01

    The prehistoric eruptions of Mount Pinatubo have followed a cycle: centuries of repose terminated by a caldera-forming eruption with large pyroclastic flows; a post-eruption aftermath of rain-triggered lahars in surrounding drainages and dome-building that fills the caldera; and then another long quiescent period. During and after the eruptions lahars descending along volcano channels may block tributaries from watersheds beyond Pinatubo, generating natural lakes. Since the 1991 eruption, the Mapanuepe River valley in the southwestern sector of the volcano has been the site of a large lahar-dammed lake. Geologic evidence indicates that similar lakes have occupied this site at least twice before. An Ayta legend collected decades before Mount Pinatubo was recognized as a volcano describes what is probably the younger of these lakes, and the caldera-forming eruption that destroyed it.

  14. The characteristics of seismic signals produced by lahars and pyroclastic flows: Volcán de Colima, México

    NASA Astrophysics Data System (ADS)

    Zobin, Vyacheslav M.; Plascencia, Imelda; Reyes, Gabriel; Navarro, Carlos

    2009-01-01

    The general characteristics of seismic signals produced by pyroclastic flows (generated by either the collapse of a lava dome or an eruptive column) and lahars at Volcán de Colima, México are discussed. The paper concentrates on the 2004-2006 activity associated with and following the extrusion of andesitic block-lava in October-November 2004. It is shown that the duration of the broad-band seismic records of pyroclastic flows lasts a few minutes while the duration of seismic records of lahars continues for tens of minutes or hours. The spectra of seismic records produced by pyroclastic flows are characterized by lower peak frequencies (around 3-4 Hz) than for lahars (around 6-8 Hz). This difference in the frequency content together with the difference in the duration of seismic signals allows early diagnostic of the events in real time.

  15. Dynamic Programming on Reduced Models and Its Evaluation through Its Application to Elevator Operation Problems

    NASA Astrophysics Data System (ADS)

    Inamoto, Tsutomu; Tamaki, Hisashi; Murao, Hajime

    In this paper, we present a modified dynamic programming (DP) method. The method is basically the same as the value iteration method (VI), a representative DP method, except the preprocess of a system's state transition model for reducing its complexity, and is called the dynamic programming on reduced models (DPRM). That reduction is achieved by imaginarily considering causes of the probabilistic behavior of a system, and then cutting off some causes with low occurring probabilities. In computational illustrations, VI, DPRM, and the real-time Q-learning method (RTQ) are applied to elevator operation problems, which can be modeled by using Markov decision processes. The results show that DPRM can compute quasi-optimal value functions which bring more effective allocations of elevators than value functions by RTQ in less computational times than VI. This characteristic is notable when the traffic pattern is complicated.

  16. Where’s the Ground Surface? – Elevation Bias in LIDAR-derived Digital Elevation Models Due to Dense Vegetation in Oregon Tidal Marshes

    EPA Science Inventory

    Light Detection and Ranging (LIDAR) is a powerful resource for coastal and wetland managers and its use is increasing. Vegetation density and other land cover characteristics influence the accuracy of LIDAR-derived ground surface digital elevation models; however the degree to wh...

  17. Statistical correction of lidar-derived digital elevation models with multispectral airborne imagery in tidal marshes

    USGS Publications Warehouse

    Buffington, Kevin J.; Dugger, Bruce D.; Thorne, Karen M.; Takekawa, John

    2016-01-01

    Airborne light detection and ranging (lidar) is a valuable tool for collecting large amounts of elevation data across large areas; however, the limited ability to penetrate dense vegetation with lidar hinders its usefulness for measuring tidal marsh platforms. Methods to correct lidar elevation data are available, but a reliable method that requires limited field work and maintains spatial resolution is lacking. We present a novel method, the Lidar Elevation Adjustment with NDVI (LEAN), to correct lidar digital elevation models (DEMs) with vegetation indices from readily available multispectral airborne imagery (NAIP) and RTK-GPS surveys. Using 17 study sites along the Pacific coast of the U.S., we achieved an average root mean squared error (RMSE) of 0.072 m, with a 40–75% improvement in accuracy from the lidar bare earth DEM. Results from our method compared favorably with results from three other methods (minimum-bin gridding, mean error correction, and vegetation correction factors), and a power analysis applying our extensive RTK-GPS dataset showed that on average 118 points were necessary to calibrate a site-specific correction model for tidal marshes along the Pacific coast. By using available imagery and with minimal field surveys, we showed that lidar-derived DEMs can be adjusted for greater accuracy while maintaining high (1 m) resolution.

  18. Elevated mazes as animal models of anxiety: effects of serotonergic agents.

    PubMed

    Pinheiro, Simone H; Zangrossi, Hélio; Del-Ben, Cristina M; Graeff, Frederico G

    2007-03-01

    This article reviews reported results about the effects of drugs that act upon the serotonergic neurotransmission measured in three elevated mazes that are animal models of anxiety. A bibliographic search has been performed in MEDLINE using different combinations of the key words X-maze, plus-maze, T-maze, serotonin and 5-HT, present in the title and/or the abstract, with no time limit. From the obtained abstracts, several publications were excluded on the basis of the following criteria: review articles that did not report original results, species other than the rat, intracerebral drug administration alone, genetically manipulated rats, and animals having any kind of experimental pathology. The reported results indicate that the effect of drugs on the inhibitory avoidance task performed in the elevated T-maze and on the spatio temporal indexes of anxiety measured in the X and plus mazes correlate with their effect in patients diagnosed with generalized anxiety disorder. In contrast, the drug effects on the one-way escape task in the elevated T-maze predict the drug response of panic disorder patients. Overall, the drug effects assessed with the avoidance task in the T-maze are more consistent than those measured through the anxiety indexes of the X and plus mazes. Therefore, the elevated T-maze is a promising animal model of generalized anxiety and panic disorder.

  19. Eruption of the nevado del ruiz volcano, Colombia, on 13 november 1985: tephra fall and lahars.

    PubMed

    Naranjo, J L; Sigurdsson, H; Carey, S N; Fritz, W

    1986-08-29

    A small Plinian eruption of the Nevado del Ruiz volcano in Colombia ejected 3.5 x 10(10) kilograms of mixed dacite and andesite tephra on 13 November 1985, with a maximum column height of 31 kilometers above sea level. Small pyroclastic flows and surges, generated during the initial stage of the eruption, caused surface melting of approximately 10% of the volcano's ice cap, leading to meltwater floods. The erosive floods incorporated soils and loose sediments from the volcano's flanks and developed into lahars, which claimed at least 25,000 lives.

  20. Elevating your elevator talk

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An important and often overlooked item that every early career researcher needs to do is compose an elevator talk. The elevator talk, named because the talk should not last longer than an average elevator ride (30 to 60 seconds), is an effective method to present your research and yourself in a clea...

  1. Frozen Martian lahars? Evaluation of morphology, degradation and geologic development in the Utopia-Elysium transition zone

    NASA Astrophysics Data System (ADS)

    Pedersen, G. B. M.

    2013-09-01

    Regional coverage of high-resolution data from the CTX camera has permitted new, detailed morphologic analysis of the enigmatic Utopia-Elysium flows which dominate the transition zone between Elysium volcanic province and Utopia Planitia. Based on topographic and morphologic analysis of the Galaxias region, this study supports the lahar hypothesis put forth by previous works and suggests that the center and the margins of the outflow deposits have very diverse morphologies that can be explained by varying degrees of water drainage and freezing. Regular channel and flood plain deposits are found in the central part of the outflow deposits, whereas the marginal deposits are interpreted to contain significant amount of ice because of their distinct morphological properties (smooth, lobate flow-fronts with upward convex snouts, unusual crater morphologies, raised rim fractures and localized flow fronts indicating rheomorphism). Thus, this study suggest that, unlike terrestrial lahars, lahar emplacement under Martian conditions only drain in the central parts, whereas the water in the margins of the outflow deposit (∼75% of the total outflow deposit in the Galaxias region) freezes up resulting in a double-layered deposit consisting of ice-rich core with an ice-poor surface layer. It is here furthermore suggested that continued intrusive volcanic activity was highly affected by the presence of the ice-rich lahar deposits, generating ground-ice-volcano interactions resulting in a secondary suite of morphologies. These morphologies include seventeen ridges that are interpreted to be möberg ridges (due to their NW-SE orientation, distinct ridge-crests and association with fractures and linear ridges) and depressions with nested faults interpreted to be similar to terrestrial ice-cauldrons, which form by enhanced subglacial geothermal activity including subglacial volcanic eruptions. These sub-lahar intrusions caused significant volatile loss in the ice-rich core of the

  2. A Seamless, High-Resolution, Coastal Digital Elevation Model (DEM) for Southern California

    USGS Publications Warehouse

    Barnard, Patrick L.; Hoover, Daniel

    2010-01-01

    A seamless, 3-meter digital elevation model (DEM) was constructed for the entire Southern California coastal zone, extending 473 km from Point Conception to the Mexican border. The goal was to integrate the most recent, high-resolution datasets available (for example, Light Detection and Ranging (Lidar) topography, multibeam and single beam sonar bathymetry, and Interferometric Synthetic Aperture Radar (IfSAR) topography) into a continuous surface from at least the 20-m isobath to the 20-m elevation contour. This dataset was produced to provide critical boundary conditions (bathymetry and topography) for a modeling effort designed to predict the impacts of severe winter storms on the Southern California coast (Barnard and others, 2009). The hazards model, run in real-time or with prescribed scenarios, incorporates atmospheric information (wind and pressure fields) with a suite of state-of-the-art physical process models (tide, surge, and wave) to enable detailed prediction of water levels, run-up, wave heights, and currents. Research-grade predictions of coastal flooding, inundation, erosion, and cliff failure are also included. The DEM was constructed to define the general shape of nearshore, beach and cliff surfaces as accurately as possible, with less emphasis on the detailed variations in elevation inland of the coast and on bathymetry inside harbors. As a result this DEM should not be used for navigation purposes.

  3. Comparison of Surface Flow Features from Lidar-Derived Digital Elevation Models with Historical Elevation and Hydrography Data for Minnehaha County, South Dakota

    USGS Publications Warehouse

    Poppenga, Sandra K.; Worstell, Bruce B.; Stoker, Jason M.; Greenlee, Susan K.

    2009-01-01

    The U.S. Geological Survey (USGS) has taken the lead in the creation of a valuable remote sensing product by incorporating digital elevation models (DEMs) derived from Light Detection and Ranging (lidar) into the National Elevation Dataset (NED), the elevation layer of 'The National Map'. High-resolution lidar-derived DEMs provide the accuracy needed to systematically quantify and fully integrate surface flow including flow direction, flow accumulation, sinks, slope, and a dense drainage network. In 2008, 1-meter resolution lidar data were acquired in Minnehaha County, South Dakota. The acquisition was a collaborative effort between Minnehaha County, the city of Sioux Falls, and the USGS Earth Resources Observation and Science (EROS) Center. With the newly acquired lidar data, USGS scientists generated high-resolution DEMs and surface flow features. This report compares lidar-derived surface flow features in Minnehaha County to 30- and 10-meter elevation data previously incorporated in the NED and ancillary hydrography datasets. Surface flow features generated from lidar-derived DEMs are consistently integrated with elevation and are important in understanding surface-water movement to better detect surface-water runoff, flood inundation, and erosion. Many topographic and hydrologic applications will benefit from the increased availability of accurate, high-quality, and high-resolution surface-water data. The remotely sensed data provide topographic information and data integration capabilities needed for meeting current and future human and environmental needs.

  4. Evaluating LMA and CLAMP: Using information criteria to choose a model for estimating elevation

    NASA Astrophysics Data System (ADS)

    Miller, I.; Green, W.; Zaitchik, B.; Brandon, M.; Hickey, L.

    2005-12-01

    The morphology of leaves and composition of the flora respond strongly to the moisture and temperature of their environment. Elevation and latitude correlate, at first order, to these atmospheric parameters. An obvious modern example of this relationship between leaf morphology and environment is the tree line, where boreal forests give way to artic (high latitude) or alpine (high elevation) tundra. Several quantitative methods, all of which rely on uniformitarianism, have been developed to estimate paleoelevation using fossil leaf morphology. These include 1) the univariate leaf-margin analysis (LMA), which estimates mean annual temperature (MAT) by the positive linear correlation between MAT and P, the proportion of entire or smooth to non-entire or toothed margined woody dicot angiosperm leaves within a flora and 2) the Climate Leaf Analysis Multivariate Program (CLAMP) which uses Canonical Correspondence Analysis (CCA) to estimate MAT, moist enthalpy, and other atmospheric parameters using 31 explanatory leaf characters from woody dicot angiosperms. Given a difference in leaf-estimated MAT or moist enthalpy between contemporaneous, synlatitudinal fossil floras-one at sea-level, the other at an unknown paleoelevation-paleoelevation may be estimated. These methods have been widely applied to orogenic settings and concentrate particularly in the Western US. We introduce the use of information criteria to compare different models for estimating elevation and show how the additional complexity of the CLAMP analytical methodology does not necessarily improve on the elevation estimates produced by simpler regression models. In addition, we discuss the signal-to-noise ratio in the data, give confidence intervals for detecting elevations, and address the problem of spatial autocorrelation and irregular sampling in the data.

  5. A comparative study of spherical and flat-Earth geopotential modeling at satellite elevations

    NASA Technical Reports Server (NTRS)

    Parrott, M. H.; Hinze, W. J.; Braile, L. W.

    1985-01-01

    Flat-Earth and spherical-Earth geopotential modeling of crustal anomaly sources at satellite elevations are compared by computing gravity and scalar magnetic anomalies perpendicular to the strike of variably dimensioned rectangular prisms at altitudes of 150, 300, and 450 km. Results indicate that the error caused by the flat-Earth approximation is less than 10% in most geometric conditions. Generally, error increase with larger and wider anomaly sources at higher altitudes. For most crustal source modeling applications at conventional satellite altitudes, flat-Earth modeling can be justified and is numerically efficient.

  6. Digital Elevation Models of TYCHO Crater and the Lunar Polar Regions

    NASA Astrophysics Data System (ADS)

    Margot, J. L.; Campbell, D. B.; Jurgens, R. F.; Slade, M. A.

    1998-09-01

    Earth-based radar interferometry [1] has been used to map the lunar polar regions and Tycho Crater at high spatial ( ~ 100 m) and height ( ~ 50 m) resolutions. Compared to existing topographic data sets, the radar observations offer digital elevation models with dense horizontal spacing and improved height resolution. Earth-based radars can also provide measurements of the largely unknown topography in the polar regions. Elevation data and radar imagery obtained with the Goldstone X-band system (lambda = 3.5 cm) are presented for the Tycho Crater area, with a spatial resolution of 200 m and a height resolution of 30 m. A careful comparison of the radar-derived topography with Clementine altimetry points [2] reveals a very good agreement between the two techniques. Rms deviations between the radar-derived heights and 87 Clementine points available over the 200 x 200 km scene are ~ 100 m. The digital elevation model allows detailed morphometry of the 85 km diameter crater: the floor of Tycho lies 3970 m below a 1738 km radius sphere, and the crater's central peak rises 2400 m above the floor. The average rim crest elevation is 730 m above the 1738 km datum, giving a mean rim to floor depth of 4700 m. The floor has two distinct units with the western section being higher in elevation by ~ 200 m. This dichotomy is consistent with an asymmetry in the crater shape which reveals that maximum wall slumping occured in the western and southwestern regions of the crater. Digital elevation models of the polar regions are being used to estimate the location of permanently shadowed areas which may harbor ice deposits [3]. The range of illumination conditions over the lunar polar regions could be sampled by an imaging instrument in a polar orbit during a full terrestrial year. Alternatively, topographic maps obtained with Earth-based radar can be used to model the illumination conditions over the entire solar illumination cycle. [1] I. I. Shapiro et al. (1972). Science, 178, 939

  7. Modelling Periglacial Processes on Low-Relief High-Elevation Surfaces

    NASA Astrophysics Data System (ADS)

    Andersen, J. L.; Knudsen, M. F.; Egholm, D. L.

    2014-12-01

    Are low-relief high-elevation surfaces generally a result of uplift of flat surfaces formed close to sea-level or can they be formed "in situ" by climate dependent surface processes such as those associated with glaciation? This question is important to resolve in order to understand the geological history in many regions of the world. The glacial buzzsaw concept suggests that intense glacial erosion focused at the equilibrium-line altitude (ELA) leads to a concentration in surface area close to the ELA. However, even in predominantly glacial landscapes, such as the Scandinavian Mountains, the high surfaces often have nonglacial characteristics and show pre-glacial inheritance of cosmogenic nuclide concentrations. This suggests that subglacial erosion is not the dominant erosion mechanism. Anderson (2002) showed that periglacial frost-driven processes working over timescales of millions of years form low-curvature parabolic surfaces at accordant elevation across intervening valleys. The rate of these erosion processes is limited by the slow diffusive transport of regolith in the periglacial domain. We elaborate on this idea by quantifying frost cracking and frost creep in a numerical model as a function of mean annual air temperature and sediment thickness. This allows us to incorporate periglacial processes into a long-term landscape evolution model where surface elevation, sediment thickness, and climate evolve over time. With this model we are able to explore the slow feedbacks between periglacial erosion, sediment transport, and the evolving topography. We show that smooth peaks, convex hillslopes, and a few meters thick regolith cover at high elevation are emergent properties of the landscape evolution model. By varying climate and other model parameters, we discuss how the landscape evolution model can be used for obtaining more insight into the conditions needed for formation of low-relief surfaces at high elevation. Anderson, R. S. Modeling the tor

  8. User-Driven Geolocation of Untagged Desert Imagery Using Digital Elevation Models

    DTIC Science & Technology

    2013-01-01

    User-Driven Geolocation of Untagged Desert Imagery Using Digital Elevation Models Eric Tzeng, Andrew Zhai, Matthew Clements, Raphael Townshend, and...normalizing skylines with respect to their features, we achieve similarity invariance. Furthermore, our system is robust to partial occlusions ; since the...feature is used as a key to an entry to the hash-table, we ensure that only a convex normalized feature can be used to get that entry in the hash-table

  9. Modeling the population dynamics of Culex quinquefasciatus (Diptera: Culcidae), along an elevational gradient in Hawaii

    USGS Publications Warehouse

    Ahumada, Jorge A.; LaPointe, Dennis; Samuel, Michael D.

    2004-01-01

    We present a population model to understand the effects of temperature and rainfall on the population dynamics of the southern house mosquito, Culex quinquefasciatus Say, along an elevational gradient in Hawaii. We use a novel approach to model the effects of temperature on population growth by dynamically incorporating developmental rate into the transition matrix, by using physiological ages of immatures instead of chronological age or stages. We also model the effects of rainfall on survival of immatures as the cumulative number of days below a certain rain threshold. Finally, we incorporate density dependence into the model as competition between immatures within breeding sites. Our model predicts the upper altitudinal distributions of Cx. quinquefasciatus on the Big Island of Hawaii for self-sustaining mosquito and migrating summer sink populations at 1,475 and 1,715 m above sea level, respectively. Our model predicts that mosquitoes at lower elevations can grow under a broader range of rainfall parameters than middle and high elevation populations. Density dependence in conjunction with the seasonal forcing imposed by temperature and rain creates cycles in the dynamics of the population that peak in the summer and early fall. The model provides a reasonable fit to the available data on mosquito abundance for the east side of Mauna Loa, Hawaii. The predictions of our model indicate the importance of abiotic conditions on mosquito dynamics and have important implications for the management of diseases transmitted by Cx. quinquefasciatus in Hawaii and elsewhere.

  10. Forecasting tidal marsh elevation and habitat change through fusion of Earth observations and a process model

    USGS Publications Warehouse

    Byrd, Kristin B.; Windham-Myers, Lisamarie; Leeuw, Thomas; Downing, Bryan D.; Morris, James T.; Ferner, Matthew C.

    2016-01-01

    Reducing uncertainty in data inputs at relevant spatial scales can improve tidal marsh forecasting models, and their usefulness in coastal climate change adaptation decisions. The Marsh Equilibrium Model (MEM), a one-dimensional mechanistic elevation model, incorporates feedbacks of organic and inorganic inputs to project elevations under sea-level rise scenarios. We tested the feasibility of deriving two key MEM inputs—average annual suspended sediment concentration (SSC) and aboveground peak biomass—from remote sensing data in order to apply MEM across a broader geographic region. We analyzed the precision and representativeness (spatial distribution) of these remote sensing inputs to improve understanding of our study region, a brackish tidal marsh in San Francisco Bay, and to test the applicable spatial extent for coastal modeling. We compared biomass and SSC models derived from Landsat 8, DigitalGlobe WorldView-2, and hyperspectral airborne imagery. Landsat 8-derived inputs were evaluated in a MEM sensitivity analysis. Biomass models were comparable although peak biomass from Landsat 8 best matched field-measured values. The Portable Remote Imaging Spectrometer SSC model was most accurate, although a Landsat 8 time series provided annual average SSC estimates. Landsat 8-measured peak biomass values were randomly distributed, and annual average SSC (30 mg/L) was well represented in the main channels (IQR: 29–32 mg/L), illustrating the suitability of these inputs across the model domain. Trend response surface analysis identified significant diversion between field and remote sensing-based model runs at 60 yr due to model sensitivity at the marsh edge (80–140 cm NAVD88), although at 100 yr, elevation forecasts differed less than 10 cm across 97% of the marsh surface (150–200 cm NAVD88). Results demonstrate the utility of Landsat 8 for landscape-scale tidal marsh elevation projections due to its comparable performance with the other sensors

  11. Modeling glaucoma in rats by sclerosing aqueous outflow pathways to elevate intraocular pressure

    PubMed Central

    Morrison, John C.; Cepurna, William O.; Johnson, Elaine C.

    2015-01-01

    Injection of hypertonic saline via episcleral veins toward the limbus in laboratory rats can produce elevated intraocular pressure (IOP) by sclerosis of aqueous humor outflow pathways. This article describes important anatomic characteristics of the rat optic nerve head (ONH) that make it an attractive animal model for human glaucoma, along with the anatomy of rat aqueous humor outflow on which this technique is based. The injection technique itself is also described, with the aid of a supplemental movie, including necessary equipment and specific tips to acquire this skill. Outcomes of a successful injection are presented, including IOP elevation and patterns of optic nerve injury. These concepts are then specifically considered in light of the use of this model to assess potential neuroprotective therapies. Advantages of the hypertonic saline model include a delayed and relatively gradual IOP elevation, likely reproduction of scleral and ONH stresses and strains that may be important in producing axonal injury, and its ability to be applied to any rat (and potentially mouse) strain, leaving the unmanipulated fellow eye as an internal control. Challenges include the demanding surgical skill required by the technique itself, a wide range of IOP response, and mild corneal clouding in some animals. However, meticulous application of the principles detailed in this article and practice will allow most researchers to attain this useful skill for studying cellular events of glaucomatous optic nerve damage. PMID:26003399

  12. Perspectives on open access high resolution digital elevation models to produce global flood hazard layers

    NASA Astrophysics Data System (ADS)

    Sampson, Christopher; Smith, Andrew; Bates, Paul; Neal, Jeffrey; Trigg, Mark

    2015-12-01

    Global flood hazard models have recently become a reality thanks to the release of open access global digital elevation models, the development of simplified and highly efficient flow algorithms, and the steady increase in computational power. In this commentary we argue that although the availability of open access global terrain data has been critical in enabling the development of such models, the relatively poor resolution and precision of these data now limit significantly our ability to estimate flood inundation and risk for the majority of the planet's surface. The difficulty of deriving an accurate 'bare-earth' terrain model due to the interaction of vegetation and urban structures with the satellite-based remote sensors means that global terrain data are often poorest in the areas where people, property (and thus vulnerability) are most concentrated. Furthermore, the current generation of open access global terrain models are over a decade old and many large floodplains, particularly those in developing countries, have undergone significant change in this time. There is therefore a pressing need for a new generation of high resolution and high vertical precision open access global digital elevation models to allow significantly improved global flood hazard models to be developed.

  13. a New High-Resolution Elevation Model of Greenland Derived from Tandem-X

    NASA Astrophysics Data System (ADS)

    Wessel, B.; Bertram, A.; Gruber, A.; Bemm, S.; Dech, S.

    2016-06-01

    In this paper we present for the first time the new digital elevation model (DEM) for Greenland produced by the TanDEM-X (TerraSAR add-on for digital elevation measurement) mission. The new, full coverage DEM of Greenland has a resolution of 0.4 arc seconds corresponding to 12 m. It is composed of more than 7.000 interferometric synthetic aperture radar (InSAR) DEM scenes. X-Band SAR penetrates the snow and ice pack by several meters depending on the structures within the snow, the acquisition parameters, and the dielectricity constant of the medium. Hence, the resulting SAR measurements do not represent the surface but the elevation of the mean phase center of the backscattered signal. Special adaptations on the nominal TanDEM-X DEM generation are conducted to maintain these characteristics and not to raise or even deform the DEM to surface reference data. For the block adjustment, only on the outer coastal regions ICESat (Ice, Cloud, and land Elevation Satellite) elevations as ground control points (GCPs) are used where mostly rock and surface scattering predominates. Comparisons with ICESat data and snow facies are performed. In the inner ice and snow pack, the final X-Band InSAR DEM of Greenland lies up to 10 m below the ICESat measurements. At the outer coastal regions it corresponds well with the GCPs. The resulting DEM is outstanding due to its resolution, accuracy and full coverage. It provides a high resolution dataset as basis for research on climate change in the arctic.

  14. Relationship between geomorphology and lithotypes of lahar deposit from Chokai volcano, Japan

    NASA Astrophysics Data System (ADS)

    Minami, Y.; Ohba, T.; Hayashi, S.; Kataoka, K.

    2013-12-01

    Chokai volcano, located in the northern Honshu arc in Japan, is an andesitic stratovolcano that collapsed partly at ca. 2500 years ago. A post collapse lahar deposit (Shirayukigawa lahar deposit) is distributed in the northern foot of the volcanic edifice. The deposit consists of 16 units of debris flow, hyperconcentrated flow and streamflow deposits. The Shirayukigawa lahar deposit has a total thickness of 30 m and overlies the 2.5-ka Kisakata debris avalanche deposit. Shirayukigawa lahar deposit forms volcanic fan and volcanic apron. The volcanic fan is subdivided into four areas on the basis of slope angles and of geomorphological features: 1) steeply sloped area, 2) moderately sloped area, 3) gently sloped area and 4) horizontal area. From sedimentary facies and structures, each unit of the Shirayukigawa lahar deposit is classified into one of four lithotypes: clast-supported debris flow deposit (Cc), matrix-supported debris flow deposit (Cm1), hyperconcentrated flow deposit (Cm2) and streamflow deposit (Sl). Each type has the following lithological characteristics. The lithotypes are well correlated with the geomorphology of the volcanic fan. The steeply-sloped and the moderately-sloped areas are dominated by Cc, Cm1, and Cm2, and The horizontal area are dominated by Sl. Debris flow deposit (Cc) is massive, very poorly sorted, partly graded, and clast-supported with polymictic clasts dominated by subrounded to rounded volcanic clasts. Matrix is sandy to muddy. Preferred clast orientation are present. Debris flow deposit (Cm1) is massive, very poorly sorted, and matrix-supported with polymictic clasts dominated by subrounded to rounded volcanic clasts. Matrix is sandy to muddy. Some layers exhibit coarse-tail normal/inverse grading. Most clasts are oriented. Hyperconcentrated flow deposit (Cm2) is massive to diffusely laminated, very poorly sorted and matrix-supported with polymictic clasts dominated by subrounded to rounded volcanic rocks. Matrix is sandy. The

  15. Lysine malonylation is elevated in type 2 diabetic mouse models and enriched in metabolic associated proteins.

    PubMed

    Du, Yipeng; Cai, Tanxi; Li, Tingting; Xue, Peng; Zhou, Bo; He, Xiaolong; Wei, Peng; Liu, Pingsheng; Yang, Fuquan; Wei, Taotao

    2015-01-01

    Protein lysine malonylation, a newly identified protein post-translational modification (PTM), has been proved to be evolutionarily conserved and is present in both eukaryotic and prokaryotic cells. However, its potential roles associated with human diseases remain largely unknown. In the present study, we observed an elevated lysine malonylation in a screening of seven lysine acylations in liver tissues of db/db mice, which is a typical model of type 2 diabetes. We also detected an elevated lysine malonylation in ob/ob mice, which is another model of type 2 diabetes. We then performed affinity enrichment coupled with proteomic analysis on liver tissues of both wild-type (wt) and db/db mice and identified a total of 573 malonylated lysine sites from 268 proteins. There were more malonylated lysine sites and proteins in db/db than in wt mice. Five proteins with elevated malonylation were verified by immunoprecipitation coupled with Western blot analysis. Bioinformatic analysis of the proteomic results revealed the enrichment of malonylated proteins in metabolic pathways, especially those involved in glucose and fatty acid metabolism. In addition, the biological role of lysine malonylation was validated in an enzyme of the glycolysis pathway. Together, our findings support a potential role of protein lysine malonylation in type 2 diabetes with possible implications for its therapy in the future.

  16. Lysine Malonylation Is Elevated in Type 2 Diabetic Mouse Models and Enriched in Metabolic Associated Proteins*

    PubMed Central

    Du, Yipeng; Cai, Tanxi; Li, Tingting; Xue, Peng; Zhou, Bo; He, Xiaolong; Wei, Peng; Liu, Pingsheng; Yang, Fuquan; Wei, Taotao

    2015-01-01

    Protein lysine malonylation, a newly identified protein post-translational modification (PTM), has been proved to be evolutionarily conserved and is present in both eukaryotic and prokaryotic cells. However, its potential roles associated with human diseases remain largely unknown. In the present study, we observed an elevated lysine malonylation in a screening of seven lysine acylations in liver tissues of db/db mice, which is a typical model of type 2 diabetes. We also detected an elevated lysine malonylation in ob/ob mice, which is another model of type 2 diabetes. We then performed affinity enrichment coupled with proteomic analysis on liver tissues of both wild-type (wt) and db/db mice and identified a total of 573 malonylated lysine sites from 268 proteins. There were more malonylated lysine sites and proteins in db/db than in wt mice. Five proteins with elevated malonylation were verified by immunoprecipitation coupled with Western blot analysis. Bioinformatic analysis of the proteomic results revealed the enrichment of malonylated proteins in metabolic pathways, especially those involved in glucose and fatty acid metabolism. In addition, the biological role of lysine malonylation was validated in an enzyme of the glycolysis pathway. Together, our findings support a potential role of protein lysine malonylation in type 2 diabetes with possible implications for its therapy in the future. PMID:25418362

  17. Spatial disaggregation of satellite-derived irradiance using a high-resolution digital elevation model

    SciTech Connect

    Ruiz-Arias, Jose A.; Tovar-Pescador, Joaquin; Cebecauer, Tomas; Suri, Marcel

    2010-09-15

    Downscaling of the Meteosat-derived solar radiation ({proportional_to}5 km grid resolution) is based on decomposing the global irradiance and correcting the systematic bias of its components using the elevation and horizon shadowing that are derived from the SRTM-3 digital elevation model (3 arc sec resolution). The procedure first applies the elevation correction based on the difference between coarse and high spatial resolution. Global irradiance is split into direct, diffuse circumsolar and diffuse isotropic components using statistical models, and then corrections due to terrain shading and sky-view fraction are applied. The effect of reflected irradiance is analysed only in the theoretical section. The method was applied in the eastern Andalusia, Spain, and the validation was carried out for 22 days on April, July and December 2006 comparing 15-min estimates of the satellite-derived solar irradiance and observations from nine ground stations. Overall, the corrections of the satellite estimates in the studied region strongly reduced the mean bias of the estimates for clear and cloudy days from roughly 2.3% to 0.4%. (author)

  18. Modeling Laser Altimeter Return Waveforms Over Complex Vegetation Using High-Resolution Elevation Data

    NASA Technical Reports Server (NTRS)

    Blair, J. Bryan; Hofton, Michelle A.

    1999-01-01

    The upcoming generation of laser altimeters record the interaction of emitted laser radiation with terrestrial surfaces in the form of a digitized waveform. We model these laser altimeter return waveforms as the sum of the reflections from individual surfaces within laser footprints, accounting for instrument-specific properties. We compare over 1000 modeled and recorded waveform pairs using the Pearson correlation. We show that we reliably synthesize the vertical structure information for vegetation canopies contained in a medium-large diameter laser footprint from a high-resolution elevation data set.

  19. Analysis of accuracy of digital elevation models created from captured data by digital photogrammetry method

    NASA Astrophysics Data System (ADS)

    Hudec, P.

    2011-12-01

    A digital elevation model (DEM) is an important part of many geoinformatic applications. For the creation of DEM, spatial data collected by geodetic measurements in the field, photogrammetric processing of aerial survey photographs, laser scanning and secondary sources (analogue maps) are used. It is very important from a user's point of view to know the vertical accuracy of a DEM. The article describes the verification of the vertical accuracy of a DEM for the region of Medzibodrožie, which was created using digital photogrammetry for the purposes of water resources management and modeling and resolving flood cases based on geodetic measurements in the field.

  20. Using geomorphological maps to improve digital elevation models in high mountains environments

    NASA Astrophysics Data System (ADS)

    Micheletti, Natan; Lane, Stuart; Chandler, Jim; Lambiel, Christophe

    2013-04-01

    Whilst current digital elevation modeling has been substantially aided by ground-based technologies, understanding environmental change impacts in mountain environments over longer timescales requires unlocking of the information held in historical aerial images. These are commonly available from the 1940s for the European Alps and digital photogrammetric approaches have been established for using such data sources to create precise digital elevation models (precise to better than c. ±0.5 m) over large spatial scales (10s and 100s of km2) that can be used to quantify erosion and deposition in response to recent environmental change. In this paper, we show why geomorphological maps are essential for this development for two reasons. The first is as expected: interpreting catchment scale patterns of erosion and deposition requires reference to the underlying spatial assemblage of landforms present. Digital geomorphological maps can be used to do this, and through classifying erosion and deposition patterns by landform, can be used to identify: those elements of the landscape most sensitive to recent environmental change; and their spatial organization, something that is central to how they interact together to drive sediment flux. The second reason is more surprising. In Alpine environments, the quality of estimation of elevation by digital photogrammetry can be spatially variable and uncertain due to local topography (occlusion caused by sudden elevation changes, areas with large elevation ranges) or varying image texture. Tests on the performance of stereomatching algorithms, including the filtering necessary to guarantee the quality of derived DEM data, show that data quality is highly variable between landform types within a given landscape. Generating high quality DEMs is therefore improved if geomorphological maps are used to define such inherent spatial variability during data processing. Here, we demonstrate these two points using aerial imagery for Val d

  1. Dynamics of the 13 October 2012 Te Maari, New Zealand Dam Breakout Lahar Determined from Multi-Parameter Data and its Implications for Monitoring

    NASA Astrophysics Data System (ADS)

    Walsh, B.; Jolly, A. D.; Procter, J.

    2015-12-01

    On 6 August 2012 a 7.0x105 m3 debris flow dammed up the Upper Te Maari flow channel forming a 50,000 m3 ephemeral lake. The ephemeral lake filled up from runoff and heavy rainfall over a two month period until 13 October 2012 where saturated sediments and trapped lake water overtopped the debris flow dam at 11:20 UTC, thus creating a lahar approximately 10 minutes later at 11:30 UTC through remobilizing the older debris flow deposits. The lahar lasted for about 30 minutes flowing down the channel as a succession of multiple surges that could possibly be attributed to a series of down cuts and subsequent breakouts of the debris flow dam. A correlation between the lahar seismic signals and active seismic source data collected in February 2013 from the same flow channel is used to understand the dynamics of the 13 October 2012 lahar. In comparing the two data sets a frequency band of 3-10 Hz is used to estimate the lahar energy at 4.87x109 Nm. The best correlated location for the lahar from the active source data is estimated to be at the ephemeral lake or within 1.0 km down the channel. Through the use of the active source method to determine the dynamics of the lahar, monitoring and the understanding of mass flows in the Te Maari area can be improved.

  2. Constitutive Modeling and Testing of Polymer Matrix Composites Incorporating Physical Aging at Elevated Temperatures

    NASA Technical Reports Server (NTRS)

    Veazie, David R.

    1998-01-01

    Advanced polymer matrix composites (PMC's) are desirable for structural materials in diverse applications such as aircraft, civil infrastructure and biomedical implants because of their improved strength-to-weight and stiffness-to-weight ratios. For example, the next generation military and commercial aircraft requires applications for high strength, low weight structural components subjected to elevated temperatures. A possible disadvantage of polymer-based composites is that the physical and mechanical properties of the matrix often change significantly over time due to the exposure of elevated temperatures and environmental factors. For design, long term exposure (i.e. aging) of PMC's must be accounted for through constitutive models in order to accurately assess the effects of aging on performance, crack initiation and remaining life. One particular aspect of this aging process, physical aging, is considered in this research.

  3. Determination of Martian Northern Polar Insolation Levels Using a Geodetic Elevation Model

    NASA Technical Reports Server (NTRS)

    Arrell, J. R.; Zuber, M. T.

    2000-01-01

    Solar insolation levels at the Martian polar caps bear significantly on the seasonal and climatic cycling of volatiles on that planet. In the northern hemisphere, the Martian surface slopes downhill from the equator to the pole such that the north polar cap is situated in a 5-km-deep hemispheric-scale depression. This large-scale topographic setting plays an important role in the insolation of the northern polar cap. Elevations measured by the Mars Orbiter Laser Altimeter (MOLA) provide comprehensive, high-accuracy topographical information required to precisely determine polar insolation. In this study, we employ a geodetic elevation model to quantify the north polar insolation and consider implications for seasonal and climatic changes. Additional information is contained in original extended abstract.

  4. Satellite Elevation Magnetic and Gravity Models of Major South American Plate Tectonic Features

    NASA Technical Reports Server (NTRS)

    Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.; Lidiak, E. G.; Keller, G. R. (Principal Investigator); Longacre, M. B.

    1984-01-01

    Some MAGSAT scalar and vector magnetic anomaly data together with regional gravity anomaly data are being used to investigate the regional tectonic features of the South American Plate. An initial step in this analysis is three dimensional modeling of magnetic and gravity anomalies of major structures such as the Andean subduction zone and the Amazon River Aulacogen at satellite elevations over an appropriate range of physical properties using Gaus-Legendre quadrature integration method. In addition, one degree average free-air gravity anomalies of South America and adjacent marine areas are projected to satellite elevations assuming a spherical Earth and available MAGSAT data are processed to obtain compatible data sets for correlation. Correlation of these data sets is enhanced by reduction of the MAGSAT data to radial polarization because of the profound effect of the variation of the magnetic inclination over South America.

  5. Geomorphological feature extraction from a digital elevation model through fuzzy knowledge-based classification

    NASA Astrophysics Data System (ADS)

    Argialas, Demetre P.; Tzotsos, Angelos

    2003-03-01

    The objective of this research was the investigation of advanced image analysis methods for geomorphological mapping. Methods employed included multiresolution segmentation of the Digital Elevation Model (DEM) GTOPO30 and fuzzy knowledge based classification of the segmented DEM into three geomorphological classes: mountain ranges, piedmonts and basins. The study area was a segment of the Basin and Range Physiographic Province in Nevada, USA. The implementation was made in eCognition. In particular, the segmentation of GTOPO30 resulted into primitive objects. The knowledge-based classification of the primitive objects based on their elevation and shape parameters, resulted in the extraction of the geomorphological features. The resulted boundaries in comparison to those by previous studies were found satisfactory. It is concluded that geomorphological feature extraction can be carried out through fuzzy knowledge based classification as implemented in eCognition.

  6. Revealing topographic lineaments through IHS enhancement of DEM data. [Digital Elevation Model

    NASA Technical Reports Server (NTRS)

    Murdock, Gary

    1990-01-01

    Intensity-hue-saturation (IHS) processing of slope (dip), aspect (dip direction), and elevation to reveal subtle topographic lineaments which may not be obvious in the unprocessed data are used to enhance digital elevation model (DEM) data from northwestern Nevada. This IHS method of lineament identification was applied to a mosiac of 12 square degrees using a Cray Y-MP8/864. Square arrays from 3 x 3 to 31 x 31 points were tested as well as several different slope enhancements. When relatively few points are used to fit the plane, lineaments of various lengths are observed and a mechanism for lineament classification is described. An area encompassing the gold deposits of the Carlin trend and including the Rain in the southeast to Midas in the northwest is investigated in greater detail. The orientation and density of lineaments may be determined on the gently sloping pediment surface as well as in the more steeply sloping ranges.

  7. Development of a seamless multisource topographic/bathymetric elevation model of Tampa Bay

    USGS Publications Warehouse

    Gesch, D.; Wilson, R.

    2001-01-01

    Many applications of geospatial data in coastal environments require knowledge of the nearshore topography and bathymetry. However, because existing topographic and bathymetric data have been collected independently for different purposes, it has been difficult to use them together at the land/water interface owing to differences in format, projection, resolution, accuracy, and datums. As a first step toward solving the problems of integrating diverse coastal datasets, the U.S. Geological Survey (USGS) and the National Oceanic and Atmospheric Administration (NOAA) are collaborating on a joint demonstration project to merge their data for the Tampa Bay region of Florida. The best available topographic and bathymetric data were extracted from the USGS National Elevation Dataset and the NOAA hydrographic survey database, respectively. Before being merged, the topographic and bathymetric datasets were processed with standard geographic information system tools to place them in a common horizontal reference frame. Also, a key part of the preprocessing was transformation to a common vertical reference through the use of VDatum, a new tool created by NOAA's National Geodetic Survey for vertical datum conversions. The final merged product is a seamless topographic/bathymetric model covering the Tampa Bay region at a grid spacing of 1 arc-second. Topographic LIDAR data were processed and merged with the bathymetry to demonstrate the incorporation of recent third party data sources for several test areas. A primary application of a merged topographic/bathymetric elevation model is for user-defined shoreline delineation, in which the user decides on the tidal condition (for example, low or high water) to be superimposed on the elevation data to determine the spatial position of the water line. Such a use of merged topographic/bathymetric data could lead to the development of a shoreline zone, which could reduce redundant mapping efforts by federal, state, and local agencies

  8. Open-Source Digital Elevation Model (DEMs) Evaluation with GPS and LiDAR Data

    NASA Astrophysics Data System (ADS)

    Khalid, N. F.; Din, A. H. M.; Omar, K. M.; Khanan, M. F. A.; Omar, A. H.; Hamid, A. I. A.; Pa'suya, M. F.

    2016-09-01

    Advanced Spaceborne Thermal Emission and Reflection Radiometer-Global Digital Elevation Model (ASTER GDEM), Shuttle Radar Topography Mission (SRTM), and Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) are freely available Digital Elevation Model (DEM) datasets for environmental modeling and studies. The quality of spatial resolution and vertical accuracy of the DEM data source has a great influence particularly on the accuracy specifically for inundation mapping. Most of the coastal inundation risk studies used the publicly available DEM to estimated the coastal inundation and associated damaged especially to human population based on the increment of sea level. In this study, the comparison between ground truth data from Global Positioning System (GPS) observation and DEM is done to evaluate the accuracy of each DEM. The vertical accuracy of SRTM shows better result against ASTER and GMTED10 with an RMSE of 6.054 m. On top of the accuracy, the correlation of DEM is identified with the high determination of coefficient of 0.912 for SRTM. For coastal zone area, DEMs based on airborne light detection and ranging (LiDAR) dataset was used as ground truth data relating to terrain height. In this case, the LiDAR DEM is compared against the new SRTM DEM after applying the scale factor. From the findings, the accuracy of the new DEM model from SRTM can be improved by applying scale factor. The result clearly shows that the value of RMSE exhibit slightly different when it reached 0.503 m. Hence, this new model is the most suitable and meets the accuracy requirement for coastal inundation risk assessment using open source data. The suitability of these datasets for further analysis on coastal management studies is vital to assess the potentially vulnerable areas caused by coastal inundation.

  9. Use of upscaled elevation and surface roughness data in two-dimensional surface water models

    USGS Publications Warehouse

    Hughes, J.D.; Decker, J.D.; Langevin, C.D.

    2011-01-01

    In this paper, we present an approach that uses a combination of cell-block- and cell-face-averaging of high-resolution cell elevation and roughness data to upscale hydraulic parameters and accurately simulate surface water flow in relatively low-resolution numerical models. The method developed allows channelized features that preferentially connect large-scale grid cells at cell interfaces to be represented in models where these features are significantly smaller than the selected grid size. The developed upscaling approach has been implemented in a two-dimensional finite difference model that solves a diffusive wave approximation of the depth-integrated shallow surface water equations using preconditioned Newton–Krylov methods. Computational results are presented to show the effectiveness of the mixed cell-block and cell-face averaging upscaling approach in maintaining model accuracy, reducing model run-times, and how decreased grid resolution affects errors. Application examples demonstrate that sub-grid roughness coefficient variations have a larger effect on simulated error than sub-grid elevation variations.

  10. Modelling the descent of nitric oxide during the elevated stratopause event of January 2013

    NASA Astrophysics Data System (ADS)

    Orsolini, Yvan J.; Limpasuvan, Varavut; Pérot, Kristell; Espy, Patrick; Hibbins, Robert; Lossow, Stefan; Raaholt Larsson, Katarina; Murtagh, Donal

    2017-03-01

    Using simulations with a whole-atmosphere chemistry-climate model nudged by meteorological analyses, global satellite observations of nitrogen oxide (NO) and water vapour by the Sub-Millimetre Radiometer instrument (SMR), of temperature by the Microwave Limb Sounder (MLS), as well as local radar observations, this study examines the recent major stratospheric sudden warming accompanied by an elevated stratopause event (ESE) that occurred in January 2013. We examine dynamical processes during the ESE, including the role of planetary wave, gravity wave and tidal forcing on the initiation of the descent in the mesosphere-lower thermosphere (MLT) and its continuation throughout the mesosphere and stratosphere, as well as the impact of model eddy diffusion. We analyse the transport of NO and find the model underestimates the large descent of NO compared to SMR observations. We demonstrate that the discrepancy arises abruptly in the MLT region at a time when the resolved wave forcing and the planetary wave activity increase, just before the elevated stratopause reforms. The discrepancy persists despite doubling the model eddy diffusion. While the simulations reproduce an enhancement of the semi-diurnal tide following the onset of the 2013 SSW, corroborating new meteor radar observations at high northern latitudes over Trondheim (63.4°N), the modelled tidal contribution to the forcing of the mean meridional circulation and to the descent is a small portion of the resolved wave forcing, and lags it by about ten days.

  11. Predicting Bed Grain Size in Threshold Channels Using Lidar Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Snyder, N. P.; Nesheim, A. O.; Wilkins, B. C.; Edmonds, D. A.

    2011-12-01

    Over the past 20 years, researchers have developed GIS-based algorithms to extract channel networks and measure longitudinal profiles from digital elevation models (DEMs), and have used these to study stream morphology in relation to tectonics, climate and ecology. The accuracy of stream elevations from traditional DEMs (10-50 m pixels) is typically limited by the contour interval (3-20 m) of the rasterized topographic map source. This is a particularly severe limitation in low-relief watersheds, where 3 m of channel elevation change may occur over several km. Lidar DEMs (~1 m pixels) allow researchers to resolve channel elevation changes of ~0.5 m, enabling reach-scale calculations of gradient, which is the most important parameter for understanding channel processes at that scale. Lidar DEMs have the additional advantage of allowing users to make estimates of channel width. We present a process-based model that predicts median bed grain size in threshold gravel-bed channels from lidar slope and width measurements using the Shields and Manning equations. We compare these predictions to field grain size measurements in segments of three Maine rivers. Like many paraglacial rivers, these have longitudinal profiles characterized by relatively steep (gradient >0.002) and flat (gradient <0.0005) segments, with length scales of several km. This heterogeneity corresponds to strong variations in channel form, sediment supply, bed grain size, and aquatic habitat characteristics. The model correctly predicts bed sediment size within a factor of two in ~70% of the study sites. The model works best in single-thread channels with relatively low sediment supply, and poorly in depositional, multi-thread and/or fine (median grain size <20 mm) reaches. We evaluate the river morphology (using field and lidar measurements) in the context of the Parker et al. (2007) hydraulic geometry relations for single-thread gravel-bed rivers, and find correspondence in the locations where both

  12. Back to the Future: Have Remotely Sensed Digital Elevation Models Improved Hydrological Parameter Extraction?

    NASA Astrophysics Data System (ADS)

    Jarihani, B.

    2015-12-01

    Digital Elevation Models (DEMs) that accurately replicate both landscape form and processes are critical to support modeling of environmental processes. Pre-processing analysis of DEMs and extracting characteristics of the watershed (e.g., stream networks, catchment delineation, surface and subsurface flow paths) is essential for hydrological and geomorphic analysis and sediment transport. This study investigates the status of the current remotely-sensed DEMs in providing advanced morphometric information of drainage basins particularly in data sparse regions. Here we assess the accuracy of three available DEMs: (i) hydrologically corrected "H-DEM" of Geoscience Australia derived from the Shuttle Radar Topography Mission (SRTM) data; (ii) the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model (ASTER GDEM) version2 1-arc-second (~30 m) data; and (iii) the 9-arc-second national GEODATA DEM-9S ver3 from Geoscience Australia and the Australian National University. We used ESRI's geospatial data model, Arc Hydro and HEC-GeoHMS, designed for building hydrologic information systems to synthesize geospatial and temporal water resources data that support hydrologic modeling and analysis. A coastal catchment in northeast Australia was selected as the study site where very high resolution LiDAR data are available for parts of the area as reference data to assess the accuracy of other lower resolution datasets. This study provides morphometric information for drainage basins as part of the broad research on sediment flux from coastal basins to Great Barrier Reef, Australia. After applying geo-referencing and elevation corrections, stream and sub basins were delineated for each DEM. Then physical characteristics for streams (i.e., length, upstream and downstream elevation, and slope) and sub-basins (i.e., longest flow lengths, area, relief and slopes) were extracted and compared with reference datasets from LiDAR. Results showed that

  13. Definition of Hydrologic Response Units in Depression Plagued Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Lindsay, J. B.; Creed, I. F.

    2002-12-01

    Definition of hydrologic response units using digital elevation models (DEMs) is sensitive to the occurrence of topographic depressions. Real depressions can be important to the hydrology and biogeochemistry a catchment, often coinciding with areas of surface saturation. Artifact depressions, in contrast, result in digital "black holes", artificially truncating the hydrologic flow lengths and altering hydrologic flow directions, parameters that are often used in defining hydrologic response units. Artifact depressions must be removed from DEMs prior to definition of hydrologic response units. Depression filling or depression trenching techniques can be used to remove these artifacts. Depression trenching methods are often considered more appropriate because they preserve the topographic variability within a depression thus avoiding the creation of spurious flat areas. Current trenching algorithms are relatively slow and unable to process very large or noisy DEMs. A new trenching algorithm that overcomes these limitations is described. The algorithm does not require finding depression catchments or outlets, nor does it need special handling for nested depressions. Therefore, artifacts can be removed from large or noisy DEMs efficiently, while minimizing the number of grid elevations requiring modification. The resulting trench is a monotonically descending path starting from the lowest point in a depression, passing through the depression's outlet, and ending at a point of lower elevation outside the depression. The importance of removing artifact depressions is demonstrated by showing hydrologic response units both before and after the removal of artifact depressions from the DEM.

  14. Ventricular dilation and elevated aqueductal pulsations in a new experimental model of communicating hydrocephalus

    SciTech Connect

    Wagshul, M.; Smith, S.; Wagshul, M.; McAllister, J.P.; Rashid, S.; Li, J.; Egnor, M.R.; Walker, M.L.; Yu, M.; Smith, S.D.; Zhang, G.; Chen, J.J.; Beneveniste, H.

    2009-03-01

    In communicating hydrocephalus (CH), explanations for the symptoms and clear-cut effective treatments remain elusive. Pulsatile flow through the cerebral aqueduct is often significantly elevated, but a clear link between abnormal pulsations and ventriculomegaly has yet to be identified. We sought to demonstrate measurement of pulsatile aqueductal flow of CSF in the rat, and to characterize the temporal changes in CSF pulsations in a new model of CH. Hydrocephalus was induced by injection of kaolin into the basal cisterns of adult rats (n = 18). Ventricular volume and aqueductal pulsations were measured on a 9.4 T MRI over a one month period. Half of the animals developed ventricular dilation, with increased ventricular volume and pulsations as early as one day post-induction, and marked chronic elevations compared to intact controls (volume: 130.15 {+-} 83.21 {mu}l vs. 15.52 {+-} 2.00 {mu}l; pulsations: 114.51 nl {+-} 106.29 vs. 0.72 {+-} 0.13 nl). Similar to the clinical presentation, the relationship between ventricular size and pulsations was quite variable. However, the pulsation time-course revealed two distinct sub-types of hydrocephalic animals: those with markedly elevated pulsations which persisted over time, and those with mildly elevated pulsations which returned to near normal levels after one week. These groups were associated with severe and mild ventriculomegaly respectively. Thus, aqueductal flow can be measured in the rat using high-field MRI and basal cistern-induced CH is associated with an immediate change in CSF pulsatility. At the same time, our results highlight the complex nature of aqueductal pulsation and its relationship to ventricular dilation.

  15. A geomorphology-based approach for digital elevation model fusion - case study in Danang city, Vietnam

    NASA Astrophysics Data System (ADS)

    Tran, T. A.; Raghavan, V.; Masumoto, S.; Vinayaraj, P.; Yonezawa, G.

    2014-07-01

    Global digital elevation models (DEM) are considered a source of vital spatial information and find wide use in several applications. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global DEM (GDEM) and Shuttle Radar Topographic Mission (SRTM) DEM offer almost global coverage and provide elevation data for geospatial analysis. However, GDEM and SRTM still contain some height errors that affect the quality of elevation data significantly. This study aims to examine methods to improve the resolution as well as accuracy of available free DEMs by data fusion techniques and evaluating the results with a high-quality reference DEM. The DEM fusion method is based on the accuracy assessment of each global DEM and geomorphological characteristics of the study area. Land cover units were also considered to correct the elevation of GDEM and SRTM with respect to the bare-earth surface. The weighted averaging method was used to fuse the input DEMs based on a landform classification map. According to the landform types, the different weights were used for GDEM and SRTM. Finally, a denoising algorithm (Sun et al., 2007) was applied to filter the output-fused DEM. This fused DEM shows excellent correlation to the reference DEM, having a correlation coefficient R2 = 0.9986, and the accuracy was also improved from a root mean square error (RMSE) of 14.9 m in GDEM and 14.8 m in SRTM to 11.6 m in the fused DEM. The results of terrain-related parameters extracted from this fused DEM such as slope, curvature, terrain roughness index and normal vector of topographic surface are also very comparable to reference data.

  16. Ventricular dilation and elevated aqueductal pulsations in a new experimental model of communicating hydrocephalus.

    PubMed

    Wagshul, M E; McAllister, J P; Rashid, S; Li, J; Egnor, M R; Walker, M L; Yu, M; Smith, S D; Zhang, G; Chen, J J; Benveniste, H

    2009-07-01

    In communicating hydrocephalus (CH), explanations for the symptoms and clear-cut effective treatments remain elusive. Pulsatile flow through the cerebral aqueduct is often significantly elevated, but a clear link between abnormal pulsations and ventriculomegaly has yet to be identified. We sought to demonstrate measurement of pulsatile aqueductal flow of CSF in the rat, and to characterize the temporal changes in CSF pulsations in a new model of CH. Hydrocephalus was induced by injection of kaolin into the basal cisterns of adult rats (n = 18). Ventricular volume and aqueductal pulsations were measured on a 9.4 T MRI over a one month period. Half of the animals developed ventricular dilation, with increased ventricular volume and pulsations as early as one day post-induction, and marked chronic elevations compared to intact controls (volume: 130.15 +/- 83.21 microl vs. 15.52 +/- 2.00 microl; pulsations: 114.51 nl +/- 106.29 vs. 0.72 +/- 0.13 nl). Similar to the clinical presentation, the relationship between ventricular size and pulsations was quite variable. However, the pulsation time-course revealed two distinct sub-types of hydrocephalic animals: those with markedly elevated pulsations which persisted over time, and those with mildly elevated pulsations which returned to near normal levels after one week. These groups were associated with severe and mild ventriculomegaly respectively. Thus, aqueductal flow can be measured in the rat using high-field MRI and basal cistern-induced CH is associated with an immediate change in CSF pulsatility. At the same time, our results highlight the complex nature of aqueductal pulsation and its relationship to ventricular dilation.

  17. Origin, characteristics, and behaviour of lahars following the 1990 eruption of Kelud volcano, eastern Java (Indonesia)

    NASA Astrophysics Data System (ADS)

    Thouret, J.-C.; Abdurachman, K. E.; Bourdier, J.-L.; Bronto, S.

    In contrast to most twentieth-century eruptions of Kelud volcano (eastern Java), the 10 February 1990 plinian eruption was not accompanied by lake-outburst lahars. However, at least 33 post-eruption lahars occurred between 15 February and 28 March 1990. They swept down 11 drainage systems and travelled as far as 24km at an estimated mean peak velocity in the range of 4-11ms-1. The deposits (volume >=30 000 000m3) were approximately 7m thick 2km from vent, and 3m thick 10km from vent, on the volcaniclastic apron surrounding the volcano. Subtle but significant sedimentological differences in the deposits relate to four flow types: (a) Early, massive deposits are coarse, poorly sorted, slightly cohesive, and commonly inversely graded. They are inferred to record hot lahars that incorporated pumice and scoria from pyroclastic-flow deposits, probably by rapid remobilization of hot proximal pyroclastic flow deposits by rainfall runoff. Sedimentary features, such as clasts subparallel to bedding and thick, reversely to ungraded beds, suggest that these flows were laminar. (b) Abundant, very poorly sorted deposits include non-cohesive, clast-supported, inversely graded beds and ungraded, finer-grained, and cohesive matrix-supported beds. These beds display layering and vertical segregation/density stratification, suggesting unsteady properties of pulsing debris flows. They are interpreted as deposited from segments of flow waves at a middle distance downstream that incorporated pre-eruption sediments. Sedimentological evidence suggests unsteady flow properties during progressive aggradation. (c) Fine-grained, poorly sorted and ungraded deposits are interpreted as recording late hyperconcentrated streamflows that formed in the waning stage of an overflow and transformed downcurrent into streamflows. (d) Ungraded, crudely stratified deposits were emplaced by flows transitional between hyperconcentrated flows and streamflows that traveled farther downvalley (as far as 27km

  18. Investigation of potential sea level rise impact on the Nile Delta, Egypt using digital elevation models.

    PubMed

    Hasan, Emad; Khan, Sadiq Ibrahim; Hong, Yang

    2015-10-01

    In this study, the future impact of Sea Level Rise (SLR) on the Nile Delta region in Egypt is assessed by evaluating the elevations of two freely available Digital Elevation Models (DEMs): the SRTM and the ASTER-GDEM-V2. The SLR is a significant worldwide dilemma that has been triggered by recent climatic changes. In Egypt, the Nile Delta is projected to face SLR of 1 m by the end of the 21th century. In order to provide a more accurate assessment of the future SLR impact on Nile Delta's land and population, this study corrected the DEM's elevations by using linear regression model with ground elevations from GPS survey. The information for the land cover types and future population numbers were derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) land cover and the Gridded Population of the Worlds (GPWv3) datasets respectively. The DEM's vertical accuracies were assessed using GPS measurements and the uncertainty analysis revealed that the SRTM-DEM has positive bias of 2.5 m, while the ASTER-GDEM-V2 showed a positive bias of 0.8 m. The future inundated land cover areas and the affected population were illustrated based on two SLR scenarios of 0.5 m and 1 m. The SRTM DEM data indicated that 1 m SLR will affect about 3900 km(2) of cropland, 1280 km(2) of vegetation, 205 km(2) of wetland, 146 km(2) of urban areas and cause more than 6 million people to lose their houses. The overall vulnerability assessment using ASTER-GDEM-V2 indicated that the influence of SLR will be intense and confined along the coastal areas. For instance, the data indicated that 1 m SLR will inundate about 580 Km(2) (6%) of the total land cover areas and approximately 887 thousand people will be relocated. Accordingly, the uncertainty analysis of the DEM's elevations revealed that the ASTER-GDEM-V2 dataset product was considered the best to determine the future impact of SLR on the Nile Delta region.

  19. Watershed boundaries and digital elevation model of Oklahoma derived from 1:100,000-scale digital topographic maps

    USGS Publications Warehouse

    Cederstrand, J.R.; Rea, A.H.

    1995-01-01

    This document provides a general description of the procedures used to develop the data sets included on this compact disc. This compact disc contains watershed boundaries for Oklahoma, a digital elevation model, and other data sets derived from the digital elevation model. The digital elevation model was produced using the ANUDEM software package, written by Michael Hutchinson and licensed from the Centre for Resource and Environmental Studies at The Australian National University. Elevation data (hypsography) and streams (hydrography) from digital versions of the U.S. Geological Survey 1:100,000-scale topographic maps were used by the ANUDEM package to produce a hydrologically conditioned digital elevation model with a 60-meter cell size. This digital elevation model is well suited for drainage-basin delineation using automated techniques. Additional data sets include flow-direction, flow-accumulation, and shaded-relief grids, all derived from the digital elevation model, and the hydrography data set used in producing the digital elevation model. The watershed boundaries derived from the digital elevation model have been edited to be consistent with contours and streams from the U.S. Geological Survey 1:100,000-scale topographic maps. The watershed data set includes boundaries for 11-digit Hydrologic Unit Codes (watersheds) within Oklahoma, and 8-digit Hydrologic Unit Codes (cataloging units) outside Oklahoma. Cataloging-unit boundaries based on 1:250,000-scale maps outside Oklahoma for the Arkansas, Red, and White River basins are included. The other data sets cover Oklahoma, and where available, portions of 1:100,000-scale quadrangles adjoining Oklahoma.

  20. Modeling Water-Surface Elevations and Virtual Shorelines for the Colorado River in Grand Canyon, Arizona

    USGS Publications Warehouse

    Magirl, Christopher S.; Breedlove, Michael J.; Webb, Robert H.; Griffiths, Peter G.

    2008-01-01

    Using widely-available software intended for modeling rivers, a new one-dimensional hydraulic model was developed for the Colorado River through Grand Canyon from Lees Ferry to Diamond Creek. Solving one-dimensional equations of energy and continuity, the model predicts stage for a known steady-state discharge at specific locations, or cross sections, along the river corridor. This model uses 2,680 cross sections built with high-resolution digital topography of ground locations away from the river flowing at a discharge of 227 m3/s; synthetic bathymetry was created for topography submerged below the 227 m3/s water surface. The synthetic bathymetry was created by adjusting the water depth at each cross section up or down until the model?s predicted water-surface elevation closely matched a known water surface. This approach is unorthodox and offers a technique to construct one-dimensional hydraulic models of bedrock-controlled rivers where bathymetric data have not been collected. An analysis of this modeling approach shows that while effective in enabling a useful model, the synthetic bathymetry can differ from the actual bathymetry. The known water-surface profile was measured using elevation data collected in 2000 and 2002, and the model can simulate discharges up to 5,900 m3/s. In addition to the hydraulic model, GIS-based techniques were used to estimate virtual shorelines and construct inundation maps. The error of the hydraulic model in predicting stage is within 0.4 m for discharges less than 1,300 m3/s. Between 1,300-2,500 m3/s, the model accuracy is about 1.0 m, and for discharges between 2,500-5,900 m3/s, the model accuracy is on the order of 1.5 m. In the absence of large floods on the flow-regulated Colorado River in Grand Canyon, the new hydraulic model and the accompanying inundation maps are a useful resource for researchers interested in water depths, shorelines, and stage-discharge curves for flows within the river corridor with 2002 topographic

  1. Predictive vegetation modeling for conservation: impact of error propagation from digital elevation data.

    PubMed

    Van Niel, Kimberly P; Austin, Mike P

    2007-01-01

    The effect of digital elevation model (DEM) error on environmental variables, and subsequently on predictive habitat models, has not been explored. Based on an error analysis of a DEM, multiple error realizations of the DEM were created and used to develop both direct and indirect environmental variables for input to predictive habitat models. The study explores the effects of DEM error and the resultant uncertainty of results on typical steps in the modeling procedure for prediction of vegetation species presence/absence. Results indicate that all of these steps and results, including the statistical significance of environmental variables, shapes of species response curves in generalized additive models (GAMs), stepwise model selection, coefficients and standard errors for generalized linear models (GLMs), prediction accuracy (Cohen's kappa and AUC), and spatial extent of predictions, were greatly affected by this type of error. Error in the DEM can affect the reliability of interpretations of model results and level of accuracy in predictions, as well as the spatial extent of the predictions. We suggest that the sensitivity of DEM-derived environmental variables to error in the DEM should be considered before including them in the modeling processes.

  2. High Resolution Photogrammetric Digital Elevation Models Across Calving Fronts and Meltwater Channels in Greenland

    NASA Astrophysics Data System (ADS)

    Le Bel, D. A.; Brown, S.; Zappa, C. J.; Bell, R. E.; Frearson, N.; Tinto, K. J.

    2014-12-01

    Photogrammetric digital elevation models (DEMs) are a powerful approach for understanding elevation change and dynamics along the margins of the large ice sheets. The IcePod system, mounted on a New York Air National Guard LC-130, can measure high-resolution surface elevations with a Riegl VQ580 scanning laser altimeter and Imperx Bobcat IGV-B6620 color visible-wavelength camera (6600x4400 resolution); the surface temperature with a Sofradir IRE-640L infrared camera (spectral response 7.7-9.5 μm, 640x512 resolution); and the structure of snow and ice with two radar systems. We show the use of IcePod imagery to develop DEMs across calving fronts and meltwater channels in Greenland. Multiple over-flights of the Kangerlussaq Airport ramp have provided a test of the technique at a location with accurate, independently-determined elevation. Here the photogrammetric DEM of the airport, constrained by ground control measurements, is compared with the Lidar results. In July 2014 the IcePod ice-ocean imaging system surveyed the calving fronts of five outlet glaciers north of Jakobshavn Isbrae. We used Agisoft PhotoScan to develop a DEM of each calving front using imagery captured by the IcePod systems. Adjacent to the ice sheet, meltwater plumes foster mixing in the fjord, moving warm ocean water into contact with the front of the ice sheet where it can undercut the ice front and trigger calving. The five glaciers provide an opportunity to examine the calving front structure in relation to ocean temperature, fjord circulation, and spatial scale of the meltwater plumes. The combination of the accurate DEM of the calving front and the thermal imagery used to constrain the temperature and dynamics of the adjacent plume provides new insights into the ice-ocean interactions. Ice sheet margins provide insights into the connections between the surface meltwater and the fate of the water at the ice sheet base. Surface meltwater channels are visualized here for the first time using

  3. Application of Low-Cost Digital Elevation Models to Detect Change in Forest Carbon Sequestration Projects

    SciTech Connect

    Kenneth Glenn MacDicken

    2007-07-31

    This two-year study evaluated advanced multispectral digital imagery applications for assessment of forest carbon stock change. A series of bench and field studies in North Carolina and Ohio tested aerial assessments of forest change between two time periods using two software packages (ERDAS and TERREST) for Digital Elevation Model (DEM) creation, automated classification software (eCognition) for canopy segmentation and a multiple ranging laser designed to improve quality of elevation data. Results of the DEM software comparison showed that while TERREST has the potential to produce much higher resolution DEM than ERDAS, it is unable to resolve crucial canopy features adequately. Lab tests demonstrated that additional laser data improves image registration and Z-axis DEM quality. Data collected in the field revealed difficult challenges in correctly modeling the location of laser strike and subsequently determining elevations in both software packages. Automated software segmentation of tree canopies provided stem diameter and biomass carbon estimates that were within 3% of comparable ground based estimates in the Ohio site and produced similar biomass estimates for a limited number of plots in the Duke forest. Tree height change between time periods and canopy segmentation from multispectral imagery allowed calculation of forest carbon stock change at costs that are comparable to those for ground-based methods. This work demonstrates the potential of lower cost imagery systems enhanced with laser data to collect high quality imagery and paired laser data for forestry and environmental applications. Additional research on automated canopy segmentation and multi-temporal image registration is needed to refine these methods for commercial use.

  4. A Methodology To Generate A Digital Elevation Model By Combining Topographic And Bathymetric Data In Fluvial Environments

    NASA Astrophysics Data System (ADS)

    Matias, Magda Paraiso; Falcano, Ana Paula; Goncalves, Alexandre B.; Alvares, Teressa; Pestana, Rita; Van Zeller, Emilia; Rodrigues, Victor; Heleno, Sandra

    2013-12-01

    In hydrodynamic simulations, a digital elevation model valid for the whole study area is a requirement. The construction of this model usually implies the use of topographic and bathymetric data collected by distinct equipment and methods, at different times and acquired with a variety of spatial resolutions and accuracies. Several methodologies have been tested in order to combine both datasets involving the use of diverse spatial interpolators. In this paper we present the first results of a new methodology that combines a digital elevation model acquired by radar for floodplain areas with cross- sections in the river bed, in order to provide the most accurate and reliable digital elevation model. Since data was collected in distinct epochs, in the overlapped areas differences in elevation might exist, due to the morphological dynamics of the river. In order to analyse and validate those differences, a dataset with SAR imagery, provided by ESA, was used.

  5. Mathematical modeling of liver enzyme elevation in HIV mono-infection.

    PubMed

    Nampala, Hasifa; Luboobi, Livingstone S; Mugisha, Joseph Y T; Obua, Celestino

    2013-03-01

    HIV-infected individuals are increasingly becoming susceptible to liver disease and, hence, liver-related mortality is on a rise. The presence of CD4+ in the liver and the presence of C-X-C chemokine receptor type 4 (CXCR4) on human hepatocytes provide a conducive environment for HIV invasion. In this study, a mathematical model is used to analyse the dynamics of HIV in the liver with the aim of investigating the existence of liver enzyme elevation in HIV mono-infected individuals. In the presence of HIV-specific cytotoxic T-lymphocytes, the model depicts a unique endemic equilibrium with a transcritical bifurcation when the basic reproductive number is unity. Results of the study show that the level of liver enzyme alanine aminotransferase (ALT) increases with increase in the rate of hepatocytes production. Numerical simulations reveal significant elevation of alanine aminotransferase with increase in viral load. The findings presuppose that while liver damage in HIV infection has mostly been associated with HIV/HBV coinfection and use of antiretroviral therapy (ART), it is possible to have liver damage solely with HIV infection.

  6. Perturbation and melting of snow and ice by the 13 November 1985 eruption of Nevado del Ruiz, Colombia, and consequent mobilization, flow and deposition of lahars

    USGS Publications Warehouse

    Pierson, T.C.; Janda, R.J.; Thouret, J.-C.; Borrero, C.A.

    1990-01-01

    A complex sequence of pyroclastic flows and surges erupted by Nevado del Ruiz volcano on 13 November 1985 interacted with snow and ice on the summit ice cap to trigger catastrophic lahars (volcanic debris flows), which killed more than 23,000 people living at or beyond the base of the volcano. The rapid transfer of heat from the hot eruptive products to about 10 km2 of the snowpack, combined with seismic shaking, produced large volumes of meltwater that flowed downslope, liquefied some of the new volcanic deposits, and generated avalanches of saturated snow, ice and rock debris within minutes of the 21:08 (local time) eruption. About 2 ?? 107 m3 of water was discharged into the upper reaches of the Molinos, Nereidas, Guali, Azufrado and Lagunillas valleys, where rapid entrainment of valley-fill sediment transformed the dilute flows and avalanches to debris flows. Computed mean velocities of the lahars at peak flow ranged up to 17 m s-1. Flows were rapid in the steep, narrow upper canyons and slowed with distance away from the volcano as flow depth and channel slope diminished. Computed peak discharges ranged up to 48,000 m3 s-1 and were greatest in reaches 10 to 20 km downstream from the summit. A total of about 9 ?? 107 m3 of lahar slurry was transported to depositional areas up to 104 km from the source area. Initial volumes of individual lahars increased up to 4 times with distance away from the summit. The sedimentology and stratigraphy of the lahar deposits provide compelling evidence that: (1) multiple initial meltwater pulses tended to coalesce into single flood waves; (2) lahars remained fully developed debris flows until they reached confluences with major rivers; and (3) debris-flow slurry composition and rheology varied to produce gradationally density-stratified flows. Key lessons and reminders from the 1985 Nevado del Ruiz volcanic eruption are: (1) catastrophic lahars can be generated on ice- and snow-capped volcanoes by relatively small eruptions; (2

  7. Modeling the effects of elevated temperatures on action potential propagation in unmyelinated axons

    NASA Astrophysics Data System (ADS)

    Ganguly, Mohit; Jenkins, Michael W.; Chiel, Hillel J.; Jansen, E. Duco

    2016-03-01

    Infrared lasers (λ=1.87 μm) are capable of inducing a thermally mediated nerve block in Aplysia and rat nerves. While this block is spatially precise and reversible in sensory and motor neurons, the mechanism of block is not clearly understood. Model predictions show that, at elevated temperatures, the rates of opening and closing of the voltage gated ion channels are disrupted and normal functioning of the gates is hindered. A model combining NEURON with Python is presented here that can simulate the behavior of unmyelinated nerve axons in the presence of spatially and temporally varying temperature distributions. Axon behavior and underlying mechanism leading to conduction block is investigated. The ability to understand the photothermal interaction of laser light and temperature dependence of membrane ion channels in-silico will help speed explorations of parameter space and guide future experiments testing the feasibility of selectively blocking pain conduction fibers (Photonic Analgesia of Nerves (PAIN)) in humans.

  8. Hydrologic analysis of a flood based on a new Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Nishio, M.; Mori, M.

    2015-06-01

    These The present study aims to simulate the hydrologic processes of a flood, based on a new, highly accurate Digital Elevation Model (DEM). The DEM is provided by the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, and has a spatial resolution of five meters. It was generated by the new National Project in 2012. The Hydrologic Engineering Center - Hydrologic Modeling System (HEC-HMS) is used to simulate the hydrologic process of a flood of the Onga River in Iizuka City, Japan. A large flood event in the typhoon season in 2003 caused serious damage around the Iizuka City area. Precise records of rainfall data from the Automated Meteorological Data Acquisition System (AMeDAS) were input into the HEC-HMS. The estimated flood area of the simulation results by HEC-HMS was identical to the observed flood area. A watershed aggregation map is also generated by HEC-HMS around the Onga River.

  9. In-flow evolution of lahar deposits from video-imagery with implications for post-event deposit interpretation, Mount Semeru, Indonesia

    NASA Astrophysics Data System (ADS)

    Starheim, Colette C. A.; Gomez, Christopher; Davies, Tim; Lavigne, Franck; Wassmer, Patrick

    2013-04-01

    The hazardous and unpredictable nature of lahars makes them challenging to study, yet the in-flow processes characterizing these events are important to understand. As a result, much of the previous research on lahar sedimentation and flow processes has been derived from experimental flows or stratigraphic surveys of post-event deposits. By comparison, little is known on the time-dependent sediment and flow dynamics of lahars in natural environments. Using video-footage of seven lahars on the flanks of Semeru Volcano (East Java, Indonesia), the present study offers new insights on the in-flow evolution of sediment in natural lahars. Video analysis revealed several distinctive patterns of sediment entrainment and deposition that varied with time-related fluctuations in flow. These patterns were used to generate a conceptual framework describing possible processes of formation for subsurface architectural features identified in an earlier lateral survey of lahar deposits on Semeru Volcano (Gomez and Lavigne, 2010a). The formation of lateral discontinuities was related to the partial erosion of transitional bank deposits followed by fresh deposition along the erosional contact. This pattern was observed over the course of several lahar events and within individual flows. Observations similarly offer potential explanations for the formation of lenticular features. Depending on flow characteristics, these features appeared to form by preferential erosion or deposition around large stationary blocks, and by deposition along channel banks during episodes of channel migration or channel constriction. Finally, conditions conducive to the deposition of fine laminated beds were observed during periods of attenuating and surging flow. These results emphasize the difficulties associated with identifying process-structure relationships solely from post-event deposit interpretation and illustrate that an improved understanding of the time-dependent sediment dynamics in lahars may

  10. A computationally efficient depression-filling algorithm for digital elevation models, applied to proglacial lake drainage

    NASA Astrophysics Data System (ADS)

    Berends, Constantijn J.; van de Wal, Roderik S. W.

    2016-12-01

    Many processes govern the deglaciation of ice sheets. One of the processes that is usually ignored is the calving of ice in lakes that temporarily surround the ice sheet. In order to capture this process a "flood-fill algorithm" is needed. Here we present and evaluate several optimizations to a standard flood-fill algorithm in terms of computational efficiency. As an example, we determine the land-ocean mask for a 1 km resolution digital elevation model (DEM) of North America and Greenland, a geographical area of roughly 7000 by 5000 km (roughly 35 million elements), about half of which is covered by ocean. Determining the land-ocean mask with our improved flood-fill algorithm reduces computation time by 90 % relative to using a standard stack-based flood-fill algorithm. This implies that it is now feasible to include the calving of ice in lakes as a dynamical process inside an ice-sheet model. We demonstrate this by using bedrock elevation, ice thickness and geoid perturbation fields from the output of a coupled ice-sheet-sea-level equation model at 30 000 years before present and determine the extent of Lake Agassiz, using both the standard and improved versions of the flood-fill algorithm. We show that several optimizations to the flood-fill algorithm used for filling a depression up to a water level, which is not defined beforehand, decrease the computation time by up to 99 %. The resulting reduction in computation time allows determination of the extent and volume of depressions in a DEM over large geographical grids or repeatedly over long periods of time, where computation time might otherwise be a limiting factor. The algorithm can be used for all glaciological and hydrological models, which need to trace the evolution over time of lakes or drainage basins in general.

  11. A time series of TanDEM-X digital elevation models to monitor a glacier surge

    NASA Astrophysics Data System (ADS)

    Wendt, Anja; Mayer, Christoph; Lambrecht, Astrid; Floricioiu, Dana

    2016-04-01

    Bivachny Glacier, a tributary of the more than 70 km long Fedchenko Glacier in the Pamir Mountains, Central Asia, is a surge-type glacier with three known surges during the 20th century. In 2011, the most recent surge started which, in contrast to the previous ones, evolved down the whole glacier and reached the confluence with Fedchenko Glacier. Spatial and temporal glacier volume changes can be derived from high-resolution digital elevation models (DEMs) based on bistatic InSAR data from the TanDEM-X mission. There are nine DEMs available between 2011 and 2015 covering the entire surge period in time steps from few months up to one year. During the surge, the glacier surface elevation increased by up to 130 m in the lower part of the glacier; and change rates of up to 0.6 m per day were observed. The surface height dataset was complemented with glacier surface velocity information from TerraSAR-X/ TanDEM-X data as well as optical Landsat imagery. While the glacier was practically stagnant in 2000 after the end of the previous surge in the 1990s, the velocity increase started in 2011 in the upper reaches of the ablation area and successively moved downwards and intensified, reaching up to 4.0 m per day. The combination of surface elevation changes and glacier velocities, both of high temporal and spatial resolution, provides the unique opportunity to describe and analyse the evolution of the surge in unprecedented detail. Especially the relation between the mobilization front and the local mass transport provides insight into the surge dynamics.

  12. Assessing the quality for hydrological applications of digital elevation models derived from contours

    NASA Astrophysics Data System (ADS)

    Wise, Stephen

    2000-07-01

    Digital elevation models (DEMs) are becoming increasingly important tools in hydrological research and in water resources management. The quality of DEMs, however, normally is reported simply as the root mean square error of elevation, a statistic that fails to capture the numerous sources of error in DEMs or to predict their effect on the result of using the DEM. This paper presents a review of other approaches to assessing DEM quality, and argues that a full assessment of DEM quality must focus on the accuracy and reliability of the final product of the DEM analysis. A number of DEMs for the Slapton Ley catchments in Devon derived from digitized contour data are compared in an initial assessment of their sustainability for use in hydrological work. Two are available for purchase from data suppliers, and five more were created using a variety of interpolation techniques in widely available geographical information system software. The different interpretation methods produce DEMs with different artefacts, although analyses of the distribution of elevation values, and visual techniques, suggested that none of these were of a particularly pronounced nature. The results of using the DEMs to derive drainage networks and catchment areas showed that at the broad scale there was a high level of agreement between the DEMs. There were, however, important differences of detail. For example, some DEMs predicted drainage lines that occasionally crossed the original contours. The results of calculating the TOPMODEL topographic index showed far more variation, because the index is calculated for each pixel in the area, rather than being an aggregate result derived from numerous pixels. The main conclusion was that care should always be taken to assess the quality of a DEM before attempting to use it, and that results should always be checked to ensure that they appear to be reasonable.

  13. ELEVATED COPPER REMODELS HEPATIC RNA PROCESSING MACHINERY IN THE MOUSE MODEL OF WILSON'S DISEASE

    PubMed Central

    Burkhead, Jason L.; Ralle, Martina; Wilmarth, Phillip; David, Larry; Lutsenko, Svetlana

    2011-01-01

    Copper is essential to mammalian physiology and its homeostasis is tightly regulated. In humans, genetic defects in copper excretion result in copper overload and Wilson's disease (WD). Previous studies in the mouse model for WD (Atp7b-/-) revealed copper accumulation in hepatic nuclei and specific changes in the mRNA profile prior to pathology onset. To find a molecular link between nuclear copper elevation and changes in hepatic transcriptome we utilized quantitative ionomic and proteomic approaches. X-ray fluorescence and ICP-MS analysis indicate that copper in Atp7b-/- nucleus, while highly elevated, does not markedly alter nuclear ion content. Widespread protein oxidation is also not observed, although glutathione reductase SelH is upregulated, likely to maintain redox balance. We further demonstrate that accumulating copper affects abundance and/or modification of a distinct subset of nuclear proteins. These proteins populate pathways most significantly associated with RNA processing. An alteration in the splicing pattern was observed for hnRNP A2/B1, itself the RNA shuttling factor and spliceosome component. Analysis of hnRNP A2/B1 mRNA and protein revealed an increased retention of exon 2 and a selective 2-fold upregulation of a corresponding protein spliced variant. Mass-spectrometry measurements suggest that the nucleo-cytoplasmic distribution of RNA binding proteins, including A2/B1, is altered in the Atp7b-/- liver. We conclude that remodeling of RNA processing machinery is an important component in cells’ response to elevated copper that may guide pathology development in early stages of WD. PMID:21146535

  14. Bathymetric survey and digital elevation model of Little Holland Tract, Sacramento-San Joaquin Delta, California

    USGS Publications Warehouse

    Snyder, Alexander G.; Lacy, Jessica R.; Stevens, Andrew W.; Carlson, Emily M.

    2016-06-10

    The U.S. Geological Survey conducted a bathymetric survey in Little Holland Tract, a flooded agricultural tract, in the northern Sacramento-San Joaquin Delta (the “Delta”) during the summer of 2015. The new bathymetric data were combined with existing data to generate a digital elevation model (DEM) at 1-meter resolution. Little Holland Tract (LHT) was historically diked off for agricultural uses and has been tidally inundated since an accidental levee breach in 1983. Shallow tidal regions such as LHT have the potential to improve habitat quality in the Delta. The DEM of LHT was developed to support ongoing studies of habitat quality in the area and to provide a baseline for evaluating future geomorphic change. The new data comprise 138,407 linear meters of real-time-kinematic (RTK) Global Positioning System (GPS) elevation data, including both bathymetric data collected from personal watercraft and topographic elevations collected on foot at low tide. A benchmark (LHT15_b1) was established for geodetic control of the survey. Data quality was evaluated both by comparing results among surveying platforms, which showed systematic offsets of 1.6 centimeters (cm) or less, and by error propagation, which yielded a mean vertical uncertainty of 6.7 cm. Based on the DEM and time-series measurements of water depth, the mean tidal prism of LHT was determined to be 2,826,000 cubic meters. The bathymetric data and DEM are available at http://dx.doi.org/10.5066/F7RX9954. 

  15. Validation of the ASTER Global Digital Elevation Model Version 2 over the conterminous United States

    USGS Publications Warehouse

    Gesch, Dean B.; Oimoen, Michael J.; Zhang, Zheng; Meyer, David J.; Danielson, Jeffrey J.

    2012-01-01

    The ASTER Global Digital Elevation Model Version 2 (GDEM v2) was evaluated over the conterminous United States in a manner similar to the validation conducted for the original GDEM Version 1 (v1) in 2009. The absolute vertical accuracy of GDEM v2 was calculated by comparison with more than 18,000 independent reference geodetic ground control points from the National Geodetic Survey. The root mean square error (RMSE) measured for GDEM v2 is 8.68 meters. This compares with the RMSE of 9.34 meters for GDEM v1. Another important descriptor of vertical accuracy is the mean error, or bias, which indicates if a DEM has an overall vertical offset from true ground level. The GDEM v2 mean error of -0.20 meters is a significant improvement over the GDEM v1 mean error of -3.69 meters. The absolute vertical accuracy assessment results, both mean error and RMSE, were segmented by land cover to examine the effects of cover types on measured errors. The GDEM v2 mean errors by land cover class verify that the presence of aboveground features (tree canopies and built structures) cause a positive elevation bias, as would be expected for an imaging system like ASTER. In open ground classes (little or no vegetation with significant aboveground height), GDEM v2 exhibits a negative bias on the order of 1 meter. GDEM v2 was also evaluated by differencing with the Shuttle Radar Topography Mission (SRTM) dataset. In many forested areas, GDEM v2 has elevations that are higher in the canopy than SRTM.

  16. The conservation value of elevation data accuracy and model sophistication in reserve design under sea-level rise.

    PubMed

    Zhu, Mingjian; Hoctor, Tom; Volk, Mike; Frank, Kathryn; Linhoss, Anna

    2015-10-01

    Many studies have explored the value of using more sophisticated coastal impact models and higher resolution elevation data in sea-level rise (SLR) adaptation planning. However, we know little about to what extent the improved models and data could actually lead to better conservation outcomes under SLR. This is important to know because high-resolution data are likely to not be available in some data-poor coastal areas in the world and running more complicated coastal impact models is relatively time-consuming, expensive, and requires assistance by qualified experts and technicians. We address this research question in the context of identifying conservation priorities in response to SLR. Specifically, we investigated the conservation value of using more accurate light detection and ranging (Lidar)-based digital elevation data and process-based coastal land-cover change models (Sea Level Affecting Marshes Model, SLAMM) to identify conservation priorities versus simple "bathtub" models based on the relatively coarse National Elevation Dataset (NED) in a coastal region of northeast Florida. We compared conservation outcomes identified by reserve design software (Zonation) using three different model dataset combinations (Bathtub-NED, Bathtub-Lidar, and SLAMM-Lidar). The comparisons show that the conservation priorities are significantly different with different combinations of coastal impact models and elevation dataset inputs. The research suggests that it is valuable to invest in more accurate coastal impact models and elevation datasets in SLR adaptive conservation planning because this model-dataset combination could improve conservation outcomes under SLR. Less accurate coastal impact models, including ones created using coarser Digital Elevation Model (DEM) data can still be useful when better data and models are not available or feasible, but results need to be appropriately assessed and communicated. A future research priority is to investigate how

  17. Assessing the quality of digital elevation models obtained from mini unmanned aerial vehicles for overland flow modelling in urban areas

    NASA Astrophysics Data System (ADS)

    Leitão, João P.; Moy de Vitry, Matthew; Scheidegger, Andreas; Rieckermann, Jörg

    2016-04-01

    Precise and detailed digital elevation models (DEMs) are essential to accurately predict overland flow in urban areas. Unfortunately, traditional sources of DEM, such as airplane light detection and ranging (lidar) DEMs and point and contour maps, remain a bottleneck for detailed and reliable overland flow models, because the resulting DEMs are too coarse to provide DEMs of sufficient detail to inform urban overland flows. Interestingly, technological developments of unmanned aerial vehicles (UAVs) suggest that they have matured enough to be a competitive alternative to satellites or airplanes. However, this has not been tested so far. In this study we therefore evaluated whether DEMs generated from UAV imagery are suitable for urban drainage overland flow modelling. Specifically, 14 UAV flights were conducted to assess the influence of four different flight parameters on the quality of generated DEMs: (i) flight altitude, (ii) image overlapping, (iii) camera pitch, and (iv) weather conditions. In addition, we compared the best-quality UAV DEM to a conventional lidar-based DEM. To evaluate both the quality of the UAV DEMs and the comparison to lidar-based DEMs, we performed regression analysis on several qualitative and quantitative metrics, such as elevation accuracy, quality of object representation (e.g. buildings, walls and trees) in the DEM, which were specifically tailored to assess overland flow modelling performance, using the flight parameters as explanatory variables. Our results suggested that, first, as expected, flight altitude influenced the DEM quality most, where lower flights produce better DEMs; in a similar fashion, overcast weather conditions are preferable, but weather conditions and other factors influence DEM quality much less. Second, we found that for urban overland flow modelling, the UAV DEMs performed competitively in comparison to a traditional lidar-based DEM. An important advantage of using UAVs to generate DEMs in urban areas is

  18. ASTER-Derived 30-Meter-Resolution Digital Elevation Models of Afghanistan

    USGS Publications Warehouse

    Chirico, Peter G.; Warner, Michael B.

    2007-01-01

    INTRODUCTION The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an imaging instrument aboard the Terra satellite, launched on December 19, 1999, as part of the National Aeronautics and Space Administration's (NASA) Earth Observing System (EOS). The ASTER sensor consists of three subsystems: the visible and near infrared (VNIR), the shortwave infrared (SWIR), and the thermal infrared (TIR), each with a different spatial resolution (VNIR, 15 meters; SWIR, 30 meters, TIR 90 meters). The VNIR system has the capability to generate along-track stereo images that can be used to create digital elevation models (DEMs) at 30-meter resolution. Currently, the only available DEM dataset for Afghanistan is the 90-meter-resolution Shuttle Radar Topography Mission (SRTM) data. This dataset is appropriate for macroscale DEM analysis and mapping. However, ASTER provides a low cost opportunity to generate higher resolution data. For this publication, study areas were identified around populated areas and areas where higher resolution elevation data were desired to assist in natural resource assessments. The higher resolution fidelity of these DEMs can also be used for other terrain analysis including landform classification and geologic structure analysis. For this publication, ASTER scenes were processed and mosaicked to generate 36 DEMs which were created and extracted using PCI Geomatics' OrthoEngine 3D Stereo software. The ASTER images were geographically registered to Landsat data with at least 15 accurate and well distributed ground control points with a root mean square error (RMSE) of less that one pixel (15 meters). An elevation value was then assigned to each ground control point by extracting the elevation from the 90-meter SRTM data. The 36 derived DEMs demonstrate that the software correlated on nearly flat surfaces and smooth slopes accurately. Larger errors occur in cloudy and snow-covered areas, lakes, areas with steep slopes, and

  19. Assessing volume change of tropical Peruvian glaciers from multi-temporal digital elevation models (DEMs)

    NASA Astrophysics Data System (ADS)

    Huh, K.; Mark, B. G.

    2012-12-01

    Although far smaller than large polar ice caps, mountain glaciers are significant contributors to sea level rise and tropical glaciers in particular are sources of critical water resources to regional societies. The glaciers in Cordillera Blanca, the Andes of Peru, hold important environmental and economic concerns of regional water supplies to communities in the arid western part of the country under continued global climate change. Yet steep relief and remote locations present challenges for measuring mass changes in tropical glaciers. Remotely sensed images provide feasible opportunities to measure glacier surface area changes. We use a combination of satellite and airborne remote sensing, digital photogrammetry and geospatial techniques to assess the surface area, volume and topographic changes of key glaciers in the Cordillera Blanca, Peru between 1962 and 2008. The intercomparison of digital elevation models (DEMs) from airborne Light Detection and Range (LiDAR) data of 2008, multispectral Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) of 2001-2008 and stereo-paired airborne photographs of 1962 for deriving elevation differences over time reveal the data quality to measure the volume loss in the area. The DEMs over non-glacier areas in the study sites were selected and differentially corrected Global Positioning System (dGPS) data points were used for comparison as well. The motivation of this study is to refine a surface area to volume scaling for tropical glaciers to enable extrapolation of more detailed inventory of glacier volume and water resources.

  20. Removal of artifact depressions from digital elevation models: towards a minimum impact approach

    NASA Astrophysics Data System (ADS)

    Lindsay, John B.; Creed, Irena F.

    2005-10-01

    Artifact depressions in digital elevation models (DEMs) interrupt flow paths and alter drainage directions. Techniques for removing depressions should enforce continuous flow paths in a way that requires the least modification of the DEM. Impacts on the spatial and statistical distributions of elevation and its derivatives were assessed for four methods of removing depressions: (1) filling; (2) breaching; (3) a combination of filling and breaching, with breaching constrained to a maximum of two grid cells; (4) a combination of filling and breaching based on an impact reduction approach (IRA). The IRA removes each depression using either filling or breaching, depending on which method has the least impact, in terms of the number of modified cells and the mean absolute difference in the DEM.Analysis of a LiDAR DEM of a landscape on the Canadian Shield showed significant differences in the impacts among the four depression removal methods. Depression filling, a removal method that is widely implemented in geographical information system software, was found to impact terrain attributes most severely. Constrained breaching, which relies heavily on filling for larger depressions, also performed poorly. Both depression breaching and the IRA impacted spatial and statistical distributions of terrain attributes less than depression filling and constrained breaching. The most sensitive landscapes to depression removal were those that contained large (i.e. >10%) flat areas, because of the occurrence of relatively large depressions in these areas.

  1. Digital Elevation Models and Derived Products from Lroc Nac Stereo Observations

    NASA Astrophysics Data System (ADS)

    Burns, K. N.; Speyerer, E. J.; Robinson, M. S.; Tran, T.; Rosiek, M. R.; Archinal, B. A.; Howington-Kraus, E.; the LROC Science Team

    2012-08-01

    One of the primary objectives of the Lunar Reconnaissance Orbiter Camera (LROC) is to acquire stereo observations with the Narrow Angle Camera (NAC) to enable production of high resolution digital elevation models (DEMs). This work describes the processes and techniques used in reducing the NAC stereo observations to DEMs through a combination of USGS integrated Software for Imagers and Spectrometers (ISIS) and SOCET SET® from BAE Systems by a team at Arizona State University (ASU). LROC Science Operations Center personnel have thus far reduced 130 stereo observations to DEMs of more than 130 stereo pairs for 11 Constellation Program (CxP) sites and 53 other regions of scientific interest. The NAC DEM spatial sampling is typically 2 meters, and the vertical precision is 1-2 meters. Such high resolution provides the three-dimensional view of the lunar surface required for site selection, hazard avoidance and planning traverses that minimize resource consumption. In addition to exploration analysis, geologists can measure parameters such as elevation, slope, and volume to place constraints on composition and geologic history. The NAC DEMs are released and archived through NASA's Planetary Data System.

  2. Construction of a 3-arcsecond digital elevation model for the Gulf of Maine

    USGS Publications Warehouse

    Twomey, Erin R.; Signell, Richard P.

    2013-01-01

    A system-wide description of the seafloor topography is a basic requirement for most coastal oceanographic studies. The necessary detail of the topography obviously varies with application, but for many uses, a nominal resolution of roughly 100 m is sufficient. Creating a digital bathymetric grid with this level of resolution can be a complex procedure due to a multiplicity of data sources, data coverages, datums and interpolation procedures. This report documents the procedures used to construct a 3-arcsecond (approximately 90-meter grid cell size) digital elevation model for the Gulf of Maine (71°30' to 63° W, 39°30' to 46° N). We obtained elevation and bathymetric data from a variety of American and Canadian sources, converted all data to the North American Datum of 1983 for horizontal coordinates and the North American Vertical Datum of 1988 for vertical coordinates, used a combination of automatic and manual techniques for quality control, and interpolated gaps using a surface-fitting routine.

  3. TecDEM: A MATLAB Based Toolbox for understanding Tectonics from Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Shahzad, F.; Mahmood, S. A.; Gloaguen, R.

    2009-04-01

    TecDEM is a MATLAB based tool box for understanding the tectonics from digital elevation models (DEMs) of any area. These DEMs can be derived from data of any spatial resolution (Low, medium and High). In the first step we extract drainage network from the DEMs using flow grid approach. Drainage network is a group of streams having elevation and catchment area information as a function of spatial locations. We implement an array of stream structure to study this drainage network. Knickpoints can be identified on each stream of the drainage network by a graphical user interface and are helpful for understanding stream morphology. Stream profile analysis in steady state condition is applied on all streams to calculate geomorphic parameters and regional uplift rates. Hack index is calculated for all the profiles at a certain interval and over the change of knickpoints. Reports menu of this tool box generates detailed statistics report, complete tabulated report, graphical output of each analyzed stream profile and Hack index profile. All the calculated values are part of stream structure and is saved as .mat file for later use with this tool box. The spatial distribution of geomorphic parameters, uplift rates and knickpoints are exported as a shape files for visualization in professional GIS software. We test this tool box on DEMs from different tectonic settings worldwide and received verifiable results with other studies.

  4. Using noble gas tracers to constrain a groundwater flow model with recharge elevations: A novel approach for mountainous terrain

    NASA Astrophysics Data System (ADS)

    Doyle, Jessica M.; Gleeson, Tom; Manning, Andrew H.; Mayer, K. Ulrich

    2015-10-01

    Environmental tracers provide information on groundwater age, recharge conditions, and flow processes which can be helpful for evaluating groundwater sustainability and vulnerability. Dissolved noble gas data have proven particularly useful in mountainous terrain because they can be used to determine recharge elevation. However, tracer-derived recharge elevations have not been utilized as calibration targets for numerical groundwater flow models. Herein, we constrain and calibrate a regional groundwater flow model with noble-gas-derived recharge elevations for the first time. Tritium and noble gas tracer results improved the site conceptual model by identifying a previously uncertain contribution of mountain block recharge from the Coast Mountains to an alluvial coastal aquifer in humid southwestern British Columbia. The revised conceptual model was integrated into a three-dimensional numerical groundwater flow model and calibrated to hydraulic head data in addition to recharge elevations estimated from noble gas recharge temperatures. Recharge elevations proved to be imperative for constraining hydraulic conductivity, recharge location, and bedrock geometry, and thus minimizing model nonuniqueness. Results indicate that 45% of recharge to the aquifer is mountain block recharge. A similar match between measured and modeled heads was achieved in a second numerical model that excludes the mountain block (no mountain block recharge), demonstrating that hydraulic head data alone are incapable of quantifying mountain block recharge. This result has significant implications for understanding and managing source water protection in recharge areas, potential effects of climate change, the overall water budget, and ultimately ensuring groundwater sustainability.

  5. Using noble gas tracers to constrain a groundwater flow model with recharge elevations: A novel approach for mountainous terrain

    USGS Publications Warehouse

    Doyle, Jessica M.; Gleeson, Tom; Manning, Andrew H.; Mayer, K. Ulrich

    2015-01-01

    Environmental tracers provide information on groundwater age, recharge conditions, and flow processes which can be helpful for evaluating groundwater sustainability and vulnerability. Dissolved noble gas data have proven particularly useful in mountainous terrain because they can be used to determine recharge elevation. However, tracer-derived recharge elevations have not been utilized as calibration targets for numerical groundwater flow models. Herein, we constrain and calibrate a regional groundwater flow model with noble-gas-derived recharge elevations for the first time. Tritium and noble gas tracer results improved the site conceptual model by identifying a previously uncertain contribution of mountain block recharge from the Coast Mountains to an alluvial coastal aquifer in humid southwestern British Columbia. The revised conceptual model was integrated into a three-dimensional numerical groundwater flow model and calibrated to hydraulic head data in addition to recharge elevations estimated from noble gas recharge temperatures. Recharge elevations proved to be imperative for constraining hydraulic conductivity, recharge location, and bedrock geometry, and thus minimizing model nonuniqueness. Results indicate that 45% of recharge to the aquifer is mountain block recharge. A similar match between measured and modeled heads was achieved in a second numerical model that excludes the mountain block (no mountain block recharge), demonstrating that hydraulic head data alone are incapable of quantifying mountain block recharge. This result has significant implications for understanding and managing source water protection in recharge areas, potential effects of climate change, the overall water budget, and ultimately ensuring groundwater sustainability.

  6. ArcticDEM; A Publically Available, High Resolution Elevation Model of the Arctic

    NASA Astrophysics Data System (ADS)

    Morin, Paul; Porter, Claire; Cloutier, Michael; Howat, Ian; Noh, Myoung-Jong; Willis, Michael; Bates, Brian; Willamson, Cathleen; Peterman, Kennith

    2016-04-01

    A Digital Elevation Model (DEM) of the Arctic is needed for a large number of reasons, including: measuring and understanding rapid, ongoing changes to the Arctic landscape resulting from climate change and human use and mitigation and adaptation planning for Arctic communities. The topography of the Arctic is more poorly mapped than most other regions of Earth due to logistical costs and the limits of satellite missions with low-latitude inclinations. A convergence of civilian, high-quality sub-meter stereo imagery; petascale computing and open source photogrammetry software has made it possible to produce a complete, very high resolution (2 to 8-meter posting), elevation model of the Arctic. A partnership between the US National Geospatial-intelligence Agency and a team led by the US National Science Foundation funded Polar Geospatial Center is using stereo imagery from DigitalGlobe's Worldview-1, 2 and 3 satellites and the Ohio State University's Surface Extraction with TIN-based Search-space Minimization (SETSM) software running on the University of Illinois's Blue Water supercomputer to address this challenge. The final product will be a seemless, 2-m posting digital surface model mosaic of the entire Arctic above 60 North including all of Alaska, Greenland and Kamchatka. We will also make available the more than 300,000 individual time-stamped DSM strip pairs that were used to assemble the mosaic. The Arctic DEM will have a vertical precision of better than 0.5m and can be used to examine changes in land surfaces such as those caused by permafrost degradation or the evolution of arctic rivers and floodplains. The data set can also be used to highlight changing geomorphology due to Earth surface mass transport processes occurring in active volcanic and glacial environments. When complete the ArcticDEM will catapult the Arctic from the worst to among the best mapped regions on Earth.

  7. Prediction of Wind Speeds Based on Digital Elevation Models Using Boosted Regression Trees

    NASA Astrophysics Data System (ADS)

    Fischer, P.; Etienne, C.; Tian, J.; Krauß, T.

    2015-12-01

    In this paper a new approach is presented to predict maximum wind speeds using Gradient Boosted Regression Trees (GBRT). GBRT are a non-parametric regression technique used in various applications, suitable to make predictions without having an in-depth a-priori knowledge about the functional dependancies between the predictors and the response variables. Our aim is to predict maximum wind speeds based on predictors, which are derived from a digital elevation model (DEM). The predictors describe the orography of the Area-of-Interest (AoI) by various means like first and second order derivatives of the DEM, but also higher sophisticated classifications describing exposure and shelterness of the terrain to wind flux. In order to take the different scales into account which probably influence the streams and turbulences of wind flow over complex terrain, the predictors are computed on different spatial resolutions ranging from 30 m up to 2000 m. The geographic area used for examination of the approach is Switzerland, a mountainious region in the heart of europe, dominated by the alps, but also covering large valleys. The full workflow is described in this paper, which consists of data preparation using image processing techniques, model training using a state-of-the-art machine learning algorithm, in-depth analysis of the trained model, validation of the model and application of the model to generate a wind speed map.

  8. Robust Mosaicking of Stereo Digital Elevation Models from the Ames Stereo Pipeline

    NASA Technical Reports Server (NTRS)

    Kim, Tae Min; Moratto, Zachary M.; Nefian, Ara Victor

    2010-01-01

    Robust estimation method is proposed to combine multiple observations and create consistent, accurate, dense Digital Elevation Models (DEMs) from lunar orbital imagery. The NASA Ames Intelligent Robotics Group (IRG) aims to produce higher-quality terrain reconstructions of the Moon from Apollo Metric Camera (AMC) data than is currently possible. In particular, IRG makes use of a stereo vision process, the Ames Stereo Pipeline (ASP), to automatically generate DEMs from consecutive AMC image pairs. However, the DEMs currently produced by the ASP often contain errors and inconsistencies due to image noise, shadows, etc. The proposed method addresses this problem by making use of multiple observations and by considering their goodness of fit to improve both the accuracy and robustness of the estimate. The stepwise regression method is applied to estimate the relaxed weight of each observation.

  9. Vegetation Cover Mapping Based on Remote Sensing and Digital Elevation Model Data

    NASA Astrophysics Data System (ADS)

    Korets, M. A.; Ryzhkova, V. A.; Danilova, I. V.; Prokushkin, A. S.

    2016-06-01

    An algorithm of forest cover mapping based on combined GIS-based analysis of multi-band satellite imagery, digital elevation model, and ground truth data was developed. Using the classification principles and an approach of Russian forest scientist Kolesnikov, maps of forest types and forest growing conditions (FGC) were build. The first map is based on RS-composite classification, while the second map is constructed on the basis of DEM-composite classification. The spatial combination of this two layers were also used for extrapolation and mapping of ecosystem carbon stock values (kgC/m2). The proposed approach was applied for the test site area (~3600 km2), located in the Northern Siberia boreal forests of Evenkia near Tura settlement.

  10. Synthetic Aperture Radar Interferometry for Digital Elevation Model of Kuwait Desert - Analysis of Errors

    NASA Astrophysics Data System (ADS)

    Jassar, H. K. Al; Rao, K. S.

    2012-07-01

    Using different combinations of 29 Advanced Synthetic Aperture Radar (ASAR) images, 43 Digital Elevations Models (DEM) were generated adopting SAR Interferometry (InSAR) technique. Due to sand movement in desert terrain, there is a poor phase correlation between different SAR images. Therefore, suitable methodology for generating DEMs of Kuwait desert terrain using InSAR technique were worked out. Time series analysis was adopted to derive the best DEM out of 43 DEMs. The problems related to phase de-correlation over desert terrain are discussed. Various errors associated with the DEM generation are discussed which include atmospheric effects, penetration into soil medium, sand movement. The DEM of Shuttle Radar Topography Mission (SRTM) is used as a reference. The noise levels of DEM of SRTM are presented.

  11. A method for extracting drainage networks with heuristic information from digital elevation models.

    PubMed

    Hou, Kun; Yang, Wei; Sun, Jigui; Sun, Tieli

    2011-01-01

    Depression filling and direction assignment over flat areas are critical issues in hydrologic analysis. This paper proposes a method to handle depressions and flat areas in one procedure. Being different from the traditional raster neighbourhoods processing with little heuristic information, the method is designed to compensate for the inadequate searching information of other methods. The proposed method routes flow through depressions and flat areas by searching for the outlet using the heuristic information. Heuristic information can reveal the general trend slope of the DEM (digital elevation models) and help the proposed method find the outlet accurately. The method is implemented in Pascal and experiments are carried out on actual DEM data. It can be seen from the comparison with the four existing methods that the proposed method can get a closer match result with the ground truth network. Moreover, the proposed method can avoid the generation of the unrealistic parallel drainage lines, unreal drainage lines and spurious terrain features.

  12. Modeling the response of plants and ecosystems to elevated CO{sub 2} and climate change

    SciTech Connect

    Reynolds, J.F.; Hilbert, D.W.; Chen, Jia-lin; Harley, P.C.; Kemp, P.R.; Leadley, P.W.

    1992-03-01

    While the exact effects of elevated CO{sub 2} on global climate are unknown, there is a growing consensus among climate modelers that global temperature and precipitation will increase, but that these changes will be non-uniform over the Earth`s surface. In addition to these potential climatic changes, CO{sub 2} also directly affects plants via photosynthesis, respiration, and stomatal closure. Global climate change, in concert with these direct effects of CO{sub 2} on plants, could have a significant impact on both natural and agricultural ecosystems. Society`s ability to prepare for, and respond to, such changes depends largely on the ability of climate and ecosystem researchers to provide predictions of regional level ecosystem responses with sufficient confidence and adequate lead time.

  13. Modeling the response of plants and ecosystems to elevated CO sub 2 and climate change

    SciTech Connect

    Reynolds, J.F.; Hilbert, D.W.; Chen, Jia-lin; Harley, P.C.; Kemp, P.R.; Leadley, P.W.

    1992-03-01

    While the exact effects of elevated CO{sub 2} on global climate are unknown, there is a growing consensus among climate modelers that global temperature and precipitation will increase, but that these changes will be non-uniform over the Earth's surface. In addition to these potential climatic changes, CO{sub 2} also directly affects plants via photosynthesis, respiration, and stomatal closure. Global climate change, in concert with these direct effects of CO{sub 2} on plants, could have a significant impact on both natural and agricultural ecosystems. Society's ability to prepare for, and respond to, such changes depends largely on the ability of climate and ecosystem researchers to provide predictions of regional level ecosystem responses with sufficient confidence and adequate lead time.

  14. Bathymetry and digital elevation models of Coyote Creek and Alviso Slough, South San Francisco Bay, California

    USGS Publications Warehouse

    Foxgrover, Amy C.; Finlayson, David P.; Jaffe, Bruce E.; Fregoso, Theresa A.

    2011-01-01

    The bathymetry surveys were conducted using the state-of-the-art research vessel R/V Parke Snavely outfitted with an interferometric sidescan sonar for swath mapping in extremely shallow water. We provide high-resolution bathymetric data collected by the USGS. For the 2010 baseline survey we have merged the bathymetry with aerial lidar data that were collected for the USGS during the same time period to create a seamless, high-resolution digital elevation model (DEM) of the study area. The series of bathymetry datasets are provided at 1 m resolution and the 2010 bathymetric/topographic DEM at 2 m resolution. The data are formatted as both X, Y, Z text files and ESRI Arc ASCII files that are accompanied by FGDC compliant metadata.

  15. Digital Elevation Model, 0.25 m, Barrow Environmental Observatory, Alaska, 2013

    DOE Data Explorer

    Cathy Wilson; Garrett Altmann

    2015-11-20

    This 0.25m horizontal resolution digital elevation model, DEM, was developed from Airborne Laser Altimetry flown by Aerometric Inc, now known as Quantum Spatial, Inc. on 12 July, 2013. One Mission was flown and the data jointly processed with LANL personnel to produce a 0.25m DEM covering a region approximately 2.8km wide and 12.4km long extending from the coast above North Salt Lagoon to south of Gas Well Road. This DEM encompasses a diverse range of hydrologic, geomorphic, geophysical and biological features typical of the Barrow Peninsula. Vertical accuracy at the 95% confidence interval was computed as 0.143m. The coordinate system, datum, and geoid for this DEM are UTM Zone 4N, NAD83 (2011), NAVD88 (GEOID09).

  16. Contour-based automatic crater recognition using digital elevation models from Chang'E missions

    NASA Astrophysics Data System (ADS)

    Zuo, Wei; Zhang, Zhoubin; Li, Chunlai; Wang, Rongwu; Yu, Linjie; Geng, Liang

    2016-12-01

    In order to provide fundamental information for exploration and related scientific research on the Moon and other planets, we propose a new automatic method to recognize craters on the lunar surface based on contour data extracted from a digital elevation model (DEM). Through DEM and image processing, this method can be used to reconstruct contour surfaces, extract and combine contour lines, set the characteristic parameters of crater morphology, and establish a crater pattern recognition program. The method has been tested and verified with DEM data from Chang'E-1 (CE-1) and Chang'E-2 (CE-2), showing a strong crater recognition ability with high detection rate, high robustness, and good adaptation to recognize various craters with different diameter and morphology. The method has been used to identify craters with high precision and accuracy on the Moon. The results meet requirements for supporting exploration and related scientific research for the Moon and planets.

  17. A digital elevation model of the Greenland ice sheet and validation with airborne laser altimeter data

    NASA Technical Reports Server (NTRS)

    Bamber, Jonathan L.; Ekholm, Simon; Krabill, William B.

    1997-01-01

    A 2.5 km resolution digital elevation model (DEM) of the Greenland ice sheet was produced from the 336 days of the geodetic phase of ERS-1. During this period the altimeter was operating in ice-mode over land surfaces providing improved tracking around the margins of the ice sheet. Combined with the high density of tracks during the geodetic phase, a unique data set was available for deriving a DEM of the whole ice sheet. The errors present in the altimeter data were investigated via a comparison with airborne laser altimeter data obtained for the southern half of Greenland. Comparison with coincident satellite data showed a correlation with surface slope. An explanation for the behavior of the bias as a function of surface slope is given in terms of the pattern of surface roughness on the ice sheet.

  18. Elevated Ozone Levels in Denmark: Analysis Employing Trajectory and Chemical Transport Modelling

    NASA Astrophysics Data System (ADS)

    Mahura, A.; Gross, A.; Petrova, I.

    2009-09-01

    In our study, among 9 Danish measurement sites, 3 sites having long-term ozone measurement (with a time resolution of 1 hour and starting in early 1990s) records were selected - Ulborg (DK31; 56.28°N, 8.43°E) and Frederiksborg (DK32; 55.97°N, 12.33°E) and Lille Valby (DK41; 55.69°N, 12.13°E) located on Jutland Peninsula and Zealand Island of Denmark, respectively. After pre-screening of the time series (covering almost 15 year period and including almost 543 thousand valid observations), the measurements with high ozone level (using threshold as 150 µg/m3) were selected accounting in total for 508 cases for these 3 locations. Among these, 42 (for DK41) and 59 (for DK31 and DK32) cases showed very high ozone concentrations (i.e. above 180 µg/m3). For all these cases, at first, the trajectory modelling approach was applied in order to estimate atmospheric transport pathway of air mass arrival at the measurement sites and potential source regions from where the elevated ozone level can be associated. In our study the Hybrid Single Particle Lagrangian Integrated Trajectory Model (HYSPLIT) model using REANALYSIS meteorological dataset (global, 1948-present) was run to calculate a set of backward trajectories (in total 508, with duration of 5 day backward in time and arriving at altitude of 100 m) and divide into groups with respect to potential source regions and dominating atmospheric transport pathways using cluster analysis technique. Several relatively long-term episodes with continuous elevated ozone were identified in the analyzed time series; in particular, for DK31 - 7 episodes (having longest duration and observed in Jun 1996 and Jun 2000), DK32 - 5 (Jul 1992 and Jun 2000), and DK41 - 4 (Jul 1992 and Jun 2000). For selected episodes the off-line Eulerian Chemistry-Aerosol-Cloud (CAC) model was run over the European domain. As meteorological driver, the High Resolution Limited Area Model (HIRLAM) generated output with 3D meteorological fields was used

  19. Textured digital elevation model formation from low-cost UAV LADAR/digital image data

    NASA Astrophysics Data System (ADS)

    Bybee, Taylor C.; Budge, Scott E.

    2015-05-01

    Textured digital elevation models (TDEMs) have valuable use in precision agriculture, situational awareness, and disaster response. However, scientific-quality models are expensive to obtain using conventional aircraft-based methods. The cost of creating an accurate textured terrain model can be reduced by using a low-cost (<$20k) UAV system fitted with ladar and electro-optical (EO) sensors. A texel camera fuses calibrated ladar and EO data upon simultaneous capture, creating a texel image. This eliminates the problem of fusing the data in a post-processing step and enables both 2D- and 3D-image registration techniques to be used. This paper describes formation of TDEMs using simulated data from a small UAV gathering swaths of texel images of the terrain below. Being a low-cost UAV, only a coarse knowledge of position and attitude is known, and thus both 2D- and 3D-image registration techniques must be used to register adjacent swaths of texel imagery to create a TDEM. The process of creating an aggregate texel image (a TDEM) from many smaller texel image swaths is described. The algorithm is seeded with the rough estimate of position and attitude of each capture. Details such as the required amount of texel image overlap, registration models, simulated flight patterns (level and turbulent), and texture image formation are presented. In addition, examples of such TDEMs are shown and analyzed for accuracy.

  20. A marked point process of rectangles and segments for automatic analysis of digital elevation models.

    PubMed

    Ortner, Mathias; Descombe, Xavier; Zerubia, Josiane

    2008-01-01

    This work presents a framework for automatic feature extraction from images using stochastic geometry. Features in images are modeled as realizations of a spatial point process of geometrical shapes. This framework allows the incorporation of a priori knowledge on the spatial repartition of features. More specifically, we present a model based on the superposition of a process of segments and a process of rectangles. The former is dedicated to the detection of linear networks of discontinuities, while the latter aims at segmenting homogeneous areas. An energy is defined, favoring connections of segments, alignments of rectangles, as well as a relevant interaction between both types of objects. The estimation is performed by minimizing the energy using a simulated annealing algorithm. The proposed model is applied to the analysis of Digital Elevation Models (DEMs). These images are raster data representing the altimetry of a dense urban area. We present results on real data provided by the IGN (French National Geographic Institute) consisting in low quality DEMs of various types.

  1. Scoria cones on Mars: Detailed investigation of morphometry based on high-resolution digital elevation models

    NASA Astrophysics Data System (ADS)

    Brož, Petr; Čadek, Ondřej; Hauber, Ernst; Rossi, Angelo Pio

    2015-09-01

    We analyze the shapes of 28 hypothesized scoria cones in three regions on Mars, i.e., Ulysses and Hydraotes Colles and Coprates Chasma. Using available High-Resolution Imaging Science Experiment and Context Camera (CTX) digital elevation models, we determine the basic morphometric characteristics of the cones and estimate from ballistic modeling the physical parameters of volcanic eruptions that could have formed them. When compared to terrestrial scoria cones, most of the studied cones show larger volumes (up to 4.2 × 109 m3), larger heights (up to 573 m), and smaller average slopes. The average slopes of the Ulysses, Hydraotes, and Coprates cones range between 7° and 25°, and the maximum slopes only rarely exceed 30°, which suggests only a minor role of scoria redistribution by avalanching. Ballistic analysis indicates that all cones were formed in a similar way, and their shapes are consistent with an ejection velocity about 2 times larger and a particle size about 20 times smaller than on Earth. Our results support the hypothesis that the investigated edifices were formed by low-energy Strombolian volcanic eruptions and hence are equivalent to terrestrial scoria cones. The cones in Hydraotes Colles and Coprates Chasma are on average smaller and steeper than the cones in Ulysses Colles, which is likely due to the difference in topographic elevation and the associated difference in atmospheric pressure. This study provides the expected morphometric characteristics of Martian scoria cones, which can be used to identify landforms consistent with this type of activity elsewhere on Mars and distinguish them from other conical edifices.

  2. An efficient assignment of drainage direction over flat surfaces in raster digital elevation models

    NASA Astrophysics Data System (ADS)

    Barnes, Richard; Lehman, Clarence; Mulla, David

    2014-01-01

    In processing raster digital elevation models (DEMs) it is often necessary to assign drainage directions over flats-that is, over regions with no local elevation gradient. This paper presents an approach to drainage direction assignment which is not restricted by a flat's shape, number of outlets, or surrounding topography. Flow is modeled by superimposing a gradient away from higher terrain with a gradient towards lower terrain resulting in a drainage field exhibiting flow convergence, an improvement over methods which produce regions of parallel flow. This approach builds on previous work by Garbrecht and Martz (1997), but presents several important improvements. The improved algorithm guarantees that flats are only resolved if they have outlets. The algorithm does not require iterative application; a single pass is sufficient to resolve all flats. The algorithm presents a clear strategy for identifying flats and their boundaries. The algorithm is not susceptible to loss of floating-point precision. Furthermore, the algorithm is efficient, operating in O(N) time whereas the older algorithm operates in O(N) time. In testing, the improved algorithm ran 6.5 times faster than the old for a 100×100 cell flat and 69 times faster for a 700×700 cell flat. In tests on actual DEMs, the improved algorithm finished its processing 38-110 times sooner while running on a single processor than a parallel implementation of the old algorithm did while running on 16 processors. The improved algorithm is an optimal, accurate, easy-to-implement drop-in replacement for the original. Pseudocode is provided in the paper and working source code is provided in the Supplemental Materials.

  3. A comparison of U.S. geological survey seamless elevation models with shuttle radar topography mission data

    USGS Publications Warehouse

    Gesch, D.; Williams, J.; Miller, W.

    2001-01-01

    Elevation models produced from Shuttle Radar Topography Mission (SRTM) data will be the most comprehensive, consistently processed, highest resolution topographic dataset ever produced for the Earth's land surface. Many applications that currently use elevation data will benefit from the increased availability of data with higher accuracy, quality, and resolution, especially in poorly mapped areas of the globe. SRTM data will be produced as seamless data, thereby avoiding many of the problems inherent in existing multi-source topographic databases. Serving as precursors to SRTM datasets, the U.S. Geological Survey (USGS) has produced and is distributing seamless elevation datasets that facilitate scientific use of elevation data over large areas. GTOPO30 is a global elevation model with a 30 arc-second resolution (approximately 1-kilometer). The National Elevation Dataset (NED) covers the United States at a resolution of 1 arc-second (approximately 30-meters). Due to their seamless format and broad area coverage, both GTOPO30 and NED represent an advance in the usability of elevation data, but each still includes artifacts from the highly variable source data used to produce them. The consistent source data and processing approach for SRTM data will result in elevation products that will be a significant addition to the current availability of seamless datasets, specifically for many areas outside the U.S. One application that demonstrates some advantages that may be realized with SRTM data is delineation of land surface drainage features (watersheds and stream channels). Seamless distribution of elevation data in which a user interactively specifies the area of interest and order parameters via a map server is already being successfully demonstrated with existing USGS datasets. Such an approach for distributing SRTM data is ideal for a dataset that undoubtedly will be of very high interest to the spatial data user community.

  4. Building a 2.5D Digital Elevation Model from 2D Imagery

    NASA Technical Reports Server (NTRS)

    Padgett, Curtis W.; Ansar, Adnan I.; Brennan, Shane; Cheng, Yang; Clouse, Daniel S.; Almeida, Eduardo

    2013-01-01

    When projecting imagery into a georeferenced coordinate frame, one needs to have some model of the geographical region that is being projected to. This model can sometimes be a simple geometrical curve, such as an ellipse or even a plane. However, to obtain accurate projections, one needs to have a more sophisticated model that encodes the undulations in the terrain including things like mountains, valleys, and even manmade structures. The product that is often used for this purpose is a Digital Elevation Model (DEM). The technology presented here generates a high-quality DEM from a collection of 2D images taken from multiple viewpoints, plus pose data for each of the images and a camera model for the sensor. The technology assumes that the images are all of the same region of the environment. The pose data for each image is used as an initial estimate of the geometric relationship between the images, but the pose data is often noisy and not of sufficient quality to build a high-quality DEM. Therefore, the source imagery is passed through a feature-tracking algorithm and multi-plane-homography algorithm, which refine the geometric transforms between images. The images and their refined poses are then passed to a stereo algorithm, which generates dense 3D data for each image in the sequence. The 3D data from each image is then placed into a consistent coordinate frame and passed to a routine that divides the coordinate frame into a number of cells. The 3D points that fall into each cell are collected, and basic statistics are applied to determine the elevation of that cell. The result of this step is a DEM that is in an arbitrary coordinate frame. This DEM is then filtered and smoothed in order to remove small artifacts. The final step in the algorithm is to take the initial DEM and rotate and translate it to be in the world coordinate frame [such as UTM (Universal Transverse Mercator), MGRS (Military Grid Reference System), or geodetic] such that it can be saved in

  5. Rejuvenating Poldered Landscapes: A Numerical Model of Elevation Equilibrium in Coastal Bangladesh

    NASA Astrophysics Data System (ADS)

    Tasich, C. M.; Gilligan, J. M.; Goodbred, S. L., Jr.; Wilson, C.; Hale, R. P.; Wallace Auerbach, L.

    2015-12-01

    The low-lying, coastal region of Bangladesh has relied on poldering (surrounding islands and flood-prone areas with embankments) since the 1960s to mitigate flooding and tidal inundation. The result has been an increase in total arable land and the ability to sustain food production for one of the most densely populated countries in the world. However, poldering has had the unintended consequences of starving embanked landscapes of sediment. To mitigate the effects of subsiding interiors, some poldered communities have used tidal river management (TRM) to allow water and sediment exchange between the polders and the tidal network. Anecdotal reports claim great success in some locations, but not in others. To date, there has been very little quantitative analysis. Here, we use a simple numerical model of tidal inundation and subsequent sediment accretion to examine the potential impacts of TRM at a poldered island, Polder 32 (P32), and the adjacent mangrove forest in southwest Bangladesh. Our model employs mass balance with variable incoming suspended sediment concentration (SSC). We use tidal gauge and SSC data as inputs and test the model against measured accretion values at P32. Sensitivity analysis of model parameters narrows the range of realistic parameter inputs. Preliminary results suggest that it would take ~10-20 years for P32 to re-equilibrate to the natural surrounding land elevations with a restored direct tidal channel connection. Since a direct tidal channel connection is unfeasible and would displace the local population, future work will attempt to constrain time frames for inundation to more closely model TRM efforts. We also plan to add a bedload component and multidimensionality. The present model provides a simple framework for understanding sediment accretion in southwest Bangladesh and helps generate more complex questions about making the delta more sustainable in the face of sea level rise and population growth.

  6. Evaluation of a gully headcut retreat model using multitemporal aerial photographs and digital elevation models

    NASA Astrophysics Data System (ADS)

    Campo-Bescós, M. A.; Flores-Cervantes, J. H.; Bras, R. L.; Casalí, J.; Giráldez, J. V.

    2013-12-01

    large fraction of soil erosion in temperate climate systems proceeds from gully headcut growth processes. Nevertheless, headcut retreat is not well understood. Few erosion models include gully headcut growth processes, and none of the existing headcut retreat models have been tested against long-term retreat rate estimates. In this work the headcut retreat resulting from plunge pool erosion in the Channel Hillslope Integrated Landscape Development (CHILD) model is calibrated and compared to long-term evolution measurements of six gullies at the Bardenas Reales, northeast Spain. The headcut retreat module of CHILD was calibrated by adjusting the shape factor parameter to fit the observed retreat and volumetric soil loss of one gully during a 36 year period, using reported and collected field data to parameterize the rest of the model. To test the calibrated model, estimates by CHILD were compared to observations of headcut retreat from five other neighboring gullies. The differences in volumetric soil loss rates between the simulations and observations were less than 0.05 m3 yr-1, on average, with standard deviations smaller than 0.35 m3 yr-1. These results are the first evaluation of the headcut retreat module implemented in CHILD with a field data set. These results also show the usefulness of the model as a tool for simulating long-term volumetric gully evolution due to plunge pool erosion.

  7. Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978–1987

    PubMed Central

    Korsgaard, Niels J.; Nuth, Christopher; Khan, Shfaqat A.; Kjeldsen, Kristian K.; Bjørk, Anders A.; Schomacker, Anders; Kjær, Kurt H.

    2016-01-01

    Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978–1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM and a 2 m black-and-white digital orthophotograph. Supporting data consist of a reliability mask and a photo footprint coverage with recording dates. Through one internal and two external validation tests, this DEM shows an accuracy better than 10 m horizontally and 6 m vertically while the precision is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps. PMID:27164457

  8. Effects of elevated temperature on the viscoplastic modeling of graphite/polymeric composites

    NASA Technical Reports Server (NTRS)

    Gates, Thomas S.

    1991-01-01

    To support the development of new materials for the design of next generation supersonic transports, a research program is underway at NASA to assess the long term durability of advanced polymer matrix composites (PMC's). One of main objectives of the program was to explore the effects of elevated temperature (23 to 200 C) on the constitutive model's material parameters. To achieve this goal, test data on the observed nonlinear, stress-strain behavior of IM7/5260 and IM7/8320 composites under tension and compression loading were collected and correlated against temperature. These tests, conducted under isothermal conditions using variable strain rates, included such phenomena as stress relaxation and short term creep. The second major goal was the verification of the model by comparison of analytical predictions and test results for off axis and angle ply laminates. Correlation between test and predicted behavior was performed for specimens of both material systems over a range of temperatures. Results indicated that the model provided reasonable predictions of material behavior in load or strain controlled tests. Periods of loading, unloading, stress relaxation, and creep were accounted for.

  9. Modeling Surface Structure Derived from Laser Altimeter Return Waveforms Using High-Resolution Elevation Data

    NASA Technical Reports Server (NTRS)

    Blair, J. Bryan; Hofton, M. A.

    1999-01-01

    The upcoming generation of operational spaceborne laser altimeters (i.e VCL and GLAS) record the interaction of emitted laser radiation with terrestrial surfaces in the form of a digitized waveform. We show that we can accurately model return laser altimeter waveforms as the sum of the reflections from individual surfaces within laser footprints. In one case, we predict return waveforms using high resolution elevation data generated by a small-footprint laser altimeter in a dense tropical forest. We compare over 3000 modeled and recorded waveform pairs using the Pearson correlation. The modeled and recorded waveforms are highly correlated, with a mean correlation of 0.90 and a median of 0.95. The mean correlation is highly dependent on the relative positions of the data sets. By shifting the relative locations of the two compared data sets, we infer that the data are colocated to within 0.4$\\sim$m horizontally and 0.12$\\sim$m vertically. The high degree of correlation shows that we can reliably synthesize the vertical structure information measured by medium-large footprint laser altimeters for complex, dense vegetation.

  10. Elevation of oxidized DJ-1 in the brain and erythrocytes of Parkinson disease model animals.

    PubMed

    Akazawa, Yoko Ogawa; Saito, Yoshiro; Hamakubo, Takao; Masuo, Yoshinori; Yoshida, Yasukazu; Nishio, Keiko; Shichiri, Mototada; Miyasaka, Tomohiro; Iwanari, Hiroko; Mochizuki, Yasuhiro; Kodama, Tatsuhiko; Noguchi, Noriko; Niki, Etsuo

    2010-10-15

    DJ-1, the causative gene of a familial form of Parkinson's disease (PD), has been reported undergo oxidation preferentially at the 106th cysteine residue (Cys-106) under oxidative stress. Recently, it has been found that the levels of oxidized DJ-1 in erythrocytes of unmedicated PD patients are markedly higher than those in medicated PD patients and healthy subjects. In the present study, we examined the changes in oxidized DJ-1 levels in the brain and erythrocytes of PD animal models using specific antibodies against Cys-106-oxidized DJ-1. Treatment with PD model compounds such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and 6-hydroxydopamine significantly elevated the levels of oxidized DJ-1 in erythrocytes. Immunohistochemical analysis also revealed that the number of oxidized DJ-1 antibody-positive cells in the substantia nigra of MPTP-treated mouse increased in a dose-dependent manner. These results suggest that the oxidative modification of DJ-1 in the brain and erythrocytes is involved in the pathogenesis of PD in animal models.

  11. Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978-1987.

    PubMed

    Korsgaard, Niels J; Nuth, Christopher; Khan, Shfaqat A; Kjeldsen, Kristian K; Bjørk, Anders A; Schomacker, Anders; Kjær, Kurt H

    2016-05-10

    Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978-1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM and a 2 m black-and-white digital orthophotograph. Supporting data consist of a reliability mask and a photo footprint coverage with recording dates. Through one internal and two external validation tests, this DEM shows an accuracy better than 10 m horizontally and 6 m vertically while the precision is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps.

  12. Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978-1987

    NASA Astrophysics Data System (ADS)

    Korsgaard, Niels J.; Nuth, Christopher; Khan, Shfaqat A.; Kjeldsen, Kristian K.; Bjørk, Anders A.; Schomacker, Anders; Kjær, Kurt H.

    2016-05-01

    Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978-1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM and a 2 m black-and-white digital orthophotograph. Supporting data consist of a reliability mask and a photo footprint coverage with recording dates. Through one internal and two external validation tests, this DEM shows an accuracy better than 10 m horizontally and 6 m vertically while the precision is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps.

  13. Validation of the ASTER Global Digital Elevation Model version 3 over the conterminous United States

    USGS Publications Warehouse

    Gesch, Dean B.; Oimoen, Michael J.; Danielson, Jeffrey J.; Meyer, David

    2016-01-01

    The ASTER Global Digital Elevation Model Version 3 (GDEM v3) was evaluated over the conterminous United States in a manner similar to the validation conducted for the original GDEM Version 1 (v1) in 2009 and GDEM Version 2 (v2) in 2011. The absolute vertical accuracy of GDEM v3 was calculated by comparison with more than 23,000 independent reference geodetic ground control points from the U.S. National Geodetic Survey. The root mean square error (RMSE) measured for GDEM v3 is 8.52 meters. This compares with the RMSE of 8.68 meters for GDEM v2. Another important descriptor of vertical accuracy is the mean error, or bias, which indicates if a DEM has an overall vertical offset from true ground level. The GDEM v3 mean error of −1.20 meters reflects an overall negative bias in GDEM v3. The absolute vertical accuracy assessment results, both mean error and RMSE, were segmented by land cover type to provide insight into how GDEM v3 performs in various land surface conditions. While the RMSE varies little across cover types (6.92 to 9.25 meters), the mean error (bias) does appear to be affected by land cover type, ranging from −2.99 to +4.16 meters across 14 land cover classes. These results indicate that in areas where built or natural aboveground features are present, GDEM v3 is measuring elevations above the ground level, a condition noted in assessments of previous GDEM versions (v1 and v2) and an expected condition given the type of stereo-optical image data collected by ASTER. GDEM v3 was also evaluated by differencing with the Shuttle Radar Topography Mission (SRTM) dataset. In many forested areas, GDEM v3 has elevations that are higher in the canopy than SRTM. The overall validation effort also included an evaluation of the GDEM v3 water mask. In general, the number of distinct water polygons in GDEM v3 is much lower than the number in a reference land cover dataset, but the total areas compare much more closely.

  14. Validation of the Aster Global Digital Elevation Model Version 3 Over the Conterminous United States

    NASA Astrophysics Data System (ADS)

    Gesch, D.; Oimoen, M.; Danielson, J.; Meyer, D.

    2016-06-01

    The ASTER Global Digital Elevation Model Version 3 (GDEM v3) was evaluated over the conterminous United States in a manner similar to the validation conducted for the original GDEM Version 1 (v1) in 2009 and GDEM Version 2 (v2) in 2011. The absolute vertical accuracy of GDEM v3 was calculated by comparison with more than 23,000 independent reference geodetic ground control points from the U.S. National Geodetic Survey. The root mean square error (RMSE) measured for GDEM v3 is 8.52 meters. This compares with the RMSE of 8.68 meters for GDEM v2. Another important descriptor of vertical accuracy is the mean error, or bias, which indicates if a DEM has an overall vertical offset from true ground level. The GDEM v3 mean error of -1.20 meters reflects an overall negative bias in GDEM v3. The absolute vertical accuracy assessment results, both mean error and RMSE, were segmented by land cover type to provide insight into how GDEM v3 performs in various land surface conditions. While the RMSE varies little across cover types (6.92 to 9.25 meters), the mean error (bias) does appear to be affected by land cover type, ranging from -2.99 to +4.16 meters across 14 land cover classes. These results indicate that in areas where built or natural aboveground features are present, GDEM v3 is measuring elevations above the ground level, a condition noted in assessments of previous GDEM versions (v1 and v2) and an expected condition given the type of stereo-optical image data collected by ASTER. GDEM v3 was also evaluated by differencing with the Shuttle Radar Topography Mission (SRTM) dataset. In many forested areas, GDEM v3 has elevations that are higher in the canopy than SRTM. The overall validation effort also included an evaluation of the GDEM v3 water mask. In general, the number of distinct water polygons in GDEM v3 is much lower than the number in a reference land cover dataset, but the total areas compare much more closely.

  15. Myocardial infarction, ST-elevation and non-ST-elevation myocardial infarction and modelled daily pollution concentrations: a case-crossover analysis of MINAP data

    PubMed Central

    Butland, Barbara K; Atkinson, Richard W; Milojevic, Ai; Heal, Mathew R; Doherty, Ruth M; Armstrong, Ben G; MacKenzie, Ian A; Vieno, Massimo; Lin, Chun; Wilkinson, Paul

    2016-01-01

    Objectives To investigate associations between daily concentrations of air pollution and myocardial infarction (MI), ST-elevation MI (STEMI) and non-ST-elevation MI (NSTEMI). Methods Modelled daily ground-level gaseous, total and speciated particulate pollutant concentrations and ground-level daily mean temperature, all at 5 km×5 km horizontal resolution, were linked to 202 550 STEMI and 322 198 NSTEMI events recorded on the England and Wales Myocardial Ischaemia National Audit Project (MINAP) database. The study period was 2003–2010. A case-crossover design was used, stratified by year, month and day of the week. Data were analysed using conditional logistic regression, with pollutants modelled as unconstrained distributed lags 0–2 days. Results are presented as percentage change in risk per 10 µg/m3 increase in the pollutant relevant metric, having adjusted for daily mean temperature, public holidays, weekly influenza consultation rates and a sine-cosine annual cycle. Results There was no evidence of an association between MI or STEMI and any of O3, NO2, PM2.5, PM10 or selected PM2.5 components (sulfate and elemental carbon). For NSTEMI, there was a positive association with daily maximum 1-hour NO2 (0.27% (95% CI 0.01% to 0.54%)), which persisted following adjustment for O3 and adjustment for PM2.5. The association appeared to be confined to the midland and southern regions of England and Wales. Conclusions The study found no evidence of an association between the modelled pollutants (including components) investigated and STEMI but did find some evidence of a positive association between NO2 and NSTEMI. Confirmation of this association in other studies is required. PMID:27621827

  16. The enormous Chillos Valley Lahar: An ash-flow-generated debris flow from Cotopaxi Volcano, Ecuador

    USGS Publications Warehouse

    Mothes, P.A.; Hall, M.L.; Janda, R.J.

    1998-01-01

    The Chillos Valley Lahar (CVL), the largest Holocene debris flow in area and volume as yet recognized in the northern Andes, formed on Cotopaxi volcano's north and northeast slopes and descended river systems that took it 326 km north-northwest to the Pacific Ocean and 130+ km east into the Amazon basin. In the Chillos Valley, 40 km downstream from the volcano, depths of 80-160 m and valley cross sections up to 337000m2 are observed, implying peak flow discharges of 2.6-6.0 million m3/s. The overall volume of the CVL is estimated to be ???3.8 km3. The CVL was generated approximately 4500 years BP by a rhyolitic ash flow that followed a small sector collapse on the north and northeast sides of Cotopaxi, which melted part of the volcano's icecap and transformed rapidly into the debris flow. The ash flow and resulting CVL have identical components, except for foreign fragments picked up along the flow path. Juvenile materials, including vitric ash, crystals, and pumice, comprise 80-90% of the lahar's deposit, whereas rhyolitic, dacitic, and andesitic lithics make up the remainder. The sand-size fraction and the 2- to 10-mm fraction together dominate the deposit, constituting ???63 and ???15 wt.% of the matrix, respectively, whereas the silt-size fraction averages less than ???10 wt.% and the clay-size fraction less than 0.5 wt.%. Along the 326-km runout, these particle-size fractions vary little, as does the sorting coefficient (average = 2.6). There is no tendency toward grading or improved sorting. Limited bulking is recognized. The CVL was an enormous non-cohesive debris flow, notable for its ash-flow origin and immense volume and peak discharge which gave it characteristics and a behavior akin to large cohesive mudflows. Significantly, then, ash-flow-generated debris flows can also achieve large volumes and cover great areas; thus, they can conceivably affect large populated regions far from their source. Especially dangerous, therefore, are snowclad volcanoes

  17. 2009 ERUPTION OF REDOUBT VOLCANO: Lahars, Oil, and the Role of Science in Hazards Mitigation (Invited)

    NASA Astrophysics Data System (ADS)

    Swenson, R.; Nye, C. J.

    2009-12-01

    In March, 2009, Redoubt Volcano erupted for the third time in 45 years. More than 19 explosions produced ash plumes to 60,000 ft asl, lahar flows of mud and ice down the Drift river ~30 miles to the coast, and tephra fall up to 1.5 mm onto surrounding communities. The eruption had severe impact on many operations. Airlines were forced to cancel or divert hundreds of international and domestic passenger and cargo flights, and Anchorage International airport closed for over 12 hours. Mudflows and floods down the Drift River to the coast impacted operations at the Drift River Oil Terminal (DROT) which was forced to shut down and ultimately be evacuated. Prior mitigation efforts to protect the DROT oil tank farm from potential impacts associated with a major eruptive event were successful, and none of the 148,000 barrels of oil stored at the facility was spilled or released. Nevertheless, the threat of continued eruptive activity at Redoubt, with the possibility of continued lahar flows down the Drift River alluvial fan, required an incident command post be established so that the US Coast Guard, Alaska Dept. of Environmental Conservation, and the Cook Inlet Pipeline Company could coordinate a response to the potential hazards. Ultimately, the incident command team relied heavily on continuous real-time data updates from the Alaska Volcano Observatory, as well as continuous geologic interpretations and risk analysis by the USGS Volcanic Hazards group, the State Division of Geological and Geophysical Surveys and the University of Alaska Geophysical Institute, all members of the collaborative effort of the Alaska Volcano Observatory. The great success story that unfolded attests to the efforts of the incident command team, and their reliance on real-time scientific analysis from scientific experts. The positive results also highlight how pre-disaster mitigation and monitoring efforts, in concert with hazards response planning, can be used in a cooperative industry

  18. Assessment of Fluctuating Reservoir Elevations Using Hydraulic Models and Impacts to Larval Pacific Lamprey Rearing Habitat in the Bonneville Pool

    SciTech Connect

    Mueller, Robert P.; Rakowski, Cynthia L.; Perkins, William A.; Richmond, Marshall C.

    2015-02-24

    This report presents the results of a modeling assessment of likely lamprey larval habitat that may be impacted by dewatering of the major tributary delta regions in the Bonneville Pool of the Columbia River. This assessment was conducted by the Pacific Northwest National Laboratory (PNNL) for the U.S. Army Corps of Engineers Portland District (CENWP). The goal of the study was to provide baseline data about how the regions of interest would potentially be impacted at three river flows (10, 50, and 90 percent exceedance flow) for four different forebay elevations at Bonneville Dam. Impacts of unsteady flows at The Dalles Dam and changing forebay elevation at Bonneville Dam for a 2-week period were also assessed. The area of dewatered regions was calculated by importing modeled data outputs into a GIS and then calculating the change in inundated area near tributary deltas for the four Bonneville forebay surface elevations. From the modeled output we determined that the overall change in area is less sensitive to elevations changes during higher river discharges. Changing the forebay elevation at Bonneville and the resulting impact to total dewatered regions was greater at the lowest modeled river flow (97 kcfs) and showed the greatest variation at the White Salmon/Hood River delta regions followed by the Wind, Klickitat and the Little White Salmon rivers. To understand how inundation might change on a daily and hourly basis. Unsteady flow models were run for a 2-week period in 2002 and compared to 2014. The water surface elevation in the upstream pool closely follows that of the Bonneville Dam forebay with rapid changes of 1 to 2-ft possible. The data shows that 2.5-ft variation in water surface elevation occurred during this period in 2002 and a 3.7-ft change occurred in 2014. The duration of these changes were highly variable and generally did not stay constant for more than a 5-hr period.

  19. Tyrosine triple mutated AAV2-BDNF gene therapy in a rat model of transient IOP elevation

    PubMed Central

    Igarashi, Tsutomu; Kobayashi, Maika; Kameya, Shuhei; Fujimoto, Chiaki; Nakamoto, Kenji; Takahashi, Hisatomo; Igarashi, Toru; Miyake, Noriko; Iijima, Osamu; Hirai, Yukihiko; Shimada, Takashi; Okada, Takashi; Takahashi, Hiroshi

    2016-01-01

    Purpose We examined the neuroprotective effects of exogenous brain-derived neurotrophic factor (BDNF), which provides protection to retinal ganglion cells (RGCs) in rodents, in a model of transient intraocular pressure (IOP) elevation using a mutant (triple Y-F) self-complementary adeno-associated virus type 2 vector encoding BDNF (tm-scAAV2-BDNF). Methods The tm-scAAV2-BDNF or control vector encoding green fluorescent protein (GFP; tm-scAAV2-GFP) was intravitreally administered to rats, which were then divided into four groups: control, ischemia/reperfusion (I/R) injury only, I/R injury with tm-scAAV2-GFP, and tm-scAAV2-BDNF. I/R injury was then induced by transiently increasing IOP, after which the rats were euthanized to measure the inner retinal thickness and cell counts in the RGC layer. Results Intravitreous injection of tm-scAAV2-BDNF resulted in high levels of BDNF expression in the neural retina. Histological analysis showed that the inner retinal thickness and cell numbers in the RGC layer were preserved after transient IOP elevation in eyes treated with tm-scAAV2-BDNF but not in the other I/R groups. Significantly reduced glial fibrillary acidic protein (GFAP) immunostaining after I/R injury in the rats that received tm-scAAV2-BDNF indicated reduced retinal stress, and electroretinogram (ERG) analysis confirmed preservation of retinal function in the tm-scAAV2-BDNF group. Conclusions These results demonstrate the feasibility and effectiveness of neuroprotective gene therapy using tm-scAAV2-BDNF to protect the inner retina from transiently high intraocular pressure. An in vivo gene therapeutic approach to the clinical management of retinal diseases in conditions such as glaucoma, retinal artery occlusion, hypertensive retinopathy, and diabetic retinopathy thus appears feasible. PMID:27440998

  20. Channel profiles around Himalayan river anticlines: Constraints on their formation from digital elevation model analysis

    NASA Astrophysics Data System (ADS)

    Robl, JöRg; Stüwe, Kurt; Hergarten, Stefan

    2008-06-01

    We present a comparison between measured and numerically modeled channel profiles of rivers in two important drainage basins of Central Nepal: the Kali-Gandaki and the Arun drainage basins. Modeled channel profiles are based on a simple stream power approach using best fit exponents defining the nonlinearities in the relative contributions of local channel gradient and water flux to erosion rate. Our analysis of the stream power in the whole river network confirms the work of other authors that a 50- to 80-km-wide zone, roughly corresponding to the High Himalayan topography, is subjected to rapid rock uplift. We suggest a model where the uplift of this zone is driven by erosion and isostatic response, so that centers of maximum uplift are located within the main channels of the north-south draining rivers. We also suggest that the rate of uplift slows down with increasing distance to the main channels. Such a spatial distribution of the uplift leads ultimately to the formation of river anticlines as observed along all major Himalayan rivers. We propose that the formation of river anticlines along south draining Himalayan rivers was accelerated by a sudden increase of the drainage area and discharge when the rivers captured orogen-parallel drainages on the north side of the range. This may follow successive headward cutting into the Tibetan Plateau. The model is confirmed by differences between main channels and east-west running tributaries. Time-dependent numerical models predict that capture events cause strongly elevated erosion rates in the main channel.

  1. Geomorphology and sedimentary features, and temporal component-change of lahar deposits at the northern foot of Chokai volcano, NE Japan

    NASA Astrophysics Data System (ADS)

    Minami, Y.; Ohba, T.; Kataoka, K.; Hayashi, S.

    2014-12-01

    Chokai volcano is an andesitic stratovolcano that collapsed to the north ca.2500 years ago. The post-collapse fan deposits are distributed in the northern foot of the volcano, and to reveal their depositional process in terms of modern sedimentology, we carried out the geological study includung digging survey, as well as geomorphological analysis, mineralogy, and 14C chronology. Consequently, the geological study revealed that the fan deposits consist of more than 16 units, which are debris flow, hyperconcentrated flow and streamflow deposits. We give hare general name lahar deposits for these deposits. The lahar deposits have a total thickness of 30 m, and overlie the 2.5-ka Kisakata debris avalanche deposit. The lahar deposits form a part of volcanic fan and volcaniclastic apron of Chokai volcano. In proximal areas (steep or moderate sloped areas), the lahar flowed down as debris flows, and in the distal area (horizontal area) the lahars transformed into hyperconcentrated flow or stream flows but partly arrived the area as debris flow. The hyperconcentrated flows or stream flows reached the horizontal area at least four times, supposed by AMS dating (the ages of some lahar deposits are 2200, 1500-1600, 1000-1200, and 100-200 yBP). The lahar deposits contain clasts of altered andesite, fresh andesite, mudstone and sandstone. Proportions of altered andesite clasts to total clasts decrease upwards in stratigraphic sequence. Matrices of the lower eight units are composed of grayish-blue clay, and are different from those of the upper eight units, composed of brownish yellow volcanic sand. The stratigraphic variation in matrix component is consistent with the change in matrix mineral assemblage, possibly reflecting changes in the source materials from Chokai volcano.

  2. Processing of Uav Based Range Imaging Data to Generate Detailed Elevation Models of Complex Natural Structures

    NASA Astrophysics Data System (ADS)

    Kohoutek, T. K.; Eisenbeiss, H.

    2012-07-01

    Unmanned Aerial Vehicles (UAVs) are more and more used in civil areas like geomatics. Autonomous navigated platforms have a great flexibility in flying and manoeuvring in complex environments to collect remote sensing data. In contrast to standard technologies such as aerial manned platforms (airplanes and helicopters) UAVs are able to fly closer to the object and in small-scale areas of high-risk situations such as landslides, volcano and earthquake areas and floodplains. Thus, UAVs are sometimes the only practical alternative in areas where access is difficult and where no manned aircraft is available or even no flight permission is given. Furthermore, compared to terrestrial platforms, UAVs are not limited to specific view directions and could overcome occlusions from trees, houses and terrain structures. Equipped with image sensors and/or laser scanners they are able to provide elevation models, rectified images, textured 3D-models and maps. In this paper we will describe a UAV platform, which can carry a range imaging (RIM) camera including power supply and data storage for the detailed mapping and monitoring of complex structures, such as alpine riverbed areas. The UAV platform NEO from Swiss UAV was equipped with the RIM camera CamCube 2.0 by PMD Technologies GmbH to capture the surface structures. Its navigation system includes an autopilot. To validate the UAV-trajectory a 360° prism was installed and tracked by a total station. Within the paper a workflow for the processing of UAV-RIM data is proposed, which is based on the processing of differential GNSS data in combination with the acquired range images. Subsequently, the obtained results for the trajectory are compared and verified with a track of a UAV (Falcon 8, Ascending Technologies) carried out with a total station simultaneously to the GNSS data acquisition. The results showed that the UAV's position using differential GNSS could be determined in the centimetre to the decimetre level. The RIM

  3. A High Elevation Aerosol Manifold Modeling Study and Inter-comparison

    NASA Astrophysics Data System (ADS)

    Hallar, A. G.; Mccubbin, I. B.; Novosselov, I.; Gorder, R.

    2012-12-01

    Via a National Science Foundation grant the Desert Research Institute required professional engineering services to design and model a new fluid dynamics aerosol sampling manifold system to be installed in the renovated Storm Peak Laboratory. The technical objectives include evaluation of the transmission efficiencies for particles with diameters from 3 nanometers to 20 micrometers in the aerosol manifold and to investigate the particulate dispersion and deposition in three different manifold designs currently used throughout the world. Information was collected pertaining to three highly regarded atmospheric aerosol manifolds. The following aerosol manifolds were considered as models: 1. DOE ASR design used throughout the world (e.g. Barrow, Alaska). 2. The aerosol manifold used at the Swiss high elevation site, Jungfraujoch, located at 3.5 km. 3. Current Storm Peak Laboratory aerosol manifold. Based on all available information, DRI assimilated 3-D CAD drawings of these three manifolds. Enertechnix, Inc (http://www.enertechnix.com) was identified by DRI as having the appropriate skills and expertise to perform the Computational Fluid Dynamic (CFD) modeling required for this project. Enertechnix Inc. has completed initial CFD modeling of the three manifold discussed above. The following results will be presented. Transient CFD simulations of the inlets were performed for the wind speed range of 2.5-15 m/s in 3-dimentional numerical wind tunnel at a sampling rate of 1000 lmp. The transmission efficiencies for these inlets were evaluated for particles in 10 nm-20um range. Two different turbulence models (k-epsilon and detached eddy simulations) were used, and the effects of particle - turbulence coupling were examined. The modeling results show that for all three inlets transmission decreases with increase of particle size, due to particle inertial impaction on the inner walls of the inlets. Additionally, the transmission efficiency decreases at higher wind speeds

  4. Modeling Elevation and Aspect Controls on Emerging Ecohydrologic Processes and Ecosystem Patterns Using the Component-based Landlab Framework

    NASA Astrophysics Data System (ADS)

    Nudurupati, S. S.; Istanbulluoglu, E.; Adams, J. M.; Hobley, D. E. J.; Gasparini, N. M.; Tucker, G. E.; Hutton, E. W. H.

    2014-12-01

    Topography plays a commanding role on the organization of ecohydrologic processes and resulting vegetation patterns. In southwestern United States, climate conditions lead to terrain aspect- and elevation-controlled ecosystems, with mesic north-facing and xeric south-facing vegetation types; and changes in biodiversity as a function of elevation from shrublands in low desert elevations, to mixed grass/shrublands in mid elevations, and forests at high elevations and ridge tops. These observed patterns have been attributed to differences in topography-mediated local soil moisture availability, micro-climatology, and life history processes of plants that control chances of plant establishment and survival. While ecohydrologic models represent local vegetation dynamics in sufficient detail up to sub-hourly time scales, plant life history and competition for space and resources has not been adequately represented in models. In this study we develop an ecohydrologic cellular automata model within the Landlab component-based modeling framework. This model couples local vegetation dynamics (biomass production, death) and plant establishment and competition processes for resources and space. This model is used to study the vegetation organization in a semiarid New Mexico catchment where elevation and hillslope aspect play a defining role on plant types. Processes that lead to observed plant types across the landscape are examined by initializing the domain with randomly assigned plant types and systematically changing model parameters that couple plant response with soil moisture dynamics. Climate perturbation experiments are conducted to examine the plant response in space and time. Understanding the inherently transient ecohydrologic systems is critical to improve predictions of climate change impacts on ecosystems.

  5. Estimating surface flow paths on a digital elevation model using a triangular facet network

    NASA Astrophysics Data System (ADS)

    Zhou, Qiming; Pilesjö, Petter; Chen, Yumin

    2011-07-01

    This study attempts to develop a method for the simulation of surface flow paths on a digital elevation model (DEM). The objective is to use a facet-based algorithm to estimate the surface flow paths on a raster DEM. A grid DEM was used to create a triangular facet network (TFN) over which the surface flow paths were determined. Since each facet in the network has a constant slope and aspect, the estimations of, for example, flow direction and divergence/convergence are less complicated compared to traditional raster-based solutions. Experiments were undertaken by estimating the specific catchment area (SCA) over a number of mathematical surfaces, as well as on a real-world DEM. Comparisons were made between the derived SCA by the TFN algorithm with some algorithms reported in the literature. The results show that the TFN algorithm produced the closest outcomes to the theoretical values of the SCA compared with other algorithms, deriving more consistent outcomes and being less influenced by surface shapes. The real-world DEM test also shows that the TFN was capable of modeling flow distribution without noticeable "artifacts," and its ability of tracking flow paths makes it an appropriate platform for dynamic surface flow simulation.

  6. Indian monsoon and the elevated-heat-pump mechanism in a coupled aerosol-climate model

    NASA Astrophysics Data System (ADS)

    D'Errico, Miriam; Cagnazzo, Chiara; Fogli, Pier Giuseppe; Lau, William K. M.; Hardenberg, Jost; Fierli, Federico; Cherchi, Annalisa

    2015-09-01

    A coupled aerosol-atmosphere-ocean-sea ice climate model is used to explore the interaction between aerosols and the Indian summer monsoon precipitation on seasonal-to-interannual time scales. Results show that when increased aerosol loading is found on the Himalayas slopes in the premonsoon period (April-May), intensification of early monsoon rainfall over India and increased low-level westerly flow follow, in agreement with the elevated-heat-pump mechanism. The increase in rainfall during the early monsoon season has a cooling effect on the land surface. In the same period, enhanced surface cooling may also be amplified through solar dimming by more cloudiness and aerosol loading, via increased dust transported by low-level westerly flow. The surface cooling causes subsequent reduction in monsoon rainfall in July-August over India. The time-lagged nature of the reasonably realistic response of the model to aerosol forcing suggests that absorbing aerosols, besides their potential key roles in impacting monsoon water cycle and climate, may influence the seasonal variability of the Indian summer monsoon.

  7. Numerical Modeling of Magnesium Alloy Sheet Metal Forming at Elevated Temperature

    SciTech Connect

    Lee, Myeong-Han; Oh, Soo-Ik; Kim, Heon-Young; Kim, Hyung-Jong; Choi, Yi-Chun

    2007-05-17

    The development of light-weight vehicle is in great demand for enhancement of fuel efficiency and dynamic performance. The vehicle weight can be reduced effectively by using lightweight materials such as magnesium alloys. However, the use of magnesium alloys in sheet forming processes is still limited because of their low formability at room temperature and the lack of understanding of the forming process of magnesium alloys at elevated temperatures. In this study, uniaxial tensile tests of the magnesium alloy AZ31B-O at various temperatures were performed to evaluate the mechanical properties of this alloy relevant for forming of magnesium sheets. To construct a FLD (forming limit diagram), a forming limit test were conducted at temperature of 100 and 200 deg. C. For the evaluation of the effects of the punch temperature on the formability of a rectangular cup drawing with AZ31B-O, numerical modelling was conducted. The experiment results indicate that the stresses and possible strains of AZ31B-O sheets largely depend on the temperature. The stress decreases with temperature increase. Also, the strain increase with temperature increase. The numerical modelling results indicate that formability increases with the decrease in the punch temperature at the constant temperature of the die and holder.

  8. Acetylcholine elevation relieves cognitive rigidity and social deficiency in a mouse model of autism.

    PubMed

    Karvat, Golan; Kimchi, Tali

    2014-03-01

    Autism spectrum disorders (ASD) are defined by behavioral deficits in social interaction and communication, repetitive stereotyped behaviors, and restricted interests/cognitive rigidity. Recent studies in humans and animal-models suggest that dysfunction of the cholinergic system may underlie autism-related behavioral symptoms. Here we tested the hypothesis that augmentation of acetylcholine (ACh) in the synaptic cleft by inhibiting acetylcholinesterase may ameliorate autistic phenotypes. We first administered the acetylcholinesterase inhibitor (AChEI) Donepezil systemically by intraperitoneal (i.p.) injections. Second, the drug was injected directly into the rodent homolog of the caudate nucleus, the dorsomedial striatum (DMS), of the inbred mouse strain BTBR T+tf/J (BTBR), a commonly-used model presenting all core autism-related phenotypes and expressing low brain ACh levels. We found that i.p. injection of AChEI to BTBR mice significantly relieved autism-relevant phenotypes, including decreasing cognitive rigidity, improving social preference, and enhancing social interaction, in a dose-dependent manner. Microinjection of the drug directly into the DMS, but not into the ventromedial striatum, led to significant amelioration of the cognitive-rigidity and social-deficiency phenotypes. Taken together, these findings provide evidence of the key role of the cholinergic system and the DMS in the etiology of ASD, and suggest that elevated cognitive flexibility may result in enhanced social attention. The potential therapeutic effect of AChEIs in ASD patients is discussed.

  9. Growing wheat in Biosphere 2 under elevated CO2: observations and modeling

    NASA Technical Reports Server (NTRS)

    Tubiello, F. N.; Mahato, T.; Morton, T.; Druitt, J. W.; Volk, T.; Marino, B. D.

    1999-01-01

    Spring wheat (Triticum aestivum L., cv. Yecora Rojo) was grown in the intensive agricultural biome (IAB) of Biosphere 2 during the l995-l996 winter/spring season. Environmental conditions were characterized by a day/night temperature regime of 27/17 degrees C, relative humidity (RH) levels around 45%, mean atmospheric CO2 concentration of 450 ppmv, and natural light conditions with mean intensities about half of outside levels. Weekly samples of above-ground plant matter were collected throughout the growing season and phenological events recorded. A computer model, CERES-Wheat, previously tested under both field and controlled conditions, was used to simulate the observed crop growth and to help in data analysis. We found that CERES-Wheat simulated the data collected at Biosphere 2 to within 10% of observed, thus suggesting that wheat growth inside the IAB was comparable to that documented in other environments. The model predicts phenological stages and final dry matter (DM) production within l0% of the observed data. Measured DM production rates, normalized for light absorbed by the crop. suggested photosynthetic efficiencies intermediate between those observed under optimal field conditions and those recorded in NASA-Controlled Ecological Life-Support Systems (CELSS). We suggest that such a difference can be explained primarily in terms of low light levels inside the IAB, with additional effects due to elevated CO2 concentrations and diffuse light fractions.

  10. Soil and biomass carbon pools in model communities of tropical plants under elevated CO2.

    PubMed

    Arnone, J A; Körner, Ch

    1995-09-01

    The experimental data presented here relate to the question of whether terrestrial ecosystems will sequester more C in their soils, litter and biomass as atmospheric CO2 concentrations rise. Similar to our previous study with relatively fertile growth conditions (Körner and Arnone 1992), we constructed four rather nutrient-limited model communities of moist tropical plant species in greenhouses (approximately 7 m(2) each). Plant communities were composed of seven species (77 individuals per community) representing major taxonomic groups and various life forms found in the moist tropics. Two ecosystems were exposed to 340 μl CO2 l(-1) and two to 610 μl l(-1) for 530 days of humid tropical growth conditions. In order to permit precise determination of C deposition in the soil, plant communities were initially established in C-free unwashed quartz sand. Soils were then amended with known amounts of organic matter (containing C and nutrients). Mineral nutrients were also supplied over the course of the experiment as timed-release full-balance fertilizer pellets. Soils represented by far the largest repositories for fixed C in all ecosystems. Almost 5 times more C (ca. 80% of net C fixation) was sequestered in the soil than in the biomass, but this did not differ between CO2 treatments. In addition, at the whole-ecosystem level we found a remarkably small and statistically non-significant increase in C sequestration (+4%; the sum of C accretion in the soil, biomass, litter and necromass). Total community biomass more than quadrupled during the experiment, but at harvest was, on average, only 8% greater (i.e. 6% per year; n.s.) under elevated CO2, mainly due to increased root biomass (+15%, P=0.12). Time courses of leaf area index of all ecosystems suggested that canopy expansion was approaching steady state by the time systems were harvested. Net primary productivity (NPP) of all ecosystems-i.e. annual accumulation of biomass, necromass, and leaf litter (but not

  11. San Francisco Bay-Delta bathymetric/topographic digital elevation model (DEM)

    USGS Publications Warehouse

    Fregoso, Theresa; Wang, Rueen-Fang; Ateljevich, Eli; Jaffe, Bruce E.

    2017-01-01

    A high-resolution (10-meter per pixel) digital elevation model (DEM) was created for the Sacramento-San Joaquin Delta using both bathymetry and topography data. This DEM is the result of collaborative efforts of the U.S. Geological Survey (USGS) and the California Department of Water Resources (DWR). The base of the DEM is from a 10-m DEM released in 2004 and updated in 2005 (Foxgrover and others, 2005) that used Environmental Systems Research Institute (ESRI), ArcGIS Topo to Raster module to interpolate grids from single beam bathymetric surveys collected by DWR, the Army Corp of Engineers (COE), the National Oceanic and Atmospheric Administration (NOAA), and the USGS, into a continuous surface. The Topo to Raster interpolation method was specifically designed to create hydrologically correct DEMs from point, line, and polygon data (Environmental Systems Research Institute, Inc., 2015). Elevation contour lines were digitized based on the single beam point data for control of channel morphology during the interpolation process. Checks were performed to ensure that the interpolated surfaces honored the source bathymetry, and additional contours and (or) point data were added as needed to help constrain the data. The original data were collected in the tidal datum Mean Lower or Low Water (MLLW) or the National Geodetic Vertical Datum of 1929 (NGVD29). All data were converted to NGVD29.The 2005 USGS DEM was updated by DWR, first by converting the DEM to the current modern datum of North American Vertical Datum of 1988 (NAVD88) and then by following the methodology of the USGS DEM, established for the 2005 DEM (Foxgrover and others, 2005) for adding newly collected single and multibeam bathymetric data. They then included topographic data from lidar surveys, providing the first DEM that included the land/water interface (Wang and Ateljevich, 2012).The USGS further updated and expanded the DWR DEM with the inclusion of USGS interpolated sections of single beam

  12. Water Uptake and Carbon Assimilation in Maize at Elevated and ambient CO2: Modeling and Measurement.

    NASA Astrophysics Data System (ADS)

    Timlin, Dennis; Chun, Jong-Ahn; Kim, Soo-Hyung; Yang, Yang; Fleisher, David; Reddy, Vangimalla

    2013-04-01

    Potential transpiration in crops is dependent on both plant and environmental properties. Carbon dioxide content of the atmosphere is linked to potential transpiration because CO2 diffuses onto water saturated surfaces within plant stomata. At high CO2 concentrations, CO2 diffuses rapidly into stomata and therefore stomata do not have to remain open to the atmosphere for long periods of time. This results in lower transpiration rates per unit CO2 assimilated at elevated CO2 concentrations. The objective of this study was to measure CO2 assimilation and water uptake by maize under different irrigation regimes and two CO2 concentrations. The data were then used to evaluate the ability of the maize model MaizSim to simulate the effects of water stress and CO2 on water use and photosynthesis. MaizSim uses a Farquhar type photosynthesis model coupled a Ball-Berry stomatal control model. Non-linear beta functions are used to estimate the effects of temperature on growth and development processes. The experimental data come from experiments in outdoor, sunlit growth chambers at the USDA-ARS Beltsville Agricultural Research Center. The eight treatments comprised two levels of carbon dioxide concentrations (400 and 800 ppm) and four levels of water stress (well-watered control, mild, moderate, and severe). The water stress treatments were applied at both CO2 levels. Water contents were monitored hourly by a Time Domain Reflectometry (TDR) system. The model simulated higher water contents at the same time after applying water stress at the high CO2 treatment than for the low CO2 treatment as was found in the measured data. Measurement of water uptake by roots and carbon assimilation rates in the chambers will be addressed.

  13. A high-fidelity multiresolution digital elevation model for Earth systems

    NASA Astrophysics Data System (ADS)

    Duan, Xinqiao; Li, Lin; Zhu, Haihong; Ying, Shen

    2017-01-01

    The impact of topography on Earth systems variability is well recognised. As numerical simulations evolved to incorporate broader scales and finer processes, accurately assimilating or transforming the topography to produce more exact land-atmosphere-ocean interactions, has proven to be quite challenging. Numerical schemes of Earth systems often use empirical parameterisation at sub-grid scale with downscaling to express topographic endogenous processes, or rely on insecure point interpolation to induce topographic forcing, which creates bias and input uncertainties. Digital elevation model (DEM) generalisation provides more sophisticated systematic topographic transformation, but existing methods are often difficult to be incorporated because of unwarranted grid quality. Meanwhile, approaches over discrete sets often employ heuristic approximation, which are generally not best performed. Based on DEM generalisation, this article proposes a high-fidelity multiresolution DEM with guaranteed grid quality for Earth systems. The generalised DEM surface is initially approximated as a triangulated irregular network (TIN) via selected feature points and possible input features. The TIN surface is then optimised through an energy-minimised centroidal Voronoi tessellation (CVT). By devising a robust discrete curvature as density function and exact geometry clipping as energy reference, the developed curvature CVT (cCVT) converges, the generalised surface evolves to a further approximation to the original DEM surface, and the points with the dual triangles become spatially equalised with the curvature distribution, exhibiting a quasi-uniform high-quality and adaptive variable resolution. The cCVT model was then evaluated on real lidar-derived DEM datasets and compared to the classical heuristic model. The experimental results show that the cCVT multiresolution model outperforms classical heuristic DEM generalisations in terms of both surface approximation precision and

  14. Seasonal and Interannual Variations of Ice Sheet Surface Elevation at the Summit of Greenland: Observed and Modeled

    NASA Technical Reports Server (NTRS)

    Zwally, H. Jay; Jun, Li; Koblinsky, Chester J. (Technical Monitor)

    2001-01-01

    Observed seasonal and interannual variations in the surface elevation over the summit of the Greenland ice sheet are modeled using a new temperature-dependent formulation of firn-densification and observed accumulation variations. The observed elevation variations are derived from ERS (European Remote Sensing)-1 and ERS-2 radar altimeter data for the period between April 1992 and April 1999. A multivariate linear/sine function is fitted to an elevation time series constructed from elevation differences measured by radar altimetry at orbital crossovers. The amplitude of the seasonal elevation cycle is 0.25 m peak-to-peak, with a maximum in winter and a minimum in summer. Inter-annually, the elevation decreases to a minimum in 1995, followed by an increase to 1999, with an overall average increase of 4.2 cm a(exp -1) for 1992 to 1999. Our densification formulation uses an initial field-density profile, the AWS (automatic weather station) surface temperature record, and a temperature-dependent constitutive relation for the densification that is based on laboratory measurements of crystal growth rates. The rate constant and the activation energy commonly used in the Arrhenius-type constitutive relation for firn densification are also temperature dependent, giving a stronger temperature and seasonal amplitudes about 10 times greater than previous densification formulations. Summer temperatures are most important, because of the strong non-linear dependence on temperature. Much of firn densification and consequent surface lowering occurs within about three months of the summer season, followed by a surface build-up from snow accumulation until spring. Modeled interannual changes of the surface elevation, using the AWS measurements of surface temperature and accumulation and results of atmospheric modeling of precipitation variations, are in good agreement with the altimeter observations. In the model, the surface elevation decreases about 20 cm over the seven years due

  15. Quantifying depression storage of snowmelt runoff over frozen ground using aerial photography and digital elevation model

    NASA Astrophysics Data System (ADS)

    Hayashi, M.; Donovan, K.; Sjogren, D.

    2004-05-01

    The northern prairie region of North America is characterized by undulating terrains with very low regional gradient, underlain by clay-rich glacial tills. The soils derived from clay-rich tills have very low permeability when they are frozen. As a result a large amount of snowmelt runoff is generated over frozen ground. Numerous depressions on the undulating terrains trap snowmelt water and focus the infiltration flux under the depressions. Therefore, the depressions have important hydrologic functions regarding runoff retention and groundwater recharge. Previous studies have investigated the storage of snowmelt runoff and subsequent infiltration at a scale of each depression (102-103 m2). However, to understand the roles of depressions in regional hydrology, depression storage needs to be evaluated at a much larger scale. Our ultimate goal is to quantify depression storage at the scale of watersheds (102-103km 2) and represent it properly in a large-scale hydrologic model. As the first step towards this goal, we quantified depression storage at 1-km2 scale using infrared (IR) aerial photographs and digital elevation model combined with the measurement of water depth in depressions. Two parcels of land were selected for the study in the watershed of West Nose Creek, located immediately north of Calgary, Alberta, Canada. Each site contained a subsection of native prairie grass and cultivated field. Snow surveys were conducted at each site to estimate the average snow water equivalent (SWE) on the ground prior to melt. SWE ranged between 26 mm and 39 mm. Water depth was measured in 111 depressions when they were filled up to the peak level, and IR photographs were taken simultaneously at a scale of 1:10,000. The soil was frozen to a depth of 1 m or greater as indicated by several thermocouple arrays installed at the site. Detailed elevation survey was conducted in summer using a total station and differential global positioning system for 10 selected depressions to

  16. Eigenvector Analysis of Digital Elevation Models in a GIS: Geomorphometry and Quality Control

    DTIC Science & Technology

    2003-01-01

    the most highly organized regions are in folded mountain belts or glacial drumlin fields. Average elevation and average slope coincide with Pike’s...on the right contains a drumlin field in Wisconsin. One km UTM grid provides scale. 204 P. L. GUTH Elevation is a true point parameter, defined at

  17. Mid-Pliocene shorelines of the US Atlantic Coastal Plain: an improved elevation database with constraints from Earth model predictions

    NASA Astrophysics Data System (ADS)

    Rovere, Alessio; Hearty, Paul; Austermann, Jacqueline; Mitrovica, Jerry X.; Gale, Jonathan; Moucha, Robert; Forte, Alessandro; Raymo, Maureen E.

    2015-04-01

    For more than half a century, the Atlantic Coastal Plain (ACP) of the southeast United States has been the focus of studies investigating Pliocene and Pleistocene shorelines where the mapping of paleo-shorelines was carried out mainly by using elevation contours on topographic maps. Here we review published geologic maps and compare them to paleoshoreline traces obtained through geomorphometric classification and satellite data. We further present the results of an extensive field campaign that measured the mid-Pliocene (~3.3 - 2.9 Ma) shorelines of the ACP using high-accuracy GPS and Digital Elevation Models. We compare our new dataset to positions and elevations extracted from published maps and find that the extracted site information from previously published maps results in large uncertainties, not only in the location, but also more critically, in the elevation of the paleoshorelines. Lastly, we investigate the causes and rates of post-depositional displacement of the shoreline from Georgia to Virginia. To do this we correct the elevation of our shoreline for glacial isostatic adjustment (GIA) and then compare the corrected elevation to predictions of mantle flow-induced dynamic topography (DT). We find a discrepancy between the GIA-corrected shoreline and the predictions of DT models, which suggests that either (i) the DT and GIA models presented here do not capture the full range of uncertainty in the input parameters and /or (ii) other influences, such as sediment loading and unloading, may have caused additional post-depositional deformation of the mid-Pliocene shoreline that are not captured in the models. In this context, our field measurements represent an important observational dataset with which to compare future generations of geodynamic models. Improvements in models for DT, GIA and other relevant processes will ultimately be the key to obtaining more accurate estimates of eustatic sea level not only for the mid-Pliocene but across the broader

  18. Evaluating the impact of lower resolutions of digital elevation model on rainfall-runoff modeling for ungauged catchments.

    PubMed

    Ghumman, Abul Razzaq; Al-Salamah, Ibrahim Saleh; AlSaleem, Saleem Saleh; Haider, Husnain

    2017-02-01

    Geomorphological instantaneous unit hydrograph (GIUH) usually uses geomorphologic parameters of catchment estimated from digital elevation model (DEM) for rainfall-runoff modeling of ungauged watersheds with limited data. Higher resolutions (e.g., 5 or 10 m) of DEM play an important role in the accuracy of rainfall-runoff models; however, such resolutions are expansive to obtain and require much greater efforts and time for preparation of inputs. In this research, a modeling framework is developed to evaluate the impact of lower resolutions (i.e., 30 and 90 m) of DEM on the accuracy of Clark GIUH model. Observed rainfall-runoff data of a 202-km(2) catchment in a semiarid region was used to develop direct runoff hydrographs for nine rainfall events. Geographical information system was used to process both the DEMs. Model accuracy and errors were estimated by comparing the model results with the observed data. The study found (i) high model efficiencies greater than 90% for both the resolutions, and (ii) that the efficiency of Clark GIUH model does not significantly increase by enhancing the resolution of the DEM from 90 to 30 m. Thus, it is feasible to use lower resolutions (i.e., 90 m) of DEM in the estimation of peak runoff in ungauged catchments with relatively less efforts. Through sensitivity analysis (Monte Carlo simulations), the kinematic wave parameter and stream length ratio are found to be the most significant parameters in velocity and peak flow estimations, respectively; thus, they need to be carefully estimated for calculation of direct runoff in ungauged watersheds using Clark GIUH model.

  19. High dose intracoronary N-acetylcysteine in a porcine model of ST-elevation myocardial infarction.

    PubMed

    Meyer, Markus; Bell, Stephen P; Chen, Zengyi; Nyotowidjojo, Iwan; Lachapelle, Richard R; Christian, Timothy F; Gibson, Pamela C; Keating, Friederike F; Dauerman, Harold L; LeWinter, Martin M

    2013-11-01

    We sought to evaluate the safety and efficacy of N-acetylcysteine (NAC) on ischemia and reperfusion in a pig model focusing on cardio-renal protection. High doses of NAC may provide protection from contrast induced nephropathy (CIN). NAC has also been demonstrated to reduce myocardial infarction size and improve left ventricular function after ischemia in both humans and animals studies. In this study we tested the safety and cardiorenal protective efficacy of intracoronary NAC delivered in the radiographic contrast agent in a pig model that simulates the catheter based reperfusion therapy of ST elevation myocardial infarctions. 27 pigs underwent 45 min of ischemia after surgical ligation of distal left descending coronary artery. With coronary reperfusion the animals received at total of 200 mL of the contrast agent Iopamidol with and without NAC to mimic radiographic contrast use during invasive reperfusion therapy. At 24 h the following endpoints were compared: LV function (MRI, echocardiography), myocardial injury (infarct size, area-at-risk, troponin, creatinine kinase) and CIN (creatinine, BUN and renal histology). The effects of NAC on platelet reactivity were also evaluated. Intracoronary administration of NAC administered in the contrast agent is safe. NAC reduces platelet reactivity and there was a trend towards a better cardiac function at 24 h. There was no significant difference in the size of the myocardial infarction. In this model of ischemia-reperfusion high dose NAC did not protect from CIN. High dose intracoronary NAC administered with the radiographic contrast is safe but does not provide significant cardio-renal protection.

  20. Modeling of Firn Compaction for Estimating Ice-Sheet Mass Change from Observed Ice-Sheet Elevation Change

    NASA Technical Reports Server (NTRS)

    Li, Jun; Zwally, H. Jay

    2011-01-01

    Changes in ice-sheet surface elevation are caused by a combination of ice-dynamic imbalance, ablation, temporal variations in accumulation rate, firn compaction and underlying bedrock motion. Thus, deriving the rate of ice-sheet mass change from measured surface elevation change requires information on the rate of firn compaction and bedrock motion, which do not involve changes in mass, and requires an appropriate firn density to associate with elevation changes induced by recent accumulation rate variability. We use a 25 year record of surface temperature and a parameterization for accumulation change as a function of temperature to drive a firn compaction model. We apply this formulation to ICESat measurements of surface elevation change at three locations on the Greenland ice sheet in order to separate the accumulation-driven changes from the ice-dynamic/ablation-driven changes, and thus to derive the corresponding mass change. Our calculated densities for the accumulation-driven changes range from 410 to 610 kg/cu m, which along with 900 kg/cu m for the dynamic/ablation-driven changes gives average densities ranging from 680 to 790 kg/cu m. We show that using an average (or "effective") density to convert elevation change to mass change is not valid where the accumulation and the dynamic elevation changes are of opposite sign.

  1. Alterations of the synapse of the inner retinal layers after chronic intraocular pressure elevation in glaucoma animal model

    PubMed Central

    2014-01-01

    Background Dendrites of retinal ganglion cells (RGCs) synapse with axon terminals of bipolar cells in the inner plexiform layer (IPL). Changes in RGC dendrites and synapses between bipolar cells in the inner retinal layer may critically alter the function of RGCs in glaucoma. Recently, synaptic plasticity has been observed in the adult central nervous system, including the outer retinal layers. However, few studies have focused on changes in the synapses between RGCs and bipolar cells in glaucoma. In the present study, we used a rat model of ocular hypertension induced by episcleral vein cauterization to investigate changes in synaptic structure and protein expression in the inner retinal layer at various time points after moderate intraocular pressure (IOP) elevation. Results Synaptophysin, a presynaptic vesicle protein, increased throughout the IPL, outer plexiform layer, and outer nuclear layer after IOP elevation. Increased synaptophysin after IOP elevation was expressed in bipolar cells in the innermost IPL. The RGC marker, SMI-32, co-localized with synaptophysin in RGC dendrites and were significantly increased at 1 week and 4 weeks after IOP elevation. Both synaptophysin and postsynaptic vesicle protein, PSD-95, were increased after IOP elevation by western blot analysis. Ribbon synapses in the IPL were quantified and structurally evaluated in retinal sections by transmission electron microscopy. After IOP elevation the total number of ribbon synapses decreased. There were increases in synapse diameter and synaptic vesicle number and decreases in active zone length and the number of docked vesicles after IOP elevation. Conclusions Although the total number of synapses decreased as RGCs were lost after IOP elevation, there are attempts to increase synaptic vesicle proteins and immature synapse formation between RGCs and bipolar cells in the inner retinal layers after glaucoma induction. PMID:25116810

  2. Echolocation with bat buzz emissions: model and biomimetic sonar for elevation estimation.

    PubMed

    Kuc, Roman

    2012-01-01

    Just prior to capture the Buzz II emissions of some mouth-emitting bats, such as Eptesicus fuscus, are observed to exhibit spectra having multiple peaks. This paper proposes an echolocation strategy that uses such spectra with energy concentrated in specific frequency bands for determining target elevation. A biomimetic sonar was implemented to produce a tri-modal spectrum by driving a speaker with a signal rich in harmonics. The emission magnitudes at these harmonic frequencies measured as a function of elevation in the zero-azimuth plane form distinct beams. A template was formed from the ratio of the first harmonic and fundamental magnitudes to determine elevation. The elevation estimator exhibited a sub-degree accuracy (SD = 0.4° over a 20° interval centered at the elevation at which these two beams intersect in the zero-azimuth plane. Spectral cues from -40° to +10° elevation allow a qualitative non-linear control of sonar orientation to drive the target to the beam-intersection point where quantitative elevation estimates are available.

  3. A New Lunar Digital Elevation Model from the Lunar Orbiter Laser Altimeter and SELENE Terrain Camera

    NASA Technical Reports Server (NTRS)

    Barker, M. K.; Mazarico, E.; Neumann, G. A.; Zuber, M. T.; Haruyama, J.; Smith, D. E.

    2015-01-01

    We present an improved lunar digital elevation model (DEM) covering latitudes within +/-60 deg, at a horizontal resolution of 512 pixels per degree ( approx.60 m at the equator) and a typical vertical accuracy approx.3 to 4 m. This DEM is constructed from approx.4.5 ×10(exp 9) geodetically-accurate topographic heights from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter, to which we co-registered 43,200 stereo-derived DEMs (each 1 deg×1 deg) from the SELENE Terrain Camera (TC) ( approx.10(exp 10) pixels total). After co-registration, approximately 90% of the TC DEMs show root-mean-square vertical residuals with the LOLA data of < 5 m compared to approx.50% prior to co-registration. We use the co-registered TC data to estimate and correct orbital and pointing geolocation errors from the LOLA altimetric profiles (typically amounting to < 10 m horizontally and < 1 m vertically). By combining both co-registered datasets, we obtain a near-global DEM with high geodetic accuracy, and without the need for surface interpolation. We evaluate the resulting LOLA + TC merged DEM (designated as "SLDEM2015") with particular attention to quantifying seams and crossover errors.

  4. The Need of Nested Grids for Aerial and Satellite Images and Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Villa, G.; Mas, S.; Fernández-Villarino, X.; Martínez-Luceño, J.; Ojeda, J. C.; Pérez-Martín, B.; Tejeiro, J. A.; García-González, C.; López-Romero, E.; Soteres, C.

    2016-06-01

    Usual workflows for production, archiving, dissemination and use of Earth observation images (both aerial and from remote sensing satellites) pose big interoperability problems, as for example: non-alignment of pixels at the different levels of the pyramids that makes it impossible to overlay, compare and mosaic different orthoimages, without resampling them and the need to apply multiple resamplings and compression-decompression cycles. These problems cause great inefficiencies in production, dissemination through web services and processing in "Big Data" environments. Most of them can be avoided, or at least greatly reduced, with the use of a common "nested grid" for mutiresolution production, archiving, dissemination and exploitation of orthoimagery, digital elevation models and other raster data. "Nested grids" are space allocation schemas that organize image footprints, pixel sizes and pixel positions at all pyramid levels, in order to achieve coherent and consistent multiresolution coverage of a whole working area. A "nested grid" must be complemented by an appropriate "tiling schema", ideally based on the "quad-tree" concept. In the last years a "de facto standard" grid and Tiling Schema has emerged and has been adopted by virtually all major geospatial data providers. It has also been adopted by OGC in its "WMTS Simple Profile" standard. In this paper we explain how the adequate use of this tiling schema as common nested grid for orthoimagery, DEMs and other types of raster data constitutes the most practical solution to most of the interoperability problems of these types of data.

  5. A guide for the use of digital elevation model data for making soil surveys

    USGS Publications Warehouse

    Klingebiel, A.A.; Horvath, Emil H.; Reybold, William U.; Moore, D.G.; Fosnight, E.A.; Loveland, T.R.

    1988-01-01

    The intent of this publication is twofold: (1) to serve as a user guide for soil scientists and others interested in learning about the value and use of digital elevation model (DEM) data in making soil surveys and (2) to provide documentation of the Soil Landscape Analysis Project (SLAP). This publication provides a step-by-step guide on how digital slope-class maps are adjusted to topographic maps and orthophotoquads to obtain accurate slope-class maps, and how these derivative maps can be used as a base for soil survey premaps. In addition, guidance is given on the use of aspect-class maps and other resource data in making pre-maps. The value and use of tabular summaries are discussed. Examples of the use of DEM products by the authors and by selected field soil scientists are also given. Additional information on SLAP procedures may be obtained from USDA, Soil Conservation Service, Soil Survey Division, P.O. Box 2890, Washington, D.C. 20013, and from references (Horvath and others, 1987; Horvath and others, 1983; Klingebiel and others, 1987; and Young, 1987) listed in this publication. The slope and aspect products and the procedures for using these products have evolved during 5 years of cooperative research with the USDA, Soil Conservation Service and Forest Service, and the USDI, Bureau of Land Management.

  6. Quality Assessment for the First Part of the Tandem-X Global Digital Elevation Model

    NASA Astrophysics Data System (ADS)

    Brautigam, B.; Martone, M.; Rizzoli, P.; Gonzalez, C.; Wecklich, C.; Borla Tridon, D.; Bachmann, M.; Schulze, D.; Zink, M.

    2015-04-01

    TanDEM-X is an innovative synthetic aperture radar (SAR) mission with the main goal to generate a global and homogeneous digital elevation model (DEM) of the Earth's land masses. The final DEM product will reach a new dimension of detail with respect to resolution and quality. The absolute horizontal and vertical accuracy shall each be less than 10 m in a 90% confidence interval at a pixel spacing of 12 m. The relative vertical accuracy specification for the TanDEM-X mission foresees a 90% point-to-point error of 2 m (4 m) for areas with predominant terrain slopes smaller than 20% (greater than 20%) within a 1° longitude by 1° latitude cell. The global DEM is derived from interferometric SAR acquisitions performed by two radar satellites flying in close orbit formation. Interferometric performance parameters like the coherence between the two radar images have been monitored and evaluated throughout the mission. In a further step, over 500,000 single SAR scenes are interferometrically processed, calibrated, and mosaicked into a global DEM product which will be completely available in the second half of 2016. This paper presents an up-todate quality status of the single interferometric acquisitions as well as of 50% of the final DEM. The overall DEM quality of these first products promises accuracies well within the specification, especially in terms of absolute height accuracy.

  7. Analyzing the evolution of the Tessina landslide using aerial photographs and digital elevation models

    NASA Astrophysics Data System (ADS)

    van Westen, C. J.; Lulie Getahun, F.

    2003-08-01

    Evolution of the Tessina landslide near Belluno, Italy, from 1954 to the present situation has been documented using multitemporal landslide maps. The maps were produced through the interpretation of sequential aerial photographs and direct field-mapping of the landslide in 1998 and 1999. The interpretations were converted to large-scale multitemporal topographical maps and digitized, resulting in detailed geomorphological maps of the Tessina landslide for the following periods: 1954, 1961, 1969, 1980, 1991, 1993, 1998 and 1999. A quantitative volumetric analysis was also carried out using a series of digital elevation models derived from the available 1:5000 scale digital contour maps with 5-m contour interval for 1948, 1964, 1980, 1991 and 1993. The total volume of material removed and accumulated was calculated for the entire Tessina landslide for the different time steps available. Results indicate that the Tessina landslide existed prior to its main reactivation in 1960, after which the landslide reduced in activity. From 1991, however, very large reactivations have taken place, and the landslide continues to be active. Although the landslide has reached the lateral boundaries of the old pre-1960 landslide, it is now expanding upslope where it may still mobilize large amounts of material.

  8. Parallel Priority-Flood depression filling for trillion cell digital elevation models on desktops or clusters

    NASA Astrophysics Data System (ADS)

    Barnes, Richard

    2016-11-01

    Algorithms for extracting hydrologic features and properties from digital elevation models (DEMs) are challenged by large datasets, which often cannot fit within a computer's RAM. Depression filling is an important preconditioning step to many of these algorithms. Here, I present a new, linearly scaling algorithm which parallelizes the Priority-Flood depression-filling algorithm by subdividing a DEM into tiles. Using a single-producer, multi-consumer design, the new algorithm works equally well on one core, multiple cores, or multiple machines and can take advantage of large memories or cope with small ones. Unlike previous algorithms, the new algorithm guarantees a fixed number of memory access and communication events per subdivision of the DEM. In comparison testing, this results in the new algorithm running generally faster while using fewer resources than previous algorithms. For moderately sized tiles, the algorithm exhibits ∼60% strong and weak scaling efficiencies up to 48 cores, and linear time scaling across datasets ranging over three orders of magnitude. The largest dataset on which I run the algorithm has 2 trillion (2×1012) cells. With 48 cores, processing required 4.8 h wall-time (9.3 compute-days). This test is three orders of magnitude larger than any previously performed in the literature. Complete, well-commented source code and correctness tests are available for download from a repository.

  9. Modeling the Physics of Sliding Objects on Rotating Space Elevators and Other Non-relativistic Strings

    NASA Astrophysics Data System (ADS)

    Golubovic, Leonardo; Knudsen, Steven

    2017-01-01

    We consider general problem of modeling the dynamics of objects sliding on moving strings. We introduce a powerful computational algorithm that can be used to investigate the dynamics of objects sliding along non-relativistic strings. We use the algorithm to numerically explore fundamental physics of sliding climbers on a unique class of dynamical systems, Rotating Space Elevators (RSE). Objects sliding along RSE strings do not require internal engines or propulsion to be transported from the Earth's surface into outer space. By extensive numerical simulations, we find that sliding climbers may display interesting non-linear dynamics exhibiting both quasi-periodic and chaotic states of motion. While our main interest in this study is in the climber dynamics on RSEs, our results for the dynamics of sliding object are of more general interest. In particular, we designed tools capable of dealing with strongly nonlinear phenomena involving moving strings of any kind, such as the chaotic dynamics of sliding climbers observed in our simulations.

  10. Topographic Phase Recovery from Stacked ERS Interferometry and a Low-Resolution Digital Elevation Model

    NASA Technical Reports Server (NTRS)

    Sandwell, David T.; Sichoix, Lydie; Frey, Herbert V. (Technical Monitor)

    2000-01-01

    A hybrid approach to topographic recovery from ERS interferometry is developed and assessed. Tropospheric/ionospheric artifacts, imprecise orbital information, and layover are key issues in recovering topography and surface deformation from repeat-pass interferometry. Previously, we developed a phase gradient approach to stacking interferograms to reduce these errors and also to reduce the short-wavelength phase noise (see Sandwell arid Price [1998] and Appendix A). Here the method is extended to use a low-resolution digital elevation model to constrain long-wavelength phase errors and an iteration scheme to minimize errors in the computation of phase gradient. We demonstrate the topographic phase recovery on 16-m postings using 25 ERS synthetic aperture radar images from an area of southern California containing 2700 m of relief. On the basis of a comparison with 81 GPS monuments, the ERS derived topography has a typical absolute accuracy of better than 10 m except in areas of layover. The resulting topographic phase enables accurate two-pass, real-time interferometry even in mountainous areas where traditional phase unwrapping schemes fail. As an example, we form a topography-free (127-m perpendicular baseline) interferogram spanning 7.5 years; fringes from two major earthquakes and a seismic slip on the San Andreas Fault are clearly isolated.

  11. A new lunar digital elevation model from the Lunar Orbiter Laser Altimeter and SELENE Terrain Camera

    NASA Astrophysics Data System (ADS)

    Barker, M. K.; Mazarico, E.; Neumann, G. A.; Zuber, M. T.; Haruyama, J.; Smith, D. E.

    2016-07-01

    We present an improved lunar digital elevation model (DEM) covering latitudes within ±60°, at a horizontal resolution of 512 pixels per degree (∼60 m at the equator) and a typical vertical accuracy ∼3 to 4 m. This DEM is constructed from ∼ 4.5 ×109 geodetically-accurate topographic heights from the Lunar Orbiter Laser Altimeter (LOLA) onboard the Lunar Reconnaissance Orbiter, to which we co-registered 43,200 stereo-derived DEMs (each 1° × 1°) from the SELENE Terrain Camera (TC) (∼1010 pixels total). After co-registration, approximately 90% of the TC DEMs show root-mean-square vertical residuals with the LOLA data of <5 m compared to ∼ 50% prior to co-registration. We use the co-registered TC data to estimate and correct orbital and pointing geolocation errors from the LOLA altimetric profiles (typically amounting to <10 m horizontally and <1 m vertically). By combining both co-registered datasets, we obtain a near-global DEM with high geodetic accuracy, and without the need for surface interpolation. We evaluate the resulting LOLA + TC merged DEM (designated as "SLDEM2015") with particular attention to quantifying seams and crossover errors.

  12. 2010 bathymetric survey and digital elevation model of Corte Madera Bay, California

    USGS Publications Warehouse

    Foxgrover, Amy C.; Finlayson, David P.; Jaffe, Bruce E.; Takekawa, John Y.; Thorne, Karen M.; Spragens, Kyle A.

    2011-01-01

    A high-resolution bathymetric survey of Corte Madera Bay, California, was collected in early 2010 in support of a collaborative research project initiated by the San Francisco Bay Conservation and Development Commission and funded by the U.S. Environmental Protection Agency. The primary objective of the Innovative Wetland Adaptation in the Lower Corte Madera Creek Watershed Project is to develop shoreline adaptation strategies to future sea-level rise based upon sound science. Fundamental to this research was the development of an of an up-to-date, high-resolution digital elevation model (DEM) extending from the subtidal environment through the surrounding intertidal marsh. We provide bathymetric data collected by the U.S. Geological Survey and have merged the bathymetry with a 1-m resolution aerial lidar data set that was collected by the National Oceanic and Atmospheric Administration during the same time period to create a seamless, high-resolution DEM of Corte Madera Bay and the surrounding topography. The bathymetric and DEM surfaces are provided at both 1 m and 10 m resolutions formatted as both X, Y, Z text files and ESRI Arc ASCII files, which are accompanied by Federal Geographic Data Committee compliant metadata.

  13. Modeling of the viscoelastic behavior of a polyimide matrix at elevated temperature

    NASA Astrophysics Data System (ADS)

    Crochon, Thibaut

    Use of Polymer Matrix Composite Materials (PMCMs) in aircraft engines requires materials able to withstand extreme service conditions, such as elevated temperatures, high mechanical loadings and an oxidative environment. In such an environment, the polymer matrix is likely to exhibit a viscoelastic behavior dependent on the mechanical loading and temperature. In addition, the combined effects of elevated temperature and the environment near the engines are likely to increase physical as well as chemical aging. These various parameters need to be taken into consideration for the designer to be able to predict the material behavior over the service life of the components. The main objective of this thesis was to study the viscoelastic behavior of a high temperature polyimide matrix and develop a constitutive theory able to predict the material behavior for every of service condition. Then, the model had to have to be implemented into commercially available finite-element software such as ABAQUS or ANSYS. Firstly, chemical aging of the material at service temperature was studied. To that end, a thermogravimetric analysis of the matrix was conducted on powder samples in air atmosphere. Two kinds of tests were performed: i) kinetic tests in which powder samples were heated at a constant rate until complete sublimation; ii) isothermal tests in which the samples were maintained at a constant temperature for 24 hours. The first tests were used to develop a degradation model, leading to an excellent fit of the experimental data. Then, the model was used to predict the isothermal data but which much less success, particularly for the lowest temperatures. At those temperatures, the chemical degradation was preceded by an oxidation phase which the model was not designed to predict. Other isothermal degradation tests were also performed on tensile tests samples instead of powders. Those tests were conducted at service temperature for a much longer period of time. The samples

  14. Coastal Digital Elevation Models (DEMs) for tsunami hazard assessment on the French coasts

    NASA Astrophysics Data System (ADS)

    Maspataud, Aurélie; Biscara, Laurie; Hébert, Hélène; Schmitt, Thierry; Créach, Ronan

    2015-04-01

    Building precise and up-to-date coastal DEMs is a prerequisite for accurate modeling and forecasting of hydrodynamic processes at local scale. Marine flooding, originating from tsunamis, storm surges or waves, is one of them. Some high resolution DEMs are being generated for multiple coast configurations (gulf, embayment, strait, estuary, harbor approaches, low-lying areas…) along French Atlantic and Channel coasts. This work is undertaken within the framework of the TANDEM project (Tsunamis in the Atlantic and the English ChaNnel: Definition of the Effects through numerical Modeling) (2014-2017). DEMs boundaries were defined considering the vicinity of French civil nuclear facilities, site effects considerations and potential tsunamigenic sources. Those were identified from available historical observations. Seamless integrated topographic and bathymetric coastal DEMs will be used by institutions taking part in the study to simulate expected wave height at regional and local scale on the French coasts, for a set of defined scenarii. The main tasks were (1) the development of a new capacity of production of DEM, (2) aiming at the release of high resolution and precision digital field models referred to vertical reference frameworks, that require (3) horizontal and vertical datum conversions (all source elevation data need to be transformed to a common datum), on the basis of (4) the building of (national and/or local) conversion grids of datum relationships based on known measurements. Challenges in coastal DEMs development deal with good practices throughout model development that can help minimizing uncertainties. This is particularly true as scattered elevation data with variable density, from multiple sources (national hydrographic services, state and local government agencies, research organizations and private engineering companies) and from many different types (paper fieldsheets to be digitized, single beam echo sounder, multibeam sonar, airborne laser

  15. Differences in topographic characteristics computed from 100- and 1000-m resolution digital elevation model data

    USGS Publications Warehouse

    Wolock, D.M.; McCabe, G.J.

    2000-01-01

    Topographic characteristics computed from 100- and 1000-m resolution digital elevation model (DEM) data are compared for 50 locations representing varied terrain in the conterminous USA. The topographic characteristics are three parameters used extensively in hydrological research and modelling - slope (S), specific catchment area (A(s)) and a wetness index computed as the logarithm of the specific catchment area divided by slope [ln(A(s)/S)]. Slope values computed from 1000-m DEMs are smaller than those computed from 100-m DEMs; specific catchment area and the wetness index are larger for the 1000-m DEMs compared with the 100-m DEMs. Most of the differences between the 100- and 1000-m resolution DEMs can be attributed to terrain-discretization effects in the computation of the topographic characteristics and are not the result of smoothing or loss of terrain detail in the coarse data. In general, the terrain-discretization effects are greatest on flat terrain with long length-scale features, and the smoothing effects are greatest on steep terrain with short length-scale features. For the most part, the differences in the average values of the topographic characteristics computed from 100- and 1000-m resolution DEMs are predictable; that is, biases in the mean values for the characteristics computed from a 1000-m DEM can be corrected with simple linear equations. Copyright (C) 2000 John Wiley and Sons, Ltd.Topographic characteristics computed from 100- and 1000-m resolution digital elevation model (DEM) data are compared for 50 locations representing varied terrain in the conterminous USA. The topographic characteristics are three parameters used extensively in hydrological research and modelling - slope (S), specific catchment area (As) and a wetness index computed as the logarithm of the specific catchment area divided by slope [In(As/S)]. Slope values computed from 1000-m DEMs are smaller than those computed from 100-m DEMs; specific catchment area and the

  16. Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO2 and contrasting site conditions

    NASA Astrophysics Data System (ADS)

    Grant, R. F.

    2013-04-01

    If increases in net primary productivity (NPP) caused by rising concentrations of atmospheric CO2 (Ca) are to be sustained, key N processes such as soil mineralization, biological fixation, root uptake and plant translocation must be hastened. Simulating the response of these processes to elevated Ca is therefore vital for models used to project the effects of rising Ca on NPP. In this modelling study, hypotheses are proposed for changes in soil mineralization, biological fixation, root uptake and plant translocation with changes in Ca. Algorithms developed from these hypotheses were tested in the ecosystem model ecosys against changes in N and C cycling measured over several years under ambient vs. elevatedCa in Free Air CO2 Enrichment (FACE) experiments at the Duke Forest in North Carolina, the Oak Ridge National Laboratory forest in Tennessee, and the USDA research forest in Wisconsin, USA. Simulating more rapid soil N mineralization was found to be vital for modelling sustained increases in NPP measured under elevated vs. ambient Ca at all three FACE sites. This simulation was accomplished by priming decomposition of N-rich humus from increases in microbial biomass generated by increased litterfall modelled under elevated Ca. Simulating more rapid nonsymbiotic N2 fixation, root N uptake and plant N translocation under elevated Ca was found to make much smaller contributions to modelled increases in NPP, although such contributions might be greater over longer periods and under more N-limited conditions than those simulated here. Greater increases in NPP with Ca were also modelled with increased temperature and water stress, and with coniferous vs. deciduous plant functional types. These increases were also associated with changes in N cycling.

  17. Testing 3D landform quantification methods with synthetic drumlins in a real digital elevation model

    NASA Astrophysics Data System (ADS)

    Hillier, John K.; Smith, Mike J.

    2012-06-01

    Metrics such as height and volume quantifying the 3D morphology of landforms are important observations that reflect and constrain Earth surface processes. Errors in such measurements are, however, poorly understood. A novel approach, using statistically valid ‘synthetic' landscapes to quantify the errors is presented. The utility of the approach is illustrated using a case study of 184 drumlins observed in Scotland as quantified from a Digital Elevation Model (DEM) by the ‘cookie cutter' extraction method. To create the synthetic DEMs, observed drumlins were removed from the measured DEM and replaced by elongate 3D Gaussian ones of equivalent dimensions positioned randomly with respect to the ‘noise' (e.g. trees) and regional trends (e.g. hills) that cause the errors. Then, errors in the cookie cutter extraction method were investigated by using it to quantify these ‘synthetic' drumlins, whose location and size is known. Thus, the approach determines which key metrics are recovered accurately. For example, mean height of 6.8 m is recovered poorly at 12.5 ± 0.6 (2σ) m, but mean volume is recovered correctly. Additionally, quantification methods can be compared: A variant on the cookie cutter using an un-tensioned spline induced about twice (× 1.79) as much error. Finally, a previously reportedly statistically significant (p = 0.007) difference in mean volume between sub-populations of different ages, which may reflect formational processes, is demonstrated to be only 30-50% likely to exist in reality. Critically, the synthetic DEMs are demonstrated to realistically model parameter recovery, primarily because they are still almost entirely the original landscape. Results are insensitive to the exact method used to create the synthetic DEMs, and the approach could be readily adapted to assess a variety of landforms (e.g. craters, dunes and volcanoes).

  18. Volcanic Plume Elevation Model Derived From Landsat 8: examples on Holuhraun (Iceland) and Mount Etna (Italy)

    NASA Astrophysics Data System (ADS)

    de Michele, Marcello; Raucoules, Daniel; Arason, Þórður; Spinetti, Claudia; Corradini, Stefano; Merucci, Luca

    2016-04-01

    The retrieval of both height and velocity of a volcanic plume is an important issue in volcanology. As an example, it is known that large volcanic eruptions can temporarily alter the climate, causing global cooling and shifting precipitation patterns; the ash/gas dispersion in the atmosphere, their impact and lifetime around the globe, greatly depends on the injection altitude. Plume height information is critical for ash dispersion modelling and air traffic security. Furthermore, plume height during explosive volcanism is the primary parameter for estimating mass eruption rate. Knowing the plume altitude is also important to get the correct amount of SO2 concentration from dedicated spaceborne spectrometers. Moreover, the distribution of ash deposits on ground greatly depends on the ash cloud altitude, which has an impact on risk assessment and crisis management. Furthermore, a spatially detailed plume height measure could be used as a hint for gas emission rate estimation and for ash plume volume researches, which both have an impact on climate research, air quality assessment for aviation and finally for the understanding of the volcanic system itself as ash/gas emission rates are related to the state of pressurization of the magmatic chamber. Today, the community mainly relies on ground based measurements but often they can be difficult to collect as by definition volcanic areas are dangerous areas (presence of toxic gases) and can be remotely situated and difficult to access. Satellite remote sensing offers a comprehensive and safe way to estimate plume height. Conventional photogrammetric restitution based on satellite imagery fails in precisely retrieving a plume elevation model as the plume own velocity induces an apparent parallax that adds up to the standard parallax given by the stereoscopic view. Therefore, measurements based on standard satellite photogrammeric restitution do not apply as there is an ambiguity in the measurement of the plume position

  19. Effects of elevated atmospheric carbon dioxide on biomass and carbon accumulation in a model regenerating longleaf pine community.

    PubMed

    Runion, G B; Davis, M A; Pritchard, S G; Prior, S A; Mitchell, R J; Torbert, H A; Rogers, H H; Dute, R R

    2006-01-01

    Plant species vary in response to atmospheric CO2 concentration due to differences in physiology, morphology, phenology, and symbiotic relationships. These differences make it very difficult to predict how plant communities will respond to elevated CO2. Such information is critical to furthering our understanding of community and ecosystem responses to global climate change. To determine how a simple plant community might respond to elevated CO2, a model regenerating longleaf pine community composed of five species was exposed to two CO2 regimes (ambient, 365 micromol mol(-1) and elevated, 720 micromol mol(-1)) for 3 yr. Total above- and belowground biomass was 70 and 49% greater, respectively, in CO2-enriched plots. Carbon (C) content followed a response pattern similar to biomass, resulting in a significant increase of 13.8 Mg C ha(-1) under elevated CO2. Responses of individual species, however, varied. Longleaf pine (Pinus palustris Mill.) was primarily responsible for the positive response to CO2 enrichment. Wiregrass (Aristida stricta Michx.), rattlebox (Crotalaria rotundifolia Walt. Ex Gmel.), and butterfly weed (Asclepias tuberosa L.) exhibited negative above- and belowground biomass responses to elevated CO2, while sand post oak (Quercus margaretta Ashe) did not differ significantly between CO2 treatments. As with pine, C content followed patterns similar to biomass. Elevated CO2 resulted in alterations in community structure. Longleaf pine comprised 88% of total biomass in CO2-enriched plots, but only 76% in ambient plots. In contrast, wiregrass, rattlebox, and butterfly weed comprised 19% in ambient CO2 plots, but only 8% under high CO2. Therefore, while longleaf pine may perform well in a high CO2 world, other members of this community may not compete as well, which could alter community function. Effects of elevated CO2 on plant communities are complex, dynamic, and difficult to predict, clearly demonstrating the need for more research in this

  20. Digital Elevation Models Aid the Analysis of Double Layered Ejecta (DLE) Impact Craters on Mars

    NASA Astrophysics Data System (ADS)

    Mouginis-Mark, P. J.; Boyce, J. M.; Garbeil, H.

    2014-12-01

    Considerable debate has recently taken place concerning the origin of the inner and outer ejecta layers of double layered ejecta (DLE) craters on Mars. For craters in the diameter range ~10 to ~25 km, the inner ejecta layer of DLE craters displays characteristic grooves extending from the rim crest, and has led investigators to propose three hypotheses for their formation: (1) deposition of the primary ejecta and subsequent surface scouring by either atmospheric vortices or a base surge; (2) emplacement through a landslide of the near-rim crest ejecta; and (3) instabilities (similar to Gortler vortices) generated by high flow-rate, and high granular temperatures. Critical to resolving between these models is the topographic expression of both the ejecta layer and the groove geometry. To address this problem, we have made several digital elevation models (DEMs) from CTX and HiRISE stereo pairs using the Ames Stereo Pipeline at scales of 24 m/pixel and 1 m/pixel, respectively. These DEMs allow several key observations to be made that bear directly upon the origin of the grooves associated with DLE craters: (1) Grooves formed on the sloping ejecta layer surfaces right up to the preserved crater rim; (2) There is clear evidence that grooves traverse the topographic boundary between the inner and outer ejecta layers; and (3) There are at least two different sets of radial grooves, with smaller grooves imprinted upon the larger grooves. There are "deep-wide" grooves that have a width of ~200 m and a depth of ~10 m, and there are "shallow-narrow" grooves with a width of <50 m and depth <5 m. These two scales of grooves are not consistent with their formation analogous to a landslide. Two different sets of grooves would imply that, simultaneously, two different depths to the flow would have to exist if the grooves were formed by shear within the flow, something that is not physically possible. All three observations can only be consistent with a model of groove formation

  1. Modelling changes in nitrogen cycling to sustain increases in forest productivity under elevated atmospheric CO2 and contrasting site conditions

    NASA Astrophysics Data System (ADS)

    Grant, R. F.

    2013-11-01

    If increases in net primary productivity (NPP) caused by rising concentrations of atmospheric CO2 (Ca) are to be sustained, key N processes such as soil mineralization, biological fixation, root uptake and nutrient conservation must also be increased. Simulating the response of these processes to elevated Ca is therefore vital for models used to project the effects of rising Ca on NPP. In this modelling study, hypotheses are proposed for changes in soil mineralization, biological fixation, root nutrient uptake and plant nutrient conservation with changes in Ca. Algorithms developed from these hypotheses were tested in the ecosystem model ecosys against changes in N and C cycling measured over several years under ambient vs. elevated Ca in Free Air CO2 Enrichment (FACE) experiments in the USA at the Duke Forest in North Carolina, the Oak Ridge National Laboratory forest in Tennessee, and the USDA research forest in Wisconsin. More rapid soil N mineralization was found to be vital for simulating sustained increases in NPP measured under elevated vs. ambient Ca at all three FACE sites. This simulation was accomplished by priming decomposition of N-rich humus from increases in microbial biomass generated by increased litterfall modelled under elevated Ca. Greater nonsymbiotic N2 fixation from increased litterfall, root N uptake from increased root growth, and plant N conservation from increased translocation under elevated Ca were found to make smaller contributions to simulated increases in NPP. However greater nutrient conservation enabled larger increases in NPP with Ca to be modelled with coniferous vs. deciduous plant functional types. The effects of these processes on productivity now need to be examined over longer periods under transient rises in Ca and a greater range of site conditions.

  2. The geometric signature: Quantifying landslide-terrain types from digital elevation models

    USGS Publications Warehouse

    Pike, R.J.

    1988-01-01

    Topography of various types and scales can be fingerprinted by computer analysis of altitude matrices (digital elevation models, or DEMs). The critical analytic tool is the geometric signature, a set of measures that describes topographic form well enough to distinguish among geomorphically disparate landscapes. Different surficial processes create topography with diagnostic forms that are recognizable in the field. The geometric signature abstracts those forms from contour maps or their DEMs and expresses them numerically. This multivariate characterization enables once-in-tractable problems to be addressed. The measures that constitute a geometric signature express different but complementary attributes of topographic form. Most parameters used here are statistical estimates of central tendency and dispersion for five major categories of terrain geometry; altitude, altitude variance spectrum, slope between slope reversals, and slope and its curvature at fixed slope lengths. As an experimental application of geometric signatures, two mapped terrain types associated with different processes of shallow landsliding in Marin County, California, were distinguished consistently by a 17-variable description of topography from 21??21 DEMs (30-m grid spacing). The small matrix is a statistical window that can be used to scan large DEMs by computer, thus potentially automating the mapping of contrasting terrain types. The two types in Marin County host either (1) slow slides: earth flows and slump-earth flows, or (2) rapid flows: debris avalanches and debris flows. The signature approach should adapt to terrain taxonomy and mapping in other areas, where conditions differ from those in Central California. ?? 1988 International Association for Mathematical Geology.

  3. A robust interpolation method for constructing digital elevation models from remote sensing data

    NASA Astrophysics Data System (ADS)

    Chen, Chuanfa; Liu, Fengying; Li, Yanyan; Yan, Changqing; Liu, Guolin

    2016-09-01

    A digital elevation model (DEM) derived from remote sensing data often suffers from outliers due to various reasons such as the physical limitation of sensors and low contrast of terrain textures. In order to reduce the effect of outliers on DEM construction, a robust algorithm of multiquadric (MQ) methodology based on M-estimators (MQ-M) was proposed. MQ-M adopts an adaptive weight function with three-parts. The weight function is null for large errors, one for small errors and quadric for others. A mathematical surface was employed to comparatively analyze the robustness of MQ-M, and its performance was compared with those of the classical MQ and a recently developed robust MQ method based on least absolute deviation (MQ-L). Numerical tests show that MQ-M is comparative to the classical MQ and superior to MQ-L when sample points follow normal and Laplace distributions, and under the presence of outliers the former is more accurate than the latter. A real-world example of DEM construction using stereo images indicates that compared with the classical interpolation methods, such as natural neighbor (NN), ordinary kriging (OK), ANUDEM, MQ-L and MQ, MQ-M has a better ability of preserving subtle terrain features. MQ-M replaces thin plate spline for reference DEM construction to assess the contribution to our recently developed multiresolution hierarchical classification method (MHC). Classifying the 15 groups of benchmark datasets provided by the ISPRS Commission demonstrates that MQ-M-based MHC is more accurate than MQ-L-based and TPS-based MHCs. MQ-M has high potential for DEM construction.

  4. Assessment of multiresolution segmentation for delimiting drumlins in digital elevation models

    NASA Astrophysics Data System (ADS)

    Eisank, Clemens; Smith, Mike; Hillier, John

    2014-06-01

    Mapping or "delimiting" landforms is one of geomorphology's primary tools. Computer-based techniques such as land-surface segmentation allow the emulation of the process of manual landform delineation. Land-surface segmentation exhaustively subdivides a digital elevation model (DEM) into morphometrically-homogeneous irregularly-shaped regions, called terrain segments. Terrain segments can be created from various land-surface parameters (LSP) at multiple scales, and may therefore potentially correspond to the spatial extents of landforms such as drumlins. However, this depends on the segmentation algorithm, the parameterization, and the LSPs. In the present study we assess the widely used multiresolution segmentation (MRS) algorithm for its potential in providing terrain segments which delimit drumlins. Supervised testing was based on five 5-m DEMs that represented a set of 173 synthetic drumlins at random but representative positions in the same landscape. Five LSPs were tested, and four variants were computed for each LSP to assess the impact of median filtering of DEMs, and logarithmic transformation of LSPs. The testing scheme (1) employs MRS to partition each LSP exhaustively into 200 coarser scales of terrain segments by increasing the scale parameter (SP), (2) identifies the spatially best matching terrain segment for each reference drumlin, and (3) computes four segmentation accuracy metrics for quantifying the overall spatial match between drumlin segments and reference drumlins. Results of 100 tests showed that MRS tends to perform best on LSPs that are regionally derived from filtered DEMs, and then log-transformed. MRS delineated 97% of the detected drumlins at SP values between 1 and 50. Drumlin delimitation rates with values up to 50% are in line with the success of manual interpretations. Synthetic DEMs are well-suited for assessing landform quantification methods such as MRS, since subjectivity in the reference data is avoided which increases the

  5. Assessment of multiresolution segmentation for delimiting drumlins in digital elevation models.

    PubMed

    Eisank, Clemens; Smith, Mike; Hillier, John

    2014-06-01

    Mapping or "delimiting" landforms is one of geomorphology's primary tools. Computer-based techniques such as land-surface segmentation allow the emulation of the process of manual landform delineation. Land-surface segmentation exhaustively subdivides a digital elevation model (DEM) into morphometrically-homogeneous irregularly-shaped regions, called terrain segments. Terrain segments can be created from various land-surface parameters (LSP) at multiple scales, and may therefore potentially correspond to the spatial extents of landforms such as drumlins. However, this depends on the segmentation algorithm, the parameterization, and the LSPs. In the present study we assess the widely used multiresolution segmentation (MRS) algorithm for its potential in providing terrain segments which delimit drumlins. Supervised testing was based on five 5-m DEMs that represented a set of 173 synthetic drumlins at random but representative positions in the same landscape. Five LSPs were tested, and four variants were computed for each LSP to assess the impact of median filtering of DEMs, and logarithmic transformation of LSPs. The testing scheme (1) employs MRS to partition each LSP exhaustively into 200 coarser scales of terrain segments by increasing the scale parameter (SP), (2) identifies the spatially best matching terrain segment for each reference drumlin, and (3) computes four segmentation accuracy metrics for quantifying the overall spatial match between drumlin segments and reference drumlins. Results of 100 tests showed that MRS tends to perform best on LSPs that are regionally derived from filtered DEMs, and then log-transformed. MRS delineated 97% of the detected drumlins at SP values between 1 and 50. Drumlin delimitation rates with values up to 50% are in line with the success of manual interpretations. Synthetic DEMs are well-suited for assessing landform quantification methods such as MRS, since subjectivity in the reference data is avoided which increases the

  6. Assessment of multiresolution segmentation for delimiting drumlins in digital elevation models

    PubMed Central

    Eisank, Clemens; Smith, Mike; Hillier, John

    2014-01-01

    Mapping or “delimiting” landforms is one of geomorphology's primary tools. Computer-based techniques such as land-surface segmentation allow the emulation of the process of manual landform delineation. Land-surface segmentation exhaustively subdivides a digital elevation model (DEM) into morphometrically-homogeneous irregularly-shaped regions, called terrain segments. Terrain segments can be created from various land-surface parameters (LSP) at multiple scales, and may therefore potentially correspond to the spatial extents of landforms such as drumlins. However, this depends on the segmentation algorithm, the parameterization, and the LSPs. In the present study we assess the widely used multiresolution segmentation (MRS) algorithm for its potential in providing terrain segments which delimit drumlins. Supervised testing was based on five 5-m DEMs that represented a set of 173 synthetic drumlins at random but representative positions in the same landscape. Five LSPs were tested, and four variants were computed for each LSP to assess the impact of median filtering of DEMs, and logarithmic transformation of LSPs. The testing scheme (1) employs MRS to partition each LSP exhaustively into 200 coarser scales of terrain segments by increasing the scale parameter (SP), (2) identifies the spatially best matching terrain segment for each reference drumlin, and (3) computes four segmentation accuracy metrics for quantifying the overall spatial match between drumlin segments and reference drumlins. Results of 100 tests showed that MRS tends to perform best on LSPs that are regionally derived from filtered DEMs, and then log-transformed. MRS delineated 97% of the detected drumlins at SP values between 1 and 50. Drumlin delimitation rates with values up to 50% are in line with the success of manual interpretations. Synthetic DEMs are well-suited for assessing landform quantification methods such as MRS, since subjectivity in the reference data is avoided which increases the

  7. Preparing for Volcanic Hazards: An Examination of Lahar Knowledge, Risk Perception, and Preparedness around Mount Baker and Glacier Peak, WA

    NASA Astrophysics Data System (ADS)

    Corwin, K.; Brand, B. D.

    2015-12-01

    As the number of people living at risk from volcanic hazards in the U.S. Pacific Northwest continues to rise, so does the need for improved hazard science, mitigation, and response planning. The effectiveness of these efforts relies not only on scientists and policymakers, but on individuals and their risk perception and preparedness levels. This study examines the individual knowledge, perception, and preparedness of over 500 survey respondents living or working within the lahar zones of Mount Baker and Glacier Peak volcanoes. We (1) explore the common disconnect between accurate risk perception and adequate preparedness; (2) determine how participation in hazard response planning influences knowledge, risk perception, and preparedness; and (3) assess the effectiveness of current lahar hazard maps for public risk communication. Results indicate that a disconnect exists between perception and preparedness for the majority of respondents. While 82% of respondents accurately anticipate that future volcanic hazards will impact the Skagit Valley, this knowledge fails to motivate increased preparedness. A majority of respondents also feel "very responsible" for their own protection and provision of resources during a hazardous event (83%) and believe they have the knowledge and skills necessary to respond effectively to such an event (56%); however, many of these individuals still do not adequately prepare. When asked what barriers prevent them from preparing, respondents primarily cite a lack of knowledge about relevant local hazards. Results show that participation in response-related activities—a commonly recommended solution to this disconnect—minimally influences preparedness. Additionally, although local hazard maps successfully communicate the primary hazard—97% of respondents recognize the lahar hazard—many individuals incorrectly interpret other important facets of the maps. Those who participate in response-related activities fail to understand these

  8. Swift snowmelt and floods (lahars) caused by great pyroclastic surge at Mount St Helens volcano, Washington, 18 May 1980

    USGS Publications Warehouse

    Waitt, R.B.

    1989-01-01

    The initial explosions at Mount St. Helens, Washington, on the moring of 18 May 1980 developed into a huge pyroclastic surge that generated catastrophic floods off the east and west flanks of the volcano. Near-source surge deposits on the east and west were lithic, sorted, lacking in accretionary lapilli and vesiculated ash, not plastered against upright obstacles, and hot enough to char wood - all attributes of dry pyroclastic surge. Material deposited at the surge base on steep slopes near the volcano transformed into high-concentration lithic pyroclastic flows whose deposits contain charred wood and other features indicating that these flows were hot and dry. Stratigraphy shows that even the tail of the surge had passed the east and west volcano flanks before the geomorphically distinct floods (lahars) arrived. This field evidence undermines hypotheses that the turbulent surge was itself wet and that its heavy components segregated out to transform directly into lahars. Nor is there evidence that meters-thick snow-slab avalanches intimately mixed with the surge to form the floods. The floods must have instead originated by swift snowmelt at the base of a hot and relatively dry turbulent surge. Impacting hot pyroclasts probably transferred downslope momentum to the snow surface and churned snow grains into the surge base. Melting snow and accumulating hot surge debris may have moved initially as thousands of small thin slushflows. As these flows removed the surface snow and pyroclasts, newly uncovered snow was partly melted by the turbulent surge base; this and accumulating hot surge debris in turn began flowing, a self-sustaining process feeding the initial flows. The flows thus grew swiftly over tens of seconds and united downslope into great slushy ejecta-laden sheetfloods. Gravity accelerated the floods to more than 100 km/h as they swept down and off the volcano flanks while the snow component melted to form great debris-rich floods (lahars) channeled into

  9. The 26 May 2006 magnitude 6.4 Yogyakarta earthquake south of Mt. Merapi volcano: Did lahar deposits amplify ground shaking and thus lead to the disaster?

    NASA Astrophysics Data System (ADS)

    Walter, T. R.; Wang, R.; Luehr, B.-G.; Wassermann, J.; Behr, Y.; Parolai, S.; Anggraini, A.; Günther, E.; Sobiesiak, M.; Grosser, H.; Wetzel, H.-U.; Milkereit, C.; Sri Brotopuspito, P. J. K.; Harjadi, P.; Zschau, J.

    2008-05-01

    Indonesia is repeatedly unsettled by severe volcano- and earthquake-related disasters, which are geologically coupled to the 5-7 cm/a tectonic convergence of the Australian plate beneath the Sunda Plate. On Saturday, 26 May 2006, the southern coast of central Java was struck by an earthquake at 2254 UTC in the Sultanate Yogyakarta. Although the magnitude reached only M w = 6.4, it left more than 6,000 fatalities and up to 1,000,000 homeless. The main disaster area was south of Mt. Merapi Volcano, located within a narrow topographic and structural depression along the Opak River. The earthquake disaster area within the depression is underlain by thick volcaniclastic deposits commonly derived in the form of lahars from Mt. Merapi Volcano, which had a major influence leading to the disaster. In order to more precisely understand this earthquake and its consequences, a 3-month aftershock measurement campaign was performed from May to August 2006. We here present the first location results, which suggest that the Yogyakarta earthquake occurred at 10-20 km distance east of the disaster area, outside of the topographic depression. Using simple model calculations taking material heterogeneity into account we illustrate how soft volcaniclastic deposits may locally amplify ground shaking at distance. As the high degree of observed damage may have been augmented by the seismic response of the volcaniclastic Mt. Merapi deposits, this work implies that the volcano had an indirect effect on the level of earthquake destruction.

  10. Variability in projected elevation dependent warming in boreal midlatitude winter in CMIP5 climate models and its potential drivers

    NASA Astrophysics Data System (ADS)

    Rangwala, Imtiaz; Sinsky, Eric; Miller, James R.

    2016-04-01

    The future rate of climate change in mountains has many potential human impacts, including those related to water resources, ecosystem services, and recreation. Analysis of the ensemble mean response of CMIP5 global climate models (GCMs) shows amplified warming in high elevation regions during the cold season in boreal midlatitudes. We examine how the twenty-first century elevation-dependent response in the daily minimum surface air temperature [d(ΔTmin)/dz] varies among 27 different GCMs during winter for the RCP 8.5 emissions scenario. The focus is on regions within the northern hemisphere mid-latitude band between 27.5°N and 40°N, which includes both the Rocky Mountains and the Tibetan Plateau/Himalayas. We find significant variability in d(ΔTmin)/dz among the individual models ranging from 0.16 °C/km (10th percentile) to 0.97 °C/km (90th percentile), although nearly all of the GCMs (24 out of 27) show a significant positive value for d(ΔTmin)/dz. To identify some of the important drivers associated with the variability in d(ΔTmin)/dz during winter, we evaluate the co-variance between d(ΔTmin)/dz and the differential response of elevation-based anomalies in different climate variables as well as the GCMs' spatial resolution, their global climate sensitivity, and their elevation-dependent free air temperature response. We find that d(ΔTmin)/dz has the strongest correlation with elevation-dependent increases in surface water vapor, followed by elevation-dependent decreases in surface albedo, and a weak positive correlation with the GCMs' free air temperature response.

  11. Mapping three-dimensional geological features from remotely-sensed images and digital elevation models

    NASA Astrophysics Data System (ADS)

    Morris, Kevin Peter

    Accurate mapping of geological structures is important in numerous applications, ranging from mineral exploration through to hydrogeological modelling. Remotely sensed data can provide synoptic views of study areas enabling mapping of geological units within the area. Structural information may be derived from such data using standard manual photo-geologic interpretation techniques, although these are often inaccurate and incomplete. The aim of this thesis is, therefore, to compile a suite of automated and interactive computer-based analysis routines, designed to help a the user map geological structure. These are examined and integrated in the context of an expert system. The data used in this study include Digital Elevation Model (DEM) and Airborne Thematic Mapper images, both with a spatial resolution of 5m, for a 5 x 5 km area surrounding Llyn Cow lyd, Snowdonia, North Wales. The geology of this area comprises folded and faulted Ordo vician sediments intruded throughout by dolerite sills, providing a stringent test for the automated and semi-automated procedures. The DEM is used to highlight geomorphological features which may represent surface expressions of the sub-surface geology. The DEM is created from digitized contours, for which kriging is found to provide the best interpolation routine, based on a number of quantitative measures. Lambertian shading and the creation of slope and change of slope datasets are shown to provide the most successful enhancement of DEMs, in terms of highlighting a range of key geomorphological features. The digital image data are used to identify rock outcrops as well as lithologically controlled features in the land cover. To this end, a series of standard spectral enhancements of the images is examined. In this respect, the least correlated 3 band composite and a principal component composite are shown to give the best visual discrimination of geological and vegetation cover types. Automatic edge detection (followed by line

  12. The dark phase intraocular pressure elevation and retinal ganglion cell degeneration in a rat model of experimental glaucoma.

    PubMed

    Kwong, Jacky M K; Vo, Nancy; Quan, Ann; Nam, Michael; Kyung, Haksu; Yu, Fei; Piri, Natik; Caprioli, Joseph

    2013-07-01

    Intraocular pressure (IOP) elevation is considered as a major risk factor causing the progression of vision deterioration in glaucoma. Although it is known that the IOP level changes widely throughout the day and night, how the dark or light phase IOP elevation contributes to retinal ganglion cell (RGC) degeneration is still largely unclear. To examine the profile of IOP, modified laser photocoagulation was applied to the trabecular meshwork of Brown Norway rats and both light and dark phase IOPs were monitored approximately 1-2 times a week. The relationship between IOP elevation and RGC degeneration was investigated while RGC body loss was analyzed with Rbpms immunolabeling on retinal wholemount and axonal injury in the optic nerve was semi-quantified. The baseline awake dark and light IOPs were 30.4 ± 2.7 and 20.2 ± 2.1 mmHg respectively. The average dark IOP was increased to 38.2 ± 3.2 mmHg for five weeks after the laser treatment on 270° trabecular meshwork. However, there was no significant loss of RGC body and axonal injury. After laser treatment on 330° trabecular meshwork, the dark and light IOPs were significantly increased to 43.8 ± 4.6 and 23 ± 3.7 mmHg respectively for 5 weeks. The cumulative dark and light IOP elevations were 277 ± 86 and 113 ± 50 mmHg days respectively while the cumulative total (light and dark) IOP elevation was 213 ± 114 mmHg days. After 5 weeks, regional RGC body loss of 29.5 ± 15.5% and moderate axonal injury were observed. Axonal injury and loss of RGC body had a high correlation with the cumulative total IOP elevation (R(2) = 0.60 and 0.65 respectively). There was an association between the cumulative dark IOP elevation and RGC body loss (R(2) = 0.37) and axonal injury (R(2) = 0.51) whereas the associations between neuronal damages and the cumulative light IOP elevation were weak (for RGC body loss, R(2) = 0.01; for axonal injury, R(2) = 0.26). Simple linear regression model

  13. Combining criteria for delineating lahar- and flash-flood-prone hazard and risk zones for the city of Arequipa, Peru

    NASA Astrophysics Data System (ADS)

    Thouret, J.-C.; Enjolras, G.; Martelli, K.; Santoni, O.; Luque, J. A.; Nagata, M.; Arguedas, A.; Macedo, L.

    2013-02-01

    Arequipa, the second largest city in Peru, is exposed to many natural hazards, most notably earthquakes, volcanic eruptions, landslides, lahars (volcanic debris flows), and flash floods. Of these, lahars and flash floods, triggered by occasional torrential rainfall, pose the most frequently occurring hazards that can affect the city and its environs, in particular the areas containing low-income neighbourhoods. This paper presents and discusses criteria for delineating areas prone to flash flood and lahar hazards, which are localized along the usually dry (except for the rainy season) ravines and channels of the Río Chili and its tributaries that dissect the city. Our risk-evaluation study is based mostly on field surveys and mapping, but we also took into account quality and structural integrity of buildings, available socio-economic data, and information gained from interviews with risk-managers officials. In our evaluation of the vulnerability of various parts of the city, in addition to geological and physical parameters, we also took into account selected socio-economic parameters, such as the educational and poverty level of the population, unemployment figures, and population density. In addition, we utilized a criterion of the "isolation factor", based on distances to access emergency resources (hospitals, shelters or safety areas, and water) in each city block. By combining the hazard, vulnerability and exposure criteria, we produced detailed risk-zone maps at the city-block scale, covering the whole city of Arequipa and adjacent suburbs. Not surprisingly, these maps show that the areas at high risk coincide with blocks or districts with populations at low socio-economic levels. Inhabitants at greatest risk are the poor recent immigrants from rural areas who live in unauthorized settlements in the outskirts of the city in the upper parts of the valleys. Such settlements are highly exposed to natural hazards and have little access to vital resources. Our

  14. The effects of digital elevation model resolution on the calculation and predictions of topographic wetness indices.

    SciTech Connect

    Drover, Damion, Ryan

    2011-12-01

    One of the largest exports in the Southeast U.S. is forest products. Interest in biofuels using forest biomass has increased recently, leading to more research into better forest management BMPs. The USDA Forest Service, along with the Oak Ridge National Laboratory, University of Georgia and Oregon State University are researching the impacts of intensive forest management for biofuels on water quality and quantity at the Savannah River Site in South Carolina. Surface runoff of saturated areas, transporting excess nutrients and contaminants, is a potential water quality issue under investigation. Detailed maps of variable source areas and soil characteristics would therefore be helpful prior to treatment. The availability of remotely sensed and computed digital elevation models (DEMs) and spatial analysis tools make it easy to calculate terrain attributes. These terrain attributes can be used in models to predict saturated areas or other attributes in the landscape. With laser altimetry, an area can be flown to produce very high resolution data, and the resulting data can be resampled into any resolution of DEM desired. Additionally, there exist many maps that are in various resolutions of DEM, such as those acquired from the U.S. Geological Survey. Problems arise when using maps derived from different resolution DEMs. For example, saturated areas can be under or overestimated depending on the resolution used. The purpose of this study was to examine the effects of DEM resolution on the calculation of topographic wetness indices used to predict variable source areas of saturation, and to find the best resolutions to produce prediction maps of soil attributes like nitrogen, carbon, bulk density and soil texture for low-relief, humid-temperate forested hillslopes. Topographic wetness indices were calculated based on the derived terrain attributes, slope and specific catchment area, from five different DEM resolutions. The DEMs were resampled from LiDAR, which is a

  15. Stable isotopes and Digital Elevation Models to study nutrient inputs in high-Arctic lakes

    NASA Astrophysics Data System (ADS)

    Calizza, Edoardo; Rossi, David; Costantini, Maria Letizia; Careddu, Giulio; Rossi, Loreto

    2016-04-01

    Ice cover, run-off from the watershed, aquatic and terrestrial primary productivity, guano deposition from birds are key factors controlling nutrient and organic matter inputs in high-Arctic lakes. All these factors are expected to be significantly affected by climate change. Quantifying these controls is a key baseline step to understand what combination of factors subtends the biological productivity in Arctic lakes and will drive their ecological response to environmental change. Basing on Digital Elevation Models, drainage maps, and C and N elemental content and stable isotope analysis in sediments, aquatic vegetation and a dominant macroinvertebrate species (Lepidurus arcticus Pallas 1973) belonging to Tvillingvatnet, Storvatnet and Kolhamna, three lakes located in North Spitsbergen (Svalbard), we propose an integrated approach for the analysis of (i) nutrient and organic matter inputs in lakes; (ii) the role of catchment hydro-geomorphology in determining inter-lake differences in the isotopic composition of sediments; (iii) effects of diverse nutrient inputs on the isotopic niche of Lepidurus arcticus. Given its high run-off and large catchment, organic deposits in Tvillingvatnet where dominated by terrestrial inputs, whereas inputs were mainly of aquatic origin in Storvatnet, a lowland lake with low potential run-off. In Kolhamna, organic deposits seem to be dominated by inputs from birds, which actually colonise the area. Isotopic signatures were similar between samples within each lake, representing precise tracers for studies on the effect of climate change on biogeochemical cycles in lakes. The isotopic niche of L. aricticus reflected differences in sediments between lakes, suggesting a bottom-up effect of hydro-geomorphology characterizing each lake on nutrients assimilated by this species. The presented approach proven to be an effective research pathway for the identification of factors subtending to nutrient and organic matter inputs and transfer

  16. Calibration of Watershed Lag Time Equation for Philippine Hydrology using RADARSAT Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Cipriano, F. R.; Lagmay, A. M. A.; Horritt, M.; Mendoza, J.; Sabio, G.; Punay, K. N.; Taniza, H. J.; Uichanco, C.

    2015-12-01

    Widespread flooding is a major problem in the Philippines. The country experiences heavy amount of rainfall throughout the year and several areas are prone to flood hazards because of its unique topography. Human casualties and destruction of infrastructure are just some of the damages caused by flooding and the Philippine government has undertaken various efforts to mitigate these hazards. One of the solutions was to create flood hazard maps of different floodplains and use them to predict the possible catastrophic results of different rain scenarios. To produce these maps with accurate output, different input parameters were needed and one of those is calculating hydrological components from topographical data. This paper presents how a calibrated lag time (TL) equation was obtained using measurable catchment parameters. Lag time is an essential input in flood mapping and is defined as the duration between the peak rainfall and peak discharge of the watershed. The lag time equation involves three measurable parameters, namely, watershed length (L), maximum potential retention (S) derived from the curve number, and watershed slope (Y), all of which were available from RADARSAT Digital Elevation Models (DEM). This approach was based on a similar method developed by CH2M Hill and Horritt for Taiwan, which has a similar set of meteorological and hydrological parameters with the Philippines. Rainfall data from fourteen water level sensors covering 67 storms from all the regions in the country were used to estimate the actual lag time. These sensors were chosen by using a screening process that considers the distance of the sensors from the sea, the availability of recorded data, and the catchment size. The actual lag time values were plotted against the values obtained from the Natural Resource Conservation Management handbook lag time equation. Regression analysis was used to obtain the final calibrated equation that would be used to calculate the lag time

  17. High-resolution digital elevation models of the Flade Iceblink feature in NE Greenland

    NASA Astrophysics Data System (ADS)

    Willis, M. J.; Juntunen, T.; Porter, C. C.; Morin, P. J.

    2013-12-01

    We produce a time series of high-resolution digital elevation models (DEM) to examine the recent evolution of an 8.7 km2 sub-glacial lake collapse feature near the southern summit of the 8500 km2 Flade Isblink Ice Cap (FIIC) in northeastern Greenland [Figure 1]. Visible imagery from the MODerate-resolution Imaging Spectroradiometer (MODIS) indicates the collapse occurred between August 16th and September 6th, 2011 at the site of a recurring moulin. DEMs are extracted using the NASA Ames Stereo Pipeline for the period between June 2012 and late 2013 from 0.5 m resolution along-track stereo image pairs available via the NGA commercial imagery program. The DEMs are compared to a 1996 ERS InSAR derived DEM [Palmer et al., 2010], and to a contemporary airborne laser altimeter swath flown by NASA Icebridge in mid-April 2013 to derive the volume of the feature and the uncertainties on the high-resolution DEMs. The 'mitten' shaped feature is bounded by crevasses on three sides, with a shallow ramp to the south. It is ~70 m deep, 3.7 km north-to-south and 3 km east-to-west and has a volume of ~0.3 km3. Ice penetrating radar from a nearby Icebridge mission in May 2011, indicates the ice is approximately 550 m thick and that the bed is very flat and smooth about 1 km to the southeast of the feature. The nearby bed topography, local geology and lack of recorded seismicity in the area indicate it is unlikely that the feature is the result of either subglacial volcanic activity or the collapse of a limestone karst feature below the ice cap - the neighboring Princess Elizabeth Alps are composed of 420 Ma Caledonide fold belt gneisses. The presence of recurring supraglacial meltwater streams and drainage into the feature, its rapid formation and its steep sided nature instead suggest that it formed during the rapid drainage of a sub-glacial lake - which is, as far as we are aware, the first recorded instance of such an occurrence in Greenland. Meltwater observed using 250 m

  18. Insights from Thermo-Mechanically Coupled Modeling of High-Elevation Regions of the Greenland Ice Sheet

    NASA Astrophysics Data System (ADS)

    Sommers, A. N.; Rajaram, H.; Colgan, W. T.

    2014-12-01

    As observations become more plentiful through remote sensing and numerical models become increasingly sophisticated, a clear priority of the ice sheet modeling community is to compare model simulations with observations. Temperature and velocity conditions within the Greenland ice sheet and at the bed remain largely unknown with the exception of sparse borehole measurements, but much can be inferred from rigorous thermo-mechanically coupled modeling. Surface velocities on the Greenland ice sheet are well constrained, both from satellite imagery and field observations. We take advantage of the observed surface velocities at the PARCA stakes around the 2,000m elevation contour of the ice sheet as modeling targets that represent a broad range of flow characteristics in different regions. Prescribing ice geometry, we use a two-dimensional thermo-mechanically coupled model to calculate 'steady-state' velocity and temperature profiles throughout the depth of the ice along flowlines from the main divide to the 2,000m elevation contour. Vertical velocity calculations are based on first principles of mass conservation, accounting for convergence and divergence of the streamtube width, and the enthalpy-based temperature calculations also incorporate the effects of liquid water content in temperate ice through the flow law parameter. Numerous insights from our simulations are presented for different regions, such as the influence of variable geothermal heat flux, the treatment of basal boundary conditions, and appropriate enhancement factors based on the age of ice. Results indicate that areas of temperate bed do exist in the high-elevation interior in certain sections of Greenland. Also highlighted is the importance of including temperature calculations in ice sheet modeling, particularly in regions with a temperate bed. For example, on the west coast, computations assuming a constant temperature of -5°C result in a 41% underestimation of the surface velocity at the 2,000m

  19. Meteorological conditions associated to high sublimation amounts in semiarid high-elevation Andes decrease the performance of empirical melt models

    NASA Astrophysics Data System (ADS)

    Ayala, Alvaro; Pellicciotti, Francesca; MacDonell, Shelley; McPhee, James; Burlando, Paolo

    2015-04-01

    Empirical melt (EM) models are often preferred to surface energy balance (SEB) models to calculate melt amounts of snow and ice in hydrological modelling of high-elevation catchments. The most common reasons to support this decision are that, in comparison to SEB models, EM models require lower levels of meteorological data, complexity and computational costs. However, EM models assume that melt can be characterized by means of a few index variables only, and their results strongly depend on the transferability in space and time of the calibrated empirical parameters. In addition, they are intrinsically limited in accounting for specific process components, the complexity of which cannot be easily reconciled with the empirical nature of the model. As an example of an EM model, in this study we use the Enhanced Temperature Index (ETI) model, which calculates melt amounts using air temperature and the shortwave radiation balance as index variables. We evaluate the performance of the ETI model on dry high-elevation sites where sublimation amounts - that are not explicitly accounted for the EM model - represent a relevant percentage of total ablation (1.1 to 8.7%). We analyse a data set of four Automatic Weather Stations (AWS), which were collected during the ablation season 2013-14, at elevations between 3466 and 4775 m asl, on the glaciers El Tapado, San Francisco, Bello and El Yeso, which are located in the semiarid Andes of central Chile. We complement our analysis using data from past studies in Juncal Norte Glacier (Chile) and Haut Glacier d'Arolla (Switzerland), during the ablation seasons 2008-09 and 2006, respectively. We use the results of a SEB model, applied to each study site, along the entire season, to calibrate the ETI model. The ETI model was not designed to calculate sublimation amounts, however, results show that their ability is low also to simulate melt amounts at sites where sublimation represents larger percentages of total ablation. In fact, we

  20. Digital Elevation Model (DEM) file of topographic elevations for the Death Valley region of southern Nevada and southeastern California processed from US Geological Survey 1-degree Digital Elevation Model data files

    SciTech Connect

    Turner, A.K.; D`Agnese, F.A.; Faunt, C.C.

    1996-04-01

    Elevation data have been compiled into a digital data base for an {approx}100,000-km{sup 2} area of the southern Great Basin, the Death Valley region of southern Nevada, and SE Calif., located between lat 35{degree}N, long 115{degree}W, and lat 38{degree}N, long 118{degree}W. This region includes the Nevada Test Site, Yucca Mountain, and adjacent parts of southern Nevada and eastern California and encompasses the Death Valley regional ground-water system. Because digital maps are often useful for applications other than that for which they were originally intended, and because the area corresponds to a region under continuing investigation by several groups, these digital files are being released by USGS.

  1. Quaternary over-elevated torrential channels. Characteristics and depositional significance: the Maresme model (Catalonia, NE Spain)

    NASA Astrophysics Data System (ADS)

    Colombo, Ferran; Rivero, Lluis

    2017-02-01

    Channel-levee deposits that occur in some large sand-dominated fluvial systems are commonly elevated above the surrounding floodplain. However, the over-elevation processes of small and isolated fluvial channels are poorly documented. The Maresme zone located NE of Barcelona (Spain) offers many examples of small over-elevated channels. This area is characterised by weathered granodiorites forming a thick coarse-grained sand-dominated regolith, which was initially covered by dense forests. In the XVIII and XIX centuries human activity led to the destruction of the vegetal cover, resulting in subsequent erosion and in the intense remobilisation of sediments during storms. Thus, large amounts of sand were transported during historical times. The intermittent discharges were confined to short (few km) and straight channels with high and uncommon gradients from 3.2 to 3.4%. These discharges flowed at high velocities towards the Mediterranean Sea, the regional base-level. High infiltration rates contributed to the accretion of sandy sediments along the channels coevally with levee development. This sandy lithosome, which is usually elevated above the surrounding floodplain, displays a characteristic convex-up cross section.

  2. Geomorphic Map of Worcester County, Maryland, Interpreted from a LIDAR-Based, Digital Elevation Model

    USGS Publications Warehouse

    Newell, Wayne L.; Clark, Inga

    2008-01-01

    A recently compiled mosaic of a LIDAR-based digital elevation model (DEM) is presented with geomorphic analysis of new macro-topographic details. The geologic framework of the surficial and near surface late Cenozoic deposits of the central uplands, Pocomoke River valley, and the Atlantic Coast includes Cenozoic to recent sediments from fluvial, estuarine, and littoral depositional environments. Extensive Pleistocene (cold climate) sandy dune fields are deposited over much of the terraced landscape. The macro details from the LIDAR image reveal 2 meter-scale resolution of details of the shapes of individual dunes, and fields of translocated sand sheets. Most terrace surfaces are overprinted with circular to elliptical rimmed basins that represent complex histories of ephemeral ponds that were formed, drained, and overprinted by younger basins. The terrains of composite ephemeral ponds and the dune fields are inter-shingled at their margins indicating contemporaneous erosion, deposition, and re-arrangement and possible internal deformation of the surficial deposits. The aggregate of these landform details and their deposits are interpreted as the products of arid, cold climate processes that were common to the mid-Atlantic region during the Last Glacial Maximum. In the Pocomoke valley and its larger tributaries, erosional remnants of sandy flood plains with anastomosing channels indicate the dynamics of former hydrology and sediment load of the watershed that prevailed at the end of the Pleistocene. As the climate warmed and precipitation increased during the transition from late Pleistocene to Holocene, dune fields were stabilized by vegetation, and the stream discharge increased. The increased discharge and greater local relief of streams graded to lower sea levels stimulated down cutting and created the deeply incised valleys out onto the continental shelf. These incised valleys have been filling with fluvial to intertidal deposits that record the rising sea

  3. Rockfall susceptibility mapping of Yosemite Valley (USA) using a high-resolution digital elevation model

    NASA Astrophysics Data System (ADS)

    Pannatier, A.; Oppikofer, T.; Jaboyedoff, M.; Stock, G. M.

    2009-04-01

    In Yosemite National Park (California, USA) rockfalls from the steep valley flanks are frequent (>600 documented events in 150 years) and threaten infrastructure in this popular tourist area. This study focuses on a methodology to map the susceptibility to rockfall initiation based on a high-resolution digital elevation model (HRDEM) obtained from aerial laser scanning (1 meter cell size). This methodology is based on geometric factors derived from the HRDEM, i.e., the steepness of the topography, the presence of joints or fractures enabling either a planar or a wedge failure mechanism, and a high denudation potential. The slope angle histogram computed using standard GIS routines was simulated using Gaussian distributions, which were attributed to different parts of the topography, i.e., the cliffs, the valley flanks and the valley floor. Slopes steeper than 36° are found to form cliffs and thus potentially lead to rockfalls. A morpho-structural analysis of the HRDEM was performed in Coltop3D software to determine the major discontinuity sets that shape the topography. Kinematic analyses were made for each of these 7 discontinuity sets in order to determine the HRDEM cells that fulfil the geometric criteria for a planar or wedge failure mechanism. Most of the cliffs in Yosemite Valley enable one or both of these failure mechanisms. The denudation potential was assessed using the sloping local base level (SLBL) concept. The SLBL defines a basal erosion surface and the above lying rock masses (up to 400 m in some of the vertical cliffs) are susceptible to erosion by mass wasting. A thickness of 20 m above the SLBL surface was chosen as lower limit for the denudation potential criterion. The HRDEM cells that satisfy 1, 2 or all 3 criteria are considered having low, moderate and high susceptibility to rockfall initiation. The areas with highest susceptibility (El Capitan, Glacier Point, Yosemite Falls and Half Dome) coincide well with post-glacial talus accumulations

  4. Synergetic merging of Cartosat-1 and RAMP to generate improved digital elevation model of Schirmacher oasis, east Antarctica

    NASA Astrophysics Data System (ADS)

    Jawak, S. D.; Luis, A. J.

    2014-11-01

    Available digital elevation models (DEMs) of Antarctic region generated by using radar altimetry and the Antarctic digital database (ADD) indicate elevation variations of up to hundreds of meters, which necessitates the generation of local DEM and its validation by using ground reference. An enhanced digital elevation model (eDEM) of the Schirmacher oasis region, east Antarctica, is generated synergistically by using Cartosat-1 stereo pair-derived photogrammetric DEM (CartoDEM)-based point elevation dataset and multitemporal radarsat Antarctic mapping project version 2 (RAMPv2) DEM-based point elevation dataset. In this study, we analyzed suite of interpolation techniques for constructing a DEM from RAMPv2 and CartoDEM-based point elevation datasets, in order to determine the level of confidence with which the interpolation techniques can generate a better interpolated continuous surface, and eventually improves the elevation accuracy of DEM from synergistically fused RAMPv2 and CartoDEM point elevation datasets. RAMPv2 points and CartoDEM points were used as primary data for various interpolation techniques such as ordinary kriging (OK), simple kriging (SK), universal kriging (UK), disjunctive kriging (DK) techniques, inverse distance weighted (IDW), global polynomial (GP) with power 1 and 2, local polynomial (LP) and radial basis functions (RBF). Cokriging of 2 variables with second dataset was used for ordinary cokriging (OCoK), simple cokriging (SCoK), universal cokriging (UCoK) and disjunctive cokriging (DCoK). The IDW, GP, LP, RBF, and kriging methods were applied to one variable, while Cokriging experiments were employed on two variables. The experiment of dataset and its combination produced two types of point elevation map categorized as (1) one variable (RAMPv2 Point maps and CartoDEM Point maps) and (2) two variables (RAMPv2 Point maps + CartoDEM Point maps). Interpolated surfaces were evaluated with the help of differential global positioning system

  5. Combining MESSENGER Data in Production and Analysis of Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Becker, K. J.; Howington-Kraus, E.; Thomas, O. H.; Neumann, G. A.; Mazarico, E.; Kirk, R. L.; Weller, L. A.; Edmundson, K. L.; Stephens, J. S.; Sawyers, R. J.; Robinson, M. S.; Solomon, S. C.

    2012-12-01

    The U.S. Geological Survey is combining image and laser altimetry data of Mercury acquired from instruments on the MESSENGER [1] spacecraft for the production and analysis of digital elevation models (DEMs). Precise image measurements that tie Mercury Laser Altimeter (MLA) [2] point data to Mercury Dual Imaging System (MDIS) [3] stereo pairs are obtained using the SOCET SET (®BAE Systems) digital photogrammetry software suite. These measurements will be added to existing Integrated Software for Imagers and Spectrometers [4] control networks used to produce global cartographic basemaps and a global DEM [5]. The MLA points serve as three-dimensional control points in a least-squares bundle adjustment [6] that improves image attitude and/or position parameters and generates improved triangulated ground coordinates for all tie and control points. The resulting point cloud is used to create an updated global DEM controlled to the MLA data. The MLA-to-MDIS image comparison also provides the boresight relationship between the two instruments. For quality assurance, several regional DEMs are created with SOCET SET for selected sites on Mercury that provide variation in terrain and observation conditions. These sites are used in the analysis and comparison of DEMs produced with a variety of methods and data sources (photogrammetry, photoclinometry, stereo techniques, and MLA), similar to comparisons that have been done for HRSC [7] and LRO [8] DEMs. Ultimately orthorectified cartographic products will be created by projecting MDIS images using the highest quality shape model available. [1] Solomon, S.C. et al., 2001. The MESSENGER mission to Mercury: Scientific objectives and implementation, Planet. Space Sci., 49, 1445-1465. [2] Zuber, M.T. et al., 2011. Orbital observations of Mercury with the Mercury Laser Altimeter, EPSC-DPS Joint Meeting, 6, abstract EPSC-DPS2011-278. [3] Hawkins, S.E. III et al., 2007. The Mercury Dual Imaging System on the MESSENGER spacecraft

  6. The use of UAV to document sloping landscapes to produce digital elevation models to examine environmental degradation

    NASA Astrophysics Data System (ADS)

    Themistocleous, K.; Agapiou, A.; Papadavid, G.; Christoforou, M.; Hadjimitsis, D. G.

    2015-10-01

    This paper focuses on the use of Unmanned Aerial Vehicles (UAVs) over the study area of Pissouri in Cyprus to document the sloping landscapes of the area. The study area has been affected by overgrazing, which has led to shifts in the vegetation patterns and changing microtopography of the soil. The UAV images were used to generate digital elevation models (DEMs) to examine the changes in microtopography. Next to that orthophotos were used to detect changes in vegetation patterns. The combined data of the digital elevation models and the orthophotos will be used to detect the occurrence of catastrophic shifts and mechanisms for desertification in the study area due to overgrazing. This study is part of the "CASCADE- Catastrophic shifts in dryland" project.

  7. Evolution and challenges of dynamic global vegetation models for some aspects of plant physiology and elevated atmospheric CO2.

    PubMed

    Rezende, L F C; Arenque, B C; Aidar, S T; Moura, M S B; Von Randow, C; Tourigny, E; Menezes, R S C; Ometto, J P H B

    2016-07-01

    Dynamic global vegetation models (DGVMs) simulate surface processes such as the transfer of energy, water, CO2, and momentum between the terrestrial surface and the atmosphere, biogeochemical cycles, carbon assimilation by vegetation, phenology, and land use change in scenarios of varying atmospheric CO2 concentrations. DGVMs increase the complexity and the Earth system representation when they are coupled with atmospheric global circulation models (AGCMs) or climate models. However, plant physiological processes are still a major source of uncertainty in DGVMs. The maximum velocity of carboxylation (Vcmax), for example, has a direct impact over productivity in the models. This parameter is often underestimated or imprecisely defined for the various plant functional types (PFTs) and ecosystems. Vcmax is directly related to photosynthesis acclimation (loss of response to elevated CO2), a widely known phenomenon that usually occurs when plants are subjected to elevated atmospheric CO2 and might affect productivity estimation in DGVMs. Despite this, current models have improved substantially, compared to earlier models which had a rudimentary and very simple representation of vegetation-atmosphere interactions. In this paper, we describe this evolution through generations of models and the main events that contributed to their improvements until the current state-of-the-art class of models. Also, we describe some main challenges for further improvements to DGVMs.

  8. Evolution and challenges of dynamic global vegetation models for some aspects of plant physiology and elevated atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Rezende, L. F. C.; Arenque, B. C.; Aidar, S. T.; Moura, M. S. B.; Von Randow, C.; Tourigny, E.; Menezes, R. S. C.; Ometto, J. P. H. B.

    2016-07-01

    Dynamic global vegetation models (DGVMs) simulate surface processes such as the transfer of energy, water, CO2, and momentum between the terrestrial surface and the atmosphere, biogeochemical cycles, carbon assimilation by vegetation, phenology, and land use change in scenarios of varying atmospheric CO2 concentrations. DGVMs increase the complexity and the Earth system representation when they are coupled with atmospheric global circulation models (AGCMs) or climate models. However, plant physiological processes are still a major source of uncertainty in DGVMs. The maximum velocity of carboxylation (Vcmax), for example, has a direct impact over productivity in the models. This parameter is often underestimated or imprecisely defined for the various plant functional types (PFTs) and ecosystems. Vcmax is directly related to photosynthesis acclimation (loss of response to elevated CO2), a widely known phenomenon that usually occurs when plants are subjected to elevated atmospheric CO2 and might affect productivity estimation in DGVMs. Despite this, current models have improved substantially, compared to earlier models which had a rudimentary and very simple representation of vegetation-atmosphere interactions. In this paper, we describe this evolution through generations of models and the main events that contributed to their improvements until the current state-of-the-art class of models. Also, we describe some main challenges for further improvements to DGVMs.

  9. Dietary phosphate restriction suppresses phosphaturia but does not prevent FGF23 elevation in a mouse model of chronic kidney disease.

    PubMed

    Zhang, Shiqin; Gillihan, Ryan; He, Nan; Fields, Timothy; Liu, Shiguang; Green, Troy; Stubbs, Jason R

    2013-10-01

    Fibroblast growth factor 23 (FGF23) is a phosphaturic hormone that in end-stage renal disease is markedly increased in serum; however, the mechanisms responsible for this increase are unclear. Here, we tested whether phosphate retention in chronic kidney disease (CKD) is responsible for the elevation of FGF23 in serum using Col4α3 knockout mice, a murine model of Alport disease exhibiting CKD. We found a significant elevation in serum FGF23 in progressively azotemic 8- and 12-week-old CKD mice along with an increased fractional excretion of phosphorus. Both moderate and severe phosphate restriction reduced fractional excretion of phosphorus by 8 weeks, yet serum FGF23 levels remained strikingly elevated. By 12 weeks, FGF23 levels were further increased with moderate phosphate restriction, while severe phosphate restriction led to severe bone mineralization defects and decreased FGF23 production in bone. CKD mice on a control diet had low serum 1,25-dihydroxyvitamin D (1,25(OH)(2)D) levels and 3-fold higher renal Cyp24α1 gene expression compared to wild-type mice. Severe phosphate restriction increased 1,25(OH)(2)D levels in CKD mice by 8 weeks and lowered renal Cyp24α1 gene expression despite persistently elevated serum FGF23. Renal klotho gene expression declined in CKD mice on a control diet, but improved with severe phosphate restriction. Thus, dietary phosphate restriction reduces the fractional excretion of phosphorus independent of serum FGF23 levels in mice with CKD.

  10. Behavioral validation of the elevated T-maze, a new animal model of anxiety.

    PubMed

    Zangrossi, H; Graeff, F G

    1997-01-01

    The elevated T-maze test of anxiety has been used to separate in the same rat conditioned from unconditioned responses of fear/anxiety. The test apparatus consists of three elevated arms-one enclosed and two open. Inhibitory avoidance--representing learned fear--is measured by recording the time taken to leave the enclosed arm in three consecutive trials. Unconditioned fear is evaluated by recording the time to escape from the open arm. In this study we investigated procedural questions raised by the use of the elevated T-maze. Experiment 1 showed that restraining the animals at the end of the enclosed arm for 30 s did not change the first (baseline) latency to leave this arm, indicating that aversion for the hands of the experimenter is not a key motivation for this response. The results of Experiment 2 indicated that open-arm experience, but not handling stress is the main cause for inhibitory avoidance acquisition, because rats trained in a T-maze with the three arms enclosed did not show the usual increase in withdrawal latency along the three consecutive trials. The same experiment also showed that the latency to leave the open arm did not undergo habituation over five consecutive trials, evidencing an aversive motivation for this response. The importance of open-arm experience for inhibitory avoidance acquisition was further suggested by the results of Experiment 3, as the removal of a shield that prevents perception of openness tended to increase avoidance latency in the elevated T-maze from the first trial.

  11. A computational model for exploratory activity of rats with different anxiety levels in elevated plus-maze.

    PubMed

    Costa, Ariadne A; Morato, Silvio; Roque, Antonio C; Tinós, Renato

    2014-10-30

    The elevated plus-maze is an apparatus widely used to study the level of anxiety in rodents. The maze is plus-shaped, with two enclosed arms and two open arms, and elevated 50cm from the floor. During a test, which usually lasts for 5min, the animal is initially put at the center and is free to move and explore the entire maze. The level of anxiety is measured by variables such as the percentage of time spent and the number of entries in the enclosed arms. High percentage of time spent at and number of entries in the enclosed arms indicate anxiety. Here we propose a computational model of rat behavior in the elevated plus-maze based on an artificial neural network trained by a genetic algorithm. The fitness function of the genetic algorithm is composed of reward (positive) and punishment (negative) terms, which are incremented as the computational agent (virtual rat) moves in the maze. The punishment term is modulated by a parameter that simulates the effects of different drugs. Unlike other computational models, the virtual rat is built independently of prior known experimental data. The exploratory behaviors generated by the model for different simulated pharmacological conditions are in good agreement with data from real rats.

  12. Source identification and budget analysis on elevated levels of formaldehyde within ship plumes: a photochemical/dynamic model analysis

    NASA Astrophysics Data System (ADS)

    Song, C. H.; Kim, H. S.; von Glasow, R.; Brimblecombe, P.; Kim, J.; Park, R. J.; Woo, J. H.

    2010-06-01

    Elevated levels of formaldehyde (HCHO) along the ship corridors have been observed by satellite sensors, such as ESA/ERS-2 GOME (Global Ozone Monitoring Experiment), and were also predicted by global 3-D chemistry-transport models. In this study, three likely sources of the elevated HCHO levels were investigated to identify the detailed sources and examine the contributions of the sources (budget) of the elevated levels of HCHO in the ship corridors using a newly-developed ship-plume photochemical/dynamic model: (1) primary HCHO emission from ships; (2) secondary HCHO production via the atmospheric oxidation of Non-methane volatile organic compounds (NMVOCs) emitted from ships; and (3) atmospheric oxidation of CH4 within the ship plumes. From multiple ship-plume model simulations, CH4 oxidation by elevated levels of in-plume OH radicals was found to be the main factor responsible for the elevated levels of HCHO in the ship corridors. More than ~91% of the HCHO for the base ship plume case (ITCT 2K2 ship-plume case) is produced by this atmospheric chemical process, except in the areas close to the ship stacks where the main source of the elevated HCHO levels would be primary HCHO from the ships (due to the deactivation of CH4 oxidation from the depletion of in-plume OH radicals). Because of active CH4 oxidation (chemical destruction of CH4) by OH radicals, the instantaneous chemical lifetime of CH4 (τ CH4) decreased to ~0.45 yr inside the ship plume, which is in contrast to τ CH4 of ~1.1 yr in the background (up to ~41% decrease). A variety of likely ship-plume situations at three locations at different latitudes within the global ship corridors was also studied to determine the extent of the enhancements in the HCHOlevels in the marine boundary layer (MBL) influenced by ship emissions. It was found that the ship-plume HCHO levels could be 20.5-434.9 pptv higher than the background HCHO levels depending on the latitudinal locations of the ship plumes (i

  13. Optimization of computer-based technology of creating large reservoir's Digital Elevation Models

    NASA Astrophysics Data System (ADS)

    Shikunova, Ekaterina; Pavlovsky, Andrew; Zemlyanov, Igor; Gorelits, Olga

    2010-05-01

    Using Digital Elevation Model of bottom and coastal zone for large-scale anthropogenic water reservoirs is very important for sustainable water management in actual conditions of Global Climate Change. DEM is unified monitoring base for different types of reservoirs in varied types of ecosystems in various environmental and economical conditions. It may be used for getting current morphometric characteristics, pollution and biodiversity analysis, monitoring bottom relief changing and making management decisions. In 2008-2009 State Oceanography Institute (SOI) carried out the DEMs for reservoirs of Volga river system. In 2008 in SOI was created DEM of Uglichsky reservoir, which is typical Russian reservoir. Methodology and computer-based technology were developed and evaluated. In 2009 in SOI were created DEMs of Gorkovsky, Volgogradsky and six reservoirs of Moscow region. Such result was achieved by optimization of DEM's creating process. Initially we used complex of GIS programs, which include GIS Map-2008 Panorama, ArcMap v.9.3.1, ArcView v.3.2a, Golden Surfer v.8, Global Mapper v.10. The input data are bathymetric survey data, large-scale maps (scale 1:10 000, 1:25 000) and remote sensing data of high resolution. Office analysis consists of several main milestones. 1. Vectorization of coastline and relief data from maps and remote sensing data using GIS Map-2008 by Panorama; ArcView v.3.2a. 2. Maps data elaboration with using bathymetric survey data. Because some maps are longstanding it is necessary to renew them. 3. Creating point's array including all data from maps, RSD and bathymetric survey. 4. Separation small calculation zones including four survey cross-sections. 5. Determine of anisotropy parameters, which depend on channel orientation. 6. Create shapes for clipping of correct grid zones. Each shape includes 2 cross-sections. Milestones 2-6 realize in ArcView v.3.2a. 7. Creating grid's array using Golden Surfer v.8 for each zone by interpolation method

  14. Seismic analysis of the 13 October 2012 Te Maari, New Zealand, lake breakout lahar: Insights into flow dynamics and the implications on mass flow monitoring

    NASA Astrophysics Data System (ADS)

    Walsh, B.; Jolly, A. D.; Procter, J. N.

    2016-09-01

    On 6 August 2012 an eruption of the upper Te Maari vent Tongariro volcano and subsequent debris flow in the Mangatetipua channel created a debris dam and ephemeral lake. The lake reached its maximum volume of 50,000 m3 by 13 October, initiating dam breaching at 22:30 NZDT (11:30 UTC) after a period of intense rainfall. The breach eventually grew to 29 × 12 m, causing eroded debris flow sediment and water to remobilize as a lahar. The event, comprising multiple surges, lasted ~ 30 min, and displaced 57,000 m3 of remobilized sediment up to 4.5 km downstream. To determine the dynamics of the event, the seismic signals generated by the lahar were compared with active seismic source data collected in February 2013. The comparison used a common frequency band range of 3-10 Hz to compute amplitude for four near-field seismic stations. For periods with signal-to-noise ratios above 2.0, we obtained lahar amplitude distributions that match best the equivalent active source amplitudes within ~ 0.5 km of the dam breakout. The accumulated seismic energy of the lahar was estimated at 1.93 × 109 Nm, whereas the peak energy was 6.88 × 107 Nm. Results of this work may improve the characterization of future mass flow events in the Te Maari/Mangatetipua area through the calibration of seismic stations used in this study.

  15. Analysis of the influence of the digital elevation model characteristics on hydrodynamic simulations: the case of the Tagus River

    NASA Astrophysics Data System (ADS)

    Falcão, Ana Paula; Pestana, Rita; Matias, Magda P.; Gonçalves, Alexandre; Heleno, Sandra

    2014-05-01

    Floods are one of the major and hazardous natural events, with the potential to cause fatalities, displacement of people and damage to the environment, to severely compromise economic development and to undermine the economic activities, as the Floods Directive of the European Union clearly recalls (Directive 2007/60/EC). This Directive establishes a framework for the assessment and management of flood risks. As such, it relies on hydrodynamic simulation of floods. For this a single digital elevation model valid for the whole study area is a requirement and its construction usually implies the use of topographic and bathymetric data collected by distinct equipment and methods, at different times and acquired with a variety of spatial resolutions and accuracies. In this paper we present a comparison of hydrodynamic simulation results, in flood extension and water elevation level, of a Tagus River flood event cover the period between 5pm of December 29th, 2000 until 1am of January 9th, 2001, by using the combined digital elevation model resampled at a cell size of 15m, 30m and 50m. The study area is a section of 70 km of the Tagus River, between Tramagal and Santarém. The Tagus River is the longest of the Iberian Peninsula and is responsible for periodical floods in one of the most important agricultural areas in Portugal. For this area a digital elevation model acquired in 2008 by advanced interferometric techniques is available (5m of spatial resolution), accurate in the floodplain area but with no information in river channel since the radar signal has no ability to penetrate into water, and 29 cross-sections acquired by eco-sounder equipment in 2012, with 3km intervals are available. In order to analyse and validate those differences, a dataset with SAR imagery, provided by ESA, and the water levels measured at Almourol hydrometric station were used.

  16. ELEVATING MECHANISM

    DOEpatents

    Frederick, H.S.; Kinsella, M.A.

    1959-02-24

    An elevator is described, which is arranged for movement both in a horizontal and in a vertical direction so that the elevating mechanism may be employed for servicing equipment at separated points in a plant. In accordance with the present invention, the main elevator chassis is suspended from a monorail. The chassis, in turn supports a vertically moveable carriage, a sub- carriage vertically moveable on the carriage, and a turntable carried by the sub- carriage and moveable through an arc of 90 with the equipment attached thereto. In addition, the chassis supports all the means required to elevate or rotate the equipment.

  17. Impacts of uncertainties in weather and streamflow observations in calibration and evaluation of an elevation distributed HBV-model

    NASA Astrophysics Data System (ADS)

    Engeland, K.; Steinsland, I.; Petersen-Øverleir, A.; Johansen, S.

    2012-04-01

    The aim of this study is to assess the uncertainties in streamflow simulations when uncertainties in both observed inputs (precipitation and temperature) and streamflow observations used in the calibration of the hydrological model are explicitly accounted for. To achieve this goal we applied the elevation distributed HBV model operating on daily time steps to a small catchment in high elevation in Southern Norway where the seasonal snow cover is important. The uncertainties in precipitation inputs were quantified using conditional simulation. This procedure accounts for the uncertainty related to the density of the precipitation network, but neglects uncertainties related to measurement bias/errors and eventual elevation gradients in precipitation. The uncertainties in temperature inputs were quantified using a Bayesian temperature interpolation procedure where the temperature lapse rate is re-estimated every day. The uncertainty in the lapse rate was accounted for whereas the sampling uncertainty related to network density was neglected. For every day a random sample of precipitation and temperature inputs were drawn to be applied as inputs to the hydrologic model. The uncertainties in observed streamflow were assessed based on the uncertainties in the rating curve model. A Bayesian procedure was applied to estimate the probability for rating curve models with 1 to 3 segments and the uncertainties in their parameters. This method neglects uncertainties related to errors in observed water levels. Note that one rating curve was drawn to make one realisation of a whole time series of streamflow, thus the rating curve errors lead to a systematic bias in the streamflow observations. All these uncertainty sources were linked together in both calibration and evaluation of the hydrologic model using a DREAM based MCMC routine. Effects of having less information (e.g. missing one streamflow measurement for defining the rating curve or missing one precipitation station

  18. New insights into the Elevation Dependent Warming in the Tibetan Plateau-Himalayas from CMIP5 models

    NASA Astrophysics Data System (ADS)

    Palazzi, Elisa; Filippi, Luca; von Hardenberg, Jost

    2016-04-01

    We use the output of twenty-seven Global Climate Models (GCMs) participating in the Coupled Model Intercomparison Project phase 5 (CMIP5) to investigate Elevation Dependent Warming (EDW) in the Tibetan Plateau, Himalayan and Karakoram mountains and surrounding areas in historical model simulations and in future projections. The model data indicate enhanced warming with elevation in the past decades and an intensification of the EDW in the future decades under a high-range IPCC emission scenario (RCP 8.5), particularly for the minimum temperature in winter and spring and for the maximum temperature in summer and autumn, which corroborates previous observational and model studies focused on the Tibetan Plateau region. However, our study suggests that the relationship between the warming rates and the elevation (for both the minimum and maximum temperature and with some seasonal differences) is far from being linear. In particular, two clearly distinct regimes emerge such that regions with temperatures below the freezing level of water show a stronger warming than regions above, suggesting that the phase of water and/or the presence of snow play a key role. This bimodal response is very robust and it is captured by the multi-model mean as well as by all individual GCMs. The mechanisms for enhanced warming trends with elevation are investigated using a multiple regression model which incorporates five predictors, associated with the variables that are expected to be important for the EDW: surface downwelling longwave radiation, surface downwelling shortwave radiation, near-surface specific humidity, albedo, and orography. We find that inclusion or exclusion of the orography as a predictor does not change significantly the amount of explained variance for the prediction of either the minimum temperature change in winter or the maximum temperature change in summer, in particular if one regression model already includes albedo and specific humidity. The albedo emerges as

  19. A Digital Elevation Model of the Greenland Ice Sheet based on Envisat and CryoSat-2 Radar Altimetry

    NASA Astrophysics Data System (ADS)

    Levinsen, J. F.; Smith, B. E.; Sandberg Sørensen, L.; Khvorostovsky, K.; Forsberg, R.

    2014-12-01

    With the launch of the first radar altimeter by ESA in 1992, more than two decades of radar altimetry data are now available. Therefore, one goal of ESA's Ice Sheet Climate Change Initiative is the estimation of surface elevation changes of the Greenland Ice Sheet (GrIS) based on ERS-1, -2, Envisat, CryoSat-2, and, in the longer term, Sentinel-3 data. This will create a data record from 1992 until present date. In addition to elevation-change records, such data can be processed to produce digital elevation models, or DEMs, of the ice sheets. The DEMs can be used to correct radar altimetry data for slope-induced errors resulting from the large footprint (e.g. 2-10 km for Envisat vs. 60 m for ICESat laser altimetry) or to correct for the underlying surface topography when applying the repeat-track method. DEMs also provide key information in e.g. SAR remote sensing of ice velocities to remove the interferograms' topographic signal or in regional climate modeling. This work focuses on the development of a GrIS DEM from Envisat and CryoSat-2 altimetry, corrected with temporally and spatially coincident NASA ICESat, ATM, and LVIS laser data. The spatial resolution is 2 x 2 km and the reference year 2010. It is based on 2009 and 2010 data, the 2009 data adjusted to 2010 by accounting for the intermediate elevation changes. This increases the spatial data coverage and reduces data errors. The GIMP DEM has been corrected for negative elevations and errors in the north, and used to constrain the final DEM. The recently acquired observations and increased data coverage give a strong advantage to this DEM relative to previous models, based on lower-resolution, more temporally scattered data (e.g. a decade of observations or only ICESat data, limited to three annual 35-day acquisition periods). Furthermore, as surface changes occur continuously, an up-to-date DEM is necessary to correctly constrain the observations, thereby ensuring an accurate change detection or modeling

  20. Holocene lahars and their byproducts along the historical path of the White River between Mount Rainier and Seattle: Geological Society of America Field Trip

    SciTech Connect

    Brown, T A; Zehfuss, P H; Atwater, B F; Vallance, J W; Brenniman, H

    2003-10-16

    Clay-poor lahars of late Holocene age from Mount Rainier change down the White River drainage into lahar-derived fluvial and deltaic deposits that filled an arm of Puget Sound between the sites of Auburn and Seattle, 110-150 km downvalley from the volcano's summit. Lahars in the debris-flow phase left cobbly and bouldery deposits on the walls of valleys within 70 km of the summit. At distances of 80-110 km, transitional (hyperconcentrated) flows deposited pebbles and sand that coat terraces in a gorge incised into glacial drift and the mid-Holocene Osceola Mudflow. On the broad, level floor of the Kent valley at 110-130 km, lahars in the runout or streamflow phase deposited mostly sand-size particles that locally include the trunks of trees probably entrained by the flows. Beyond 130 km, in the Duwamish valley of Tukwila and Seattle, laminated andesitic sand derived from Mount Rainier built a delta northward across the Seattle fault. This distal facies, warped during an earthquake in A.D. 900-930, rests on estuarine mud at depths as great as 20 m. The deltaic filling occurred in episodes that appear to overlap in time with the lahars. As judged from radiocarbon ages of twigs and logs, at least three episodes of distal deposition postdate the Osceola Mudflow. One of these episodes occurred about 2200-2800 cal yr B.P., and two others occurred 1700-1000 cal yr B.P. The most recent episode ended by about the time of the earthquake of A.D. 900-930. The delta's northward march to Seattle averaged between 6 and 14 m/yr in the late Holocene.

  1. Topogrid Derived 10 Meter Resolution Digital Elevation Model of Charleston, and Parts of Berkeley, Colleton, Dorchester and Georgetown Counties, South Carolina

    USGS Publications Warehouse

    Chirico, Peter G.

    2005-01-01

    EXPLANATION The purpose of developing a new 10m resolution digital elevation model (DEM) of the Charleston Region was to more accurately depict geologic structure, surfical geology, and landforms of the Charleston County Region. Previously, many areas northeast and southwest of Charleston were originally mapped with a 20 foot contour interval. As a result, large areas within the National Elevation Dataset (NED) depict flat terraced topography where there was a lack of higher resolution elevation data. To overcome these data voids, the new DEM is supplemented with additional elevation data and break-lines derived from aerial photography and topographic maps. The resultant DEM is stored as a raster grid at uniform 10m horizontal resolution. The elevation model contained in this publication was prodcued utilizing the ANUDEM algorthim. ANUDEM allows for the inclusion of contours, streams, rivers, lake and water body polygons as well as spot height data to control the development of the elevation model. A preliminary statistical analysis using over 788 vertical elevation check points, primarily located in the northeastern part of the study area, derived from USGS 7.5 Minute Topographic maps reveals that the final DEM, has a vertical accuracy of ?3.27 meters. A table listing the elevation comparison between the elevation check points and the final DEM is provided.

  2. An automated approach for extracting Barrier Island morphology from digital elevation models

    NASA Astrophysics Data System (ADS)

    Wernette, Phillipe; Houser, Chris; Bishop, Michael P.

    2016-06-01

    The response and recovery of a barrier island to extreme storms depends on the elevation of the dune base and crest, both of which can vary considerably alongshore and through time. Quantifying the response to and recovery from storms requires that we can first identify and differentiate the dune(s) from the beach and back-barrier, which in turn depends on accurate identification and delineation of the dune toe, crest and heel. The purpose of this paper is to introduce a multi-scale automated approach for extracting beach, dune (dune toe, dune crest and dune heel), and barrier island morphology. The automated approach introduced here extracts the shoreline and back-barrier shoreline based on elevation thresholds, and extracts the dune toe, dune crest and dune heel based on the average relative relief (RR) across multiple spatial scales of analysis. The multi-scale automated RR approach to extracting dune toe, dune crest, and dune heel based upon relative relief is more objective than traditional approaches because every pixel is analyzed across multiple computational scales and the identification of features is based on the calculated RR values. The RR approach out-performed contemporary approaches and represents a fast objective means to define important beach and dune features for predicting barrier island response to storms. The RR method also does not require that the dune toe, crest, or heel are spatially continuous, which is important because dune morphology is likely naturally variable alongshore.

  3. Dune development and migration to damage long established vegetation colonies in the lahar deposition zone of Ruapehu Volcano, New Zealand

    NASA Astrophysics Data System (ADS)

    Ohno, Y.; Kasai, M.; Marutani, T.

    2012-04-01

    This study reports migration of dunes that mainly originate from lahar deposits and gully erosion, in the Rangipo Desert on the skirts of the Ruapehu Volcano, New Zealand. Although the Rangipo Desert is not a dry desert (average annual rainfall: 1100mm), the occasional supply of volcanic materials from Ruapehu, strong wind (average maximum speed in a day: 12 m/s) together with low winter temperatures has created a desert-like landscape. The study site consists of a flood plain with sporadic tussock and alpine to sub-alpine vegetation colonies which often form mound-like structures and sand dunes on terraces on the flanks of the volcano. The accretionary mounds and dunes comprise layers of tephra and pumice of various ages, together with interstitial wind-blown materials. While shrubs thrive on these terrace tops, it was observed that migrating dunes of 3 m in height have progressively buried and killed vegetation at two sites. Aerial photographs taken in 2000 and 2011 indicated that the dunes originated from pockets of lahar deposits and gully out-wash materials on the flood plain and were migrating in the major leeward wind direction (Northeast), or towards the sites. The migration rate at one site was estimated at 5 m/year from the photography. The flood plain pockets had formed at points where the floor slope changed from steep to gentle. As they contain finer materials than their surroundings, they have produced a series of sequential dunes. The exposed floor between the dunes comprises pumice layers of low infiltration capacity, suggesting that dunes migrate and develop as they strip off floor deposits. Subsequent exposure of the layers induces surface flow concentration in wet weather to cause gully incision. In conclusion, lahar occurrence is a major controlling factor in development in the landscape of the Rangipo Desert, by not only directly flowing at times into the flood plain, but also by producing migrating dunes that impact on existing vegetation

  4. On the limits and capability of modeling water, energy and carbon fluxes in deciduous forest exposed to elevated CO2

    NASA Astrophysics Data System (ADS)

    Fatichi, Simone; Leuzinger, Sebastian

    2013-04-01

    Understanding future patterns of carbon cycle is strongly connected to forest behavior in an atmosphere with increasing CO2. Observations in mature, steady-state forests are logistically challenging and difficult to upscale, therefore most of our experimental knowledge is derived from results obtained for young trees or homogenous stands. A combination of numerical modeling and observations can complement our knowledge on the behavior of heterogeneous forests where the leaf-level photosynthetic response to elevated CO2 typically does not translate into a proportional increase in plant growth. We compare data from a free air CO2 enrichment (FACE) experiment in a mature deciduous forest in Switzerland with realizations from a state-of-the-art ecohydrological model (Tethys-Chloris). Model realizations compare favorably with field observations of photosynthesis, stomatal conductance, sap flow, leaf and fruit litter, and stem growth. The model captures the observed CO2-induced difference in transpiration and its sensitivity to atmospheric demand, as well as qualitative changes in soil moisture. The simulated differences between CO2 scenarios for both the carbon and water balance are generally less than 10% and fall within the uncertainty of experimental observations. Simulated allocation to stem growth is c. 50 gC yr-1 m-2 higher in the modeled CO2 scenario, which is within the uncertainty of stand upscaled observations. These results demonstrate that while ecohydrological models can be used to reliably simulate multi-year energy, water, and carbon fluxes, evaluating the modeled carbon allocation remains critical. Simplified and rather empirical carbon allocation rules used in the model cannot be confirmed or rejected given the current accuracy of field measurements. Despite such uncertainties we conclude that, taken together both modeling and experimental results, for this type of forest, ecosystem responses to elevated CO2 in terms of energy and water fluxes are

  5. Tsunami Inundation, North of Phuket, Thailand ASTER Images and SRTM Elevation Model

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1

    The Indian Ocean coastline north of Phuket, Thailand is a major tourist destination that was in the path of the tsunami produced by a giant offshore earthquake on December 26, 2004. This disaster resulted in a heavy loss of life. These simulated natural color ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) images show a 27 kilometer (17-mile) long stretch of coast 80 kilometers (50 miles) north of the Phuket airport in the Khao Lak area on December 31 (middle) and also two years earlier (left). The changes along the coast are obvious (changing from green to grey) where the vegetation was stripped away by the tsunami.

    The image on the right is a copy of the later ASTER scene but it includes highlighting in red for areas that have elevations within 10 meters (33 feet) of sea level. This elevation information was supplied by the Shuttle Radar Topography Mission (SRTM). The red areas appear to include most of the tsunami inundated areas.

    The geographic correspondence of the imaged damage and the highlighted elevation range is quite good in the middle and upper parts of the scene and is consistent with an early field report of about 10 meters of inundation. In the south, the elevation range corresponds to a much wider area than the actual damage, but this is to be expected for areas increasingly far from the coast. Offshore bathymetry (depth variations), coastal landforms, distance from the coast, and additional factors other than elevation range control the damage extent. But elevation measurements along the coast, as provided by SRTM, give a general indication of areas at risk, as now confirmed by ASTER.

    ASTER images Earth to map and monitor the changing surface of our planet with its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet). These data provide scientists

  6. Tsunami Inundation, North of Phuket, Thailand ASTER Images and SRTM Elevation Model

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Figure 1

    The Indian Ocean coastline north of Phuket, Thailand is a major tourist destination that was in the path of the tsunami produced by a giant offshore earthquake on December 26, 2004. This disaster resulted in a heavy loss of life. These simulated natural color ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) images show a 27 kilometer (17-mile) long stretch of coast 80 kilometers (50 miles) north of the Phuket airport in the Khao Lak area on December 31 (middle) and also two years earlier (left). The changes along the coast are obvious (changing from green to grey) where the vegetation was stripped away by the tsunami.

    The image on the right is a copy of the later ASTER scene but it includes highlighting in red for areas that have elevations within 10 meters (33 feet) of sea level. This elevation information was supplied by the Shuttle Radar Topography Mission (SRTM). The red areas appear to include most of the tsunami inundated areas.

    The geographic correspondence of the imaged damage and the highlighted elevation range is quite good in the middle and upper parts of the scene and is consistent with an early field report of about 10 meters of inundation. In the south, the elevation range corresponds to a much wider area than the actual damage, but this is to be expected for areas increasingly far from the coast. Offshore bathymetry (depth variations), coastal landforms, distance from the coast, and additional factors other than elevation range control the damage extent. But elevation measurements along the coast, as provided by SRTM, give a general indication of areas at risk, as now confirmed by ASTER.

    ASTER images Earth to map and monitor the changing surface of our planet with its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet). These data provide scientists

  7. Analytical model of sea level elevation during a storm: Support for coastal flood risk assessment associated with cyclone passage

    NASA Astrophysics Data System (ADS)

    Maia, Natan Zambroni; Calliari, Lauro Julio; Nicolodi, João Luiz

    2016-08-01

    Sea level oscillations are a result of continuous astronomic, oceanographic, and atmospheric interactions on different time and intensity scales. Thus, the collective action of forcing factors such as tide, wind, atmospheric pressure, and wave action may lead to elevated sea levels during cyclone events over the continental shelf, abruptly impacting adjacent coasts. The objective of this study is to evaluate the potential risks of sea level rise and coastal flooding associated with the passage of cyclones in southern Brazil. An analytical model was developed based on extreme storm events from 1997 to 2008. The model identifies the impact of each forcing factor during temporary sea level rise. Through the development of a digital terrain model, it was possible to identify the areas most vulnerable to flooding by superimposing the terrain model onto calculated sea levels. During storm events, sea level elevations ranged from 2 to 5 m and show wind as the major forcing factor, followed by swells waves, astronomical tide and finally atmospheric pressure.

  8. Development of an object-based classification model for mapping mountainous forest cover at high elevation using aerial photography

    NASA Astrophysics Data System (ADS)

    Lateb, Mustapha; Kalaitzidis, Chariton; Tompoulidou, Maria; Gitas, Ioannis

    2016-08-01

    Climate change and overall temperature increase results in changes in forest cover in high elevations. Due to the long life cycle of trees, these changes are very gradual and can be observed over long periods of time. In order to use remote sensing imagery for this purpose it needs to have very high spatial resolution and to have been acquired at least 50 years ago. At the moment, the only type of remote sensing imagery with these characteristics is historical black and white aerial photographs. This study used an aerial photograph from 1945 in order to map the forest cover at the Olympus National Park, at that date. An object-based classification (OBC) model was developed in order to classify forest and discriminate it from other types of vegetation. Due to the lack of near-infrared information, the model had to rely solely on the tone of the objects, as well as their geometric characteristics. The model functioned on three segmentation levels, using sub-/super-objects relationships and utilising vegetation density to discriminate forest and non-forest vegetation. The accuracy of the classification was assessed using 503 visually interpreted and randomly distributed points, resulting in a 92% overall accuracy. The model is using unbiased parameters that are important for differentiating between forest and non-forest vegetation and should be transferrable to other study areas of mountainous forests at high elevations.

  9. Elevation of Il6 is associated with disturbed let-7 biogenesis in a genetic model of depression

    PubMed Central

    Wei, Y B; Liu, J J; Villaescusa, J C; Åberg, E; Brené, S; Wegener, G; Mathé, A A; Lavebratt, C

    2016-01-01

    Elevation of the proinflammatory cytokine IL-6 has been implicated in depression; however, the mechanisms remain elusive. MicroRNAs (miRNAs) are small non-coding RNAs that inhibit gene expression post-transcriptionally. The lethal-7 (let-7) miRNA family was suggested to be involved in the inflammation process and IL-6 was shown to be one of its targets. In the present study, we report elevation of Il6 in the prefrontal cortex (PFC) of a genetic rat model of depression, the Flinders Sensitive Line (FSL) compared to the control Flinders Resistant Line. This elevation was associated with an overexpression of LIN28B and downregulation of let-7 miRNAs, the former an RNA-binding protein that selectively represses let-7 synthesis. Also DROSHA, a key enzyme in miRNA biogenesis was downregulated in FSL. Running was previously shown to have an antidepressant-like effect in the FSL rat. We found that running reduced Il6 levels and selectively increased let-7i and miR-98 expression in the PFC of FSL, although there were no differences in LIN28B and DROSHA expression. Pri-let-7i was upregulated in the running FSL group, which associated with increased histone H4 acetylation. In conclusion, the disturbance of let-7 family biogenesis may underlie increased proinflammatory markers in the depressed FSL rats while physical activity could reduce their expression, possibly through regulating primary miRNA expression via epigenetic mechanisms. PMID:27529677

  10. Elevated Temperature Primary Load Design Method Using Pseudo Elastic-Perfectly Plastic Model

    SciTech Connect

    Carter, Peter; Sham, Sam; Jetter, Robert I

    2012-01-01

    A new primary load design method for elevated temperature service has been developed. Codification of the procedure in an ASME Boiler and Pressure Vessel Code, Section III Code Case is being pursued. The proposed primary load design method is intended to provide the same margins on creep rupture, yielding and creep deformation for a component or structure that are implicit in the allowable stress data. It provides a methodology that does not require stress classification and is also applicable to a full range of temperature above and below the creep regime. Use of elastic-perfectly plastic analysis based on allowable stress with corrections for constraint, steady state stress and creep ductility is described. This approach is intended to ensure that traditional primary stresses are the basis for design, taking into account ductility limits to stress re-distribution and multiaxial rupture criteria.

  11. Topogrid Derived 10 Meter Resolution Digital Elevation Model of the Shenandoah National Park and Surrounding Region, Virginia

    USGS Publications Warehouse

    Chirico, Peter G.; Tanner, Seth D.

    2004-01-01

    Explanation The purpose of developing a new 10m resolution DEM of the Shenandoah National Park Region was to more accurately depict geologic structure, surfical geology, and landforms of the Shenandoah National Park Region in preparation for automated landform classification. Previously, only a 30m resolution DEM was available through the National Elevation Dataset (NED). During production of the Shenandoah10m DEM of the Park the Geography Discipline of the USGS completed a revised 10m DEM to be included into the NED. However, different methodologies were used to produce the two similar DEMs. The ANUDEM algorithm was used to develop the Shenadoah DEM data. This algorithm allows for the inclusion of contours, streams, rivers, lake and water body polygons as well as spot height data to control the elevation model. A statistical analysis using over 800 National Geodetic Survey (NGS) first and second order vertical control points reveals that the Shenandoah10m DEM, produced as a part of the Appalachian Blue Ridge Landscape project, has a vertical accuracy of ?4.87 meters. The metadata for the 10m NED data reports a vertical accuracy of ?7m. A table listing the NGS control points, the elevation comparison, and the RMSE for the Shenandoah10m DEM is provided. The process of automated terrain classification involves developing statistical signatures from the DEM for each type of surficial deposit and landform type. The signature will be a measure of several characteristics derived from the elevation data including slope, aspect, planform curvature, and profile curvature. The quality of the DEM is of critical importance when extracting terrain signatures. The highest possible horizontal and vertical accuracy is required. The more accurate Shenandoah 10m DEM can now be analyzed and integrated with the geologic observations to yield statistical correlations between the two in the development of landform and surface geology mapping projects.

  12. Modeled responses of terrestrial ecosystems to elevated atmospheric CO2: A comparison of simulations by the biogeochemistry models of the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP)

    USGS Publications Warehouse

    Pan, Y.; Melillo, J.M.; McGuire, A.D.; Kicklighter, D.W.; Pitelka, L.F.; Hibbard, K.; Pierce, L.L.; Running, S.W.; Ojima, D.S.; Parton, W.J.; Schimel, D.S.; Borchers, J.; Neilson, R.; Fisher, H.H.; Kittel, T.G.F.; Rossenbloom, N.A.; Fox, S.; Haxeltine, A.; Prentice, I.C.; Sitch, S.; Janetos, A.; McKeown, R.; Nemani, R.; Painter, T.; Rizzo, B.; Smith, T.; Woodward, F.I.

    1998-01-01

    Although there is a great deal of information concerning responses to increases in atmospheric CO2 at the tissue and plant levels, there are substantially fewer studies that have investigated ecosystem-level responses in the context of integrated carbon, water, and nutrient cycles. Because our understanding of ecosystem responses to elevated CO2 is incomplete, modeling is a tool that can be used to investigate the role of plant and soil interactions in the response of terrestrial ecosystems to elevated CO2. In this study, we analyze the responses of net primary production (NPP) to doubled CO2 from 355 to 710 ppmv among three biogeochemistry models in the Vegetation/Ecosystem Modeling and Analysis Project (VEMAP): BIOME-BGC (BioGeochemical Cycles), Century, and the Terrestrial Ecosystem Model (TEM). For the conterminous United States, doubled atmospheric CO2 causes NPP to increase by 5% in Century, 8% in TEM, and 11% in BIOME-BGC. Multiple regression analyses between the NPP response to doubled CO2 and the mean annual temperature and annual precipitation of biomes or grid cells indicate that there are negative relationships between precipitation and the response of NPP to doubled CO2 for all three models. In contrast, there are different relationships between temperature and the response of NPP to doubled CO2 for the three models: there is a negative relationship in the responses of BIOME-BGC, no relationship in the responses of Century, and a positive relationship in the responses of TEM. In BIOME-BGC, the NPP response to doubled CO2 is controlled by the change in transpiration associated with reduced leaf conductance to water vapor. This change affects soil water, then leaf area development and, finally, NPP. In Century, the response of NPP to doubled CO2 is controlled by changes in decomposition rates associated with increased soil moisture that results from reduced evapotranspiration. This change affects nitrogen availability for plants, which influences NPP. In

  13. Stratigraphic And Lithofacies Study Of Distal Rain-Triggered Lahars: The Case Of West Coast Of Ecuador

    NASA Astrophysics Data System (ADS)

    Mulas, M.; Chunga, K.; Peña Carpio, E.; Falquez Torres, D. A.; Alcivar, R., Sr.; Lopez Coronel, M. C.

    2015-12-01

    The central zone of the coast of Ecuador at the north of Manabí Province, on the area comprised between Salango and Jama communities, is characterized by the presence of whitish to grey, centimeters to meters thick, consolidated to loose distal ash deposits. Recent archeological studies on Valdivia (3500 BC) and Manteña (800-1500 AC - Harris et al. 2004) civilizations remains link this deposits with the intense eruptive phases that afflicted Ecuador 700-900 years ago (Usselman, 2006). Stratigraphic evidences and bibliographic datations of paleosols (Estrada, 1962; Mothes and Hall, 2008), allowed to estimate that these deposits are linked with the 800 BP eruption of Quilotoa and the following eruptions of Cotopaxi. According to the Smith and Lowe classification (1991), the deposits outcropping on the coast (located at a distance greater than 160 km from the volcanic vents), varied from whitish to grey, loose to weakly consolidated, massive to weakly stratified, centimeters to meters thick, coarse to fine ash matrix layers (diluite streamflow facies) to massive, large angular to sub-rounded siltitic blocks-rich and coarse to medium ash matrix deposits (debris flow facies). These types of lithofacies are associated to a rain-triggered lahar (De Belizal et al., 2013). The presence in some stratigraphic sections of sharp contacts, laminated layers of very fine ash, and also cm-thick sand and silt layers between the ash beds of the same deposits permit to understand that the different pulses were generated in short periods and after a long period. Structures like water pipes imply that the lahar went into the sea (Schneider, 2004), and allow the reconstruction of the paleotopographic condition during the emplacement of these deposits. This study focuses on the characterization of these types of deposits, permit to understand the kind of risk that may affect the towns located on the coast of Ecuador after VEI 4 to 6 eruptions on short time and within years.

  14. Volcanic Risk Perception and Preparedness in Communities within the Mount Baker and Glacier Peak Lahar Hazard Zones

    NASA Astrophysics Data System (ADS)

    Corwin, K.; Brand, B. D.

    2014-12-01

    A community's ability to effectively respond to and recover from natural hazards depends on both the physical characteristics of the hazard and the community's inherent resilience. Resilience is shaped by a number of factors including the residents' perception of and preparedness for a natural hazard as well as the level of institutional preparedness. This study examines perception of and preparedness for lahar hazards from Mount Baker and Glacier Peak in Washington's Skagit Valley. Through an online survey, this study isolates the influence of specific variables (e.g., knowledge, past experience, scientific background, trust in various information sources, occupation, self-efficacy, sense of community) on risk perception and explores reasons behind the frequent disconnect between perception and preparedness. We anticipate that individuals with more extensive education in the sciences, especially geology or earth science, foster greater trust in scientists and a more accurate knowledge, understanding, and perception of the volcanic hazards in their community. Additionally, little research exists examining the extent to which first responders and leaders in response-related institutions prepare on a personal level. Since these individuals work toward community preparedness professionally, we hypothesize that they will be more prepared at home than members of the general public. Finally, the Skagit Valley has a significant history of flooding. We expect that the need to respond to and recover from frequent flooding creates a community with an inherently higher level of preparedness for other hazards such as lahars. The results of this study will contribute to the understanding of what controls risk perception and the interplay between perception and preparedness. At a broader level, this study provides local and state-level emergency managers information to evaluate and improve response capabilities and communication with the public and key institutions in order to

  15. Comparing a FACE experiment with mechanistic ecohydrological modeling: which processes are reliably simulated under elevated CO2?

    NASA Astrophysics Data System (ADS)

    Fatichi, S.; Leuzinger, S.

    2013-12-01

    Scenarios for the future terrestrial carbon and water cycle rely on numerical tools that simulate the dynamics of vegetation from assimilation of carbon through stomata to long-term forest development at the global scale. However, these tools are rarely tested to perform well in conditions different from the historical climate and comparisons are mostly limited to carbon and energy fluxes. A combination of numerical modeling and observations is used here to investigate the capability of a mechanistic approach to simulate the hydrology and the vegetation behavior of a forest exposed to elevated CO2 concentrations. Specifically, we thoroughly compare data from a free air CO2 enrichment (FACE) experiment in a mature deciduous forest in Switzerland with realizations from a state-of-the-art ecohydrological model (Tethys-Chloris). Model realizations compare favorably with field observations of photosynthesis, stomatal conductance, sap flow, leaf and fruit litter, as well as qualitative changes in soil moisture. The simulated differences between CO2 scenarios for both the carbon and water balance are generally very small (less than 10%) and fall within the uncertainty of experimental observations. More problematic is the simulation of stem growth which is significantly higher in the modeled scenario with elevated CO2 but not in the observations even though current accuracy of field measurements precludes robust conclusions. These results demonstrate that while ecohydrological models can be used to reliably simulate multi-year energy, water, and carbon fluxes, evaluating the modeled carbon allocation remains critical. However, experimental evidence suggests that the structure of current vegetation models which use the photosynthesized carbon to directly drive plant growth should be revised because plant tissue growth is very sensitive to direct controls of environmental variables, independently of the amount of assimilated carbon.

  16. Evaluating the sensitivity of an ice sheet model to changes in bed elevation and inclusion of membrane stresses

    NASA Astrophysics Data System (ADS)

    Aschwanden, Andy; Bueler, Ed; Khroulev, Constantine

    2010-05-01

    To predict Greenland's contribution to global sea level rise in the next few centuries with some confidence, an accurate representation of its current state is crucial. Simulations of the present state of Greenland using the "Parallel Ice Sheet Model" (PISM) capture the essential flow features but overestimate the current volume by about 30%. Possible sources of error include (1) limited understanding of physical processes involved, (2) the choice of approximations made by the numerical model, (3) values of tunable parameters, and (4) uncertainties in boundary conditions. The response of an ice sheet model to given forcing contains the above mentioned error sources, with unknown weights. In this work we focus on a small subset, namely errors arising from uncertainties in bed elevation and whether or not membrane stresses are included in the stress balance. CReSIS provides recently updated bedrock maps for Greenland include high-resolution data for Jacobshavn Isbræ and Petermann Glacier. We present a four-way comparison between the original BEDMAP, the new CReSIS bedrock data, a non-sliding shallow ice model, and hybrid model which includes the shallow shelf approximation as a sliding law. Large gradients possibly found in high-resolution bedrock elevation are expected to make a hybrid model the more appropriate choice. To elucidate this question, runs are performed on a unprecedented high spatial resolution of 2km for the whole ice sheet. Finally, model predictions are evaluated against observed quantities such as surface velocities, ice thickness, and temperature profiles in bore holes using different metrics.

  17. Rat, Mouse, and Primate Models of Chronic Glaucoma Show Sustained Elevation of Extracellular ATP and Altered Purinergic Signaling in the Posterior Eye

    PubMed Central

    Lu, Wennan; Hu, HuiLing; Sévigny, Jean; Gabelt, B'Ann T.; Kaufman, Paul L.; Johnson, Elaine C.; Morrison, John C.; Zode, Gulab S.; Sheffield, Val C.; Zhang, Xiulan; Laties, Alan M.; Mitchell, Claire H.

    2015-01-01

    Purpose. The cellular mechanisms linking elevated IOP with glaucomatous damage remain unresolved. Mechanical strains and short-term increases in IOP can trigger ATP release from retinal neurons and astrocytes, but the response to chronic IOP elevation is unknown. As excess extracellular ATP can increase inflammation and damage neurons, we asked if sustained IOP elevation was associated with a sustained increase in extracellular ATP in the posterior eye. Methods. No ideal animal model of chronic glaucoma exists, so three different models were used. Tg-MyocY437H mice were examined at 40 weeks, while IOP was elevated in rats following injection of hypertonic saline into episcleral veins and in cynomolgus monkeys by laser photocoagulation of the trabecular meshwork. The ATP levels were measured using the luciferin-luciferase assay while levels of NTPDase1 were assessed using qPCR, immunoblots, and immunohistochemistry. Results. The ATP levels were elevated in the vitreal humor of rats, mice, and primates after a sustained period of IOP elevation. The ecto-ATPase NTPDase1 was elevated in optic nerve head astrocytes exposed to extracellular ATP for an extended period. NTPDase1 was also elevated in the retinal tissue of rats, mice, and primates, and in the optic nerve of rats, with chronic elevation in IOP. Conclusions. A sustained elevation in extracellular ATP, and upregulation of NTPDase1, occurs in the posterior eye of rat, mouse, and primate models of chronic glaucoma. This suggests the elevation in extracellular ATP may be sustained in chronic glaucoma, and implies a role for altered purinergic signaling in the disease. PMID:26024091

  18. Contextualization of Holocene beach ridge systems for relative sea-level reconstruction using the SRTM elevation model

    NASA Astrophysics Data System (ADS)

    Sander, Lasse; Raniolo, Luís Ariel; Alberdi, Ernesto; Pejrup, Morten

    2014-05-01

    Beach ridge plains are a common feature of prograding coastlines and they have in the past been widely used as geomorphological archives for the reconstruction of past coastal dynamics, event chronologies or late quaternary sea-level change. The most critical parameters for sea-level related research are the consistent definition and confidence of information on surface elevation of the beach ridge deposits. In most parts of the world, the availability of high-resolution geodata is very limited. The measurement of e.g. high-precision GPS (Global Positioning System) data is costly, time-consuming and essentially of limited spatial coverage. The SRTM (Shuttle Radar Topography Mission) dataset is a freely-available digital surface model covering landmasses between approximately 60° N and 56° S at a 90 m (3 arc seconds) resolution. The model elevations are indicated without decimals (integer) and are projected for the WGS84 ellipsoid. On a beach ridge plain at Caleta de los Loros, Río Negro, Argentina, we observed a good correlation of GPS-RTK (GPS-Real Time Kinematic) measurements (estimated vertical accuracy: <0,1 m) with the SRTM elevation model along a cross-ridge transect. An average vertical deviation of 0,96 m (SD: 0,48m) between the SRTM and the GPS-RTK-based elevations was determined for mostof the beach ridge transect (79% of length). Larger errors (maximum average error: 2,78 m, SD: 1,88 m) can be explained by eolian deposition and dune migration during the approx. 13 years between the date of SRTM data acquisition and our GPS measurement. This interpretation is supported by a multi-decadal sequence of Landsat false-color composites. Vegetation cover and rounding errors are further possible factors in explaining vertical deviation. The consistency of data quality was confirmed by a comparison study using a LiDAR (Light detection and ranging)-based digital elevation model (vertical accuracy: <0,1 m) to extract surface elevations on an extensive beach ridge

  19. Modeling evapotranspiration based on plant hydraulic theory can predict spatial variability across an elevation gradient and link to biogeochemical fluxes

    NASA Astrophysics Data System (ADS)

    Mackay, D. S.; Frank, J.; Reed, D.; Whitehouse, F.; Ewers, B. E.; Pendall, E.; Massman, W. J.; Sperry, J. S.

    2012-04-01

    In woody plant systems transpiration is often the dominant component of total evapotranspiration, and so it is key to understanding water and energy cycles. Moreover, transpiration is tightly coupled to carbon and nutrient fluxes, and so it is also vital to understanding spatial variability of biogeochemical fluxes. However, the spatial variability of transpiration and its links to biogeochemical fluxes, within- and among-ecosystems, has been a challenge to constrain because of complex feedbacks between physical and biological controls. Plant hydraulics provides an emerging theory with the rigor needed to develop testable hypotheses and build useful models for scaling these coupled fluxes from individual plants to regional scales. This theory predicts that vegetative controls over water, energy, carbon, and nutrient fluxes can be determined from the limitation of plant water transport through the soil-xylem-stomata pathway. Limits to plant water transport can be predicted from measurable plant structure and function (e.g., vulnerability to cavitation). We present a next-generation coupled transpiration-biogeochemistry model based on this emerging theory. The model, TREEScav, is capable of predicting transpiration, along with carbon and nutrient flows, constrained by plant structure and function. The model incorporates tightly coupled mechanisms of the demand and supply of water through the soil-xylem-stomata system, with the feedbacks to photosynthesis and utilizable carbohydrates. The model is evaluated by testing it against transpiration and carbon flux data along an elevation gradient of woody plants comprising sagebrush steppe, mid-elevation lodgepole pine forests, and subalpine spruce/fir forests in the Rocky Mountains. The model accurately predicts transpiration and carbon fluxes as measured from gas exchange, sap flux, and eddy covariance towers. The results of this work demonstrate that credible spatial predictions of transpiration and related

  20. Automated delineation of karst sinkholes from LiDAR-derived digital elevation models

    NASA Astrophysics Data System (ADS)

    Wu, Qiusheng; Deng, Chengbin; Chen, Zuoqi

    2016-08-01

    Sinkhole mapping is critical for understanding hydrological processes and mitigating geological hazards in karst landscapes. Current methods for identifying sinkholes are primarily based on visual interpretation of low-resolution topographic maps and aerial photographs with subsequent field verification, which is labor-intensive and time-consuming. The increasing availability of high-resolution LiDAR-derived digital elevation data allows for an entirely new level of detailed delineation and analyses of small-scale geomorphologic features and landscape structures at fine scales. In this paper, we present a localized contour tree method for automated extraction of sinkholes in karst landscapes. One significant advantage of our automated approach for sinkhole extraction is that it may reduce inconsistencies and alleviate repeatability concerns associated with visual interpretation methods. In addition, the proposed method has contributed to improving the sinkhole inventory in several ways: (1) detection of non-inventoried sinkholes; (2) identification of previously inventoried sinkholes that have been filled; (3) delineation of sinkhole boundaries; and (4) characterization of sinkhole morphometric properties. We applied the method to Fillmore County in southeastern Minnesota, USA, and identified three times as many sinkholes as the existing database for the same area. The results suggest that previous visual interpretation method might significantly underestimate the number of potential sinkholes in the region. Our method holds great potential for creating and updating sinkhole inventory databases at a regional scale in a timely manner.

  1. A digital elevation model of the Greenland Ice Sheet derived from combined laser and radar altimetry data

    NASA Astrophysics Data System (ADS)

    Fredenslund Levinsen, Joanna; Smith, Ben; Sørensen, Louise S.; Forsberg, René

    2014-05-01

    When estimating elevation changes of ice-covered surfaces from radar altimetry, it is important to correct for slope-induced errors. They cause the reflecting point of the pulse to move up-slope and thus return estimates in the wrong coordinates. Slope-induced errors can be corrected for by introducing a Digital Elevation Model (DEM). In this work, such a DEM is developed for the Greenland Ice Sheet using a combination of Envisat radar and ICESat laser altimetry. If time permits, CryoSat radar altimetry will be included as well. The reference year is 2010 and the spatial resolution 2.5 x 2.5 km. This is in accordance with the results obtained in the ESA Ice Sheets CCI project showing that a 5 x 5 km grid spacing is reasonable for ice sheet-wide change detection (Levinsen et al., 2013). Separate DEMs will be created for the given data sets, and the geostatistical spatial interpolation method collocation will be used to merge them, thus adjusting for potential inter-satellite biases. The final DEM is validated with temporally and spatially agreeing airborne lidar data acquired in the NASA IceBridge and ESA CryoVex campaigns. The motivation for developing a new DEM is based on 1) large surface changes presently being observed, and mainly in margin regions, hence necessitating updated topography maps for accurately deriving and correcting surface elevation changes, and 2) although radar altimetry is subject to surface penetration of the signal into the snowpack, data is acquired continuously in time. This is not the case with e.g. ICESat, where laser altimetry data were obtained in periods of active lasers, i.e. three times a year with a 35-day repeat track. Previous DEMs e.g. have 2007 as the nominal reference year, or they are built merely from ICESat data. These have elevation errors as small as 10 cm, which is lower than for Envisat and CryoSat. The advantage of an updated DEM consisting of combined radar and laser altimetry therefore is the possibility of

  2. Digital Elevation Models of Greenland based on combined radar and laser altimetry as well as high-resolution stereoscopic imagery

    NASA Astrophysics Data System (ADS)

    Levinsen, J. F.; Smith, B. E.; Sandberg Sorensen, L.; Khvorostovsky, K.; Simonsen, S. B.; Forsberg, R.

    2015-12-01

    A number of Digital Elevation Models (DEMs) of Greenland exist, each of which are applicable for different purposes. This study presents two such DEMs: One developed by merging contemporary radar and laser altimeter data, and one derived from high-resolution stereoscopic imagery. All products are made freely available. The former DEM covers the entire Greenland. It is specific to the year 2010, providing it with an advantage over previous models suffering from either a reduced spatial/ temporal data coverage or errors from surface elevation changes (SEC) occurring during data acquisition. Radar data are acquired with Envisat and CryoSat-2, and laser data with the Ice, Cloud, and land Elevation Satellite, the Land, Vegetation, and Ice Sensor, and the Airborne Topographic Mapper. Correcting radar data for errors from slope effects and surface penetration of the echoes, and merging these with laser data, yields a DEM capable of resolving both surface depressions as well as topographic features at higher altitudes. The spatial resolution is 2 x 2 km, making the DEM ideal for application in surface mass balance studies, SEC detection from radar altimetry, or for correcting such data for slope-induced errors. The other DEM is developed in a pilot study building the expertise to map all ice-free parts of Greenland. The work combines WorldView-2 and -3 as well as GeoEye1 imagery from 2014 and 2015 over the Disko, Narsaq, Tassilaq, and Zackenberg regions. The novelty of the work is the determination of the product specifications after elaborate discussions with interested parties from government institutions, the tourist industry, etc. Thus, a 10 m DEM, 1.5 m orthophotos, and vector maps are produced. This opens to the possibility of using orthophotos with up-to-date contour lines or for deriving updated coastlines to aid, e.g., emergency management. This allows for a product development directly in line with the needs of parties with specific interests in Greenland.

  3. Shuttle Radar Topography Mission (SRTM) Digital Elevation Model (DEM): A Year 2000 Global Baseline for Measuring Topographic Change

    NASA Astrophysics Data System (ADS)

    Crippen, R. E.

    2002-12-01

    The SRTM DEM is the first near-global, high-resolution elevation model. The data were acquired in February 2000 aboard the Space Shuttle Endeavour and cover the Earth's land masses between 60N and 56S latitudes at about 30 meters spatial resolution. The data are a virtual global snapshot in that they were acquired in about 10 days by a single sensor. Absolute vertical accuracy was targeted at 16 meters. However, spatially broad temporal changes in topography have been detected and measured down to about one-meter precision by comparing the SRTM DEM to the USGS National Elevation Dataset (NED). NED has similar spatial properties, but was independently derived, commonly years (or decades) earlier. Such changes already noted include those related to volcanic processes, alluvial fan deposition, subsidence related to oil extraction, and direct anthropogenic changes such as landfills and major road cuts and fills. Large tectonic changes in topography are likewise potentially evident in such comparisons. New and forthcoming satellites include capabilities to produce elevation models that can be used to detect and measure ongoing and future topographic change when compared to the SRTM DEM. For example, the ASTER instrument on the Terra satellite (launched in 1999) produces targeted DEMs, and SPOT-5 (launched in 2002) is expected to produce a global DEM over a five-year period. Both of these DEM sources (and the NED and others) use optical wavelength sensors which may "observe a different surface" than the SRTM radar, particularly in heavily vegetated areas, and this must be considered in making the comparisons. However, having a "before" data set is often the roadblock in measuring change, and SRTM has now provided the first detailed "before" DEM for most of Earth's land surface.

  4. A Coarse Grained Model for Methylcellulose: Spontaneous Ring Formation at Elevated Temperature

    NASA Astrophysics Data System (ADS)

    Huang, Wenjun; Larson, Ronald

    Methylcellulose (MC) is widely used as food additives and pharma applications, where its thermo-reversible gelation behavior plays an important role. To date the gelation mechanism is not well understood, and therefore attracts great research interest. In this study, we adopted coarse-grained (CG) molecular dynamics simulations to model the MC chains, including the homopolymers and random copolymers that models commercial METHOCEL A, in an implicit water environment, where each MC monomer modeled with a single bead. The simulations are carried using a LAMMPS program. We parameterized our CG model using the radial distribution functions from atomistic simulations of short MC oligomers, extrapolating the results to long chains. We used dissociation free energy to validate our CG model against the atomistic model. The CG model captured the effects of monomer substitution type and temperature from the atomistic simulations. We applied this CG model to simulate single chains up to 1000 monomers long and obtained persistence lengths that are close to those determined from experiment. We observed the chain collapse transition for random copolymer at 600 monomers long at 50C. The chain collapsed into a stable ring structure with outer diameter around 14nm, which appears to be a precursor to the fibril structure observed in the methylcellulose gel observed by Lodge et al. in the recent studies. Our CG model can be extended to other MC derivatives for studying the interaction between these polymers and small molecules, such as hydrophobic drugs.

  5. Interrelations among pyroclastic surge, pyroclastic flow, and lahars in Smith Creek valley during first minutes of 18 May 1980 eruption of Mount St. Helens, USA

    USGS Publications Warehouse

    Brantley, S.R.; Waitt, R.B.

    1988-01-01

    A devastating pyroclastic surge and resultant lahars at Mount St. Helens on 18 May 1980 produced several catastrophic flowages into tributaries on the northeast volcano flank. The tributaries channeled the flows to Smith Creek valley, which lies within the area devastated by the surge but was unaffected by the great debris avalanche on the north flank. Stratigraphy shows that the pyroclastic surge preceded the lahars; there is no notable "wet" character to the surge deposits. Therefore the lahars must have originated as snowmelt, not as ejected water-saturated debris that segregated from the pyroclastic surge as has been inferred for other flanks of the volcano. In stratigraphic order the Smith Creek valley-floor materials comprise (1) a complex valley-bottom facies of the pyroclastic surge and a related pyroclastic flow, (2) an unusual hummocky diamict caused by complex mixing of lahars with the dry pyroclastic debris, and (3) deposits of secondary pyroclastic flows. These units are capped by silt containing accretionary lapilli, which began falling from a rapidly expanding mushroom-shaped cloud 20 minutes after the eruption's onset. The Smith Creek valley-bottom pyroclastic facies consists of (a) a weakly graded basal bed of fines-poor granular sand, the deposit of a low-concentration lithic pyroclastic surge, and (b) a bed of very poorly sorted pebble to cobble gravel inversely graded near its base, the deposit of a high-concentration lithic pyroclastic flow. The surge apparently segregated while crossing the steep headwater tributaries of Smith Creek; large fragments that settled from the turbulent surge formed a dense pyroclastic flow along the valley floor that lagged behind the front of the overland surge. The unusual hummocky diamict as thick as 15 m contains large lithic clasts supported by a tough, brown muddy sand matrix like that of lahar deposits upvalley. This unit contains irregular friable lenses and pods meters in diameter, blocks incorporated from

  6. Interrelations among pyroclastic surge, pyroclastic flow, and lahars in Smith Creek valley during first minutes of 18 May 1980 eruption of Mount St. Helens, USA

    NASA Astrophysics Data System (ADS)

    Brantley, Steven R.; Waitt, Richard B.

    1988-09-01

    A devastating pyroclastic surge and resultant lahars at Mount St. Helens on 18 May 1980 produced several catastrophic flowages into tributaries on the northeast volcano flank. The tributaries channeled the flows to Smith Creek valley, which lies within the area devastated by the surge but was unaffected by the great debris avalanche on the north flank. Stratigraphy shows that the pyroclastic surge preceded the lahars; there is no notable “wet” character to the surge deposits. Therefore the lahars must have originated as snowmelt, not as ejected water-saturated debris that segregated from the pyroclastic surge as has been inferred for other flanks of the volcano. In stratigraphic order the Smith Creek valley-floor materials comprise (1) a complex valley-bottom facies of the pyroclastic surge and a related pyroclastic flow, (2) an unusual hummocky diamict caused by complex mixing of lahars with the dry pyroclastic debris, and (3) deposits of secondary pyroclastic flows. These units are capped by silt containing accretionary lapilli, which began falling from a rapidly expanding mushroom-shaped cloud 20 minutes after the eruption's onset. The Smith Creek valley-bottom pyroclastic facies consists of (a) a weakly graded basal bed of fines-poor granular sand, the deposit of a low-concentration lithic pyroclastic surge, and (b) a bed of very poorly sorted pebble to cobble gravel inversely graded near its base, the deposit of a high-concentration lithic pyroclastic flow. The surge apparently segregated while crossing the steep headwater tributaries of Smith Creek; large fragments that settled from the turbulent surge formed a dense pyroclastic flow along the valley floor that lagged behind the front of the overland surge. The unusual hummocky diamict as thick as 15 m contains large lithic clasts supported by a tough, brown muddy sand matrix like that of lahar deposits upvalley. This unit contains irregular friable lenses and pods meters in diameter, blocks incorporated

  7. White House Suggests Model Used in Reading to Elevate Math Skills

    ERIC Educational Resources Information Center

    Cavanagh, Sean

    2006-01-01

    This article discusses the Bush administration's aim to improve mathematics education through a suggested reading model. The White House is focusing on research to shape how students across the country are taught the most basic mathematical concepts. This undertaking would be modeled on the government's action toward reading, which includes the…

  8. Catchment properties in the Kruger National Park derived from the new TanDEM-X Intermediate Digital Elevation Model (IDEM)

    NASA Astrophysics Data System (ADS)

    Baade, J.; Schmullius, C.

    2015-04-01

    Digital Elevation Models (DEM) represent fundamental data for a wide range of Earth surface process studies. Over the past years the German TanDEM-X mission acquired data for a new, truly global Digital Elevation Model with unpreceded geometric resolution, precision and accuracy. First processed data sets (i. e. IDEM) with a geometric resolution of 0.4 to 3 arcsec have been made available for scientific purposes. This includes four 1° x 1° tiles covering the Kruger National Park in South Africa. Here we document the results of a local scale IDEM validation exercise utilizing RTK-GNSS-based ground survey points from a dried out reservoir basin and its vicinity characterized by pristine open Savanna vegetation. Selected precursor data sets (SRTM1, SRTM90, ASTER-GDEM2) were included in the analysis and highlight the immense progress in satellite-based Earth surface surveying over the past two decades. Surprisingly, the high precision and accuracy of the IDEM data sets have only little impact on the delineation of watersheds and the calculation of catchment size. But, when it comes to the derivation of topographic catchment properties (e.g. mean slope, etc.) the high resolution of the IDEM04 is of crucial importance, if - from a geomorphologist's view - it was not for the disturbing vegetation.

  9. Documentation of programs used to determine a wetlands hydroperiod from model-simulated water-surface elevations

    USGS Publications Warehouse

    Sonenshein, R.S.

    1996-01-01

    A technique has been developed to determine a wetlands hydroperiod by comparing simulated water levels from a ground-water flow model and land- surface elevation data through a geographic information system. The simulated water levels are compared with the land-surface elevation data to determine the height of the water surface above or below land surface for the area of interest. Finally, the hydroperiod is determined for established time periods using criteria specified by the user. The program application requires the use of geographic information system software (ARC/INFO), including the TIN and GRID subsystems of the software. The application consists of an ANSI compatible C program to translate ground- water data output from the U.S. Geological Survey modular three-dimensional, finite-difference, ground-water flow model (MODFLOW) into a format that can be used as input for the geographic information system programs (AML's). The application uses ARC/INFO AML programs and ARC/INFO menu interface programs to create digital spatial data layers of the land surface and water surface and to determine the hydroperiod. The technique can be used to evaluate and manage wetlands hydrology.

  10. Parameter variation effects on temperature elevation in a steady-state, one-dimensional thermal model for millimeter wave exposure of one- and three-layer human tissue.

    PubMed

    Kanezaki, Akio; Hirata, Akimasa; Watanabe, Soichi; Shirai, Hiroshi

    2010-08-21

    The present study describes theoretical parametric analysis of the steady-state temperature elevation in one-dimensional three-layer (skin, fat and muscle) and one-layer (skin only) models due to millimeter-wave exposure. The motivation of this fundamental investigation is that some variability of warmth sensation in the human skin has been reported. An analytical solution for a bioheat equation was derived by using the Laplace transform for the one-dimensional human models. Approximate expressions were obtained to investigate the dependence of temperature elevation on different thermal and tissue thickness parameters. It was shown that the temperature elevation on the body surface decreases monotonically with the blood perfusion rate, heat conductivity and heat transfer from the body to air. Also revealed were the conditions where maximum and minimum surface temperature elevations were observed for different thermal and tissue thickness parameters. The surface temperature elevation in the three-layer model is 1.3-2.8 times greater than that in the one-layer model. The main reason for this difference is attributed to the adiabatic nature of the fat layer. By considering the variation range of thermal and tissue thickness parameters which causes the maximum and minimum temperature elevations, the dominant parameter influencing the surface temperature elevation was found to be the heat transfer coefficient between the body surface and air.

  11. Flow behaviour and constitutive modelling of a ferritic stainless steel at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Zhao, Jingwei; Jiang, Zhengyi; Zu, Guoqing; Du, Wei; Zhang, Xin; Jiang, Laizhu

    2016-05-01

    The flow behaviour of a ferritic stainless steel (FSS) was investigated by a Gleeble 3500 thermal-mechanical test simulator over the temperature range of 900-1100 °C and strain rate range of 1-50 s-1. Empirical and phenomenological constitutive models were established, and a comparative study was made on the predictability of them. The results indicate that the flow stress decreases with increasing the temperature and decreasing the strain rate. High strain rate may cause a drop in flow stress after a peak value due to the adiabatic heating. The Zener-Hollomon parameter depends linearly on the flow stress, and decreases with raising the temperature and reducing the strain rate. Significant deviations occur in the prediction of flow stress by the Johnson-Cook (JC) model, indicating that the JC model cannot accurately track the flow behaviour of the FSS during hot deformation. Both the multiple-linear and the Arrhenius-type models can track the flow behaviour very well under the whole hot working conditions, and have much higher accuracy in predicting the flow behaviour than that of the JC model. The multiple-linear model is recommended in the current work due to its simpler structure and less time needed for solving the equations relative to the Arrhenius-type model.

  12. A comparative study of spherical and flat-Earth geopotential modeling at satellite elevations

    NASA Technical Reports Server (NTRS)

    Parrott, M. H.; Hinze, W. J.; Braile, L. W.; Vonfrese, R. R. B.

    1985-01-01

    Flat-Earth modeling is a desirable alternative to the complex spherical-Earth modeling process. These methods were compared using 2 1/2 dimensional flat-earth and spherical modeling to compute gravity and scalar magnetic anomalies along profiles perpendicular to the strike of variably dimensioned rectangular prisms at altitudes of 150, 300, and 450 km. Comparison was achieved with percent error computations (spherical-flat/spherical) at critical anomaly points. At the peak gravity anomaly value, errors are less than + or - 5% for all prisms. At 1/2 and 1/10 of the peak, errors are generally less than 10% and 40% respectively, increasing to these values with longer and wider prisms at higher altitudes. For magnetics, the errors at critical anomaly points are less than -10% for all prisms, attaining these magnitudes with longer and wider prisms at higher altitudes. In general, in both gravity and magnetic modeling, errors increase greatly for prisms wider than 500 km, although gravity modeling is more sensitive than magnetic modeling to spherical-Earth effects. Preliminary modeling of both satellite gravity and magnetic anomalies using flat-Earth assumptions is justified considering the errors caused by uncertainties in isolating anomalies.

  13. Using LAHARZ to Forecast Inundation from lahars, debris flows, and rock avalanches: Confidence Limits on Prediction

    NASA Astrophysics Data System (ADS)

    Schilling, S. P.; Griswold, J. P.; Iverson, R. M.

    2008-12-01

    LAHARZ is a computational model that uses statistical descriptions of areas inundated by past mass-flow events to forecast areas likely to be inundated by hypothetical future events. The forecasts are based on sets of physically motivated and statistically calibrated power-law equations that each have a form A = cV2/3, relating mass-flow volume (V) to planimetric or cross-sectional areas (A) inundated by an average flow as it descends a given drainage. Calibration of the equations utilizes logarithmic transformation and linear regression to determine the best-fit values of c. The LAHARZ software uses specified values of V, an algorithm for idenitifying mass-flow source areas, and digital elevation models of topography to portray forecast hazard zones on maps. In typical applications, a range of plausible V values results in a set of nested hazard zones showing areas likely to be inundated by a range of hypothetical flows. LAHARZ forecasts have not included explicit confidence limits for areas likely to be inundated by individual flows, however; here we describe work that remedies this shortcoming. The basic elements required to generate explict confidence limits in LAHARZ forecasts are the sets of data pairs relating values of V and A, the statistically calibrated prediction equations, a user-specified level of confidence, and t-distribution statistics. The prediction equations and data are used to calculate the standard error of regression, standard error of the mean, and standard error of prediction. Calculation of these standard errors closely parallels procedures described in many statistics books, but differs subtly because the LAHARZ prediction equations have only one calibrated parameter (c), not two as in typical linear regression. Standard errors do not fully determine prediction uncertainty, however, because it does not account for the fact that predictions are based on an incomplete sample of the population of V and A values. The effect of incomplete

  14. A Combined SRTM Digital Elevation Model for Zanjan State of Iran Based on the Corrective Surface Idea

    NASA Astrophysics Data System (ADS)

    Kiamehr, Ramin

    2016-04-01

    One arc-second high resolution version of the SRTM model recently published for the Iran by the US Geological Survey database. Digital Elevation Models (DEM) is widely used in different disciplines and applications by geoscientist. It is an essential data in geoid computation procedure, e.g., to determine the topographic, downward continuation (DWC) and atmospheric corrections. Also, it can be used in road location and design in civil engineering and hydrological analysis. However, a DEM is only a model of the elevation surface and it is subject to errors. The most important parts of errors could be comes from the bias in height datum. On the other hand, the accuracy of DEM is usually published in global sense and it is important to have estimation about the accuracy in the area of interest before using of it. One of the best methods to have a reasonable indication about the accuracy of DEM is obtained from the comparison of their height versus the precise national GPS/levelling data. It can be done by the determination of the Root-Mean-Square (RMS) of fitting between the DEM and leveling heights. The errors in the DEM can be approximated by different kinds of functions in order to fit the DEMs to a set of GPS/levelling data using the least squares adjustment. In the current study, several models ranging from a simple linear regression to seven parameter similarity transformation model are used in fitting procedure. However, the seven parameter model gives the best fitting with minimum standard division in all selected DEMs in the study area. Based on the 35 precise GPS/levelling data we obtain a RMS of 7 parameter fitting for SRTM DEM 5.5 m, The corrective surface model in generated based on the transformation parameters and included to the original SRTM model. The result of fitting in combined model is estimated again by independent GPS/leveling data. The result shows great improvement in absolute accuracy of the model with the standard deviation of 3.4 meter.

  15. A New Constitutive Model for the Plastic Flow of Metals at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Spigarelli, S.; El Mehtedi, M.

    2013-11-01

    A new constitutive model based on the combination of the Garofalo and Hensel-Spittel equations has been used to describe the plastic flow behavior of an AA6005 aluminum alloy tested in torsion. The analysis of the experimental data by the constitutive model resulted in an excellent description of the flow curves. The model equation was then rewritten to explicitly include the Arrhenius term describing the temperature dependence of plastic deformation. The calculation indicated that the activation energy for hot working slowly decreased with increasing strain, leading to thermally activated flow softening. The combined use of the new equation and torsion testing led to the development of a constitutive model which can be safely adopted in a computer code to simulate forging or extrusion.

  16. Evaluation of Three Constitutive Models for the Prediction of Hastelloy X Elevated Temperature Cyclic Response

    NASA Technical Reports Server (NTRS)

    Moreno, V.

    1983-01-01

    The approach for the method development assumes that, for a thermally loaded structure, the overall strain history is defined by linear elastic analysis. The local stress history at a fatigue critical location is then determined from a one dimensional material behavior model and the local strain and temperature conditions. Three material models are currently being evaluated to assess their ability to predict relevant high temperature cyclic material response characteristics. They are: a time independent classical plasticity and creep representation, a time dependent viscoplastic model capable of predicting combined creep and plasticity effects, and an approximate elastic analysis approach that uses a series of stress-strain curves and a cyclic hardening model to determine reverse plasticity.

  17. Determining the Suitability of Different Digital Elevation Models and Satellite Images for Fancy Maps. An Example of Cyprus

    NASA Astrophysics Data System (ADS)

    Drachal, J.; Kawel, A. K.

    2016-06-01

    The article describes the possibility of developing an overall map of the selected area on the basis of publicly available data. Such a map would take the form designed by the author with the colors that meets his expectations and a content, which he considers to be appropriate. Among the data available it was considered the use of satellite images of the terrain in real colors and, in the form of shaded relief, digital terrain models with different resolutions of the terrain mesh. Specifically the considered data were: MODIS, Landsat 8, GTOPO-30, SRTM-30, SRTM-1, SRTM-3, ASTER. For the test area the island of Cyprus was chosen because of the importance in tourism, a relatively small area and a clearly defined boundary. In the paper there are shown and discussed various options of the Cyprus terrain image obtained synthetically from variants of Modis, Landsat and digital elevation models of different resolutions.

  18. Repeat-swap homology modeling of secondary active transporters: updated protocol and prediction of elevator-type mechanisms

    PubMed Central

    Vergara-Jaque, Ariela; Fenollar-Ferrer, Cristina; Kaufmann, Desirée; Forrest, Lucy R.

    2015-01-01

    Secondary active transporters are critical for neurotransmitter clearance and recycling during synaptic transmission and uptake of nutrients. These proteins mediate the movement of solutes against their concentration gradients, by using the energy released in the movement of ions down pre-existing concentration gradients. To achieve this, transporters conform to the so-called alternating-access hypothesis, whereby the protein adopts at least two conformations in which the substrate binding sites are exposed to one or other side of the membrane, but not both simultaneously. Structures of a bacterial homolog of neuronal glutamate transporters, GltPh, in several different conformational states have revealed that the protein structure is asymmetric in the outward- and inward-open states, and that the conformational change connecting them involves a elevator-like movement of a substrate binding domain across the membrane. The structural asymmetry is created by inverted-topology repeats, i.e., structural repeats with similar overall folds whose transmembrane topologies are related to each other by two-fold pseudo-symmetry around an axis parallel to the membrane plane. Inverted repeats have been found in around three-quarters of secondary transporter folds. Moreover, the (a)symmetry of these systems has been successfully used as a bioinformatic tool, called “repeat-swap modeling” to predict structural models of a transporter in one conformation using the known structure of the transporter in the complementary conformation as a template. Here, we describe an updated repeat-swap homology modeling protocol, and calibrate the accuracy of the method using GltPh, for which both inward- and outward-facing conformations are known. We then apply this repeat-swap homology modeling procedure to a concentrative nucleoside transporter, VcCNT, which has a three-dimensional arrangement related to that of GltPh. The repeat-swapped model of VcCNT predicts that nucleoside transport

  19. Priority-flood: An optimal depression-filling and watershed-labeling algorithm for digital elevation models

    NASA Astrophysics Data System (ADS)

    Barnes, Richard; Lehman, Clarence; Mulla, David

    2014-01-01

    Depressions (or pits) are areas within a digital elevation model that are surrounded by higher terrain, with no outlet to lower areas. Filling them so they are level, as fluid would fill them if the terrain was impermeable, is often necessary in preprocessing DEMs. The depression-filling algorithm presented here - called Priority-Flood - unifies and improves the work of a number of previous authors who have published similar algorithms. The algorithm operates by flooding DEMs inwards from their edges using a priority queue to determine the next cell to be flooded. The resultant DEM has no depressions or digital dams: every cell is guaranteed to drain. The algorithm is optimal for both integer and floating-point data, working in O(n) and O(n log2 n) time, respectively. It is shown that by using a plain queue to fill depressions once they have been found, an O(m log2 m) time-complexity can be achieved, where m does not exceed the number of cells n. This is the lowest time complexity of any known floating-point depression-filling algorithm. In testing, this improved variation of the algorithm performed up to 37% faster than the original. Additionally, a parallel version of an older, but widely used, depression-filling algorithm required six parallel processors to achieve a run-time on par with what the newer algorithm's improved variation took on a single processor. The Priority-Flood Algorithm is simple to understand and implement: the included pseudocode is only 20 lines and the included C++ reference implementation is under a hundred lines. The algorithm can work on irregular meshes as well as 4-, 6-, 8-, and n-connected grids. It can also be adapted to label watersheds and determine flow directions through either incremental elevation changes or depression carving. In the case of incremental elevation changes, the algorithm includes safety checks not present in prior works.

  20. Mars elevation distribution

    NASA Technical Reports Server (NTRS)

    Wu, Sherman S. C.; Howington-Kraus, Annie E.; Ablin, Karyn K.

    1991-01-01

    A Digital Terrain Model (DTM) of Mars was derived with both Mercator and Sinusoidal Equal-Area projections from the global topographic map of Mars (scale 1:15 million, contour interval 1 km). Elevations on the map are referred to Mars' topographic datum that is defined by the gravity field at a 6.1-millibar pressure surface with respect to the center of mass of Mars. The DTM has a resolution at the equator of 1/59.226 degrees (exactly 1 km) per pixel. By using the DTM, the volumetric distribution of Mars topography above and below the datum has previously been calculated. Three types of elevation distributions of Mars' topography were calculated from the same DTM: (1) the frequency distribution of elevations at the pixel resolution; (2) average elevations in increments of 6 degrees in both longitude and latitude; and (3) average elevations in 36 separate blocks, each covering 30 degrees of latitude and 60 degrees of longitude.

  1. The National Map - Elevation

    USGS Publications Warehouse

    Gesch, Dean; Evans, Gayla; Mauck, James; Hutchinson, John; Carswell, William J.

    2009-01-01

    The National Elevation Dataset (NED) is the primary elevation data product produced and distributed by the USGS. The NED provides seamless raster elevation data of the conterminous United States, Alaska, Hawaii, and the island territories. The NED is derived from diverse source data sets that are processed to a specification with a consistent resolution, coordinate system, elevation units, and horizontal and vertical datums. The NED is the logical result of the maturation of the long-standing USGS elevation program, which for many years concentrated on production of topographic map quadrangle-based digital elevation models. The NED serves as the elevation layer of The National Map, and provides basic elevation information for earth science studies and mapping applications in the United States. The NED is a multi-resolution dataset that is updated bimonthly to integrate newly available, improved elevation source data. NED data are available nationally at grid spacings of 1 arc-second (approximately 30 meters) for the conterminous United States, and at 1/3 and 1/9 arc-seconds (approximately 10 and 3 meters, respectively) for parts of the United States. Most of the NED for Alaska is available at 2-arc-second (about 60 meters) grid spacing, where only lower resolution source data exist. Part of Alaska is available at the 1/3-arc-second resolution, and plans are in development for a significant upgrade in elevation data coverage of the State over the next 5 years. Specifications for the NED include the following: *Coordinate system: Geographic (decimal degrees of latitude and longitude), *Horizontal datum: North American Datum of 1983 (NAD 83), *Vertical datum: North American Vertical Datum of 1988 (NAVD 88) over the conterminous United States and varies in other areas, and *Elevation units: Decimal meters.

  2. An experimental comparison of several current viscoplastic constitutive models at elevated temperature

    NASA Technical Reports Server (NTRS)

    James, G. H.; Imbrie, P. K.; Hill, P. S.; Allen, D. H.; Haisler, W. E.

    1988-01-01

    Four current viscoplastic models are compared experimentally for Inconel 718 at 593 C. This material system responds with apparent negative strain rate sensitivity, undergoes cyclic work softening, and is susceptible to low cycle fatigue. A series of tests were performed to create a data base from which to evaluate material constants. A method to evaluate the constants is developed which draws on common assumptions for this type of material, recent advances by other researchers, and iterative techniques. A complex history test, not used in calculating the constants, is then used to compare the predictive capabilities of the models. The combination of exponentially based inelastic strain rate equations and dynamic recovery is shown to model this material system with the greatest success. The method of constant calculation developed was successfully applied to the complex material response encountered. Backstress measuring tests were found to be invaluable and to warrant further development.

  3. A model of ocean basin crustal magnetization appropriate for satellite elevation anomalies

    NASA Technical Reports Server (NTRS)

    Thomas, Herman H.

    1987-01-01

    A model of ocean basin crustal magnetization measured at satellite altitudes is developed which will serve both as background to which anomalous magnetizations can be contrasted and as a beginning point for studies of tectonic modification of normal ocean crust. The model is based on published data concerned with the petrology and magnetization of the ocean crust and consists of viscous magnetization and induced magnetization estimated for individual crustal layers. Thermal remanent magnetization and chemical remanent magnetization are excluded from the model because seafloor spreading anomalies are too short in wavelength to be resolved at satellite altitudes. The exception to this generalization is found at the oceanic magnetic quiet zones where thermal remanent magnetization and chemical remanent magnetization must be considered along with viscous magnetization and induced magnetization.

  4. Evaluation of the U.S. Geological Survey standard elevation products in a two-dimensional hydraulic modeling application for a low relief coastal floodplain

    NASA Astrophysics Data System (ADS)

    Witt, Emitt C.

    2015-12-01

    Growing use of two-dimensional (2-D) hydraulic models has created a need for high resolution data to support flood volume estimates, floodplain specific engineering data, and accurate flood inundation scenarios. Elevation data are a critical input to these models that guide the flood-wave across the landscape allowing the computation of valuable engineering specific data that provides a better understanding of flooding impacts on structures, debris movement, bed scour, and direction. High resolution elevation data are becoming publicly available that can benefit the 2-D flood modeling community. Comparison of these newly available data with legacy data suggests that better modeling outcomes are achieved by using 3D Elevation Program (3DEP) lidar point data and the derived 1 m Digital Elevation Model (DEM) product relative to the legacy 3 m, 10 m, or 30 m products currently available in the U.S. Geological Survey (USGS) National Elevation Dataset. Within the low topographic relief of a coastal floodplain, the newer 3DEP data better resolved elevations within the forested and swampy areas achieving simulations that compared well with a historic flooding event. Results show that the 1 m DEM derived from 3DEP lidar source provides a more conservative estimate of specific energy, static pressure, and impact pressure for grid elements at maximum flow relative to the legacy DEM data. Better flood simulations are critically important in coastal floodplains where climate change driven storm frequency and sea level rise will contribute to more frequent flooding events.

  5. Evaluation of the U.S. Geological Survey standard elevation products in a two-dimensional hydraulic modeling application for a low relief coastal floodplain

    USGS Publications Warehouse

    Witt, Emitt C.

    2015-01-01

    Growing use of two-dimensional (2-D) hydraulic models has created a need for high resolution data to support flood volume estimates, floodplain specific engineering data, and accurate flood inundation scenarios. Elevation data are a critical input to these models that guide the flood-wave across the landscape allowing the computation of valuable engineering specific data that provides a better understanding of flooding impacts on structures, debris movement, bed scour, and direction. High resolution elevation data are becoming publicly available that can benefit the 2-D flood modeling community. Comparison of these newly available data with legacy data suggests that better modeling outcomes are achieved by using 3D Elevation Program (3DEP) lidar point data and the derived 1 m Digital Elevation Model (DEM) product relative to the legacy 3 m, 10 m, or 30 m products currently available in the U.S. Geological Survey (USGS) National Elevation Dataset. Within the low topographic relief of a coastal floodplain, the newer 3DEP data better resolved elevations within the forested and swampy areas achieving simulations that compared well with a historic flooding event. Results show that the 1 m DEM derived from 3DEP lidar source provides a more conservative estimate of specific energy, static pressure, and impact pressure for grid elements at maximum flow relative to the legacy DEM data. Better flood simulations are critically important in coastal floodplains where climate change driven storm frequency and sea level rise will contribute to more frequent flooding events.

  6. Experimental vs. modeled water use in mature Norway spruce (Picea abies) exposed to elevated CO(2).

    PubMed

    Leuzinger, Sebastian; Bader, Martin K-F

    2012-01-01

    Rising levels of atmospheric CO(2) have often been reported to reduce plant water use. Such behavior is also predicted by standard equations relating photosynthesis, stomatal conductance, and atmospheric CO(2) concentration, which form the core of dynamic global vegetation models (DGVMs). Here, we provide first results from a free air CO(2) enrichment (FACE) experiment with naturally growing, mature (35 m) Picea abies (L.) (Norway spruce) and compare them to simulations by the DGVM LPJ-GUESS. We monitored sap flow, stem water deficit, stomatal conductance, leaf water potential, and soil moisture in five 35-40 m tall CO(2)-treated (550 ppm) trees over two seasons. Using LPJ-GUESS, we simulated this experiment using climate data from a nearby weather station. While the model predicted a stable reduction of transpiration of between 9% and 18% (at concentrations of 550-700 ppm atmospheric CO(2)), the combined evidence from various methods characterizing water use in our experimental trees suggest no changes in response to future CO(2) concentrations. The discrepancy between the modeled and the experimental results may be a scaling issue: while dynamic vegetation models correctly predict leaf-level responses, they may not sufficiently account for the processes involved at the canopy and ecosystem scale, which could offset the first-order stomatal response.

  7. Overland Flow Analysis Using Time Series of Suas-Derived Elevation Models

    NASA Astrophysics Data System (ADS)

    Jeziorska, J.; Mitasova, H.; Petrasova, A.; Petras, V.; Divakaran, D.; Zajkowski, T.

    2016-06-01

    With the advent of the innovative techniques for generating high temporal and spatial resolution terrain models from Unmanned Aerial Systems (UAS) imagery, it has become possible to precisely map overland flow patterns. Furthermore, the process has become more affordable and efficient through the coupling of small UAS (sUAS) that are easily deployed with Structure from Motion (SfM) algorithms that can efficiently derive 3D data from RGB imagery captured with consumer grade cameras. We propose applying the robust overland flow algorithm based on the path sampling technique for mapping flow paths in the arable land on a small test site in Raleigh, North Carolina. By comparing a time series of five flights in 2015 with the results of a simulation based on the most recent lidar derived DEM (2013), we show that the sUAS based data is suitable for overland flow predictions and has several advantages over the lidar data. The sUAS based data captures preferential flow along tillage and more accurately represents gullies. Furthermore the simulated water flow patterns over the sUAS based terrain models are consistent throughout the year. When terrain models are reconstructed only from sUAS captured RGB imagery, however, water flow modeling is only appropriate in areas with sparse or no vegetation cover.

  8. Digital elevation model of King Edward VII Peninsula, West Antarctica, from SAR interferometry and ICESat laser altimetry

    USGS Publications Warehouse

    Baek, S.; Kwoun, Oh-Ig; Braun, Andreas; Lu, Zhiming; Shum, C.K.

    2005-01-01

    We present a digital elevation model (DEM) of King Edward VII Peninsula, Sulzberger Bay, West Antarctica, developed using 12 European Remote Sensing (ERS) synthetic aperture radar (SAR) scenes and 24 Ice, Cloud, and land Elevation Satellite (ICESat) laser altimetry profiles. We employ differential interferograms from the ERS tandem mission SAR scenes acquired in the austral fall of 1996, and four selected ICESat laser altimetry profiles acquired in the austral fall of 2004, as ground control points (GCPs) to construct an improved geocentric 60-m resolution DEM over the grounded ice region. We then extend the DEM to include two ice shelves using ICESat profiles via Kriging. Twenty additional ICESat profiles acquired in 2003-2004 are used to assess the accuracy of the DEM. After accounting for radar penetration depth and predicted surface changes, including effects due to ice mass balance, solid Earth tides, and glacial isostatic adjustment, in part to account for the eight-year data acquisition discrepancy, the resulting difference between the DEM and ICESat profiles is -0.57 ?? 5.88 m. After removing the discrepancy between the DEM and ICESat profiles for a final combined DEM using a bicubic spline, the overall difference is 0.05 ?? 1.35 m. ?? 2005 IEEE.

  9. CALIPSO Satellite Lidar Identification Of Elevated Dust Over Australia Compared With Air Quality Model PM60 Forecasts

    NASA Technical Reports Server (NTRS)

    Young, Stuart A.; Vaughan, Mark; Omar, Ali; Liu, Zhaoyan; Lee, Sunhee; Hu, Youngxiang; Cope, Martin

    2008-01-01

    Global measurements of the vertical distribution of clouds and aerosols have been recorded by the lidar on board the CALIPSO (Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations) satellite since June 2006. Such extensive, height-resolved measurements provide a rare and valuable opportunity for developing, testing and validating various atmospheric models, including global climate, numerical weather prediction, chemical transport and air quality models. Here we report on the initial results of an investigation into the performance of the Australian Air Quality Forecast System (AAQFS) model in forecasting the distribution of elevated dust over the Australian region. The model forecasts of PM60 dust distribution are compared with the CALIPSO lidar Vertical Feature Mask (VFM) data product. The VFM classifies contiguous atmospheric regions of enhanced backscatter as either cloud or aerosols. Aerosols are further classified into six subtypes. By comparing forecast PM60 concentration profiles to the spatial distribution of dust reported in the CALIPSO VFM, we can assess the model s ability to predict the occurrence and the vertical and horizontal extents of dust events within the study area.

  10. Coastal Storm Surge Analysis System Digital Elevation Model: Report 1: Intermediate Submission No. 1.1

    DTIC Science & Technology

    2011-03-01

    the development and application of a state - of - the - art storm surge risk assessment capability for the FEMA Region III domain which...within the states of Virginia, Maryland, and Delaware, and the District of Columbia including the Atlantic Ocean, Chesapeake Bay and its tributaries...to calculate the combined effects of surge and wind -induced waves. A seamless modeling grid was developed to support the

  11. 3D-geological structures with digital elevation models using GPU programming

    NASA Astrophysics Data System (ADS)

    Mateo Lázaro, Jesús; Sánchez Navarro, José Ángel; García Gil, Alejandro; Edo Romero, Vanesa

    2014-09-01

    We present an application that visualises three-dimensional geological structures with digital terrain models. The three-dimensional structures are displayed as their intersections with two-dimensional surfaces that may be defined analytically (e.g., sections) or with grid meshes in the case of irregular surfaces such as the digital terrain models. The process begins with classic techniques of terrain visualisation using hypsometric shading with textures. Then, geometric transformations that are easily conceived and programmed are added, thus representing the three-dimensional structures with their location and orientation. Functions of three variables are used to define the geological structures, and data from digital terrain models are used as one of the variables. This provides a simple source code and results in a short calculation time. Additionally, the process of generating new textures can be performed by a Graphics Processing Unit (GPU), thereby making real-time processing very effective and providing the possibility of displaying the simulation of geological structures in motion.

  12. Detection of Digital Elevation Model Errors Using X-band Weather Radar

    NASA Technical Reports Server (NTRS)

    Young, Steven D.; deHaag, Maatren Uijt

    2007-01-01

    Flight in Instrument Meteorological Conditions requires pilots to manipulate flight controls while referring to a Primary Flight Display. The Primary Flight Display indicates aircraft attitude along with, in some cases, many other state variables such as altitude, speed, and guidance cues. Synthetic Vision Systems have been proposed that overlay the traditional information provided on Primary Flight Displays onto a scene depicting the location of terrain and other geo-spatial features.Terrain models used by these displays must have sufficient quality to avoid providing misleading information. This paper describes how X-band radar measurements can be used as part of a monitor, and/or maintenance system, to quantify the integrity of terrain models that are used by systems such as Synthetic Vision. Terrain shadowing effects, as seen by the radar, are compared in a statistical manner against estimated shadow feature elements extracted from the stored terrain model from the perspective of the airborne observer. A test statistic is defined that enables detection of errors as small as the range resolution of the radar. Experimental results obtained from two aircraft platforms hosting certified commercial-off-the-shelf X-band radars test the premise and illustrate its potential.

  13. A New Creep Constitutive Model for 7075 Aluminum Alloy Under Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Lin, Y. C.; Jiang, Yu-Qiang; Zhou, Hua-Min; Liu, Guan

    2014-12-01

    Exposure of aluminum alloy to an elastic loading, during "creep-aging forming" or other manufacturing processes at relatively high temperature, may lead to the lasting creep deformation. The creep behaviors of 7075 aluminum alloy are investigated by uniaxial tensile creep experiments over wide ranges of temperature and external stress. The results show that the creep behaviors of the studied aluminum alloy strongly depend on the creep temperature, external stress, and creep time. With the increase of creep temperature and external stress, the creep strain increases quickly. In order to overcome the shortcomings of the Bailey-Norton law and θ projection method, a new constitutive model is proposed to describe the variations of creep strain with time for the studied aluminum alloy. In the proposed model, the dependences of creep strain on the creep temperature, external stress, and creep time are well taken into account. A good agreement between the predicted and measured creep strains shows that the established creep constitutive model can give an accurate description of the creep behaviors of 7075 aluminum alloy. Meanwhile, the obtained stress exponent indicates that the creep process is controlled by the dislocation glide, which is verified by the microstructural observations.

  14. Automated identification of stream-channel geomorphic features from high‑resolution digital elevation models in West Tennessee watersheds

    USGS Publications Warehouse

    Cartwright, Jennifer M.; Diehl, Timothy H.

    2017-01-17

    High-resolution digital elevation models (DEMs) derived from light detection and ranging (lidar) enable investigations of stream-channel geomorphology with much greater precision than previously possible. The U.S. Geological Survey has developed the DEM Geomorphology Toolbox, containing seven tools to automate the identification of sites of geomorphic instability that may represent sediment sources and sinks in stream-channel networks. These tools can be used to modify input DEMs on the basis of known locations of stormwater infrastructure, derive flow networks at user-specified resolutions, and identify possible sites of geomorphic instability including steep banks, abrupt changes in channel slope, or areas of rough terrain. Field verification of tool outputs identified several tool limitations but also demonstrated their overall usefulness in highlighting likely sediment sources and sinks within channel networks. In particular, spatial clusters of outputs from multiple tools can be used to prioritize field efforts to assess and restore eroding stream reaches.

  15. Elevated dietary magnesium prevents connective tissue mineralization in a mouse model of pseudoxanthoma elasticum (Abcc6(-/-)).

    PubMed

    LaRusso, Jennifer; Li, Qiaoli; Jiang, Qiujie; Uitto, Jouni

    2009-06-01

    Pseudoxanthoma elasticum (PXE) is an autosomal recessive multisystem disorder characterized by ectopic connective tissue mineralization, with clinical manifestations primarily in the skin, eyes, and cardiovascular system. There is considerable, both intra- and interfamilial, variability in the spectrum of phenotypic presentation. Previous studies have suggested that mineral content of the diet may modify the severity of the clinical phenotype in PXE. In this study, we utilized a targeted mutant mouse (Abcc6(-/-)) as a model system for PXE. We examined the effects of changes in dietary phosphate and magnesium on the mineralization process using calcification of the connective tissue capsule surrounding the vibrissae as an early phenotypic biomarker. Mice placed on custom-designed diets either high or low in phosphate did not show changes in mineralization, which was similar to that noted in Abcc6(-/-) mice on control diet. However, mice placed on diet enriched in magnesium (fivefold) showed no evidence of connective tissue mineralization in this mouse model of PXE. The inhibitory capacity of magnesium was confirmed in a cell-based mineralization assay system in vitro. Collectively, our observations suggest that assessment of dietary magnesium in patients with PXE may be warranted.

  16. Elevated carbon dioxide is predicted to promote coexistence among competing species in a trait-based model.

    PubMed

    Ali, Ashehad A; Medlyn, Belinda E; Aubier, Thomas G; Crous, Kristine Y; Reich, Peter B

    2015-10-01

    Differential species responses to atmospheric CO 2 concentration (Ca) could lead to quantitative changes in competition among species and community composition, with flow-on effects for ecosystem function. However, there has been little theoretical analysis of how elevated Ca (eC a) will affect plant competition, or how composition of plant communities might change. Such theoretical analysis is needed for developing testable hypotheses to frame experimental research. Here, we investigated theoretically how plant competition might change under eC a by implementing two alternative competition theories, resource use theory and resource capture theory, in a plant carbon and nitrogen cycling model. The model makes several novel predictions for the impact of eC a on plant community composition. Using resource use theory, the model predicts that eC a is unlikely to change species dominance in competition, but is likely to increase coexistence among species. Using resource capture theory, the model predicts that eC a may increase community evenness. Collectively, both theories suggest that eC a will favor coexistence and hence that species diversity should increase with eC a. Our theoretical analysis leads to a novel hypothesis for the impact of eC a on plant community composition. This hypothesis has potential to help guide the design and interpretation of eC a experiments.

  17. Constraining the Kinematics of the A.D. 900 Seattle Fault Earthquake With Geomechanical Modeling and LIDAR Surface Elevation Data

    NASA Astrophysics Data System (ADS)

    Muller, J. R.; Harding, D. J.

    2005-05-01

    Within the Puget Sound region of Washington State, several lines of geological evidence suggest that the largest upper-crustal earthquake within the past 2500 years occurred on the Seattle fault system in A.D. 900. Constraining the rupture characteristics of this event is of singular importance in evaluating the upper-bound seismic hazard and tsunami threat posed by upper-crustal (non-subduction) earthquakes to the Puget Lowland region. It is only possible to model the fault geometry, slip distribution, and moment magnitude of this earthquake with a data set of the surface elevation changes caused by this event. Due to the historic age of this earthquake, we use elevations of an uplifted marine terrace, digitally extracted from LIDAR images, as a novel source of coseismic surface deformation data for this event. Ideal for this forested region, LIDAR images, acquired via airborne laser swath mapping (ALSM), offer a drastic improvement over earlier topographic mapping techniques due to its improved resolution and its ability to measure the ground surface beneath dense vegetative cover. The LIDAR images reveal a single uplifted terrace, dated to 1000 cal yr B.P. near Restoration Point, that is morphologically continuous along the southern shoreline of Bainbridge Island and is visible at comparable elevations within a 25 km by 12 km region encompassing coastlines of West Seattle, Bremerton, East Bremerton, Port Orchard, and Waterman Point. Considering sea level changes since A.D. 900, the maximum uplift magnitudes of shoreline inner edges approach nine meters and are located at the southernmost coastline of Bainbridge Island and the northern tip of Waterman Point, while tilt magnitudes are modest - approaching 0.1 degrees. Although the terrace is locally offset and tilted near the Toe Jam Hill and Waterman north-dipping, reverse fault scarps, the regional uplift pattern is a doubly-plunging antiform with steepened north limb, consistent with its location directly above

  18. Human cytomegalovirus infection leads to elevated levels of transplant arteriosclerosis in a humanized mouse aortic xenograft model.

    PubMed

    Abele-Ohl, S; Leis, M; Wollin, M; Mahmoudian, S; Hoffmann, J; Müller, R; Heim, C; Spriewald, B M; Weyand, M; Stamminger, T; Ensminger, S M

    2012-07-01

    Recent findings emphasized an important role of human cytomegalovirus (HCMV) infection in the development of transplant arteriosclerosis. Therefore, the aim of this study was to develop a human peripheral blood lymphocyte (hu-PBL)/Rag-2(-/-) γc(-/-) mouse-xenograft-model to investigate both immunological as well as viral effector mechanisms in the progression of transplant arteriosclerosis. For this, sidebranches from the internal mammary artery were recovered during coronary artery bypass graft surgery, tissue-typed and infected with HCMV. Then, size-matched sidebranches were implanted into the infrarenal aorta of Rag-2(-/-) γc(-/-) mice. The animals were reconstituted with human peripheral blood mononuclear cells (PBMCs) 7 days after transplantation. HCMV-infection was confirmed by Taqman-PCR and immunofluorescence analyses. Arterial grafts were analyzed by histology on day 40 after transplantation. PBMC-reconstituted Rag-2(-/-) γc(-/-) animals showed splenic chimerism levels ranging from 1-16% human cells. After reconstitution, Rag-2(-/-) γc(-/-) mice developed human leukocyte infiltrates in their grafts and vascular lesions that were significantly elevated after infection. Cellular infiltration revealed significantly increased ICAM-1 and PDGF-R-β expression after HCMV-infection of the graft. Arterial grafts from unreconstituted Rag-2(-/-) γc(-/-) recipients showed no vascular lesions. These data demonstrate a causative relationship between HCMV-infection as an isolated risk factor and the development of transplant-arteriosclerosis in a humanized mouse arterial-transplant-model possibly by elevated ICAM-1 and PDGF-R-β expression.

  19. Development of status epilepticus, sustained calcium elevations and neuronal injury in a rat survival model of lethal paraoxon intoxication

    PubMed Central

    Deshpande, Laxmikant S.; Carter, Dawn S.; Phillips, Kristin F.; Blair, Robert E.; DeLorenzo, Robert J.

    2014-01-01

    Paraoxon (POX) is an active metabolite of organophosphate (OP) pesticide parathion that has been weaponized and used against civilian populations. Exposure to POX produces high mortality. OP poisoning is often associated with chronic neurological disorders. In this study, we optimize a rat survival model of lethal POX exposures in order to mimic both acute and long-term effects of POX intoxication. Male Sprague-Dawley rats injected with POX (4 mg/kg, ice-cold PBS, s.c.) produced a rapid cholinergic crisis that evolved into status epilepticus (SE) and death within 6–8 min. The EEG profile for POX induced SE was characterized and showed clinical and electrographic seizures with 7–10 Hz spike activity. Treatment of 100% lethal POX intoxication with an optimized three drug regimen (atropine, 2 mg/kg, i.p., 2-PAM, 25 mg/kg, i.m. and diazepam, 5 mg/kg, i.p.) promptly stopped SE and reduced acute mortality to 12% and chronic mortality to 18%. This model is ideally suited to test effective countermeasures against lethal POX exposure. Animals that survived the POX SE manifested prolonged elevations in hippocampal [Ca2+]i (Ca2+ plateau) and significant multifocal neuronal injury. POX SE induced Ca2+ plateau had its origin in Ca2+ release from intracellular Ca2+ stores since inhibition of ryanodine/ IP3 receptor lowered elevated Ca2+ levels post SE. POX SE induced neuronal injury and alterations in Ca2+ dynamics may underlie some of the long term morbidity associated with OP toxicity. PMID:24785379

  20. Elevated fecal peptidase D at onset of colitis in Galphai2-/- mice, a mouse model of IBD

    PubMed Central

    Kruse, Robert; Sapnara, Maria; Halfvarson, Jonas; Hörnquist, Elisabeth Hultgren

    2017-01-01

    Background The identification of novel fecal biomarkers in inflammatory bowel disease (IBD) is hampered by the complexity of the human fecal proteome. On the other hand, in experimental mouse models there is probably less variation. We investigated the fecal protein content in mice to identify possible biomarkers and pathogenic mechanisms. Methods Fecal samples were collected at onset of inflammation in Galphai2-/- mice, a well-described spontaneous model of chronic colitis, and from healthy littermates. The fecal proteome was analyzed by two-dimensional electrophoresis and quantitative mass spectrometry and results were then validated in a new cohort of mice. Results As a potential top marker of disease, peptidase D was found at a higher ratio in Galphai2-/- mouse feces relative to controls (fold change 27; p = 0.019). Other proteins found to be enriched in Gαi2-/- mice were mainly pancreatic proteases, and proteins from plasma and blood cells. A tendency of increased calprotectin, subunit S100-A8, was also observed (fold change 21; p = 0.058). Proteases are potential activators of inflammation in the gastrointestinal tract through their interaction with the proteinase-activated receptor 2 (PAR2). Accordingly, the level of PAR2 was found to be elevated in both the colon and the pancreas of Galphai2-/- mice at different stages of disease. Conclusions These findings identify peptidase D, an ubiquitously expressed intracellular peptidase, as a potential novel marker of colitis. The elevated levels of fecal proteases may be involved in the pathogenesis of colitis and contribute to the clinical phenotype, possibly by activation of intestinal PAR2. PMID:28323866