1,129 Matching Results

Search Results

Advanced search parameters have been applied.

ARAC simulations of the ash plume from the December 1997 eruption of Soufriere Hills Volcano, Montserrat

Description: Ash clouds generated by erupting volcanoes represent a serious hazard to military and civil aviation. The dispersion modeling system of the Atmospheric Release Advisory Capability (ARAC) has been used to model the cloud resulting from the eruption of the Soufriere Hills volcano, Montserrat in December 1997. A clone of parts of the ARAC system, now being installed at the Air Force Weather Agency (AFWA), will enable AFWA to provide hazard guidance to military operations in the vicinity of erupting volcanoes. This paper presents ARAC� s modeling results and discusses potential application of similar calculations for AFWA support during future events.
Date: October 1, 1998
Creator: Ellis, J. S.; Lefevre, R. J.; Pace, J. C.; Vogt, P. J. & Voight, B.
Partner: UNT Libraries Government Documents Department

The Use of Reciprocity in Atmospheric Source Inversion Problems

Description: The goal of the Event Reconstruction Project is to find the location and strength of atmospheric release points, both stationary and moving. Source inversion relies on observational data as input. The methodology is sufficiently general to allow various forms of data. In this report, the authors will focus primarily on concentration measurements obtained at point monitoring locations at various times. The algorithms being investigated in the Project are the MCMC (Markov Chain Monte Carlo), SMC (Sequential Monte Carlo) Methods, classical inversion methods, and hybrids of these. They refer the reader to the report by Johannesson et al. (2004) for explanations of these methods. These methods require computing the concentrations at all monitoring locations for a given ''proposed'' source characteristic (locations and strength history). It is anticipated that the largest portion of the CPU time will take place performing this computation. MCMC and SMC will require this computation to be done at least tens of thousands of times. Therefore, an efficient means of computing forward model predictions is important to making the inversion practical. In this report they show how Green's functions and reciprocal Green's functions can significantly accelerate forward model computations. First, instead of computing a plume for each possible source strength history, they can compute plumes from unit impulse sources only. By using linear superposition, they can obtain the response for any strength history. This response is given by the forward Green's function. Second, they may use the law of reciprocity. Suppose that they require the concentration at a single monitoring point x{sub m} due to a potential (unit impulse) source that is located at x{sub s}. instead of computing a plume with source location x{sub s}, they compute a ''reciprocal plume'' whose (unit impulse) source is at the monitoring locations x{sub m}. The reciprocal plume is computed using ...
Date: October 13, 2004
Creator: Nitao, J J
Partner: UNT Libraries Government Documents Department

Final Technical Report-the Ecology and Genomics of co2 Fixatiion in Oceanic River Plumes

Description: Oceanic river plumes represent some of the most productive environments on Earth. As major conduits for freshwater and nutrients into the coastal ocean, their impact on water column ecosystems extend for up to a thousand km into oligotrophic oceans. Upon entry into the oceans rivers are tremendous sources of CO2 and dissolved inorganic carbon (DIC). Yet owing to increased light transmissivity from sediment deposition coupled with the influx of nutrients, dramatic CO2 drawdown occurs, and plumes rapidly become sinks for CO2. Using state-of-the-art gene expression technology, we have examined the molecular biodiversity of CO2 fixation in the Mississippi River Plume (MRP; two research cruises) and the Orinoco River Plume (ORP; one cruise). When the MRP extends far into the Gulf because of entrainment with the Loop Current, MRP production (carbon fixation) can account for up to 41% of the surface production in the Gulf of Mexico. Nearer-shore plume stations (“high plume,” salinity< 32 ppt) had tremendous CO2 drawdown that was correlated to heterokont (principally diatom) carbon fixation gene expression. The principal form of nitrogen for this production based upon 15N studies was urea, believed to be from anthropogenic origin (fertilizer) from the MRP watershed. Intermediate plume environments (salinity 34 ppt) were characterized by high levels of Synechococcuus carbon fixation that was fueled by regenerated ammonium. Non-plume stations were characterized by high light Prochlorococcus carbon fixation gene expression that was positively correlated with dissolved CO2 concentrations. Although data from the ORP cruise is still being analyzed, some similarities and striking differences were found between the ORP and MRP. High levels of heterokont carbon fixation gene expression that correlated with CO2 drawdown were observed in the high plume, yet the magnitude of this phenomenon was far below that of the MRP, most likely due to the lower levels of anthropogenic nutrient input. ...
Date: June 21, 2013
Creator: Paul, John H.
Partner: UNT Libraries Government Documents Department

Electromagnetic Borehole Flowmeter Testing at the Southwest Plume Test Pad

Description: Multiple-well aquifer tests were recently conducted at the Southwest Plume Test Pad near the Burial Ground Complex (BGC) in accordance with the BGC Field Investigation Plan (WSRC, 1999). The pumping tests were performed in the Upper Three Runs and Gordon aquifers in February and March of 1999. The tests provide reliable estimates of horizontal conductivity averaged over aquifer thickness, and a relatively large horizontal zone of influence.
Date: January 29, 2001
Creator: Flach, G.P.
Partner: UNT Libraries Government Documents Department

Faraday cup measurements of the plasma plume produced at an x-ray converter

Description: The next generation of radiographic machines based on induction accelerators is expected to generate multiple, small diameter x-ray spots of high intensity. Experiments to study the interaction of the electron beam with the x-ray converter are being performed at the Lawrence Livermore National Laboratory (LLNL) using the 6-MeV, 2-kA Experimental Test Accelerator (ETA) electron beam. The physics issues of greatest concern can be separated into two categories. The multiple pulse issue involves the interaction of subsequent beam pulses with the expanding plasma plume generated by earlier pulses striking the x-ray converter. The plume expands at several millimeters per microsecond and defines the minimum transverse spacing of the pulses. The single pulse issue is more subtle and involves the extraction of light ions by the head of the beam pulse. These light ions might propagate at velocities of several millimeters per nanosecond through the body of the incoming pulse resulting in a moving focus prior to the converter. In this paper we describe Faraday cup measurements performed to quantify the plasma plume expansion and velocities of light ions.
Date: August 17, 1998
Creator: Garcia, M; Houck, T L & Sampayan, S E
Partner: UNT Libraries Government Documents Department

Surface and borehole electromagnetic imaging of conducting contaminant plumes

Description: Electromagnetic induction tomography is a promising new tool for imaging electrical conductivity variations in the earth. The EM source field is produced by induction coil (magnetic dipole) transmitters deployed at the surface or in boreholes. Vertical and horizontal component magnetic field detectors are deployed in other boreholes or on the surface. Sources and receivers are typically deployed in a configuration surrounding the region of interest. The goal of this procedure is to image electrical conductivity variations in the earth, much as x-ray tomography is used to image density variations through cross-sections of the body. Although such EM field techniques have been developed and applied, the algorithms for inverting the magnetic field data to produce the desired images of electrical conductivity have not kept pace. One of the main reasons for the lag in the algorithm development has been the fact that the magnetic induction problem is inherently three dimensional; other imaging methods such as x-ray and seismic can make use of two-dimensional approximations that are not too far from reality, but we do not have this luxury in EM induction tomography. In addition, previous field experiments were conducted at controlled test sites that typically do not have much external noise or extensive surface clutter problems often associated with environmental sites. To use the same field techniques in environments more typical of cleanup sites requires a new set of data processing tools to remove the effects of both noise and clutter. The goal of this project is to join theory and experiment to produce enhanced images of electrically conducting fluids underground, allowing better localization of contaminants and improved planning strategies for the subsequent remediation efforts. After explaining the physical context in more detail, this report will summarize the progress made in the first 18 months of this project: (1) on code ...
Date: July 1, 1998
Creator: Berryman, J. G., LLNL
Partner: UNT Libraries Government Documents Department

ARAC dispersion modeling of the August 1998 Tracy, California tire fire

Description: At about 4:30 pm PDT on Friday, August 7, 1998 a fire ignited the large tire disposal pit of Royster Tire Co. on Macarthur Drive about 5 km (3 miles) south of downtown Tracy, California. While providing on-scene mutual aid late Friday night, the LLNL Fire Department called and requested that the Atmospheric Release Advisory Capability (ARAC) make a plume forecast for Saturday. The response team in the field was interested in the forecasted location as well as an estimate of potential health effects on the following day. Not having any previous experience with tire fire source terms, ARAC assessors used a constant unit source rate (1 g/s) of particulate and produced plots showing only the location of the ground-level normalized time-integrated air concentrations from the smoke plume. Very early Saturday morning the assessors faxed plots of ground-level smoke air concentrations forecasted for Saturday from 6 am through 6 pm PDT to the Tracy Fire Emergency Operations Center. (As a part of standard procedure, before delivering the plots, the assessors notified ARAC's DOE sponsor.) Fortunately due to the intense heat from the fire, the dense black smoke immediately lofted into the air preventing high ground-level concentrations close to the tire dump. Later on Saturday morning ARAC forecasted a second set of plume integrated air concentrations for Sunday. By Monday the intensity of the fire lessened, and ARAC's support was no longer requested. Following ARAC's response, we made a third calculation on a large scale of the continuous smoke dispersion for 3 days after the fire. A newspaper photograph showed the plume initially rising toward the northeast and the upper part of the smoke cloud turning counterclockwise toward the north. Winds from ARAC's mesoscale prognostic model reproduced this plume structure, while data from the Friday afternoon sounding from Oakland did not. ...
Date: August 28, 1998
Creator: Aluzzi, F J; Baskett, R L; Bowen, B M; Foster, C S; Pace, J C; Pobanz, B et al.
Partner: UNT Libraries Government Documents Department

A RESOLUTION ANALYSIS OF TWO GEOPHYSICAL IMAGING METHODS FOR CHARACTERIZING AND MONITORING HYDROLOGIC CONDITIONS IN THE VADOSE ZONE

Description: The objective of this study is to characterize and analyze in-situ flow and transport within the vadose zone during a mid-scale hydrologic infiltration experiment. This project has employed numerical and experimental tools developed under a previously funded EMSP proposal (project number 55332) to provide 3-D unsaturated hydrologic property distributions. In the present project, geophysical imaging techniques have been employed to track analogue contaminant plumes. The results are providing a better understanding of transport modes including the influence of natural heterogeneities and man-made structures within the vadose zone at DOE sites. In addition the data is providing checks against which numerical flow and transport simulations can be compared
Date: June 4, 2003
Creator: Alumbaugh, David L. & Brainard, James R.
Partner: UNT Libraries Government Documents Department

A RESOLUTION ANALYSIS OF TWO GEOPHYSICAL IMAGING METHODS FOR CHARACTERIZING AND MONITORING HYDROLOGIC CONDITIONS IN THE VADOSE ZONE

Description: The objective of this study is to characterize and analyze in-situ flow and transport within the vadose zone during a mid-scale hydrologic infiltration experiment. This project has employed numerical and experimental tools developed under a previously funded EMSP proposal (project number 55332) to provide 3-D unsaturated hydrologic property distributions. In the present project, geophysical imaging techniques have been employed to track analogue contaminant plumes. The results are providing a better understanding of transport modes including the influence of natural heterogeneities and man-made structures within the vadose zone at DOE sites. In addition the data is providing checks against which numerical flow and transport simulations can be compared.
Date: June 1, 2003
Creator: Alumbaugh, David L. & Brainard, James R.
Partner: UNT Libraries Government Documents Department

Integrated Hydrogeophysical and Hydrogeologic Driven Parameter Upscaling for Dual-Domain Transport Modeling

Description: Our research project is motivated by the observations that conventional characterization approaches capture only a fraction of heterogeneity affecting field-scale transport, and that conventional modeling approaches, which use this sparse data, typically do not successfully predict long term plume behavior with sufficient accuracy to guide remedial strategies. Our working hypotheses are that improved prediction of contaminant transport can be achieved using a dual-domain transport approach and field-scale characterization approaches.
Date: June 1, 2006
Creator: Flach, Gregory; Harris, Mary; Hubbard, Susan; Knapp, Camelia; Kowalsky, Mike; Millings, Maggie et al.
Partner: UNT Libraries Government Documents Department

Development of a chemical vision spectrometer to detect chemical agents.

Description: This paper describes initial work in developing a no-moving-parts hyperspectral-imaging camera that provides both a thermal image and specific identification of chemical agents, even in the presence of nontoxic plumes. The camera uses enhanced stand-off chemical agent detector (ESCAD) technology based on a conventional thermal-imaging camera interfaced with an acousto-optical tunable filter (AOTF). The AOTF is programmed to allow selected spectral frequencies to reach the two dimensional array detector. These frequencies are combined to produce a spectrum that is used for identification. If a chemical agent is detected, pixels containing the agent-absorbing bands are given a colored hue to indicate the presence of the agent. In test runs, two thermal-imaging cameras were used with a specially designed vaporizer capable of controlled low-level (low ppm-m) dynamic chemical releases. The objective was to obtain baseline information about detection levels. Dynamic releases allowed for realistic detection scenarios such as low sky, grass, and wall structures, in addition to reproducible laboratory releases. Chemical releases consisted of dimethylmethylphosphonate (DMMP) and methanol. Initial results show that the combination of AOTF and thermal imaging will produce a chemical image of a plume that can be detected in the presence of interfering substances.
Date: February 23, 1999
Creator: Demirgian, J.
Partner: UNT Libraries Government Documents Department

Expansion of radiative cooling of the laser induced plasma

Description: To study the expansion and cooling process of the laser induced plasma generated by nanosecond pulsed laser ablation, experiments have been conducted which measure the position of the external shockwaves and the temperature of the vapor plumes. The positions of external shockwaves were determined by a femtosecond laser time-resolved imaging system. Vapor plume temperature was determined from spectroscopic measurements of the plasma emission lines. A model which considers the mass, momentum, and energy conservation of the region affected by the laser energy was developed. It shows good agreement to the experimental data.
Date: May 5, 2006
Creator: Wen, Sy-Bor; Mao, Xianglei; Liu, Chunyi; Greif, Ralph & Russo,Richard
Partner: UNT Libraries Government Documents Department

ENHANCEMENTS TO NATURAL ATTENUATION: SELECTED CASE STUDIES

Description: In 2003 the US Department of Energy (DOE) embarked on a project to explore an innovative approach to remediation of subsurface contaminant plumes that focused on introducing mechanisms for augmenting natural attenuation to achieve site closure. Termed enhanced attenuation (EA), this approach has drawn its inspiration from the concept of monitored natural attenuation (MNA).
Date: May 15, 2007
Creator: Vangelas, K; W. H. Albright, W; E. S. Becvar, E; C. H. Benson, C; T. O. Early, T; E. Hood, E et al.
Partner: UNT Libraries Government Documents Department

PARTICLE TRACKING ANALYSIS & ANIMATIONS DEPICTING MOVEMENT OF THE CARBON TETRACHLORIDE PLUME REPORT

Description: The purpose of the hydraulic particle tracking animation files is to show where carbon tetrachloride that reached groundwater from the known discharge facilities would have been likely to travel fin the groundwater, and from where carbon tetrachloride presently observed in the aquifer likely would have started. These analyses support the 200-PW-1 Operable Unit activity to identify sources of carbon tetrachloride currently observed in groundwater or locations where carbon tetrachloride may have entered the groundwater. The animation files show travel paths (both forward and backward in time) for hypothetical particles of carbon tetrachloride carried in the groundwater. The travel paths represent the movement of the carbon tetrachloride at the average groundwater velocity. The particles only represent an estimation of where the carbon tetrachloride would be expected to be (or have come from) and do not indicate or imply what the concentration in the groundwater would be.
Date: November 2, 2006
Creator: MCMAHON, W.J. & ROHAY, V.J.
Partner: UNT Libraries Government Documents Department

Predicting detection probabilities for gas mixtures over HSI backgrounds

Description: Detecting and identifying weak gaseous plumes using thermal image data acquired by airborne detectors is an area of ongoing research. This contribution investigates the relative detectability of gas mixtures over different backgrounds and a range of plume temperatures that are warmer and cooler than the ground. The focus of this analysis to support mission planning. When the mission is intended to collect evidence of particular chemicals, the analysis presented is this report can be used to determine conditions under which useful data can be acquired. Initial analyses can be used to determine whether LWIR is useful for the anticipated gas, temperature, and background combination.
Date: December 29, 2009
Creator: Tardiff, Mark F.; Walsh, Stephen J.; Anderson, Kevin K. & Chilton, Lawrence
Partner: UNT Libraries Government Documents Department

Dust Plume Modeling at Fort Bliss: Move-Out Operations, Combat Training and Wind Erosion

Description: The potential for air-quality impacts from heavy mechanized vehicles operating in the training ranges and on the unpaved main supply routes at Fort Bliss was investigated. This report details efforts by the staff of Pacific Northwest National Laboratory for the Fort Bliss Directorate of Environment in this investigation. Dust emission and dispersion from typical activities, including move outs and combat training, occurring on the installation were simulated using the atmospheric modeling system DUSTRAN. Major assumptions associated with designing specific modeling scenarios are summarized, and results from the simulations are presented.
Date: September 29, 2006
Creator: Chapman, Elaine G.; Rishel, Jeremy P.; Rutz, Frederick C.; Seiple, Timothy E.; Newsom, Rob K. & Allwine, K Jerry
Partner: UNT Libraries Government Documents Department

Dust Plume Modeling from Ranges and Maneuver Areas on Fort Bliss and the White Sands Missile Range: Final Report

Description: The potential for air quality impacts from heavy mechanized vehicles operating on and between the unpaved main supply routes at Fort Bliss and White Sands Missile Range was investigated. This report details efforts by the staff of Pacific Northwest National Laboratory for the Fort Bliss Directorate of Environment in this investigation. Dust emission and dispersion from typical move-out activities occurring on the installations were simulated using the atmospheric modeling system DUSTRAN. Major assumptions associated with designing the modeling scenarios are summarized and results of simulations conducted under these assumptions are presented for four representative meteorological periods.
Date: May 4, 2009
Creator: Chapman, Elaine G.; Barnard, James C.; Rutz, Frederick C.; Pekour, Mikhail S.; Rishel, Jeremy P. & Shaw, William J.
Partner: UNT Libraries Government Documents Department

The Solution To: Which way is up? A fluid dynamics riddle

Description: For flows of the Rayleigh-Taylor type, asymmetries develop in the flow's structure when the density ratio between the two pure fluids is sufficiently different from unity. The flow depicted in the images has a density ratio of three, and consequently an Atwood number (the difference of the densities divided by their sum) of one half. For this Atwood number, the asymmetries are still subtle. The characteristic ''bubble'' and ''spike'' shapes are not prominent, as they are for, say, Atwood numbers of 0.8 (a density ratio of nine) or more. The key to the riddle solution lies with the mixed fluid--the grayish regions within the plumes. The Probability Density Function, or PDF, of the fluid composition is not symmetric for these conditions. Rather, the PDF is skewed, leaning toward the low-density compositions, corresponding to the predominant mixed compositions containing a greater proportion of light fluid. For a color scale with white representing the lighter fluid and black representing the heavier fluid, this implies that the mixed fluid should appear lighter than with the color scale reversed. Note that the gray plumes of mixed fluid in both frames are not the same shade of gray; the plumes in the bottom frame are lighter than those in the top frame. From the discussion above, this indicates that the lower frame is correctly oriented while the upper frame is upside down.
Date: June 21, 2005
Creator: Miller, P L; Cabot, W H & Cook, A W
Partner: UNT Libraries Government Documents Department

Cassini detection of Enceladus's cold water-group plume ionosphere

Description: This study reports direct detection by the Cassini plasma spectrometer of freshly-produced water-group ions (O{sup +}, OH{sup +}, H{sub 2}O{sup +}, H{sub 3}O{sup +}) and heavier water dimer ions (H{sub x}O{sub 2}{sup +}) very close to Enceladus and where the plasma begins to emerge from the Enceladus plume The data wcre obtained during two close (52 and 25 km) flybys of Enceladus in 2008, and are similar to ion data in cometary comas. The ions are observed in detectors looking in the Cassini ram direction at energies consistent with the Cassini speed, indicating a nearly stagnant plasma flow in the plume. North of Enceladus the plasma slowing commences about 4 to 6 Enceladus radii away, while south of Enccladus signatures ofthe interaction are detected as far as 22 Enceladus radii away.
Date: January 1, 2009
Creator: Tokar, Robert L; Thomsen, Michelle F; Wilson, Robert J; Johnson, R E; Young, D T; Crary, F J et al.
Partner: UNT Libraries Government Documents Department

A Fast Running Test Bed Model to Evaluate Atmospheric Plume Source Properties I: Initial Test Scenario

Description: Given an unknown but detected release of a toxic agent, the current NARAC capability for reconstructing source characteristics is a highly manual procedure that often relies on analyst judgment and requires many hours of computations for a refined analysis. There is no automated, optimization approach to estimating the source characteristics. A fast running, prototype atmospheric inversion model has been developed for use as a test bed for the evaluation of source inversion schemes. The model was applied to a simple puff release scenario to test the relationship between the amount of sampled data obtained and the accuracy of the determination of the inverted source parameters. The initial inversion scheme chosen for the test bed model utilizes the Marquardt method coupled to a Gaussian puff atmospheric dispersion model driven by a COAMPS model wind field. The inversion scheme results are used in conjunction with a sensor realization probability model for a sensor realization scenario consisting of 1000 possible sensor realizations. The results of the initial test calculations indicate that the inversion procedure produces good results for the four source parameters, location (x, y), release time, and strength along with reasonably well defined maximum probabilities for the sensor realization scenarios. The model runs relatively fast, taking {approx}100 seconds per inversion on a Sparc 10 workstation.
Date: June 1, 2001
Creator: Grossman, A S; Molenkamp, C F & Grant, K E
Partner: UNT Libraries Government Documents Department