U.S. Army West Desert Test Center

We report on the results from an operational forecast system built to predict local circulationsforced by complex terrain and other variations in land-surface characteristics. The cornerstoneof the prediction system is the Penn State University/National Center for Atmospheric Research(PSU/NCAR) mesoscale model, version 5 (MM5), a nonhydrostatic regional model. The specificapplication reported herein is for the region surrounding Dugway Proving Ground (DPG) inwest-central Utah. The nature of the terrain requires a horizontal resolution of about 1 km inorder to capture the important local features. This resolution is achieved by the use of gridnesting. To our knowledge, this resolution is finer than that being used in any other currentlyoperational forecast system tasked with local and regional weather prediction. For verificationpurposes, forecasts are stratified according to season and mean-flow characteristics. Data forverification consist of DPG surface mesonet data. Root-mean-square errors (RMSE), time meancirculations and spatial anomaly correlation statistics are computed and composited for eachhour of the day. These are compared with identical forecasts of lagged persistence, with thetime lag being 24 h (MM5 forecasts are all initialized at 1200 UTC). For wind and temperature, the RMSE from MM5 is consistently lower than that of persistence. In addition, MM5 showsskill in predicting the time-mean circulations on the test range (variations of a few m/sand °Celsius). MM5 forecast errors grow slowly with time until around sunset, after which theydecrease slightly, suggesting that local nighttime “forcing” dominates the error growth, as thesurface layer decouples from the free atmosphere. Finally, spatial anomaly correlations suggestthat the non-systematic, range-scale circulations exhibit low predictability.

Abstract The purpose of this observation- and model-based study of the Great Basin Desert boundary layer is to illustrate the variety of locally forced circulations that can affect such an area during a diurnal cycle. The area of the Great Basin Desert (or Great Salt Lake Desert) that is studied is located to the southwest of Salt Lake City, Utah. It is characteristic of the arid “basin and range” province of North America in that it contains complex terrain, varied vegetation and substrates, and high water tables associated with salt-encrusted basin flats (playas). The study area is especially well instrumented with surface meteorological stations operated by the U.S. Army's West Desert Test Center and a collection of cooperating mesonets in northeastern Utah. The study period was chosen based on the availability of special radiosonde data in this area. One of the processes that is documented here that is unique to desert environments is the salt breeze that forms around the edge of playas as a result of...

The nerve agent VX (O-ethyl S-2-diisopropylaminoethyl methyl phosphonothiolate) was analyzed on the surface of concrete samples using an ion trap secondary ion mass spectrometer (IT-SIMS). It was found that VX could be detected down to an absolute quantity of 5 ng on a concrete chip, or to a surface coverage of 0.0004 monolayers on crushed concrete. To achieve these levels of detection, the m/z 268-->128 ion fragmentation was measured using MS2, where m/z 268 corresponds to [VX + H]+, and 128 corresponds to a diisopropylvinylammonium isomer, that is formed by the elimination of the phosphonothiolate moiety. Detection at these levels was accomplished by analyzing samples that had been recently exposed to VX, i.e., within an hour. When the VX-exposed concrete samples were aged, the SIMS signature for intact VX had disappeared, which signaled the degradation of the compound on the concrete surface. The VX signature was replaced by ions which are interpreted in terms of VX degradation products, which appear to be somewhat long lived on the concrete surface. These compounds include ethylmethylphosphonic acid (EMPA), diisopropyl taurine (DIPT), diisopropylaminoethanethiol (DESH), bis(diisopropylaminoethane) disulfide [(DES)2], and a particularly tenacious compound that may correspond to diisopropylvinylamine (DIVA), or an isomer thereof. It was found that the thiolamine-derived degradation products DIPT, DESH, and (DES)2 were removed with isopropyl alcohol extraction. However, the DIVA-related degradation product was observed to strongly adhere to the concrete surface for longer than one week. Although quantitation was not possible in this set of experiments, the results clearly show the rapid degradation of VX on concrete, as well as the surface sensitivity of the IT-SIMS for intact VX and its adsorptive degradation products.

The direct detection of the nerve agent VX (methylphosphonothioic acid, S-[2-[bis(1-methylethyl)amino]ethyl] O-ethyl ester) on milligram quantities of soil particles has been achieved using ion trap secondary ion mass spectrometry (IT-SIMS). VX is highly adsorptive toward a wide variety of surfaces; this attribute makes detection using gas-phase approaches difficult but renders the compound very amenable to surface detection. An ion trap mass spectrometer, modified to perform SIMS, was employed in the present study. A primary ion beam (ReO4-) was fired on axis through the ion trap, where it impacted the soil particle samples. [VX + H]+, [VX + H]+ fragment ions, and ions from the chemical background were sputtered into the gas-phase environment of the ion trap, where they were either scanned out or isolated and fragmented (MS2). At a surface concentration of 0.4 monolayer, intact [VX + H]+, and its fragment ions, were readily observable above background. However, at lower concentrations, the secondary ion signal from VX became obscured by ions derived from the chemical background on the surface of the soil particles. MS2 analysis using the ion trap was employed to improve detection of lower concentrations of VX: detection of the 34S isotopic ion of [VX + H]+, present at a surface concentration of approximately 0.002 monolayer, was accomplished. The study afforded the opportunity to investigate the fragmentation chemistry of VX. Semiempirical calculations suggest strongly that the molecule is protonated at the N atom. Deuterium labeling showed that formation of the base peak ion (C2H4)N(i-C3H7)2+ involves transfer of the amino proton to the phosphonothioate moiety prior to, or concurrent with, C-S bond cleavage. To manage the risk associated with working with the compound, the vacuum unit of the IT-SIMS was located in a hood, connected by cables to the externally located electronics and computer.

The nerve agent VX (O-ethyl S-2-diisopropylaminoethyl methylphosphonothiolate) is lethal at very low levels of exposure, which can occur by dermal contact with contaminated surfaces. Hence, behavior of VX in contact with common urban or industrial surfaces is a subject of acute interest. In the present study, VX was found to undergo complete degradation when in contact with concrete surfaces. The degradation was directly interrogated at submonolayer concentrations by periodically performing secondary ion mass spectrometry (SIMS) analyses after exposure of the concrete to VX. The abundance of the [VX + H]+ ion in the SIMS spectra was observed to decrease in an exponential fashion, consistent with first-order or pseudo-first-order behavior. This phenomenon enabled the rate constant to be determined at 0.005 min(-1) at 25 degrees C, which corresponds to a half-life of about 3 h on the concrete surface. The decrease in [VX + H]+ was accompanied by an increase in the abundance of the principal degradation product diisopropylaminoethanethiol (DESH), which arises by cleavage of the P-S bond. Degradation to form DESH is accompanied by the formation of ethyl methylphosphonic acid, which is observable only in the negative ion spectrum. A second degradation product was also implicated, which corresponded to a diisopropylvinylamine isomer (perhaps N,N-diisopropyl aziridinium) that arose via cleavage of the S-C bond. No evidence was observed for the formation of the toxic S-2-diisopropylaminoethyl methylphosphonothioic acid. The degradation rate constants were measured at four different temperatures (24-50 degrees C), which resulted in a linear Arrhenius relationship and an activation energy of 52 kJ mol(-1). This value agrees with previous values observed for VX hydrolysis in alkaline solutions, which suggests that the degradation of submonolayer VX is dominated by alkaline hydrolysis within the adventitious water film on the concrete surface.

We study temperature structure functions of second, fourth, and sixth orders at heights of up to 2 m above the ground in moderately heated atmosphere. Most of the data come from measurements over salt flats of the Utah desert, with well-defined wind direction and uniform temperature boundary conditions. As in high-Rayleigh-number convection in a closed container, a thermal boundary layer develops near the ground, its thickness here being of the order of 50 cm. We demonstrate the coexistence of two scaling ranges, one of which corresponds to the classical inertial range and the other to the buoyant range influenced by thermal convection. The determination of scaling exponents in the two ranges is facilitated by the use of a scaling function. We present the variations with height of scaling exponents in both ranges, as well as the crossover scales from one range to another.

Pyrolysis mass spectrometry (Py-MS), incorporating an in situ thermal hydrolysis and methylation (THM) step, was used to profile methylated lipids (e.g., fatty acids and cholesterol) from pathogenic viruses and bacteria by means of a field-portable ion-trap MS instrument referred to as the chemical/biological mass spectrometer (CBMS). The CBMS has been successfully tested for biological warfare agents to give correct classification (three classes—spore, vegetative cell, and toxin) in both field and chamber tests. Incorporating an in situ THM step in the CBMS will improve its capabilities to better identify biomarkers from bacteria and viruses. Mass spectra of one bacterial and two viral pathogens (grown by cell cultures) were produced with a total analysis time of 3 min per profile and could be separated when examined by principal-component analysis (PCA). © 1999 John Wiley & Sons, Inc. Field Analyt Chem Technol 3: 357–374, 1999

Abstract Aerosol stability of ovalbumin at various environmental conditions was examined in terms of aerodynamic particle size/mass, particle concentration, and detection by enzyme-linked immunosorbent assay (ELISA). Aerosols of ovalbumin were generated in a 1000 liter dynamic aerosol toroid (DAT) drum and the aerosol was sampled over a two hour period with all-glass impingers (AGIs) and an aerodynamic particle sizer (APS®). Aerodynamic size and mass increases, associated with increases in temperature and relative humidity, were shown to be small but statistically significant (p ≤ 0.0014). A minimum of 50% of the aerosolized ovalbumin was detectable by ELISA after 2 h under all conditions tested. The stability of ovalbumin as demonstrated would allow it to be used as an aerosolized protein challenge material in biological defense testing under the temperature and humidity conditions tested.

West Desert Test Center (WDTC) at Dugway Proving Ground uses measurement, modeling and simulation capabilities to characterize and referee customer standoff biological and, to a lesser extent, chemical detection systems. The WDTC LIDAR model of aerosol clouds uses a Mie scattering model and associated joint aerosol cloud distribution function N(a,r), where a is the particle radius and r is the position vector of the particle. We make the key simplifying assumption that the two parameters a and r are statistically independent. Justification for this well-mixed assumption is that aerosol particles with dimensions of less than a few microns remain in the atmosphere for a long time, typically days. Large particles are removed by gravity segregation. For the associated inverse problem, the LIDAR elastic scattering equation is formally inverted to yield an estimate of the aerosol particle concentration /spl rho//spl circ/(r). Inversion requires knowledge of boundary conditions along an arc of constant range R=R/sub f/. Given a seed value on the arc from a point detector, a two-frequency algorithm is shown to correctly populate all values on the arc R=R/sub f/, leading to near-real-time accurate inversions over the entire LIDAR sweep. Numerical results in a noise background and a representative choice of numerical parameters are given.

More than 500,000 tons of obsolete and unwanted conventional weapons exist in the United States. The disposal of these unexploded ordnances, in an environmentally sound and cost-effective way, is of paramount importance. Different types of incinerators and detonation chambers have been proposed to eliminate these unwanted energetic materials. However, questions about the design of such facilities and the environmental consequences of their use must be answered. This paper describes numerical simulations of a large-scale, partially confined detonation facility. Detonation facility designs were evaluated by a series of axisymmetric, time-dependent simulations using FAST3D, a numerical model based on flux-corrected transport coupled to the virtual cell embedding algorithm for simulating complex geometries. The simulations assisted in determining the shape and size of the detonation charge mass that maintained the structural integrity of the facility. Comparisons of the pressure and structural analyses for spherically and cylindrically shaped RDX charges in a fixed volume show that the 50-lb spherically shaped charge resulted in an efficient detonation and maintained the structural integrity of the detonation facility.

It is estimated that more than 500,000 tons of obsolete and unwanted conventional weapons exist in the United States. The disposal of these unexploded ordnances, in an environmentally sound and cost-effective way, is of paramount importance. Open-air burning and open-air detonation (OB/OD) are two of the most widely used methods to dispose of these unwanted energetic materials. This paper describes our efforts to improve OB/OD operations through the design and testing of a new, large-scale, partially confined facility that minimizes the adverse affects of far-field noise and maximizes the afterburn of explosive by-products. Several designs were evaluated by a series of axisymmetric, time-dependent numerical simulations using FAST3D, a flux-corrected transport-based code optimized for parallel processing. The simulations are used to test various facility geometries and placements and sizes of charges to determine combinations that result in acceptable environmental impact. Comparisons of the pressure and structural analyses for 50 and 100 lb of spherically shaped RDX charges show that the 50-lb spherically shaped charge placed at a height of approximately 2.0 m resulted in an efficient detonation and maintained the structural integrity of the detonation facility.