Army Dugway Proving Ground Research Articles

Detection of bioaerosols using hyperspectral LIF-LIDAR during S/K challenge II campaign at Dugway

This study showcases the importance of the remote sensing of biological aerosols for both homeland security and environmental protection. We demonstrate the application of a hyperspectral Laser Induced Fluorescence Light Detection and Ranging (LIF-LIDAR) system for the remote sensing of bioaerosols during the international S/K CHALLENGE II field campaign at the U.S. Army Dugway Proving Ground (DPG). The system employs UV photoexcitation at 266 nm and fluorescence spectral analysis in the range of 250–650 nm at a resolution of approximately 2 nm. A two-stage Microchannel Plate (MCP)-ICCD-based receiver capable of single photon-counting detection limit was used. During the campaign, four different bioaerosol simulants were studied in enclosed chambers and open space experiments at night and at distances of 0.5–2 km. A real-time Spectral Angle Mapping (SAM) algorithm was implemented to identify unknown bioaerosol clouds, dust, and combustion plumes as they spread in the open atmosphere. Additionally, we conducted preliminary tests in our institute, which demonstrated the system's ability to identify Ovalbumin (OV) aerosol despite being covered by a thick dust cloud. During the field measurements in DPG, we continuously tracked the fluorescence signature of OV aerosol as it spread in the atmosphere from a distance of 1.5 km for over 20 min. The overall detection performance during the S/K CHALLENGE II was 49 out of 52 trials, indicating a success rate of about 94%. The discussion centers on spectral identification statistics of the unknown dispersed bioaerosol as well as the implications of false-positive and false-negative events.

Distinguishing Time Scales of Katabatic Flow in Complex Terrain

To examine spatial and temporal scales of katabatic flow, a distributed temperature sensing (DTS) optical fiber was deployed 2 km down a mild slope irregularly interrupted by small-scale drainage features as part of the Mountain Terrain Atmospheric Modeling and Observation (MATERHORN) experiment conducted at the U.S. Army Dugway Proving Ground, Utah. The fiber was suspended at two heights near the surface, enabling measurement of variations in lapse rate near the surface at meter-scale spatial resolution with 1-min temporal resolution. Experimental results derived from the DTS and tower-mounted instrumentation indicate that airflow through small-scale drainage features regulated the local cooling rate whereas topographic slope and distance along the drainage strongly influenced the larger-scale cooling rate. Empirical results indicate that local cooling rate decays exponentially after local sunset and basin-wide cooling rate decreases linearly with time. The difference in the functional form for cooling rate between local and basin-wide scales suggests that small-scale features have faster timescales that manifests most strongly shortly after local sunset. More generally, partitioning drainage flow by scale provides insight and a methodology for improved understanding of drainage flow in complex terrain.

Overview of the Jack Rabbit II (JR II) field experiments and summary of the methods used in the dispersion model comparisons

This paper serves as an introduction to the special Atmospheric Environment issue on comparisons of 17 widely-used dense-gas dispersion models using observations from the Jack Rabbit II (JR II) chlorine release experiments, which were led by the U.S. Department of Homeland Security Science & Technology (DHS S&T) Chemical Security Analysis Center (CSAC) and a collaborative team of interagency partners, and conducted at the U.S. Army Dugway Proving Ground in 2015 and 2016. Nine of the 17 models that were compared were from outside the U.S. Other papers in the Special Issue describe specific aspects (e.g., observations of emissions, meteorology, and concentrations) of the JR II field experiments, results of individual dispersion model simulations for the models and comparisons of model predictions with JR II observations and other models. This paper provides a general overview of the field experiments and a brief summary of the model comparison goals and methods.

Portable membrane inlet mass spectrometric detection and analysis of chemical warfare agent simulants at the U.S. Army Dugway Proving Ground S/K challenge event

There has been a significant demand for the development and improvement of technology used for the detection and identification of Chemical Warfare Agents (CWAs). Some of the current detection technology being used by the U.S. government includes multipass gas cell coupled Fourier Transform Infrared (FTIR) spectroscopy and Lightweight Chemical Detectors (LCD) systems. While these systems possess adequate sensitivity to detect CWAs in general, their analysis times are not considered 'rapid' nor are they able to identify the specific CWA. The U.S. Army Dugway Proving Ground's annual S/K Challenge event provides the opportunity to assess the performance and reliability of prospective detection instrumentation being developed by researchers worldwide to optimize their performance. To do so, trial testing of CWA simulants in both indoor and outdoor environments was performed, mimicking past attack scenarios. Membrane Inlet Mass Spectrometric (MIMS) technology on a portable system was successful in performing a rapid analysis along with identification of each CWA simulant utilized during the trials. The MIMS system can detect and quantify low-mass permeable compounds with parts-per-trillion limits of detection. This allows for analysis to be achieved within seconds after the initial exposure time, which is significantly faster than the FTIR and LCD systems currently used.

The Impact of Surface Temperature Heterogeneity on Near-Surface Heat Transport

Experimental closure of the surface energy balance during convective periods is a long-standing problem. With experimental data from the Idealized horizontal Planar Array experiment for Quantifying Surface heterogeneity, the terms of the temperature-tendency equation are computed, with an emphasis on the total derivative. The experiment occurred at the Surface Layer Turbulence and Environmental Science Test facility at the U.S. Army Dugway Proving Ground during the summer of 2019. The experimental layout contained an array of 21 flux stations over a 1 km $$^2$$ grid. Sensible heat fluxes show high spatial variability, with maximum variability occurring during convective periods. Maximum variability in the vertical heat flux is 50–80 W m $$^{-2}$$ (median variability of 40%), while in the horizontal flux, it is 200–500 W m $$^{-2}$$ (median variability of 48% for the streamwise and 40% for the spanwise fluxes). Ensemble averages computed during convective afternoon periods show large magnitudes of horizontal advection (48 W m $$^{-3}$$ or 172 K h $$^{-1}$$ ) and vertical flux divergence (13 W m $$^{-3}$$ or 47 K h $$^{-1}$$ ). Probability density functions of the total derivative from convective cases show mean volumetric heating rates of 43 W m $$^{-3}$$ (154 K h $$^{-1}$$ ) compared to 13 W m $$^{-3}$$ (47 K h $$^{-1}$$ ) on non-convective days. A conceptual model based on persistent mean flow structures from local-surface-temperature heterogeneities may explain the observed advection. The model describes the difference between locally-driven advection and advection driven by larger-scale forcings. Of the cases examined, 83% with streamwise and 81% with spanwise advection during unstable periods are classified as locally driven by nearby surface thermal heterogeneities.

Group effects of a non‐native plant invasion on rodent abundance

AbstractCheatgrass (Bromus tectorum) is the most prolific invading plant in western North America. Investigations determining the impact of this invasion on population state variables and community dynamics of rodents have largely occurred at the community or species level, creating a knowledge gap as to whether rodents affiliated by a shared taxonomy or other grouping are differentially affected by cheatgrass invasion. We examined rodent abundance along a gradient of cheatgrass cover using various groupings of two nocturnal rodent taxa comprising the majority of the rodent community in the Great Basin Desert. In the summers of 2010–2013, rodents were sampled and vegetation was measured on the U.S. Army Dugway Proving Ground in the Great Basin Desert of Utah, USA. We separately examined estimates of rodent abundance for all combined species within the Cricetidae and Heteromyidae families, the most numerically dominant species, and uncommon species pooled in relation to cheatgrass invasion severity. We detected an expected negative linear relationship between invasion severity and abundance for all cricetid groupings, including the most numerically dominant species, the deer mouse (Peromyscus maniculatus). Unexpectedly, heteromyid abundance exhibited an initial positive relationship, reached a threshold, and then exhibited a negative relationship, a phenomenon driven by Ord's kangaroo rats (Dipodomys ordii), the most numerically dominant species. We speculate this non‐linear finding was caused by a combination of trophic and non‐trophic pathways. Our findings provide new insight as to the potential for differential effects of cheatgrass on rodents in arid portions of the western United States. We suggest that future investigations on cheatgrass, and plant invader effects in general, consider parsing animal communities of interest by various taxonomic and/or ecological groupings rather than focusing exclusively on individual species or entire communities.

Simulation of stably stratified flow in complex terrain: flow structures and dividing streamline

The advanced research version of the weather research and forecasting model was employed to simulate Intense Operational Periods of the field campaigns of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program with a 0.5 km horizontal resolution. The focus was on synoptically dominated stably stratified periods, with the mean flow approaching a strongly non-symmetrical rugged topography—the Granite Mountain of the US Army Dugway Proving Ground, Utah. The model was validated against a comprehensive set of MATERHORN data. The special in-house developed software enabled calculations of energetics and pressure anomalies along individual streamlines and tracing of spatial trajectories of streamlines. Owing to complexities of natural flows, for example, the directional shear (skewed vertical velocity profiles) and irregular topographic shape, the flow patterns depend on multiple parameters, although in idealized cases the flow is described by a single parameter (Froude number or a variant). Streamlines at different altitudes of a given location diverged rapidly, making it difficult to study the dividing streamline concept. The new software allowed identification of the dividing streamline passing over the highest crest (summit) of the mountains and its trajectory. The upstream height of the dividing streamline did not follow the well-known Sheppard’s formula. Three cases of flow patterns are presented, identified based on the presence of lee waves, flow separation, horizontal vortex shedding and hydraulics jumps.

Mesoscale Ensemble Weather Prediction at U.S. Army Dugway Proving Ground, Utah

Abstract Since 2007, meteorologists of the U.S. Army Test and Evaluation Command (ATEC) at Dugway Proving Ground (DPG), Utah, have relied on a mesoscale ensemble prediction system (EPS) known as the Ensemble Four-Dimensional Weather System (E-4DWX). This article describes E-4DWX and the innovative way in which it is calibrated, how it performs, why it was developed, and how meteorologists at DPG use it. E-4DWX has 30 operational members, each configured to produce forecasts of 48 h every 6 h on a 272-processor high performance computer (HPC) at DPG. The ensemble’s members differ from one another in initial-, lateral-, and lower-boundary conditions; in methods of data assimilation; and in physical parameterizations. The predictive core of all members is the Advanced Research core of the Weather Research and Forecasting (WRF) Model. Numerical predictions of the most useful near-surface variables are dynamically calibrated through algorithms that combine logistic regression and quantile regression, generating statistically realistic probabilistic depictions of the atmosphere’s future state at DPG’s observing sites. Army meteorologists view E-4DWX’s output via customized figures posted to a restricted website. Some of these figures summarize collective results—for example, through means, standard deviations, or fractions of the ensemble exceeding thresholds. Other figures show each forecast, individually or grouped—for example, through spaghetti diagrams and time series. This article presents examples of each type of figure.

Environmental Reviews and Case Studies: Addressing the Public Outreach Responsibilities of the National Historic Preservation Act: Argonne National Laboratory's Box Digital Display Platform

Federal agencies are made responsible for managing the historic properties under their jurisdiction by the National Historic Preservation Act of 1966, as amended. A component of this responsibility is to mitigate the effect of a federal undertaking on historic properties through mitigation often through documentation. Providing public access to this documentation has always been a challenge. To address the issue of public access to mitigation information, personnel from Argonne National Laboratory created the Box Digital Display Platform, a system for communicating information about historic properties to the public. The platform, developed for the US Army Dugway Proving Ground, uses short introductory videos to present a topic but can also incorporate photos, drawings, GIS information, and documents. The system operates from a small, self-contained computer that can be attached to any digital monitor via an HDMI cable. The system relies on web-based software that allows the information to be republished ...

Influence of free water availability on a desert carnivore and herbivore.

Anthropogenic manipulation of finite resources on the landscape to benefit individual species or communities is commonly employed by conservation and management agencies. One such action in arid regions is the construction and maintenance of water developments (i.e., wildlife guzzlers) adding free water on the landscape to buttress local populations, influence animal movements, or affect distributions of certain species of interest. Despite their prevalence, the utility of wildlife guzzlers remains largely untested. We employed a before–after control-impact (BACI) design over a 4-year period on the US Army Dugway Proving Ground, Utah, USA, to determine whether water availability at wildlife guzzlers influenced relative abundance of black-tailed jackrabbits Lepus californicus and relative use of areas near that resource by coyotes Canis latrans, and whether coyote visitations to guzzlers would decrease following elimination of water. Eliminating water availability at guzzlers did not influence jackrabbit relative abundance. Coyote relative use was impacted by water availability, with elimination of water reducing use in areas associated with our treatment, but not with areas associated with our control. Visitations of radio-collared coyotes to guzzlers declined nearly 3-fold following elimination of water. Our study provides the first evidence of a potential direct effect of water sources on a mammalian carnivore in an arid environment, but the ecological relevance of our finding is debatable. Future investigations aimed at determining water effects on terrestrial mammals could expand on our findings by incorporating manipulations of water availability, obtaining absolute estimates of population parameters and vital rates and incorporating fine-scale spatiotemporal data.

The MATERHORN: Unraveling the Intricacies of Mountain Weather

Abstract Emerging application areas such as air pollution in megacities, wind energy, urban security, and operation of unmanned aerial vehicles have intensified scientific and societal interest in mountain meteorology. To address scientific needs and help improve the prediction of mountain weather, the U.S. Department of Defense has funded a research effort—the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program—that draws the expertise of a multidisciplinary, multi-institutional, and multinational group of researchers. The program has four principal thrusts, encompassing modeling, experimental, technology, and parameterization components, directed at diagnosing model deficiencies and critical knowledge gaps, conducting experimental studies, and developing tools for model improvements. The access to the Granite Mountain Atmospheric Sciences Testbed of the U.S. Army Dugway Proving Ground, as well as to a suite of conventional and novel high-end airborne and surface measurement platforms, has provided an unprecedented opportunity to investigate phenomena of time scales from a few seconds to a few days, covering spatial extents of tens of kilometers down to millimeters. This article provides an overview of the MATERHORN and a glimpse at its initial findings. Orographic forcing creates a multitude of time-dependent submesoscale phenomena that contribute to the variability of mountain weather at mesoscale. The nexus of predictions by mesoscale model ensembles and observations are described, identifying opportunities for further improvements in mountain weather forecasting.

Field-scale remote sensing of soil moisture based on polarimetric characterization of microwave reflections

A field-scale remote soil moisture sensing technique that exploits polarization mode dispersion (PMD) associated with radio frequency (RF) signal propagation is considered in this paper. Microwave polarization responses from rough surface scattering are quantified using a dual-polarized receiver system to estimate PMD responses. Changes in PMD response are elicited by changes in the dielectric properties due to soil moisture changes. The ability of PMD characterizations to remotely detect changes in soil moisture, with responses that exhibit good correlation to ground probe measurements, is demonstrated using a prototype with widely separated transmitter/receiver system deployed at the MATERHORN field experiments conducted at the US Army Dugway Proving Ground, Utah.

An iterative process for verification of a meteorological data server

Key aspects of the verification performed on US Army Dugway Proving Ground (DPG) WeatherServer (WXS) are described. WXS is a Test and Training Enabling Architecture (TENA)-based modeling and simulation that distributes three-dimensional meteorological data over time to participants in a distributed test event or joint exercise environment. The verification features an iterative process as an effective measure to reduce time and costs while still allowing a comprehensive review. In addition, the unique role that WXS serves in efficiently providing real-time meteorological data to support Test and Evaluation (T&E) exercises is discussed. The verification process demonstrated the fidelity of the WXS output and the correctness of the coded technical algorithms (e.g., altitude-to-pressure conversions). The iterative process involved cycles of testing and improved software builds that continued until a build of WXS was developed that functioned as designed. Insights obtained during the iterative process applied to the WXS verification included realizing the full benefits of (1) periodic communications and issue resolution among the developer, verification team, and sponsor; (2) allocating sufficient budget for the software developer’s time to support the verification process; and (3) strategically customizing the verification process to allow for an efficient testing and review process following applicable standards.

Brain acetylcholinesterase activity of the American pronghorn antelope (Antilocapra americana) collected from the US Army Dugway Proving Ground, Utah

Brain tissue was analyzed for acetylcholinesterase (AChE) activity from 24 American pronghorn antelope (Antilocapra americana) collected on the US Army Dugway Proving Ground (DPG) (latitude 40°13' 52" N, longitude 112°45' 01" W), Tooele County, Utah. Pronghorn antelope from DPG were evaluated against 26 pronghorn antelope collected in Wyoming. The mean AChE activity was significantly greater (P < 0.001) in the Wyoming control group (4.612 ± 0.193 µM/gm brain tissue/min) relative to DPG (4.032 ± 0.621 µM/gm brain tissue/min). The DPG database exhibited a fourfold greater coefficient of variation, a tenfold greater variance, and a threefold increase in the standard deviation when compared to control AChE activity. Furthermore, the 95% confidence interval for the control and for the DPG data were not overlapping; the entire control data set was greater than the mean DPG AChE activity. A post hoc sequential Bonferroni statistical procedure showed two significantly (P < 0.001) distinct subsets in the DPG data. Mean DPG Subset I AChE activity (4.528 ± 0.347 µM/gm brain tissue/min) was indistinct from the mean control AChE value (4.612 ± 0.193 µM/gm brain tissue/min). The mean DPG Subset II AChE activity (3.537 ± 0.387 µM/gm brain tissue/min) differed significantly (P < 0.001) from the mean control AChE activity. The sum of resulting α values from the multiple statistical tests did not exceed the selected α value of P < 0.05, validating the post hoc sequential Bonferroni statistical procedure. Pronghorn antelope represented by Subset II, experienced a 23.3% mean loss of AChE activity suggesting sub-lethal organophosphate (OP) exposure rather than a low level chronic environmental influence was experienced by a population subset of the DPG pronghorn antelope herd. The origin of the DPG sublethal OP exposure and its long-term effects are speculative.

Niche Overlap and Resource Partitioning Between Sympatric Kit Foxes and Coyotes in the Great Basin Desert of Western Utah

Successful coexistence of sympatric canid species often relies on the subdominant species' ability to reduce competition through the differential selection of niche space. Information regarding the process of niche selection and its effect on the structure of canid communities in the Great Basin Desert is unavailable. From Dec. 1999 to Aug. 2001, we quantified the spatial, dietary and temporal resource overlap of kit foxes (Vulpes macrotis) and coyotes (Canis latrans) on the U.S. Army Dugway Proving Ground, Utah. Kit foxes and coyotes demonstrated substantial levels of spatial, temporal and dietary overlap. However, where the two species had overlapping home ranges, space use within the home range differed between the two species, with kit foxes using vegetative and landscape ruggedness characteristics not regularly used by coyotes. Although there was little evidence of seasonal change in either canid's use of habitat, in some areas kit foxes made nightly movements to more productive habitats with moderate ruggedness. Regardless of spatial partitioning, incidents of interference competition were high; 56% of known kit fox deaths were attributed to coyotes. In our study, high levels of temporal and dietary overlap, kit fox movement from extreme to moderate topography during foraging and selection for abundant cover demonstrated competitive pressures exerted on the kit fox population by the sympatric coyote population.

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The ability to detect relative changes in backscatter polariza- tion from a scanning high-pulse-energy lidar system at 1.54-m wave- length is demonstrated. The new capability was tested during the dis- semination of various biological aerosol simulants and other particulate emissions at the U.S. Army's Dugway Proving Ground. Results demon- strate that the lidar is sensitive to different types of aerosols, and depar- tures from the atmospheric background depolarization ratio are consis- tent with the limited amount of information available on the degree of particle sphericity. We conclude that the polarization-sensitive coatings of the beam-steering unit mirrors are presently the largest source of error and that this error is minimized when scanning with a near-zero elevation angle. This is an encouraging result for aerosol source surveillance ap- plications, where the depolarization information may be useful in deter- mining the aerosol generation mechanism or provide an additional scalar variable for use in delineating the plume from the background. © 2007

Serologic survey for diseases in free-ranging coyotes (Canis latrans) from two ecologically distinct areas of Utah.

The influence of habitat and associated prey assemblages on the prevalence of canine diseases in coyotes (Canis latrans) has received scant attention. From December 1997 through December 1999, we captured 67 coyotes in two ecologically distinct areas of Utah (USA): Deseret Land and Livestock Ranch and US Army Dugway Proving Ground. These areas differ in habitat and prey base. We collected blood samples and tested for evidence of various canine diseases. Prevalence of antibodies against canine parvovirus (CPV) was 100% in the Deseret population and 93% in the Dugway population. All juveniles in both populations had been exposed. We found no difference in the prevalence of antibodies against canine distemper virus (CDV) between the two populations (7% versus 12%; P = 0.50). However, we did find an increase in antibodies with age in the Deseret population (P = 0.03). Evidence of exposure to canine adenovirus (CAV) was found in both populations (52% and 72%; P = 0.08). Prevalence of CAV antibodies was influenced by age on both areas (Deseret: P = 0.003; Dugway: P = 0.004). Antibodies to Francisella tularensis were low on both areas (2% and 4%). We found a significant difference (P = 0.001) in the prevalence of exposure to Yersinia pestis between the two populations: 73% in Deseret compared to 11% in Dugway. This difference is most likely due to the prey species available in the two ecologically distinct study areas.

Evaluation of annual radiation and windiness over a playa: possibility of harvesting the solar and wind energies

We set up an automatic weather station over a playa (the flat floor of an undrained desert basin that becomes at times a shallow lake), approximately 65 km east–west by 130 km north–south, located at the U.S. Army Dugway Proving Ground (40°08′N, 113°27′W, 1124 m above mean sea level) in north-western Utah, U.S.A., in 1999. This station measured the incoming ( R si) and outgoing ( R so) solar or shortwave radiation using two CM21 Kipp & Zonen pyranometers (one inverted), the incoming ( R li or atmospheric) and outgoing ( R lo or terrestrial) longwave radiation, using two CG1 KippZonen pyrgeometers (one inverted), and the net ( R n) radiation using a Q*7 net radiometer (Radiation Energy Balance System, REBS). We also measured the 10-m wind speed ( U 10) and direction (R.M. Young wind monitor) and precipitation (Campbell Sci., Inc.). The measurements were taken every 2 s, averaged into 20-min, continuously, throughout the year. The annual (August 1999 – August 2000) comparisons of global or solar radiation and windiness with two other stations in central (Hunter) and northern (Logan) Utah, indicate higher solar radiation ( R si,Dugway=7797 MJ m −2 period −1 vs. R si, Hunter=7021 MJ m −2 period −1 and R si, Logan=6865 MJ m −2 period −1) and much higher annual mean windiness ( U Dugway=387 km day −1 vs. U Hunter=275 km day −1 and U Logan=174 km day −1) throughout the period over the playa. These data reveal the possibility of simultaneously harvesting these two sources of clean energies at this vast and uniform playa.

Chemical warfare agent decontamination studies in the plasma decon chamber

A decon has been developed at Los Alamos National Laboratory (LANL), Albuquerque, NM, to study the decontamination of chemical and biological warfare agents. This technology is targeted at sensitive electronic equipment for which there is currently no acceptable, nondestructive means of decontamination. Chemical reactivity is provided by a downstream flux of reactive radicals such as atomic oxygen and atomic hydrogen, produced in a capacitively coupled plasma. In addition, the decon chamber provides an environment that accelerates the evaporation of chemical agents from contaminated surfaces by vacuum, heat, and forced convection. Once evaporated, agents and agent byproducts are recirculated directly through the plasma, where they undergo further chemical breakdown. Preliminary studies on actual chemical agents were conducted at the U.S. Army Dugway Proving Ground, Dugway, UT. Exposures were conducted at a system pressure of 30 torr, exposure temperature of 70/spl deg/C, plasma-to-sample standoff distance of 10 cm, and 10% addition of oxygen or hydrogen to a helium balance. This exposure condition was based on optimization studies conducted at LANL on agent simulants. The agents studied were VX and soman (GD) nerve agents and sulfur mustard (HD) blister agent, as well as a thickened simulant. All agents were decontaminated off aluminum substrates to below the detection limit of /spl sim/0.1% of the initial contamination level of approximately 1 mg/cm/sup 2/. For VX, this level of decontamination was achieved in 8-16 min of exposure, while only 2 min were required for the more volatile HD and GD. Evaporation and subsequent gas-phase chemical breakdown in the plasma appears to be the dominant decontamination mechanism for all of the agents. However, an observed difference in the decontamination process between oxygen and hydrogen indicates that chemical reactivity in the liquid phase also plays an important role.

Viscous sublayer flow visualizations at Rθ≂1 500 000

Plan view flow visualization experiments were conducted in the atmospheric surface layer that flows over the Great Salt Lake Desert at the U.S. Army Dugway Proving Ground, Dugway, Utah. Measurements were acquired on a nonconductive, polyethylene platform made flush with the desert floor. Surface conditions upstream of the measurement site were flat, devoid of vegetation, and because of the dried mud/clay/salt composition, essentially dust free. Local surface variations ranged between 1 and 3 mm, which corresponded to three to ten viscous units during the experiments. Flow visualizations were accomplished by continuously injecting theatrical fog through a tangential slit covering a smoke reservoir buried under the platform. During the visualizations, the atmospheric surface layer flow was near neutral thermal stability. Flow velocities at 2.0 m above the surface maintained directional constancy, with a magnitude of about 1.5 m/s. A single element hot-wire probe positioned near y+=3.4 was used to measure the wall shear. Visualization results indicate the existence of the pocket and streak motions seen at much lower Reynolds number. The average inner normalized streak spacing was found to be λ+=93.1, with a positively skewed, nearly lognormal distribution. The average maximum inner normalized pocket width was found to be w+=127.2, with a positively skewed distribution. The average time between pockets was determined to be T+=36.6. Comparisons are made with existing low Reynolds number results, and a brief discussion is provided regarding the physics underlying the present observations.