Southeast Colorado Research Articles

Broad-scale changes in lesser prairie-chicken habitat.

Lesser prairie-chicken (Tympanuchus pallidicinctus) populations of in the Sand Sagebrush Prairie Ecoregion of southwest Kansas and southeast Colorado, USA, have declined sharply since the mid-1980s. Decreased quality and availability of habitat are believed to be the main drivers of declines. Our objective was to reconstruct broad-scale change in the ecoregion since 1985 as a potential factor in population declines. We assessed temporal change from 1985-2015 in landcover types and calculated landscape metrics using Land Change Monitoring, Assessment, and Projection imagery layers. We also documented presence of anthropogenic structures including oil wells and electrical transmission lines. Landcover type composition changed little since 1990 across the Sand Sagebrush Prairie Ecoregion. However, anthropogenic structures (i.e., oil/gas wells, cell towers, wind farms, and transmission lines) notably increased, potentially causing functional habitat loss at a broad scale. Increased anthropogenic structures may have decreased habitat availability as well as the quality of existing habitat for lesser prairie-chickens, possibly contributing to recent population declines throughout the Sand Sagebrush Prairie Ecoregion.

Using Climatological Data to Identify Locations with Viticultural Potential in Colorado

Western Colorado’s warm, dry summers and access to mountain river water for irrigation create ideal conditions for the growth of wine grapes, specifically cultivars of the European grape species Vitis vinifera. The largest limiting factor to Vitis vinifera production is nocturnal temperatures cold enough to damage crops, or Low Temperature Injury Events (LTIEs). LTIEs require producers to undergo the time-and-cost prohibitive venture of retraining vines. Eastern Mesa County Colorado has sustained large-scale grape production due to the area’s relatively mild cold season weather. Areas with similarly hospitable conditions may exist elsewhere within western Colorado. Parametrized Regression on Independent Slopes Model (PRISM) temperatures (1981-2020) were used to estimate the frequency of LTIEs across Colorado, and identify trends associated with a warming climate. In the interest of comparing PRISM temperatures to observations over actual vineyards, thermometers were placed on current vineyards in Montezuma County from 2016 to 2020. Findings suggest additional areas of opportunity for Vitis vinifera production exist in Colorado, particularly western Montezuma County, and western Mesa and Montrose Counties. Like eastern Mesa County, these areas experience a LTIE in fewer than 20 % of years. PRISM data also suggest southeast Colorado is becoming more hospitable for Vitis vinifera growth over time. Temperature measurements in Montezuma County during potentially lethal weather events compared closely with PRISM data, with a mean absolute difference of 1.8 ˚C. This comparison suggests PRISM is a reliable tool for identifying areas of opportunity in spite of western Colorado’s complex terrain.

Mastication Treatments Increase Perennial Herbaceous Cover Across Soil Types in Southeastern Colorado Piñon-Juniper Woodlands

Tree-removal treatments have been broadly applied across piñon-juniper ecosystems of the western United States to reduce tree cover, stimulate understory plant production, and promote habitat for shrub- and grassland-obligate wildlife species. Mastication treatments have become an increasingly common approach, yet the efficacy of these treatments can vary on the basis of a variety of factors, including soil characteristics, woodland structure, and grazing pressures. Here, we assessed vegetation responses to mastication treatments across three dominant soil types in two-needle piñon (Pinus edulis Engelm. [Pinaceae])−one-seed juniper (Juniperus monosperma [Engelm.] Sarg.) woodlands in southeast Colorado, United States, a region characterized by monsoonal precipitation, limited presence of introduced plant species, and relatively high grazing intensity by cattle and wildlife. We found that mastication treatments were effective at increasing herbaceous plant cover and species diversity (by 1.2 × and 1.5 ×) and at reducing the amount of exposed soil (60% reduction) 3 yr following treatment. This was mainly due to increases in native perennial grasses. Further, there were limited (and insignificant) increases in cover of annual plants and low abundance of introduced species in treated plots. Understory plant responses to treatment were similar across soils with a range of available water capacities. The increase in understory plant cover and richness paired with the low abundance of introduced species suggests that mastication treatments increase forage production for cattle and wild ungulates. In addition, the lack of soil type differences in treatment response suggests that mastication treatment placement does not need to prioritize soil type and can instead focus on other key areas of importance, such as wildlife habitat connectivity, historic woodland structure, and treatment feasibility.

Change in Piñon-Juniper Woodland Cover Since Euro-American Settlement: Expansion Versus Contraction Associated with Soil Properties

Woodland and forest ecosystems across western North America have experienced increased density and expansion since the early 1900s, including in the widely distributed piñon-juniper vegetation type of the western United States. Fire suppression and grazing are often cited as the main drivers of these historic changes and have led to extensive tree-reduction treatments across the region. However, much of the scientific literature on piñon-juniper expansion dates back only to the early 1900s, which is generally half a century after Euro-American settlement. Yet US General Land Office (GLO) surveys provide valuable insight into the historical extent and density of woodland and forest ecosystems as surveyors would note where on the landscape they entered and exited woodlands or forests and provided qualitative estimates of relative tree density. This study uses these GLO surveys to establish piñon-juniper woodland extent in the late 19th century at the incipient stages of Euro-American settlement in southeastern Colorado and compares these data with 2017 aerial imagery of woodland cover. We found substantial amounts of woodland contraction, as well as expansion: ≈61% of historically dense woodland is now savanna or open (treeless), whereas ≈57% of historically open areas are now savannas or woodlands. The highest rates of expansion occurred on shallow, rocky soil types with low soil available water capacity, which support little herbaceous vegetation and were consequently less likely to be affected by fire suppression or grazing. Meanwhile, the significant contractions in woodland extent occurred on deeper, upland soils with higher soil available water capacity, which were likely where early settlement and tree cutting was most prevalent. Our results provide mixed support for the widespread assumption of woodland expansion since Euro-American settlement in southeast Colorado and suggest that the expansion that has occurred in our study area is unlikely a result of past grazing or fire suppression.

The Southeast Colorado PE Academy: Implementation and Outcomes in Rural Elementary Schools, 2014-16

This paper describes the implementation and outcomes of the Southeast Colorado Physical Education Academy (SECPEA). The SECPEA intervention aimed to improve the quality of physical education taught by 21 teachers in 19 rural schools in Southeast Colorado over a two-year period by supporting the implementation of an enhanced physical education program (EPE). The System for Observing Fitness Instruction Time was used to evaluate the effectiveness of the intervention at baseline, post year one, and post year two. Post year one, a moderate and significant increase was observed in overall MVPA% per lesson. The largest increase was observed in the MVPA% during the first five minutes of lessons. Significant increases were also observed in girls’ MVPA% and for teacher promotion of MVPA. Post year two, significant positive increases were observed in the percentage of vigorous physical activity and energy expenditure rate. The SECPEA was a successful model for implementation of an EPE. Continued testing of the model in diverse settings is warranted.

Calf Creek Horizon Evidence at the Gault Site (41BL323); a description of the imagery found in the Volume 5 cover border design

Dated to ca. 6,000 – 5,750 cal BP considerable amounts of material culture associated with what is identified as the Calf Creek Horizon by Don G. Wyckoff, has been recovered from the Gault site (Wyckoff pp. 1-8, 1994). The natural response to this evidence was to expand upon previous understandings of this time period (Wyckoff and Shockey 1994) (Weber 1994) (Wyckoff and Shockey 1995) (Drass 1999). Directed by Michael B. Collins, a considerable amount of effort was invested by the author to develop a deeper understanding of the human manufacturing behaviors behind the production of the dart points of this horizon throughout the Southern Plains. An upcoming book edited by Jon C. Lohse, Don G. Wyckoff, and Margorie Duncan (Lohse In Press) will feature many insights into this horizon and these point technologies by the author from the Gault School of Archaeological Research (GSAR) and Elton Prewitt from the Texas Archaeological Research Laboratory (TARL). The sample of imagery presented here comes from two primary periods of investigation. There is material from the Pearce Collection located at TARL, excavated by J. E. Pearce and his crewmen in 1929 and 1930 (Collins 2011). There are also specimens that relate to GSAR investigations between 1999 and the current day (Williams 2018). The assembled imagery consists of significantly refurbished Andice points, point fragments, Andice stems, several Bell point specimens that have clearly seen service in the ancient past, potential Andice preforms from the Pearce Collection (illustrated by Sergio J Ayala), a practice notching piece, and notching flakes that are a byproduct of Andice point manufacturing. These images comprise a tiny fraction of the Calf Creek Horizon materials from the Gault site. This evidence demonstrates both the discard of exhausted points and tremendous quantities of Andice and Bell point manufacturing at the Gault site. This does not include the nearly 3,000 Andice and Bell point specimens that are said to have been collected from the site during the years when the property was a pay-to-dig operation (Hester 1992) (Collins 2011). Archaeologically, we know very little about the hunter gatherer groups that are the creators of the extraordinarily complex dart points that mark this horizon in time throughout the Southern Plains. Technologically however, we now understand that there are three dart point forms that are contemporaneous, intergrade morphologically, and share similar reduction strategies, techniques, flaking patterns, and reduction sequences. They are the Andice and Bell dart points of Texas and the Calf Creek dart points associated with southeast Colorado, Kansas, Missouri, and Oklahoma (Ayala, Technology and Typology of the Calf Creek Horizon In Press).

Design and Construction of a Precision Weighing Lysimeter in Southeast Colorado

Abstract. Accurate estimates of crop evapotranspiration (ET) are needed to effectively manage irrigation resources in the Arkansas River basin in Colorado and to maintain compliance with the Arkansas River compact with Kansas. This was a major impetus for the construction of a precision weighing lysimeter in the Arkansas River basin at the Colorado State University (CSU) Arkansas Valley Research Center (AVRC) near Rocky Ford, Colorado. The objective of this article is to describe the design and construction of the weighing lysimeter and characterize its performance and unique features. The main components of the lysimeter facility are the foundation, the scale system, the soil monolith tank, and the outer tank that houses the aforementioned components. The foundation, which was 4.12 m below the ground surface, consisted of a reinforced concrete slab 2.00 m wide by 6.31 m long and 0.20 m thick that was anchored to six square shaft helical anchors. The outer tank was secured onto the foundation and had a rectangular floor area of 6.10 m × 1.79 m (10.92 m2), an interior vertical clearance of 2.15 m, and walls made of reinforced 8 mm thick steel plates. The floor scale system (mechanical levers and load cell) was installed inside the outer tank and had a gross capacity of 17 Mg. The monolith tank (1.50 m × 1.50 m area, 2.44 m depth, 10 mm steel walls) containing an undisturbed soil profile was set on the scale system. The lysimeter facility was installed in the middle of a 3.5 ha field. Calibration of the scale system resulted in a linear response (R2 = 1.000), with an equivalent conversion coefficient (slope) of 151.09 mm H2O (mV V-1)-1. The sensitivity of the scale system was 0.023 mm of water, which is sufficient for measuring diurnal (15 min to hourly) changes in ET and soil water. Load cell readings taken at a frequency of 0.5 Hz were averaged in 15 min intervals (450 readings per 15 min) to filter out the measurement noise that was attributed to wind. The lysimeter was found to adequately detect ET, irrigation, and precipitation perturbations with an actively growing alfalfa hay crop ( L.) in 2011. The lysimeter facility is a state-of-the-art tool for quantifying ET of irrigated crops in the lower Arkansas basin in southeast Colorado. Keywords: Calibration, Evapotranspiration, Load cell, Weighing lysimeter.

Apishapa rock art and Great Basin shamanism: power, souls, and pilgrims

ABSTRACTThe Apishapa archaeological phase in southeast Colorado, USA, was more likely an eastern extension of the Great Basin Desert Culture than a western extension of the Plains Village pattern. For this reason, Archaic Period rock art in the Great Basin and the Apishapa area are remarkably similar. curvilinear and rectilinear styles in both areas share several motifs and combinations. Because of Apishapa origins, we use Great Basin ethnography to discuss abstract rock art in the lower Apishapa canyon. The Great Basin version of shamanism, especially the interrelated concepts of dynamic power, soul travel, and sacred pilgrimages help to explain many images. Overall, sacred pilgrimages provided the social context for much of the art.

Joint elastic side-scattering LIDAR and Raman LIDAR measurements of aerosol optical properties in south east Colorado

We describe an experiment, located in south-east Colorado, U.S.A., that measured aerosol optical depth profiles using two LIDAR techniques. Two independent detectors measured scattered light from a vertical UV laser beam. One detector, located at the laser site, measured light via the inelastic Raman backscattering process. This is a common method used in atmospheric science for measuring aerosol optical depth profiles. The other detector, located approximately 40 km distant, viewed the laser beam from the side. This detector featured a 3.5 m2 mirror and measured elastically scattered light in a bistatic LIDAR configuration following the method used at the Pierre Auger cosmic ray observatory. The goal of this experiment was to assess and improve methods to measure atmospheric clarity, specifically aerosol optical depth profiles, for cosmic ray UV fluorescence detectors that use the atmosphere as a giant calorimeter. The experiment collected data from September 2010 to July 2011 under varying conditions of aerosol loading. We describe the instruments and techniques and compare the aerosol optical depth profiles measured by the Raman and bistatic LIDAR detectors.

Using sterilization to change predation rates of wild coyotes: A test case involving pronghorn fawns

Surgical sterilization of coyotes (Canis latrans) reduced their predation rate on domestic sheep. We investigated whether sterilizing coyotes would similarly change coyote predation rates on pronghorn antelope (Antilocapra americana) neonates. From May 2006 to March 2008, we radio-collared 71 pronghorn fawns to determine survival rates in southeast Colorado, USA. During the first year of the study, all coyotes were reproductively intact. During the second year, we surgically sterilized 15 coyotes from 10 packs in the southern half of the study area, while nine coyotes from seven packs in the northern half were given sham sterilizations (i.e., remained reproductively intact). In addition, we estimated the availability of alternative prey and coyote density on both areas to evaluate predator–prey factors that could interact with the sterilization treatment. Using the known fate model in Program Mark, we constructed models with and without a treatment effect, plus year, area, individual covariates, alternative prey indices, and predator density to estimate pronghorn fawn survival rates. Results from model averaged parameter estimates and cumulative summer survival indicated coyote sterilization increased survival rates of pronghorn fawns by reducing predation rates of fawns. While fawn survival was higher overall in the north area, after treatment was applied, cumulative pronghorn fawn survival during the summer of 2007 in the south area was 242% higher for pronghorn fawns captured in sterile coyote territories (0.44; 79-day interval survival rate) compared to fawns captured in intact coyote territories (0.18). There was also a significant local area effect, but no relationship between fawn survival and individual fawn covariates of sex, birth weight, birth date, or age. No relationship was detected between fawn survival and lagomorph abundance index, rodent abundance index, or coyote density. Surgical sterilization of coyotes was useful in reducing predation rates on pronghorn fawns.

Testing to Prevent Colon Cancer: Results From a Rural Community Intervention

Colon cancer is the second leading cause of cancer death in the United States. Despite tests that can detect and enable removal of precancerous polyps, effectively preventing this disease, screening for colon cancer lags behind other cancer screening. The purpose of this study was to develop and test a community-based participatory approach to increase colon cancer screening. Using a community-based participatory research approach, the High Plains Research Network and their Community Advisory Council developed a multicomponent intervention-Testing to Prevent Colon Cancer-to increase colon cancer screening. A controlled trial compared 9 intervention counties in northeast Colorado with 7 control counties in southeast Colorado. We performed a baseline and postintervention random digit-dial telephone survey and conducted both intent-to-treat and on-treatment analyses. In all, 1,050 community members completed a preintervention questionnaire and 1,048 completed a postintervention questionnaire. During the study period, there was a 5% absolute increase in the proportion of respondents who reported ever having had any test in the intervention region (from 76% to 81%) compared with no increase in the control region (77% at both time points) (P = .22). No significant differences between these groups were found in terms of being up to date generally or on specific tests. The extent of exposure to intervention materials was associated with a significant and cumulative increase in screening. This community-based multicomponent intervention engaged hundreds of community members in wide dissemination aimed at increasing colorectal cancer screening. Although we did not find any statistically significant differences, the findings are consistent with an intervention-related increase in screening and provide preliminary evidence on the effectiveness of such interventions to improve colon cancer screening.

Translating Wind-Speed Measurements over Alfalfa Having Varying Height for Use in the ASCE Standardized Reference ET Equation

The ASCE Standardized Reference Evapotranspiration (ET) Equation expects wind speed measured at a height of 2 m over and downwind of a smooth measurement surface, such as actively growing clipped grass. Many agricultural weather stations used for evapotranspiration estimation may not meet such siting conditions. A physically based approach to translate wind speeds measured at various heights and weather measurement surface conditions to equivalent wind speed at 2-m height over actively growing clipped grass is tested in agricultural settings. The translation algorithm assumes neutral or near-neutral boundary layer stability conditions. Mean daily wind speeds measured at 2- and 3-m heights above ground surface over and downwind of variable-height alfalfa during the 2008, 2009, and 2010 growing seasons in several southeast Colorado locations were translated to equivalent mean daily wind speed at 2-m height over clipped grass and compared. Translated alfalfa weather station mean daily wind speeds were also compared with mean daily wind speeds measured at 2-m height over 0.12-m grass for parts of the 2009 and 2010 seasons at two pairs of sites. The translation algorithm produced translated mean daily wind speeds in good agreement with wind speeds measured under the standard weather station condition. The effects on computed daily tall crop reference evapotranspiration are illustrated.

Predicting water intake by yearling feedlot steers,

Data from 4 separate beef cattle feedlot experiments, which were conducted at the Southeast Colorado Research Center (SECRC) in Lamar, CO, in 2001, 2003, 2004, and 2007, were utilized in a retrospective longitudinal study investigating possible relationships between daily water consumption (WC), DMI, and weather variables. The data set consisted of 8,209 records from 2001, 2003, 2004, and 2007, with pen based daily WC (L•animal(-1)) and DMI measurements and calculated daily steer BW from April to October in each year. Daily weather data were obtained from the weather station located at Lamar Municipal Airport located approximately 1.9 km from SECRC. Data collected consisted of daily high, low, and mean temperature; high, low, and mean humidity; high, low, and mean sea level pressure; mean wind speed; total precipitation; and average daily wind direction (cosine of radians from due north). Univariate analysis demonstrated that the continuous variables of BW, humidity, and sea level pressure were negatively related (P < 0.0001), whereas DMI, temperature the previous day, daily temperature, change in temperature from the previous day, average wind speed, and the temperature-humidity index (THI) were positively related (P < 0.001) to daily WC. There was a trend (P < 0.06) for the cosine of wind direction (1 = due north and -1 = due south) to be negatively related to WC. The multivariate, parsimonious model predicting average daily WC included (P < 0.05) average humidity, average humidity squared, high temperature squared, high humidity squared, low temperature, low temperature squared, low humidity, average sea level pressure, average wind speed, average daily BW, high sea level pressure, low sea level pressure, high humidity, and low humidity. The generalized R(2) of the parsimonious multivariate model was 0.32. These results indicate that BW and numerous weather factors are related to WC by yearling feedlot steers. Dry matter intake had minimal impact on WC for yearling feedlot steers consuming steam-flaked corn-based high concentrate diets from mid-spring to early fall.

Influence of Reduced Nitrogen Diets on Ammonia Emissions from Cattle Feedlot Pens

Reducing crude protein (CP) in livestock diets may lower ammonia emissions. A feeding trial was conducted with crossbred steers at the Southeast Colorado Research Center in Lamar, Colorado from December 2009 to March 2010. Three diet treatments were investigated: Reduced (11.6% CP), Oscillating (13.5% crude protein 4 days/week and 11.6% CP 3 days/week) and Control (13.5% CP). Intact soil core samples (n = 36 per sampling date) were collected from the pen surfaces on three dates corresponding to 45, 92, and 148 days into the feeding cycle. Four pens from each diet treatment were sampled. Cores were placed into flow-through laboratory chambers for seven days and ammonia fluxes were trapped in acid bubblers that were refreshed every 24 h. Average daily ammonia emissions for the Control diet ranged from 6.6 to 9.4 g NH3 m−2·day−1; average daily emission for the Oscillating diet ranged from 6.3 to 8.8 g NH3 m−2·day−1; and average daily flux for the Reduced diet ranged from 4.1 to 5.8 g NH3 m−2·day−1. Ammonia fluxes from the reduced N treatment were significantly lower (21% to 40%) than from the control diet on the first two sample dates. There was no significant difference between the Oscillating and Control treatments. Reducing CP in cattle feedlot diets may be an effective method for reducing ammonia emissions from pen surfaces. More research is needed to validate these results at commercial scales in different environments to determine if reductions in ammonia can be sustained with lower CP diets without affecting rate of gain, feed efficiency and health.

The northern site of the Pierre Auger Observatory

The Pierre Auger Observatory is a multi-national project for research on ultra- high energy cosmic rays. The Southern Auger Observatory in Mendoza province, Argentina, is approaching completion in 2007 with an instrumented area of 3,000 km 2 . It will accurately measure the spectrum and composition of ultra-high energy cosmic rays up to and beyond the predicted GZK feature. We are obtaining results on the energy spectrum, mass composition and distribution of arrival directions on the southern sky. The Northern Auger Observatory is designed to complete and extend the investigations begun in the South. It will establish charged particle astronomy and thus open a new window into the universe. The distribution of arrival directions of the highest energy events will point the way to unveiling the almost century old mystery of the origin and nature of ultra-high energy cosmic rays. Achieving this goal requires collecting many more events in spite of the steeply falling energy spectrum. The planned northern site will have an instrumented area of 4,000 square miles (10,370 km 2 ) in Southeast Colorado, USA. The presentation covers the science of charged particle astronomy, the layout and the technical implementation of the Northern Auger Observatory.

Exploring Cloud-to-Ground Lightning Earth Highpoint Attachment Geography by Peak Current

Abstract This study applied remotely sensed cloud-to-ground (CG) lightning strike location data, a digital elevation model (DEM), and a geographic information system (GIS) to characterize negative polarity peak current CG lightning Earth attachment behavior. It explored the propensity for (i) flashes to favor topographic highpoint attachment and (ii) striking distance (a near-Earth attachment force) to increase with peak current. On a 16 000 km2 10-m DEM covering a section of southeast and south-central Colorado, a GIS extraction method identified approximately 5000 hilltop and outcrop highpoints containing at least 15 m of vertical gain in a 300-m radius neighborhood with a minimum horizontal separation of 600 m. Flashes with peak currents ranging from −20 to −119 kiloamps (kA), collected between February 2005 and May 2009, were subdivided into 10 kA classes and mapped on this modified DEM. Buffers of 100-, 200-, and 300-m radii created around each highpoint were used to assess the hypothesis that striking distance increases with higher negative peak current. Point-in-polygon counts compared actual CG strike totals to random point totals received inside buffers. CG strikes favored topographic highpoints by as much as 5.0% when compared to random points. Chi-square goodness-of-fit tests further corroborated that actual CG strikes at highpoints were generated by a more nonrandom process. A positive trend between striking distance and peak current was also observed. Although this correlation has been characterized in controlled settings, this study is the first to document this physical process at real-world landscape scales over multiple years.

The Northern site of the Pierre Auger Observatory

To increase statistics for cosmic ray events with energies above 50EeV and to obtained a full sky coverage, a Northern Auger Observatory with a surface of 20,000km2 is planned in South East Colorado, USA. The design will use the well proven hybrid concept: a surface array combined with fluorescence telescopes. In this paper, the basic elements of Auger North will be described.

Case Study: The Effects of Severe Winter Weather on Net Energy for Maintenance Required by Yearling Steers

<h2>ABSTRACT</h2> Severe winter storms in southeast Colorado in December of 2006 and January 2007 resulted in severe economic losses for the cattle feeding industry. Two hundred fourteen steers were weighed on December 26, 2006, and average BW (minus 4% pencil shrink) was 558kg ± 21.7. Over the following 58-d period there was a 7.0% death loss and ADG was −0.13kg ± 0.21. Average steer BW (minus 4% pencil shrink) was 550kg ±18.7 on February 22, 2007. Total DM delivered was 53,436.7kg and average NE_m concentration in the diet was 2.263 Mcal/kg DM. Daily DMI averaged 9.67 kg/d per head. Average shrunk BW (SBW) was 554.1kg and average empty body weight (497.7 kg), empty body gain (−0.00686 kg/d), and retained energy (−0.0283 Mcal/d) were calculated from NRC (2000) equations. The required NE_m was 21.9176 Mcal/d per head or 0.1919 Mcal/kg of SBW^0.75 These data indicate that NE_m required during and in the aftermath of a major winter weather event may be 2.5 fold higher than NE_m required (0.077 × SBW^0.75) under thermal neutral conditions. Calculations of lower critical temperature and external insulation indicate that the insulation value of the hair coat may have been destroyed by the moisture, mud, and snow following the storm.

Turbulent Velocity-Variance Profiles in the Stable Boundary Layer Generated by a Nocturnal Low-Level Jet

Abstract Profiles of mean winds and turbulence were measured by the High Resolution Doppler lidar in the strong-wind stable boundary layer (SBL) with continuous turbulence. The turbulence quantity measured was the variance of the streamwise wind velocity component σ2u. This variance is a component of the turbulence kinetic energy (TKE), and it is shown to be numerically approximately equal to TKE for stable conditions—profiles of σ2u are therefore equivalent to profiles of TKE. Mean-wind profiles showed low-level jet (LLJ) structure for most of the profiles, which represented 10-min averages of mean and fluctuating quantities throughout each of the six nights studied. Heights were normalized by the height of the first LLJ maximum above the surface ZX, and the velocity scale used was the speed of the jet UX, which is shown to be superior to the friction velocity u* as a velocity scale. The major results were 1) the ratio of the maximum value of the streamwise standard deviation to the LLJ speed σu/UX was found to be 0.05, and 2) the three most common σ2u profile shapes were determined by stability (or Richardson number Ri). The least stable profile shapes had the maximum σ2u at the surface decreasing to a minimum at the height of the LLJ; profiles that were somewhat more stable had constant σ2u through a portion of the subjet layer; and the most stable of the profiles had a maximum of σ2u aloft, although it is important to note that the Ri for even the most stable of the three profile categories averaged less than 0.20. The datasets used in this study were two nights from the Cooperative Atmosphere–Surface Exchange Study 1999 campaign (CASES-99) and four nights from the Lamar Low-Level Jet Project, a wind-energy experiment in southeast Colorado, during September 2003.

Tracing Comanche history: Eighteenthcentury rock art depictions of leatherarmoured horses from the Arkansas River basin, south-eastern Colorado, USA

Depictions on rock in south-east Colorado show mounted warriors with horses clad in leather armour. This was the military strategy adopted by Comanche and Apache peoples between 1650 and 1750 – after the arrival of the horse and before the availability of firearms.