Ronald Calhoun

University of Utah, Salt Lake City, Utah, United States

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Publications (53)87.51 Total impact

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    ABSTRACT: AbstractThe second Meteor Crater Experiment (METCRAX II) was conducted in October 2013 at Arizona's Meteor Crater. The experiment was designed to investigate nighttime downslope-windstorm-type flows that form regularly above the inner southwest sidewall of the 1.2-km-diameter crater as a southwesterly mesoscale katabatic flow cascades over the crater rim. The objective of METCRAX II is to determine the causes of these strong, intermittent, and turbulent inflows that bring warm-air intrusions into the southwest part of the crater. This article provides an overview of the scientific goals of the experiment, summarizes the measurements, the crater topography and the synoptic meteorology of the study period, and presents initial analysis results.
    Bulletin of the American Meteorological Society 04/2015; DOI:10.1175/BAMS-D-14-00238.1 · 11.57 Impact Factor
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    ABSTRACT: The second Meteor Crater Experiment (METCRAX II) was designed to study downslope-windstorm-type flows occurring at the Barringer Meteorite Crater in Arizona. Two Doppler wind lidars were deployed to perform a coplanar dual-Doppler lidar analysis to capture the two-dimensional (2-D) vertical structure of these flows in the crater basin. This type of analysis allows the flow to be resolved on a 2-D Cartesian grid constructed in the range height indicator scan overlap region. Previous studies have shown that the dominant error in the coplanar dual-Doppler analysis mentioned above is due to the under sampling of radial velocities. Hence, it is necessary to optimize the setup and choose a scan strategy that minimizes the under sampling of radial velocities and provides a good spatial as well as temporal coverage of these short-lived events. A lidar simulator was developed using a large Eddy simulation wind field to optimize the lidar parameters for METCRAX II field experiment. A retrieval technique based on the weighted least squares technique with weights calculated based on the relative location of the lidar range gate centers to the grid intersection point was developed. The instrument configuration was determined by comparing the simulator retrievals to the background wind field and taking into account the limitations of commercially available lidars.
    Journal of Applied Remote Sensing 12/2014; 9(1). DOI:10.1117/1.JRS.9.096090 · 0.89 Impact Factor
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    ABSTRACT: The Second Meteor Crater Experiment (METCRAX II) was designed to study downslope-windstorm-type flows occurring at the Barringer Meteorite Crater in Arizona. Two Doppler wind lidars were deployed to perform a Co-planar Dual Doppler lidar analysis to capture the 2D vertical structure of these flows in the crater basin. This type of analysis allows the flow to be resolved on a 2D Cartesian grid constructed in the RHI scan overlap region. Previous studies have shown that the dominant error in the Co-planar Dual Doppler analysis mentioned above is due to the under sampling of radial velocities. Hence, it is necessary to optimize the setup and choose a scan strategy that minimizes the under sampling of radial velocities and provides a good spatial as well as temporal coverage of these short-lived events, which in turn strongly depend on the lidar parameters and the grid spacing. To optimize the lidar parameters for the METCRAX II field experiment, a lidar simulator was developed using an LES wind field. A wind retrieval technique based on the weighted least squares method with weights calculated based on the relative location of the lidar range gate centers to the grid intersection points was developed. An optimal instrument configuration was devised by comparing the simulator retrievals to the LES-modeled background wind field. Details about the lidar simulator and early results from the field experiment will be presented.
    16th Conf. Mountain Meteorology, San Diego, CA; 08/2014
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    ABSTRACT: The Second Meteor Crater Experiment (METCRAX II) was designed to study downslope-windstorm-type flows (DWF) that occur above the south and west inner sidewalls of the 1.2 km diameter Barringer Meteorite Crater in Arizona. These DWFs occur intermittently within the crater basin on clear, undisturbed nights in connection with a mesoscale drainage flow that approaches the crater from higher terrain to the southwest of the crater. During DWF events a wave descends in the lee of the upwind crater rim, producing strong and turbulent downslope flow above the slope, which rebounds in a hydraulic jump-like flow feature at the base of the slope. Multiple break-ins of these flows occur on suitable nights, and the individual break-ins vary in strength and duration. This presentation will provide an overview of the October 2013 METCRAX II field experiment. This experiment was supported by the National Center for Atmospheric Research's Earth Observing Laboratory and by other organizations, with an extensive complement of field equipment including a radar wind profiler, 2 radio acoustic sounding systems, three scanning Doppler LiDARs, a vertically pointing LiDAR, instrumented 40- and 50-m towers, 3 surface flux stations, 3 SoDARs, a scintillometer, a ceilometer, automatic weather stations, an array of temperature data loggers, multiple pressure sensors, and visual and thermal IR time-lapse cameras. Seven overnight Intensive Observational Periods (IOPs) were selected during the month on the basis of weather forecasts. Three continuously operated tethersondes and 3-hourly radiosondes provided supplementary vertical sounding data during the IOPs. The forecasts were successful in selecting nights when the DWF phenomenon occurred, and analyses of the data are now underway. This presentation will summarize first results, with detailed analyses presented in other related presentations at the conference.
    16th Conference on Mountain Meteorology American Meteorological Society 2014; 08/2014
  • 16th Conf. on Mountain Meteorology, San Diego, CA; 08/2014
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    ABSTRACT: The second Meteor Crater Experiment (METCRAX-II) was conducted in October 2013 to study downslope-windstorm-type flows that occur on the upwind inner sidewall of the basin of Arizona's Meteor Crater during synoptically quiescent nights under clear sky conditions. The formation of these flows, which lead to warm-air intrusions into the upwind part of the crater basin, is associated with a nocturnal mesoscale drainage flow that develops on the slightly inclined plane surrounding the crater. Three scanning Doppler wind LiDARs were operated during METCRAX-II. Two scanned continuously in a coplanar configuration to measure a vertical cross section through the intruding flows, while a third LiDAR was deployed upwind of the crater basin to measure the characteristics of the evolving drainage flow impinging on the crater topography. We will show initial results of the wind fields retrieved from the three LiDARs, showing (1) the temporal evolution of the drainage flow outside of the crater topography (2) flow splitting of the approach flow around the crater and (3) the development and evolution of the downslope-wind-storm-type intrusions into the crater basin.
    16th Conference on Mountain Meteorology American Meteorological Society 2014; 08/2014
  • Bulletin of the American Meteorological Society 05/2014; 95(5):743-756. DOI:10.1175/BAMS-D-12-00111.1 · 11.57 Impact Factor
  • EGU General Assembly 2014; 05/2014
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    ABSTRACT: Pulsed Doppler lidars are powerful tools for long-range, high-resolution measurements of radial wind velocities. With the development of commercial Doppler lidars and the reduction of acquisition costs, dual-Doppler lidar systems will be become increasingly accessible in upcoming years. This study reviews the most common dual-Doppler techniques, describes the setup of a highly synchronized long-range dual-Doppler lidar system, and discusses extensively the different kinds of errors connected with this complex measurement technique. Sources of errors and their interactions are traced through the retrieval algorithm, including errors from single-Doppler lidar and those occurring from a combination of instruments related to various parameters, such as relative beam angles, time and spatial scales of the scan pattern, and atmospheric conditions.
    Journal of Atmospheric and Oceanic Technology 09/2013; 30(9):2044-2062. DOI:10.1175/JTECH-D-12-00244.1 · 1.82 Impact Factor
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    ABSTRACT: Coherent Doppler lidar measurements are of increasing interest for the wind energy industry. Wind measurements are fundamental inputs for the evaluation of potential energy yield and performance of wind farms. Three-dimensional scanning Doppler lidar may provide a new basis for wind farm site selection, design and optimization. In this paper, the authors discuss Doppler lidar measurements obtained for a wind energy development. The possibility of using lidar measurements to more fully characterize the wind field is discussed, specifically terrain effects, spatial variation of winds, power density and the effect of shear at different layers within the rotor swept area. Vector retrieval methods have been applied to the lidar data, and results are presented on an elevated terrain-following surface at hub height. The vector retrieval estimates are compared with tower measurements, after interpolation to the appropriate level. Doppler lidar data are used to estimate the spatial power density at hub height (for the period of the deployment). An example wind farm layout is presented for demonstration purposes based purely on lidar measurement, even though the lidar data acquisition period cannot be considered climatological. The strength of this approach is the ability to directly measure spatial variations of the wind field over the wind farm. Also, because Doppler lidar can measure winds at different vertical levels, an approach for estimating wind power density over the rotor swept area (rather than only the hub height) is explored. Finally, advanced vector retrieval algorithms have been applied to better characterize local wind variations and shear. Copyright (c) 2012 John Wiley & Sons, Ltd.
    Wind Energy 03/2013; DOI:10.1002/we.539 · 2.56 Impact Factor
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    ABSTRACT: Wind measurements are fundamental inputs for wind resource assessment and the performance of wind farms. Common approaches for wind energy yield assessment are based on (1) observational data from surface station networks and (2) high-resolution computational fluid dynamic or mesoscale models. In this letter, we investigate the potential of applying a high-resolution nested mesoscale model, Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS), to predict low-level wind characteristics for wind farm domains. The model results are compared to scanning coherent Doppler lidar and tower measurements for a wind energy development. This letter focuses on the magnitude of difference between observations and simulations used for wind energy assessment. The results highlight the challenge for straight-forward application of mesoscale models, even well-established models with a relatively fine resolution on the inner nest (333 m), to produce wind predictions of sufficient fidelity and accuracy appropriate for resource assessment or operational support for individual wind farms. While many of the average wind flow features are captured by the model, their detailed spatial and temporal evolution may be improved through tighter integration with local sensor data.
    Remote Sensing Letters 01/2013; 4(6):579-588. DOI:10.1080/2150704X.2013.769285 · 1.43 Impact Factor
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    ABSTRACT: Several modifications to the optimal interpolation (OI) technique for light-detection-and-ranging vector retrieval are proposed and shown to result in significant improvement in velocity retrieval accuracy. These modifications include changes to innovation covariance portioning, covariance binning, and analysis increment calculation. A validation of the modified OI technique is presented, comparing the retrievals with the original technique in each case. The modified technique is able to perform retrievals with better accuracy, preserves local information better, and compares well with tower measurements.
    IEEE Geoscience and Remote Sensing Letters 11/2012; 9(6):1132-1136. DOI:10.1109/LGRS.2012.2191762 · 1.81 Impact Factor
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    ABSTRACT: A study of an interesting meteorological episode over the Owens Valley, California, USA during the Terrain-Induced Rotor EXperiment was conducted using a recently adapted statistical interpolation method to retrieve wind-velocity vectors from Doppler lidar data. This vector retrieval method has been adapted from radar data assimilation techniques. Results show that the method allows better preservation of local variations in the flow field than other techniques. In addition, a high resolution Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS®) run is used to understand the large-scale flow within the valley and compared with lidar retrievals. Observations from 1030 UTC to 1230 UTC (0230 local time to 0430 local time) on March 27, 2006 are presented. Lidar observations show complex and uncharacteristic flows such as sudden bursts of westerly cross-valley wind mixing with the dominant up-valley wind. Model results from COAMPS and other in-situ instrumentation are used to corroborate and complement these observations. The optimal interpolation technique for Doppler lidar data vector retrieval appears well suited for scenarios with complex spatial variations in the flow field.
    Boundary-Layer Meteorology 09/2012; 144(3). DOI:10.1007/s10546-012-9729-2 · 2.53 Impact Factor
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    ABSTRACT: In this paper, the effect of several turbulence parameters during various flow conditions in Owens Valley, educed from coherent Doppler lidar data have been studied. Radial velocity structure functions are processed to estimate the turbulent kinetic energy (TKE) dissipation rate, integral length scale and velocity variance, assuming a theoretical model for isotropic wind fields. Corrections for turbulence measurements have been considered to address the complications due to inherent volumetric averaging of radial velocity over each range gate, noise of the lidar data, and the assumptions required to estimate effects of smaller scales of motion on turbulence quantities. Using data from the Terrain-induced Rotor Experiment (T-REX) in April–May 2006, vertical profiles of wind and turbulence parameters have been retrieved. During T-REX, unusual valley flows were detected by the lidar data, for example on 19 and 27 March 2006, daytime down-valley and night time up-valley flows, respectively, were observed. This paper focuses on understanding various turbulence parameters during these flow events. Turbulence estimates during daytime down-valley conditions were observed to be constant for most of the day, while for night time up-valley circumstances the turbulence increased steadily as the day progressed. Good comparison was observed between lidar and tower measurements, which validate the lidar turbulence retrieval assumptions. Comparison between TKE estimates from lidar and the Coupled Ocean/Atmosphere Mesoscale Prediction System (COAMPS) model is also presented. This analysis will be helpful for improving the current turbulence parameterization schemes in COAMPS. Finally, differences and similarities in turbulence measurements between both the flow regimes are discussed. Copyright © 2011 Royal Meteorological Society
    Meteorological Applications 08/2011; 18(3):361 - 371. DOI:10.1002/met.263 · 1.52 Impact Factor
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    ABSTRACT: Dispersion modelling is a key component of modern emergency responses to catastrophic atmospheric releases. However, periodic algorithmic advances are needed to effectively use new datasets acquired with modern remote sensing instruments. This work demonstrates that coherent Doppler lidar can be used to provide valuable new inputs for dispersion models. While related research seeks to retrieve other required inputs for dispersion modelling systems, for example velocity vectors from radial velocities, this paper assembles and contextualizes analytical and algorithmic approaches for an improved understanding of dispersion characteristics in specific atmospheric scenarios using Doppler lidar data. Longitudinal (along-wind), lateral (cross-wind), and vertical dispersion parameters are calculated and used to estimate eddy diffusivities based on Gaussian curve fitting and first-order closure. Empirical relations based on similarity theory are used to verify these estimates, and reasonable agreement is found between the two approaches. Several improvements are also suggested for the lidar scanning techniques to facilitate retrieval of dispersion parameters. Copyright © 2010 Royal Meteorological Society
    Meteorological Applications 06/2011; 18(2):188 - 197. DOI:10.1002/met.228 · 1.52 Impact Factor
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    Bulletin of the American Meteorological Society 05/2011; DOI:10.1175/2010BAMS2614.1 · 11.57 Impact Factor
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    Meteorological Applications 01/2011; · 1.52 Impact Factor
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    ABSTRACT: Thermal storage is advocated as a means for energy storage in some grid-scale electric powerplants, such as for concentrating solar power (CSP). The efficiency of concentrating solar thermal collectors, however, decreases with increasing output temperature, making it difficult to achieve high thermal storage temperatures. A heat pump, as is well known, can operate in either cooling mode or heating mode, and in either case, the coefficient of performance is generally greater than one, enabling a multiplier effect that can serve to either increase or decrease the temperature of thermal storage. A simple steady-state analysis of the “round-trip” system efficiency for storing energy reveals the potential benefits of utilizing a heat pump or refrigerator in such systems. Provided that an inexpensive heat input source is available, the system storage efficiency can reach or even exceed unity, assuming that the energy supplied to the system as heat is neglected. For ice storage at 0 °C, increasing thermal input temperatures above 209 °C increases the system storage efficiency above unity.
    ASME/JSME 2011 8th Thermal Engineering Joint Conference; 01/2011
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    ABSTRACT: A better understanding of the interaction between the built environment and the atmosphere is required to more effectively manage urban airsheds. This paper reports an analysis of data from an atmospheric measurement campaign in Oklahoma City, Oklahoma, during the summer of 2003 that shows wind flow patterns, turbulence, and thermal effects in the downtown area. Experimental measurements within a street canyon yielded airflow patterns, stability conditions, and turbulence properties as a function of the incoming wind direction and time of the day. Air and surface temperatures at two different sites, one within the downtown urban canyon and the other in a nearby park, were measured. A study of the stability conditions within the urban canyon during the campaign indicates that dynamically stable conditions did not occur within the canyon. This provides evidence that the built environment can strongly influence the thermal characteristics in cities. Mean flow patterns close to the street level are analyzed for two different ranges of incoming wind directions and are compared with those obtained from a previous field experiment featuring idealized building configurations. This paper presents an approach allowing the estimation of wind direction in an urban canyon, given inflow conditions, that shows good agreement with wind patterns in the Oklahoma City street canyon. Turbulence statistics were calculated and normalized using different velocity scales to investigate the efficacy of the latter in specifying turbulence levels in urban canopies. The dependence of turbulence quantities on incoming wind direction and time of the day was investigated.
    Journal of Applied Meteorology and Climatology 01/2011; 50(1):203-223. DOI:10.1175/2010JAMC2525.1 · 2.10 Impact Factor
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    ABSTRACT: Accurate estimation of dissipation rate is important in understanding and analyzing turbulent flows found in environment and engineering processes. Many previous studies have focused on measuring the local dissipation rate at a single point or averaged dissipation rate over a suitable area. Since coherent Doppler lidar is capable of providing multi-point measurements covering a large spatial extent, it is well-suited for examining the distribution of dissipation in the atmosphere. In this paper, an approach is presented that is based on retrieving the dissipation rate from coherent Doppler lidar data using large-eddy simulation. Two Coherent Doppler lidars performed range height indicator (RHI) scans of a vertical/cross-barrier plane during the Terrain-induced Rotor Experiment (T-REX). Two-dimensional velocity vectors were retrieved using a least squares method. The velocity vectors retrieved from co-planar RHI scans are used to estimate subgrid scale (SGS) quantities through a known SGS parameterization. For the T-REX datasets analyzed, the dissipation rate was found to increase in the presence of rotors, subrotors, and, as expected, in regions of high wind shear. Owing to the presence of sharper gradients in subrotors, their dissipation rate is generally larger than that of rotors. KeywordsDissipation rate-Doppler lidar-Large-eddy simulations-Rotors-Subgrid scales-Subrotors-T-REX
    Boundary-Layer Meteorology 07/2010; 136(1):45-57. DOI:10.1007/s10546-010-9495-y · 2.53 Impact Factor

Publication Stats

176 Citations
87.51 Total Impact Points

Institutions

  • 2014
    • University of Utah
      Salt Lake City, Utah, United States
  • 2003–2014
    • Arizona State University
      • • School for Engineering of Matter, Transport and Energy
      • • Department of Mechanical Engineering
      Phoenix, Arizona, United States