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Yelena L. Pichugina
,
Robert M. Banta
,
W. Alan Brewer
,
Scott P. Sandberg
, and
R. Michael Hardesty

Abstract

Accurate measurement of wind speed profiles aloft in the marine boundary layer is a difficult challenge. The development of offshore wind energy requires accurate information on wind speeds above the surface at least at the levels occupied by turbine blades. Few measured data are available at these heights, and the temporal and spatial behavior of near-surface winds is often unrepresentative of that at the required heights. As a consequence, numerical model data, another potential source of information, are essentially unverified at these levels of the atmosphere. In this paper, a motion-compensated, high-resolution Doppler lidar–based wind measurement system that is capable of providing needed information on offshore winds at several heights is described. The system has been evaluated and verified in several ways. A sampling of data from the 2004 New England Air Quality Study shows the kind of analyses and information available. Examples include time–height cross sections, time series, profiles, and distributions of quantities such as winds and shear. These analyses show that there is strong spatial and temporal variability associated with the wind field in the marine boundary layer. Winds near the coast show diurnal variations, and frequent occurrences of low-level jets are evident, especially during nocturnal periods. Persistent patterns of spatial variability in the flow field that are due to coastal irregularities should be of particular concern for wind-energy planning, because they affect the representativeness of fixed-location measurements and imply that some areas would be favored for wind-energy production whereas others would not.

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Sara C. Tucker
,
Carl S. Weimer
,
Sunil Baidar
, and
R. Michael Hardesty

Abstract

We present the motivation, instrument concept, hardware descriptions, and initial validation testing for a Doppler wind lidar (DWL) system that uses optical autocovariance (OA) in a field-widened quadrature Mach–Zehnder interferometer lidar to measure Doppler shifts from atmospheric-aerosol-backscattered laser light. We describe system architectures for three different generations of the direct-detection aerosol Optical Autocovariance Wind Lidar (OAWL) system, including the current two-line-of-sight, dual-wavelength (355 and 532 nm) airborne configuration, designed to be an airborne demonstrator for potential space-based global wind measurement applications. We provide meter-per-second-precision results from a ground-based 355-nm OAWL aerosol winds measurement validation study alongside another DWL, results from an autumn 2011 airborne validation testing performed with radar wind profiler data, and wind measurement results from airborne validation flight testing using the 532-nm wavelength in spring 2016.

Open access
Robert M. Banta
,
Yelena L. Pichugina
,
Neil D. Kelley
,
R. Michael Hardesty
, and
W. Alan Brewer

Addressing the need for high-quality wind information aloft in the layer occupied by turbine rotors (~30–150 m above ground level) is one of many significant challenges facing the wind energy industry. Without wind measurements at heights within the rotor sweep of the turbines, characteristics of the flow in this layer are unknown for wind energy and modeling purposes. Since flow in this layer is often decoupled from the surface, near-surface measurements are prone to errant extrapolation to these heights, and the behavior of the near-surface winds may not reflect that of the upper-level flow.

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David B. Parsons
,
Melvyn A. Shapiro
,
R. Michael Hardesty
,
Robert J. Zamora
, and
Janet M. Intrieri

Abstract

During spring and early summer, a surface confluence zone, often referred to as the dryline, forms in the midwestern United States between continental and maritime air masses. The dewpoint temperature across the dryline can vary in excess of 18°C in a distance of less than 10 km. The movement of the dryline varies diurnally with boundary layer growth over sloping terrain leading to an eastward apparent propagation of the dryline during the day and a westward advection or retrogression during the evening. In this study, we examine the finescale structure of a retrogressing, dryline using data taken by a Doppler lidar, a dual-channel radiometer, and serial rawinsonde ascents. While many previous studies were unable to accurately measure the vertical motions in the vicinity of the dryline, our lidar measurements suggest that the convergence at the dryline is intense with maximum vertical motions of ∼5 m s−1. The winds obtained from the Doppler lidar Measurements were combined with the equations of motion to derive perturbation fields of pressure and virtual potential temperature θ v . Our observations indicate that the circulations associated with this retrogressing dryline were dominated by hot, dry air riding over a westward moving denser, moist flow in a manner similar to a density current. Gravity waves were observed above the dryline interface. Previous observational and numerical studies have shown that differential heating across the dryline may sometimes enhance regional pressure gradients and thus impact dryline movement. We propose that this regional gradient in surface heating in the presence of a confluent flow results in observed intense wind shifts and large horizontal gradients in θ v across the dryline. The local gradient in θ v influences the movement and flow characteristics of the dryline interface. This study is one of the most complete and novel uses of Doppler lidar to date.

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Ryan R. Neely III
,
Matthew Hayman
,
Robert Stillwell
,
Jeffrey P. Thayer
,
R. Michael Hardesty
,
Michael O'Neill
,
Matthew D. Shupe
, and
Catherine Alvarez

Abstract

Accurate measurements of cloud properties are necessary to document the full range of cloud conditions and characteristics. The Cloud, Aerosol Polarization and Backscatter Lidar (CAPABL) has been developed to address this need by measuring depolarization, particle orientation, and the backscatter of clouds and aerosols. The lidar is located at Summit, Greenland (72.6°N, 38.5°W; 3200 m MSL), as part of the Integrated Characterization of Energy, Clouds, Atmospheric State, and Precipitation at Summit Project and NOAA's Earth System Research Laboratory's Global Monitoring Division's lidar network. Here, the instrument is described with particular emphasis placed upon the implementation of new polarization methods developed to measure particle orientation and improve the overall accuracy of lidar depolarization measurements. Initial results from the lidar are also shown to demonstrate the ability of the lidar to observe cloud properties.

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Jeffrey L. Stith
,
Darrel Baumgardner
,
Julie Haggerty
,
R. Michael Hardesty
,
Wen-Chau Lee
,
Donald Lenschow
,
Peter Pilewskie
,
Paul L. Smith
,
Matthias Steiner
, and
Holger Vömel

Abstract

Although atmospheric observing systems were already an important part of meteorology before the American Meteorological Society was established in 1919, the past 100 years have seen a steady increase in their numbers and types. Examples of how observing systems were developed and how they have enabled major scientific discoveries are presented. These examples include observing systems associated with the boundary layer, the upper air, clouds and precipitation, and solar and terrestrial radiation. Widely used specialized observing systems such as radar, lidar, and research aircraft are discussed, and examples of applications to weather forecasting and climate are given. Examples drawn from specific types of chemical measurements, such as ozone and carbon dioxide, are included. Sources of information on observing systems, including other chapters of this monograph, are also discussed. The past 100 years has been characterized by synergism between societal needs for weather observations and the needs of fundamental meteorological research into atmospheric processes. In the latter half of the period, observing system improvements have been driven by the increasing demands for higher-resolution data for numerical models, the need for long-term measurements, and for more global coverage. This has resulted in a growing demand for data access and for integrating data from an increasingly wide variety of observing system types and networks. These trends will likely continue.

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Volker Wulfmeyer
,
Shravan Kumar Muppa
,
Andreas Behrendt
,
Eva Hammann
,
Florian Späth
,
Zbigniew Sorbjan
,
David D. Turner
, and
R. Michael Hardesty

Abstract

Atmospheric variables in the convective boundary layer (CBL), which are critical for turbulence parameterizations in weather and climate models, are assessed. These include entrainment fluxes, higher-order moments of humidity, potential temperature, and vertical wind, as well as dissipation rates. Theoretical relationships between the integral scales, gradients, and higher-order moments of atmospheric variables, fluxes, and dissipation rates are developed mainly focusing on the entrainment layer (EL) at the top of the CBL. These equations form the starting point for tests of and new approaches in CBL turbulence parameterizations. For the investigation of these relationships, an observational approach using a synergy of ground-based water vapor, temperature, and wind lidar systems is proposed. These systems measure instantaneous vertical profiles with high temporal and spatial resolution throughout the CBL including the EL. The resolution of these systems permits the simultaneous measurement of gradients and fluctuations of these atmospheric variables. For accurate analyses of the gradients and the shapes of turbulence profiles, the lidar system performances are very important. It is shown that each lidar profile can be characterized very well with respect to bias and system noise and that the constant bias has negligible effect on the measurement of turbulent fluctuations. It is demonstrated how different gradient relationships can be measured and tested with the proposed lidar synergy within operational measurements or new field campaigns. Particularly, a novel approach is introduced for measuring the rate of destruction of humidity and temperature variances, which is an important component of the variance budget equations.

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Timothy A. Bonin
,
Brian J. Carroll
,
R. Michael Hardesty
,
W. Alan Brewer
,
Kristian Hajny
,
Olivia E. Salmon
, and
Paul B. Shepson

Abstract

A Halo Photonics Stream Line XR Doppler lidar has been deployed for the Indianapolis Flux Experiment (INFLUX) to measure profiles of the mean horizontal wind and the mixing layer height for quantification of greenhouse gas emissions from the urban area. To measure the mixing layer height continuously and autonomously, a novel composite fuzzy logic approach has been developed that combines information from various scan types, including conical and vertical-slice scans and zenith stares, to determine a unified measurement of the mixing height and its uncertainty. The composite approach uses the strengths of each measurement strategy to overcome the limitations of others so that a complete representation of turbulent mixing is made in the lowest km, depending on clouds and aerosol distribution. Additionally, submeso nonturbulent motions are identified from zenith stares and removed from the analysis, as these motions can lead to an overestimate of the mixing height. The mixing height is compared with in situ profile measurements from a research aircraft for validation. To demonstrate the utility of the measurements, statistics of the mixing height and its diurnal and annual variability for 2016 are also presented. The annual cycle is clearly captured, with the largest and smallest afternoon mixing heights observed at the summer and winter solstices, respectively. The diurnal cycle of the mixing layer is affected by the mean wind, growing slower in the morning and decaying more rapidly in the evening with lighter winds.

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Sara C. Tucker
,
Christoph J. Senff
,
Ann M. Weickmann
,
W. Alan Brewer
,
Robert M. Banta
,
Scott P. Sandberg
,
Daniel C. Law
, and
R. Michael Hardesty

Abstract

The concept of boundary layer mixing height for meteorology and air quality applications using lidar data is reviewed, and new algorithms for estimation of mixing heights from various types of lower-tropospheric coherent Doppler lidar measurements are presented. Velocity variance profiles derived from Doppler lidar data demonstrate direct application to mixing height estimation, while other types of lidar profiles demonstrate relationships to the variance profiles and thus may also be used in the mixing height estimate. The algorithms are applied to ship-based, high-resolution Doppler lidar (HRDL) velocity and backscattered-signal measurements acquired on the R/V Ronald H. Brown during Texas Air Quality Study (TexAQS) 2006 to demonstrate the method and to produce mixing height estimates for that experiment. These combinations of Doppler lidar–derived velocity measurements have not previously been applied to analysis of boundary layer mixing height—over the water or elsewhere. A comparison of the results to those derived from ship-launched, balloon-radiosonde potential temperature and relative humidity profiles is presented.

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Paul J. Neiman
,
M. A. Shapiro
,
R. Michael Hardesty
,
B. Boba Stankov
,
Rhidian T. Lawrence
,
Robert J. Zamora
, and
Tamara Hampel

Abstract

The NOAA/WPL pulsed coherent Doppler lidar was used during the Texas Frontal Experiment in 1985 to study mesoscale preconvective atmospheric conditions. On 22 April 1985, the Doppler lidar, in conjunction with serial rawinsonde ascents and National Weather Service rawinsonde ascents, observed atmospheric features such as middle-tropospheric frontal and vertical wind shear layers and the planetary boundary layer. The lidar showed unique evidence of the downward transport of strong winds from an elevated vertical speed shear (frontal) layer into the planetary boundary layer. The lidar provided further evidence of atmospheric processes such as clear-air turbulence within frontal layers, and dry convection turbulence within the superadiabatic planetary boundary layer. As a result, high-technology remote sensing instruments such as the Doppler lidar show considerable promise for future studies of small-scale weather systems in a nonprecipitating atmosphere.

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