In-Situ, Field Profiling of Optical Turbulence using 3D Sonic Anemometers

2019 ◽  
Author(s):  
Steven Fiorino ◽  
Santasri R. Bose-Pillai ◽  
Kevin Keefer
Keyword(s):  
Optical Turbulence ◽  
Sonic Anemometers

scholarly journals Velocity-Based EDR Retrieval Techniques Applied to Doppler Radar Measurements from Rain: Two Case Studies

2019 ◽  
Vol 36 (9) ◽  
pp. 1693-1711 ◽  
Author(s):  
A. C. P. Oude Nijhuis ◽  
C. M. H. Unal ◽  
O. A. Krasnov ◽  
H. W. J. Russchenberg ◽  
A. G. Yarovoy
Keyword(s):  
Case Studies ◽  
Doppler Radar ◽  
Energy Dissipation Rate ◽  
Accurate Estimation ◽  
Retrieval Technique ◽  
Sonic Anemometers ◽  
Radar Measurements ◽  
Rain Events ◽  
Kolmogorov Constant

In this article, five velocity-based energy dissipation rate (EDR) retrieval techniques are assessed. The EDR retrieval techniques are applied to Doppler measurements from Transportable Atmospheric Radar (TARA)—a precipitation profiling radar—operating in the vertically fixed-pointing mode. A generalized formula for the Kolmogorov constant is derived, which gives potential for the application of the EDR retrieval techniques to any radar line of sight (LOS). Two case studies are discussed that contain rain events of about 2 and 18 h, respectively. The EDR values retrieved from the radar are compared to in situ EDR values from collocated sonic anemometers. For the two case studies, a correlation coefficient of 0.79 was found for the wind speed variance (WSV) EDR retrieval technique, which uses 3D wind vectors as input and has a total sampling time of 10 min. From this comparison it is concluded that the radar is able to measure EDR with a reasonable accuracy. Almost no correlation was found for the vertical wind velocity variance (VWVV) EDR retrieval technique, as it was not possible to sufficiently separate the turbulence dynamics contribution to the radar Doppler mean velocities from the velocity contribution of falling raindrops. An important cause of the discrepancies between radar and in situ EDR values is thus due to insufficient accurate estimation of vertical air velocities.

scholarly journals Monitoring the optical turbulence in the surface layer at Dome C, Antarctica, with sonic anemometers

2015 ◽  
Vol 454 (4) ◽  
pp. 4304-4315 ◽  
Author(s):  
E. Aristidi ◽  
J. Vernin ◽  
E. Fossat ◽  
F.-X. Schmider ◽  
T. Travouillon ◽  
...  
Keyword(s):  
Surface Layer ◽  
Optical Turbulence ◽  
Sonic Anemometers

THERMOSONDE 2007: In-Situ Measurement of Optical Turbulence

2007 ◽  
Author(s):  
E. A. Murphy ◽  
P. Tracy ◽  
R. R. Beland ◽  
G. Y. Jumper ◽  
K. Robinson ◽  
...  
Keyword(s):  
In Situ Measurement ◽  
Optical Turbulence

scholarly journals In Situ Calibration of Hot-Film Probes Using a Collocated Sonic Anemometer: Implementation of a Neural Network

2010 ◽  
Vol 27 (1) ◽  
pp. 23-41 ◽  
Author(s):  
E. Kit ◽  
A. Cherkassky ◽  
T. Sant ◽  
H. J. S. Fernando
Keyword(s):  
Neural Network ◽  
Sonic Anemometer ◽  
Input Voltage ◽  
Calibration Method ◽  
Calibration Procedure ◽  
Approximation Technique ◽  
Sonic Anemometers ◽  
Standard Calibration ◽  
Hot Film

Abstract Although the integral quantities of atmospheric turbulence are conveniently measured using sonic anemometers, obtaining relevant finescale variables such as the kinetic energy dissipation using conventional hot-film/wire techniques remains a challenge because of two main difficulties. The first difficulty is the mean wind variability, which causes violation of the requirement that mean winds have a specific alignment with the hot-film/wire probe. To circumvent this problem, a combination of collocated sonic and hot-film anemometers, with the former measuring mean winds and aligning the latter in the appropriate wind direction via an automated platform, is successfully designed and implemented. The second difficulty is the necessity of frequent and onerous calibrations akin to hot-film anemometry that lead to logistical difficulties during outdoor (field) measurements. This is addressed by employing sonic measurements to calibrate the hot films in the same combination, with the output (velocity) to input (voltage) transfer function for the hot film derived using a neural network (NN) model. The NN is trained using low-pass-filtered hot-film and sonic data taken in situ. This new hot-film calibration procedure is compared with the standard calibration method based on an external calibrator. It is inferred that the sonic-based NN method offers great potential as an alternative to laborious standard calibration techniques, particularly in the laboratory and in stable atmospheric boundary layer settings. The NN approximation technique is found to be superior to the conventionally used polynomial fitting methods when used in conjunction with unevenly spaced calibration velocity data generated by sonic anemometers.

scholarly journals Estimation of turbulence parameters from scanning lidars and in-situ instrumentation in the Perdigão 2017 campaign

2019 ◽  
Author(s):  
Norman Wildmann ◽  
Nicola Bodini ◽  
Julie K. Lundquist ◽  
Ludovic Bariteau ◽  
Johannes Wagner
Keyword(s):  
Temporal Variability ◽  
Shear Zones ◽  
Spectral Width ◽  
Early Morning ◽  
Spatial And Temporal Variability ◽  
Atmospheric Conditions ◽  
Sonic Anemometers ◽  
Spatio Temporal ◽  
Lifting System

Abstract. The understanding of the sources, spatial distribution and temporal variability of turbulence in the atmospheric boundary layer (ABL) and improved simulation of its forcing processes require observations in a broad range of terrain types and atmospheric conditions. In this study, we estimate turbulence kinetic energy (TKE) dissipation rate using multiple techniques, including traditional in-situ measurements of sonic anemometers on meteorological towers, a hot-wire anemometer on a tethered lifting system (TLS), as well as remote-sensing retrievals from a vertically staring lidar and two lidars performing range-height indicator (RHI) scans. For the retrieval of ε from the lidar RHI scans, we introduce a modification of the Doppler Spectral Width (DSW) method. This method uses spatio-temporal averages of the variance of the line-of-sight (LOS) velocity and the turbulent broadening of the Doppler backscatter spectrum. We validate this method against the observations from the other instruments, also including uncertainty estimations for each method. The synthesis of the results from all instruments enables a detailed analysis of the spatial and temporal variability of ε across a valley between two parallel ridges at the Perdigão 2017 campaign. We find that the shear zones above and below nighttime low-level jets (LLJ) experience turbulence enhancements, as does the wake of a wind turbine (WT). We analyze in detail how ε varies in the early morning of 14 June 2017, when the turbulence in the valley, approximately eleven rotor diameters downstream of the WT, is still significantly enhanced by the WT wake.

scholarly journals Towards improved turbulence estimation with Doppler wind lidar VAD scans

2020 ◽  
Author(s):  
Norman Wildmann ◽  
Eileen Päschke ◽  
Anke Roiger ◽  
Christian Mallaun
Keyword(s):  
Theoretical Model ◽  
Dissipation Rate ◽  
Elevation Angle ◽  
Turbulence Measurement ◽  
Sonic Anemometers ◽  
Tke Dissipation Rate ◽  
Wind Lidar ◽  
Turbulence Parameters ◽  
Doppler Wind Lidar

Abstract. The retrieval of turbulence parameters with profiling Doppler wind lidars (DWL) is of high interest for boundarylayer meteorology and its applications. The DWL measurements extend beyond the observations with meteorological masts and are comparably flexible in their installation. Velocity-azimuth display (VAD) type scans can be used to retrieve turbulence kinetic energy (TKE) dissipation rate through a fit of measured azimuth structure functions to a theoretical model. At the elevation angle of 35.3° it is also possible to derive TKE. We show in this study how modifications to existing methods allow to retrieve TKE and its dissipation rate even with a small number of scans, how a simple correction for advection improves the results at low altitudes and that VAD scans at different elevation angles with the same instrument provide comparable results of TKE dissipation rate after all filters and corrections. For this purpose, data of two experiments are utilized: First, measurements at the Observatory Lindenberg – Richard-Aßmann Observatory (MOL-RAO) are used for validation of the DWL retrieval with sonic anemometers on a meteorological mast. Second, distributed measurements of three DWL during the CoMet campaign are analyzed and compared to in-situ measurements of the DLR Cessna Grand Caravan 208B. The comparison to in-situ instruments shows that the methods to improve turbulence retrievals from VAD scans introduced in this study are effective, especially at low altitudes and for narrow cone angles, but it also shows the limits of turbulence measurement with state-ofthe-art DWL in low turbulence regimes.

Wind Gust Quantification Using Seismic Measurements

2017 ◽  
Author(s):  
F. Letson ◽  
W. Hu ◽  
R. J. Barthelmie ◽  
J. Tytell ◽  
S. C. Pryor
Keyword(s):  
Cumulative Probability ◽  
Wind Gust ◽  
Independent Data ◽  
Ground Acceleration ◽  
Wind Speeds ◽  
In Situ Data ◽  
Sonic Anemometers ◽  
One Year ◽  
Wind Resource

Improved understanding of wind gust climates may be of great value to the wind energy industry, and is currently hampered by a lack of high-quality in situ data in wind resource rich environments. Thus, we are examining the potential to supplement anemometry with data from seismometers, including those deployed as part of the USArray Transportable Array (TA). Two models of the relationship between gust magnitude and ground motion are evaluated based on their skill at describing the distribution of gust wind speeds over 1 year using seismic data. The approach is illustrated, using observed gust magnitudes obtained from sonic anemometers located at or near the 15 TA seismic stations. One deterministic and one probabilistic wind-seismic model are conditioned using one year of 5-minute resolution data and tested on a second year of independent data. Both models relate the variance of ground acceleration in the frequency range of 0.01 to 0.1 Hz (P) to gust speed (Ug) but differ in their functional form. The probabilistic model is found to perform well in predicting the gust distribution in independent data, and at the 15 sites considered herein has an integrated error across the entire cumulative probability distribution that is only 5% of the mean gust magnitude.

scholarly journals Estimation of turbulence dissipation rate from Doppler wind lidars and in situ instrumentation for the Perdigão 2017 campaign

2019 ◽  
Vol 12 (12) ◽  
pp. 6401-6423 ◽  
Author(s):  
Norman Wildmann ◽  
Nicola Bodini ◽  
Julie K. Lundquist ◽  
Ludovic Bariteau ◽  
Johannes Wagner
Keyword(s):  
Wind Turbine ◽  
Temporal Variability ◽  
Dissipation Rate ◽  
Shear Zones ◽  
Spectral Width ◽  
Energy Dissipation Rate ◽  
Spatial And Temporal Variability ◽  
Atmospheric Conditions ◽  
Sonic Anemometers

Abstract. The understanding of the sources, spatial distribution and temporal variability of turbulence in the atmospheric boundary layer, and improved simulation of its forcing processes require observations in a broad range of terrain types and atmospheric conditions. In this study, we estimate turbulence kinetic energy dissipation rate ε using multiple techniques, including in situ measurements of sonic anemometers on meteorological towers, a hot-wire anemometer on a tethered lifting system and remote-sensing retrievals from a vertically staring lidar and two lidars performing range–height indicator (RHI) scans. For the retrieval of ε from the lidar RHI scans, we introduce a modification of the Doppler spectral width method. This method uses spatiotemporal averages of the variance in the line-of-sight velocity and the turbulent broadening of the Doppler backscatter spectrum. We validate this method against the observations from the other instruments, also including uncertainty estimations for each method. The synthesis of the results from all instruments enables a detailed analysis of the spatial and temporal variability in ε across a valley between two parallel ridges at the Perdigão 2017 campaign. We analyze in detail how ε varies in the night from 13 to 14 June 2017. We find that the shear zones above and below a nighttime low-level jet experience turbulence enhancements. We also show that turbulence in the valley, approximately 11 rotor diameters downstream of an operating wind turbine, is still significantly enhanced by the wind turbine wake.

scholarly journals Accurate measurements of Optical Turbulence with Sonic- anemometers

2015 ◽  
Vol 595 ◽  
pp. 012036 ◽  
Author(s):  
T Travouillon ◽  
A Otarola ◽  
S Els ◽  
R Riddle ◽  
M Schöck ◽  
...  
Keyword(s):  
Optical Turbulence ◽  
Sonic Anemometers
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