scholarly journals A statistical study of underestimates of wind speeds by VHF radar

1997 ◽  
Vol 15 (6) ◽  
pp. 805-812 ◽  
Author(s):  
L. Thomas ◽  
I. Astin ◽  
R. M. Worthington
Keyword(s):  
Statistical Treatment ◽  
Vertical Direction ◽  
Spatial Separation ◽  
Horizontal Wind ◽  
Vhf Radar ◽  
Height Range ◽  
Wind Speeds ◽  
Radar Echoes ◽  
Wind Measurements ◽  
Radar Measurements

Abstract. Comparisons are made between horizontal wind measurements carried out using a VHF-radar system at Aberystwyth (52.4°N, 4.1°W) and radiosondes launched from Aberporth, some 50 km to the south-west. The radar wind results are derived from Doppler wind measurements at zenith angles of 6° in two orthogonal planes and in the vertical direction. Measurements on a total of 398 days over a 2-year period are considered, but the major part of the study involves a statistical analysis of data collected during 75 radiosonde flights selected to minimise the spatial separation of the two sets of measurements. Whereas good agreement is found between the two sets of wind direction, radar-derived wind speeds show underestimates of 4–6% compared with radiosonde values over the height range 4–14 km. Studies of the characteristics of this discrepancy in wind speeds have concentrated on its directional dependence, the effects of the spatial separation of the two sets of measurements, and the influence of any uncertainty in the radar measurements of vertical velocities. The aspect sensitivity of radar echoes has previously been suggested as a cause of underestimates of wind speeds by VHF radar. The present statistical treatment and case-studies show that an appropriate correction can be applied using estimates of the effective radar beam angle derived from a comparison of echo powers at zenith angles of 4.2° and 8.5°.

Spatial variability of the aspect sensitivity of VHF radar echoes in the troposphere and lower stratosphere during jet stream passages

1994 ◽  
Vol 12 (8) ◽  
pp. 733-745 ◽  
Author(s):  
J. G. Yoe ◽  
P. Czechowsky ◽  
R. Rüster ◽  
G. Schmidt
Keyword(s):  
Lower Stratosphere ◽  
Radar Data ◽  
Horizontal Wind ◽  
Jet Stream ◽  
Wind Maximum ◽  
Vhf Radar ◽  
Wind Speeds ◽  
Radar Echoes ◽  
Wind Speed Maximum ◽  
Aspect Sensitivity

Abstract. The aspect sensitivity of SOUSY-VHF-radar oblique-beam echoes from the troposphere and lower stratosphere has been examined for a number of jet stream passages during the years 1990 - 1992. When the core of the jet is overhead or nearly so, vertical profiles of the aspect sensitivity display two notable features. First, the distinction between mainly isotropic and strongly aspect-sensitive echoes in the troposphere and the lower stratosphere, respectively, often reported for measurements made during calm conditions, does not necessarily prevail in the vicinity of the jet stream. Second, echoes obtained at altitudes near the height of the horizontal wind maximum are found to be more aspect sensitive for beams directed parallel to the horizontal flow or nearly so, than for other beam directions. It is demonstrated that time-averaged horizontal wind speeds estimated from the radar data, taking into account the reduced effective oblique-beam zenith angle resulting from aspect sensitivity, may exceed uncorrected wind speeds by as much as 10 m s-1 in these circumstances. Implications for wind profiling and for describing the backscattering process are discussed. Doppler spectral widths examined for one jet stream passage are found to be narrower in a beam aligned with the horizontal wind at heights near the wind speed maximum than corresponding widths measured in a beam projected at right angles to the jet. The narrowest spectra thus coincide with the most aspect-sensitive echoes, consistent with the hypothesis that such returns result from specular backscattering processes.

scholarly journals Coastal Wind Measurements Using a Single Scanning LiDAR

2020 ◽  
Vol 12 (8) ◽  
pp. 1347 ◽  
Author(s):  
Susumu Shimada ◽  
Jay Prakash Goit ◽  
Teruo Ohsawa ◽  
Tetsuya Kogaki ◽  
Satoshi Nakamura
Keyword(s):  
Wind Speed ◽  
Goodness Of Fit ◽  
Sonic Anemometer ◽  
Data Availability ◽  
Horizontal Wind ◽  
Research Station ◽  
Lidar Measurement ◽  
Wind Speeds ◽  
Wind Measurements ◽  
Scanning Lidar

A wind measurement campaign using a single scanning light detection and ranging (LiDAR) device was conducted at the Hazaki Oceanographical Research Station (HORS) on the Hazaki coast of Japan to evaluate the performance of the device for coastal wind measurements. The scanning LiDAR was deployed on the landward end of the HORS pier. We compared the wind speed and direction data recorded by the scanning LiDAR to the observations obtained from a vertical profiling LiDAR installed at the opposite end of the pier, 400 m from the scanning LiDAR. The best practice for offshore wind measurements using a single scanning LiDAR was evaluated by comparing results from a total of nine experiments using several different scanning settings. A two-parameter velocity volume processing (VVP) method was employed to retrieve the horizontal wind speed and direction from the radial wind speed. Our experiment showed that, at the current offshore site with a negligibly small vertical wind speed component, the accuracy of the scanning LiDAR wind speeds and directions was sensitive to the azimuth angle setting, but not to the elevation angle setting. In addition to the validations for the 10-minute mean wind speeds and directions, the application of LiDARs for the measurement of the turbulence intensity (TI) was also discussed by comparing the results with observations obtained from a sonic anemometer, mounted at the seaward end of the HORS pier, 400 m from the scanning LiDAR. The standard deviation obtained from the scanning LiDAR measurement showed a greater fluctuation than that obtained from the sonic anemometer measurement. However, the difference between the scanning LiDAR and sonic measurements appeared to be within an acceptable range for the wind turbine design. We discuss the variations in data availability and accuracy based on an analysis of the carrier-to-noise ratio (CNR) distribution and the goodness of fit for curve fitting via the VVP method.

scholarly journals Wind sensing with drone-mounted wind lidars: proof of concept

2020 ◽  
Vol 13 (2) ◽  
pp. 521-536
Author(s):  
Nikola Vasiljević ◽  
Michael Harris ◽  
Anders Tegtmeier Pedersen ◽  
Gunhild Rolighed Thorsen ◽  
Mark Pitter ◽  
...  
Keyword(s):  
Wind Speed ◽  
Continuous Wave ◽  
Position Control ◽  
Horizontal Wind ◽  
Lidar Measurement ◽  
Proof Of Concept ◽  
Horizontal Wind Speed ◽  
Wind Speeds ◽  
Potential Applications ◽  
Wind Measurements

Abstract. The fusion of drone and wind lidar technology introduces the exciting possibility of performing high-quality wind measurements virtually anywhere. We present a proof-of-concept (POC) drone–lidar system and report results from several test campaigns that demonstrate its ability to measure accurate wind speeds. The POC system is based on a dual-telescope continuous-wave (CW) lidar, with drone-borne telescopes and ground-based optoelectronics. Commercially available drone and gimbal units are employed. The demonstration campaigns started with a series of comparisons of the wind speed measurements acquired by the POC system to simultaneous measurements performed by nearby mast-based sensors. On average, an agreement down to about 0.1 m s−1 between mast- and drone-based measurements of the horizontal wind speed is found. Subsequently, the extent of the flow disturbance caused by the drone downwash was investigated. These tests vindicated the somewhat conservative choice of lidar measurement ranges made for the initial wind speed comparisons. Overall, the excellent results obtained without any drone motion correction and with fairly primitive drone position control indicate the potential of drone–lidar systems in terms of accuracy and applications. The next steps in the development are outlined and several potential applications are discussed.

scholarly journals Combined wind measurements by two different lidar instruments in the Arctic middle atmosphere

2012 ◽  
Vol 5 (3) ◽  
pp. 4123-4156 ◽  
Author(s):  
J. Hildebrand ◽  
G. Baumgarten ◽  
J. Fiedler ◽  
U.-P. Hoppe ◽  
B. Kaifler ◽  
...  
Keyword(s):  
Middle Atmosphere ◽  
The Arctic ◽  
Horizontal Wind ◽  
Small Scale ◽  
Wind Component ◽  
Lower Altitude ◽  
Wind Speeds ◽  
Lidar Measurements ◽  
Wind Measurements ◽  
Good Agreement

Abstract. During a joint campaign in January 2009 the Rayleigh/Mie/Raman (RMR) lidar and the sodium lidar at the ALOMAR Observatory (69° N, 16° E) in Northern Norway were operated simultaneously for more than 40 h, collecting data for wind measurements in the middle atmosphere from 30 up to 110 km altitude. At the upper (lower) altitude range where the RMR (sodium) lidar can operate, both lidars probe the same sounding volume, allowing to compare the derived wind speeds. We present the first simultaneous common volume wind measurements in the middle atmosphere using two different lidar instruments. The comparison of winds derived by RMR and sodium lidar is excellent for long integration times of 10 h as well as shorter ones of 1 h. Combination of data from both lidars allows identifying wavy structures between 30 and 110 km altitude, whose amplitudes increase with height. We have also performed lidar measurements of the same wind component using two independent branches of the RMR lidar and found a good agreement of the results but also identified inhomogeneities in the horizontal wind at about 55 km altitude of up to 20 ms−1. Such small scale inhomogeneities in the horizontal wind field are an essential challenge when comparing data from different instruments.

scholarly journals Observations of Atmospheric Dynamics Using Radar Techniques

1993 ◽  
Vol 46 (1) ◽  
pp. 127 ◽  
Author(s):  
BH Briggs
Keyword(s):  
Momentum Flux ◽  
Atmospheric Dynamics ◽  
Research Groups ◽  
Atmospheric Physics ◽  
Height Range ◽  
Radar Echoes ◽  
History Of ◽  
Radar Measurements ◽  
The University ◽  
Future Work

A surprisingly large amount of information about atmospheric dynamics can be obtained by studying the fluctuations of the amplitude and phase of radar echoes back-scattered from density irregularities. The method has been extensively used by the Atmospheric Physics Group at the University of Adelaide, and elsewhere. In the present paper these techniques are traced back to their origin in the pioneering work of J. L. Pawsey in the 1930s, and followed through to the present day. The reasons which led to the construction of the large antenna array near Adelaide (the 'Buckland Park array') are explained, and the observations which can be made with it are described. These include radar measurements of winds, turbulence and momentum flux in the height range 60 to 95 km. Plans for instrumental improvements and for future work are outlined. The paper is not intended to be a general review of the field, but rather a history of a technique and its development in the research groups with which the author has been associated.

scholarly journals Intercomparison of middle-atmospheric wind in observations and models

2018 ◽  
Vol 11 (4) ◽  
pp. 1971-1987 ◽  
Author(s):  
Rolf Rüfenacht ◽  
Gerd Baumgarten ◽  
Jens Hildebrand ◽  
Franziska Schranz ◽  
Vivien Matthias ◽  
...  
Keyword(s):  
Wind Profile ◽  
Microwave Radiometer ◽  
Horizontal Wind ◽  
Random Errors ◽  
Good Correspondence ◽  
Mesopause Region ◽  
Wind Speeds ◽  
Wind Measurements ◽  
Remote Sensing Techniques

Abstract. Wind profile information throughout the entire upper stratosphere and lower mesosphere (USLM) is important for the understanding of atmospheric dynamics but became available only recently, thanks to developments in remote sensing techniques and modelling approaches. However, as wind measurements from these altitudes are rare, such products have generally not yet been validated with (other) observations. This paper presents the first long-term intercomparison of wind observations in the USLM by co-located microwave radiometer and lidar instruments at Andenes, Norway (69.3∘ N, 16.0∘ E). Good correspondence has been found at all altitudes for both horizontal wind components for nighttime as well as daylight conditions. Biases are mostly within the random errors and do not exceed 5–10 m s−1, which is less than 10 % of the typically encountered wind speeds. Moreover, comparisons of the observations with the major reanalyses and models covering this altitude range are shown, in particular with the recently released ERA5, ECMWF's first reanalysis to cover the whole USLM region. The agreement between models and observations is very good in general, but temporally limited occurrences of pronounced discrepancies (up to 40 m s−1) exist. In the article's Appendix the possibility of obtaining nighttime wind information about the mesopause region by means of microwave radiometry is investigated.

scholarly journals A Study on Optimum Tilt Angle for Wind Estimation Using Indian MST Radar

2008 ◽  
Vol 25 (9) ◽  
pp. 1579-1589 ◽  
Author(s):  
V. K. Anandan ◽  
I. Srinivasa Rao ◽  
P. Narasimha Reddy
Keyword(s):  
Tilt Angle ◽  
Horizontal Wind ◽  
Percentage Error ◽  
Height Range ◽  
Wind Estimation ◽  
Mst Radar ◽  
Wind Measurements ◽  
True Values ◽  
Effective Beam

Abstract The effect of tilt angle on horizontal wind estimation is studied using Indian mesosphere–stratosphere–troposphere (MST) radar located at Gadanki (13.45°N, 79.18°E). It operates in Doppler beam swinging (DBS) mode with a beamwidth of 3°. Horizontal winds are computed for different tilt angles from 3° to 15° with an increment of 3° from a height range of 3.6–18 km. The effective beam pointing angle (θeff) is calculated to determine the effect of aspect sensitivity on the determination of horizontal wind components. For different tilt angles radar-derived winds are compared with simultaneous GPS sonde wind measurements, which were launched from a nearby site. The first method utilizes direct comparison of radar-derived winds with those of GPS sondes using the actual beam pointing angle; the second method uses the effective beam pointing angle derived from the ratios of two oblique beams. For this study a variety of statistics were explored in terms of standard deviation, correlation coefficient, and percentage error. From the results it is observed that in agreement with previous studies, the effective beam pointing angle deviates from the actual beam pointing angle, which results in the underestimation of horizontal wind components, and also when tilt angle is close to zenith and far from zenith, the estimation of horizontal winds is found to be far from true values at different heights. Radar wind estimation has better agreement with GPS sonde measurement when the off-zenith angle is around 10°. It is also found that correction to the actual beam pointing angle provides 3%–6% improved agreement between the radar and GPS wind measurements.

scholarly journals Validation of middle-atmospheric wind in observations and models

2017 ◽  
Author(s):  
Rolf Rüfenacht ◽  
Gerd Baumgarten ◽  
Jens Hildebrand ◽  
Franziska Schranz ◽  
Vivien Matthias ◽  
...  
Keyword(s):  
Wind Profile ◽  
Microwave Radiometer ◽  
Horizontal Wind ◽  
Random Errors ◽  
Good Correspondence ◽  
Mesopause Region ◽  
Wind Speeds ◽  
Wind Measurements ◽  
Remote Sensing Techniques

Abstract. Wind profile information throughout the upper stratosphere and lower mesosphere (USLM) is important for the understanding of atmospheric dynamics but became available only recently, thanks to developments in remote sensing techniques and modelling approaches. However, as wind measurements from these altitudes are still very rare, such products have generally not yet been validated with (other) observations. This paper presents the first long-term intercomparison of wind observations in the USLM by opposing co-located microwave radiometer and lidar instruments at Andenes (69.3° N, 16.0° E). Good correspondence has been found at all altitudes for both horizontal wind components for nighttime as well as daylight conditions. Biases are mostly within the random errors and do not exceed 5–10 m/s which is less than 10 % of the typically encountered wind speeds. Moreover, comparisons of the observations with the major re-analyses and models covering this altitude range are shown, especially also with the freshly released ERA5, ECMWF's first re-analysis to cover the whole USLM region. The agreement between models and observations is very good in general, but temporally limited occurrences of pronounced discrepancies (up to 40 m/s) exist. In the article's appendix the possibility of obtaining nighttime wind information about the mesopause region by means of microwave radiometry is investigated.

scholarly journals Measuring Wind Speed Using the Internal Stabilization System of a Quadrotor Drone

Drones ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 23 ◽  
Author(s):  
Magdalena Simma ◽  
Håvard Mjøen ◽  
Tobias Boström
Keyword(s):  
Wind Speed ◽  
Test Site ◽  
Horizontal Wind ◽  
Mean Square ◽  
Flight Tests ◽  
Wind Speeds ◽  
Internal Stabilization ◽  
Ultrasonic Anemometer ◽  
Wind Measurements ◽  
The Cost

This article proposes a method of measuring wind speed using the data logged by the autopilot of a quadrotor drone. Theoretical equations from works on quadrotor control are utilized and supplemented to form the theoretical framework. Static thrust tests provide the necessary parameters for calculating wind estimates. Flight tests were conducted at a test site with laminar wind conditions with the quadrotor hovering next to a static 2D ultrasonic anemometer with wind speeds between 0–5 m/s. Horizontal wind estimates achieve exceptionally good results with root mean square error (RMSE) values between 0.26–0.29 m/s for wind speed, as well as between 4.1–4.9 for wind direction. The flexibility of this new method simplifies the process, decreases the cost, and adds new application areas for wind measurements.

scholarly journals <i>Letter to the Editor</i>: Complete maps of the aspect sensitivity of VHF atmospheric radar echoes

1999 ◽  
Vol 17 (8) ◽  
pp. 1116-1119 ◽  
Author(s):  
R. M. Worthington ◽  
R. D. Palmer ◽  
S. Fukao
Keyword(s):  
Power Distribution ◽  
Middle Atmosphere ◽  
Vertical Shear ◽  
Horizontal Wind ◽  
Vhf Radar ◽  
Meteorology And Atmospheric Dynamics ◽  
Mu Radar ◽  
Radar Echoes ◽  
Instruments And Techniques ◽  
Aspect Sensitivity

Abstract. Using the MU radar at Shigaraki, Japan (34.85°N, 136.10°E), we measure the power distribution pattern of VHF radar echoes from the mid-troposphere. The large number of radar beam-pointing directions (320) allows the mapping of echo power from 0° to 40° from zenith, and also the dependence on azimuth, which has not been achieved before at VHF wavelengths. The results show how vertical shear of the horizontal wind is associated with a definite skewing of the VHF echo power distribution, for beam angles as far as 30° or more from zenith, so that aspect sensitivity cannot be assumed negligible at any beam-pointing angle that most existing VHF radars are able to use. Consequently, the use of VHF echo power to calculate intensity of atmospheric turbulence, which assumes only isotropic backscatter at large beam zenith angles, will sometimes not be valid.Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics; turbulence; instruments and techniques)

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