Investigation on horizontal wind estimation around high aspect sensitivity

Radio Science ◽  
2001 ◽  
Vol 36 (6) ◽  
pp. 1477-1492 ◽  
Author(s):  
Noriyuki Kawano ◽  
Shoichiro Fukao
Keyword(s):  
Horizontal Wind ◽  
Wind Estimation ◽  
Aspect Sensitivity

Shuttle subsonic horizontal wind estimation

1983 ◽  
Vol 20 (4) ◽  
pp. 390-397 ◽  
Author(s):  
G. Mel Kelly ◽  
John T. Findlay ◽  
Harold R. Compton
Keyword(s):  
Horizontal Wind ◽  
Wind Estimation

scholarly journals Evaluation of wind profiles from the NERC MST Radar, Aberystwyth, UK

2014 ◽  
Vol 7 (5) ◽  
pp. 4589-4621
Author(s):  
C. F. Lee ◽  
G. Vaughan ◽  
D. A. Hooper
Keyword(s):  
Wind Speed ◽  
Standard Error ◽  
Random Error ◽  
Sampling Error ◽  
Weather Prediction ◽  
Horizontal Wind ◽  
Wind Speeds ◽  
Mst Radar ◽  
Wind Profiles ◽  
Aspect Sensitivity

Abstract. This study quantifies the uncertainties in winds measured by the Aberystwyth Mesosphere-Stratosphere-Troposphere (MST) radar (52.4° N, 4.0° W), before and after its renovation in March 2011. 127 radiosondes provide an independent measure of winds. Differences between radiosonde and radar-measured horizontal winds are correlated with long-term averages of vertical velocities, suggesting an influence from local mountain waves. These local influences are an important consideration when using radar winds as a measure of regional conditions, particularly for numerical weather prediction. In those applications, local effects represent a source of sampling error additional to the inherent uncertainties in the measurements themselves. The radar renovation improved the SNR of measurements, with correspondingly improved altitude coverage. It also corrected an under-estimate of horizontal wind speeds attributed to beam formation problems, due to component failure pre-renovation. The standard error in radar-measured winds averaged over half-an-hour increases with wind speed and altitude, and is 0.6–2.5 m s−1 (5–20% of wind speed) for post-renovation horizontal winds. Pre-renovation values are typically 0.4 m s−1 (0.03 m s−1) larger. The standard error in radial velocities is < 0.04 m s−1. Eight weeks of special radar operation are used to investigate the effects of echo power aspect sensitivity. Corrections for echo power aspect sensitivity remove an underestimate of horizontal wind speeds, however aspect sensitivity is azimuthally anisotropic at the scale of routine observations (≈ 1 h). This anisotropy introduces additional random error into wind profiles. For winds averaged over half-an-hour, the random error is around 3.5% above 8 km, but as large as 4.5% in the mid-troposphere.

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 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 Evaluation of wind profiles from the NERC MST radar, Aberystwyth, UK

2014 ◽  
Vol 7 (9) ◽  
pp. 3113-3126 ◽  
Author(s):  
C. F. Lee ◽  
G. Vaughan ◽  
D. A. Hooper
Keyword(s):  
Wind Speed ◽  
Sampling Error ◽  
Signal To Noise Ratio ◽  
Weather Prediction ◽  
Horizontal Wind ◽  
Mountain Waves ◽  
Wind Speeds ◽  
Mst Radar ◽  
Wind Profiles ◽  
Aspect Sensitivity

Abstract. This study quantifies the uncertainties in winds measured by the Aberystwyth Mesosphere–Stratosphere–Troposphere (MST) radar (52.4° N, 4.0° W), before and after its renovation in March 2011. A total of 127 radiosondes provide an independent measure of winds. Differences between radiosonde and radar-measured horizontal winds are correlated with long-term averages of vertical velocities, suggesting an influence from local mountain waves. These local influences are an important consideration when using radar winds as a measure of regional conditions, particularly for numerical weather prediction. For those applications, local effects represent a source of sampling error additional to the inherent uncertainties in the measurements themselves. The radar renovation improved the signal-to-noise ratio (SNR) of measurements, with a corresponding improvement in altitude coverage. It also corrected an underestimate of horizontal wind speeds attributed to beam formation problems, due to pre-renovation component failure. The root mean square error (RMSE) in radar-measured horizontal wind components, averaged over half an hour, increases with wind speed and altitude, and is 0.8–2.5 m s−1 (6–12% of wind speed) for post-renovation winds. Pre-renovation values are typically 0.1 m s−1 larger. The RMSE in radial velocities is <0.04 m s−1. Eight weeks of special radar operation are used to investigate the effects of echo power aspect sensitivity. Corrections for echo power aspect sensitivity remove an underestimate of horizontal wind speeds; however aspect sensitivity is azimuthally anisotropic at the scale of routine observations (≈1 h). This anisotropy introduces random error into wind profiles. For winds averaged over half an hour, the RMSE is around 3.5% above 8 km, but as large as 4.5% in the mid-troposphere.

scholarly journals Aspect sensitivity in the VHF radar backscatters studied using simultaneous observations of Gadanki MST radar and GPS sonde

2004 ◽  
Vol 22 (11) ◽  
pp. 4013-4023 ◽  
Author(s):  
A. K. Ghosh ◽  
S. S. Das ◽  
A. K. Patra ◽  
D. N. Rao ◽  
A. R. Jain
Keyword(s):  
Vertical Shear ◽  
Horizontal Wind ◽  
Vhf Radar ◽  
Upper Troposphere ◽  
Power Difference ◽  
Mst Radar ◽  
Favorable Conditions ◽  
Tropical Station ◽  
Aspect Sensitivity

Abstract. Simultaneous observations made on four days using the MST radar and GPS-sonde at Gadanki (13.5° N, 79.2° E), a tropical station in India, are presented to address the aspect sensitivity of radar backscatters observed at different heights. The observations show that wherever stability parameter N2 is high, vertical shear of horizontal wind is low and Richardson number (Ri) is high, the aspect sensitivity is high indicating that the aspect sensitive radar backscatters are due to thermal structures in the atmosphere. Such a case can be seen very clearly in the upper troposphere and lower stratosphere. At some heights, where N2 is high, Ri is high, but shears are relatively weak, the aspect sensitivity is found to almost disappear, indicating that some amount of shear provides favorable conditions for causing aspect sensitivity. Aspect sensitivity does not occur at all where N2 is low or negative and Ri is low in spite of wind shear being either high or low, indicating that the regions are well mixed and hence turbulent. The study also shows a power difference in the symmetric beams. A case study on this aspect suggests that this asymmetry is due to the tilting of layers by the action of atmospheric waves. There is indication that these waves are generated through Kelvin-Helmholtz-instability (KHI).

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)

scholarly journals Wind Profiling in the Lower Atmosphere from Wind-Induced Perturbations to Multirotor UAS

Sensors ◽  
2020 ◽  
Vol 20 (5) ◽  
pp. 1341 ◽  
Author(s):  
Javier González-Rocha ◽  
Stephan F. J. De Wekker ◽  
Shane D. Ross ◽  
Craig A. Woolsey
Keyword(s):  
Wind Velocity ◽  
Closed Loop ◽  
Sonic Anemometer ◽  
Unmanned Aircraft ◽  
Lower Atmosphere ◽  
Horizontal Wind ◽  
Model Parameters ◽  
Wind Estimation ◽  
Wind Measurement ◽  
Comparison Results

We present a model-based approach to estimate the vertical profile of horizontal wind velocity components using motion perturbations of a multirotor unmanned aircraft system (UAS) in both hovering and steady ascending flight. The state estimation framework employed for wind estimation was adapted to a set of closed-loop rigid body models identified for an off-the-shelf quadrotor. The quadrotor models used for wind estimation were characterized for hovering and steady ascending flight conditions ranging between 0 and 2 m/s. The closed-loop models were obtained using system identification algorithms to determine model structures and estimate model parameters. The wind measurement method was validated experimentally above the Virginia Tech Kentland Experimental Aircraft Systems Laboratory by comparing quadrotor and independent sensor measurements from a sonic anemometer and two SoDAR instruments. Comparison results demonstrated quadrotor wind estimation in close agreement with the independent wind velocity measurements. However, horizontal wind velocity profiles were difficult to validate using time-synchronized SoDAR measurements. Analysis of the noise intensity and signal-to-noise ratio of the SoDARs proved that close-proximity quadrotor operations can corrupt wind measurement from SoDARs, which has not previously been reported.

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