A study on aspect sensitivity of clear-air turbulence using coherent radar imaging of VHF atmospheric radar

2012 ◽  
Author(s):  
J. -S. Chen ◽  
J. Furumoto
Keyword(s):  
Radar Imaging ◽  
Air Turbulence ◽  
Coherent Radar ◽  
Aspect Sensitivity

scholarly journals Measurement of Atmospheric Aspect Sensitivity Using Coherent Radar Imaging after Mitigation of Radar Beam Weighting Effect

2013 ◽  
Vol 30 (2) ◽  
pp. 245-259 ◽  
Author(s):  
Jenn-Shyong Chen ◽  
Jun-ichi Furumoto
Keyword(s):  
Power Distribution ◽  
Signal To Noise Ratio ◽  
Radar Imaging ◽  
Brightness Distribution ◽  
Beam Direction ◽  
Very High Frequency ◽  
Aspect Angle ◽  
Radar Beam ◽  
Coherent Radar ◽  
Aspect Sensitivity

Abstract The aspect angle, a measurement of the aspect sensitivity of atmospheric refractivity irregularities, was estimated with multiple-receiver coherent radar imaging (CRI) of very high frequency (VHF) atmospheric radar. Two CRI parameters retrieved by Capon’s method were utilized to derive the aspect angle: brightness width from the vertical radar beam and the direction of arrival (DOA) of the echo center from the oblique radar beam. Differing from previous studies with CRI, the radar beam weighting effect on the CRI brightness distribution was considered, and moreover, the radar beamwidth used in study was adaptive to the signal-to-noise ratio (SNR) of data as well as the off-beam direction angle. The study is based on statistical results. It is shown that the brightness width, a representative of the aspect angle, obtained from the modified CRI brightness distribution of the vertical radar beam was generally larger than that without correction, and it was very close to the values derived from the DOA of the 1° oblique radar beam and the power distribution of multiple beam directions. Moreover, the aspect angle derived from the DOA varied with the radar beam direction, which was similar to that obtained from the comparison of echo powers of a radar beam pair; however, the DOA approach yielded a much larger aspect angle in the low-SNR condition. This study recommended a feasibility of improving the measurements of atmospheric parameters with CRI after removing the radar beam weighting effect suitably from the CRI brightness distribution.

scholarly journals Aspect sensitivity measurements of polar mesosphere summer echoes using coherent radar imaging

2002 ◽  
Vol 20 (2) ◽  
pp. 213-223 ◽  
Author(s):  
P. B. Chilson ◽  
T.-Y. Yu ◽  
R. D. Palmer ◽  
S. Kirkwood
Keyword(s):  
Middle Atmosphere ◽  
Radar Imaging ◽  
Brightness Distribution ◽  
High Signal ◽  
Vhf Radar ◽  
Radio Science ◽  
Summer Echoes ◽  
Polar Mesosphere Summer Echoes ◽  
Coherent Radar ◽  
Aspect Sensitivity

Abstract. The Esrange VHF radar (ESRAD), located in northern Sweden (67.88° N, 21.10° E), has been used to investigate polar mesosphere summer echoes (PMSE). During July and August of 1998, coherent radar imaging (CRI) was used to study the dynamic evolution of PMSE with high temporal and spatial resolution. A CRI analysis provides an estimate of the angular brightness distribution within the radar’s probing volume. The brightness distribution is directly related to the radar reflectivity. Consequently, these data are used to investigate the aspect sensitivity of PMSE. In addition to the CRI analysis, the full correlation analysis (FCA) is used to derive estimates of the prevailing three-dimensional wind associated with the observed PMSE. It is shown that regions within the PMSE with enhanced aspect sensitivity have a correspondingly high signal-to-noise ratio (SNR). Although this relationship has been investigated in the past, the present study allows for an estimation of the aspect sensitivity independent of the assumed scattering models and avoids the complications of comparing echo strengths from vertical and off-vertical beams over large horizontal separations, as in the Doppler Beam Swinging (DBS) method. Regions of enhanced aspect sensitivity were additionally shown to correlate with the wave-perturbation induced downward motions of air parcels embedded in the PMSE.Key words. Ionosphere (polar ionosphere) Meteorology and Atmospheric Dynamics (middle atmosphere dynamics) Radio Science (Interferometry)

scholarly journals On the relationship between aspect sensitivity, wave activity, andmultiple scattering centers of mesosphere summer echoes: a case study using coherent radar imaging

2004 ◽  
Vol 22 (3) ◽  
pp. 807-817 ◽  
Author(s):  
J.-S. Chen ◽  
P. Hoffmann ◽  
M. Zecha ◽  
J. Röttger
Keyword(s):  
Middle Atmosphere ◽  
Layer Structure ◽  
Radar Imaging ◽  
Short Wave ◽  
High Angular Resolution ◽  
Radio Science ◽  
Scattering Centers ◽  
Coherent Radar ◽  
Aspect Sensitivity

Abstract. A mesosphere-summer-echo layer, observed by the OSWIN VHF radar (54.1°N, 11.8°E) with vertical and 7° oblique radar beams, was examined using the method of coherent radar imaging (CRI). We disclosed the echo events having multiple scattering centers (MSC) in the radar volume by means of the high angular resolution of the CRI technique and found that the MSC events occurred more frequently in the upper portion of the echo layer. More examinations showed that the characteristics were different between the upper and lower portions of the layer. For example, the differences in echo power between vertical and oblique beams changed mostly from positive to negative along the increase of altitude, and strong turbulent echoes were seen in the upper portion of the layer. These observations indicate that the aspect sensitivity of the echoes became less and less with the increase of altitude. Moreover, the scattering centers of the echoes were close to zenith for the lower portion of the layer but were usually several degrees from the zenith for the upper portion of the layer. Observable wave-like variation in the scattering center was also seen in the upper part of the layer. Based on these features, we drew some conclusions for this case study: (a) the MSC events might result from the slanted layer/anisotropic structure tilted by short-wave activities, (b) the tilt angle of the layer structure could be 6°–10°, causing the echo power received by the 7° oblique beam was larger than or comparable to that received by the vertical beam, and (c) short-wave activities not only tilted the layer structure, but also induced isotropic irregularities. Key words. Meteorology and atmospheric dynamics (middle atmosphere dynamics). Radio science (interferometry; instruments and techniques)

scholarly journals Simulation of Coherent Radar Imaging Using Continuous Wave Noise Radar

2009 ◽  
Vol 26 (9) ◽  
pp. 1956-1967
Author(s):  
Jing Xu ◽  
M. W. Hoffman ◽  
B. L. Cheong ◽  
R. D. Palmer
Keyword(s):  
Theoretical Analysis ◽  
Time Domain ◽  
Cross Correlation ◽  
Continuous Wave ◽  
Radar Imaging ◽  
Brute Force ◽  
Correlation Model ◽  
Noise Radar ◽  
Force Time ◽  
Coherent Radar

Abstract A computationally simple cross-correlation model for multiple backscattering from a continuous wave (CW) noise radar is developed and verified with theoretical analysis and brute-force time-domain simulations. Based on this cross-correlation model, a modification of an existing numerical method originally developed by Holdsworth and Reid for spaced antenna (SA) pulsed radar is used to simulate the estimated cross correlation corresponding to atmospheric backscattering using a coherent CW noise radar. Subsequently, coherent radar imaging (CRI) processing comparisons between the CW noise radar and a conventional pulsed radar are presented that verify the potential of CW noise radar for atmospheric imaging.

On a Bayesian approach to coherent radar imaging

1992 ◽  
Vol 4 (4) ◽  
pp. 245-255
Author(s):  
David Styerwalt ◽  
Glenn R. Heidbreder
Keyword(s):  
Bayesian Approach ◽  
Radar Imaging ◽  
Coherent Radar

Coherent radar imaging based on compressed sensing

Radio Science ◽  
2015 ◽  
Vol 50 (12) ◽  
pp. 1271-1285 ◽  
Author(s):  
Qian Zhu ◽  
Ryan Volz ◽  
John D. Mathews
Keyword(s):  
Compressed Sensing ◽  
Radar Imaging ◽  
Coherent Radar
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