A study of signal statistics of VHF radar echoes from clear air

Sheen, D.R.; Liu, C.H; Röttger, J.

doi:10.1016/0021-9169(85)90103-5

Cited by 12 publications

(8 citation statements)

References 11 publications

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“…6) It was stressed by many authors that diffuse reflection or scattering by anisotropic turbulence is very difficult to differentiate since the roughness of the layer surface and the refractive index fluctuations within the turbulent layer may be described by similar statistics. One can speculate that the conclusions obtained by Sheen et al (1985) or Kuo et al (1987) mentioned above result from this property. Hocking and Hamza (1997) proposed a quantitative relation between the degree of anisotropy of turbulence and the prevailing atmospheric conditions.…”

Section: Various Interpretations Of Aspect Sensitive Echoing Layersmentioning

confidence: 76%

“…Moreover, the comparisons are usually in relative power levels leading to a simplification of the problem. Sheen et al (1985) and Kuo et al (1987) studied statistical distributions of radar echo power. The studies performed with the signals received along the zenith showed distributions fully compatible with volume turbulent scattering.…”

Section: Various Interpretations Of Aspect Sensitive Echoing Layersmentioning

confidence: 99%

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Temperature sheets and aspect sensitive radar echoes

Luce

Crochet

Dalaudier³

2001

Ann. Geophys.

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Abstract. There have been years of discussion and controversy about the existence of very thin and stable temperature sheets and their relationship to the VHF radar aspect sensitivity. It is only recently that very high-resolution insitu temperature observations have brought credence to the reality and ubiquity of these structures in the free atmosphere and to their contribution to radar echo enhancements along the vertical. Indeed, measurements with very highresolution sensors are still extremely rare and rather difficult to obtain outside of the planetary boundary layer. They have only been carried out up to the lower stratosphere by Service d'Aéronomie (CNRS, France) for about 10 years. The controversy also persisted due to the volume resolution of the (Mesosphere)-Stratosphere-Troposphere VHF radars which is coarse with respect to sheet thickness, although widely sufficient for meteorological or meso-scale investigations. The contribution within the range gate of many of these structures, which are advected by the wind, and decay and grow at different instants and could be distorted either by internal gravity waves or turbulence fields, could lead to radar echoes with statistical properties similar to those produced by anisotropic turbulence. Some questions thus remain regarding the manner in which temperature sheets contribute to VHF radar echoes. In particular, the zenithal and azimuthal angular dependence of the echo power may not only be produced by diffuse reflection on stable distorted or corrugated sheets, but also by extra contributions from anisotropic turbulence occurring in the stratified atmosphere. Thus, for several years, efforts have been put forth to improve the radar height resolution in order to better describe thin structures. Frequency interferometric techniques are widely used and have been recently further developed with the implementation of high-resolution data processings. We begin by reviewing briefly some characteristics of the ST radar echoes with a particular emphasis on recent works. Their possible coupling with stable sheets is then presented and their known characteristics are described with some hypotheses concernCorrespondence to: H. Luce (luce@kurasc.kyoto-u.ac.jp) ing their generation mechanisms. Finally, measurement campaigns that took recently place or will be carried out in the near future for improving our knowledge of these small-scale structures are presented briefly.

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Section: Various Interpretations Of Aspect Sensitive Echoing Layersmentioning

confidence: 76%

Section: Various Interpretations Of Aspect Sensitive Echoing Layersmentioning

confidence: 99%

Temperature sheets and aspect sensitive radar echoes

Luce

Crochet

Dalaudier³

2001

Ann. Geophys.

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“…Accordingly, the Nakagami parameter m was con-sidered to be a good coefficient to parameterize the radar echo signal. However, by analyzing the data of the vertical radar returns from troposphere and lower stratosphere, Sheen et al [1985] found that there were many cases in which signals with narrow Doppler spectrum had an rn coefficient very close to 0.5. This discovery prompted us to reexamine the data and the theory.…”

Section: <(A • -mentioning

confidence: 99%

Systematic behavior of signal statistics of MST radar echoes from clear air and their interpretation

Kuo¹,

Chen²,

Liu³

et al. 1987

Radio Science

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Signal statistics of data from the SOUSY‐VHF radar were analyzed. Mean, variance, skewness and kurtosis of the distribution of the quadrature components of the signals as well as Nakagami m coefficient of the amplitude distribution were calculated. We found a systematic behavior in the correlation between kurtosis and Nakagami coefficient, and we propose a stochastic model for its explanation. These stochastic effects on the signal are generated in the variable echoing process itself. Numerical simulation and analytical calculation of the model were carried out for comparison with the data, and the results are encouraging.

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“…It has been demonstrated that sensitive mesosphere-stratosphere-troposphere (MST) radars can be used to study the dynamics of the atmosphere from troposphere to mesospheric heights because there is a strong relation between the echo production mechanisms and atmospheric turbulence [e.g., Gage and Balsley, 1980;Gage et al, 1981;Gage and Green, 1978;Green and Gage, 1980;Kuo et al, 1987;Kuo and Lue, 1989;Lue and Kuo, 1988;Liu and Yeh, 1980;Rastogi and Bowhill, 1976;R6ttger, 1980;R6ttger and Liu, 1978;Sheen et al, 1985;Van Zandt et al, 1977]. Three major mechanisms have been considered to be responsible for the MST radar returns' volume scattering, Fresnel scattering and Fresnel reflection.…”

Section: Introductionmentioning

confidence: 99%

“…A procedure to obtain information about the scatterers involves studies of the amplitude statistics of the received signal. Amplitude histograms have been compared variously with Rayleigh, Rice, Hoyt, Lognormal, and Nakagami-m distributions [e.g., Von Biel, 1971, 1979Mathews et al, 1973;Newman and Ferraro, 1976;Chandra and Vincent, 1977;Vincent and Belrose, 1978;R6ttger, 1980;Rastogi and Holt, 1981;Sheen et al, 1985]. Among these, the most commonly applied have been the Rice distribution and Nakagami-m distribution [Nakagarni, 1960], which are the distributions expected if the signal is the sum of a fluctuating component (volume/Fresnel scattering contribution) and a steady component (Fresnel reflection contribution).…”

Section: Introductionmentioning

confidence: 99%

Reduction of nonstationarity and parameter analysis of VHF radar returns from the atmosphere

Kuo¹,

Lue²,

Liu³

1990

Radio Science

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An optimization process to reduce nonstationarity problems yet preserve the reliability of the radar echo signal distribution is developed combining the conventional χ2 test and numerical simulation techniques. As an application to the real data, we determine the optimized data length to be 128 elements per set for SOUSY data and 256 elements per set for Chung‐Li data. For each of such data sets, the echo power P and the modified Rice parameter γ are calculated and their statistics are examined. When their time averages are plotted as functions of height, we frequently observe the existence of maximum P along with minimum γ in Chung‐Li data. Such a coupling can be explained as an evidence of the existence of turbulence layer. The cause of the occurrence of turbulence layers in the troposphere over Chung‐Li area is briefly discussed.

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A study of signal statistics of VHF radar echoes from clear air

Cited by 12 publications

References 11 publications

Temperature sheets and aspect sensitive radar echoes

Temperature sheets and aspect sensitive radar echoes

Systematic behavior of signal statistics of MST radar echoes from clear air and their interpretation

Reduction of nonstationarity and parameter analysis of VHF radar returns from the atmosphere

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