Evidence for specular reflection from monostatic VHF radar observations of the stratosphere

Gage, K. S.; Green, J. L.

doi:10.1029/rs013i006p00991

Cited by 177 publications

(91 citation statements)

References 20 publications

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“…The term MST radar is usually reserved for the most powerful VHF radars, while the less powerful ones are often referred to as ST radars.) This "VHF aspect sensitivity" was discovered by ROttger and Liu [1978] and Gage and Green [1978], and there is general agreement among researchers in the field that the VHF aspect sensitivity is the manifestation of a significant anisotropy in the spatial spectrum of the 3-m-scale, clear-air, refractiveindex irregularities in the free atmosphere. Correspondingly, the absence of a significant aspect sensitivity at UHF frequencies in the atmospheric boundary layer as well as in the free atmosphere is seen as evidence for isotropy of decimeter-scale, refractive-index irregularities throughout the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

First synthesis of wind‐profiler signals on the basis of large‐eddy simulation data

Muschinski¹,

Sullivan²,

Wuertz³

et al. 1999

Radio Science

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Abstract. Radar wind profilers detect scatter from clear-air refractive-index irregularities. The Doppler shift calculated from the time series of the backscattered signal provides an estimate of the radial velocity of the air within the radar's resolution volume. It is known that there are quite a number of effects that can give rise to intrinsic biases in these radial-velocity estimates. It is extremely difficult to unambiguously identify these biases on the basis of observations since it is impossible to independently probe the threedimensional, time-dependent fine structure of the relevant atmospheric variables (wind and refractive index) within the radar's resolution volume down to the relevant spatial and temporal scales associated with the scattering process itself. In this paper the large-eddy simulation (LES) technique is used to generate, with high spatial and temporal resolution where X is the radar wavelength [e.g., Doviak and Zrnid, 1984, 1993;Muschinski, 1998]. That is, as long as Rayleigh scatter does not play a role, wind profilers see only refractive-index structures at the Bragg wave 1437

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Section: Introductionmentioning

confidence: 99%

First synthesis of wind‐profiler signals on the basis of large‐eddy simulation data

Muschinski¹,

Sullivan²,

Wuertz³

et al. 1999

Radio Science

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“…The generation mechanisms of these irregularities, at various height levels in the troposphere and lower stratosphere (up to 25 km) are yet to be fully understood. There are two main causative mechanisms for aspect sensitive radar backscatter: 1) specular reflectors and 2) anisotropic refractive index irregularities (Gage and Green, 1978;Doviak and Zrinc, 1984;Hocking and Hamza, 1997). The contribution of each of these mechanisms at various height levels, however, could not be well determined due to lack of simultaneous high resolution radar and in-situ measurements of background atmospheric parameters.…”

Section: Introductionmentioning

confidence: 99%

“…Radar echoes from lower and middle atmosphere at VHF are known to be aspect sensitive, which is characterized by a decrease in echo power as the radar beam is pointed away from the zenith (Gage and Green, 1978;Röttger and Liu, 1978;Fukao et al, 1980). Study of aspect sensitivity at VHF in the lower atmosphere is of significant interest to the radar community, as it is important to understand the characteristics of the radar backscatters for better interpretation of the spectral Correspondence to: A. K. Ghosh (asish gh@rediffmail.com) parameters, which represent various atmospheric parameters.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2004

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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 N 2 is high, vertical shear of horizontal wind is low and Richardson number (R i ) 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 N 2 is high, R i 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 N 2 is low or negative and R i 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).

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“…As suggested by Fukao et al (1980) negative correlations could imply radiowave reflections from sharp gradients in electron density. Such gradients, if they persist, would require static stability of the atmosphere (e.g., Gage and Green, 1978) and partial reflected radiowaves from the stable gradients would appear on SNR maps as thin horizontal lines or "sheets". Backscatter from 27-28 May displayed some occurrences of such thin sheets and many more were observed on 29 May.…”

Section: Thin Sheets and Isolated Negative Correlationsmentioning

confidence: 99%

A high-resolution study of mesospheric fine structure with the Jicamarca MST radar

et al. 2006

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Abstract. Correlation studies performed on data from recent mesospheric experiments conducted with the 50-MHz Jicamarca radar in May 2003 and July 2004 are reported. The study is based on signals detected from a combination of vertical and off-vertical beams. The nominal height resolution was 150 m and spectral estimates were obtained after ∼1 min integration. Spectral widths and backscattered power generally show positive correlations at upper mesospheric heights in agreement with earlier findings (e.g., Fukao et al., 1980) that upper mesospheric echoes are dominated by isotropic Bragg scatter. In many instances in the upper mesosphere, a weakening of positive correlation away from layer centers (towards top and bottom boundaries) was observed with the aid of improved height resolution. This finding supports the idea that layer edges are dominated by anisotropic turbulence. The data also suggests that negative correlations observed at lower mesospheric heights are caused by scattering from anisotropic structures rather than reflections from sharp vertical gradients in electron density.

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Evidence for specular reflection from monostatic VHF radar observations of the stratosphere

Cited by 177 publications

References 20 publications

First synthesis of wind‐profiler signals on the basis of large‐eddy simulation data

First synthesis of wind‐profiler signals on the basis of large‐eddy simulation data

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

A high-resolution study of mesospheric fine structure with the Jicamarca MST radar

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