Radar Backscattering from the Turbulent Clear Atmosphere

Óttersten, Hans

doi:10.1029/rs004i012p01251

Cited by 92 publications

(31 citation statements)

References 11 publications

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“…In clear-air or cloudy conditions (precipitation-free atmosphere), UHF-range and VHF-range profilers detect the fluctuations of refractive index with a scale of one-half the radar wavelength, through the following expression (Ottersten, 1969):…”

Section: Theoretical Backgroundmentioning

confidence: 99%

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High-resolution humidity profiles retrieved from wind profiler radar measurements

Saïd

Campistron²,

Girolamo

2018

Atmos. Meas. Tech.

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Abstract. The retrieval of humidity profiles from wind profiler radars has already been documented in the past 30 years and is known to be neither as straightforward and nor as robust as the retrieval of the wind velocity. The main constraint to retrieve the humidity profile is the necessity to combine measurements from the wind profiler and additional measurements (such as observations from radiosoundings at a coarser time resolution). Furthermore, the method relies on some assumptions and simplifications that restrict the scope of its application. The first objective of this paper is to identify the obstacles and limitations and solve them, or at least define the field of applicability. To improve the method, we propose using the radar capacity to detect transition levels, such as the top level of the boundary layer, marked by a maximum in the radar reflectivity. This forces the humidity profile from the free troposphere and from the boundary layer to coincide at this level, after an optimization of the calibration coefficients, and reduces the error. The resulting mean bias affecting the specific humidity profile never exceeds 0.25 g kg −1 . The second objective is to explore the capability of the algorithm to retrieve the humidity vertical profiles for an operational purpose by comparing the results with observations from a Raman lidar.

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Section: Theoretical Backgroundmentioning

confidence: 99%

“…Following Ottersten (1969), Gossard et al (1982) and Stankov et al (2003) used another expression for the turbulence structure parameter, based on the energy equation:…”

Section: Theoretical Backgroundmentioning

confidence: 99%

High-resolution humidity profiles retrieved from wind profiler radar measurements

Saïd

Campistron²,

Girolamo

2018

Atmos. Meas. Tech.

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“…A VHF ST radar offers the possibility of performing experimental studies on atmospheric turbulence, for example, theoretically investigated by Booker and Gordon (1950), Ottersten (1969), or Tatarski (1971. In a stratified fluid, turbulent events are classically interpreted as the result of flow instabilities (e.g.…”

Section: Errors In Isotropic Turbulence Parameter Measurementsmentioning

confidence: 99%

“…Booker and Gordon, 1950;Batchelor, 1955;Ottersten, 1969;Tatarskii, 1971). The isotropic scattering from refractive index irregularities is usually advocated for explaining the echoes at UHF (because aspect sensitivity is not observed) and at VHF, for echoes received far from the zenith (e.g.…”

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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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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“…It is well known that, in clear air conditions, the backscattered radar echo power is proportional to the 3D spectrum of the refractive index fluctuation field for the radial wavenumber, corresponding to twice the incident wavenumber (Tatarski, 1961;Ottersten, 1969). If specular reflection is negligible, as it may be for wavelengths less than one meter, the refractive index irregularities at the considered scale (15 cm for the PROUST radar) are assumed to be due to isotropic inertial turbulence only.…”

Section: Introductionmentioning

confidence: 99%

Energetics of small scale turbulence in the lower stratosphere from high resolution radar measurements

2001

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Abstract. Very high resolution radar measurements were performed in the troposphere and lower stratosphere by means of the PROUST radar. The PROUST radar operates in the UHF band (961 MHz) and is located in St. Santin, France (44 • 39' N, 2 • 12' E). A field campaign involving high resolution balloon measurements and the PROUST radar was conducted during April 1998. Under the classical hypothesis that refractive index inhomogeneities at half radar wavelength lie within the inertial subrange, assumed to be isotropic, kinetic energy and temperature variance dissipation rates were estimated independently in the lower stratosphere. The dissipation rate of temperature variance is proportional to the dissipation rate of available potential energy. We therefore estimate the ratio of dissipation rates of potential to kinetic energy. This ratio is a key parameter of atmospheric turbulence which, in locally homogeneous and stationary conditions, is simply related to the flux Richardson number, R f .

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Radar Backscattering from the Turbulent Clear Atmosphere

Cited by 92 publications

References 11 publications

High-resolution humidity profiles retrieved from wind profiler radar measurements

High-resolution humidity profiles retrieved from wind profiler radar measurements

Temperature sheets and aspect sensitive radar echoes

Energetics of small scale turbulence in the lower stratosphere from high resolution radar measurements

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