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29 April 2010 Atmospheric cross-wind and turbulence measurements using turbulence-induced scintillations
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We report on remote measurements of cross-wind and atmospheric turbulence, using a one-station scheme. As most remote wind-sensing methods, our method is based on observing the drift of the scintillation pattern across the line of sight. The scintillations are caused by naturally-occurring turbulence-induced refractive index irregularities in the atmosphere, which drift at wind speed. Analyzing spatial-temporal cross-correlation function of the signals of two elements in the array, it is possible to obtain the cross-wind speed. We use the zero-crossings technique for measuring the cross-wind value, while the cross-wind direction is determined by comparing areas from both sides of the peak of the cross-correlation function. Here we present results obtained using these techniques in comparison to independent measurements of the anemometers. The experiments were performed along a uniform path over a flat beach parallel to the Mediterranean Sea shore. Four white-screen diffusive targets were placed at distances of 300, 600, 850 and 1200m. Five anemometers were placed along the laser beam path, one near each target and at the measurement station. Each target was illuminated with a beam from a glass fiber pulsed infrared laser with a repetition rate of several thousand Hz, and a sub-microsecond pulse-length, and output beam divergence of ~300 μrad. The receiver has an entrance aperture of 80mm, and the incoming radiation is focused onto an array of four 50×250um InGaAs detectors by a lens with f=500mm. The results show good agreement. From the fluctuations of the signal on the detector array, our system also measures the turbulence structure parameter Cn 2, using the angle-of arrival technique. The obtained results show reasonable agreement with independent scintillometer measurements of Cn2, performed with a CW He-Ne laser in a two-station setup with a detector at a distance of 60m from the laser.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. Shapira, O. Porat, M. Livneh, Z. Wies, D. Heflinger, S. Fastig, Y. Glick, and A. Engel "Atmospheric cross-wind and turbulence measurements using turbulence-induced scintillations", Proc. SPIE 7684, Laser Radar Technology and Applications XV, 76841L (29 April 2010);

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