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Title: Laser scintillation caused by turbulence near the ground
Authors: University of Michigan. Dept. of Meteorology and Oceanography.
Portman, Donald J., 1922-
Ryznar, Edward.
Waqif, Arif A., 1943-
Keywords: Lasers
Laser scintilliation
Optical scintilliation
Electromagnetic wave propagation
Spectral analysis
Meteorological optics
Cold regions
Turbulent flow
Publisher: Cold Regions Research and Engineering Laboratory (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Research report (Cold Regions Research and Engineering Laboratory (U.S.)) ; 225.
Description: Research Report
Abstract: Laser scintillation was measured for a horizontal optical path 500 m long and 1 m high for various conditions of horizontally homogeneous turbulence. Wind direction, average vertical distributions of wind speed and temperature, and, in some cases, turbulent fluctuations of wind velocity were measured simultaneously. The results of the measurements were analyzed in relation to a set of theoretical relationships derived by Tatarski (1961) for electromagnetic wave propagation in turbulent flow. Tatarski's derivation of the scintillation frequency spectrum (at a point in a plane perpendicular to the optical path) in relation to the three-dimensional spectral density of index of refraction inhomogeneities is summarized and interpreted in relation to its validity for various conditions of turbulence. Analysis of the spectral data showed that their characteristics were similar to Tatarski's theoretical spectrum if the divergence of the laser beam, the size of the receiver aperture, the intensity of scintillation and turbulence spectra were considered. Specific results of the analysis revealed: (1) Agreement between a theoretical variance for scintillation calculated from meteorological data and the variance measured from the spectral densities; (2) A linear increase of the frequency of maximum power with wind speed component normal to the optical path in agreement with Tatarski's model (3) A decrease of scintillation intensity with path height and an accompanying increase in its frequency of maximum power, both closely related to height variations of stability and wind speed; (4) A relative decrease in intensity of scintillation at low frequencies when the potential temperature increases with height. The Appendix consists of a description and discussion of the method of spectral analysis and its application to processing the scintillation and turbulence data.
Appears in Collections:CRREL Research Report

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