Laser Studies of Atmospheric Turbulence in the Surface Layer

Abstract

The ‘scintillation’ or ‘irradiance fluctuation’ of laser beam characteristics has been recognized to be more feasible and perspective technique for the measurement of path-integrated atmospheric turbulence over line-of-sight (LOS) paths in the surface layer. Such LOS measurements of atmospheric turbulence from estimations of C2A have been made during March 1990–December 1991 using an Helium-Neon laser scintillometer developed at the Indian Institute of Tropical Meteorology (HTM), Pune. The results of the above scintillation observations obtained during different atmospheric conditions revealed an association between the optical turbulence characteristics and geometrical as well as meteorological parameters. The turbulence measurements made-with the laser scintillometer have been in good agreement with those obtained simultaneously using the thermal techniques. A comprehensive picture of the results of the experiments and related theory dealing with wind and thermal stratifications in the surface layer, and optical pathlength dependence is presented in this paper. The usefulness of the scintillometer (with minor modifications) for the determination of crosswinds, and importance of the laser scintillation technique for the measurements of atmospheric turbulence and winds over inaccessible areas are outlined.