Near ground measurements of beam shaping and anisotropic turbulence over concrete runway and grass range

Researchers from the University of Central Florida recently carried out a series of measurements over a concrete runway and a grass range using a 632.8 nm Gaussian beam propagated for 100 or 125 m at a height of 2 m. Mean intensity and scintillation index contours varied significantly throughout these measurements in ways that corresponded to more than simple isotropy or anisotropy of optical turbulence. A simple theory is developed to show the effect of a nonlinear index of refraction gradient in addition to the possibility of anisotropic turbulence. Theoretical contours are compared to experimental results which seem to indicate the presence of a beam shaping phenomena near the ground in addition to anisotropy.