Abstract

An optical scintillometer has recently been developed to measure C_n², I₀, and the surface fluxes of heat and momentum. This scintillometer uses a diverged HeNe laser beam received through a 1 mm aperture and, on the same path, a 4.4 cm diameter incoherently illuminated aperture with a 4.4 cm diameter receiver aperture. Because of the wide dynamic range of atmospheric turbulence and the need for an unattended, reliable scintillometer, both received signals are logarithmically amplified. Two such scintillometers were operated simultaneously, one on a 500 m path so that strong scintillations are observed, and another on a 150 m path in the center of the longer path so that C_n² and Io could be obtained with weak scintillation approximations. This operation provides all the parameters needed to compare the data with theory, because the experiment site is horizontally homogeneous. The laser-beam scintillation from the 500 m path is compared with the heuristic theory for log-amplitude scintillation. The large-aperture data is compared with the first-term asymptotic theory for strong scintillations of a spatially extended incoherent source. It is found that the effects of saturation can be corrected, and the values of Cn², Io, and heat momentum fluxes can be obtained, even for such long paths and strong scintillations.

© 1990 Optical Society of America