Atmospheric turbulence and the extension of the radio horizon

The possibility that atmospheric turbulence (clear air turbulence) can cause extended propagation beyond the optical line of sight is examined. It is possible for a distant transmitter to interfere with a receiver via scattering from atmospheric turbulence, but it is not likely that a radar will receive distant ground echo via scattering from turbulence. From a compilation of published data it is shown that the structure constant of the atmosphere (a measure of scattering) is a function of altitude with an apparent maximum in the vicinity of 500 to 1000 m.