Inner-scale dependence of scintillation variances measured in weak scintillation

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Abstract
We report results of an experiment in which scintillation variances of log intensity are measured simultaneously with micrometeorological measurements. The latter give four methods for estimating the turbulence inner scale. The propagation path was short, 150 m, such that weak scintillation occurred. The variances were from an effective spherical-wave transmitter and point receiver as well as a large, phase-incoherent transmitter with a similar receiver. We show that the former variance arises from the dissipation range of the refractiveindex spectrum and the latter from the spectral bump that lies at the high-wave-number end of the inertial range. When an inner scale deduced from micrometeorological measurements is used, the ratio of these scintillation variances agrees well with theoretical predictions that use an accurate model of the refractive-index spectrum. The measurements extend deeper into the dissipation range than previous similar measurements, further verifying this spectrum model. The measurements from a wide variety of micrometeorological conditions all lie on a single theoretical curve, verifying the universality of small-scale turbulence.