Impact of Non-Kolmogorov Turbulence on Scintillometer

This study explores the effect of experimentally measured non-Kolmogorov turbulence on scintillometer readings. Atmospheric turbulence measurements taken using thermoson-des beneath a weather balloon show layered turbulence with statistics that depart from Kolmogorov theory. The data shows elevated layers of increased turbulence strength. Within the inertial subrange of each layer, the power spectral density of the turbulence differs from the -11/3 power law of Kolmogorov theory. To understand how these departures from theory impact the measurements of a scintillometer, we ingest the turbulence data into a wave-optics model. The model uses the traditional split-step propagation method with phase screens that represent the turbulence for each layer of the path. Unlike the thermosondes, which measure turbulence directly, the scintillometer produces a path-averaged estimate of the turbulence strength. Further, it assumes Kolmogorov statistics. We investigate the ability of the scintillometer to characterize the non-Kolmogorov turbulence. This effort is an extension of previous work that indicated that scintillometers provide useful measurements of non-Kolmogorov turbulence for at least some conditions. The conditions studied here are broader than in the previous work. The metrics for the comparisons include scintillation index, Strehl ratio, power-in-the-bucket, and relative error in irradiance. The results show that the scintillometer prescribes turbulence that is a passable surrogate for the true non-Kolmogorov turbulence when small aperture sizes are involved, but not large ones. These results will lead to a better understanding of optical turbulence, how it can be measured, and how it affects optical beams during propagation.