Equivalent refractive-index structure constant of non-Kolmogorov turbulence: comment
The paper by Y. Li, W. Zhu, X. Wu, and R. Rao entitled “Equivalent refractive-index structure constant of non-Kolmogorov turbulence,” Opt. Express 23(18), 23004 (2015). [CrossRef] relates the non-Kolmogorov turbulence structure constant to the classical structure constant for Kolmogorov turbulence by imposing equality of their respective structure functions at large separation distances, higher than the outer scale. As opposed to previous attempts to relate the two structure constants, the approach of Li et al. is anchored on a measurable meteorological parameter, the outer scale. The error lies in the fact that the authors have used a default Kolmogorov structure function with an infinite outer scale. A subsequent assumption of a finite outer scale is not compatible with the initial assumption. In this paper we show the correct procedure to obtain the relationship between the non-Kolmogorov and Kolmogorov structure constants which is based on an explicitly finite outer scale used throughout all calculations.