Refractivity turbulence, inner scale, and eddy dissipation rate observations using a balloon-ring platform

摘要

Understanding the turbulence along a propagation path is required to evaluate new methods for tracking, pointing, and compensation of laser beams, studying image degradation, and interpreting remote sensing observations. This paper presents observations using a new balloon-ring platform equipped with multiple fine wire probes (1 μm diameter) at various separations for sensing both temperature and velocity fluctuations. These measurements provide profiles of the temperature structure parameter (C_T~2), refractive index structure parameter (C_n~2), eddy dissipation rate (ε), inner scale (l_o), and outer scale (L_o) values. Of particular interest is the path variability of C_n~2, ε, l_o, and L_o, and the relationship of these parameters to atmospheric stability. Since all "raw" data is archived, spectra are shown and discussed as to how often the atmosphere truly follows the "Kolmogorov-5/3 law", or under what atmospheric conditions for which the structure function is represented by the r~(2/3) law. Also the concerns of local isotropy and intermittency can be addressed. The interpretation of these results to propagation effects is discussed. Salient features of the new measuring system are presented as well as the rationale for its implementation, including the longstanding concern of wake contamination on conventional measuring systems tethered under a single balloon.