# Re-Visiting Acoustic Sounding to Advance the Measurement of Optical Turbulence
This suggests the rationale for employing arrays of sonic anemometers as control research and test instrumentation to capture more fully the physics that create optical turbulence effects. This study demonstrates the implementation of 3D sonic anemometers arrayed in a way to do what each sonic anemometer was originally designed to do best: acoustically interrogate eddies and sense temperature, moisture, and wind velocity (and hence pressure) gradients, which, in combination, lead to index of refraction gradients. [PERSON] et al. [5] have similarly demonstrated a calibrated method to obtain \(C_{T}^{2}\), \(C_{v}^{2}\), and \(C_{n}^{2}\) from a small array of ultrasonic anemometers. This paper extends the relationships shown in [5] with evidence demonstrating optical turbulence strength, \(C_{n}^{2}\), can be derived from a parameter, \(C_{v}^{2}\), which is more directly tied to the turbulent eddy distribution independent of non-adiabatic temperature gradients that many techniques tend to exploit to their advantage, but that can disappear when turbulence does not. [PERSON] et al. [6] have noted the potential importance of quantifying the non-temperature gradient component that partially drives turbulent eddy production with their seasonal study of \(C_{n}^{2}\) strength near Lake Baykal that peaked in winter when winds are strongest. While underlining the benefits of employing local sonic anemometer arrays, this paper also seeks to set forth a solid set of relationships of equal relevance when one is using acoustic sounding--whether sonic anemometry or other familiar techniques such as Sound Detection and Ranging (SODAR)--to evaluate and characterize optical turbulence. A validation of these relationships will primarily be accomplished through a comparative evaluation of the results obtained through path-resolved optical means. Materials and Methods for the present work are described in Section 2. Thissection derives, or when of common usage simply references, the key physical expressions enabling an investigation of optical turbulence strengths and effects using acoustically observed micro-meteorological parameters. Section 2 also provides a description of the sonic anemometer arrays, supporting instrumentation, and the general field experiment set-up. It is in this section that the equivalency of the sonic and virtual temperature is demonstrated (they have previously been assumed different but approximately equal), and a new method to remove the non-turbulent layer vertical temperature change that is independent of atmospheric stability is introduced. Furthermore, a summary description of a path-resolved optical turbulence profiler used for comparative reference is included here as well. Representative optical turbulence point measurements, as collected from sonic anemometers installed on a static tower, will be profiled, analyzed, and comparatively evaluated with the reference path-resolved optical turbulence measurements in Section 3. Section 4 will conclude by summarizing the analysis and discussion of the preceding section, the implications of the findings, and future research directions.