Investigation of the correlation between mechanical turbulence and optical turbulence in the atmosphere

The United States Air Force Research Laboratory (AFRL) has conducted a series of experiments which measure optical and mechanical turbulence in the upper troposphere and lower stratosphere using a NC-135E airplane. Specifically, mechanical turbulence was sampled using an accelerometer and a constant temperature anemometer (CTA), while optical turbulence was sampled using a constant current anemometer (CCA). The CTA and CCA are the components of an aerothermal probe, which sampled at a rate of 6000 Hertz while the plane flew at a speed of approximately 0.8 Mach. The velocity structure function, C_v², and the temperature structure function, C_t², were calculated from the CTA and CCA measurements, respectively. Due to the configuration of the aerothermal probe, the C_t² values must then be corrected for the dynamic heating resulting from flow around the aircraft nose. The corrected C_t² that results is based on static temperature fluctuations, providing an accurate measure of optical turbulence. This data is then analyzed to explore the relationship between mechanical and optical turbulence. In addition, this study evaluates the meteorological conditions that produced measured levels of turbulence and explores that relationship. This evaluation is based on use of the Air Force Combat Climatology Center’s (AFCCC) Advanced Climate Modeling and Environmental Simulation (ACMES) gridded analysis data. Synoptic analysis and & aerothermal probe data analysis is described in detail.