High Spatial Resolution Measurements Of Atmospheric Turbulence Over The Altitude Range Of 0.5 To 23 Kilometers

A balloon borne, high bandwidth instrumentation package has been developed for measuring atmospheric temperature fluctuations (used to derive the refractive index structure parameter,Cn^2)as well as wind fluctuations for deriving the eddy dissipation rate,ɛ. To date, modeling and simulation of imaging and laser beam propagation through atmospheric turbulence have relied upon a traditional theoretical basis that assumes the existence of homogeneous, isotropic, stationary, and Kolmogorov turbulence. A main objective of this effort is to address and quantify the non-classical turbulence issues of the real atmosphere. The instrumentation platform keeps the sensors out of the balloon wake, and at an ascent rate of 5 meters/second, we can obtain a spatial resolution of less than 1 cm. The raw time series from 5 temperature sensors and one velocity sensor is telemetered to a ground station. Also measured is the pressure and GPS position and altitude as a function of time. Results are presented showing the altitude variation of the vertical structure function. Over an altitude range of 0.5 to 23 km, we see abrupt changes in the strength and character of the thermal turbulence. The logarithmic slope of the turbulence Power Spectral Density between the outer scale and the dissipation scale ranged between -0.9 to -2.6. The -5/3 slope associated with the Kolmogorov hypothesis of an inertial subrange is observed over less than 7% of the altitude range.