Scintillation And Turbulence Measurements; Comparisons Over A Horizontal Path

Turbulence parameters are determined from measurements along a 183 m line-of-sight at Palm Bay, Florida and a 300 m path at Sudbury, Massachusetts. A horizontal scintillometer is used to obtain o 2, the variance of log amplitude of the irradiance, and the path-averaged C 2, the atmospheric refractive index structure constant. Thermosondes are also used to obElain Cn 2 at several locations along the optical path. The mean C 2 is determined from three thermosondes and compared to that from the scintillometer. Statistics obtained from processing the 2 sec sampled data over 10 minute periods are presented. Excellent agreement is obtained between the two systems when averaged over 10 minutes. Statistics obtained over shorter periods show a considerable variation in the Cn 2 estimates within the 10 minute period. The range of variation within 10 minute intervals can exceed 50%. Volume averaging, wind speed and direction fluctuations are discussed as possible causes of short time variations in the Cn 2 estimates.