Comparisons Of The Transverse Coherence Length And Isoplanatic Angle From Measurements Taken With The Flatlands Very High Frequency Radar, Optical Techniques, And Thermosondes

Comparisons are made of the transverse coherence length (ro) and isoplanatic angle (θo) derived from measurements taken with the Flatlands very high frequency (VHF) radar, an ro system, an isoplanometer, and temperature fluctuation sensors mounted on a thermosonde. The measurements were conducted at the Flatlands location near Urbana, Illinois, from 7-13 June 1988. The site was selected because of the lack of orographic effects on airflow and the refractive index structure parameter (Cn2). The radar was operated with alternating beams in the north and east directions at 20° zenith angle in order to avoid contamination by specular reflections. Contributions of the refractive index structure parameter (Cn2) from different altitudes above ground to the integrated-path ro and θo values are presented and discussed. Diurnal variations of ro and θo obtained from the suite of instruments are shown with particular emphasis on the "neutral" events. Measured results are compared to results from the Aeronomy Laboratory's theoretical model of Cn2.