Velocity spectra and turbulence using direct detection lidar and comparison with thermosonde measurements

[1] Observations of turbulence have been performed in New Hampshire near Mount Washington using two independent instruments: a ground-based direct detection Doppler lidar and a balloon-borne thermosonde. The Doppler lidar measures a time series of the velocity component parallel to the laser beam for each altitude. Spectra of the velocity time series are determined using the Scargle technique. Turbulence levels are estimated from the spectra assuming Kolmogorov behavior. The thermosonde measures the temperature difference between two sensors spaced 1 m apart, computes a running RMS average, and then determines the temperature turbulence parameter, CT2, also assuming Kolmogoroff behavior. The results show that the strongest levels of turbulence exist in a Kelvin-Helmholtz layer in the altitude range of 1.2 < z < 1.9 km. This layer shows a three-tier structure consisting of a well-mixed layer in the center with strong velocity fluctuations bounded on top and bottom by layers with strong temperature fluctuations.