7B.2 Measurements of turbulent kinetic energy dissipation rate derived from Doppler lidar

Tuesday, 10 June 2008: 1:45 PM
Aula Magna Höger (Aula Magna)
Ewan J. O'Connor, University of Reading, Reading, Berks., United Kingdom; and R. J. Hogan, A. J. Illingworth, and C. D. Westbrook

Estimates of turbulent kinetic energy (TKE) dissipation rate can be derived from the variation of the mean Doppler velocity over short timescales. If it is assumed that turbulence is a homogeneous and isotropic process of energy dissipation then the Kolmogorov hypothesis states that the statistical representation of the turbulent energy spectrum follows a 5/3 power law for the length scale. We can integrate a portion of this spectrum, and so derive the dissipation rate, if we can identify two length scales that relate to the largest and smallest scales that the Doppler lidar observes and that these length scales lie within the inertial subrange of the turbulent spectrum. We show that this is directly related to the variance of the individual mean Doppler velocities (measured every profile) computed over a few minutes. This parameter is available whenever there is reasonable lidar signal, which, since there is strong backscatter from aerosol, is throughout the boundary layer, as well as in the presence of clouds. At Chilbolton we have an opportunity to compare these measurements with the same parameter derived from Doppler radar and also standard measurements of turbulence from a sonic anemometer at the surface.
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