Low-wavenumber spectral characteristics of velocity and temperature in the atmospheric surface layer

The structure of atmospheric surface layer turbulence at low wavenumbers was analyzed using 56 Hz triaxial velocity and temperature measurements above a uniform dry lake bed. A key feature of this experiment was the small roughness length of the surface that resulted in a small roughness Reynolds number. Under near-neutral atmospheric stability conditions, a -1 power law was observed in both measured velocity and temperature spectra. The wavenumber at which the -1 power law terminates and the -5/3 power law commences was derived as a function of the Kolmogorov and von Karman constants. Good agreement between the predicted and the measured transition wavenumber from -1 to -5/3 was noted for fully rough-flow conditions. -from Authors