Spectral models for the neutral atmospheric surface layer

Measurements of atmospheric turbulence spectra and cospectra at low heights in a rural atmospheric surface layer are presented. These show that at low frequencies the streamwise and transverse spectral densities vary in proportion to the square of the mean velocity. It is also shown that in the inertial sub-range the data is well matched by the Kolmogorov law with the Kolmogorov constant invariant with height. At intermediate frequencies the data exhibit spectral power-law regions with exponents that decrease with height. Spectral models are proposed which closely match these observed behaviours.