On scaling parameters for turbulence spectra within plant canopies

A nondimensional frequency f ∗ = nλ/U is suggested as having limited application for the intercomparison of turbulence spectra above and within plant canopies, where n is the frequency and U is the mean windspeed at height z. It is suggested that under appropriate conditions the length scale, λ, is constant within the canopy and is proportional to z— d above the canopy, where d is the zero-plane displacement. Temperature spectra for corn canopies appear to scale well with this approach. By example it is shown that variations in mean wind flow must be taken into account in order to avoid errors in the interpretation of spectra within a canopy.