Turbulence and Wind Speed Spectra within a Japanese Larch Plantation

Abstract

Mean horizontal wind speed profiles within and above a plantation of Japanese larch were obtained. A log-profile analysis of above-vegetation wind speeds yielded a wide range of values for the roughness length parameter z0 and the zero-plane displacement height D. The computed Eulerian space scale of turbulence within the vegetation showed deeper penetration of large eddies after needle fall and during high winds. Power spectra showed that at the base of the plantation most of the variation in wind speed was associated with gusts of about 100 m wavelength. Power spectra at the most dense portion of the plantation canopy showed considerable modification due to the tree spacing.