Estimated and Measured Roughness Parameters for a Pine Forest

Abstract

A topographic map of the upper surface of the canopy of a red pine (Pinus resinosa) plantation was drawn from 275 canopy heights measured on a grid of 0.9 ? 1.5 m. The distribution of heights was approximately normal, with a mean of 11.6 m; and a standard deviation of 1.6 m; this is an improved method of designating stand height. The roughness parameter s0 and zero-plane displacement of the stand were estimated from the canopy map data, using both Kung's logarithmic formula and Lettau's equation for obstacle size and shape. These values were compared with measured s0 and d from wind and temperature profiles in near-neutral conditions. Lettau's formula, assuming the obstacles were uniform square-packed paraboloids, gave s0=138cm and d10.6 m. Kung's formula gave s0=75 cm and d=9.7 m. Measured profiles gave a median s0=100 cm after d was fixed at its median value of 9.6 m.