Estimation of Surface Roughness Length and Displacement Height from Single-Level Sonic Anemometer Data

Abstract

The problem of finding joint values of both the roughness length z0 and the displacement height d is discussed in the context of the Monin?Obukhov similarity law for the wind speed profile. When focused on single-level datasets from one sonic anemometer (i.e., wind velocity, Reynolds stress, and sensible heat flux datasets at one height), it has been shown that this problem can be reduced to a simpler least squares procedure for one variable only. This procedure is carried out over a proper function of the data, representing the relative uncertainty of the roughness length, σz0/z0. This function is minimized with respect to d, giving a direct estimate of d, z0, and their statistical uncertainty. The scheme is tested against two datasets in homogeneous and nonhomogeneous surface conditions.