Roughness length

In the logarithmic wind profile, the roughness length is the height at which wind speed is zero (indicated by z0). It provides an estimate of the average roughness elements of the surface. With vegetated surfaces, because the vegetation itself provides a certain roughness, the logarithmic wind profile goes to zero at a height equal to the displacement height plus the roughness length.

If not entered explicitly, EddyPro computes the roughness length as