Surface roughness

From Glossary of Meteorology

surface roughness

The geometric characteristic of a surface associated with its efficiency as a momentum sink for turbulent flow, due to the generation of drag forces and increased vertical wind shear.

In micrometeorology, the surface roughness is usually measured by the roughness length, a length scale that arises as an integration constant in the derivation of the logarithmic wind profile relation. In neutral stability the logarithmic wind profile extrapolates to zero wind velocity at a height equal to the surface roughness length. Several formulas exist to parameterize this length scale as a function of the roughness element geometry (e.g., spacing and silhouette area). Tabulated values for various surface types are published in most micrometeorological texts.
See momentum flux, zero-plane displacement.

Stull, R. B. 1988. An Introduction to Boundary Layer Meteorology. 666 pp.