Change in the aerodynamic roughness height by saltating grains: Experimental assessment, test of theory, and operational parameterization

Data from an experiment at Owens Lake provided an opportunity to verify the validity of Raupach's formula that predicts the apparent roughness height at equilibrium with saltation during wind erosion episodes. In addition to that verification, a simplification of Raupach's formula is presented which allows the computation of the wind friction velocity affected by saltating sand grains without the need to measure the threshold wind friction velocity and to do iterative calculations. This method estimates the increase of the wind friction velocity Δ u * , above the nonsaltating wind friction velocity caused by the saltating grains: Δ u * = 0.3 [ U − U t ] 2 where U and U t are the wind speed and the threshold wind speed, respectively, at 10m.