Abstract:

Improvement in modeling dust emission is very important for predictions of sand-dust storms and climatic and ecological effects of soil-derived dust events. It has not been validated since overestimation from one classical scheme for modeling saltation threshold over roughness surfaces and underestimation from another scheme were found in terms of condition analysis. As a result， wind friction threshold velocities over find-medium sand surfaces with roughness elements with various aspect ratios （0.25-25）， densities （0.0072-0.51）， and porosities （0.15-0.75） were measured in a wind tunnel. It indicates that overestimation （the relative error around 80%-100%） and incorrectness from one scheme and underestimation （the relative error from -50% to -20%） from another scheme will occur as roughness length more than 1 mm. An improved scheme for modeling saltation threshold is proposed here， dependent on aspect ratio of individual element， the ratio of overall aerodynamic roughness to erodible roughness. The new scheme can be applied to predicate wind friction velocity over beds with sparse， medium and dense roughness elements， having very low relative error around \pm0.1 m·s^-1.

Key words: dust emission, wind friction threshold velocity, aspect ratio, aerodynamic roughness length, wind tunnel experiment