Aerodynamic roughness of cultivated soil and its influences on soil erosion by wind in a wind tunnel

Serious soil erosion on cultivated soil by wind occurs extensively in semiarid regions. Surface roughness of cultivated soil that can be characterized by aerodynamic roughness length (z0) has important implications to wind erosion. Here we report the wind tunnel results of aerodynamic roughness lengths of five treated soils and soil wind erosion rates at different z0 and wind velocities. The results suggest that the diameter of the largest soil clods exposed and uniformly distributed on the soil surface is an important factor that controls aerodynamic roughness length. Negatively related to aerodynamic roughness length under provided wind velocity, wind erosion rate is a function of z0 and wind velocity for cultivated soil. Erosion rates decreased with aerodynamic roughness length especially when z0 is smaller than 0.1 cm and increase non-linearly with wind velocity, and that the smaller the aerodynamic roughness is, the more rapid that increase will be. Regression model comprising z0 and wind velocity is developed for predicting wind erosion rates for cultivated soil, which quantitatively reflects the influences of aerodynamic roughness length on soil erosion at various wind velocities.