Wind shear with a blowing‐sand boundary layer

In aeolian science, it is thought that the velocity profile of a wind modified by the presence of a cloud of saltating particles bears significant information about the movement of the saltating grains. In this study, we obtained detailed wind‐velocity profiles in the presence of a cloud of saltating particles using a state‐of‐the‐art non‐intrusive measurement technique (particle image velocimetry). The convex‐upward velocity profiles of sand‐laden wind resulted in varying wind shear stress as a function of height. The variation with height in wind‐shear stress was characterized by curves with a maximum shear stress at some height above the surface. The maximum shear stress was well correlated with the sand transport rate and their relationship was close to the Bagnold's transport equation that relates transport rate to shear velocity. Our results suggest that the best estimate of shear velocity during saltation is provided by the maximum shear stress.