Structural variations of sand-bearing airflow over dune at southeastern fringe of Tengger Desert

From the analytical results of observed data on sand transport rates at different positions of dune surface at southeastern fringe of Tengger Desert, it has been found that the vertical distribution of blown sand flux exhibits a noticeable variation when sand grains move upslope and downslope of dune surface under the action of wind force. Within the height of 20 cm above the sand surface, the vertical distribution of mass flux at different positions from toe to dune crest of stoss slope of sand dunes coincides with a single exponentially decaying law; while the vertical distribution of mass flux over the lee slope occurs as two variable zones, with the height of 8–12 cm as the dividing line, the sand transport rate below this height exponentially decreases with increasing height, but above this height decreases in a power function law. On the stoss slope, the relative sand transport rate in the upper layer of sand flow tends to decrease with the increasing wind velocity and the total sand transport rate towards the dune crest due to the shortened trajectory length of saltation sand grains moving upslope. On the lee slope, the increase in lift-off height and trajectory length of saltation sand grains moving downslope leads to the increase in relative sand transport rate in the upper layer of sand flow.