Wind Fluctuation over Semi-fixed Longitudinal Dune in Gurbantunggut Desert

Field measurement of wind direction at 2-m height and wind velocity at five heights(0.2 m,0.4 m,0.6 m,1 m and 2 m) over semi-fixed longitudinal dune was conducted in Gurbantunggut Desert in order to understand the characteristics of fluctuation of wind direction and velocity on dune surface.The dune morphology affects both the change of average wind velocity and fluctuation of wind direction and velocity.The average wind velocity increases up the stoss slope and decreases down the lee slope.With increasing of incidence angle,the change range of average wind velocity and fluctuation of absolute wind velocity increase,and the fluctuation increases with height.The fluctuation of relative wind velocity is greater on the lee slope than on the stoss slope because of existence of whirlpool on the lee slope.The fluctuation of wind direction on the lee slope is far stronger than on the stoss slope,and with the reduction of incidence angle,the deflexion of wind direction enhances,and the effect of the whirlpool weakens.