The feature of stratification in the blowing sand cloud

The profiles of particle concentration in saltation layer versus height are calculated, by the motion equations for a saltating grain in conjunction with different probability distribution functions of the vertical liftoff velocities of grains and an empirical expression of wind velocity. The numerical results demonstrated that the stratification phenomenon exists in the particle concentration profiles and showed increasing, saturating and decreasing features, respectively, when the probability distribution functions of liftoff velocities adopted in the calculation are similar to a normal distribution or a two-parameter gamma distribution. When the distribution function of liftoff velocities is taken as an exponential form, the profile of particle concentration decreases monotonically. A numerical simulation of mass flux of grains, performed by the model suggested in this paper, is in reasonable accordance with the measured data.