Wind-sand flux stratification and saltation mechanisms

On Earth and on Mars, the processes of transport of sand and aleurite particles in the near-surface layer of the atmosphere, which, in particular, affect the vertical distribution of particles in the wind-sand flux, play an important role [1]. Using published measurements of particle concentration and flux density in the wind-sand flux, the variability of wind-sand flux stratification was analyzed. It is proposed to use piecewise exponential approximation of profiles and dimensionless height scale to quantify the variability of wind-sand flux concentration. It is shown that in a number of cases on the concentration profiles the breakpoints of profiles separating layers with different values of height scale are observed. The analysis of the results of experimental studies of particle lift-off velocity from the underlying surface in the wind-sand flux has shown that there are modes of low- and high-speed saltation. The dependences of the maximum height of the trajectory of a salting particle on its velocity of lift-off from the underlying surface were obtained. It is shown that the mechanism of classical (aerodynamic) saltation corresponds to the lower segment of the piecewise exponential concentration profile of saltation particles. The upper segment of the concentration profile can be caused by electrodynamic saltation (discharges on the underlying surface), which allows the occurrence of high-speed saltation particles in the wind-sand flux.

1.       Zhang Z. C., Dong Z. B., Qian G. Q. Field observations of the vertical distribution of sand transport characteristics over fine, medium and coarse sand surfaces //Earth Surface Processes and Landforms. – 2017. – Т. 42. – №. 6. – С. 889-902.