A source term model for drifting snow based on the assumption of local equilibrium saltation

Abstract

This paper presents a source term model to predict the drifting snow near the ground, which is based on the assumption of local equilibrium saltation. The features of the one way coupled conservation equation for the snow transport in the Eulerian reference frame are examined through calibrating the input sources versus output snow concentrations by using a numerical experiment method. The target source term for the snow concentration compensation due to the surface erosion is derived with the help of a semi-empirical mass flow rate of the equilibrium saltation and the calibration results under different friction velocities, threshold friction velocities and settling velocities. With the validation on the equilibrium saltation above an open and flat snow bed, rational saltation mass concentration is solved. Using this source term model, good adaptabilities for various wind and snow conditions are confirmed. With the application to the non-equilibrium saltation around a cube, intuitively plausible distributions of the snow concentration near the ground and the transient topography changes in the snow surface are predicted through a time dependent dynamic mesh solution. The non-equilibrium properties of the drifting snow revealed in space and time are further evidenced by the spatial distributions and time histories of the friction velocity and the saltation snow concentration