A review in snow saltation dynamics and its implications for the surface mass balance

Snow covered regions are frequently subjected to strong winds. This leads to the erosion of the snow surface and the occurrence of drifting and blowing snow events. To correctly predict and model these phenomena is of the utmost importance to assess snowpack stability and avalanche formation, as well as airborne snow sublimation and the resultant surface mass balance. Nonetheless, snow transport is frequently neglected or misrepresented in regional and mesoscale models. One of the main challenges is the accurate representation of snow transport close to the ground, where snow particles are transported by a process called saltation. This shallow layer comprises most of the horizontal mass flux and sets the lower boundary condition to model snow suspension clouds. A detailed study of snow saltation dynamics has been conducted using a Large-Eddy-Simulation flow solver coupled with a Lagrangian model for particle trajectories. The effect of particle size distribution and interparticle cohesion on particle speed, mass flux and surface friction velocity has systematically been investigated. The results show that snow cohesion and grain size heterogeneity can significantly increase saltation mass flux, specially at high friction velocities. Moreover, the agreement between simulation results and the saltation models typically used in large scale atmospheric models is highly dependent on the assumed bed characteristics. These findings can support the development of comprehensive saltation models that specifically take into account snow bed properties. These new saltation models can be implemented in mesoscale atmospheric models and have the potential to significantly improve surface mass balance predictions if grain-scale snow surface properties are available. This is possible in the newly developed CRYOWRF model which expands WRF’s surface modeling suite by including the advanced complexity, grain-scale snow model, SNOWPACK, along with a blowing snow scheme.