The Preferential Deposition of Snow in Complex Terrain: An LES Investigation

Abstract:

The drifting and blowing of snow due to atmospheric turbulence is a significant process in the context of hydrology, avalanche forecasting, and micrometeorology in alpine and polar regions. Spatial variability in snow deposition, erosion, and transport due to turbulence can lead to large spatial variations in snowpack depth, which is a determining factor for the timing of surface runoff. In mountainous regions, blowing snow can also lead to the formation of snow cornices on the leeward side of mountain peaks, thereby increasing avalanche risk. Despite the importance of snow transport, only a few studies that account for the effects of turbulent airflow on snow erosion, transport, and deposition over complex topography have been conducted to date.

In this study, we investigate the effects of turbulence on snow deposition and erosion in complex terrain using large eddy simulation (LES). A finite-volume Eulerian code for heavy particles is used to evolve the snow concentration field, and wall models are developed for the snow erosion and deposition fluxes. The surface topography is represented using an immersed boundary method following the direct forcing approach. We conduct simulations of snow deposition and erosion over realistic and idealized surface topography. An area source of particles is imposed near the top of the boundary layer. The relationships between the topography, turbulent flow structures, and snow erosion and deposition will be explored, and numerical considerations will be discussed.