Modeling snow saltation: the effect of grain size and interparticle cohesion

Abstract

Wind erosion of snow covered surfaces is frequently observed in alpine and polar regions. Snow transport leads to the formation of bedforms, intensifies snow sublimation and modifies the microstructure of surface snow layers. Moreover, the interaction between the wind field and the complex topography creates regions of enhanced snow erosion and deposition, which greatly contributes to snow height heterogeneity. In alpine regions, these processes are of great importance for water management and avalanche risk assessment (Lehning et al., 2008). In Antarctica, snow transport is enhanced by the katabatic winds, dominating large areas from the inner plateau to the coast, and clouds of blowing snow particles with a height of hundreds of meters can be observed (Palm et al., 2017).The aeolian transport of snow occurs at different heights above the ground. The terms drifting snow and blowing snow are commonly used to indicate, respectively, the movement of snow particles close to the surface (up to ∼2 m height) and the movement of smaller snow particles transported at high elevations. Three transport modes (creep, saltation and suspension) are commonly distinguished during snow transport events (Bagnold, 1941). The rolling and sliding of snow grains along the surface is defined as creep. Creeping particles are typically too large and heavy to be lifted by the flow. During drifting snow events, their motion is mainly driven by impacting particles. Saltation refers to the ballistic motion of particles close to the ground. Particles in saltation generally hit the ground with enough kinetic energy to hop again (rebound) or eject other particles on the bed (splash). They are mostly concentrated in the first 10 cm above the surface and the ensemble of saltating particles constitute the saltation layer. Suspension refers to the motion of smaller snow particles transported above the saltation layer. They mainly follow the wind flow and travel great distances before being deposited on the ground or sublimate.At low wind speeds, the mass flux in saltation is greater than the mass flux of suspended particles (Gordon et al., 2009;Nishimura & Nemoto, 2005). At high wind speeds, snow transport in suspension becomes relevant and is currently simulated in mesoscale models by advection-diffusion equations (

Environmental Conditions for Snow Cornice Formation tested in a Wind Tunnel

“…5. For all wind conditions, the mass flux exponentially decreases with increasing height, which is consistent with previous results (Takeuchi, 1980;Lehning et al, 2002;Kosugi et al, 2008;Lü et al, 2012;Crivelli et al, 2016;Melo et al, 2022). It also increases overall with the increasing wind speed.…”

Towards a fully physical representation of snow on Arctic sea ice using a 3D snow-atmosphere model

“…Therefore, we believe that this approach could provide an advantage when studying snow cover on Arctic sea ice in a warming climate including warm air intrusions in winter, as well as during warmer months. In a saltation model inter-comparison, Melo et al (2021) could show that with respect to integrated mass flux, the model from Doorschot and Lehning (2002) performed well for the tested specific bed types.…”

“…When this threshold is exceeded, grains may start to creep, going into saltation or suspension mode when wind speeds are higher (Bagnold, 1941;R. A. Schmidt, 1980;Melo et al, 2021).…”

“…The saltating mass flux itself is computed with the model from Pomeroy and Gray (1990). However, (Melo et al, 2021) showed in a model-intercomparison that this model underestimated the integrated mass flux significantly. Liston et al (2018Liston et al ( , 2020 modeled snow transport in a very detailed way with their SnowModel, with statistically computed 2D-wind fields (Liston & Elder, 2006b) and a bulk-density snow cover representation.…”

Introducing CRYOWRF v1.0: multiscale atmospheric flow simulations with advanced snow cover modelling

“…It is important to note that parameterizations of saltation for large-scale models are an active area of research both with new field measurement campaigns (Sigmund et al, 2022) and theoretical studies (Melo et al, 2021). CRYOWRF is designed to rapidly include newer parameterizations, and future studies aim to study the implications of these updates on larger-scale phenomena.…”