Abstract
AbstractThe surface of the Earth is snow‐covered at least seasonally over large areas. This snow surface is highly dynamic, particularly under the influence of strong winds. The motion of snow particles driven by the wind not only changes the snow cover but has important consequences for the atmosphere in that it adds mass and moisture and extracts heat. Large scale meteorological and climatological models neglect these surface dynamics or produce conflicting results from too simplified process representation. With recent progress in the detailed understanding of the saltation process, in particular with respect to sand saltation, and the advancement of numerical models, we can systematically investigate the influence of snow properties on saltation. This contribution uses a Large Eddy Simulation model with full surface particle dynamics to investigate how snow cohesion and size distribution influence saltation dynamics and in particular the total mass flux. The model reproduces some known characteristics of the saltation system such as a focus point or a constant near surface particle speed. An interesting result is that cohesion and grain size heterogeneity can increase the overall saltation mass flux at high friction velocities. Moreover, some simplified models agree reasonably well with the simulations for given bed characteristics, while others clearly do not. These results are valid for continuous saltation while intermittent saltation, which often occurs in nature, needs further investigation. In order to successfully parameterize saltation in large scale models, progress must be made in correctly representing snow surface properties in these models, in particular cohesion.
Highlights
Wind erosion of snow covered surfaces is frequently observed in alpine and polar regions
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)
Saltation models based on the Discrete Element Method (DEM) simulate these complex interactions, but are not suitable for simulating particle transport over large computational domains (Comola, Gaume, et al, 2019; Durán et al, 2012; Pähtz et al, 2015)
Summary
Wind erosion of snow covered surfaces is frequently observed in alpine and polar regions. Aksamit and Pomeroy (2018) have observed that both low- and high-frequency turbulence structures impact drifting snow dynamics These findings strongly support the need for an accurate description of the turbulent flow field when modeling the wind-particle interaction intrinsic to snow saltation. A detailed study on the effect of grain size and interparticle cohesion on the vertical profiles, integrated mass flux and surface friction velocity is performed To this end, the properties of the granular bed are varied in a systematic way in a suite of simulations, which cover a range of wind velocities. This article shows the potential of LES-based models coupled with state-of-the-art splash functions to simulate steady state saltation and to improve our understanding of saltation dynamics It sheds light onto the relative importance of grain size and interparticle cohesion for snow saltation characteristics.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
