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Modeling snow saltation: the effect of grain size and interparticle cohesion
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  • Daniela Brito Melo,
  • Varun Sharma,
  • Francesco Comola,
  • Armin Sigmund,
  • Michael Lehning
Daniela Brito Melo
Ecole Polytechnique Fédérale de Lausanne

Corresponding Author:[email protected]

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Varun Sharma
École Polytechnique Fédérale de Lausanne
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Francesco Comola
University of California, Los Angeles
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Armin Sigmund
Ecole Polytechnique Fédérale de Lausanne
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Michael Lehning
EPFL and SLF Davos
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The 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 (LES) 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.
16 Jan 2022Published in Journal of Geophysical Research: Atmospheres volume 127 issue 1. 10.1029/2021JD035260