Modelling Small-Scale Drifting Snow with a Lagrangian Stochastic Model Based on Large-Eddy Simulations

Observations of drifting snow on small scales have shown that, in spite of nearly steady winds, the snow mass flux can strongly fluctuate in time and space. Most drifting snow models, however, are not able to describe drifting snow accurately over short time periods or on small spatial scales as the...

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Bibliographic Details
Published in:Boundary-layer meteorology 2014-10, Vol.153 (1), p.117-139
Main Authors: Groot Zwaaftink, C. D., Diebold, M., Horender, S., Overney, J., Lieberherr, G., Parlange, M. B., Lehning, M.
Format: Article
Language:English
Subjects:
Aerodynamics
Atmospheric Protection/Air Quality Control/Air Pollution
Atmospheric Sciences
Convection, turbulence, diffusion. Boundary layer structure and dynamics
Drift
Earth and Environmental Science
Earth Sciences
Earth, ocean, space
Exact sciences and technology
External geophysics
Flux
Lagrange multiplier
Large eddy simulation
Marine
Mathematical models
Meteorology
Shear stress
Small scale
Snow
Stochasticity
Turbulent flow
Wind
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Summary:Observations of drifting snow on small scales have shown that, in spite of nearly steady winds, the snow mass flux can strongly fluctuate in time and space. Most drifting snow models, however, are not able to describe drifting snow accurately over short time periods or on small spatial scales as they rely on mean flow fields and assume equilibrium saltation. In an attempt to gain understanding of the temporal and spatial variability of drifting snow on small scales, we propose to use a model combination of flow fields from large-eddy simulations (LES) and a Lagrangian stochastic model to calculate snow particle trajectories and so infer snow mass fluxes. Model results show that, if particle aerodynamic entrainment is driven by the shear stress retrieved from the LES, we can obtain a snow mass flux varying in space and time. The obtained fluctuating snow mass flux is qualitatively compared to field and wind-tunnel measurements. The comparison shows that the model results capture the intermittent behaviour of observed drifting snow mass flux yet differences between modelled turbulent structures and those likely to be found in the field complicate quantitative comparisons. Results of a model experiment show that the surface shear-stress distribution and its influence on aerodynamic entrainment appear to be key factors in explaining the intermittency of drifting snow.
ISSN:0006-8314
1573-1472
DOI:10.1007/s10546-014-9934-2