Numerical simulation of the falling snow deposition over complex terrain

Abstract

Snow is one of the most dynamic natural elements on the Earth's surface, and the variations in its distribution in time and space profoundly affect the hydrological cycle, climate system, and ecological evolution as well as other natural processes. Most previous studies have paid less attention to the process determining the distribution of snow on the ground as a result of the effect of nonuniform mountain wind on the trajectories of snow particles. In this paper, we present a numerical study on the falling snow deposition process involving snow particles of mixed grain sizes over complex terrain. A three‐dimensional large‐eddy simulation code was used to predict the wind field by considering the fluid‐solid coupling effect, and the Lagrangian particle tracking method was employed to track the movement of each tracking snow particle. The grid resolution and model parameters were determined by the best fit with the field experiment, and the coupling effect between snow particles and wind field was found to be nonnegligible when the drifting snow occurred. In general, the preferential deposition on a single ridge showed a tendency from windward slope toward leeward slope with the increasing advection, while it was hard to describe the snow distribution over complex terrains with a unified deposition model due to the interaction of surrounding topographies and different atmospheric stabilities, and the particle tracking approach was substantially suitable for this issue. Our study significantly improved the understanding of the evolution of snow distributions at high levels of resolution.

High‐Resolution Large Eddy Simulation of Snow Accumulation in Alpine Terrain

“…Particle inertia is also not considered in our model contrary to Wang and Huang (). Atmospheric conditions in our case study differ also from the experiments of Mott and Lehning () and Wang and Huang (). In particular, the wind speed at crest level is higher in our experiments (typically 10–15 m s −1 ) compared to 7–11 m s −1 in Mott and Lehning () and 3–8 m s −1 in Wang and Huang ().…”

“…Atmospheric conditions in our case study differ also from the experiments of Mott and Lehning () and Wang and Huang (). In particular, the wind speed at crest level is higher in our experiments (typically 10–15 m s −1 ) compared to 7–11 m s −1 in Mott and Lehning () and 3–8 m s −1 in Wang and Huang (). Therefore, additional experiments will be required in the future with Meso‐NH/Crocus to investigate in details the influence of atmospheric conditions and modeling assumptions on near‐surface flow and subsequent snowfall deposition.…”

“…In LES mode, at 50 m grid spacing, part of the turbulent flow is explicitly resolved and influences the transport of snow aggregates by the advection scheme. In particular, vertical updrafts reduce their sedimentation and eventually modify their deposition as in Wang and Huang (). Despite the fact that Meso‐NH includes these effects, simulation CTRL at 50 m grid spacing shows only little evidence of preferential deposition of snowfall.…”

“…These results are consistent with Mott et al () and suggest that microphysical processes can influence small‐scale snowfall pattern in alpine terrain. Model results show little evidence of preferential deposition of snowfall at 50 m grid spacing contrary to previous studies in complex terrain (Lehning et al, ; Wang & Huang, ) due to different modeling approaches. The simulation including wind‐induced snow transport is characterized by a large increase in the variability of snow accumulation compared to the simulation without snow transport as shown on variograms.…”

Diffusion Process of Aerosol Particles with Different Diameter over Complex Terrain

“…The solution of wind field can be obtained based on the three-dimensional and fully compressible Navier-Stokes equations. The continuity and momentum conservation government equations can be written as [11] ( ) 0…”