(29) 2D numerical simulation on migration and accumulation of snow bedforms
Keisuke Taniguchi (Nagoya Univ.) and Noritaka Endo (Kanazawa Univ.)
In cold region, snow barchans have been observed after snowstorm. Although
the planer forms of the snow barchans are similar and the cross-sectional profiles are flatter than those of sandy barchans. The difference can be caused by the phenomena acting on snow only such as sintering, which means cohesion between nearby snow particles.
We attempt to construct a numerical model of snow barchans including effect of sintering. The model is a cellular automata using probability of particle migration Pm. On the steep upslope and gentle downslope, the value of Pm becomes smaller. On the steep downslope, particle avalanche makes slipface regardless of the value of Pm. This model can simulate longitudinal profiles of the sandy barchans and collision between two barchans. Sintering is implemented as a coefficient multiplied by the probability of particle migration. The sintering coefficient α decreases with the time when the particle stayed at the position, that is, the snow particle become difficult to move from the cell. In this study, α (and also Pm) becomes zero when the particle does not move in 100 time steps. In each experimental run, snowfall was started every 20000 time steps. The numbers of falling snow particles in a snowfall event were varied between experimental runs (500, 2500, and 5000 particles). The resultant profiles after 500000 time steps were different between the cases whether the sintering effect was available or not. The barchan in sintering-free runs was large and had sharp slipface at the leeward side. On the other hand, in the cases of runs with sintering, the small barchans and mildly-sloped and longer-wavelength topographies were formed.