12.5
Mass transport in snow saltation
PAPER WITHDRAWN
Judith J. J. Doorschot, Swiss Federal Institute for Snow and Avalanche Research, Davos Dorf, Switzerland; and M. Lehning
Wind transport of snow has a major impact on the avalanche hazard, and on the ecology and hydrology in mountainous environments. Saltation is the wind transport of granular material that takes place close to the ground, where particles follow ballistic trajectories. A numerical model is developed, which computes the mass flux in saltation on the basis of particles trajectories and conservation of momentum. The feedback of saltating particles on the turbulent airflow is parameterised. Model results as well as theoretical arguments indicate that for snow, contrary to sand, aerodynamic entrainment (opposed to rebound) is the main process that sets particles in motion. The model formulations are also applicable to slopes; it is demonstrated that the mass flux over downhill slopes increases sharply when a critical slope angle is reached. Field measurements of mass transport in snow saltation were done to validate the model results. Also measurements of the threshold friction velocity for snow drift were made; the demonstrate that the threshold conditions are strongly dependent on the snow characteristics. Furthermore, he measurement results show that the short-term fluctuations of the turbulent shear stress need to be taken into account in the numerical mass flux simulations.
Session 12, Coupled Surface-BL studies
Thursday, 18 July 2002, 10:30 AM-12:30 PM
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