HR: 17:15h
AN: NG34A-06    [Abstracts]
TI: Scaling Properties of Fresh Snow Roughness
AU: * Manes, C
EM: manes@slf.ch
AF: Swiss Federal Institute for Snow and Avalanche Research, SLF, Fluelastrasse 11, Davos Dorf, 7260, Switzerland
AU: Guala, M
EM: guala@slf.ch
AF: Swiss Federal Institute for Snow and Avalanche Research, SLF, Fluelastrasse 11, Davos Dorf, 7260, Switzerland
AU: Bartlett, S
EM: bartlett@slf.ch
AF: Swiss Federal Institute for Snow and Avalanche Research, SLF, Fluelastrasse 11, Davos Dorf, 7260, Switzerland
AU: Loewe, H
EM: loewe@slf.ch
AF: Swiss Federal Institute for Snow and Avalanche Research, SLF, Fluelastrasse 11, Davos Dorf, 7260, Switzerland
AU: Luca, E
EM: egli@slf.ch
AF: Swiss Federal Institute for Snow and Avalanche Research, SLF, Fluelastrasse 11, Davos Dorf, 7260, Switzerland
AU: Lehning, M
EM: lehning@slf.ch
AF: Swiss Federal Institute for Snow and Avalanche Research, SLF, Fluelastrasse 11, Davos Dorf, 7260, Switzerland
AB: The roughness characteristics of snow covered surfaces are one of the key parameters influencing surface energy and mass transfer. In particular, finding relationships between surface roughness geometry and the aerodynamic roughness length z₀ is very desirable since z₀ is an important parameter in any numerical model designed to simulate processes of snow-atmosphere interaction. This study focuses on fresh snow roughness for which these relationships have not been developed yet. We present results coming from a series of experiments where fresh snow roughness was measured by means of image analysis. The data were then analysed by using a statistical approach based on the pth-order structure functions (p=1 to 5). We show how this simple technique allows to estimate important roughness length scales, including the average size of the falling snow particles, which can be an important parameter for snow drift models. Overall, it was noted that very often fresh snow roughness covers length scales much larger than the size of the falling snow particles. We argue that such scales are built up during snow fall and that their scaling behaviour is captured by a well known continuum growth model, i.e. the Kardar Parisi Zhang equation. This study represents the first step towards finding key roughness parameters to be used for the modelling of z₀. The use of the SLF cold wind tunnel will allow to find empirical relationships between such parameters and z₀. Preliminary results confirm that z₀ is mostly influenced by roughness scales larger than the falling snow particles.
DE: 4425 Critical phenomena
DE: 4440 Fractals and multifractals
DE: 4445 Nonlinear differential equations
DE: 4475 Scaling: spatial and temporal (1872, 3270, 4277)
DE: 4485 Self-organization
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting