HR: 13:40h
AN: NG43A-01    [Abstracts]
TI: Physically Based Numerical Model of Wind-Blown Sand Suggests Deficiencies in Classical Saltation Theory
AU: * Kok, J F
EM: jfkok@umich.edu
AF: Applied Physics Program, University of Michigan., 2477 Randall Laboratory, Ann Arbor, mi 48109-1120, United States
AU: Renno, N O
EM: nrenno@umich.edu
AF: Applied Physics Program, University of Michigan., 2477 Randall Laboratory, Ann Arbor, mi 48109-1120, United States
AU: Renno, N O
EM: nrenno@umich.edu
AF: Atmospheric, Oceanic, and Space Sciences, University of Michigan., 2455 Hayward St, Ann Ar bor, MI 48109, United States
AB: Wind-blown sand, or ‘saltation,' is an important geological process, as well as the primary source of atmospheric dust aerosols. Despite its importance in geological and atmospheric processes, saltation is not well understood yet. We present here the first physically based model of saltation that is rigorously tested with data from field measurements. The model explicitly simulates the trajectories of sand grains moved by wind, calculates the wind profile resulting from the transfer of wind momentum to saltating grains, and accounts for the impact of saltating grains with the soil bed, including the ejection of surface grains. The results of the model, verified by field measurements of saltation mass flux profiles, reveal some surprising deficiencies in the classical understanding of saltation. Model results strongly suggest that the common assumption that particle speed scales linearly with the wind shear velocity (Bagnold, 1941) is incorrect. Moreover, the common hypothesis that the fluid shear stress at the surface remains at the threshold value for particle entrainment results in large discrepancies between model results and experiments. This classical hypothesis, proposed by Owen (1964), is thus probably incorrect. Our model is general and can be adapted to study saltation under a variety of physical conditions, including on sloped terrain such as sand dunes, and on other planetary bodies such as Mars, Venus, and Titan.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 1622 Earth system modeling (1225)
DE: 1631 Land/atmosphere interactions (1218, 1843, 3322)
DE: 3307 Boundary layer processes
DE: 3311 Clouds and aerosols
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting