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Linear scaling of aeolian saltation flux with wind shear stress

Raleigh L. Martin, Jasper F. Kok
University of California, Los Angeles, Los Angeles, CA, USA

Wind-driven sand transport generates atmospheric dust and sculpts dunes, yet aeolian models generally perform poorly. A paradigm underlying most such models is that particle velocity increases linearly with wind shear velocity, resulting in the long-established 3/2 scaling of saltation flux with wind shear stress. Here, we present comprehensive measurements at three field sites showing that saltation heights, and thus particle velocities, remain approximately constant with shear velocity. This implies a linear dependence of saltation flux on wind shear stress, which we confirm by direct observation of the stress-flux relationship at all sites. Our observations support the hypothesis that impact-dominated particle entrainment buffers changes to saltator trajectories in aeolian saltation, which contrasts with fluid-lifting entrainment in fluvial bed load. This contrast suggests the importance of determining the particle entrainment mechanism when formulating aeolian saltation models for Mars and other planetary bodies.