Wind-invariant saltation heights imply linear scaling of aeolian saltation flux with shear stress

TL;DR

This study demonstrates that saltation heights and particle speeds are wind-invariant, leading to a linear relationship between sand flux and shear stress, challenging previous nonlinear models in aeolian processes.

Contribution

The paper provides comprehensive field measurements showing saltation heights are constant with shear velocity, establishing a linear flux-shear stress relationship in aeolian sand transport.

Findings

Saltation heights are approximately constant with shear velocity.

Saltation flux scales linearly with shear stress.

Models should be revised to incorporate linear flux scaling.

Abstract

Wind-driven sand transport generates atmospheric dust, forms dunes, and sculpts landscapes. However, it remains unclear how the sand flux scales with wind speed, largely because models do not agree on how particle speed changes with wind shear velocity. Here, we present comprehensive measurements from three new field sites and three published studies, showing that characteristic saltation layer heights, and thus particle speeds, remain approximately constant with shear velocity. This result implies a linear dependence of saltation flux on wind shear stress, which contrasts with the nonlinear 3/2 scaling used in most aeolian process predictions. We confirm the linear flux law with direct measurements of the stress-flux relationship occurring at each site. Models for dust generation, dune migration, and other processes driven by wind-blown sand on Earth, Mars, and several other planetary surfaces should be modified to account for linear stress-flux scaling.