Size‐Independent Susceptibility to Transport in Aeolian Saltation

Abstract

AbstractNatural wind‐eroded soils contain a mixture of particle sizes. However, models for aeolian saltation are typically derived for sediment bed surfaces containing only a single particle size. To nonetheless treat natural mixed beds, models for saltation and associated dust aerosol emission have typically simplified aeolian transport either as a series of noninteracting single particle size beds or as a bed containing only the median or mean particle size. Here we test these common assumptions underpinning aeolian transport models using measurements of size‐resolved saltation fluxes at three natural field sites. We find that a wide range of sand size classes experience “equal susceptibility” to saltation at a single common threshold wind shear stress, contrary to the “selective susceptibility” expected for treatment of a mixed bed as multiple single particle size beds. Our observation of equal susceptibility refutes the common simplification of saltation as a series of noninteracting single particle sizes. Sand transport and dust emission models that use this incorrect assumption can be both simplified and improved by instead using a single particle size representative of the mixed bed.