Measurement and Modeling of Dust Emissions

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9972960GilliesThe emissions of dust sized mineral particles (50 micron diameter) from susceptible surfaces such as playas, alluvial fans, and washes in arid and semi-arid environments remains poorly understood. Under certain wind conditions these surfaces provide a significant source of particulates that can result in high background atmospheric dust loadings, or in some cases, major dust storms. Dust can be entrained by the shearing force of the wind and also ejected from the surface into the air stream by the ballistic impact of sand grains moving in saltation. Models that consider only saltation bombardment and an unlimited supply of upwind sediment do not adequately explain observed dust emission relationships, data scatter notwithstanding. PIs are proposing a combined portable wind tunnel and tower monitoring field study to quantify in situ the horizontal and vertical fluxes of coarse and fine particles as a function of wind parameters and surface characteristics. The collected database will also allow them to test the performance of three dust emission models that have been described in the literature with dust emission and surface characterization measurements. This knowledge is essential for revising or improving models that describe the emission process. A model that can accurately characterize dust entrainment rates and vertical flux is a practical necessity for predicting soil loss due to wind erosion and for estimating relative source contributions of mineral aerosols to the atmosphere.