A soil-derived dust emission scheme has been designed to provide an explicit representation of the desert dust sources for the atmospheric transport models dealing with the simulation of the desert dust cycle. Two major factors characterizing the erodible surface are considered: (1) the size distribution of the erodible loose particles of the soil which controls the erosion threshold and the emission strength and (2) the surface roughness which imposes the efficient wind friction velocity acting on the erodible surface. These two parameters are included in a formulation of the threshold wind friction velocity by adapting a size-dependent parameterization proposed by Iversen and White (1982) and by applying to the rough erodible surfaces a drag partition scheme derived from Arya (1975). This parameterization of the threshold friction velocity has been included in an horizontal flux equation proposed by White (1979). This allows to attribute a specific production rate to each soil size range for each type of surface. The dust flux F is then considered as a fraction of the total horizontal flux G, the value of the ratio F/G being imposed, at this time, by the soil clay content. In summary, the computed mass fluxes depend on the soil size distribution, the roughness lengths, and the wind friction velocity. The different steps of this scheme have been independently validated by comparison with relevant experimental data. Globally, the agreement is satisfying, so that the dust fluxes could be retrieved with less uncertainties than those observed in previous simulations of the desert dust cycle.

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Modeling the atmospheric dust cycle: 1. Design of a soil-derived dust emission scheme

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols This article presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices We also discuss the physics of wind-blown sand and dune formation on Venus and Titan

/pdf/the-physics-of-wind-blown-sand-and-dust-4kx7jekt62.pdf

The physics of wind-blown sand and dust

The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.

/pdf/the-physics-of-wind-blown-sand-and-dust-4ggy9vm6xy.pdf

17 ± 2 Tg; and optical depth at 0.63 mm, 0.030 ± 0.004. This emission, burden, and optical depth are significantly lower than some recent estimates. The model underestimates transport and deposition of East Asian and Australian dust to some regions of the Pacific Ocean. An underestimate of long-range transport of particles larger than 3 mm contributes to this bias. Our experiments support the hypothesis that dust emission ‘‘hot spots’’ exist in regions where alluvial sediments have accumulated and may be disturbed. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0322 Atmospheric Composition and Structure: Constituent sources and sinks; 4801 Oceanography: Biological and Chemical: Aerosols (0305); 5415 Planetology: Solid Surface Planets: Erosion and weathering; KEYWORDS: mineral dust aerosol, aerosol climatology, mineral deposition, aerosol scavenging, saltation sandblasting, ecosystem fertilization

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Mineral Dust Entrainment and Deposition (DEAD) model: Description and 1990s dust climatology

Global review and synthesis of trends in observed terrestrial near-surface wind speeds; implications for evaporation

Saltation is the wind-driven, hopping motion of sand-sized particles across an erodible surface. This mode of motion not only transports sand and similar materials in its own right but can also initiate (through bombardment of the surface) the entrainment and subsequent transport by suspension of smaller dust particles. In this paper, we report a wind tunnel study of the effect of saltation bombardment on dust entrainment. The technique is to allow sand grains to saltate from an upwind sand source onto a bed of dust particles. The experiment confirms that the ejection of dust particles by saltation bombardment (as opposed to detachment of dust particles by aerodynamic forces) is the principal mechanism for the natural entrainment of dust by wind. The data are used to examine the dependence of the dust emission flux Fa (mass per unit ground area per unit time) upon the friction velocity u,; it is found that Fa is closely proportional to the streamwise flux of saltating sand grains, which in turn is approximately proportional to u, 3. At a given u,, Fa increases as the size of the bombarding sand grains increases. On the basis of the hypothesis that Fa is proportional to the kinetic energy flux of the saltating sand grains, we derive theoretically the result that Fa scales with the streamwise saltating sand grain flux and thence approximately with u, 3, as observed in this experiment.

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P. A. Findlater

Papers

Effect of Saltation Bombardment on the Entrainment of Dust by Wind