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

TLDR

Dust emission is governed by soil particle size distribution and surface roughness, which determine erosion thresholds and wind friction velocity. The study develops a soil‑derived dust emission scheme to explicitly represent desert dust sources in atmospheric transport models. The scheme computes threshold wind friction velocity from soil size and roughness, applies a horizontal flux equation to derive dust flux as a clay‑dependent fraction of total flux, and validates each step against experimental data. The resulting dust production rates vary with soil size, roughness, and wind friction, and the model reproduces experimental fluxes more accurately than prior simulations, reducing uncertainty.

Abstract

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.