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lies in the physical understanding of the dust released by the impact of saltating
grains, which has implications for the capability of dust emission models to predict
the size distribution of the emitted dust. Different models predict different dust
size distributions as a function of
U
*
and of the soil properties. Available field
experimental data of size-resolved dust emission fluxes are not sufficient to estimate
these dependences correctly. Thus, a rigorous intercomparison of the dust emission
models remains to be done, based on experiments of size-resolved dust emission
fluxes where all input parameters are experimentally determined and independently
constrained. Among the required input data, specific attention must be paid to the
determination of the undisturbed and fully disturbed soil size distributions. Such
an experiment should also cover the largest possible range of dust particle sizes.
As a matter of fact, dust emission flux measurements, especially those resolved in
size, remain a difficult task. The experimental determination of emission fluxes is
generally based on the method of gradients, which has theoretical limitations (Shao
2008
) and is often difficult to implement in the field. Alternatives such as eddy-
covariance methods (Porch and Gillette
1977
; Fratini et al.
2007
)couldhelpto
limit the uncertainties associated with the gradient method to provide more reliable
size-resolved dust fluxes. Differences in the prediction of the emitted dust size
distribution may also be explained by the way in which saltation processes are
modelled (Kok
2011b
). Revisiting the description of the saltation processes with
respect to dust emission may significantly improve the capability of dust emission
models to simulate the dust size distribution and its dependence on soil properties
and dynamical conditions. Lastly, a better quantification of dust emission in semi-
arid areas is required, which implies further efforts in the description of the impact
of vegetation and cultivation on dust emission processes. Indeed, the contribution
of anthropogenic sources to the total atmospheric dust load and the evolution of
the dust emissions in semi-arid areas resulting from climate changes are still very
uncertain.
References
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intensities and aerosol distributions in source areas. J Geophys Res 106:18075-18084
Alfaro SC, Gaudichet A, Gomes L, Maillé M (1997) Modeling the size distribution of a soil aerosol
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Alfaro SC, Gaudichet A, Gomes L, Maillé M (1998) Mineral aerosol production by wind erosion:
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Alfaro SC, Rajot JL, Nickling W (2004) Estimation of PM20 emissions by wind erosion: main
sources of uncertainties. Geomorphology 59:63-74
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