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Experimental Protocol to Investigate Particle Aerosolization of a Product Under Abrasion and Under Environmental Weathering

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Are vegetation-related roughness changes the cause of the recent decrease in dust emission from the Sahel?

Sophie M Cowie¹, Peter Knippertz¹, John H Marsham²

¹Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds Leeds, UK, LS2 9JT.

Geophysical Research Letters

|March 31, 2015

Summary

This summary is machine-generated.

Increased vegetation in the Sahel has reduced wind speeds, causing a significant drop in North African dust emissions. This finding highlights vegetation

Keywords:

Sahel decadal trends dust emission roughness length vegetation wind-speed

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Area of Science:

Atmospheric Science
Climate Science
Environmental Science

Background:

Observed dramatic downward trend in North African dustiness and transport since the 1980s.
Previous understanding of causes was limited by sparse observational data.
Existing explanations focused on soil moisture and vegetation impacts on dust emission thresholds.

Purpose of the Study:

To identify the primary cause of the observed decrease in North African dust emission.
To investigate the role of vegetation-related surface roughness changes.
To assess the contribution of other factors like turbulence, evapotranspiration, and large-scale circulation.

Main Methods:

Utilized novel diagnostic tools applied to long-term surface observations.
Analyzed the relationship between vegetation cover, surface wind speeds, and dust emission.
Compared findings with existing data sets and methods for dust transport.

Main Results:

A decrease in surface wind speeds, attributed to increased vegetation-related roughness in the Sahel, is the most likely cause of reduced dust emission.
Changes in turbulence, evapotranspiration, and large-scale circulation are secondary contributors.
Results contradict the hypothesis that soil moisture and vegetation cover directly alter emission thresholds as the dominating effect.

Conclusions:

Vegetation-related roughness changes are the primary driver of the recent decrease in Sahelian dust emission.
Findings align with the global phenomenon of surface wind speed reduction ('stilling').
Emphasizes the importance of incorporating vegetation-induced roughness in climate models and understanding land-use impacts on the Sahelian climate.