Derivation of an observation-based map of North African dust emission

Amato T Evan,Owen Doherty,Stephanie Fiedler,Cyrille Flamant,Laurent Menut,Chun Zhao,Kerstin Schepanski

doi:10.1016/j.aeolia.2015.01.001

Abstract

Changes in the emission, transport and deposition of aeolian dust have profound effects on regional climate, so that characterizing the lifecycle of dust in observations and improving the representation of dust in global climate models is necessary. A fundamental aspect of characterizing the dust cycle is quantifying surface dust fluxes, yet no spatially explicit estimates of this flux exist for the World’s major source regions. Here we present a novel technique for creating a map of the annual mean emitted dust flux for North Africa based on retrievals of dust storm frequency from the Meteosat Second Generation Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the relationship between dust storm frequency and emitted mass flux derived from the output of five models that simulate dust. Our results suggest that 64 (±16)% of all dust emitted from North Africa is from the Bodele depression, and that 13 (±3)% of the North African dust flux is from a depression lying in the lee of the Air and Hoggar Mountains, making this area the second most important region of emission within North Africa.

Highlights

By mass, aeolian dust is the most pervasive aerosol on the planet, and the largest fraction of all global dust emission is in North Africa (e.g. Engelstaedter et al 2006, Ginoux et al, 2006)
3.1 Dust Emission Frequency We compare the spatial structure of dust emission frequency in the models and from Spinning Enhanced Visible and InfraRed Imager (SEVIRI) (Fig 1)
Here we have performed a statistical analysis of North African dust emission in five models and one satellite-based data set

Summary

Introduction

Aeolian dust is the most pervasive aerosol on the planet, and the largest fraction of all global dust emission is in North Africa (e.g. Engelstaedter et al 2006, Ginoux et al, 2006). African dust emission and transport is both affected by—and affects—the climate. Once transported over the Atlantic, direct radiative forcing by dust both warms the atmosphere and cools the surface (Evan and Mukhopadhyay 2010), contributing interannual to decadal scale variability of tropical Atlantic sea surface temperatures (Evan et al 2012) and exciting coupled modes of equatorial variability (Evan et al 2011). The influence of these aerosols on the climate system extends well beyond the direct radiative effect. Phosphorus and iron, all of which are required for primary productivity in oceanic and terrestrial ecosystems, and there is a large body of work demonstrating the importance of the atmospheric input of these elements via dust transported from western Africa (Das et al 2013; Okin et al 2011; Mahowald et al 2010)

Results

Discussion

Conclusion