Modeling mineral dust emissions from the Sahara desert using new surface properties and soil database

Abstract

The present study investigates the mineral dust emissions and the occurrence of dust emission events over the Sahara desert from 1996 to 2001. Mineral dust emissions are simulated over a region extending from 16°N to 38°N and from 19°W to 40°E with a ° × ° spatial resolution. The input parameters required by the dust emission model are surface features data (aerodynamic roughness length, dry soil size distribution and texture for erodible soils), and meteorological surface data (mainly surface wind velocity and soil moisture). A map of the aerodynamic roughness lengths is established based on a composition of protrusion coefficients derived from the POLDER‐1 surface products. Soil dry size distribution and texture are derived from measurements performed on soil samples from desert areas, and from a soil map derived from a geomorphologic analysis of desert landscapes. Surface re‐analyzed meteorological databases (ERA‐40) of the European Centre for Medium range Weather Forecasts (ECMWF) are used. The influence of soil moisture on simulated dust emissions is quantified. The main Saharan dust sources identified during the 6‐year simulated period are in agreement with the previous studies based on in situ or satellite observations. The relevance of the simulated large dust sources and point sources (“hot spots”) is tested using aerosol indexes derived from satellite observations (TOMS Absorbing Aerosol Index and Infrared Dust Difference Index Meteosat). The Saharan dust emissions simulated from 1996 to 2001 range from 585 to 759 Tg a−1. The simulations show marked seasonal cycles with a maximum in summer for the western Sahara and in spring for the eastern Sahara. The interannual variability of dust emissions is pronounced in the eastern part of the Sahara while the emissions from the western Sahara are more regular over the studied period. The soil moisture does not noticeably affect the Saharan dust emissions, their seasonal cycle or their interannual variability, but it can partly control and limit the dust emissions in some parts of the northern desert margin, where the precipitation rates are higher. Our simulations also tend to confirm that the Sahara is the major terrestrial source of mineral dust.

Mapping the physico-chemical properties of mineral dust in western Africa: mineralogical composition

“…1 in Klaver et al, 2011). We do not necessary regard this as a problem, as the atmospheric dust load, both in short-and large-scale transport, is often due to a variety of sources active at the same time (Glaccum and Prospero, 1980;Reid et al, 2003;Formenti et al, 2003;Schepanski et al, 2007;Laurent et al, 2008;McConnell et al, 2008;Marticorena et al, 2010). Also, this supra-imposition, both in the vertical and in the horizontal, is what is actually seen by spaceborne sensors.…”

“…This is largely explained by the alternance of two meteorological regimes. Throughout the year, the "Harmattan", a north-eastern dry wind, is responsible for intense dust emissions in the arid areas of the Sahara and very efficient transport towards the Atlantic Ocean and across the Sahel (Pye, 1987;Sokolik et al, 2001;Laurent et al, 2008). Wintertime is also the biomass burning season south of approximately 13 • N , and mixing between dust and biomass burning aerosols might occur during southward transport .…”

“…In this paper, we relate the mineralogical and chemical composition of mineral dust from western Africa at emission or at most within 1-2 days from emission. The southern Sahara is the location of two of the most persistent dust sources on the global scale: the Bodélé depression in between the Tibesti and the Ennedi mountain chains in Chad and the areas in between the east of Mauritania, the north of Mali and the south of Algeria (Prospero et al, 2002;Laurent et al, 2008;Washington et al, 2006;Shao et al, 2011). These sources are relevant on the global scale as their emissions are transported across the Atlantic Ocean towards South and Central America (Reid et al, 2003;Koren et al, 2006;Ben-Ami et al, 2009.…”

Diapause as escape strategy to exposure to toxicants: response of Brachionus calyciforus to arsenic

“…Desert zones are commonly characterized by naturally high concentrations of minerals (Laurent et al 2008). The region including Southern Peru and Northern Chile is one of the driest places in the world.…”

Deciphering human–climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500years (Misten bog, Belgium)

“…North African deserts currently represent the largest worldwide source of mineral dust (Moulin et al, 1997), supplying $0.8 Â 10 9 tons per year of material transported in suspension in the atmosphere (Goudie and Middleton, 2001;Laurent et al, 2008). According to Vanderstraeten et al (2008), "the amount of airborne dust varies in accordance with the general and local meteorological situation, the complexity of relief forms, lithology and provenance (direction and distance from the source) of the dust".…”