Assessment of the African airborne dust mass over the western Mediterranean Sea using Meteosat data

Abstract

The mass of African dust present over the western Mediterranean during a transport episode from northwestern Africa, which occurred in early July 1985, is estimated using a desert aerosol model, an Earth‐atmosphere radiative transfer model and Meteosat visible channel data from 4 days running. Dust pixels are selected from Meteosat images, and their aerosol optical thickness is retrieved. A proportionality factor between aerosol optical thickness and atmospheric columnar aerosol loading is computed and applied to the dust pixels. The total mass of atmospheric particles over the basin is obtained by interpolation and spatial integration. The maximum aerosol optical thickness is 1.8. The maximum aerosol columnar loading is evaluated to be 2.3 g m−2. The integrated mass of particles present at a given time is estimated to raise up to about 0.6 × 1012 g at the maximum and the total mass of dust exported from Africa to be of the order of 1012 g. The method is carefully evaluated and uncertainties are discussed, with particular emphasis on the relationship between atmospheric dust mass and aerosol optical depth. The overall uncertainty on the total mass is roughly a factor ±3. In the absence of clouds it appears that the major uncertainty results from the lack of knowledge of the actual mass‐size distribution of suspended dust particles, pointing out the lack of relevant data on particles larger than 10 μm in diameter. A simple calculation based on results from both computations and simultaneous field measurements yields a net transfer velocity of particles from the dust layer of approximately 1 cm s−1.

Satellite perspective of aerosol intercontinental transport: From qualitative tracking to quantitative characterization

“…Although similar efforts have attempted using early satellite measurements more than two decades ago to estimate columnar atmospheric density and transport of desert dust, pollution, and fire smoke (Fraser, 1976;Mekler et al, 1977;Fraser et al, 1984;Sirocko and Sarnthein, 1989;Ferrare et al, 1990;Dulac et al, 1992), such estimates were subject to large uncertainties because of poor data accuracy and the lack of constraints on aerosol microphysical properties and vertical distributions. Most recently, EOS-era measurements have been used to estimate the trans-Atlantic transport of dust mass (Kaufman et al, 2005c;Koren et al, 2006), trans-Pacific transport of combustion aerosol mass (including industrial pollution and biomass burning smoke) and dust mass (Yu et al, 2012a), and cross-Mediterranean Sea transport of European pollution mass (Rudich et al, 2008).…”

“…Indeed, ever since meteorological satellites were put into orbit, satellite imagers have been used to detect the aerial extent and motion of large-scale aerosol plumes (e.g., Prospero and Carlson, 1972;Fraser, 1976;Lyons et al, 1978;Fraser et al, 1984;Chung, 1986;Ferrare et al, 1990;Dulac et al, 1992;J. Herman et al, 1997).…”

“…Herman et al, 1997). Some studies also attempted to go beyond simply detection with imagery to estimate columnar atmospheric density and mass transport of desert dust (Fraser, 1976;Mekler et al, 1977;Sirocko and Sarnthein, 1989;Dulac et al, 1992), sulfate pollution (Fraser et al, 1984), and fire smoke (Ferrare et al, 1990) using early satellite measurements. However, such estimates were subject to large uncertainties because of poor data accuracy and the lack of constraints on aerosol microphysical properties and vertical distributions.…”

Radiogenic isotopes for deciphering terrigenous input provenance in the western Mediterranean

“…Furthermore, at the scale of Quaternary climatic oscillations, eolian dust fluxes to the ocean may have been higher during stadial (Greenland Stadial, GS) than interstadial periods (Greenland Interstadial, GI: nomenclature based on INTIMATE group, Lowe et al., 2008), as the result of a general southward displacement of the ITCZ during boreal summer (e.g., Reader et al, 1999;Elenga et al, 2000). At present, the relative amount of dust input from the Sahara and Sahelian regions to the western Mediterranean is low and occurs in winter (Bergametti et al, 1989b;Dulac et al, 1992), while in the eastern Mediterranean it is favored during stronger summer westerlies (Jilbert et al, 2010). The terrigenous particles deflated from the surface depend on several factors including wind speed, atmospheric instability, height of the source area, particle size, particle exposure, soil moisture, vegetative cover, and mineralogical composition (e.g., deMenocal, 1995deMenocal, , 2004Moreno et al, 2006;Mulitza et al, 2008).…”

Operational remote sensing of tropospheric aerosol over land from EOS moderate resolution imaging spectroradiometer

“…Such methods have been successfully applied over water [Griggs, 1975[Griggs, , 1979; Mekler et al, 1977;Koepke and Quenzel, 1979] to produce an operational product from NOAA-AVHRR measurements [Rao et al, 1989;Ignatov et al, 1995]. Most of the remote sensing studies have been devoted to Saharan dust [Fraser, 1976;Carlson, 1979;Norton et al, 1980;Dulac et al, 1992;Jankowiak and Tanr& 1992]. Over the land, so far there has been no real attempt to retrieve aerosol at a global scale.…”