Size distribution and optical properties of African mineral dust after intercontinental transport

Cyrielle Denjean (1, 2, 3) , Paola Formenti , Karine Desboeufs , Servanne Chevaillier , Sylvain Triquet , Michel Maillé , Mathieu Cazaunau , Benoit Laurent , Olga L. Mayol-Bracero , Pamela Vallejo , Mariana Quiñones , Ian E. Gutierrez-Molina , Federico Cassola , Paolo Prati , Elisabeth Andrews , John Ogren

1 Météo-France
2 LISA (UMR_7583) - Laboratoire Interuniversitaire des Systèmes Atmosphériques
3 IPSL (FR_636) - Institut Pierre-Simon-Laplace

The transatlantic transport of mineral dust from Africa is a persistent atmospheric phenomenon, clue for understanding the impacts of dust at the global scale. As part of the DUST Aging and Transport from Africa to the Caribbean (Dust-ATTACk) intensive field campaign, the size distribution and optical properties of mineral dust were measured in June-July 2012 on the east coast of Puerto Rico, more than 5000 km from the west coast of Africa. During the recorded dust events, the PM₁₀ (particulate matter 10 micrometers or less in diameter) concentrations increased from 20 to 70 µg m^-3. Remote sensing observations and modeling analysis were used to identify the main source regions, which were found in the Western Sahara, Mauritania, Algeria, Niger, and Mali. The microphysical and optical properties of the dust plumes were almost independent of origin. The size distribution of mineral dust after long-range transport may have modal diameters similar to those on the eastern side of the Atlantic short time after emission, possibly depending on height of transport. Additional submicron particles of anthropogenic absorbing aerosols (likely from regional marine traffic activities) can be mixed within the dust plumes, without affecting in a significant way the PM₁₀ absorption properties of dust observed in Puerto Rico. The Dust-ATTACk experimental data set may be useful for modeling the direct radiative effect of dust. For accurate representation of dust optical properties over the Atlantic remote marine region, we recommend mass extinction efficiency (MEE) and single-scattering albedo values in the range 1.1-1.5 m² g^-1 and 0.97-0.98, respectively, for visible wavelengths.

Keywords: aerosols; mineral dust; size distribution; single-scattering albedo; transport

Domains: Sciences of the Universe [physics]

Cyrielle Denjean, Paola Formenti, Karine Desboeufs, Servanne Chevaillier, Sylvain Triquet, et al.. Size distribution and optical properties of African mineral dust after intercontinental transport. Journal of Geophysical Research: Atmospheres, 2016, 121, pp.7117-7138. ⟨10.1002/2016JD024783⟩. ⟨insu-03737484⟩