Airborne observations of mineral dust over western Africa in the summer Monsoon season: spatial and vertical variability of physico-chemical and optical properties 1LISA, CNRS, UMR7583 Université Paris Est Créteil et Université Paris Diderot Institut Pierre Simon Laplace, Créteil, France
06 Jul 2011
2BIOEMCO, IRD, UMR211, Paris, France
3Laboratoire d'Aérologie, Université de Toulouse/CNRS 5560, Toulouse, France
Received: 31 December 2010 – Published in Atmos. Chem. Phys. Discuss.: 24 January 2011 Abstract. We performed airborne measurements of aerosol particle concentration,
composition, size distribution and optical properties over Western Africa in
the corridor 2–17° N and 3–5° E. Data were collected on board the
French ATR-42 research aircraft in June–July 2006 as part of the African
Monsoon Multidisciplinary Analysis (AMMA) intensive field phases in
June–July 2006 using the AVIRAD airborne aerosol sampling system.
Revised: 06 June 2011 – Accepted: 22 June 2011 – Published: 06 July 2011
The aerosol vertical distribution was documented on an almost daily basis.
In particular, the vertical distribution of mineral dust emitted locally by
Mesoscale Convective Systems (MSC) was distinguished from that of mineral
dust that was transported from the Saharan by the African Easterly Jet
(AEJ). Mineral dust emitted in the Sahel by convection-driven erosion was
mostly confined in the boundary layer. One episode of injection of Sahelian
mineral dust in the AEJ was observed. The elemental composition was found to
be an element of difference between episodes, whereas the volume size
distribution was more uniform.
For non-mixed dust, the single scattering albedo ranged between 0.88–0.93
at 370 nm and between 0.91–0.99 at 950 nm, lower values being observed for
Sahelian dust. In correspondence, the imaginary part of the complex
refractive index varied between 0.002–0.004 at 370 nm and between
0.001–0.002 at 950 nm.
Citation: Formenti, P., Rajot, J. L., Desboeufs, K., Saïd, F., Grand, N., Chevaillier, S., and Schmechtig, C.: Airborne observations of mineral dust over western Africa in the summer Monsoon season: spatial and vertical variability of physico-chemical and optical properties, Atmos. Chem. Phys., 11, 6387-6410, doi:10.5194/acp-11-6387-2011, 2011.