1. J.L. Rajot (1,2), B. Marticorena (2), P. Formenti (2), S. Alfaro (2), B. Chatenet (2), F. Dulac (2,3), K. Desboeufs (2) S. Caquineau (4), M. Maille (2) G. Bergametti (2), A. Gaudichet (2), A.O. Manga (5), A. Diallo (6), L. Menut (2), G. Cautenet (7) (1) Institut de Recherche pour le Développement (IRD), UR 049 ECU, (2) Laboratoire Interuniversitaire des Systèmes Atmosphériques, (LISA), Universités Paris 7-12, (3) Commissariat à lEnergie Atomique, Laboratoire des sciences du Climat et de lEnvironnement (LSCE), (4) IRD UR 058 Geotrope, (5) Université A. Moumouni, Niamey Niger, (6) IRD MBour, Sénégal, (7) Laboratoire de Météorologie Physique (LaMP), Univ. de Clermont-Ferrand African Monsoon Multidisciplinary Analysis MINERAL DUST IN SAHELIAN AFRICA: THE AMMA 2005-2007 FIELD EXPERIMENT 1.How much mineral dust is emitted from the Sahel, and what are the main factors controlling the variability of emissions at various scale ? 2. What are the physico-chemical properties of mineral dust, and how they can be linked to their spectral optical properties and their hygroscopicity? 3. What is the resulting radiative forcing at the regional scale ? Scientific questions Optical depth in June 2003Optical depth in January 2003 Optical depth in the Sahel are always very high. Dust emissions are linked to the seasonal cycle of the monsoon. Their quantification remains questionable specially concerning the effect of human land use (cultivation and breeding), which are expected to increase in the future. (Chiapello et al., JGR, 1995) Over transport regions such as Cape Verde, the aerosol optical depth is maximum during the wet season, while concentrations at the ground are at their minimum. Rationale Experimental strategy In situ ground-based and airborne measurements Physico-chemical characteristics Validation of 3D atmospheric models of the dust cycle at two time-scales: squall line events (RAMS) - SOP seasonal and interannual variability (CHIMERE-DUST) -EOP Evaluation of emissions for the Sahelian area Spectral optical properties Radiative forcing Schedule 2006 Special observation periods (SOP) Banizoumbou February 2006 (during Harmattan period) May-July 2006 (during Monsoon period) 2005-2007 Enhanced observation periods (EOP) MBour, Ségou, Banizoumbou MBour EOP Sampling sites SAFIRE ATR-42 Inlet AVIRAD / LSCE (Filippi, 2000) allows sampling of supermicron particles GRIMM DILUTEUR TOPAS SESSES TEOM GRIMM DILUTEUR TOPAS SESSES TEOM DILUTEUR ATTOUI NEPHELOMETRE TSI AETHALOMETRE Magee TEOM PM 10 PM2.5 PM 1 AOT, Size distribution, Cimel sun photometer Wet and dry deposition Total deposition SOP Ground Based experimental set up Mass concentration With PM 10, 2.5 and 1µm inlets GRIMM optical counter Casacad impactor TEOM / filter Dedicated filter Nephelometer 3 Aethalometer 7 Number size distribution Mass size distribution Mass concentration Mineralogy Individual characteristics Free iron oxides Diffusion coefficient Absorbtion coefficient Airborne measured parameters Concentration and composition vs. size Number size distribution Individual particle characteristics Spectral optical properties (scattering/absorption) PIP Inlets allow the simultaneous measurements of mineral aerosol physico-chemical properties Hygroscopicity sequential wet deposition scavenged and CCN particles In the wet season, dust is emitted by soil erosion due to squall lines. Cumulated Rainfall Wind direction Wind velocity Time (hh:mn) Wind Velocity at 50 cm height (m s-1) Wind dir. (°), saltation (counts s-1) Cumulated rainfall (mm x 10) EOP Ground Based experimental set up Vertical distribution LIDAR Ségou EOP Banizoumbou EOP + SOP Aircraft study area