African Monsoon Multidisciplinary Analysis

1. PM 10 PM2.5 PM 1 DILUTEUR TOPAS DILUTEUR TOPAS GRIMM GRIMM SES SES AETHALOMETRE Magee (Chiapello et al., JGR, 1995) TEOM TEOM Cumulated Rainfall Wind direction Wind dir. (°), saltation (counts s-1) Cumulated rainfall (mm x 10) Wind Velocity at 50 cm height (m s-1) Wind velocity 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. Time (hh:mn) In the wet season, dust is emitted by soil erosion due to squall lines. DILUTEUR ATTOUI NEPHELOMETRE TSI Number size distribution Mass size distribution Mass concentration Mineralogy Individual characteristics Free iron oxides Diffusion coefficient Absorbtion coefficient GRIMM optical counter Casacad impactor TEOM / filter Dedicated filter Dedicated filter Dedicated filter Nephelometer 3  Aethalometer 7 TEOM African Monsoon Multidisciplinary Analysis MINERAL DUST IN SAHELIAN AFRICA: THE AMMA 2005-2007 FIELD EXPERIMENT 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 l’Energie Atomique, Laboratoire des sciences du Climat et de l’Environnement (LSCE), (4) IRD UR 058 Geotrope, (5) Université A. Moumouni, Niamey Niger, (6) IRD M’Bour, Sénégal, (7) Laboratoire de Météorologie Physique (LaMP), Univ. de Clermont-Ferrand Rationale Scientific questions Optical depth in June 2003 Optical depth in January 2003 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 ? • 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. Experimental strategy In situ ground-based and airborne measurements Schedule Sampling sites 2005-2007 Enhanced observation periods (EOP) M’Bour, Ségou, Banizoumbou 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 M’Bour EOP Hygroscopicity Spectral optical properties Banizoumbou EOP + SOP • 2006 • Special observation periods (SOP) Banizoumbou • February 2006 (during Harmattan period) • May-July 2006 (during Monsoon period) Ségou EOP Evaluation of emissions for the Sahelian area Radiative forcing Aircraft study area SOP Ground Based experimental set up Airborne measured parameters Concentration and composition vs. size Number size distribution Individual particle characteristics Spectral optical properties (scattering/absorption) EOP Ground Based experimental set up scavenged and CCN particles PIP Inlets allow the simultaneous measurements of mineral aerosol physico-chemical properties Total deposition sequential wet deposition Vertical distribution LIDAR Wet and dry deposition SAFIRE ATR-42 AOT, Size distribution, Cimel sun photometer Inlet AVIRAD / LSCE (Filippi, 2000) allows sampling of supermicron particles Mass concentration With PM 10, 2.5 and 1µm inlets