Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 9 1 2009 10.5194/acpd-9-1831-2009 http://www.atmos-chem-phys-discuss.net/9/1831/2009/ http://www.atmos-chem-phys-discuss.net/9/1831/2009/acpd-9-1831-2009.html http://www.atmos-chem-phys-discuss.net/9/1831/2009/acpd-9-1831-2009.pdf 1831 1871 2009-01-21 Transport and vertical structure of aerosols and water vapor over West Africa during the African monsoon dry season S.-W. Kim kimsw@air.snu.ac.kr P. Chazette F. Dulac J. Sanak B. Johnson S.-C. Yoon Laboratoire des Sciences du Climat et de l'Environnement, CEA-CNRS-UVSQ, Gif-Sur-Yvette, France Met Office, Exeter, UK School of Earth and Environmental Sciences, Seoul National University, Seoul, Korea now at: School of Earth and Environmental Sciences, Seoul National University, Seoul, Korea We present observations of tropospheric aerosol and water vapor transport over West Africa and the associated meteorological conditions during the AMMA SOP-0 dry season experiment, which was conducted in West Africa in January–February 2006. This study combines data from ultra-light aircraft (ULA)-based lidar, airborne in-situ aerosol and gas measurements, standard meteorological measurements, satellite-based aerosol measurements, airmass trajectories, and radiosonde measurements. At Niamey (13.5° N, 2.2° E) the prevailing surface wind was from the northeast bringing dry dusty air from the Sahara desert. High concentrations of mineral dust aerosol were typically observed from the surface to 1.5 or 2 km associated with the Saharan airmasses. At higher altitudes the prevailing wind veered to the south or southeast bringing relatively warm and humid airmasses from the biomass burning regions to the Sahel (<10° N). These elevated layers had high concentrations of biomass burning aerosol and were typically observed between altitudes of 2–5 km. Meteorological analyses show these airmasses were advected upwards over the biomass burning regions through large-scale ascent, presumably driven by surface heating rather than pyro-convection. Aerosol vertical profiles obtained from the space-based lidar CALIOP onboard CALIPSO during January 2007 also showed the presence of dust particles (depolarization ~30%, color ratio <0) at low levels (<1.5 km) and biomass burning smoke aerosol (depolarization ratio <10%) between 2 and 5 km. 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