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Journal Article: BibTeX citation key:  Kim2009b
Kim, S.-W., Chazette, P., Dulac, F., Sanak, J., Johnson, B. T. & Yoon, S.-C. (2009) Vertical structure of aerosols and water vapor over West Africa during the African monsoon dry season. IN Atmospheric Chemistry and Physics, 9. 8017–8038.
Added by: Boichard Jean-Luc 2010-08-05 10:13:48    Last Edited by: Fanny Lefebvre 2010-12-08 17:07:36
Categories: General
Creators: Chazette, Dulac, Johnson, Kim, Sanak, Yoon
Collection: Atmospheric Chemistry and Physics

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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 (i.e. Harmattan) 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 ascent in Inter-Tropical Discontinuity (ITD) zone. Aerosol vertical profiles obtained from the space-based lidar CALIOP onboard CALIPSO during January 2007 also showed the presence of dust particles (particle depolarization (δ)~30%, lidar Ångström exponent (LAE)<0, aerosol backscatter to extinction ratio (BER): 0.026~0.028 sr−1) at low levels (<1.5 km) and biomass burning smoke aerosol (δ<10%, LAE: 0.6~1.1, BER: 0.015~0.018 sr−1) between 2 and 5 km. CALIOP data indicated that these distinct continental dust and biomass burning aerosol layers likely mixed as they advected further south over the tropical Atlantic Ocean, as indicated an intermediate values of δ (10~17%), LAE (0.16~0.18) and BER (0.0021~0.0022 sr−1).
Added by: Fanny Lefebvre    Last Edited by: Fanny Lefebvre