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Chemical and aerosol characterisation of the troposphere over West Africa during the monsoon period as part of AMMA

Reeves, C.E. and Formenti, P. and Afif, C. and Ancellet, G. and Attié, J.-L. and Bechara, J. and Borbon, A. and Cairo, F. and Coe, H. and Crumeyrolle, S. and Fierli, F. and Flamant, C. and Gomes, L. and Hamburger, T. and Jambert, C. and Law, K.S. and Mari, C. and Jones, R.L. and Matsuki, A. and Mead, M.I. and Methven, J. and Mills, G.P. and Minikin, A. and Murphy, J.G. and Nielsen, J.K. and Oram, D.E. and Parker, D.J. and Richter, A. and Schlager, H. and Schwarzenboeck, A. and Thouret, V. (2010) Chemical and aerosol characterisation of the troposphere over West Africa during the monsoon period as part of AMMA. Atmospheric Chemistry and Physics, 10, pp. 7575-7601. DOI: 10.5194/acp-10-7575-2010.

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Official URL: http://www.atmos-chem-phys.net/10/7575/2010/acp-10-7575-2010.html

Abstract

During June, July and August 2006 five aircraft took part in a campaign over West Africa to observe the aerosol content and chemical composition of the troposphere and lower stratosphere as part of the African Monsoon Multidisciplinary Analysis (AMMA) project. These are the first such measurements in this region during the monsoon period. In addition to providing an overview of the tropospheric composition, this paper provides a description of the measurement strategy (flights performed, instrumental payloads, wing-tip to wing-tip comparisons) and points to some of the important findings discussed in more detail in other papers in this special issue. The ozone data exhibits an "S" shaped vertical profile which appears to result from significant losses in the lower troposphere due to rapid deposition to forested areas and photochemical destruction in the moist monsoon air, and convective uplift of ozone-poor air to the upper troposphere. This profile is disturbed, particularly in the south of the region, by the intrusions in the lower and middle troposphere of air from the southern hemisphere impacted by biomass burning. Comparisons with longer term data sets suggest the impact of these intrusions on West Africa in 2006 was greater than in other recent wet seasons. There is evidence for net photochemical production of ozone in these biomass burning plumes as well as in urban plumes, in particular that from Lagos, convective outflow in the upper troposphere and in boundary layer air affected by nitrogen oxide emissions from recently wetted soils. This latter effect, along with enhanced deposition to the forested areas, contributes to a latitudinal gradient of ozone in the lower troposphere. Biogenic volatile organic compounds are also important in defining the composition both for the boundary layer and upper tropospheric convective outflow. Mineral dust was found to be the most abundant and ubiquitous aerosol type in the atmosphere over Western Africa. Data collected within AMMA indicate that injection of dust to altitudes favourable for long-range transport (i.e. in the upper Sahelian planetary boundary layer) can occur behind the leading edge of mesoscale convective system (MCS) cold-pools. Research within AMMA also provides the first estimates of secondary organic aerosols across the West African Sahel and have shown that organic mass loadings vary between 0 and 2 μg m−3 with a median concentration of 1.07 μg m−3. The vertical distribution of nucleation mode particle concentrations reveals that significant and fairly strong particle formation events did occur for a considerable fraction of measurement time above 8 km (and only there). Very low concentrations were observed in general in the fresh outflow of active MCSs, likely as the result of efficient wet removal of aerosol particles due to heavy precipitation inside the convective cells of the MCSs. This wet removal initially affects all particle size ranges as clearly shown by all measurements in the vicinity of MCSs.

Document Type:Article
Title:Chemical and aerosol characterisation of the troposphere over West Africa during the monsoon period as part of AMMA
Authors:
AuthorsInstitution or Email of Authors
Reeves, C.E.Univ. of East Anglia, Norwich, UK
Formenti, P.Univ. Paris Est Creteil, Créteil, F
Afif, C.Univ. Paris Est Creteil, Créteil, F
Ancellet, G.Univ. Versailles-St-Quentin, Paris, F
Attié, J.-L.Univ. de Toulouse, Toulouse, F
Bechara, J.Univ. Paris Est Creteil, Créteil, F
Borbon, A.Univ. Paris Est Creteil, Créteil, F
Cairo, F.Consiglio Nazionale delle Ricerche, I
Coe, H.Univ. of Manchester, Manchester, UK
Crumeyrolle, S.Meteo-France, Toulouse, F
Fierli, F.Consiglio Nazionale delle Ricerche, I
Flamant, C.Consiglio Nazionale delle Ricerche, I
Gomes, L.Meteo-France, Toulouse, F
Hamburger, T.DLR
Jambert, C.Univ. de Toulouse, Toulouse, F
Law, K.S.Univ. Versailles-St-Quentin, Paris, F
Mari, C.Univ. de Toulouse, Toulouse, F
Jones, R.L.Univ. of Cambridge, Cambridge, UK
Matsuki, A.Univ. Blaise Pascal, Clermont-Ferrand, F
Mead, M.I.Univ. of Cambridge, Cambridge, UK
Methven, J.Univ. of Reading, Reading, UK
Mills, G.P.Univ. of East Anglia, Norwich, UK
Minikin, A.DLR
Murphy, J.G.Univ. of Toronto, Toronto, CND
Nielsen, J.K.Research and Development Division, Copenhagen, DK
Oram, D.E.Univ. of East Anglia, Norwich, UK
Parker, D.J.Univ. of Leeds, Leeds, UK
Richter, A.Univ. of Bremen, Bremen
Schlager, H.DLR
Schwarzenboeck, A.Univ. Blaise Pascal, Clermont-Ferrand, F
Thouret, V.Univ. de Toulouse, Toulouse, F
Date:2010
Journal or Publication Title:Atmospheric Chemistry and Physics
Refereed publication:Yes
In Open Access:Yes
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:10
DOI:10.5194/acp-10-7575-2010
Page Range:pp. 7575-7601
Status:Published
Keywords:ozone, monsoon, west Africa, AMMA
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben Atmosphären- und Klimaforschung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Trace Species
Deposited By: Jana Freund
Deposited On:24 Aug 2010 11:52
Last Modified:26 Mar 2013 13:19

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