Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 11, 13395-13419, 2011
© Author(s) 2011. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
22 Dec 2011
Emission sources contributing to tropospheric ozone over Equatorial Africa during the summer monsoon
I. Bouarar1, K. S. Law1, M. Pham1, C. Liousse2, H. Schlager3, T. Hamburger3, C. E. Reeves4, J.-P. Cammas2, P. Nédéléc2, S. Szopa5, F. Ravegnani6, S. Viciani7, F. D'Amato7, A. Ulanovsky8, and A. Richter9 1UPMC Université Paris 06: Université Versailles Saint-Quentin: CNRS/INSU; UMR8190, LATMOS/IPSL, Paris, France
2Université de Toulouse, UPS, LA (Laboratoire d'Aerologie), CNRS UMR5560, Toulouse, France
3DLR Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germay
4School of Environmental Sciences, University of East Anglia, Norwich, UK
5Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, Saclay, France
6Instituto di Scienze dell'Atmosfera e del Clima, Consiglio Nazionale delle Ricerche (ISAC-CNR), Italy
7Consiglio Nazionale dell Ricerche-Istituto Nazionale di Ottica (CNR-INO), Firenze, Italy
8Central Aerological Observatory, Moscow, Russia
9Institute of Environmental Physics, University of Bremen, Bremen, Germany
Abstract. A global chemistry-climate model LMDz_INCA is used to investigate the contribution of African and Asian emissions to tropospheric ozone over Central and West Africa during the summer monsoon. The model results show that ozone in this region is most sensitive to lightning NOx and to Central African biomass burning emissions. However, other emission categories also contribute significantly to regional ozone. The maximum ozone changes due to lightning NOx occur in the upper troposphere between 400 hPa and 200 hPa over West Africa and downwind over the Atlantic Ocean. Biomass burning emissions mainly influence ozone in the lower and middle troposphere over Central Africa, and downwind due to westward transport. Biogenic emissions of volatile organic compounds, which can be uplifted from the lower troposphere to higher altitudes by the deep convection that occurs over West Africa during the monsoon season, lead to maximum ozone changes in the lower stratosphere region. Soil NOx emissions over the Sahel region make a significant contribution to ozone in the lower troposphere. In addition, convective uplift of these emissions and subsequent ozone production are also an important source of ozone in the upper troposphere over West Africa. Concerning African anthropogenic emissions, they only make a small contribution to ozone compared to the other emission categories. The model results indicate that most ozone changes due to African emissions occur downwind, especially over the Atlantic Ocean, far from the emission regions. The import of Asian emissions also makes a considerable contribution to ozone concentrations above 150 hPa and has to be taken into account in studies of the ozone budget over Africa. Using IPCC AR5 (Intergovernmental Panel on Climate Change; Fifth Assessment Report) estimates of anthropogenic emissions for 2030 over Africa and Asia, model calculations show larger changes in ozone over Africa due to growth in Asian emissions compared to African emissions over the next 20 yr.

Citation: Bouarar, I., Law, K. S., Pham, M., Liousse, C., Schlager, H., Hamburger, T., Reeves, C. E., Cammas, J.-P., Nédéléc, P., Szopa, S., Ravegnani, F., Viciani, S., D'Amato, F., Ulanovsky, A., and Richter, A.: Emission sources contributing to tropospheric ozone over Equatorial Africa during the summer monsoon, Atmos. Chem. Phys., 11, 13395-13419, doi:10.5194/acp-11-13395-2011, 2011.
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