Scientific Results

Emission sources contributing to tropospheric ozone over Equatorial Africa during the summer monsoon

Year: 2011

Authors: Bouarar I., Law K.S., Pham M., Liousse C., Schlager H., Hamburger T., Reeves C. E., Cammas J.-P., Nedelec P., Szopa S., Ravegnani F., Viciani S., D’Amato F., Ulanovsky A., Richter A.

Autors Affiliation: UPMC Universite Paris 06: Universite Versailles Saint-Quentin: CNRS/INSU; UMR8190, LATMOS/IPSL, Paris, France; Universite de Toulouse, UPS, LA (Laboratoire d’Aerologie), CNRS UMR5560, Toulouse, France; DLR Institut fur Physik der Atmosphare, Oberpfaffenhofen, Germay; School of Environmental Sciences, University of East Anglia, Norwich, UK; Laboratoire des Sciences du Climat et de l’Environnement, LSCE/IPSL, Saclay, France; Istituto di Scienze dell’Atmosfera e del Clima, Consiglio Nazionale delle Ricerche (ISAC-CNR), Italy; Consiglio Nazionale dell Ricerche-Istituto Nazionale di Ottica (CNR-INO), Firenze, Italy; Central Aerological Observatory, Moscow, Russia; Institute 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.

Journal/Review:

Volume: 11 (24)      Pages from: 13395  to: 13419

More Information: The authors acknowledge the AMMA-EU and SCOUT-O3 projects for support and funding. AMMA was built by an international scientific group and was funded by a large number of agencies, especially from France, the UK, US and Africa. Detailed information on scientific coordination and funding is available on the AMMA International web site at www.amma-international.org. Computer time has been provided by the Institut du Developpement et des Ressources en Informatique Scientifique (IDRIS). We acknowledge FAAM for operating the BAe-146. We also acknowledge the RETRO EU and GEIA projects for providing emissions used in this study. MOZAIC is presently funded by INSU-CNRS (France), Meteo-France, and Forschungszentrum (FZJ, Julich, Germany). The MOZAIC data base is supported by ETHER (CNES and INSU-CNRS). We are also grateful for F. Fierli for providing information about the air masses impacted by convection which were sampled by the M55 aircraft during the AMMA campaign. The M55 Geophysica data were collected as part of the EU AMMA and SCOUT-O3 projects.
KeyWords: anthropogenic source; atmospheric chemistry; biogenic emission; biomass burning; climate modeling; monsoon; nitrogen oxides; ozone; soil emission; stratosphere; summer; troposphere; volatile organic compound, Asia; Atlantic Ocean; Central Africa; Sahel [Sub-Saharan Africa]; West Africa
DOI: 10.5194/acp-11-13395-2011

Citations: 6
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