Tropospheric ozone production related to West African city emissions during the 2006 wet season AMMA campaign

Gérard Ancellet (1) , E. Orlandi (2) , Elsa Real (1) , Kathy S. Law (1) , H. Schlager (3) , F. Fierli (2) , J. K. Nielsen (4) , V. Thouret (5) , C. Mari (5)

1 TROPO - LATMOS
2 ISAC - CNR Institute of Atmospheric Sciences and Climate
3 IPA - DLR Institut für Physik der Atmosphäre = DLR Institute of Atmospheric Physics
4 DMI - Danish Meteorological Institute
5 LAERO - Laboratoire d'aérologie

During the African Monsoon Multidisciplinary Analyses (AMMA) airborne measurements of ozone, CO and nitrogen oxides by the French and German falcon aircraft took place near three cities in West Africa (Cotonou, Niamey and Ouagadougou). Significant ozone production (O3 increase of 40-50 ppbv) took place during two specific events: one near Cotonou on the coast of the Guinea Gulf, and the other near Niamey in the Sahel region. In both cases a high level of NOx (>3 ppbv) is related to the ozone production. The ozone production is mainly driven by the Lagos-Cotonou anthropogenic emissions in Cotonou. In Niamey the combined effect of advection of VOC emissions from the forest and stagnation over the city area and the poorly vegetated soils recently wetted by convected systems is needed to achieve a similar level of ozone precursors. In Ouagadougou no ozone plume is found because of the absence of a pause in the convective activity and of the larger vegetated area around the city which prevented ozone plume formation during the wet season.

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]

Gérard Ancellet, E. Orlandi, Elsa Real, Kathy S. Law, H. Schlager, et al.. Tropospheric ozone production related to West African city emissions during the 2006 wet season AMMA campaign. Atmospheric Chemistry and Physics, 2011, 11 (13), pp.6349-6366. ⟨10.5194/acp-11-6349-2011⟩. ⟨hal-00535800⟩