What caused extreme ozone concentrations over Cotonou in December 2005?

Minga, A.; Thouret, V.; Saunois, Marielle; Delon, Claire; Serça, D.; Mari, C.; Sauvage, Bastien; Mariscal, A.; Leriche, Maud; Cros, B.

doi:10.5194/acp-10-895-2010

Cited by 19 publications

(14 citation statements)

References 51 publications

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“…African cities along the southern coast and industrialized countries (e.g. Nigeria) release important amounts of anthropogenic emissions (Hopkins et al, 2009), related to oil gas exploration, which can influence O 3 regionally (Minga et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2011

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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 NO x and to Central African biomass burning emissions. However, other emission categories also contribute significantly to regional ozone. The maximum ozone changes due to lightning NO x 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 NO x 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 AfricanCorrespondence to: I. Bouarar (idir.bouarar@latmos.ipsl.fr) 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.

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Section: Introductionmentioning

confidence: 99%

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

et al. 2011

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“…An isolated maximum at the surface was observed around 6 • N in correspondence to the position of the town of Cotonou. With over 1.2 million inhabitants and a large active industrial harbor with transiting oil and metals, Cotonou is the economic capital of Benin (Minga et al, 2010).…”

Section: Aerosol Spatial Variabilitymentioning

confidence: 99%

Airborne observations of mineral dust over western Africa in the summer Monsoon season: spatial and vertical variability of physico-chemical and optical properties

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Rajot²,

Desboeufs³

et al. 2011

Atmos. Chem. Phys.

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Abstract. We performed airborne measurements of aerosol particle concentration, composition, size distribution and optical properties over Western Africa in the corridor 2-17 • N and 3-5 • E. Data were collected on board the French ATR-42 research aircraft in June-July 2006 as part of the African Monsoon Multidisciplinary Analysis (AMMA) intensive field phases in June-July 2006 using the AVIRAD airborne aerosol sampling system.The aerosol vertical distribution was documented on an almost daily basis. In particular, the vertical distribution of mineral dust emitted locally by Mesoscale Convective Systems (MSC) was distinguished from that of mineral dust that was transported from the Saharan by the African Easterly Jet (AEJ). Mineral dust emitted in the Sahel by convectiondriven erosion was mostly confined in the boundary layer. One episode of injection of Sahelian mineral dust in the AEJ was observed. The elemental composition was found to be an element of difference between episodes, whereas the volume size distribution was more uniform.For non-mixed dust, the single scattering albedo ranged between 0.88-0.93 at 370 nm and between 0.91-0.99 at 950 nm, lower values being observed for Sahelian dust. In correspondence, the imaginary part of the complex refractive index varied between 0.002-0.004 at 370 nm and between 0.001-0.002 at 950 nm.

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“…Over West Africa, between 5 • N and 15 • N, ozone precursors are emitted from soils and vegetation, (Guenther et al, 1995;Serça et al, 1998;Jaeglé et al, 2004;Delon et al, 2008) and from urban areas (Aghedo et al, 2007;Minga et al, 2010). When on the MCSs path track, the emitted gases and aerosols are transported efficiently by convective updrafts in the upper troposphere where they modify the budget of ozone (Ancellet et al, 2009;Law et al, 2010), water vapor Khaykin et al, 2009) and aerosols .…”

Section: Introductionmentioning

confidence: 99%

Numerical study of tracers transport by a mesoscale convective system over West Africa

et al. 2011

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Abstract.A three-dimensional cloud-resolving model is used to investigate the vertical transport from the lower to the upper troposphere in a mesoscale convective system (MCS) that occurred over Niger on 15 August 2004. The redistribution of five passive tracers initially confined in horizontally homogeneous layers is analyzed. The monsoon layer tracer (0-1.5 km) is the most efficiently transported in the upper troposphere with concentrations 3 to 4 times higher than the other tracers in the anvil. On the contrary the African Easterly Jet tracer (∼3 km) has the lowest contribution above 5 km. The vertical profiles of the mid-troposphere tracers (4.5-10 km) in the MCS exhibit two peaks: one in their initial layers, and the second one at 13-14 km altitude, underlying the importance of mid-tropospheric air in feeding the upper troposphere. Mid-tropospheric tracers also experience efficient transport by convective downdrafts with a consequent increase of their concentrations at the surface. The concentration of the upper troposphere-lower stratosphere tracer exhibits strong gradients at the edge of the cloud, meaning almost no entrainment of this tracer into the cloud. No downward transport from the upper troposphere is simulated below 5 km. A proxy for lightning produced NO x is transported preferentially in the forward anvil in the upper troposphere. Additionally, lateral inflows significantly contribute to the updraft and downdraft airflows emphasizing the threedimensional structure of the West African MCSs.

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What caused extreme ozone concentrations over Cotonou in December 2005?

Cited by 19 publications

References 51 publications

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

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

Airborne observations of mineral dust over western Africa in the summer Monsoon season: spatial and vertical variability of physico-chemical and optical properties

Numerical study of tracers transport by a mesoscale convective system over West Africa

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