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Impact of West African Monsoon convective transport and lightning NOx production upon the upper tropospheric composition: a multi-model study

Barret , B. and Williams, J. E. and Bouarar, I. and Yang, X. and Josse, B. and Law, K. and Pham, M. and Le Flochmoen, E. and Liousse, C. and Peuch, V. H. and Carver, G. D. and Pyle, J. A. and Sauvage, B. and van Velthoven, P. and Schlager, H. and Mari, C. and Cammas, J.-P. (2010) Impact of West African Monsoon convective transport and lightning NOx production upon the upper tropospheric composition: a multi-model study. Atmospheric Chemistry and Physics, 10, pp. 5719-5738. DOI: 10.5194/acp-10-5719-2010.

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Official URL: http://www.atmos-chem-phys.net/10/5719/2010/

Abstract

Within the African Monsoon Multidisciplinary Analysis (AMMA), we investigate the impact of nitrogen oxides produced by lightning (LiNOx) and convective transport during the West African Monsoon (WAM) upon the composition of the upper troposphere (UT) in the tropics. For this purpose, we have performed simulations with 4 state-of-the-art chemistry transport models involved within AMMA, namely MOCAGE, TM4, LMDz-INCA and p-TOMCAT. The model intercomparison is complemented with an evaluation of the simulations based on both spaceborne and airborne observations. The baseline simulations show important differences between the UT CO and O3 distributions simulated by each of the 4 models when compared to measurements from the MOZAIC program and fom the Aura/MLS spaceborne sensor. We show that such model discrepancies can be explained by differences in the convective transport parameterizations and, more particularly, the altitude reached by convective updrafts (ranging between ~200–125 hPa). Concerning UT O3, the models exhibit a good agreement with the main observed features. Nevertheless the majority of models simulate low O3 concentrations compared to both MOZAIC and Aura/MLS observations south of the equator, and rather high concentrations in the Northern Hemisphere. Sensitivity studies are performed to quantify the effect of deep convective transport and the influence of LiNOx production on the UT composition. These clearly indicate that the CO maxima and the elevated O3 concentrations south of the equator are due to convective uplift of air masses impacted by Southern African biomass burning, in agreement with previous studies. Moreover, during the WAM, LiNOx from Africa are responsible for the highest UT O3 enhancements (10–20 ppbv) over the tropical Atlantic between 10° S–20° N. Differences between models are primarily due to the performance of the parameterizations used to simulate lightning activity which are evaluated using spaceborne observations of flash frequency. Combined with comparisons of in-situ NO measurements we show that the models producing the highest amounts of LiNOx over Africa during the WAM (INCA and p-TOMCAT) capture observed NO profiles with the best accuracy, although they both overestimate lightning activity over the Sahel.

Document Type:Article
Title:Impact of West African Monsoon convective transport and lightning NOx production upon the upper tropospheric composition: a multi-model study
Authors:
AuthorsInstitution or Email of Authors
Barret , B. Univ. de Toulouse, Toulouse, F
Williams, J. E. KNMI, NL
Bouarar, I.LATMOS/IPSL, UPMC, Paris, F
Yang, X. Univ. of Cambridge, Cambridge, UK
Josse, B. Météo-France, Toulouse, F
Law, K.UPMC, Paris, F
Pham, M. UPMC, Paris, F
Le Flochmoen, E. Univ. de Toulouse, Toulouse, F
Liousse, C. Univ. de Toulouse, Toulouse, F
Peuch, V. H. Météo-France, Toulouse, F
Carver, G. D. Univ. of Cambridge, Cambridge, UK
Pyle, J. A. Univ. of Cambridge, Cambridge, UK
Sauvage, B. Univ. de Toulouse, Toulouse, F
van Velthoven, P. KNMI, NL
Schlager, H.DLR
Mari, C. Univ. de Toulouse, Toulouse, F
Cammas, J.-P.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-10-5719-2010
Page Range:pp. 5719-5738
Status:Published
Keywords:Monsoon, West Africa, lightning NOx
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: Yasemin Yilmaz
Deposited On:10 Dec 2010 10:22
Last Modified:26 Mar 2013 13:24

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