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| Titel |
Impact of West African Monsoon convective transport and lightning NOx production upon the upper tropospheric composition: a multi-model study |
| VerfasserIn |
B. Barret, J. E. Williams, I. Bouarar, X. Yang, B. Josse, K. Law, M. Pham, E. Flochmoën, C. Liousse, V. H. Peuch, G. D. Carver, J. A. Pyle, B. Sauvage, P. Velthoven, H. Schlager, C. Mari, J.-P. Cammas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 12 ; Nr. 10, no. 12 (2010-06-30), S.5719-5738 |
| Datensatznummer |
250008579
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| Publikation (Nr.) |
 copernicus.org/acp-10-5719-2010.pdf |
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| Zusammenfassung |
| 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. |
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