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| Titel |
HOx observations over West Africa during AMMA: impact of isoprene and NOx |
| VerfasserIn |
D. Stone, M. J. Evans, R. Commane, T. Ingham, C. F. A. Floquet, J. B. McQuaid, D. M. Brookes, P. S. Monks, R. Purvis, J. F. Hamilton, J. Hopkins, J. Lee, A. C. Lewis, D. Stewart, J. G. Murphy, G. Mills, D. Oram, C. E. Reeves, D. E. Heard |
| 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. 19 ; Nr. 10, no. 19 (2010-10-06), S.9415-9429 |
| Datensatznummer |
250008809
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| Publikation (Nr.) |
 copernicus.org/acp-10-9415-2010.pdf |
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| Zusammenfassung |
| Aircraft OH and HO2 measurements made over West Africa during the AMMA field
campaign in summer 2006 have been investigated using a box model constrained to observations
of long-lived species and physical parameters. "Good" agreement was found for
HO2 (modelled to observed gradient of 1.23 ± 0.11). However, the model
significantly overpredicts OH concentrations. The reasons for this are not clear, but may
reflect instrumental instabilities affecting the OH measurements. Within the
model, HOx concentrations in West Africa are controlled by relatively simple
photochemistry, with production dominated by ozone photolysis and reaction of O(1D)
with water vapour, and loss processes dominated by HO2 + HO2 and
HO2 + RO2. Isoprene chemistry was found to influence forested
regions. In contrast to several recent field studies in very low NOx and high
isoprene environments, we do not observe any dependence of model success for HO2 on
isoprene and attribute this to efficient recycling of HOx through RO2 + NO
reactions under the moderate NOx concentrations (5–300 ppt NO in the boundary layer, median 76 ppt)
encountered during AMMA. This suggests that some of the problems with understanding
the impact of isoprene on atmospheric composition may be limited to the extreme low range of
NOx concentrations. |
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