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Title: HO[subscript x] observations over West Africa during AMMA: impact of isoprene and NO[subscript x]
Authors: Stone, D.
Evans, M.J.
Commane, R.
Ingham, T.
Floquet, C.F.A.
McQuaid, J.B.
Brookes, D.M.
Monks, P.S.
Purvis, R.
Hamilton, J.F.
Hopkins, J.
Lee, J.
Lewis, A.C.
Stewart, D.
Murphy, J.G.
Mills, G.
Oram, D.
Reeves, C.E.
Heard, D.E.
First Published: 2010
Publisher: Copernicus GmbH (Copernicus Publications) on behalf of the European Geosciences Union (EGU).
Citation: Atmospheric Chemistry and Physics, 2010, 10 (19), pp. 9415-9429
Abstract: Aircraft OH and HO[subscript 2] 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 HO[subscript 2] (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, HO[subscript x] concentrations in West Africa are controlled by relatively simple photochemistry, with production dominated by ozone photolysis and reaction of O([superscript 1]D) with water vapour, and loss processes dominated by HO[subscript 2] + HO[subscript 2] and HO[subscript 2] + RO[subscript 2]. Isoprene chemistry was found to influence forested regions. In contrast to several recent field studies in very low NO[subscript x] and high isoprene environments, we do not observe any dependence of model success for HO[subscript 2] on isoprene and attribute this to efficient recycling of HO[subscript x] through RO[subscript 2] + NO reactions under the moderate NO[subscript x] 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 NO[subscript x] concentrations.
DOI Link: 10.5194/acp-10-9415-2010
ISSN: 1680-7316
eISSN: 1680-7324
Version: Publisher Version
Status: Peer-reviewed
Type: Journal Article
Rights: © Author(s) 2010. This is an open-access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Appears in Collections:Published Articles, Dept. of Chemistry

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