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Impacts of HOx regeneration and recycling in the oxidation of isoprene: Consequences for the composition of past, present and future atmospheres

By A.T. Archibald, James G. Levine, N.L. Abraham, M.C. Cooke, P.M. Edwards, D.E. Heard, M.E. Jenkin, A. Karunaharan, R.C. Pike, P.S. Monks, D.E. Shallcross, P.J. Telford, L.K. Whalley and J.A. Pyle


A global chemistry-climate model is used to assess the impact on atmospheric composition of the regeneration and recycling of HOx in the photo-oxidation of isoprene. The impact is explored subject to present-day, pre-industrial and future climate/emission scenarios. Our calculations show that, in all cases, the inclusion of uni-molecular isomerisations of the isoprene hydroxy-peroxy radicals leads to enhanced production of HOx radicals and ozone. The global burden of ozone increases by 25–36 Tg (8–18%), depending on the climate/emissions scenario, whilst the changes in OH lead to decreases in the methane lifetime of between 11% in the future and 35% in the pre-industrial. Critically the size of the change in methane lifetime depends on the VOC/NOx emission ratio. The results of the present-day calculations suggest a certain amount of parameter refinement is still needed to reconcile the updated chemistry with field observations (particularly for HO2+RO2). However, the updated chemistry could have far-reaching implications for: future-climate predictions; projections of future oxidising capacity; and our understanding of past changes in oxidising capacity

Topics: Meteorology and Climatology, Chemistry, Atmospheric Sciences
Publisher: American Geophysical Union
Year: 2011
DOI identifier: 10.1029/2010GL046520
OAI identifier: oai:nora.nerc.ac.uk:14045

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