Improved global modelling of HOx recycling in isoprene oxidation: evaluation against the GABRIEL and INTEX-A aircraft campaign measurements

• Published in: Atmospheric chemistry and physics 2010-01, Vol.10 (20), p.9863-9878
• Main Authors: Stavrakou, T, Peeters, J, Müller, J.-F
• Format: Article
• Language: English
• ISSN: 1680-7316; 1680-7324
• DOI: 10.5194/acp-10-9863-2010

Stimulated by recent important developments regarding the oxidation chemistry of isoprene, this study evaluates and quantifies the impacts of different mechanism updates on the boundary layer concentrations of OH and HO2 radicals using the IMAGESv2 global chemistry transport model. The model results for HOx , isoprene, NO, and ozone are evaluated against air-based observations from the GABRIEL campaign, conducted over the Guyanas in October 2005, and from the INTEX-A campaign over the Eastern US in summer 2004. The version 2 of the Mainz Isoprene Mechanism (MIM2, Taraborrelli et al., 2009) used as reference mechanism in our simulations, has been modified to test (i) the artificial OH recycling proposed by Lelieveld et al. (2008), (ii) the epoxide formation mechanism proposed by Paulot et al. (2009b), and finally (iii) the HOx regeneration of the Leuven Isoprene Mechanism (LIM0) proposed by Peeters and Müller (2010). The simulations show that the LIM0 scheme holds by far the largest potential impact on HOx concentrations over densely vegetated areas in the Tropics as well as at mid-latitudes. Strong increases, by up to a factor of 4 in the modelled OH concentrations, and by a factor of 2.5-3 in the HO2 abundances are estimated through the LIM0 mechanism compared to the traditional isoprene degradation schemes. Comparatively much smaller OH increases (