Articles | Volume 10, issue 1
Atmos. Chem. Phys., 10, 169–199, 2010

Special issue: OP3/ACES: Oxidant and particle photochemical processes above...

Atmos. Chem. Phys., 10, 169–199, 2010

  12 Jan 2010

12 Jan 2010

Overview: oxidant and particle photochemical processes above a south-east Asian tropical rainforest (the OP3 project): introduction, rationale, location characteristics and tools

C. N. Hewitt1, J. D. Lee2, A. R. MacKenzie1, M. P. Barkley3, N. Carslaw4, G. D. Carver5, N. A. Chappell1, H. Coe6, C. Collier7, R. Commane8,*, F. Davies7, B. Davison1, P. DiCarlo9, C. F. Di Marco10, J. R. Dorsey6, P. M. Edwards8, M. J. Evans11, D. Fowler10, K. L. Furneaux, M. Gallagher6, A. Guenther12, D. E. Heard8, C. Helfter10, J. Hopkins13, T. Ingham8, M. Irwin6, C. Jones13, A. Karunaharan14, B. Langford1, A. C. Lewis13, S. F. Lim15, S. M. MacDonald8, A. S. Mahajan8, S. Malpass4, G. McFiggans6, G. Mills16, P. Misztal10,17, S. Moller13, P. S. Monks14, E. Nemitz10, V. Nicolas-Perea14, H. Oetjen8, D. E. Oram16, P. I. Palmer3, G. J. Phillips10, R. Pike5, J. M. C. Plane8, T. Pugh1, J. A. Pyle5, C. E. Reeves16, N. H. Robinson6, D. Stewart16,***, D. Stone8,11, L. K. Whalley8, and X. Yin5 C. N. Hewitt et al.
  • 1Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK
  • 2National Centre for Atmospheric Science, University of York, York YO10 5DD, UK
  • 3School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JW, UK
  • 4Environment Department, University of York, York YO10 5DD, UK
  • 5Centre for Atmospheric Science, Department of Chemistry, Cambridge University, Cambridge, CB2 1EW, UK
  • 6School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 3PL, UK
  • 7Centre for Environmental Systems Research, University of Salford, Salford M5 4WT, UK
  • 8School of Chemistry, University of Leeds, Leeds LS2 9JT, UK
  • 9CETEMPS – Dipartimento di Fisica, Università di L'Aquila, 67010 Coppito, L'Aquila, Italy
  • 10Biogeochemistry Programme, Centre for Ecology and Hydrology, Penicuik, EH26 0QB, UK
  • 11School of the Environment, University of Leeds, Leeds, LS2 9JT, UK
  • 12National Center for Atmospheric Research, Boulder CO 80301, USA
  • 13Department of Chemistry, University of York, York YO10 5DD, UK
  • 14Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK
  • 15Retired, formerly at Malaysian Meteorological Department, Jalan Sultan, Petaling Jaya, Selangor Darul Ehsan, Malaysia
  • 16School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK
  • 17Department of Chemistry, University of Edinburgh, Edinburgh EH9 3JW, UK
  • *now at: School of Engineering and Applied Sciences, Harvard University, MA, USA
  • deceased
  • **formerly at: School of Chemistry, University of Leeds, Leeds LS2 9JT, UK
  • ***now at: Department of Chemistry, University of Reading, Reading RG6 6AH, UK

Abstract. In April–July 2008, intensive measurements were made of atmospheric composition and chemistry in Sabah, Malaysia, as part of the "Oxidant and particle photochemical processes above a South-East Asian tropical rainforest" (OP3) project. Fluxes and concentrations of trace gases and particles were made from and above the rainforest canopy at the Bukit Atur Global Atmosphere Watch station and at the nearby Sabahmas oil palm plantation, using both ground-based and airborne measurements. Here, the measurement and modelling strategies used, the characteristics of the sites and an overview of data obtained are described. Composition measurements show that the rainforest site was not significantly impacted by anthropogenic pollution, and this is confirmed by satellite retrievals of NO2 and HCHO. The dominant modulators of atmospheric chemistry at the rainforest site were therefore emissions of BVOCs and soil emissions of reactive nitrogen oxides. At the observed BVOC:NOx volume mixing ratio (~100 pptv/pptv), current chemical models suggest that daytime maximum OH concentrations should be ca. 105 radicals cm−3, but observed OH concentrations were an order of magnitude greater than this. We confirm, therefore, previous measurements that suggest that an unexplained source of OH must exist above tropical rainforest and we continue to interrogate the data to find explanations for this.

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