Atmos. Chem. Phys. Discuss., 9, 18899-18963, 2009
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Oxidant and particle photochemical processes above a south-east Asian tropical rain forest (the OP3 project): introduction, rationale, location characteristics and tools
C. N. Hewitt1, J. Lee2, M. P. Barkley3, N. Carslaw4, N. A. Chappell1, H. Coe5, C. Collier6, R. Commane7, F. Davies6, P. DiCarlo8, C. F. Di Marco9, P. M. Edwards7, M. J. Evans10, D. Fowler9, K. L. Furneaux7,†, M. Gallagher5, A. Guenther11, D. E. Heard7, C. Helfter9, J. Hopkins12, T. Ingham7, M. Irwin5, C. Jones12, A. Karunaharan13, B. Langford1, A. C. Lewis12, S. F. Lim14, S. M. MacDonald8, A. R. MacKenzie1, A. S. Mahajan7, S. Malpass4, G. McFiggans5, G. Mills15, P. Misztal9,16, S. Moller12, P. S. Monks13, E. Nemitz9, V. Nicolas-Perea13, H. Oetjen7, D. Oram15, P. I. Palmer3, G. J. Phillips9, J. M. C. Plane7, T. Pugh1, J. A. Pyle17, C. E. Reeves15, N. H. Robinson5, D. Stewart15,*, D. Stone7,10, and L. K. Whalley7
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
5School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester M13 3PL, UK
6Centre for Environmental Systems Research, University of Salford, Salford M5 4WT, UK
7School of Chemistry, University of Leeds, Leeds LS2 9JT, UK
8CETEMPS – Dipartimento di Fisica, Università di L'Aquila, 67010 Coppito, L'Aquila, Italy
9Biogeochemistry Programme, Centre for Ecology and Hydrology, Penicuik, EH26 0QB, UK
10School of the Environment, University of Leeds, Leeds, LS2 9JT, UK
11National Center for Atmospheric Research, Boulder CO 80301, USA
12Department of Chemistry, University of York, York YO10 5DD, UK
13Department of Chemistry, University of Leicester, Leicester LE1 7RH, UK
14retired, formerly at: Malaysian Meteorological Department, Jalan Sultan, Petaling Jaya, Selangor Darul Ehsan, Malaysia
15School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, UK
16Department of Chemistry, University of Edinburgh, Edinburgh EH9 3JW, UK
17Centre for Atmospheric Science, Department of Chemistry, Cambridge University, Cambridge, CB2 1EW, 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 rain forest" (OP3) project. Fluxes and concentrations of trace gases and particles were made from and above the rain forest 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 impacted by significant sources of anthropogenic pollution, and this is confirmed by satellite retrievals of NO2 and HCHO. The dominant modulators of atmospheric chemistry at the rain forest site were therefore emissions of BVOCs and soil emissions of reactive nitrogen oxides. At the observed BVOC:NOx volume mixing ratio (~104 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 which suggest that an unexplained source of OH must exist above tropical forests and continue to interrogate the data to find explanations for this.

Citation: Hewitt, C. N., Lee, J., Barkley, M. P., Carslaw, N., Chappell, N. A., Coe, H., Collier, C., Commane, R., Davies, F., DiCarlo, P., Di Marco, C. F., Edwards, P. M., Evans, M. J., Fowler, D., Furneaux, K. L., Gallagher, M., Guenther, A., Heard, D. E., Helfter, C., Hopkins, J., Ingham, T., Irwin, M., Jones, C., Karunaharan, A., Langford, B., Lewis, A. C., Lim, S. F., MacDonald, S. M., MacKenzie, A. R., Mahajan, A. S., Malpass, S., McFiggans, G., Mills, G., Misztal, P., Moller, S., Monks, P. S., Nemitz, E., Nicolas-Perea, V., Oetjen, H., Oram, D., Palmer, P. I., Phillips, G. J., Plane, J. M. C., Pugh, T., Pyle, J. A., Reeves, C. E., Robinson, N. H., Stewart, D., Stone, D., and Whalley, L. K.: Oxidant and particle photochemical processes above a south-east Asian tropical rain forest (the OP3 project): introduction, rationale, location characteristics and tools, Atmos. Chem. Phys. Discuss., 9, 18899-18963, doi:10.5194/acpd-9-18899-2009, 2009.
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