Influence of boundary layer dynamics and isoprene chemistry on the organic aerosol budget in a tropical forest

Authors

  • R. H. H. Janssen,

    Corresponding author
    1. Earth System Science and Climate Change, Wageningen University and Research Center, Wageningen, Netherlands
    2. Now at Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
    • Corresponding author: R. H. H. Janssen, Atmospheric Chemistry Department, Max Planck Institute for Chemistry, Hahn-Meitner-Weg 1, Mainz, D-55128, Germany. (ruud.janssen@mpic.de)

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  • J. Vilà-Guerau de Arellano,

    1. Meteorology and Air Quality Section, Wageningen University and Research Center, Wageningen, Netherlands
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  • J. L. Jimenez,

    1. Cooperative Institute for Research in the Environmental Sciences and Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, Colorado, USA
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  • L. N. Ganzeveld,

    1. Earth System Science and Climate Change, Wageningen University and Research Center, Wageningen, Netherlands
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  • N. H. Robinson,

    1. Centre for Atmospheric Science, School of Earth Atmospheric and Environmental Science, University of Manchester, Manchester, UK
    2. Now at Seasonal to Decadal Prediction, The Met Office, Exeter, United Kingdom
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  • J. D. Allan,

    1. Centre for Atmospheric Science, School of Earth Atmospheric and Environmental Science, University of Manchester, Manchester, UK
    2. National Centre for Atmospheric Science, The University of Manchester, Manchester, UK
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  • H. Coe,

    1. Centre for Atmospheric Science, School of Earth Atmospheric and Environmental Science, University of Manchester, Manchester, UK
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  • T. A. M. Pugh

    1. Lancaster Environment Centre, University of Lancaster, Lancaster, UK
    2. Now at Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research/Atmospheric Environmental Research (IMK-IFU), Garmisch-Partenkirchen, Germany
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Abstract

[1] We study the organic aerosol (OA) budget in a tropical forest by analyzing a case that is representative for the OP3 campaign at Borneo. A model is designed that combines the essential dynamical and chemical processes that drive the diurnal evolution of reactants in the atmospheric boundary layer (BL). In this way, the model simultaneously represents the effects and interactions of various dynamical and chemical factors on the OA budget. The model is able to reproduce the observed diurnal dynamics of the BL, including the evolution of most chemical species involved in secondary organic aerosol (SOA) formation. A budget analysis of the contributions of the dynamic and chemical processes reveals the significance of the entrainment process in the diurnal evolution of SOA. Further, we perform a series of sensitivity analyses to determine the effect of meteorological forcings and isoprene chemical pathways on the OA budget. Subsidence and advection of cool air have opposing effects on the OA concentration, although both suppress BL growth. Recycling of the OH radical in the oxidation of isoprene may affect the amount of SOA that is formed, but must be understood better before its impact can be definitely determined. SOA formation from isoprene is calculated for both the low- and high-NOx pathway, with the latter dominating the isoprene peroxy radical chemistry. Finally, we study the significance of SOA formation through the reactive uptake of isoprene epoxydiols on acidic sulfate aerosol. Despite the incorporation of these new pathways, the OA concentration is systematically underestimated by about a factor of 2.

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