Sensitivity of aerosol concentrations and cloud properties to nucleation and secondary organic distribution in ECHAM5-HAM global circulation model

Risto Makkonen, Ari Asmi, H Korhonen, H Kokkola, S Järvenoja, P Räisänen, Kari Lehtinen, A Laaksonen, Veli-Matti Kerminen, Heikki Järvinen, Ulrike Lohmann, Ralf Bennartz, Johann Feichter, Markku Kulmala

    Research output: Contribution to journalArticleScientificpeer-review

    Abstract

    The global aerosol-climate model ECHAM5-HAM was modified to improve the representation of new particle formation in the boundary layer. Activation-type nucleation mechanism was introduced to produce observed nucleation rates in the lower troposphere. A simple and computationally efficient model for biogenic secondary organic aerosol (BSOA) formation was implemented. Here we study the sensitivity of the aerosol and cloud droplet number concentrations (CDNC) to these additions. Activation-type nucleation significantly increases aerosol number concentrations in the boundary layer. Increased particle number concentrations have a significant effect also on cloud droplet number concentrations and therefore on cloud properties. We performed calculations with activation nucleation coefficient values of 2 x 10(-7) s(-1), 2 x 10(-6) s(-1) and 2 x 10(-5) s(-1) to evaluate the sensitivity to this parameter. For BSOA we have used yields of 0.025, 0.07 and 0.15 to estimate the amount of monoterpene oxidation products available for condensation. The hybrid BSOA formation scheme induces large regional changes to size distribution of organic carbon, and therefore affects particle optical properties and cloud droplet number concentrations locally. Although activation-type nucleation improves modeled aerosol number concentrations in the boundary layer, the use of a global activation coefficient generally leads to overestimation of aerosol number. Overestimation can also arise from underestimation of primary emissions.
    Original languageEnglish
    JournalAtmospheric Chemistry and Physics
    Volume9
    Issue number5
    Pages (from-to)1747-1766
    Number of pages20
    ISSN1680-7316
    DOIs
    Publication statusPublished - 2009
    MoE publication typeA1 Journal article-refereed

    Fields of Science

    • 114 Physical sciences

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