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Geoscientific Model Development An interactive open-access journal of the European Geosciences Union
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Volume 11, issue 8
Geosci. Model Dev., 11, 3235-3260, 2018
https://doi.org/10.5194/gmd-11-3235-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Geosci. Model Dev., 11, 3235-3260, 2018
https://doi.org/10.5194/gmd-11-3235-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Model description paper 13 Aug 2018

Model description paper | 13 Aug 2018

Isoprene-derived secondary organic aerosol in the global aerosol–chemistry–climate model ECHAM6.3.0–HAM2.3–MOZ1.0

Scarlet Stadtler1, Thomas Kühn2,3, Sabine Schröder1, Domenico Taraborrelli1, Martin G. Schultz1,a, and Harri Kokkola2 Scarlet Stadtler et al.
  • 1Institut für Energie- und Klimaforschung, IEK-8, Forschungszentrum Jülich, Jülich, Germany
  • 2Finnish Meteorological Institute, P.O. Box 1627, 70211 Kuopio, Finland
  • 3Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland
  • anow at: Jülich Supercomputing Centre, JSC, Forschungszentrum Jülich, Jülich, Germany

Abstract. Within the framework of the global chemistry climate model ECHAM–HAMMOZ, a novel explicit coupling between the sectional aerosol model HAM-SALSA and the chemistry model MOZ was established to form isoprene-derived secondary organic aerosol (iSOA). Isoprene oxidation in the chemistry model MOZ is described by a semi-explicit scheme consisting of 147 reactions embedded in a detailed atmospheric chemical mechanism with a total of 779 reactions. Semi-volatile and low-volatile compounds produced during isoprene photooxidation are identified and explicitly partitioned by HAM-SALSA. A group contribution method was used to estimate their evaporation enthalpies and corresponding saturation vapor pressures, which are used by HAM-SALSA to calculate the saturation concentration of each iSOA precursor. With this method, every single precursor is tracked in terms of condensation and evaporation in each aerosol size bin. This approach led to the identification of dihydroxy dihydroperoxide (ISOP(OOH)2) as a main contributor to iSOA formation. Further, the reactive uptake of isoprene epoxydiols (IEPOXs) and isoprene-derived glyoxal were included as iSOA sources. The parameterization of IEPOX reactive uptake includes a dependency on aerosol pH value. This model framework connecting semi-explicit isoprene oxidation with explicit treatment of aerosol tracers leads to a global annual average isoprene SOA yield of 15% relative to the primary oxidation of isoprene by OH, NO3 and ozone. With 445.1Tg (392.1TgC) isoprene emitted, an iSOA source of 138.5Tg (56.7TgC) is simulated. The major part of iSOA in ECHAM–HAMMOZ is produced by IEPOX at 42.4Tg (21.0TgC) and ISOP(OOH)2 at 78.0Tg (27.9TgC). The main sink process is particle wet deposition, which removes 133.6 (54.7TgC). The average iSOA burden reaches 1.4Tg (0.6TgC) in the year 2012.

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Atmospheric aerosols interact with our climate system and have adverse health effects. Nevertheless, these particles are a source of uncertainty in climate projections and the formation process of secondary aerosols formed by organic gas-phase precursors is particularly not fully understood. In order to gain a deeper understanding of secondary organic aerosol formation, this model system explicitly represents gas-phase and aerosol formation processes. Finally, this allows for process discussion.
Atmospheric aerosols interact with our climate system and have adverse health effects....
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