Atmos. Chem. Phys. Discuss., 13, 5961-6005, 2013
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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.
Updated aerosol module and its application to simulate secondary organic aerosols during IMPACT campaign May 2008
Y. P. Li1,2,3, H. Elbern2,3, K. D. Lu1, E. Friese2, A. Kiendler-Scharr3, Th. F. Mentel3, X. S. Wang1, A. Wahner3, and Y. H. Zhang1
1State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
2Rhenish Institute for Environmental Research at the University of Cologne, Cologne, Germany
3Institut für Energie- und Klimaforschung Troposphäre (IEK-8), Forschungszentrum Jülich, Jülich, Germany

Abstract. The formation of Secondary organic aerosol (SOA) was simulated with the Secondary ORGanic Aerosol Model (SORGAM) by a classical gas-particle partitioning concept, using the two-product model approach, which is widely used in chemical transport models. In this study, we extensively updated SORGAM including three major modifications: firstly, we derived temperature dependence functions of the SOA yields for aromatics and biogenic VOCs, based on recent chamber studies within a sophisticated mathematic optimization framework; secondly, we implemented the SOA formation pathways from photo oxidation (OH initiated) of isoprene; thirdly, we implemented the SOA formation channel from NO3-initiated oxidation of reactive biogenic hydrocarbons (isoprene and monoterpenes). The temperature dependence functions of the SOA yields were validated against available chamber experiments. Moreover, the whole updated SORGAM module was validated against ambient SOA observations represented by the summed oxygenated organic aerosol (OOA) concentrations abstracted from Aerosol Mass Spectrometer (AMS) measurements at a rural site near Rotterdam, the Netherlands, performed during the IMPACT campaign in May 2008. In this case, we embedded both the original and the updated SORGAM module into the EURopean Air pollution and Dispersion-Inverse Model (EURAD-IM), which showed general good agreements with the observed meteorological parameters and several secondary products such as O3, sulfate and nitrate. With the updated SORGAM module, the EURAD-IM model also captured the observed SOA concentrations reasonably well especially those during nighttime. In contrast, the EURAD-IM model before update underestimated the observations by a factor of up to 5. The large improvements of the modeled SOA concentrations by updated SORGAM were attributed to the mentioned three modifications. Embedding the temperature dependence functions of the SOA yields, including the new pathways from isoprene photo oxidations, and switching on the SOA formation from NO3 initiated biogenic VOCs oxidations contributed to this enhancement by 10%, 22% and 47%, respectively. However, the EURAD-IM model with updated SORGAM still clearly underestimated the afternoon SOA observations up to a factor of two. More work such as to improve the simulated OH concentrations under high VOCs and low NOx concentrations, further including the SOA formation from semi-volatile organic compounds, the correct aging process of aerosols, oligomerization process and the influence on the biogenic SOA by the anthropogenic SOA, are still required to fill the gap.

Citation: Li, Y. P., Elbern, H., Lu, K. D., Friese, E., Kiendler-Scharr, A., Mentel, Th. F., Wang, X. S., Wahner, A., and Zhang, Y. H.: Updated aerosol module and its application to simulate secondary organic aerosols during IMPACT campaign May 2008, Atmos. Chem. Phys. Discuss., 13, 5961-6005, doi:10.5194/acpd-13-5961-2013, 2013.
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