Atmos. Chem. Phys. Discuss., 4, 2089-2115, 2004
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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.
A parameterisation of the soot aging for global climate models
N. Riemer1, H. Vogel1, and B. Vogel2
1Department of Mechanical and Aeronautical Engineering, University of California, Davis, USA
2Institut für Meteorologie und Klimaforschung, Forschungszentrum Karlsruhe, Karlsruhe, Germany

Abstract. The representation of soot in global climate models is desirable since it contributes to both the direct and indirect climate effect. While freshly emitted soot is initially hydrophobic and externally mixed, it can be transferred into an internal mixture by coagulation, condensation or photochemical processes. These aging processes affect the hygroscopic qualities and hence the growth behaviour, the optical properties and eventually the lifetime of the soot particles. However, due to computational limits the aging of soot in global climate models is often only parameterised by an estimated turnover rate resulting in a lifetime of soot of several days. Based on the results of our simulations with a comprehensive mesoscale model, we derive the timescale on which diesel soot is transferred from an external to internal mixture, and propose a parameterisation for the use in global climate models. This parameterisation is applicable to continental conditions in industrialised areas as can be found in Central Europe and North America. For daytime conditions, away from the sources, condensation is dominant and the aging process occurs very fast with a timescale of τ=2 h. During night time condensation is not effective. Then coagulation is the most important aging process and our parameterisation leads to a timescale between 10 h and 40 h.

Citation: Riemer, N., Vogel, H., and Vogel, B.: A parameterisation of the soot aging for global climate models, Atmos. Chem. Phys. Discuss., 4, 2089-2115, doi:10.5194/acpd-4-2089-2004, 2004.
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