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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-986
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
A simple model for the time evolution of the condensation sink in the atmosphere for intermediate Knudsen numbers
Ekaterina Ezhova1, Veli-Matti Kerminen1, Kari E. J. Lehtinen2, and Markku Kulmala1 1Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
2Department of Applied Physics, University of Eastern Finland, P.O. Box 1627, 70211 Kuopio, Finland
Abstract. Transformation of the mass flux towards the particle from the kinetic regime to the continuum regime is often described by the Fuchs-Sutugin coefficient. Kinetic regime can be obtained as a limiting case when only one term of the expansion of the Fuchs-Sutugin coefficient at small 1 / Kn is considered. Here we take into account the two first terms, and get the mass flux which agrees well with the full mass flux up to Kn ≈ 0.5. This procedure allows to obtain an analytical solution of the condensation equation valid for the range of intermediate Knudsen numbers. The expansion is further applied to calculate analytically the condensation sink. The formula for the condensation sink is tested against field observations. The relative contribution of different aerosol modes to the condensation sink is discussed. Furthermore, we present a simple model describing a coupled dynamics of the condensing vapour and the condensation sink. The model gives reasonable predictions of the condensation sink dynamics during the periods of the aerosol modes growth by condensation in the atmosphere.

Citation: Ezhova, E., Kerminen, V.-M., Lehtinen, K. E. J., and Kulmala, M.: A simple model for the time evolution of the condensation sink in the atmosphere for intermediate Knudsen numbers, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-986, in review, 2017.
Ekaterina Ezhova et al.
Ekaterina Ezhova et al.
Ekaterina Ezhova et al.

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Short summary
A condensation sink (CS) quantifies the rate of uptake of condensing vapours by pre-existing aerosol and can be used as well to quantify losses of monomers/clusters. An analytical solution of the condensation equation valid in a wide range of particle diameters is presented. We describe the dynamics of atmospheric CS, test the formulas against field observations and further use them to develop a simplified model of the coupled dynamics of aerosol and condensing vapours in the atmosphere.
A condensation sink (CS) quantifies the rate of uptake of condensing vapours by pre-existing...
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