Articles | Volume 17, issue 13
https://doi.org/10.5194/acp-17-8343-2017
https://doi.org/10.5194/acp-17-8343-2017
Research article
 | 
10 Jul 2017
Research article |  | 10 Jul 2017

On the limits of Köhler activation theory: how do collision and coalescence affect the activation of aerosols?

Fabian Hoffmann

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Cited articles

Albrecht, B. A.: Aerosols, cloud microphysics, and fractional cloudiness, Science, 245, 1227–1230, 1989.
Andrejczuk, M., Reisner, J. M., Henson, B., Dubey, M. K., and Jeffery, C. A.: The potential impacts of pollution on a nondrizzling stratus deck: does aerosol number matter more than type?, J. Geophys. Res., 113, D19204, https://doi.org/10.1029/2007JD009445, 2008.
Ardon-Dryer, K., Huang, Y.-W., and Cziczo, D. J.: Laboratory studies of collection efficiency of sub-micrometer aerosol particles by cloud droplets on a single-droplet basis, Atmos. Chem. Phys., 15, 9159–9171, https://doi.org/10.5194/acp-15-9159-2015, 2015.
Ayala, O., Rosa, B., and Wang, L.-P.: Effects of turbulence on the geometric collision rate of sedimenting droplets. Part 2. Theory and parameterization, New J. Phys., 10, 075016, https://doi.org/10.1088/1367-2630/10/7/075016, 2008.
Böhm, J. P.: A general hydrodynamic theory for mixed-phase microphysics. Part II: Collision kernels for coalescence, Atmos. Res., 27, 275–290, https://doi.org/10.1016/0169-8095(92)90036-A, 1992.
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Short summary
This study analyzes at which aerosol radius the mass growth leading to activation switches from diffusion to collection, marking the limit of traditional Köhler activation theory. It is found that collection becomes increasingly important for aerosols larger than 0.1 µm in dry radius and is responsible for all activations of aerosols larger than 1.0 µm. A novel particle-based cloud modeling approach is applied, in which activation can be represented without parameterizations.
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