10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Adsorption Nucleation Theory for Ice Formation from the Vapour Phase
ANDRÉ WELTI, Ana A. Piedehierro, Yrjö Viisanen, Annele Virtanen, Lise Deschutter, Outi Meinander, Ari Laaksonen, Finnish Meteorological Institute
Abstract Number: 1265 Working Group: Unraveling the Many Facets of Ice Nucleating Particles and Their Interactions with Clouds
Abstract The recently developed framework of adsorption nucleation is applied to describe ice formation from the vapour phase on insoluble particles. The theory (Laaksonen, 2015; Laaksonen and Malila, 2016) is based on a combination of the Frenkel-Halsey-Hill (FHH) adsorption isotherm and the Kelvin equation, and it describes the adsorption of water in spherical clusters on a substrate and predicts, in dependence of substrate properties the critical saturation at which clusters reach a stable size. These ice clusters then serve as centres for ice to grow into a macroscopic ice crystal. The theory has previously been applied successfully to predict onset conditions of ice nucleation triggered by several soot species at low temperatures (Laaksonen et al., 2018).
Here we investigate if the theory works equally well for ice formation on natural mineral dust samples including Arizona Test Dust and Islandic dust of volcanic origin. Input parameters for the adsorption nucleation theory (contact angle and FHH adsorption parameters between water and the substrate) are determined experimentally for the same samples the ice nucleation efficiency has been measured. The theoretical predictions of the adsorption nucleation framework and of classical nucleation theory are contrasted with measurements from the literature, so that the comparison serves as a test of correctness of the theories.
[1] Laaksonen, A.: A unifying model for adsorption and nucleation of vapors on solid surfaces. J. Phys. Chem. A, 119, 3736-3745, 2015. [2] Laaksonen A., and Malila, J.: An adsorption theory of heterogeneous nucleation of water vapour on nanoparticles. Atmos. Chem. Phys. 16, 135-143, 2016. [3] Laaksonen, A., Malila, J., and Nenes, A.: Unifying the heterogeneous nucleation of water and ice. In preparation, 2018.