PUB - Publikationen an der Universität Bielefeld

Water condensation and subsequent freezing on porous aerosol particles may occur at lower saturation conditions than on particles with more planar surfaces in a process termed pore condensation and freezing. Here, we provide a thermodynamic treatment of the pore condensation and freezing process for various types of pore shapes and surface materials of different hydrophilicity and icephilicity as a function of temperature. In detail, we studied cylindrical pores and cone-shaped pores and provide a scheme for treating pores of arbitrary shape. Moreover, we analyzed the optimal conditions for the escape of nanometersized ice crystals from cylindrical pores. Finally, we show that the pores occurring in aggregates of spherical primary particles may be particularly suited to act as cloud condensation nuclei and ice nucleating particles, practically without any significant supersaturation when their surface is very hydrophilic or icephilic, respectively. This ability may have implications for the formation of water clouds and ice clouds under conditions where such aggregates exist in the atmosphere, for example, oxidized soot particles or aggregates formed by freeze-drying of water-soluble organics.