The role of pore condensation and freezing is assessed in a continuous flow diffusion chamber using spherical mesoporous silica particles with a defined particle size and pore diameter. The results indicate that pores play an important role in ice nucleation, challenging the role of deposition nucleation as an ice nucleation pathway.

Ice nucleation plays an important role in moderating the Earth’s climate and precipitation formation (Sassen et al., 2008; Mülmenstädt et al., 2015). As such, classical nucleation theory (CNT) has been developed to explain and parameterize atmospheric ice nucleation for climate models. Deposition nucleation is the only ice nucleation pathway that does not involve the liquid phase but occurs through direct vapor deposition.  However, the dependence on the homogeneous freezing temperature of water for ice nucleation below water saturation (Welti et al., 2014) has raised some doubts. To explain this dependence, Marcolli (2014) proposed that deposition nucleation is actually pore condensation and freezing (PCF). In this work, the role of PCF is assessed in a continuous flow diffusion chamber.