The interactions between atmospheric particles and clouds are the least understood aspect of our climate system.  Clouds can contain water, ice, or a combination of the two.  To nucleate ice at temperatures warmer than approximately -40 degrees C, a heterogeneous nucleus is needed.  The properties of the heterogeneous surface that promote ice nucleation are not well understood.  To determine the interplay of crystallinity, crystal structure, defects, and functional groups in ice nucleation, we work with engineered materials in which these properties can be precisely tuned.  For example, we investigated many types of alumina with different crystal structures. For these systems, crystallinity was most important in determining the ice nucleation activity, followed by crystal structure.  In other words, the most highly crystalline samples had the highest nucleation activity regardless of crystal structure, and of these, the crystal structure dictated which sample had the highest activity.  I will also present a similar study on iron oxides, as well as exploring the effect of aging on the ice nucleation activity of these systems.  Through these studies, we can determine which properties of a surface are most important for promotion of ice nucleation, which is important for understanding cloud formation in the atmosphere.

Surface features that promote heterogeneous ice nucleation

2019 Fall National Meeting

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