Collaborative Research: Exploring the Role of Organics in Atmospheric Contact Nucleation

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This project is focused on the study of a mechanism for the formation of ice particles in mixed phase clouds in the atmosphere. This mechanism, called contact nucleation, occurs when an ice nucleating particle collides with the surface of a supercooled cloud droplet. The results of this research will improve the ability to model particles and clouds in the Earth's atmosphere.The research will test the following hypotheses: (1) Organic particles can act as contact nuclei to promote efflorescence of mixed organic-inorganic aqueous droplets, and the effectiveness of the organic will depend on composition of the aqueous phase; temperature and relative humidity; and composition, oxidation, viscosity, morphology, and size of the contact nuclei; and (2) Organic particles can act as contact nuclei to promote ice nucleation, and the effectiveness of the organic will depend on composition of the aqueous phase; temperature; and composition, oxidation, viscosity, morphology, and size of the contact nuclei. The experiments will be conducted using two complementary levitation techniques that allow freely-floating droplets to undergo single collisions with well-defined contact nuclei: a long working distance optical trap and a dual stage electrodynamic balance.These studies are expected to provide fundamental data on contact nucleation that currently are not available in the literature. This effort will lead to improved theoretical descriptions of heterogeneous nucleation and enable contact nucleation to be included in atmospheric models that predict the formation of ice particles in the atmosphere.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.