Ice nucleation in aerosols containing biomolecules

Biological aerosols represent a small but efficient contribution to populations of ice nucleating particles in the atmosphere. The resultant ice formation is crucial to cloud microphysics and plays a role in cloud radiative properties and precipitation. However, applications to climate models are currently limited by a lack of understanding of the heterogeneous ice nucleation process and the properties of effective nucleating agents. Furthermore, differing nucleating abilities between particles hinder the determination of the time dependence of freezing. The aim of this research is to use model biomolecules to produce samples of ice nucleating particles with uniform nucleating ability and to study nucleating efficiency as a function of surface geometry and chemistry. Nucleation rates will be measured by droplet freezing assays and by adaptation of an electrodynamic balance for levitated single droplet freezing. This will aid understanding of the ice nucleation mechanism in atmospheric conditions.