Abstract: Aerosol-cloud interactions play a key role in the earth’s energy budget yet contribute to a large uncertainty in radiative forcing in climate models. My group is interested in organic aerosols and its chemical composition to inform on the freezing of supercooled water droplets in mixed-phased clouds. To explore the mechanism of freezing of organic matter in cloud water conditions, we’ve developed drop freezing techniques relevant for immersion freezing.(1) We’ve also been exploring different types of samples: field-collected dissolved organic matter from lakes and rivers relevant for lake spray aerosols,(2) humic substance standards,(2) lignin as a subcomponent of biomass burning organic aerosol,(3) firewood smoke, ammonium sulfate methyl glyoxal brown carbon solutions, lab-generated secondary organic aerosols,(4) soil dust and proteinaceous material. These different samples are demonstrating that the size of the macromolecules and their functional groups are playing competitive roles in the ability of organic matter to template ice. In all, organic aerosols can alter the aerosol-cloud radiative effects by modifying the supercooled liquid water-to-ice crystal ratio in mixed-phase clouds with implications for cloud lifetime, precipitation patterns and the hydrological cycle.
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