Supercooled Organics Inhibit Freezing

SAMANTHA GREENEY, Brianna Hendrickson, Jessica Mirrielees, Sarah Brooks, Texas A&M University

     Abstract Number: 417
     Working Group: Aerosols, Clouds and Climate

Abstract
Viscous aerosol particles may provide flexible surfaces which promote ice nucleation. However, the ability of viscous aerosol particles to act as ice nucleating particles (INPs) is not well characterized. In this study, viscosity was determined for aqueous organic solutions (citric acid, sucrose, maltose, glyoxal, and methylglyoxal) at varying weight percent (40%, 50%, and 65%), saturated solutions (citric acid, sucrose, maltose, and ammonium sulfate), and three eutonic solutions (composed of ammonium sulfate and one organic compound). Viscosity of each solution was measured at a range of temperatures. According to the measurements, it was determined each solution was in the liquid phase except for the 65 weight percent glyoxal solution which reached the semi-solid regime (>10³ poise) at -23°C. Additionally, a custom-built freezing stage was used to determine the immersion ice nucleation temperatures. The saturated citric acid solution and the ammonium sulfate/citric acid eutonic solution remained liquid until -80°C indicating they were supercooled droplets. Since viscosity increases as temperature decreases, these results indicate that particle phase may restrict the range of altitude at which organic aerosol can serve as INPs. Additionally, these organic solution droplets will remain liquid in the upper troposphere and stratosphere.