Tony Prenni
The microphysical composition, temperature, and frequency of formation of cirrus clouds strongly impact their radiative properties. Aerosol particles have an indirect effect on these properties through their role in ice formation processes. Laboratory studies of homogeneous ice nucleation from inorganic solution particles at upper tropospheric temperatures have greatly advanced our understanding of ice nucleation in sulfate and nitrate aerosols. However, little work has been done on ice nucleation in organic aerosols. The ubiquitous presence of organic compounds in tropospheric particles requires that their role in aerosol/cloud interactions be accounted for in climate models.
We have begun to investigate the efficiency of organic compounds as cloud condensation nuclei and ice nuclei. In initial studies, we have focused on soluble and partially soluble dicarboxylic acids that have been observed in atmospheric aerosol. At room temperature, we use a humidified tandem differential mobility analyzer to characterize the water uptake behavior of these acids. The studies are extended to lower temperatures using a continuous flow thermal diffusion chamber to investigate the role of these organic species in ice nucleation. Future studies will also include insoluble organics commonly found in atmospheric aerosol.