Examining Ice Nuclei Efficiency and Optical Properties of the Resulting Ice Crystals

Much uncertainty remains in our knowledge of heterogeneous ice nucleation mechanisms and the optical properties of the resulting ice crystals. Since atmospheric ice crystals have a large impact on Earth's radiative balance by serving as effective scatterers of incoming sunlight, an improved understanding of ice nucleation processes and the optical properties of the resulting crystals could enhance our understanding of weather and climate. In this study, data collected during the Fifth International Ice Nucleation Workshop (FIN-02) is used to compare the effectiveness of various aerosols at nucleating ice and to examine the optical properties of the resulting ice crystals. Ice nucleation data was collected during FIN-02 by sampling the AIDA cloud chamber at the Karlsruhe Institute of Technology (KIT) in Germany with the Texas A&M University Continuous Flow Diffusion Chamber- Chamber - Cloud Aerosol Spectrometer with Polarization CASPOL (CFDC-CASPOL). A wide range of ice nucleation efficiencies was found between the four types of ice nuclei examined in this study (Argentine Soil, Desert Dust, Snomax, and Illite), with Snomax being by far the most efficient. Based on the single particle backscatter and depolarization measured by the CASPOL detector optical signature plots were constructed for each type of ice nucleus. Differences were found between the optical signature plots constructed for ice nucleated on each composition of ice nuclei. However, it is unclear whether this is a result of the limited data available to plot for each type of ice nucleus or an actual variation in the optical properties of the ice crystals. Additional efforts to evaluate the optical properties of ice nuclei measured by the CASPOL are underway.