Marine Earth and Atmospheric Sciences
NC State University
HOW MICROBES MAY SCULPT THE CLOUD ENVIRONMENT
Processes that cause the first appearance of ice crystals in supercooled clouds at temperatures warmer than -20°C remain enigmatic. Laboratory studies strongly suggest that biological particles - bacteria, fungi, algae, or pollen - provide the most efficient surfaces for catalyzing freezing in this temperature range. Strong plausible feedbacks between bioaerosol emissions, cloud glaciation, and precipitation have been suggested in the literature. These feedbacks, however, are contingent on emissions into the atmosphere coupled with suitable meteorological conditions for the microbes to be entrained into the cloud environment. In my presentation I will provide an overview over emerging issues in the fascinating and resurgent field of ice nucleation research, report on laboratory and field experiments that quantify fluorescent aerosol and ice nuclei concentrations in air and rainwater, and present evidence for a new mechanism that causes widespread seeding of continental cold-frontal cloud systems with biological aerosols.