Evidence of liquid dependent ice nucleation in high-latitude stratiform clouds from surface remote sensors

Ground-based lidar, radar and microwave radiometer observations at Eureka, Canada, Barrow, Alaska and over the western Arctic Ocean measure physical characteristics and morphology of stratiform clouds. Despite transition of a cold atmosphere (-15 C) through ice supersaturated conditions, ice is not observed until soon after a liquid layer. Several cases illustrating this phenomenon are presented in addition to long-term observations from three measurement sites characterizing cloud phase frequency. This analysis demonstrates that clouds composed entirely of ice occur less frequently than liquid-topped mixed-phase clouds at temperatures warmer than -25 to -30 C. These results indicate ice formation generally occurs in conjunction with liquid at these temperatures, and suggest the importance of liquid-dependent ice nucleation mechanisms. Citation: de Boer, G., H. Morrison, M. D. Shupe, and R. Hildner (2011), Evidence of liquid dependent ice nucleation in high-latitude stratiform clouds from surface remote sensors, Geophys. Res. Lett., 38, L01803, doi:10.1029/2010GL046016.