10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Evaluation of Immersion Freezing Properties of Dark-Colored Particles under Mixed-Phase Cloud Conditions
YUTAKA TOBO, Nobuhiro Moteki, Kouji Adachi, Sho Ohata, Atsushi Yoshida, Makoto Koike, Yutaka Kondo, National Institute of Polar Research
Abstract Number: 1074 Working Group: Unraveling the Many Facets of Ice Nucleating Particles and Their Interactions with Clouds
Abstract Dark-colored aerosols are thought to have an influence on the Earth’s climate system by heating the atmosphere and by reducing snow albedo. It is well recognized that black carbon (BC) is a major type of dark-colored particles. In addition, recent work has shown that certain amounts of anthropogenic iron oxides having similar color and morphology to BC are present in the atmosphere. Understanding the influence of such dark-colored aerosols on heterogeneous ice nucleation is important to evaluate their impact on ice formation in supercooled clouds and subsequent ice-induced precipitation (i.e., their deposition process to the snow surface); however, their ice nucleating ability remains uncertain and controversial. In this study, we evaluate the roles of different types of dark-colored particles (e.g., BC, iron oxide) as ice nucleating particles (INPs) under conditions relevant to mixed-phase clouds. Immersion freezing experiments using an original cold-stage-based technique (NIPR-CRAFT) indicate that although the particles used here can serve as INPs at temperatures colder than -20°C, their ice nucleating abilities are much lower than those of other types of insoluble particles reported previously. Furthermore, based on field measurements and modeling estimates, we suggest that the contribution of the dark-colored particles to the population of INPs in the atmosphere may be negligibly small, at least in the Arctic region.