The microphysical properties of ice fog measured in urban environments of Interior Alaska

The National Center for Atmospheric Research Video Ice Particle Sampler probe and Formvar (polyvinyl formal)-coated microscope slides were used to sample airborne ice particles at two polluted sites in the Fairbanks region. Both sites were significantly influenced by anthropogenic emission and additional water vapor from nearby open water power plant cooling ponds.

Measurements show that ice fog particles were generally droxtal shaped (faceted, quasi-spherical) for sub-10 µm particles, while plate-shaped crystals were the most frequently observed particles between 10 and 50 µm. A visibility cutoff of 3 km was used to separate ice fog events from other observations which were significantly influenced by larger (50-150 µm) diamond dust particles. The purpose of this study is to more realistically characterize ice fog microphysical properties in order to facilitate better model predictions of the onset of ice fog in polluted environments.