
Physics Photo of the Week October 21, 2022 First Rime Ice - Fall 2022 This Wednesday morning (October 19, 2022) brought the first rime ice deposit on the Great Craggy Mountains overlooking Warren Wilson College in the midst of fall colors. This is a sign that winter is about to descend. The whiteness on top of Craggy Gardens, which I call "Craggy", is due to the frost on the twigs and remaining leaves on the trees of the mountaintop at high elevations (higher than 5000 ft above sea-level). What looks like frost from a distance, is frozen cloud droplets, that were below the freezing point while within a descended cloud. The cloud droplets were super-cooled below the freezing point of water (32 deg F). As soon as the droplets collided with a leaf or twig, they were stimulated to freeze immediately because the twigs and leaves provided nucleation sites to attract the crystallizing super-cooled water. A much more vivid color photo was made the last time Physic...