Freezing fog Tuesday morning created a lot of cool views across the Tennessee Valley. A variety of surfaces were covered in the familiar layer of icy rime, from vegetation to spider webs! Rime is a layer of ice that develops when water droplets freeze on contact with a surface, creating a rough layer of frost.
Even more unique than rime though, are the light displays that are created from freezing fog. Tiny ice crystals are usually found in very high thin clouds, but freezing fog can create those crystals closer to the surface. If light hits the crystals just right, we can get a lot of cool optical phenomena!
Peggy Ponds caught an ice halo at ground level here in the Tennessee Valley on Tuesday, showcasing some of the optical effects of ice crystals. We weren’t the only ones to deal with freezing fog this week though; farther north in Wisconsin, where the freezing fog is more common, rare light pillars formed. Light pillars occur when light reflects through ice crystals, like those in freezing fog. The light is reflected in its original color too, so red light will yield a red light pillar.
Light pillars require a lot of tiny ice crystals to be suspended in the air, which typically only happens during extremely cold temperatures – often below zero. That makes it very rare for any kind of optical phenomena like this to occur at the ground here in the Tennessee Valley.
It is still possible though, so next time your yard is overtaken with fog, step outside to see what might appear! Pay special attention to any light sources (including the sun)!