Mount Hood Rime Ice
August 12, 2014
On a cold February morning this past winter at Mount Hood Wilderness, Oregon, the temperature dropped to near 0 F (-18 C). During the day, it warmed to near the freezing mark (32 F or 0 C). The sunny, calm conditions were perfect for my first snowshoe hike of 2014. I hadn’t walked a quarter mile (0.6 km) from the trailhead before the Sun, glistening off the surface of the snow, captured my attention. Tree branches looked as though each had long, white spikes attached. Everything was decorated with dainty crystals.
Rime ice forms when liquid water droplets in the air freeze onto a surface, growing into combs, needles or feathery forms. This rime was deposited over the course of many hours, as a freezing fog had lingered for most of the morning. Without anything solid to nucleate around, the suspended fog droplets remained liquid, even as they cooled to temperatures where you’d expect them to be frozen. Water droplets can remain in this supercooled state until they bump into something solid, a pine needle for example, they then freeze upon contact. The riming conditions I experience this midwinter's day allowed me to snowshoe in a winter wonderland. Photo taken on February 2, 2014.