#cache valley

snow in the canyon a couple weekends ago

I love stormy days in the warmer months. 

From Earth Science Picture of the Day; January 2, 2018:

Beware the Pogonip! Photographer and Summary Author: Ray Boren

Pogonip sounds like it could be a word coined by Lewis Carroll for his poem “Jabberwocky”, about battling the manxome Jabberwock and the frumious Bandersnatch, and that’s not too far from the truth of it. The term — popularized in part by The Old Farmer’s Almanac, which sometimes cautions “Beware the Pogonip” — describes a wintertime cold spell with freezing fog, during which super-cooled droplets condense in frigid temperatures and form crystalline particles and layers on trees, grasses, fences — most anything.

In the photograph above, taken on December 9, 2017, just such a fog is beginning to lift along waterways near Mendon, in Utah’s Cache Valley, revealing a white landscape of frosted trees and farm fields. The temperature was about 20 degrees F (-6.7 degrees C). A second photo, taken on December 13, 2017, in suburban Bountiful, Utah, features a ghostly birch tree with frosty platinum-tinted tresses. The images were captured during a week when a huge high-pressure weather system was sitting over much of the American West, creating inland temperature inversions, and thus fog (and smog), particularly in the valleys of northern Utah, southern Idaho and western Wyoming. In these situations, temperatures are actually warmer at higher elevations than they are at lower elevations. The effect is like clamping a lid atop the valleys, trapping moisture and, unfortunately, airborne particulate pollution.

The American Meteorological Society describes conditions when humidity is high in a deep stable layer with surface radiative cooling, as ice fog. Ice fog is also known as ice crystal fog, frozen fog, ice crystal haze, Arctic mist, frost fog, frost flakes, air hoar, rime fog, and pogonip, along with many names in other languages. When ice crystals form and fall like snow in such a fog, the phenomenon is often poetically called diamond dust. Merriam-Webster’s online dictionary etymologically reports that 19th-century English-speaking settlers of the interior valleys of the West experienced these sometimes frighteningly cold and dangerous conditions, and needed a word for it. Modifying the Shoshone word payinappih, for cloud, they came up with pogonip.

Photo Details: Top - Camera: NIKON D3200; Exposure Time: 0.0020s (1/500); Aperture: ƒ/11.0; ISO equivalent: 220; Focal Length (35mm): 33. Bottom - same except: ISO equivalent: 400; Focal Length (35mm): 153.

Coordinates

Cache Valley, Utah: 38.7250, -109.5212

Bountiful, Utah: 40.8894, -111.8808

Related Links

Rime Ice (Pogonip) on Trees

Cloaked in Winter White

Ice Fog: The Current State of Knowledge and Future Challenges

Student Links

Different Types of Fog

What's the difference between fog and clouds?

Earth Observatory