News.bytesNews.bytes extra, issue 186

Pogonip hits northern California public lands

Pogonip rhas paid several visits to Northern California this winter. It brought bone-chilling cold for area residents, but left behind a winter wonderland of scenery. These photos were taken before the recent major snowstorm hit the area.

grass stems coated with hoarfrost

Pogonip, or ice fog, results in a phenomenon called "hoarfrost," which is a deposit of interlocking ice crystals on objects exposed to cold, foggy air. Dazzling winter scenes are revealed as tree limbs, leaves, fence wires are coated with the ice. As the fog burns off in the daylight hours, there are a few magical moments when the hoarfrost glistens in the sun, beautifully contrasted against azure skies.

Seen from BLM-managed public lands north of Susanville, the Honey Lake Valley is blanketed by a thick layer of ice fog, or pogonip:
Honey Lake Valley is blanketed by a thick layer of ice fog

For a short time after the pogonip leaves, the hoarfrost remains. The interlocking ice crystals encase leaves:
Feathery structures of ice crystals surround a yellowing leaf

The crystals attach themselves even to the tiniest grass plants close to the ground.
close-up of a plant covered in hoarfrost

The crystals settle along pine needles....
ice crystals along evergreen needles

And onto the autumn leaves still stubbornly clinging to their branches:
fading fall foliage brightened up with an outline of ice crystals
a set of red leaves edged with ice crystals
a single leaf edged with ice

As the day warms, the ice begins to drop from the edges of the leaves, and a winter wonderland begins to melt into memory:
leaves still green, connected by a network of ice crystals

Photographs by Jeff Fontana, BLM northern California public affairs specialist, 12/4/04

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