16 Nebraskaland • January-February 2020
Feathers on a fence post. No, not that of a bird, but
rather wisps of white interlocking crystals that form as
water transitions directly from vapor to solid form. This is
hoarfrost.
This specific type of frost is voluminous, feathery and
light, extending out from leaves and tree branches, wires or
poles. Most of us are familiar with frost, the thin coating of
ice on the landscape that occurs when water vapor deposits
on surfaces at temperatures that are below freezing, termed
deposition. But hoarfrost has much more structure than
frost and may in fact look like a dusting of snow from a
distance.
The occurrence is most common under clear and calm
nights as the earth cools and loses its daytime heat energy
to the atmosphere. If there is just a light wind, the crystalline
structure will act as a wind vane and tell you the direction
the air is moving. Hoarfrost can also form as liquid dew that
cools and subsequently freezes, in which it is then called
silver or white frost.
As with everything else when it comes to our weather,
conditions change as quickly as a bird taking flight. Catch
these "feathers" before the faint winter sun turns them back
into liquid phantoms.
Martha D. Shulski, at the University of Nebraska-Lincoln, is
the director of the Nebraska State Climate office.
IN THE FIELD
PHOTO
BY
ERIC
FOWLER
HOARFROST
By Martha D. Shulski
