14 Nebraskaland • January-February 2021
IN THE FIELD
By Martha D. Shulski
DOGS IN THE SKY
Winter is my favorite season. There lies
a lot of beauty in the seemingly pulsing
landscape as snow-covered ground melts to
reveal the browns of winter, only to establish
again with the next passing storm. We can
see animals much easier without the cover
of foliage. The pastel optics of a winter sky
are aided by low sun angles and layered
clouds, as opposed to the bright intensity
of summer. An optical phenomenon visible
primarily, but not exclusively, in winter is
called "parhelion."
Better known as sun dogs, these mock suns
are in the halo family of optical weather. Sun
dogs result from light changing direction, or
refracting, as it passes through ice crystals.
Similar to rainbows, the frozen plate-shaped
crystals act as tiny prisms suspended in cirrus
clouds that are cold and at high altitudes.
Parhelia appear in close proximity to the
sun, 22 degrees to be exact, and sometimes
the rainbow of colors are distinguishable,
though muted. If you look closely, you may
see other interesting optics along with these
sun dogs.
A halo is a circular feature surrounding the
sun with parhelia appearing on the east and
west sides. The top of the halo can have arced
features extending skyward.
Viewing these complete set of optical
illusions is quite rare at middle latitudes. One
would need to be in Arctic or Antarctic skies
to get the full experience. Until then, when
thin and wispy cirrus clouds don our view,
look near the low winter sun for these dogs to
illuminate the sky.
Martha D. Shulski, at the University of
Nebraska-Lincoln, is the director of the
Nebraska State Climate Office.
