The
U.S. National Weather Service in Amarillo, Texas posted this photo on its
Facebook page this weekend. Joshua Thomas in Red River, New Mexico captured
these magnificent arcs in the sky on the morning of January 9, 2015. Look below
for a labeled version of the same photo.
Ice
halos are commonly seen by those who look at the skies; we receive several
photos of ice halos from somewhere in the world every week, especially in
wintertime. Often, we’ll receive many such photos, across a particular region, sometimes
for several days in a row. Most ice halos appear as a circle or ring around the
sun or moon. Sometimes, if conditions are just right, you do see these
wonderful, rare events when the whole sky is filled with halo arcs.
Ice
halos are caused by ice crystals in the upper atmosphere, which both refract
and reflect sunlight or moonlight.
A
ring or circle of light around the sun or moon is called a halo by scientists.
We get many messages throughout each year from people who’ve just spotted a
ring around the sun or moon. People want to know: what causes a halo around the
sun or moon? Follow the links below to learn more about lunar and solar halos.
What
makes a halo around the sun or moon?
If
you see a halo, notice this!
What
makes a halo around the sun or moon? There’s an old weather saying: ring around
the moon means rain soon. There’s truth to this saying, because high cirrus
clouds often come before a storm. Notice in these photos that the sky looks
fairly clear. After all, you can see the sun or moon. And yet halos are a sign
of high thin cirrus clouds drifting 20,000 feet or more above our heads.
These
clouds contain millions of tiny ice crystals. The halos you see are caused by
both refraction, or splitting of light, and also by reflection, or glints of
light from these ice crystals. The crystals have to be oriented and positioned
just so with respect to your eye, in order for the halo to appear.
That’s
why, like rainbows, halos around the sun – or moon – are personal. Everyone
sees their own particular halo, made by their own particular ice crystals,
which are different from the ice crystals making the halo of the person
standing next to you.
If
you see a halo, notice this! Because moonlight isn’t very bright, lunar halos
are mostly colorless, but you might notice more red on the inside and more blue
on the outside of the halo. These colors are more noticeable in halos around
the sun. If you do see a halo around the moon or sun, notice that the inner
edge is sharp, while the outer edge is more diffuse. Also, notice that the sky
surrounding the halo is darker than the rest of the sky.
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