Circumzenithal arc

Who can fail to love the circumzenithal arc?

It is uncommon and it displays one of the purest colour spectra to be found in nature.

More information about when and how the circumzenithal and circumhorizontal arcs form is found on the Kootenay Lake website page about haloes.

Indeed, at its best the circumzenithal arc shows an even purer spectrum than does the rainbow. Its only serious competitor in the sky is the circumhorizontal arc. Never seen together, these two arcs are brothers, both being formed by sunlight passing through the same types of ice crystals. The circumzenithal arc is seen high in the sky when the Sun is low in the sky; the circumhorizontal arc is seen low in the sky when the Sun is high.

I used to see the circumzenithal arc every two or three months when I lived at the Coast. Around here, I only see it every two or three years (a spectacular display appeared over Kaslo in March 2009). Yet, the one I saw yesterday while on the road to Trail was close to the best I have seen anywhere.

The first picture shows only the arc; the second, wide–angle picture shows it in relation to the Sun, the 22° halo, and the two sundogs (parhelia).