Turn That Rainbow Upside Down

Don’t know about you, but I’d be rubbing my eyes if a upside down rainbow crossed my path. Who knew? Seems weather phenomena has an arsenal of tricks up her sleeve. Technically, upside down doesn’t qualify as rainbow. They’re known as circumzenithal arc or CZA, elite members of the halo family. Whereas rainbows form when light (most commonly sunlight, sometimes bright moonlight ) passes through low atmosphere water droplets, CZA require atmospheric ice crystals and just the right degree of sunlight.

A rainbow-like arc in the sky, with red on the bottom of the arc, behind a tree.

David Lamberti caught this circumzenithal arc in 2019. Notice the kite in the tree! He wrote: “It was a beautiful January day in southeast Michigan. I looked up, and there it was, a beautiful circumzenithal arc. It was enormous, and the colors were very deep. It faded within 5 minutes.” From – https://earthsky.org/earth/i-saw-an-upside-down-rainbow-circumzenithal-arc?utm_source=EarthSky+News&utm_campaign=2be56154d1-EMAIL_CAMPAIGN_2018_02_02_COPY_01&utm_medium=email&utm_term=0_c643945d79-2be56154d1-393970565

Long parallel streamer-like clouds in a blue sky with very bright arc across them.

“A lovely circumzenithal arc amidst high clouds by Dudley Williams on December 18, 2011.” – Earthsky

Check out Atmospheric Optics for more – https://www.atoptics.co.uk/halo/cza.htm

No nonsense rainbow primer – https://www.worldatlas.com/articles/how-is-a-rainbow-formed.html