Smaller and larger
When a glory is large and colorful, Ulloa’s circle is weak and white. When glories are small and weak, cloudbows or fogbows can become distinct and colorful. It’s important then to know about Ulloa’s circle and this relationship because the best cloudbows can rival rainbows! “Cloudbows are indeed a form of rainbow, but made by cloud or fog droplets far smaller than the raindrops of an ordinary rainbow,” explains Les Cowley of Atmospheric Optics (
www.atoptics.co.uk). “The smaller the droplets, the whiter and broader is the cloudbow.”
I witnessed an extraordinary example of this phenomenon August 15, 2012, while flying between islands in Hawaii. The cloudbow was a vibrant orange on the outside with spectral colors mixing to a soft sky-blue. An intense dark band then separated these colored rings to a fainter set, with colors reversed, from an inner set of what’s known as supernumerary bows. The ring itself was distorted: It was wider close to the jet, as it rose above the clouds, then tapered to distant cumulonimbus cloud tops in the distance. Never had I seen such a fine display with an unseen glory.
As always, good luck in your visual journeys and email me your thoughts and observations at
someara@interpac.net.