« Carcieri touts new graduation requirements / Photo | Today | Update: Bay View mercury spill from home thermometer »

December 18, 2007

Photo: Upside-down rainbow over Union Street

projo.com photo/ Brandie Jefferson
A circumzenithal arc in the sky above downtown Providence.

The circumzenithal arc floated over Union Street early this afternoon.

The arcs are sometimes called upside-down rainbows -- although they're not. Rainbows are caused by reflection and refraction of light through rain drops.

The arcs are formed when sunlight passes through flat, horizontally oriented ice crystals in the atmosphere.

The center of the arc always faces the sun, and if the arc were to be drawn out into a circle, it would circle the zenith point in the sky -- directly overhead. This means, of course, that you almost have to be looking straight up to notice them.

Circumzenithal arcs one of a handful of cool atmospheric phenomenon that are more common in during the colder months.

Keep an eye out.

-- projo.com staff writer Brandie M. Jefferson

Posted by Brandie Jefferson  at 3:10 PM | Permalink

Comments

Post a comment

Please be civil. Vicious comments, personal attacks and profanity won't be published. Name and email are required; email address will not publish.

Name:

Email Address:

URL:
Remember Me? YesNo

Comments: (you may use HTML tags for style)