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In the last year I have observed two different "rainbows". I understand the physics of the sun behind me and the water droplets. Have you ever observed a rainbow that followed the form of the cloud? It was not the arc type but followed the edge of the cloud. My daughter saw one in Pittsburgh. I saw one here in Seven Lakes. Both hers and mine were seen after a tornado event. Significance? The other type was on the golf course, with the sun behind our backs on a dewy morning. There were two rainbows radiating from our feet both left and right. EAch of us saw their own rainbows. Interesting? Unusual?

Posted May 15, 2007

MIKE MOSS SAYS:     Nancy,    It's always interesting to hear about the optical phenomena people see associated with water droplets and ice crystals. The variety can be amazing! As for the two that you mentioned:

The first I can't be absolutely sure about, but my guess from your description would be something iridescence, which can be seen occasionally in cirrus clouds or along the edges of "glaciating" towering cumulus or cumulonimbus clouds, especially when those cloud edges are hiding the sun and are "silhouetted" to some degree. These can be associated with severe weather, but not necessarily. Here is an address for a web site that shows examples, and some explanations for, iridescence. Maybe they will help you figure out if I'm speculating correctly as to what you observed.

http://www.atoptics.co.uk/droplets/irid1.htm   (be sure to click the "more images" link along the left side of the page)

The other effect you was is given away by the fact that it radiates away from your feet and occurred on a dewy morning. It is known as none other than a "dew bow" and represents almost the inversion of a typical rainbow, since the water droplets involved are below, rather than above, the horizon. See

http://www.atoptics.co.uk/rainbows/dewbow.htm

As with many optical effects, especially those that relate to an "antisolar point" like rainbows and dew bows, each person will see a bow or other effect that is centered around their own antisolar point (pretty much where the shadow of your head is or would be located). A good illustration of this is given with regard to another dew effect called the "heiligenschein," or "Holy Light." You'll see why it has that name, and how it moves with the location of the viewer, at

http://www.atoptics.co.uk/droplets/heilig.htm

 

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