Fog bow
A fog bow is similar to a rainbow, but because of the very small size of water droplets that cause fog, smaller than 0.05 mm, the fog bow has only very weak colors, a red outer edge and bluish inner. In some cases when the droplets are very small it appears white. Fogbows are therefore sometimes called "white rainbows". A fogbow seen in clouds, typically from an aircraft looking downwards, is called a "cloudbow". Mariners sometimes call them "sea-dogs."
When the droplets forming it are almost all of the same size the fogbow can have multiple inner rings, supernumeraries, that are more strongly colored than the main bow.
The fogbow's lack of colors is a result of the smaller water drops... so small that the wavelength of light becomes important. Diffraction smears out colors that would be created by larger rainbow water drops.
Direction
A fogbow is seen in the same direction as a rainbow, thus the sun would be behind the head of the observer and the direction of view would be into a bank of fog (which may not be noticeable in directions away from the bow itself). Its outer radius is slightly less than that of a rainbow.
When a fog bow appears at night it is called a lunar fog bow.[1]
See also
References
External links
- Photos and explanation of fogbows at Atmospheric Optics.
- Fogbow image gallery at AKM website.
- Fogbows at Glows, Bows and Haloes site.
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