Fog bow

{{Short description|Type of rainbow formed by fog droplets}} thumb|Fogbow over a field 360-degree fogbow|thumb A '''fog bow''', sometimes called a '''white rainbow''',<ref name="BBC 22 November 2016">{{cite web |url= https://www.bbc.co.uk/news/uk-scotland-highlands-islands-38063662?SThisFB|title= Amazing white rainbow snapped over Scottish moor| author=  |date= 22 November 2016|website= BBC News Online |publisher= BBC| accessdate= 22 November 2016 }}</ref> is a phenomenon similar to a rainbow; however, as its name suggests, it appears as a bow in fog rather than rain.<ref name="Met Office">{{cite web |url= http://www.metoffice.gov.uk/learning/rainbows/fogbow|title= What is a fogbow?|author=  |date= |website= metoffice.gov.uk/ |publisher= Met Office| accessdate= 22 November 2016 }}</ref> Because of the very small size of water droplets that cause fog—smaller than {{convert|0.05|mm|in|sp=us}}—the fog bow has only very weak colors, with a red outer edge and bluish inner edge.<ref>See:

* [https://www.atoptics.org.uk/droplets/fogbow.htm Atmospheric Optics: Fogbow] * Auguste Bravais (1847) [https://books.google.com/books?id=PJ45AAAAcAAJ&pg=PA348 "Sur le phénomène de l'arc-en-ciel blanc"] (On the phenomenon of the white bow in the sky), ''Annales de Chimie et de Physique'', 3rd series, '''21''': 348–361. * H. Mohn (February 23, 1888) [https://books.google.com/books?id=-skKAAAAYAAJ&pg=PA391 "Letters to Nature: The fog bow and Ulloa's ring,"] ''Nature'', '''37''': 391–392. * James C. McConnel (March 22, 1888) [https://books.google.com/books?id=-skKAAAAYAAJ&pg=PA486 "Letters to Nature: The fog bow,"] ''Nature'', '''37''': 486–487. * James C. McConnel (1890) [https://books.google.com/books?id=fFAEAAAAYAAJ&pg=PA453 "The theory of fog-bows,"] ''Philosophical Magazine'', series 5, '''29''' (181): 453–461. </ref> The colors fade due to being smeared out by the diffraction effect of the smaller droplets.<ref>[http://antwrp.gsfc.nasa.gov/apod/ap061115.html APOD: 2006 November 15 - A Fog Bow Over California]</ref>

In many cases, when the droplets are very small, fog bows appear white, and are therefore sometimes called ''white rainbows''. Along with its larger angular size, this lack of color is a feature of a fog bow that distinguishes it from a glory, which has multiple pale-colored rings caused by diffraction. When droplets forming it are almost all of the same size, the fog bow can have multiple inner rings, or supernumeraries, which are more strongly colored than the main bow.

alt=Fogbow in the Gulf of Mexico/Suwannee River, John Donaldson, 19 Dec 2017|thumb|Fogbow over the ocean A fog bow seen in clouds, typically from an aircraft looking downwards, is called a ''cloud bow''. Mariners sometimes call fog bows ''sea-dogs''.

==Direction== A fog bow 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''.<ref>[http://www.atoptics.org.uk/droplets/fogmoon.htm Lunar Fogbow]</ref>

==References== {{reflist}}

==External links== {{Commons category}}

*[https://www.atoptics.org.uk/droplets/fogbow.htm Photos and explanation of fogbows] at Atmospheric Optics. *[https://web.archive.org/web/20110106073252/http://www.meteoros.de/bildarchiv/view.php?gallery_id=52 Fogbow image gallery at AKM website]. *[http://www.dewbow.co.uk/bows/fogbow.html Fogbows at Glows, Bows and Haloes site].

Category:Atmospheric optical phenomena Category:Atmospheric sciences Category:Earth phenomena Category:Rainbow