Supralateral arc: Difference between revisions
m clean up using AWB |
added photo, and identified supralateral arc in other photo |
||
| Line 1: | Line 1: | ||
[[File:Complex halo display 01-03-09.jpg|300px|Complex halo display.[[22° halo]], |
[[File:Complex halo display 01-03-09.jpg|300px|Complex halo display.[[22° halo]], supralateral arc, [[Parry arc]], [[Upper tangent arc|UTA]] and [[sundog]]|thumb]] |
||
[[File:Solar halos with foreground, Salem, MA, Oct 27, 2012.JPG|thumb|right|[[Circumzenithal arc]], Supralateral arc, [[Parry arc]], and [[Upper tangent arc]], in [[Salem, Massachusetts]], Oct 27, 2012.]] |
|||
A '''supralateral arc''' is a rare [[Halo (optical phenomenon)|halo]], an [[optical phenomenon]] often confused with the indeed infrequently appearing [[46° halo]]. Distinguishing between the two is furthermore difficult as supralateral arcs typically only appears in fragments while the 46° halo is very faint. |
A '''supralateral arc''' is a rare [[Halo (optical phenomenon)|halo]], an [[optical phenomenon]] often confused with the indeed infrequently appearing [[46° halo]]. Distinguishing between the two is furthermore difficult as supralateral arcs typically only appears in fragments while the 46° halo is very faint. |
||
Revision as of 20:46, 29 October 2012
A supralateral arc is a rare halo, an optical phenomenon often confused with the indeed infrequently appearing 46° halo. Distinguishing between the two is furthermore difficult as supralateral arcs typically only appears in fragments while the 46° halo is very faint.
In contrast to the static 46° halo, the shape of a supralateral arc varies with the elevation of the sun. Before the sun reaches 15°, the bases of the arc touches the lateral (oriented sidewise) sides of the 46° halo. As the sun rises from 15° to 27°, the supralateral arc almost overlap the 46° halo, why most reported observations of the latter most likely are observations of the former. As the sun goes from 27° to 32°, the apex of the arc touches the circumzenithal arc centred around zenith (as do the 46° halo when the sun is located between 15° and 27°). In addition, the supralateral arc is always located above the parhelic circle (below is the infralateral arc) and is never perfectly circular.[1][2]
Arguably the best way of distinguishing the halo from the arc is to carefully study the difference in colour and brightness. The 46° halo is six times fainter than the 22° halo and generally white with a possible red inner edge. The supralateral arc, in contrast, can even be confused with the rainbow with clear blue and green strokes.[1]
Supralateral arcs form when sun light enters horizontally oriented, rod-shaped hexagonal ice crystals through a hexagonal base and exits through one of the prism sides. Supralateral arcs occur about once a year.[1]
Gallery
-
Solar Halo, Upper Tangent Arc, Supralateral Arc : 20 June 2009 : Khonkaen, Thailand
See also
References
- ^ a b c "Supralateral arc". Arbeitskreis Meteore e.V. Retrieved 2007-04-16. (Including a photo from January 1996, a 1980 computer simulation of a supralateral arc relative to a 46° halo, and a table pinning down differences between 46° halos and supralateral arcs.)
- ^ "Supralateral Arcs". www.paraselene.de. Retrieved 2009-03-08.
External links
- Atmospheric Optics - Supralateral & infralateral arcs - including HaloSim computer simulations and crystal illustrations.
- paraselene.de - Gallery of images from March 2002
- paraselene.de - Gallery of images from December 2007
 | This optics-related article is a stub. You can help Wikipedia by expanding it. |
 | This article about atmospheric science is a stub. You can help Wikipedia by expanding it. |