Circumscribed halo

From Wikipedia, the free encyclopedia

A circumscribed halo is a halo, an optical phenomenon which circumscribes a 22° halo centred around the sun.

When observed, a circumscribed halo is normally oval in shape and tangential to the 22° halo directly under and above the sun. It form when sun rises and the upper tangent and lower tangent arcs extends into each other and closes in on the 22° halo.^[1] As the sun rises above 70° it basically covers the 22° halo.^[2]

A circumscribed halo is generally weaker than but more intensive in colour than the 22° halo. Like many other halos, it is reddish on the inner edge facing the sun while bluish on the outer edge. ^[2]

[edit] References

1. ^ Les Cowley (?). Circumscribed Halo. Atmospheric Optics. Retrieved on 2007-04-15. (including a composite image of a circumscribed halo)
2. ^ ^{a b} Circumscribed Halo. Arbeitskreis Meteore e.V.. Retrieved on 2007-04-15. (including a fish eye photo of the phenomenon)

[edit] See also

• Circumzenithal arc
• Circumhorizontal arc

[edit] External links

• www.paraselene.de - HaloSim Computer simulations of a circumscribed halo.
• Atmospheric Optics - Circumscribed Halo - solar altitude - an animation showing how the shape of the phenomenon changes as the sun rises.