1 Atmospheric Halos Columnar and Plate Ice Crystals 22° and 46

Dr. Christopher M. Godfrey Atmospheric Halos University of North Carolina at Asheville Columnar and Plate Ice Crystals

Complex Display at South Pole Image © Marko Riikonen ATMS 455: Physical Meteorology – Spring 2021 ATMS 455: Physical Meteorology – Spring 2021

Good/Bad Crystals for Halo Formation 22° and 46° Halos

Crystals collected during a superb Crystals from a mediocre halo South Pole display on 17 January display 16 days earlier. They have 1986. Apart from a few small air large inclusions and their faces are bubble inclusions, the crystals imperfect. (Photographs from really are like their hexagonal plate Atmospheric Halos by Walter Tape) and column ideals.

Source: http://www.atoptics.co.uk/halo/xtalreal.htm

ATMS 455: Physical Meteorology – Spring 2021 ATMS 455: Physical Meteorology – Spring 2021

22º Halo Sundog (Parhelion)

ATMS 455: Physical Meteorology – Spring 2021 ATMS 455: Physical Meteorology – Spring 2021

1 Ice Crystal Phenomena Halos and Sundog

22º Halo 46º Halo

Parhelic Circle

Sundog

Parhelic Circle

Sun

Sundog Sundog

Sundog (parhelion)

2 Circumzenithal Arc Upper Tangent Arc with Circumzenithal Arc Circumzenithal Arc

 You are looking almost straight up with the sun at the bottom of the image  Formed by refraction through hexagonal plate crystals Supralateral Arc  The supralateral arc is more common than, and is often 22º Halo mistaken for, the 46° halo  Sun is below 32° elevation

Sundog, parhelic circle, 22° halo, and a dim More information upper tangent arc

Image © Jim Hoida (http://apod.nasa.gov/apod/ap060923.html) For more great images and explanations, visit © C. Godfrey http://www.atoptics.co.uk/halosim.htm

ATMS 455: Physical Meteorology – Spring 2021 ATMS 455: Physical Meteorology – Spring 2021