Cibiana di Cadore and Circumzenithal Arc 

November 20, 2020


Photographer: Marcella Giulia Pace 
Summary Authors: Marcella Giulia Pace, Jim Foster

Shown above is a cheery circumzenithal arc (CZA) as observed from the clock tower in Cibiana di Cadore, Italy, a municipality in the Alps of northeastern Italy. These colorful arcs result when sunlight is refracted by similarly oriented, hexagonal ice crystals in the atmosphere. Sunlight passes through a crystal’s upper basal face and then exits through one of its side faces. However, they only appear when the Sun is positioned lower than 32 degrees above the horizon. Photo taken on August 11, 2015.

Photo Details: Canon Powershot sx50hs camera; 1/500 sec. exposure; f/5,6; ISO 80.