photo #9319364

High above Chilliwack, British Columbia, Canada, four bright optical phenomena appeared at once. The light effects, spotted by Philip Tingey (Cloud Appreciation Society Member 45,142), make an excellent introduction to the many arcs, rings, and spots of light known collectively as halo phenomena.The circle of light centred around the Sun is a 22-degree halo. In reality, it would have been perfectly circular. Philip’s wide-angle lens has slightly distorted it here. The kidney-bean-shaped arc showing colours where it touches the top and bottom of the 22-degree halo is called a circumscribed halo. The shape of this effect varies according to the elevation of the Sun in the sky. Passing through the Sun is the broad white parhelic circle. When enough ice crystals are present, the parhelic circle can extend all the way around the sky, centred on the zenith, the point directly upwards. Finally, off to the side of Philip’s display is an infralateral arc. This rare phenomenon forms on one or both sides of the Sun, appearing here only to its left.All four halo phenomena formed as sunlight was refracted or reflected by tiny prism-like ice crystals within a high, thin layer of Cirrostratus cloud. Just when you thought you were getting the hang of the cloud names, along comes a whole collection of equally intriguing light effects to learn.