Subsun and Subsundog

June 11, 2018


Photographer: Christina Irakleous 
Summary Authors: Christina Irakleous; Jim Foster

During my flight from Thessaloniki, Greece to Eindhoven, the Netherlands. earlier this year, I noticed when looking through a cirrus cloud deck curious reflections below where the Sun was positioned (right center of photo). This picture was snapped about an hour before sunset on March 24, 2018. The elongated patch of light at lower right is a subsun, found at the same distance below the horizon (the horizon from the window seat of an airplane, for example) that the Sun would be above it. It should be pointed out that this horizon is level with your eyes and not the clouds or surface of the Earth that you might see when looking downward. The subsun is simply a reflection of the Sun from horizontally-aligned, plate-shaped ice crystals. Note also the subsundog at lower center -- another reason to select a window seat.