Lady Goodman

While driving home from Cal Poly to Los Osos this afternoon, I came across a great example of an atmospheric optical phenomenon: a sun dog (or parhelion, as it's known in the scientific world). I took that photo with an iPhone at 4.15 pm. What causes a sun dog? Sun dogs form when sunlight passes through small, hexagonal, plate-shaped ice crystals suspended high in the air, generally within a thin cirrus or cirrostratus cloud. As the ice crystals drift through the atmosphere, they tend to align themselves horizontally. When the Sun's rays pass through them, they refract at about a 22-degree angle from the Sun. Much like a prism, these ice crystals split sunlight into its constituent colors, producing a spectacular display of red, orange, yellow, and occasionally blue. Sun dogs occur at roughly 22 degrees either side of the Sun, appearing as brilliant patches of light or 'mock suns' of various colors. They're particularly obvious when the sun is low in the sky, i.e., at sunrise or sunset. One thing that stands out is that the reds are closest to the Sun and the yellows and blues go outwards. Unlike rainbows (which are formed when sunlight is refracted by liquid water droplets) sun dogs are the result of sunlight being refracted by ice crystals high in the atmosphere. It's another great reminder that you don't have to look very far to see something truly special in the atmosphere. Sometimes all you have to do is just look up! ☀️🌤️🌈 – at Los Osos, CA