Posts Tagged ‘sun dogs’
Crepuscular rays occur when objects such as mountain peaks or clouds partially shadow the sun’s rays. The name crepuscular means “relating to twilight” and these rays are observed at sunrise and sunset. Crepuscular rays appear to diverge outward from the setting sun, and are visible only when the atmosphere contains enough haze or dust particles so that sunlight in unshadowed areas can be scattered toward the observer.
The light rays are actually parallel, but appear to converge to the sun due to “perspective”, the same visual effect that makes parallel railroad tracks appear to converge in the distance. Crepuscular rays are often red or yellow in appearance because blue light from the sun is selectively scattered out of the beam by air molecules.
I live about 15 miles WSW of Tampa and crepuscular rays are a common occurrence. I suspect that what is causing them here are the buildings in downtown Tampa to the east in conjunction with the “flatness” of Florida. I’ve been observing them for years about 1/2 hour before sunrise and have never really considered them uncommon phenomena. It will be interesting over the next few days to see if they appear in the same configuration. If so then they are not caused by clouds… and CERTAINLY not by mountains. 😉