Weather Phenomena – Crepuscular Rays

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I have always loved weather phenomena and one of my favorites are crepuscular rays.   They are dramatic, inspiring and nothing short of remarkable.   Even the most seasoned weather watchers can stand with mouth agape as they observe shafts of light shift and change as the clouds move, but what are they really?

Crepuscular rays are columns of light that appear to emanate from the Sun’s position through gaps in the clouds. The term crepuscular means “relating to twilight” because these rays are often seen close to sunrise and sunset. In order for them to appear a high degree of haze is needed in the atmosphere to scatter the light. The rays themselves are often orange in color and appear to alternate between light and dark bands, which are the result of light selectively passing through the clouds.  Crepuscular rays also seem to converge on the Sun, but this is not true.  Our Sun is much larger than the Earth and light travels in parallel lines so the convergence effect is just a result of perspective.

These are not visible everyday so diligence is required if you want to see or photograph them.  Make a check of the morning or evening skies part of your daily ritual.  It’s a fantastic time to take a brief walk and reflect upon the day, observe the moon phase, or check for Mercury and Venus in the twilight.  While you’re out, be sure to be searching for crepuscular rays and also look for anti-crepuscular rays.   The latter type is only located in the sky opposite the sun at the antisolar point and appear to converge in a similar fashion.

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About Author

Chris Morrison

Chris is an avid amateur astronomer, birder, photographer and general nature and science nut. He was a Vice President at a major telescope manufacturer, where he was directly involved in product development and testing for much of his 15 year tenure. His passion for all things science and nature is what led him to found localmeridian.com, an online outlet for his desire to share his love of the natural world.

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