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Name: Loretta
Status: Other
Age: 30s
Location: N/A
Country: N/A
Date: N/A 


Question:
I have just came from outside, it was about 9:00 p.m. e.p.t. The sky had clouds that where the most radiant red, pink, purple that I have ever saw, almost glowing. Brilliant hot pinks. What caused this? They weren't around the moon on the opposite side, the moon looked as if it were a eclipse it was so beautiful. I have never seen any thing like it! I live in Virginia U.S.A. any comments would be greatly appreciated.



Replies:
Dear Loretta-

The colors you saw in the clouds were spectacular, and were due to a combination of factors that produced such a display. First you need to have the right kind and right amount of clouds...and mid-level, or altostratus or altocumulus are the best type for this display. These clouds are composed mainly of water droplets, but may have some ice crystals in them also. They usually exist at altitudes between 7,000-15,000 feet above the ground. Scattered or broken sky conditions are the best, because some open sky is necessary for the sunlight to shine through.

Then, you need the right time of day...and around sunrise and sunset are the best times of day. This is because the sunlight can strike the clouds from the bottom, rather than their tops. The water drops in the clouds refract some of the sunlight, much the way a glass prism does, and you see different colors, depending on the alignment of the sun, and clouds, and you, the observer.

A low sun angle, around sunrise and sunset, allows the sunlight to travel a greater distance through the atmosphere, and this allows certain wavelengths of the spectrum of the sunlight to be absorbed or reflected by particles in the air, such as dust, or smoke. This "altered" sunlight contributes to the colors observed, by filtering out some of the spectrum.

As the sun rises or sets, the amount of the cloud layer that is illuminated changes quickly. Lower clouds receive less illumination, and their color will become a darker shade as the sunlight fades. In the morning, the opposite effect occurs. As the illumination increases, the colors become brighter.

Loretta, that is why no two sunrises or sunsets are exactly the same...because rarely are all the conditions that affect the character of the sunrise or sunset the same. So enjoy each one, because they are unique.

Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO



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