Dear Tom,

I’m wondering if there is a way you could predict when the sunrise is going to be colorful?

Thanks, Bridget, Chicago

Dear Bridget,

Sunset colors are caused by sunlight traveling through a long distance of the atmosphere, thousands of miles. This causes the shorter wavelengths of light (blue, indigo, and violet) to scatter. The remaining long wavelengths (red, orange, and yellow) predominate. With clear skies, the upper twilight will be streaked pale green, paralleled at lower depths by yellow and pink tints. The light touching the horizon is heavy with orange and red tones, with a ruddy glow marking where the sun has set.   With clouds, two types of sunsets are possible. Low and middle clouds composed of water droplets tend to obscure the sunset color, even with breaks in the clouds. High cirrus clouds often produce spectacular sunsets due to the scattering and reflection of light in its many hues from the base and translucent parts of the cirrus. Dust, haze, smoke, and other particulates in the air also help create colorful sunsets as the particles enhance the scattering of the light.

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