JACKSON, Wyo. — The reddish-pink light reflecting off the Teton Range at the end of a day is a sight to behold during the winter season.
And amid a dry spell like this one, alpenglow has been visible more evenings than not. That’s no coincidence, National Park Service (NPS) says.
“Although alpenglow can occur throughout the year, moisture can block sunlight and dilute colors,” said the NPS. In dry areas and in the winter, there is often less moisture in the atmosphere which then causes more brilliant colors.”
The NPS discussed why the phenomenon occurs and the debate surrounding alpenglow.
“During sunset or sunrise, light from the sun’s low angle in the sky takes a long path through the atmosphere. The atmosphere acts like a camera filter, filtering out blues and greens and leaving behind oranges, reds, and yellows.”
There is some debate whether alpenglow is indirect light or direct light. A setting sun that looks below the horizon to someone in a valley, may still be above the horizon reflecting on a mountaintop (direct).
However, some feel that true alpenglow is when the sun is below the horizon for both the person in the valley and the top of the mountain. The red wavelengths are hitting the mountaintops after they are reflected off elements in the atmosphere (indirect).