JACKSON, Wyo. — The reddish-pink light reflecting off the Teton Range at sunrise or sunset is a sight to behold during the winter season.
The National Park Service (NPS) describes why the phenomenon of alpenglow occurs during early morning and evening hours.
“During sunset or sunrise, light from the sun’s low angle in the sky takes a long path through the atmosphere,” according to the NPS. “The atmosphere acts like a camera filter, filtering out blues and greens and leaving behind oranges, reds and yellows.”
According to the NPS, alpenglow is more visible during dry weather patterns.
“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.”
There is some debate about 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 occurs 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).
Whatever one chooses to believe, this is a sight worth seeing.
Editor’s note: This story runs annually.
