Alpenglow

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Alpenglow on the Latemar in the Dolomites

The alpenglow is a light mood at sunset and sunrise in the high mountains . It describes two different phenomena called first coloring and second coloring .

First coloring

Alpenglow on the Zugspitze from Ehrwald (Tyrol)
Alpenglow on Mount Everest

In the first coloration, the rocky slopes and snow surfaces of the peaks are reached by the light of the low-lying sun and stand out in this red-colored lighting from the foreground, which is already or still in the dark.

Two effects come together for the mountain peaks, which are dramatically illuminated at sunset. The first is that when the sun was low, a particularly large proportion of the blue light was scattered in other directions due to the long path through the earth's atmosphere . The remaining sunlight appears orange to red. This is also the mechanism by which the sunset gets its color. With alpenglow, there is also indirect lighting of the area directly above the shadow border. This light falls at a very flat angle onto the landscape behind the observer. It is reflected and is noticeable as a lightening above the shadow. The efficiency of this reflection decreases rapidly as the angle increases. This results in a light stripe instead of a general brightening.

Second coloring

In the second color, the sun is below the horizon and no longer (or not yet) illuminates the mountain peaks directly. The sunlight is scattered on particles in the atmosphere (such as ice crystals, dust, etc.) so that it can fall on the peaks in a weakened manner. In front of the violet-colored sky, snow-covered and light-rocky peaks then continue to appear in a faint, but very clear and even red.

literature

Web links

Commons : Alpenglow  - Album with pictures, videos and audio files

swell

  1. Alpenglow. Meyers Großes Konversations-Lexikon , accessed on March 26, 2019 .