During alpenglow, the peaks in the high mountains are illuminated with a visually impressive red light at sunset and sunrise.
Alpenglow is a special mood of light that occurs at sunset and sunrise in the Alps and in others high mountains occurs. Alpenglow describes two distinct natural optical phenomena, referred to as first coloration and second coloration.
At sunset, the first tint appears first, and then the second tint. At sunrise, on the other hand, the order of the coloring is reversed. The second hue of the alpenglow thus occurs before the first hue at sunrise.
The first coloring of the alpenglow
During the first coloring, the snow-capped areas of the peaks and its rocky slopes are replaced by the low-lying ones Sonne reached. The red-colored lighting ensures that the bright peaks of the Berge in the foreground stand out clearly from the background, which is still or once more in the dark.
The second coloring of the alpenglow
During the second coloring, the sun is already below the horizon. It no longer illuminates the mountain peaks, or only indirectly. The smallest particles in the atmosphere, such as fine dust and ice crystals, scatter the sunlight, which is then weakened when it reaches the summit. The snow-capped and light-rocky peaks appear an even, faint red once morest the violet-tinted sky.
How is alpenglow formed?
The alpenglow at sunrise and sunset is caused by two effects.
- The first effect of alpenglow is caused because much of the light which is strongly scattered on its long way through the earth’s atmosphere when the sun is low in the sky. The orange to red range of sunlight, on the other hand, is hardly scattered and gives the peaks their strong coloring during the alpenglow
- The second optical effect of alpenglow is triggered by the indirect lighting of the mountains above the shadow line. Sunlight hits the landscape behind the Alpenglow observer at a very low angle. From there it is reflected, brightening the peaks above the shadows. With an increasing angle, the efficiency of this reflection decreases sharply. This does not lead to a general brightening of the mountains, but a conspicuous bright stripe.
Phosphorescence causes alpenglow at night
The Alpenglow occurs mainly at sunset and sunrise. In individual cases, however, the phosphorescence also causes a slight alpenglow into the night. Phosphorescence is a property that ensures that a substance still glows or glows following strong lighting in absolute darkness.
