Snow, Clouds and Light on a Winter's Day

February 05, 2020


Photographer: Michael Sanchez; Skier: Stan Wagon
Summary Authors: Jim Foster; Stan Wagon

The photo above showing a wintry scene and a wavy sky was taken four miles north of Vail Pass, Colorado, on January 5, 2020. Sculpted by wind after a recent snowfall, the ripples are called sastrugi. The altostratus clouds seem to mimic the rippled patterns of the snowy landscape and are just thin enough to permit the Sun to peek through.

Because snow crystals are large compared to the wavelengths of visible light, sunlight is more effectively scattered in a forward direction -- the scene seems brighter, with less contrast, when facing the Sun. However, since this snow surface appears corrugated, light is both forward-scattered and backscattered when looking toward the Sun. Of course, a cloudy sky, as is the case here, noticeably dampens this effect. On his alpine touring skis, Stan Wagon is taking in all that this winter’s day has to offer.