Worldview Image of the Week

Snow and clouds in the Alps

Image captured Dec. 20, 2021, by the VIIRS instrument aboard the joint NASA/NOAA NOAA-20 satellite.


False-color (Bands M3-I3-M11) corrected reflectance image of snow and clouds in the Alps on December 20, 2021. This image was acquired by the Visible Infrared Imaging Radiometer Suite (VIIRS), aboard the joint NASA/NOAA NOAA-20 satellite. View the image of snow and clouds over the Alps in Worldview.

The Bands M3-I3-M11 combination is useful for mapping snow and ice. Snow and ice are very reflective in the visible part of the spectrum (Band M3), and very absorbent in Bands I3 and M11 (short-wave infrared, or SWIR). This band combination is good for distinguishing liquid water from frozen water, for example, clouds over snow, ice cloud versus water cloud; or floods from dense vegetation. Since the only visible light used in these images (Band M3) is assigned to red, snow and ice appear bright red. The more ice, the stronger the absorption in the SWIR bands, and the more red the color. Thick ice and snow appear vivid red (or dark pink), while small ice crystals in high-level clouds will appear pinkish and lower level clouds appear white.

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