Weather Satellites

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• Infrared satellite imagery senses surface and cloud top temperatures by measuring the wavelengths of electromagnetic radiation emitted from these objects.  High clouds are very cold, so they appear white.  Warmer, mid-level clouds will be light gray.  Low clouds, which are even warmer, appear dark gray or black.  When low clouds are actually the same temperature as the surrounding terrain, they cannot be distinguished at all.
• Visible satellite imagery uses reflected solar radiation (sunlight) to distinguish objects in the atmosphere and on Earth's surface.  Clouds and fresh snow reflect sunlight well, so they appear white.  Clouds and snow can be differentiated because clouds move and snow does not.  Ground surfaces without snow cover reflect less sunlight, so they appear black.  This imagery cannot, of course, be used during the night because it relies on reflections from the sun's rays.

For satellite images of the United States, from infrared, visible light, and water vapor perspectives, visit the Satellite Images page on the Weather.gov website.

Weather Satellite Map