Background Information about Weather-Satellite Images

U.S. Geostationary Weather Satellites

The time and date appearing on most satellite images is in Universal Time Coordinates (UTC), formerly known as Greenwich Mean Time (GMT). (See comments about time labels for more information.)

GOES-10 was launched in the fall of 1997 and became operational in July, 1998. It orbits above the eastern equatorial Pacific Ocean (at 135 degrees west longitude) and provides images of the western U.S. and eastern Pacific Ocean.

GOES-12, the newest of the U.S.'s operational geostationary satellite, was launched in the summer of 2001 and became operational in spring, 2003. It orbits above Brazil (at 75 degrees west longitude) and provides images of the central and eastern U.S. and western Atlantic Ocean.

GOES-West and GOES-East were launched and are maintained by NASA (the National Aeronautics and Space Administration) and are managed by NOAA (the National Oceanographic and Atmospheric Administration).

Visible Images

Infrared Images

Using a computer, we can take the intensities of infrared radiation recorded by a weather satellite and translate them arbitrarily into different shades of gray and/or different colors, constructing images that humans can see. On the infrared images available at most WWWeb weather sites, including SFSU's California Regional Weather Server, darker shades of gray represent relatively warmer features, and lighter shades of gray represent relatively colder features. (For examples of gray-scale infrared satellite images, see below).

On the color-enhanced infrared images available at SFSU's California Regional Weather Server, colors other than gray are assigned to some of the coldest temperatures. (For examples of color-enhanced infrared satellite images, see below). Far from the polar regions, features this cold invariably comprise the tops of clouds in the upper troposphere or lower stratosphere and are often associated with thunderstorms, hurricanes or midlatitude cyclones. Hence, color-enhanced infrared images help highlight storms of various types.

A scale along the lower left-hand edge of some color-enhanced infrared images (for example, see large-scale North American overviews) relates colors and shades of gray to relative temperatures. Each shade of gray or distinct color represents a range of 5 degrees Celsius (9 degrees Fahrenheit). In particular, colors are assigned to the following temperatures:

• Blue: -40 to -45 degrees C (or -40 to -49 degrees F);
• Cyan: -45 to -50 degrees C (or -49 to -58 degrees F);
• Green: -50 to -55 degrees C (or -58 to -67 degrees F);
• Yellow: -55 to -60 degrees C (or -67 to -76 degrees F);
• Red: -60 to -65 degrees C (or -76 to -85 degrees F);
• Violet: -65 to -70 degrees C (or -85 to -94 degrees F).

• Composite Sea-Level Pressure-Field/Satellite-Image Map
  (North America Overview)

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Examples of Color-Enhanced Infrared Satellite Images:

• Composite Sea-Level Pressure-Field/Satellite-Image Map
  (West Coast Overview)

• Infrared Satillite Image
  (GOES-West Eastern Pacific/Western North America Overview)

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Additional References

• NOAA's National Environmental Satellite, Data, and Information Service (NESDIS) provides information about several types of U.S. satellites, including Geostationary Operational Environmental Satellites (GOES; this includes links to global images from Europe's METEOSAT satellite), Polar Operational Environmental Satellites (POES), and others.


• NOAA's National Climate Data Center (NCDC) also provides information about U.S. geostationary satellites (GOES) and information about U.S. polar orbiting satellites (POES).


• David Baron, a weather hobbyist, maintains an extensive set of links to international satellite images and satellite information.


• The National Weather Association (NWA), a private professional organization, maintains extensive (though not exhaustive) links to WWWeb servers from around the globe offering satellite images.