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ADDS - Satellite Help Page (2 of 3)
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Satellite help page 3
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What do the numbers on the images mean?
The answer depends on the channel so you may want to read the
item below this one for more details on channels. The Visble
channel displays albedo or reflectance expressed as a percentage.
For example, a bright white shade may indicate 70% albedo.
The Infrared (IR) channel is calibrated to temperature and
expressed in degrees Celcius. Where clouds exist, the temperature
is that of the tops of clouds. Where clouds do not exist, the
temperature is that of the ground or the ocean. This information
could be very valuable to aviators since clouds with tops below
0°C, may indicate that an Icing hazard exists. [An icing hazard
could also exist in clouds warmer than freezing particularly if
there is a strong temperature inversion beneath the cloud.]
The Water Vapor channel is also calibrated to temperature
in degrees Celcius. Interpreting the actual values displayed on
the water vapor images is not useful.
- What do the different channels show?
The latest generation of GOES weather satellites (GOES-8,9,10)
all carry 5 imaging sensors. They are in the following portions
of the electromagnetic spectrum:
- Channel 1: Visible (0.6 microns)
- Channel 2: Shortwave Infrared (3.9 microns)
- Channel 3: Water Vapor (.67 microns)
- Channel 4: Infrared (11 microns)
- Channel 5: Infrared (12 microns)
These web pages provide images from channels 1, 3, and 4 which
are generally the most useful to aviators and meteorologists.
More details
in plain English, please.
The other 2 channels can be quite useful to scientists and
developers of new products. (An example where all 5 channels
are used in an
aircraft icing application can be found at
Research Applications Program of NCAR.)
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