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The VIS
Channel
- Because the VIS channel
senses reflected sunlight (solar radiation), it is
available only during daylight hours
- In VIS imagery, clouds
tend to be a brighter white than in IR
imagery
- When severe weather is
threatening during daylight hours, the VIS channel can
provide imagery of the threatened area every minute (the
typical time interval is every 15 minutes)
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The IR
Channel
- By sensing heat
radiation, the IR channel provides temperature
information
- The IR channel is
available 24 hours a day
- IR satellite imagery is
often colorized to highlight different cloud-top
temperatures
- In the absence of
clouds, IR satellite imagery provides surface temperature
information
- Temperature information
from the IR channel can be used to estimate cloud-top
height
- Temperature information
from the IR channel illustrates storm
intensity
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What VIS and IR Have in
Common
- Both the IR and VIS
channels are used to track the movement of weather
systems
- Both the IR and VIS
channels on the satellite are remote sensors because they
are not in contact with the medium they are
sensing
- Both VIS and IR imagery
are displayed at different spatial scales. For example,
some images show both North America and South America.
Other images show only the United States while still
other images show a close-up of a few states within the
United States
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