What does the brightness of a cloud mean on the TV weather shows?
The image to the left is an example of an infrared (IR) image made from
a radiometer flown on the GOES-8 satellite. This is very typical of the
images you see on TV weather shows. A piece of this image has been extracted
and appears as a square below the larger satellite image. This portion
of the image contains a cloud and some clear sky areas. You can change
the appearance of this extracted image by changing the cloud
altitude (and its associated ambient air temperature) or
the surface temperature. You do this by moving the sliding scales (scroll
bars) accompanying the picture on the right.
The vertical scale changes the cloud altitude and its temperature. The
numbers on each side of figure show the altitude and corresponding temperature,
assuming standard atmospheric conditions.
You can modify the surface temperature with the horizontal sliding scale.
What happens to the image when you lower the cloud?
What happens to the image when you decrease the ground temperature?
Adjust the cloud altitude and ground temperature so that the cloud is no
longer visible in the image. Can you think of a situation when this might
Adjust the cloud and altitude and ground temperature so that the cloud
appears darker than the ground. Can you think of a time of year and geographic
region when this meteorological situation might occur?
This example Java applet developed by Tom Whittaker and Steve Ackerman of
the Department of Atmospheric and
Oceanic Sciences and the Space Science
and Engineering Center at the University