Published: 2008-09-20 13:29:07
Updated: 2008-09-20 13:29:07
Posted September 20, 2008
By Jennifer Olsen
MIKE MOSS SAYS: Jennifer, When a satellite image is labeled IR, that stands for Infra Red, which is the portion of the electromagnetic spectrum that the satellite sensor is tuned to receive. Because infrared radiation is proportional to the temperature of an object (that is, warmer objects emit more IR radiation and vice versa) it can be used to make images that give a good idea of the location of clouds, since clouds are usually a different temperature from the ground below. A major reason for using IR is so that the satellite can be used to follow storm systems and weather patterns 24 hours a day. The other primary sensor for viewing clouds uses visible light, which allows for better detail but fades to black at night when there is no light from the sun.
Since IR satellite imagery is proportional to temperature, you can also make inferences about the depth and altitude of clouds based on their temperature.
When you see the word Doppler on an image, that is usually a radar product, based on one or more ground-based radar transmitters, rather than a satellite image taken from a platform in orbit.