Water vapor is transparent to radiation at visible and 10-12 micron wavelengths. This is why visible and IR satellite imagery are used to observe surface features and clouds. However, water vapor is a very efficient absorber and emitter of radiation with wavelengths between 6.5 and 6.9 microns. So, satellite radiometers measuring the amount of radiation emitted by the atmosphere at these wavelengths can be used to detect water vapor in the atmosphere. The water vapor satellite image displays the water vapor concentration in the atmospheric layer between 200 and 500 mb. Black indicates low amounts of water vapor and milky white indicates high concentrations. Bright white regions correspond to cirrus clouds. In the middle latitude regions, zones with strong contrast in the amount of water vapor often indicate the presence of a jet stream.

Click here to see an applet allowing fading between the visible, infrared, and water vapor images

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