Water vapor imagery is a valuable tool for weather analysis and forecasting, because it represents flow patterns of the upper troposphere. 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 600 and 300 millibars, or approximately 4000 to 9000 meters above the surface of the earth. This is the middle and upper parts of the troposphere, a key region for storm development and growth.

Explore the properties of water vapor satellite images by clicking on this hands-on activity.

In water vapor images, black indicates low amounts of water vapor and milky white indicates high concentrations. Bright white corresponds to high clouds. Water vapor images provide information in all regions, even those that lack clouds.

The best way to become familiar with common water vapor images is by looking at them!
Please proceed to this Practice Session to learn more about water vapor images.