Infrared satellite measurements are related to the brightness temperature. For an infrared picture, warmer objects appear darker than colder objects, as in the example below (a composite of data from GOES-8 and GOES-10 satellites).

Since temperature in the troposphere decreases with height, high level clouds are colder than low level clouds. Therefore, low clouds (like those found over North Carolina and Virginia) appear darker on an infrared image and higher clouds (like those found throughout the eastern U.S.) appear brighter. The very dark shades of gray in parts of the Rocky Mountains and in the deserts of the Southwest indicate regions where the ground is being heated by the sun.

visible (vis)

Terms for using data resources. CD-ROM available. Credits and Acknowledgments for WW2010. Department of Atmospheric Sciences (DAS) at the University of Illinois at Urbana-Champaign.

vis -vs- ir