Infrared images are produced day and night by the heat sensors onboard the satellite. This is because the earth is always radiating heat. The satellite interprets the heat emanating from the earth's surfaces and clouds and assigns each pixel (picture element) area a gray scale number from 0 to 254. Zero (0) depicts a value of pure white and 254 indicates a value of pure black.

The warmer the area, the higher the gray scale value, the darker the image. Cloud tops which extend high into the atmosphere are white. This indicates that they are cold. Low lying clouds, water, and land surfaces are varying shades of gray to black. The warmer the day, the darker the surface "color." In fact, one can determine the approximate time of day an infrared image was taken by looking at the surface gray scale color.

This image is an enhanced infrared view of Hurricane Opal. It has been color coded to provide information that will help meteorologist determine the areas of thunderstorm development. The higher the thunderstorm clouds, the colder their tops become. The satellite translates this information into a lighter gray scale "color" value. Computers then "colorize" these values so that meteorologist can interpret them and provide appropriate warnings. Take a look at the scale that comes with the image and determine where thunderstorms may be occurring around the country.

Take a look at the surface of the United States, can you determine which areas are warmer that others? If not, refer to paragraph two above.

VISIBLE IMAGES