The IR channel can show the temperatures of both sea and land surfaces, especially when depicted as a colorized image. While computer programs use mathematical calculations to determine the most accurate land and sea-surface temperatures (SST) from IR images, you can use the legend to quickly estimate temperatures.

Many types of sensors gather land temperatures. Infrared imagery shows thermal differences on a broad scale. The broad yellow area (no blue) is an arctic airmass moving over snow-covered ground. This is a cloud-free area. To the east of the arctic airmass is a cold front (blues and yellows). This area is cloudy. In this case, the land temperature is nearly as cold as the adjacent cloud-top temperatures.

Sea-surface temperatures are important for the fishing industry, for monitoring the location of ocean currents, such as the Gulf Stream, and the development of El Niño events. While buoys and ships (in-situ sensors) provide temperatures at discrete locations, IR imagery provides more complete spatial coverage.

The adjacent graphic is a conceptual view of an El Niño event in which warm SSTs off the coast of South America are shown in red.