Biome
Well-defined terrestrial environment (e.g., desert, tundra, or tropical forest). The complex of living organisms found in an ecological region.


Ecosystem
Any natural unit or entity including living and non-living parts that interact to produce a stable system through cyclic exchane of materials.


Radiometer
An instrument that quantitatively measures electromagnetic radiation. Weather satellites carry radiometers to measure radiation from snow, ice, clouds, bodies of water, the Earth's surface, and the sun.