Longwave refers to a type of electromagnetic radiation with wavelengths longer than those of visible light, typically ranging from 30 centimeters to 10 kilometers. This category includes radio waves used in communication, such as AM radio broadcasts, which can travel long distances and penetrate obstacles like buildings and hills. In the context of meteorology, longwave radiation is significant as it relates to the Earth's heat emission. After absorbing solar energy, the Earth emits this energy back into space in the form of longwave infrared radiation, which plays a crucial role in regulating the planet's temperature and climate systems.