Water vapor windows
In the Earth's atmosphere, water vapor absorbs many wavelengths of Infrared (IR) energy, while others are not absorbed. The remaining sections of the Electromagnetic spectrum that the water vapor does not absorb are like an opening in the atmosphere, allowing electromagnetic energy to flow freely in and out of the system, much like a window that allows light to enter and leave. Originally discovered by John Tyndall, most of the infrared coming from the Universe is blocked, and absorbed by water vapor (and other greenhouse gases) in the Earth's atmosphere. These wavelength ranges that can  partially reach the surface are coming through what is called 'water vapor windows'. These windows are how astronomers can view the Universe with IR telescopes, called Infrared astronomy. These windows also allow orbiting satellites to measure the IR energy leaving the planet, the SSTs, and other important matters. See "Electromagnetic absorption by water: Atmospheric effects".