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Geosciences LibreTexts

2.5: Review

  • Page ID
    9538
  • The variations of temperature and humidity that you feel near the ground are driven by the diurnal cycle of solar heating during the day and infrared cooling at night. Both diurnal and seasonal heating cycles can be determined from the geometry of the Earth’s rotation and orbit around the sun. The same orbital mechanics describes weather-satellite orbits, as is discussed in the Satellites & Radar chapter.

    Short-wave radiation is emitted from the sun and propagates through space. It illuminates a hemisphere of Earth. The portion of this radiation that is absorbed is the heat input to the Earth-atmosphere system that drives Earth’s weather. 

    IR radiation from the atmosphere is absorbed at the ground, and IR radiation is also emitted from the ground. The IR and short-wave radiative fluxes do not balance, leaving a net radiation term acting on the surface at any one location. But when averaged over the whole globe, the earth-atmosphere system is approximately in radiative equilibrium.

    Instruments to measure radiation are called actinometers or radiometers. Radiometers and spectrometers can be used in remote sensors such as weather satellites.