Outgoing longwave radiation

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Not to be confused with E-rays.
2003-2010 Annual mean OLR

Outgoing Longwave Radiation (OLR) is the energy radiating from the Earth as infrared radiation at low energy to Space.

Atmospheric energy radiation[edit]

OLR is a critical component of the Earth's energy budget, and represents the total radiation going to space emitted by the atmosphere.[1] Earth's radiation balance is quite closely achieved since the OLR very nearly equals the Shortwave Absorbed Radiation received at high energy from the sun. Thus, the Earth's average temperature is very nearly stable. The OLR is affected by clouds and dust in the atmosphere, which tend to reduce it to below clear sky values.

Role in greenhouse effect[edit]

Greenhouse gases, such as methane (CH4), nitrous oxide (N2O), water vapor (H2O) and carbon dioxide (CO2), absorb certain wavelengths of OLR adding heat to the atmosphere, which in turn causes the respective absorbing layer of the atmosphere to emit more radiation. Some of this radiation is directed back towards the Earth, increasing the average temperature of the Earth's surface. Therefore, an increase in the concentration of a greenhouse gas would contribute to global warming by increasing the amount of radiation that is absorbed and emitted by these atmospheric constituents.

The OLR is dependent on the temperature of the radiating body. It is affected by the Earth's skin temperature, skin surface emissivity, atmospheric temperature, water vapor profile, and cloud cover.[1]


Longwave radiation typically refers to radiation in the spectral region from 3 to 100 microns. In the Earth’s climate system, longwave radiation involves processes of absorptions, scattering, and emissions from atmospheric gases, aerosols, clouds and the surface. Measuring outgoing longwave radiation at the top of atmosphere and downwelling longwave radiation at the surface are important for understanding how much radiative energy is kept in our climate system, how much reaches and warms the surface, and how the energy in the atmosphere is distributed to affect developments of clouds.

Outgoing longwave radiation (OLR) has been monitored globally since 1975 by a number of successful and valuable satellite missions. These missions include broadband measurements from the Earth Radiation Balance (ERB) instrument on the Nimbus-6 and Nimbus-7 satellites;[2][3] Earth Radiation Budget Experiment (ERBE) scanner and the ERBE non scanner on NOAA-9, NOAA-10 and NASA Earth Radiation Budget Satellite (ERBS); The Clouds and the Earth's Radiant Energy System (CERES) instrument aboard NASA's Aqua and Terra satellites; and Geostationary Earth Radiation Budget instrument (GERB) instrument on the Meteosat Second Generation (MSG) satellite.

Downwelling longwave radiation at the surface is mainly measured by Pyrgeometer. A most notable ground-based network for monitoring surface longwave radiation is Baseline Surface Radiation Network (BSRN), which provides crucial well-calibrated measurements for studying global dimming and brightening.[4]

See also[edit]


  1. ^ a b Susskind, Joel; Molnar, Gyula; Iredell, Lena. "Contributions to Climate Research Using the AIRS Science Team Version-5 Products". NASA. Goddard Space Flight Center. Retrieved 14 September 2011. 
  2. ^ Jacobowitz, Herbert; Soule, Harold V.; Kyle, H. Lee; House, Frederick B. (30 June 1984). "The Earth Radiation Budget (ERB) Experiment: An overview". Journal of Geophysical Research: Atmospheres 89 (D4): 5021–5038. doi:10.1029/JD089iD04p05021. 
  3. ^ Kyle, H. L.; Arking, A.; Hickey, J. R.; Ardanuy, P. E.; Jacobowitz, H.; Stowe, L. L.; Campbell, G. G.; Vonder Haar, T.; House, F. B.; Maschhoff, R.; Smith, G. L. (May 1993). "The Nimbus Earth Radiation Budget (ERB) Experiment: 1975 to 1992". Bulletin of the American Meteorological Society 74 (5): 815–830. doi:10.1175/1520-0477(1993)074<0815:TNERBE>2.0.CO;2. 
  4. ^ Wild, Martin (27 June 2009). "Global dimming and brightening: A review". Journal of Geophysical Research 114. doi:10.1029/2008JD011470. 

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