Outgoing Longwave Radiation (
OLR) is the energy leaving the earth as infrared radiation at low
energy. OLR is a critical component of the Earth’s radiation budget and represents the total radiation going to space emitted by the atmosphere.
Earth's radiation balance is very closely achieved since the OLR very nearly equals the Shortwave Absorbed Radiation received at high energy from the sun. Thus, the
first law of thermodynamics (energy conservation) is satisfied and 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 below clear sky values.
Greenhouse gases, such as
methane (CH[SUB]4[/SUB]),
nitrous oxide (N[SUB]2[/SUB]O),
water vapour (H[SUB]2[/SUB]O) and
carbon dioxide (CO[SUB]2[/SUB]), absorb certain wavelengths of OLR adding heat to the atmosphere, which in turn causes 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
An abbreviastion for "Outgoing Longwave Radiation". Anomalies in OLR can be related to cloud cover and precipitation. Negative OLR anomalies generally indicate increased cloudiness and likelihood of precipitation while positive anomalies imply decreased cloudiness. The relationship between OLR anomalies and precipitation holds most strongly in tropical regions.
ناهنجاری های OLR می تواند مربوط به پوشش ابر و بارش باران باشد. به طور کلی ناهنجاری منفی OLR اشاره دارد به افزایش ابرناکی و احتمال بارش باران در حالی که ناهنجاری مثبت OLR اشاره به کاهش ابرناکی دارد. ارتباط بین ناهنجاری های OLR و بارش در مناطق استوایی قوی تر است.