The daily Outgoing Longwave Radiation (OLR) Climate Data Record (CDR) measures the amount of terrestrial radiation released into space and, by extension, the amount of cloud cover and water vapor that intercepts that radiation in the atmosphere. Input data for the Daily OLR record primarily comes from the high-resolution infrared radiation sounder (HIRS) radiance observations since 1979, and new generation infrared hyperspectral sounder radiance data, including from the Infrared Atmospheric Sounding Interferometer (IASI) since 2007 and the Cross-track Infrared Sounder (CrIS) since 2012.
The OLR is also retrieved from the combination of operational geostationary Imagers that helps to achieve better accuracy for the OLR daily integral. The final record is generated through a combination of statistical techniques, including OLR regression, instrument ambient temperature prediction coefficients, and inter-satellite bias corrections. The daily OLR record spans from 1979 - present.
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