Outgoing Longwave Radiation (OLR) data at the top of the atmosphere are observed from the AVHRR instrument aboard the NOAA polar orbiting spacecraft. The units are watts/meter².

These data are available as twice daily observation NOAA-16 and NOAA-17, pentad means and monthly means. Daily OLR data from January 1979 to present are available at the Climate Diagnostic Center ftp site.

The data are on a 2.5 x 2.5 degree lat/lon grid and are stored in 144 X 73 arrays that are oriented North Pole -> South Pole and eastward from Greenwich; note that all 144 values for j=1 and j=73 are for the north & south poles, respectively.

Pentad anomalies are computed with respect to the 1979 - 1995 base period.

References:

Chelliah, M. and P. Arkin, 1992: Large-Scale Interannual Variability of Monthly Outgoing Longware Radiation Anomalies over the Global Tropics. J. Climate, 5, 371-389.

Gruber A. and A. F. Krueger, 1984: The Status of hte NOAA Outgoing Longwave Radiation Data Set. Bull. Amer. Meteor. Soc., 65, 958-962

Janowiak J. E., A.F.Krueger, P.A. Arkin and A. Gruber, 1985: Atlas of Outgoing Longwave Radiation Derived from NOAA Satellite Data NOAA Atlas No. 6 ( Available from Climate Prediction Center ), 44pp.

Liebmann B. and C.A.Smith, 1996: Description of a Complete ( Interpolated ) Outgoing Longwave Radiation Dataset. Bull. Amer. Meteor. Soc., 77, 1275-1277.