Interannual Variance of Earth Radiation

The unterannual variability of outgoing longwave radiation (OLR) and reflected solar radiation (RSR) is intimately connected to interannual variaitons of other weather and climate parameters. Variance maps are computed for OLR and RSR for each month of the year based on the 15-year data set developed using measurements from the Earth Radiation Budget Experiment. This data set covers the Earth between 60 degrees north to 60 degrees south, for 86% of the Earth's surface, with a grid system with 5 degrees resolution in latitude and longitude.

For OLR most of the variability is within the Tropics and much is associated with ENSO. The OLR variability is greatest in November through February and is minimum in June through August. Regions near the Amazon Basin have standard dveiations of 12 to 18 Wm-2 in November through May. The OLR variability over the Indian Ocean is greatest over the eastern part ijn January and the region of highest variability moves during the year. These variations are likely associated with the interannual variations of the monsoons. Most of theocean regions poleward of 30 degrees have standard deviatiohs of less than 6 Wm-2 for both OLR and RSR.

The RSR variability is greatest in December through February, again in the ENSO region of the Pacific Ocean. For June through September, there are regions over or near western North America with standard deviations of 15 to 18 Wm-2. During April through August there are regions from central Europe to central Asia with standard deviations of 15 to 18 Wm-2 of RSR.