Characteristics of the earth's radiation budget derived from the first year of data from the Earth Radiation Budget Experiment

The first year of broadband Earth Radiation Budget Experiment (ERBE) data is analyzed for top-of-theatmosphere regional variations of outgoing longwave (LW) flux and planetary albedo for total scene as well as clear-sky conditions. The annual variation of radiative parameters is examined for February 1985 through January 1986 for selected regions, latitude zones, and the entire globe. Results show significant seasonal variations for both LW fluxes and albedo. A broad longwave flux maximum (with a relative minimum corresponding to the Intertropical Convergence Zone in the middle) covers the Tropics and the sub-tropics with its center moving about 200 latitude between seasonal extremes. Minimum albedo (about 20%) occurs within 15° of the Equator. In the Tropics and midlatitudes, there is a tendency toward higher albedos during the summer. Larger albedos at the higher latitudes are caused by solar zenith angle effects and by increased snow and ice cover. Net warming occurs between 35°N and 35°S latitude near the equinoxes and in a 90°-wide latitude band at the solstices centered around 35° latitude in the summer hemisphere. This energy surplus at lower latitudes coupled with an energy deficit in the poleward regions is the primary driver of atmospheric circulations. For the year, the global net radiation is nearly in balance. Clouds were found to have a net cooling effect on Eartlfs climate for all seasons. The annual mean net cloud radiative cooling for the globe from ERBE is 18 Wm-2.