Earth radiation budgets

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Abstract
This paper presents the annual and seasonal averaged earth atmosphere radiation budgets derived from the most complete set of satellite observations available in late 1979. The budgets are derived from a composite of 48 monthly mean radiation budget maps. The annual, global average emitted infrared flux is 234 W m−2, planetary albedo is 0.30, and the net flux is zero within measurement uncertainty. The annual cycle of net flux is also studied in detail, and the observed globally averaged net flux displays an annual cycle that is of similar magnitude and phase to the annual cycle imposed by the influence of sun‐earth distance variations on solar radiation input into the atmosphere. A study of the geographical distribution of the annual variability of the net flux reveals that generally greater than 95% of this variability occurs as a result of the semi and annual cycles that may be forced by the regular variation of solar declination throughout the year. However, the amounts of energy contained in the variance from year to year is large. Thus, we direct radiation modeling studies to these regions and situations where the potential for climate impact due to radiation budget variability is the greatest. The individual components of emitted flux and planetary albedo display expectedly more high‐frequency variability particularly equatorward of 30° latitude governed by weather features and their attendant cloud distributions. Radiative transfer model simulations of the observed budget quantities at the ‘top‐of‐the‐atmosphere’ are good at least for the zonally averaged case. Significant differences exist between the present surface radiation budget calculations and those previously estimated. The differences, largely a result of the exclusion of enhanced absorption in the window region (8–14 μm) in earlier budget calculations, provide some 35 W m−2 more radiant energy into the oceans in the tropics than previously estimated. The validity of this result was verified by using GATE radiation budget measurements.