The First 18 Months of Planetary Radiation Budget Measurements from the Nimbus 6 ERB Experiment

Abstract

The Nimbus 6 satellite Earth Radiation Budget (ERB) experiment has continuously monitored the solar radiation input and the reflected shortwave and emitted longwave radiation exitance from the earth-atmosphere system since July 1975. In this paper, the planetary radiation budget parameters observed during the first eighteen months in orbit (July 1975–December 1976) are presented. The results show that the annual mean planetary albedo and longwave radiation flux are 31% and 234 W m^−2> (radiative equilibrium temperature of 254 K), respectively. The earth atmosphere system is observed to be in complete radiation balance over a one-year period to within the experimental error of observation. There is an annual cycle of the mean monthly planetary net radiation which is due predominantly to the annual cycle of incoming solar radiation caused by the time variation of earth-sun distance and the sun's declination. Monthly variations in outgoing longwave radiation due to variation in global cloudiness and snow and ice cover are generally compensated by the simultaneous variations in the planetary albedo so that there is generally little monthly variability of the total radiation to space compared to that of the net radiation.