The Radiation Balance of the Planet Earth from Radiation Measurements of the Satellite Nimbus II

Abstract

The net flux of radiation at the top of the atmosphere and associated quantities (albedo and outgoing longwave radiation) were computed for five successive semimonthly periods from measurements of the radiance of emitted longwave radiation and reflected solar radiation obtained over the entire globe from the satellite Nimbus II during the period 16 May–28 July 1966. The anisotropy of the reflection characteristics of the earth-atmosphere system was considered for the first time with gross empirical models derived from airplane and balloon observations. The global planetary albedo was found to be between 29 and 31%, while the mean planetary temperature ranged between 254 and 255K. Both results deviate from the corresponding values of earlier investigations in such a way as to suggest that in those investigations the cloudiness or its effect on radiative tranfer, especially in the tropics and subtropics, was overestimated. The global averages of the radiation balance indicate a slight deficit of about 0.005 cal cm−2 min−1, when computed with a value of the solar constant of 2.00 cal cm−2 min−1. Seasonal trends and day-to-day variations of the earth's radiation field are also discussed.