The Annual Radiation Balance of the Earth-Atmosphere System During 1969–70 from Nimbus 3 Measurements

Measurements of reflected solar radiation and emitted thermal radiation taken with a radiometer on the meteorological satellite Nimbus 3 during 10 semi-monthly periods (April–15 August, 3–17 October, 1969; 21 January–3 February, 1970) provided for the first time high-resolution data on the earth's annual global radiation budget. Results on the planetary albedo, the amount of absorbed solar radiation, the infrared radiation loss to space, and the radiation balance of the earth-atmosphere system are discussed at various scales: global, hemispherical, and zonal averages., as well as global and polar maps with a spatial resolution of about synoptic scale (102–103 km). The incoming solar radiation (taking the most recent value of the solar constant S0=1.95 cal cm−2 min−1) is balanced within the accuracy of the measurements and evaluation procedure by a global albedo of 28.4% and an infrared heat loss to space of 0.345 cal cm−2 min−1, which corresponds to a mean planetary effective radiation temperature of 255K. These results confirm those found from earlier satellite data, which showed that our planet is darker and radiatively warmer than previously assumed from estimates with climatic data. From zonal averages of the radiation balance the required poleward transport of energy was found to be larger over the Northern than over the Southern Hemisphere during the 1969–70 observational period.