From the solar radiation... At TOA ERBE Top-of-Atmosphere 3WINC 00 MnM Mean 152 80N 标卡卡持特 July 1286 500 500- 60 100 100 400- 200 200 40 300 300 20 400 SQLAR 200 DECLNATION 400 0 400 1D0- &x 20 300 0 00 30 5 -30 (0 -90 lattade 500 200 500 40 Figures:the zonally averaged incident solar 100 radiation,observed in the Earth Radiation Budget Experiment(ERBE).(from Randall 2009) 60 80S J FM A M JJ A S From Peixoto and Oort.1992 授课教师：张洋 9授课教师：张洋 9 From the solar radiation... to the astronomical theory of the ice ages, extensive glaciation is favored when the minimum insolation occurs during the Northern Hemisphere winter, because the Northern Hemisphere contains about twice as much land as the Southern Hemisphere (e.g., Crowley and North, 1991). As you probably already know, the infrared radiation emitted by the Earth is very nearly equal to the solar radiation absorbed by the Earth, i.e., it is about 240 W m-2. This near balance between absorbed solar radiation and emitted terrestrial radiation has been directly confirmed by analysis of satellite data. The balance is observed to hold within a few Watts per square meter, which is the within the uncertainty of the measurements. Fig. 2.3 shows aspects of the Earth's radiation budget as observed in the Earth Radiation Budget Experiment (ERBE; Barkstrom et al., 1989). The zonally averaged incident (i.e. incoming) solar radiation at the top of the atmosphere varies seasonally in response to the Earth's motion around the sun. The zonally averaged albedo, which is the fraction of the zonally averaged incident radiation that is reflected back to space, is highest near the poles, due to snow and ice as well as cloudiness, but it tends to have a weak secondary maximum in the tropics, again associated with high cloudiness there. The zonally averaged terrestrial radiation at the top Figure 2.2: The seasonal variation of the zonally (or diurnally) averaged insolation at the top of the atmosphere. The units are W m-2. 200 300 400 500 500 500 200 200 300 300 400 400 100 100 100 SOLAR DECLINA TION J F M A M J J A S O N D 0 80N 80S 60 40 20 20 40 60 Revised Tuesday, February 10, 2009 3 An Introduction to the General Circulation of the Atmosphere n At TOA Figures: the zonally averaged incident solar radiation, observed in the Earth Radiation Budget Experiment (ERBE). (from Randall 2009) From Peixoto and Oort, 1992