The energy of 66 kcal used for evaporation of water from the surface of the earth becomes entirely sensible when the water vapor is condensed and precipitated in the atmosphere. The amount of water vapor (12.4 trillion ton) in the air, mentioned earlier, is maintained by evaporation of water on the Earth as well as condensation and precipitation in the air, and is at a dynamic equilibrium. This condensation heat (lr = 66 kcal), together with solar radiation energy absorbed in the earth atmosphere (61 kcal), the heat transport from the surface of the earth to atmosphere (13 kcal), is emitted as outgoing infrared radiation (Is = 179 kcal) into the space.
While the situation of the Earth as a whole has been discussed so far, the earth is a sphere with a radius of 6,380 km, and the earth the quantities of incidenting solar energy, distribution of continents and that of seas greatly vary depending on latitude zones. As seen from the many observations, the weather of the earth is relaxed unexpectedly. This is because the global flows; general circulation of the atmosphere and that of the ocean are formed in the atmosphere and in the oceans and they transfer great amount of heat to the south and the north, as described in Figure 2.
Figure 2-a shows latitudinal variations of solar energy absorbed by the Earth and outgoing infrared radiation emitted by the Earth. In the zone between latitudes 35 degrees north and 35 degrees south, absorption of solar energy exceeds emission of infrared radiation. To the south and the north of this zone, on the contrary, the latter exceeds the former. Therefore, without the transfer of heat energy from the low latitude zone to the high latitude zone by general circulation of the atmosphere and the oceans, the temperature in the low latitude zone would become higher, and that in the high latitude zone lower as the time passes.
However, it has been observed that the respective temperatures of the low, middle, and high latitude zones are 25 to 30℃, 15 to 0℃, and 0 - 15℃. This means that excess heat energy in the low latitude zone is transferred to the high latitude zone via the atmospheric and oceanic general circulation, supplementing shortage of energy shown in Figure 2-a. Figures 2-b and 2-c express transfer of sensible heat and latent heat in the atmosphere, whereas Figure 2-d indicates those in the oceans.
