Unit 1 Fundamentals of Environmental Sciences - Heat balance of Earth

Earth's Energy balance describes how the incoming energy from the sun is used and returned to space.  If incoming and outgoing energy are in balance, the earth's temperature remains constant. The insolation received by the earth is in shortwaves forms and heats up its surface. 2. The earth after being heated itself becomes a radiating body and it radiates energy to the atmosphere in long wave form. 3. This energy heats up the atmosphere from below. 4. This process is known as terrestrial radiation. 5. The long wave radiation is absorbed by the atmospheric gases particularly by carbon dioxide and the other green house gases. Thus, the atmosphere is indirectly heated by the earth’s radiation. The atmosphere in turn radiates and transmits heat to the space. Finally the amount of heat received from the sun is returned to space, thereby maintaining constant temperature at the earth’s surface and in the atmosphere. Consider that the insolation received at the top of the atmosphere is 100 percent. 4. While passing through the atmosphere some amount of energy is reflected, scattered and absorbed. 5. Only the remaining part reaches the earth surface. 6. Roughly 35 units are reflected back to space even before reaching the earth’s surface. 7. Of these, 27 units are reflected back from the top of the clouds 8. Only 2 units from the snow and ice-covered areas of the earth. 9. The remaining 65 units are absorbed, 10. 14 units within the atmosphere and 51 units by the earth’s surface. The earth radiates back 51 units in the form of terrestrial radiation. 2. 17 units are radiated to space directly 3. the remaining 34 units are absorbed by the atmosphere 4.6 units absorbed directly by the atmosphere, 5.9 units through convection and turbulence 6. 19 units through latent heat of condensation 7.48 units absorbed by the atmosphere (14 units from insolation +34 units from terrestrial radiation) are also radiated back into space. Thus, the total radiation returning from the earth and the atmosphere respectively is 17+48=65 units which balance the total of 65 units received from the sun. This is termed the heat budget or heat balance of the earth. There is a surplus of net radiation balance between 40 degrees north and south and the regions near the poles have a deficit. The surplus heat energy from the tropics is redistributed pole wards and as a result the tropics do not get progressively heated up due to the accumulation of excess heat or the high latitudes get permanently frozen due to excess deficit. #evs4ntanet #environmentalscience #heatbudgetofearth #earth'sheatbalance