Heat Budget of the Earth - Notes | Geography for UPSC 2024 (Pre & Mains) PDF Download

 Page 1


HEAT BUDGET OF THE EARTH  
? The earth as a whole does not accumulate or lose heat  
? This balance of heat is known as heat budget . 
SHORT WAVE HEAT BUDGET  
? While passing through the atmosphere some amount 
of energy is reflected scattered and absorbed. Only 
the remaining part reaches the Earth surface  
? Roughly 35 units are deflected back to the space even 
before reaching the Earth's surface. Of these 27 units 
are reflected back from the top of the clouds and two 
units from the snow and ice covered areas of the earth  
? The reflected amount of radiation is called the albedo of 
Earth  
? The remaining 65 units are absorbed. 14 units within 
the atmosphere and 51 units by the Earth surface  
? The earth radiates back 51 units in the form of 
Terrestrial radiation  
LONG WAVE HEAT BUDGET  
- The earth radiates back 51 units in the form of Terrestrial 
radiation  
- Of 20- 17 units irradiated to space directly and the 
remaining 34 units are absorbed by the atmosphere (6 
units absorbed directly by the atmosphere, 9 units true 
convention and turbulence and 19 unit through latent 
heat of condensation  
Page 2


HEAT BUDGET OF THE EARTH  
? The earth as a whole does not accumulate or lose heat  
? This balance of heat is known as heat budget . 
SHORT WAVE HEAT BUDGET  
? While passing through the atmosphere some amount 
of energy is reflected scattered and absorbed. Only 
the remaining part reaches the Earth surface  
? Roughly 35 units are deflected back to the space even 
before reaching the Earth's surface. Of these 27 units 
are reflected back from the top of the clouds and two 
units from the snow and ice covered areas of the earth  
? The reflected amount of radiation is called the albedo of 
Earth  
? The remaining 65 units are absorbed. 14 units within 
the atmosphere and 51 units by the Earth surface  
? The earth radiates back 51 units in the form of 
Terrestrial radiation  
LONG WAVE HEAT BUDGET  
- The earth radiates back 51 units in the form of Terrestrial 
radiation  
- Of 20- 17 units irradiated to space directly and the 
remaining 34 units are absorbed by the atmosphere (6 
units absorbed directly by the atmosphere, 9 units true 
convention and turbulence and 19 unit through latent 
heat of condensation  
- 48 units are absorbed by the atmosphere, (14 units 
from insolation and 34 units from Terrestrial 
radiation) also radiated back into space  
thus, the total long wavelength radiation and returning from 
the Earth and the atmosphere respectively is 17 + 48 is equal 
to 65 units which balance the total of 65 units received from 
the Sun. 
 
 
This is termed the heat budget and heat balance of the 
earth. This explains why the earth neither warms up not 
cools down despite the huge transfer of heat that takes 
place  
ADDITIONAL INFO: 
LATITUDINAL HEAT BALANCE 
MERIDIONAL TRANSPORT OF HEAT  
Page 3


HEAT BUDGET OF THE EARTH  
? The earth as a whole does not accumulate or lose heat  
? This balance of heat is known as heat budget . 
SHORT WAVE HEAT BUDGET  
? While passing through the atmosphere some amount 
of energy is reflected scattered and absorbed. Only 
the remaining part reaches the Earth surface  
? Roughly 35 units are deflected back to the space even 
before reaching the Earth's surface. Of these 27 units 
are reflected back from the top of the clouds and two 
units from the snow and ice covered areas of the earth  
? The reflected amount of radiation is called the albedo of 
Earth  
? The remaining 65 units are absorbed. 14 units within 
the atmosphere and 51 units by the Earth surface  
? The earth radiates back 51 units in the form of 
Terrestrial radiation  
LONG WAVE HEAT BUDGET  
- The earth radiates back 51 units in the form of Terrestrial 
radiation  
- Of 20- 17 units irradiated to space directly and the 
remaining 34 units are absorbed by the atmosphere (6 
units absorbed directly by the atmosphere, 9 units true 
convention and turbulence and 19 unit through latent 
heat of condensation  
- 48 units are absorbed by the atmosphere, (14 units 
from insolation and 34 units from Terrestrial 
radiation) also radiated back into space  
thus, the total long wavelength radiation and returning from 
the Earth and the atmosphere respectively is 17 + 48 is equal 
to 65 units which balance the total of 65 units received from 
the Sun. 
 
 
This is termed the heat budget and heat balance of the 
earth. This explains why the earth neither warms up not 
cools down despite the huge transfer of heat that takes 
place  
ADDITIONAL INFO: 
LATITUDINAL HEAT BALANCE 
MERIDIONAL TRANSPORT OF HEAT  
To balance the energy rich and efficient areas it is clear that 
there must be 2 way transfer of heat from 
1)  The Earth surface to the atmosphere  
2)  The equator to the poles  
- This transport of heat from equator towards the poles by 
the atmosphere is known as meridional transport of 
heat . The meridional transport of heat energy in form of 
sensible heat is accomplished by the atmospheric 
circulation and ocean currents . 
 
The amount of insolation received varies from latitude to 
latitude. 
Regions within the equator and 40° N and S latitudes receive 
abundant sunlight .Hence they are energy surplus regions. 
Regions beyond 40° N and S latitudes lose more heat than 
that gained from sunlight. Hence they are energy deficit 
regions.  
But alternatively; The planetary winds and ocean currents 
transfer excess heat from the tropics (energy surplus 
region) towards the poles (energy deficit regions) making 
up for heat loss at higher latitudes. 
Thus, the transfer of surplus energy from the lower 
latitudes to the deficit energy zone of the higher latitudes, 
maintains an overall balance over the earth’s surface.