SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE

SOLAR RADIATION, HEAT BALANCE AND TEMPERATURE

 Earth receives almost all of its energy from sun. The energy in Sun is produced from nuclear reactions(nuclear fission and fusion).

 • The earth in turn radiates back to space the energy received from sun. 

• SOLAR RADIATION: 

The radiation emitted from sun in form of short wave is called as Solar Radiation.

 • INSOLATION:

The energy received by Earth from incoming solar radiation is called as insolation. On average Earth receives around 1.94 calories per square kilometer per minute at the top of its atmosphere. It is called as solar constant..

 • TERRESTRIAL RADIATION:

These incoming short wave solar radiation are absorbed by atmosphere, heats it up and it is also reflected back into space in the form of long wave radiation. This type of energy which heats up the atmosphere is called Terrestrial radiation.

PROCESSES INVOLVED IN HEATING OF ATMOSPHERE

 • 1. Convection: 

The transfer of heat through rising of warm air and sinking of cold air is called Convection. These currents of moving air is called as Convection Currents. 

• 2. Conduction:

 Conduction is transfer of heat when between two bodies of unequal temperature are contact with one another. The flow of energy is from warmer to cooler body. The transfer continues until both bodies maintain the same temperature. The air gets heated and slowly and it heats the upper layer of atmosphere. This process is called Conduction. 

• Radiation:

 Radiation is the form of energy that is transmitted in the form of waves. The energy received from sun is in the form of short wave radiation and the atmosphere emits it in the form of long wave radiation.

 • Advection:

 It is the horizontal transfer of energy . In Middle latitudes variation in daily weather is caused by Advection alone. It is opposite to process of Convection in terms of Direction of flow of energy.

FACTORS RESPONSIBLE FOR DIFFERENCE OF INSOLATION AT SURFACE OF EARTH 

• The factors which cause variations in insolation are:

 • 1. Rotation of Earth: Rotation refers to movement of Earth around its own axis. The part of the Earth facing the sun will receive the maximum insolation as compared to the other side of Earth.

 • 2. Revolution of Earth: Revolution refers to movement of Earth around Sun.4 positions of Earth is determined when it revolves: 

• A) June 22 is called the summer solistice when the sun rays are vertical on tropic of Cancer as a result of which there is summer in the northern hemisphere and winters in the southern hemisphere. 

• B) December 22 is called the winter solistice when the sun rays are vertical in tropic of Capricorn in the southern hemisphere as a result of which there is winter season in northern hemisphere and summers in southern hemisphere. 

• C) On March 21 and September 23 the sun rays are falling vertical on Equator and days and nights seems to be equal these two days . These two are also called as Equinox. 

 • 3.Inclination of Sun rays.: 

• if rays are vertical, it will cover less area but net energy received and distributed is more heat whereas area which receives oblique rays covers more area but net energy received and distributed is less.

• 3.Length of day

( Longer the day, greater is the insolation. Example days are longer and nights are shorter during summer therefore more insolation is received during summer seaon.

 • in winters days are shorter and nights are longer and therfore less insolation is received in this season. 

• 4. Latitude of Place: 

Places at high latitudes like polar areas receive less insolation. Middle latitudes receive high insolation. 

• 5. Distance of Earth from Sun 

• Earth moves around sun in a elliptical orbit.

 • Earth is nearest to sun on 3 rd January at distance of 147 million kms. It is called as Perehelion. 

• Earth is farthest away from Sun on 4 th July at a distance of 152 million kms and this concept is called as Aphelion. 

• 6. Impact of Land and Water: 

Specific capacity of water is 5 times more that land. It means that if same energy if provided to water as well as land , land will get heated as well as cool easily as compared to water. Water in turn takes five times more energy to heat as well as cool down. 

• Therefore areas on the earth surface where portion of land is more will get heated more and will generate more insolation. 

• Areas with less portion of land will have less insolation.