Discuss the factors affecting the distribution of Insolation.
( UPPSC / UPPCS, 2019, 15 Marks)
सूर्याताप के वितरण को प्रभावित करने वाले कारकों की विवेचना किजिए।
What is Insolation?
Solar energy comes to the earth in the form of short wave radiation, the short wave solar radiation coming to the earth is called insolation.
In general, there is a close relationship between the insolation received at a place on Earth's surface and the temperature of that place. For example,
- The insolation decreases as we move from the equator to the poles, and because of this, the temperature also decreases on the surface of the earth as we move from the equator to the poles.
Due to the spherical shape of the Earth, the tilt of the Earth on its axis, its rotation, and the presence of an atmosphere on the Earth, the insolation distribution on the Earth is not uniform. There are both spatial and temporal [changing with time] variations of insolation on Earth.
The following factors affect the distribution of insolation:
- Duration of day and night in different latitude
- The angle of incidence of sun rays
- Water vapor in the atmosphere
- Dust particles in the atmosphere
- Cloud in the atmosphere
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| factor affecting Insolation |
Duration of day and night in different latitude:
- The shape of the Earth is roughly spherical and the Earth makes an angle of 66.5 degrees with its orbital plane or is inclined by 23.5 degrees to its axis.
- Because of the Earth's rotation and rotation through its inclined axis, the duration of day and night at different latitudes is not the same, and the spatial variation of the duration of day and night, as well as the duration of day and night in that location, is not the same throughout the year. The day length of the place is longer in the summer season and shorter in the cold season.
- The equatorial region has a longer day length throughout the year and the temperate and polar regions have shorter day duration, thus the equatorial region has more insolation than the higher latitudes.
The angle of incidence of sun rays:
- Since we know that the Earth is in a spherical shape and is inclined 66.5 degrees to the orbital plane, the Sun's rays reach the surface at different angles at different latitudes. A low angle is formed at higher latitudes and an angle of about 90 degrees between the Tropic of Cancer and the Tropic of Capricorn is formed at least once a year.
- Because of the oblique rays, the sun's rays travel long distances in the atmosphere and cover large areas on the surface, so at higher latitudes, less insolation is received per unit area.
- Because of the vertical sun rays, the sun's rays travel less distance in the atmosphere and cover fewer areas on the surface, so there is more insolation per unit area between the Tropic of Cancer and the Tropic of Capricorn.
Water vapor present in the atmosphere:
- Due to the presence of water vapor in the atmosphere, it prevents the insolation from reaching the surface of the earth and also absorbs some part of the insolation.
- For this reason, the insolation is more in hot deserts because water vapor is absent there.
Dust particles in the atmosphere:
- The presence of dust particles in the atmosphere prevents insolation from reaching the surface of the earth because fine dust particles scatter the insolation into space and larger dust particles spread the insolation in the atmosphere.
Presence of clouds in the atmosphere:
- Ice crystals are present in atmospheric clouds, as we know that ice has a high albedo, thus the clouds reflect the insolation from the atmosphere into space.
All of the above factors affect the distribution of insolation on Earth.
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