How does terrestrial radiation compare to solar radiation in heating of the atmosphere
The heating of the atmosphere is a complex interplay between incoming solar radiation and outgoing terrestrial radiation. Here’s a detailed explanation of both types of radiation and how they compare in terms of their effects on atmospheric heating.
Solar Radiation
Definition and Characteristics:
– Solar radiation, also known as insolation, consists primarily of short-wave electromagnetic radiation emitted by the sun, including visible light, ultraviolet light, and some infrared radiation.
– When solar radiation reaches the Earth, approximately one-third is reflected back into space by clouds and the Earth’s surface, while the remaining two-thirds is absorbed by the Earth’s surface (land and oceans) and warms it.
Process:
1. Transmission: The atmosphere is largely transparent to short-wave solar radiation, allowing most of it to pass through and reach the Earth’s surface.
2. Absorption: The Earth’s surface absorbs this energy, leading to an increase in temperature.
3. Re-emission: The heated surface then emits energy back into the atmosphere in the form of long-wave infrared radiation, which is known as terrestrial radiation.
Terrestrial Radiation
Definition and Characteristics:
– Terrestrial radiation refers to the long-wave infrared radiation emitted by the Earth after it has absorbed solar energy. This process occurs continuously, both day and night.
– The Earth’s surface acts as a radiating body, emitting energy primarily in long wavelengths due to its lower temperature compared to the sun.
Process:
1. Emission: Once warmed by solar absorption, the Earth’s surface radiates energy in long-wave infrared form.
2. Absorption by Greenhouse Gases: This long-wave radiation is absorbed by greenhouse gases (such as carbon dioxide and water vapor) present in the atmosphere. These gases are particularly effective at trapping heat, which leads to warming of the lower atmosphere.
3. Greenhouse Effect: The absorbed terrestrial radiation is then re-emitted in all directions, including back towards the Earth’s surface, contributing to a warming effect known as the greenhouse effect.
Comparison of Heating Effects
– Dominance of Terrestrial Radiation: The atmosphere is heated more significantly by terrestrial radiation than by direct solar radiation. While solar radiation initially warms the Earth’s surface, it is the long-wave radiation emitted from this warmed surface that primarily heats the atmosphere through absorption by greenhouse gases.
– Energy Balance: The balance between incoming solar energy and outgoing terrestrial energy is crucial for maintaining a stable climate. The Earth continuously radiates some of this energy back into space, ensuring that temperatures remain relatively constant over time.
Q. Consider the following statements: Statement I: The atmosphere is heated more by incoming solar radiation than by terrestrial radiation.
Statement II: Carbon dioxide and other greenhouse gases in the atmosphere are good absorbers of long-wave radiation.
Which one of the following is correct in respect of the above statements?
(a) Both Statement I and Statement II are correct and Statement II explains Statement I
(b) Both Statement I and Statement II are correct, but Statement II does not explain Statement I
(c) Statement I is correct, but Statement II is incorrect
(d) Statement I is incorrect, but Statement II is correct
Correct Answer: (d) Statement I is incorrect, but Statement II is correct
Statement I:
The atmosphere is heated more by incoming solar radiation than by terrestrial radiation.
– This statement is incorrect. The atmosphere is primarily heated by terrestrial radiation, which is the long-wave radiation emitted by the Earth’s surface after absorbing solar energy. While incoming solar radiation does warm the atmosphere, a significant portion of this energy is absorbed by the Earth’s surface and then re-radiated as long-wave radiation, which in turn heats the atmosphere.
Statement II:
Carbon dioxide and other greenhouse gases in the atmosphere are good absorbers of long-wave radiation.
– This statement is correct. Greenhouse gases, including carbon dioxide, methane, and water vapor, effectively absorb and re-radiate long-wave (infrared) radiation emitted by the Earth. This process is crucial for maintaining the Earth’s temperature and is a fundamental aspect of the greenhouse effect.
Thus, the correct answer is:
(d) Statement I is incorrect, but Statement II is correct.
