Backward Forward Home Exit How is the atmosphere heated? How is the atmosphere heated? Unit 1 Unit 1

Backward Forward Home Exit I. How is the atmosphere heated? Solar energy Solar energy is the earth’s primary source of heat radiation The sun emits energy in the form of radiation 1. What is insolation?

Backward Forward Home Exit solar radiation insolationshort- wave radiationThis incoming solar radiation ( insolation ) is a kind of short- wave radiation It travels through space to reach the earth

Backward Forward Home Exit Solar radiation Click the Screen to Start

Backward Forward Home Exit atmosphere air The atmosphere is a thick layer of gases wrapping the earth. These gases are mixed together and we call the mixture ‘ air ’Gas Percentage by volume in troposphere Nitrogen (N 2 ) 78.1 Oxygen (O 2 ) 20.9 Argon (A) 0.9 Carbon dioxide (CO 2 ) 0.03 Water vapour (H 2 O) What are the characteristics of the atmosphere? Composition of the earth’s atmosphere includes nitrogen, oxygen, argon, carbon dioxide and other trace gases

Backward Forward Home Exit Scientists divide the atmosphere into different layers because some characteristics of air change with elevation If you cannot see the movie, click here to download the Macromedia Shockwave Player click here troposphere The lowest part of the atmosphere is known as the troposphere

Backward Forward Home Exit When sunlight penetrates or passes through the atmosphere, some energy is absorbed by carbon dioxide, water vapour and other particles in the air 3. Is air directly heated by insolation? If you cannot see the movie, click here to download the Macromedia Shockwave Playerclick here

Backward Forward Home Exit Air is not good at absorbing solar radiationAir is not good at absorbing solar radiation Only a small proportion of energy in the atmosphere comes from direct insolationOnly a small proportion of energy in the atmosphere comes from direct insolation Part of incoming short- wave radiation is scattered or reflectedPart of incoming short- wave radiation is scattered or reflected Air is not good at absorbing solar radiationAir is not good at absorbing solar radiation Only a small proportion of energy in the atmosphere comes from direct insolationOnly a small proportion of energy in the atmosphere comes from direct insolation Part of incoming short- wave radiation is scattered or reflectedPart of incoming short- wave radiation is scattered or reflected

Backward Forward Home Exit Clouds are very good at scattering and reflecting sunlightClouds are very good at scattering and reflecting sunlight That is why a cloudy day is darkerThat is why a cloudy day is darker Clouds are very good at scattering and reflecting sunlightClouds are very good at scattering and reflecting sunlight That is why a cloudy day is darkerThat is why a cloudy day is darker Only about 50% of incoming short-wave radiation is absorbed by the earth’s surface

Backward Forward Home Exit 4. What is the main source of heat in the atmosphere? terrestrial radiationAfter the ground is heated by incoming solar radiation, it radiates heat known as terrestrial radiation long-wave radiation infrared radiationTerrestrial radiation is largely long-wave radiation because much of this is infrared radiation

Backward Forward Home Exit Long-wave radiation is the major source of heat in the atmosphereLong-wave radiation is the major source of heat in the atmosphere because carbon dioxide, water vapour and other particles in the air are effective at absorbing infrared radiation returns to the earth’s surface and the remaining part goes into spaceOnce the atmosphere is heated, it also radiates energy in the form of long-wave radiation. Part of this radiation returns to the earth’s surface and the remaining part goes into space

Backward Forward Home Exit Most of the heat comes from terrestrial radiation, so: Higher places are farther away from the heat source and thus receive less energy Higher places are farther away from the heat source and thus receive less energy Air is thinner at higher altitudes, there are fewer gas particles to absorb terrestrial radiation Air is thinner at higher altitudes, there are fewer gas particles to absorb terrestrial radiation Most of the heat comes from terrestrial radiation, so: Higher places are farther away from the heat source and thus receive less energy Higher places are farther away from the heat source and thus receive less energy Air is thinner at higher altitudes, there are fewer gas particles to absorb terrestrial radiation Air is thinner at higher altitudes, there are fewer gas particles to absorb terrestrial radiation Air temperature falls with increasing altitude in the troposphere

Backward Forward Home Exit Normally, given a fixed amount of incoming solar radiation, about one-third is reflected back into space Normally, given a fixed amount of incoming solar radiation, about one-third is reflected back into space The remaining two-thirds is absorbed by the surface of the earth or by the atmosphere The remaining two-thirds is absorbed by the surface of the earth or by the atmosphere The heated earth surface and atmosphere emit long-wave radiation back into space The heated earth surface and atmosphere emit long-wave radiation back into space 5. Does insolation reception equal terrestrial radiation loss?

Backward Forward Home Exit The amount of incoming short-wave solar radiation is balanced by the outgoing (reflected short-wave and terrestrial long-wave) radiationThe amount of incoming short-wave solar radiation is balanced by the outgoing (reflected short-wave and terrestrial long-wave) radiation In the natural environment, our temperature should therefore not become warmer and warmer, or cooler and cooler, but remain stableIn the natural environment, our temperature should therefore not become warmer and warmer, or cooler and cooler, but remain stable