atmosphere heat

Slide2: 

Solar Radiation Heats the Atmosphere The sun supplies the earth with an enormous amount of energy. A large amount of this energy is reflected or absorbed by the atmosphere. Absorption of of solar energy by the atmosphere is selective. Visible light passes through almost undiminished Ultra-violet light is absorbed mostly by ozone in the stratosphere Infrared radiation is absorbed mostly by carbon dioxide and water in the troposphere. Aerosols also scatter light. Heavy cloud can absorb as much as 90% of solar energy.

Slide3: 

Most visible light passes through almost undiminished Ultra-violet light is absorbed mostly by ozone in the stratosphere Infrared radiation is absorbed mostly by carbon dioxide and water.

Slide4: 

Some solar radiation is reflected from the Earth’s surface. The percentage of energy reflected is called the Albedo. Fresh clean snow has an albedo of 90%. Dark surfaces like black top soil or a dark forest canopy have an albedo of only 3% Earth’s average albedo is 30%, due mainly to clouds. Eventually all the energy absorbed at the earth’s surface is reradiated back into space. But there is an important difference between the incoming and outgoing radiation. Incoming radiation is mainly visible light. The outgoing radiation is infrared radiation (heat). This long wavelength radiation is absorbed by greenhouse gases in the lower atmosphere. This is the Greenhouse Effect.

Slide5: 

Nitrogen and Oxygen gas can neither absorb or emit thermal radiation. It is the ‘greenhouse gases’ such as water vapor, carbon dioxide, and some other minor gases which absorb long-wave thermal radiation leaving the surface. This is why the average surface temperature is 15C instead of -6C which it should be it balanced. 1. Solar radiation 2. Radiation from greenhouse gases 3. Radiation scattered by atmosphere.

Slide6: 

Because of this cycling of infrared between the planet and the atmosphere, the amount of energy emitted from the earth’s surface is about 30% greater than the total incoming solar radiation. The amount of energy reflected reflected or reradiated from the top of the atmosphere must balance with the total coming from the sun. Or the earth would not have a constant temperature.

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Income is 100 units 3 losses due to reflection Total of 31 reflected which means earth’s albedo is 31% 69 is absorbed 3 by O3 ,O2 in stratosphere 20 by H2O, CO2, O2 in troposphere. 46 by land and sea Outgoing = incoming, but what happens inside doesn’t balance!! 115 emitted by earth, of which only 9 can escape the atmospheric window. 106 is absorbed by atmosphere. Of the 106, 60 is re-emitted into space, 100 is re-emitted back to the surface. 31 units are emitted from surface in latent and sensible heat. Total emitted by surface is 115+7+24 = 146 which is the same amount absorbed by the planet.

Slide9: 

Some wavelengths of radiation from the Earth can escape into space if there are no clouds. Other wavelengths are absorbed by gases and re-emitted into space or back to the surface. Graph of radiation emitted from Earth’s surface that is absorbed by the Atmosphere.

Slide10: 

Homework: Read chapter 14 in text book Answer Q 2, 3, 4, 5, 6 Due on Monday

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How does the Earth keep itself warm? The average radiant energy from the sun falling on the surface at about 343 watts /m2. But the amount of energy is not balanced. The Earth emits long-wave length radiation in the form of infrared radiation. (this depends on the temperature of the surface and the type of surface) To balance this the Earth itself needs to radiate the same amount of energy back into space. The remaining 84% actually heats up the surface. As it passes through the atmosphere, 6% is scattered back into space by atmospheric molecules.10% is reflected back into space from land and ocean surface.