5-Energy Balance and Temperature-2011

5-Energy Balance and Temperature-2011 - Energy Balance and...

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Energy Balance and Temperature Leila M. V. Carvalho
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A Few questions that you might have wondered in a sunny day … Why is the sky blue? Why is the sky red near the horizon during sunrises and sunsets? Why is the sky often hazy near the horizon above the ocean? Why in polluted regions the sunsets are sometimes exceptionally red? What is the fate of solar radiation?
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Ø Solar radiation is attenuated by a variety of processes as it pass through the atmosphere. 1) A portion of the solar radiation (basically UV) is absorbed and is transformed to heat (mainly by the ozone in the stratosphere). 2) Visible radiation, in contrast is not absorbed by the atmosphere. If that was not true, what color would appear the sky? 3) Near infrared (approximately 0.7-5 μm), which represents ~ 50% of Sun’s radiation is absorbed by water vapor and to a lesser extent by CO2. 4) This is why direct sunlight in the desert feels so hot and shade is so welcome, where in humid regions it does not make much difference Why is the sky blue? VERY DARK
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But…Why is the sky blue??? Because of scattering… Some particles and molecules found in the atmosphere have the ability to scatter solar radiation in all directions. The particles/molecules which scatter light are called scatterers and can also include particulates made by human industry Blue skies are produced as shorter wavelengths of the incoming visible light (violet and blue) are selectively scattered by small molecules of oxygen and nitrogen - which are much smaller than the wavelength of the light . The violet and blue light has been scattered over and over by the molecules all throughout the atmosphere, so our eyes register it as blue light coming from all directions, giving the sky its blue appearance. Selective scattering ( or Rayleigh scattering ) occurs when certain particles are more effective at scattering a particular wavelength of light
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On the moon, which has no atmosphere, there is no scattering and this explains why astronauts saw the moon sky black even during the daylight The bluish of the Earth is also the effect of backscatterin g by the atmosphere
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Let’s see if I understand… Income Visible radiation violet and blue are selectively scattered by small molecules of oxygen and nitrogen -which are much smaller than the wavelength of the light Scattering occurs in all directions and multiple times λ π r x 2 = Rayleigh x - < < 1
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The intensity of the ‘blue’ depends on the presence of bigger particles such as aerosols or droplets Can you guess why the sky is not as blue near the ocean as it is up in the mountains?
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what is reflection and what is the difference? Reflection of energy is a process whereby radiation making contact with some material is simply redirected away from the surface without being absorbed. This is why we see the objects around us:
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5-Energy Balance and Temperature-2011 - Energy Balance and...

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