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CH 18 PP Atmospheric energy

CH 18 PP Atmospheric energy - EnergyBalanceinthe Atmosphere...

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Energy Balance in the  Atmosphere
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Light – behaves like a wave and a particle Photons – elementary particles of light Travel at 3 x 10 meters per second (300,000 km/sec) in a  vacuum Electromagnetic radiation – light also behave as energy  waves, perpendicular electrical and magnetic waves Wavelength – distance between wave crests Frequency – number of waves passing a point/sec. Electromagnetic spectrum – continuum of electromagnetic  wavelengths
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Not to  scale!
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Absorption – when something absorbs radiation, the  photon’s energy can initiate chemical and/or physical  reactions May cause molecules to vibrate Excited state – absorbed photons makes electrons get  “excited” Emission of radiation – when the exited electrons “settle  down” they emit light All objects emit some radiation Emission color (wavelength) relates to temperature Earth absorbs high energy short wavelength energy  from the sun and then re-emits it as longer  wavelength lower energy radiation (IR)
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Reflection –electromagnetic radiation bouncing from  a surface Albedo – proportional reflectance of a surface (e.g.: a perfect mirror would have an albedo of 100%) Glaciers & snowfields approach 80-90% Clouds – 50-55% Pavement and some buildings – only 10-15% Scattering – gases and water droplets scatter light in  all directions short “blue” wavelengths scatter more than longer  wavelengths; so skies are blue The sun appears yellow because white light with most of  the blue removed yields yellow
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Glaciers and snowfields reflect light and cool the earth.  The Jeffries Glacier, St Elias Range, Alaska
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Albedos of common Earth surfaces 
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When radiation scatters, its  direction changes but the  wavelength remains constant.
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Iron glows red when  heated in a forge.  If it is  heated further, it emits  white light.
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