PICASSO-CENA SRR

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Light and Aerosols
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What are Aerosols?
Aerosols are small particles that can remain
suspended in the atmosphere for days or weeks.

• Natural Sources
• desert dust
• forest fires
• sea spray
• volcanic eruptions
• Human-related Sources
• fossil fuel burning
• biomass burning
• dust resulting from land clearing

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What are Aerosols?

• Definition Aerosols are particles, liquid or
  solid, that are suspended in the air. They
  are NOT gases.

• Human-Induced Aerosols Aerosols are made
  when people burn coal, gasoline, and other
  fossil fuels. Humans also produce aerosols when
  they burn wood in their fireplaces or when
  forests or grasslands are burned. ( biomass
  burning )

Biomass burning(human induced)

• Naturally Occurring Aerosols Volcanic
  eruptions hurl tons of ash into the atmosphere
  and natural forest fires caused by
  lightning also produce many aerosols. Some
  other examples include sea salt spray, desert
  dust, and pollen from plants.

Volcanic Ash(naturally occurring)
Saharan Dust off West Africa(naturally occurring)
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Aerosols Directly Influence Earths Energy
Balance
Aerosols may have a warming or cooling effect
depending on their optical properties and surface
brightness key measurements by CALIPSO.
Human-Related Sources
Natural Sources
Desert Dust
Sulfates, Soot
Biomass Burning
Sea Salt
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Satellite Aura measures Aerosols
Aura orbits the Earth - (animation)
http//sci.gallaudet.edu/MSSDScience/Auraanimation
.mpg
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Natural Man-made Aerosols
Dust from China (animation)
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Natural Man-made Aerosols
Circulation of Water Vapor Aerosols(animation)
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Natural Man-made Aerosols
Mt. Pinatubo(animation)
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Natural Man-made Aerosols
Circulation of Volcanic Ash Aerosols(animation)
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Mechanisms of Energy Transport
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How Do Aerosols Affect Climate?
Aerosols absorb and scatter the suns
energy.(animation)
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How Do Aerosols Affect Climate?

• Atmospheric aerosols directly affect Earths
  energy balance by
• absorbing and scattering solar radiation
• absorbing and emitting infrared radiation

• Atmospheric aerosols indirectly affect Earths
  energy balance by
• acting as cloud condensation nuclei
• modifying the reflectance and lifetime of clouds

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Kinds of Scattering

• There are two kinds of scattering
• Mie Scattering
• Rayleigh Scattering

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Mie Scattering
Mie Scattering is caused by particles or aerosols
that are larger than the wavelengths of
radiation. Water droplets and large particles
scatter all wavelengths equally, making hazy
skies and white clouds.
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Rayleigh Scattering
Rayleigh Scattering happens when some particles
are better at scattering a particular wavelength
of light. Air molecules, like oxygen and
nitrogen, are small in size and better at
scattering shorter wavelengths of light (blue and
violet). The selective scattering by air
molecules is responsible for producing our blue
skies on a clear sunny day.
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Rayleigh Scattering, Red Sunsets
When great amounts of particles are in the
atmosphere, Rayleigh Scattering filters out
almost all of the shorter wavelengths,
leaving the red wavelengths.
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Rayleigh Scattering, Red Sunsets
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Aerosol Demonstration(with overhead projector)
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Aerosol Demonstration(with overhead projector)
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Fun Webpages
http//members.aol.com/physgeo4/sr2_8.htm