Ozone and UV radiation

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• Lesson 1
• Ozone and UV radiation

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Learning Objectives

• To understand the role ozone plays in the Earths
  system.
• To understand how surface Ultraviolet (UV)
  radiation varies.

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What is ozone?

• The ozone molecule contains three oxygen atoms,
  hence O3 is ozone.
• How is ozone produced?
• It is formed when oxygen absorbs solar radiation
• O2 h?(?lt240nm) ? OO
• O O2 ? O3
• Ozone reacts with various other chemicals, and
  thus is highly reactive.
• Ozone also absorbs incoming UV radiation
• O3 h?(? lt320nm) ? O2O

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Ozone formation
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(No Transcript)
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Good ozone/bad ozone
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Why is the ozone layer important

• Ozone acts as the Earths protective shield
  against the Suns harmful Ultraviolet radiation
  (UV radiation).
• Without the ozone layer, life would not exist on
  Earth!
• The natural development of the ozone layer
  permitted life to evolve above water.

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Ozone in the Atmosphere

• Ozone is mainly produced in the tropics because
  of the higher amounts of solar radiation.
• Ozone is mainly destroyed at middle and higher
  latitudes by chemical processes.
• Ozone is also largely affected by atmospheric
  winds.
• Thus, ozone naturally has large variations in
  space and time.

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Satellite Ozone Observations
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The ozone layer for one day
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Dobson Units (DU) as a measure of total ozone

• definition of ozone hole
• lt 220 DU
• Melbourne Avg. 280-380DU
• Darwin Avg. 260DU

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UV radiation

• UV radiation is emitted from the sun with
  wavelength from 200-400 nm (nanometers)
• UV radiation is divided into three ranges
• UV-A, 320 - 400 nm
• UV-B, 290 - 320 nm
• UV-C, 200 - 290 nm
• The shorter wavelength are more harmful to
  biological life.

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Ozone profile with height and UV
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Typical UV forecast
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UV radiation

• What affects the amount of UV radiation hitting
  the Earth?
• -Location (latitude)
• -Time of day
• -Time of the year
• -cloud cover
• Thus, UV radiation naturally has large variations
  in space and time!!!

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UV changes during the day
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Satellite UV measurements
July 1, 2000
January 14, 2000
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Summary

• Ozone is produced and destroyed naturally in the
  atmosphere (ozone bucket picture).
• Ozone is responsible for absorbing much of the
  suns harmful UV radiation.
• UV radiation varies due to time of day, season,
  cloud amount, and ozone amount.