Lecture4 - Stratospheric Ozone 1 Homework: Analyze data...

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1 1 Stratospheric Ozone 2 Solar occultation instruments view the sun as it is occulted by the atmosphere, measuring the attenuation of sunlight as this occurs. Measurements are made as the satellite enters into the dayside (sunrise) or into the nightside (sunset). Thus, they only occur at the intersection of the satellite orbit and the terminator (boundary separating day from night). Characteristics of Solar Occultation Measurements Occultation: The disappearance of a star, planet, or other celestial body as it moves out of sight behind another celestial body. Homework: Analyze data from the Polar Ozone and Aerosol Measurement (POAM) III instrument
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2 3 POAM: Polar Ozone and Aerosol Measurement POAM II: Oct 1993–Nov 1996 POAM III: Apr 1998–Dec 2005 Solar Occultation: Vertical Range: 10-60 km Vertical Resolution: 1 km POAM Latitudes: 55-73 N, 63-88 S POAM Measures: Ozone Aerosol Extinction (353-1060 nm) Nitrogen Dioxide Water Vapor (POAM III) 4 What is ozone ?? Gas made from interaction of sunlight and oxygen (O 2 ): O 2 + h ν O + O O + O 2 + M O 3 Present in troposphere and stratosphere Has a “sharp” or “sweet” odor Can be both “good” and “bad” Ozone = O 3
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3 5 Where is ozone located ? Good Ozone Bad Ozone 6 Bad Ozone *** Troposphere *** Toxic component of smog: Damages lung tissue, foliage, rubber, paint Contributes to the greenhouse effect: Absorbs heat emitted by earth Why is tropospheric ozone “bad” ?
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4 7 Why is stratospheric ozone good ? Good Ozone *** In the Stratosphere *** Absorbs solar ultraviolet (UV-B) radiation Protection against: sunburn, cataracts, skin cancer, immune deficiencies, and adverse effects on phytoplankton, plant growth, & synthetic materials (e.g., plastics) 8 Why isn’t tropospheric ozone also good? All ozone absorbs UV, but so much ozone is in the stratosphere, that it absorbs most of the hazardous radiation before it reaches the troposphere. So tropospheric ozone doesn’t have the chance to be “good”. Stratopause Tropopause
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5 9 Major absorbers of UV radiation at different altitudes 10 Ozone Absorption Spectrum Removes UV-C Used to remotely measure mesospheric ozone Removes most of UV-B and some UV-A Used to remotely measure stratospheric ozone
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6 11 12 Total Ozone: The amount of ozone in a column of air above a particular location on the earth. 1 Dobson Unit = 1 DU = 2.7x10 16 molecules cm -2
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7 13 How is stratospheric ozone produced? O 2 + h ν O + O 2 {O + O 2 + M O 3 + M} Net: 3O 2 + h ν 2O 3 (M is any molecule or atom) Requires sunlight Maximizes in equatorial upper stratosphere 14 How is ozone destroyed ? O 3 + h ν O 2 + O O + O 3 2 O 2 Net: 2 O 3 + h ν 3 O 2 Requires sunlight Maximizes in equatorial upper stratosphere UV is absorbed (protecting the troposphere) Energy is released as heat (warming the stratosphere)
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8 15 Summary of Ozone Production & Loss via Chapman Reactions In 1921, Chapman proposed set of
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Lecture4 - Stratospheric Ozone 1 Homework: Analyze data...

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