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Ozone Depletion, Greenhouse Gases, and Climate Change (1989) / Chapter Skim
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7 Free Radicals in the Earth's Atmosphere: Measurement and Interpretation
Pages 56-65

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From page 56...
... suggested that the couplet, chlorine atoms plus ozone reacting to form chlorine monoxide (ClO) plus oxygen followed by chlorine monoxide reacting with oxygen atoms to reform chlorine atoms plus oxygen in a catalytic cycle, constitutes a loss process for ozone in the stratosphere.
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From page 57...
... The reverse is true in the nitrogen system, in which OH reacting with nitrogen dioxide forms nitric acid. The OH concentration in a highly simplified form is established by a balance between excited oxygen atoms, O(iD)
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From page 58...
... results of increasing the reaction rate constant of NO + HO2 ~ NO2 + OH, which increased the modelcalculated column integral of ozone depletion by more than a factor of three. Subsequent refinements, such as the introduction of OH loss terms (nitric acid plus OH and pernitric acid plus OH)
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From page 59...
... But that is not true because OH, we now believe, is controlled by nitric and pernitric acid, which means it is susceptible to linkage through the chlorine-induced removal of nitrogen oxides. So, while the OH concentration is low, it is susceptible to change with increas ing mixing ratios of total chlorine in the atmosphere.
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From page 60...
... is receiving significantly more focused attention. As Watson mentioned, their high-altitude ER-2 aircraft flew from the southern tip of Chile (Pumas Arenas)
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From page 61...
... Whatever took place on the stratospheric ice crystal structures during the dark winter months had little effect on the ozone concentration. But after August 23, the sun penetrated the South Polar vortex region for a small but increasing number of hours per day.
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From page 63...
... So, we can take slices into the rotating polar vortex "disk" and sample the chlorine monoxide and ozone concentrations simultaneously. The kinetics are determined by calculating the time rate of change of ozone bred on the observed chlorine monoxide concentrations.
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From page 64...
... If one compares the recent winter data with mean July data, the difference at 36°N latitude is about a factor of two. The 60 parts per trillion at 61°N is not nearly as high a concentration as the 1,000 parts per trillion observed in the Antarctic, but then the Northern Hemisphere measurements probably did not extend all the way into the polar vortex.
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From page 65...
... 1985. A zonal mean model of stratospheric tracer transport in isentropic coordinates: numerical simulations for nitrous oxide and nitric acid.
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Key Terms

  • polar vortex
  • nitric acid
  • free radicals
  • nitrogen dioxide
  • antarctic ozone

  • ozone depletion
  • upper stratosphere
  • northern hemisphere
  • catalytic cycle
  • chlorine nitrate

  • pernitric acid
  • nitrogen oxides
  • observed clo
  • mixing ratio
  • lower stratosphere

  • nitric oxide
  • chlorine radicals
  • total chlorine
  • plus oxygen
  • clo concentration

  • potential temperature
  • atoms plus
  • oxygen atoms
  • ozone destruction
  • chlorine radical

  • free radical
  • radical form
  • acid concentration
  • acid plus
  • column ozone


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