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Stratospheric Chemistry

Stratospheric Chemistry. Stratospheric Chemistry - Ozone. Solar Emission: 250 – 1000 um. UV Radiation:. UV-A 315- 400nm ~7% total solar flux UV-B 280-315nm ~1.5% total flux UV-C <280nm ~0.5% total solar flux. Ozone absorbs UV-C and partially absorbs UV-B region.

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Stratospheric Chemistry

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  1. Stratospheric Chemistry

  2. Stratospheric Chemistry - Ozone Solar Emission: 250 – 1000 um UV Radiation: UV-A 315- 400nm ~7% total solar flux UV-B 280-315nm ~1.5% total flux UV-C <280nm ~0.5% total solar flux Ozone absorbs UV-C and partially absorbs UV-B region

  3. Ozone Damage to the Red Alder Tree

  4. Dobson units (DU) for the measurement of ozone 100 DU equivalent to 1mm thick layer of ozone at 0 oC and Po World Average ~ 300 DU Antarctic “Ozone Hole” < 150 DU Range 250 DU – 450 DU

  5. Ground Based Ozone Detection Systems Dobson Ozone Spectrometer (1920s)

  6. Stratospheric Ozone Lidar Trailer Equipiment (STROZ-LITE) Ozone Two Lasers (308 and 351nm): (light backscattered elastically, collected with a 30” telescope) Temperature: (from 351 nm backscatter, signal related to density) Aerosol: (records both elastically and inelastically scattered light…ratio gives Aerosol Scatter Ratio…~measure of aerosol conc.)

  7. STROZ-LITE Temperature and Aerosol Scattering Data

  8. Airborne Raman, Ozone, Temperature and Aerosol Lidar (AROTEL) Vertical profile of ozone between 12-30km Veritcal profile of temperature, 13 ~60km Vertical profile of aerosol scattering Aeosol depolarization at 532 nm Instrument: Transmitter: XeCl excimer laser (308nm) Nd-YAG laser (1064, 532, 355nm) Reciever: 16” Newton telescope

  9. Satellite Remote Sensing LIDAR Systems, Light Detection and Ranging Systems

  10. Satellite-Based Systems EOS Aura Spacecraft HIRDLS: High Resolution Dynamic Limb Sounder MLS: Microwave Limb Sounder TES: Tropospheric Emission Spectrometer OMI: Ozone Monitoring Instrument

  11. OMI Data Products OMI: Ozone Monitoring Instrument OMI Data Products

  12. OMI: Ozone Monitoring Instrument

  13. Oxygen-only Chemistry – formation and turnover of ozone First proposed by Chapman

  14. Chapman Reaction Sequence O2 + hn (l < 240 nm)  2 O +498.4kJ – E(hn) (slow) O + O2 + M  O3 + M -106.5kJ (fast) O3 + hn (l = 230-320nm)  O2* +O* 386.5kJ – E(hn) (fast) O + O3 2 O2 -391.9 kJ (slow)

  15. Catalytic Decomposition of Ozone X + O3 XO + O2 XO + O  X + O2 O + O3  2 O2 X = HOx NOx ClOx ~70% @ 50km ~70% @ 30km .H .OH HOO..NO .NO2 .Cl ClO.

  16. HOx Species Formation: O + H2O  2 .OH H2O + hn  .H + .OH Catalytic Decomposition of Ozone: .H + O3  .OH + O2.OH + O3 HOO. + O2 .OH + O  .H + O2HOO. + O  .OH + O2 O + O3  2 O2O + O3  2 O2

  17. NOx SpeciesfromN2O (~300 ppbv) Formation: < 30km N2O + O*  2NO >30km N2 + hn (l<126nm)  N* + N N + O2  NO + O Catalytic Decomposition of Ozone: NO + O3 NO2 + O2 NO2 + O  NO + O2 O + O3  2 O2

  18. ClOx Species Natural Source: CH3Cl Formed: CH3Cl + hn .CH3 + .Cl Removed: CH3Cl + .OH  .CH2Cl + H2O Catalytic Decomposition of Ozone .Cl + O3 ClO. + O2 ClO. + O  .Cl + O2 O + O3  2 O2

  19. Chlorofluorocarbons (CFCs) CFC-xyz x = # C atoms -1 y = # H atoms z = # F atoms +1 remainder Cl CFC-114 2 C, 0 H, 4 F ….. 2 Cl 114 + 90 = 204….. 2Cl CFCl2CF3 CF2ClCF2Cl CFC-114a CFC114b CFC-11 11 + 90 = 101 CFCl3 CFCl3 + hn (l<290)  .CFCl2 + .Cl

  20. Null Cycles: Holding Cycles: NO + O3 NO2 + O2NO3 + NO2 + M  N2O5 + M NO2 + hn  NO + O.NO2 + .OH + M  HNO3 + M O3 + hn  O2 + O .Cl + CH4  HCl + .CH3 NO2 + O3  NO3 + O2 ClO. + HOO.  HOCl + O2 NO3 + hn  NO2 + OHOO. + .NO2 + M  HO2NO2 + M O3 + hn  O2 + OClO. + .NO2 + M  ClONO2 + M

  21. Antarctica Ozone Chemistry Winter: HCl + ClONO2 Cl2 + HNO3 (on PSCs) H2O + ClONO2  HOCl + HNO3 (on PSCs) Spring: Cl2 + hn 2 .Cl HOCl + hn  ClOO. + .Cl

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