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The Stratospheric Chemistry and The Ozone Layer *Stratospheric circulation *Stratospheric photochemistry *Gas phase reactions *Ozone and Catalytic cycles.

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Presentation on theme: "The Stratospheric Chemistry and The Ozone Layer *Stratospheric circulation *Stratospheric photochemistry *Gas phase reactions *Ozone and Catalytic cycles."— Presentation transcript:

1 The Stratospheric Chemistry and The Ozone Layer *Stratospheric circulation *Stratospheric photochemistry *Gas phase reactions *Ozone and Catalytic cycles Dr Tony Cox ERCA Lecture 2

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3 Temperature Structure of the Atmosphere

4 Height/km Latitude Mesosphere Stratosphere Troposphere Stratopause Tropopause

5 Satellite measurements of aerosol as a tracer for stratospheric circulation Black region is troposphere Eruption of Mt Pinatubo, Phillipine Is, 5 O N, June 1991

6 Mesosphere Stratosphere Upper troposphere

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8 MEAN (11yr) ATMOSPHERIC WINDS AT 20 km ALTITUDE (NOAA Analysis)

9 MEAN (11yr) ATMOSPHERIC TEMPERATURE AT 20 km ALTITUDE (NOAA Analysis)

10 Potential Vorticity At ~20 km in the S.Polar Vortex

11 km Altitude 16 km 1978 The QBO In equatorial regions

12 Variations in mean O 3 column(DU) due to QBO (from satellite observations)

13 Climatology of Global O 3 column (after Dutsch, 1971) In Dobson units, i.e. mmHgx100 at STP

14 Chemical Kinetics I

15 Chemical Kinetics II

16 Chemical Kinetics III

17 O( 3 P) O2O2 O3O3 O3O3

18 Window region where UV radiation penetrates into the lower stratosphere giving: O 2 + h  O + O

19 Chemical lifetime of O3:calculated daily averaged photodissociation rate of molecular oxygen

20 Release of catalysts by Photolysis in the lower Stratosphere

21 O 2 + h  nm  O + O oxygen photolysis O + O 2 + M  O 3 + M  ozone formation O + O 3  O 2 + O 2 ozone destruction O 3 + h  nm  O( 1 D) + O 2 O 3 + h  nm  O + O 2 oxygen photolysis NO 2 + h  nm  NO + O NO 2 photolysis O + O 2 + M  O 3 + M  ozone formation X + O 3  XO + O 2 XO + O  X + O 2 Net O + O 3  O 2 + O 2 ozone destruction [X = H, OH, NO, Cl, Br, etc]

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27 Interconversion of Cl & ClOFormation and release from reservoirs of Cl & ClO

28 STRATOSPERE  heterogeneous reactions on sulphate aerosol

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33 OZONE DEPLETION CYCLES IN THE LOWER STRATOSPHERE Concentration of O atoms fall off in lower stratosphere as photolysis of O 2 and O 3 reduces. Catalytic destruction through cycles involving participation of atomic O is less important. Other cycles not involving O( 3 P) can occur.

34 Involving ClOx/NOx coupling ClO + NO 2 = ClONO 2 ClONO 2 + h = Cl + NO 3 NO 3 + h = NO + O 2 NO + O 3 = NO 2 + O 2 Cl + O 3 = ClO + O 2 net O 3 + O 3 = 3O 2 Involving NOx/Halogen (X = Br or I) coupling XO + HO 2 = HOX + O 2 HOX + h = X + HO OH + O 3 = HO 2 + O 2 X + O 3 = XO + O 2 net O 3 + O 3 = 3O 2 OZONE DEPLETION CYCLES INVOLVING HALOGENS THE LOWER STRATOSPHERE

35  heterogeneous reactions on sulphate aerosol

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