Published on February 21, 2008
The Stratospheric Chemistry and The Ozone Layer: The Stratospheric Chemistry and The Ozone Layer *Stratospheric circulation *Stratospheric photochemistry *Gas phase reactions *Ozone and Catalytic cycles Dr Tony Cox ERCA 2004 -Lecture 2 Slide3: Temperature Structure of the Atmosphere Slide4: Height/km Latitude Mesosphere Stratosphere Troposphere Stratopause Tropopause Slide5: Satellite measurements of aerosol as a tracer for stratospheric circulation Black region is troposphere Eruption of Mt Pinatubo, Phillipine Is, 5ON, June 1991 Slide6: Mesosphere Stratosphere Upper troposphere Slide8: MEAN (11yr) ATMOSPHERIC WINDS AT 20 km ALTITUDE (NOAA Analysis) Slide9: MEAN (11yr) ATMOSPHERIC TEMPERATURE AT 20 km ALTITUDE (NOAA Analysis) Slide10: Potential Vorticity At ~20 km in the S.Polar Vortex Slide11: 1950 30 km Altitude 16 km 1978 The QBO In equatorial regions Slide12: Variations in mean O3 column(DU) due to QBO (from satellite observations) Slide13: Climatology of Global O3 column (after Dutsch, 1971) In Dobson units, i.e. mmHgx100 at STP Slide14: Chemical Kinetics I Slide15: Chemical Kinetics II Slide16: Chemical Kinetics III Slide17: O(3P) O2 O3 O3 Slide18: Window region where UV radiation penetrates into the lower stratosphere giving: O2 + hn O + O Slide19: Chemical lifetime of O3:calculated daily averaged photodissociation rate of molecular oxygen Slide20: Release of catalysts by Photolysis in the lower Stratosphere Slide21: O2 + hn(l<243nm) O + O oxygen photolysis O + O2 + M O3 + M ozone formation O + O3 O2 + O2 ozone destruction O3 + hn(l<310nm) O(1D) + O2 O3 + hn(l<1180nm) O + O2 oxygen photolysis NO2 + hn(l<243nm) NO + O NO2 photolysis O + O2 + M O3 + M ozone formation X + O3 XO + O2 XO + O X + O2 Net O + O3 O2 + O2 ozone destruction [X = H, OH, NO, Cl, Br, etc] Slide27: Interconversion of Cl & ClO Formation and release from reservoirs of Cl & ClO Slide28: STRATOSPERE heterogeneous reactions on sulphate aerosol OZONE DEPLETION CYCLES IN THE LOWER STRATOSPHERE: OZONE DEPLETION CYCLES IN THE LOWER STRATOSPHERE Concentration of O atoms fall off in lower stratosphere as photolysis of O2 and O3 reduces. Catalytic destruction through cycles involving participation of atomic O is less important. Other cycles not involving O(3P) can occur. Slide34: Involving ClOx/NOx coupling ClO + NO2 = ClONO2 ClONO2 + hn = Cl + NO3 NO3 + hn = NO + O2 NO + O3 = NO2 + O2 Cl + O3 = ClO + O2 net O3 + O3 = 3O2 Involving NOx/Halogen (X = Br or I) coupling XO + HO2 = HOX + O2 HOX + hn = X + HO OH + O3 = HO2 + O2 X + O3 = XO + O2 net O3 + O3 = 3O2 OZONE DEPLETION CYCLES INVOLVING HALOGENS THE LOWER STRATOSPHERE Slide35: heterogeneous reactions on sulphate aerosol
OZONE DEPLETION CYCLES IN THE LOWER STRATOSPHERE The Stratospheric Chemistry and The Ozone Layer *Stratospheric circulation *Stratospheric ...