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

3. Temperature Structure
of the Atmosphere

4. Height/km Latitude Mesosphere Stratopause Stratosphere Tropopause
Troposphere
Latitude

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

6. Mesosphere
Stratosphere
Upper troposphere

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. 30 km
Altitude
16 km
1950
The QBO
In equatorial
regions
1978

12. Variations in mean O3 column(DU) due to QBO (from satellite observations)

13. Climatology of Global O3 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(3P) O3 O2 O3

18. O2 + hn  O + O Window region where UV radiation penetrates
into the lower stratosphere
giving:
O2 + hn  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. O2 + hn(l<243nm)  O + O oxygen photolysis
O + O2 + M  O3 + M ozone formation
O + O3  O2 + O ozone destruction
O3 + hn(l<310nm)  O(1D) + O2
O3 + hn(l<1180nm)  O + O 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]

27. Interconversion of Cl & ClO
Formation and release from reservoirs of Cl & ClO

28. STRATOSPERE
 heterogeneous
reactions on
sulphate aerosol

33. 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.

34. OZONE DEPLETION CYCLES INVOLVING HALOGENS THE LOWER STRATOSPHERE
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

35.  heterogeneous
reactions on
sulphate aerosol