Stratospheric Ozone Depletion

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Features of the ozone hole • Ozone depletion occurs at altitudes between 10 and 20 km – If O3 depletion resulted from the ClOx cycle, the depletion would occur at middle and lower latitude and altitudes between 35 and 45 km. – The ClOx cycle requires O atom, but in the polar stratosphere, the low sun elevation results in essentially no photodissociation of O2 . – The above observation could not be explained by the ClOx destruction mechanism alone. • Depletion occurs in the Antarctic spring
Special Features of Polar Meteorology • During the winter polar night, sunlight does not reach the south pole. • A strong circumpolar wind develops in the middle to lower stratosphere; These strong winds are known as the 'polar vortex'. • In the winter and early spring, the polar vortex is extremely stable, sealing off air in the vortex from that outside. • The exceptional stability of the vortex in Antarctic is the result of the almost symmetric distribution of ocean around Antarctica. • The air within the polar vortex can get very cold. • Once the air temperature gets to below about -80C (193K), Polar Stratospheric Clouds (or PSCs for short) are formed.
Page 1 and 2: Environmental Chemistry Part 2 Atmo
Page 3 and 4: The ozone layer
Page 5 and 6: Ultraviolet protection by ozone The
Page 7 and 8: Typical ozone column values • Tot
Page 9 and 10: Ozone formation and destruction in
Page 11 and 12: Prediction by Chapman theory vs. Ob
Page 13 and 14: The important catalysts for stratos
Page 15 and 16: Chlorine atom Sources: Photolysis o
Page 17 and 18: Chlorine atom (Continued) Terminati
Page 19 and 20: The two-sided effect of NOx • NOx
Page 21 and 22: Numbering system for CFCs and HCFCs
Page 23: The discovery of the ozone hole •
Page 28 and 29: Polar vortex • The polar vortex i
Page 30 and 31: Why do PSCs occur at heights of 15-
Page 32 and 33: PSCs promote the conversion of inor
Page 34 and 35: Active Cl species can rapidly yield
Page 36 and 37: How does the polar ClOx cycle stop?
Page 38 and 39: Denitrification by PSCs enhances po
Page 40 and 41: Summary of the roles played by PSCs
Page 42 and 43: Schematic of photochemical and dyna
Page 44 and 45: Does ozone hole occur in the north
Page 46 and 47: Summary on ozone hole (Continued)
Page 48 and 49: What influences ODP? • Lifetime i
Page 50 and 51: ODPs of Selected Compounds Compound

Stratospheric Ozone Depletion

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