The chemistry of the stratosphere

Stratospheric ozone is produced by the processes of O 2 +h nu =O+O and O+O 2 +M=O 3 +M. The first of these reactions and the process O 3 +h nu =O 2 +O merely recycle 'odd oxygen' species. The main processes destroying odd oxygen are the reaction O+O 3 =O 2 +O 2 and the catalytic cycles X+O 3 =XO+O 2 and XO+O=X+O 2 with X=NO, Cl, HO and H. The processes which control the concentration of the trace species X are considered: the sources, sinks and interconversion reactions. The measurement of trace species in the stratosphere as a test of our understanding of atmospheric chemistry is discussed as is the 'ozone hole' in the Antarctic.