An introduction to stratospheric chemistry - Survey article

This paper is an expansion of the lectures presented by the authors at the Canadian Middle Atmosphere Model (CMAM) summer school, 25-29 August 1997. I t attempts to fulfill several goals as did the curriculum for the summer sc hool. Firstly it has a large tutorial component allowing newcomers a rapid introduction to the field secondly it surveys the field of stratospheric ch emistry and thirdly it attempts to bring the render to the forefront of som e of the problem areas in stratospheric chemistry. As such, it includes muc h background information such as the magnitude of rate coefficients, photol ysis rates and their calculation and time constants. The intended audience is individuals about to commence study or research in the field of atmosphe ric chemistry or established atmospheric scientists in other ar eas wishing to expand their knowledge of this topic. The basic chemistry of the ozone layer is described with an emphasis on the catalytic cycles and the equilibria between "reservoir" and "active" speci es. To this end, ct compendium of the important aspects of heterogeneous he terogeneous chemistry is also provided The application of box (0-dimensiona l) and more elaborate (1-, 2- and 3-dimensional) models to compare and vali date with measurements is discussed. Also, factors affecting the present an d future trends in ozone concentration both at mid-latitudes and in the pol ar region, are presented.