Recent developments in photochemistry of atmospheric ozone

Summary A review is given of the increasingly rapid development of the photochemistry of odd oxygen particles which has taken place since the validity of the classical (oxygen only) theory was for the first time questioned by Hampson and Hunt less than 10 years ago. The relative importance of different reactions is discussed as a function of altitude and also the alterations of the H-system, introduced by NO_x, are investigated. It is shown that the fact that not only the observed ozone but also the HNO₃ distribution should be explained considerably limits the acceptable values of poorly known rate constants. The influence of stratospheric pollution on ozone concentration is also discussed under the assumption of photochemical equilibrium.List of symbols Õ Odd oxygen particles - active hydrogen particles - O^* excited (¹ D)-O-atom - NO_x nitrogen oxides (odd nitrogen) - n ₁ concentration of atomic oxygen particles cm^–3] - n ₁ ^* concentration of excited ¹ D]-oxygen-atoms - n ₂ concentration of molecular oxygen - n _m concentration of air molecules - s =n _m /n ₂ - ñ n ₁+n ^*+n ₃, concentration of odd oxygen particles - x concentration of atomic hydrogen - y concentration of OH-radicals - z concentration of HO₂-radicals - NO] concentration of nitric oxide - NO₂] concentration of nitrogen dioxide - NO₃] concentration of nitrogen trioxide - NO_x] concentration of total odd nitrogen - HNO₃] concentration of nitric acid - k _i reaction rates - f _i dissociation rates - a ₃ fraction off ₃ yielding excited O-atoms - nomix] NO _x /air mixing ratio - relaxation time Part of the research reported in this article was done at the National Center for Atmospheric Research, Boulder, Colo. (sponsored by the National Science Foundation). The opportunity of using NCAR's computing facilities is especially acknowledged. This study has also been supported by the Swiss National Foundation.