Ozonschicht und stratosphärisches Spurengassystem

Abstract

During the last 12 years is has become evident that the “classical” photochemical theory by which Chapman explained in 1930 the atmospheric ozone layer with a stratospheric maximum does not give full representation of the important processes. However, the subsequent developments of the theory do not question the fact that transport processes considerably modify the photochemical ozone distribution. In the lower stratosphere they determine the distribution while above a transition layer where transport and photochemistry are of comparable importance, i.e. above 30-35 km, the latter is predominant. 
It has become clear that ozone is not predominantly destroyed by direct reaction with atomic oxygen but rather by catalytic cycles involving different groups of radicals (HO_x, NO_x, ClO_x). Those radicals are formed either by reaction of (ozone produced) excited oxygen atoms with or by photodissociation (by UV-radiation already absorbed in the stratosphere) of otherwise rather stable compounds. Strong coupling between the different radical groups and also transport processes acting on all of its members further complicate the rather complex system. 
While the Chapman theory did not predict any human influence on the ozone layer the new photochemical system points to its vulnerability. Some of the parent substances are either of anthropogenic origin or their natural formation may be anthropogenically influenced (CFM- and fertilizer problem); it is also possible that radicals are directly injected into the stratosphere (SST-problem). An anthropogenic reduction of the ozone layer is thus a real possibility and accelerated research on the complex system is therefore urgently needed, especially as the biological or climatic consequences of changes in the ozone layer are only extremely poorly known.