German Title: Untersuchungen der Stickstoff- und Jodchemie der Stratosphäre mittels ballongetragener DOAS-Messungen und Modellrechnungen

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Translation of abstract (English)

It is well known, that the stratospheric ozone depletion is controlled mainly by halogen and nitrogen compounds. As a result of the complex interaction between chemical and dynamical processes, a quantitative understanding of the ozone loss has not been achieved till now, although it was subject of several years of intensive scientific research. This thesis reports and discusses balloon-borne Differential Optical Absorption Spectroscopy (DOAS) measurements of stratospheric trace gas profiles. The focus of this study was to measure the vertical distribution of O3, NO2, IO, and OIO during different geophysical conditions. In combination with the results of a Fourier Transform Interferometer, sharing the gondola with the DOAS instrument, and with 3-D chemistry model calculations it was possible to investigate the nitrogen chemistry in detail. Large deficits in the model's treatment of the atmospheric transport processes as well as in the understanding of the processes that control the partitioning of the nitrogen species have been found. Upper limits of the stratospheric amounts of IO and OIO were simultaneously inferred. The combination of these observations with photochemical model calculations allowed to precisely infer the upper limit of total gaseous iodine in the lower stratosphere. It is noteworthy, that even within the inferred upper limits of total iodine of 0.1 ppt or 0.065 ppt (allowing or omitting OIO photolysis), iodine still has the potential to significantly reduce the mid-latitudinal stratospheric ozone level.