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Abstract

Exact knowledge about the isotopic composition of water vapor in the tropopause region and the stratosphere provides important information for the understanding of atmospheric transport and photochemistry. The presented thesis describes with the help of models the processes governing the isotopic composition of atmospheric water vapor. The stable isotopologues - HDO, H17 2 O and H18 2 O - and the radioactive isotopologue HTO are discussed. A complete analytical procedure has been developed for the purpose of precise measurements of the mentioned water isotopologues. For the stable isotopologues, it consists of three instruments: a continuous-flow system for the chemical decomposition of H2O to H2 and O2 for subsequent mass-spectrometrical analysis, a calibration v vi unit for the production of water vapor with known isotopic composition, and a cryogenic sampling unit for operation aboard airplanes and balloons. The required sample amount could be reduced to about 100ng. Further, experiments with a sampling unit for tritiated water vapor have been performed. With these apparatus, samples of atmospheric water vapor have been taken on 6 flights between New Zealand and Antarctica, and have later been analyzed in the laboratory.