Tellus, Series B: Chemical and Physical Meteorology

Chlorine partitioning in the stratosphere based on in situ measurements

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Balloon-borne cryogenic air sampler experiments have been conducted from a tropical (Hyderabad, 17.5°N) and a midlatitude (GAP, southern France, 44°N) station since 1987 in the altitude range of about 8-35 km. Air samples are analysed at the Max Planck Institute for Aeronomy (MPAE) and Physical Research Laboratory (PRL) using various gas chromatographic techniques to obtain the vertical distributions of several halogenated source gases and long-lived dynamical tracers. These observations are used to determine the stratospheric partitioning of the chlorine species into their organic and inorganic forms for the altitude range of 20 to 35 km. Distributions of inorganic chlorine indicate increase in their abundances with altitude, latitude and time. Mixing ratio correlations of organic and inorganic chlorine with N2O have been obtained which also suggest that the rate of increase in inorganic halogens component in the stratosphere is larger than the increase rate of total organic halogen. This supports previous assessments that halogen-induced ozone depletion will continue to be observed for a few more years, despite the decrease of halocarbon loading into the stratosphere since 1994.