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Mysterious Chemistry of the Polar Stratosphere

Since the discovery of the ozone hole more than three decades ago, the processes leading to ozone depletion in the stratosphere have been largely understood: This is caused by chlorine emissions into the atmosphere from chlorofluorocarbons (CFCs), which were used, for example, as refrigerants in refrigerators. In recent years, research has therefore concentrated on still unresolved issues relating atmospheric chemistry. An international research team with Jülich participation has now discovered a discrepancy when comparing models with measurements of hydrogen chloride in early polar winter, the period before the ozone hole forms. According to this, hydrogen chloride is depleted much faster in the polar stratosphere than simulated by the models. The results have now been published in the journal Atmospheric Chemistry and Physics.

The results indicate that there should be an unknown chemical process in this layer of the atmosphere that leads to the depletion of hydrogen chloride. The researchers showed that the hitherto unexplained process is related to the occurrence of so-called polar stratospheric clouds (PSCs). Further studies will show whether a reaction with these clouds may be triggered by cosmic radiation. The scientists now want to find this missing atmospheric chemical process using laboratory or field measurements in order to improve the forecasts and thus the models.

Original publication:

Grooß, J.-U., R. Müller, R. Spang, I. Tritscher, T. Wegner, M. P. Chipperfield, W. Feng, D. E. Kinnison, and S. Madronich, On the discrepancy of HCl processing in the core of the wintertime polar vortices, Atmos. Chem. Phys., 18, 8647-8666,


More informations

Press release "New findings on the chemistry of chlorine radicals in the ozone hole"

Satellite observations and model simulations of hydrogen chloride in about 21 km altitude for 20 July 2011Satellite observations and model simulations of hydrogen chloride in about 21 km altitude for 20 July 2011