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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 20
Atmos. Chem. Phys., 18, 15363–15386, 2018
https://doi.org/10.5194/acp-18-15363-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Atmos. Chem. Phys., 18, 15363–15386, 2018
https://doi.org/10.5194/acp-18-15363-2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Review article 26 Oct 2018

Review article | 26 Oct 2018

Chlorine nitrate in the atmosphere

Thomas von Clarmann and Sören Johansson Thomas von Clarmann and Sören Johansson
  • Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Karlsruhe, Germany

Abstract. This review article compiles the characteristics of the gas chlorine nitrate and discusses its role in atmospheric chemistry. Chlorine nitrate is a reservoir of both stratospheric chlorine and nitrogen. It is formed by a termolecular reaction of ClO and NO2. Sink processes include gas-phase chemistry, photo-dissociation, and heterogeneous chemistry on aerosols. The latter sink is particularly important in the context of polar spring stratospheric chlorine activation. ClONO2 has vibrational–rotational bands in the infrared, notably at 779, 809, 1293, and 1735 cm−1, which are used for remote sensing of ClONO2 in the atmosphere. Mid-infrared emission and absorption spectroscopy have long been the only concepts for atmospheric ClONO2 measurements. More recently, fluorescence and mass spectroscopic in situ techniques have been developed. Global ClONO2 distributions have a maximum at polar winter latitudes at about 20–30 km altitude, where mixing ratios can exceed 2 ppbv. The annual cycle is most pronounced in the polar stratosphere, where ClONO2 concentrations are an indicator of chlorine activation and de-activation.

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This review article compiles the characteristics of the gas chlorine nitrate and discusses its role in atmospheric chemistry. Chlorine nitrate is a reservoir of both stratospheric chlorine and nitrogen. Formation and sink processes are discussed, as well as spectral features and spectroscopic studies. Remote sensing, fluorescence, and mass spectroscopic measurement techniques are introduced, and global distributions and the annual cycle are discussed in the context of chlorine de-/activation.
This review article compiles the characteristics of the gas chlorine nitrate and discusses its...
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