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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-550
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
03 Jul 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Delayed Recovery of mid-latitude lower stratospheric Halogen Loading
Andreas Engel1, Harald Bönischa, and Jennifer Ostermöller1 1University of Frankfurt, Institute for Atmospheric and Environmental Sciences, Altenhöferallee 1, 60438 Frankfurt, Germany
anow at: Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
Abstract. Chlorine and bromine atoms can lead to catalytic destruction of ozone in the stratosphere. Therefore the use and production of ozone depleting substances (ODS) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent Effective Stratospheric Chlorine (EESC) has been adapted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a new formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the release time distribution. The improved formulation shows that EESC levels in the year 1980 for the mid latitude lower stratosphere were significantly lower than previously calculated. 1980 marks the year commonly defined as the onset of anthropogenic ozone depletion in the stratosphere. Assuming that the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than currently assumed in this region of the stratosphere. Based on the improved formulation, EESC level at mid-latitudes will reach this landmark only in 2060. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We conclude that, under the assumptions that all other atmospheric parameters like stratospheric dynamics and chemistry are unchanged, the recovery of mid latitude stratospheric ozone would be expected to be delayed by about a 10 years, in a similar way as EESC.

Citation: Engel, A., Bönisch, H., and Ostermöller, J.: Delayed Recovery of mid-latitude lower stratospheric Halogen Loading, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-550, in review, 2017.
Andreas Engel et al.
Andreas Engel et al.
Andreas Engel et al.

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Short summary
WE present a new method to derive Equivalent Effective Stratospheric Chlorine (EESC), which is based on an improved formulation of the propagation of trends of species with chemical loss from the troposphere to the stratosphere. Based on this new formulation, we expect the anthropogenic halogen impact on stratospheric ozone to return about10 years later to 1980 values then using the current formulation.
WE present a new method to derive Equivalent Effective Stratospheric Chlorine (EESC), which is...
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