Atmos. Chem. Phys. Discuss., 13, 16597-16660, 2013
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Chemical composition and severe ozone loss derived from SCIAMACHY and GOME-2 observations during Arctic winter 2010/2011 in comparisons to Arctic winters in the past
R. Hommel1, K.-U. Eichmann1, J. Aschmann1, K. Bramstedt1, M. Weber1, C. von Savigny1,*, A. Richter1, A. Rozanov1, F. Wittrock1, R. Bauer1, F. Khosrawi2, and J. P. Burrows1
1Institute of Environmental Physics (IUP), University of Bremen, Bremen, Germany
2Department of Meteorology, Stockholm University, Stockholm, Sweden
*now at: Institute of Physics, Ernst-Moritz-Arndt-University of Greifswald, Greifswald, Germany

Abstract. Record breaking losses of ozone (O3) in the Arctic stratosphere have been reported in winter and spring 2011. Trace gas amounts and polar stratospheric cloud (PSC) distributions retrieved using differential optical absorption spectroscopy (DOAS) and scattering theory applied to the measurements of radiance and irradiance by satellite-born and ground-based instrumentation, document the unusual behaviour. A chemical transport model has been used to relate and compare Arctic winter-spring conditions in 2011 with those in previous years. We examine in detail the composition and transformations occurring in the Arctic polar vortex using total column and vertical profile data products for O3, bromine oxide (BrO), nitrogen dioxide (NO2), chlorine dioxide (OClO), and PSCs retrieved from measurements made by the instrument SCIAMACHY onboard the ESA satellite Envisat, as well as the total column ozone amount, retrieved from the measurements of GOME-2 on the EUMETSAT operational meteorological polar orbiter Metop-A. In the late winter and spring 2010/2011 the chemical loss of O3 in the polar vortex is consistent with and confirms findings reported elsewhere. More than 70% of O3 was depleted between the 425 K and 525 K isentropic surfaces, i.e. in the altitude range ~16–20 km. In contrast, during the same period in the previous winter only slightly more than 20% depletion occurred below 20 km, whereas 40% of the O3 was removed above the 575 K isentrope (~23 km). This loss above the 575 K isentrope is explained by the catalytic destruction by the NOx descending from the mesosphere. At lower altitudes O3 loss results from processing by halogen driven O3 catalytic removal cycles, activated by the large volume of PSC generated throughout this winter and spring. The mid-winter 2011 conditions, prior to the catalytic cycles being fully effective, are also investigated. Surprisingly, a significant loss of O3 with 60% is observed in mid-January 2011 below 500 K (~19 km), which was then sustained for approximately a week. This "mini-hole" event had an exceptionally large spatial extent. Such meteorologically driven changes in polar stratospheric O3 are expected to increase in frequency as anthropogenically induced climate change evolves.

Citation: Hommel, R., Eichmann, K.-U., Aschmann, J., Bramstedt, K., Weber, M., von Savigny, C., Richter, A., Rozanov, A., Wittrock, F., Bauer, R., Khosrawi, F., and Burrows, J. P.: Chemical composition and severe ozone loss derived from SCIAMACHY and GOME-2 observations during Arctic winter 2010/2011 in comparisons to Arctic winters in the past, Atmos. Chem. Phys. Discuss., 13, 16597-16660, doi:10.5194/acpd-13-16597-2013, 2013.
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