Investigating stratospheric chlorine chemistry by SCIAMACHY measurements in limb and occulation geometry: Retrieval and intepretation of vertical OCIO profiles

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It is well established that the major cause for the ozone hole (the massive depletion of ozone in the polar lower stratosphere in springtime) is the heterogeneous processing of chlorine species during polar winter, the stratospheric chlorine activation. Despite their immense effect on the ozone layer, daily and global measurements of active chlorine compounds like ClO and ClOOCl are rare. On the other hand, chlorine dioxide (OClO), an important indicator for chlorine activation, can be measured by remote sensing methods more easily than ClO or ClOOCl. We propose to develop algorithms for the retrieval of vertical OClO profiles from the limb and occultation measurements of the satellite instrument SCIAMACHY. The retrievals will be optimised in terms of spectroscopy, radiative transfer modeling and inversion approach. After validation, the obtained profiles will be applied to various scientific studies like inter-annual and inter-hemispheric comparisons (variability and evolution of the magnitude and profile peak height of chlorine activation), case studies (relation to stratospheric temperatures, other stratospheric trace gases, and activation by mountain waves), and comparison to results from established model simulations.In combination with NO2, BrO and O3 profiles, also retrieved from the SCIAMACHY measurements, the obtained dataset of day and night time profiles of OClO will be utilized to investigate current open questions in stratospheric chemistry.