Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 5 3 2005 10.5194/acpd-5-2989-2005 http://www.atmos-chem-phys-discuss.net/5/2989/2005/ http://www.atmos-chem-phys-discuss.net/5/2989/2005/acpd-5-2989-2005.html http://www.atmos-chem-phys-discuss.net/5/2989/2005/acpd-5-2989-2005.pdf 2989 3046 2005-05-13 Retrieving the vertical distribution of stratospheric OClO from Odin/OSIRIS limb-scattered sunlight measurements P. Krecl C. S. Haley J. Stegman S. M. Brohede G. Berthet Department of Meteorology, Stockholm University, Stockholm, Sweden Centre for Research in Earth and Space Science, York University, Toronto, Canada Department of Radio and Space Science, Chalmers University of Technology, Güteborg, Sweden Service d’Aéronomie, Institut Pierre-Simon Laplace, Paris, France now at: Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, UK The first vertical profiles of stratospheric OClO retrieved from Odin/OSIRIS limb-scattered sunlight radiances are presented. The retrieval method is based on a two-step approach, using differential optical absorption spectroscopy combined with the maximum a posteriori estimator. The details of the spectral window selection, spectral corrections and inversion technique are discussed. The results show that OClO can be detected inside the South polar vortex region between about 12 and 20 km altitude with a 2–5 km height resolution and an estimated retrieval error better than 60% at the peak. OClO concentrations are consistent with chemical transport model simulations and show the expected relation to the atmospheric conditions in the lower stratosphere in the austral spring 2002. This unique data set of OClO profiles is very promising to study the stratospheric chlorine activation in both polar regions.