Atmos. Chem. Phys. Discuss., 7, 12959-12999, 2007
www.atmos-chem-phys-discuss.net/7/12959/2007/
doi:10.5194/acpd-7-12959-2007
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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.
Observations of iodine monoxide (IO) columns from satellite
A. Schönhardt1, A. Richter1, F. Wittrock1, H. Kirk1, H. Oetjen1,*, H. K. Roscoe2, and J. P. Burrows1
1Institute of Environmental Physics, University of Bremen, Otto-Hahn-Allee 1, 28359 Bremen, Germany
2British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge CB3 0ET, UK
*now at: School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK

Abstract. Iodine species in the troposphere are linked to ozone depletion and new particle formation. In this study, a full year of iodine monoxide (IO) columns retrieved from measurements of the SCIAMACHY satellite instrument is presented, alongside a discussion of their uncertainties and the detection limit. The largest amounts of IO are found near springtime Antarctica, where ground-based measurements have positively detected iodine compounds before. A seasonal variation of iodine monoxide in Antarctica is revealed with high values in springtime, slightly less IO in the summer period and again larger amounts in autumn. In winter, no elevated IO levels are found in the areas accessible to satellite measurements. This seasonal cycle is in good agreement with recent ground-based measurements in Antarctica. In the Arctic region, no elevated IO levels were found in the whole time period analysed, arguing for different conditions existing in the two Polar Regions. To investigate possible release mechanisms such as inorganic release or biogenic precursors, comparisons of IO results with tropospheric BrO maps, measurements of chlorophyll concentration, and ice coverage are discussed. Some parallels and interesting differences between IO and BrO temporal and spatial distributions are pointed out. Although no full interpretation can be given at this point, the large spatial coverage of satellite measurements and the availability of a long-term dataset give some new indications and understandings of the abundances and distributions of iodine compounds in the troposphere.

Citation: Schönhardt, A., Richter, A., Wittrock, F., Kirk, H., Oetjen, H., Roscoe, H. K., and Burrows, J. P.: Observations of iodine monoxide (IO) columns from satellite, Atmos. Chem. Phys. Discuss., 7, 12959-12999, doi:10.5194/acpd-7-12959-2007, 2007.
 
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