1SRON – Netherlands Institute for Space Research, Utrecht, The Netherlands
2Institut für Umweltphysik, University of Heidelberg, Heidelberg, Germany
3Department of Physics, University of Leicester, Leicester, UK
4Laboratoire de Physique Moléculaire pour l'Atmosphère et l'Astrophysique (LPMAA), Université Pierre et Marie Curie, Paris, France
5Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, UK
*formerly at: Institut für Umweltphysik, University of Heidelberg, Heidelberg, Germany
Abstract. We report upper limits of IO and OIO in the tropical upper troposphere and stratosphere inferred from solar occultation spectra recorded by the LPMA/DOAS (Limb Profile Monitor of the Atmosphere/Differential Optical Absorption Spectroscopy) payload during two stratospheric balloon flights from a station in Northern Brazil (5.1° S, 42.9° W). In the tropical upper troposphere and lower stratosphere, upper limits for both, IO and OIO, are below 0.1 ppt. Photochemical modelling is used to estimate the compatible upper limits for the total gaseous inorganic iodine burden (Iy) amounting to 0.09 to 0.16 (+0.10/−0.04) ppt in the tropical lower stratosphere (21.0 km to 16.5 km) and 0.17 to 0.35 (+0.20/−0.08) ppt in the tropical upper troposphere (16.5 km to 13.5 km). In the middle stratosphere, upper limits increase with altitude as sampling sensitivity decreases. Our findings imply that the amount of gaseous iodine transported into the stratosphere through the tropical tropopause layer is small and that iodine-mediated ozone loss plays only a minor role for stratospheric photochemistry. However, photochemical modelling uncertainties are large and iodine might be transported into the stratosphere in particulate form.