Halogen compounds play a central role in ozone layer depletion in the stratosphere and upper troposphere. Source gases that contain chlorine or bromine, the majority of them from anthropogenic sources, are destroyed by light in the stratosphere, releasing chlorine and bromine atoms. These are converted relatively fast into stable reservoir gases (e.g. hydrochloric acid and chlorine nitrate). Under very cold conditions, droplets of liquid or ice particles can form – polar stratospheric clouds or cirrus clouds. On their surface, the chlorine reservoir compounds react to form active chlorine species. These very effectively destroy ozone. At IEK-7, both balloon-borne and airborne measuring instruments have been developed (HALOX) to measure active chlorine and bromine compounds as well as the reservoir gas chlorine nitrate. These instruments are employed in international measurement campaigns. The measurements are then used to verify and refine the chemistry models.
Contact: Dr. Fred Stroh