A chemical mechanism explaining the observed wintertime HCl in the Antarctic vortex

It is well established that the drastic ozone loss in the Antarctic stratosphere, commonly known as the ozone hole, is caused by gas-phase and heterogeneous processes.  Chemistry models generally reproduce observed ozone depletion reasonable well.  However, models have been unable to reproduce observations of rapid HCl loss at the beginning of the polar winter.  Here we examine the impact of the heterogeneous reaction between Cl₂O₂ and HCl to form HOOCl and its subsequent photolysis on chlorine compounds. A chemical mechanism with these reactions added is able to clearly better reproduce the observed temporal development of the chlorine compounds HCl, ClONO₂, ClO, and HOCl in the polar vortex lower stratosphere. The proposed chemical mechanism does moderately increase the chemical ozone column depletion, about 10\% in the lower stratospheric vortex core in September. Laboratory measurements of the proposed reactions are needed to confirm this mechanism.