Uncertainties of the photolysis cross sections of ClOOCl have long been a limiting factor in our theoretical understanding of the rate of polar stratospheric ozone losses. Previous work suggested that values slightly larger than current recommendations, which are based on laboratory measurements, result in improved agreement between model calculations of polar stratospheric ozone loss rates and observations while at the same time also leading to improved agreement between observations of the diurnal variation of ClO and model calculations of this species. But new laboratory work (Pope et al, 2007) on the cross sections of ClOOCl suggest that its photolysis under polar stratospheric winter/spring conditions is nearly an order of magnitude slower than what would be required to explain the observations of ozone loss and ClO in the atmosphere and a factor of six slower than a value based on the current recommendations. We show what the impact of these new results on our understanding of polar ozone chemistry is and will discuss the potential for unknown chemical mechanisms that would lead to improved agreement between calculations of ozone loss based on the new cross sections with in-situ observations of ClO and ozone loss rates in the stratosphere.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL1-Processes and interactions in the polar climate system