Impact of recent laboratory measurements of the absorption cross section of ClOOCl on our understanding of polar ozone chemistry: Part II, Modeled and Measured ClOx during SOLVE

The photolysis of ClOOCl limits loss of polar ozone by the ClO+ClO cycle. New laboratory measurements of the ClOOCl cross section suggest that its photolysis is about a factor of six slower than a value based on current recommendations. We show the incorporation of these new cross sections into a photochemical model leads to poor agreement with values of ClO and ClOOCl measured during the SOLVE campaign, with the model under-estimating measured ClO and over-estimating measured ClOOCl by amounts that are much larger than the measurement uncertainties. These comparisons indicate that a model using the new cross section, and no other changes, provides a poor description of the partitioning of ClO and ClOOCl. Such a simulation also results in much slower ozone loss rates compared to a model using standard chemistry. It should be noted that, in the absence of the new cross section, there is still inconsistencies in our understanding of stratospheric chlorine when compared to stratospheric observations. We use the SOLVE data set to test a variety of postulated processes, discussed in a companion presentation, that could be invoked to resolve these discrepancies. The SOLVE data set is noteworthy because it provides a comprehensive description of the diurnal variation ClO and ClOOCl partitioning. For example, sufficient data was obtained during morning and evening to test hypothesis that result in predicted diurnal asymmetries in the partitioning. Implications of proposed new chemical mechanisms for ozone loss rates will also be discussed.