Subpolar Activation of Halogen Heterogeneous Chemistry in Austral Spring

Heterogeneous halogen chemistry plays a dominant role in driving changes in polar chemical composition and ozone depletion. Activation of halogens outside the polar regions may result in depletion of local ozone, along with changes in the chemical budgets of various species in the lower stratosphere (LS). In this study, the means and distributions of NO2 measurements from the Stratospheric Aerosol and Gas Experiment III (SAGE3m) are compared to simulations from a coupled climate-chemistry model, in order to better characterize and quantify subpolar heterogeneous halogen chemistry. NO2 abundances from a simulation with heterogeneous chemistry are drawn from the same distribution as the SAGE3m observations, while the NO2 distribution is different in a simulation without heterogeneous chemistry. Results indicate that heterogeneous chemistry plays a significant role in determining the chemical composition of the subpolar LS in austral spring and show how analysis of distribution functions can provide useful insights into chemical processes. Plain Language Summary Much research has been done on the impacts of ozone-depleting substances on the atmospheres of the polar regions, where their impacts, including the infamous Antarctic ozone hole, are greatest. However, it is possible for these same chemicals to be active outside the polar regions, where they can destroy ozone locally as they do near the poles. In this study, we analyze observations of NO2 outside the polar region. Because its concentrations are also impacted by the same chemistry that destroys ozone, NO2 is a good indicator of where chemistry involving ozone-depleting substances is occurring. We provide important evidence for the active presence of ozone-depleting substances outside of the polar regions. In addition, we use a model to show that the chemistry is essential to explain the observed NO2 distributions. The results presented here should motivate further research on the impacts of ozone-depleting substances on ozone abundances throughout the atmosphere.