Low temperatures after sudden stratospheric warming lead to atypical atmospheric composition

The temporal evolution of all chlorine contained in ClONO₂, HCl and ClO in northern winter 2009 differs only weakly from that in other years (top panel). The fraction of ClONO₂, however, is remarkably larger in February 2009, after the sudden stratospheric warming on January 24. The increase of ClONO₂ happened at the expense of HCl (lower panel).

Also record high ozone was observed and attributed to the fact that low temperatures favour a greater O3/O ratio. This ratio controls the active chlorine partitioning and leads to larger abundances of ClO, resulting in the large ClONO₂ amounts observed.

For more details see:  http://onlinelibrary.wiley.com/doi/10.1002/2014JD021698/pdf