The influence of ozone feedbacks on Final Stratospheric Warmings and their surface impact

In the Arctic, the timing of the Final Stratospheric Warming (FW), which marks the transition from winter to summer, is subject to a large interannual variability. Early and late FWs have previously been linked to different mechanism and are associated with different surface responses. While early FWs are predominantly wave driven and followed by a negative Arctic Oscillation (AO) at the surface, late FWs are more radiatively driven and not linked to a specific surface pattern. Simultaneously, the time around the vortex weakening in spring is marked by large year-to-year variations in stratospheric ozone concentrations which both respond and feed back into dynamics. A causal connection between stratospheric ozone anomalies and the FW date via ozone-dynamic feedbacks is thus plausible, but still largely unstudied. We investigate the relationship between springtime ozone anomalies and the FW date at both 10 and 50 hPa in Chemistry Climate model simulations with fully interactive and prescribed climatological ozone. For years with low springtime ozone concentrations, we find that the FW at 50 hPa is significantly delayed by 1-2 weeks and is not followed by surface anomalies. In contrast, in years with high springtime ozone concentrations, the 50 hPa FW happens 1-2 weeks earlier than average and precedes a negative AO pattern at the surface. Most importantly, the connection between springtime ozone concentrations and 50 hPa FW date is only present in model simulations where ozone anomalies are radiatively active. In addition, surface patterns after early FWs are enhanced when interactive ozone is included in the simulations. No clear relationship between stratospheric ozone anomalies and 10 hPa FW date is found. We identify additional radiative heating/cooling due to high/low ozone anomalies as the main mechanism whereby ozone feedbacks affect the FW date and discuss subsequent impacts on wave dissipation. Following our results, stratospheric ozone anomalies contribute to the occurrence of late and early FWs in spring and significantly enhance surface impacts of early FWs, which emphasizes the importance of interactive ozone chemistry for subseasonal to seasonal predictions.