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Abstract:
Recent studies have suggested that using interactive instead of prescribed ozone in models can alter the stratospheric circulation variability. However, the key processes regarding the underlying dynamics and feedbacks of this effect are only poorly understood. Here, we use a dry-dynamical core model with a simplified linear ozone scheme and a shortwave radiation parameterization to study the ozone-circulation feedback in an idealized setting. From two long control simulations using either interactive or prescribed ozone we find significant increases in the persistence time scale and interannual variability of the stratospheric circulation from interactive ozone. The effect is strongest during northern spring, a time when there is sufficient solar radiation over the northern Arctic to create significant ozone-related heating anomalies. Since perturbations in the polar vortex are known to be associated with considerable ozone anomalies, we focus our subsequent analysis on strong and weak polar vortex events. While interactive ozone does not change the overall frequency of the events, we find significant changes in their seasonal occurrence frequency and clear signs for ozone-enhanced radiative heating anomalies in the aftermath of the events. This increases the circulation anomalies of the events and the strength and persistence of their annular mode signature at the surface. Our findings suggest that the ozone-circulation feedback is positive, and that ozone is important for the simulation of the stratospheric circulation, its variability, and its impacts at the surface.
