Abstract
Abstract. Modeling and observational studies have reported effects of stratospheric ozone extremes on Northern Hemisphere spring climate. Recent work has further suggested that the coupling of ozone chemistry and dynamics amplifies the surface response to midwinter sudden stratospheric warmings (SSWs). Here we study the importance of interactive ozone chemistry in representing the stratospheric polar vortex and Northern Hemisphere winter surface climate variability. We contrast two simulations from the interactive and specified chemistry (and thus ozone) versions of the Whole Atmosphere Community Climate Model, which is designed to isolate the impact of interactive ozone on polar vortex variability. In particular, we analyze the response with and without interactive chemistry to midwinter SSWs, March SSWs, and strong polar vortex events (SPVs). With interactive chemistry, the stratospheric polar vortex is stronger and more SPVs occur, but we find little effect on the frequency of midwinter SSWs. At the surface, interactive chemistry results in a pattern resembling a more negative North Atlantic Oscillation following midwinter SSWs but with little impact on the surface signatures of late winter SSWs and SPVs. These results suggest that including interactive ozone chemistry is important for representing North Atlantic and European winter climate variability.
Highlights
The climate impacts of stratospheric ozone extremes, Antarctic ozone depletion, have been widely studied (Previdi and Polvani, 2014, and references therein)
Polar cap ozone anomalies are strongly related to interannual variability in stratospheric polar vortex strength, which is larger in the Northern Hemisphere than the Southern Hemisphere
Years with low wave activity tend to correspond to a stronger vortex and a weaker Brewer– Dobson circulation (BDC), resulting in weaker ozone transport from the tropics into the poles and decreased mixing across the vortex edge, as well as the enhanced formation of polar stratospheric clouds, which contribute to increased springtime destruction of ozone
Summary
The climate impacts of stratospheric ozone extremes, Antarctic ozone depletion, have been widely studied (Previdi and Polvani, 2014, and references therein). SPVs in which abnormally strong westerly zonal mean zonal winds occur are the result of anomalously weak planetary wave activity over a protracted period As such, they are not rapid dynamical events in the same way as SSWs, but they may still have surface impacts, which are typically a positive North Atlantic Oscillation (Baldwin and Dunkerton, 2001). SPVs are accompanied by an anomalously weak BDC because of the lack of planetary wave activity and an anomalously low transport of ozone as well Because they affect both stratospheric ozone and the NAO in the troposphere, extreme vortex events offer an ideal case in which to study wintertime surface impacts of ozone chemistry. We conclude the paper with a discussion of these results
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