The effect of interactive ozone chemistry on weak and strong stratospheric polar vortex events

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, 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.

The Atlantic Jet Response to Stratospheric Events: A Regime Perspective

“…These occur with a mean frequency of ∼0.6 per year (Charlton & Polvani, 2007). Some of the earliest studies of these phenomena arose from observations of very large temperature spikes in the stratosphere, on the order of 60K (e.g., Geisler, 1974), which were dynamically coupled to the changes in the stratospheric wind profile induced by the breakdown and displacement of the polar vortex, giving rise to the name “Sudden Stratospheric Warmings.” Analogous events of the opposite sign, in which the polar vortex becomes substantially stronger than normal, have been described in the literature (e.g., Dunn‐Sigouin & Shaw, 2015; Oehrlein et al., 2020; Scaife et al., 2016; Shaw & Perlwitz, 2013; Smith et al., 2018) and are known as Strong Polar Vortex events (SPVs). Less is understood about the dynamical causes and impacts of SPVs.…”

Sudden Stratospheric Warmings

“…At the same time, the relative importance of characteristics of this stratospheric signal such as the morphology of vortex splits for the tropospheric fingerprint is still debated. Even interactive stratospheric chemistry has recently been suggested to modulate the tropospheric response to stratospheric variability associated with SSWs (Calvo et al, 2015; Haase & Matthes, 2019; Oehrlein et al, 2020). Consequently, we still do not have a confident answer to why some SSWs appear to have a strong surface impact, whereas the troposphere appears to be unaffected by some others.…”

Long Range Prediction and the Stratosphere

“…Although reports of impacts and benefits have varied, it is thought that surface signals on interannual timescales come mainly from dynamical rather than chemical changes (Seviour et al 2014;Harari et al, 2019). Nevertheless, some studies suggest detectable effects from interannual variability of ozone and it may be that ozone fluctuations could help to amplify surface signals (Karpechko et al, 2014;Son et al, 2013;Smith and Polvani 2014;Oehrlein et al, 2020;Hendon et al, 2020), providing a further area for future development. Given that the cost of full atmospheric chemistry schemes remains computationally expensive, it seems likely that simple parametrizations of ozone chemistry (e.g.…”