Arctic Ozone Amplifies Stratospheric Circulation Extremes

Arctic Ozone Amplifies Stratospheric Circulation Extremes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Arctic Ozone Amplifies Stratospheric Circulation Extremes Hao-Jhe Hong, Thomas Reichler, Huang-Hsiung Hsu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-5626578/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Stratospheric ozone has long been suspected to drive interactions involving chemistry, radiation, and the circulation. However, the significance of these interactions, the underlying mechanisms, and the specific conditions that facilitate them remain poorly understood. In this study, we use a dry-dynamical core model with a simplified linear ozone scheme and a shortwave radiation parameterization to investigate these interactions. Our analysis, based on two long control simulations with either interactive or prescribed ozone, reveals that interactive ozone increases the persistence and interannual variability of the stratospheric circulation during northern spring, a period with sufficient solar radiation over the northern polar cap. This effect is closely linked to late-winter extreme stratospheric circulation events, such as stratospheric sudden warmings (SSWs) and vortex intensifications (VIs). While interactive ozone does not alter the frequency of these events, the ozone perturbations induced by the circulation amplify the associated temperature and wind anomalies. Specifically, late-winter VIs are followed by a colder and more persistent polar vortex in spring when interactive ozone is used, compared to fixed ozone. This results in a five-day delay in the breakdown date of the vortex and a more positive North Atlantic Oscillation at the surface. Although interactive ozone also amplifies perturbations following SSWs, these effects are less pronounced than those observed for VIs. Our findings contribute to a growing body of evidence highlighting the importance of ozone-dynamics interactions for simulating the stratospheric circulation, its variability, and its surface impacts. Atmospheric Sciences stratosphere ozone Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Ozone is a key constituent of the stratosphere, essential for the complex interactions between chemistry, radiation, and dynamics (Hartmann, 1981 ). Ozone absorbs solar radiation and thereby significantly influences the temperature and wind structure of the stratosphere (Cicerone, 1987 ; Wallace and Hobbs, 2006 ). Conversely, the distribution of ozone is strongly affected by stratospheric winds, particularly in the lower stratosphere (Butchart, 2014 ; Tegtmeier et al., 2010 ). These mutual influences can lead to notable effects, especially during winter and spring when stratospheric ozone can experience substantial perturbations. These perturbations may result from anthropogenic chemical depletion (Manney et al., 2011 , 2020 ; Solomon, 1999 ; Stolarski and Cicerone, 1974 ) or dynamical transports linked to extreme stratospheric circulation events, such as stratospheric sudden warmings (SSWs) and vortex intensification events (VIs) (e.g., Butler et al., 2017 ; de la Cámara et al., 2018 ; Hocke et al., 2015 ; Hong and Reichler, 2021a ; Lubis et al., 2017 ). The important role that stratospheric ozone plays in the circulation was first recognized over the high latitudes of the Southern Hemisphere. Early studies focused on the effects of Antarctic stratospheric ozone depletion and found that the declining trend of ozone was accompanied by stratospheric cooling and an intensification of the polar circulation that extended from the stratosphere to the troposphere (Randel and Wu, 1999 ; Thompson and Solomon, 2002 ; Gillett and Thompson, 2003 ). In the Arctic stratosphere, understanding the interactions between ozone and the circulation is more complicated due to the large internal variability of the circulation and the induced transport dynamics on polar ozone (Harzer et al., 2023 ). The upward propagation and dissipation of planetary waves modulate the strength of the northern wintertime stratospheric polar vortex (Limpasuvan et al., 2004 ; 2005 ), which—through anomalous mixing and transports—changes the amount and distribution of polar ozone. Ozone, in turn, and especially zonal asymmetries in the distribution of ozone and the resulting radiative heating anomalies, can change the planetary waves and how they propagate and break (Gabriel et al., 2007 ; Nathan and Cordero, 2007 ). These and other processes can create complicated situations, and most often complex Chemistry Climate Models (CCMs) are used to study the interactions between ozone and the circulation. However, most models from the Coupled Model Intercomparison Project use prescribed climatological means of ozone to represent the approximate radiative effects of ozone and to avoid the large computational burden from the chemistry components (Keeble et al., 2021 ). Prescribing ozone in models, however, inhibits the interaction between ozone and the circulation, leads to inconsistencies between the two, and may create simulation errors (Ivanciu et al., 2021 ). To understand these errors and to find out whether interactive ozone leads to more reliable simulations, past studies compared simulations in which ozone was either interactively simulated or prescribed. For the Southern Hemisphere, it was found that using interactive ozone increases the circulation effects from Antarctic ozone depletion (Haase et al., 2020 ; Ivanciu et al., 2021 ; Li et al, 2016 ). Analyzing CMIP6 model output, Revell et al. ( 2022 ) found that models without interactive chemistry project a substantially stronger tropospheric westerly jet by the end of the 21st century than models with interactive chemistry because the prescribed ozone recovery is smaller than the predicted one. For the Northern Hemisphere, several recent studies have demonstrated the significance of interactive stratospheric ozone for simulating Arctic circulation and surface conditions. Rae et al. ( 2019 ) showed that simulations with dynamically consistent ozone produce a polar vortex shape and sea level pressure pattern that more closely resemble those from a full CCM compared to simulations with fixed ozone. Haase and Matthes ( 2019 ) found that interactive ozone results in more realistic and persistent circulation anomalies in the stratosphere and at the surface after SSWs compared to prescribed ozone. Romanowsky et al. ( 2019 ) observed that in response to sea ice retreat, the coupling between the stratosphere and troposphere is more intense with an interactive ozone scheme. Rieder et al. ( 2019 ) demonstrated that interactive ozone chemistry increases simulated stratospheric temperature variability and extremes. Friedel et al. ( 2022 ) found that the interaction between ozone and the stratospheric circulation results in a more variable timing for the breakdown of the Arctic polar vortex during spring. In the present study, we also investigate the effects of interactive ozone on Arctic circulation and surface conditions. Unlike previous studies with complex CCMs, we employ a relatively simple idealized general circulation model with dry physics. By coupling this model with an ozone scheme and implementing a basic shortwave radiation parameterization, we reproduce the fundamental mechanisms governing the interaction between ozone and dynamics. This approach has several advantages. Firstly, our model avoids the complexities and parameterizations found in more comprehensive models, focusing on the essential physical processes (Held, 2005 ). This simplification allows for a clearer analysis of the interactions between ozone and dynamics. Additionally, the model's computational efficiency and ease of management make it a valuable research tool, offering a fresh perspective on understanding ozone-dynamics interactions and providing a foundation for future investigations. We employ the simplified linear ozone scheme by Cariolle and Teyssèdre ( 2007 ) in our model. Variations of this scheme are used in other atmospheric models, including the ECMWF Integrated Forecasting System (IFS) (Monge-Sanz et al., 2022 ), the NCEP 20th Century Reanalysis (20CR) (Compo et al., 2011 ), the NCEP Global Forecast System (GFS), and the NCEP Climate Forecast System Version 2 (CFSv2) (Saha et al., 2014 ; McCormack et al., 2006 ). As such, the results from our study can also serve as a test of the performance of this widely used ozone model. The main goal of this study is to better understand the influence of interactive ozone on Arctic stratospheric circulation and surface conditions. We also aim to compare how these influences are simulated by our idealized model with those simulated by full CCMs. A particular focus is on Arctic stratospheric circulation extremes, such as SSWs and VIs, as these events are known to be associated with significant perturbations in stratospheric polar ozone (Hong and Reichler, 2021a ). To ensure that these ozone perturbations are dynamically relevant, we focus on circulation extremes that occur in late northern winter (February-March) and persist into northern spring. This period is critical because there is sufficient sunlight over the polar cap for ozone to generate radiative heating anomalies. Our paper is structured as follows: Section 2 describes our model and methodology, Section 3 presents our results, focusing on the impact of interactive ozone on Arctic circulation variability, and Section 4 provides a summary and conclusion. 2 Model and Methods a. The Simplified Chemistry-Dynamical Model (SCDM) We employ the Simplified Chemistry-Dynamical Model (SCDM V1.0), developed by Hong and Reichler (2021b). SCDM is based on the GFDL spectral dynamical core (Held and Suarez, 1994) with simplified physics. Modifications were made according to Wu and Reichler (2018), incorporating realistic topography and forcing the model with empirically derived, zonally asymmetric, and seasonally varying equilibrium temperatures. This minimizes the climatological temperature differences between the reanalysis and the model, resulting in effective diabatic heating rates that reasonably match observations. The model successfully captures seasonal variations in stationary waves, polar vortex strength, and SSW frequency, validating its use for our study. Hong and Reichler (2021b) further enhanced the model by incorporating ozone as a tracer advected by the dynamics, implementing a linear photochemical ozone scheme (Cariolle and Teyssèdre, 2007) that responds to changes in temperature, shortwave radiation, and ozone concentrations, and adding a shortwave radiation parameterization for ozone (Lacis and Hansen, 1974) to simulate heating from shortwave absorption by ozone. These modifications enable SCDM to simulate the interactions between dynamics and ozone in the stratosphere. We conducted two 2000-year simulations with the model. VARO3 is our control run with variable, fully interactive ozone. FIXO3 is identical to VARO3, except that ozone is prescribed using the fixed, zonally-asymmetric, daily varying but annually repeating ozone climatology derived from VARO3. The differences between the two simulations are therefore entirely due to the mutual influences between the dynamics and ozone. b. Methods 1) Persistence of the Northern Annular Mode We followed Kim and Reichler (2016) to estimate the persistence time scale τ of the Northern Annular Mode (NAM) index, represented at each level by the standardized geopotential height anomalies averaged over the polar cap area (60°-90°N). τ is defined as the time in which the daily autocorrelation of the NAM index decreases by a factor of e . To calculate the mean and variability of τ, we divided the 2000-year dataset into forty 50-year intervals and calculated τ separately for each interval. This process was repeated for each latitude, level, and calendar day. A two-sample Student's t-test was used to test the significance of the differences in τ between VARO3 and FIXO3. 2) Stratospheric circulation events Ozone in the stratosphere is well-known to be influenced by the anomalous advection and temperatures during the life cycles of stratospheric circulation events. The two types of events we consider are SSWs and VIs. SSWs are characterized by a relatively warm and weak northern wintertime stratospheric polar vortex, while VIs are characterized by a relatively cold and strong vortex. We defined SSWs based on Charlton and Polvani (2007). According to this definition, the central or onset date of an SSW is the day when the zonal-mean zonal wind at 10 hPa and 60° N (U1060) reverses from westerly to easterly between November and March. After the wind reversal, U1060 must return to westerly for at least 10 consecutive days before the end of April; otherwise, the event is classified as a final warming (FW) event. If two SSWs occur in the same winter, a period of at least 20 consecutive days of westerlies is required to distinguish the events. For VIs, we followed the definition by Hong and Reichler (2021a). This definition is based on daily anomalies of U1060, low-pass filtered using a 20-day running mean. The central date of a VI is defined when the filtered U1060 anomaly exceeds 16 m/s, which is about one standard deviation of U1060 estimated from reanalysis data. Similar to SSWs, a separation interval of at least 20 days is required for two VIs occurring in the same winter to be recognized as separate events. We only considered events occurring in February and March, as this is when sufficient sunlight is available over the polar cap for ozone to create shortwave radiative heating and thus provide a radiative feedback on the circulation. For the 2000-year-long VARO3 (FIXO3) simulation, this resulted in 830 (821) SSW events and 449 (445) VI events. All other years were considered normal years. Given the similarity of these numbers between the two simulations, we conclude that using interactive chemistry in our model leads only to minor changes in the number of extreme circulation events. This contrasts with a similar CCM-based study by Haase and Matthes (2019), who found that compared to prescribed ozone, interactive ozone leads to significant changes in the overall frequency of SSWs and their seasonal distribution. 3) Event compositing We formed composites of all February-March events by focusing on the -90 to 90 day interval centered on the onset date of each event, then averaging over all events. A one-sample t-test was used to determine whether the composite anomalies were significant, and a two-sample t-test was used to assess the significance of composite difference anomalies. 3 Results In this section, we investigate the impact of interactive ozone by comparing the two simulations. We begin by exploring the circulation variability, followed by an examination of specific changes in ozone, ozone heating, and the circulation associated with the two event types. Finally, we assess whether the stratospheric changes translate into observable signals at the surface. As mentioned before, we focus on events during boreal spring (February-March), as this is when the signals are most pronounced. a. Changes in circulation variability An interaction between ozone and the dynamics should be evident through changes in stratospheric variability. This interaction can result in either constructive or destructive interference between initial perturbations and the additional response from interactive ozone. Constructive interference would amplify the initial perturbations, increase variability, and potentially create a positive feedback loop; otherwise, the initial perturbations will be dampened, leading to decreased variability. To investigate these possibilities, we examine the interannual standard deviation of the zonal-mean zonal wind at 60°N (U60), a common measure of the Arctic polar vortex strength. The standard deviation is calculated for each calendar date and atmospheric level. The top two panels in Figure 1 compare the variability between the ECMWF Reanalysis v5 (ERA5) (Hersbach et al. 2020) and the VARO3 simulation. Generally, the variability of the polar vortex in the observations is large in winter and small in summer, and this is well simulated by VARO3. Simulation VARO3 also replicates the ERA5 variability structure of the Antarctic polar vortex at 60°S quite well (Figure S1). Next, we compare simulations VARO3 and FIXO3 to investigate the impact of interactive ozone on circulation variability. Figure 1c shows the difference in U60 variability between the two simulations. As expected, the differences are mostly small during winter (November-March), as ozone’s influence on the polar stratosphere is linked to the presence of sufficient sunlight. However, starting in April and continuing into May, Figure 1c reveals a 20-25% increase in circulation variability in VARO3 compared to FIXO3. During boreal summer, interactive ozone decreases the stratospheric variability. However, this change is relatively small, as it coincides with the natural low variability during this time of the year. Therefore, for the remainder of this paper, we focus on understanding the reasons for and consequences of the increase in variability during boreal spring. This increase in variability in VARO3 during spring is consistent with constructive interference between the stratospheric dynamics and Arctic ozone, occurring when there is sufficient sunlight for stratospheric ozone perturbations to induce radiative heating anomalies that, in turn, influence the circulation. Our results align with those of Rieder et al. (2019), who found from a complex CCM that stratospheric temperature variability and temperature extremes during spring are increased in simulations with interactive chemistry compared to simulations with fixed climatological mean ozone. To better understand the nature of the increased interannual circulation variability due to interactive ozone, we next examine the NAM persistence time scale, τ. Figure 2a shows a pronounced springtime maximum in τ for VARO3, reaching up to 70 days in the lower stratosphere (100-50 hPa) during May and June. From observations and more complex models, Kim and Reichler (2016) found a similar but less pronounced increase in τ, reaching about 40 days during spring in the lower stratosphere. Next, we compare τ from VARO3 against that from FIXO3 (Figure 2b). The differences demonstrate that using interactive ozone makes the stratospheric NAM, and thus the polar vortex, more persistent compared to using fixed ozone. The increase in τ of about 10-30 days extends from February to July and maximizes in the lower stratosphere during May and June, coinciding with the time and level where persistence is highest in VARO3 (Figure 2a). b. Changes in ozone during stratospheric circulation events Previous studies have shown that SSWs and VIs, the major stratospheric circulation events, are associated with persistent anomalies in stratospheric ozone that can last for up to two months (de la Cámara et al., 2018; Hocke et al., 2015; Hong and Reichler, 2021a). Therefore, we focus next on the ozone perturbations simulated by our model during these events. The thin curves in Figure 3a represent individual annual time series (October-September) of the polar cap averaged ozone mixing ratio at 70 hPa for the first hundred years of VARO3. The color coding indicates whether a SSW, VI, or no circulation event occurred during each winter. Consistent with previous studies, the dynamical transports associated with SSWs lead to increased amounts of ozone from January to April compared to neutral years, while VIs result in larger and more persistent decreases in ozone. This can also be seen from the thick curves in Figure 3a, which show the annual evolution of ozone averaged over the events from all simulated years of VARO3. Figures 3b and 3c illustrate the spatial structure of February-April mean ozone anomalies in latitude-height cross-sections for SSW and VI years, respectively, based on all years of the VARO3 simulation. Both increased ozone during SSWs and decreased ozone during VIs reach their maximum in the lower stratosphere (~40 hPa) near the pole. The magnitude of the ozone anomaly associated with VIs is approximately 2.7 times larger than that associated with SSWs, suggesting that the impact of ozone on the circulation during VIs is substantially larger than during SSWs. c. Changes in final warming date Friedel et al. (2022) demonstrated that reductions in ozone during strong and cold vortex events (VIs) result in decreased solar absorption, more persistent cold anomalies in the lower stratosphere, and a stronger and more enduring polar vortex and NAM. Consequently, the breakup of the spring polar vortex, known as the final warming (FW), is significantly delayed by up to ten days compared to simulations with fixed climatological ozone. We will next investigate whether similar changes in the seasonal timing of the FW are observed in our simulations and whether SSWs have the anticipated opposite effect. We classified FWs based on whether they were preceded by stratospheric circulation events during February-March. We then calculated the mean date of FWs following SSWs and VIs for both the VARO3 and FIXO3 simulations (Table 1). Consistent with the findings of Friedel et al. (2022), the VARO3 simulation shows that FWs following VIs are on average significantly delayed by 5 days compared to those in the FIXO3 simulation. In contrast, there is no significant change in the date of FWs following SSWs. This difference between VIs and SSWs can be largely attributed to the much more substantial ozone perturbations associated with VIs compared to SSWs (Figure 3). Additionally, Table 1 indicates that VARO3 results in greater variability in the FW date compared to FIXO3. Overall, our results corroborate previous studies by demonstrating that interactive ozone leads to a more persistent polar vortex and a later FW date when preceded by a VI. This outcome further validates our model's ability to effectively simulate the interactions between ozone and stratospheric dynamics. Table 1: Mean and standard deviation (days) of the final warming date associated with February–March SSWs and VIs. Asterisks (*) indicate that the difference in mean FW date between VARO3 and FIXO3 is significant at the 5% level based on a two-sample t-test. FWs following SSWs FWs following VIs FWs all 2000 years VARO3 MEAN DATE Apr 9 Apr 16 (*) Apr 5 (*) STD (days) 16 19 21 FIXO3 MEAN DATE Apr 9 Apr 11 Apr 4 STD (days) 14 17 20 d. Interactions between ozone and the stratospheric circulation In the previous sections, we demonstrated how late winter (February-March) SSWs and VIs induce distinct anomalies in springtime Arctic ozone. We now aim to explore the dynamical consequences of these anomalies by examining their spatio-temporal evolution and their radiative impacts. As before, our analysis focuses on years with VIs or SSWs occurring during February–March, a period when sunlight is available over the polar cap to drive significant radiative effects. Figure 4 illustrates the differences in composite anomalies between VARO3 and FIXO3 for ozone (top) and the associated ozone shortwave heating rate (bottom). For SSWs, ozone shows a rapid increase following event onset, persisting in the lower stratosphere (Figure 4a). This increase is driven by the upward propagation and breaking of planetary waves prior to SSW onset, which weakens the stratospheric polar vortex, accelerates the downwelling branch of the Brewer-Dobson circulation (BDC), and results in the anomalous transport of ozone-rich air from the tropical upper stratosphere into the Arctic lower stratosphere (de la Cámara et al., 2018; Hong and Reichler, 2021a). The ozone increase in turn is linked to persistent shortwave heating anomalies in the lower stratosphere and smaller cooling anomalies above, around 10 hPa (Figure 4c). This heating structure is similar to results from a previous study using a CCM (Oehrlein et al., 2020, Figure 5d). During VIs, the planetary wave activity is reduced, creating a weaker BDC and less ozone transport into the Arctic stratosphere. Starting about 60 to 30 days before event onset, this results in persistent negative ozone anomalies (Figure 4b). The magnitude of these anomalies is about twice that observed during SSWs after onset, as also suggested by the February–April mean ozone anomalies shown in Figure 3. The reductions in ozone lead to radiative cooling anomalies in the lower stratosphere, which start at about event onset, last for more than 60 days, and are much stronger than the heating anomalies observed during SSWs (Figure 4d). Compared to Hong and Reichler (2021a), who investigated the observed ozone responses to SSWs and VIs using the MERRA2 reanalysis (Bosilovich et al., 2015), the SCDM simulates the evolution of ozone during the lifecycles of the two circulation events overall quite well. However, the ozone anomalies in the SCDM are somewhat more persistent than in the observations, which is presumably due to shortcomings in how changes in wave activity after the circulation events are simulated by the model (Hong and Reichler, 2021b). This leads to a somewhat longer simulated radiative impact from ozone. Nevertheless, the primary purpose of our study is to qualitatively understand the ozone-dynamics feedback, and the realistic ozone response of the SCDM justifies the use of this model. Next, we investigate how the changes in ozone and heating seen in Figure 4 influence temperatures and the circulation. Figure 5 shows the composite anomalies of Arctic temperatures during SSWs and VIs for simulations VARO3, FIXO3, and their differences. During SSWs, the temperatures exhibit a warming center at 10 hPa with a downward propagating structure (Figures 5a and 5b), similar to observation-based studies (Hong and Reichler, 2021a; Limpasuvan et al., 2004). As with ozone, this warming is primarily a consequence of the intensified downwelling branch of the BDC during SSWs and the associated adiabatic warming. Comparing the temperatures between the two simulations, the warm anomalies in VARO3 last somewhat longer than in FIXO3. This is more clearly seen in Figure 5c, which displays the temperature differences between the two simulations. The simulation with interactive ozone shows a small (0.05 to 0.1 K) but significant warming difference in the lower stratosphere 30 to 90 days after event onset, consistent with the increase in ozone shortwave heating (Figure 4). The timing of the warming difference is somewhat delayed with respect to the time of the maximum ozone heating (Figure 4c), reflecting the thermal inertia of the atmosphere. VARO3 and FIXO3 also show some robust and statistically significant temperature differences before the onset date, a point to which we come back later in our discussion. In contrast to SSWs, VIs are associated with a weaker BDC, less adiabatic warming, and hence temperature cooling (Figures 5d and 5e). Compared to the warming during SSWs, this cooling has a much broader and more persistent structure, reflecting dynamical differences between the two opposing circulation events. VIs are not associated with abrupt changes in planetary wave activity like SSWs, but with more gradual and long-lasting reductions in upward planetary wave propagation that start long before the actual onset date (Figures S2d and S2e) (Hong and Reichler, 2021a), leading to much broader signals than SSWs. Comparing the cooling during VIs between VARO3 and FIXO3, it becomes clear that interactive ozone enhances its amplitude and persistence. This can be better seen from the differences in cooling in Figure 5f. As expected from the differences in shortwave heating (Figure 4d), there is a rather strong (-0.2 to -0.3 K) and significant additional cooling in VARO3 compared to FIXO3, mostly limited to the time after event onset. Compared to the additional heating during SSWs (Figure 5c), the magnitude of this extra cooling is about 3-6 times larger. This is a consequence of the difference in the ozone perturbations, which are stronger and more persistent during VIs than during SSWs. We next discuss how interactive ozone modulates the response of the stratospheric polar vortex to SSWs and VIs. This is presented in Figure 6 in terms of U60, the zonal-mean zonal wind at 60ºN. The weakening of the polar vortex in the aftermath of SSWs is stronger in VARO3 (Figure 6a) compared to FIXO3 (Figure 6b). The difference plot between the two (Figure 6c) shows additional vortex weakening from ozone from day 30 to 90, which is temporally consistent with the additional polar cap warming seen in Figure 5c and dynamically consistent with the thermal wind relationship and the reduction of the meridional temperature gradient by the extra heating. Compared to the mean reduction in vortex strength at day 30 after SSWs (~3 m/s), the magnitude of this ozone-related extra vortex weakening is quite sizable (~1 m/s). An analogous structure of weakening U60 after SSWs caused by interactive ozone has been shown by the CCM study of Haase and Matthes (2019, their Figure 8), reinforcing the findings from our simulations. During VIs, the polar vortex strengthens (Figure 6d-e), and this strengthening is amplified by interactive ozone (Figure 6f). Since the extra cooling after VIs has a larger magnitude (Figure 5f) than the warming after SSWs (Figure 5c), the thermal wind relationship predicts that the circulation change from interactive ozone must also be larger for VIs than for SSWs. This is confirmed by comparing Figure 6f with Figure 6c. The ozone-related extra strengthening of the vortex following VIs is large enough to create the previously shown 5-day delay in the mean break-up date of the polar vortex (Table 1). An ozone effect on the vortex break-up date after SSWs could not be detected, likely because during SSWs the ozone influence on the vortex is rather weak. Some previous CCM studies described a negative feedback between the dynamics and ozone in the stratosphere (Lin et al., 2017; Haase and Matthes, 2019). This feedback involves the modulation of upward propagating planetary waves by the varying atmospheric background winds (Charney and Drazin, 1961). For example, an initial strengthening of the polar vortex (e.g., from ozone depletion) would increase the westerly background winds, and, if the winds are not too strong, favor the planetary wave propagation upward. This would weaken the polar vortex, intensify the BDC, transport more ozone into the polar regions, and overall counteract the initial reasons for the changes. Hence, this would be a negative feedback. Haase and Matthes (2019) found that using interactive ozone in a CCM strengthens the polar vortex in early winter and spring, and that the spring strengthening is connected to a negative feedback mechanism. In contrast, our study finds that the effects of interactive ozone outside the spring season are negligibly small (Figures 1 and 2), and that interactive ozone during spring amplifies the polar vortex anomalies. Hence, our study does not support the relevance of this negative feedback. We investigated whether we could at least identify some elements of this negative feedback in our simulations. As shown in Figures S2d and S2e, VI events are followed by an increase in upward planetary wave propagation, indicated by the positive anomaly of the vertical component of the Eliassen-Palm flux. The difference between VARO3 and FIXO3 (Figure S2f) is quite noisy but shows an anomaly difference that is generally somewhat negative, suggesting that interactive ozone slightly reduces the upward wave propagation after VIs. Although these changes are not statistically significant, they would further decrease the strength of the BDC and result in a positive feedback. There are several possible reasons for why we are unable to detect this negative feedback. For example, Haase and Matthes (2019) based their study on climatological (monthly) mean values and focused on the influence of spring ozone depletion on the dynamics of the vortex breakdown. Our study, on the other hand, focused on late-winter extreme stratospheric circulation events and the anomalies that follow. Additionally, for the negative feedback to work, the background winds must be weak, a condition that usually holds in spring before the vortex breaks down. It is, however, questionable whether this is also true in our case, because VIs are followed by relatively strong westerlies (Figure 6). e. Surface impacts It is well known that the dynamical interaction of the stratospheric polar vortex with the tropospheric circulation affects the surface, particularly over the North Atlantic (Baldwin and Dunkerton, 2001; Kidston et al., 2015). Specifically, SSWs are associated with a more negative phase of the North Atlantic Oscillation (NAO), while VIs are linked to a more positive NAO phase. The more practical question to be addressed in this section is whether the ozone-induced additional perturbations of the polar vortex are strong enough to cause detectable impacts at the surface, or in other words, whether interactive ozone matters for the simulation and prediction of tropospheric weather and climate. Our analysis focuses on changes in sea level pressure (SLP) because, in this idealized model, this is the most meaningful surface quantity. Figure 7 presents time-mean SLP anomaly composites for the February-March stratospheric circulation events discussed previously. The selected time-mean interval spans from day 30 to 90 after event onset, capturing the period of maximum stratospheric circulation anomalies induced by interactive ozone (see Figures 6c and 6f). SSWs in both VARO3 and FIXO3 are followed by a negative NAO over the North Atlantic (Figures 7a and 7b), but the associated SLP anomalies are weaker than in previous CCM-based studies (e.g., Oehrlein et al., 2020). Besides differences regarding the averaging period, this discrepancy may be due to the simplified nature of our model, which does not reproduce the feedback between the polar vortex and the tropospheric circulation in its full strength. Nevertheless, the negative NAO after SSWs is clearer in VARO3 than in FIXO3. This is likely a consequence of the additional shortwave heating from interactive ozone, amplifying and extending the lifetime of the SSW perturbations in the stratosphere, and thereby increasing their downward effect onto the surface. This can also be seen from the differences between VARO3 and FIXO3 after SSWs (Figure 7c), although the differences are not significant everywhere. The more pronounced negative NAO in VARO3 is consistent with findings from previous studies using full CCMs (Haase and Matthes, 2019; Oehrlein et al., 2020). In contrast to SSWs, both simulations show that VIs are followed by a positive NAO (Figures 7d and 7e), with SLP magnitudes generally larger than after SSWs. This finding contrasts with Oehrlein et al. (2020), who reported stronger SLP anomalies following SSWs compared to VIs in their CCM study. Differences in the definition of strong polar vortex events may contribute to this discrepancy. More importantly, however, our model shows that interactive ozone enhances the positive phase of the NAO (Figure 7f), consistent with the ozone-related extra strengthening of the polar vortex (Figure 6f). Finally, returning to Figure 6, we find that interactive ozone also generates signals in the stratosphere prior to SSW and VI events. For instance, at -60 to -30 days before VI events, the polar vortex is weaker in VARO3 compared to FIXO3 (Figure 6f), leading to a less positive NAO in VARO3 than in FIXO3 (not shown). The typical reduction in upward directed wave activity that precedes VIs is also weaker in VARO3 than in FIXO3 (Figure S2), resulting in a reduced acceleration of the polar vortex (Figure S3). While the reasons for these differences are not fully understood, shortwave radiative processes over the polar cap must be ruled out because, during this time of the year (December-January), there is little to no sunlight over this region. Therefore, the interaction of stratospheric ozone with shortwave radiation and circulation over the lower latitudes is a plausible explanation. A possible mechanism could be the interaction of ozone with planetary waves, which weakens the polar vortex in the middle to lower stratosphere (Albers and Nathan, 2012). However, addressing this issue requires additional research and must be left to future studies. 4 Summary and discussion This study used an idealized general circulation model with a simplified ozone and radiation parameterization to investigate the interaction of ozone with the northern wintertime stratospheric polar vortex. Two long simulations were performed: one in which ozone is allowed to freely evolve and interact with the circulation in dynamically consistent ways (VARO3), and one in which the daily-evolving but annually-repeating climatological mean ozone distribution of VARO3 is prescribed to the model (FIXO3). The study focused on years with extreme circulation events during February and March, where the polar vortex is either weaker and warmer (SSWs) or stronger and colder (VIs) than normal. By comparing the differences between the two simulations, the importance of interactive ozone was assessed. Our findings suggest that compared to using fixed ozone, interactive ozone increases the interannual circulation variability of the Arctic stratosphere by 20-25% during boreal spring (Figure 1) and prolongs the persistence of the NAM index in the lower stratosphere during boreal spring (Figure 2). We further found that interactive ozone amplifies the temperature and circulation anomalies that typically follow late-winter SSW and especially VI events during northern spring. This amplification can be attributed to the ozone anomalies, which are created by the extreme circulation events (SSWs or VIs) during the prior winter (Figures 3 and 4), persist into spring, and reinforce the temperature (Figure 5) and circulation anomalies (Figure 6) of the events. This increases the lifetime of the polar vortex perturbations, extends the persistence time scale of the stratospheric NAM (Figure 2), and increases the surface impact of the stratospheric circulation events (Figure 7). Additionally, the increased persistence accounts for the observed rise in interannual U60 variability during spring (Figure 1) and explains why, after VIs, the mean breakdown date of the polar vortex is delayed by 5 days (Table 1). The above-described effects are the result of circulation-induced changes in polar ozone. In spring, when there is sufficient sunlight, the changes in ozone create shortwave heating anomalies that reinforce the original anomalies associated with the perturbed polar vortex. Several factors may contribute to the changes in polar ozone: 1. VIs are associated with a decrease in upward planetary wave propagation and dissipation, which stabilizes the polar vortex, weakens the downwelling branch of the BDC, and consequently reduces the transport of ozone-rich air into polar latitudes. Conversely, upward planetary wave propagation is increased during SSWs, disturbing the polar vortex, strengthening the BDC, and increasing the ozone transport into polar latitudes. 2. The reduced (increased) BDC during VIs (SSWs) leads to anomalous adiabatic cooling (warming). By the thermal wind relationship, this creates a dynamical response that further strengthens (weakens) the polar vortex. This reduces (increases) the meridional mixing of polar air with relatively ozone-rich surrounding air, contributing to a further decrease (increase) in polar ozone. 3. The cooling (warming) associated with VIs (SSWs) enhances (decreases) catalytic ozone depletion and further reduces (increases) ozone levels. The combined changes in ozone create shortwave heating anomalies that reinforce the original temperature and circulation anomalies associated with the perturbed polar vortex. However, we hesitate to label this effect as a positive feedback. The primary driver of the changes in ozone is likely the anomalous transport by the BDC. While changes in ozone do amplify the anomalies in polar vortex strength, a true feedback loop would require the vortex anomalies to modify ozone in turn. This could involve additional factors, such as meridional mixing and catalytic ozone depletion, but we believe that the transport-induced changes in ozone by the BDC are the most significant. The results from our study mostly corroborate and extend findings from similar studies using more complex CCMs. However, we also observed some discrepancies compared to some previous studies. For example, we were unable to identify the negative feedback described by Lin et al. (2017) and Haase and Matthes (2019). Further, the perturbed signals in our study were generally weaker than those found in studies using full CCMs, especially at the surface. Some of these differences may be due to the simplifying assumptions made in our model. For instance, our model underestimates the strength of the dynamical downward influence of the stratosphere on the troposphere, a problem which we suspect is systemic to models with Held–Suarez forcing. Another limitation of our model may be the linear photochemical ozone scheme. In this scheme, ozone is relaxed towards a prescribed ozone climatology at predefined time scales (Hong and Reichler, 2021b), which may not always match the real persistence of the circulation-induced ozone anomalies. This study presents several key take-home messages. Firstly, the SCDM is a valuable tool for studying the fundamental interactions between ozone and stratospheric dynamics. It effectively captures the essential physical principles of these interactions while operating at a fraction of the cost of more complex models. Secondly, our study shows that interactive ozone amplifies the effects of stratospheric circulation anomalies during spring. In contrast, other studies suggest that interactive ozone might moderate these effects. Thirdly, all studies agree that the interaction between ozone and stratospheric circulation has substantial effects and is crucial for climate predictions on sub-seasonal to multi-decadal time scales. Fourthly, the differences between our findings and those of previous studies indicate that there are still significant uncertainties in understanding the ozone-circulation interaction. This underscores the necessity for additional research to reconcile these conflicting results and enhance our understanding of the underlying mechanisms. Declarations Acknowledgments. We thank the National Science Foundation (Grants 1446292 and 2103013) and the Department of Atmospheric Sciences at the University of Utah for their support. The use of the computing infrastructure from the Center for High Performance Computing at the University of Utah is gratefully acknowledged. We also thank the Postdoctoral Scholar Program of the Academia Sinica and the Research Center for Environmental Changes for their support. Data Availability Statement. The SCDM simulation data can be made available upon request. References Albers, J. R., and Nathan, T. R.: Pathways for communicating the effects of stratospheric ozone to the polar vortex: Role of zonally asymmetric ozone, J. Atmos. Sci., 69, 785–801, https://doi.org/10.1175/JAS-D-11-0126.1, 2012. Baldwin, M. P., and Dunkerton, T. J.: Stratospheric harbingers of anomalous weather regimes, Science, 294, 581–584, https://doi.org/10.1126/science.1063315, 2001. Bosilovich, M. G., Akella, S., Coy, L., Cullather, R., Draper, C., Gelaro, R., Kovach, R., Liu, Q., Molod, A., Norris, P., Wargan, K., Chao, W., Reichle, R., Takacs, L., Vikhliaev, Y., Bloom, S., Collow, A., Firth, S., Labows, G., Partyka, G., Pawson, S., Reale, O., Schubert, S. D., and Suarez, M.: MERRA-2: Initial Evaluation of the Climate, Technical Report Series on Global Modeling and Data Assimilation, Tech. Rep. NASA/TM-2015-104606, availabe at: http://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/docs/ (last access: 13 January 2020), 2015. Butchart, N.: The Brewer-Dobson circulation, Rev. Geophys., 52, 157–184, https://doi.ogr/10.1002/2013RG000448, 2014. Butler, A. H., Sjoberg, J. P., Seidel, D. J., and Rosenlof, K. H.: A sudden stratospheric warming compendium, Earth Syst. Sci. Data, 9, 63–76, https://doi.org/10.5194/essd-9-63-2017, 2017. de la Cámara, A., Abalos, M., Hitchcock, P., Calvo, N., and Garcia, R. R.: Response of Arctic ozone to sudden stratospheric warmings, Atmos. Chem. Phys., 18, 16499–16513, https://doi.org/10.5194/acp-18-16499-2018, 2018. Cariolle, D., and Teyssèdre, H.: A revised linear ozone photochemistry parameterization for use in transport and general circulation models: multi-annual simulations, Atmos. Chem. Phys., 7, 2183–2196, https://doi.org/10.5194/acp-7-2183-2007, 2007. Charlton, A. J., and Polvani, L. M.: A new look at stratospheric sudden warmings. Part I: Climatology and modeling benchmarks, J. Clim., 20, 449–469, https://doi.org/10.1175/JCLI3996.1, 2007. Charney, J. G., and Drazin, P. G.: Propagation of planetary-scale disturbances from the lower into the upper atmosphere, J. Geophys. Res., 66, 83–109, https://doi.org/10.1029/JZ066i001p00083, 1961. Cicerone, R. J.: Changes in stratospheric ozone, Science, 237, 35–42, https://doi.org/10.1126/science.237.4810.35, 1987. Compo, G. P., Whitaker, J. S., Sardeshmukh, P. D., Matsui, N., Allan, R. J., Yin, X., Gleason, B. E., Jr., Vose, R. S., Rutledge, G., Bessemoulin, P., Brönnimann, S., Brunet, M., Crouthamel, R. I., Grant, A. N., Groisman, P. Y., Jones, P. D., Kruk, M. C., Kruger, A. C., Marshall, G. J., Maugeri, M., Mok, H. Y., Nordli, Ø., Ross, T. F., Trigo, R. M., Wang, X. L., Woodruff, S. D., and Worley, S. J.: The Twentieth Century Reanalysis Project, Q. J. R. Meteorol. Soc., 137, 1–28, https://doi.org/10.1002/qj.776, 2011. Friedel, M., Chiodo, G., Stenke, A., Domeisen, D. I. V., and Peter, T.: Effects of Arctic ozone on the stratospheric spring onset and its surface impact, Atmos. Chem. Phys., 22, 13997–14017, https://doi.org/10.5194/acp-22-13997-2022, 2022. Gabriel, A., Peters, D., Kirchner, I., and Graf, H.-F.: Effect of zonally asymmetric ozone on stratospheric temperature and planetary wave propagation, Geophys. Res. Lett., 34, L06897, https://doi.org/10.1029/2006GL028998, 2007. Gillett, N. P., and Thompson, D. W. J.: Simulation of recent Southern Hemisphere climate change, Science, 302, 273–275, https://doi.org/10.1126/science.1087440, 2003. Haase, S., Fricke, J., Kruschke, T., Wahl, S., and Matthes, K.: Sensitivity of the Southern Hemisphere circumpolar jet response to Antarctic ozone depletion: prescribed versus interactive chemistry, Atmos. Chem. Phys., 20, 14043–14061, https://doi.org/10.5194/acp-20-14043-2020, 2020. Haase, S., and Matthes, K.: The importance of interactive chemistry for stratosphere-troposphere coupling, Atmos. Chem. Phys., 19, 3417–3432, https://doi.org/10.5194/acp-19-3417-2019, 2019. Hartmann, D. L.: Some aspects of the coupling between radiation, chemistry, and dynamics in the stratosphere, J. Geophys. Res., 86, 9631–9640, https://doi.org/10.1029/JC086iC10p09631, 1981. Harzer, F., Garny, H., Ploeger, F., Bönisch, H., Hoor, P., and Birner, T.: On the pattern of interannual polar vortex–ozone co-variability during northern hemispheric winter, Atmos. Chem. Phys., 23, 10661–10675, https://doi.org/10.5194/acp-23-10661-2023, 2023. Held, I. M.: The gap between simulation and understanding in climate modeling, Bull. Amer. Meteor. Soc., 86, 1609–1614, https://doi.org/10.1175/BAMS-86-11-1609, 2005. Held, I. M., and Suarez, M. J.: A proposal for the intercomparison of the dynamical cores of atmospheric general circulation models, Bull. Amer. Meteor. Soc., 75, 1825–1830, https://doi.org/10.1175/1520-0477(1994)075%3C1825:APFTIO%3E2.0.CO;2, 1994. Hersbach, H., Bell, B., Berrisford, P., Hirahara, S., Horányi, A., Muñoz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmons, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., De Chiara, G., Dahlgren, P., Dee, D., Diamantakis, M., Dragani, R., Flemming, J., Forbes, R., Fuentes, M., Geer, A., Haimberger, L., Healy, S., Hogan, R. J., Hólm, E., Janisková, M., Keeley, S., Laloyaux, P., Lopez, P., Lupu, C., Radnoti, G., de Rosnay, P., Rozum, I., Vamborg, F., Villaume, S., and Thépaut, J.-N.: The ERA5 global reanalysis, Q. J. Roy. Meteor. Soc., 146, 1999–2049, 2020. Hocke, K., Lainer, M., and Schanz, A.: Composite analysis of a major sudden stratospheric warming, AnGeo. Comm., 33, 783–788, https://doi.org/10.5194/angeo-33-783-2015, 2015. Hong, H.-J. and Reichler, T.: Local and remote response of ozone to Arctic stratospheric circulation extremes, Atmos. Chem. Phys., 21, 1159–1171, https://doi.org/10.5194/acp-21-1159-2021, 2021a. Hong, H.-J. and Reichler, T.: The Simplified Chemistry-Dynamical Model (SCDM V1.0), Geosci. Model Dev., 14, 6647–6660, https://doi.org/10.5194/gmd-14-6647-2021, 2021b. Ivanciu, I., Matthes, K., Wahl, S., Harlaß, J., and Biastoch, A.: Effects of prescribed CMIP6 ozone on simulating the Southern Hemisphere atmospheric circulation response to ozone depletion, Atmos. Chem. Phys., 21, 5777–5806, https://doi.org/10.5194/acp-21-5777-2021, 2021. Keeble, J., Hassler, B., Banerjee, A., Checa-Garcia, R., Chiodo, G., Davis, S., Eyring, V., Griffiths, P. T., Morgenstern, O., Nowack, P., Zeng, G., Zhang, J., Bodeker, G., Burrows, S., Cameron-Smith, P., Cugnet, D., Danek, C., Deushi, M., Horowitz, L. W., Kubin, A., Li, L., Lohmann, G., Michou, M., Mills, M. J., Nabat, P., Olivié, D., Park, S., Seland, Ø., Stoll, J., Wieners, K.-H., and Wu, T.: Evaluating stratospheric ozone and water vapour changes in CMIP6 models from 1850 to 2100, Atmos. Chem. Phys., 21, 5015–5061, https://doi.org/10.5194/acp-21-5015-2021, 2021. Kidston, J., Scaife, A. A., Hardiman, S. C., Mitchell, D. M., Butchart, N., Baldwin, M. P., and Gray, L. J.: Stratospheric influence on tropospheric jet streams, storm tracks and surface weather, Nature Geosci., 8, 433–440, https://doi.org/10.1038/ngeo2424, 2015. Kim, J., and Reichler, T.: Quantifying the uncertainty of the annular mode time scale and the role of the stratosphere, Clim. Dyn., 47, 637–649, https://doi.org/10.1007/s00382-015-2860-2, 2016. Lacis, A. A., and Hansen, J. E.: A parameterization for the absorption of solar radiation in the earth’s atmosphere, J. Atmos. Sci., 31, 118–133, https://doi.org/10.1175/1520-0469(1974)031%3C0118:APFTAO%3E2.0.CO;2, 1974. Li, F., Vikhliaev, Y. V., Newman, P. A., Pawson, S., Perlwitz, J., Waugh, D. W., and Douglass, A. R.: Impacts of interactive stratospheric chemistry on Antarctic and Southern Ocean climate change in the Goddard Earth Observing System, version 5 (GEOS-5), J. Clim., 29, 3199–3218, https://doi.org/https://doi.org/10.1175/JCLI-D-15-0572.1, 2016. Limpasuvan, V., Hartmann, D. L., Thompson, D. W. J., Jeev, K., and Yung, Y. L.: Stratosphere-troposphere evolution during polar vortex intensification, J. Geophys. Res., 110, D24101, https://doi.org/10.1029/2005JD006302, 2005. Limpasuvan, V., Thompson, D. W. J., and Hartmann, D. L.: The life cycle of the Northern Hemisphere sudden stratospheric warmings, J. Clim., 17, 2584–2596, https://doi.org/10.1175/1520-0442(2004)017%3C2584:TLCOTN%3E2.0.CO;2, 2004. Lin, P., Paynter, D., Polvani, L., Correa, G. J. P., Ming, Y., and Ramaswamy, V.: Dependence of model-simulated response to ozone depletion on stratospheric polar vortex climatology, Geophys. Res. Lett., 44, 6391–6398, doi:10.1002/2017GL073862, 2017. Lubis, S. W., Silverman, V., Matthes, K., Harnik, N., Omrani, N.-E., and Wahl, S.: How does downward planetary wave coupling affect polar stratospheric ozone in the Arctic winter stratosphere?, Atmos. Chem. Phys., 17, 2437–2458, https://doi.org/10.5194/acp-17-2437-2017, 2017. Manney, G. L., Livesey, N. J., Santee, M. L., Froidevaux, L., Lambert, A., Lawrence, Z. D., Millán, L. F., Neu, J. L., Read, W. G., Schwartz, M. J., and Fuller, R. A.: Record-low Arctic stratospheric ozone in 2020: MLS observations of chemical processes and comparisons with previous extreme winters, Geophys. Res. Lett., 47, e2020GL089063, https://doi.org/10.1029/2020GL089063, 2020. Manney, G. L., Santee, M. L., Rex, M., Livesey, N. J., Pitts, M. C., Veefkind, P., Nash, E. R., Wohltmann, I., Lehmann, R., Froidevaux, L., Poole, L. R., Schoeberl, M. R., Haffner, D. P., Davies, J., Dorokhov, V., Gernandt, H., Johnson, B., Kivi, R., Kyrö, E., Larsen, N., Levelt, P. F., Makshtas, A., McElroy, C. T., Nakajima, H., Parrondo, M. C., Tarasick, D. W., Gathen, P., Walker, K. A., and Zinoviev, N. S.: Unprecedented Arctic ozone loss in 2011, Nature, 478, 469–475, https://doi.org/10.1038/nature10556, 2011. McCormack, J. P., Eckermann, S. D., Siskind, D. E., and McGee, T. J.: CHEM2D-OPP: A new linearized gas-phase ozone photochemistry parameterization for high-altitude NWP and climate models, Atmos. Chem. Phys., 6, 4943–4972, https://doi.org/10.5194/acp-6-4943-2006, 2006. Monge-Sanz, B. M., Bozzo, A., Byrne, N., Chipperfield, M. P., Diamantakis, M., Flemming, J., Gray, L. J., Hogan, R. J., Jones, L., Magnusson, L., Polichtchouk, I., Shepherd, T. G., Wedi, N., and Weisheimer, A.: A stratospheric prognostic ozone for seamless Earth system models: performance, impacts and future, Atmos. Chem. Phys., 22, 4277–4302, https://doi.org/10.5194/acp-22-4277-2022, 2022. Nathan, T. R., and Cordero, E. C.: An ozone-modified refractive index for vertically propagating planetary waves, J. Geophys. Res., 112, D02105, https://doi.org/10.1029/2006JD007357, 2007. Oehrlein, J., Chiodo, G., and Polvani, L. M.: The effect of interactive ozone chemistry on weak and strong stratospheric polar vortex events, Atmos. Chem. Phys., 20, 10531–10544, https://doi.org/10.5194/acp-20-10531-2020, 2020. Rae, C. D., Keeble, J., Hitchcock, P., and Pyle, J. A.: Prescribing zonally asymmetric ozone climatologies in climate models: Performance compared to a chemistry‐climate model, J. Adv. Model. Earth Syst., 11, 918–933, https://doi.org/10.1029/2018MS001478, 2019. Randel, W. J., and Wu, F.: Cooling of the Arctic and Antarctic polar stratospheres due to ozone depletion, J. Clim., 12, 1467–1479, https://doi.org/10.1175/1520-0442(1999)012%3C1467:COTAAA%3E2.0.CO;2, 1999. Revell, L. E., Robertson, F., Douglas, H., Morgenstern, O., and Frame, D.: Influence of ozone forcing on 21st century Southern Hemisphere surface westerlies in CMIP6 models, Geophys. Res. Lett., 49, e2022GL098252, https://doi.org/10.1029/2022GL098252, 2022. Rieder, H. E., Chiodo, G., Fritzer, J., Wienerroither, C., and Polvani, L. M.: Is interactive ozone chemistry important to represent polar cap stratospheric temperature variability in Earth-System Models?, Environ. Res. Lett., 14, 044026, https://doi.org/10.1088/1748-9326/ab07ff, 2019. Romanowsky, E., Handorf, D., Jaiser, R., Wohltmann, I., Dorn, W., Ukita, J., Cohen, J., Dethloff, K., and Rex, M.: The role of stratospheric ozone for Arctic-midlatitude linkages, Sci Rep, 9, 7962, https://doi.org/10.1038/s41598-019-43823-1, 2019. Saha, S., Moorthi, S., Wu, X., Wang, J., Nadiga, S., Tripp, P., Behringer, D., Hou, Y., Chuang, H., Iredell, M., Ek, M., Meng, J., Yang, R., Mendez, M. P., van den Dool, H., Zhang, Q., Wang, W., Chen, M., and Becker, E.: The NCEP Climate Forecast System Version 2, J. Clim., 27(6), 2185–2208, https://doi.org/10.1175/JCLI-D-12-00823.1, 2014. Solomon, S.: Stratospheric ozone depletion: A review of concepts and history, Rev. Geophys., 37, 275–316, https://doi.org/10.1029/1999RG900008, 1999. Stolarski, R. S., and Cicerone, R. J.: Stratospheric chlorine: a possible sink for ozone, Can. J. Chem., 52, 1610–1615, https://doi.org/10.1139/v74-233, 1974. Tegtmeier, S., Fioletov, V. E., and Shepherd, T. G.: A global picture of the seasonal persistence of stratospheric ozone anomalies, J. Geophys. Res., 115, D18119, https://doi.org/10.1029/2009JD013011, 2010. Thompson, D. W. J., and Solomon, S.: Interpretation of recent Southern Hemisphere climate change, Science, 296, 895–899, https://doi.org/10.1126/science.1069270, 2002. Wallace, J. M., and Hobbs, P. V.: Atmospheric Science, Elsevier Academic Press, Massachusetts, 483 pp, 2006. Wu, Z., and Reichler, T.: Towards a more Earth-like circulation in idealized models, J. Adv. Model. Earth Syst, 10, 1458–1469, https://doi.org/10.1029/2018MS001356, 2018. Additional Declarations The authors declare no competing interests. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-5626578","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":389190045,"identity":"6bab5420-8411-4d1e-a709-a6d1d2d0b46d","order_by":0,"name":"Hao-Jhe Hong","email":"","orcid":"","institution":"Univ. of Utah","correspondingAuthor":false,"prefix":"","firstName":"Hao-Jhe","middleName":"","lastName":"Hong","suffix":""},{"id":389190046,"identity":"cb2c152a-c72e-46ea-bb2e-a0e3208794d2","order_by":1,"name":"Thomas Reichler","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA+0lEQVRIiWNgGAWjYDACCRiDmYGN4QEDgxyQyQbm4gI8KFoSGBiMgRSxWhggWhIbCGmxl24+uuHHH4Z8fnbmZw8SKu6lb7jf/OwBQ4V1YgMuW2SOpd3sbWOwnNnMZm6QcKY4d8MxIIPhTDpuLRI5Zjd4GxgMDA7zsEkktiUAtTCYSTC2Hcar5eafPwwG9mAt/xLSDY6xf5Ng/Idfy20eNqAtzCAtDQkJBsd4gLY04NFyIy3ttmybhIHEYTYziYRjCYYzj+WUARnpxri0sM9IPnbzzR8bA/7+w88kPtQkyPMdPr4NyLCWxaUFCiTQ+An4lY+CUTAKRsEoIAAAtENSIqJPKbUAAAAASUVORK5CYII=","orcid":"","institution":"Univ. of Utah","correspondingAuthor":true,"prefix":"","firstName":"Thomas","middleName":"","lastName":"Reichler","suffix":""},{"id":389190047,"identity":"3a369ebe-f3a0-4126-b79c-02cd5d5d1c3a","order_by":2,"name":"Huang-Hsiung Hsu","email":"","orcid":"","institution":"Research Center for Environmental Changes, Academia Sinica","correspondingAuthor":false,"prefix":"","firstName":"Huang-Hsiung","middleName":"","lastName":"Hsu","suffix":""}],"badges":[],"createdAt":"2024-12-11 18:42:24","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-5626578/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-5626578/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":71318077,"identity":"e6c2a810-69f0-468c-80ed-0212bbb6c727","added_by":"auto","created_at":"2024-12-13 09:34:19","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":153637,"visible":true,"origin":"","legend":"\u003cp\u003eInterannual variability of the zonal-mean zonal wind at 60⁰N (U60). Shown are (a) ERA5 (1980-2018), (b) VARO3 (interactive ozone), and (c) VARO3 minus FIXO3 (interactive ozone minus fixed ozone). The interannual variability is the standard deviation of zonal-mean zonal wind on any given day of the year. Stippling in (c) indicates statistically significant differences at the 5% level based on a F-test.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-5626578/v1/c1f67689847d6d0e78e6c2b1.png"},{"id":71318080,"identity":"3efdded3-9f48-40da-90f4-e7872417637a","added_by":"auto","created_at":"2024-12-13 09:34:19","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":164321,"visible":true,"origin":"","legend":"\u003cp\u003ePersistence time scale τ (days) of the NAM index for (top) VARO3 and (bottom) VARO3 minus FIXO3. Stippling in (b) indicates statistically significant differences at the 5% level.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-5626578/v1/ae4ed63c947f70098239cbd3.png"},{"id":71317593,"identity":"032362d5-9e5e-4881-a8f8-504bb97f7c1f","added_by":"auto","created_at":"2024-12-13 09:26:19","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":183023,"visible":true,"origin":"","legend":"\u003cp\u003eAnnual time series of ozone during stratospheric circulation events in VARO3. (top) Northern polar cap (65°-90°N) averaged ozone volume mixing ratio at 70 hPa. Thick curves represent mean ozone for SSW, VI, and neutral years (NEU) from the 2000-year long VARO3 simulation. Thin curves show ozone during individual years with SSW (red) and VI (blue) events; for clarity, only the first 100 years of VARO3 are included. (bottom) Spatial structure of composite ozone anomalies for years with (left) SSW and (right) VI events. Shown are latitude-height cross-sections of zonal-mean ozone volume mixing ratio anomalies averaged from February to April.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-5626578/v1/1c3b80db2a5e7dc71a1bd128.png"},{"id":71318076,"identity":"6e8e75cb-e800-4bc3-b559-eed22259063d","added_by":"auto","created_at":"2024-12-13 09:34:19","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":252380,"visible":true,"origin":"","legend":"\u003cp\u003eDifferences in (top) ozone and (bottom) shortwave heating (DTSW) between interactive and fixed ozone during (left) years with SSWs and (right) years with VIs. Shown are composite anomaly differences between VARO3 and FIXO3 for February-March (left) SSWs and (right) VIs. The quantities are polar cap (60°-90°N) averaged (top) ozone volume mixing ratio (ppbv) and (bottom) shortwave ozone heating rate (10\u003csup\u003e-3\u003c/sup\u003e K day\u003csup\u003e-1\u003c/sup\u003e). Stippling indicates statistically significant differences at the 5% level.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-5626578/v1/50f313cd2e70341a3fe3038c.png"},{"id":71318079,"identity":"1a8a333a-9f8e-4c1c-ad68-30fdc17e525e","added_by":"auto","created_at":"2024-12-13 09:34:19","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":309308,"visible":true,"origin":"","legend":"\u003cp\u003eTemperature response to stratospheric events. Shown are composite anomalies of polar cap (60°-90°N) averaged temperature for February-March (top) SSWs and (bottom) VIs for simulations (left) VARO3, (middle) FIXO3, and (right) VARO3 minus FIXO3. Stippling represents statistically significant (a-b, d-e) anomalies and (c, f) anomaly differences at the 5% level.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-5626578/v1/9084052c0966812b1d9bfb98.png"},{"id":71318675,"identity":"6be358d1-e40a-483c-83b2-f530ed4c486d","added_by":"auto","created_at":"2024-12-13 09:42:19","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":282484,"visible":true,"origin":"","legend":"\u003cp\u003eZonal wind response to stratospheric events. Shown are composite anomalies of zonal-mean zonal wind at 60°N for February-March (top) SSWs and (bottom) VIs for simulations (left) VARO3, (middle) FIXO3, and (right) VARO3 minus FIXO3. Stippling represents statistically significant (a-b, d-e) anomalies and (c-f) anomaly differences at the 5% level.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-5626578/v1/b82e4b70c456655b433dcacb.png"},{"id":71317595,"identity":"ec391611-22c7-4e3c-8145-56c20d2698ef","added_by":"auto","created_at":"2024-12-13 09:26:19","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":362424,"visible":true,"origin":"","legend":"\u003cp\u003eSea level pressure (SLP) response to stratospheric events. Shown are composite SLP anomalies averaged from lag 30 to 90 days with respect to the onset of (top) SSWs and (bottom) VIs that occur during February-March. Stippling represents statistically significant (a-b, d-e) anomalies and (c, f) anomaly differences between VARO3 and FIXO3 at the 5% level.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-5626578/v1/b9098345ab9a6189a222d86f.png"},{"id":71320032,"identity":"2c3994eb-f3c6-4c78-b461-4fd84224637b","added_by":"auto","created_at":"2024-12-13 09:58:20","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1813518,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-5626578/v1/b40d7a9e-99b1-4c22-b932-ae36a17f1e37.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003eArctic Ozone Amplifies Stratospheric Circulation Extremes\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eOzone is a key constituent of the stratosphere, essential for the complex interactions between chemistry, radiation, and dynamics (Hartmann, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1981\u003c/span\u003e). Ozone absorbs solar radiation and thereby significantly influences the temperature and wind structure of the stratosphere (Cicerone, \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Wallace and Hobbs, \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Conversely, the distribution of ozone is strongly affected by stratospheric winds, particularly in the lower stratosphere (Butchart, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Tegtmeier et al., \u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e2010\u003c/span\u003e). These mutual influences can lead to notable effects, especially during winter and spring when stratospheric ozone can experience substantial perturbations. These perturbations may result from anthropogenic chemical depletion (Manney et al., \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2011\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Solomon, \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Stolarski and Cicerone, \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e1974\u003c/span\u003e) or dynamical transports linked to extreme stratospheric circulation events, such as stratospheric sudden warmings (SSWs) and vortex intensification events (VIs) (e.g., Butler et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; de la C\u0026aacute;mara et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Hocke et al., \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Hong and Reichler, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e; Lubis et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2017\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe important role that stratospheric ozone plays in the circulation was first recognized over the high latitudes of the Southern Hemisphere. Early studies focused on the effects of Antarctic stratospheric ozone depletion and found that the declining trend of ozone was accompanied by stratospheric cooling and an intensification of the polar circulation that extended from the stratosphere to the troposphere (Randel and Wu, \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Thompson and Solomon, \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e2002\u003c/span\u003e; Gillett and Thompson, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2003\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the Arctic stratosphere, understanding the interactions between ozone and the circulation is more complicated due to the large internal variability of the circulation and the induced transport dynamics on polar ozone (Harzer et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). The upward propagation and dissipation of planetary waves modulate the strength of the northern wintertime stratospheric polar vortex (Limpasuvan et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2004\u003c/span\u003e; \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2005\u003c/span\u003e), which\u0026mdash;through anomalous mixing and transports\u0026mdash;changes the amount and distribution of polar ozone. Ozone, in turn, and especially zonal asymmetries in the distribution of ozone and the resulting radiative heating anomalies, can change the planetary waves and how they propagate and break (Gabriel et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Nathan and Cordero, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2007\u003c/span\u003e). These and other processes can create complicated situations, and most often complex Chemistry Climate Models (CCMs) are used to study the interactions between ozone and the circulation.\u003c/p\u003e \u003cp\u003eHowever, most models from the Coupled Model Intercomparison Project use prescribed climatological means of ozone to represent the approximate radiative effects of ozone and to avoid the large computational burden from the chemistry components (Keeble et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Prescribing ozone in models, however, inhibits the interaction between ozone and the circulation, leads to inconsistencies between the two, and may create simulation errors (Ivanciu et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). To understand these errors and to find out whether interactive ozone leads to more reliable simulations, past studies compared simulations in which ozone was either interactively simulated or prescribed.\u003c/p\u003e \u003cp\u003eFor the Southern Hemisphere, it was found that using interactive ozone increases the circulation effects from Antarctic ozone depletion (Haase et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Ivanciu et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Li et al, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Analyzing CMIP6 model output, Revell et al. (\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) found that models without interactive chemistry project a substantially stronger tropospheric westerly jet by the end of the 21st century than models with interactive chemistry because the prescribed ozone recovery is smaller than the predicted one.\u003c/p\u003e \u003cp\u003eFor the Northern Hemisphere, several recent studies have demonstrated the significance of interactive stratospheric ozone for simulating Arctic circulation and surface conditions. Rae et al. (\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) showed that simulations with dynamically consistent ozone produce a polar vortex shape and sea level pressure pattern that more closely resemble those from a full CCM compared to simulations with fixed ozone. Haase and Matthes (\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) found that interactive ozone results in more realistic and persistent circulation anomalies in the stratosphere and at the surface after SSWs compared to prescribed ozone. Romanowsky et al. (\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) observed that in response to sea ice retreat, the coupling between the stratosphere and troposphere is more intense with an interactive ozone scheme. Rieder et al. (\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) demonstrated that interactive ozone chemistry increases simulated stratospheric temperature variability and extremes. Friedel et al. (\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) found that the interaction between ozone and the stratospheric circulation results in a more variable timing for the breakdown of the Arctic polar vortex during spring.\u003c/p\u003e \u003cp\u003eIn the present study, we also investigate the effects of interactive ozone on Arctic circulation and surface conditions. Unlike previous studies with complex CCMs, we employ a relatively simple idealized general circulation model with dry physics. By coupling this model with an ozone scheme and implementing a basic shortwave radiation parameterization, we reproduce the fundamental mechanisms governing the interaction between ozone and dynamics. This approach has several advantages. Firstly, our model avoids the complexities and parameterizations found in more comprehensive models, focusing on the essential physical processes (Held, \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). This simplification allows for a clearer analysis of the interactions between ozone and dynamics. Additionally, the model's computational efficiency and ease of management make it a valuable research tool, offering a fresh perspective on understanding ozone-dynamics interactions and providing a foundation for future investigations.\u003c/p\u003e \u003cp\u003eWe employ the simplified linear ozone scheme by Cariolle and Teyss\u0026egrave;dre (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2007\u003c/span\u003e) in our model. Variations of this scheme are used in other atmospheric models, including the ECMWF Integrated Forecasting System (IFS) (Monge-Sanz et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), the NCEP 20th Century Reanalysis (20CR) (Compo et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), the NCEP Global Forecast System (GFS), and the NCEP Climate Forecast System Version 2 (CFSv2) (Saha et al., \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; McCormack et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). As such, the results from our study can also serve as a test of the performance of this widely used ozone model.\u003c/p\u003e \u003cp\u003eThe main goal of this study is to better understand the influence of interactive ozone on Arctic stratospheric circulation and surface conditions. We also aim to compare how these influences are simulated by our idealized model with those simulated by full CCMs. A particular focus is on Arctic stratospheric circulation extremes, such as SSWs and VIs, as these events are known to be associated with significant perturbations in stratospheric polar ozone (Hong and Reichler, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e). To ensure that these ozone perturbations are dynamically relevant, we focus on circulation extremes that occur in late northern winter (February-March) and persist into northern spring. This period is critical because there is sufficient sunlight over the polar cap for ozone to generate radiative heating anomalies.\u003c/p\u003e \u003cp\u003eOur paper is structured as follows: Section \u003cspan refid=\"Sec2\" class=\"InternalRef\"\u003e2\u003c/span\u003e describes our model and methodology, Section \u003cspan refid=\"Sec5\" class=\"InternalRef\"\u003e3\u003c/span\u003e presents our results, focusing on the impact of interactive ozone on Arctic circulation variability, and Section \u003cspan refid=\"Sec7\" class=\"InternalRef\"\u003e4\u003c/span\u003e provides a summary and conclusion.\u003c/p\u003e"},{"header":"2 Model and Methods","content":"\u003cp\u003ea. The Simplified Chemistry-Dynamical Model (SCDM)\u003c/p\u003e\n\u003cp\u003eWe employ the Simplified Chemistry-Dynamical Model (SCDM V1.0), developed by Hong and Reichler (2021b). SCDM is based on the GFDL spectral dynamical core (Held and Suarez, 1994) with simplified physics. Modifications were made according to Wu and Reichler (2018), incorporating realistic topography and forcing the model with empirically derived, zonally asymmetric, and seasonally varying equilibrium temperatures. This minimizes the climatological temperature differences between the reanalysis and the model, resulting in effective diabatic heating rates that reasonably match observations. The model successfully captures seasonal variations in stationary waves, polar vortex strength, and SSW frequency, validating its use for our study.\u003c/p\u003e\n\u003cp\u003eHong and Reichler (2021b) further enhanced the model by incorporating ozone as a tracer advected by the dynamics, implementing a linear photochemical ozone scheme (Cariolle and Teyssèdre, 2007) that responds to changes in temperature, shortwave radiation, and ozone concentrations, and adding a shortwave radiation parameterization for ozone (Lacis and Hansen, 1974) to simulate heating from shortwave absorption by ozone. These modifications enable SCDM to simulate the interactions between dynamics and ozone in the stratosphere.\u003c/p\u003e\n\u003cp\u003eWe conducted two 2000-year simulations with the model. VARO3 is our control run with variable, fully interactive ozone. FIXO3 is identical to VARO3, except that ozone is prescribed using the fixed, zonally-asymmetric, daily varying but annually repeating ozone climatology derived from VARO3. The differences between the two simulations are therefore entirely due to the mutual influences between the dynamics and ozone.\u003c/p\u003e\n\u003cp\u003eb. Methods\u003c/p\u003e\n\u003cp\u003e1) Persistence of the Northern Annular Mode\u003c/p\u003e\n\u003cp\u003eWe followed Kim and Reichler (2016) to estimate the persistence time scale τ of the Northern Annular Mode (NAM) index, represented at each level by the standardized geopotential height anomalies averaged over the polar cap area (60°-90°N). τ is defined as the time in which the daily autocorrelation of the NAM index decreases by a factor of \u003cem\u003ee\u003c/em\u003e. To calculate the mean and variability of τ, we divided the 2000-year dataset into forty 50-year intervals and calculated τ separately for each interval. This process was repeated for each latitude, level, and calendar day. A two-sample Student's t-test was used to test the significance of the differences in τ between VARO3 and FIXO3.\u003c/p\u003e\n\u003cp\u003e2) Stratospheric circulation events\u003c/p\u003e\n\u003cp\u003eOzone in the stratosphere is well-known to be influenced by the anomalous advection and temperatures during the life cycles of stratospheric circulation events. The two types of events we consider are SSWs and VIs. SSWs are characterized by a relatively warm and weak northern wintertime stratospheric polar vortex, while VIs are characterized by a relatively cold and strong vortex.\u003c/p\u003e\n\u003cp\u003eWe defined SSWs based on Charlton and Polvani (2007). According to this definition, the central or onset date of an SSW is the day when the zonal-mean zonal wind at 10 hPa and 60° N (U1060) reverses from westerly to easterly between November and March. After the wind reversal, U1060 must return to westerly for at least 10 consecutive days before the end of April; otherwise, the event is classified as a final warming (FW) event. If two SSWs occur in the same winter, a period of at least 20 consecutive days of westerlies is required to distinguish the events.\u003c/p\u003e\n\u003cp\u003eFor VIs, we followed the definition by Hong and Reichler (2021a). This definition is based on daily anomalies of U1060, low-pass filtered using a 20-day running mean. The central date of a VI is defined when the filtered U1060 anomaly exceeds 16 m/s, which is about one standard deviation of U1060 estimated from reanalysis data. Similar to SSWs, a separation interval of at least 20 days is required for two VIs occurring in the same winter to be recognized as separate events.\u003c/p\u003e\n\u003cp\u003eWe only considered events occurring in February and March, as this is when sufficient sunlight is available over the polar cap for ozone to create shortwave radiative heating and thus provide a radiative feedback on the circulation. For the 2000-year-long VARO3 (FIXO3) simulation, this resulted in 830 (821) SSW events and 449 (445) VI events. All other years were considered normal years. Given the similarity of these numbers between the two simulations, we conclude that using interactive chemistry in our model leads only to minor changes in the number of extreme circulation events. This contrasts with a similar CCM-based study by Haase and Matthes (2019), who found that compared to prescribed ozone, interactive ozone leads to significant changes in the overall frequency of SSWs and their seasonal distribution.\u003c/p\u003e\n\u003cp\u003e3) Event compositing\u003c/p\u003e\n\u003cp\u003eWe formed composites of all February-March events by focusing on the -90 to 90 day interval centered on the onset date of each event, then averaging over all events. A one-sample t-test was used to determine whether the composite anomalies were significant, and a two-sample t-test was used to assess the significance of composite difference anomalies.\u003c/p\u003e"},{"header":"3 Results","content":"\u003cp\u003eIn this section, we investigate the impact of interactive ozone by comparing the two simulations. We begin by exploring the circulation variability, followed by an examination of specific changes in ozone, ozone heating, and the circulation associated with the two event types. Finally, we assess whether the stratospheric changes translate into observable signals at the surface. As mentioned before, we focus on events during boreal spring (February-March), as this is when the signals are most pronounced.\u003c/p\u003e\n\u003cp\u003ea. Changes in circulation variability\u003c/p\u003e\n\u003cp\u003eAn interaction between ozone and the dynamics should be evident through changes in stratospheric variability. This interaction can result in either constructive or destructive interference between initial perturbations and the additional response from interactive ozone. Constructive interference would amplify the initial perturbations, increase variability, and potentially create a positive feedback loop; otherwise, the initial perturbations will be dampened, leading to decreased variability. To investigate these possibilities, we examine the interannual standard deviation of the zonal-mean zonal wind at 60\u0026deg;N (U60), a common measure of the Arctic polar vortex strength. The standard deviation is calculated for each calendar date and atmospheric level.\u003c/p\u003e\n\u003cp\u003eThe top two panels in Figure 1 compare the variability between the ECMWF Reanalysis v5 (ERA5) (Hersbach et al. 2020) and the VARO3 simulation. Generally, the variability of the polar vortex in the observations is large in winter and small in summer, and this is well simulated by VARO3. Simulation VARO3 also replicates the ERA5 variability structure of the Antarctic polar vortex at 60\u0026deg;S quite well (Figure S1).\u003c/p\u003e\n\u003cp\u003eNext, we compare simulations VARO3 and FIXO3 to investigate the impact of interactive ozone on circulation variability. Figure 1c shows the difference in U60 variability between the two simulations. As expected, the differences are mostly small during winter (November-March), as ozone\u0026rsquo;s influence on the polar stratosphere is linked to the presence of sufficient sunlight. However, starting in April and continuing into May, Figure 1c reveals a 20-25% increase in circulation variability in VARO3 compared to FIXO3. During boreal summer, interactive ozone decreases the stratospheric variability. However, this change is relatively small, as it coincides with the natural low variability during this time of the year. Therefore, for the remainder of this paper, we focus on understanding the reasons for and consequences of the increase in variability during boreal spring.\u003c/p\u003e\n\u003cp\u003eThis increase in variability in VARO3 during spring is consistent with constructive interference between the stratospheric dynamics and Arctic ozone, occurring when there is sufficient sunlight for stratospheric ozone perturbations to induce radiative heating anomalies that, in turn, influence the circulation. Our results align with those of Rieder et al. (2019), who found\u0026nbsp;from a complex CCM that stratospheric temperature variability and temperature extremes during spring are increased in simulations with interactive chemistry compared to simulations with fixed climatological mean ozone.\u003c/p\u003e\n\u003cp\u003eTo better understand the nature of the increased interannual circulation variability due to interactive ozone, we next examine the NAM persistence time scale, \u0026tau;. Figure 2a shows a pronounced springtime maximum in \u0026tau; for VARO3, reaching up to 70 days in the lower stratosphere (100-50 hPa) during May and June. From observations and more complex models, Kim and Reichler (2016) found a similar but less pronounced increase in \u0026tau;, reaching about 40 days during spring in the lower stratosphere.\u003c/p\u003e\n\u003cp\u003eNext, we compare \u0026tau; from VARO3 against that from FIXO3 (Figure 2b). The differences demonstrate that using interactive ozone makes the stratospheric NAM, and thus the polar vortex, more persistent compared to using fixed ozone. The increase in \u0026tau; of about 10-30 days extends from February to July and maximizes in the lower stratosphere during May and June, coinciding with the time and level where persistence is highest in VARO3 (Figure 2a).\u003c/p\u003e\n\u003cp\u003eb. Changes in ozone during stratospheric circulation events\u003c/p\u003e\n\u003cp\u003ePrevious studies have shown that SSWs and VIs, the major stratospheric circulation events, are associated with persistent anomalies in stratospheric ozone that can last for up to two months (de la C\u0026aacute;mara et al., 2018; Hocke et al., 2015; Hong and Reichler, 2021a). Therefore, we focus next on the ozone perturbations simulated by our model during these events.\u003c/p\u003e\n\u003cp\u003eThe thin curves in Figure 3a represent individual annual time series (October-September) of the polar cap averaged ozone mixing ratio at 70 hPa for the first hundred years of VARO3. The color coding indicates whether a SSW, VI, or no circulation event occurred during each winter. Consistent with previous studies, the dynamical transports associated with SSWs lead to increased amounts of ozone from January to April compared to neutral years, while VIs result in larger and more persistent decreases in ozone. This can also be seen from the thick curves in Figure 3a, which show the annual evolution of ozone averaged over the events from all simulated years of VARO3.\u003c/p\u003e\n\u003cp\u003eFigures 3b and 3c illustrate the spatial structure of February-April mean ozone anomalies in latitude-height cross-sections for SSW and VI years, respectively, based on all years of the VARO3 simulation. Both increased ozone during SSWs and decreased ozone during VIs reach their maximum in the lower stratosphere (~40 hPa) near the pole. The magnitude of the ozone anomaly associated with VIs is approximately 2.7 times larger than that associated with SSWs, suggesting that the impact of ozone on the circulation during VIs is substantially larger than during SSWs.\u003c/p\u003e\n\u003cp\u003ec. Changes in final warming date\u003c/p\u003e\n\u003cp\u003eFriedel et al. (2022) demonstrated that reductions in ozone during strong and cold vortex events (VIs) result in decreased solar absorption, more persistent cold anomalies in the lower stratosphere, and a stronger and more enduring polar vortex and NAM. Consequently, the breakup of the spring polar vortex, known as the final warming (FW), is significantly delayed by up to ten days compared to simulations with fixed climatological ozone. We will next investigate whether similar changes in the seasonal timing of the FW are observed in our simulations and whether SSWs have the anticipated opposite effect.\u003c/p\u003e\n\u003cp\u003eWe classified FWs based on whether they were preceded by stratospheric circulation events during February-March. We then calculated the mean date of FWs following SSWs and VIs for both the VARO3 and FIXO3 simulations (Table 1). Consistent with the findings of Friedel et al. (2022), the VARO3 simulation shows that FWs following VIs are on average significantly delayed by 5 days compared to those in the FIXO3 simulation. In contrast, there is no significant change in the date of FWs following SSWs. This difference between VIs and SSWs can be largely attributed to the much more substantial ozone perturbations associated with VIs compared to SSWs (Figure 3). Additionally, Table 1 indicates that VARO3 results in greater variability in the FW date compared to FIXO3. Overall, our results corroborate previous studies by demonstrating that interactive ozone leads to a more persistent polar vortex and a later FW date when preceded by a VI. This outcome further validates our model\u0026apos;s ability to effectively simulate the interactions between ozone and stratospheric dynamics.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1:\u003c/strong\u003e Mean and standard deviation (days) of the final warming date associated with February\u0026ndash;March SSWs and VIs. Asterisks (*) indicate that the difference in mean FW date between VARO3 and FIXO3 is significant at the 5% level based on a two-sample t-test.\u003c/p\u003e\n\u003ctable border=\"0\" cellspacing=\"0\" cellpadding=\"0\" width=\"585\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd colspan=\"2\" style=\"width: 198px;\"\u003e\u003cbr\u003e\u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFWs following SSWs\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFWs following VIs\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFWs all 2000 years\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 74px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eVARO3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003eMEAN DATE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003eApr 9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003eApr 16 (*)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003eApr 5 (*)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003eSTD (days)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e16\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e19\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003e21\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" style=\"width: 74px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFIXO3\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003eMEAN DATE\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003eApr 9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003eApr 11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003eApr 4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003eSTD (days)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 132px;\"\u003e\n \u003cp\u003e17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 123px;\"\u003e\n \u003cp\u003e20\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003ed. Interactions between ozone and the stratospheric circulation\u003c/p\u003e\n\u003cp\u003eIn the previous sections, we demonstrated how late winter (February-March) SSWs and VIs induce distinct anomalies in springtime Arctic ozone. We now aim to explore the dynamical consequences of these anomalies by examining their spatio-temporal evolution and their radiative impacts. As before, our analysis focuses on years with VIs or SSWs occurring during February\u0026ndash;March, a period when sunlight is available over the polar cap to drive significant radiative effects.\u003c/p\u003e\n\u003cp\u003eFigure 4 illustrates the differences in composite anomalies between VARO3 and FIXO3 for ozone (top) and the associated ozone shortwave heating rate (bottom). For SSWs, ozone shows a rapid increase following event onset, persisting in the lower stratosphere (Figure 4a). This increase is driven by the upward propagation and breaking of planetary waves prior to SSW onset, which weakens the stratospheric polar vortex, accelerates the downwelling branch of the Brewer-Dobson circulation (BDC), and results in the anomalous transport of ozone-rich air from the tropical upper stratosphere into the Arctic lower stratosphere (de la C\u0026aacute;mara et al., 2018; Hong and Reichler, 2021a). The ozone increase in turn is linked to persistent shortwave heating anomalies in the lower stratosphere and smaller cooling anomalies above, around 10 hPa (Figure 4c). This heating structure is similar to results from a previous study using a CCM (Oehrlein et al., 2020, Figure 5d).\u003c/p\u003e\n\u003cp\u003eDuring VIs, the planetary wave activity is reduced, creating a weaker BDC and less ozone transport into the Arctic stratosphere. Starting about 60 to 30 days before event onset, this results in persistent negative ozone anomalies (Figure 4b). The magnitude of these anomalies is about twice that observed during SSWs after onset, as also suggested by the February\u0026ndash;April mean ozone anomalies shown in Figure 3. The reductions in ozone lead to radiative cooling anomalies in the lower stratosphere, which start at about event onset, last for more than 60 days, and are much stronger than the heating anomalies observed during SSWs (Figure 4d).\u003c/p\u003e\n\u003cp\u003eCompared to Hong and Reichler (2021a), who investigated the observed ozone responses to SSWs and VIs using the MERRA2 reanalysis (Bosilovich et al., 2015), the SCDM simulates the evolution of ozone during the lifecycles of the two circulation events overall quite well. However, the ozone anomalies in the SCDM are somewhat more persistent than in the observations, which is presumably due to shortcomings in how changes in wave activity after the circulation events are simulated by the model (Hong and Reichler, 2021b). This leads to a somewhat longer simulated radiative impact from ozone. Nevertheless, the primary purpose of our study is to qualitatively understand the ozone-dynamics feedback, and the realistic ozone response of the SCDM justifies the use of this model.\u003c/p\u003e\n\u003cp\u003eNext, we investigate how the changes in ozone and heating seen in Figure 4 influence temperatures and the circulation. Figure 5 shows the composite anomalies of Arctic temperatures during SSWs and VIs for simulations VARO3, FIXO3, and their differences. During SSWs, the temperatures exhibit a warming center at 10 hPa with a downward propagating structure (Figures 5a and 5b), similar to observation-based studies (Hong and Reichler, 2021a; Limpasuvan et al., 2004). As with ozone, this warming is primarily a consequence of the intensified downwelling branch of the BDC during SSWs and the associated adiabatic warming.\u003c/p\u003e\n\u003cp\u003eComparing the temperatures between the two simulations, the warm anomalies in VARO3 last somewhat longer than in FIXO3. This is more clearly seen in Figure 5c, which displays the temperature differences between the two simulations. The simulation with interactive ozone shows a small (0.05 to 0.1 K) but significant warming difference in the lower stratosphere 30 to 90 days after event onset, consistent with the increase in ozone shortwave heating (Figure 4). The timing of the warming difference is somewhat delayed with respect to the time of the maximum ozone heating (Figure 4c), reflecting the thermal inertia of the atmosphere. VARO3 and FIXO3 also show some robust and statistically significant temperature differences before the onset date, a point to which we come back later in our discussion.\u003c/p\u003e\n\u003cp\u003eIn contrast to SSWs, VIs are associated with a weaker BDC, less adiabatic warming, and hence temperature cooling (Figures 5d and 5e). Compared to the warming during SSWs, this cooling has a much broader and more persistent structure, reflecting dynamical differences between the two opposing circulation events. VIs are not associated with abrupt changes in planetary wave activity like SSWs, but with more gradual and long-lasting reductions in upward planetary wave propagation that start long before the actual onset date (Figures S2d and S2e) (Hong and Reichler, 2021a), leading to much broader signals than SSWs.\u003c/p\u003e\n\u003cp\u003eComparing the cooling during VIs between VARO3 and FIXO3, it becomes clear that interactive ozone enhances its amplitude and persistence. This can be better seen from the differences in cooling in Figure 5f. As expected from the differences in shortwave heating (Figure 4d), there is a rather strong (-0.2 to -0.3 K) and significant additional cooling in VARO3 compared to FIXO3, mostly limited to the time after event onset. Compared to the additional heating during SSWs (Figure 5c), the magnitude of this extra cooling is about 3-6 times larger. This is a consequence of the difference in the ozone perturbations, which are stronger and more persistent during VIs than during SSWs.\u003c/p\u003e\n\u003cp\u003eWe next discuss how interactive ozone modulates the response of the stratospheric polar vortex to SSWs and VIs. This is presented in Figure 6 in terms of U60, the zonal-mean zonal wind at 60\u0026ordm;N. The weakening of the polar vortex in the aftermath of SSWs is stronger in VARO3 (Figure 6a) compared to FIXO3 (Figure 6b). The difference plot between the two (Figure 6c) shows additional vortex weakening from ozone from day 30 to 90, which is temporally consistent with the additional polar cap warming seen in Figure 5c and dynamically consistent with the thermal wind relationship and the reduction of the meridional temperature gradient by the extra heating. Compared to the mean reduction in vortex strength at day 30 after SSWs (~3 m/s), the magnitude of this ozone-related extra vortex weakening is quite sizable (~1 m/s). An analogous structure of weakening U60 after SSWs caused by interactive ozone has been shown by the CCM study of Haase and Matthes (2019, their Figure 8), reinforcing the findings from our simulations.\u003c/p\u003e\n\u003cp\u003eDuring VIs, the polar vortex strengthens (Figure 6d-e), and this strengthening is amplified by interactive ozone (Figure 6f). Since the extra cooling after VIs has a larger magnitude (Figure 5f) than the warming after SSWs (Figure 5c), the thermal wind relationship predicts that the circulation change from interactive ozone must also be larger for VIs than for SSWs. This is confirmed by comparing Figure 6f with Figure 6c. The ozone-related extra strengthening of the vortex following VIs is large enough to create the previously shown 5-day delay in the mean break-up date of the polar vortex (Table 1). An ozone effect on the vortex break-up date after SSWs could not be detected, likely because during SSWs the ozone influence on the vortex is rather weak.\u003c/p\u003e\n\u003cp\u003eSome previous CCM studies described a negative feedback between the dynamics and ozone in the stratosphere (Lin et al., 2017; Haase and Matthes, 2019). This feedback involves the modulation of upward propagating planetary waves by the varying atmospheric background winds (Charney and Drazin, 1961). For example, an initial strengthening of the polar vortex (e.g., from ozone depletion) would increase the westerly background winds, and, if the winds are not too strong, favor the planetary wave propagation upward. This would weaken the polar vortex, intensify the BDC, transport more ozone into the polar regions, and overall counteract the initial reasons for the changes. Hence, this would be a negative feedback.\u003c/p\u003e\n\u003cp\u003eHaase and Matthes (2019) found that using interactive ozone in a CCM strengthens the polar vortex in early winter and spring, and that the spring strengthening is connected to a negative feedback mechanism. In contrast, our study finds that the effects of interactive ozone outside the spring season are negligibly small (Figures 1 and 2), and that interactive ozone during spring amplifies the polar vortex anomalies. Hence, our study does not support the relevance of this negative feedback.\u003c/p\u003e\n\u003cp\u003eWe investigated whether we could at least identify some elements of this negative feedback in our simulations. As shown in Figures S2d and S2e, VI events are followed by an increase in upward planetary wave propagation, indicated by the positive anomaly of the vertical component of the Eliassen-Palm flux. The difference between VARO3 and FIXO3 (Figure S2f) is quite noisy but shows an anomaly difference that is generally somewhat negative, suggesting that interactive ozone slightly reduces the upward wave propagation after VIs. Although these changes are not statistically significant, they would further decrease the strength of the BDC and result in a positive feedback.\u003c/p\u003e\n\u003cp\u003eThere are several possible reasons for why we are unable to detect this negative feedback. For example, Haase and Matthes (2019) based their study on climatological (monthly) mean values and focused on the influence of spring ozone depletion on the dynamics of the vortex breakdown. Our study, on the other hand, focused on late-winter extreme stratospheric circulation events and the anomalies that follow. Additionally, for the negative feedback to work, the background winds must be weak, a condition that usually holds in spring before the vortex breaks down. It is, however, questionable whether this is also true in our case, because VIs are followed by relatively strong westerlies (Figure 6).\u003c/p\u003e\n\u003cp\u003ee. Surface impacts\u003c/p\u003e\n\u003cp\u003eIt is well known that the dynamical interaction of the stratospheric polar vortex with the tropospheric circulation affects the surface, particularly over the North Atlantic (Baldwin and Dunkerton, 2001; Kidston et al., 2015). Specifically, SSWs are associated with a more negative phase of the North Atlantic Oscillation (NAO), while VIs are linked to a more positive NAO phase. The more practical question to be addressed in this section is whether the ozone-induced additional perturbations of the polar vortex are strong enough to cause detectable impacts at the surface, or in other words, whether interactive ozone matters for the simulation and prediction of tropospheric weather and climate.\u003c/p\u003e\n\u003cp\u003eOur analysis focuses on changes in sea level pressure (SLP) because, in this idealized model, this is the most meaningful surface quantity. Figure 7 presents time-mean SLP anomaly composites for the February-March stratospheric circulation events discussed previously. The selected time-mean interval spans from day 30 to 90 after event onset, capturing the period of maximum stratospheric circulation anomalies induced by interactive ozone (see Figures 6c and 6f).\u003c/p\u003e\n\u003cp\u003eSSWs in both VARO3 and FIXO3 are followed by a negative NAO over the North Atlantic (Figures 7a and 7b), but the associated SLP anomalies are weaker than in previous CCM-based studies (e.g., Oehrlein et al., 2020). Besides differences regarding the averaging period, this discrepancy may be due to the simplified nature of our model, which does not reproduce the feedback between the polar vortex and the tropospheric circulation in its full strength. Nevertheless, the negative NAO after SSWs is clearer in VARO3 than in FIXO3. This is likely a consequence of the additional shortwave heating from interactive ozone, amplifying and extending the lifetime of the SSW perturbations in the stratosphere, and thereby increasing their downward effect onto the surface. This can also be seen from the differences between VARO3 and FIXO3 after SSWs (Figure 7c), although the differences are not significant everywhere. The more pronounced negative NAO in VARO3 is consistent with findings from previous studies using full CCMs (Haase and Matthes, 2019; Oehrlein et al., 2020).\u003c/p\u003e\n\u003cp\u003eIn contrast to SSWs, both simulations show that VIs are followed by a positive NAO (Figures 7d and 7e), with SLP magnitudes generally larger than after SSWs. This finding contrasts with Oehrlein et al. (2020), who reported stronger SLP anomalies following SSWs compared to VIs in their CCM study. Differences in the definition of strong polar vortex events may contribute to this discrepancy. More importantly, however, our model shows that interactive ozone enhances the positive phase of the NAO (Figure 7f), consistent with the ozone-related extra strengthening of the polar vortex (Figure 6f).\u003c/p\u003e\n\u003cp\u003eFinally, returning to Figure 6, we find that interactive ozone also generates signals in the stratosphere prior to SSW and VI events. For instance, at -60 to -30 days before VI events, the polar vortex is weaker in VARO3 compared to FIXO3 (Figure 6f), leading to a less positive NAO in VARO3 than in FIXO3 (not shown). The typical reduction in upward directed wave activity that precedes VIs is also weaker in VARO3 than in FIXO3 (Figure S2), resulting in a reduced acceleration of the polar vortex (Figure S3). While the reasons for these differences are not fully understood, shortwave radiative processes over the polar cap must be ruled out because, during this time of the year (December-January), there is little to no sunlight over this region. Therefore, the interaction of stratospheric ozone with shortwave radiation and circulation over the lower latitudes is a plausible explanation. A possible mechanism could be the interaction of ozone with planetary waves, which weakens the polar vortex in the middle to lower stratosphere (Albers and Nathan, 2012). However, addressing this issue requires additional research and must be left to future studies.\u003c/p\u003e"},{"header":"4 Summary and discussion","content":"\u003cp\u003eThis study used an idealized general circulation model with a simplified ozone and radiation parameterization to investigate the interaction of ozone with the northern wintertime stratospheric polar vortex. Two long simulations were performed: one in which ozone is allowed to freely evolve and interact with the circulation in dynamically consistent ways (VARO3), and one in which the daily-evolving but annually-repeating climatological mean ozone distribution of VARO3 is prescribed to the model (FIXO3). The study focused on years with extreme circulation events during February and March, where the polar vortex is either weaker and warmer (SSWs) or stronger and colder (VIs) than normal. By comparing the differences between the two simulations, the importance of interactive ozone was assessed.\u003c/p\u003e\n\u003cp\u003eOur findings suggest that compared to using fixed ozone, interactive ozone increases the interannual circulation variability of the Arctic stratosphere by 20-25% during boreal spring (Figure 1) and prolongs the persistence of the NAM index in the lower stratosphere during boreal spring (Figure 2). We further found that interactive ozone amplifies the temperature and circulation anomalies that typically follow late-winter SSW and especially VI events during northern spring. This amplification can be attributed to the ozone anomalies, which are created by the extreme circulation events (SSWs or VIs) during the prior winter (Figures 3 and 4), persist into spring, and reinforce the temperature (Figure 5) and circulation anomalies (Figure 6) of the events. This increases the lifetime of the polar vortex perturbations, extends the persistence time scale of the stratospheric NAM (Figure 2), and increases the surface impact of the stratospheric circulation events (Figure 7). Additionally, the increased persistence accounts for the observed rise in interannual U60 variability during spring (Figure 1) and explains why, after VIs, the mean breakdown date of the polar vortex is delayed by 5 days (Table 1).\u003c/p\u003e\n\u003cp\u003eThe above-described effects are the result of circulation-induced changes in polar ozone. In spring, when there is sufficient sunlight, the changes in ozone create shortwave heating anomalies that reinforce the original anomalies associated with the perturbed polar vortex. Several factors may contribute to the changes in polar ozone:\u003c/p\u003e\n\u003cp\u003e1. VIs are associated with a decrease in upward planetary wave propagation and dissipation, which stabilizes the polar vortex, weakens the downwelling branch of the BDC, and consequently reduces the transport of ozone-rich air into polar latitudes. Conversely, upward planetary wave propagation is increased during SSWs, disturbing the polar vortex, strengthening the BDC, and increasing the ozone transport into polar latitudes.\u003c/p\u003e\n\u003cp\u003e2. The reduced (increased) BDC during VIs (SSWs) leads to anomalous adiabatic cooling (warming). By the thermal wind relationship, this creates a dynamical response that further strengthens (weakens) the polar vortex. This reduces (increases) the meridional mixing of polar air with relatively ozone-rich surrounding air, contributing to a further decrease (increase) in polar ozone.\u003c/p\u003e\n\u003cp\u003e3. The cooling (warming) associated with VIs (SSWs) enhances (decreases) catalytic ozone depletion and further reduces (increases) ozone levels.\u003c/p\u003e\n\u003cp\u003eThe combined changes in ozone create shortwave heating anomalies that reinforce the original temperature and circulation anomalies associated with the perturbed polar vortex. However, we hesitate to label this effect as a positive feedback. The primary driver of the changes in ozone is likely the anomalous transport by the BDC. While changes in ozone do amplify the anomalies in polar vortex strength, a true feedback loop would require the vortex anomalies to modify ozone in turn. This could involve additional factors, such as meridional mixing and catalytic ozone depletion, but we believe that the transport-induced changes in ozone by the BDC are the most significant.\u003c/p\u003e\n\u003cp\u003eThe results from our study mostly corroborate and extend findings from similar studies using more complex CCMs. However, we also observed some discrepancies compared to some previous studies. For example, we were unable to identify the negative feedback described by Lin et al. (2017) and Haase and Matthes (2019). Further, the perturbed signals in our study were generally weaker than those found in studies using full CCMs, especially at the surface. Some of these differences may be due to the simplifying assumptions made in our model. For instance, our model underestimates the strength of the dynamical downward influence of the stratosphere on the troposphere, a problem which we suspect is systemic to models with Held–Suarez forcing. Another limitation of our model may be the linear photochemical ozone scheme. In this scheme, ozone is relaxed towards a prescribed ozone climatology at predefined time scales (Hong and Reichler, 2021b), which may not always match the real persistence of the circulation-induced ozone anomalies.\u003c/p\u003e\n\u003cp\u003eThis study presents several key take-home messages. Firstly, the SCDM is a valuable tool for studying the fundamental interactions between ozone and stratospheric dynamics. It effectively captures the essential physical principles of these interactions while operating at a fraction of the cost of more complex models. Secondly, our study shows that interactive ozone amplifies the effects of stratospheric circulation anomalies during spring. In contrast, other studies suggest that interactive ozone might moderate these effects. Thirdly, all studies agree that the interaction between ozone and stratospheric circulation has substantial effects and is crucial for climate predictions on sub-seasonal to multi-decadal time scales. Fourthly, the differences between our findings and those of previous studies indicate that there are still significant uncertainties in understanding the ozone-circulation interaction. This underscores the necessity for additional research to reconcile these conflicting results and enhance our understanding of the underlying mechanisms.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eAcknowledgments.\u003c/p\u003e\n\u003cp\u003eWe thank the National Science Foundation (Grants 1446292 and 2103013) and the Department of Atmospheric Sciences at the University of Utah for their support. The use of the computing infrastructure from the Center for High Performance Computing at the University of Utah is gratefully acknowledged. We also thank the Postdoctoral Scholar Program of the Academia Sinica and the Research Center for Environmental Changes for their support.\u003c/p\u003e\n\u003cp\u003eData Availability Statement.\u003c/p\u003e\n\u003cp\u003eThe SCDM simulation data can be made available upon request.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAlbers, J. R., and Nathan, T. R.: Pathways for communicating the effects of stratospheric ozone to the polar vortex: Role of zonally asymmetric ozone, J. Atmos. Sci., 69, 785\u0026ndash;801, https://doi.org/10.1175/JAS-D-11-0126.1, 2012.\u003c/li\u003e\n \u003cli\u003eBaldwin, M. P., and Dunkerton, T. J.: Stratospheric harbingers of anomalous weather regimes, Science, 294, 581\u0026ndash;584, https://doi.org/10.1126/science.1063315, 2001.\u003c/li\u003e\n \u003cli\u003eBosilovich, M. G., Akella, S., Coy, L., Cullather, R., Draper, C., Gelaro, R., Kovach, R., Liu, Q., Molod, A., Norris, P., Wargan, K., Chao, W., Reichle, R., Takacs, L., Vikhliaev, Y., Bloom, S., Collow, A., Firth, S., Labows, G., Partyka, G., Pawson, S., Reale, O., Schubert, S. D., and Suarez, M.: MERRA-2: Initial Evaluation of the Climate, Technical Report Series on Global Modeling and Data Assimilation, Tech. Rep. NASA/TM-2015-104606, availabe at: http://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/docs/ (last access: 13 January 2020), 2015.\u003c/li\u003e\n \u003cli\u003eButchart, N.: The Brewer-Dobson circulation, Rev. Geophys., 52, 157\u0026ndash;184, https://doi.ogr/10.1002/2013RG000448, 2014.\u003c/li\u003e\n \u003cli\u003eButler, A. H., Sjoberg, J. P., Seidel, D. J., and Rosenlof, K. H.: A sudden stratospheric warming compendium, Earth Syst. Sci. Data, 9, 63\u0026ndash;76, https://doi.org/10.5194/essd-9-63-2017, 2017.\u003c/li\u003e\n \u003cli\u003ede la C\u0026aacute;mara, A., Abalos, M., Hitchcock, P., Calvo, N., and Garcia, R. R.: Response of Arctic ozone to sudden stratospheric warmings, Atmos. Chem. Phys., 18, 16499\u0026ndash;16513, https://doi.org/10.5194/acp-18-16499-2018, 2018.\u003c/li\u003e\n \u003cli\u003eCariolle, D., and Teyss\u0026egrave;dre, H.: A revised linear ozone photochemistry parameterization for use in transport and general circulation models: multi-annual simulations, Atmos. Chem. Phys., 7, 2183\u0026ndash;2196, https://doi.org/10.5194/acp-7-2183-2007, 2007.\u003c/li\u003e\n \u003cli\u003eCharlton, A. J., and Polvani, L. M.: A new look at stratospheric sudden warmings. Part I: Climatology and modeling benchmarks, J. Clim., 20, 449\u0026ndash;469, https://doi.org/10.1175/JCLI3996.1, 2007.\u003c/li\u003e\n \u003cli\u003eCharney, J. G., and Drazin, P. G.: Propagation of planetary-scale disturbances from the lower into the upper atmosphere, J. Geophys. Res., 66, 83\u0026ndash;109, https://doi.org/10.1029/JZ066i001p00083, 1961.\u003c/li\u003e\n \u003cli\u003eCicerone, R. J.: Changes in stratospheric ozone, Science, 237, 35\u0026ndash;42, https://doi.org/10.1126/science.237.4810.35, 1987.\u003c/li\u003e\n \u003cli\u003eCompo, G. P., Whitaker, J. S., Sardeshmukh, P. D., Matsui, N., Allan, R. J., Yin, X., Gleason, B. E., Jr., Vose, R. S., Rutledge, G., Bessemoulin, P., Br\u0026ouml;nnimann, S., Brunet, M., Crouthamel, R. I., Grant, A. N., Groisman, P. Y., Jones, P. D., Kruk, M. C., Kruger, A. C., Marshall, G. J., Maugeri, M., Mok, H. Y., Nordli, \u0026Oslash;., Ross, T. F., Trigo, R. M., Wang, X. L., Woodruff, S. D., and Worley, S. J.: The Twentieth Century Reanalysis Project, Q. J. R. Meteorol. Soc., 137, 1\u0026ndash;28, https://doi.org/10.1002/qj.776, 2011.\u003c/li\u003e\n \u003cli\u003eFriedel, M., Chiodo, G., Stenke, A., Domeisen, D. I. V., and Peter, T.: Effects of Arctic ozone on the stratospheric spring onset and its surface impact, Atmos. Chem. Phys., 22, 13997\u0026ndash;14017, https://doi.org/10.5194/acp-22-13997-2022, 2022.\u003c/li\u003e\n \u003cli\u003eGabriel, A., Peters, D., Kirchner, I., and Graf, H.-F.: Effect of zonally asymmetric ozone on stratospheric temperature and planetary wave propagation, Geophys. Res. Lett., 34, L06897, https://doi.org/10.1029/2006GL028998, 2007.\u003c/li\u003e\n \u003cli\u003eGillett, N. P., and Thompson, D. W. J.: Simulation of recent Southern Hemisphere climate change, Science, 302, 273\u0026ndash;275, https://doi.org/10.1126/science.1087440, 2003.\u003c/li\u003e\n \u003cli\u003eHaase, S., Fricke, J., Kruschke, T., Wahl, S., and Matthes, K.: Sensitivity of the Southern Hemisphere circumpolar jet response to Antarctic ozone depletion: prescribed versus interactive chemistry, Atmos. Chem. Phys., 20, 14043\u0026ndash;14061, https://doi.org/10.5194/acp-20-14043-2020, 2020.\u003c/li\u003e\n \u003cli\u003eHaase, S., and Matthes, K.: The importance of interactive chemistry for stratosphere-troposphere coupling, Atmos. Chem. Phys., 19, 3417\u0026ndash;3432, https://doi.org/10.5194/acp-19-3417-2019, 2019.\u003c/li\u003e\n \u003cli\u003eHartmann, D. L.: Some aspects of the coupling between radiation, chemistry, and dynamics in the stratosphere, J. Geophys. Res., 86, 9631\u0026ndash;9640, https://doi.org/10.1029/JC086iC10p09631, 1981.\u003c/li\u003e\n \u003cli\u003eHarzer, F., Garny, H., Ploeger, F., B\u0026ouml;nisch, H., Hoor, P., and Birner, T.: On the pattern of interannual polar vortex\u0026ndash;ozone co-variability during northern hemispheric winter, Atmos. Chem. Phys., 23, 10661\u0026ndash;10675, https://doi.org/10.5194/acp-23-10661-2023, 2023.\u003c/li\u003e\n \u003cli\u003eHeld, I. M.: The gap between simulation and understanding in climate modeling, Bull. Amer. Meteor. Soc., 86, 1609\u0026ndash;1614, https://doi.org/10.1175/BAMS-86-11-1609, 2005.\u003c/li\u003e\n \u003cli\u003eHeld, I. M., and Suarez, M. J.: A proposal for the intercomparison of the dynamical cores of atmospheric general circulation models, Bull. Amer. Meteor. Soc., 75, 1825\u0026ndash;1830, https://doi.org/10.1175/1520-0477(1994)075%3C1825:APFTIO%3E2.0.CO;2, 1994.\u003c/li\u003e\n \u003cli\u003eHersbach, H., Bell, B., Berrisford, P., Hirahara, S., Hor\u0026aacute;nyi, A., Mu\u0026ntilde;oz-Sabater, J., Nicolas, J., Peubey, C., Radu, R., Schepers, D., Simmons, A., Soci, C., Abdalla, S., Abellan, X., Balsamo, G., Bechtold, P., Biavati, G., Bidlot, J., Bonavita, M., De Chiara, G., Dahlgren, P., Dee, D., Diamantakis, M., Dragani, R., Flemming, J., Forbes, R., Fuentes, M., Geer, A., Haimberger, L., Healy, S., Hogan, R. J., H\u0026oacute;lm, E., Janiskov\u0026aacute;, M., Keeley, S., Laloyaux, P., Lopez, P., Lupu, C., Radnoti, G., de Rosnay, P., Rozum, I., Vamborg, F., Villaume, S., and Th\u0026eacute;paut, J.-N.: The ERA5 global reanalysis, Q. J. Roy. Meteor. Soc., 146, 1999\u0026ndash;2049, 2020.\u003c/li\u003e\n \u003cli\u003eHocke, K., Lainer, M., and Schanz, A.: Composite analysis of a major sudden stratospheric warming, AnGeo. Comm., 33, 783\u0026ndash;788, https://doi.org/10.5194/angeo-33-783-2015, 2015.\u003c/li\u003e\n \u003cli\u003eHong, H.-J. and Reichler, T.: Local and remote response of ozone to Arctic stratospheric circulation extremes, Atmos. Chem. Phys., 21, 1159\u0026ndash;1171, https://doi.org/10.5194/acp-21-1159-2021, 2021a.\u003c/li\u003e\n \u003cli\u003eHong, H.-J. and Reichler, T.: The Simplified Chemistry-Dynamical Model (SCDM V1.0), Geosci. Model Dev., 14, 6647\u0026ndash;6660, https://doi.org/10.5194/gmd-14-6647-2021, 2021b.\u003c/li\u003e\n \u003cli\u003eIvanciu, I., Matthes, K., Wahl, S., Harla\u0026szlig;, J., and Biastoch, A.: Effects of prescribed CMIP6 ozone on simulating the Southern Hemisphere atmospheric circulation response to ozone depletion, Atmos. Chem. Phys., 21, 5777\u0026ndash;5806, https://doi.org/10.5194/acp-21-5777-2021, 2021.\u003c/li\u003e\n \u003cli\u003eKeeble, J., Hassler, B., Banerjee, A., Checa-Garcia, R., Chiodo, G., Davis, S., Eyring, V., Griffiths, P. T., Morgenstern, O., Nowack, P., Zeng, G., Zhang, J., Bodeker, G., Burrows, S., Cameron-Smith, P., Cugnet, D., Danek, C., Deushi, M., Horowitz, L. W., Kubin, A., Li, L., Lohmann, G., Michou, M., Mills, M. J., Nabat, P., Olivi\u0026eacute;, D., Park, S., Seland, \u0026Oslash;., Stoll, J., Wieners, K.-H., and Wu, T.: Evaluating stratospheric ozone and water vapour changes in CMIP6 models from 1850 to 2100, Atmos. Chem. Phys., 21, 5015\u0026ndash;5061, https://doi.org/10.5194/acp-21-5015-2021, 2021.\u003c/li\u003e\n \u003cli\u003eKidston, J., Scaife, A. A., Hardiman, S. C., Mitchell, D. M., Butchart, N., Baldwin, M. P., and Gray, L. J.: Stratospheric influence on tropospheric jet streams, storm tracks and surface weather, Nature Geosci., 8, 433\u0026ndash;440, https://doi.org/10.1038/ngeo2424, 2015.\u003c/li\u003e\n \u003cli\u003eKim, J., and Reichler, T.: Quantifying the uncertainty of the annular mode time scale and the role of the stratosphere, Clim. Dyn., 47, 637\u0026ndash;649, https://doi.org/10.1007/s00382-015-2860-2, 2016.\u003c/li\u003e\n \u003cli\u003eLacis, A. A., and Hansen, J. E.: A parameterization for the absorption of solar radiation in the earth\u0026rsquo;s atmosphere, J. Atmos. Sci., 31, 118\u0026ndash;133, https://doi.org/10.1175/1520-0469(1974)031%3C0118:APFTAO%3E2.0.CO;2, 1974.\u003c/li\u003e\n \u003cli\u003eLi, F., Vikhliaev, Y. V., Newman, P. A., Pawson, S., Perlwitz, J., Waugh, D. W., and Douglass, A. R.: Impacts of interactive stratospheric chemistry on Antarctic and Southern Ocean climate change in the Goddard Earth Observing System, version 5 (GEOS-5), J. Clim., 29, 3199\u0026ndash;3218, https://doi.org/https://doi.org/10.1175/JCLI-D-15-0572.1, 2016.\u003c/li\u003e\n \u003cli\u003eLimpasuvan, V., Hartmann, D. L., Thompson, D. W. J., Jeev, K., and Yung, Y. L.: Stratosphere-troposphere evolution during polar vortex intensification, J. Geophys. Res., 110, D24101, https://doi.org/10.1029/2005JD006302, 2005.\u003c/li\u003e\n \u003cli\u003eLimpasuvan, V., Thompson, D. W. J., and Hartmann, D. L.: The life cycle of the Northern Hemisphere sudden stratospheric warmings, J. Clim., 17, 2584\u0026ndash;2596, https://doi.org/10.1175/1520-0442(2004)017%3C2584:TLCOTN%3E2.0.CO;2, 2004.\u003c/li\u003e\n \u003cli\u003eLin, P., Paynter, D., Polvani, L., Correa, G. J. P., Ming, Y., and Ramaswamy, V.: Dependence of model-simulated response to ozone depletion on stratospheric polar vortex climatology, Geophys. Res. Lett., 44, 6391\u0026ndash;6398, doi:10.1002/2017GL073862, 2017.\u003c/li\u003e\n \u003cli\u003eLubis, S. W., Silverman, V., Matthes, K., Harnik, N., Omrani, N.-E., and Wahl, S.: How does downward planetary wave coupling affect polar stratospheric ozone in the Arctic winter stratosphere?, Atmos. Chem. Phys., 17, 2437\u0026ndash;2458, https://doi.org/10.5194/acp-17-2437-2017, 2017.\u003c/li\u003e\n \u003cli\u003eManney, G. L., Livesey, N. J., Santee, M. L., Froidevaux, L., Lambert, A., Lawrence, Z. D., Mill\u0026aacute;n, L. F., Neu, J. L., Read, W. G., Schwartz, M. J., and Fuller, R. A.: Record-low Arctic stratospheric ozone in 2020: MLS observations of chemical processes and comparisons with previous extreme winters, Geophys. Res. Lett., 47, e2020GL089063, https://doi.org/10.1029/2020GL089063, 2020.\u003c/li\u003e\n \u003cli\u003eManney, G. L., Santee, M. L., Rex, M., Livesey, N. J., Pitts, M. C., Veefkind, P., Nash, E. R., Wohltmann, I., Lehmann, R., Froidevaux, L., Poole, L. R., Schoeberl, M. R., Haffner, D. P., Davies, J., Dorokhov, V., Gernandt, H., Johnson, B., Kivi, R., Kyr\u0026ouml;, E., Larsen, N., Levelt, P. F., Makshtas, A., McElroy, C. T., Nakajima, H., Parrondo, M. C., Tarasick, D. W., Gathen, P., Walker, K. A., and Zinoviev, N. S.: Unprecedented Arctic ozone loss in 2011, Nature, 478, 469\u0026ndash;475, https://doi.org/10.1038/nature10556, 2011.\u003c/li\u003e\n \u003cli\u003eMcCormack, J. P., Eckermann, S. D., Siskind, D. E., and McGee, T. J.: CHEM2D-OPP: A new linearized gas-phase ozone photochemistry parameterization for high-altitude NWP and climate models, Atmos. Chem. Phys., 6, 4943\u0026ndash;4972, https://doi.org/10.5194/acp-6-4943-2006, 2006.\u003c/li\u003e\n \u003cli\u003eMonge-Sanz, B. M., Bozzo, A., Byrne, N., Chipperfield, M. P., Diamantakis, M., Flemming, J., Gray, L. J., Hogan, R. J., Jones, L., Magnusson, L., Polichtchouk, I., Shepherd, T. G., Wedi, N., and Weisheimer, A.: A stratospheric prognostic ozone for seamless Earth system models: performance, impacts and future, Atmos. Chem. Phys., 22, 4277\u0026ndash;4302, https://doi.org/10.5194/acp-22-4277-2022, 2022.\u003c/li\u003e\n \u003cli\u003eNathan, T. R., and Cordero, E. C.: An ozone-modified refractive index for vertically propagating planetary waves, J. Geophys. Res., 112, D02105, https://doi.org/10.1029/2006JD007357, 2007.\u003c/li\u003e\n \u003cli\u003eOehrlein, J., Chiodo, G., and Polvani, L. M.: The effect of interactive ozone chemistry on weak and strong stratospheric polar vortex events, Atmos. Chem. Phys., 20, 10531\u0026ndash;10544, https://doi.org/10.5194/acp-20-10531-2020, 2020.\u003c/li\u003e\n \u003cli\u003eRae, C. D., Keeble, J., Hitchcock, P., and Pyle, J. A.: Prescribing zonally asymmetric ozone climatologies in climate models: Performance compared to a chemistry‐climate model, J. Adv. Model. Earth Syst., 11, 918\u0026ndash;933, https://doi.org/10.1029/2018MS001478, 2019.\u003c/li\u003e\n \u003cli\u003eRandel, W. J., and Wu, F.: Cooling of the Arctic and Antarctic polar stratospheres due to ozone depletion, J. Clim., 12, 1467\u0026ndash;1479, https://doi.org/10.1175/1520-0442(1999)012%3C1467:COTAAA%3E2.0.CO;2, 1999.\u003c/li\u003e\n \u003cli\u003eRevell, L. E., Robertson, F., Douglas, H., Morgenstern, O., and Frame, D.: Influence of ozone forcing on 21st century Southern Hemisphere surface westerlies in CMIP6 models, Geophys. Res. Lett., 49, e2022GL098252, https://doi.org/10.1029/2022GL098252, 2022.\u003c/li\u003e\n \u003cli\u003eRieder, H. E., Chiodo, G., Fritzer, J., Wienerroither, C., and Polvani, L. M.: Is interactive ozone chemistry important to represent polar cap stratospheric temperature variability in Earth-System Models?, Environ. Res. Lett., 14, 044026, https://doi.org/10.1088/1748-9326/ab07ff, 2019.\u003c/li\u003e\n \u003cli\u003eRomanowsky, E., Handorf, D., Jaiser, R., Wohltmann, I., Dorn, W., Ukita, J., Cohen, J., Dethloff, K., and Rex, M.: The role of stratospheric ozone for Arctic-midlatitude linkages, Sci Rep, 9, 7962, https://doi.org/10.1038/s41598-019-43823-1, 2019.\u003c/li\u003e\n \u003cli\u003eSaha, S., Moorthi, S., Wu, X., Wang, J., Nadiga, S., Tripp, P., Behringer, D., Hou, Y., Chuang, H., Iredell, M., Ek, M., Meng, J., Yang, R., Mendez, M. P., van den Dool, H., Zhang, Q., Wang, W., Chen, M., and Becker, E.: The NCEP Climate Forecast System Version 2, J. Clim., 27(6), 2185\u0026ndash;2208, https://doi.org/10.1175/JCLI-D-12-00823.1, 2014.\u003c/li\u003e\n \u003cli\u003eSolomon, S.: Stratospheric ozone depletion: A review of concepts and history, Rev. Geophys., 37, 275\u0026ndash;316, https://doi.org/10.1029/1999RG900008, 1999.\u003c/li\u003e\n \u003cli\u003eStolarski, R. S., and Cicerone, R. J.: Stratospheric chlorine: a possible sink for ozone, Can. J. Chem., 52, 1610\u0026ndash;1615, https://doi.org/10.1139/v74-233, 1974.\u003c/li\u003e\n \u003cli\u003eTegtmeier, S., Fioletov, V. E., and Shepherd, T. G.: A global picture of the seasonal persistence of stratospheric ozone anomalies, J. Geophys. Res., 115, D18119, https://doi.org/10.1029/2009JD013011, 2010.\u003c/li\u003e\n \u003cli\u003eThompson, D. W. J., and Solomon, S.: Interpretation of recent Southern Hemisphere climate change, Science, 296, 895\u0026ndash;899, https://doi.org/10.1126/science.1069270, 2002.\u003c/li\u003e\n \u003cli\u003eWallace, J. M., and Hobbs, P. V.: Atmospheric Science, Elsevier Academic Press, Massachusetts, 483 pp, 2006.\u003c/li\u003e\n \u003cli\u003eWu, Z., and Reichler, T.: Towards a more Earth-like circulation in idealized models, J. Adv. Model. Earth Syst, 10, 1458\u0026ndash;1469, https://doi.org/10.1029/2018MS001356, 2018.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[{"identity":"e97a3ecf-79a7-4814-91ec-af0ed523988d","identifier":"10.13039/100000001","name":"National Science Foundation","awardNumber":"1446292 and 2103013","order_by":0}],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"stratosphere, ozone","lastPublishedDoi":"10.21203/rs.3.rs-5626578/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-5626578/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eStratospheric ozone has long been suspected to drive interactions involving chemistry, radiation, and the circulation. However, the significance of these interactions, the underlying mechanisms, and the specific conditions that facilitate them remain poorly understood. In this study, we use a dry-dynamical core model with a simplified linear ozone scheme and a shortwave radiation parameterization to investigate these interactions. Our analysis, based on two long control simulations with either interactive or prescribed ozone, reveals that interactive ozone increases the persistence and interannual variability of the stratospheric circulation during northern spring, a period with sufficient solar radiation over the northern polar cap. This effect is closely linked to late-winter extreme stratospheric circulation events, such as stratospheric sudden warmings (SSWs) and vortex intensifications (VIs). While interactive ozone does not alter the frequency of these events, the ozone perturbations induced by the circulation amplify the associated temperature and wind anomalies. Specifically, late-winter VIs are followed by a colder and more persistent polar vortex in spring when interactive ozone is used, compared to fixed ozone. This results in a five-day delay in the breakdown date of the vortex and a more positive North Atlantic Oscillation at the surface. Although interactive ozone also amplifies perturbations following SSWs, these effects are less pronounced than those observed for VIs. Our findings contribute to a growing body of evidence highlighting the importance of ozone-dynamics interactions for simulating the stratospheric circulation, its variability, and its surface impacts.\u003c/p\u003e","manuscriptTitle":"Arctic Ozone Amplifies Stratospheric Circulation Extremes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-12-13 09:26:14","doi":"10.21203/rs.3.rs-5626578/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"bacc6630-6961-477a-8c85-52682898b7d4","owner":[],"postedDate":"December 13th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":41479836,"name":"Atmospheric Sciences"}],"tags":[],"updatedAt":"2024-12-13T09:26:15+00:00","versionOfRecord":[],"versionCreatedAt":"2024-12-13 09:26:14","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-5626578","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-5626578","identity":"rs-5626578","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}