Sudden Stratospheric Warming Events Research Articles

Opposite spectral properties of Rossby waves during weak and strong stratospheric polar vortex events

Abstract. In this study we provide a systematic characterization of Rossby wave activity during the 25 sudden stratospheric warming (SSW) and 31 strong polar vortex (SPV) events that occurred in the period 1979–2021, identifying the specific tropospheric and stratospheric waves displaying anomalous behaviour during such events. Space–time spectral analysis is applied to ERA5 data for this purpose, so that both the wavenumber and the zonal phase speed of the waves can be assessed. We find that SSW events are associated with a reduction in the phase speed of Rossby waves, first in the stratosphere and then in the troposphere; SPV events are tied to a simultaneous increase of phase speed across vertical levels. Phase speed anomalies become significant around the event and persist for 2–3 weeks afterwards. Changes of Rossby wave properties in the stratosphere during SSW and SPV events are dominated by changes in the background flow, with a systematic reduction or increase, respectively, in eastward propagation of the waves across most wavenumbers. In the troposphere, on the other hand, the effect of the background flow is also complemented by changes in wave properties, with a shift towards higher wavenumbers during SSW events and towards lower wavenumbers for SPV events. The opposite response between SSW and SPV events is also visible in the meridional heat and momentum flux co-spectra, which highlight from a novel perspective the connection between stratospheric Rossby waves and upward propagation of waves.

Impacts of the Sudden Stratospheric Warming on Equatorial Plasma Bubbles: Suppression of EPBs and Quasi-6-Day Oscillations

This study investigates the day-to-day variability of equatorial plasma bubbles (EPBs) over the Atlantic–American region and their connections to atmospheric planetary waves during the sudden stratospheric warming (SSW) event of 2021. The investigation is conducted on the basis of the GOLD (Global Observations of the Limb and Disk) observations, the ICON (Ionospheric Connection Explorer) neutral wind dataset, ionosonde measurements, and simulations from the WACCM-X (Whole Atmosphere Community Climate Model with thermosphere–ionosphere eXtension). We found that the intensity of EPBs was notably reduced by 35% during the SSW compared with the non-SSW period. Furthermore, GOLD observations and ionosonde data show that significant quasi-6-day oscillation (Q6DO) was observed in both the intensity of EPBs and the localized growth rate of Rayleigh–Taylor (R-T) instability during the 2021 SSW event. The analysis of WACCM-X simulations and ICON neutral winds reveals that the Q6DO pattern coincided with an amplification of the quasi-6-day wave (Q6DW) in WACCM-X simulations and noticeable ∼6-day periodicity in ICON zonal winds. The combination of these multi-instrument observations and numerical simulations demonstrates that certain planetary waves like the Q6DW can significantly influence the day-to-day variability of EPBs, especially during the SSW period, through modulating the strength of prereversal enhancement and the growth rate of R-T instability via the wind-driven dynamo. These findings provide novel insights into the connection between atmospheric planetary waves and ionospheric EPBs.

Influence of temperature changes and vertically transported trace species on the structure of MLT region during major SSW events

Sudden stratospheric warming (SSW) events are large-scale dynamic phenomena which can significantly affect the circulation, temperature, and composition of different atmospheric layers. The circulation changes during these events induce variations in the atmospheric neutral and ion densities and cause the vertical transport of various trace species. The severity of effects induced by major SSW events in the mesosphere and lower thermosphere (MLT) region has received less attention than that in the lower atmosphere. The major influence of temperature and vertically transported trace species on the energetics, thermal and compositional structure of the MLT region has been investigated during two major SSW events with elevated stratopause. Variations in the nitric oxide volume emission rates (NO-VER), a measure of Infrared radiative cooling by NO, are reported for the first time in the context of the dynamical changes during events. This study investigates the role of temperature and NO variability on the energetics of the MLT region, particularly during the formation of elevated stratopause. The effects of supplemented NO density on the secondary ozone layer has also been investigated during these events, the anti-correlation between secondary ozone and NO does not conclude on the role of NO in the secondary ozone peak density variations. Notwithstanding the similarity in terms of defining characteristics, both SSW events impact the secondary ozone layer differently. In contrast to earlier studies, it is suggested that along with temperature, the availability of atomic oxygen is the major factor for the observed variation in secondary ozone during the SSW events.

Quasi‐5‐Day Oscillations During Arctic Major Sudden Stratospheric Warmings From 2005 to 2021

AbstractTraveling quasi‐5‐day oscillations (Q5DOs) with different wavenumbers are independently observed in the mesosphere and the lower thermosphere during many recent sudden stratospheric warming (SSW) events, but their common activities during SSWs are still unclear. Based on the geopotential height data measured by the Aura/Microwave Limb Sounder (MLS) from August 2004 to March 2021, we statistically investigate the characteristics of the Q5DOs during eight Arctic major SSW events. The amplitudes of the Q5DOs are obtained by a new fitting method, which inhibits the effect of rapid changes in stationary planetary waves during SSWs. Our results reveal a robust feature that Q5DOs were enhanced during all interested SSW events. Our analysis indicates that eastward and westward propagating Q5DOs can be simultaneously enhanced during SSWs. Additionally, the wavenumbers of the enhanced Q5DOs are found to be associated with the geometry of polar vortices. Extremely strong westward Q5DOs with wavenumber 2 are consistently observed during split‐type major SSWs.

Connections between low- and high- frequency variabilities of stratospheric northern annular mode and Arctic ozone depletion

Previous studies have demonstrated a dynamical linkage between the ozone and stratospheric polar vortex strength, but only a few have mentioned the persistence of the anomalous vortex. This study uses the complete ensemble empirical mode decomposition with adaptive noise to decompose the winter stratospheric northern annular mode (NAM) variabilities into relatively low frequencies (>4 months) and high frequencies (<2 months) (denoted as NAML and NAMH) and investigates their relationship with the Arctic ozone concentration in March. A closer relationship is found between the Arctic ozone and the NAML, i.e. a persistently strong stratospheric polar vortex in winter (especially February–March) is more critical than a short-lasting extremely strong vortex in contributing to Arctic ozone depletion. We find that a negative NAMH or major stratospheric sudden warming event in early winter could be a precursor for the anomalous depletion of Arctic ozone in March. The NAML changes are further related to the warm North Pacific sea surface temperature (SST) anomalies and ‘central-type’ El Niño-like or La Niña-like SST anomalies in early winter months, as well as cold North Atlantic SST anomalies and higher sea ice concentration in the Barents–Kara Sea from late-autumn to early-spring.

Analysis of Planetary Scale Waves Using Idealized Sudden Stratospheric Warming Simulations in Different Dynamical Cores

AbstractPlanetary waves from the troposphere are known to play an important role in sudden stratospheric warming (SSW). To evaluate the representation of large‐scale waves in idealized SSW simulations, three dynamical cores of the National Center for Atmospheric Research Community Atmosphere Model were tested in this study: the Eulerian (EUL) spectral‐transform, finite‐volume (FV), and spectral element (SE) models. Notable differences were observed among the dynamical cores, with FV being unable to generate major SSWs and simulating minor SSWs less effectively than the other models. Wave decomposition analysis revealed distinct planetary wave propagation patterns during the development of each event. Zonal Wave Number 2 wave activities primarily determined SSW types, and ZWN1 led SSWs to recovery during the ensuing periods. However, FV failed to adequately propagate large‐scale waves in minor SSW events, preventing the reversal of stratospheric zonal‐mean zonal winds. Interestingly, FV showed decreased upward Eliassen–Palm flux compared to that of other dynamical cores, even during climatology. Additional tests were performed to examine the reasons for FV's atypical results, but the dynamic impacts on planetary waves remain poorly understood.

Effects of the Northern Hemisphere sudden stratospheric warmings on the Sporadic-E layers in the Brazilian sector

Tidal and Planetary Wave (PWs) amplitudes are strongly influenced by Sudden Stratospheric Warming (SSW) events. A nonlinear interaction between the tidal winds and planetary waves during the SSW may contribute to the intensification of sporadic-E (Es) layers in the lower thermosphere. This work investigated the relationship between SSW events in the Northern Hemisphere and the Es layer occurrence at low latitudes in the Brazilian sector. We used data from digital ionosondes installed in the observatories of Araguatins (ARA, 5.65° S; 48.12° W; dip lat. −5.44°) and São José dos Campos (SJC, 23.18° S; 45.89° W; dip lat. −21.37°) to analyze the Es layers. Additionally, we used the temperature, zonal wind, and PWs data at high latitudes in the Northern Hemisphere during the major SSW event that occurred in February/2018 and during the events of Dec/2018–Jan/2019 and Dec/2020–Jan/2021. The results showed a maximum frequency peak of 20 MHz (∼5 × 106 electrons.cm−3) at ARA and SJC during these SSW events. The large values of ftEs, fbEs, and electronic densities were observed between 100 and 115 km height in the Esf/l type layers during daytime or nighttime periods. The results also showed that the number of large values of ftEs, fbEs, and electronic density of the Es layer was much higher in ARA than in SJC, in general. The wavelet power spectrum analyses of the ftEs and fbEs showed a periodicity of 2-days before and after the central day of the SSWs events at the station of ARA, with three prominent peaks in the 2018/2019 event. At the SJC station the quasi-2-day periodicity in the wavelet analyses of the ftEs was observed after the central day in all three SSW events, with a peak before the central day during the 2020/2021 event.

Technical note: Multi-year changes in the Brewer–Dobson circulation from Halogen Occultation Experiment (HALOE) methane

Abstract. This study makes use of Halogen Occultation Experiment (HALOE) methane (CH4) in a search for multi-year changes in the Brewer–Dobson circulation (BDC). Changes in CH4 are determined for three successive 5-year time spans from 1992 to 2005, and there are significant differences between them. There is a clear separation between the changes in the Northern Hemisphere near 30 hPa and at the transition of the shallow and deep branches of the BDC. The CH4 changes are positive and large in the shallow branch following the eruption of Pinatubo, but they then decrease and agree with tropospheric trends in the late 1990s and early 2000s. CH4 decreases in the upper part of the deep branch from 1992 to 1997 or following the eruption of Pinatubo. CH4 continues to decrease in the deep branch in the late 1990s but then increases in the early 2000s, although those changes are small compared with the seasonal and interannual variations of CH4. Multi-year changes are due, in part, to wave forcings during the El Niño–Southern Oscillation (ENSO) of 1997–1998 and beyond and to episodic, sudden stratospheric warming (SSW) events during both time spans. It is concluded that time series of HALOE CH4 provide effective tracer diagnostics for studies of the nature of the BDC from 1992 to 2005.

The Impact of the Tropical Sea Surface Temperature Variability on the Dynamical Processes and Ozone Layer in the Arctic Atmosphere

Tropical sea surface temperature (SST) variability, mainly driven by the El Niño–Southern Oscillation (ENSO), influences the atmospheric circulation and hence the transport of heat and chemical species in both the troposphere and stratosphere. This paper uses Met Office, ERA5 and MERRA2 reanalysis data to examine the impact of SST variability on the dynamics of the polar stratosphere and ozone layer over the period from 1980 to 2020. Particular attention is paid to studying the differences in the influence of different types of ENSO (East Pacific (EP) and Central Pacific (CP)) for the El Niño and La Niña phases. It is shown that during the CP El Niño, the zonal wind weakens more strongly and changes direction more often than during the EP El Niño, and the CP El Niño leads to a more rapid decay of the polar vortex (PV), an increase in stratospheric air temperature and an increase in the concentration and total column ozone than during EP El Niño. For the CP La Niña, the PV is more stable, which often leads to a significant decrease in Arctic ozone. During EP La Niña, powerful sudden stratospheric warming events are often observed, which lead to the destruction of PV and an increase in column ozone.

Impact of sudden stratospheric warming on middle atmospheric circulation in the southern hemisphere: A comparative study

A comparative study on the impact of rare Southern Hemisphere (SH) Sudden Stratospheric Warmings (SSW) on the middle atmospheric circulation is investigated using a global reanalysis dataset. Since the SH SSW generally occur around spring equinox marking the seasonal transition, so an attempt has been made to isolate the seasonal transition effect from the actual data by carrying out deseasoning to delineate the effects mainly due to the warming. The deseasoned winds are able to extract relatively weak dynamical signatures of SSW at lower altitudes in terms of prominent zonal mean easterly forcing around the peak warming day (PWD) which are not evident from the actual winds. The influence of 2002 SSW seems to reach the troposphere in terms of easterly deseasoned forcing, which is not the case in 2019. Also the deseasoned winds in the stratosphere reveals earlier occurrence of easterly forcing in the extratropical latitudes, which progresses poleward around the PWD indicating a possible tropical precursor to the SH SSW. In general, the actual upper mesospheric wind is dominated by seasonal transition but the deseasoned winds reveal easterly and southerly forcing due to the SSW. Interestingly, the horizontal flow is found to be very different or even opposite in direction at different longitudes indicating uneven longitudinal response of the atmosphere to the warming events across the globe. Overall, the present study provides a detailed and comparative overview of the middle atmospheric circulation in terms of zonal mean flow and concomitant zonal variability during two rare major and minor SSW events in the SH.

A Data-Driven Study of the Drivers of Stratospheric Circulation via Reduced Order Modeling and Data Assimilation

Stratospheric dynamics are strongly affected by the absorption/emission of radiation in the Earth’s atmosphere and Rossby waves that propagate upward from the troposphere, perturbing the zonal flow. Reduced order models of stratospheric wave–zonal interactions, which parameterize these effects, have been used to study interannual variability in stratospheric zonal winds and sudden stratospheric warming (SSW) events. These models are most sensitive to two main parameters: Λ, forcing the mean radiative zonal wind gradient, and h, a perturbation parameter representing the effect of Rossby waves. We take one such reduced order model with 20 years of ECMWF atmospheric reanalysis data and estimate Λ and h using both a particle filter and an ensemble smoother to investigate if the highly-simplified model can accurately reproduce the averaged reanalysis data and which parameter properties may be required to do so. We find that by allowing additional complexity via an unparameterized Λ(t), the model output can closely match the reanalysis data while maintaining behavior consistent with the dynamical properties of the reduced-order model. Furthermore, our analysis shows physical signatures in the parameter estimates around known SSW events. This work provides a data-driven examination of these important parameters representing fundamental stratospheric processes through the lens and tractability of a reduced order model, shown to be physically representative of the relevant atmospheric dynamics.

Mesospheric Water Vapor From SABER as a Tracer for the Residual Mean Circulation During SSW Events

AbstractThe sparse wind observations and reanalysis winds in the mesosphere make it challenging to accurately determine the residual mean meridional circulation (MMC). As winds distribute tracers, an alternative approach is to utilize long‐lived trace species such as water vapor (H2O). The recently released H2O data from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) version 2.07, combined with simulations by the Whole Atmosphere Community Climate Model eXtension with specified dynamics (SD‐WACCM‐X) and with the Data Assimilation Research Testbed (WACCMX + DART), provide an opportunity to assess the accuracy of using H2O isopleths to derive the vertical component of the residual MMC during the 2009 sudden stratospheric warming (SSW) event. In winter, the impact of photochemistry and diffusion on the distribution of mesospheric H2O is negligible compared to advective processes. H2O poleward of 70°N accurately captures the anomalous ascent that occurs a few days prior to the onset of the SSW and the subsequent descent. The derived vertical velocity in SD‐WACCM‐X and WACCMX + DART is qualitatively consistent with SABER observations. However, the derivation of vertical motion from isopleth analysis has limitations at the beginning of 2009 when the meridional transport is stronger than the vertical transport. While measuring winds in the mesosphere is challenging, satellite observations of mesospheric H2O prove to be an effective dynamical tracer during time periods characterized by strong vertical coupling.

Role of Southern Hemisphere sudden stratospheric warming in altering the intensity of Brewer-Dobson circulation and its impact on stratospheric ozone and water vapor

The changes in the intensity of Brewer-Dobson circulation (BDC) in the record-breaking Southern Hemisphere sudden stratospheric warming (SH SSW) event in 2019 are investigated in the present study. Wave driving was observed to be at its highest in 2019 SH SSW, despite the event being classified as a minor warming event. The Eliassen-Palm flux divergence, indicative of wave driving, was observed to be increasing before the SSW, and subsiding afterwards. The stratospheric circulation followed the wave driving and intensified along the warming episode. The resulting stratospheric distribution from Aura Microwave Limb Sounder showed a negative ozone anomaly (∼20%) in the tropical lower stratosphere and a downward propagating positive anomaly in the Southern Hemisphere polar stratosphere around the central dates. The water vapor mixing ratio showed an increase of more than 25% in the polar lower stratosphere and 10% in the tropical upper stratosphere. A cooling of about 5 K was observed in the tropical middle stratosphere. The results indicate that SH SSW can change the intensity of the stratospheric circulation which in turn affects the ozone and water vapor transport from the tropics to the pole.

Precursory Analysis Ensemble Spread Signals That Foreshadow Stratospheric Sudden Warmings

Abstract This study conducts a thorough investigation into the behaviors of analysis ensemble spreads linked to stratospheric sudden warming (SSW) events. A stratosphere-resolving ensemble data assimilation system is used here to document the evolution of analysis spread leading up to a pair of warming events. Precursory signals of the increased ensemble spreads were found a few days prior to two SSW events that occurred during December 2018 and August–September 2019 in the Northern and Southern Hemispheres, respectively. The signals appeared in the upper and middle stratosphere and did not appear at lower heights. When the signals appeared, it was found that both tendency by forecast and analysis increment in a forecast-analysis (data assimilation) cycle simultaneously became large. An empirical orthogonal function analysis showed that the dominant structures of the precursory signals were equivalent barotropic and were 90° out-of-phase with the analysis ensemble-mean field. Over the same period, the upper and middle stratosphere became more susceptible to barotropic instability than in their previous states. We conclude that the differing growth of barotropically unstable modes across ensemble members can amplify spread during the lead-up to SSW events. Significance Statement Winds in the winter stratospheric polar vortex are typically westerly. Occasionally, however, warming over the pole leads to a reversal of the flow through a process known as stratospheric sudden warming. These events are difficult to predict even in state-of-the-art analysis and forecasting systems. In this study, we identify a precursor signal in the form of increased ensemble spread that appears to originate from differing realizations of growing barotropic modes across the ensemble. This signal could serve as a useful forecasting tool by enhancing situational awareness in the lead-up to potential stratospheric sudden warming events.

The Evolution of Solar Tide‐Like Signatures in the Ionospheric Total Electron Content During Major Sudden Stratospheric Warming Events

AbstractBy using total electron content (TEC) from the global ionospheric maps, the solar tide‐like signatures in the ionosphere are explored. We further study how the main components evolve during the 2009 and 2018 major stratospheric sudden warming events (SSWs). The method of a least‐square fit is applied for extracting the solar tide‐like components. The three predominant components are SW2, D0, and SW1, amplitude of which increase in the equatorial ionization anomaly region after the onset of both SSW events, especially in the northern hemisphere. During the SSW events, the solar tide‐like components vary significantly with latitude and their evolutions show hemispherical asymmetries. Each same component presents similar evolutionary trend during both events. The characteristics of ionospheric tide‐like signatures and related mechanisms are discussed. The SW2 tide‐like responses in TEC closely follow the changes in the tidal wind fields in the lower thermosphere, which provide evidences of the atmosphere‐ionosphere coupling during SSW events. In addition, the latitudinal asymmetric distributing of stratospheric ozone and ionospheric TEC background during the SSW may be influence factors for the hemispherical asymmetries in tide‐like signatures responses in TEC.

Reasons for Low Fraction of Arctic Stratospheric Cloud in 2014/2015 Winter

AbstractPolar stratospheric clouds (PSCs) play a key role in Arctic amplification and stratospheric ozone destruction in polar regions. In this paper, we used the CALIPSO data to analyze the spatiotemporal distribution of Arctic PSCs from 2006 to 2021. We found that Arctic PSCs mainly appear in December, peak in late December and early January, disappearing in late February and early March. PSCs can extend from heights near the tropopause to over 25 km. However, there is the lowest fraction of PSCs in the 2014/2015 winter. This study found that the temperature in the 2014/2015 winter was warmer than the 15‐year average temperature, with the lowest temperature slightly below the PSCs formation temperature of about 5 K. The formation of the Ural blocking high accompanied by the poleward propagation of the planetary wave caused a sudden stratospheric warming (SSW) event on 3 January 2015, during which the warm air entered the polar vortex and divided it into two lobes. Additionally, a reduction in SO2 column mass density before the SSW event resulted PSCs occurring with a frequency of only 0.148 and dissipating rapidly in December. Moreover, the concentration of H2O and HNO3 in the gravitational settling process of PSCs decreased by 20–50%, the reduction of condensation nuclei made PSCs with the highest frequency of 0.074 in February appear briefly and then disappear. The chemical and dynamic analysis of PSCs formation is needed to further understand the spatiotemporal distribution of Arctic PSCs and to better predict future Arctic amplification and ozone destruction.

Statistics of sudden stratospheric warmings using a large model ensemble

AbstractUsing a large ensemble of initialised retrospective forecasts (hindcasts) from a seasonal prediction system, we explore various statistics relating to sudden stratospheric warmings (SSWs). Observations show that SSWs occur at a similar frequency during both El Niño and La Niña northern hemisphere winters. This is contrary to expectation, as the stronger stratospheric polar vortex associated with La Niña years might be expected to result in fewer of these extreme breakdowns. Here we show that this similar frequency may have occurred by chance due to the limited sample of years in the observational record. We also show that in these hindcasts, winters with two SSWs, a rare event in the observational record, on average have an increased surface impact. Multiple SSW events occur at a lower rate than expected if events were independent but somewhat surprisingly, our analysis also indicates a risk, albeit small, of winters with three or more SSWs, as yet an unseen event.

Role of Quasi-Biennial oscillation on the link between sudden stratospheric warming and tropical weather events

This paper illustrates the modulation of meteorological parameters over the tropics in the east and west phases of the quasi-biennial oscillation (QBO) during the sudden stratospheric warming (SSW). Twenty years composite of SSW episodes have been analysed, and the results show a teleconnection between northern polar SSW and changes in meteorological parameters throughout tropical troposphere to stratosphere during both the phases of QBO. The tropical troposphere shows different temperature pattern in the two opposite phases of QBO during polar SSW. The lower tropospheric temperature decreases about five days prior to the onset day, persisting as such as for about five days post-onset day, and increases rapidly during the east phase whereas a sudden dip in temperature is observed in the west phase. The easterly wind at the upper tropospheric region is observed to be coupled to the easterly wind in the QBO core region of stratosphere during the easterly phase of QBO whereas they are decoupled in the westerly phase. Prior to the peak polar warming, a strong convective cell develops over the southern hemispheric tropics, and a convective cell develops over northern hemisphere during the peak warming period. This study indicates that during the easterly QBO-SSW period, increasing tropopause easterly wind causes tropopause cooling due to easterly wind's coupling with the QBO core region around the onset day of SSW. As a result, the changes in the tropopause strengthen the Hadley cell circulation thus enhancing the convective activity over the tropical region associated with northern polar SSW. Contrary to the prior knowledge of convection being centred mostly along 5°S–10°S, it is found that other convection band located at around 10°N also produces rainfall in the tropical region.

Skilful predictions of the Summer North Atlantic Oscillation

The Summer North Atlantic Oscillation is the primary mode of atmospheric variability in the North Atlantic region and has a significant influence on regional European, North American and Asian summer climate. However, current dynamical seasonal prediction systems show no significant Summer North Atlantic Oscillation prediction skill, leaving society ill-prepared for extreme summers. Here we show an unexpected role for the stratosphere in driving the Summer North Atlantic Oscillation in both observations and climate prediction systems. The anomalous strength of the lower stratosphere polar vortex in late spring is found to propagate downwards and influence the Summer North Atlantic Oscillation. Windows of opportunity are identified for useful levels of Summer North Atlantic Oscillation prediction skill, both in the 50% of years when the late spring polar vortex is anomalously strong/weak and possibly earlier if a sudden stratospheric warming event occurs in late winter. However, we show that model dynamical signals are spuriously weak, requiring large ensembles to obtain robust signals and we identify a summer ‘signal-to-noise paradox’ as found in winter atmospheric circulation Our results open possibilities for a range of new summer climate services, including for agriculture, water management and health sectors.

The Composite Response of Traveling Planetary Waves in the Middle Atmosphere Surrounding Sudden Stratospheric Warmings through an Overreflection Perspective

Abstract Traveling planetary waves surrounding sudden stratospheric warming events can result from direct propagation from below or in situ generation. They can have significant impacts on the circulation in the mesosphere and lower thermosphere. Our study runs a series of ensembles initialized from the Whole Atmosphere Community Climate Model, version 4, nudged up to 50 km by 6-hourly Modern-Era Retrospective Analysis for Research and Application, version 2, reanalysis to compile a library of sudden stratospheric warming events. To our knowledge, we present the first composite or ensemble study that attempts to link direct propagation and in situ generation by evaluating the wave geometries associated with the overreflection perspective, a framework used to describe how planetary waves interact with critical and turning levels. The present study looks at the evolution of these interactions through the onset of sudden stratospheric warmings with an elevated stratopause (ES-SSWs). Robust and unique features of ES-SSWs are determined by employing an ensemble study that compares ES-SSWs with normal winters. Our study evaluates the production and impacts of westward-propagating, quasi-stationary, and eastward-propagating planetary waves surrounding ES-SSWs. Our results show that eastward-propagating planetary waves are generated within the westward stratospheric wind layer after ES-SSW onset which aids in restoring the eastward stratospheric wind. The interaction of quasi-stationary and westward-propagating waves with the westward stratospheric wind is explored from an overreflection perspective and reaffirms that westward-propagating planetary waves are produced from instabilities at the top of the westward stratospheric wind reversal.