Dynamics of Anomalous Stratospheric Eddy Heat Flux Events in an Idealized Model

Dunn‐Sigouin, Etienne; Shaw, Tiffany A.

doi:10.1175/jas-d-19-0231.1

Cited by 8 publications

(6 citation statements)

References 56 publications

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“…Roughly two thirds of observed SSWs are more consistent with the top‐down category or do not fit into either prototype (i.e., tropospheric wave fluxes are anomalously strong but not extreme). Similar ratios have been observed in modeling studies by White et al (2019) and de la Cámara et al (2019), although results from mechanistic GCM experiments by Dunn‐Sigouin and Shaw (2020) reemphasize the role of tropospheric wave fluxes.…”

Section: Development Of Dynamical Theoriessupporting

confidence: 84%

Sudden Stratospheric Warmings

Baldwin

Ayarzagüena

Birner

et al. 2021

Reviews of Geophysics

310

226

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Sudden stratospheric warmings (SSWs) are impressive fluid dynamical events in which large and rapid temperature increases in the winter polar stratosphere (∼10–50 km) are associated with a complete reversal of the climatological wintertime westerly winds. SSWs are caused by the breaking of planetary‐scale waves that propagate upwards from the troposphere. During an SSW, the polar vortex breaks down, accompanied by rapid descent and warming of air in polar latitudes, mirrored by ascent and cooling above the warming. The rapid warming and descent of the polar air column affect tropospheric weather, shifting jet streams, storm tracks, and the Northern Annular Mode, making cold air outbreaks over North America and Eurasia more likely. SSWs affect the atmosphere above the stratosphere, producing widespread effects on atmospheric chemistry, temperatures, winds, neutral (nonionized) particles and electron densities, and electric fields. These effects span both hemispheres. Given their crucial role in the whole atmosphere, SSWs are also seen as a key process to analyze in climate change studies and subseasonal to seasonal prediction. This work reviews the current knowledge on the most important aspects of SSWs, from the historical background to dynamical processes, modeling, chemistry, and impact on other atmospheric layers.

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Section: Development Of Dynamical Theoriessupporting

confidence: 84%

Sudden Stratospheric Warmings

Baldwin

Ayarzagüena

Birner

et al. 2021

Reviews of Geophysics

310

226

View full text Add to dashboard Cite

show abstract

“…Approximately, once every two years in the Northern Hemisphere during winter, breaking planetary-scale waves rapidly warm the polar stratosphere over several days and split or displace the stratospheric polar vortex—a sudden stratospheric warming (SSW) 9 , 10 . SSWs can be driven by enhanced wave energy propagating upward from the troposphere 11 – 13 , sometimes produced by atmospheric blocking 14 ; by waves generated at the boundary between the troposphere and the stratosphere 15 , 16 ; and by variations in the stratosphere that focus and enhance the effect of otherwise normal wave energy 17 – 21 . While they are dynamically forced events that occur over a matter of days, they can be skillfully predicted even at the seasonal timescale 22 .…”

Section: Introductionmentioning

confidence: 99%

Limited surface impacts of the January 2021 sudden stratospheric warming

et al. 2022

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Subseasonal weather prediction can reduce economic disruption and loss of life, especially during “windows of opportunity” when noteworthy events in the Earth system are followed by characteristic weather patterns. Sudden stratospheric warmings (SSWs), breakdowns of the winter stratospheric polar vortex, are one such event. They often precede warm temperatures in Northern Canada and cold, stormy weather throughout Europe and the United States - including the most recent SSW on January 5th, 2021. Here we assess the drivers of surface weather in the weeks following the SSW through initial condition “scrambling” experiments using the real-time CESM2(WACCM6) Earth system prediction framework. We find that the SSW itself had a limited impact, and that stratospheric polar vortex stretching and wave reflection had no discernible contribution to the record cold in North America in February. Instead, the tropospheric circulation and bidirectional coupling between the troposphere and stratosphere were dominant contributors to variability.

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“…Then, increasingly strong mid‐stratospheric zonal winds also require ever stronger forcings to generate the large‐scale wave breaking necessary for the wind reversal of a SSW (Hall et al., 2021; Jucker et al., 2014). While some studies suggest that particularly strong anomalous tropospheric wave activity is sufficient to decelerate the SPV (Dunn‐Sigouin & Shaw, 2020), others require a vortex that is structured to focus and even enhance upward wave activity (Albers & Birner, 2014). Thus, the strength and structure of simulated SPVs likely contributes to the magnitude or even sign of their response to forcings.…”

Section: Introductionmentioning

confidence: 99%

Exploring Mechanisms for Model‐Dependency of the Stratospheric Response to Arctic Warming

Mudhar,

Seviour,

Screen

et al. 2024

JGR Atmospheres

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The Arctic is estimated to have warmed up to four times faster than the rest of the globe since the 1980s. There is significant interest in understanding the mechanisms by which such warming may impact weather and climate at lower latitudes. One such mechanism is the “stratospheric pathway”; Arctic warming is proposed to induce a wave‐driven weakening of the stratospheric polar vortex, which may subsequently impact large‐scale tropospheric circulation. However, recent comprehensive model studies have found systematic differences in both the magnitude and sign of the stratospheric response to Arctic warming. Using a series of idealized model simulations, we show that this response is sensitive to characteristics of the warming and mean polar vortex strength. In all simulations, imposed polar warming amplifies upward wave propagation from the troposphere, consistent with comprehensive models. However, as polar warming strength and depth increases, the region through which waves can propagate is narrowed, inducing wave breaking and deceleration of the flow in the lower stratosphere. Thus, the mid‐stratosphere is less affected, with reduced sudden stratospheric warming frequency for stronger and deeper warming compared to weaker and shallower warming. We also find that the sign of the stratospheric response depends on the mean strength of the vortex, and that the stratospheric response in turn plays a role in the magnitude of the tropospheric jet response. Our results help explain the spread across multimodel ensembles of comprehensive climate models.

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Dynamics of Anomalous Stratospheric Eddy Heat Flux Events in an Idealized Model

Cited by 8 publications

References 56 publications

Sudden Stratospheric Warmings

Sudden Stratospheric Warmings

Limited surface impacts of the January 2021 sudden stratospheric warming

Exploring Mechanisms for Model‐Dependency of the Stratospheric Response to Arctic Warming

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