Can the Delay in Antarctic Polar Vortex Breakup Explain Recent Trends in Surface Westerlies?

Sheshadri, Aditi; Plumb, R. Alan; Domeisen, Daniela I. V.

doi:10.1175/jas-d-12-0343.1

Cited by 20 publications

(13 citation statements)

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“…FWs are also observed to have a similar tropospheric impact, although its latitudinal structure differs somewhat from the annular-mode form (Black et al 2006;Black and McDaniel 2007a,b;Hu et al 2014b), and uppertropospheric planetary-scale waves may play a role (Sun et al 2011). Similar results have been found in simplified global models (Sun and Robinson 2009;Sun et al 2011;Sheshadri et al 2014).…”

Section: Introductionsupporting

confidence: 57%

Seasonal Variability of the Polar Stratospheric Vortex in an Idealized AGCM with Varying Tropospheric Wave Forcing

Sheshadri

Plumb

Gerber

2015

Journal of the Atmospheric Sciences

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The seasonal variability of the polar stratospheric vortex is studied in a simplified AGCM driven by specified equilibrium temperature distributions. Seasonal variations in equilibrium temperature are imposed in the stratosphere only, enabling the study of stratosphere-troposphere coupling on seasonal time scales, without the complication of an internal tropospheric seasonal cycle. The model is forced with different shapes and amplitudes of simple bottom topography, resulting in a range of stratospheric climates. The effect of these different kinds of topography on the seasonal variability of the strength of the polar vortex, the average timing and variability in timing of the final breakup of the vortex (final warming events), the conditions of occurrence and frequency of midwinter warming events, and the impact of the stratospheric seasonal cycle on the troposphere are explored. The inclusion of wavenumber-1 and wavenumber-2 topographies results in very different stratospheric seasonal variability. Hemispheric differences in stratospheric seasonal variability are recovered in the model with appropriate choices of wave-2 topography. In the model experiment with a realistic Northern Hemisphere-like frequency of midwinter warming events, the distribution of the intervals between these events suggests that the model has no year-to-year memory. When forced with wave-1 topography, the gross features of seasonal variability are similar to those forced with wave-2 topography, but the dependence on forcing magnitude is weaker. Further, the frequency of major warming events has a nonmonotonic dependence on forcing magnitude and never reaches the frequency observed in the Northern Hemisphere.

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Section: Introductionsupporting

confidence: 57%

Seasonal Variability of the Polar Stratospheric Vortex in an Idealized AGCM with Varying Tropospheric Wave Forcing

Sheshadri

Plumb

Gerber

2015

Journal of the Atmospheric Sciences

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“…Due to the relatively quiescent nature of the SH stratospheric winter, the timing of the final warming is not as variable in the SH compared to the NH (Black et al, ; Waugh & Rong, ). However, a trend toward a later breakup of the polar vortex due to the stratospheric cooling trend has been observed (Waugh et al, ), with potentially important implications for the SH troposphere (Byrne et al, ; Sheshadri et al, ; L. Sun et al, ).…”

Section: A Brief Overview Of the Stratospheric Circulationmentioning

confidence: 99%

The Teleconnection of El Niño Southern Oscillation to the Stratosphere

Domeisen

Garfinkel²,

Butler

2019

Reviews of Geophysics

309

284

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El Niño and La Niña events in the tropical Pacific have significant and disrupting impacts on the global atmospheric and oceanic circulation. El Niño Southern Oscillation (ENSO) impacts also extend above the troposphere, affecting the strength and variability of the stratospheric polar vortex in the high latitudes of both hemispheres, as well as the composition and circulation of the tropical stratosphere. El Niño events are associated with a warming and weakening of the polar vortex in the polar stratosphere of both hemispheres, while a cooling can be observed in the tropical lower stratosphere. These impacts are linked by a strengthened Brewer-Dobson circulation. Anomalous upward wave propagation is observed in the extratropics of both hemispheres. For La Niña, these anomalies are often opposite. The stratosphere in turn affects surface weather and climate over large areas of the globe. Since these surface impacts are long-lived, the changes in the stratosphere can lead to improved surface predictions on time scales of weeks to months. Over the past decade, our understanding of the mechanisms through which ENSO can drive impacts remote from the tropical Pacific has improved. This study reviews the possible mechanisms connecting ENSO to the stratosphere in the tropics and the extratropics of both hemispheres while also considering open questions, including nonlinearities in the teleconnections, the role of ENSO diversity, and the impacts of climate change and variability.Plain Language Summary El Niño and La Niña events, the irregular warming and cooling of the tropical Pacific that occurs every couple of years, have disrupting impacts spanning the entire world. These remote impacts, so-called "teleconnections", also reach the stratosphere, the layer of the atmosphere starting at around 10 km above the Earth's surface. El Niño leads to a warming of the stratosphere in both hemispheres, while the lower tropical stratosphere cools. These signatures are linked by a strengthened stratospheric circulation from the tropics to the polar regions. El Niño also leads to more frequent breakdowns of the stratospheric polar vortex, a band of strong eastward winds in the polar stratosphere. For La Niña, these effects tend to be opposite, though they are not always robust, suggesting nonlinear or nonstationary effects, long-term variability, and trends in the teleconnections. The observational data record is not yet long enough to make conclusions with certainty, and models that try to reproduce the teleconnections indicate that teleconnections might be more linear than the limited number of observations indicate. Further research will be needed to separate the El Niño and La Niña teleconnections from other effects and to determine to what extent nonlinearity and nonstationarity are indeed present.

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“…In the Southern Hemisphere, the polar vortex also exhibits a strong long-term trend: a strengthening trend can be observed for the season from November to March (Thompson and Solomon 2002), accompanied by a trend in the timing of the final warming toward a later breakup of the polar vortex (Waugh et al 1999;Black and McDaniel 2007;Sheshadri et al 2014), which is suggested to be caused by ozone depletion in spring (Ramaswamy et al 2001;Thompson et al 2011). Ozone depletion was observed to be especially strong between 1979 and about 2000 (Solomon 1999), with a recovery starting after that (Oman et al 2010).…”

Section: Introductionmentioning

confidence: 93%

“…Here, JFM is used for the definition of the summer season to avoid including the large variability due to mixing following Rossby wave breaking, which is associated with the final warming, which, for example, in NCEP reanalysis for 1960-2010 occurs between late October and early December (e.g., Sheshadri et al 2014). Here, JFM is used for the definition of the summer season to avoid including the large variability due to mixing following Rossby wave breaking, which is associated with the final warming, which, for example, in NCEP reanalysis for 1960-2010 occurs between late October and early December (e.g., Sheshadri et al 2014).…”

Section: Probability Density Functionsmentioning

confidence: 99%

A Search for Chaotic Behavior in Stratospheric Variability: Comparison between the Northern and Southern Hemispheres

Badin

Domeisen

2014

Journal of the Atmospheric Sciences

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Southern Hemisphere (SH) stratospheric variability is investigated with respect to chaotic behavior using time series from three different variables extracted from four different reanalysis products. The results are compared with the same analysis applied to the Northern Hemisphere (NH). The probability density functions (PDFs) for the SH show persistent deviations from a Gaussian distribution. The variability is given by white spectra for low frequencies, a slope of 21 for intermediate frequencies, and 23 slopes for high frequencies. Considering the time series for winter and summer separately, PDFs show a Gaussian distribution and the variability spectra change their slopes, indicating the role of the transition between winter and summer variability in shaping the time series. The correlation (D 2 ) and the Kaplan-Yorke (D KY ) dimensions are estimated. A finite value of the dimensions can be computed for each variable and data product, except for the NCEP zonal-mean zonal wind and temperature data, which violate the requirement D 2 # D KY , possibly owing to the presence of spurious trends and inconsistencies in the data. The value of D 2 ranges between 2.6 and 3.9, while D KY ranges between 3.0 and 4.5. The results show that both D 2 and D KY display large variability in their values both for different datasets and for different variables within the same dataset. The variability of the values of D 2 and D KY thus leaves open the question about the existence of a low-dimensional attractor or if the finite dimensions of the system are the result of the projection of a larger attractor in a lowdimensional embedding space.

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Can the Delay in Antarctic Polar Vortex Breakup Explain Recent Trends in Surface Westerlies?

Cited by 20 publications

References 20 publications

Seasonal Variability of the Polar Stratospheric Vortex in an Idealized AGCM with Varying Tropospheric Wave Forcing

Seasonal Variability of the Polar Stratospheric Vortex in an Idealized AGCM with Varying Tropospheric Wave Forcing

The Teleconnection of El Niño Southern Oscillation to the Stratosphere

A Search for Chaotic Behavior in Stratospheric Variability: Comparison between the Northern and Southern Hemispheres

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