Here are the current Papers & Articles under the research topic Stratosphere - Stratospheric Polar Vortex (SPV). Click on the title of a paper you are interested in to go straight to the full paper.
Persistent shift of the Arctic polar vortex towards the Eurasian continent in recent decades
2016 paper. Abstract:
The wintertime Arctic stratospheric polar vortex has weakened over the past three decades, and consequently cold surface air from high latitudes is now more likely to move into the middle latitudes. However, it is not known if the location of the polar vortex has also experienced a persistent change in response to Arctic climate change and whether any changes in the vortex position have implications for the climate system. Here, through the analysis of various data sets and model simulations, we show that the Arctic polar vortex shifted persistently towards the Eurasian continent and away from North America in February over the past three decades. This shift is found to be closely related to the enhanced zonal wavenumber-1 waves in response to Arctic sea-ice loss, particularly over the Barents–Kara seas (BKS). Increased snow cover over the Eurasian continent may also have contributed to the shift. Our analysis reveals that the vortex shift induces cooling over some parts of the Eurasian continent and North America which partly offsets the tropospheric climate warming there in the past three decades. The potential vortex shift in response to persistent sea-ice loss in the future6, 7, and its associated climatic impact, deserve attention to better constrain future climate changes.
Preconditioning of Arctic Stratospheric Polar Vortex Shift Events
2018 paper. Abstract:
This study examines the preconditioning of events in which the Arctic stratospheric polar vortex shifts towards Eurasia (EUR events), North America (NA events) and the Atlantic (ATL events) using composite analysis. An increase in blocking days over northern Europe and a decrease in blocking days over the Bering Strait favor the movement of the vortex towards Eurasia, while the opposite changes in blocking days over those regions favor the movement of the vortex towards North America. An increase in blocking days over the eastern North Atlantic and a decrease in blocking days over the Bering Strait are conducive to movement of the stratospheric polar vortex towards the Atlantic. These anomalous precursor blocking patterns are interpreted in terms of the anomalous zonal wave-1 or wave-2 planetary wave fluxes into the stratosphere that are known to influence the vortex position and strength. In addition, the polar vortex shift events are further classified into events with small and large polar vortex deformation, since the two types of events are likely to have a different impact at the surface. A significant difference in the zonal wave-2 heat flux into the lower stratosphere exists prior to the two types of events and this is linked to anomalous blocking patterns. This study further defines three types of tropospheric blocking events in which the spatial patterns of blocking frequency anomalies are similar to the blocking patterns prior to EUR, NA and ATL events, respectively, and our reanalysis reveals that the polar vortex is indeed more likely to shift towards Eurasia, North America and the Atlantic in the presence of the above three defined tropospheric blocking events. These shifts of the polar vortex towards Eurasia, North America and the Atlantic lead to statistically significant negative height anomalies near the tropopause and corresponding surface cooling anomalies over these three regions.
Response of the northern stratospheric polar vortex to the seasonal alignment of QBO phase transitions.
2008 paper. Abstract:
This study considers the strength of the Northern Hemisphere Holton‐Tan effect (HTE) in terms of the phase alignment of the quasi‐biennial oscillation (QBO) with respect to the annual cycle. Using the ERA‐40 Reanalysis, it is found that the early winter (Nov–Dec) and late winter (Feb–Mar) relation between QBO phase and the strength of the stratospheric polar vortex is optimized for subsets of the 44‐year record that are chosen on the basis of the seasonality of QBO phase transitions at the 30 hPa level. The timing of phase transitions serves as a proxy for changes in the vertical structure of the QBO over the whole depth of the tropical stratosphere. The statistical significance of the Nov–Dec (Feb–Mar) HTE is greatest when 30 hPa QBO phase transitions occur 9–14 (4–9) months prior to the January of the NH winter in question. This suggests that there exists for both early and late winter a vertical structure of tropical stratospheric winds that is most effective at influencing the interannual variability of the polar vortex, and that an early (late) winter HTE is associated with an early (late) progression of QBO phase towards that structure. It is also shown that the seasonality of QBO phase transitions at 30 hPa varies on a decadal timescale, with transitions during the first half of the calendar year being relatively more common during the first half of the tropical radiosonde wind record. Combining these two results suggests that decadal changes in HTE strength could result from the changing seasonality of QBO phase transitions.
The 2018–2019 Arctic stratospheric polar vortex
2019 paper. Abstract:
The stratospheric polar vortex forms each winter 10–50 km above the surface over the pole, and variations in its strength and position are known to influence the weather we experience. During winter 2018–2019, the Arctic polar vortex was highly variable – with both a sudden stratospheric warming and a strong vortex event. We discuss this unusual evolution of the vortex in terms of climatology and its impacts on surface weather patterns.
Weakening of the stratospheric polar vortex by Arctic sea-ice loss
2014 paper. Abstract:
Successive cold winters of severely low temperatures in recent years have had critical social and economic impacts on the mid-latitude continents in the Northern Hemisphere. Although these cold winters are thought to be partly driven by dramatic losses of Arctic sea-ice, the mechanism that links sea-ice loss to cold winters remains a subject of debate. Here, by conducting observational analyses and model experiments, we show how Arctic sea-ice loss and cold winters in extra-polar regions are dynamically connected through the polar stratosphere. We find that decreased sea-ice cover during early winter months (November-December), especially over the Barents-Kara seas, enhances the upward propagation of planetary-scale waves with wavenumbers of 1 and 2, subsequently weakening the stratospheric polar vortex in mid-winter (January-February). The weakened polar vortex preferentially induces a negative phase of Arctic Oscillation at the surface, resulting in low temperatures in mid-latitudes.