Stratospheric variability contributed to and sustained the recent hiatus in Eurasian winter warming

Garfinkel, Chaim I.; Son, Seok‐Woo; Song, Kwang Ho; Aquila, Valentina; Oman, Luke D.

doi:10.1002/2016gl072035

Cited by 96 publications

(92 citation statements)

References 54 publications

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“…Although clarifying the causes of the vertical coupling intensity is beyond our scope, the obtained results suggest that WPV events occurring in light‐ice years over the BKS tend to strongly affect tropospheric circulation and midlatitude surface temperature. This is consistent with the results of Garfinkel et al () and Kretschmer et al (), showing that a recent low temperature anomaly over Eurasia in winter was preceded by stratospheric polar vortex weakening.…”

Section: Resultssupporting

confidence: 93%

“…This Eurasian surface temperature signals are also apparent in horizontal maps averaged 30 days after Day 0 (Figures b and d). These results suggest that the recent Eurasian cold conditions (Cohen et al, ; Garfinkel et al, ) were partly related to stronger vertical coupling of the WPV events modulated by sea‐ice loss. A question remains about the mechanisms of the stronger vertical coupling.…”

Section: Discussionmentioning

confidence: 75%

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Weak Stratospheric Polar Vortex Events Modulated by the Arctic Sea‐Ice Loss

et al. 2019

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We characterize the differences in the upward planetary‐scale wave propagation during observed weak polar vortex (WPV) events between heavy‐ and light‐sea‐ice years in the Barents‐Kara Sea based on a composite analysis for the period of 1979–2015. Upward wave propagation during WPV events in heavy‐ice years is dominated by the wavenumber 1 component. In contrast, WPV events occurring in light‐ice years are characterized by stronger wavenumber 2 propagation, which is caused by the tropospheric wavenumber 2 response to sea‐ice reduction in the Barents‐Kara Sea. The above observed features are supported by an Atmospheric General Circulation Model experiment. Thus, under present climate conditions, Arctic sea‐ice loss is a possible factor modulating the wave propagation during the WPV events. We also find that the WPV events in light‐ice years have stronger stratosphere‐troposphere coupling, followed by colder midlatitude surface conditions particularly over Eurasia.

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Section: Resultssupporting

confidence: 93%

Section: Discussionmentioning

confidence: 75%

Weak Stratospheric Polar Vortex Events Modulated by the Arctic Sea‐Ice Loss

et al. 2019

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“…Seviour (2017) examined large ensembles of coupled climate model simulations and concluded that the forced response of the vortex was small relative to internal variability, and that vortex trends of similar magnitude to those observed can be generated purely by internal climate variability [43]. The latter conclusion was also reached by Garfinkel et al (2017), who found no consistent change in the strength of the polar vortex in model simulations forced with observed GHG concentrations, sea surface temperatures and sea ice [42]. However, unforced internal variability was sufficiently strong that some individual ensemble members reproduced the observed polar vortex weakening.…”

Section: The Arcticmentioning

confidence: 92%

Polar Climate Change as Manifest in Atmospheric Circulation

Screen

Bracegirdle

Simmonds

2018

Curr Clim Change Rep

144

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Purpose of ReviewDynamic manifestations of climate change, i.e. those related to circulation, are less well understood than are thermodynamic, or temperature-related aspects. However, this knowledge gap is narrowing. We review recent progress in understanding the causes of observed changes in polar tropospheric and stratospheric circulation, and in interpreting climate model projections of their future changes.Recent FindingsTrends in the annular modes reflect the influences of multiple drivers. In the Northern Hemisphere, there appears to be a “tug-of-war” between the opposing effects of Arctic near-surface warming and tropical upper tropospheric warming, two predominant features of the atmospheric response to increasing greenhouse gases. Future trends in the Southern Hemisphere largely depend on the competing effects of stratospheric ozone recovery and increasing greenhouse gases.SummaryHuman influence on the Antarctic circulation is detectable in the strengthening of the stratospheric polar vortex and the poleward shift of the tropospheric westerly winds. Observed Arctic circulation changes cannot be confidently separated from internal atmospheric variability.

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“…In particular, the occurrence of sudden stratospheric warming (SSW) events favours negative NAO phases that are often associated with cold extremes over Eurasia. It has been shown that during periods with a weak stratospheric polar vortex, extremely low temperatures over northern Europe are more likely (Kidston et al ., ) and longer lasting (Garfinkel et al ., ). These studies reinforce the hypothesis that the state of the stratospheric polar vortex may be important for the evolution, intensity and – in particular – the persistence of surface cold anomalies.…”

Section: Introductionmentioning

confidence: 99%

Enhanced extended‐range predictability of the 2018 late‐winter Eurasian cold spell due to the stratosphere

Kautz

Polichtchouk

Birner

et al. 2020

Quart J Royal Meteoro Soc

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A severe cold spell with surface temperatures reaching 10 K below its climatology hit Eurasia during late February/early March 2018. This cold spell was associated with a Scandinavian blocking pattern followed by an extreme negative North Atlantic Oscillation (NAO) phase. Here we explore the predictability of this cold spell/NAO event using ensemble forecasts from the Subseasonal‐to‐Seasonal (S2S) archive of the European Centre for Medium‐Range Weather Forecasts. We find that this event was predicted with the observed strength roughly 10 days in advance. However, the probability of the cold spell occurring doubled up to 25 days in advance, when a sudden stratospheric warming (SSW) occurred. Our results indicate that the amplitude of the cold spell was increased by a regime shift to the negative NAO phase at the end of February, which was likely favoured by the SSW. We quantify the contribution of the SSW to the enhanced extended‐range forecast skill for this particular event by running forecast ensembles in which the evolution of the stratosphere is nudged to (a) the observed evolution, and (b) a time‐invariant state. In the experiment with nudging to the observed stratospheric evolution, the probability of a strong cold spell occurring is enhanced to 45%, while it is at its climatological value of 5% when the stratosphere is nudged to a time‐invariant state. These results showing enhanced predictability of surface extremes following SSWs extend previous observational evidence, which is mostly based on composite analyses, to a single event. Our results suggest that it is the subsequent evolution throughout the lower stratosphere following the SSW, rather than the occurrence of the SSW itself, that is crucial in coupling to large‐scale tropospheric flow patterns. However, we caution that probabilistic gain in predictability alone is insufficient to conclude a causal link between the SSW and the cold spell event.

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Stratospheric variability contributed to and sustained the recent hiatus in Eurasian winter warming

Cited by 96 publications

References 54 publications

Weak Stratospheric Polar Vortex Events Modulated by the Arctic Sea‐Ice Loss

Weak Stratospheric Polar Vortex Events Modulated by the Arctic Sea‐Ice Loss

Polar Climate Change as Manifest in Atmospheric Circulation

Enhanced extended‐range predictability of the 2018 late‐winter Eurasian cold spell due to the stratosphere

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