Classifying the tropospheric precursor patterns of sudden stratospheric warmings

Bao, Mengying; Tan, Xinsheng; Hartmann, Dennis L.; Ceppi, Paulo

doi:10.1002/2017gl074611

Cited by 33 publications

(27 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In contrast, the S2S models simulated more frequent polar stratospheric easterlies during EN over this period ( Figure 5). This discrepancy between the models and observations as to which ENSO phase preferentially leads to more SSW is consistent with the discrepancy in the ridging over eastern Europe (Bao et al, 2017;Cohen & Jones, 2011;Kretschmer et al, 2017).…”

Section: Discussion and Summarysupporting

confidence: 76%

“…The stratospheric response to EN events is driven by a deepened Aleutian low (e.g., Barnston & Livezey, ), which constructively interferes with the climatological stationary planetary wave pattern and leads to strengthened wave flux into the stratosphere (i.e., linear interference; Garfinkel & Hartmann, ; Garfinkel et al, ; Smith et al, ; Smith & Kushner, ), as recently reviewed by Domeisen et al (). Other modes of tropospheric variability (e.g., October Eurasian snow) can affect the vortex through a similar pathway but via variability over western Siberia/eastern Europe, where a ridge constructively interferes with the climatological stationary planetary wave pattern and leads to strengthened wave flux into the stratosphere (Bao et al, ; Cohen & Jones, ; Garfinkel et al, ; Kretschmer et al, ). Episodes of prolonged upward wave flux can lead to sudden stratospheric warming (SSW) events (Polvani & Waugh, ; Sjoberg & Birner, ), induce a tendency toward a negative phase of the North Atlantic Oscillation (Bell et al, ; Ineson & Scaife, ), and increase weather predictability (Sigmond et al, ) in the Euro‐Atlantic region for more than a month.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Weakening of the Teleconnection From El Niño–Southern Oscillation to the Arctic Stratosphere Over the Past Few Decades: What Can Be Learned From Subseasonal Forecast Models?

et al. 2019

View full text Add to dashboard Cite

While a connection between the El Niño–Southern Oscillation (ENSO) and the Northern Hemisphere wintertime stratospheric polar vortex appears robust in observational studies focusing on the period before 1979 and in many modeling studies, this connection is not evident over the past few decades. In this study, the factors that have led to the disappearance of the ENSO‐vortex relationship are assessed by comparing this relationship in observational data and in operational subseasonal forecasting models over the past few decades. For reforecasts initialized in December, the models simulate a significantly weaker vortex during El Niño than La Niña (LN) as occurred before 1979, but no such effect was observed to have occurred. The apparent cause of this is the eastern European and western Siberian height anomalies present during ENSO. The observed LN events were associated with persistent ridging over eastern Europe as compared to El Niño. Although the Subseasonal‐to‐Seasonal models are initialized with this ridge, the ridge quickly dissipates. As ridging over this region enhances wave flux entering the stratosphere, the net effect is no robust stratospheric response to ENSO in the observations despite a North Pacific teleconnection that would, in isolation, lead to less wave flux for LN. The anomalies in the eastern European sector in response to ENSO likely reflect unforced internal atmospheric variability.

show abstract

Section: Discussion and Summarysupporting

confidence: 76%

Section: Introductionmentioning

confidence: 99%

Weakening of the Teleconnection From El Niño–Southern Oscillation to the Arctic Stratosphere Over the Past Few Decades: What Can Be Learned From Subseasonal Forecast Models?

et al. 2019

View full text Add to dashboard Cite

show abstract

“…Furthermore, Bao et al . () demonstrated lows over the Western Hemisphere, and highs over Pacific–North America to be an even stronger precursor to SSWs than Pacific lows and European highs.…”

Section: Introductionmentioning

confidence: 87%

“…Surface pressure lows and decreased blocking in the northern Pacific, along with surface highs and increased blocking in Europe are connected to vortex disturbances by constructive interference with climatological planetary waves (Garfinkel et al, 2010;Huang et al, 2017). Furthermore, Bao et al (2017) demonstrated lows over the Western Hemisphere, and highs over Pacific-North America to be an even stronger precursor to SSWs than Pacific lows and European highs.…”

Section: Introductionmentioning

confidence: 99%

A thermodynamic climatology of the disturbed stratospheric polar vortex

Ehrmann

Colucci

2019

Intl Journal of Climatology

View full text Add to dashboard Cite

A climatology of polar vortex disturbances in the Northern Hemisphere winter stratosphere is constructed from MERRA2 Reanalysis data for the winter seasons of 1981–2017. Sixty disturbances (splits or displacements) of the polar vortex are identified during the 37 winter seasons using geometric moments of stratospheric potential vorticity. The likelihood of a disturbed day is negatively correlated with the stratospheric quasi‐biennial oscillation (positively correlated with its easterly phase). It is also, surprisingly, negatively correlated with the presence of a stratospheric Aleutian anticyclone (the Aleutian high). The position of the polar vortex during each disturbance event is averaged to generate an area‐averaging filter that is applied to thermodynamic diagnostic quantities in the air column enclosed by the polar vortex. This diagnosis reveals that the location of the disturbed polar vortex experiences, on average, cooling driven by horizontal temperature advection in the lower and middle stratosphere prior to the onset of the disturbance, along with significant residual (likely adiabatic) cooling in the troposphere in the weeks surrounding the onset. How these thermodynamic signatures associated with a disturbed polar vortex relate to the Aleutian high and the quasi‐biennial oscillation is also explored.

show abstract

“…Tropospheric blocking is one such feature (e.g., Colucci & Kelleher, ; Garfinkel et al, ; Julian & Labitzke, ; Martius et al, ; Quiroz, ). For example, Bao et al () used cluster analysis to assess 500‐hPa geopotential height patterns in the month before 37 SSWs in reanalysis and found the patterns to be associated with linear interference with climatological stationary waves. Kolstad and Charlton‐Perez () used reanalysis alongside climate model simulations and found a particularly strong signal for a height anomaly dipole over northern Eurasia preceding “weak vortex months.” Other studies have considered more transient features associated with specific stratospheric events.…”

Section: Introductionmentioning

confidence: 99%

Abrupt Stratospheric Vortex Weakening Associated With North Atlantic Anticyclonic Wave Breaking

et al. 2019

View full text Add to dashboard Cite

The sudden stratospheric warming (SSW) of 12 February 2018 was not forecast by any extended-range model beyond 12 days. From early February, all forecast models that comprise the subseasonal-to-seasonal (S2S) database abruptly transitioned from indicating a strong stratospheric polar vortex (SPV) to a high likelihood of a major SSW. We demonstrate that this forecast evolution was associated with the track and intensity of a cyclone in the northeast Atlantic, with an associated anticyclonic Rossby wave break, which was not well forecast. The wave break played a pivotal role in building the Ural high, which existing literature has shown was a precursor of the 2018 SSW. The track of the cyclone built an anomalously strong sea level pressure dipole between Scandinavia and Greenland (termed the S-G dipole), which we use as a diagnostic of the wave break. Forecasts that did not capture the magnitude of this event had the largest errors in the SPV strength and did not show enhanced vertical wave activity. A composite of 49 similarly strong wintertime (November-March) S-G dipoles in reanalysis shows associated anticyclonic wave breaking leading to significantly enhanced vertical wave activity and a weakened SPV in the following days, which occurred in 35% of the 15-day periods preceding observed major SSWs. Our results indicate a particular transient trigger for weakening the SPV, complementing existing results on the importance of tropospheric blocking for disruptions to the Northern Hemisphere extratropical stratospheric circulation.Plain Language Summary During winter, a large circulation 10-50 km above the pole (known as the stratospheric polar vortex) can influence the day-to-day weather patterns in the troposphere beneath from weeks to months later. Thus, being able to predict the behavior of the stratospheric polar vortex is important for predicting the weather on longer time frames. In February 2018, the Northern Hemisphere stratospheric polar vortex broke apart in an event known as a sudden stratospheric warming, which was not well forecast. This event led to unusually cold conditions across Eurasia. In this article we find the poor predictability of the event was due to a poorly forecast weather system in the Atlantic. We also show that this pattern was present in previously observed cases where the stratospheric polar vortex has weakened. Our results demonstrate a trigger mechanism for these extreme events and have implications for our ability to predict the weather at longer ranges.

show abstract

Classifying the tropospheric precursor patterns of sudden stratospheric warmings

Cited by 33 publications

References 34 publications

Weakening of the Teleconnection From El Niño–Southern Oscillation to the Arctic Stratosphere Over the Past Few Decades: What Can Be Learned From Subseasonal Forecast Models?

Weakening of the Teleconnection From El Niño–Southern Oscillation to the Arctic Stratosphere Over the Past Few Decades: What Can Be Learned From Subseasonal Forecast Models?

A thermodynamic climatology of the disturbed stratospheric polar vortex

Abrupt Stratospheric Vortex Weakening Associated With North Atlantic Anticyclonic Wave Breaking

Contact Info

Product

Resources

About