Stratospheric role in interdecadal changes of El Niño impacts over Europe

Ayarzagüena, Blanca; López‐Parages, Jorge; Iza, Maddalen; Calvo, Natalia; Rodríguez‐Fonseca, Belén

doi:10.1007/s00382-018-4186-3

Cited by 29 publications

(15 citation statements)

References 51 publications

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“…Previous studies have argued that the PDO can modulate the occurrence ratio of EP and CP El Niños, which might explain the nonstationarity of the ENSO teleconnection (Ayarzagüena et al 2019;Domeisen et al 2019). Table 3 shows the occurrence frequencies of the two flavors of ENSO.…”

Section: Ep Enso Versus Cp Enso In the Cmip5 Mme A Two Flavors Of Enso Sst Pattern In The Cmip5 Mmementioning

confidence: 98%

“…ENSO's impact on the northern winter stratosphere appears to be nonstationary (Hu et al 2017;Yang et al 2017;Domeisen et al 2019): no robust connection between ENSO and the Arctic stratospheric vortex can be established if one only samples El Niño or La Niña events after 1979. This nonstationarity may be related to the flavor of El Niño events that have occurred, as CP El Niños occurred more frequently over this period than before (Calvo et al 2017;Hu et al 2017;Yang et al 2017;Ayarzagüena et al 2019;Domeisen et al 2019). The convective center over the equatorial Pacific during El Niño winters, as well as the extratropical height response, has shifted (e.g., Meehl and Teng 2007;Wittenberg 2009;Deser et al 2010;Zhou et al 2014).…”

Section: Introductionmentioning

confidence: 99%

“…For example, the intensity and spatial pattern of the PNA teleconnection have been reported to be destructively modulated by the diabatic heating forcing over the tropical Indian and Atlantic Oceans (Annamalai et al 2007;Fletcher and Kushner 2011;Ren 2016a, 2018;Zhou et al 2018). The internal variability of the atmosphere-ocean system in the North Pacific may also lead to nonstationarity of stratospheric ENSO teleconnections (Gershunov and Barnett 1998;López-Parages et al 2015Newman et al 2016;Ayarzagüena et al 2019). As the principal empirical orthogonal function (EOF) of the extratropical Pacific SST (Zhang et al 1997;Newman et al 2003Newman et al , 2016, the Pacific decadal oscillation (PDO) has been reported to influence the stratosphere (Jadin et al 2010;Hurwitz et al 2012;Mills and Walsh 2013;Woo et al 2015;Kren et al 2016;Hu and Guan 2018).…”

Section: Introductionmentioning

confidence: 99%

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Modulation of the Northern Winter Stratospheric El Niño–Southern Oscillation Teleconnection by the PDO

Rao¹,

Garfinkel

2019

J. Climate

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Using the CMIP5 multimodel ensemble (MME) historical experiments, the modulation of the stratospheric El Niño–Southern Oscillation (ENSO) teleconnection by the Pacific decadal oscillation (PDO) is investigated in this study. El Niño (La Niña) significantly impacts the extratropical stratosphere mainly during the positive (negative) PDO in the MME. Although the composite tropical ENSO SST intensities are similar during the positive and negative PDO in models, the Pacific–North American (PNA) responses are only significant when the PDO and ENSO are in phase. The local SST anomalies in the North Pacific can constructively (destructively) interfere with the tropical ENSO forcing to influence the extratropical eddy height anomalies when the PDO and ENSO are in (out of) phase. The difference between the positive and negative PDO in El Niño or La Niña winters filters out the tropical SST forcing, permitting the deduction of the extratropical SST contribution to the atmospheric response. The composite shows that the cold (warm) SST anomalies in the central North Pacific associated with the positive (negative) PDO have a similar impact to that of the warm (cold) SST anomalies in the tropical Pacific, exhibiting a positive (negative) PNA-like response, enhancing (weakening) the upward propagation of waves over the western coast of North America. The composite difference between the positive and negative PDO in El Niño or La Niña winters, as well as in eastern Pacific ENSO or central Pacific ENSO winters, presents a highly consistent atmospheric response pattern, which may imply a linear interference of the PDO’s impact with ENSO’s.

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Section: Ep Enso Versus Cp Enso In the Cmip5 Mme A Two Flavors Of Enso Sst Pattern In The Cmip5 Mmementioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modulation of the Northern Winter Stratospheric El Niño–Southern Oscillation Teleconnection by the PDO

Rao¹,

Garfinkel

2019

J. Climate

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“…While the stratospheric response weakened after 1977, there is no indication of a recovery from 1998 to 2014, and hence, there is a mismatch between the phasing of North Pacific decadal variability and decadal variability in the ENSO‐vortex relationship. Another possibility is that decadal variability in the Atlantic sector SSTs may modulate the Atlantic sector impacts of ENSO (Ayarzagüena, López‐Parages, et al, ; López‐Parages & Rodríguez‐Fonseca, ; López‐Parages et al, ; López‐Parages, Rodríguez‐Fonseca, Dommenget, et al, ; López‐Parages, Rodríguez‐Fonseca, Mohino, et al, ), though again the timing of decadal changes in the Atlantic are not consistent with the timing of decadal changes in the stratospheric response.…”

Section: Factors Influencing Enso Teleconnectionsmentioning

confidence: 99%

The Teleconnection of El Niño Southern Oscillation to the Stratosphere

Domeisen

Garfinkel²,

Butler

2019

Reviews of Geophysics

316

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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“…Consistent with this, decadal variability is also present in the Atlantic sector response to ENSO, with a negative correlation between ENSO and the North Atlantic Oscillation from 1958 to 1978 and a weak response afterward (Domeisen et al, ; Greatbatch et al, ). This leads to differences in the precipitation response over Europe to ENSO (Ayarzagüena et al, ). The frequency of extreme transient wave activity flux events from the North Pacific to the North Atlantic also changed after 1978 (Jiménez‐Esteve & Domeisen, ).…”

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

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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.

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Stratospheric role in interdecadal changes of El Niño impacts over Europe

Cited by 29 publications

References 51 publications

Modulation of the Northern Winter Stratospheric El Niño–Southern Oscillation Teleconnection by the PDO

Modulation of the Northern Winter Stratospheric El Niño–Southern Oscillation Teleconnection by the PDO

The Teleconnection of El Niño Southern Oscillation to the Stratosphere

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?

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