The Impact of Strong El Niño and La Niña Events on the North Atlantic

Hardiman, Steven C.; Dunstone, Nick; Scaife, Adam A.; Smith, Doug; Ineson, Sarah; Lim, J.; Fereday, David

doi:10.1029/2018gl081776

Cited by 65 publications

(93 citation statements)

References 55 publications

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“…Deser et al 2017;Ayarzagüena et al 2018;Weinberger et al 2019) and others claiming asymmetry (e.g. Trascasa-Castro et al 2019;Hardiman et al 2019; Jiménez-Esteve and Domeisen 2019). The actual "linearity" of the ENSO-NAE teleconnection thus remains unresolved, and addressing this issue is the primary objective of this study.…”

Section: Introductionmentioning

confidence: 93%

Multi-model assessment of the late-winter extra-tropical response to El Niño and La Niña

et al. 2020

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El Niño-Southern Oscillation (ENSO) is known to affect the Northern Hemisphere tropospheric circulation in late-winter (January-March), but whether El Niño and La Niña lead to symmetric impacts and with the same underlying dynamics remains unclear, particularly in the North Atlantic. Three state-of-the-art atmospheric models forced by symmetric anomalous sea surface temperature (SST) patterns, mimicking strong ENSO events, are used to robustly diagnose symmetries and asymmetries in the extra-tropical ENSO response. Asymmetries arise in the sea-level pressure (SLP) response over the North Pacific and North Atlantic, as the response to La Niña tends to be weaker and shifted westward with respect to that of El Niño. The difference in amplitude can be traced back to the distinct energy available for the two ENSO phases associated with the non-linear diabatic heating response to the total SST field. The longitudinal shift is embedded into the large-scale Rossby wave train triggered from the tropical Pacific, as its anomalies in the upper troposphere show a similar westward displacement in La Niña compared to El Niño. To fully explain this shift, the response in tropical convection and the related anomalous upper-level divergence have to be considered together with the climatological vorticity gradient of the subtropical jet, i.e. diagnosing the tropical Rossby wave source. In the North Atlantic, the ENSO-forced SLP signal is a well-known dipole between middle and high latitudes, different from the North Atlantic Oscillation, whose asymmetry is not indicative of distinct mechanisms driving the teleconnection for El Niño and La Niña.

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Section: Introductionmentioning

confidence: 93%

Multi-model assessment of the late-winter extra-tropical response to El Niño and La Niña

et al. 2020

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“…Recent studies have explored the response of the stratosphere to extreme ENSO activity (Christiansen et al, 2016;Dunkerton, 2016;Avery et al, 2017;Palmeiro et al, 2017;Varotsos et al, 2017). Rao and Ren (2016b) and Hardiman et al (2019) reported the nonlinear responses of the NH stratosphere to ENSO events of different intensities in winter. In contrast, Zhou et al (2018) found more linear responses to El Niño intensity change in early spring.…”

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confidence: 99%

Independent and joint influences of eastern Pacific El Niño–southern oscillation and quasi‐biennial oscillation on Northern Hemispheric stratospheric ozone

Xie

Zhang

et al. 2020

Intl Journal of Climatology

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Using ozone observations, reanalysis data, and climate model simulations, this study investigates in detail the independent and joint influences of the eastern Pacific (EP) El Niño-Southern Oscillation (ENSO) and the quasi-biennial oscillation (QBO) on stratospheric ozone in the Northern Hemisphere (NH) during winter. Statistically, the stratospheric ozone in the NH in winter increases during El Niño events but decreases during La Niña events. Stratospheric ozone increases in the east wind phases of the QBO (EQBO) and decreases in the west wind phases of the QBO (WQBO). The stratospheric ozone anomalies in the middle and high latitudes caused by ENSO activities are clearly larger than those related to the QBO phase. Since the phases of wave-1 and wave-2 planetary waves anomalies related to ENSO activities are broadly similar to those of QBO phases, the joint effect of ENSO and QBO on stratospheric ozone is approximately equal to the linear superposition of their independent impacts. This means that during EQBO phases, the stratospheric ozone anomalies are increased during El Niño events but reduced during La Niña events, and vice versa during WQBO phases. Numerical sensitivity experiments are performed to further investigate the independent and joint influences of EP ENSO and QBO on stratospheric ozone in the NH during winter. The results from simulations agree well with the results from statistical analysis. K E Y W O R D S eastern Pacific El Niño-southern oscillation, independent and joint influences, quasi-biennial oscillation, stratospheric ozone 1 | INTRODUCTION Ozone protects life on Earth by absorbing ultraviolet radiation (e.g., Lubin and Jensen, 1995; Chipperfield et al., 2015; Zhang et al., 2018). It has recently been found to significantly influence tropospheric climate change. For instance, many studies have pointed out that Antarctic ozone depletion has substantial influence on Southern Hemispheric climate change (

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“…There are statistically significant RWS anomalies in the tropical Atlantic below 15 • N. Wet and dry composites for both Z250 and RWS show qualitative linearity of these anomalies. Although the RWS has a quadratic form, Hardiman et al (2019) also showed linearity in the RWS, to different ENSO strengths. Figure 2d shows the GPCP precipitation regression.…”

Section: Observational Analysesmentioning

confidence: 96%

“…Although the RWS has a quadratic form, Hardiman et al . () also showed linearity in the RWS, to different ENSO strengths.…”

Section: Observational Analysesmentioning

confidence: 99%

Tropical atmospheric drivers of wintertime European precipitation events

Woollings

O’Reilly

et al. 2020

Quart J Royal Meteoro Soc

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From observations, we identify a wave‐like pattern associated with northwestern European seasonal precipitation events. These events are associated with tropical precipitation anomalies, prompting us to investigate if there are any tropical–extratropical teleconnections, in particular the role of tropical anomalies in driving extratropical dynamics through Rossby wave propagation. Using a hierarchy of models from ray tracing to barotropic and baroclinic models, we investigate the Rossby wave mechanism and test potential tropical drivers and yield qualitative results. Using a barotropic model, we identify potential Rossby wave source regions which are consistent between the observations and the model. These regions include the tropical western and eastern Atlantic, the subtropical eastern Atlantic and, to a smaller degree, the subtropical eastern Pacific. Zonal wavenumber 2 and 3 components of the barotropic model responses match well with the observations and ray tracing supports the importance of these components. We use a baroclinic model to investigate the link between the observed Rossby wave source anomalies and the observed tropical precipitation anomalies. The reduced precipitation observed in the tropical Atlantic just north of the Equator can generate some of the observed Rossby wave source anomalies in the tropical Atlantic, while the increased precipitation observed in the tropical eastern Pacific can generate some of the observed Rossby wave source anomalies in the subtropical eastern Pacific. Our results can also be applied to European drought events because of the qualitative linearity in the observations and in our linear methods.

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The Impact of Strong El Niño and La Niña Events on the North Atlantic

Cited by 65 publications

References 55 publications

Multi-model assessment of the late-winter extra-tropical response to El Niño and La Niña

Multi-model assessment of the late-winter extra-tropical response to El Niño and La Niña

Independent and joint influences of eastern Pacific El Niño–southern oscillation and quasi‐biennial oscillation on Northern Hemispheric stratospheric ozone

Tropical atmospheric drivers of wintertime European precipitation events

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