Dynamics of the ENSO Teleconnection and NAO Variability in the North Atlantic–European Late Winter

Mezzina, Bianca; Garcı́a-Serrano, Javier; Bladé, Ileana; Kucharski, Fred

doi:10.1175/jcli-d-19-0192.1

Cited by 50 publications

(56 citation statements)

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“…García-Serrano et al 2011). Here, we adopt a complementary approach to confirm the results of Mezzina et al (2020), who used reanalysis data and AMIP-like simulations to show that the ENSO-NAE teleconnection, despite some similarity at the surface, is dynamically distinct from the NAO.…”

Section: Introductionmentioning

confidence: 88%

“…Regarding the tropospheric pathway, the poleward-propagating Rossby wave train (see "Appendix 1") driving the well-established teleconnection in the North Pacific (Trenberth et al 1998), first described by Horel and Wallace (1981) and Hoskins and Karoly (1981), is a suitable candidate (e.g. García-Serrano et al 2011;Mezzina et al 2020), although other mechanisms have been proposed (e.g. Toniazzo and Scaife 2006;Jiménez-Esteve and Domeisen 2018).…”

Section: Introductionmentioning

confidence: 99%

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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: 88%

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

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“…In the model, moist and radiative processes are considered through evaporation from the surface and fast condensation (i.e., no explicit liquid water content in the atmosphere), which interacts with the radiation and the convection scheme. We use the multiband radiation scheme (rrtm) (Mlawer et al, 1997) used in the MiMA model (Jucker and Gerber, 2017), which allows configurable levels of ozone and CO 2 concentrations. We also use realistic topography and the continental outline from the ECMWF model (Dee et al, 2011).…”

Section: Model Description and Experimentsmentioning

confidence: 99%

Nonlinearity in the tropospheric pathway of ENSO to the North Atlantic

Jiménez‐Esteve

Domeisen

2020

Weather Clim. Dynam.

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Abstract. The El Niño–Southern Oscillation (ENSO) can exert a remote impact on North Atlantic and European (NAE) winter climate. This teleconnection is driven by the superposition and interaction of different influences, which are generally grouped into two main pathways, namely the tropospheric and stratospheric pathways. In this study, we focus on the tropospheric pathway through the North Pacific and across the North American continent. Due to the possible nonstationary behavior and the limited time period covered by reanalysis datasets, the potential nonlinearity of this pathway remains unclear. In order to address this question, we use a simplified physics atmospheric model forced with seasonally varying prescribed sea surface temperatures (SST) following the evolution of different ENSO phases with linearly varying strength at a fixed location. To isolate the tropospheric pathway the zonal mean stratospheric winds are nudged towards the model climatology. The model experiments indicate that the tropospheric pathway of ENSO to the North Atlantic exhibits significant nonlinearity with respect to the tropical SST forcing, both in terms of the location and amplitude of the impacts. For example, strong El Niño leads to a significantly stronger impact on the North Atlantic Oscillation (NAO) than a La Niña forcing of the same amplitude. For La Niña forcings, there is a saturation in the response, with no further increase in the NAO impact even when doubling the SST forcing, while this is not the case for El Niño. These findings may have important consequences for long-range prediction of the North Atlantic and Europe.

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“…The teleconnection may be nonstationary (Greatbatch et al, 2004), and depend nonlinearly on ENSO strength (Hardiman et al, 2019; Jiménez‐Esteve & Domeisen, 2019; Toniazzo & Scaife, 2006). Deser et al (2017) find less robust NAE teleconnections than for the Pacific/North America (PNA) region and attribute the different NAE responses to individual ENSO events to atmospheric internal variability, while Mezzina et al (2020) argue the ENSO‐NAE teleconnection is distinct from the NAO. Others find different NAE region responses to central Pacific and East Pacific El Niño events (Ashok et al, 2007; Graf & Zanchettin, 2012).…”

Section: Introductionmentioning

confidence: 99%

Tropical Rainfall Linked to Stronger Future ENSO‐NAO Teleconnection in CMIP5 Models

Fereday

Chadwick

Knight

et al. 2020

Geophysical Research Letters

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The El Niño-Southern Oscillation (ENSO) has previously been shown to influence the winter North Atlantic Oscillation (NAO). Here we investigate the ENSO-NAO teleconnection in historical and RCP8.5 scenario CMIP5 simulations and show a future strengthening of the teleconnection under RCP8.5. The teleconnection strength is associated with increased East Pacific tropical rainfall variability. Stratospheric and tropospheric teleconnection pathways are examined, with both pathways having stronger links in the future. The stratospheric pathway involves the Aleutian Low and the stratospheric polar vortex with a downward influence on the NAO. This pathway is clearest in the high-top models that better resolve the stratosphere. The tropospheric pathway is driven by the Pacific subtropical jet strengthening and extending further into the Atlantic in the future, generating increased baroclinicity in the Caribbean and influencing the Atlantic storm track. These results suggest increasing influence of tropical rainfall on extratropical circulation in the future. Plain Language Summary Winter weather over Europe is driven by the North Atlantic Oscillation (NAO) an atmospheric circulation pattern linked to the fluctuating strength of westerly winds across the North Atlantic. Previous work has shown that the NAO is influenced by rainfall in the tropical East Pacific linked to the El Niño-Southern Oscillation (ENSO) an irregular warming and cooling of the tropical Pacific Ocean. We show that the ENSO-NAO link strengthens in a future warmer climate according to climate models. Models with stronger links simulate bigger year-to-year changes in tropical east Pacific rainfall. We investigate two pathways in which the tropical rainfall influences the NAO. In the first pathway, the rainfall is linked to a persistent low-pressure system over the North Pacific; this then weakens the winter stratospheric polar vortex, which in turn affects the NAO. The models that best simulate the stratosphere show this pathway is stronger in the future. In the second pathway, the jet stream over the Pacific extends further into the Atlantic in the future. This affects the Atlantic storm track, which is itself closely linked to the NAO. These results suggest that tropical rainfall has an increasing influence on the winter weather over Europe in the future, which may lead to better future predictability.

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Dynamics of the ENSO Teleconnection and NAO Variability in the North Atlantic–European Late Winter

Cited by 50 publications

References 54 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

Nonlinearity in the tropospheric pathway of ENSO to the North Atlantic

Tropical Rainfall Linked to Stronger Future ENSO‐NAO Teleconnection in CMIP5 Models

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