A Review of ENSO Influence on the North Atlantic. A Non-Stationary Signal

Abstract

Abstract:The atmospheric seasonal cycle of the North Atlantic region is dominated by meridional movements of the circulation systems: from the tropics, where the West African Monsoon and extreme tropical weather events take place, to the extratropics, where the circulation is dominated by seasonal changes in the jetstream and extratropical cyclones. Climate variability over the North Atlantic is controlled by various mechanisms. Atmospheric internal variability plays a crucial role in the mid-latitudes. However, El Niño-Southern Oscillation (ENSO) is still the main source of predictability in this region situated far away from the Pacific. Although the ENSO influence over tropical and extra-tropical areas is related to different physical mechanisms, in both regions this teleconnection seems to be non-stationary in time and modulated by multidecadal changes of the mean flow. Nowadays, long observational records (greater than 100 years) and modeling projects (e.g., CMIP) permit detecting non-stationarities in the influence of ENSO over the Atlantic basin, and further analyzing its potential mechanisms. The present article reviews the ENSO influence over the Atlantic region, paying special attention to the stability of this teleconnection over time and the possible modulators. Evidence is given that the ENSO-Atlantic teleconnection is weak over the North Atlantic. In this regard, the multidecadal ocean variability seems to modulate the presence of teleconnections, which can lead to important impacts of ENSO and to open windows of opportunity for seasonal predictability.

Stratospheric role in interdecadal changes of El Niño impacts over Europe

“…3b). These patterns are in very good agreement with Rodríguez-Fonseca et al (2016) and those obtained by Iza and Calvo (2015) for EP and CP El Nino events in reanalysis data. To verify the effects of mid-tropospheric changes on the injection of tropospheric wave activity into the stratosphere, the daily distribution of anomalous daily extratropical eddy heat flux at 100 hPa is shown in Fig.…”

“…• Only periods with strong European precipitation response to EN show an active role of the polar stratosphere in this teleconnection in agreement with Rodríguez-Fonseca et al (2016). The location of EN SST anomalies is different in periods with strong and weak EN impact on Europe, such that periods with strong and weak EN impact on Europe are mostly related to Eastern and Central EN SST anomalies, respectively.…”

“…Since multi-decadal changes in SST lead to changes in the upper tropospheric flow, it would be expected that the stratospheric pathway also becomes affected, but all mentioned work only focused on the modulation of the tropospheric pathway. Only Rodríguez-Fonseca et al (2016) in their Fig. 3 gave a first hint that the first co-variability mode of European precipitation and tropical SST for periods with a strong ENSO significant impact on Europe might be associated with perturbations in the polar stratosphere, but not for periods with a negligible European response to ENSO.…”

Independent Subspace Analysis of the Sea Surface Temperature Variability: Non-Gaussian Sources and Sensitivity to Sampling and Dimensionality

“…Moreover, that agrees with the dynamical interactions between ENSO, PDO, and NPGO which have been discussed by several authors [74][75][76]. The quite relevant EOF11 pattern in IC1 is mostly correlated with the El Niño SST composite (asymmetric with respect to La Niña) at mid-latitudes in all oceans, during the DecemberFebruary season [68,77], which explains the above referred coherence of PC1 and PC11 during strong El Niños. The IC2 loading map ( Figure 12) mainly coincides with the symmetrical EOF6, that is, with the positive Atlantic Niño phase, while the remaining dominant EOF contributors to IC2, that is, EOF1, EOF7, and EOF9 (Table 5), practically cancel each other, especially in tropical Pacific El Niño region, despite the presence of non-null correlation in that region ( Figure 11).…”

Influence of finite-time Lyapunov exponents on winter precipitation over the Iberian Peninsula

“…These patterns, though dominant on a large scale, often fail to provide forecast skill in specific regions. Precipitation predictability in Europe using NAO and ENSO as predictors is limited due to nonstationarity (Vicente- Serrano and López-Moreno, 2008;Rodríguez-Fonseca et al, 2016). One way to improve the seasonal forecast would be to identify new predictors.…”