Abstract
El Niño Southern Oscillation (ENSO) can bring about inter-basin interactions, whereby Pacific sea surface temperature anomalies (SSTAs) may influence the North Atlantic European (NAE) region. However, ENSO's overall influence on the NAE remains unclear. One potential reason for this uncertainty may arise due to the region being dominated by several different mechanisms. Here we focus on one potential region, namely the Tropical North Atlantic (TNA), and determine how the SSTAs modulate the ENSO teleconnection towards the NAE region. As numerous pathways from the TNA may exist for this modulation, we further center our analysis onto the Caribbean region and Walker cells. We force an idealized atmospheric circulation model with three different seasonally varying sea surface temperature patterns that represent an ENSO event with or without the influence of the Atlantic. Our results demonstrate that modulation of the NAE region by the TNA SSTA and Caribbean region occurs in the boreal spring and summer following an ENSO event. In boreal spring, this modulation is primarily through a propagating Rossy wave train, while in the summer, the TNA's influence is nonlinear and tends to strengthen the ENSO influence over the NAE sector. Overall, this study offers a deeper understanding of the inter-basin interactions of the Walker cell following an ENSO event and the central role of tropical Atlantic SSTAs in modulating the teleconnection to the NAE region.
Highlights
El Niño-Southern Oscillation (ENSO) dominates interannual variability within the tropics and has global impacts through teleconnections
Understanding this interplay is salient as the combined influence over South America and the Caribbean region may be crucial for creating an Rossby wave source (RWS) that can propagate a Rossby wave train that influences the extratropics
The multiple linear regression (MLR) analysis allows for an approximate separation of the influences from the respective equatorial basins, which is necessary since El Niño Southern Oscillation (ENSO) and the Tropical North Atlantic (TNA) sea surface temperature anomalies (SSTAs) co-vary to a high degree
Summary
El Niño-Southern Oscillation (ENSO) dominates interannual variability within the tropics and has global impacts through teleconnections. North Atlantic European (NAE) region (Fraedrich and Müller, 1992; Fraedrich, 1994; Brönnimann, 2007). While it is not yet fully understood how ENSO impacts the NAE region, there is great potential for ENSO to create a relevant impact, which in turn may benefit long-range predictability over Europe (Domeisen et al, 2015). The complexity present in the ENSO-NAE teleconnection results in part from several ENSO teleconnections influencing the region simultaneously. These pathways can be separated into several different parts, including signals through different geographical regions as well as different atmospheric levels (Rodríguez-Fonseca et al, 2016).
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