El Niño Southern Oscillation (ENSO) represents the major driver of interannual climate variability at global scale. Observational and model-based studies have fostered a long-standing debate on the shape and intensity of the ENSO influence over the Euro-Mediterranean sector. Indeed, the detection of this signal is strongly affected by the large internal variability that characterizes the atmospheric circulation in the North Atlantic–European (NAE) region. This study explores if and how the low-frequency variability of North Pacific sea surface temperature (SST) may impact the El Niño-NAE teleconnection in late winter, which consists of a dipolar pattern between middle and high latitudes. A set of idealized atmosphere-only experiments, prescribing different phases of the anomalous SST linked to the Pacific Decadal Oscillation (PDO) superimposed onto an El Niño-like forcing in the tropical Pacific, has been performed in a multi-model framework, in order to assess the potential modulation of the positive ENSO signal. The modelling results suggest, in agreement with observational estimates, that the PDO negative phase (PDO₋) may enhance the amplitude of the El Niño-NAE teleconnection, while the dynamics involved appear to be unaltered. On the other hand, the modulating role of the PDO positive phase (PDO₊) is not reliable across models. This finding is consistent with the atmospheric response to the PDO itself, which is robust and statistically significant only for PDO₋. Its modulation seems to rely on the enhanced meridional SST gradient and the related turbulent heat-flux released along the Kuroshio–Oyashio extension. PDO₋ weakens the North Pacific jet, whereby favoring more poleward propagation of wave activity, strengthening the El Niño-forced Rossby wave-train. These results imply that there might be conditional predictability for the interannual Euro-Mediterranean climate variability depending on the background state.

厄尔尼诺南方涛动（ENSO）代表了全球尺度年际气候变化的主要驱动力。基于观测和基于模型的研究引发了关于ENSO对欧洲地中海部门影响的形式和强度的长期争论。的确，此信号的检测受到内部巨大变化的强烈影响，内部变化是北大西洋—欧洲（NAE）地区大气环流的特征。这项研究探讨了北太平洋海表温度（SST）的低频变化是否以及如何影响冬季后期的ElNiño-NAE遥连接，该连接由中纬度和高纬度之间的偶极模式组成。一组理想的仅限大气的实验，为了评估正ENSO的潜在调制，已经在多模型框架中规定了异常SST的不同阶段，该异常SST与叠加在热带太平洋ElNiño强迫上的太平洋年代际涛动（PDO）有关信号。建模结果表明，与观测估计一致，PDO负相（PDO₋）可能会增强ElNiño-NAE远程连接的幅度，而所涉及的动力学似乎没有改变。另一方面，PDO正相（PDO ₊）的调节作用在所有模型中都不可靠。这一发现与对PDO本身，这是强大的，只为PDO统计显著大气响应一致_- 。它的调制似乎依赖于增强的子午SST梯度以及沿黑潮-矢潮延展线释放的相关湍流通量。PDO _-削弱了北太平洋急流，从而有利于波活动的更多向极传播，从而增强了厄尔尼诺现象造成的Rossby波列。这些结果表明，根据背景状况，欧洲地中海气候年际变化可能存在条件可预测性。