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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. This work has been performed in the framework of the MEDSCOPE (MEDiterranean Services Chain based on climate PrEdictions) ERA4CS project (grant agreement no. 690462) funded by the European Union. J.G.-S. was supported by the “Ramón y Cajal” programme (RYC-2016-21181). F.M.P. was partially supported by the Spanish DANAE (CGL2015-68342-R) and GRAVITOCAST (ERC2018-092835) projects. We greatly thank the two anonymous reviewers for the insightful and constructive comments and suggestions.

A dominant paradigm for mid-latitude air-sea interaction identifies the synoptic-scale atmospheric “noise” as the main driver for the observed ocean surface variability. While this conceptual model successfully holds over most of the mid-latitude ocean surface, its soundness over frontal zones (including western boundary currents; WBC) characterized by intense mesoscale activity, has been questioned in a number of studies suggesting a driving role for the small scale ocean dynamics (mesoscale oceanic eddies) in the modulation of air-sea interaction. In this context, climate models provide a powerful experimental device to inspect the emerging scale-dependent nature of mid-latitude air-sea interaction. This study assesses the impact of model resolution on the representation of air-sea interaction over the Gulf Stream region, in a multi-model ensemble of present-climate simulations performed using a common experimental design. Lead-lag correlation and covariance patterns between sea surface temperature (SST) and turbulent heat flux (THF) are diagnosed to identify the leading regimes of air-sea interaction in a region encompassing both the Gulf Stream system and the North Atlantic subtropical basin. Based on these statistical metrics it is found that coupled models based on “laminar” (eddy-parameterised) and eddy-permitting oceans are able to discriminate between an ocean-driven regime, dominating the region controlled by the Gulf Stream dynamics, and an atmosphere-driven regime, typical of the open ocean regions. However, the increase of model resolution leads to a better representation of SST and THF cross-covariance patterns and functional forms, and the major improvements can be largely ascribed to a refinement of the oceanic model component. The authors of this study wish to thank two reviewers for their many insightful comments. AB, PA, ES, RH, JG-S, DP, ESG, MJR, CR, JS, PV acknowledge PRIMAVERA funding received from the European Commission under Grant Agreement 641727 of the Horizon 2020 research programme. JG-S was additionally supported by the Spanish ‘Ramón y Cajal’ programme (RYC-2016-21181). The authors declare that they have no conflict of interest. The datasets used in this work are cited in this manuscript with appropriate doi’s in publicly available archives.

Objectives: To assess risk factors of retinopathy of prematurity leading to delayed retinal vascularization in the first stage of ROP. Methods: A retrospective study (2000 - 2016) was performed in 275 infants who were born at a gestational age of ≤ 32 weeks. Delayed vascular development was calculated as the difference in avascular area measured in terms of disc diameters between patients with risk factor and those with no risk factor. Results: Intrauterine fetal demise of one twin, apnea, exchange tranfusion and intubation days (≥ 10 days) lead to delayed retinal vascularization of 1.74, 1.58, 1.17, and 1.11 disc diameters and of 3.35, 3.04, 2.25 and 2.13 weeks respectively. Delayed retinal vascular development was less than 1 disc diameter in other factors such as HS-PDA, sepsis, degree of hyaline membrane ≥ III, cerebral hemorrhage, birth weight (every 100 g less), gestational age (every week less), postnatal weight gain (every 1 g less/day) and cerebral hemorrhage. However, since these factors are quantitative (birth weight, gestational age and postnatal weight gain), the greater the adverse effect, the greater the delay will be. Conclusions: Intrauterine fetal demise of one twin, apnea, exchange tranfusion and intubation days (≥ 10 days) lead to delayed retinal vascular development more than 1 disc diameter at 4 - 6 weeks of postnatal life.