Jet Configurations Leading to Extreme Winter Temperatures Over Europe

The North Atlantic eddy-driven jet (EDJ) is the main driver of winter weather in Europe and is typically described by its latitude or strength. Here, we show that the relationship between the EDJ and European winter temperature extremes can be better understood by using a multiparametric perspective that accounts for additional aspects of the EDJ structure (tilt, zonal elongation, etc.). First, we identify four regions where the influence of the EDJ on extreme temperatures is different: Scandinavia, Central Europe, Eastern Europe, and Western Mediterranean (WMED). Overall, the main mechanism leading to extreme event occurrence is the anomalous horizontal advection induced by blockings during cold spells and enhanced westerlies during warm events. In the case of the WMED region, diabatic processes play though a principal role in the occurrence of warm events. Additionally, the circulation anomalies and radiative fluxes involved in both processes generate asymmetric effects in minimum and maximum temperatures, leading to more intense cold than warm events. These extreme events are accompanied by different EDJ configurations entailing perturbed EDJs during cold spells and strong tilted EDJs during warm events, but with distinguishable characteristic depending on the region. In almost every region, the probability of cold and warm events is increased when considering the combined effects of more than two EDJ parameters, suggesting an oversimplification of traditional approaches based on a single EDJ parameter. More importantly, our results derived from logistic regression models highlight the relevance of EDJ parameters others than latitude and intensity to drive the largest changes in the odds of extremes.