The stratospheric pathway is a major driver of El Niño–Southern Oscillation (ENSO) impacts on mid-latitude tropospheric circulation and winter weather. The weak vortex induced by El Niño conditions has been shown to increase the risk of cold spells, especially over Eurasia, but its role for North American winters is less clear. This study involved idealized experiments with the Whole Atmosphere Community Climate Model to examine how the weak winter vortex induced by extreme El Niño events is linked to North American coldness in spring. Contrary to the expected mid-latitude cooling associated with a weak vortex, extreme El Niño events do not lead to North American cooling overall, with daily cold extremes actually decreasing, especially in Canada. The expected cooling is absent in most of North America because of the advection of warmer air masses guided by an enhanced ridge over Canada and a trough over the Aleutian Peninsula. This pattern persists in spring as a result of the trapping of stationary waves from the polar stratosphere and troposphere, implying that the stratospheric influence on North America is sensitive to regional downward wave activities.

平流层路径是厄尔尼诺现象的主要驱动因素-南方涛动对中纬度对流层环流和冬季天气的影响。厄尔尼诺现象引起的弱涡流已显示出增加感冒的风险，尤其是在欧亚大陆，但其在北美冬季的作用尚不清楚。这项研究涉及整个大气社区气候模型的理想实验，以检验极端厄尔尼诺事件引起的弱冬季涡与春季北美寒冷之间的关系。与预期的中纬度降温和弱涡相关的相反，极端的厄尔尼诺现象并没有导致北美整体降温，特别是在加拿大，每日的极端寒冷实际上在减少。在北美大部分地区，由于在加拿大上空的山脊和阿留申半岛上的低谷引导下，更热的空气对流平流，预期的降温没有出现。由于捕获来自极地平流层和对流层的固定波，这种模式在春季持续存在，这意味着平流层对北美的影响对区域性向下波活动很敏感。