The position of the subtropical jet over the Himalayas (Himalayan jet) affects extreme precipitation and heat over Central and South Asia. We examine the influence of two major natural factors-the El Niño/Southern Oscillation (ENSO) and explosive volcanic eruptions—on Himalayan jet interannual variability during the past millennium using simulations from the Community Earth System Model. We find that both El Niño events and eruptions shift the Himalayan jet equatorward by up to 3°. If an El Niño occurs following an eruption, this enhances the equatorward Himalayan jet shift, while La Niña tends to favor poleward jet migration. Subtropical cooling during El Niño or following eruptions is the primary cause of equatorward Himalayan jet shifts, while poleward shifts are associated with subtropical warming. Consistent across the CMIP6 models over the historical period, our results suggest that both ENSO and eruptions are the key drivers of interannual Himalayan jet variability.

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ENSO 和火山喷发对喜马拉雅急流纬度的影响


喜马拉雅山上空副热带急流（喜马拉雅急流）的位置影响中亚和南亚的极端降水和高温。我们利用社区地球系统模型的模拟，研究了过去千年中两个主要自然因素——厄尔尼诺/南方涛动（ENSO）和火山喷发——对喜马拉雅急流年际变化的影响。我们发现厄尔尼诺事件和火山喷发都使喜马拉雅急流向赤道移动了多达 3°。如果火山喷发后发生厄尔尼诺现象，则会增强喜马拉雅急流向赤道的移动，而拉尼娜现象则往往有利于急流向极地迁移。厄尔尼诺现象期间或火山喷发后的副热带变冷是喜马拉雅急流向赤道移动的主要原因，而向极地移动则与副热带变暖有关。我们的结果与历史时期的 CMIP6 模型一致，表明 ENSO 和火山喷发都是喜马拉雅急流年际变率的关键驱动因素。