Using the JRA-55 reanalysis datasets and radiosonde observations, the impact of the quasi-biennial oscillation (QBO) on the downward extension of stratospheric Northern Annular Mode (NAM) signals in its positive and negative phases (positive and negative NAM hereafter) is examined. The results show that the average number of days per month on which stratospheric negative NAM signals extend downward into the troposphere is more than twice as large during the easterly phase of the QBO (EQBO) as those during the westerly phase of the QBO (WQBO). The increasing likelihood of downward extension of stratospheric negative NAM signals during the EQBO is related to three factors: enhanced upward wave-1 fluxes entering the stratosphere, anomalous poleward wave fluxes below 100 hPa and EQBO-induced residual circulation. It is also revealed that the EQBO-induced subtropical tropospheric easterly anomalies lead to positive height anomalies over the subtropical North Atlantic, which are amplified by transient eddies and maintained by convection. These subtropical positive height anomalies further stimulate an anomalous wave train, forcing subpolar positive height anomalies over the Euro-Atlantic sector and enhancing wave 1. Over the Pacific, the EQBO could also induce positive height anomalies in the tropical troposphere, and these anomalies are related to convection and vertical motion. The positive height anomalies can induce anomalous poleward-propagating waves, forcing negative height anomalies over the North Pacific at mid-high latitudes and the enhancing wave 1. Fewer stratospheric positive NAM signals extend downward into the troposphere during the EQBO than during the WQBO, with mechanisms similar to those of negative NAM.

使用JRA-55再分析数据集和探空仪观测数据，研究了准双年振荡（QBO）对平流层北环空模式（NAM）信号正向和负向（此后为正向和负向NAM）信号向下扩展的影响。结果表明，平流层负NAM信号每月向下扩散到对流层的平均天数是QBO东风阶段（EQBO）的两倍，是QBO西风阶段（WQBO）的两倍。 。EQBO期间平流层负NAM信号向下扩展的可能性增加与三个因素有关：进入平流层的上升波1通量增加，低于100 hPa的异常向极波通量以及EQBO引起的残留环流。还发现，EQBO引起的副热带对流层东风异常导致北大西洋副热带正高度高度异常，这些异常被瞬变涡旋放大并通过对流维持。这些副热带正高度异常进一步激发了异常的波列，迫使欧洲-大西洋地区的子极正高度异常增加了波1的强度。在太平洋，EQBO也可能在热带对流层引起正高度异常，这些异常与对流和垂直运动。正高度异常可诱发异常向极传播波，迫使中高纬度北太平洋上空负高度异常和增强波1。