The longer predictability limit and downward impact on the extratropical circulations and weather have made the winter Stratospheric Polar Vortex (SPV) variability a new source for sub-seasonal prediction in extratropical wintertime. Using the PM2.5 observation data and high-resolution ERA5 reanalysis data during 2014–2019, we investigate the characteristics of SPV and its linkage to the tropospheric meteorological condition during the abnormal PM_2.5 diffusion event in North China in 2015/2016 winter. Results show that this diffusion event includes two stages: rapid diffusion stage (December 22–28, 2015) and persistent diffusion stage (January 1–23, 2016). The tropospheric meteorological condition in both stages was characterized by enhanced northerlies over North China, which dominantly led to the anomalous PM_2.5 concentration drop. An active coupling process between SPV and surface Arctic Oscillation (AO) is found at the persistent diffusion stage, rather than at the rapid diffusion stage. The amplified tropospheric waves associated with the negative AO in the end of December propagated upward and helped split the SPV into two sub-vortices respectively over North Atlantic and North Asia in the beginning of January; the SPV weakening signal then propagated downward, helping intensify the negative AO since January 11, which further strengthened the northerly as well as PM_2.5 diffusion over the entire East Asia. This case study demonstrates that the stratosphere-troposphere coupling effectively favors and extend the duration of PM_2.5 diffusion, and the weakening of SPV provides a long lead information (1–2 weeks) to the meteorological diffusion condition, thus showing appreciable potential for extending the predictability limit of meteorological diffusion condition in North China.

更长的可预测性限制以及对温带环流和天气的向下影响，使得冬季平流层极涡（SPV）变率成为温带冬季亚季节预测的新来源。利用2014-2019年PM2.5观测数据和高分辨率ERA5再分析数据，我们研究了异常PM _2.5期间SPV的特征及其与对流层气象条件的联系2015/2016 冬季华北地区扩散事件. 结果表明，该扩散事件包括两个阶段：快速扩散阶段（2015年12月22-28日）和持续扩散阶段（2016年1月1-23日）。两阶段对流层气象条件均以华北地区偏北风增强为主，导致PM _2.5异常浓度下降。SPV与地表北极涛动（AO）之间的主动耦合过程是在持续扩散阶段，而不是在快速扩散阶段。12月底与负AO相关的放大对流层波向上传播，并帮助SPV在1月初分别在北大西洋和北亚分裂成两个子涡旋；SPV 减弱信号随后向下传播，帮助加强了自 1 月 11 日以来的负 AO，进一步加强了整个东亚的北风和 PM _2.5扩散。本案例研究表明，平流层-对流层耦合有效地有利于并延长 PM _2.5的持续时间 扩散，SPV 的减弱为气象扩散条件提供了较长的前导信息（1-2 周），从而显示出扩大华北气象扩散条件的可预测性极限的可观潜力。