Effects of Stratospheric Warming on Ural blocking Events in Winter.

Utilizing the Open Integrated Forecasting System, the responses of Ural blocking (UB) to different stratospheric warming scenarios are investigated. Numerical results show that stratospheric warming with moderate strength in minor patterns prolongs the UB duration and enhances its intensity, while strong stratospheric warming in minor patterns tends to shorten its duration and weaken its intensity, even leading to the collapse of the UB events. Further diagnosis reveals that the planetary wave activity flux propagates downward from the stratosphere to the troposphere after stratospheric warming. Moreover, the convergence of planetary wave activity flux is a key factor for UB enhancement and maintenance. In addition, the weakened meridional temperature gradients, decelerated zonal westerly winds, and a reduced meridional potential vorticity gradient (PVy) result in UB enhancement in response to stratospheric warming with moderate strength. As stratospheric warming strengthens, planetary wave activity flux diverges, westerly winds in the tropospheric mid‐latitudes accelerate and the PVy in the Ural sector enlarges, which further weakens UB. Regarding the stratospheric perturbations in major patterns, they have similar influences on UB events, that is, UB enhances with moderate stratospheric warming and weakens with strong warming. However, the strengthened warming would trigger UB re‐enhancement, which is closely associated with anomalous activities of tropospheric synoptic‐scale waves induced by stratospheric perturbations. These results reveal UB events respond differently to stratospheric warming with various intensities and patterns in the short term, which makes a contribution to understanding stratosphere‐troposphere coupling. Plain Language Summary: Tropospheric Ural blocking (UB) is an important factor in modulating the weather and climate in East Asia, while stratospheric warming in the Arctic has great influences on UB in winter. Therefore, the influence of stratospheric warming on UB events is investigated with a complicated atmospheric model. We find that the anomalous energy from stratospheric warming propagates downward to the troposphere within 15 days, which in turn affects the UB events. Moderate stratospheric warmings can decelerate the mid‐latitude westerly winds, leading to enhanced UB. As the stratospheric warming strengthens, the UB weakens or even collapses due to the accelerated mid‐latitude westerly winds. These findings reveal the impact of stratospheric warming on UB events in the short term and contribute to a better understanding of the relationship between the stratosphere and the troposphere. Key Points: Stratospheric warming has notable effects on Ural blocking (UB) events within 15 daysThe moderate stratospheric warmings both in minor and major patterns enhance UB eventsStrengthened warming in major patterns would trigger UB re‐enhancement [ABSTRACT FROM AUTHOR]