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Zusammenfassung:
In recent years, frequent extreme weather events associated with the enlargement of atmospheric blocking are recorded in the northern extratropics, with a significant impacting on ecosystems. This study reveals the direct influence of the stratospheric polar vortex on tropospheric blocking, especially over the North Atlantic sector, based on both reanalysis data and large ensemble experiment using climate model. It is found that the stratospheric polar vortex intensity can influence both the formation and evolution of the blockings over the Atlantic sector. Under the conditions of weak stratospheric polar vortex, blockings are more likely to be generated over Greenland and move westward, subsequently may affect the weather over North America. Under conditions of strong stratospheric polar vortex, blockings are more likely to be generated and moves eastward, and would affect the weather over Western Europe. The stratospheric polar vortex can modulate synoptic-scale eddy activities, which play a critical role in shaping the observed and simulated blocking anomalies over the North Atlantic sector. Under conditions of weak stratospheric polar vortex, the generation of synoptic scale eddies decreases, which is unfavorable for the maintenance of eddy-driven jet and may possibly lead to the formation of low-frequency positive geopotential height anomalies and more blockings over Greenland. The above processes during strong stratospheric polar vortex are nearly opposite.
