On the specificity of the tropospheric configurations related to stratospheric vortex decelerations

Abstract

The wintertime stratospheric circulation over the Northern Hemisphere is characterized by a persistent westerly polar vortex. This circulation can undergo substantial decelerations of varying intensity, accompanied by a pronounced warming of the polar stratosphere. In the most extreme cases, such decelerations may lead to a reversal of the zonal-mean winds from westerly to easterly. The impacts of such events on the troposphere are well documented, and due to their relevance, considerable interest lies in identifying the tropospheric configurations that favor them, as well as those emerging once a polar vortex deceleration occurs. Yet, a common finding across studies is the diversity of tropospheric responses associated with these disturbances, including cases where no clear tropospheric precursors or impacts are observed. In this paper, we build on recent advances in dynamical systems theory applied to the atmosphere to show that, while the majority of anomalous states of the geopotential field at 10hPa correspond to vortex decelerations, no distinct tropospheric configurations appear to be systematically linked to such events. This suggests that both the tropospheric precursors conducive to vortex decelerations and the subsequent circulation patterns resulting from them may be inherently nonspecific.