第一届未来大气科学论坛

The Antarctic weak polar vortex events (WPVs) can induce noticeable impacts on the tropospheric circulation. The vortex preconditioning refers to the anomalous stratospheric state favoring the occurrence of vortex disruption. Motivated by the limited research on the stratospheric preconditioning of Antarctic WPVs, the detailed role of preconditioned stratospheric anomalies in triggering WPVs is investigated, using the latest ERA5.1 reanalysis data. The vortex preconditioning of WPVs originates from the planetary wave breaking in the middle-upper stratosphere. It features a poleward shift of the polar night jet that occurs within 80 days before the onset of WPVs, coinciding with the sharpening of meridional potential vorticity (PV) gradient along the vortex edge. Our results indicate that the stratospheric modulation during vortex preconditioning is the essential factor for triggering most Antarctic WPVs, regardless of the presence of an anomalously strong wave source in the troposphere. About 84% of WPVs are preceded by robustly positive meridional PV gradient anomalies along the vortex edge. Furthermore, about 36% of WPVs are only preceded by strong stratospheric anomalies but without anomalously strong tropospheric wave pulse. Compared to the Northern Hemisphere, preconditioned stratospheric signals in the Southern Hemisphere have a longer duration and larger proportion linking to WPVs. More Antarctic WPVs are preceded by more frequency wave-1 minor warming-like disturbances in the middle-upper stratosphere than Arctic WPVs. Especially, the stratospheric indicator can at least account for about 41% and 65% magnitudes of 10-day zonal-wind deceleration for the two consensus Antarctic WPVs in 2002 and 2019, respectively.

平流层极涡,平流层爆发性增温,行星波