Stratospheric polar vortex variability

Compared with the tropospheric variability, the stratospheric polar vortex variability usually has a longer autocorrelation or persistence timescale. The stratospheric polar vortex can vary substantially in a single winter between an extremely weak and an extremely strong state. Weakening polar vortex events can coincide with sudden stratospheric warming and final stratospheric warming events, and extremely strong polar vortex events can result in Arctic ozone loss. This chapter summarizes different aspects of the stratospheric polar vortex, involving the external forcings that significantly modulate the polar vortex variability, the downward impacts of stratospheric variability, simulation of the vortex in models, projected changes in the future, and subseasonal-to-seasonal predictability of the stratospheric polar vortex in both hemispheres.