Dynamical evolution of a minor sudden stratospheric warming in the Southern Hemisphere in 2019

Abstract. A major strong sudden stratospheric warming (SSW) occurred in the Southern Hemisphere (SH) stratosphere 2002 (hereafter referred to as SSW2002), which is one of most unusual winters SH. Following several warmings, polar vortex broke down midwinter. Eastward-traveling waves and their interaction with quasi-stationary planetary played an important role during this event. This study analyzed Japanese 55-year reanalysis (JRA-55) dataset examine SSW event that SH 2019 SSW2019). In 2019, a rapid temperature increase decelerated westerly winds were observed at cap, but since there was no reversal easterly 60∘ S middle lower stratosphere, SSW2019 classified minor The results showed zonal wavenumber 1 developed SSW2019. vertical component Eliassen–Palm flux indicative pronounced propagation stratosphere. wave driving September larger than 2002. Major SSWs tend accompany preceding preconditioning, changes flow weaken night jet seen SSW2002. similar preconditioning hardly high latitudes. Waveguides (i.e., positive values refractive index squared) found latitudes upper period, provided favorable conditions for propagate upward poleward.