Waviness of the Southern Hemisphere wintertime polar and subtropical jets

The recently developed average latitudinal displacement (ALD) methodology is applied to assess the waviness of the austral winter subtropical and polar jets using three different reanalysis data sets. The analysis reveals both similarities and differences between the hemispheres with respect to aspects of the tendencies exhibited by both species of jets over the last 6 decades. As in the wintertime Northern Hemisphere, both jets in the Southern Hemisphere have become systematically wavier over the time series and the waviness of each jet evolves quite independently of the other during most cold seasons. Also, like its Northern Hemisphere equivalent, the Southern Hemisphere polar jet exhibits no trend in speed (though it is notably slower) while its poleward creep is statistically significant. In contrast to its Northern Hemisphere counterpart, the austral subtropical jet has undergone both a systematic increase in speed as well as a statistically significant poleward migration. Finally, composite differences between the waviest and least wavy seasons for each species suggest that the Southern Hemisphere’s lower stratospheric polar vortex is negatively impacted by unusually wavy tropopause-level jets of either species.