Stratospheric drivers of precipitation and temperature in southern Africa

 

The winter stratosphere has been shown to influence surface climate, leading to persistent changes in temperature and precipitation patterns, which can be associated with extreme events such as cold air outbreaks, heavy precipitation and flooding, dry spells, as well as dust storms. These influences on surface weather have dominantly been investigated for the Northern Hemisphere, especially with respect to extreme stratospheric events such as sudden stratospheric warmings and strong vortex events, which have their dominant impact over the North Atlantic area. In the Southern Hemisphere, although such extreme stratospheric events are much less frequent, surface impacts of the stratosphere have also been observed. However, some regions, like southern Africa, have received very little attention. We here explore to what extent stratospheric variability related to the final stratospheric warming, the final breakdown of the stratospheric polar vortex in winter through spring, can have an impact on southern African weather through variability of the Southern Annular Mode (SAM). We find that indeed, the influence of anomalies in the SAM driven by the stratosphere extends to the southern part of Africa, leading to anomalous pressure patterns that influence temperature and precipitation distribution. This contribution is intended to spark research into less explored regions of stratospheric influence in the Southern Hemisphere.