Zonal Wave Three: Trends and links to extreme events

In the Southern Hemisphere atmospheric circulation, one of the most prominent wave patterns is zonal wave three (ZW3), which exhibits three positive and three negative anomalies in the zonal eddy field around the Southern Hemisphere, with maximum amplitude over the Southern Oceans. Using ERA5 data, this presentation will describe the form of ZW3 and trends in its behaviour. Over the past 60 years, the amplitude of ZW3 exhibits significant upward trends throughout the year but most prominently in summer (Dec-Feb). Such trends are related to increasing meridional temperature gradients and to trends in eddy activity in general and to trends in poleward energy fluxes. Implications for surface climate temperature and precipitation extremes will be outlined.