The Southern Hemisphere experienced its first recorded polar sudden stratospheric warming during  September 2002. This warming and reversal of the westerly polar vortex winds to easterly was associated with subsequent development of strong low polarity of the Southern Annular Mode (low SAM) and extreme high temperatures over Australia during October 2002. The earlier than normal breakdown of the vortex was associated with anomalously high values of polar stratospheric ozone, which possibly could have constructively sustained the weakened vortex and strong shift to low SAM.

In this study, we explore the impact of the interannual variation of ozone concentration on the prediction of the anomalous vortex weakening and its downward coupling to surface climate during spring-summer of 2002.  We conduct a forecast experiment using the ACCESS-S1 coupled model seasonal prediction system, whose atmospheric model well resolves the stratosphere. The ACCESS-S1 control forecasts are generated with prescribed climatological ozone whereas experimental forecasts are generated with prescribed observed time-varying ozone. While the control forecasts demonstrate reasonably good skill in predicting the weakening of the polar vortex and related lower stratospheric warming in spring 2002 and resultant occurrence of low SAM, the strength and persistence of the stratospheric vortex weakening and the extremity of surface climate anomalies are significantly under-predicted when forecasts are initialised on 1 August 2002. Prescribing the observed ozone variation during these forecasts results in substantial sustained weakening of the stratospheric vortex in late spring and stronger development of low SAM and concomitant extreme warm conditions in eastern Australia during October 2002. These results suggest that polar ozone variation is a potential source of long lead climate variability, which can be tapped with future ACCESS-S development.