The Combined Influence of the Madden-Julian Oscillation and El Nin?o-Southern Oscillation on Australian Rainfall

This study first re-examines the impact of the Madden-Julian oscillation (MJO) on weekly rainfall probabil-ities and wind anomalies across Australia, motivated by the need for a contemporary understanding of the MJO's influence on Australian rainfall, whether this has changed from a previous assessment published in 2009. With an extra 15 years of observations, we show that the strong impact of MJO phases 5 and 6 on northern Australia's austral summer rainfall has weakened by around 5% over Australia's Top End. In addition, austral spring has seen a weakening of the suppressed rainfall teleconnection with MJO phases 2 and 3 over southeast Australia. The weakened relationships make it a little harder to use the MJO to explain rainfall variations over northern Australia in summer and southeast Australia in spring in the current climate. The study's second motivation is to further document the combined influence of El Nin similar to o-Southern Oscillation (ENSO) and the MJO on rainfall. In summer during El Nin similar to o, as compared with La Nin similar to a or neutral ENSO conditions, there are stronger reductions in rainfall probabilities over northern Australia associated with the dry MJO phases 8,1, and 2, but the significantly increased rainfall probabilities in MJO phases 5 and 6 remain much the same. Indeed, the MJO dominates over ENSO in its influence on weekly rainfall probabilities in the north in summer. In contrast, ENSO tends to dominate across subtropical and southern Australia in spring. The updated probability maps are an important resource for estimating the intraseasonal influence of the MJO and ENSO on Australian rainfall.