The decadal modulation of the ENSO-Australian monsoon rainfall teleconnection 

<p>We analyse the decadal variability in the relationship between Australian monsoon rainfall (AUMR) and the El Ni&#241;o Southern Oscillation (ENSO). A composite analysis is conducted to examine monsoon season (December to March) rainfall anomalies over northern Australia during central and eastern Pacific ENSO events between 1920 to 2020. These composites are evaluated separately for positive and negative phases of the Interdecadal Pacific Oscillation (IPO) and reveal differences in AUMR anomalies with respect to ENSO event diversity. During central Pacific (CP) El Ni&#241;o events, the key month is February, in which the AUMR is above average in positive IPO phases and below average during negative IPO phases. This is due to low-level circulation anomalies northwest of Australia, which are cyclonic in the positive IPO phases and anticyclonic in negative IPO phases, in addition to moisture fluxes directed towards the central Pacific, away from northern Australia. During CP La Ni&#241;a events, there are insignificant rainfall anomalies over northern Australia in December during positive IPO phases. In contrast, during negative IPO phases, strong and significant positive rainfall anomalies cover much of northern and eastern Australia, which relate to large-scale convergence of moisture and an intensification of the Walker Circulation. In summary, AUMR anomalies during CP ENSO events differ between positive and negative phases of the IPO due to variability in the large-scale atmospheric circulation.</p>