Potential influence of the Atlantic Multi-decadal Oscillation in modulating the biennial relationship between Indian and Australian summer monsoons

Abstract

Using observed and reanalysed data sets, we investigate the potential role of Atlantic Multi-decadal Oscillations (AMO) in weakening the in-phase association between Indian summer monsoon rainfall (ISMR) and following Australian summer monsoon rainfall (ASMR) during the 1932–1966 period. This weakened inter-monsoon link was earlier attributed to a complete breakdown of the El Niño–Southern Oscillation (ENSO) links with the ASMR. We now find that this weakening was associated with strengthening of low-level westerlies and an increase in local low-level convergence in the northern Australia associated with the warm phase of the AMO during this period. This increased background convergence resulted in relatively enhanced ASMR during the El Niño summers during this period.