The response of AUSM to precession forcing and its relation to EASM and EAWM

The East Asian monsoon (EAM) and the Australian monsoon (AUM), which constitute the two subsystems of the Asian-Australian monsoon system, are dynamically linked through cross-equatorial flows while also responding distinctly to external forcings. Although previous studies have examined their relationships across various timescales, their connection at the orbital timescale remains underexplored. Through a series of simulations, we demonstrate that Australian Summer Monsoon (AUSM) precipitation varies out of phase with East Asian Summer Monsoon (EASM) precipitation at the precession timescale due to local insolation changes. At the same timescale, the relationship between AUSM circulation and East Asian winter monsoon (EAWM) circulation is weak. This weak linkage arises from the precession-induced inter-hemispheric insolation gradient, which diminishes cross-equatorial flow and consequently weakens the dynamical links between AUSM and EAWM circulations.