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

The East Asian monsoon (EAM) and the Australian monsoon (AUM) are two subsystems of the Asian-Australian monsoon system. The EAM and AUM can be linked dynamically through the cross-equatorial outflow, in addition to their own distinct responses to external forcing. Despite previous studies on their relationships for different timescales, their relationship at the orbital timescale has remained poorly explored. In a set of simulations, we demonstrate that the Australian Summer Monsoon (AUSM) precipitation varies out-of-phase to the East Asian Summer Monsoon (EASM) at precession timescale due to the local insolation. At the same time scale, the relation between the AUSM and the East Asian winter monsoon (EAWM) is weak. The weak relation is due to the precession induced inter-hemispheric insolation gradient, which weakens the cross-equatorial flow and thus the dynamical links between the AUSM and the EAWM