Mid-Holocene summer monsoon dynamics over East Asia: robust physics underlying large inter-model spread

Abstract:

The mid-Holocene (MH; 6 ka BP), one benchmark period for the Paleoclimate Modelling Intercomparison Project (PMIP) during Quaternary. This period is of distinct orbital parameters configuration from those of today. Consequently, MH is widely used to examine the climate in responses to orbital forcings. This study aims to reveal orbital-forced monsoon dynamics by analyzing the three phases of PMIP simulations for MH. We show large inter-model spread in orbital-scale variation of East Asian summer monsoon (EASM) precipitation associated with a reduced thermodynamic response. Nevertheless, robust monsoon dynamics underneath is revealed by a decomposition of moisture budget variations into thermodynamic component, dynamic component and covariation in both. It was shown that the cloud cooling effect reduces the thermodynamic contribution to precipitation in EASM domains. The dynamical component contributes to precipitation increase during the MH by the enhanced monsoonal moisture transport, which is undertaken by the intensified stationary eddy anti-Hadley circulation with ascending branch arising from Tibetan Plateau. Mid-latitude atmospheric rivers are main vapor source of enhanced moisture transport.