The Influence of Arctic Oscillation on South China Precipitation in Winter Is Modulated by the Atlantic Multidecadal Oscillation

As the dominant mode of low-frequency atmospheric variability in extratropical Northern Hemisphere, the Arctic Oscillation (AO) exerts strong impacts on East Asian climate, with the positive AO leading to increased South China winter precipitation (SCWP). Here, we find that such AO–SCWP relationship is nonstationary and controlled by the remote Atlantic Multidecadal Oscillation (AMO). Especially, the relationship between positive AO and SCWP is significantly weakened during the warm phase of AMO. Observational analyses and idealized Atlantic pacemaker simulations indicate that warm AMO forcing is accompanied by a teleconnection wave train extending eastward from the North Atlantic to West Pacific and the western North Pacific sea surface temperature warming, which together induce northerly wind anomalies over South China by enhancing the land–ocean pressure gradient. Such climate background state changes associated with the warm AMO prohibit the positive AO induced water vapor transport to South China, thereby weakening the AO–SCWP relationship.