Pacific multi‐decadal oscillation modulates the effect of Arctic oscillation and El Ni?o southern oscillation on the East Asian winter monsoon

摘要

>In this study, the relationship between the East Asian winter monsoon (EAWM) and the Arctic oscillation (AO) and El Ni?o southern oscillation (ENSO) are reanalysed using long‐term reanalysis data. The AO and ENSO influence the EAWM by means of a significant inter‐decadal oscillation with a periodicity of approximately 60 years. When the linkage between the AO and EAWM is strengthened (weakened), the ENSO has a weakened (strengthened) relationship with the EAWM. The AO and ENSO alternately affect the EAWM for approximately 30 years. Furthermore, an analysis is completed regarding the possible mechanism of the inter‐decadal relationship between the EAWM and ENSO, as well as the AO. Such an inter‐decadal relationship could be due to the phase transition of the Pacific multi‐decadal oscillation (PMO). When the PMO is positive, sea surface temperatures (SSTs) in the Bering Strait and Alaska Current region are warmer than average, which results in a decrease in the East Asian trough and an increase in the Aleutian low and northeastern Pacific vertical wave activity flux. In this case, the vertical wave activity flux propagates upward and is reflected in the polar vortex, which significantly strengthens the relationship between the Asia‐Pacific climate and AO. Simultaneously, during the positive phase of the PMO, the increase in the SST in the eastern South Pacific is stronger than in the west, which leads to a weakening of the east–west temperature gradient and southern oscillation. Thus, the relationship between the ENSO and Asia‐Pacific region is significantly weakened and vice versa. The results of this study deepen the understanding of the Asia‐Pacific climate and may improve the inter‐decadal prediction of the Asia‐Pacific regional climate in the future.