Interannual variation in the East Asian summer monsoon-tropical Atlantic SST relationship modulated by the Interdecadal Pacific Oscillation

Tropical Atlantic (TA) SST variability can impact the East Asian summer monsoon (EASM). Here, we find that the interannual EASM-TA relationship exhibits an evident interdecadal variation modulated by the Interdecadal Pacific Oscillation (IPO). The EASM-TA interannual relationship is strong during the positive phase of the IPO (pIPO) but weak during the negative phase of the IPO (nIPO). The pIPO (nIPO)-related warm (cold) SST anomalies in the central tropical Pacific (CTP) intensify (weaken) the convection over the CTP. Therefore, a Matsuno-Gill response of the TA-induced CTP SST change is strong (weak) during the pIPO (nIPO) period. The strong Matsuno-Gill response excites an anomalous anticyclone over the western North Pacific (WNPAC), leading to a significantly positive EASM-TA relationship. However, the WNPAC is absent in the nIPO periods due to the weak Mastono-Gill response, suggesting an insignificant EASM-TA relationship. Understanding the IPO-modulated EASM-TA relationship helps better forecast EASM variability.