The Interdecadal Changes of the Relationship Between May‐June and July‐August NWPSH and Their Physical Mechanisms

Abstract Unlike prior researches focusing on interannual or interdecadal changes of the Northwest Pacific subtropical high (NWPSH), this paper emphasizes the interdecadal changes in the relationship between May‐June and July‐August NWPSH. The correlation coefficients between them are 0.66 (passing the 99.9% confidence level) and 0.12 during 1979–2002 and 2003–2023. Therefore, the May‐June NWPSH has a strong connection with July‐August East Asian precipitation during 1979–2002, but not during 2003–2023. The interdecadal variations in the relationship of NWPSH are due to interdecadal changes of ENSO. During 1979–2002, the eastern‐type ENSO in prior winter, having longer durations, can influence May‐June and July‐August NWPSH and the North Indian Ocean. However, the central‐type ENSO in prior winter only persists it's influence until May‐June, and changes into a Pacific Dipole pattern in July‐August during 2003–2023. Despite the North Indian Ocean continually warms during 2003–2023, the tropical Pacific Dipole offsets its impacts on the NWPSH.