Synergistic Interdecadal Effects of the North Pacific and North Atlantic SST on Precipitation over eastern China as revealed in the ECHAM5 simulations

Abstract

In this investigation, we examine the individual and synergistic effects of sea surface temperature (SST) in the North Pacific and North Atlantic on precipitation interdecadal variations over eastern China using the Multi-Taper Method-Singular Value Decomposition (MTM-SVD) method based on the European Center Hamburg model version 5 (ECHAM5) simulations. Results reveal that the model adequately reproduces the quasi-periodic precipitation responses corresponding to interdecadal SST forcing in the North Pacific, North Atlantic and both regions. The Pacific Decadal Oscillation (PDO) is closely related to a meridional tri-polar precipitation pattern over eastern China. This precipitation pattern is attributed to the western Pacific subtropical high and surface pressure anomalies over northern East Asia, influenced by the joint effects of a mid-latitude wave train and SST anomalies in the central-western North Pacific. The North Atlantic basin-scale SST (NABS) correlates positively with precipitation over North China and negatively with precipitation over Southwest China. This precipitation pattern is affected by the westward shift of the atmospheric activity center over East Asia associated with the mid-latitude wave train across Eurasia. The combined SST forcing from the North Pacific and North Atlantic results in a meridional precipitation dipole pattern, and partially explains the precipitation interdecadal variation as observed. That is, as the PDO warm phase transitions to the NABS warm phase, rainbands experience an interdecadal northward shift from South China to North China. These results are pivotal for understanding how interdecadal SST forcing in the North Pacific and North Atlantic influences the precipitation distribution over China, thereby contributing to improvements in interdecadal climate prediction.