Synergistic Impacts of the Atlantic and Pacific Oceans on Interdecadal Variations of Summer Rainfall in Northeast Asia

This study presents a comprehensive analysis of the synergistic impacts of the Atlantic multidecadal oscillation (AMO) and Pacific decadal oscillation (PDO) on the interdecadal variations of summer rainfall in Northeast Asia. Following the construction of four probable scenarios under various combinations of the AMO and PDO phases, it is found that when the AMO and PDO are out of phase, both of them induce a strong or weak East Asian summer monsoon and a low or high pressure system over Northeast Asia through atmospheric teleconnection, which results in significant wet or dry conditions over the whole of Northeast Asia through the effects of superimposition. In contrast, when the AMO and PDO are in-phase, they induce moderate and regional wet or dry conditions in Northeast Asia, and only a slightly strong or weak East Asian summer monsoon through the effects of cancellation. During the mid-1960s–1990s, a period of drought first began in Northeast Asia under a negative AMO and negative PDO in the mid-1960s, which then increased in severity under a negative AMO and positive PDO in the 1980s, before finally coming to an end under a positive AMO and negative PDO in the late 1990s. The interdecadal predictability of summer rainfall in Northeast Asia may reside in the interdecadal behavior of the North Atlantic and Pacific Oceans.