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The interdecadal change of the relationship between the tropical Indian Ocean dipole (IOD) mode and the summer climate anomaly in China is investigated by using monthly precipitation and temperature records at 210 stations in China and the NCEP/NCAR reanalysis data for 1957–2005. The results indicate that along with the interdecadal shift in the large-scale general circulation around the late 1970s, the relationship between the IOD mode and the summer climate anomaly in some regions of China has significantly changed. Before the late 1970s, a developing IOD event is associated with an enhanced East Asian summer monsoon, which tends to decrease summer precipitation and increase summer temperature in South China; while after the late 1970s, it is associated with a weakened East Asian summer monsoon, which tends to increase (decrease) precipitation and decrease (increase) temperature in the south (north) of the Yangtze River. During the next summer, following a positive IOD event, precipitation is increased in most of China before the late 1970s, while it is decreased (increased) south (north) of the Yangtze River after the late 1970s. There is no significant correlation between the IOD and surface air temperature anomaly in most of China in the next summer before the late 1970s; however, the IOD tends to increase the next summer temperature south of the Yellow River after the late 1970s.

The interannual-to-interdecadal relationship between the Pacific sea surface temperature (SST) and the northern hemispheric midlatitude’s atmosphere represented by the circumpolar vortex was documented with the global oceanic and atmospheric reanalysis data of recent 50 years. Two covarying modes of the Pacific SST and northern circumpolar vortex anomalies during winter were examined using the singular value decomposition and wavelet analysis techniques. One is the interannual, ENSO-related mode and the other is the interdecadal, North Pacific SST-related mode with a period of around 20 years. The two modes exhibit distinct spatial structures. For the interannual mode, the SST anomaly is characterized by a typical ENSO pattern with the principal signature in the tropical eastern Pacific and secondary one in the central North Pacific, while the atmospheric anomaly is regional, characterized by a Pacific-North American pattern. For the interdecadal mode, large SST anomaly is located in the central North Pacific, while the atmospheric anomaly is zonally global, associated with the midlatitute’s standing long-wave variations. When the central North Pacific is colder, the long-wave is stronger, and vice versa. Further investigations suggest that the interdecadal mode could involve an interaction between “two oceans and an atmosphere”.