Variations in Northeast Asian Summer Precipitation Driven by the Atlantic Multidecadal Oscillation
The AMO affects Northeast Asia via a circumglobal teleconnection pattern extending from the North Atlantic to North America. Corresponding with the positive phase of this teleconnection pattern, a tripolar pattern emerges in the Asian–North Pacific sector, with anomalous low pressure over Northeast Asia and high pressure over Lake Baikal and the mid-latitude western North Pacific. These results suggest that the positive phase of the AMO favors the occurrence of the cold vortex over Northeast Asia and anomalous highs over Lake Baikal and the mid-latitude western North Pacific in summer, which enhances the East Asian summer monsoon and southward intrusion of high-latitude cold air, and eventually increases the summer precipitation in Northeast Asia. Furthermore, initialized decadal prediction simulations using the CCSM4 model reproduce well the observed variations of the AMO and its associated atmospheric teleconnection but with slightly shifted geographic locations. The simulated anomalous Northeast Asia cold vortex and strong East Asian summer monsoon, lead to above-normal summer precipitation over Northeast Asia. The modeling results confirm that the multidecadal variability in the North Atlantic can cause the observed interdecadal variations of Northeast Asia summer precipitation. Our results suggest that to understand and predict interdecadal climate change over Northeast Asia, it is important to consider the key role of the AMO.
The initialized decadal prediction simulations using the CCSM4 model are capable of reproducing the observed time evolution of the AMO index and its associated atmospheric teleconnections, but with slightly shifted geographic locations. In East Asia to North Pacific sector, the model captures well the low–level anticyclone–cyclone–anticyclone pattern seen in observations. An anomalous tilted cyclone occupies Northeast Asia and leads an anomalous strong summer monsoon in East Asia and above-normal summer precipitation over Northeast Asia. Therefore, the model is capable to reproduce the observed in-phase relationship between the AMO and summer precipitation over Northeast Asia. Moreover, the model captures well the opposite signs in summer precipitation change over Northeast Asia during AMO phase shifts in the mid-1960s and late 1990s.
The initialized decadal prediction simulations using the CCSM4 model are capable of reproducing the observed time evolution of the AMO index and its associated atmospheric teleconnections, but with slightly shifted geographic locations. In East Asia to North Pacific sector, the model captures well the low–level anticyclone–cyclone–anticyclone pattern seen in observations. An anomalous tilted cyclone occupies Northeast Asia and leads an anomalous strong summer monsoon in East Asia and above-normal summer precipitation over Northeast Asia. Therefore, the model is capable to reproduce the observed in-phase relationship between the AMO and summer precipitation over Northeast Asia. Moreover, the model captures well the opposite signs in summer precipitation change over Northeast Asia during AMO phase shifts in the mid-1960s and late 1990s.