Water vapour transport changes associated with the interdecadal decrease in the summer rainfall over Northeast Asia around the late-1990s

This study reveals an obvious interdecadal change in the summer water vapour budget over Northeast Asia around the late-1990s accompanied with the abrupt rainfall decrease. After the late-1990s, water vapour transported into Northeast Asia is apparently reduced under control of a local anomalous anti-cyclone. The water vapour transport is further explored by decomposing the water vapour flux into stationary and transient components, which are associated with the mean flow and transient eddy, respectively. The results indicate that the stationary component accounts for nearly 84% of the total water vapour budget change, much larger than the contribution from the transient component (16%). The correlation coefficient between the interdecadal variation of net and stationary (transient) water vapour budget is 0.95 (0.14). Hence, the stationary term plays a dominant role in contributing to interdecadal change in the total water vapour transport. In addition, change in the water vapour budget over Northeast Asia around the late-1990s is primarily attributed to the wind field change at the lower troposphere. A further comparison of the water vapour budgets in four boundaries of Northeast Asia shows that the water vapour budgets via the southern and northern boundaries display remarkable changes around the late-1990s, exerting significant influences on the total moisture budget change. The anomalous atmospheric water vapour transport circulations in association with the southern and northern boundaries both present a wave-like teleconnection pattern over the Eurasia, whose formation may be partly due to the combined impacts from the Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation.