Circulation changes associated with the interdecadal shift of Korean August rainfall around late 1960s

The impacts of local/remote thermodynamic conditions and large-scale circulations on the timing of the peak rainy season shift over the Korean Peninsula are investigated. The Korean August rainfall is strongly associated with the westward expansion of the western North Pacific subtropical high and the presence of the Bonin high. The westward expansion of the subtropical high is primarily associated with the teleconnection due to the energy propagation of the stationary Rossby wave along the Asian jet from the upstream region. The enhanced north-south thermal gradient plays an important role in modulating the interdecadal change in the East Asian jet stream, which in turn increases the August rainfall. Both the July and August rainfall are influenced by the interdecadal variability in upper-level temperature and Asian jet stream, which are significantly associated with the dynamical circulation change after the late 1960s. However, the influence on the July rainfall seems to be offset by the impact of a predominant Pacific-Japan pattern, whereas the August rainfall is affected by a strong Eurasian wave-like pattern.