Possible Mechanisms of Long-Term Trend of June Rainfall over the Korean Peninsula

The June rainfall over the Korean peninsula has exhibited a significant decrease in particular after late 1990s. From the Empirical Orthogonal Function (EOF) analyses on the surface temperature, this study found two modes to be closely related to the decrease of rainfall over the peninsula. The first (second) EOF mode is associated with the enhanced surface temperature and anticyclonic circulation over the eastern Lake Baikal to northeastern China (the far East of Russia). The second mode also appears to be related to the cyclonic circulation over the East China Sea and south of Japan islands. These circulation patterns induce southeastward or eastward water vapor transports, and then contribute to the decreased moisture flux convergence and rainfall over Korea. In conclusion, the recent decrease of June rainfall over the Korean peninsula is thought to be, in part, associated with changes in the East Asian Summer Monsoon circulation possibly caused by the local warming trends over the eastern Lake Baikal to Mongolia and far East of Russia.