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.

Characteristics of Aerosols over the Summer Monsoon Transition Zone

A survey was conducted in the summer monsoon transition region of China. By combining data from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSOs) and Moderate Resolution Imaging Spectroradiometer (MODIS), the effects of East Asian summer monsoon circulation on the spatial distribution of aerosol, as well as the response mechanisms of different aerosols in an abundant and a deficient summer monsoon year, were analyzed. It was found that, in the summer monsoon transition region, the aerosol optical depth (AOD) in abundant monsoon years was lower than that in deficient years. Only in the Gobi Desert region of the Loess Plateau, the AOD in abundant monsoon years was significantly larger than that in deficient years. When the AOD was less than 0.06, the frequency of dust aerosol was higher than that of polluted aerosol in both the abundant and deficient monsoon years. When the AOD was over 0.06, the frequency of polluted aerosol was higher than that of dust aerosol in both the abundant and deficient monsoon years. In summer, the AOD was larger and the frequency of polluted aerosol in abundant monsoon years was higher than that in deficient years.