In this study, we investigated spatial and temporal changes in precipitation over the Coordinated Regional Climate Downscaling Experiment (CORDEX) East Asia domain, for present (1986)(1987)(1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) and future (2031-2050) periods using the Regional Climate Model version 4 (RegCM4). Future meteorology produced by the Hadley Center Global Environmental Model version 2 coupled with the Atmosphere-Ocean (HadGEM2-AO) following global climate change scenarios (Representative Concentration Pathways (RCP) 4.5 and 8.5) was used as meteorological boundary conditions for the RegCM4. Six subregions (South Korea, North China, South China, Japan, Mongolia, and India) in the CORDEX East Asia domain were considered for analysis. The RegCM4 simulated spatial distributions of precipitation over East Asia with a correlation coefficient of 0.7 against Climate Research Unit data. The simulation skills of its temporal variability varied based on geographical regions and seasons, showing relatively poorer performance (underestimation in rainfall amount) in summer than in winter, in general. The future climate simulations by the RegCM4 presented that the East Asian continental regions will be warmer and more humid, leading to increased precipitation amounts, especially in the summer. The summer precipitation amount was projected to increase by about 5%, on average, over the East Asian domain, 5À15% in most subregions, and even higher (44% and 24%) in the South Korean region for the RCP 4.5 and 8.5 scenarios, respectively. It was also expected that heavy rainfall (> 50 mm/d) events may occur more frequently in the future possibly owing to meteorological changes that are favorable to convective heavy precipitation.

[1] The impact of boundary conditions (BCs) on simulations of precipitation characteristics using the Regional Climate Model version 4 (RegCM4) driven by two BCs (ERA-Interim: ERA, NCEP/DOE 2: R2) was investigated using 18 years (1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006) of simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX) East Asia region. The RegCM4 adequately simulated spatial distribution of precipitation over the East Asia region and its temporal variations, irrespective of the BC used. It overestimated precipitation over the central region of the model domain except for India and South Korea and underestimated precipitation over equatorial ocean regions. The RegCM4's simulation skills were better in winter than in summer regardless of the BC, which can be related to the low spatial resolution (50 km) of the model, but detailed simulations of precipitation are significantly impacted by the BCs, although the impact varies with geographical location and season. Driven by ERA, the RegCM4 reproduces more precipitation in the central inland region of the model's domain and less precipitation in the southern coastal areas than when driven by R2. The differences occur because RegCM4 driven by ERA simulated the lower troposphere as being warmer and more humid and the upper troposphere as being cooler than that by R2. The transport of moisture into the central region of the model domain is also enhanced when the RegCM4 is driven by ERA. Although the RegCM4 accurately simulated the seasonal variations in precipitation, it failed to capture diurnal variations over South Korea, particularly when driven by R2, and overestimated and underestimated light precipitation (<25 mm/day) and heavy precipitation (> 50 mm/day), respectively.