Future Changes in Precipitation over East Asia Projected by the Global Atmospheric Model MRI-AGCM3.2

A set of global warming projections was conducted using global atmospheric models with high-horizontal resolution of 20-km (MRI-AGCM3.2S, the 20-km model) and 60-km (MRI-AGCM3.2H, the 60-km mode) grid sizes. For the present-day climate (1983-2003, 21 years), models were forced with observed historical sea surface temperatures (SST). For the future climate (2079-2099, 21 years), models were forced with future SST distributions projected by the models of the Fifth phase of Couple Model Intercomparison Project (CMIP5). The uncertainty of projection was evaluated by ensemble simulations for four different SST distributions and three different cumulus convection schemes. 

The simulations by the 20-km and 60-km models consistently project the increase of precipitation over China for all months. In June, precipitation decreases over Japan and increases over the ocean to the south of Japan. The geographical distribution of precipitation change tends to depend relatively on the cumulus convection scheme and horizontal resolution of models rather than on SST distributions. The time evolution of pentad mean precipitation over Japan indicates the delay in the onset of Japanese rainy season in June. This delay can be attributed to the decrease of water vapor transport toward Japan associated with the southward shift of the subtropical high. Change in the subtropical high can be interpreted as the southward shift of the local Hadley circulation. The intensity of precipitation increases most part of East Asia, while the possibility of drought will increase over Japan, the East China Sea and the area to the south of Japan.