Future changes in extreme precipitation in East Asia and their uncertainty based on large ensemble simulations with a high-resolution AGCM

Large ensemble simulations with about 100 members are performed by using a 60-km mesh atmospheric general circulation model (AGCM) for the present and a 4K warmer climates, using 6 different sea surface temperature (SST) spatial patterns projected by state-of-the-art climate models participating in CMIP5. Under the 4K warmer climate, precipitation extremes such as annual maximum 1-day precipitation total (Rx1d) are projected to increase everywhere in East Asia with robustness. However, there is large uncertainty in their quantitative estimates, arising from (1) internal variability and (2) uncertainty in future SST patterns. Over land region such as inland of China, internal variability is the major source of uncertainty in the climatological mean Rx1d change. Meanwhile, over oceanic region including Japan, Korea and coastal area of China, the SST factor largely affects the Rx1d change mainly through modulation of tropical cyclone activity, suggesting large regional variations in relative importance of these two factors to uncertainty in extreme precipitation projections.