Climate models are indispensable tools for future climate projection, including predictions of the Mei-yu front rainfall, which is the major rain-bearing system of the East Asian summer monsoon. Adaptation to climate change relies heavily on the data of climate projection from the Coupled Model Intercomparison Project (CMIP). However, resolutions of CMIP models such as CMIP5 are generally around 100 to 200 kilometers, which are not high enough to resolve some regional rainfall systems, for instance, the Mei-yu rain belt along the Yangtze River valley. Uncertainty in regional rainfall projection due to model resolution needs to be quantified.