Downscaling of the Climatic Change in the Mei-yu Rainband in East Asia by a Pseudo Climate Simulation Method

This study focuses on the reproducibility of the climatic change in the early summer rainfall in East Asia (Mei-yu rainband) by the Pseudo Climate Simulation (PCS) using a regional climate model. In the PCS, the lateral boundary condition is given by the composite of six hourly reanalysis data and the difference between two decadal climate means. The daily variation on the lateral boundary of the PCS is similar to that of the control hindcast in one decade, but its climate is the same as the other decadal mean. The PCS accurately reproduces the change in the Mei-yu rainband over Southern China between the 1960s and the 1990s. suggesting that the climatic features of the Mei-yu rainband are controlled by the climatic change in a large-scale circulation. The PCS reduces the uncertainty caused by the interannual variability in case of the downscaling of global warming projected by the General Circulation Models (GCMs) even if the number of sample years is the same as that in the conventional dynamical downscaling. The PCS can also exclude model biases in the present climatology reproduced by each GCM.