Evaluation of Very High-Resolution Regional Climate Downscaling over CORDEX East Asia: Climatology and Interannual Variability

Under the framework of Coordinated Regional Downscaling Experiment–East Asia (CORDEX-EA) project, two regional climate simulations were conducted at a very high resolution (12.5 km) using the Regional Climate Model version 4 (RegCM4) and the Weather Research and Forecasting (WRF) driven by ERA5 reanalysis data from 1980 to 2019. Evaluation against observations indicates that both RegCM4 and WRF can reproduce the mean climatology, interannual variability, and annual cycle of precipitation and surface air temperature (T2m), although some biases exist. WRF demonstrates skill in simulating the spatial pattern of annual and seasonal mean precipitation by reducing wet biases over land and warm bias in winter. RegCM4 can better capture the interannual variability of precipitation and T2m, exhibiting higher temporal correlation, while WRF tends to overestimate the interannual variability. Additionally, assessment of the simulated circulations against ERA5 reveals that the wet bias in summer is mainly attributed to the enhanced simulated low-level southwesterly jet. Moreover, compared with the results at 50- and 25-km resolutions in the first and second phases of CORDEX-EA, higher resolution (12.5 km) effectively improves the interannual variability of the regional climate simulations.