Impact of Horizontal Resolution on Regional Climate Simulation over South Korea

Abstract

Added values of regional climate models (RCMs) can be generated by increasing model resolution. However, systematic errors can also be increased due to enhanced internal forcing and inconsistent boundary condition when using RCMs with high resolution. Thus, it is essential to investigate the impacts of model resolution on regional climate simulation. In this study, we examine the positive and negative effects of increasing model resolution on 19-year (1989-2007) regional climate simulation over East Asia. In particular, the impact of horizontal resolution on simulated precipitation over South Korea is focused on. ERA-Interim data are dynamically downscaled using a regional climate model, which have two different horizontal resolutions (50 km and 25 km). Spatial distributions of both mean and extreme precipitation in the experiment with 25 km are more reasonably reproduced compared to those in the experiment with 50 km. This is because higher model resolution improves the simulation of smaller-scale features such as mesoscale convective systems and typhoon, which are substantially relevant to precipitation processes over South Korea. In addition, more detailed topography in the experiment with 25 km leads to the advanced simulation of orographic precipitation. On the other hand, precipitation amount, especially for spring and summer, tends to be overestimated in the experiment with higher resolution, indicating poorer statistics of model performance such as bias and RMSE. These systematic errors can be efficiently reduced by a bias correction method, indicating more improved added values by RCMs.