The NCAR/CCM3 general circulation model (GCM) is coupled with regional weather prediction model PSU/NCAR MM5 for the regional climate studies. The main motivation for this effort comes from the observation that the representation of sub-GCM grid scale forcing is critical to accurately simulate the regional distribution of climatic variables such as air temperature and precipitation over meso-scale region. Using PSU/NCAR MM5 driven by NCAR/CCM3 large scale fields, I-day events over Northeastern Asia (centered in Korean Peninsular) is simulated. In this case study, the mechanical coupling methodology and the results of test simulation are shown. This work illustrates the use of the coupled modeling technique for the long-term regional climate simulation.