Projected Change in Mean and Extreme Climate over Korea from a Double-Nested Regional Climate Model Simulation

We present an analysis of a simulated climate projection covering the period 1971-2080 over the Korean Peninsula with a regional climate model (RegCM3) using a one-way double-nested system. The mother and nested domain cover the East Asian region at 60 km grid spacing and the Korean Peninsula at 20 km grid spacing, respectively. The mean climate state as well as the frequency and intensity of daily extreme events are investigated at various temporal and spatial scales, with a focus on surface air temperature and precipitation. Our analysis is primarily centered on the comparison of two 30-year climate periods between 2021-2050 and 2051-2080, in order to assess climatic changes at different time periods in response to anthropogenic forcings under the IPCC B2 emission scenario. Regarding the interdecadal variation of projected temperature and precipitation over the whole integration period, we find that the temperature change gradually increases by 3.2 K for the 2070s, with a persistently increasing trend. The projected precipitation in the future shows generally greater amounts than in the reference run despite significant interdecadal variation. A substantial increase (decrease) of hot (frost) spells is projected along with increasing of maximum and minimum temperature. Wet spells of long periods tend to be more frequent, accompanying the increase of precipitation amounts. The temperature changes are statistically significant at the 90% confidence level in all seasons and regions, indicating robustness of the projected change while the precipitation changes show low statistical confidence, especially summer season, due to the large natural variability. Based on the spatial distribution, although the general pattern between the mother and nested domain simulations shows similarity, more detailed structure over Korea is found in the nested domain simulation. By comparison of the change between 2021-2050 and 2051-2080 periods, the climate change signal of both temperature and precipitation becomes more pronounced in the late 21 st century as the greenhouse gas concentration is increased.