Effects of the high-resolution river routing model on seasonal prediction model

To improve the prediction skill of Korea Meteorological Administration climate prediction system (KMA-GloSea6), high-resolution river routing model in land surface model are implemented. The characteristics of the current river routing model were investigated and pointed out the weakness. It was found that GloSea6 uses a relatively simple river routing model, and the simulated river storage is overestimated compared to the observation. To simulate accurate river flow and air-land-sea interaction, it is most desirable to coupling a sophisticated and realistic river routing model. As a simple method, it was tried to reduce the amount of freshwater flowing into the ocean by increasing the resolution in same river routing model. The GloSea6, which can replace the existing 1-degree resolution with 0.5-degree and 0.125-degree resolution for river routing model, was newly constructed. Also, as the resolution of the river routing model changed, the setting coefficients for the meandering and river flow velocity were optimized. It is clear that the newly conducted system reduces errors in river flow and discharge compared to existing operational system. The simulation with optimized high-resolution river routing model shows reduced biases in ocean circulation and temperature, especially in the Pacific and Indian Oceans. These results can be useful in improving seasonal prediction due to more accurate air-sea interaction and in applied and policy research on water resources.