The Operational Very Short Range Forecast of Precipitation and its Hydrological Applications in South Korea

The Meteorological Research Institute of Korea Meteorological Administration(METRI/KMA) has been operating the Very Short Range Forecast of precipitation(VSRF) model supported from Japan Meteorological Agency (JMA) since 2003. KMA is hourly operating two kinds of VSRF models based on the simple extrapolation version and the blended version with meso-scale numerical prediction model to monitor the performance. Both are one hour forecast up to 6 hours ahead with 5km resolution on real-time mode. The precipitation analysis field of VSRF is derived from the radar quantitative precipitation estimation system that is automatically calculating by Window Probability Matching Method using the composite radar reflectivity from 11 KMA radars and highly densed rain gauge data. For blended version, the concept of pattern distance and the transformed hyperbolic tangent function are employed for the spatial and temporal blending scheme. The spatial blending technique of forecasted precipitation plays a significant role of compensating for the regionally mistaken forecast fields. During the heavy rainfall the performance of blended VSRF seemed to be better than that of simple extrapolation.

For the hydrological application of precipitation forecast field of VSRF model, it is performed the hydrological verification of VSRF model(only extrapolation version) and combination with rainfall-runoff model(PC version, National Weather Service) in Kyoungan River Basin. It is compared the Mean Area Precipitation(MAP) between VSRF and Rain gauge. The correlation coefficient between hydrological runoff model using precipitation field forecasted(6 hour ahead) by VSRF model and observed runoff data is up to 0.6 within 3 hour lead time during heavy rainy season. It represents that the VSRF of precipitation is very useful for water resources application.