Various approaches using ensemble prediction system in KMA

The ensemble prediction system based on the Korean Integrated Model (KIM) has been in operation at Korea Meteorological Administration (KMA) since October 2021. KIM is KMA’s new generation global model which is based on the cubed sphere grid system and has 12km horizontal resolution and 91 vertical levels. It was developed over 9 years from 2011 to 2019 and operationally launched in April 2020. KIM-based ensemble forecast system consists of 50 perturbation members (25 members for long-range forecast) and 1 control member. Four-dimensional LETKF (Local Ensemble Transform 
Kalman Filter) with additive and RTPS inflation scheme is used to make initial perturbation.
The performance of KIM-based ensemble system was evaluated. It is generally more skillful compared to the KIM deterministic global model and shows similar performance with UM-based ensemble system which KMA is operating. An increase in the number of ensemble members results in an overall improvement in prediction performance, especially at higher latitudes. Details of results from KIM ensemble system and impacts of increased ensemble size will be discussed.
Multi-model ensemble is another type of ensemble prediction system KMA is operating. KMA’s multi-model ensemble prediction system that merges six global domain models(KIM, UM, ECMWF global and global ensemble models) is used for short and medium-range forecast. Multi-model ensemble mean shows better performance than the ECMWF ensemble model, which is the best member model. 
In addition, multi-model ensemble system that incorporate regional models in addition to global models is used for impact-based forecast of heat waves and cold waves.  Impact-based forecast for high risk level(`warning` and `alarm`) is improved by using multi-model ensemble system.