Classification of Heat Wave Weather Patterns for Probabilistic Ensemble Medium-Range Forecasts in South Korea

In this study, weather patterns associated with the heat wave over the Korean peninsula are classified for the probabilistic ensemble medium-range forecast. To select the heat wave events in South Korea, daily maximum temperature of 95 Automated Synoptic Observing Systems (ASOSs) of Korea Meteorological Administration (KMA) from 1981 to 2010 is used. The k-means clustering analysis with geopotential height (gpm) at 500 hPa pressure level of European Centre for Medium?Range Weather Forecast (ECMWF) ERA-Interim reanalysis data is applied to classify the heat wave weather patterns. The number of clusters over study area (20∼50°N, 110∼150°E) defined by Explained Cluster Variance (ECV) is three (k = 3). Three weather patterns are then classified through k-means clustering analysis for 500 hPa geopotential height. In Cluster 1, the isobar of 5,880 gpm is located in south of Japan, which causes a humid and warm southeasterly winds toward the southern Korea. In Cluster 2, 5,880 gpm is located middle of Korea and this weather pattern causes a heat wave in Korea due to weak wind and strong insolation. In Clusters 3, center of the high-pressure system and 5,880 gpm is located western north pacific. The western North Pacific subtropical high pressure system does not extend to Korea. To investigate the relationship between casualties and heat wave range, casualties according to heat wave weather patterns are analyzed. In cluster 1, there were most casualties in southern region of Korea. The casualties in cluster 2 were found nationwide. In cluster 3, casualties occurred mainly in the middle western of Korea. In the future, we will develop a medium-range ensemble probability forecast system utilizing the type of heat wave event.

Acknowledgements: This work was funded by the Korea Meteorological Administration Research and Development Program "Research of convergence technology of analysis and numerical model for severe weather" under Grant (1365003081).