Time-varying relationship between the Indian Ocean Dipole and extreme rainfall event in South Korean modulated by the Pacific Decadal Oscillation

The patterns of extreme rainfall in South Korea are becoming increasingly complex over time influenced by multiple climate factors which shift under different climatic system. Under such complex system, understanding the dynamic teleconnection between extreme rainfall and climate variability is essential especially for unveiling mechanisms of extreme climate in South Korea. This study investigates the linkage between summer extreme rainfall events (exceeding 110 mm in 12 hours) over South Korea and two climate variability factors: the Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO). To categorize rainfall patterns according to the dynamic features, clustering is applied on the extreme precipitation events based on the 850 hPa geopotential height pattern, and four distinct patterns (northern cyclonic pattern, frontal pattern between low and high, extratropical cyclone pattern, and dominant high pattern) are identified. The influence of climate variabilities varies across different clusters. Notably, interannual variability of extreme rainfall events associated with frontal pattern show a significant correlation with preceding spring IOD. Our findings suggest that this relationship fluctuates over time, which are found to be closely depending on the PDO phase. We analyze how the PDO modulates the atmospheric fields to alter the teleconnection between the IOD and frontal extreme rainfall in South Korea, which is the predominant extreme rainfall patterns in South Korea. These findings deepen our understanding of extreme rainfall events in response to climate variability and provide a basis for enhancing the predictability of extreme rainfall frequency in South Korea.