Atmospheric River activities and their effects on precipitation over South Korea

Atmospheric rivers (ARs) have been recognized as the main mechanism of water supply to many coastal regions across the globe, and large fractions of extreme precipitation events have been attributed to them in coastal landforms. Though more than 70% boundary of South Korea is coastal, the research literature on ARs and their impacts on precipitation is scarce, if not absent. In this study, we aim to explore the AR activity over South Korea and estimate their seasonal and spatial impact on the precipitation and its extremes over the region. To this end, we use gridded reanalysis data for identifying ARs and a recently developed high-resolution precipitation dataset for South Korea. As results, we find that ARs are an important source of precipitation over South Korea by occurring in all seasons, though their frequency varies significantly across the seasons. Further, we conclude that more than half of precipitation extremes may be attributed to ARs, and most of the top-ten extreme precipitation events witnessed by South Korea happen concurrently with ARs, especially in winter and spring seasons. Lastly, our analysis indicates that recent the changes in inter-annual variations of winter precipitation may be attributed to the strengthening of AR contributions, implying that more research on ARs and their impacts in a warmer world is critical for the region. Overall, our findings demonstrate that ARs are one of the main mechanisms of oceanic moisture inflow into South Korea, which will likely have important implications to water management in the country, through targeted forecasting of ARs and by utilizing the information in climate mechanism-based water planning and management.