Long-term change of summer mean and extreme precipitations in Korea and East Asia

The change of the precipitation characteristics over South Korea is investigated using long-term (60 years) hourly precipitation records from surface stations focusing on extended summer (June–September) and rainy season (Changma). The precipitation characteristics including extreme events (>30 mm·h⁻¹ or >100 mm·day⁻¹) are also compared for the past (1961–1990) and recent (1991–2020) climatology. The amount of summer precipitation shows a notable increase over South Korea (2.6 mm·day⁻¹·century⁻¹) during the last 60 years (1961–2020) although it is smaller than recent 48-year trend measured in North Korea (9.7 mm·day⁻¹·century⁻¹). Precipitation amounts are significantly increased than past climatology particularly in 70–100 and 200 mm·day⁻¹ intensity ranges. The frequency of extreme precipitation also exhibits an increasing trend (1.0 frequency·century⁻¹) during the last 60 years over South Korea. The frequency of extreme precipitation has been doubled in the recent climatology compared to the past climatology. Daily precipitations in top 1 percentile present clear increasing trends during the extended summer and Changma season in South Korea. Further investigation using gridded precipitation reveals that the similar mean and extreme precipitation increases are observed over the wider regions in East Asia, including central China and southern Japan. This result implies that the long-term precipitation change over South Korea is related to a large-scale circulation change in the East Asian summer monsoon.