On Uncertainty in Extreme Weather Forecasts in a Changing Climate: August 2022 Floods in South Korea

Abstract

In August 2022, South Korea experienced massive and large-scale flooding, preceded by the highest record in 80 years. The torrential rain over several consecutive days caused devastating flooding events and landslides in Seoul, and underestimated rainfall forecasts forced several hundred people to evacuate, leaving infrastructures damaged substantially. In this study, we use high-resolution observational reanalysis data to investigate spatial and temporal evolutions of atmospheric and oceanic conditions during the 2022 August flooding events. We show that a prolonged dipole atmospheric system, with low in the north and high pressure in the south, reinforces a persistent and strong stationary front causing succeeding rain. Given the prominent westerly winds accompanied by the dipole pressure system, which acts as a channel of westerly winds across middle Korea, anomalously warm sea surface temperature (SST) over the Yellow sea located west of Korea plays a key role in supplying moisture and heat for the rainfall events. The principal component analysis and SST trend results suggest that the intensity of distinct dipole modes of atmospheric pressure and Yellow sea SST have significantly increased over the recent decades as known consequences of global warming. Our findings indicate that climate change may increase uncertainties in climate and weather extremes forecasts; thus, further efforts and attempts to improve our understanding of current and future climate systems are highly important.