Analysis of the Impact of Preceding Drought on Heatwave Extremes: Focusing on South Korea.

ABSTRACT

Compound drought–heat events are increasing under climate change, yet quantitative assessment of how antecedent drought alters extreme heat risk remains limited. This study examines the relationship between antecedent moisture conditions and extreme summer temperatures in Korea by combining correlation analysis with copula-based probabilistic modeling. Spearman’s rank correlation analysis reveals a consistent negative association between antecedent Standardized Precipitation Index (SPI) and daily maximum temperature (Tmax), indicating that drier conditions are systematically linked to higher summer temperatures. Copula models are then used to characterize the joint dependence between SPI and Tmax and to estimate conditional exceedance probabilities and return periods under different moisture states. The results show that dry and extremely dry conditions increase the probability of exceeding high Tmax thresholds and substantially shorten return periods, whereas wet conditions suppress extreme heat risk. The influence of antecedent drought becomes more pronounced for longer return periods, highlighting enhanced sensitivity in the extreme tail of the temperature distribution. These findings suggest that extreme heat risk is dynamically conditioned by prior hydrological states, emphasizing the importance of accounting for antecedent drought in interpreting and anticipating high-impact temperature extremes.

Acknowledgments

This work was supported by Korea Environment Industry & Technology Institute(KEITI) through Research and Development on the Technology for Securing the Water Resources Stability in Response to Future Change Project, funded by Korea Ministry of Climate, Energy, Environment(MCEE)(RS-2024-00332300) and by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT)(RS-2025-00563294).