SPI-based assessment of precipitation whiplash and its relationship with winter wildfire damage area in South Korea

Precipitation whiplash, defined as a rapid transition between anomalously wet and anomalously dry conditions, has emerged as an important hydroclimatic extreme under climate change, with potential implications for wildfire activity. Although previous studies have linked precipitation whiplash to wildfire regimes in arid and semi-arid regions, its occurrence and impacts in monsoon-dominated East Asia remain poorly understood. This study investigated the occurrence of precipitation whiplash across South Korea and examined its relationship with interannual variability in winter wildfire damage. Using a high-resolution (500 m) daily precipitation dataset derived from multi-source observational data provided by the Korea Meteorological Administration, Standardised Precipitation Index (SPI) values were calculated at one-month (SPI1) and three-month (SPI3) timescales. Precipitation whiplash events were identified using SPI-based thresholds, including moderate (+/-1) and extreme (+/-1.6) definitions. In addition, a persistence-weighted whiplash intensity metric was developed to integrate anomaly magnitude and temporal reinforcement. National wildfire-damaged area from January to March during 2001 - 2016 was used to assess climate - fire relationships. The results showed that precipitation whiplash occurred recurrently across South Korea, with substantial interannual variability in both spatial extent and intensity. Pearson correlation analysis revealed positive associations between winter wildfire-damaged area and whiplash indicators, with the strongest relationship observed for the spatial extent of extreme short-term whiplash (SPI1-Whiplash1.6; r = 0.806). Moderate positive correlations were also found for SPI1-Whiplash1, SPI3-Whiplash1, and national mean persistence-weighted whiplash intensity. These findings indicate that extreme, spatially extensive wet-to-dry transitions are closely linked to increased winter wildfire damage in South Korea, highlighting precipitation whiplash as a relevant climate-based indicator for wildfire risk assessment in monsoon-influenced regions.