Investigating effect of climate change on drought propagation from meteorological to hydrological drought using multi-model ensemble projections

Climate change is a main driving force that affects the hydrological cycle, leading to an increase in natural hazards. Among these natural hazards, drought is one of the most destructive and becomes more complex considering climate change. Therefore, it is necessary to investigate the effect of climate change on different types of drought. In this study, we examined the propagation probability of meteorological drought into hydrological drought using a probabilistic graphical model across South Korea. We performed correlation analyses among meteorological drought represented by Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) and hydrological drought by Standardized Runoff Index (SRI) on different time scales. Drought characteristics were examined under a baseline period, RCP 4.5, and 8.5 climate change scenarios, and the results illustrated that drought characteristics varied spatially. On average, drought severity of SPI increased in P1 (2011-2040) and then deceased in P2 (2041-2070) and P3 (2071-2099) under RCP 4.5, whereas drought severity also increased in P1 under RCP 8.5. However, average drought severity of SPEI increased in P3, whereas that of SRI showed a decreasing trend for all the periods. Finally, propagation occurrence probabilities of different states of meteorological drought resulting in different states of hydrological drought were examined under climate change scenarios. The average propagation probability of extreme state of meteorological drought resulting in moderate and severe condition of hydrological drought increased by 13% and 2%, respectively, under RCP 4.5; while average propagation probability of extreme state of meteorological drought resulting in severe and extreme conditions of hydrological drought increased by 1.5% and 84%, respectively, under RCP 8.5. We concluded that propagation probability of meteorological drought into hydrological drought increased significantly under climate change. These findings will be helpful for early mitigation of hydrological drought.