Risk propagation from meteorological to hydrological droughts in a changing climate for main catchments in China

Global climate change has altered the spatial-temporal regimes of hydro-meteorological variables. The impact of climate change on the risk transferability from meteorological to hydrological droughts needs to be investigated. Based on the gridded meteorological data and 19 global climate model simulations from the Coupled Model Inter-comparison Project Phase 5, the climate change scenarios were generated over 135 catchments in China for two future periods (2011—2055 and 2056—2100). The best performed hydrological model over four lumped models was selected for hydrological simulations. Based on precipitation scenarios and hydrological simulations, the Standard Precipitation Index (SPI) and the Standard Runoff Index (SRI) were respectively calculated for each catchment and time period. The meteorological and hydrological drought episodes were extracted based on the runoff theory. Finally, drought risks by incorporating the most likely selection into the Copula function were calculated, and the risk transferability from meteorological to hydrological droughts under the current and future climates were investigated. The results show that: ① Meteorological and hydrological droughts are highly sensitive to future warming climates. Specifically, drought return periods are projected to lengthen in northern China, indicating mitigating risks, while they become shortened by 2 to 5 times over most catchments in central and southern China, indicating deteriorated conditions. ② The meteorological drought risks positively correlate with the hydrological drought risks under the current and future climates, with the Pearson correlation coefficients being higher than 0.99. ③ The sensitivity of hydrological to meteorological drought risks almost stay unchanged for each catchments for different future periods, whereas the co-occurrence of hydrological and meteorological droughts is projected to slightly increase over northern China under future warming climates.