Historical and Future Changes in Meteorological–Hydrological Compound Drought in China

Drought is typically divided into meteorological, agricultural, hydrological, and socioeconomic categories. Generally, the transition from meteorological drought to other types of droughts is known as drought propagation. When drought propagation occurs, different types of droughts may still exist simultaneously or successively. In this study, compound droughts are divided into three categories: hydrological meteorological compound drought (HMD), meteorological hydrological compound drought (MHD), and simultaneous compound drought (SD). ERA5 and CMIP6 data are used for analysis under historical and future scenarios. Different types of compound droughts have emerged in extreme centers in different basins. Our analysis indicates a significant upward trend in the duration of these three compound droughts from 1979 to 2022. Additionally, our projections under SSP5-8.5 and SSP2-4.5 suggest a substantial increase in the occurrence of various compound droughts. HMD, MHD and SD all show a consistent upward trend under the future scenario above the moderate-drought level. MHDs are projected to experience the most significant increase compared to the historical period in the far-future period (2066–2099) under SSP5-8.5.