Mapping future droughts under global warming across China: A combined multi-timescale meteorological drought index and SOM-Kmeans approach

Global warming will exacerbate the damages and losses caused by drought and significantly affect human society and economic development. Future drought outlook is of vital importance for policy-making to combat drought risk and water crises over the long term. Here, 3- and 12-month standardized precipitation evapotranspiration indices, which can aid short- and long-term drought monitoring, respectively, are coupled with the SOM-Kmeans two-stage clustering technique to map the future drought conditions in China for the future period (2021–2050) relative to the baseline period (1976–2005). The calculation is based on downscaled outputs of 10 models from the Coupled Model Intercomparison Project Phase 5 (CMIP5) under two representative concentration pathways (RCPs). The temperature increases by 0.5–2.0 °C and 1.0–2.5 °C under the selected RCP4.5 and RCP8.5 scenarios, respectively. The results show that the differences between precipitation and potential evapotranspiration are projected to increase throughout China. Most parts of China are projected to experience more severe, more frequent and longer duration droughts in the next three decades compared with the baseline period. Global warming is projected to have a serious impact on future droughts in the basins located in the northern part of China. The drought conditions in the northwest region of the “Hu Huanyong Line” in China are projected to be serious and complex in the future, while the opposite is true in the southeastern region. Drought conditions in northern China are more complex under high temperature changes (1.0–2.5 °C) than under low changes (0.5–2.0 °C). The results of this study provide insights on future drought planning and management in China and demonstrate that SOM-Kmeans can be used for the classification of drought conditions.