Attributing changes in future extreme droughts based on PDSI in China

Climate change in mean-state or variability could lead to more/less frequency of extreme drought. In this study, we developed a new framework for decomposing the contributing factors of changes in future extreme drought frequency in China in accordance to the Palmer Drought Severity Index (PDSI). We performed a series of numerical experiments to ensure that the sensitivity of trend and variability in individual climatic variables can be distinguished. In addition, an extreme drought rate with warming (EDRW, unit: %.K-1) is defined to quantify the relative change in extreme drought frequency per Kelvin. Overall, the EDRW will increase dramatically by an average of 27.71%.K-1. The ascended EDRW are attributed to increases in temperature (+56.90%.K-1), net radiation (14.80%.K-1) and precipitation variability (+8.23%.K-1); a decrease in relative humidity (+4.61%K-1), but is partly offset by an increase in precipitation (i.e., wetting, -60.12%.K-1). A smaller increase in the frequency of extreme droughts is found in high-latitude regions due to their enhanced sensitivity to wetting.