Projected Effects of Climate Change on Meteorological Droughts over China: A Study Based on High-Resolution NEX-GDDP Data

Abstract While historical observations reveal increases in meteorological drought frequency across China during 1960–2021, future drought characteristics at the regional scale are uncertain. We evaluate historic and twenty-first-century-projected dryness changes using the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) 0.25° resolution dataset for representative concentration pathways (RCPs) 4.5 and 8.5. The 20-model NEX-GDDP ensemble mean precipitation and derived potential evapotranspiration, which is calculated by utilizing the Thornthwaite approach, are consistent with gridded station data over China from 1961 to 2005. Results show that the projections of occurrence frequency of moderate drought based on the standardized precipitation evapotranspiration index (SPEI) increase remarkably under the RCP4.5 scenario, and a significant increasing frequency is seen for severe drought under the RCP8.5 scenario, while few droughts of extreme dryness occur during the twenty-first century under both emission scenarios. More moderate drought projections are found over northwestern, northern, and southeastern regions under the RCP4.5 scenario, but all of China will face severe droughts for RCP8.5. The areas affected by moderate droughts begin to extend rapidly around 2030s at both national and regional scales for the RCP4.5 scenario, and the substantial increases in drying area extension for RCP8.5 appear around the 2050s. Particularly, the severe drought areas are found to grow much more sharply after the 2070s under the RCP8.5 scenario, implying that the occurrences of severe droughts over China are more sensitive to greenhouse gas emissions. Significance Statement Both temperature and rainfall are closely associated with drought variability; therefore, this study examines the changes in frequency and intensity of projected droughts across China based on the standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI). Severe droughts are projected to increase over most of the regions according to SPEI. The substantial increases in moderate and severe droughts are seen over all of China under the RCP4.5 and RCP8.5 scenarios, respectively. At the temporal scale, most of the areas are projected to experience more severe droughts by the end of twenty-first century, while the areas of moderate droughts are projected to exhibit fluctuating variations during the twenty-first century. These results indicate more future droughts, which may increase the vulnerability of more areas of China from exposure to the consequences of global warming.