Changes in compound drought and hot extreme events in summer over populated eastern China

Abstract

Compound extreme events always cause severe impacts on human society and the natural system, especially in the populated areas. However, studies on their changes depend on definitions of the related extreme events. In this study, a newly defined compound drought and hot extreme events (CDHEEs) index based on the day-night concurrent hot extreme index and daily drought monitoring index is defined to explore possible changing features in summer-time CDHEEs from 1961 to 2018 in the densely populated areas of eastern China. Results reveal that the occurrence of CDHEEs shows a significant increase in the densely populated areas with the strengthening interaction of drought and hot extreme events, especially since the late 1990s. Further analyses indicate that urbanization and regional climate also moderate changes in CDHEEs, as we found that CDHEEs increased more prominently in the cities, especially in the drier regions. As a result, the population exposed to CDHEEs has doubled since the late 1990s in the densely populated areas of eastern China.