Compound drought-heatwaves in China: driving factors and risks

Warming climate is amplifying frequency and intensity of compound drought-heatwaves events (CDHs). As a country with a large population and booming socio-economy, spatiotemporal variations, driving factors, and risks of CDHs across China remain unclear. Here we mapped spatiotemporal features of CDHs during the 1961–2020 period, unraveled prime drivers behind CDHs, and evaluated CDH risks across China, based on hazard, exposure and vulnerability. We observed increased CDH during 1961 to 2020 and this increasing tendency was marked by the year 1990 that there occurred a decreasing (increasing) trend before (after) 1990. Regions with high occurrence frequency of CDHs were identified in Western arid zone (WAZ), the Eastern arid zone (EAZ), the southern part of Southwest China (SWC), the southern part of the Qinghai-Tibet Plateau (QTP) and Central China (CC). Analyses indicated that, at both the regional and pixel scales, daily maximum temperature, mean temperature and sunshine duration were significantly positively correlated with CDHs, while precipitation and relative humidity were significantly negatively correlated with CDHs. Average wind speed potentially favored the occurrence of CDHs. Since Northeast China (NEC), North China (NC) and CC have large populations, rapid socio-economic development, high vegetation coverage, and are major grain-producing areas, so the risk of CDHs disasters is relatively high. The WAZ and the QTP have small populations, low socio-economic development levels, and low vegetation coverage, so the losses caused by CDH are relatively small and the risk is relatively low. The results provide observational evidences for mitigation of CDHs in China in a warming climate.