Drought-heatwave compound events are stronger in drylands

Abstract

Climate change is exacerbating the occurrence of compound droughts and heatwaves (CDHWs), which pose a serious threat to human health and socio-economic development. Using daily maximum temperature (Tmax) and monthly self-calibrating Palmer drought severity index (sc-PDSI) dataset, the evolution patterns of CDHWs and compound wet-heatwave events, the dominant drivers and the relative contributions of droughts and heatwaves in the drylands and humid areas from 1961 to 2020 were compared and analyzed. The results show that the CDHWs are stronger in drylands than in humid areas, the growth rate of CDHWs in drylands was almost twice that of the humid areas, the CDHWs are greater than the multi-year average intensity of compound wet-heatwave events by up to 2.4 times. Moreover, CDHWs has increased significantly from the past period (1961–1990) to the recent warm period (1991–2020), and the heatwave threshold has increased by about 5 °C. In most drylands, the contribution of heatwaves to CDHWs dominates, whereas in humid areas, the droughts contribution to CDHWs does. The compounding effects of droughts and heatwaves may exacerbate the severity of CDHWs regionally and are most pronounced in drylands, taking into account optimal lags. The study findings could provide scientific and technological support to actively address global climate change risks.