Compound droughts and heatwaves over the Huai River Basin of China: From a perspective of the magnitude index

Abstract

AbstractCompound droughts and heatwaves have garnered increasing research attentions due to their disastrous impacts on the structure and function of ecosystems and societies. A drought is generally characterized by precipitation deficit, and its negative impact can be amplified by the simultaneous occurrence of a heatwave. More recent studies have highlighted the multi characteristics of compound droughts and heatwaves, which may call for improved efforts on assessing the impact of compound extremes. In this study, a compound drought and heatwave magnitude index (CDHMI) is built to characterize the severity of compound extremes in the Huai River Basin (HRB) during 1961-2017. The CDHMI considers the impact of both drought/extreme heat conditions and the duration of extreme heat. In addition, the magnitude index has been graded according to the degree of severity to detect the most drastic extreme compound events. The results show that from 1961 to 2017, mild and moderate events occurred more often than severe events. A significant increase in all compound events was observed from 2003 to 2017. Compound droughts and heatwaves events, especially in drought status, have increased significantly with the global climate warming in recent decades. The assessment of the impact for compound droughts and heatwaves events over the HRB needs to be improved in the context of global climate changing. Therefore, the CDHMI can be used to accurately assess the risk of compound droughts and heatwaves.