Increased frequency and severity of global compound dry and heat wave events in a daily scale

Abstract

Compound dry and hot events have severe impacts on human health, ecosystems, and social economy. However, daily-scale compound dry and heat wave events (CDHWs), which enable a more detailed analysis of CDHWs changes and their contributing factors, have not been fully investigated across global land regions. Here, we examine the spatiotemporal variations in the frequency, duration, dry conditions, and excessive heat of CDHWs from 1961 to 2020, as well as the occurrence probability of extreme CDHWs and the effect of individual heat wave and dry events on their probability changes. Results show widespread intensification of CDHWs in different aspects, particularly in western North America, eastern South America, Europe, northern Africa, and parts of Asia. Notably, extreme CDHWs generally exhibit more severe changes during 1991–2020 compared to 1961–1990. Furthermore, nearly all global land regions have experienced significant reductions in the return period of extreme CDHWs between these two periods, with decreases exceeding 60 %. Variations in heat wave events play a dominant role in contributing the frequent occurrence of extreme CDHWs, while changes in dry events contribute as well, with an obviously weaker impact. This study enhances the understanding of compound dry and heat wave events on a finer temporal scale and emphasizes more attention should be paid to extreme compound events.