Amplified intensity and duration of heatwaves by concurrent droughts in China

Compound hot-dry climate extremes could lead to severer natural disasters and socio-economic impacts compared to individual events. An improved understanding of historical heatwave-drought compounds and their differences compared to heatwaves alone is needed for better predicting the occurrence and impacts of extremes under a changing climate. In this study, we investigated spatiotemporal variations of heatwave-drought compounds using meteorological data from more than 2000 stations in China during 1980-2017, and compared the heatwave intensity and duration in heatwave-drought compounds with that in heatwaves alone. The annual occurrence of heatwave-drought compounds increased significantly during 1980-2017. At the national level, heatwave intensity in heatwave-drought compounds was 34.24 degrees C +/- 4.39 degrees C, which was higher than that in heatwaves alone of 33.33 degrees C +/- 4.35 degrees C. The occurrence of long-lasting (duration >7 days) heatwaves accounted for about 34.42% - 50.70% in heatwave-drought compounds, while this ratio was only 11.82% -21.55% in heatwaves alone. The quantitative evaluation of heatwave-drought compounds and heatwaves alone in China highlighted the amplified heatwave severity and duration in heatwave-drought compounds versus that in heatwaves alone.