Changes and Dependencies of Compound Hot–Dry Extremes in China During 1961–2022

Compound hot–dry extremes have attracted widespread attention owing to their disastrous impacts on human society and natural ecosystems. Based on the daily maximum temperature and precipitation observations, the spatiotemporal distribution and long‐term variations of summer compound hot–dry days (CHDDs) and compound hot–dry events (CHDEs), as well as their dependence on individual extremes, were analyzed by using relative thresholds that vary with dates and stations. Results showed that there were more CHDDs and CHDEs in southern North China (NC), western Northwest China (NWC), and the northern parts of the middle and lower reaches of the Yangtze River (YR), with stronger intensity in NC, southern Southwest China (SWC), and northern and central Northeast China (NEC). From 1961 to 2022, the number/frequency of CHDDs/CHDEs increased significantly in China, with the linear rate of 1.72 days/0.25 times per decade. Meanwhile, the start and end of compound extremes became earlier and later, respectively, and the occurrence period was prolonged in most regions of China. Hot extremes had significant positive effects on the number/frequency of CHDDs/CHDEs and significant negative effects on intensity of CHDDs and CHDEs, with the relative contribution (RC) of 92%–94% and 68%–74%, respectively, while dry extremes had significant positive effects on the intensity of CHDDs and CHDEs and contributed 26%–32%. By applying thresholds that vary with dates and stations, as well as the latest daily observation data, especially the daily maximum temperature data, new insights can be gained into the dynamics of compound hot–dry extremes.