Process-oriented compound long-duration dry and hot events in China

Summertime compound dry and hot events pose severe threats to human health and agriculture, particularly when events are persistent. Based on the joint evolution of such hazards in space and time, we identified spatiotemporal compound long-duration dry and hot (SLDDH) events across China (1961-2022) using a process-oriented method. These events are consistently associated with anomalous high-pressure systems, which induce sinking air motions, increase solar radiation at the surface, and reduce moisture convergence. The primary driver of precipitation deficits is the dynamical suppression of vertical moisture transport by this subsidence, not atmospheric moisture content changes. For the accompanying high temperatures, anomalous subsidence and the resulting adiabatic warming are the dominant cause across most of China, with surface heating (diabatic processes) playing a minor or even cooling role. However, in northern regions like North China and Xinjiang, extreme heat results from a combination of diabatic heating and adiabatic warming. These findings suggest that the anomalous sinking motion associated with the high pressure systems is partially responsible for the occurrence of these compound extremes over different regions of China.