Complex networks uncover the growing regional connectivity of humid-heat events in China

Extreme humid-heat events, characterized by concurrent high temperature and humidity, pose severe threats to human health and socioeconomic stability. However, our understanding of their spatial synchronization and propagation mechanisms in China remains limited. Here we show the spatial synchronization and propagation mechanisms of extreme humid-heat events over China from 1980 to 2023 by applying complex network theory. The findings reveal that central China acts as a synchronization hub, characterized by a high degree centrality (DC > 0.09) and a long mean synchronization distance (MSD > 420 km). Under global warming, DC and MSD have increased at rates of 0.002/decade and 21.18 km/decade, respectively ( P < 0.001), indicating that the spatial connectivity of extreme humid-heat events has intensified significantly. The directed network revealed that the Sichuan Basin served as a key source region, while arid and semi-arid areas in northwest China functioned as primary sinks. The number of source nodes has increased since 2002 (671.3 nodes/decade), indicating enhanced triggering capacity in western China. Mechanistically, source events are driven by strong local anomalies in temperature, humidity, and high pressure, whereas sink events are more influenced by remote triggers propagated from sources. These findings provide a complex network framework for improving early warning systems and regional climate adaptation strategies.