Historical Analysis of Heatwaves in China Based on Complex Network Theory

Under global warming, the frequency and intensity of extreme heat events have increased markedly, having widespread impacts on terrestrial ecosystems and human society. Based on daily maximum temperature observations across China during 1961–2020 and high-resolution ERA5 reanalysis datasets, this study constructs a heatwave synchronization network by integrating event synchronization and complex network theory. The spatiotemporal variations of heatwave occurrence and synchronization during 1961–2020 are systematically investigated. The results reveal a pronounced increase in heatwave frequency across China, with the number of heatwave events during 1991–2020 nearly doubling compared with that in 1961–1990, and the most prominent increase occurring in South China. Although the large-scale spatial pattern of heatwave synchronization remained relatively stable, node connectivity increased substantially, with persistently high values over Northwest China and an evident strengthening trend across North China and the Huang–Huai region in recent decades. Concurrently, heatwave events during the later period were generally accompanied by drier soil conditions, reduced latent heat flux, and enhanced sensible heat flux, indicating strengthened land–atmosphere coupling during heatwave events. These findings provide new insights into the spatiotemporal evolution of heatwave synchronization and contribute to a better understanding of large-scale heatwave hazards under a warming climate.