LANZHOU -- Chinese researchers have recently revealed how surface heat sources in urban clusters contribute to extreme heat events, according to the Northwest Institute of Eco-Environment and Resources (NIEER) under the Chinese Academy of Sciences.

The study unveiled the changing characteristics of surface heat sources and their relationship with compound high-temperature events, highlighting the importance of surface energy analysis in understanding urban climate change, the NIEER said.

Urban clusters are becoming a dominant form of urbanization. However, the combined effects of global warming and rapid urban development have further intensified climate risks for these areas.

As a direct source of atmospheric energy, surface heat sources have been strongly affected by changes in land surface features and human activities during urbanization. Notably, compound extreme heat events now pose significant threats to economic development, social operations and public health.

Aiming to explore the correlation between ground heat sources and compound high-temperature events, the NIEER team examined the temporal and spatial distribution, as well as the evolution, of ground heat sources in four major urban clusters across China, according to Gao Xiaoqing, a researcher at the NIEER who led the study.

These clusters are the Beijing-Tianjin-Hebei region, the Pearl River Delta, the Yangtze River Delta and the Chengdu-Chongqing region.

The research team conducted statistical analysis of regional differences in ground heat sources and compound hot events in these urban clusters, while also tracing the correlation mechanism.

The results indicated that surface heat sources in all four urban clusters generally follow a seasonal pattern of being "strong in summer and weak in winter." Moreover, they exhibit different spatial characteristics.

For example, the Beijing-Tianjin-Hebei region shows a pattern of "strong in the south and weak in the north," with the northern part prone to turning into a heat sink in winter. In the Yangtze River Delta, major heat sources are primarily distributed along the rivers, whereas large cities exhibit comparatively lower surface heat levels, according to the study.

The differences in surface heat sources in these urban clusters reflect the combined regulatory effects of topography, climatic conditions and the level of urbanization, according to Gao.

The study also found that changes in surface heat sources have a significant impact on the frequency of compound high-temperature events, but their influence on event intensity is relatively limited.

The findings have been published in the journal Science China Earth Sciences.

"Findings of the study are significant for addressing environmental challenges in urban clusters, enhancing urban climate resilience, and improving quality of life for urban residents," Gao said.