Influences of landform and urban form factors on urban heat island: Comparative case study between Chengdu and Chongqing

Although the degraded urban thermal environment has been widely concerned, whether monocentric or polycentric urban development can alleviate urban heat island (UHI) is still debatable, particularly considering different types of cities in plain and mountainous settings. To fill the gap, this study chose the cases of Chengdu on alluvial flatlands and Chongqing on mountainous landforms in China for comparison. Adapting to natural landforms, Chengdu has a dominated monocentric urban form, whereas Chongqing has a naturally polycentric urban form. This study found that areas with high UHI intensity were located in the urban center and peripheral suburbs in Chengdu, while those were located in the peripheral industrial zones in Chongqing. The spatial error model and random forest regression results showed that natural elements such as vegetation and water had similar influences and contributions to UHI. However, distinct landforms and urban forms played critical roles in UHI differences among the two cities. Impervious surface and building density were the dominant variables to UHI of Chengdu, while sky view factor and industrial zones were the main contributors to UHI of Chongqing. The findings called for corresponding policy strategies to optimize urban form and improve the urban thermal environment.