Examining Spatio-Temporal Characteristics of Urban Heat Islands and Factors Driving Them in Hangzhou, China

The urban environment is a complex system featuring interactions between nature and humans. Scant research on urban areas has analyzed and assessed urban heat islands (UHIs) from the perspectives of nature and humans. This article analyzes the spatio-temporal characteristics of UHIs in Hangzhou in China in the context of the relationship between nature and humans based on the standard deviational ellipse, Pearson correlation analysis, and principal component analysis (PCA). The results show the following: First, from 2000 to 2020, the coverage of UHIs in the main urban area of Hangzhou decreased, but areas with subhigh temperatures and high temperatures increased. Second, from 2000 to 2020, the main axis of the spatial development of UHIs persisted along the northwest-southeast direction. The spatial pattern of UHIs in Hangzhou was closely related to the direction of urban development. Third, the results of PCA show that socio-economic activities, surface coverage and topography were the major factors influencing UHIs in Hangzhou. Finally, natural factors have slowed the development of UHIs while human factors have aggravated their formation, where the former contributed more significantly to them than the latter. For each unit of change in nine factors that were considered, the surface temperature in the study area decreased by 0.166 units.