The Relationship Between Urban Morphology and the Urban Heat Island Effect: A Study of Cooling Strategies in Urbanized Areas

With more and more cities experiencing urbanisation, the issue of Urban Heat Island (UHI) effects has become a concern in urban areas worldwide. This paper evaluates the impact of urban morphology, particularly urban expansion and densification, on the UHI effect, and examines the trajectory of UHI in Chinese cities. The 2D Layout BCR (Building Coverage Ratio) model shows that horizontal expansion tending to increase impervious surfaces, and the increased proportion of impervious surfaces will lead to more heat retention, while the physical air barrier in densely built environments can worsen the UHI effect by obstructing the natural ventilation of air. The longitudinal data of urban planning variables of Beijing, Shanghai, Guangzhou and Shenzhen showed that expansion and densification had a long-term trend in recent decades, and the increase of night-time temperature had a positive correlation with expansion rate and building intensity. Through the analysis of urban characteristics and the discussion of heat mitigation measures, this paper emphasises the role of proactive urban planning in balancing urban expansion and cooling needs, and the importance of the cooling strategy embedded in the urban form. Heat mitigation measures, especially greening, reflective roofs and district cooling systems, can offset the UHI effect to some extent.