The characteristic and transformation of 3D urban morphology in three Chinese mega-cities

Abstract

Urban morphology exerts an important influence on human settlements and serves to promote sustainable development. However, few studies have focused on the three dimensions (3D) of urban morphology. Therefore, to explore 3D urban morphological characteristics and transformations, we adopted a standard urban morphology classification scheme, the local climate zone (LCZ), and selected three Chinese megacities as case studies. Remote sensing images and machine-learning technology were used to create spatiotemporal LCZ maps. Our results reveal that cities have diverse forms, with the dominant urban morphology varying across different cities and periods. However, cities still share several common patterns. The dynamic spatial distribution of LCZ density can be divided into three patterns: spreading, shrinking and relocation. In recent years, Chinese megacities have mainly expanded with open high-rise (OHR) and large low-rise (LLR) classes. Combined with the increase in building height, urban landscapes have been homogeneous. Additionally, 3D urban morphology is driven by several factors, such as economic activity and the dissociation of population growth from urban expansion. Detailed spatiotemporal LCZ maps can help us better understand urban morphology transformations and explore the corresponding driving forces, providing a reference for urban planners and policymakers seeking to make cities healthier and more livable.