Abstract
Urban agglomeration is an advanced spatial form of integrating cities, resulting from the global urbanization of recent decades. Understanding spatiotemporal patterns and evolution is of great importance for improving urban agglomeration management. This study used continuous time-series NTL data from 2000 to 2018 combined with land-use images to investigate the spatiotemporal patterns of urbanization in the three most developed urban agglomerations in China over the past two decades: the Beijing–Tianjin–Hebei urban agglomeration (BTH), the Yangtze River Delta urban agglomeration (YRD), and the Guangdong–Hong Kong–Macao Greater Bay Area (GBA). The NTL intensity indexes, dynamic thresholds, extracted urban areas, and landscape metrics were synthetically used to facilitate the analysis. This study found that the urbanization process in the study areas could be divided into three stages: rapid urbanization in core cities from 2000 to 2010, a fluctuating urbanization process in both core cities and surrounding cities from 2010 to 2015, and stable urbanization, mainly in surrounding cities with a medium size after 2015. Meanwhile, the urbanization level of GBA was higher than that of YRD and BTH. However, with the acceleration of urban development in YRD, the gap in the urbanization level between GBA and YRD narrowed significantly in the third stage. In addition, this study confirmed that the scattered, medium-sized cities in YRD and GBA were more developed than those in BTH. This study showed that continuous NTL data could be effectively applied to monitor the urbanization patterns of urban agglomerations.
Highlights
By comparing the coefficients of the nighttime light (NTL) indexes, this study found that the average NTL intensity (NTLAI )
Had the largest coefficients, which indicated that NTLAI was the most optimal index for indicating the urbanization level and spatiotemporal patterns of urban agglomerations
Combining the variation in the NTLAI and lit pixel count with spatial patterns of urban expansion, this study found that human activities and urban expansion in Yangtze River Delta urban agglomeration (YRD) and Greater Bay Area (GBA) gradually shifted to satellite cities, such as Nanjing (YRD), Hangzhou (YRD), and Foshan (GBA), which might have resulted from the Strategies of Regional Coordinated
Summary
As the centers of capital, labor, and information, were home to more than 55%. Of the world’s population in 2018, and this number is expected to reach 68% in 2050 [1]. Measuring spatial urbanization patterns is a crucial task in urbanization studies [2,3]. Angel and Blei [4] proposed the constrained dispersal structure of American cities based on the geographic information of workplaces and commuters. Taubenböck et al [3] calculated spatial dispersion indexes and concluded that long-term urbanization created compact urban patterns. Under the processes of economic globalization and global urbanization, central cities and their neighbors develop to a specific spatial size with a high population density and continuity in the spatial landscape [5].
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