Differences in intercity economic convergence in the Pearl River Delta based on nighttime light data and its interpretation

The development of regional economic integration/ convergence in the Pearl River Delta has been the planning goal for 40 years since the reform and opening up. On the basis of methodology about economic convergence, this study investigates the intercity border effects of nine cities in the Pearl River Delta from 2013 to 2020, according to the NPP-VIIRS nighttime light data. Geographically, in addition to Guangzhou being located in the center, the integration trend on the east bank of the Pearl River Delta is clear, whereas three different clusters are found on the west bank. Based on the clustering of three metropolitan areas, namely, Guangzhou–Foshan–Zhaoqing, Shenzhen–Dongguan–Huizhou, and Zhuhai–Zhongshan–Jiangmen, the convergence development and common improvement among the cities in the three metropolitan areas have large differences. Guangzhou–Foshan–Zhaoqing has no convergence trend at all, whereas narrowing gaps are found in Shenzhen-Dongguan-Huizhou. Economic convergence among cities are related to the industrial synergy development. On the basis of the research conclusion, attention should be given to the advantageous industries in each city instead of standing on the original metropolitan area planning. Periphery cities should understand their own industry advantages to proceed the industrial synergy development within core cities.