Analysis of Spatio-Temporal Development Patterns in Key Port Cities Along the Belt and Road Using Nighttime Light Data

The Belt and Road Initiative (BRI) has reshaped global trade and infrastructure, with port cities as key nodes in its Maritime Silk Road. Quantifying their spatiotemporal development is challenging due to data limitations in emerging economies. This study employs VIIRS nighttime light (NTL) data from 2013 to 2023 to analyze urbanization patterns in twelve BRI port cities spanning Asia, Africa, Europe, and South America. We compile a 12-city cohort; inferential analyses are conducted for a pre-specified six-city subset, while descriptive NTL trends cover all 12. This study makes three contributions: (i) we assemble a cross-sensor harmonized VIIRS NTL record for 12 BRI port cities during 2013–2023; (ii) we integrate Standard Deviational Ellipse(SDE) parameters with rank-size dynamics as a joint diagnostic of urban hierarchy; and (iii) we triangulate NTL with external indicators (GDP, population, port throughput) to validate interpretation. Three key findings emerge: Asian ports experienced pronounced NTL growth, with Singapore approaching saturation, consistent with the luminosity-ceiling hypothesis; SDE analysis shows varied expansion patterns shaped by geophysical and policy factors; and rank-size trends indicate decentralization during the BRI decade, with |q| declining in most cities, challenging the primate-city model. To optimize development, we highlight polycentric infrastructure investment, institutionalized NTL monitoring, and green port certification aligned with sustainability goals.