Nighttime Artificial Light Intensity in Local Climate Zones: A Comparative Study for Global Cities

Abstract

Recent studies have proved various impacts of urban light pollution, from public health, shifted vegetated phase of trees, socio-economic consequences, to the energy budget. However, a detailed structure of urban forms and functions was not incorporated into the analysis yet. Using the concept of local climate zones LCZs) in this study, we assess the nighttime lights (NTL) of 32 urban agglomerations between the years 2012 and 2023, remotely accessed by the VIIRS instrument. We found significant statistical differences between the individual LCZs as well as various trends in the analyzed metropolitan areas. LCZ 1, typically representing densely built-up areas with skyscrapers, had the highest mean NTL of all classes. It was followed by LCZ 10 (heavy industry), LCZ 4 (openly arranged buildings tens of stories tall), and LCZ 3 (tightly packed buildings several stories tall). Lower values were identified in LCZ 9, a sparse arrangement of buildings. Significant temporal and regional trends in the NTL of built types of LCZs were detected, showing that changes in NTL cannot be explained simply by population growth. Marked differences in the contribution of individual LCZs to the overall NTL of the cities could provide a tool to focus on hot-spot areas in light pollution mitigation policies.