城市夜间灯光强度空间衰减规律及应用

夜间灯光强度是城市社会经济活动强弱的直观表征，通常随到城市中心距离增加而逐渐降低。但其空间衰减过程是否可以定量化、模型化，以及空间衰减规律关于城市形态的指示意义仍不明确。论文获取32个中国主要城市2012年和2020年NPP-VIIRS夜间灯光年度合成数据，以城市中心为圆心，计算同心圆圈层内平均夜光强度；受建设用地密度空间衰减函数启发，采用反S函数拟合城市夜间灯光强度空间衰减特征。结果表明：反S函数可以很好地拟合夜间灯光强度空间衰减特征，模型参数D和α的变化分别反映了城市扩张过程和形态变化。2012—2020年间，各城市半径(参数D)增长到1.1～3.6倍；城市规模较小的长春、银川和西宁经历的夜光亮度增长幅度最大，而东部沿海城市增长幅度较小。参数α的变化说明中国主要城市由夜间灯光反映的空间形态趋于紧凑。反S函数为刻画夜间灯光强度空间衰减提供了新工具，为测度城市扩张和形态变化提供了新指标。

Distance decay of nighttime lights from urban centers and its application

Nighttime lights are one of the direct representations of urban social and economic activities, which usually decrease with the distance from urban centers. However, quantifying and modeling the process of distance decay can be challenging, and the potential applications of nighttime light data are not specified. In this study, the annual composites of NPP-VIIRS nighttime lights for 32 major cities in China in 2012 and 2020 were obtained and used to calculate the nighttime light intensity within concentric circle layers by taking the city center as the center of the circle. Inspired by the spatial attenuation function of urban land density, this study used the inversed-S function to fit the distance decay characteristics of urban nighttime light intensity. The results show that the inversed-S function model fits the distance decay characteristics well, and the parameters D and α of the model reflect the process of urban expansion and urban form changes, respectively. From 2012 to 2020, the radius of the cities (parameter D) increased by 1.1-3.6 times. Among the sample cities, smaller cities—Changchun, Yinchuan, and Xining—experienced the greatest expansion of nighttime lights, while eastern coastal cities experienced the least expansion. The change of parameter α indicates that the expansion pattern of nighttime lights in China's major cities tends to be compact. The inversed-S function provides a new tool for describing the spatial pattern of nighttime light intensity and a new indicator for measuring urban expansion and urban form change.