Characterizing Spatio-Temporal Dynamics of Urbanization in China Using Time Series of DMSP/OLS Night Light Data

Tao Xu,Ting Ma,Chenghu Zhou,Yuke Zhou

doi:10.3390/rs6087708

Abstract

Stable nighttime light (NTL) data, derived from the Defense Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS), are typically considered a proxy measure of the dynamics of human settlements and have been extensively used to quantitative estimates of demographic variables, economic activity, and land-use change in previous studies at both regional and global scales. The utility of DMSP data for characterizing spatio-temporal trends in urban development at a local scale, however, has received less attention. In this study, we utilize a time series of DMSP data to examine the spatio-temporal characteristics of urban development in 285 Chinese cities from 1992 to 2009, at both the local and national levels. We compare linear models and piecewise linear models to identify the turning points of nighttime lights and calculate the trends in nighttime light growth at the pixel level. An unsupervised classification is applied to identify the patterns in the nighttime light time series quantitatively. Our results indicate that nighttime light brightness in most areas of China exhibit a positive, multi-stage process over the last two decades; however, the average trends in nighttime light growth differ significantly. Through the piecewise linear model, we identify the saturation of nighttime light brightness in the urban center and significant increases in suburban areas. The maps of turning points indicate the greater the distance to the city center or sub-center, the later the turning point occurs. Six patterns derived from the classification illustrate the various characteristics of the nighttime light time series from the local to the national level. The results portray spatially explicit patterns and conspicuous temporal trends of urbanization dynamics for individual Chinese cities from 1992 to 2009.

Highlights

Over the past few decades, there has been increasing interest among policy makers and researchers in the spatio-temporal changes of urban areas
Decreased night light brightness was recognized in only 2% of pixels, including 1% identified by the linear model and 1% identified by the piecewise linear model
A few cities exhibit a negative trend in the growth of nighttime light, such as Chaozhou, Dongguan and Wenzhou, which decreased from more than 2.4 digital number (DN) per year in 1994 to less than 0.8 DN per year in 2007. These results suggest diverse trends in night light growth that correspond to diverse trends in the urbanization of Chinese cities, which implies the unbalanced development of Chinese cities; most cities exhibit increasing growth rate of NTL brightness indicate Chinese cities experienced continuing development over the last two decades

Summary

Introduction

Over the past few decades, there has been increasing interest among policy makers and researchers in the spatio-temporal changes of urban areas. The world is experiencing rapid urbanization, accompanied by economic and population growth. The share of the world’s urban population has grown to over one-half, and this urban population is projected to grow by more than two billion people by 2050 [1]. The effects of urbanization, such as increasing human activity and impervious surfaces, may contribute to water and air contamination and climate change [2,3]. Vegetation deterioration and biodiversity reduction are usually associated with the land-cover changes that accompany urbanization [4,5,6]. Because urbanization is associated with many crucial issues, various data and methods have been applied to investigate the spatio-temporal dynamics of urbanization.

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Results

Conclusion