Spatio-temporal Pattern Of Chinese Cities Development Based On Nightlight Data

Since the reform and opening up,with the rapid progress and development of my country's economy and technology,the process of urbanization has been accelerating continuously,which has promoted the development of the regional economy and improved human life,medical care and education.However,rapid urbanization has caused a large number of natural land types to be replaced by man-made surfaces,affecting land use and cover changes,greatly changing local and global climate changes,and bringing about a series of social and ecological environmental problems.Therefore,timely and accurate quantification of the urban development process from a local or global scale,analysis of the temporal and spatial dynamic evolution process and spatial distribution law of urban development are of great significance to the future development of the city.The rapid development of remote sensing and geographic information technology has broken the traditional urban research method based on statistical data,making it no longer restricted by geographic space,providing data foundation and technical support for urbanization research under long-term series,and greatly optimized The efficiency and timeliness of urban research.Night light data provides a novel data source for timely and accurate acquisition of urbanization information.This paper uses multi-source night light data to conduct in-depth research on urbanization identification,dynamic monitoring,and spatial pattern changes based on night light images at the national,regional,and urban agglomeration scales.The main conclusions are:(1)From the perspective of saturated pixels and unsaturated pixels,the NDI value of DMSP/OLS data of the same year acquired by different satellites after correction by the pseudo-invariant target area method was greatly reduced,and the TDN value was greatly increased,Which showed that this method can effectively alleviate the discontinuity and saturation between DMSP/OLS images,and enhance the comparability between images.(2)On the provincial and municipal scales,using the overlapping years of DMSP/OLS and NPP/VIIRS data,respectively construct the lighting index and perform linear fitting.On the provincial scale,the fitting accuracy of the two data in 2013 is high,R2 is 0.94 Therefore,a long-term series of urbanization intensity shifting research is feasible.From 1992 to 2018,the center of urbanization intensity in China's mainland shifted to the south,and the shift distance reached a maximum of 87.99 km from 1992 to2000,and the east-west shift was not obvious.(3)From the pixel scale,the brightness value of pixels in China's mainland showed a significant increasing trend during 1992-2013.The average coefficient of variation in the study area was 7.3,the average slope was 0.714,and the percentage of pixel types increased.As high as 92.5%,it shows that urbanization was developing rapidly.In terms of spatial distribution,most of the more prominent changes in pixel brightness growth were concentrated in the eastern coastal urban agglomeration areas,while in the western region,the overall change in pixel brightness was small and the pixel growth was slow,showing the development of urbanization in China The level has the characteristics of spatial differentiation,and the urbanization development between the east and the west was quite different.In the future,the development of urbanization in my country will show a development trend of clusters in space,and a large number of cities and large urban agglomerations will also appear.(4)From 1992 to 2018,the expansion of built-up areas of the Beijing-Tianjin-Hebei urban agglomeration,the Yangtze River Delta urban agglomeration,and the Pearl River Delta urban agglomeration showed differences.The expansion rate of the built-up areas of the three major urban agglomerations has increased in different periods.The expansion rate of the built-up areas in the early period(1992-2000)increased slowly,and the expansion rate in the mid-term(2000-2010)increased significantly.2010-2018)the rate of expansion slowed down.The urban land in the Beijing-Tianjin-Hebei urban agglomeration presents a typical multi-center and multi-axis spatial distribution;the urban land in the Yangtze River Delta urban agglomeration also presented a multi-center structure,but the urban agglomeration structure was relatively stable and the surrounding cities were well developed;the Pearl River Delta cities The urban land of the cluster presents a typical single-center structure,with built-up areas clustered and distributed,and the surrounding cities develop slowly.The expansion of built-up areas of the three major urban agglomerations was restricted by topography.The steep terrain of Yanshan and Taihang Mountains in the northwest of the Beijing-Tianjin-Hebei urban agglomeration and the mountainous regions in the north of the Pearl River Delta urban agglomeration restrict urban expansion.(5)From 1992 to 2018,the center of gravity of cities and towns in the Beijing-Tianjin-Hebei region and the Yangtze River Delta shifted from northwest to southeast.The center of gravity of cities in the Pearl River Delta urban agglomeration shifted from southeast to northwest,with the most concentrated distribution of built-up areas.