Research On Spatio-temporal Changes And Influencing Factors Of Urban Expansion In Central Plains Urban Agglomeration Based On Lighting Data

Urban agglomeration is the main form that promotes urban development under the background of new urbanization.It conforms to the general trend of urbanization development and plays a vital role in promoting both regional competitiveness and healthy urbanization.However,with the acceleration of the process of urbanization,the majority of urban agglomerations lack substantial construction and development.They are just “a group of cities” that relatively concentrated in spatial distribution.Besides,the cluster distribution of cities has also brought about a series of problems,such as disorderly expansion of urban land,big city diseases and disordered competition.The Central Plains Urban Agglomeration(CPUA)is the backbone of urban agglomeration development,and urban land is the space carrier for the development of urban agglomerations.Therefore,studying on the urban sprawl of the CPUA and deeply analyzing the dynamic development process,changes and influencing factors of spatial patterns of urban land can not only clarify the features of urban land sprawl,but also provide some suggestions for the more efficient and reasonable development of the CPUA under the condition of new urbanization.In this paper,30 prefecture-level cities of the CPUA were united as a cell for the research.Firstly,DMSP/OLS and NPP/VIIRS night lighting data from 2002 to 2017 are selected to extract urban built-up area,then combined with measurement methods such as light intensity statistics,urban expansion dynamic index,center of gravity shift index,standard deviation ellipse index and landscape pattern index to reveal its temporal and spatial changes from the aspects of urban expansion pattern change,expansion direction,and landscape pattern change.Finally,by selecting explanatory variables to establish a multiple linear regression equation to analyze the influencing factors of urban sprawl,and provide certain decision-making reference for the sustainable development of the CPUA.The main conclusions are as follows:(1)From the results of the built-up area extraction,compared with the actual urban built-up area data,the average accuracy of the urban built-up area extracted from the night lighting of the CPUA is more than95.5%,and the average error is controlled within 2.7%.The DMSP/OLS and NPP/VIIRS night lighting extraction of urban built-up areas has a certain degree of credibility,which can reflect the development of cities in urban agglomerations on a larger spatial scale across administrative regions.(2)From the perspective of the urban spatial and temporal expansion pattern of urban agglomerations,from 2002 to 2017,the total amount of night lights in the CPUA continued to rise and the growth rate was rapid,the difference in the light anomaly decreased,and the light value of the Zhengzhou metropolitan area was greater than that of the urban agglomeration fringe cities;urban expansion presents volatile and phased growth.The urban area has increased by 2.15 times,and the number of urban built-up areas has increased by 1.97 times;it presents a center-peripheral spatial expansion structure dominated by existing cities.The characteristics of urban expansion are filled with contiguous development on the original basis.As a central city,Zhengzhou's primacy is continuously increasing,and its polarization is obvious.Radiation drives the development of surrounding cities,and urban agglomerations tend to be agglomeration and integration.(3)Through the analysis of the expansion center and evolution direction of urban agglomerations,it is shown that between 2002 and2017,the center of urban lighting and the expansion of urban built-up areas have all shifted to the southeast,which further illustrates the trend of urban land expansion from northwest to southeast and there is a tendency to turn the east,but the overall change is small,the degree of deviation is not obvious,the scope of activities has been in the central core area of Zhengzhou and Kaifeng,indicating that the development of urban agglomerations is slow and the imbalance is prominent.(4)Through multiple linear regression analysis of the factors affecting the urban expansion of urban agglomerations,the results show that policy factors,regional economic development,market factors,and external forces all have a positive effect on urban land expansion.Among them,policy factors,namely public budget expenditure indicators,have the most obvious impact on the expansion of urban agglomerations with an impact coefficient of 0.800,indicating that government policies have become the main factors driving urban expansion and urban evolution,followed by per capita GDP and employees Economic factors represented by average wages also play an important role in promoting urban expansion.The actual use of foreign investment in general reflects the vitality of urban economic development.With a high level of outward economic development,urban development is relatively fast to a certain extent.