Spatial-Temporal Pattern Evolution of Xi’an Metropolitan Area Using DMSP/OLS and NPP/VIIRS Nighttime Light Data

Abstract

A metropolitan area provides valuable space for economic development, and it is the home on which human beings depend for their survival. However, metropolitan areas are often faced with prominent problems caused by the natural environment and city layout. Therefore, understanding metropolitan areas’ spatial-temporal pattern evolution is of vital significance for medium-to-long-term city growth. This study uses the nighttime light data to monitor the urban pattern evolution of the Xi’an Metropolitan Area (XMA) over the past 30 years. The study results suggest that the continuity correction and consistency correction used in this study can construct a stable long-term, multi-source nighttime light dataset and, at the same time, accurately reflect the changes in the urban pattern. The determination coefficient between gross domestic product (GDP) and total nighttime light (TNL) reached 0.90; the nighttime light index (NLI) of the XMA is characterized by high spatial heterogeneity. The NLI of the core areas has been saturated before 2004, while the CNLI value of the peripheral Chang’an District was 0.31 by 2021. Urban land expanded in all directions, with an average expansion rate of 12.9% and an expansion intensity of 2.6%. The nighttime light gravity center generally shifted towards southwest, from (108.915° E, 34.355° N) in 1992 to (108.922° E, 34.343° N) in 2021. The urban pattern of the metropolitan area is influenced by the natural environment, and the southwest and northeast directions will be the primary development directions in the future. The local development policy is a crucial driving factor in the urban pattern evolution, which significantly affects the location and intensity of urban expansion; the center of gravity of the XMA has different migration directions in different periods, meaning that the development of the metropolitan area tends to be balanced.