Use of the DMSP-OLS Nighttime Light Data to Study Urbanization and Its Influence on NDVI in Taihu Basin, China

This study investigates the urbanization of Taihu Basin and its influence on Satellite Pour l'Observation de la Terre (SPOT)-Normalized Difference Vegetation Index (NDVI). The correction model of the Defense Meteorological Satellite Program-Operational Linescan System (DMSP-OLS) of nighttime images was built to extract the dynamics of urban expansion. Tempo-spatial correlations between a vegetation index and nighttime light intensity are discussed to quantitatively assess the urbanization effect. The results show that Taihu Basin is in a period of rapid urbanization. Urban expansion is developing not only surrounding the city center circle but also along the main traffic arteries and rivers, which show a linear expansion resulting in an urban agglomeration. Under the influence of urbanization, the NDVI shows a slight decrease, and there is a significant negative tempo-spatial correlation in the urban areas of the eastern watershed between NDVI and nighttime light intensity, which are predominantly the low vegetation abundant areas. The contribution of urbanization to NDVI is negative in the eastern region. The contribution rates are greater than 14.0% and, in some cases, exceed 30%. This paper indicates the urbanization characteristics and their effect on the surface vegetation in Taihu Basin. In addition, based on the calibration model, the DMSP-OLS nighttime light data have a strong ability to examine the spatiotemporal evolution of urbanization. The results can provide support for the study of urban hydrology.