Digital Cities II: Monitoring the Urban Environment from Space

摘要

Monitoring spatiotemporal changes in large urban agglomorations will become increasingly important as the number and proportion of urban residents continue to increase. The synoptic view of urban landcover provided by satellite and airborne sensors is an important complement to in situ measurements of physical, environmental and socioeconomic variables in urban settings. The 10 to 80 m spatial resolution of most operational satellites has impeded the use of remotely sensed imagery for studies of urban infrastructure but this resolution is sufficient for measurement of some important environmental parameters that would be logistically difficult or prohibitively expensive to measure directly. Intra-urban variations in vegetation abundance influence environmental conditions and energy fluxes by selective reflection and absorbition of solar radiation and by modulation of evapotraspiration. Operational satellites such as Landsat provide the ability to monitor spatiotemporal dynamics of urban vegetation and thermal emission simultaneously on seasonal to interannual time scales to better understand their relationship to the urban environment. Similarly, monitoring of spatiotemporal variations of urban vegetation abundance may allow the effect of the urban environment on vegetation phenology to be determined. In this study, we discuss methodology for measurement of urban vegetation and compare vegetation distributions in the New York and Guangzhou metropolitan areas using Landsat TM imagery. A systematic analysis of the spatiotemporal dynamics of vegetation in the world s major evolving urban centers would facilitate comparative studies of urban environment and its role in public health and energy consumption as well as constraining the role of the urban center in the dynamics of larger metro-agro-plex systems.