Follow this link to skip to the main content
jpl header

Nghiem's Banner
home about science megacities meetings Data publications outreach Nghiem's Banner


Summary of a NASA Inter-Disciplinary Science (IDS) project to investigate
mega urban changes and impacts in the decade of the 2000s.

The IPCC Working Groups II and III recognize that a large fraction of greenhouse gases from power generation, industry, transportation, and consumption can be attributed to human settlements. Conversely, cities become increasingly vulnerable to climate change due to the rapid growth of population and infrastructures that may exacerbate both natural and man-made hazards. It is hypothesized that the exodus from rural to urban areas and economic booms in developing countries such as China and India in the decade of the 2000s has led to rapid and haphazard urban development that disproportionally impact the urban environment. These impacts may be far reaching to include not only the urban vicinity but also across regional and perhaps global scales. Nevertheless, major gaps exist in the assessment of urban impacts on environment where key parameters such as urban extent, residential areas, and commercial/industrial cores are needed.

The objective of this project is to investigate impacts of urban changes on the environment during the unprecedented growth of large cities (what we call, mega-urbanization) in the decade of 2000s. The research will study these environmental changes, among others: urban heat island, urban dome, greenhouse gas emission, and pollutions in the atmosphere and water systems. It will consider various urban regions in different continents. The research will also study demographic factors associated with urbanization during this decade of change including population distribution, population dynamics and changes in livelihoods such as housing, living arrangements and socioeconomic status. As such, the science team will consist of interdisciplinary researchers from multiple national and international institutions, covering a wide range of disciplines including satellite remote sensing of land use and land cover, urban remote sensing from microwave to optical frequencies, atmospheric science, chemistry, geohydrology, energy, demographics, and socioeconomics.

We will use decadal data from multiple satellites to observe urban extent, urban typology, urban infrastructures, urban change, road networks, atmospheric chemicals, soil moisture, stream flow, and other environmental parameters within and beyond urban areas across multiple spatial and temporal scales. Moreover, we will use measurements from aircraft campaigns and surface networks, and socioeconomic data (e.g., SEDAC/CIESIN), and global-to-rural-scale model results. Beyond traditional methods used for land use and land change observations, we implement an innovative method based on a new mathematical transformation, called the Rosette Transform operated on satellite scatterometer radar data, to consistently delineate urban environment (such as urban extent, commercial and industrial cores, residential and suburban areas, etc.) and monitor inter-annual urban changes in each 1-km pixel for each year in the 2000s.

As a component of this interdisciplinary science research, the GATOR-GCMOM (Gas, Aerosol, Transport, Radiation, General Circulation, Mesoscale, and Ocean Model) will simulate the global, regional, and urban climate and air pollution health impacts resulting from urbanization during the period that satellite data are gathered for. This model nests climate, meteorological, gas, aerosol, and radiative parameters simultaneously from the global through urban scale. A stretched-grid version is developed to allow for one continuous domain stretching from high resolution over an urban area to coarse resolution over the remainder of the globe. A goal of the model simulations will be to estimate the effects on climate and air quality of annual changes in the extent of urbanization over regions of China, U.S., or mega urbanization regions between the years of 2000 and 2010.

We will measure the rate of infrastructure change and compare it with the rates of change of pollution, urban temperature change, and demographic and socioeconomic factors. The research includes major cities in Asia, Europe, America, and Africa. Urban changes may present complications such as relative effects between urban heat island and greenhouse gas in identifying temperature trends. We will use the comprehensive set of urban delineation and annual changes across areas with various rates of urban change to compare and contrast the impacts between areas with large and small changes. We anticipate the research results from this to offer explanations on the pace and scale of urbanization and an understanding of what may lie ahead for urban environments in the coming decades.