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Atlanta Urban Growth and Effects on Climate and Air Quality

In the last half of the 20th century, Atlanta, Georgia has risen as the premier commercial, industrial, and transportation urban area of the southeastern United States. The rapid growth of the Atlanta area, particularly within the last 25 years, has made Atlanta one of the fastest growing metropolitan areas in the United States. The population of the Atlanta metropolitan area increased 27% between 1970 and 1980, and 33% between 1980-1990 (Research Atlanta, Inc., 1993). Concomitant with this high rate of population growth, has been an explosive growth in retail, industrial, commercial, and transportation services within the Atlanta region. This has resulted in tremendous land cover change dynamics within the metropolitan region, wherein urbanization has consumed vast acreages of land adjacent to the city proper and has pushed the rural/urban fringe farther and farther away from the original Atlanta urban core. An enormous transition of land from forest and agriculture to urban land uses has occurred in the Atlanta area in the last 25 years, along with subsequent changes in the land-atmosphere energy balance relationships.

Air quality has degenerated over the Atlanta area, particularly in regard to elevations in ozone and emissions of volatile organic compounds (VOCs), as indicated by results from the Southern Oxidants Study (SOS) which has focused a major effort on measuring and quantifying the air quality over the Atlanta metropolitan region. SOS modeling simulations for Atlanta using U.S. Environmental Protection Agency (EPA) State Implementation Plan guidelines suggest that a 90% decrease in nitrogen oxide emissions, one of the key elements in ozone production, will be required to bring Atlanta into attainment with the present ozone standard (SOS, 1995).

Science Approach - (At-A-Glance)

We are relating land cover changes with modifications in the local and regional climate and in air quality.Analysis of remote sensing data in conjunction with in situ data (e.g., meteorological measurements) are employed to initialize local and regional-level numerical models of land-atmosphere interactions. Remote sensing data form the basis for quantifying how land covers have changed within the Atlanta metropolitan area through time from the mid-1970's, when Atlanta's dramatic growth began in earnest, to the present. These remotely sensed data will be used to provide input to numerical models that relate land cover change through time with surface energy flux and meteorological parameters to derive temporal models of how land cover changes have impacted both the climatology and the air quality over the Atlanta region. Remote sensing data will be used to calibrate the models and as baseline data for extending the models to predict how prospective future land cover changes will effect the local and regional climate and air quality over the Atlanta-north Georgia region. Additionally, remote sensing data will be used as an indirect modeling method to describe urbanization and deforestation parameters that can be used to assess, as well as predict, the effects of land use changes on the local microclimate.

In concert with the remote sensing-based analysis and modeling of land cover changes is an extensive numerically-based modeling effort to better understand the cause-and-effect relationships between urbanization and trends in climatology and air quality. Sophisticated numerical meteorological models can complement extensive field monitoring projects and help improve our understanding of these relationships and the evolution of the urban climate on a location-specific basis. Measured data alone cannot resolve the relationships between the many causes of urban heat islands/urban climates and observations. For example, measured data cannot directly attribute a certain fraction of temperature rise to a certain modification in land use patterns, change in energy consumption, or release of anthropogenic heat into the atmosphere. These are aspects that numerical modeling can help resolve. Similarly, monitored air quality data cannot be used to establish a direct cause-and-effect relationship between emission sources, activities, or urbanization and observed air quality (e.g., smog). In this sense, photochemical models can be used in testing the sensitivity of ozone concentrations to changes in various land-use components, emission modifications and control, or other strategies. Thus, we are incorporating an assessment of land cover/land use change as measured from remote sensing data, with temporal numerical modeling simulations to better understand the effects that the growth of Atlanta has had on local and regional climate characteristics and air quality.

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Last Updated: August 5, 1999