NOAA scientists are now using satellite data to characterize urban areas to help researchers assess global climate change and determine the effect of urbanization on temperature records, the Commerce Department's National Oceanic and Atmospheric Administration announced.

Data derived from the Operational Linescan System of the Defense Meteorological Satellite Program was originally only used to monitor the global distribution of clouds and cloud top temperatures. However, the data acquired by the visible sensor at night under cloud-free conditions can provide a view of the light emitted from the Earth's surface. This data is capable of identifying urban and rural locations as it identifies the light associated with urban locales.

Kevin Gallo, a scientist with NOAA's National Environmental, Satellite, Data, and Information Services, along with other NOAA scientists, has demonstrated that there is an important function for this distinction between urban and rural areas. As a result of this distinction, new analysis is being made on the influence of urbanization on temperature records.

Urban development usually results in a dramatic change of the Earth's surface, as natural vegetation is removed and replaced by surfaces such as stone, metal, asphalt and concrete. Urban surfaces generally store and release more heat to the surrounding environment than natural vegetation, which results in increased temperatures observed within the urban environment. Changes in surface features -- from natural vegetation to urban surfaces -- may therefore result in greater temperatures. Knowledge of the past and present environment where temperatures are observed is important for long-term climate analysis.

"We compared vegetation indices and radiant surface temperatures acquired by the AVHRR--a radiometer aboard NOAA polar orbiting satellites--with air temperatures observed for urban and rural locations," explained Gallo. "The satellite data were found to be useful for monitoring the differences observed between urban and rural air temperatures."

Using the DMSP-OLS data to determine whether an area is urban or rural is beneficial to assessing the climatic implications of urbanization. The future influence of urban areas on temperature records will likely be obtained from analyses that combine satellite and surface-based data.

Further information of the use of satellite-derived data to monitor urban environments can be found at: http://research.umbc.edu/~tbenja1//gallo/gallo.html