Air Pollution Prevention Through Urban Heat Island Mitigation: An Update on the Urban Heat Island Pilot Project Virginia Gorsevski, U.S. Environmental Protection Agency, Washington, DC Haider Taha, Lawrence Berkeley National Laboratory, Berkeley, CA Dale Quattrochi, National Aeronautics Space Administration, Huntsville, AL Jeff Luvall, National Aeronautics Space Administration, Huntsville, AL ABSTRACT Urban heat islands increase the demand for cooling energy and accelerate the formation of smog. They are created when natural vegetation is replaced by heat-absorbing surfaces such as building roofs and walls, parking lots, and streets. Through the implementation of measures designed to mitigate the urban heat island, communities can decrease their demand for energy and effectively "cool" the metropolitan landscape. In addition to the economic benefits, using less energy leads to reductions in emissions of CO 2 - a greenhouse gas - as well as ozone (smog) precursors such as NOx and VOCs. Because ozone is created when NOx and VOCs photochemically combine with heat and solar radiation, actions taken to lower ambient air temperature can significantly reduce ozone concentrations in certain areas. Measures to reverse the urban heat island include afforestation and the widespread use of highly reflective surfaces. To demonstrate the potential benefits of implementing these measures, EPA has teamed up with NASA and LBNL to initiate a pilot project with three U.S. cities. As part of the pilot, NASA will use remotely-sensed data to quantify surface temperature, albedo, the thermal response number and NDVI vegetation of each city. This information will be used by scientists at Lawrence Berkeley National Laboratory (LBNL) along with other data as inputs to model various scenarios that will help quantify the potential benefits of urban heat island mitigation measures in terms of reduced energy use and pollution. This paper will briefly describe this pilot project and provide an update on the progress to date. Introduction One of the fundamental components that sets a city apart from its rural surroundings is the climate that prevails over urban environments. In urban areas, buildings and paved surfaces have gradually replaced preexisting natural landscapes. As a result, solar energy is absorbed into roads and rooftops, causing the surface temperature of urban structures to become 50 - 70 °F higher than the ambient air temperatures. (Taha, Akbari & Sailor 1992). As surfaces throughout an entire community or city become hotter, overall ambient air temperature increases. This phenomenon, known as an "urban heat island," can raise air temperature in a city by 2 - 8 °F. (Oke 1987 and World Meteorological Organization 1984). The resulting higher temperature caused by the urban heat island has the effect of increasing the demand for cooling energy in commercial and residential buildings. Increased demand for energy can cost consumers and municipalities thousands of additional dollars in air conditioning bills in order to maintain comfort levels. In addition, increased electricity generation by power plants leads to higher emissions of sulfur dioxide, carbon monoxide, nitrous oxides, and suspended particulates, as well as carbon dioxide, a greenhouse gas known to contribute to global warming and climate change. Finally, summer heat islands often accelerate the formation of harmful smog, as ozone precursors such as nitrous oxides (NO x ) and