The US EPA contracted the Center for Environmental Modeling for Policy Development (CEMPD) through the University of North Carolina at Chapel Hill (UNC) Institute for the Environment (IE) to establish a [Community Modeling and Analysis System (CMAS) for supporting community-based air quality modeling. CMAS is an approach to the development, application, and analysis of environmental models that leverages the complementary talents and resources of the modeling community in order to set new standards for quality in science and in the reliability of the application of the technology.