The American Meteorological Society (AMS) and the U.S. Environmental Protection Agency (US EPA) initiated a formal collaboration with the aim of introducing current planetary boundary layer (PBL) concepts into regulatory dispersion models in 1991. A group comprising AMS and EPA scientists was formed for this collaborative function, which was known as the AMS/EPA Regulatory Model Improvement Committee (AERMIC). The AERMIC model (AERMOD), wich is an improved version of the Industrial Source Complex Model (ISC3) that has been the EPA regulatory model for some time, was developed (Schulze and Turner, 1996). AERMOD is a freely available software package provided by the EPA (US-EPA, 2014).