A climatological air quality dispersion was developed which provides more powerful analyses capabiIities than are avaiIable in traditional CDM-type models. The model incorporates a time series approach to satisfy identified user needs. The three components of the model are: the time series file of meteorological variables, the program (GLCGEN) used to generate ground level concentrations, and the frequency analysis program (FRQDTN) which defines the analyses for a particular run. The time series fiIe contains the meteoroIogicaI data necessary to define dispersion classes and also includes other meteoroIogicaI parameters which can be used to further cIassify the ground IeveI concentrations anaIyzed in the frequency distribution program. Program GLCGEN incorporates the disperision formulations and computes ground level concentrations for each receptor source pair for each dispersion class utiIizing user-defined source characteristics and an emission rate of unity. This array of ground level concentration vaIues is stored on a random access file for access by FRQDTN. This precalculation of procedure permits considerable saving of computer costs when long time series of data are processed.