A climatological air quality dispersion was developed which provides more powerful analyses capabilities than are available in traditional COM-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 file contains the meteorological data necessary to define dispersion classes and also includes other meteorological parameters which can be used to further classify the ground level concentrations analyzed in the frequency distribution program. Program GLCGEN incorporates the dispersion formulations and computes ground level concentrations for each receptor source pair for each dispersion class utilizing user-defined source characteristics and an emission rate of unity. This array of ground level concentration values 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.