A model development investigation has been performed to better quantify the dispersion of pollutants from various source types in the region of Cape Cod Massachusetts. The technology developed will be used by epidemiologists to better understand the role of sea and land breeze circulations in the dispersal of pollutants from important sources in the region. Other papers at this conference may discuss the adaptation of the MM5 mesoscale model for the prediction of the meteorological aspects of this work. The fine grid scale meteorological model was used to drive another flow field model, CALMET, and three different atmospheric dispersion models (SCIPUFF,CALPUFF and ISC3) for purposes of predicting air quality concentrations. These dispersion models have varying capabilities to incorporate the complexities of the predicted flows. This paper will focus on comparing the results of the three dispersion models for the same case study events. The case study events consist of summertime periods of strong sea breeze circulations as well as occasions when land breeze effects are evident. Because of the specific topography of Cape Cod, converging sea breezes are apparent and important.

The circulations cause very different air quality impacts from low-level pollutant releases than from high level releases. Also the locations of the sources relative to the three nearby large water bodies is shown to be a very important factor for the models that better simulate the complex three dimensional aspects of the flows involved. Four sources are simulated: two are large power plants. One is a ground level area source and the fourth is a highway.

In addition to a description of the comparative predictions for the different models and source types, the paper will discuss the relative merits of using one model versus another for the differing applications and differing meteorological flows modeled.