Effects of the Selected Domain in Mesoscale Atmospheric Simulations and Dispersion Calculations

The role of the various-scale circulations (synoptic, regional, sub-regional, mesoscale, microscale) in the dispersion of air pollutants, released from different type of sources, is considered as very important because the 3-D meteorological and turbulence fields show significant temporal variations (e.g. Pielke et al., 1983; Glendening et al., 1986; Segal et al., 1988; Ulrickson and Mass, 1990; Kallos, 1990 among others). This is especially true in areas with significant physiographic variations. Today, allot of mesoscale models are able to provide meteorological and turbulence fields adequate for use in dispersion and/or transformation models (Pielke, 1988; Seigneur, 1989). The combined use of such models is considered as superior from the existing regulatory models because they should provide a more realistic description of the dispersion characteristics and the spatial and temporal variations of the concentration fields of air pollutants on more accurate manner. Despite this fact, the use of such models may lead in erroneous calculations for several reasons. The most important reasons are the mishandling from the models the physical processes taking place under certain circumstances and of course the improper use of them. The improper use may be due to the violations of physical rules which are not necessarily associated with the algorithms and the chosen initial and boundary conditions.