TEMPERATURE-FIELDS AND AIR-POLLUTION BUILDUP OVER THE ATHENS BASIN

The wind and temperature fields, and the associated vehicle-induced at mospheric pollution build-up over the Athens Basin have been simulated using a time-dependent, three-dimensional numerical model. The model utilizes the continuity equation to produce a non-divergent wind field adopting a mass consistent methodology; then the heat conservation eq uation is solved, while a two-equation (k-epsilon) turbulence model is used for obtaining the turbulent exchange coefficients. Finally the c oncentration equation is numerically solved in transformed space and t he passive contaminants distribution over the Athens complex topograph y is obtained. The model has been used to predict the temperature dist ribution and the surface concentrations of pollutants over the Athens area for South wind and a certain traffic scenario during a 24-hour cy cle. The obtained results reproduced successfully the diurnal variatio n of the atmospheric stability conditions; the variation of the result ing surface temperature agreed well with available measurements, while the results for the atmospheric pollution showed that the banning of the car traffic in the city-center is effective only for certain time periods within the day, and that in the early afternoon hours the traf fic could be allowed without any harmful effects to the air quality of the city as at this time unstable atmospheric conditions prevail. Als o the use of the model revealed that the daily variation of the CO con centration can be mainly attributed to the atmospheric stability chang es during the day rather than to traffic volume variations.