Temperature fields and air pollution build-up over the Athens basin

Abstract

The wind and temperature fields, and the associated vehicle-induced atmospheric 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 conseration equation is solved, while a two-equation (k-ϵ) turbulence model is used for obtaining the turbulent exchange coefficients. Finally the concentration equation is numerically solved in transformed space and the passive contaminants distribution over the Athens complex topography is obtained. The model has been used to predict the temperature distribution and the surface concentrations of pollutants over the Athens area for South wind and a certain traffic scenario during a 24-hour cycle. The obtained results reproduced successfully the diurnal variation of the atmospheric stability conditions; the variation of the resulting 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 traffic could be allowed without any harmful effects to the air quality of the city as at time this unstable atmospheric conditions prevail. Also the use of the model revealed that the daily variation of the CO concentration can be mainly attributed to the atmospheric stability changes during the day rather than to traffic volume variations.