A numerical model for wind field and pollutant concentration calculations over complex terrain. Application to Athens, Greece

A non-hydrostatic, three-dimensional, prognostic, mesoscale model is developed for the calculation of the flow field and pollutant concentrations over complex terrain. The model solves numerically in an implicit, time-dependent manner the full Reynolds equations, in Cartesian, collocated grid arrangement. The differential equations are discretized by the finite volume method and solved iteratively with the SIMPLE algorithm. Turbulence closure is obtained by the two-equation (k-epsilon) turbulence model. A technique of partially covered cells is introduced for an accurate representation of complex terrain features. The greater area of Athens, Greece, which combines significant topographic and sea-breeze aerodynamic complexities, is chosen for the model performance evaluation. The results reproduce reasonably well the diurnal variation of the wind and pollutant concentration fields, and the comparison with available observations is satisfactory. (C) 1998 Elsevier Science B.V. All rights reserved.