A numerical model for the computation of the wind field, air temperature and humidity in the atmospheric boundary layer including the urban canopy layer was developed for urban and architectural planning. The model is a k-ε type used widely in the environmental engineering. The ensemble-spatial averaged three-dimensional Reynolds equations, equation of continuity, turbulent kinetic energy (Adequation) and turbulent energy dissipation equation (ε-equation) are solved together with equations of heat and moisture transfer in the air. Inside the urban canopy layer, effects of buildings and other urban structures on the momentum transfer are modeled by introducing a form drag force, and volumes of them are accounted for by a spatial averaging procedure. The values of the coefficient for eddy viscosity evaluation C_μ and turbulent Prandtl number P_<rt> are defined as the atmospheric stability function and compared with Level 2.5 model. Numerical results by the new model show that the flow behavior of the air in the urban canopy layer is extremely affected by the existence of buildings and thermal stratification.
