Abstract
Large-eddy simulation（ LES） is performed to investigate the mechanism of the momentum and heat transport in an urban boundary layer with thermal stratification. From the results of LES, strong ejections which are generated at the top of the urban canopy （z/H=1.0） and are transported upward greatly contribute to Reynolds stress and turbulent heat flux. Model coefficient of eddy diffusivity for momentum Cμ and turbulent Prandtl number Prt which are estimated from the results of LES are smaller than the values which are used in standard k-ε model at some height. It is thought that the prediction accuracy of standard k-ε model decreases in the urban boundary layer.
