MODELING OF THERMAL ENVIRONMENT IN URBAN CANYON WITH SOLAR RADIATION SHADING OF TREES

In this study, a theoretical model of an urban canyon was developed to investigate the effects of canyon structure and street trees on the thermal environment. The numerical model includes the amount of sunlight that falls on the canyon surface, and the effect of the wind field in the canyon. The results show that the model has a good agreement with measured thermal data. The urban canyon structure has a significant effect on the thermal environment, especially around H/D=0.6(building height/road width). Both the field study and the modeling study confirm street trees can improve the thermal environment of the urban canyon by lowering the air temperature and the surface temperature. About a 2℃ decrease of the maximum air temperature was been obtained in the field measurement and the simulation for north-south urban canyon with a higher trees. In addition, the effect of the street trees become much more effective with an increase of the road width. Street with a ratio of H/D around 0.6 has a good shading effect in summer as well as a good solar gain effect in winter. Wider streets are recommended in order to provide a good sun access in winter; however higher trees are necessary during summer to prevent the urban canyon from absorbing excessive solar irradiance