Abstract
The averaged minimum temperature in August at Osaka City is rising about 2 degrees in 100 years. It can be considered that the cause induced heat island phenomenon is the increase of energy consumption and the alteration of the ground surface. In this study, we simulated the influence of the building configration on the wind velocity and potential temperature within the urban canopy layer, using one dimensional atmospheric boundary layer model. It was assumed that the building of the same size had been regularly arranged in the shape of a lattice within the urban canopy, and the shortwave radiation and long wave radiation fluxes in the urban canopy were independently estimated correctly by the photon tracking method based on the Monte Carlo method. When a fraction of an area covered with the buildings (η) increased or the urban canopy height (hc) became high, it was found that the shortwave radiation flux which the ground surface receives at the daytime decreases, and the long wave radiation flux emitted to the sky decreases at the night time. Next, the heat budget equation model on the building and ground surface, and one dimensional atmospheric boundary layer model were combined, and the temperature and the wind velocity distribution in the urban canopy were predicted. Whenη increased or hc became high, the wind velocity in the urban canopy decreased, and the potential temperature rise at the daytime became small and the potential temperature fall at the night time became also small. It became clear by these results that the increase of η and the rise of hc are one of the causes of the heat island phenomenon.
