Atsumasa Yoshida

Field measurements on energy balance of an urban canyon in the summer season

Abstract Field measurements on the energy balance of an east—west oriented urban canyon were performed continuously for several days in the summer season, as preliminary research of the heat transfer in the urban atmospheric boundary layer. The urban canyon consisted of concrete buildings, 16 m high and partially covered with windows, standing face to face across an asphalt road 17 m wide. The energy balance of the urban canyon is represented by the balance at the imaginary surface named “the top surface”. The top surface is a plane above the canyon at the same level as the roof surface of the buildings. In the daytime, the energy budget into the top surface is much larger than that into the roof surface. At nighttime, there is no significant difference in the energy balance between the roof surface and the top surface.

Two-dimensional numerical simulation of thermal structure of urban polluted atmosphere (effects of aerosol characteristics)☆

Abstract A two-dimensional numerical simulation is carried out on the unsteady heat transfer in the urban polluted boundary layer containing aerosols. The effects of aerosols upon the thermal structure over the region including an urban area are studied in full consideration of radiative heat transfer. The results indicate the strong interaction among the distributions of air temperature, wind velocity and aerosol concentration in connection with the scattering and absorbing characteristics of aerosols. When the scattering of solar radiation by aerosols is predominant, the air temperature in urban area drops greatly, and the convergent flow to the urban area becomes weak, causing the aerosol concentration in urban areas to become high. When the absorption of solar radiation is predominant, the convergent flow to the urban area is not weakened. Air temperature drops near the Earths surface, but the change in the upper air temperature is small.

Measurement of the Thermal Diffusivity of Metallic Foils and Films by the Photoacoustic Method1

The thermal diffusivities of four kinds of metallic foils from 20 to 200μμm in thickness were measured by a photoacoustic method on the basis of the Rosencwaig and Gersho theory. The measured data for continuous foils of uniform microscopic structure almost agreed with the literature values. Measurements were also carried out on two kinds of metallic thin films with of 10μμm thickness produced by sputtering. The difference in thermal diffusivity between the foils and the sputtered films depended on the uniformity of the microscopic structure.